Oil Spill Science and Technology

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Oil Spill Science and Technology

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Oil Spill Science and Technology Prevention, Response, and Cleanup

Edited by

Mervin Fingas

Amsterdam l Boston l Heidelberg l London l New York l Oxford Paris l San Diego l San Francisco l Singapore l Sydney l Tokyo Gulf Professional Publishing is an imprint of Elsevier

Gulf Professional Publishing is an imprint of Elsevier 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA The Boulevard, Langford Lane, Kidlington, Oxford, OX5 1GB, UK Copyright Ó 2011 Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Library of Congress Cataloging in Publication Data Oil spill science and technology : prevention, response, and clean up / edited by Mervin Fingas. – 1st ed. p. cm. Summary: “The National Academy of Sciences estimate that 1.7 to 8.8 million tons of oil are released into world’s water every year, of which more than 70% is directly related to human activities. The effects of these spills are all too apparent: dead wildlife, oil covered marshlands and contaminated water chief among them. This reference will provide scientists, engineers and practitioners with the latest methods use for identify and eliminating spills before they occur and develop the best available techniques, equipment and materials for dealing with oil spills in every environment. Topics covered include: spill dynamics and behaviour, spill treating agents, and cleanup techniques such as: in situ burning, mechanical containment or recovery, chemical and biological methods and physical methods are used to clean up shorelines. Also included are the fate and effects of oil spills and means to assess damage”– Provided by publisher. ISBN 978-1-85617-943-0 1. Oil spills–Prevention. 2. Oil spills–Cleanup. 3. Oil spils–Managements. I. Fingas, Mervin F. TD427.P4O38785 2010 628.1’6833–dc22 2010033465 British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. ISBN: 978-1-85617-943-0 For information on all Gulf Professional Publishing publications visit our Web site at www.elsevierdirect.com

11 12 13 10 9 8 7 6 5 4 3 2 1 Printed and bound in the USA

Contents

Preface About the Contributors

xxv xxvii

Part I Introduction and the Oil Spill Problem 1.

2.

Introduction

3

Merv Fingas 1.1. Introduction 1.2. A Word on the Frequency of Spills

3 4

Spill Occurrences: A World Overview

7

Dagmar Schmidt-Etkin 2.1. Introduction 2.2. Executive Summary 2.3. Overview of Spill Occurrences 2.3.1. Natural Oil Seepage 2.3.2. Historical Concern Over Oil Pollution 2.3.3. Sources of Oil Spills and Patterns of Spillage 2.3.4. Spillage from Oil Exploration and Production Activities 2.3.5. Spills During Oil Transport 2.3.6. Spillage from Oil Refining 2.3.7. Spillage Related to Oil Consumption and Usage 2.3.8. Oil Inputs from Potentially Polluting Sunken Shipwrecks 2.3.9. Summary of Oil Spillage References

7 8 8 8 11 12 17 23 28 32 39 41 46

Part II Types of Oils and Their Properties 3.

Introduction to Oil Chemistry and Properties

51

Merv Fingas 3.1. Introduction

51

v

vi

Contents

3.2. The Composition of Oil 3.3. Properties of Oil References

51 54 59

Part III Oil Analysis and Remote Sensing 4.

5.

Measurement of Oil Physical Properties

63

Bruce Hollebone 4.1. Introduction 4.2. Bulk Properties of Crude Oil and Fuel Products 4.2.1. Density and API Gravity 4.2.2. Dynamic Viscosity 4.2.3. Surface and Interfacial Tensions 4.2.4. Flash Point 4.2.5. Pour Point 4.2.6. Sulphur Content 4.2.7. Water Content 4.2.8. Evaluation of the Stability of Emulsions Formed from Brine and Oils and Oil Products 4.2.9. Evaluation of the Relative Dispersability of Oil and Oil Products 4.2.10. Adhesion to Stainless Steel 4.3. Hydrocarbon Groups 4.4. Quality Assurance and Control 4.5. Effects of Evaporative Weathering on Oil Bulk Properties 4.5.1. Weathering 4.5.2. Preparing Evaporated (Weathered) Samples of Oils 4.5.3. Quantifying Equation(s) for Predicting Evaporation References Appendix 4.1

71 72 73 77 78 78 79 81 83 85

Introduction to Oil Chemical Analysis

87

Merv Fingas 5.1. Introduction 5.2. Sampling and Laboratory Analysis 5.2.1. Incorrect and Obsolete Methods 5.3. Chromatography 5.3.1. Introduction to Gas Chromatography 5.3.2. Methodology 5.4. Identification and Forensic Analysis 5.4.1. Biomarkers 5.4.2. Sesquiterpanes and Diamondoids 5.5. Field Analysis References

63 63 66 67 67 69 70 70 70 71

87 87 88 89 89 93 96 99 105 107 107

Contents

6.

Oil Spill Remote Sensing: A Review Merv Fingas and Carl E. Brown 6.1. Introduction 6.2. Visible Indications of Oil 6.3. Optical Sensors 6.3.1. Visible 6.3.2. Infrared 6.3.3. Ultraviolet 6.4. Laser Fluorosensors 6.5. Microwave Sensors 6.5.1. Radiometers 6.5.2. Radar 6.5.3. Microwave Scatterometers 6.5.4. Surface Wave Radars 6.5.5. Interferometric Radar 6.6. Slick Thickness Determination 6.6.1. Visual Thickness Indications 6.6.2. Slick Thickness Relationships in Remote Sensors 6.6.3. Specific Thickness Sensors 6.7. Acoustic Systems 6.8. Integrated Airborne Sensor Systems 6.9. Satellite Remote Sensing 6.10. Oil Under Ice Detection 6.11. Underwater Detection and Tracking 6.12. Small Remote-Controlled Aircraft 6.13. Real-Time Displays and Printers 6.14. Routine Surveillance 6.15. Future Trends 6.16. Recommendations Acknowledgments References

7.

vii

111 111 112 114 114 120 123 123 124 124 125 134 135 135 135 135 136 138 139 139 140 144 145 149 150 150 153 154 158 158

Laser Fluorosensors

171

Carl E. Brown 7.1. Principles of Operation 7.1.1. Active versus Passive Sensors 7.1.2. Sensor Features 7.1.3. Pros/Cons 7.2. Oil Classification 7.2.1. Real-Time Analysis 7.2.2. Sensor Outputs 7.3. Existing Operational Units 7.3.1. Airborne 7.3.2. Ship-Borne 7.4. Aircraft Requirements 7.4.1. Power

171 171 171 174 175 175 176 179 179 179 180 180

viii

Contents

7.4.2. Weight 7.4.3. Operational Altitude 7.5. Cost Estimates 7.6. Conclusions References

181 181 182 182 182

Part IV Behaviour of Oil in the Environment and Spill Modeling 8.

9.

Introduction to Spill Modeling

187

Merv Fingas 8.1. Introduction 8.2. An Overview of Weathering 8.2.1. Evaporation 8.2.2. Emulsification 8.2.3. Natural Dispersion 8.2.4. Dissolution 8.2.5. Photo-Oxidation 8.2.6. Sedimentation, Adhesion to Surfaces, and Oil-Fines Interaction 8.2.7. Biodegradation 8.2.8. Sinking and Overwashing 8.2.9. Formation of Tarballs 8.3. Movement of Oil and Oil Spill Modeling 8.3.1. Spreading 8.3.2. Movement of Oil Slicks 8.3.3. Spill Modeling References

192 193 194 195 196 196 197 198 199

Evaporation Modeling

201

Merv Fingas 9.1. Introduction 9.2. Review of Theoretical Concepts 9.3. Development of New Diffusion-Regulated Models 9.3.1. Wind Experiments 9.3.2. Evaporation Rate and Area 9.3.3. Study of Mass and Evaporation Rate 9.3.4. Study of the Evaporation of Pure Hydrocarbonsdwith and Without Wind 9.3.5. Other Factors 9.3.6. Temperature Variation and Generic Equations Using Distillation Data 9.3.7. A Simplified Means of Estimation 9.4. Complexities to the Diffusion-Regulated Model 9.4.1. Thickness of the Oil

187 187 188 190 191 192 192

201 205 212 212 215 215 216 217 217 227 229 229

Contents

9.4.2. The Bottle Effect 9.4.3. Skinning 9.4.4. Rises from the 0-Wind Values 9.5. Use of Evaporation Equations in Spill Models 9.6. Comparison of Model Approaches 9.7. Summary References

10.

11.

ix 229 230 233 233 235 240 241

Models for Water-in-Oil Emulsion Formation

243

Merv Fingas 10.1. Introduction 10.2. Early Modeling of Emulsification 10.3. First Two Model Developments 10.4. New Model Development 10.5. Development of an Emulsion Kinetics Estimator 10.6. Discussion 10.7. Conclusions References

243 249 251 253 260 260 269 270

Oil Spill Trajectory Forecasting Uncertainty and Emergency Response

275

Debra 11.1. 11.2. 11.3.

Simecek-Beatty Introduction: The Importance of Forecast Uncertainty The Basics of Oil Spill Modeling Trajectory Model Uncertainties 11.3.1. Release Details 11.3.2. Wind 11.3.3. Current 11.3.4. Turbulent Diffusion 11.3.5. Oil Weathering 11.3.6. Ensemble Forecasting 11.3.7. Communicating Trajectory Forecast Uncertainty 11.4. Trajectory Forecast Verification 11.4.1. Diagnostic Verification 11.5. Summary and Conclusions Acknowledgments References

275 276 280 281 282 284 287 288 289 291 292 294 295 297 297

Part V Physical Spill Countermeasures on Water 12.

Physical Spill Countermeasures

303

Merv Fingas 12.1. Containment on Water

303

x

13.

Contents

12.1.1. Types of Booms and Their Construction 12.1.2. Uses of Booms 12.1.3. Boom Failures 12.1.4. Ancillary Equipment 12.1.5. Sorbent Booms and Barriers 12.1.6. Special-Purpose Booms 12.2. Skimmers 12.2.1. Oleophilic Surface Skimmers 12.2.2. Weir Skimmers 12.2.3. Suction or Vacuum Skimmers 12.2.4. Elevating Skimmers 12.2.5. Submersion Skimmers 12.2.6. Skimmer Performance 12.2.7. Special-Purpose Ships 12.3. Sorbents 12.4. Manual Recovery 12.5. Temporary Storage 12.6. Pumps 12.6.1. Performance of Pumps 12.7. Separation 12.8. Disposal Acknowledgments References

303 306 309 313 314 314 315 316 320 321 322 323 323 325 325 329 330 332 334 334 335 337 337

Weather Effects on Oil Spill Countermeasures

339

Merv Fingas 13.1. Introduction 13.1.1. Spreading Compared to Weathering 13.1.2. Important Components of Weather 13.1.3. Oil Properties Regardless of Weathering 13.2. Review of Literature on Spill Countermeasures and Weather 13.2.1. A Priori Decision Guides 13.2.2. General Countermeasures 13.2.3. Booms 13.2.4. Skimmers 13.2.5. Dispersants 13.2.6. In-Situ Burning 13.2.7. Others 13.2.8. Ice Conditions 13.3. Development of Models for Effectiveness of Countermeasures 13.3.1. Overall 13.3.2. Booms 13.3.3. Skimmers 13.3.4. Dispersants 13.3.5. In-Situ Burning

339 340 340 343 343 343 345 345 353 372 378 381 381 383 383 383 383 398 403

Contents

13.3.6. Others 13.4. Overview of Weather Limitations 13.5. Summary and Conclusions Acknowledgments References

xi 404 405 407 416 416

Part VI Treating Agents 14.

15.

Spill-Treating Agents

429

Merv Fingas 14.1. Introduction 14.2. Dispersants 14.3. Surface-Washing Agents 14.4. Emulsion Breakers and Inhibitors 14.5. Recovery Enhancers 14.6. Solidifiers 14.7. Sinking Agents 14.8. Biodegradation Agents

429 429 430 430 431 431 431 432

Oil Spill Dispersants: A Technical Summary

435

Merv Fingas 15.1. Introduction 15.1.1. What Are Dispersants? 15.2. The Basic Physics and Chemistry of Dispersants 15.2.1. Formulations 15.2.2. Nature of Surfactant Interaction with Oil 15.3. The Basic Nature of Dispersions or Oil-in-Water Emulsions 15.3.1. Forces of Destabilization 15.3.2. The Science of Stabilization 15.3.3. Oil Spill Dispersions 15.3.4. Significance of Emulsion Stability 15.4. Effectiveness 15.4.1. Introduction to Effectiveness 15.4.2. Field Trials 15.4.3. Laboratory Tests 15.4.4. Tank Tests 15.4.5. Analytical Means 15.5. Monitoring 15.5.1. Introduction to Monitoring 15.5.2. Review of SMART Protocol 15.5.3. The SERVS Protocol 15.5.4. Review of Other Protocols 15.5.5. Review of Goodman Analysis of SMART 15.5.6. Considerations for Monitoring in the Field

435 437 437 437 438 440 441 443 447 449 451 452 454 464 467 480 481 481 482 483 486 487 488

xii

Contents

15.5.7. 15.5.8. 15.5.9. 15.5.10. 15.5.11. 15.5.12. 15.5.13. 15.5.14. 15.5.15. 15.6.

15.7.

15.8. 15.9.

15.10.

Visual Surveillance Remote Sensing Tracking of Oil on Surface Tracking of Oil Underwater Mass Balance Use of Undispersed Slick(s) as a Control Background Levels of Hydrocarbons Using and Computing Values Recommended Procedures for Monitoring Dispersant Applications Studies Energy Composition of Oil Amount of Dispersant Temperature Salinity Particle or Droplet Size

Physical 15.6.1. 15.6.2. 15.6.3. 15.6.4. 15.6.5. 15.6.6. Toxicity 15.7.1. Toxicity of Dispersants 15.7.2. Photoenhanced Toxicity 15.7.3. Testing Protocols Biodegradation Other Information 15.9.1. Component Separation 15.9.2. Dispersant Use 15.9.3. Application of Dispersants 15.9.4. Assessment of the Use of Dispersants 15.9.5. Spills-of-Opportunity Research 15.9.6. Interaction with Sediment Particles 15.9.7. Modeling Oil and Dispersed Oil Behavior and Fate 15.9.8. Separation of Dispersants from Water 15.9.9. Dispersant Breakthrough Oil Slicks 15.9.10. Overall Effects of Weather on Dispersion 15.9.11. Joint Effect of Temperature and Salinity on Effectiveness 15.9.12. Dispersibility of Biodiesels 15.9.13. Application Systems 15.9.14. Accelerated Weathering Summary and Conclusions 15.10.1. Effectiveness Testing Overall 15.10.2. Laboratory Effectiveness Tests 15.10.3. Tank Testing 15.10.4. Analytical Methods for Effectiveness 15.10.5. Toxicity of Dispersed Oil and Dispersants 15.10.6. Biodegradation of Oil Treated by Dispersants

492 493 494 494 494 495 495 496 496 500 500 506 512 512 513 519 519 532 533 534 535 539 539 539 551 553 555 555 556 557 557 557 558 559 560 560 562 563 563 564 564 564 565

xiii

Contents

15.10.7. 15.10.8. 15.10.9. 15.10.10. 15.10.11. 15.10.12. 15.10.13. 15.10.14. Acknowledgments References

16.

Spill-of-Opportunity Research 565 Monitoring Dispersant Applications 565 Dispersant Use in Recent Times 566 Interaction with Sediment Particles 566 Stability of Dispersions and Resurfacing with Time 566 Fate of Dispersed Oil 566 Application Technology and Issues 566 Correlation of Oil Properties with Effectiveness 566 566 567

A Practical Guide to Chemical Dispersion for Oil Spills Merv Fingas 16.1. Introduction and Decision Making 16.1.1. An OverviewdHow, When, and Where Dispersants Are Used 16.1.2. Net Environmental Benefit Analysis 16.1.3. Scenarios For Which Dispersants Might Be Used 16.1.4. Planning Process and Checklists 16.2. How Dispersants Are Used 16.2.1. Dispersion Spray Equipment 16.2.2. Spray Aircraft 16.2.3. Spray Nomograms and Calculations 16.2.4. Monitoring, Sampling, and Analytical Equipment 16.2.5. Equipment Availability 16.2.6. Equipment Checklist 16.2.7. Conducting the Operation 16.3. Safety and Postdispersion Actions 16.3.1. Worker Health and Safety Precautions 16.3.2. Follow-Up Monitoring Additional Information Appendix A. Specific Spill Scenarios and Dispersion Strategies Appendix B. Nomograms to Calculate Spreading and Viscosity with Time

17.

583 583 584 587 589 589 591 592 593 594 596 596 597 597 598 598 599 601 603 605

Procedures for the Testing and Approval of Oil Spill Treatment Products in the United Kingdomd What They Are and Considerations for Development

611

Mark Kirby 17.1. Background and Introduction 17.1.1. Preassessment Requirements 17.2. Toxicity Testing Procedures

611 612 613

xiv

18.

Contents

17.2.1. Reference Oil 17.2.2. Test water 17.2.3. The Sea Test 17.3. Test Description 17.3.1. The Rocky Shore Test 17.3.2. Rationale 17.3.3. Test Species 17.3.4. Test Description 17.3.5. Test Validity and Pass/Fail Assessment 17.4. Testing with Heavy Fuel Oils 17.5. The 2007 UK Scheme Review 17.5.1. Review and Improvement 17.5.2. Specific Issues 17.6. Conclusions References

613 613 615 615 616 617 618 618 619 619 620 620 620 626 627

Formulation Changes in Oil Spill Dispersants: Are They Toxicologically Significant?

629

Mark F. Kirby, Paula Neall, Jennifer Rooke, and Heather Yardley 18.1. Introduction 18.2. Materials and Methods 18.2.1. General Approach 18.2.2. Dispersants and Constituents 18.2.3. Toxicity Tests 18.2.4. Testing Schedule 18.3. Results 18.3.1. Inherent Toxicity of Constituent Chemicals and Dispersants 18.3.2. Toxicity of Reformulated Dispersants in the Sea Test 18.3.3. Toxicity of Reformulated Dispersants in the Rocky Shore Test 18.3.4. Inherent Toxicity of Reformulated Dispersants 18.4. Discussion 18.4.1. Do Formulation Changes Matter? 18.4.2. Sea Test 18.4.3. Rocky Shore Test 18.4.4. Are Specific Constituents of Concern? 18.4.5. Significance of Inherent Toxicity Changes of Formulations? Acknowledgments References

19.

Environment Canada’s Methods for Assessing Oil Spill Treating Agents Carl E. Brown, Ben Fieldhouse, Trevor C. Lumley, Patrick Lambert and Bruce P. Hollebone

629 630 630 631 631 633 633 633 634 635 635 638 638 639 639 640 641 641 642

643

Contents

19.1. 19.2.

Introduction Toxicity and Effectiveness of Treating Agents for Oil Spills 19.2.1. Dispersants 19.2.2. Shoreline-Washing Agents 19.2.3. Deemulsifiers and Emulsion Inhibitors 19.2.4. Herding Agents 19.2.5. Recovery Agents 19.2.6. Solidifiers and Gelling Agents 19.2.7. Biodegradation Agents 19.2.8. Sinking Agents 19.3. Approval for Use of Treating Agents in Canadian Waters 19.4. Challenges to Current Toxicity Test Protocols 19.4.1. Endocrine Disrupting Capacity 19.4.2. Genotoxicity 19.4.3. Sublethal Effects 19.5. Conclusions References

20.

The United States Environmental Protection Agency: National Oil and Hazardous Substances Pollution Contingency Plan, Subpart J Product Schedule (40 Code of Federal Regulations 300.900) William 20.1. 20.2. 20.3. 20.4. 20.5. 20.6. 20.7. 20.8.

21.

xv 643 645 645 653 657 658 658 658 659 661 662 662 664 664 665 666 667

673

J. Nichols Introduction Why Is There a Product Schedule? Authorities for a Product Schedule Information Requested from Manufacturers Agency Activities Practical Utility of the Data Authorities for Use Federal Agencies’ Role within the Regional Response Team 20.9. Does Listing Mean the Environmental Protection Agency Approves and Endorses a Product? 20.10. Conclusions 20.10.1. Proper Uses and Lessons Learned References

681 681 682 682

Surface-Washing Agents or Beach Cleaners

683

Merv Fingas and Ben Fieldhouse 21.1. Introduction to Surface-Washing Agents

683

673 674 675 675 679 679 680 680

xvi

22.

Contents

21.1.1. Motivations for Using Surface-Washing Agents 21.1.2. Surface Washing Agent Issues 21.1.3. Surface-Washing Agent Chemistry 21.2. Review of Major Surface-Washing Agent Issues 21.2.1. Effectiveness 21.2.2. Toxicity 21.3. Other Issues 21.3.1. Application 21.3.2. Dispersion with Higher Applied Energy 21.3.3. Assessment of the Use of Surface-Washing Agents References Appendix 21.1. Environment Canada’s Test Method Summary Method EPA Draft Protocol Summary Fieldhouse High-Energy Protocol

685 685 686 686 686 697 697 697 700 700 704 707 707 707 709 709 709

Review of Solidifiers

713

Merv Fingas and Ben Fieldhouse 22.1. Introduction to Solidifiers 22.1.1. Motivations for Using Solidifiers 22.1.2. Solidifier Issues 22.1.3. Solidifier Chemistry 22.2. Review of Major Solidifier Issues 22.2.1. Effectiveness 22.2.2. Toxicity 22.2.3. Biodegradation 22.3. Other Issues 22.3.1. Spill Size 22.3.2. Solidifier Use in Recent Times 22.3.3. Solidifiers or Sorbents 22.3.4. Potential for Sinking 22.3.5. Modeling Solidifier and Solidified Oil Behavior and Fate 22.3.6. Solidified Oil Stability 22.3.7. Fate of Unreacted Solidifier 22.3.8. Recovery of Solidified Oil 22.3.9. Solidification Time 22.3.10. Application Systems 22.3.11. Reduction of Flash Point 22.3.12. Assessment of the Use of Solidifiers 22.3.13. Disposal Methods or Recycling 22.4. Summary Acknowledgments References

713 713 714 714 717 717 728 728 728 728 729 729 729 729 729 729 729 730 730 730 730 730 730 731 731

Contents

Appendix 22.1. Testing Procedures from Environment Canada Solidifier Test Procedures Used in Early Years Oil Solidifier Effectiveness Test Used 1998 to Present Brief Description of the Test Equipment and Supplies Procedure Calculation

xvii 732 732 732 733 733 733 733

Part VII In-Situ Burning 23.

An Overview of In-Situ Burning 737 Merv Fingas 23.1. Introduction 737 23.2. An Overview of In-Situ Burning 737 23.2.1. The Science of Burning 737 23.2.2. Summary of In-Situ Burning Research and Trials 743 23.2.3. How Burns at Sea Are Conducted 750 23.2.4. Advantages and Disadvantages 755 23.2.5. Comparison of Burning to Other Response Measures 756 23.3. Assessment of Feasibility of Burning 758 23.3.1. Burn Evaluation Process 758 23.3.2. Areas Where Burning May Be Prohibited 758 23.3.3. Regulatory Approvals 763 23.3.4. Environmental and Health Concerns 765 23.3.5. Oil Properties and Conditions 793 23.3.6. Weather and Ambient Conditions 799 23.3.7. Burning in Special Locations 801 23.3.8. Burning on Land 806 23.3.9. Burning In or On Ice 809 23.4. EquipmentdSelection, Deployment, and Operation 811 23.4.1. Burning Without Containment 811 23.4.2. Oil Containment and Diversion Methods 814 23.4.3. Ignition Devices 834 23.4.4. Treating Agents 849 23.4.5. Support Vessels/Aircraft for At-Sea Burns 851 23.4.6. Monitoring, Sampling, and Analytical Equipment 852 23.4.7. Final Recovery of Residue 856 23.4.8. Equipment Checklist 858 23.5. Possible Spill Situations 858 23.6. Post-Burn Actions 870 23.6.1. Follow-Up Monitoring 870 23.6.2. Estimation of Burn Efficiency 873 23.6.3. Burn Rate 877 23.7. Health and Safety Precautions during Burning 878

xviii

Contents

23.7.1. Worker Health and Safety Precautions 23.7.2. Public Health and Safety Precautions 23.7.3. Establishing Safety Zones 23.7.4. Monitoring Burn Emissions Acknowledgments References

878 887 888 888 894 894

Part VIII Shoreline Countermeasures 24.

25.

Shoreline Countermeasures

907

Edward H. Owens 24.1. Introduction 24.1.1. Control At or Near the Source 24.1.2. Control on Water 24.1.3. Shoreline Protection Strategy 24.1.4. Shoreline Treatment 24.2. Shoreline Treatment Decision Process 24.3. Treatment Options 24.3.1. Natural Recovery 24.3.2. Physical Removal 24.3.3. In-Situ Treatment 24.4. Treatment by Shore Type 24.5. Waste Generation References

907 908 908 909 909 910 912 912 913 915 916 919 920

Automated Assessment and Data Management

923

Alain Lamarche 25.1. Introduction 25.2. Automated Processing and Data Management: Goals and Definition 25.2.1. Understanding the Use of Shoreline Assessment Data During a Response 25.2.2. The Nature of Shoreline Assessment Data 25.2.3. Practical Use of Shoreline Observations 25.3. Shoreline Observations Data Processing 25.3.1. Data Processing Organization 25.3.2. Responsibilities of the Shoreline Assessment Data Management Team 25.3.3. Data Management Tasks and Processes 25.3.4. Why and When to Establish a Shoreline Assessment Data Management Team 25.4. Assessment Automation Methods and Tools 25.4.1. Basic Tools 25.4.2. Combining Tools Within a Data Management Support System

923 924 924 924 927 929 929 931 935 939 939 940 944

xix

Contents

25.4.3. Information Distribution Shoreline Assessment Data Management Issues 25.5.1. Equipment Failure 25.5.2. Software Corruption 25.5.3. Overwhelming Amounts of Data 25.5.4. Conditions Unique to the Response References 25.5.

947 948 948 949 949 949 955

Part IX Submerged Oil 26.

Submerged Oil Jacqueline Michel 26.1. Introduction 26.2. Submerged Oil Characteristics 26.3. Review of Recent Submerged Oil Spills 26.3.1. M/V Athos I 26.3.2. T/B DBL-152 26.3.3. Lake Wabamun Spill 26.4. Submerged Oil Spill Response Methods and Recommendations for Future Work 26.4.1. Methods for Detection of Oil Suspended in the Water Column 26.4.2. Methods for Detection of Oil on the Bottom 26.4.3. Containment of Suspended Oil/Protection of Water Intakes 26.4.4. Containment of Submerged Oil on the Bottom 26.4.5. Recovery of Submerged Oil on the Bottom References

959 959 961 965 965 967 972 975 975 976 978 979 979 981

Part X Effects of Oil in the Environment 27.

Effects of Oil in the Environment Gary 27.1. 27.2. 27.3. 27.4. 27.5. 27.6. 27.7. 27.8. 27.9. 27.10. 27.11.

Shigenaka Introduction Some Definitions Size Matters: Seeps vs. Spills An “Equation” to Convey Toxic Impact Route of Exposure: The Anthrax Example Route of Exposure: Oil Oil Chemistry, Physical Behavior, and Oil Effects Freshwater/Saltwater Differences Tropical Environments Arctic Environments Ecological Effects of Oil Spills

985 985 987 989 991 999 1000 1003 1008 1010 1013 1014

xx

Contents

27.12. The Future of Oil Effects Science 27.13. Summary and Conclusions Acknowledgments Disclaimer References

1017 1019 1019 1019 1020

Part XI Contingency Planning and Command 28.

29.

Introduction to Oil Spill Contingency Planning and Response Initiation

1027

Merv Fingas 28.1. An Overview of Response to Oil Spills 28.2. Activation of Contingency Plans 28.3. Training 28.4. Structure of Response Organizations 28.5. Oil Spill Cooperatives 28.6. Private and Government Response Organizations

1027 1028 1029 1030 1030 1031

The Role of the International Tanker Owners Pollution Federation Limited

1033

Karen Purnell

30.

Safety Issues at Spills

1037

Quek Qiuhui 30.1. Introduction 30.2. Organization Structure 30.3. Health and Safety Risk Analysis/Risk Assessment 30.4. Air Monitoring 30.5. Site Safety and Health Plan 30.6. Different Types of Hazards on Site 30.7. Recommended Safety Procedures 30.7.1. Site Evaluation Process 30.7.2. Site Control Measures 30.7.3. Personal Protective Equipment 30.7.4. Excessive Noise 30.7.5. Heat Stress 30.7.6. Cold Stress 30.7.7. Monitoring Program 30.8. Emergency Procedures During a Response 30.8.1. Fire and Explosion 30.8.2. Hazardous Atmosphere/Hazardous Chemicals 30.8.3. Medical Emergencies 30.9. Other Issues

1037 1037 1038 1038 1043 1048 1049 1049 1050 1052 1052 1052 1054 1054 1054 1054 1058 1058 1059

Contents

30.9.1. Personnel Training 30.9.2. Volunteers 30.10. Conclusion Acknowledgments References

xxi 1059 1059 1062 1062 1062

Part XII Postassessment and Restoration 31.

32.

Natural Resource Damage Assessment

1067

Gary S. Mauseth and Heather Parker 31.1. Introduction 31.2. Regulatory Regimes 31.3. Objectives 31.4. Making the Public Whole 31.4.1. Injury Assessment 31.4.2. Interpretation of Restoration or Reinstatement 31.5. Alternative Sites 31.6. Use of Models 31.7. The NRDA Process in the United States 31.7.1. DOI CERCLA NRDA Regulations 31.7.2. NOAA NRDA Regulations Acronyms References

1067 1067 1069 1070 1071 1072 1075 1076 1077 1078 1079 1081 1082

Seafood Safety and Oil Spills

1083

Greg Challenger and Gary Mauseth 32.1. Introduction 32.2. Seafood Exposure to Oil 32.3. Spill Response and Seafood Safety Management 32.4. Seafood Safety Assessment: Reopening a Closed Fishery 32.5. Chemical Analytical Evaluation 32.6. Seafood Sensory Evaluation 32.7. Trends in Lifting Fishery Bans 32.8. Long-Term Implications of Oil Spills on Seafood References

1083 1085 1087 1090 1090 1092 1096 1098 1099

Part XIII Specific Case Studies 33.

The Torrey Canyon Oil Spill, 1967

1103

Robin J. Law 33.1. Case Study References

1103 1105

xxii

34.

35.

36.

Contents

The Ekofisk Bravo Blowout, 1977

1107

Robin J. Law 34.1. Case Study References

1107 1108

The Sea Empress Oil Spill, 1996

1109

Robin J. Law 35.1. Introduction 35.2. Mechanical Recovery at Sea 35.3. Dispersant Spraying at Sea 35.4. Shoreline Cleanup 35.5. Dispersant Use on Beaches 35.6. Impacts on Seabirds 35.7. Mortalities of Fish and Shellfish 35.8. Effects on Fish and Shellfish Stocks and Plankton 35.9. Contamination of Fish and Shellfish 35.9.1. Finfish 35.9.2. Crustacea 35.9.3. Whelks 35.9.4. Bivalve Mollusks 35.10. Removal of Fishery Restrictions 35.11. Conclusion References

1109 1110 1111 1112 1113 1113 1113 1114 1114 1114 1115 1115 1115 1115 1116 1116

The Braer Oil Spill, 1993

1119

Robin 36.1. 36.2. 36.3. 36.4.

37.

J. Law and Colin F. Moffat Introduction At-Sea and Shoreline Response Fate of the Braer Oil Impacts of the Braer Oil 36.4.1. On Land 36.4.2. On Seabirds 36.4.3. On Otters and Seals 36.4.4. On Commercial Fish and Shellfish 36.4.5. On Farmed Salmon 36.4.6. On Benthic Communities 36.4.7. On the Human Population 36.5. Conclusion References

1119 1119 1121 1121 1121 1121 1121 1123 1124 1125 1125 1125 1126

1991 Gulf War Oil Spill

1127

Jacqueline Michel 37.1. Review of the Spill References

1127 1131

Contents

38.

xxiii

Tanker SOLAR 1 Oil Spill, Guimaras, Philippines: Impacts and Response Challenges

1133

Ruth Yender and Katharina Stanzel 38.1. Incident Summary 38.2. Impact Summary 38.3. Shoreline Cleanup 38.4. Mangrove Cleanup and Recovery 38.5. Fisheries Impacts and Health Concerns 38.6. Summary Disclaimer References

1133 1134 1139 1143 1144 1145 1146 1146

Conversions Index

1147 1149

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Preface

Oil spill studies continue to evolve. While there are few books on the topic, there are regular conferences and symposiums which provide updates. This is the first book on the topic of oil spills for some time. As such, this book focuses on providing material that is more practical and somewhat introductory. While every attempt was made to include the essential material, there may be some gaps. The importance of many sub-topics changes with time and current spill situations. All material in this book, including introductions have been peer reviewed by at least two persons. The following peer reviewers are acknowledged (in alphabetical order): Carl Brown, Phil Campagna, Francois Charbonneau, Dagmar Schmidt Etkin, Ken Doe, Eric Gundlach, Kurt Hansen, Mike Kirby, Debra French McCay, Hugh Parker, Roger Percy, Karen Purnell, Doug Reimer, Gary Sergy, Debra Simecek-Beatty, Heidi Stout, Jordan Stout, Zhendi Wang, and Chun Yang. A special thanks goes out to the following reviewers who reviewed several papers (again in alphabetical order): Fred Beech, Leigh de Haven, Ben Fieldhouse, Anita George-Ares, Ron Goodman, Peter Lane, Robin Law, Bill Lehr, Jacqui Michel, and William Nichols. A special thanks goes out to the authors, many of whom put in their own time to complete their chapters. Their names appear throughout the text. Following this forward, I have a brief biography of each of them. I would also like to thank the many people who provided support and encouragement throughout this project, especially Meibing. I also thank Environment Canada and my former colleagues for their help and support. Environment Canada is acknowledged for permission to use materials and photos from my former employment.

xxv

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About the Contributors

Carl Brown Dr. Carl E. Brown is the Manager of the Emergencies Science and Technology Section, in the Water Science and Technology Directorate of Environment Canada. Dr. Brown has a doctorate degree in Physical Chemistry from McMaster University and a BSc in Laboratory Science from Ryerson Polytechnical University. Prior to joining Environment Canada, Dr. Brown was a research scientist on a Natural Sciences and Engineering Research Council (NSERC) Industrial Fellowship with Intera Information Technologies (now Intermap). Dr. Brown has post-doctoral experience as a research associate with the Organic Reaction Dynamics and the Laser Chemistry Groups at the Steacie Institute for Molecular Sciences, at the National Research Council of Canada and held a Canadian Government Laboratory Visiting Fellowship in Chemistry, with the Laser Chemistry Group, Division of Chemistry, National Research Council of Canada in Ottawa. His specialities include airborne oil spill sensor development, and the application of laser technologies to environmental problems. He has authored over 180 scientific papers and publications. Dr. Brown is the Chemical Science Cluster Leader for the CRTI (Chemical, Biological, Radiological, Nuclear, and Explosives Research and Technology Initiative) Program lead by Defence Research and Development Canada (DRDC) and Public Safety Canada. Dr. Brown was one of 24 scientists who recently completed the inaugural Scientists as Leaders program. Greg Challenger Greg Challenger is a Principal Marine Scientist for Polaris Applied Sciences, Incorporated in Seattle, Washington, U.S.A. Mr. Challenger is a marine ecologist by training and is involved in scientific support for oil spill and ship grounding response, natural resource injury assessment and development of habitat restoration programs. He has been a lead investigator for nearly 50 large vessel groundings, oil spills, and wreck removal operations in the Western Atlantic, Caribbean Sea, and Indo-Pacific Oceans. Dagmar Etkin Dagmar Schmidt Etkin has 35 years of experience in environmental analysis e 14 years investigating issues in population biology and ecological systems, and 21 years specializing in the analysis of oil spills. For the past 10 years, she has been president of Environmental Research Consulting (ERC), focusing on providing regulatory agencies and industry with sound scientific data and perspectives for responsible environmental decision-making. Dr. Etkin has a BA from University of Rochester, and M.A. and PhD from Harvard University. She is a member of the American Salvage

xxvii

xxviii

About the Contributors

Association, Maritime Law Association, and the UN Joint Group of Experts on the Scientific Aspects of Marine Protection. Merv Fingas Merv Fingas is a scientist focussing on oil and chemical spills. He was a spill researcher in Environment Canada for over 30 years and is currently working privately in Western Canada. Mr. Fingas has a PhD in Environmental Physics from McGill University, three masters degrees; Chemistry, Business, and Mathematics, all from University of Ottawa. His specialities include: spill dynamics and behaviour, spill treating agent studies, remote sensing and detection, and in-situ burning. He has over 750 papers and publications in the field. Dr. Fingas has been editor of the Journal of Hazardous Materials for 6 years. He has served on two committees on the U.S. National Academy of Sciences on oil spills including the recent ‘Oil in the Sea’. He is chairman of several ASTM and inter-governmental committees on spill matters. Bruce Hollebone Bruce Hollebone is a chemist with 14 years experience in the field of chemical and oil spill research and development. He has a PhD in Chemistry from the University of British Colombia. His research interests include: the fate and behaviour of oil and petroleum products in the environment, including simulation of spill behaviours in the laboratory; the development of new methods for physical and chemical analyses relevant to spills studies; environmental forensics for oil spill suspect-source identification; and environmental emergencies response. He currently works at the Oil Research Laboratory of Environment Canada. Mark Kirby Mark is an internationally recognised senior Ecotoxicologist with over 20 years experience working on studies pertaining to aquatic pollution. He has worked extensively on the toxicological impacts of oil and chemical spills and the assessment of appropriate methods of mitigation and has been involved in impact assessments in the UK from the Sea Empress to the MSC Napoli. He is a key advisor to the UK government and industry on the effects of oil and chemical spills in the marine environment and of any subsequent treatment actions (e.g. dispersants, sorbents etc.). Mark oversees the toxicological testing and approval of oil spill treatment products for use in UK waters and is the coordinator of a national initiative in the UK, PREMIAM (www.premiam.org), to implement improved post spill monitoring and impact assessment practices. He is first author of over 15 scientific papers and numerous reports in the field and continues to be actively involved in associated environmental research. Alain Lamarche Mr Lamarche is a recognized expert in spill response management systems. He has been involved in the analysis and management of environmental data since 1979. Mr. Lamarche has been responsible for the development and implementation of many computerized environmental decision support systems databases. He is also the original designer of the ShoreCleanÒ and ShoreAssess software, dedicated to the provision of Shoreline Cleanup Assessment Technique (SCAT) data management support, and

About the Contributors

xxix

Personal Digital Assistant (PDA) based geo-referenced field data acquisition tools. Mr. Lamarche has acted as a SCAT data manager and Geographical Information System (GIS) specialist during a number of oil spills, including: the Kure, New Carissa, Swanson Creek, Lake Wabamun, Westridge Line and Cosco Busan incidents. As principal of EPDS, Mr Lamarche is also responsible for all aspects of environmental software development projects including design, management, and implementation. Robin Law Robin Law is a chemist who joined Cefas (The UK Centre for Environment, Fisheries, and Aquaculture Science) in 1975. During the last 35 years he has been involved in the response and impact assessment activities following a number of major oil and chemical incidents, including the blowout on the Ekofisk Bravo platform, and from the oil tankers Amoco Cadiz, Eleni V, and Sea Empress, and the chemical tankers Ievoli Sun and Ece. Most recently, he designed and operated an environmental monitoring programme targeting oil and chemicals following the grounding of the container ship MSC Napoli on the south coast of the UK in 2007. Currently, he leads an emergency response team that advises UK government following oil and chemical spills at sea. Gary Mauseth Mr. Gary Mauseth has over 35 years of experience in the management and technical aspects of a wide variety of projects in the marine and freshwater environments. He has provided scientific support to vessel interests in over 90 spills, groundings, and natural resource damage assessment cases in the United States and its territories, as well as Canada, Mexico, the Caribbean and Mediterranean Seas, Micronesia, South America, and Europe. He has conducted research on the fate and effects of spilled oil, as well as the environmental effectiveness of response techniques, and has authored numerous publications and presentations on oil spill response, NRDA, and ecological restoration. Mr. Mauseth is a principal and President of Polaris Applied Sciences in Kirkland, Washington, USA. He has a Bachelor of Science in Biology from Whitman College in Walla Walla, Washington and a Master of Marine Biology from University of the Pacific, Pacific Marine Station, Dillon Beach, California. Jacqui Michel Dr. Jacqueline Michel is the President of Research Planning, Inc., and an internationally recognized expert in oil and hazardous materials spill planning and response. Her primary areas of expertise are in oil fates and effects, non-floating oils, shoreline cleanup, alternative response technologies, and natural resource damage assessment. Much of her expertise is derived from her role, since 1978, as part of the Scientific Support Team to the U.S. Coast Guard provided by the National Oceanic and Atmospheric Administration (NOAA). Under this role, she is on 24-hour call and provides technical support for 50-100 spill events per year. She leads shoreline assessment teams and assists in selecting cleanup methods to minimize the environmental impacts of the spill. She has evaluated and used a wide range of alternative response technologies, including surface washing agents, solidifiers, bioremediation

xxx

About the Contributors

agents, in-situ burning (mostly on wetlands and inland habitats), and methods to track and recover non-floating oils. William Nichols William (Nick) Nichols was born in Baltimore, Maryland and now lives in Ellicott City, Maryland. He has a Bachelor’s in Economics \Geography from Salisbury State University, Salisbury, Maryland and a Masters of Environmental Science from Johns Hopkins University, Baltimore. He has been an environmental scientist in the U.S. Environmental Protection Agency Office of Emergency Management (OEM) from 1997 and was U.S. National Contingency Plan Product Schedule Manager from 1998 to 2006. He is the national expert on chemical and biological oil spill countermeasures. He is also the OEM Tribal Coordinator from 2004 to the present. Ed Owens Dr. Owens is recognized internationally as an expert on oil spill shoreline cleanup and has worked on spill-related projects in the Arctic, North-South America, Africa, Russia, the Caspian, Australia, throughout South America, and in the Middle East. He has over 40 years experience providing technical and scientific support on oil response operations worldwide including: T/V Arrow (Canada), Hasbah 6 blowout (Arabian Gulf), T/V Exxon Valdez (USA), Arabian Gulf/Desert Storm (Bahrain, Qatar), Komineft pipeline (Russia), M/V Iron Baron (Australia), T/V Estrella Pampeana (Argentina), Desaguadero River (Bolivia), and M/V Cosco Busan spill (USA). Dr. Owens has conducted oil spill related missions as a United Nations Expert Consultant for the International Maritime Organization and as a consultant for the World Bank and the European Bank of Reconstruction and Development, and was a member of the U.S. National Academy of Science Oil Spill R&D Committee. Karen Purnell Dr Karen Purnell has been Managing Director of ITOPF since May 2009. She is a graduate of the Royal Society of Chemistry, with a PhD in Chemical Physics. Before joining ITOPF as a technical adviser in 1994, she worked on toxic waste management and environmental remediation in the nuclear industry and as a research chemist at several universities. Whilst at ITOPF, she has attended several major oil spills, including the sea empress (UK, 1996), prestige (Spain, 2002), and tasman spirit (Pakistan, 2003). Prominent amongst Karen’s achievements is the expansion of ITOPF’s capability to respond to spills of HNS (Hazardous & Noxious Substances). She has also worked closely with key U.S. agencies and the International Group of P&I Clubs on environmental issues. Dr Purnell has established a constructive dialogue with shipowners and is highly respected in the maritime community. Qiuhui Quek Qiuhui Quek holds a Bachelor’s degree in Environmental Engineering and has attended a number of responses in Australia, India, Indonesia, Korea, Libya, and Singapore. She has also delivered several workshops for Oil Spill Response members in various countries in the region. Qiuhui recently completed a secondment in Southampton as part of the Duty Manager rotation program. She also presented papers in international conferences such

About the Contributors

xxxi

as IOSC, Interspill, and SPE. Qiuhui has since left Oil Spill Response and is working in the HSE Management Unit of A)STAR Research Institutes. Gary Shigenaka Gary Shigenaka is the lead marine biologist with the Emergency Response Division (ERD) of the NOAA, based in Seattle. Gary received both his bachelor of science and masters degrees from the University of Washington in Seattle. As a graduate student, he served as a Knauss Sea Grant Policy Fellow in Washington D.C., and was awarded the Donald L. McKernan prize for outstanding marine affairs thesis. He has provided biological and shoreline assessment support during spills of oil and hazardous chemicals across the country and internationally over the last two decades. Gary was part of the early scientific mobilization for the Exxon Valdez oil spill in 1989, and continues to monitor the long-term effects in Prince William Sound. He also oversees other research initiatives for NOAA/ERD designed to improve oil spill impact understanding, and also to develop and improve biological tools for response and assessment. He has published numerous articles on the science and applied aspects of his spill-related research. Debra Simecek-Beatty Debra Simecek-Beatty has been a physical scientist for the NOAA’s Emergency Response Division for 25 years. She has a Masters degree in Marine Affairs from the University of Washington. During an emergency response, she is responsible for providing estimates of the movement and behavior of the spill. This includes collecting visual observations, remote sensing information, wind and current data, and computer modeling output to form an analysis. In addition, she is responsible for interfacing with local experts (i.e., meteorologist, academia, researchers) in formulating the trajectory analysis. Ruth Yender Ruth Yender is a marine ecologist with NOAA’s Office of Response and Restoration, based in Seattle, Washington. As NOAA’s Scientific Support Coordinator for the U.S. Pacific Northwest and Pacific Islands regions, Ruth provides remote and on-scene support to the U.S. Coast Guard during responses to oil and hazardous materials spills. Since joining NOAA in 1992, she has responded to more than 100 oil and chemical spills in the U.S. and internationally. Ruth also participates in spill response planning, conducts training for responders, and writes response technical guides.

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Part I

Introduction and the Oil Spill Problem

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Chapter 1

Introduction Merv Fingas

Chapter Outline 1.1. Introduction 1.2. A Word on the Frequency of Spills

3 4

1.1. INTRODUCTION Major oil spills attract the attention of both the public and the media. In past years, this attention created a global awareness of the risks of oil spills and the damage they do to the environment. In recent years, there have been fewer major spill incidents, as noted by Dagmar Etkin in Chapter 2. The public usually becomes aware of major spills, but generally does not recognize that spills are a daily fact of life. Oil is a necessity in our industrial society and a major element of our lifestyle. Most of the energy used in much of the developed world is for transportation that runs on oil and petroleum products. As current energy usage trends show, this situation is not likely to change much in the future. Industry uses oil and petroleum derivatives to manufacture such vital products as plastics, fertilizers, and chemical feedstocks, all of which will continue to be required in the future. In fact, production and consumption of oil and petroleum products are increasing worldwide, and the risk of oil pollution is increasing accordingly. The movement of petroleum from the oil fields to the consumer involves as many as 10 to 15 transfers between many different modes of transportation, including tankers, pipelines, railcars, and tank trucks. Oil is stored at transfer points and at terminals and refineries along the route. Accidents can occur during any of these transportation steps or storage times. Fortunately, in the past few years the actual number of spills has decreased. Obviously, an important part of protecting the environment is ensuring that there are as few spills as possible. Both government and industry are working to reduce the risk of oil spills by introducing strict new legislation and stringent operating codes. Industry has invoked new operating and maintenance Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10001-2 Copyright Ó 2011 Elsevier Inc. All rights reserved.

3

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Introduction and the Oil Spill Problem

procedures to reduce accidents that lead to spills. Intensive training programs have been developed to reduce the potential for human error. Despite these measures, spill experts estimate that 30 to 50% of oil spills are either directly or indirectly caused by human error, with 20 to 40% of these incidents caused by equipment failure or malfunction. There are also many deterrents to oil spills, including government fines, loss of reputation, and high cleanup costs. In Canada, it costs an average of $20 to clean up each liter (about 1/4 gallon) of oil spilled. In the United States, these costs average about $100 per liter spilled, whereas the average cost of cleanup worldwide ranges from $20 to $200 per liter, depending on the type of oil and where it is spilled. Cleaning up oil on shorelines is usually the most expensive cleanup process.

1.2. A WORD ON THE FREQUENCY OF SPILLS Smaller oil spills are a frequent occurrence in the world, particularly because of the heavy use of oil and petroleum products in our daily lives. Canada uses about 260,000 tons of these products every day; the United States uses about 10 times this amount, and, worldwide, about 10 million tons are used per day. Most domestic oil production in Canada comes from approximately 350,000 oil wells in Alberta and Saskatchewan. There are 22 oil refineries in Canada, 5 of which are classified as large. Canada imports about 100,000 tons of crude oil or other products per day but exports about 600,000 tons per day, mostly to the United States. In the United States, more than half of the approximately 3 million tons of oil and petroleum products used daily is imported, primarily from Canada, Africa, Saudi Arabia, and other Arabic countries. About 40% of the daily demand in the United States is for automotive gasoline, and about 15% is for diesel fuel used in transportation. About 40% of the energy used in the United States comes from petroleum, 35% from natural gas, and 24% from coal. Spill statistics are collected by a number of agencies around the world. In Canada, provincial offices collect data, and Environment Canada maintains a database of spills. In the United States, the Coast Guard handles a database of spills into navigable waters, while state agencies keep statistics on spills on land which are sometimes gathered into national statistics. The Minerals Management Service (MMS) in the United States maintains records of spills from offshore exploration and production activities. It can sometimes be misleading to compare oil spill statistics, however, because different countries use different methods to collect the data. In general, statistics on oil spills are not easily obtainable, and any data set should be viewed with caution. Determining or estimating the spill volume or amount is the most difficult aspect of data collection. For example, in the case of a vessel accident, the exact volume in a given compartment may be known before the accident, but the remaining oil may have been transferred to other ships

Chapter | 1

Introduction

5

immediately after the accident. Some spill accident data banks do not include the amounts burned, if and when that occurs, whereas others include all the oil lost by whatever means. Sometimes the exact character or physical properties of the oil lost are not known, thereby leading to different estimates of the amount lost. Spill data are often collected for purposes other than future improvement of the spill response. Reporting procedures vary in different jurisdictions and organizations, such as government or private companies. Minimum spill amounts that must be reported according to federal regulations in Canada and the United States vary from 400 to 8,000 liters (100 to 2000 gals), depending on the product spilled. Spill statistics compiled in the past are less reliable than those based on more recent data because few agencies or individuals collected spill statistics before about 1975. Today, although techniques for collecting statistics are continually being improved, the resources allocated for this purpose have been reduced. The number of spills reported also depends on the minimum size or volume of the spill. In both Canada and the United States, most oil spills reported total more than 4000 L (about 1000 gals). In Canada, about 12 such oil spills take place every day, of which only about one of these spills is into navigable waters. These 12 spills amount to about 40 tons of oil or petroleum product. In the United States, there are about 25 spills per day into navigable waters and an estimated 75 spills on land. Despite the apparently large number of spills, only a small percentage of oil used in the world is actually spilled. There are proportionately more spills into navigable waters in the United States than in Canada because more oil is imported by sea and more fuel is transported by barge. In fact, the largest volume of oil spilled in U.S. waters comes from barges, while the largest number of spills is from vessels other than tankers, bulk carriers, or freighters. In Canada, most spills take place on land, and this accounts for a high volume of oil spilled. Pipeline spills account for the highest volume of oil spilled. In terms of the actual number of spills, most oil spills happen at petroleum production facilities, wells, production collection facilities, and battery sites. On water, the greatest volume of oil spilled comes from marine or refinery terminals, although the largest number of spills is from the same source as in the United Statesdvessels other than tankers, bulk carriers, or freighters. The public has the wide misconception that oil spills from tankers are the primary source of oil pollution in the marine environment. Although some of the large spills are indeed from tankers, these spills still make up less than about 5% of all oil pollution on the seas. The sheer volume of oil spilled from tankers and the high profile given these incidents in the media have contributed to this misconception. In fact, as stated earlier, half of the oil spilled in the seas is the runoff of oil and fuel from land-based sources rather than from accidental spills. In conclusion, it is important to study spill incidents from the past to learn how the oil has affected the environment, what cleanup techniques work, and what improvements can be made, as well as to identify the gaps in technology.

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Chapter 2

Spill Occurrences: A World Overview Dagmar Schmidt-Etkin

Chapter Outline 2.1. Introduction 2.2. Executive Summary

7 8

2.3. Overview of Spill Occurrences

8

2.1. INTRODUCTION Asked to picture an oil spill, most people envision a large tank ship (tanker) grounded on a large rock or reef after having gone off-course in a storm or due to navigational errors. Depending on one’s frame of reference and nationality, this might be the Exxon Valdez incident, the Hebei Spirit spill, or perhaps the Prestige spill. Oil-coated beaches, dead birds, angry fishermen, and massive cleanup efforts complete the picture. Although these types of “catastrophic” spill incidents do indeed occur occasionally and receive considerable media coverage, they are, fortunately, relatively rare events. Much more commonly, oil spills are much smaller in scope. On any given day, hundreds, if not thousands, of spills are likely to occur worldwide in many different types of environments, on land, at sea, and in inland freshwater systems. The spills are coming from the various parts of the oil industrydfrom oil exploration and production activities, from transport of that oil by tank ships, pipelines, and railroad tankcars to the refineries, and from the refineries where the oil is refined to create the many types of fuels that are then transported by pipeline, rail, truck, or tank vessel to the consumers of that oil. Consumption-related spillage comes from manufacturing facilities, nontank vessels that carry oil only as fuel and for machinery, tanker trucks bringing oils to service stations and heating oil tanks, and many miscellaneous sources. The spills occur because of structural failures, operational errors, weather-related Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10002-4 Copyright Ó D.S. Etkin 2011.

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Introduction and the Oil Spill Problem

events, earthquakes, human errors and negligence, and even vandalism or terrorism. The spills involve many different types of oil ranging from various types of crude oil to a large array of refined products, from heavy persistent fuels to lighter, less persistent, but very toxic lighter fuels. Because each spill occurs in a different location under different circumstances of oil type and volume, proximity to sensitive resources, season, weather effects, and currents, each spill is a relatively unique event in terms of impacts, damages, and response challenges.

2.2. EXECUTIVE SUMMARY Worldwide oil spillage rates have decreased dramatically since the 1960s and 1970s, from about 635,000 tons annually to about 300,000 tons per year from all sources, not counting the anomalous intentional spillage associated with the 1991 Gulf War, which amounted to over 82 million tons on land and at sea. The largest sources of oil spills in the last two decades have been related to oil transportation by tank ships (tankers) or through pipelines. Oil inputs from spills and other chronic discharge sources, such as urban runoff, refinery effluents, and vessel operational discharges, currently total about 1.2 million tons worldwide annually. While most spills are relatively small and cause localized impacts, occasionally very large spills occur that cause significant environmental and socioeconomic damages. Despite significant progress in reducing spillage through a variety of technological and regulatory prevention measures along with better industry practices, the risk for significant oil spills remains. A more detailed analysis of oil spillage in the United States, for which there are more accurate data than many other parts of the world, reveals that during the decade of 1998e2007, inland pipelines spilled an average of nearly 11,000 tons annually, with the next largest source being refineries, which spilled 1,700 tons. Inland tanker truck spills amounted to 1,300 tons annually. Tank ships only spilled an average of 500 tons annually during this decade. Nevertheless, the risk for large spills from tank ships, facilities, and offshore oil exploration and production, all of which contain large volumes of oil, remains a concern for contingency planners and spill responders.

2.3. OVERVIEW OF SPILL OCCURRENCES 2.3.1. Natural Oil Seepage Oil slicks on water and oiled shorelines are not new phenomena. A considerable amount of crude oil is discharged each year from “natural seeps”dnatural springs from which liquid and gaseous hydrocarbons (hydrogen-carbon compounds) leak out of the ground. Oil seeps are fed by natural underground

Chapter | 2

Spill Occurrences: A World Overview

9

accumulations of oil and natural gas. Oil from submarine (and inland subterranean) oil reservoirs comes to the surface each year, as it has for millions of years due to geological processes. Natural discharges of petroleum from submarine seeps have been recorded throughout history going back to the writings of Herodotus1 and Marco Polo.2 Archaeological studies have shown that products of oil seeps were used by Native American groups living in California, including the Yokuts, Chumash, Achomawi, and Maidu tribes, well before the arrival of European settlers.3 In recent times, the locations of natural seeps have been used for exploration purposes to determine feasible locations for oil extraction. Regional assessments of natural seepage have been conducted in some locations, particularly nearshore in California,4-7 the Indian Ocean,8-10 and the Gulf of Mexico.11 The most comprehensive worldwide assessment of natural seepage is still the study conducted by Wilson et al.12 Even the two more recent international assessments of oil inputs into the sea13 relied heavily on the estimates of natural oil seepage conducted by Wilson et al.,12 having found no more recent comprehensive studies. While industry studies have been conducted for the purpose of determining potential locations for oil exploration and production using various forms of increasingly sophisticated technology, no results have been openly published in the scientific or technical literature. Natural seeps are of such great magnitude that, according to the prominent geologists Kvenvolden and Cooper,14 “natural oil seeps may be the single most important source of oil that enters the ocean, exceeding each of the various sources of crude oil that enters the ocean through its exploitation by humankind.” Assessments of natural oil seepage involve few actual measurements, though certain seep locations along the Southern California coast of the Pacific Ocean have been studied to some extent. Natural seep studies have also included identification of hydrothermically sourced hydrocarbons (especially polycyclic aromatic hydrocarbons) in sediments. The most well-known studies have relied on estimation methodologies based on field data, observations, and various basic assumptions. Wilson et al. estimated that total worldwide natural seepage ranged from 0.2 to 6.0 106 tonsy annually, with the best estimate being 0.6 106 tons, based largely on observations of seepage rates off California and western Canada.12 Estimates of the areas of ocean with natural seeps are shown in Table 2.1, and estimates of seepage rates by ocean are shown in Table 2.2. y

Oil measurements are in metric tons (tons). Within the industry, oil is often measured in barrels (equivalent of 42 U.S. gallons or 159 liters), roughly equal to one-seventh of a ton, depending on specific gravity. Conversion between tons (weight) and barrels (volume) is per the formula: tons ¼ 0.173 barrels specific gravity.

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Introduction and the Oil Spill Problem

TABLE 2.1 Seepage-prone Areas of the World’s Oceans (based on Wilson et al.12) Number of 1,000 Square Kilometers

Ocean

High-potential Seepage

Moderate-potential Seepage

Low-potential Seepage

Pacific

1,943

9,285

4,244

Atlantic

1,303

10,363

11,248

Indian

496

7,928

3,010

Arctic

0

5,636

2,456

Southern

0

486

458

3,741

33,697

21,416

Total

Wilson et al. based their estimates on five basic assumptions: More seeps exist in offshore basins than have been observed; factors that determine seepage rates in a particular area are related to general geological structural type and stage of sedimentary basin evolution; seepage is dependent on the area of exposed rock rather than on rock volume; most marine seeps are clustered at continental margins; and seepage rates are lognormally distributed.12

TABLE 2.2 Summary of World Seepage Rates (based on Wilson et al.12) Estimated Oil Seepage (106 tons per year) Ocean

Case I, P16z

Case II, P1.0x

Case III, P0.3**

Pacific

2.83 106

2.69 105

0.689 105

Atlantic

2.06 106

1.96 105

5.04 104

Indian

9.30 105

8.85 104

2.28 104

Arctic

2.14 105

2.30 103

5.20 103

Southern

1.88 104

1.74 103

4.51 102

Total

6.05 3 106

0.558 3 105

0.148 3 106

z

Probability percentile 16 with a worldwide estimate of 6 106 tons annually, likely a high estimate. Probability percentile 1.0 with a worldwide estimate of 0.6 106 tons annually. **Probability percentile 0.3 with a worldwide estimate of 0.2 106 tons annually, likely a minimal estimate. x

Chapter | 2

Spill Occurrences: A World Overview

11

Kvenvolden and Harbaugh15 concluded that the minimal worldwide estimate (0.2 106 tons annually) from the Wilson et al.12 study is most likely correct and that an error margin of an order of magnitude above and below this value should be applied (i.e., 0.02 106 to 2.0 106 tons annually). Their theory was based on a reduced value for the assumed and known oil resources that would be available for seepage. There is some evidence that seepage rates are decreasing in some locations, such as those near Coal Point, off Santa Barbara, California.16 In a 2003 National Research Council (NRC) study, a worldwide estimate of natural seepage into the marine environment of between 0.02 106 to 2.0 106 tons annually was made, with a “best estimate” of 600,000 tons.17 These estimates were made based on the Kvenvolden and Harbaugh15 reassessment of the estimates made by Wilson et al.,12 as well as an acceptance of the original estimates of Wilson et al.,12 resulting from a “new appreciation” for the magnitude of natural seepage, particularly in the Gulf of Mexico. Relying largely on the Wilson et al.12 and Kvenvolden and Harbaugh15 studies, the 2007 Joint Group of Experts on Scientific Aspects of Marine Protection (known as GESAMP) study on oil inputs into the marine environment included an estimate of the range of natural seepage as 0.22.0 106 tons per year, with a best estimate of 600,000 tons per year.13 Natural seeps often release oil sporadically in relatively small amounts, but occasionally release larger amounts that can have the same environmental impacts as crude oil spills from tankers or other sources. But while natural seeps have had impacts on the marine and terrestrial environment since prehistoric times, it was not until the occurrence of several larger anthropogenic oil spills in the late 1960s, which coincided with a greater public awareness of general environmental issues, that concern over oil pollution came to the forefront.

2.3.2. Historical Concern Over Oil Pollution When the tanker Torrey Canyon spilled 130,000 tons of crude oil off the western coast of the UK in March 1967, killing 15,000 seabirds and oiling nearly 300 kilometers of English and French coastline, there was a large public outcry. The environmental damage from this spill was multiplied by the use of highly toxic first-generation dispersant chemicals in the response. The Torrey Canyon spill was not the first oil tanker spill by any means. A large number of oil tankers were torpedoed and sunk during World War II. According to Campbell et al., during the first six months of 1942 alone, a total of 484,200 tons of oil were released from torpedoed tankers within 90 kilometers of the eastern U.S. coast.18 This came to about one tanker spill of about 20,000 tons per week over six months. Cleanup efforts consisted of burning incidental to the torpedoing and minimal cosmetic actions on swimming beaches. While the occurrence of these incidents during wartime may explain the

12

PART | I

Introduction and the Oil Spill Problem

relatively low concern about environmental damage from the spilled oil, there was, arguably, a general lesser awareness of environmental protection in these times as well. The Torrey Canyon spill in 1967 was notable in that when it occurred, it is the largest spill to date. The tanker’s capacity had recently been increased to hold 130,000 tons of oil cargo. Subsequently, there were at least five significantly larger worst-case discharge (complete cargo loss) tanker spills, as well as several other large spills associated with oil wells and pipelines. Following on the 1967 Torrey Canyon incident, the 1969 Union Alpha Well 21 blowout off Santa Barbara, California, which released 14,300 tons of crude oil, is often credited with being the impetus for the environmental movement in the United States, as well as for the establishment of the federal Environmental Protection Agency (EPA).19 In the 1970s, other significant oil spills around the world brought greater attention to the problem on an international scaledthe tanker Metula (Chile in 1974), the tanker Urquiola (Spain in 1977), the tanker Amoco Cadiz (France in 1978), the largest tanker spill of all time, Atlantic Empress (Trinidad and Tobago/Barbados in 1979), and the largest nonewar-related spill in historydthe Ixtoc I well blowout (Gulf of Mexico in 1979).20 The largest oil spills in history are listed in Table 2.3. The 1989 tanker Exxon Valdez spill in Alaska is perhaps the most notorious spill incident, though it is by no means the largest. The spillage of over 37,000 tons of Alaskan crude oil into what was considered to be a “pristine” location, Prince William Sound, precipitated the most expensive and the lengthiest spill response and damage settlements in history. Its repercussions were felt worldwide, resulting in the passage of significant spill prevention and liability legislation in the United Statesdthe Oil Pollution Act of 1990 (OPA 90)das well as international conventions on spill prevention that included such measures as the requirement for double-hulls on tankers by 2015 and increased financial liability. The significant financial consequences for tanker owners and operators as a result of the Exxon Valdez spill and the spiller liability inherent in subsequent regulations brought the consequences for spills to an unprecedented level. The financial risk associated with large spills may have had as much impact on spill prevention as any actual preventive measures, such as double-hulls on tankers.

2.3.3. Sources of Oil Spills and Patterns of Spillage Spills occur around the worlddanywhere that oil is produced, transported, stored, or consumed. The vast majority of spills are relatively small. As shown in Figure 2.1, 72% of spills are 0.003 to 0.03 ton or less. The total of amount of these small spills comes to 0.4% of the total spillage. The largest spills (over 30 tons) make up 0.1% of incidents but involve nearly 60% of the total amount spilled. Naturally, the relatively rare large spill incidents get the most public attention owing to their greater impact and visibility, though spill size itself is

Chapter | 2

13

Spill Occurrences: A World Overview

TABLE 2.3 Largest Oil Spills in History Worldwide Environmental Research Consulting (ERC data)** Date

Source Name*

Location

Tons

10-Mar-1991

700 oil wells

y

Kuwait

71,428,571

20-Jan-1991

Min al Ahmadi Terminalyz

Kuwait

857,143

3-Aug-2000

oil wells

Russia

700,000

3-Jun-1979

Ixtoc I well

Mexico

476,190

Iraq

377,537

Uzbekistan

299,320

Trinidad/Tobago

286,354

Russia

285,714

y

1-Feb-1991

Bahra oil fields

2-Mar-1990

oil well x

19-Jul-1979

T/V Atlantic Empress

25-Oct-1994

Kharyaga-Usinsk Pipeline y

4-Feb-1983

No. 3 Well (Nowruz)

Iran

272,109

6-Aug-1983

T/V Castillo de Bellver

South Africa

267,007

16-Mar-1978

T/V Amoco Cadiz

France

233,565

10-Nov-1988

T/V Odyssey

Canada

146,599

11-Apr-1991

T/V Haven

Italy

144,000

1-Aug-1980

D-103 concession well

Libya

142,857

6-Jan-2001

pipeline

Nigeria

142,857

Kuwait

139,690

19-Jan-1991

yz

T/V Al Qadasiyah y

19-Jan-1991

T/V Hileen

Kuwait

139,690

18-Mar-1967

T/V Torrey Canyon

United Kingdom

129,857

19-Dec-1972

T/V Sea Star

Oman

128,891

23-Feb-1980

T/V Irenes Serenade

Greece

124,490

yz

19-Jan-1991

T/V Al-Mulanabbi

Kuwait

117,239

7-Dec-1971

T/V Texaco Denmark

Belgium

107,143

19-Jan-1991

T/V Tariq Ibn Ziyadyz

Kuwait

106,325

20-Aug-1981

storage tanks

Kuwait

106,003

yz

26-Jan-1991

Min al Bakar Terminal

Kuwait

100,000

15-Nov-1979

T/V Independentza

Turkey

98,255

11-Feb-1969

T/V Julius Schindler

Portugal

96,429

(Continued )

14

PART | I

Introduction and the Oil Spill Problem

TABLE 2.3 Largest Oil Spills in History Worldwide Environmental Research Consulting (ERC data)**dcont’d Date

Source Name*

Location

12-May-1976

T/V Urquiola

Spain

95,714

25-May-1978

No. 126 Well/pipeline

Iran

95,238

28-Mar-1995

pipeline

Nigeria

90,000

5-Jan-1993

T/V Braer

United Kingdom

85,034

Kuwait

83,897

yz

Tons

1-Mar-1991

pipeline

29-Jan-1975

T/V Jakob Maersk

Portugal

82,503

6-Jul-1979

storage tank (Tank #6)

Nigeria

81,429

19-Nov-2002

T/V Prestige

Spain

77,000

3-Dec-1992

T/V Aegean Sea

Spain

74,490

6-Dec-1985

T/V Nova

Iran

72,626

15-Feb-1996

T/V Sea Empress

United Kingdom

72,361

19-Dec-1989

T/V Khark 5

Morocco

70,068

27-Feb-1971

T/V Wafra

South Africa

68,571

11-Dec-1978

fuel storage depot

Zimbabwe

68,027

26-Apr-1992

T/V Katina P.

South Africa

66,700

12-Jun-1978

Sendai Oil Refinery

Japan

60,204

6-Dec-1960

T/V Sinclair Petrolore

Brazil

60,000

7-Jan-1983

T/V Assimi

Oman

53,741

9-Nov-1974

T/V Yuyo Maru No. 10

Japan

53,571

28-May-1991

T/V ABT Summer

Angola

51,020

22-May-1965

T/V Heimvard

Japan

50,000

31-Dec-1978

T/V Andros Patria

Spain

49,660

30-Jan-1991

T/V Ain Zalah yz

Kuwait

49,543

13-Jun-1968

T/V World Glory

South Africa

48,214

13-Jan-1975

T/V British Ambassador

Japan

48,214

9-Dec-1983

T/V Pericles GC

Qatar

47,619

9-Aug-1974

T/V Metula

Chile

47,143

Chapter | 2

15

Spill Occurrences: A World Overview

TABLE 2.3 Largest Oil Spills in History Worldwide Environmental Research Consulting (ERC data)**dcont’d Date

Source Name*

Location

Tons

1-Jun-1970

T/V Ennerdale

Seychelles

46,939

7-Dec-1978

T/V Tadotsu

Indonesia

44,878

29-Feb-1968

T/V Mandoil

United States

42,857

10-Jun-1973

T/V Napier

Chile

38,571

13-Mar-1994

T/V Nassia

Turkey

38,500

26-Aug-1979

T/V Patianna

United Arab Emirates

38,000

11-Jun-1972

T/V Trader

Greece

37,500

24-Mar-1989

T/V Exxon Valdez

United States

37,415

29-Dec-1980

T/V Juan Antonio Lavalleja

Algeria

37,279

21-Oct-1994

T/V Thanassis A.

Hong Kong

37,075

22-Apr-1988

T/V Athenian Venture

Canada

36,061

7-Feb-1977

T/V Borag

Taiwan

35,357

Mar-1986

Pemex Abkatun 91

Mexico

35,286

6-Feb-1976

T/V St. Peter

Colombia

35,100

*“T/V” ¼ “tank vessel” and refers to tank ships or tankers. **Ended in January 2010. y War-related intentional spillage. z Several intentional spills occurred nearly simultaneously during the 1991 Gulf War. They are often aggregated into one large “spill.” In this list, the individual spill sources are separated. x T/V Atlantic Empress spilled 145,250 tons of oil off Trinidad and Tobago on 19 July 1979, then another 141,000 tons while under tow off Barbados.

not a direct measure of damage. Location and oil type are extremely important in determining the degree of environmental and socioeconomic damage. Oil spills and discharges* can occur at any point in the “life cycle” of petroleumdduring oil exploration and production; transport by vessel, pipeline, railroad, or tanker truck; refining; storage, consumption or usage as fuel or as raw material for manufacturing; or waste disposal. The regional and national patterns of spillage depend on the oil-related activities in those *

A “spill” is a discrete event in which oil is accidentally or, occasionally, intentionally released. A “discharge” is a legal permitted release of oil (usually in a highly diluted state in water) as part of normal operations.

16

PART | I

Introduction and the Oil Spill Problem

% Total Spills 80%

71.9%

70%

# spills

60%

amount

50% 39.5%

40% 30%

22.8%

22.2%

20.3%

20% 6.2%

10% 0%

11.7%

0.4%

0.003

1.6%

0.03

4.3%

0.3

1.6%

3

0.3%

3,000

0.1%

30

0.0%

300

Spill Size (tonnes) FIGURE 2.1 Size classes of U.S. marine oil spills, 1990e1999 (ERC data).

locations, the amount of oil handled, and the degree to which oil prevention measures have been implemented and enforced. Overall, oil spillage has decreased significantly in the United States and internationally due to the implementation and enforcement of prevention measures as well as more responsible operations on the part of the shipping and oil industries.13,17,21,22 In the 1970s, an estimated 6.3 million tons of oil spilled into marine waters from all sources, excluding war-related incidents.22 By the 1980s, an estimated 3.8 million tons of oil spilled worldwide, a 40% reduction since the decade 1988e1997. Spillage reduced another 20% by the 1990s. These reductions in spillage are all the more remarkable considering the increases in production, shipping, and handling of oil during this time period (Table 2.4). In a series of studies that estimated total oil inputs into the marine environment from spills, as well as from operational discharges* from shipping and other sources, especially urban runoff,y a definitive trend of input reduction is apparent (Table 2.5). It is important to note that some of the variations between the studies are due to differences in methodology rather than to actual differences in inputs. *

A legal permitted release of oil (usually in a highly diluted state in water) as part of normal operations. y “Urban runoff” is the accumulation of drops of oil that leak from automobiles, trucks, and other vehicles, as well as small chronic spillages that occur from other land-based sources. The oil washes off into storm sewers, culverts, and other waterways into streams and rivers that enter marine waters. Because the exact source of this spillage cannot be pinpointed, it is termed nonpoint source pollution.

Chapter | 2

17

Spill Occurrences: A World Overview

TABLE 2.4 Annual Worldwide Marine Oil Spillage (ERC Data) Estimated Average Annual Tons Spilledy Source Type

1970s

1980s

1990s

428,646

190,180

126,743

2,735

23,811

10,248

Pipelines

59,087

36,744

85,664

Facilities

66,067

58,047

35,655

Offshore Exploration/ Production

69,111

68,099

38,351

9,241

1,775

3,905

634,887

378,656

300,546

Tank Vessels Nontank Vessels

Unknown/Other Total y

Excluding war-related spills.

The tracking of oil spills is generally conducted by those authorities involved in initiating emergency spill response operations, such as Coast Guard agencies or state and local governments. The accuracy of reporting, particularly of smaller spills, varies considerably from one jurisdiction to another. There have been increases in the reporting of increasingly smaller spills, though not necessarily in the actual incidence of such spills, which reflects broader public awareness of spills and greater concern about and responsibility for these incidents by spillers. As larger spills become increasingly rarer, it is important that contingency planners and spill responders maintain preparedness for these large spills owing to the potential damages associated with them.22,23 A detailed recent overview of oil spills in the United States is presented here based on Environmental Research Consulting (ERC) data, along with analytical results from some past international studies on oil spills.24-28

2.3.4. Spillage from Oil Exploration and Production Activities During the years 1998e2007, an estimated 182 tons of crude oil spilled annually from offshore exploration and production platforms into U.S. waters. An additional 373 tons spilled annually from pipelines associated with offshore oil production, for a total of 555 tons per year. This represents a nearly 66% reduction in spillage since 1988e1997, and an 87% reduction in spillage since the 1970s (1969e1977). Oil spillage from offshore platforms in U.S. Outer Continental Shelf (OCS) and state waters is shown in Figure 2.2 for 1969e2007.

TABLE 2.5 Estimated Worldwide Oil Inputs Based on Various Studies 18

Oil Input Estimates (Tons) Source Natural Seeps Municipal/Industrial Urban Runoff Coastal Refinery Other Coastal

Tanker Accidents Other Shipping

Atmospheric

zzz

Offshore Expl/Prod TOTAL z

1981**

1981yy

1990zz

1997xx

2000***

600,000

600,000

300,000

200,000

258,500

600,000

600,000

2,700,000

2,250,000

1,480,000

1,230,000

1,175,000

114,900

156,900

2,500,000

2,100,000

1,430,000

1,080,000

e

n/a

140,000

200,000

e

e

100,000

e

112,500

4,900

e

150,000

50,000

50,000

e

2,400

12,000

2,130,000

1,100,000

1,440,000

1,420,000

564,000

389,000

413,100

300,000

300,000

390,000

400,000

e

157,900

100,000

yyy

7,100

750,000

200,000

340,000

320,000

e

586,500

1,080,000

600,000

710,000

700,000

e

225,800

306,000

600,000

600,000

300,000

300,000

305,000

68,000

24,700

80,000

60,000

50,000

50,000

47,000

19,750

38,000

10,940,000

7,960,000

6,490,000

5,850,000

2,349,500

2,246,750xxx

1,802,700

[24] [25] **[26] yy [27] zz [28] xx [13] ***[17] yyy Includes 53,000 tons from small-craft activity. zzz Atmospheric deposition of petroleum hydrocarbons from volatile organic compounds (VOCs) that evaporate during the handling of oil and incomplete fuel combustion that are then deposited into the sea. xxx Does not include urban runoff. x

Introduction and the Oil Spill Problem

Operational

1979x

PART | I

Transportation

1973z

Chapter | 2

19

Spill Occurrences: A World Overview

Tonnes 18,000 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2,000 0 1969

1974

1979

1984

1989

1994

1999

2004

FIGURE 2.2 Annual U.S. offshore oil platform spillage, 1969e2007 (ERC data).

Average platform spillage by decade is shown in Table 2.6. There has been a 30% reduction in annual spillage since 1988e1997 and a 95% reduction since the 1970s. Annual oil spillage from pipelines connected to offshore platforms is shown in Figure 2.3, and by decade in Table 2.7. There has been a 68% reduction in offshore pipeline spillage since 1988e1997. Of the total spillage, 96% is in the Gulf of Mexico. Offshore oil exploration and production spillage was combined to include offshore platforms and pipelines, as well as offshore supply vessels servicing the platforms, as shown in Table 2.8. There has been a 61% reduction in total spillage since 1988e1997 and an 87% reduction since the 1970s.

TABLE 2.6 Average Annual Spillage from U.S. Offshore Oil Platforms (ERC data) Years

Average Annual Spills One Ton or More

Average Annual Tons Spilled

1969e1977

45

3,694

1978e1987

29

192

1988e1997

14

259

1998e2007

20

182

1969e2007

27

1,015

20

PART | I

Introduction and the Oil Spill Problem

Tonnes 5,000 4,500 4,000 3,500 3,000 2,500 2,000 1,500 1,000 500 0 1969

1974

1979

1984

1989

1994

1999

2004

FIGURE 2.3 Annual oil spillage from U.S. offshore pipelines, 1969e2007 (ERC data).

TABLE 2.7 Average Annual Spillage from U.S. Offshore Oil Pipelines (ERC data) Years

Average Annual Spills One Ton or More

Average Annual Tons Spilled

1969e1977

15

640

1978e1987

10

495

1988e1997

14

1,161

1998e2007

13

373

1969e2007

13

668

Oil spillage per production (i.e., barrels spilled per barrels produced) has decreased over time, as shown in Table 2.9. In other words, despite increases in production, spillage rates have decreased. For every ton of oil produced in the United States, less than 0.000005 tons have spilled from offshore exploration and production activities in the last decade. This is a 71% reduction since the 1988e1997 decade and an 87% reduction since the 1969e1977 decade. While the majority of oil production spills have been recorded in offshore waters, there are reported spills of inland-based oil production wells to inland areas, as shown in Table 2.10. During the oil extraction process at offshore oil platforms, water in the oil reservoir is also pumped to the surface. Industry practice is to treat this

Chapter | 2

21

Spill Occurrences: A World Overview

TABLE 2.8 Average Annual Spillage (tons) from U.S. Offshore Oil Activities (ERC data) Years

Platforms

Pipelines

Offshore Vessels

Total

1969e1977

3,694

640

14

4,348

1978e1987

192

495

39

726

1988e1997

259

1,161

7

1,427

1998e2007

182

373

1

556

1969e2007

1,015

668

15

1,698

TABLE 2.9 U.S. Offshore Oil Exploration/Production Spillage per Production (ERC data) Years

Average Annual Tons Spilled per Tons Produced

1969e1977

0.0000089

1978e1987

0.0000015

1988e1997

0.0000040

1998e2007

0.0000012

1969e2007

0.0000038

TABLE 2.10 Average Annual U.S. Inland Oil Exploration/Production Spillage (ERC data) Years

Average Annual Tons Spilled

1980e1987

521

1988e1997

742

1998e2004

863

1980e2004

705

“produced water” to separate free crude oil, and then to inject the water back into the reservoir, or to discharge the water overboard from the platform. Increasingly, the reinjection process is becoming the preferred technique. The highly diluted oil content in produced water (with a maximum allowable oil

22

PART | I

Introduction and the Oil Spill Problem

TABLE 2.11 Estimated Oil Inputs in Produced Water from U.S. Offshore Oil Exploration/Production

U.S. Region

Produced Water (tons/yr)

Oil/Grease Content (ppm)

Oil/Grease Discharge (tons/yr)

Low

High

“Best”*

Low

High

“Best”

Gulf of Mexico OCS

67,571,429

15

29

20

1,300

2,500

1,700

Louisiana State

26,571,429

15

29

20

450

860

600

e

e

6.6

0

0

5

Texas State

614,286

California Offshore

5,157,143

15

29

18

85

170

85

Alaska State

6,528,571

15

29

15

110

210

110

e

e

20

2,000

3,740

2,500

Total US

106,442,858

*Best estimate as determined by panel of experts in the 2003 NRC study.17

content of 29 ppm) from offshore oil exploration and production processes is generally dispersed very quickly in the open waters where offshore oil platforms are located. The impacts from these inputs in offshore waters have been studied extensively, and, as concluded by the 2003 NRC study, “there is little evidence of significant effects from petroleum around offshore platforms in deep water.”17 The oil inputs from produced water are calculated as shown in Table 2.11don average, 2,500 tons per year, based on the methodology used by the 2003 NRC study based on measurements and assumptions of maximum allowable oil content in produced water (“high”) or lower oil content as reported by offshore operators.17 It is important to note that these inputs are permitted operational discharges that are distinct from accidental spillage previously reviewed. Worldwide estimates on oil spillage and discharges from offshore oil exploration and production activities are shown in Table 2.12. The greatest concern associated with oil pollution from offshore oil and gas exploration is the unlikely event of a catastrophic well “blowout”*. The largest well blowout incidents worldwide are shown in Table 2.13. Fortunately, most blowouts release relatively little oil.29 *

Loss of well control or a blowout is defined as: the uncontrolled flow of formation or other fluids, including flow to an exposed formation (an underground blowout) or at the surface (a surface blowout), flow through a diverter, or uncontrolled flow resulting from a failure of surface equipment or procedures.

Chapter | 2

23

Spill Occurrences: A World Overview

TABLE 2.12 Worldwide Spillage and Discharge from Offshore Oil Exploration and Production Annual Oil Input Estimate (tons)

Study

Estimate Year

Spillage

Operational

Atmospheric

Total

NRC, 1975 [24]

1973

e

e

e

80,000

Kornberg, 1981 [25]

1979

e

e

e

60,000

Baker, 1983 [26]

1981

e

e

e

50,000

NRC, 1985 [27]

1981

e

e

e

50,000

GESAMP, 1993 [28]

1990

e

e

e

47,000

GESAMP, 2007 [13]

1997

3,400

16,350

e

19,750

NRC, 2003 [17]

2000

860

19,000

1,300

21,160

2.3.5. Spills During Oil Transport After extraction from offshore or terrestrial wells, oil is transported by a variety of means to refineries and ultimately to industrial or individual consumersdby tank vessel (tank ships or tankers; tank barges), pipeline, railroad, and tanker truck, each potentially a source of spillage.

2.3.5.1. Spillage from Tank Vessels Tank ships can carry the greatest amount of oildas much as 300,000 tonsdand thus can be the sources of the largest transport-related spills. Tank ships (tankers) carrying crude oil or refined petroleum as cargo spilled an average of 514 tons of oil annually in U.S. waters over the last decade, a 90% reduction since the decade 1988e1997. A breakdown of annual spillage from oil tankers is shown in Figure 2.4. Average annual spillage by decade is shown in Table 2.14. Tank barges carrying oil as cargo spilled an average of 771 tons of oil annually over the last decade, a nearly 67% reduction from the spillage in the decade 1988e1997. Annual spillage volumes are shown in Figure 2.5. A breakdown of average annual spillage from oil tank barges is shown in Table 2.15. Oil transport by tank vessels (tankers and barges) has decreased over the last decades in the United States. Oil spillage from tank vessels in the United States in relation to oil transported by this mode decreased by 71% since the decade 1988e1997 and 81% since the 1980s (Table 2.16). Worldwide estimates of tanker and tank barge spillage made in international studies are shown in Table 2.17.

24

PART | I

Introduction and the Oil Spill Problem

TABLE 2.13 Largest Offshore Exploration and Production Well Blowouts Worldwide (ERC data) Well

Location

Date

Tons

Ixtoc I

Bahia del Campeche, Mexico

June 1979

471,430

Pemex Abkatun 91

Bahia del Campeche, Mexico

October 1986

35,286

Phillips Ekofisk Bravo

North Sea, Norway

April 1977

28,912

Nigerian National Funiwa 5

Forcados, Nigeria

January 1980

28,571

Aramco Hasbah 6

Gulf, off Saudi Arabia

October 1980

15,000

Iran Marine International

Gulf, off Laban Island, Iran

December 1971

14,286

Union Alpha Well 21

Santa Barbara, California, USA

January 1969

14,286

Chevron Main Pass 41-C

Gulf of Mexico, Venice, Louisiana, USA

March 1970

9,286

Pemex Yum II/Zapoteca

Bahia del Campeche, Mexico

October 1987

8,378

Shell South Timabalier B-26

Gulf of Mexico, Bay Marchand, Louisiana, USA

December 1970

7,585

2.3.5.2. Spills from Pipelines In inland areas, underground and above-ground pipelines transport large quantities of crude oil and refined fuels, particularly diesel, gasoline, heavy fuel oil, and trans-mix.* Spillage from pipelines in coastal and inland areas is shown in Table 2.18 and Figure 2.6. During the last decade, coastal and inland pipelines spilled an average of 11,000 tons of oil annually. This represents a 35% reduction in spillage since 1988e1997 and 70% since the 1970s. In these analyses, coastal and inland pipelines were considered to encompass all parts of the pipeline system, including gathering pipes, transmission pipes, breakout tanks, pump stations, and tank farms directly associated with and operated by pipeline companies. Offshore pipelines were considered separately under *

Usually a combination of No. 2 fuel oil (diesel) and No. 6 heavy fuel oil.

Chapter | 2

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Spill Occurrences: A World Overview

Tonnes 90,000 80,000 70,000 60,000 50,000 40,000 30,000 20,000 10,000 0

1962

1967

1972

1977

1982

1987

1992

1997

2002

2007

FIGURE 2.4 Spills into U.S. waters from tank ships, 1962e2007 (ERC data).

TABLE 2.14 Average Annual Oil Spillage from Tank Ships in U.S. Waters (ERC data) Years

Average Number of Spills One Ton or More

Average Annual Tons Spilled

1962e1967

e

7,162

1968e1977

301

27,513

1978e1987

153

8,607

1988e1997

55

6,028

1998e2007

19

514

offshore exploration and production. It should be noted that a significant portion of oil (about 85%) that spills from inland pipelines goes to containment areas around breakout tanks or to solid ground rather than directly into surface waters. With concerns about the aging pipeline infrastructure and vulnerability of pipelines for spillage, there have been a number of regulatory changes for pipelinesdthe Oil Pollution Act of 1990 (OPA 90), the 2002 Pipeline Safety Act (PSA), and the 2006 Pipeline Integrity, Protection, Enforcement, and Safety (PIPES) Act, which have improved pipeline safety and reduced spillage. Pipeline spillage amounts by oil type and per unit of oil transport are shown in Table 2.19. Spillage per unit transport has decreased 37% since the decade 1988e1997, and 57% since the 1980s.

26

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Introduction and the Oil Spill Problem

Tonnes 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2,000 0

1968

1973

1978

1983

1988

1993

1998

2003

FIGURE 2.5 Spills into U.S. waters from tank barges, 1968e2007 (ERC data).

TABLE 2.15 Average Annual Oil Spillage from Tank Barges in U.S. Waters (ERC data) Years

Average Number of Spills One Ton or More

Average Annual Tons Spilled

1968e1977

368

4,547

1978e1987

290

7,570

1988e1997

123

3,269

1998e2007

54

776

1968e2007

186

4,040

2.3.5.3. Spills from Railroads Railroads spilled 200 tons of oil annually as cargo in tankcars and as fuel. This is a 34% reduction since the decade 1988e1997. Average annual railroad spillage and spillage by ton-miles transported are shown in Table 2.20. (A tonmile is a measure of the transport of oil one ton the distance of one mile.) The spillage rate has decreased in the last three decades. Spills from railroads often go to ballast and do not always directly impact waterways. 2.3.5.4. Spillage from Tanker Trucks Tanker trucks carrying oil (usually fuels) as cargo spilled an average of 1,300 tons of oil annually in the last decade, a 76% increase since the decade 1988e1997.

Chapter | 2

27

Spill Occurrences: A World Overview

TABLE 2.16 Oil Spillage by Tank Vessels in Relation to Oil Transported in U.S. Waters (ERC data) Average Annual Spillage (tons) Tankers

Tank Barges

Combined

Average Annual Spillage per Billion Ton-Miles* Oil Transport

1978e1987

8,607

7,570

16,177

27.40

1988e1997

6,028

3,269

9,297

18.22

1998e2007

514

776

1,290

5.28

Time Period

*Ton-miles combine volume and distance of transport.

TABLE 2.17 Estimates of Worldwide Annual Tank Vessel Spillage Estimate of Average Annual Tank Vessel (Tank Ship and Tank Barge) Spillage (tons) Study

1970s

1980s

1990s

NRC, 1975

300,000

e

e

Kornberg, 1981

300,000

e

e

Baker, 1983

e

390,000

e

NRC, 1985

e

400,000

e

GESAMP, 1993

e

564,000*

e

GESAMP, 2007

e

e

157,900

NRC, 2003

e

e

100,000

Etkin, 2001

372,878

98,866

184,460y

ERC Data

431,381

213,991

136,991z

*Includes operational discharges from vessels. y Includes 1991 Gulf War-related tanker spillage. z Excludes 1991 Gulf War-related tanker spillage.

This may be attributed to better reporting of these incidents to local authorities that usually handle these incident responses. Spills from tanker trucks often go to pavements and do not directly impact waterways. Average annual spillage is in Table 2.21. There are no reliable international data on this source type.

28

PART | I

Introduction and the Oil Spill Problem

TABLE 2.18 Oil Spillage from U.S. Inland and Coastal Pipeline Systems (ERC data) Years

Average Annual Number of Spills One Ton or More

Average Annual Tons

1968e1977

276

37,049

1978e1987

172

25,885

1988e1997

140

16,900

1998e2007

195

10,965

1968e2007

196

22,828

Tonnes 70,000 60,000 50,000 40,000 30,000 20,000 10,000 0

1968

1974

1979

1984

1989

1994

1999

2004

FIGURE 2.6 Spills into U.S. waters from pipelines, 1968e2007 (ERC data).

2.3.6. Spillage from Oil Refining Each year, on average, over 8.6 billion tons of imported and domesticallyproduced crude oil are refined into hundreds of petroleum-based products and fuels at the 162 refineries in the United States. Spillage from oil refineries averaged 1,700 barrels annually over the last decade, about a 19% reduction since the decade 1988e1997 and a 27% reduction in spillage per barrel of oil throughput at refineries. Average annual spillage is shown in Table 2.22. The lower spillage for the 1980e1987 time period is likely a data artifact since spill sources in reports were not always accurately identified (e.g.,

Chapter | 2

29

Spill Occurrences: A World Overview

TABLE 2.19 Average Annual U.S. Oil Pipeline Spillage by Oil Type and Transport (ERC data) Tons Spilled per Billion Ton-Miles* Transport

Spillage (tons) Years

Crude

Refined

Total

Crude

Refined

Total

1980e1987

11,314

6,157

17,471

35.24

25.06

30.71

1988e1997

16,384

9,292

25,676

48.99

40.42

45.50

1998e2007

10,855

6,558

17,413

32.38

25.95

29.71

1980e2007

7,716

3,249

10,965

27.11

11.89

19.88

*A ton-mile is one ton of oil being transported one mile.

TABLE 2.20 Average Annual Estimated U.S. Oil Spillage from Railroads (ERC data) Years

Tons Spilled per Year

Tons Spilled per Billion Ton-Miles Transport

1980e1987

332

26.7

1988e1997

309

18.6

1998e2007

204

10.3

1980e2007

278

16.2

TABLE 2.21 Average Annual Estimated U.S. Oil Spillage from Tanker Trucks (ERC data) Years

Tons per Year

Tons Spilled per Billion Ton-Miles Transport

1980e1987

698

25.5

1988e1997

745

26.2

1998e2007

1,312

41.2

1980e2007

934

31.6

30

PART | I

Introduction and the Oil Spill Problem

TABLE 2.22 Average Annual Oil Spillage from U.S. Refineries (ERC data)

Years

Tons Spilled

Annual Refining Capacity (tons)

Refinery Utilization

Annual Throughput (tons)

Spillage per Refinery Throughput

1980e1987

502

9.17 109

78.95%

0.66 109

0.00000076

1988e1997

2,145

9.41 109

89.71%

0.72 109

0.00000296

91.62%

0.80 10

9

0.00000216

87.32%

0.73 10

9

0.00000208

1998e2007 1980e2007

1,734

10.33 10

1,529

9.66 10

9

9

a refinery may merely have been identified as a “facility”). There were also changes in reporting requirements in 1986 that authorized the Toxics Release Inventory (TRI) to track facility releases of a variety of chemicals and toxic substances. While crude oil and refined petroleum products themselves are not encompassed by the TRI-reporting requirements, some of their additives and chemical components are listed. Overall, this created a greater awareness of the need to report discharges from refineries. During refining, wastewater containing minute concentrations of oil is legally discharged in effluents, as permitted under the National Pollutant Discharge Elimination System (NPDES). The NPDES-permitted refinery effluents contain no more than five parts of oil per million parts of wastewater. The effluents are generally discharged in rivers and coastal areas where the already dilute oil concentrations are quickly diluted even further. The environmental impacts of refinery effluents have been studied fairly extensively. Environmental impacts from the oil in the effluents are extremely low and localized. Refineries are, however, generally located in industrial areas that have other permitted discharges, making it difficult to separate the effects of oil in effluents from those of background concentrations of other contaminants from other point and nonpoint sources. A comprehensive review of the ecological impacts of refinery effluents concluded that any minor impacts are limited to the areas close to the outfalls, but that it is difficult to distinguish these impacts from other pollution sources.30 The total amount of aqueous effluent discharged from oil refineries has decreased by 20% over the last 40 years due to increases in the use of air cooling and recirculation of cooling water. In addition, the toxicity of effluent discharges has decreased significantly owing to the implementation of various wastewater treatment systems.30,31 The estimated maximum discharge of oil in refinery effluents over the last decade is 7,700 tons per year. This estimate is the equivalent of less than 0.00001 ton of oil for each ton of oil processed, and is based on the following assumptions: wastewater production as a function of refinery capacity average for the last decade is 2.37

Chapter | 2

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Spill Occurrences: A World Overview

TABLE 2.23 Estimated Annual Oil Discharged in U.S. Oil Refinery Effluents (ERC data)

Years

Throughput (billion tons)

Wastewater Tons per Ton Throughput

Wastewater (billion bbl)

Oil in Effluent (tons)

1985e2007

0.66

2.15

1.17

5,837

1985e1987

0.72

1.69

1.49

7,465

1988e1997

0.80

2.05

1.91

9,538

1998e2007

0.73

2.38

1.55

7,740

barrels of wastewater (refinery effluent) produced per barrel of refining capacity; and effluents contain 5 ppm of oil (based on NPDES guidelines). There are a number of estimates of the amount of wastewater produced per unit of refining capacity. The average of the two best-documented sources was taken.31,32 Average annual refinery effluent discharges in the United States are shown in Table 2.23. The average annual oil in legally-permitted refinery effluent discharges is based on an assumption of maximum effluent oil concentration of 5 ppm. This value is the maximum allowed. Actual oil concentrations in effluents are likely to be lower. Estimates of international coastal refinery spillage and effluent oil content were made as shown in Table 2.24. Estimates in the 2007 GESAMP study were made using the same methodology as for U.S. refinery effluents, with the exception that the oil content in the effluent was assumed to vary between 5 ppm and 25 ppm, depending on national laws and practices.13

TABLE 2.24 Estimates of Worldwide Oil Refinery Spillage and Effluent Discharges Estimated Average Annual Inputs to Marine Waters (tons)

Study

Year(s)

Refinery Spillage

Oil in Refinery Effluent

Total Refinery Inputs

NRC, 1975

1970s

200,000

e

200,000

Baker, 1983

1980s

100,000

e

100,000

GESAMP, 2007

1990s

e

179,547

179,547

32

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Introduction and the Oil Spill Problem

2.3.7. Spillage Related to Oil Consumption and Usage Refined petroleum products are used in a wide variety of applications, including fuels for transportation, heating, manufacturing, and electricity production. Spillage of oil from sources that “consume” or use oil is generally outside of the realm of the petroleum industry itself, but is presented here for perspective on total oil inputs.

2.3.7.1. Spillage from Nontank Vessels “Nontank vessels” (e.g., cargo ships) carrying oil as bunker fuel and for operations spill an average of 230 tons of oil annually, a 43% reduction since the decade 1988e1997. Average annual spillage from these vessels is shown in Table 2.25. At the same time, the shipment of dry cargo (i.e., nonpetroleum shipments) by vessels has increased by 43% over the last 30 years in the United States (U.S. Army Corps of Engineers). The rate of spillage from these cargo ships in relation to the tonnage of cargo moved in U.S. waters during that time period is shown in Table 2.26. Spillage per cargo shipment has declined by 50% since the decade 1988e1997. Worldwide nontank vessel spillage was estimated in several international studies (Table 2.27). Spillage from smaller vessels (e.g., passenger, fishing, recreational, and unclassified vessels) averaged under 600 tons annually over the last decade in the United States, a nearly 34% reduction since the decade 1988e1997. Average annual spillage from these vessels is shown in Table 2.28. There are no reliable worldwide estimates of spillage from smaller vessels. Operational discharges of lubricant oils from the vessels within ports, during transit within ports, and while moored at docks contribute a significant amount of oil to U.S. watersdabout 2,800 tons annually.33 Leakages occur from stern tubes and other submerged machinery, as well as from on-deck

TABLE 2.25 Average Annual Oil Spillage from Nontank Vessels in U.S. Waters (ERC data) Years

Annual Number of Spills (1 ton or more)

Annual Tons Spilled

1973e1977

100

149

1978e1987

85

969

1988e1997

83

402

1998e2007

37

229

1973e2007

73

479

Chapter | 2

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Spill Occurrences: A World Overview

TABLE 2.26 Cargo Vessel Oil Spillage per Dry Cargo Shipments in U.S. Waters (ERC data) Years

Dry Cargo Shipment (million short tons)

Annual Tons Spilled

Tons Spilled per Million Short Tons Shipped

1978e1987

1,057

969

0.90

1988e1997

1,256

402

0.32

1998e2007

1,382

229

0.16

1978e2007

1,232

534

0.46

TABLE 2.27 Estimates of Worldwide Nontank Vessel Spillage Estimate of Average Annual Nontank Vessel Spillage (tons) Study

1970s

1980s

1990s

NRC, 1975

750,000*

e

e

Kornberg, 1981

200,000*

e

e

Baker, 1983

e

340,000*

e

NRC, 1985

e

320,000*

e

GESAMP, 2007

e

NRC, 2003

e

533,000* 7,100

Etkin, 2001

1,000

4,024

5,454

ERC Data

2,735

23,811

10,248

*Includes operational discharges from nontank vessels.

machinery. Based on a study by Etkin, these inputs are estimated to be as shown in Table 2.29, as calculated for the past five years.33 Previous time periods were adjusted based on the overall amount of shipping in U.S. waters. Operational inputs of oil and gasoline from two-stroke engines in the United States were estimated by the 2003 NRC study17 to average 7,000 tons annually and by the 2007 GESAMP study13 to average 53,000 tons annually worldwide (Table 2.30). It should be noted that this estimate has been questioned by a number of researchers (personal communications) with regard to the assumption that all of the gasoline enters the water rather than combusts or evaporates. The use of two-stroke engines of the type mentioned in this study has significantly decreased in the last few years.

34

PART | I

Introduction and the Oil Spill Problem

TABLE 2.28 Estimated Oil Spillage from Smaller Vessels in U.S. Waters (ERC data) Years

Annual Tons Spilled

1973e1977

2,123

1978e1987

939

1988e1997

900

1998e2007

595

1973e2007

999

TABLE 2.29 Vessel Operational Lubricant Leakage in U.S. and Worldwide Ports33 Lubricant Discharges (average annual tons) Stern Tube

Other Operational

Total

Years

U.S.

Worldwide

U.S.

Worldwide

U.S.

Worldwide

1980e1987

1,064

19,558

1,036

22,082

2,101

41,488

1988e1997

1,246

22,903

1,213

25,859

2,460

48,584

1998e2007

1,400

25,734

1,363

29,055

2,764

54,589

1980e2007

1,237

22,738

1,204

25,672

2,442

48,233

2.3.7.2. Spillage from Facilities Coastal facilities (other than refineries) spill an estimated 600 tons of oil in the United States annually, a 72% reduction from the decade 1988e1997. Average annual facility spillage in the United States and worldwide is presented in Table 2.31. It is important to note that spillage volumes from coastal facilities often include oil that spills into secondary containment. A secondary containment system provides an essential line of defense in preventing oil from spreading and reaching waterways in the event of the failure of an oil container (e.g., a storage tank) or the primary containment. The system provides temporary containment of the spilled oil until a response can be mounted. In the last decade, gas stations and truck stops spilled an average of 100 tons of oil annually, a nearly 48% decrease since the decade 1988e1997. This

Chapter | 2

Spill Occurrences: A World Overview

35

TABLE 2.30 Estimates of Oil Inputs from Two-Stroke Recreational Vessels in the United States and Worldwide Estimated Average Annual Tons Input

Region U.S. Atlantic*

3,100

U.S. Gulf of Mexico*

1,540

U.S. Pacific and Alaska*

2,306

U.S. Total*

6,946

Worldwide*

53,000

*Estimates based on analyses in the 2003 NRC study.17

TABLE 2.31 Estimated Oil Spillage from Coastal Marine Facilities in U.S. and Worldwide Waters Years

U.S. Annual Tons Spilledy

Worldwide Annual Tons Spilled

1973e1977

8,889

150,000z

1978e1987

6,112

50,000x

1988e1997

2,151

1998e2007

604

1973e2007

3,803

e 2,400*e12,000** e 13

*From 2007 GESAMP study based on methods in the 2003 NRC study.17 The 2007 GESAMP study13 had a second estimate of 3.9 106 tons annually. y ERC data z [24] x [25, 26] **[23]

includes all spillages that occur at gas station facilities and truck stops, including spills that occur during the transfer of fuels from tanker trucks. Average annual spillage from these sources is shown in Table 2.32. Spills at gas stations and truck stops often go to pavements and other substrates, reducing the direct impacts to waterways. There are no reliable estimates of worldwide spillage rates. Inland facilities regulated under the United States’ Environmental Protection Agency’s Spill Prevention, Control, and Countermeasures (SPCC) program other than refineries and production wells, covered separately in these analyses,

36

PART | I

Introduction and the Oil Spill Problem

TABLE 2.32 Estimated U.S. Oil Spillage from Gas Stations and Truck Stops (ERC data)* Year

Annual Spillage (tons)

1980e1987

171

1988e1997

223

1998e2007

116

1980e2007

170

*Based on reported data reported to the relevant state and local authorities in the 50 U.S. states, as well as data reported to federal authorities. These data do not include leaking underground storage tanks that leak over long periods of time. These data are tracked separately and are not considered emergency spill incidents. Since gas stations are regulated by the EPA, facilities spillage at these facilities of at least 50 gallons (0.17 tons) that occur during these facilities are included. Smaller spills (less than 50 gallons) are not included.

TABLE 2.33 Estimated U.S. Oil Spillage from Inland EPA-Regulated Facilities (ERC data) Years

Annual Spillage (tons)

1980e1987

4,963

1988e1997

35,002

1998e2007

8,525

1980e2007

16,963

spill an average of 8,500 tons of oil annually, a 76% reduction since the decade 1988e1997 (Table 2.33). Spills at inland facilities often go to pavements and other substrates, including secondary containments, reducing direct impacts to waterways. There are no reliable estimates of worldwide spillage rates. Oil spillage from home-heating oil tanks, which are not regulated by the EPA unless the tanks are in sizes larger than 34 tons, amounts to 70 tons of oil annually, a slight decrease from the decade 1988e1997 (Table 2.34). Note that this does not include slow leakages from underground storage tanks. There are no reliable estimates of worldwide spillage rates from residential tanks. Motor vehicles that carry oil as fuel rather than cargo spill about 285 tons of oil annually in the United States, double that for the decade 1988e1997 (Table 2.35). The spillage is associated with greater motor vehicle traffic, as well as

Chapter | 2

Spill Occurrences: A World Overview

37

TABLE 2.34 Estimated Oil Spillage from U.S. Residential Heating Oil Tanks (ERC data) Years

Annual Tons Spilled

1980e1987

26

1988e1997

74

1998e2007

71

1980e2007

59

TABLE 2.35 Estimated U.S. Oil Spillage from Motor Vehicles (excluding tanker trucks) (ERC data) Year

Annual Tons Spilled

Average 1980e1987

39

Average 1988e1997

170

Average 1998e2007

295

Average 1980e2007

168

better reporting by local authorities that are often the emergency responders. Motor vehicle spills* often go to pavements and do not directly impact waterways. Since the data only include spills of less than 1 ton, most passenger vehicles are excluded. There are no reliable estimates of worldwide spillage from motor vehicles.

2.3.7.3. Spillage from Aircraft and Other Sources Aircraft spill an estimated 50 tons of jet fuel annually to inland areas. These spills generally occur at airports during fueling, or occasionally from an accident. Aircraft spill an additional 530 tons annually to U.S. marine waters, based on a 2003 NRC study.17 These spills occur from two sources: through the deliberate discharge or jettisoning of jet fuel due to emergency conditions aboard an aircraft, or through the release of partially burned fuel in inefficient engines or operating modes.17,34 This type of spillage also occurs over inland areas, but there are no *

Note that tanker trucks carrying oil as cargo are considered separately.

38

PART | I

Introduction and the Oil Spill Problem

TABLE 2.36 Estimated U.S. Oil Spillage (bbl) from Other Inland Sources (ERC data) Years

Inland Aircraft (annual tons)

Inland Unknown (annual tons)

1980e1987

2

138

1988e1997

23

314

1998e2007

49

74

1980e2007

26

190

current estimates of these inputs. Total aircraft input in the United States is estimated to be about 580 tons of oil annually. The 2003 NRC study estimated worldwide marine inputs from jettisoned aircraft fuel to be about 7,500 tons annually.17 Average annual spillage from aircraft and miscellaneous unknown (unidentified) inland sources in the United States is shown in Table 2.36.

2.3.7.4. Oil Inputs from Urban Runoff About 50,000 tons of oil enters U.S. marine waters each year through urban runoff, based on a 2003 NRC study.17 Urban runoff is the accumulation of drops of oil that leak from automobiles, trucks, and other vehicles, as well as small chronic spillages that occur from other land-based sources. Oil washes off into storm sewers, culverts, and other waterways into streams and rivers that enter marine waters. Because the exact spillage source cannot be pinpointed, it is termed “nonpoint source” pollution. The U.S. inputs are broken down by region in Table 2.37. Studies that included worldwide estimates of oil in urban runoff are shown in Table 2.38.

TABLE 2.37 Estimates of U.S. Oil Inputs from Urban Runoff Region

Estimated Average Annual Tons of Oil Input*

Atlantic

31,500

Gulf of Mexico

12,600

Pacific

5,829

Alaska

80

Total

50,009

*Estimates based on analyses in the NRC 2003 study.17

Chapter | 2

39

Spill Occurrences: A World Overview

TABLE 2.38 Estimates of Worldwide Marine Oil Inputs from Urban Runoff Estimate of Average Annual Oil Inputs from Urban Runoff (tons) Study

1970s

1980s

1990s

NRC, 1975

2,500,000

e

e

Kornberg, 1981

2,100,000

e

e

Baker, 1983

e

1,430,000

e

NRC, 1985

e

1,080,000

e

NRC, 2003

e

e

140,000

2.3.8. Oil Inputs from Potentially Polluting Sunken Shipwrecks Potential future and documented current oil leakage and discharges from sunken ships in marine waters is an issue of concern worldwide. A study conducted in 1977 drew attention to the oil discharges from a large number of oil tankers sunk during military operations in World War II along the U.S. western, eastern, and southern (Gulf of Mexico) coasts.18 While the tankers had been sunk over 30 years earlier, oil was still periodically leaking from the vessels, which were acting as “seeps.” Many of the tankers were still relatively intact, though their structural integrity was uncertain. The issue of oil pollution from sunken World War II tankers and military vessels was further brought to public attention after several incidents of oil leaking from several vessels (notably the S.S. Jacob Luckenbach off the Pacific coast of the United States, the USS Mississinewa in Micronesia, and the German warship Blu¨cher off Oslo, Norway) in the late 1990s to 2004. These sunken vessels were identified as the sources of “mystery spills” and discharges that impacted shorelines and other resources.35 The South Pacific Environment Programme (SPREP) has conducted surveys of wrecks in the South Pacific region particularly impacted by World War II military vessel sinkings.36,37 In 2005, the American Petroleum Institute and the sponsors of the International Oil Spill Conference* commissioned a study, Potentially Polluting Wrecks in Marine Waters, which involved developing a databasey of recorded *

International Maritime Organization, U.S. Coast Guard, U.S. Environmental Protection Agency, International Petroleum Industry Environmental Conservation Association, Minerals Management Service, and National Oceanic and Atmospheric Administration.

y

The proprietary database was developed by ERC.

40

PART | I

Introduction and the Oil Spill Problem

FIGURE 2.7 Approximate location of potentially polluting shipwrecks* (ERC data).

vessel sinkings for tankships of at least 150 gross registered tons (GRTs) carrying oil and nontank vessels of at least 400 GRTs that carried oil as fuel/ bunkers (and for operations); an analysis of the distribution of and likely amount of oil contained in these vessels; and an examination of the environmental, regulatory, political, technical, and financial issues associated with these sources of petroleum.38 The data analysis revealed that there were at least 8,569 recorded vessel sinkings worldwide, of which 1,583 were tankships and 6,986 were nontank vessels. An estimated 2.5 to 20.4 million tons of oil is thought to be present in these shipwrecks. The shipwrecks are distributed throughout the world, as shown in Figure 2.7. The data in the 2005 Michel et al. study were analyzed regionally, as summarized in Table 2.39.38 This oil will not necessarily discharge, but there is the potential that it will, with the actual probability of discharge depending on vessel integrity and condition, age, depth at which the wrecks rest, temperature of the waters, and type of oil. Heavier fuels at greater depths may be nearly solid, and many of the vessels may be largely intact. On the other hand, the greatest potential for spillage is with the older vessels, particularly those from World War II, which were often built according to lower standards than more modern vessels. The potential for impacts depends largely on the location of the wrecks. Those in nearshore waters tend to present the greatest potential for impacting *

Dots indicate approximate locations based on Marsden square (10-degree latitude/longitude). Because many of the vessels are “war-graves” and there are also safety concerns, authorities aim to prevent plundering or diving exploration. The exact locations of many vessels are uncertain or are classified or confidential.

Chapter | 2

Spill Occurrences: A World Overview

41

TABLE 2.39 Worldwide Potential Pollution from Sunken Tankers and Nontank Vessels (ERC data) Estimated Oil Content of Shipwrecks (tons) Region

Minimum

Maximum

North Atlantic Ocean

951,000

7.5 million

South Atlantic Ocean

165,000

0.5 million

North Pacific Ocean

221,000

1.7 million

South Pacific Ocean

521,000

4.2 million

Indian Ocean

264,000

2.2 million

shorelines. The impacts of discharges from these vessels in the open ocean are likely to be less severe than those closer to shore because of the natural dispersion that would break the oil into smaller concentrations. Much of the oil involved is likely to be heavier and would most likely form tar balls rather than larger slicks unless released in a large mass. The experts who conducted the 2005 Michel et al. study concluded that most of the vessels were likely to release oil in small quantities over a longer period of time or had already started to do so, acting almost as a “natural seep.” Nevertheless, there is the potential for a vessel to suddenly release a much larger quantity of oil if a radical change takes place in the vessel’s structural integrity.38 The political, regulatory, and financial issues associated with these shipwrecks are extremely complex due to jurisdictional concerns. Removing the oil and other hazardous materials, as well as munitions, from these vessels involves complex, dangerous, and expensive salvage operations. It is unclear who would finance or regulate these operations, especially for the large number of World War II vessels involved. Because of the complex issues presented by these wrecks and the overwhelming number of potentially polluting wrecks, an approach involving scientifically based risk assessments and cost-benefit analyses has been promoted by several organizations, government agencies, and researchers to prioritize those wrecks that poset the highest environmental risk for oil and hazardous material removal operations.38-44

2.3.9. Summary of Oil Spillage Estimates of average annual U.S. oil spillage by decade from all source categories are summarized in Table 2.40. Over the last decade, the largest source category of spillage is inland pipelines, followed by EPA-regulated facilities. The oil spillage reported here does not reflect the amounts of oil

42

PART | I

Introduction and the Oil Spill Problem

TABLE 2.40 Estimated Total Average Annual U.S. Oil Spillage (tons) 1969e 1977

1978e 1987

1988e 1997

1998e 2007

Production

4,491

1,243

2,169

1,420

5.07%

Offshore Platform Spills

3,694

192

259

182

0.65%

640

495

1,161

373

1.33%

Offshore Supply Vessels

14

35

7

1

0.00%

Inland Production Wells

143

521

742

863

3.08%

Refining

429

502

2,145

1,734

6.19%

Refinery Spills

429

502

2,145

1,734

6.19%

Transport

69,809

43,092

27,250

13,770

49.16%

Inland Pipelines

37,049

25,885

16,900

10,965

39.15%

Tanker Trucks

429

698

745

1,312

4.68%

Railroads

286

332

309

204

0.73%

Tank Ships

27,499

8,607

6,028

514

1.83%

Tank Barges

4,547

7,570

3,269

776

2.77%

16,932

13,887

39,789

11,088

39.58%

714

969

402

229

0.82%

2,123

939

900

595

2.12%

171

171

223

116

0.41%

21

26

74

71

0.25%

4,286

4,963

35,002

8,525

30.43%

529

531

552

578

2.06%

Coastal Facilities

8,889

6,112

2,151

604

2.16%

Inland Unknown

129

138

314

74

0.26%

71

39

170

295

1.05%

91,660

58,723

71,354

28,011

100.00%

Source Type

Offshore Pipelines

Storage and Consumption Nontank Vessels Other Vessels Gas Stations and Truck Stops Residential Inland EPA-Reg Facilities* Aircrafty

Motor Vehicles Total

% Total 1998e2007

*Excludes refineries, gas stations, and production wells. y Includes aircraft in inland areas plus estimates of marine inputs (based on NRC, 2003).

Chapter | 2

43

Spill Occurrences: A World Overview

that were contained or recovered. It also does not reflect the differences between oil that is spilled directly into marine or freshwater systems and oil that is spilled onto other surfaces, including containment areas around storage tanks in tank farms. The properties of the oil spilled (crude vs. refined, heavy vs. light) and the locations in which the oil spills (marine waters, inland waters, dry surfaces, wetlands, industrial zones) will largely determine the impacts of these spills and should be considered in addition to the actual amounts of oil spilled. Total U.S. oil inputs to marine and inland waters, including spills, runoff, and all operational discharges are shown in Table 2.41. TABLE 2.41 Estimated Total Average Annual U.S. Oil Inputs (tons) Source Type

1969e 1977

1978e 1987

1988e 1997

1998e 2007

% Total 1998e2007

Production

5,876

2,431

3,438

2,930

2.15%

Offshore Platform Spills

3,694

192

259

182

0.13%

Offshore Pipeline Spills

640

495

1,161

373

0.27%

Offshore Supply Vessel Spills

14

39

7

1

0.00%

Inland Production Well Spills

521

742

863

705

0.52%

1,007

963

1,148

1,669

1.23%

35,963

52,758

68,910

55,915

41.09%

429

502

2,145

1,734

1.27%

Refinery Effluents

35,534

52,256

66,765

54,181

39.82%

Transport

69,882

43,084

27,163

13,864

10.19%

Inland Pipelines

37,049

25,885

16,900

10,965

8.06%

Tanker Trucks

429

698

745

1,312

0.96%

Railroads

332

309

204

278

0.20%

Tank Ships

27,513

8,607

6,028

514

0.38%

Tank Barges

4,547

7,570

3,269

776

0.57%

12

15

17

19

0.01%

67,841

65,497

91,595

63,357

46.56%

Produced Water Refining Refinery Spills

Tank Vessel Operational Discharge Storage and Consumption

(Continued )

44

PART | I

Introduction and the Oil Spill Problem

TABLE 2.41 Estimated Total Average Annual U.S. Oil Inputs (tons)dcont’d Source Type Nontank Vessels

1969e 1977

1978e 1987

1988e 1997

1998e 2007

% Total 1998e2007

149

969

402

229

0.17%

Other Vessels

2,123

939

900

595

0.44%

Vessel Operational Discharge

2,000

2,086

2,443

2,745

2.02%

171

223

116

170

0.12%

21

26

74

71

0.05%

4,286

4,963

35,002

8,525

6.27%

2

2

23

49

0.04%

Coastal Facilities (Nonrefining)

8,889

6,112

2,151

604

0.44%

Inland Unknown

129

138

314

74

0.05%

71

39

170

295

0.22%

50,000

50,000

50,000

50,000

36.75%

179,562

163,770

191,106

136,066

100.00%

Gas Stations and Truck Stops Residential Inland EPA-Regulated Facilities** Aircrafty

Motor Vehicles Urban Runoff Total

**Excludes refineries, gas stations, and production wells. y Includes aircraft in inland areas, plus estimates of marine inputs based on the 2003 NRC study [17].

Although annual spill amounts vary from year to year, often due to one or two particularly large incidents, there has been a general downward trend in U.S. spills in the past decade, and an even greater downward trend since 1989, the year of the Exxon Valdez spill (Figure 2.8). Worldwide trends are shown in Figure 2.9. The large spill in 1979 from the Ixtoc I well blowout dominates the spillage. War-related intentional spillage, such as that in the 1991 Gulf War, has not been included. Despite general downward trends in spills in the United States and worldwide, it is important that spill response preparedness be maintained due to the continuing risk of spills, including worst-case discharge scenarios. Most spills will continue to be “routine” in that they are relatively small and easily responded to with local resources. At the same time, occasional large spills, along with increasing public expectations for effective spill response and increased spiller liability, have necessitated complex contingency planning for

Chapter | 2

45

Spill Occurrences: A World Overview

Tonnes 140,000 120,000 100,000 80,000 60,000 40,000 20,000 0

1968

1973

1978

1983

1988

1993

1998

2003

FIGURE 2.8 Annual oil spillage into U.S. waters with reduction trends (ERC data).

Tonnes 2,000,000 1,800,000 1,600,000 1,400,000 1,200,000 1,000,000 800,000 600,000 400,000 200,000 0

1970

1975

1980

1985

1990

1995

2000

FIGURE 2.9 Worldwide oil spillage with reduction trends (ERC data).

increasingly rare high-impact events.22 For example, the United States with its experience in the 1989 tanker Exxon Valdez, which involved the spillage of over 37,000 tons of oil, has not experienced a worst-case discharge scenario, defined as the complete release of the contents of a fully loaded oil tanker or large storage facility. Had the Exxon Valdez released its entire contents, about five times as much oil would have spilled into Prince William Sound. The complexity of the spill response and the impact of the spill is difficult to envision, but must be planned for. The magnitude of the spill from the MC-252

46

PART | I

Introduction and the Oil Spill Problem

well (otherwise referred to as Deepwater Horizon spill) that occurred during April through July 2010 has not yet been verified, though it has been been confirmed to be the largest spill in US history.

REFERENCES 1. Lees GM, et al. The Eastern Hemisphere. In: Pratt WE, Good D, editors. World Geography of Petroleum, 159. Princeton University Press; 1950. 2. Levorson AI. Geology of Petroleum, 14. San Francisco, CA: Freeman Press; 1954. 3. Hodgson SF. Onshore Oil and Gas Seeps in California, California Division of Oil and Gas. Department of Conservation; 1987. 4. Allen A, Schlueter RS, Mikolaj PG. Natural Oil Seepage at Coal Oil Point, Santa Barbara, California. Science 1970;974. 5. Hornafius JS, Quigley D, Luyendyk BP. The World’s Most Spectacular Marine Hydrocarbon Seeps (Coal Point, Santa Barbara Channel, California): Quantification of Emissions. J. Geophys. Res 1999;703. 6. Kvenvolden KA, Simoneit BRT. Hydrothermically Derived Petroleum: Examples from Guaymas Basin, Gulf of California, and Escanaba Trough, Northeast Pacific Ocean. Amer. Assoc. Petrol. Geolog. Bull. 1990;223. 7. Leifer I, Luyendyk B, Broderick K. Tracking Seep Oil from Seabed to Sea Surface and beyond at Coal Oil Point, California, Proceedings of the American Association of Petroleum Geologists (AAPG). Salt Lake City: Utah; 2003. 8. Chernova TG, Rao PS, Pikovskii Y, Alekseeva TA, Nagender NB, Ramalingeswara RB, et al. The Composition and the Source of Hydrocarbons in Sediments Taken from the Tectonically Active Andaman Backarc Basin, Indian Ocean. Mar. Chem. 2001;1. 9. Gupta RS, Qasim SZ, Fondekar SP, Topgi RS. Dissolved Petroleum Hydrocarbons in Some Regions of the Northern Indian Ocean. Mar. Pollut. Bull. 1980;65. 10. Venkatesan MI, Ruth E, Rao PS, Nath BN, Rao BR. Hydrothermal Petroleum in the Sediments of the Andaman Backarc Basin, Indian Ocean. Appl. Geochem. 2003;845. 11. MacDonald IR. Natural Oil Spills. Scientific American 1998;57 (Nov). 12. Wilson RD, Monaghan PH, Osanik A, Price LC, Rogers MA. Natural Marine Oil Seepage. Science 1974;857. 13. GESAMP (IMO/FAO/UNESCO-IOC/UNIDO/WMO/IAEA/UN/UNEP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection). Estimates of Oil Entering the Marine Environment from Sea-Based Activities. GESAMP Reports and Studies 2007;75. 14. Kvenvolden KA, Cooper CK. Natural Seepage of Crude Oil into the Marine Environment. Geo-Marine Letters 2003;140. 15. Kvenvolden KA, Harbaugh JW. Reassessment of the Rates at Which Oil from Natural Sources Enters the Marine Environment. Mar. Environ. Res. 1983;223. 16. Quigley DC, Hornafius JS, Luyendyk BP, Francis RD, Clark J, Washburn L. Decrease in Natural Marine Hydrocarbon Seepage near Coal Oil Point, California, Associated with Offshore Oil Production. Geology 1999;1:047. 17. National Research Council Committee on Oil in the Sea. Oil in the Sea III: Inputs, Fates, and Effects, National Research Council Ocean Studies Board and Marine Board Divisions of Earth and Life Studies and Transportation Research Board. Washington, DC: National Academy Press; 2003.

Chapter | 2

Spill Occurrences: A World Overview

47

18. Campbell B, Kern E, Horn D. Impact of Oil Spillage from World War II Tanker Sinkings, Report No. MITSG 77e4 Index No. 77-304-Nnt. Cambridge: Massachusetts Institute of Technology Sea Grant Program; 1977. 19. Easton R. Black Tide: The Santa Barbara Oil Spill and Its Consequences. New York: Delacorte Press; 1999. 20. Hayes MO. Black Tides. Austin: University of Texas Press; 1999. 21. Etkin DS. Analysis of Oil Spill Trends US and Worldwide. IOSC 2001;291. 22. Etkin DS. Analysis of Past Marine Oil Spill Rates and Trends for Future Contingency Planning. AMOP 2002;227. 23. Etkin DS. Analysis of US Oil Spill Trends to Develop Scenarios for Contingency Planning. IOSC 2003;47. 24. National Research Council. Petroleum in the Marine Environment. Washington, DC: National Academy of Sciences; 1975. 25. Kornberg H. Royal Commission on Environmental Pollution: 8th Report. London: Her Majesty’s Stationery Office; 1981. 26. Baker JM. Impact of Oil Pollution on Living Resources, Comm. Ecology Paper No. 4. Gland, Switzerland: International Union for Conservation of Nature and Natural Resources; 1983. 27. National Research Council. Oil in the Sea: Inputs, Fates, and Effects. Washington, DC: National Academy Press; 1985. 28. GESAMP (IMO/FAO/UNESCO/WMO/WHO/IAEA/UN/UNEP Joint Group of Experts on the Scientific Aspects of Marine Pollution). Impact of Oil and Related Chemicals and Wastes on the Marine Environment. GESAMP Reports and Studies 1993;Vol. 50. 29. Etkin DS. Analysis of US Oil Spillage. American Petroleum Institute Publication 356, Environmental Research Consulting; 2009. 30. Wake H. Oil Refineries: A Review of Their Ecological Impacts on the Aquatic Environment. Estuarine, Coastal and Shelf Science 2005;131. 31. CONCAWE, Trends in Oil Discharged in Aqueous Effluents from Oil Refineries in Europe: 2000 Survey, Report No. 4/04, CONCAWE (The Oil Companies’ European Association for Environmental, Health, and Safety in Refining and Distribution), Brussels, 2004. 32. American Petroleum Institute (API). Water Reuse Studies. Washington, DC: API Publication No. 949. American Petroleum Institute; 1977. 33. Etkin DS. Worldwide Analysis of In-Port Vessel Operational Lubricant Discharges and Leakages. AMOP; 2010. 34. Canadian Environmental Assessment Agency (CEAA), Military Flying Activities in Labrador and Quebec, Ottawa, 1995. 35. Symons L, Hodges MK. Undersea Pollution Threats and Trajectory Modeling. Mar. Techn, Soc. J. 2004;78. 36. Nawadra S, Gilbert TD. Risk of Marine Spills in the Pacific Island Region and Its Evolving Response Arrangements. Sydney, Australia: Proceedings of the International Spill Conference, SpilCon 2002; 2002. 37. South Pacific Regional Environment Programme (SPREP). Regional Strategy to Address Marine Pollution from World War II Shipwrecks. Majuro, Marshall Islands: Thirteenth SPREP Meetings of Officials (Item 7.2.2.1); July 2002, 21e25. 38. Michel J, Etkin DS, Gilbert T, Urban R, Waldron J, Blocksidge CT. Potentially Polluting Wrecks in Marine Waters. IOSC; 2005. 39. Etkin DS, van Rooij JAC, French-McCay D. Risk Assessment Modeling Approach for the Prioritization of Oil Removal Operations from Sunken Wrecks. Interspill; 2009.

48

PART | I

Introduction and the Oil Spill Problem

40. Etkin DS. Cost-Benefit Analyses for Wreck Oil Removal Projects, Proceedings of the Wrecks of the World: Hidden Risks of the Deep Conference. Linthicum, MD: Maritime Institute of Technology (MITAGS); 2009. 41. Etkin DS. Magnitude of Worldwide Potentially-Polluting Wreck Problem, Proceedings of the Wrecks of the World: Hidden Risks of the Deep Conference. Linthicum, MD: Maritime Institute of Technology (MITAGS); 2009. 42. Hassello¨v I-M, Morrison G, Rose´n L, Dahllo¨f I, Lindgren F, Knutsson J. Development of a Protocol for Risk Assessment of Potentially Polluting Shipwrecks in Scandinavian Waters, Proceedings of the Wrecks of the World: Hidden Risks of the Deep Conference. Linthicum, MD: Maritime Institute of Technology (MITAGS); 2009. 43. Cabioc’h F. The Wreck Concern in France and European Waters: Prioritization, Proceedings of the Wrecks of the World: Hidden Risks of the Deep Conference. Linthicum, MD: Maritime Institute of Technology (MITAGS); 2009. 44. Westerholm D. Repercussions of a Reactive Strategy and Need for a Proactive Strategy, Proceedings of the Wrecks of the World: Hidden Risks of the Deep Conference. Linthicum, MD: Maritime Institute of Technology (MITAGS); 2009.

Part II

Types of Oils and Their Properties

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Chapter 3

Introduction to Oil Chemistry and Properties Merv Fingas

Chapter Outline 3.1. Introduction 3.2. The Composition of Oil

51 51

3.3. Properties of Oil

54

3.1. INTRODUCTION Oil is a general term that describes a wide variety of natural substances of plant, animal, or mineral origin, as well as a range of synthetic compounds.1 This section covers mineral oil or petroleum oil. The many different types of crude oil are made up of hundreds of major constituents and thousands of minor ones. As their composition varies, each type of oil or petroleum product has certain unique characteristics or properties. These properties influence how the oil behaves when it is spilled and determines the fate and effects of the oil in the environment. These properties also influence the efficiency of cleanup operations. This section deals specifically with crude oils and petroleum products derived from crude oils and describes the chemical composition and physical properties.

3.2. THE COMPOSITION OF OIL Crude oils are mixtures of hydrocarbon compounds ranging from smaller, volatile compounds to very large, nonvolatile compounds.2 This mixture of compounds varies according to the geological formation of the area in which the oil is found and strongly influences the properties of the oil. For example, crude oils that consist primarily of large compounds are viscous and dense. Petroleum products such as gasoline or diesel fuel are mixtures of fewer compounds, and thus their properties are more specific and less variable. Crude oil contains many compounds of different sizes and different classes. In fact, Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10003-6 Copyright Ó 2011 Elsevier Inc. All rights reserved.

51

52

PART | II

Types of Oils and Their Properties

there are so many that as time goes by more and more compounds are identified in oil.3 Figure 3.1 shows the number of compounds that are identified and quantified in oils by year as well as the prediction for the future. Some analysts have preliminarily identified up to 17,500 compounds in an oil. Hydrocarbon compounds are composed of hydrogen and carbon, which are therefore the main elements in oils. Oils also contain varying amounts of sulphur, nitrogen, oxygen, and sometimes mineral salts, as well as trace metals such as nickel, vanadium, and chromium. In general, the hydrocarbons found in oils are characterized by their structure. A common and older method of classification is by SARA dsaturates, aromatics, resins, and asphaltenes. Figure 3.2 illustrates the SARA classification along with classes of compounds typically found in this overall classification. The saturate group of components in oils consists primarily of alkanes, which are compounds of hydrogen and carbon with the maximum number of hydrogen atoms around each carbon. Thus, the term saturate is used because the carbons are “saturated” with hydrogen. The saturate group includes straight-chain alkanes and branched-chain alkanes and also includes cycloalkanes, which are compounds made up of the same carbon and hydrogen constituents, but with the carbon atoms bonded to each other in rings or circles. Straight-chain saturate compounds from C18 and up are often referred to as waxes. The aromatic compounds include at least one benzene ring of six carbons. Three carbon-to-carbon double-bonds float around the ring and provide

Compounds Identified

4000

3000

Prediction

2000

1000

0 1970

1980

1990

2000

Year

2010

2020

FIGURE 3.1 The number of compounds identified and quantified in crude oils by year, including prediction in the future.

Chapter | 3

53

Introduction to Oil Chemistry and Properties

Groupings

Example Classes, Names, and Compounds

Saturates

alkanes

Chemical class Alternate name

Description

paraffins

Example compound

dodecane C12H26

cycloalkanes waxes

Aromatics

naphthanates

decalin n-alkanes C18-C80

Benzenes BTEX

benzene Benzene, Toluene, Ethylbenzene, Xylenes

PAHs

Naphthenoaromatics

Resins Asphaltenes

anthracene

combinations of aromatics and cycloalkanes

tetralin

class of mostly anomalous polar compounds carbazole sometimes containing oxygen, nitrogen, sulphur, or metals

N

class of large anomalous compounds structures not known sometimes containing oxygen, nitrogen, metals, or sulphur

FIGURE 3.2 An overview of the classification of compounds with specific examples.

stability. Because of this stability, benzene rings are very persistent and can have toxic effects on the environment. The most common smaller aromatic compounds found in oil are often referred to as BTEX, or Benzene, Toluene, Ethyl-benzene, and Xylenes. Polyaromatic hydrocarbons or PAHs are compounds consisting of at least two benzene rings. PAHs make up between 0 and 60% of the composition of oil. The olefins, or unsaturated compounds, are another group of compounds that contain less hydrogen atoms than the maximum possible. Olefins have at least one double carbon-to-carbon bond that displaces two hydrogen atoms. Significant amounts of olefins are found only in refined products. Polar compounds are those that have a significant molecular charge as a result of bonding with compounds such as sulphur, nitrogen, or oxygen. The “polarity” or charge that the molecule carries results in behavior that may be different from that of other compounds. In the petroleum industry, the smallest polar compounds are called resins, which are largely responsible for oil adhesion. The larger polar compounds are called asphaltenes because they often make up the largest percentage of the asphalt commonly used for road construction. Asphaltenes often have very large molecules and, if in abundance in an oil, they have a significant effect on oil behavior.4 Bitumen, which comes from heavy oil deposits or tar sands, consists largely of asphaltenes that must be broken down to smaller compounds before refining. Crude oil is processed in refineries to yield petroleum products that are used for heating, transport, and chemical synthesis. Table 3.1 lists some of the

54

PART | II

Types of Oils and Their Properties

TABLE 3.1 General Characterizations of Product Distillation Ranges Product

Distillation Temperature Range ( C)

Approximate Carbon Number Range

Gasoline

30e200

5e12

Naphtha

100e200

8e12

Jet Fuel & Kerosene

150e250

11e13

Diesel fuel

160e400

13e17

Gas-Oil

220e350

Heavy fuel oils

315e540

20e45

Atmospheric residue

>450

30þ

Vacuum residue

>600

60þ

products produced by distillation, a primary refinery process. Table 3.2 gives the general composition of some typical fuels and oils.5 The following are the oils or fuels that be used to illustrate the fate, behavior, and cleanup of oil spills: l l l l l

l

gasolinedas used in automobiles diesel fueldas used in trucks, trains, and buses a light crude oil a heavy crude oil an intermediate fuel oil (IFO)da mixture of a heavy residual oil and diesel fuel used primarily as a propulsion fuel for ships (the intermediate refers to the fact that the fuel is between a diesel and a heavy residual fuel) bunker fueldsuch as Bunker C, which is a heavy residual fuel remaining after the production of gasoline and diesel fuel in refineries and often used in heating plants

3.3. PROPERTIES OF OIL The properties of oil discussed here are viscosity, density, specific gravity, solubility, flash point, pour point, distillation fractions, interfacial tension, and vapor pressure. These properties for the oils noted as examples above are listed in Table 3.3.5 Viscosity is the resistance to flow in a liquid. The lower the viscosity, the more readily the liquid flows. For example, water has a low viscosity and flows readily, whereas honey, with a high viscosity, flows slowly. The viscosity of the

(% e except for metals) Group

Compound Class

alkanes cyclo-alkanes

Diesel

Light Crude

50 to 60

65 to 95

55 to 90

25 to 80

25 to 35

20 to 30

45 to 55

35 to 45

0 to 20

0 to 10

2 to 10

5 to 15

5

waxes Olefins Aromatics BTEX

IFO

Bunker C

30 to 50 0 to 1

5 to 10

0 to 10

25 to 40

5 to 25

10 to 35

15 to 40

40 to 60

30 to 50

15 to 25

0.5 to 2.0

0.1 to 2.5

0.01 to 2.0

0.05 to 1.0

0.00 to 1.0

0 to 5

10 to 35

15 to 40

30 to 50

30 to 50

0 to 2

1 to 15

5 to 40

15 to 25

10 to 30

0 to 2

0 to 10

2 to 25

10 to 15

10 to 20

0 to 10

0 to 20

5 to 10

5 to 20

30 to 250

100 to 500

100 to 1000

100 to 2000

0 to 2

0 to 5

0.5 to 2.0

2 to 4

PAHs Polar Compounds resins asphaltenes Metals (in parts per million) Sulphur

Heavy Crude

0.02

0.1 to 0.5

Introduction to Oil Chemistry and Properties

Saturates

Gasoline

Chapter | 3

TABLE 3.2 Typical Composition of Some Oils and Petroleum Products

55

56

TABLE 3.3 Typical Oil Properties Property Viscosity

Units

mPa.s at 15 C

Gasoline

Diesel

0.5

2

Light Crude 5 to 50

Heavy Crude 50 to 50,000

0.72

0.84

0.78 to 0.88

0.88 to 1.00

Flash Point

C

35

45

30 to 30

30 to 60

Solubility in Water

ppm

200

40

10 to 50

Pour Point

NR

35 to 10 40 to 30

65

35

27

100 C 200 C

C

API Gravity Interfacial Tension

mN/m at 15 C

1000 to 15,000

10,000 to 50,000

0.94 to 0.99

0.96 to 1.04

80 to 100

>100

5 to 30

10 to 30

1 to 5

40 to 30

10 to 10

5 to 20

30 to 50

10 to 30

10 to 20

5 to 15

27

10 to 30

15 to 30

25 to 30

25 to 35

70

1

2 to 15

1 to 10

e

e

100

2 to 5

2 to 5

Distillation Fractions % distilled at

30

15 to 40

2 to 25

85

30 to 60

15 to 45

15 to 25

5 to 15

100

45 to 85

25 to 75

30 to 40

15 to 25

15 to 55

25 to 75

60 to 70

75 to 85

300 C 400 C residual NR ¼ not relevant

Types of Oils and Their Properties

g/mL at 15 C

Bunker C

PART | II

Density

Intemediate Fuel Oil

Chapter | 3

Introduction to Oil Chemistry and Properties

57

oil is largely determined by the amount of lighter and heavier fractions that it contains. The greater the percentage of light components, such as small saturates, and the lesser the amount of asphaltenes, the lower the viscosity. As with other physical properties, viscosity is affected by temperature, with a lower temperature giving a higher viscosity. For most oils, the viscosity varies as the logarithm of the temperature, which is a very significant variation. Oils that flow readily at high temperatures can become a slow-moving, viscous mass at low temperatures. In terms of oil spill cleanup, viscosity can affect the oil’s behavior. Viscous oils do not spread rapidly, do not penetrate soil as readily, and are difficult to pump and skim. Density is the mass (weight) of a given volume of oil and is typically expressed in grams per cubic centimeter (g/cm3). It is the property used by the petroleum industry to define light or heavy crude oils. Density is also important as it indicates whether a particular oil will float or sink in water. As the density of fresh water is 1.0 g/cm3 at 15 C and the density of most oils ranges from 0.7 to 0.99 g/cm3, most oils will float on water. As the density of seawater is 1.03 g/cm3, even heavier oils will usually float on it. The density of oil increases with time, as the light fractions evaporate. Occasionally, when the density of an oil becomes greater than the density of freshwater or seawater, the oil will sink. Sinking is rare, however, and happens only with a few oils, usually residual fuels such as Bunker C. Significant amounts of oil have sunk in only about 25 incidents out of thousands. However, as heavier and heavier oils are being used more frequently, this may become more common in the future. Another measure of density is specific gravity, which is an oil’s relative density compared to that of water. If the oil-specific gravity is greater than 1, it sinks; if it is less than 1, it floats. Another gravity scale is that of the American Petroleum Institute (API). The API gravity is based on the density of pure water that has an arbitrarily assigned API gravity value of 10 (10 degrees). Oils with progressively lower specific gravities have higher API gravities. The following is the formula for calculating API gravity: API gravity ¼ [141.5 O (oil density at 15.5 C)] 131.5. Oils with high densities have low API gravities and vice versa. Solubility in water is the measure of how much of an oil will dissolve in the water column on a molecular basis. Solubility is important in that the soluble fractions of the oil are sometimes toxic to aquatic life, especially at higher concentrations. As the amount of oil lost to solubility is always small, this is not as great a loss mechanism as evaporation. In fact, the solubility of oil in water is so low (generally less than 100 parts per million) that it would be the equivalent of approximately one grain of sugar dissolving in a cup of water. Yet, even this small amount is important to the environment as even small amounts may be toxic to certain biota. The flash point of an oil is the temperature at which the liquid gives off sufficient vapors to ignite upon exposure to an open flame. A liquid is considered to be flammable if its flash point is less than 60 C. There is a broad range of flash points for oils and petroleum products, many of which are

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Types of Oils and Their Properties

considered flammable, especially when fresh. Gasoline, which is flammable under all ambient conditions, poses a serious hazard when spilled. Many fresh crude oils have an abundance of volatile components and may be flammable for as long as one day until the more volatile components have evaporated. On the other hand, Bunker C and heavy crude oils generally are not flammable even when spilled. The pour point of an oil is the temperature at which it takes longer than a specified time to pour from a standard measuring vessel. As oils are made up of hundreds of compounds, some of which may still be liquid at the pour point, the pour point is not the temperature at which the oil will no longer pour. The pour point represents a consistent temperature at which an oil will pour very slowly and therefore has limited use as an indicator of the state of the oil. In fact, pour point has been overused in the past to predict how oils will behave in the environment. For example, waxy oils can have very low pour points, but may continue to spread slowly at that temperature and can evaporate to a significant degree. It is important to note that pour point is not the solidification temperature. As produced crude oils become heavier, pour point becomes less relevant. Distillation fractions of an oil represent the fraction (generally measured by volume) of an oil that is boiled off at a given temperature. This data is obtained on most crude oils so that oil companies can adjust parameters in their refineries to handle the oil. This data also provides environmentalists with useful insights into the chemical composition of oils. For example, while 70% of gasoline will boil off at 100 C, only about 5% of a crude oil will boil off at that temperature and an even smaller amount of a typical Bunker C. The distillation fractions correlate strongly to the composition as well as to other physical properties of the oil. Equations to predict evaporation can use distillation fraction data as input. The oil/water interfacial tension, sometimes called surface tension, is the force of attraction or repulsion between the surface molecules of oil and water. Together with viscosity, surface tension is an indication of how rapidly and to what extent an oil will spread on water. The lower the interfacial tension with water, the greater the extent of spreading. In actual practice, the interfacial tension must be considered along with the viscosity because it has been found that interfacial tension alone does not account for spreading behavior. The vapor pressure of an oil is a measure of how the oil partitions between the liquid and gas phases, or how much vapor is in the space above a given amount of liquid oil at a fixed temperature. Because oils are a mixture of many compounds, the vapor pressure changes as the oil weathers. Vapor pressure is difficult to measure and is not frequently used to assess oil spills. Again as oil is a mixture of hundreds of compounds, vapor pressure is not entirely relevant. Although there is a high correlation between the various properties of an oil, these correlations should be used cautiously as oils vary so much in composition. For example, the density of many oils can be predicted based on their

Chapter | 3

Introduction to Oil Chemistry and Properties

59

viscosity. For other oils, however, this could result in errors. For example, waxy oils have much higher viscosities than would be implied from their densities. There are several mathematical equations for predicting one property of an oil from another property, but these must be used carefully as there are many exceptions.

REFERENCES 1. Neumann H-J, Paczynska-Lahme B, Severin D. Composition and Properties of Petroleum. New York: Halsted Press; 1981. 2. Speight JG. The Chemistry and Technology of Petroleum. 4th ed. Boca Raton, FL: CRC Press; 2007. 3. Marshall AG, Hendrickson CL. High-Resolution Mass Spectrometers, chapter in Annual Review of Analytical Chemistry, Volume 1, 2008, Young ES and Zare RN, editors., Annual Reviews, Palo Alto, CA, p. 579e99, 2008. 4. Groenzin H, Mullins OC. Asphaltene Molecular Size and Weight by Time-Resolved Fluorescence Depolarization, Chapter 2 in Asphaltenes, Heavy Oils and Petroleomics. In: Mullins OC, Sheu EY, Hammami A, Marshall AG, editors. New York: Springer Publications; 2007. p. 17. 5. Fingas MF. The Basics of Oil Spill Cleanup. 2nd ed. Boca Raton, FL: CRC Press; 2000.

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Part III

Oil Analysis and Remote Sensing

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Chapter 4

Measurement of Oil Physical Properties Bruce Hollebone

Chapter Outline 4.1. Introduction 4.2. Bulk Properties of Crude Oil and Fuel Products 4.3. Hydrocarbon Groups 4.4. Quality Assurance and Control

63 63 73 77

4.5. Effects of Evaporative Weathering on Oil Bulk Properties Appendix 4.1

78

85

4.1. INTRODUCTION During any uncontrolled release of oil, the properties of the spilled oil, including the bulk physical property changes due to weathering, must be immediately available, so that models can be used to predict the environmental impacts of the spill and guide the selection of various remediation alternatives. Unfortunately, the properties routinely measured by oil producers and refiners are not the ones that spill responders need to know most urgently. Questions important to responders include the following: l l

l l l l

the physical properties of the oil and how these change over time how the compositional and bulk property changes affect an oil’s behavior and fate whether emulsions will form whether the oil is likely to submerge the hazard to on-site personnel during cleanup the oil toxicity to marine or aquatic organisms

4.2. BULK PROPERTIES OF CRUDE OIL AND FUEL PRODUCTS The physical properties of the almost limitless variety of crude oils are generally correlated with aspects of chemical composition. Some of these key Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10004-8 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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properties for determining the fate and behavior of oil and petroleum products in the environment are viscosity, density, specific gravity (density relative to water), flash point, pour point, distillation, and interfacial tension. These properties for the oils are listed in Table 4.1. Viscosity is the resistance to flow in a liquid. The lower the viscosity, the more readily the liquid flows. The viscosity of an oil is a function of its composition; therefore, crude oil has a wide range of viscosities. For example, the viscosity of Federated oil from Alberta is 5 mPa$s, while a Sockeye oil from California is 45 mPa$s at 15 C . In general, the greater the fraction of saturates and aromatics and the lower the amount of asphaltenes and resins, the lower the viscosity. As oil weathers, the evaporation of the lighter components leads to increased viscosity. As with other physical properties, viscosity is affected by temperature, lower temperatures giving higher viscosities. For most oils, the viscosity varies approximately exponentially with temperature. Oils that flow readily at high temperature can become a slow-moving, viscous mass at low temperature. In terms of oil spill cleanup, viscous oils do not spread rapidly, do not penetrate soils readily, and affect the ability of pumps and skimmers to handle the oil. The dynamic viscosity of an oil can be measured by a viscometer using a variety of standard cup-and-spindle sensors at controlled temperatures. Density is the mass of a unit volume of oil, usually expressed as grams per millilitre (g/mL) or, equivalently, as kilograms per cubic metre (kg/m3). It is used by the petroleum industry to grade light or heavy crude oils. Density is also important because it indicates whether a particular oil will float or sink in water. As the density of water is 1.0 g/mL at 15 C and the density of most oils ranges from 0.7 to 0.99 g/mL, oils typically float on water. As the density of seawater is 1.03 g/mL, even heavier oils will usually float on it. Only a few bitumens have densities greater than water at higher temperatures. However, as water has a minimum density at 4 C and oils will continue to contract as temperature decreases, heavier oils, including heavy crudes and residual fuel oils, may sink in freezing waters. Furthermore, as density increases as the light ends of the oil evaporate off, a heavily weathered oil, long after a spill event, may sink or be prone to overwashing, where the fresh oil, immediately after the spill, may have floated readily. A related measure is specific gravity, an oil’s density relative to that of water. As the densities of both water and oil vary differently with temperature, this quantity can be highly variable. The American Petroleum Institute (API) uses the specific gravity of petroleum at 50 F (15.56 C) as a quality indicator for oil. Pure water has an API gravity of 10. Oils with progressively lower specific gravities have higher API gravities. Heavy, inexpensive oils have less than 25 API; medium oils are 25 to 35API; and light commercially valuable oils are 35 to 45API. API gravities generally vary inversely with viscosity and asphaltene content. Interfacial tensions are the net stresses at the boundaries between different substances. They are expressed as the increased energy per unit area (relative to the bulk materials), or equivalently as force per unit length. The ‘Standard

Chapter | 4

Intermediate Fuel Oil

Bunker C

Crude Oil Emulsion

1,000 to 15,000

10,000 to 50,000

20,000 to 100,000

0.88 to 1.00

0.94 to 0.99

0.96 to 1.04

30 to 50

10 to 30

10 to 20

5 to 15

10 to 15

10 to 30

15 to 30

25 to 30

25 to 35

N/A

80 to 100

>100

>80

5 to 20

>50

Property

Units

Gasoline

Diesel

Light Crude

Viscosity

m.Pa$s

0.5

2

5 to 50

Density

g/mL

0.72

0.84

0.78 to 0.88

50 to 65

35 to 40

27

27

API Gravity Interfacial Tension

mN/m

Heavy Crude 50 to 50,000

Flash Point

C

35

55 to 65

30 to 30

30 to 60

Pour Point

C

N/A

60

55 to 0

30 to 30

10 to 10

0.95 to 1.0

Measurement of Oil Physical Properties

TABLE 4.1 Typical Oil and Fuel Properties at 15 C

65

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International (SI)’ units for interfacial tension are milliNewtons per meter (mN/ m). Surface tension is thought to be related to the final size of a slick. The lower the interfacial tension of oil with water, the greater the extent of spreading and thinner terminal thickness of oil. In actual practice, the interfacial tension alone does not apparently account for spreading behavior; environmental effects and other effects seem to be dominant. The flash point of an oil is the temperature at which the vapor over the liquid can be ignited. A liquid is considered to be flammable if its flash point is less than 60 C. Flash point is an important consideration for the safety of spill cleanup operations. Gasoline and other light fuels can ignite under most ambient conditions and therefore are a serious hazard when spilled. Many freshly spilled crude oils also have low flash points until the lighter components have evaporated or dispersed. On the other hand, Bunker C and heavy crude oils generally are not flammable when spilled. The pour point of an oil is the temperature at which no flow of the oil is visible over a period of 5 seconds from a standard measuring vessel. The pour point of crude oils ranges from 60 C to 30 C. Lighter oils with low viscosities generally have lower pour points. As oils are made up of hundreds of compounds, some of which may still be liquid at the pour point, the pour point is not the temperature at which an oil will no longer pour. The pour point represents a consistent temperature at which an oil will pour very slowly and therefore has limited use as an indicator of the state of the oil. For example, waxy oils can have a very low pour point, but may continue to spread slowly at that temperature and can evaporate to a significant degree.

4.2.1. Density and API Gravity The density of an oil sample, in g/mL, is best measured using a digital density meter following American Society for Testing and Materials (ASTM) method D 5002.1 The instrument is calibrated using air and distilled, deionized water. Acoustically measured densities must be corrected for sample viscosity, as specified by the instrument manufacturer. API gravity (API 82) is calculated using the specific gravity of an oil at 60 F (15.56 C).2 The oil density at 15.56 C can be estimated by exponential extrapolation from the higher (THi) and lower (TLo) data points, if necessary. This is converted to specific gravity by division by the density of water at 15.5 C, using the following equation: s:g:15:56 ¼ rTHi exp

h

.

THi TLo i. THi 15:56 þ In rTHi rðH2 OÞ15:56 In rTHi In rTLo

(1)

where s.g.15.56 is the specific gravity of the oil or product at 15.56 C (60 F), rTLo and rTHi are the measured oil densities at TLo and THi, respectively, and

Chapter | 4

Measurement of Oil Physical Properties

67

r(H2O)15.56 is the density of water at 15.56 C. The API gravity is then determined using the formula (API 82): API ¼ 141:5= s:g:15:56 131:5 (2)

4.2.2. Dynamic Viscosity The dynamic viscosity of an oil sample, in mPa$s or cP, is measured using an enclosed spinning cup viscometer using standard NV and SV1 cup-and-spindle sensors.3 Check standards of pure ethylene glycol and glycerine can be conveniently used to validate the NV and SV1 methods, respectively. From a qualitative observation of the oil, either the NV or the SV1 sensor is chosen to measure the sample. The NV sensor is used for oils with viscosities below 100 mPa$s, and the SV1 sensor, for oils above 70 mPa$s to 10,000 mPa$s. For oils with higher viscosity, measurements must be made on cone and plate or parallel plate instruments (see below). For both cases using the rotary viscometer, the measurement cup is filled with a sample to the edge or the rotating surface. The sensor is mounted onto the instrument, and the sample volume is adjusted to the proper level. The sample is allowed to equilibrate until the sample temperature probe stabilizes at the measurement temperature and remains stable for 5 minutes. Samples and sensors are kept chilled at the appropriate temperature prior to use. For the NV sensor, the rotational shear rate is set at 1,000/s, the SV1 sensor at 50/s. If the oil is observed to be non-Newtonian, single samples are run at shear rates of 1/s, 10/s, and 100/s. In all cases, the sensors are ramped up to speed over a period of 5 minutes. The viscosity is measured for a subsequent 5 minutes, sampled once per second. The viscosity reported is that at time zero of the second, constant-shear rate interval. This may be obtained by the mean of the constant-shear rate interval data or by linear fit to the time-viscosity series if friction-heating has occurred during the measurement. For Newtonian samples, triplicate measurements are averaged and the mean is reported as the absolute or dynamic viscosity. For non-Newtonian samples, viscosities are reported for each of the three shear rates. Viscosities above 50,000 mPa$s are measured on a parallel plate rheometer with an air bearing. Measurement for most oils can be performed with a 35 mm plate/plate geometry at a gap of 2 mm between plates. A stress sweep in forced oscillation mode at 1 Hz performed over an appropriate range will determine the stress independent regions. A creep test can then be performed at a stress value selected in the stable “sol” range of flow response for the material. This provides the zero shear viscosity value.

4.2.3. Surface and Interfacial Tensions Surface and interfacial tensions, in mN/m, are normally determined by one of two methods. The de No€ uy ring is a common technique, used by many laboratories,

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Oil Analysis and Remote Sensing

and has been codified as ASTM method D 971.4 It depends on accurate measurement of the maximum force that a platinum ring can exert on the surface of a liquid before detachment. A second emerging technique that shows much promise for improved speed and accuracy is the pendant/rising drop method, which depends on shape calculations of a droplet of oil in air or water.5,6 The values that are important for spill responders include the oil/air, oil/ water, and the oil/seawater interfacial tensions. The oil/air interfacial tension is often called surface tension. As interfacial tensions are temperature dependent, it is often convenient to determine these quantities for several temperatures. Two measurements at freezing, 0 C, and at ambient temperature, 25 C, allow for a wide range of interpolated values. Measurement at 50 F/15 C also allows determination of common marine temperatures.

€ Ring Determination of Interfacial Tensions De Nouy A measurement apparatus specific to the de No€ uy ring test is required. Manual machines are common, but automated systems are now available that make measurements much quicker and repeatable. All measurement equipment, rings, measurement vessels, transfer, and storage containers must be scrupulously clean before measurement. Surface and interfacial tension measurements are very sensitive to contamination by organic chemicals or salts. For sample/air surface tensions, the instrument is zeroed with the measurement ring in the air. A small amount of sample, approximately 15 mL, is poured into a vessel of sufficient diameter that the wall effects on the meniscus do not affect the area through which the ring will pass. The ring is dipped into the sample to a depth of no more than 5 mm and is then pulled up such that it is just visible on the surface of the liquid. The system is allowed to rest for 30 seconds. The measurement is initiated, terminating when the upward pulling force on the ring just balances the downward force exerted by the liquid. The apparent surface tension, sAPP, is recorded. For sample/water and sample/brine interfacial tensions, the ring is zeroed in the sample at a depth of not more than 5 mm. The ring is removed and cleaned. A volume of water or brine is dispensed into the measurement vessel. The ring is dipped 5 mm into the aqueous phase. A small volume of sample is carefully poured down the side of the vessel wall, with great care taken so as to disturb the aqueous/oil interface as little as possible. The overlying layer should be at least 5 mm thick. The ring is then raised to the bottom on the interface, and the system is allowed to rest for exactly 30 seconds. The measurement is started, and the apparent interfacial tension is recorded, sAPP, when the force balance is reached. The apparent surface tension is corrected for mass of the upper phase lifted by the ring during measurement using the Zuidema and Waters6 correction: sﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ 1:452sAPP 1:679 þ 0:04534 (3) s ¼ sAPP 0:7250 þ C2 ðD dÞ R=r

Chapter | 4

Measurement of Oil Physical Properties

69

where s is the interfacial tension, sAPP is the instrument scale reading, C is the ring diameter, D is the density of the lower phase, d is the density of the upper phase, R is the radius of the du No€ uy ring, and r is the radius of the ring wire. As these measurements depend on temperature, samples, aqueous phases and glassware should be kept at the measurement temperature for a minimum of 30 minutes before a determination is made.

Pendant/Rising Drop Determination of Interfacial Tensions In this test, the interfacial tension is determined by calculation with comparison to the shape of a drop hanging from the end of a needle. A camera is used to photograph a picture of a drop hanging from a needle. The digital picture is analyzed by software; then a parameterized curve shape is developed, from which the surface tension is calculated.6 In the case of a liquideliquid interfacial tension, the surrounding fluid must be clear, so that a good image may be generated. For oil in water, this requires that the oil be suspended in water. However, as most oils are less dense than water, the rising oil bubble, rather than the pendant drop, must be measured. In this case, the image is inverted in software and, instead of the force of gravity, the buoyant force, determined as the fraction of gravity based on the specific gravity of the oil is used: b ¼ gðrwater roil Þ=rwater

(4)

where b is the buoyant force, g is the acceleration due to gravity, rwater is the density of water at the measurement temperature, and roil is the oil density.

4.2.4. Flash Point The flash point of an oil product can be determined by several methods, depending on the oil product and the quantity available. Lower viscosity products, including light fuel oils and most fresh crudes, are measured by the Tag closed-cup method. This follows ASTM method D 1310.7 Though accurate, the Tag method uses a comparatively large volume of oil, 50 to 70 mL. Smaller volumes, 1e2 mL, can be measured by ASTM D6450.8 The practical working range of these two methods is e10 C to approximately 100 C. With subambient cooling, using dry ice baths and/or liquid nitrogen baths, much lower flash point temperatures can be measured, but this is often not necessary for emergency response considerations. Heavier products, including intermediate and heavy fuel oils, can be measured by a Pensky-Martins analyzer, following ASTM D 93.9 As with the Tag method, this method uses 50e70 mL of crude oil. Smaller volumes can be used with the newer method ASTM D7094, which uses only 2 mL of oil.10 The working range for these heavier type tests is approximately 50 C to 225 C.

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PART | III

Oil Analysis and Remote Sensing

The standard test material for assuring quality control for a lowertemperature flash point apparatus historically has been para-xylene; however, heavier normal alkane standards, n-decane, n-undecane, n-tetradecane, and n-hexadecane have also been found to be suitable and offer a wider range of test temperatures.11

4.2.5. Pour Point The pour point of an oil sample, in degrees Celsius, can only be determined by following ASTM method D 97.12 Sample aliquots are poured into ASTMapproved jars, stopped and fixed with ASTM-certified thermometers. The temperature regime described in the standard is critical; particularly in waxy oils, with high normal alkane contents, a crust of waxy crystals can form on the surface of the oil as it cools. The ASTM D 97 heating and cooling process for oil is designed to ensure that the formation of these microstructures does not interfere with reproducible measurement of the pour point.

4.2.6. Sulphur Content The mass fraction of atomic sulphur in oil is conveniently determined using X-ray fluorescence closely following ASTM method D 4294.13 In brief, the method is as follows: approximately 3 g of oil is weighed out into standard 31 mm XRF cells. The sealed cells are then measured in an XRF spectrometer. The spectrometer response is calibrated using a series of certified reference material standards. Spectra should be corrected for interference by chlorine by subtraction, based on a calibration curve established by the certified reference materials. Matrix effects, X-ray absorption by the base oil, can be corrected by subtraction of a spectrum of an oil free of sulphur, such as a mineral or lubricating oil.

4.2.7. Water Content The mass fraction of water in oil or an emulsion, expressed as a percentage, is best determined by Karl Fischer titration, using ASTM method D 4377.14 The Karl Fischer reaction is an amine-catalyzed reduction of water in a methanolic solution: CH3 OH þ SO2 þ RN/½RNHþ þ ½SO3 CH3 2RN þ H2 O þ I2 þ ½RNHþ ½SO3 CH3 /½RNHþ ½SO4 CH3 þ 2½RNHþ I

(5)

The amine, RN, or mixture of amines is proprietary to each manufacturer. An aliquot of approximately 1 g of oil is accurately weighed, then introduced to the reaction vessel of the autotitrator. A solution of 1:1:2 (by volume) mixture of methanol:chloroform:toluene is used as a working fluid.

Chapter | 4

Measurement of Oil Physical Properties

71

4.2.8. Evaluation of the Stability of Emulsions Formed from Brine and Oils and Oil Products Water-in-oil emulsions are formed in 2.2-liter fluorinated vessels on an endover-end rotary mixer at a rotational speed of 50 RPM.15,16 1. 600 mL of salt water (3.3% w/v NaCl) is placed in each mixing vessel. 2. 30 mL of oil is added to each vessel for a 1:20 oil:water ratio. 3. The vessels are sealed and placed in the rotary mixer such that the cap of each mixing vessel follows, rather than leads, the direction of rotation. The rotary mixer is kept in a temperature-controlled cold room at 15 C. 4. The vessels and their contents are allowed to stand for approximately 4 hours before rotation begins, then mixed continuously for 12 hours. 5. At the conclusion of the mixing time, the emulsions are collected from the vessels for measurement of water content, viscosity, and the complex modulus. The emulsions are stored at 15 C for one week, then observed for changes in physical appearance. Water content for the emulsions should be determined. The Karl-Fischer titration method works well for all types of emulsion and watereoil mixtures. The complex modulus of the emulsion is measured on a rheometer using a 35 mm plate-plate geometry. A stress sweep is performed in the range 100 to 10,000 mPa in the oscillation mode at a frequency of 1 Hz. The complex modulus value in the linear viscoelastic region is reported.

4.2.9. Evaluation of the Relative Dispersability of Oil and Oil Products This method determines the relative ranking of effectiveness for the dispersibility of an oil sample by to a dispersant test mixture. It is used either to determine the effectiveness of a dispersant product for a standard crude oil or to test the dispersability of a crude oil against a standard dispersant. This method follows ASTM F 2059 closely.17 A premix of 1:25.0 dispersant:oil is made up by adding oil to 100 mg of dispersant (approximately 2.50 mL of oil in total). Six ASTM-standard swirling conical flasks modified with side spouts, containing 120 mL of 33& brine, are placed into an incubator-shaker. An aliquot of 100 mL of premix is added to the surface of the liquid in each flask, care being taken not to disturb the bulk brine. The flasks are mechanically shaken at 20.0 C with a rotation speed of 150 rpm for exactly 20 minutes. The solutions are allowed to settle for 10 minutes. Using the side spout, 30 mL of the oil-in-water phase is transferred to a 250 mL separatory funnel, first clearing the spout by draining 3 mL of liquid. The 30 mL aliquot is extracted with 35 mL of 70:30 (v:v) dichloromethane:pentane, collected into a 25 mL graduated cylinder.

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PART | III

Oil Analysis and Remote Sensing

A Gas Chromatograph-Flame Ionization Detector (GC/FID) is used to determine the oil concentration in the solvent. A 900 mL aliquot of the 15 mL solvent extract is combined with 100 mL of internal standard (200 ppm of 5-aandrostane in hexane) in a crimp-top injection vial and shaken well. The total petroleum hydrocarbon content of the sample is quantified by the internal standard method using the total resolved peak area and the average hydrocarbon response factor over the entire analytical range: RPH ¼ ATOTAL =AI:S: =RRF 20 15 120=30=0:9

(6)

where RPH is the resolved petroleum hydrocarbon (mg/mL), ATOTAL is the total resolved peak area, AI.S. is the internal standard peak area, and RRF is the relative response factor for a series of alkane standards covering the analytical range. The method is calibrated using a series of six oil-in-solvent mixtures prepared from the premix for each oil. The volume of premix dispersant/oil solution for each standard is selected to represent a percentage efficiency of the dispersed oil. The volume of the premix is then carefully applied to the surface of the brine in a shaker flask and shaken exactly as one of the samples, as described previously. Upon removal from the shaker however, the entire contents of the flask is transferred to the separatory funnel. This is extracted with 3 20 mL of 70:30 (v:v) dichloromethane:pentane and made up to 60 mL. Chromatographic quantitation is then performed using the formula: RPH ¼ ATOTAL =AI:S: =RRF 20 60 120=120=0:9

(7)

The RPH values as a function of % effectiveness for the calibration standards are plotted. The sample RPH values are then used to determine the percentage effectiveness of the dispersant. Note that these effectiveness percentages are not expected to correlate to real-world dispersabilities. It is important to remember that these values are relative rankings only.

4.2.10. Adhesion to Stainless Steel Adhesion to stainless steel is useful to responders in order to judge the “stickiness” of oil to certain drum skimmer configurations. Environment Canada has developed a quantitative test for this purpose.18,19 An analytical balance is prepared by hanging an ASTM method D 6 standard penetrometer needle from the balance hook and allowing the apparatus to stabilize and tare. Approximately 80 mL of oil sample is poured into a 100 mL beaker. The beaker is elevated until the oil reaches the top of the stainless steel needle. Care is taken not to coat the brass segment of the needle. The needle rests for 30 seconds immersed in the oil. The beaker is lowered until the needle is clear of the oil. The system is left undisturbed, closed inside a draft shield. After 30 minutes, the weight of the oil adhering to the needle is recorded. The

Chapter | 4

Measurement of Oil Physical Properties

73

mass of the oil divided by the surface area of the needle is the adhesion of the oil in g/cm2. Typically, four measurements are taken for each oil sample and the mean reported as the final value.

4.3. HYDROCARBON GROUPS The fate and behavior of crude oils and petroleum products are strongly determined by their chemistries. The main constituents of oils can be grouped into four categories: saturated hydrocarbons (including waxes), aromatics, resins, and asphaltenes. Saturates: A group of hydrocarbons composed of only carbon and hydrogen with no double bonds or aromaticity. They are said to be “saturated” with hydrogen. They may by straight-chain (normal), branched, or cyclic. Typically, however, the group of “saturates” refers to the aliphatics generally including alkanes, as well as a small amount of alkenes. The lighter saturates, those less than ~C18, make up the components of an oil most prone to weathering. The larger saturates, generally those heavier than C18, are termed waxes. Aromatics: These are cyclic organic compounds that are stabilized by a delocalized p-electron system. They include such compounds as BTEX (benzene, toluene, ethylbenzene, and the three xylene isomers), polycyclic aromatic hydrocarbons (PAHs, such as naphthalene), and some heterocyclic aromatics such as the dibenzothiophenes. Benzene and its alkylated derivatives can constitute several percent in crude oils. PAHs and their alkylated derivatives can also make up as much as a percent in crude oils. Resins: This is the name given to a large group of polar compounds in oil. They include heterosubstituted aromatics (typically oxygen- or nitrogencontaining PAHs), acids, ketones, alcohols, and monoaromatic steroids. Because of their polarity, these compounds are more soluble in polar solvents than the nonpolar compounds, such as waxes and aromatics, of similar molecular weight. Asphaltenes: A complex mixture of very large organic compounds that precipitate from oils and bitumen by natural processes. For the purposes of this method, asphaltenes are defined as the fraction that precipitates in n-pentane. The separation of petroleum and its products into these four characteristic groups is known as fractionation. The quantification of the groups is often referred to as SARA analysis, an acronym of the characteristic groups: saturates, aromatics, resins, and asphaltenes. Historically, many techniques have been used to perform this separation, including distillation, solvent precipitation (ASTM D6560)20, treatment with strong acids (ASTM D2006)21, adsorption (ASTM D2007 and D4124)22,23, and thin-layer chromatography.24 For reviews of the methods, see Speight and Becker.24-26 While excellent methods for the determination of the SARA groups have been developed using thin-layer chromatograph (TLC), there has been continuing interest in alternate

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test methods based on solvent separation and adsorption techniques.22-24 Gravimetric methods are typically based on the solubilities of the groups in n-pentane, hexane/benzene, and methanol.3 Such methods can rely on gravimetric determinations of all components, including the saturate and aromatic groups. However, the drawback of such methods is that they contain significant volatile components. This is particularly true of crude oils and lighter fuels. More sophisticated methods rely on a combination method involving determination of the saturate and aromatic fractions by gas chromatography, an adaptation of total petroleum hydrocarbon methods, while gravimetrically determining the nonvolatile resin and asphaltene components.27,28

Resin and Asphaltene Gravimetric Determination A 100 mL quantity of n-pentane is added to a preweighed sample of approximately 5 g of oil. The flask is shaken well and allowed to stand for 30 minutes.27 The sample is filtered through a 0.45 mm membrane using a minimum of rinsings of n-pentane. The precipitate is allowed to dry, then weighed. The weight of the precipitate as a fraction of the initial oil sample weight is reported as the percentage asphaltenes. The filtrate from the precipitation, the “maltene” fraction, is recovered and made up to 100 mL with n-pentane. A 15 g, a 1 cm diameter column of activated silica gel is prepared. The top of the column is protected by a 1 cm layer of sodium sulphate. A 5 mL aliquot of the maltene fraction is loaded onto the column. A 60 mL volume of 1:1 (v:v) benzene:hexane is eluted through the column and discarded. A 60 mL volume of methanol, followed by a 60 mL volume of dichloromethane, are eluted through the column and combined. The methanol/dichloromethane fractions are reduced by rotary evaporation and blown down to dryness under nitrogen. The mass fraction of this dried eluent, compensating for the volume fraction used, is reported as the percentage of resins in the sample. Resin and Asphaltene Thin-Layer Chromatography Determination While no standard method for this technique exists, it has the advantages over the gravimetric methods of being much faster, requiring much less oil or product and being more reproducible. It has the disadvantage of requiring a sophisticated instrument, a TLC with a flame ionization detector (FID). A TLC that quantifies analytes developed on silica gel-coated glass rods, such as the Iatroscan Mark 6, is necessary for this method. Briefly, an aliquot of sample dissolved in dichloromethane at a concentration of 1 mg/mL is spotted at a point, the origin, near one end of a rod, the foot of the rod. The rods are then developed by immersion of the feet into a series of solvents to separate the four hydrocarbon groups. The origin points must remain above the liquid surface, but the feet of the rods must be immersed sufficiently to cause solvent to travel up the rods by capillary action.

Chapter | 4

Measurement of Oil Physical Properties

75

The first solvent used is n-hexane to develop the saturates. Toluene develops the aromatics. Finally, a 95% dichloromethane, 5% methanol mixture is used to develop the resins. The asphaltenes remain at the spotting origin. The hydrocarbon groups that are not quantified by this method, the saturates and aromatics, are removed by pyrolysis. A known standard is then applied to the chromarod and then quantified using an FID and an internal standard. A sample of 1 octadecanol at 1 mg/mL concentration is a convenient internal standard. This is spotted on the rod just prior to measurement, on the part of the rod pyrolyzed to remove the saturate and aromatic fractions. The development of the chemicals on the rods critically depends on the conditions. The rods must be developed in tanks to control the vapors in atmosphere. Also, temperature and humidity must remain as consistent as possible in order to achieve reproducible results. When drying after each development, the rods must rest in a controlled humidity chamber. Resin and asphaltene contents are determined as follows: %Resin ¼ CIS VIS AR =AIS

(8)

%Asphaltene ¼ CIS VIS AA =AIS

(9)

where: CIS: Internal standard concentration VIS: Internal standard volume AIS: Internal standard area from TLC integration AR: Resin area from TLC integration AA: Asphaltene area from TLC integration Note that while saturate and aromatic fractions are separated by the development process and could, in principle, be measured by TLC-FID, the drying process between development stages requires significant evaporation. This level of evaporation is significant enough to remove most of the volatile components, which includes a large fraction of both saturates and aromatics (but not the resins or asphaltenes). For this reason, this TLC-FID method is not suitable for saturate or aromatic determination.

Saturate and Aromatic Chromatographic Determination This method is adapted and simplified from a previously published method for crude oil and petroleum product determination.28 An 80 mg/mL solution of oil is prepared in hexane. A 3.0 g column of activated silica-gel is prepared, topped with 0.5 cm anhydrous sodium sulphate. The column is conditioned with 20 mL of hexane. An amount of 200 mL of the oil solution, approximately 16 mg of oil, is quantitatively transferred onto the column using an additional 3 mL of hexane to complete the transfer. The eluent is also discarded. Just prior to exposure of

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Oil Analysis and Remote Sensing

the sodium sulphate to the air, 12 mL of hexane is added to the column. The eluent is labeled fraction “F1.” F1 is considered to contain all the saturates, including the waxy components in the oil. The column is then eluted with 15 mL of 1:1 (volume:volume) benzene/ hexane or dichloromethane/hexane. The eluent is collected and labeled fraction “F2.” F2 is considered to contain the aromatic compounds in the oil, including the BTEX compounds, other alkylated benzene species, PAHs, and the alkylated PAH homologues. Half of fractions F1 and F2 are combined. This composite fraction is labeled “F3.” This fraction is used for analysis of total petroleum hydrocarbons (TPH). All the three fractions are concentrated under dry nitrogen. The fractions are then spiked with the internal standard, 100 mL of 200 ppm 5-a-androstane, and made up with hexane to 1 mL. The analysis for total petroleum hydrocarbons and saturates is performed by high-resolution capillary GC/FID using the following conditions: Column: Carrier Gas: Injection volume: Injector temperature: Detector temperature: Oven program:

30 m 0.32 mm ID HP DB5-HT fused silica column (0.10 mm film thickness); Helium, 3.0 mL/min, constant flow; 1.0 mL; 290 C; 325 C; 40 C for 2 minutes, followed by 25 C/minute to a final temperature of 340 C, then held for 15 minutes. The total run time is 29 minutes.

To calculate the concentration of hydrocarbons in each fraction, the area response attributed to the petroleum hydrocarbons must be determined. This area includes all of the resolved peaks and unresolved “hump.” This total area must be adjusted to remove the area response of the internal standards and GC column bleed. Column bleed is the reproducible baseline shift that occurs during the oven cycle of the GC. To determine this area, a hexane blank injection is analyzed before and after every 10 samples to determine the baseline response. The integration baseline is then set at a stable reproducible point just before the solvent peak. This baseline area for the blank run is subtracted from the actual sample run. The total areas of the chromatograms of F1, F2, and F3 are obtained by integration of all peaks, corrected by removal of the baseline. The area response attributable to the internal standard is calculated. The F3 fraction is used to calculate the TPH values for the oil.28 The F1 and F2 fractions are used to calculate the total saturate (TSH) and total aromatic (TAH) contents. Note that TPH should be within 10% of TSH þ TAH.

Chapter | 4

Measurement of Oil Physical Properties

77

As not all the oil is passed through the GC column, a simple sum of TSH, TAH, resin, and asphaltene contents will not equal 100%. This missing portion of the oil, which does not precipitate or get analyzed by the GC method, is approximated by proportionally dividing it into the saturate and aromatic portions. Thus the saturate content of the oil is commuted using: % Saturates ¼ TSH=ðTSH þ TAHÞð1 % Asphaltenes % ResinsÞ (10) Likewise, the aromatic content is computed using: % Aromatic ¼ TAH=ðTSH þ TAHÞð1 % Asphaltenes % ResinsÞ (11) Note that the asphaltene and resin contents may be determined by either gravimetric or TLC-FID method described earlier. For crude oils or products with high water content, it is necessary to dry the sample prior to the gravimetric determination of the hydrocarbon group contents. If a Karl-Fischer water content determination can be made, then the composition of the original product can be reported and adjusted for the observed water content. If not, the values should be reported as for dried product only.

4.4. QUALITY ASSURANCE AND CONTROL Most of the physical property methods described here rely on a single instrument and involve a simple measurement with little sample manipulation.28 For these methods, the instruments are calibrated as directed by the manufacturer or the appropriate ASTM method with chemical and/or gravimetric standards as appropriate. In addition, instrumental and operator performance should be monitored by periodic measurement of check standards. A control chart should be kept for each procedure, for the check or performance standard measurements. The check standard measurements are monitored closely. Failure of the check standard measurement to fall within the smaller of either a historical 95% confidence limit or the appropriate ASTM required repeatability should result in an investigation of the procedure. This typically includes required instrument maintenance, cleaning, recalibration, and measurement of the check standard until the desired precision and accuracy is reached. The chromatographic methods described here, including the dispersability tests and the hydrocarbon group analysis, involves significant sample preparation, followed by a measurement by gas chromatography. Such techniques require a higher level of effort to maintain quality assurance. Check or surrogate samples of either pure materials or certified reference standards should be processed in the same manner as the samples. Calibration should be accomplished with a second, separate set of certified reference materials. Internal standards should also be certified reference materials from reputable suppliers. Surrogate recovery, calibration stability, and internal standard response control charts should all be checked regularly to ensure procedure

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and measurement accuracy. Chromatograms should be checked to ensure that chromatographic quality, including good peak shape, baseline drift, column bleed, sample carryover, and chromatographic resolution are within acceptable limits.

4.5. EFFECTS OF EVAPORATIVE WEATHERING ON OIL BULK PROPERTIES Long experience has shown that the physical characteristics and chemical fingerprint of a crude oil can change greatly over the course of a spill incident. These changes have a profound effect on the fate, behavior, and effects of an oil in the environment. The oil may transmute to other states, evaporating, dissolving in water, or condensing to a semisolid residue, each new state having unique behaviors and eventual fates. In order to aid in the estimation and prediction of spill behavior, it is useful to know not only the characteristics of the fresh crude oil, but also those of oils at different stages of “weathering” in the environment. Previous work has shown that immediately after a spill, the dominant process of oil weathering is evaporation. The following discussion focuses on the effects of evaporative weathering on changes of oil physical properties and chemical compositions.

4.5.1. Weathering When oil is spilled, on either water or land, a number of transformation processes operate on the oil. In general, there are two types of transformation processes: the first is weathering, and the second is a group of processes (including spreading, movement of oil slicks, and sinking and ove-washing) related to the movement of oil in the environment. Weathering and movement processes overlap, with weathering strongly influencing how oil moves in the environment and vice versa. These processes depend very much on the type of oil spilled and the weather conditions during and after the spill. Thoroughly understanding the behavior of spilled oil in the environment is extremely important for development of oil spill models. Today’s sophisticated spill models combine the latest information on oil fate and behavior with computer technology to predict where the oil will go, what state it will be in, and when it gets there. “Weathering” is the term referring to a combination of a wide variety physical, chemical, and biological processes of a spilled oil in the environment. The weathering processes include evaporation, emulsification, natural dispersion, dissolution, microbial degradation, photo-oxidation, and other processes such as sedimentation, and oil-suspended particle interactions. Weathering has a very significant effect on most bulk oil properties. Unlike the chemical compositions, however, where environmental parameters only affect the rate and type of weathering, bulk properties of the oil are also highly variable depending on the physical conditions. The most important of these is

Chapter | 4

Measurement of Oil Physical Properties

79

temperature, but other factors such as pressure and the materials with which the oil is in contact also play a role. As an oil loses mass and changes in composition, several general trends in physical property changes can be observed: l

l

l

Density increases approximately linearly with increasing weathering. Density decreases approximately linearly with temperature. Viscosity increases with increasing weathering, but a simple functional relationship is not easy to develop. Viscosity increases approximately exponentially with decreasing temperature. Surface and interfacial tensions tend to increase slightly with increasing weathering.

4.5.2. Preparing Evaporated (Weathered) Samples of Oils A common technique for simulating weathering in the laboratory is evaporation. While this is only one of the possible processes in the natural environment, it is probably the dominant one for most spills, particularly in the first few hours or days following a spill. A laboratory oil-weathering technique by rotary evaporation allows for convenient preparation of artificially weathered oils with varying degrees of weight loss. A typical oil-weathering system consists of a rotary evaporator. The bath temperature of the evaporator should be variable from 20 C to 100 C 0.5 C. The rotation speed should be continuously variable from 10 to 135 rpm. The following evaporation procedure is used to evaporate oils: (1) The water bath is brought to a temperature of 80 C. (2) The empty rotary flask is weighed, and no more than one-third the volume of the rotary flask in oil is added and the flask reweighed. (3) The flask is mounted on the apparatus and the flask partially immersed in the water bath and spun at high speed, at least 120 rpm. A constant flow of air through the apparatus should be maintained by a vacuum pump. (4) At set intervals, the sample flask is removed and weighed. It is convenient to prepare two to three weathered samples for each type of oil measured. With a moderate flow rate through the instrument, a duration of 48 hours evaporation will come close, within 5 to 10%, to simulating the eventual final state of an oil in the environment. Intermediate fractions of approximately one- and two-thirds of the 48-hour loss by weight will simulate approximately the condition of the oil after a few hours to days and a few days to weeks of natural evaporation. The exact time taken to prepare these intermediate fractions is determined by estimation from the measured fractional mass-loss as a function of time for the 48-hour sample. The fraction mass-loss is calculated as: % weathering ¼ ðmi mf Þ=ðmi me Þ x 100%

(12)

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PART | III

Oil Analysis and Remote Sensing

where % weathering is the percentage evaporative mass-loss over the 48-hour period, mi is the initial mass of the flask and oil, mf is the final mass of the flask and oil, and me is the mass of the empty flask. A graph of % weathering as a function of time is plotted using the interval weighing data. The times for one-third (t1/3) and two-thirds (t2/3) of the 48-hour mass loss are interpolated from a time-weathering graph. Typical times for t1/3 range from 30 minutes to 2 hours, for t2/3, 8 to 12 hours. This technique allows for precise control of the evaporative weight loss for a target oil and can be directly correlated to bulk property and compositional changes of the weathered oil. By tracking weight loss as a function of time, an equation for predicting evaporation can be found. Also, from this same graph, it is possible to determine a point at which the evaporation rate is sufficiently slow that the oil may be considered to have achieved the maximum evaporative loss likely to be observed under the conditions of a marine spill. 0.94

0.94

Cook Inlet 2003 vs.T

Density (g/mL)

0.92

Cook Inlet 2003 0.92

0.90

25.0%

0.88

11.4%

0.86 Fresh 0.84 0.82

vs.W(%)

34.4%

Density (g/mL)

(a)

0.90 0.88 0.86

5 °C 15 °C

0.84 30 °C 0.82

0

5

10

15

20

25

30

0.80

35

0

10

Temperature (°C)

(b) 1.02

40

Platform Elly vs.W(%) 1.00

0.98

13.3% 7.9% 4.6%

0.96

Density (g/mL)

1.00

Density (g/mL)

30

1.02

Platform Elly vs.T

0.98 5 °C 0.96

Fresh 0.94

20

Weathering (%)

0

5

10

15

20

25

Temperature (°C)

30

35

15 °C 30 °C

0.94

0

2

4

6

8

10

12

14

Weathering (%)

FIGURE 4.1 Density versus temperature and weathering for a light (Cook Inlet) (a) and heavy (Platform Elly) (b) crude oil.

Chapter | 4

81

Measurement of Oil Physical Properties

4.5.3. Quantifying Equation(s) for Predicting Evaporation The evaporation kinetics are determined for each oil by measuring the weight loss over time from a shallow dish.30,31 Approximately 20 g of oil is weighed into a 139 mm petri dish. The oil weight is recorded by an electronic balance accurate to 0.01 g at set intervals and collected on a computer logging system. Measurements are conducted in a climate-controlled chamber at 15 C. Temperatures are monitored by a digital thermometer. The evaporation period can last from a few days for light oils to weeks for heavier products. The time versus weight-loss data series are fitted to a set of simple equations. The best curve-fit is chosen as the equation for predicting evaporation.

Effects of Evaporative Weathering on Crude Oil Density Densities of oils typically increase approximately 5 to 10% as oil weathers. Cook Inlet, a light oil, changes from 0.84 g/mL to 0.91 g/mL at 30 C (see 10000

10000

Cook Inlet 2003 vs.W(%)

1000

Viscosity (mPas)

Viscosity (mPas)

Cook Inlet 2003 vs.T

100 34.4% 25.0% 10

1000

100

10

11.4% Fresh

1

0

5

10

15

20

25

30

5 °C 15 °C 30 °C

1

35

0

10

1e+7

1e+5 13.3% 1e+4

7.9% 4.6%

1e+3

Fresh

0

5

10

15

20

25

Temperature (°C)

30

35

1e+6

Viscosity (mPas)

Viscosity (mPas)

30

40

1e+7

Platform Elly vs.T

1e+6

1e+2

20

Weathering (%)

Temperature (°C)

Platform Elly vs.W(%)

1e+5

1e+4

1e+3

1e+2

5 °C 15 °C 30 °C

0

2

4

6

8

10

12

14

Weathering (%)

FIGURE 4.2 Viscosity versus temperature and weathering for light (Cook Inlet) and heavy (Platform Elly) crude oils.

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Oil Analysis and Remote Sensing

Figure 4.1a), while Platform Elly, a very heavy crude oil, has a fresh density of 0.9531 g/mL and increases to 0.9843 g/mL in its most weathered state at 30 C (Figure 4.1b). From Figure 4.1, it can be seen that, to a first approximation,

30

34.4%

29

25.0%

28 27 26

Fresh

25 0

5

10

15

20

25

30

34 o/w

vs.T

32 30 28 26

34.4% 25.0%

24 22

11.4% Fresh 0

5

10

15

20

25

30

35

34

vs.T

o/b

32 30 28 26 24

34.4% 25.0% 11.4%

22

Fresh

20

0

5

10

15

20

25

Temperature (°C)

30

35

31

Cook Inlet 2003 vs.W(%) o/a

5 °C 15 °C

30

30 °C

29 28 27 26 25 24

35

Interfacial Tension (oil/water) (mN/m)

Interfacial Tension (oil/water) (mN/m)

11.4%

Surface Tension (oil/air) (mN/m)

31

24

Interfacial Tension (oil/3.3%brine) (mN/m)

32

Cook Inlet 2003 vs. T o/a

Interfacial Tension (oil/3.3%brine) (mN/m)

Surface Tension (oil/air) (mN/m)

32

30 °C 15 °C 5 °C 0

10

20

30

40

34

vs.W(%)

o/a

32 30 28 26

5 °C 15 °C

24 30 °C 22

0

10

20

30

40

34

vs.W(%)

32

o/b

30 28 26 24

5 °C 15 °C

22 30 °C 20

0

10

20

30

40

Weathering (%)

FIGURE 4.3 Surface and interfacial tensions as a function of temperature and weathering for Cook Inlet (2003).

Chapter | 4

Measurement of Oil Physical Properties

83

density increases linearly with increasing mass-loss and decreasing temperature. Better extrapolations can be made from log-log extrapolations of both quantities. Note that the uncertainties in density are very small: 0.0002 g/mLdapproximately 1 part in 5,000.

Effects of Evaporative Weathering on Crude Oil Viscosity In contrast to most other physical properties, the viscosity of an oil can change by orders of magnitude with weathering and changes in temperature. For example, the viscosity of Cook Inlet (2003) changes from 5.8 mPa s to 67.0 mPa s at 30 C (see Figure 4.2), while fresh Platform Elly has a viscosity of 1070 mPa s, and reaches 52280 mPa s in the most weathered fraction (Figure 4.3). As can be seen from the logarithm of viscosity is roughly inversely linear with temperature, but the effects of weathering on viscosity are more complex. Uncertainties in viscosity are 5%. Effects of Evaporative Weathering on Crude Oil Surface and Interfacial Tensions Surface and interfacial tensions have no simple quantitative relationships in general to either the degree of weathering or the temperature. Surface tensions however, do not vary greatly from oil to oil; values from 25 mN/m to 32 mN/m are typical for almost all types of oil. Interfacial tensions for oil/water and oil/ 3.3% brine are often marginally lower than the corresponding oil/air surface tension. Oil/brine interfacial tensions are usually somewhat higher than the corresponding oil/(pure) water values. Typical values for both range from 18 mN/m to 32 mN/m. Surface and interfacial tensions tend to decrease with temperature and increase with weathering. Care should be taken not to overinterpret the significance of surface and interfacial tension values; however, the errors on these measurements are relatively large, 15%, and the relative variations of the values are fairly small.

REFERENCES 1. ASTM D 5002. Standard Test Method for Density and Relative Density of Crude Oils by Digital Density Analyzer. Conshohocken, PA: American Society for Testing and Materials (ASTM); 2009. 2. API 82. American Petroleum Institute (API), Petroleum Measurement TablesdVolume XI/XII. West Conshohocken, PA: American Society for Testing and Materials; 1982. 3. Jokuty P, Fingas M, Whiticar S. Oil Analytical Techniques for Environmental Purposes. AMOP 1994;245. 4. ASTM D 971. Standard Test Method for Interfacial Tension of Oil Against Water by the Ring Method. West Conshohocken, PA: American Society for Testing and Materials; 2009. 5. Jokuty P, Fingas M, Whiticar S, Fieldhouse B. A Study of Viscosity and Interfacial Tension of Oils and Emulsions, Manuscript Report EE-153, Ottawa, ON: Environment Canada, 1995.

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6. Song B, Springer J. Determination of Interfacial Tension from the Profile of a Pendant Drop Using Computer-aided Image Processing. Colloid Interface Sci. 1996;64. 7. ASTM D1310. Standard Test Method for Flash Point and Fire Point of Liquids by Tag Open-Cup Apparatus. West Conshohocken, PA: American Society for Testing and Materials; 2007. 8. ASTM D 6450. , Standard Test Method for Flash Point by Continuously Tester. West Conshohocken, PA: American Society for Testing and Materials; 2009. 9. ASTM D 93. American Society for Testing and Materials (ASTM), Standard Test Method for Flash Point by Pensky-Martens Closed Cup Tester. West Conshohocken, PA: American Society for Testing and Materials; 2009. 10. ASTM D 7094. Standard Test Method for Flash Point by Modified Continuously Closed Tester. West Conshohocken, PA: American Society for Testing and Materials; 2009. 11. Montemayor RG, Rogerson JE, Colbert JC, Schiller SB. Reference Verification Fluids for Flash Point Determination. J. Test. Eval. 1999;27. 12. ASTM D 97. Standard Test Method for Pour Point of Petroleum Oils. West Conshohocken, PA: American Society for Testing and Materials; 2009. 13. ASTM D 4294. Standard Test Method for Sulfur in Petroleum Products by Energy-Dispersive X-ray Fluorescence Spectroscopy. West Conshohocken, PA: American Society for Testing and Materials; 2009. 14. ASTM D 4377. Standard Test Method for Water in Crude Oils by Potentiometric Karl Fischer Titration. West Conshohocken, PA: American Society for Testing and Materials; 2009. 15. Fingas M, Fieldhouse B, Mullin J. Studies of Water-in-oil Emulsions: Stability and Oil Properties. AMOP 1998;1. 16. Fingas M, Fieldhouse B. Studies on Crude Oil and Petroleum Product Emulsions: Water Resolution and Rheology. Colloids Surf. A. 2009;67. 17. ASTM F 2059. Standard Test Method for Laboratory Oil Spill Dispersant Effectiveness Using the Swirling Flask. West Conshohocken, PA: American Society for Testing and Materials; 2007. 18. Jokuty P, Whiticar S, McRoberts K, Mullin J. Oil Adhesion TestingdRecent Results. AMOP 1996;9. 19. ASTM D 5. Standard Test Method for Penetration of Bituminous Materials. West Conshohocken, PA: American Society for Testing and Materials; 2009. 20. ASTM D 6560. Standard Test Method for Determination of Asphaltenes (Heptane Insolubles) in Crude Petroleum and Petroleum Products. West Conshohocken, PA: American Society for Testing and Materials; 2006. 21. ASTM D 2006. Method of Test for Characteristic Groups in Rubber Extender and Processing Oils by the Precipitation Method (Withdrawn 1975). West Conshohocken, PA: American Society for Testing and Materials; 1965. 22. ASTM D 2007. American Society for Testing and Materials (ASTM), Standard Test Method for Characteristic Groups in Rubber Extender and Processing Oils and Other PetroleumDerived Oils by Clay-Gel Absorption Chromatographic Method. West Conshohocken, PA: American Society for Testing and Materials; 2007. 23. ASTM D 4124. Standard Test Methods for Separation of Asphalt into Four Fractions. West Conshohocken, PA: American Society for Testing and Materials; 2006. 24. Barman BN. Hydrocarbon-Type Analysis of Base Oils and Other Heavy Distillates by ThinLayer Chromatography with Flame-Ionization Detection and by the Clay-Gel Method. J. Chromat. Sci. 1996;219. 25. Speight JG. The Chemistry and Technology of Petroleum. New York: Marcel Dekker; 2007. 26. Becker JR. Chapter 13, Asphaltene Test Methods, Crude Oil Waxes, Emulsions and Asphaltenes. Tulsa, OK: Penn Well Publishing Co; 1991.

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27. Hollebone B, Wang Z, Landriault M, Smith P. A New Method for the Determination of the Hydrocarbon Groups in Oils: Saturates, Aromatics, Resins, and Asphaltenes (SARA). AMOP 2003;31. 28. Wang ZD, Fingas M, Li K. Fractionation of ASMB Oil, Identification and Quantitation of Aliphatic Aromatic and Biomarker Compounds by GC/FID and GC/MSD (Parts I and II). J. Chromat. Sci. 1994;361. 29. Environment Canada, Oil Properties Database, http://www.etc-cte.ec.gc.ca/databases/ OilProperties/oil_prop_e.html, accessed May 2010. 30. Fingas M. The Evaporation of Oil Spills. AMOP 1995;43. 31. Fingas M. Modeling Evaporation Using Models That Are Not Boundary-Layer Regulated. J. Haz. Mat. 2004;27.

APPENDIX 4.1 Table A4.1 gives the environmentally relevant properties of selected crude oils. TABLE A4.1 Environmentally-Relevant Properties of Selected Crude Oils29 Alaska North Slope Prudhoe Bay, Alaska, USA

Saudi Arabia

Mississippi Brent Canyon Blend Federated Block 807 Gulf of North Mexico, Sea, United Alberta, Louisiana, USA Kingdom Canada

Arabian Light

West Texas Intermediate

Texas USA

0 C

0.8777

0.8776

0.8472

0.8413

0.9310

0.8594

15 C

0.8663

0.8641

0.8351

0.8293

0.9461

0.8474

30.89

31.30

37.8

38.9

17.5

34.38

0 C

23.2

32.6

16

10

88.1

19.2

11.5

13

6

4

4.8

8.6

mN/m 0 C

27.3

27.2

28.0

27.3

28.8

27.4

26.4

26

25.5

25.8

28.2

26.0

mN/m 0 C

26.7

23.5

25.7

18.7

24.4

19.3

23.6

23.8

22.7

15.9

24.1

15.8

Oil-sea water Interfacial tension

mN/m 0 C

22.5

21.3

24.9

17.6

26.0

18.8

20.2

21.6

22.5

16.2

26.6

15.6

Flashpoint

C

<8

<10

<30

15

<0

<10

Pour Point

C

32

21

42

57

22

Density

g/mL

API Gravity Viscosity

mPas

15 C Surface Tension Oil-water Interfacial tension

15 C

15 C

15 C

(Continued )

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Oil Analysis and Remote Sensing

TABLE A4.1 Environmentally-Relevant Properties of Selected Crude Oils29dcont’d Alaska North Slope Prudhoe Bay, Alaska, USA Emulsion Formation

Arabian Light

Saudi Arabia

Visual Unstable Meso Stability Complex 92.7 Modulus (Pa) 91.1 Emulsion Water Content

Mississippi Brent Canyon Blend Federated Block 807 Gulf of North Mexico, Sea, United Alberta, Louisiana, USA Kingdom Canada NM

NM

Meso

West Texas Intermediate

Texas USA Unstable

26 79.7

Water

% (w/w)

<0.1

<0.1

0.4

NM

11.9

<0.1

Sulphur

% (w/w)

1.11

1.93

0.39

0 29

0.83

0.86

Saturate

% (w/w)

75.0

75.5

72

74

73.3

78.5

Aromatic

% (w/w)

15.0

15.2

23

21

15.45

14.8

Resin

% (w/w)

6.1

5.7

4

3

6.22

6.0

Asphaltene

% (w/w)

4.0

3.6

1

1

5.03

0.7

Wax

% (w/w)

2.6

2.7

7

0.6

2.8

Adhesion

g/m2

20

17

12

2

NM

12

47

19

45

61

49.6

28

Chemical % (Corexit Dispersability 9500)

Chapter 5

Introduction to Oil Chemical Analysis Merv Fingas

Chapter Outline 5.1. Introduction 87 5.2. Sampling and Laboratory 87 Analysis 5.3. Chromatography 89

5.4. Identification and Forensic 96 Analysis 5.5. Field Analysis 107

5.1. INTRODUCTION An important part of the field of oil spill control is the analysis of oil in various media. Oil analytical techniques are a necessary part of the scientific, environmental, and engineering aspects of oil spills.1-4 Analytical techniques are used extensively in environmental assessments of fate and effects. Laboratory analysis can provide information to help identify an oil if its source is unknown or what its sources might be. With a sample of the source oil, the degree of weathering and the amount of evaporation or biodegradation can be determined for the spilled oil. Through laboratory analysis, the more toxic compounds in the oil can be measured, and the relative composition of the oil at various stages of the spill can be determined. This is valuable information to have as the spill progresses. In nonspill situations, analytical techniques are used extensively to measure the oil content of soil and water for environmental quality purposes. Many jurisdictions have standards on the petroleum content of waters and soils for various uses. In addition, many laws exist for the maximum oil content in soils. Soils must often be removed for treatment before lands can be transferred from one owner to another.

5.2. SAMPLING AND LABORATORY ANALYSIS Taking a sample of oil and then transporting it to a laboratory for subsequent analysis is common practice. While there are many procedures for taking oil Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10005-X Copyright Ó 2011 Elsevier Inc. All rights reserved.

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samples, it is always important to ensure that the oil is not tainted from contact with other materials and that the sample bottles are precleaned with solvents, such as hexane, that are suitable for the oil.5 The simplest and most common form of analysis is to measure how much oil is in a water, soil, or sediment sample.6 Such analysis results in a value known as total petroleum hydrocarbons (TPH). The TPH measurement can be obtained in many ways, including extracting the soil, or evaporating a solvent such as hexane and measuring the weight of the residue that is presumed to be oil. There now exist certified laboratories that use certified petroleum hydrocarbon measurement techniques.6 These should be used for all studies. One of the most serious difficulties in older studies occurred when inexperienced staff tried to conduct chemical procedures. Analytical methods are complex and cannot be conducted correctly without chemists familiar with the exact procedures. Furthermore, field instrumentation requires calibration using standard procedures and field samples during the actual test. These samples must be taken and handled by standard procedures. Certified standards must be used throughout to ensure good Quality Assurance/Quality Control (QA/QC) procedures. In this era, it is simply unacceptable not to use certified methods, laboratories, and chemists.

5.2.1. Incorrect and Obsolete Methods Several attempts to perform oil analysis have been made using methods that are not scientifically valid. One of these is the use of colorimetry. This method has never been scientifically valid for oil measurement as oil does not have what is known as a color center, that is, a molecular absorption center for a specific band of light.7-9 As oil is a mixture of hundreds of compounds, there is obviously not a single light-absorbing centre. This method results in oil measurements that are typically 100% incorrect. Another series of methods involved extracting oil from soil or water using fluorinated or chlorinated hydrocarbons. Since these extractants were ozonedepleting, they were removed from the market over 20 years ago. The extracted hydrocarbons were then “measured” using infrared light, as hydrocarbons in such solvents do absorb at specific wavelengths. The method was the standard oil in soil technique in several countries and yielded repeatable results. The ozone-depleting substances were replaced with hexane. Hexane is not a good extractant of oil from soil, and thus these methods are not as popular as the older methods were. The use of hexane also led to renaming the results of these methods from Total Petroleum Hydrocarbons (TPH) to hexaneextractables.10 There are several “meters” sold on the market that offer oil readings; however, none of these are reliable or accurate.8

Chapter | 5

Introduction to Oil Chemical Analysis

89

Fluorometry is a technique sometimes used for measuring or estimating concentrations of oil in water. A fluorometer uses UV or near UV to activate aromatic species in the oil.11 The UV activation energy is more sensitive to the naphthalenes and phenanthrenes, whereas the near UV is more sensitive to large species such as fluorenes. The composition of the oil changes with respect to aromatic content as it weathers and is dispersed in water, with the concentration of aromatics increasing. Thus, the apparent fluorescent quantity increases in this process. It must be noted that fluorometers cannot truly be calibrated for the oil as there are many variables, as explained above. The errors encountered all increase the apparent value of the oil concentration in the water column. Incorrect calibration procedures can distort concentration values up to 10 times their actual value, or even more. Correct analytical methods involve performing accurate gas chromatograph (GC) measurements both in the laboratory and in the field.

5.3. CHROMATOGRAPHY The primary method for oil analysis, as well as for many chemicals in the environment, is gas chromatography; this method will be described in the subsequent section. One should note that other chromatography methods and other analytical methods are sometimes used for oils. These include liquid chromatography, sometimes used for PAH analysis and inductively coupled plasma (ICP) instruments for measuring metals in oils. These and many other techniques are not described in this section.

5.3.1. Introduction to Gas Chromatography The standard method for oil analysis is to use a GC.2,3,12,13,14 A small sample of the oil extract (typically measured in microliters, mL), often in hexane, and a carrier gas, usually helium or hydrogen, are passed through a capillary column. The sample is injected into a heated chamber from where its vapors pass into the silica column. The silica column is coated with absorbing materials, and, because the various components of the oil have varying rates of adhesion, the oil separates because these components are absorbed at different rates onto the column walls. The gases then pass through a sensitive detector. The injector, column, and detector are often maintained at constant temperatures to ensure repeatability. The system is calibrated by passing known amounts of standard materials through the unit. The amount of many individual components in the oil is thereby measured. The components that pass through the detector can also be totaled, and a TPH value determined. It is important to note that only the vapors pass into the column initially. Heavier contaminants can foul the injector and first part of the column. It is therefore important that the sample be subjected to a cleanup procedure before it is injected into the column. Cleanup procedures can be complex and involve several steps.

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While a GC measurement is highly accurate, this measurement does not include resins, asphaltenes, and some other components of the oil with higher molecular weight that do not vaporize and pass through the column. These heavier components can be determined separately using open column chromatography or precipitation techniques. The detectors used in chromatography are important. An important detector for petroleum hydrocarbons is the flame ionization detector (FID).2,3 The principle behind this instrument is simple as most compounds show variable ion conductivity burned in a hydrogen flame. This detector is simple and has the advantage of yielding relatively similar signals for different hydrocarbons, thus making calibration and quantification simple. Another detector commonly used for oils is the mass spectrometric detector. The analytes from the GC column are introduced into a vacuum chamber and ionized, and then these ions are separated according to mass and passed to a detector. The detected signals are then analyzed by a computer and output to the user as peaks of given mass or even possible compound identification. The mass spectrometer provides information about the structure of the substance so that each peak in the chromatogram can be more positively identified. The methods are abbreviated as GC-FID, if a gas chromatograph and flame ionization detector are used or GC-MS, if a gas chromatograph and a mass spectrometer detector are used. A typical GC-FID chromatogram of a light crude oil with some of the more prominent components of the oil identified is shown in Figure 5.1.2,3 This chromatogram shows some of the many features of oil that are identified by this analytical technique. The bulk of crude oils, especially light ones, have a large proportion of n-alkanes, as can be seen by the large peaks that constitute a large portion of this chromatogram. This is a light crude oil that can be evidenced by the fact that the highest peak is C15. A more weathered crude might have its highest peak at C18 or more. The top of the chromatogram is typically shaped as a curve, peaking to C15, as it is here. Under the peaks is a hump, often called the unresolved complex mixture, or UCM. This is an aggregate of largely unresolved peaks of alkane origin. At C16, for example, there are already thousands of isomers that cannot be resolved by typical GC methods. Between the n-alkane peaks are smaller peaks, most of which are aromatic compounds. Two standard biomarkers (here, isoprenoids and branched alkanes) are usually evident in such a chromatogram, Pristane (near nC17) and Phytane (near nC18). These have been used to assess state of weathering; however, other compounds are now typically used. Figure 5.2 shows the GC-FID chromatograms of 10 oils. Figure 5.2A to C shows the chromatograms of three lighter crude oils: Arabian medium crude oil, Hedrun crude oil, and Gullfaks,2,3 Figure 5.2D shows a chromatogram of Orimulsion, a bitumen. In this chromatogram one notes that almost all n-alkanes are not present, and the chromatogram largely consists of the

91

C28

C26

C24

C22

C20

Introduction to Oil Chemical Analysis

C21

Chapter | 5

Chromatographic retention time FIGURE 5.1 GC-FID of a light crude oil. This chromatogram illustrates many features of the chromatograms of crude oils. The bulk of crude oils, especially light ones, have a large proportion of n-alkanes, as can be seen by the large peaks that constitute a large portion of this chromatogram.

unresolved complex mixtures, or UCM. Figure 5.2E shows the chromatogram of IFO-30, Intermediate fuel oil, which is a mixture of a diesel fraction and Bunker C. Figure 5.2F shows the chromatogram of Bunker C, and Figures 5.2G-J show jet fuel, diesel fuel, lubrication oil, and number 6 fuel oil, respectively. The mass spectrometer provides information about the structure of the substance so that each peak in the chromatogram can be positively identified. An important technique is that of SIM (selective ion monitoring), where one can monitor the ion most typically associated with the target compound. This technique enables the detection and quantification of many compounds in oil that otherwise would not be separately resolved.2,3 Figure 5.3 shows three chromatograms first by GC-FID and then by GC-MS using SIM. Figures 5.3A and B are chromatograms of a light Alberta crude oil; Figures 5.3C and D are chromatograms of California heavy crude oil, and Figures 5.3E and 5.3F are chromatograms of Orimulsion Bitumen. The two chromatograms (e.g., FID/ SIM) are quite different. The SIM chromatograms are no longer recognized as the types of oils as shown by FID. However, one can see that the peaks are more clearly defined and that the SIM can provide different and important information. The disadvantage of the SIM is that each peak must be quantified separately using an internal standard. Most fuels and oils show a typical distribution pattern in GC-FID. The idealized patterns can be seen in Figure 5.4, a figure that shows the alkane distribution. All graphs are n-alkanes except for the lube oils where the alkanes are highly branched. These bar graphs were created from

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Oil Analysis and Remote Sensing

FIGURE 5.2 GC-FIDs of several oils. Figure 5.2A shows the chromatogram of Arabian medium crude oil. Figure 5.2B is a chromatogram of Hedrun crude oil, a light oil. Figure 5.2C is a chromatogram of Gullfaks, another light oil. Figure 5.2D shows a chromatogram of Orimulsion, a bitumen. In this chromatogram one notes that almost all n-alkanes are not present, and the chromatogram largely consists of the unresolved complex mixtures or UCM. Figure 5.2E shows the chromatogram of IFO-39, Intermediate fuel oil, which is a mixture of a diesel fraction and Bunker C. One can see the peaks of diesel fuel, peaking at about C14 and that of Bunker C, peaking at about C28. In Figure 5.2F the chromatogram of Bunker C is shown. Figures 5.2G, 2H, 2I, and 2J show jet fuel B, diesel fuel, lubrication oil, and number 6 fuel oil, respectively.

Chapter | 5

Introduction to Oil Chemical Analysis

93

FIGURE 5.2 Continued

quantitative analysis and approximate the alkane chromatograms of the same oils.

5.3.2. Methodology Modern chromatographic methods require that the injected sample contents be of certain types and that they do not foul the injector or column. Thus, several cleanup methods have developed over the years.1,6 The basic methods involve extracting the oil using dichloromethane (DCM), sometimes in combination with other solvents such as hexane. This procedure will leave the DCM insoluble material, such as soil and wood, and remove the DCM soluble material, which is largely petroleum oil. Surrogate chemicals are often added at this stage; these substances are compounds, typically deuterated hydrocarbons, that are not present in oil and will serve to identify peaks in subsequent analyses. The DCM extract is often filtered and treated to

94

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Oil Analysis and Remote Sensing

FIGURE 5.3 The GC-FID and GC-MS with SIM at ion 85m/e. The left-hand columns are the GC-FID chromatograms, and the right-hand side are the GC-MS and SIM chromatograms. Figures A and B are chromatograms of a light Alberta crude oil; Figures C and D are chromatograms of California heavy crude oil, and Figures E and F are chromatograms of Orimulsion Bitumen. One notes that the two chromatograms (e.g., FID/SIM) are quite different. The SIM chromatograms no longer have the recognizability of the types of oils as shown by FID. However, one can see that the peaks are more clearly defined and that the SIM can provide separate information. The disadvantage of the SIM is that each peak must be quantified separately using a standard.

Chapter | 5

95

Introduction to Oil Chemical Analysis

Lube Oil

Gasoline

4 6

8 10 12 14 Carbon Number

15

20

25

30

35

40

Carbon Number

Jet Fuel

Typical Crude

6 8 10 12 14 16 18 Carbon Number 0

5

15 10 Carbon Number

20

25

30

35

40

35

40

Diesel Fuel Bunker C 6 8 10 12 14 16 18 20 22 24 Carbon Number

10

15

20

25 30 Carbon Number

FIGURE 5.4 The bar graph distribution of alkanes for typical oils and fuels. These graphs were generated from the quantitative analysis of several oils. It should be noted that the alkanes are typically n-alkanes for all oils except for lube oils, where they are highly branched alkanes.

remove water before injection into the GC. At each point in this cleanup, the sample is quantified to allow measurement of those groups of materials removed. These measurements then form the basis for various forms of TPH measurement. One such method as developed by Dr. Zhendi Wang of Environment Canada is shown in Figure 5.5.2,3 In the method illustrated in Figure 5.5, the sample is separated into aliphatic, aromatic, and polar fractions using an open silica column. Several tests of this have been carried out to ensure that separation is complete. Having these fractions separated ensures that subsequent chromatographic analysis is not affected by interferences between the three fractions. The peaks that are typically quantified for analysis and possibly for identification are listed in Table 5.1.2,3 As described later, many of the these peaks are useful when combined in ratios. Often these ratios are unique and can be used for positive identification of an oil. There are many published methods and standards for oil analysis; several of these are listed in Table 5.2.

96

PART | III

Oil Analysis and Remote Sensing

Weigh Sample add surrogates

serially extract sample with dichloromethane/hexane

filter and concentrate extract

gravimetrically determine TPH

silica column fractionation fraction 1 aliphatics

fraction 2

fraction 3

aromatics

mixed

50% DCM/Hexane hexane gravimetric saturates aromatics determinations 5-- -Androstane d14-Terphenyl internal standards Hopane

GC/MS SIM

GC/MS (SIM)

GC/FID PAHs n-alkane hopanes n-alkane quantification distribution & steranes

half F1&F2 TPH 5- -Androstane

fraction 4 polars Methanol polars polars

GC/FID

Benzenes PAH alkylated homologues

TPH

FIGURE 5.5 Illustration of the Dr. Wang analysis method developed for Environment Canada. After cleanup procedures, the sample is separated into aliphatic, aromatic, and polar fractions. This enables very clear chromatographic analysis without interference between these fractions. This method yields many analytical parameters.

5.4. IDENTIFICATION AND FORENSIC ANALYSIS The foregoing information can then be used to predict how long the oil has been in the environment and what percentage of it has evaporated or biodegraded.15-23 This is possible because some of the components in oils, particularly crude oils, are very resistant to biodegradation, whereas others are resistant to evaporation. This difference in the distribution of components then allows the degree of weathering of the oil to be measured. The same technique can be used to “fingerprint” an oil and positively identify its source. Certain compounds are consistently distributed in oil, regardless of weathering, and these are used to identify the specific type of oil. The effect of weathering is particularly important as it may negate the use of standard GC-FID to positively identify an oil.23, 28-31 Figure 5.6 shows the effect of weathering on the GC-FID chromatogram of a light crude oil. As the oil weathers, more and more of the lower n-alkanes are lost to evaporation, the most important component of weathering. Figure 5.6A shows the

Chapter | 5

97

Introduction to Oil Chemical Analysis

TABLE 5.1 Target Analytes/Compounds for Oil Spill Studies Analyte

Analyte

Target Ion

Aliphatic Hydrocarbons

BTEX and C3 Benzenes

n-C8

Benzene

78

n-C9

Toluene

91

n-C10

Ethylbenzene

105

n-C11

Xylenes

105

n-C12

C2 - benzenes

105

n-C13

C3 - benzenes

105

n-C14

PAHs

n-C15

Naphthalene

128

n-C16

C1 - naphthalene

142

n-C17

C2 - naphthalene

156

Pristane

C3 - naphthalene

170

n-C18

C4 - naphthalene

184

Phytane

Phenanthrene

178

n-C19

C1 - phenanthrene

192

n-C20

C2 - phenanthrene

206

n-C21

C3 - phenanthrene

220

n-C22

C4 - phenanthrene

234

n-C23

Fluorene

166

n-C24

C1 - fluorene

180

n-C25

C2 - fluorene

194

n-C26

C3 - fluorene

208

n-C27

Chrysene

228

n-C28

C1 - chrysene

242

n-C29

C2 - chrysene

256

n-C30

C3 - chrysene

270

n-C31

Biphenyl

154

(Continued )

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TABLE 5.1 Target Analytes/Compounds for Oil Spill Studiesdcont’d Analyte

Analyte

Target Ion

n-C32

Benzo[e]pyrene

252

n-C33

Benzo[a]pyrene

252

n-C34

Perylene

252

n-C35

Dibenzothiophene

184

n-C36

C1 - Dibenzothiophene

198

n-C37

C2 - Dibenzothiophene

212

n-C38

C3 - Dibenzothiophene

226

n-C39 n-C40 EPA Priority PAH pollutants Naphthalene

128

Phenanthrene

178

Fluorene

166

Chrysene

228

Acenaphthylene

152

Acenaphthene

153

Anthracene

178

Fluoranthene

202

Pyrene

202

Benz[a]anthracene

228

Benz[b]fluoranthene

252

Benzo[k]fluoranthene

252

Benzo(g,h,i)perylene

276

Biomarkers Triterpanes Tricyclic terpanes

191

Chapter | 5

99

Introduction to Oil Chemical Analysis

TABLE 5.1 Target Analytes/Compounds for Oil Spill Studiesdcont’d Analyte

Analyte

Target Ion

Tetracyclic terpanes

191

Pentacyclic terpanes

191

C23H42

191

C24H44

191

C27H46 (Ts) & (Tm)

191

C29H50&C30H52 ab-hopane

191

C30-35H52-62 22S/22R

191

Steranes C27 20 R/S-cholestanes

217,218

C28 20 R/S-ergostanes

217,218

C29 20 R/S-stigmastanes

217,218

unweathered oils with the Cn Benzenes and naphthalenes very obvious. After about a 30% loss of oil through evaporation, the Cn Benzenes are lost, and many of the lower alkanes are shown in Figure 5.6B. After 44.5% of the mass is evaporated, as shown in Figure 5.6C, even the naphthalenes are not clearly present. It would be very difficult to simply compare weathered and unweathered oils simply by comparing the chromatograms. Although there are some ways to partially compensate for this, modern technology uses other components of the oil to forensically identify oils.

5.4.1. Biomarkers Biological markers or biomarkers are an important hydrocarbon group in petroleum analysis.32-34 Biomarkers are complex molecules derived from formerly living organisms. Biomarkers found in crude oils, rocks, and sediments show little change in structures from their parent organic molecules, or so-called biogenic precursors (for example, hopanoids, and steroids), in living organisms. Biomarker concentrations are relatively low in oil, often in the range of several hundred ppm. Biomarkers are useful because they retain all or most of the original carbon skeleton of the original natural product; this structural similarity reveals more information about oil origins than other compounds. Petroleum geochemists have historically used biomarker

100

TABLE 5.2 List of Standards Applicable to Oil Measurement Standards Organization

Method Number

ASTM

Analyte

Description

Reference

D5739-06

Standard Practice for Oil Spill Source Identification by Gas Chromatography and Positive Ion Electron Impact Low Resolution Mass Spectrometry

GC-EI

GC pattern

Fingerprinting for oil identification

24

ASTM

D3328-06

Standard Test Methods for Comparison of Waterborne Petroleum Oils by Gas Chromatography

GC-EI

GC pattern

Fingerprinting for oil identification

24

ASTM

D3415-98

Standard Practice for Identification of Waterborne Oils

GC-FID

oil ID

Identification of oils on water

24

ASTM

D3326-07

Standard Practice for Preparation of Samples for Identification of Waterborne Oils

GC-FID

oil ID

Identification of oils on water

24

ASTM

D5739-00

Standard Practice for Oil Spill Source Identification by Gas Chromatography and Positive Ion Electron Impact Low Resolution Mass Spectrometry

GC-EI

GC pattern

Fingerprinting for oil identification

24

Oil Analysis and Remote Sensing

Technique

PART | III

Title

TABLE 5.2 List of Standards Applicable to Oil Measurementdcont’d Method Number

ASTM

Technique

Analyte

Description

Reference

F2059-06

Standard Test Method for Laboratory Oil Spill Dispersant Effectiveness Using the Swirling Flask

GC-FID

TPH

TPH for water, chemical dispersion quantification

24

ASTM

D5412-93

Standard Test Method for Quantification of Complex Polycyclic Aromatic Hydrocarbon Mixtures or Petroleum Oils in Water

GC-EI

PAHs

Quantification of PAHS

24

ASTM

D6352-04

Standard Test Method for Boiling Range Distribution of Petroleum Distillates in Boiling Range from 174 to 700 C by Gas Chromatography

SIM-DIS

Boiling Distribution

Method to carry out a simulated distillation on oil e extended range

24

ASTM

D2887-08

Standard Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography

SIM-DIS

Boiling Distribution

Method to carry out a simulated distillation on oil

24

ASTM

D5307-97

Standard Test Method for Determination of Boiling Range Distribution of Crude Petroleum by Gas Chromatography

SIM-DIS

Boiling Distribution

Method to carry out a simulated distillation on crude oil

24

ASTM

D7169-05

Standard Test Method for Boiling Point Distribution of Samples with Residues Such as Crude Oils and Atmospheric

SIM-DIS

Boiling Distribution

Method to carry out a simulated distillation

24

101

(Continued )

Introduction to Oil Chemical Analysis

Title

Chapter | 5

Standards Organization

102

TABLE 5.2 List of Standards Applicable to Oil Measurementdcont’d Standards Organization

Method Number

Title

Technique

Analyte

Reference

Method to preserve oil samples

24

and Vacuum Residues by High Temperature Gas Chromatography D3325-90

Standard Practice for Preservation of Waterborne Oil Samples

Sample Preservation

API

PHC

Determination of Petroleum Hydrocarbons

GC-FID

PHC

Petroleum Hydrocarbons

25

API

GRO

Determination of Petroleum Hydrocarbons

GC-FID

GRO

Gasoline range organic compounds

25

API

DRO

Determination of Petroleum Hydrocarbons

GC-FID

DRO

Diesel range organic compounds

25

EPA

846

Gas Chromatographic (GC) Methods

GC-FID/EI

organics

General GC method

26

Oil Analysis and Remote Sensing

ASTM

PART | III

Description

TABLE 5.2 List of Standards Applicable to Oil Measurementdcont’d Method Number

EPA

Technique

Analyte

Description

Reference

610

Determination of priority PAHS in municipal and industrial wastes

GC-EI

PAHs

PAHs in wastes

26

EPA

1664

N-hexane Extractable Material (HEM; Oil and Grease) and Silica Gel Treated N-Hexane Extractable Material (SGT-HEM: Non-polar Material) by Extraction and Gravimetry

gravimetry

TPH

N-hexane extractables in various substrates

26

CCME

1397

Canada-Wide Standard for Petroleum Hydrcarbons (PHC) in Soil

GC-FID/EI

TPH

Suite of analysis techniques for hydrocarbons in soil

27

CCME

1399

Canada-Wide Standard for Petroleum Hydrcarbons (PHC) in Soil: Scientific Rationale

GC-FID/EI

TPH

Background to suite of analysis techniques for hydrocarbons in soil

27

Reference Method for CanadaWide Standard for Petroleum Hydrcarbons (PHC) in Soil- Tier 1 Method

GC-FID/EI

TPH

Reference method to above for hydrocarbons in soil

27

CCME

Introduction to Oil Chemical Analysis

Title

Chapter | 5

Standards Organization

103

104

PART | III

Oil Analysis and Remote Sensing

FIGURE 5.6 Illustration of the effect of oil weathering on the chromatograms. As the oil weathers, more and more of the lower n-alkanes are lost to evaporation, the most important component of weathering. Figure A shows the unweathered oils with the Cn Benzenes and naphthalenes marked. After about 30% loss of oil through evaporation, the Cn Benzenes are lost and also many of the lower alkanes as shown in Figure B. After 44.5% of the mass is evaporated as shown in Figure C, even the naphthalenes are not clearly present. It would be very difficult to compare weathered and unweathered oils simply by comparing the chromatograms.

fingerprinting in characterizing oils in terms of (1) the type(s) of precursor organic matter in the source rock (such as bacteria, algae, or higher plants); (2) correlation of oils with their source rocks; (3) determination of depositional

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environmental conditions (such as marine, terrestrial, deltaic, or hypersaline environments); (4) assessment of thermal maturity and thermal history of oil and the degree of oil biodegradation; and (5) providing information on the age of the source rock for petroleum. For example, oleanane (C30H52) is a biomarker characteristic of angiosperms (flowering plants) found only in Tertiary and Cretaceous (<130 million years) oils.35 The conversion of precursor biochemical compounds from living organisms into biomarkers creates a vast suite of compounds in crude oils that have distinct structures. Due to the wide variety of geological conditions under which oil has formed, every crude oil exhibits a unique biomarker fingerprint. Biomarkers can be detected in very low quantities (ppm and below) in the presence of many other types of petroleum hydrocarbon by using GC-MS. Relative to other hydrocarbon groups such as alkanes and many aromatic compounds, biomarkers are highly stable and degradation-resistant. Therefore, the usefulness of analyzing biomarkers is that they generate information useful in determining the source of spilled oil, monitoring the degradation process, and weathering the state of oils. They have proven useful in identifying petroleum-derived contaminants in the marine environment.22,36-38 In the past decades, the use of biomarker fingerprinting techniques to study spilled oils has rapidly increased, and biomarker parameters have been playing a prominent role in almost all oil-spill forensic investigations. Table 5.1 lists some typical biomarkers used in forensic analysis. The concentration of the biomarkers is important, while the ratio of various biomarkers in an oil is extremely useful in making the comparisons. The ratios of the biomarker contents in most oils are constant throughout processes such as weathering and biodegradation, and thus serve as an identity tag for an oil.

5.4.2. Sesquiterpanes and Diamondoids The commonly used biomarkers that occur within crudes and heavier refined products include pentacyclic triterpanes (e.g., hopanes), regular and rearranged steranes, and mono- and tri-aromatic steranes.2,39,40 However, the high boiling point pentacyclic triterpanes and steranes are generally absent or in very low abundances in lighter petroleum products such as jet fuels and midrange diesels. For lighter petroleum products, refining processes have removed most high-molecular-weight biomarkers from the crude oil feed stocks, while the smaller compounds of bicyclic sesquiterpanes are greatly concentrated in these petroleum products. Figure 5.7 shows some of the typical biomarkers used for oil identification. Sesquiterpanes are ubiquitous components of crude oils and ancient sediments. Bicyclic sesquiterpanes are also widely found in intermediate petroleum distillates and finished petroleum products. The abundance of the three major compounds in the m/z 123 chromatograms has been employed to differentiate the organic matter input from various sedimentary environments. Early studies

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hopane - general

Steranes

general sterane structure

Sesquiterpanes

8 (H) - drimane

Diamondoid

Adamantane

Oil Analysis and Remote Sensing

FIGURE 5.7 Illustration of some typical biomarkers used for oil identification.

focused mainly on geological application of sesquiterpane compounds. The naturally occurring bicyclic sesquiterpanes are stable in biodegradation, and therefore in recent years, they found potential applications in oil-source correlation and differentiation. Recently, environmental scientists have also considered fingerprinting the diamondoid hydrocarbons as a promising forensic technique for oil spill studies.41-47 These naturally occurring compounds are thermodynamically stable, and therefore, they may have potential applications both in oil-source correlation and differentiation for those cases where the traditional biomarker terpanes and steranes are absent due to removal in the refining processes. There is increased awareness of possible application of diamondoid compounds for source identification. Diamondoids have the general molecular formula C4nþ6H4nþ12 and are a class of saturated hydrocarbons that consist of threedimensional fused cyclohexane rings, which results in a diamond-like structure. The simplest compound of these polycyclic diamondoids is adamantane (C10H16), followed by its homologues diamantane (C14H20), tri-, tetra-, penta-, and hexamantane. Adamantine and diamantane and their various substituted equivalents are widely found in crude oils, intermediate petroleum distillates, and other petroleum products. Diamondoid compounds (adamantanes and diamantanes) in petroleum are believed to be the result of carbonium ion rearrangements of suitable cyclic precursors on clay substances in the source rock. The higher homologues of diamondoids are considered to be formed from

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the smaller diamondoid compounds under extreme temperature and pressure conditions.

5.5. FIELD ANALYSIS Analysis performed in the field is faster and more economical than analysis done in a laboratory.8 As analytical techniques are constantly improving and lighter and more portable equipment is being developed, more analytical work can be carried out directly in the field. Test kits have also been developed that can measure total petroleum hydrocarbons directly in the field. Some new methods use enzymes that are selectively affected by oil components. While these test kits are less accurate than laboratory methods, they are a rapid screening tool that minimize laboratory analysis and may provide adequate data for making response decisions. It is important to stress, however, that these field kits may have limitations and that results should be verified by laboratory analysis.

REFERENCES 1. Environment Canada, Analytical Method for the Determination of Individual and Total Petroleum Hydrocarbons, PAHs and Biomarkers in Oil and Oil-Spill-Related Environmental Samples (ETC Standard Method 5.3/1.4/M), Environment Canada, 2003. 2. Wang Z, Fingas M. Oil and Petroleum Product Fingerprinting Analysis by Gas Chromatographic Techniques, Chapter 27. In: Nollet Leo ML, editor. Chromatographic Analysis of the Environment, 1027. Boca Raton, FL: Taylor and Francis; 2005. 3. Wang ZD, Fingas M, Page D. Oil Spill Identification: Review. J Chromatogr 1999;369. 4. Wang ZD, Fingas M. Development of Oil Hydrocarbon Fingerprinting and Identification Techniques. Mar Pollut Bull 2003;423. 5. Wang ZD, Hollebone B, Fingas M, Fieldhouse B, Sigouin L, Landriault M, et al. Development of a Composition Database for Selected Multicomponent Oils. Vancouver: Environment Canada, 2002. 6. Wang Z, Fingas M, Sigouin L, Yang C, Hollebone B. Comparison Study for the CCME Reference Method for Determination of PHC in Soil by Using Internal and External Standard Methods and by Using Silica Gel Column Cleanup and in-situ Silica Gel Cleanup Methods. AMOP 2003;193. 7. Encyclopedia of Chemistry. New York: Wiley-Interscience; 2005. p. 241. 8. Lambert P, Fingas MF, Goldthorp M. An Evaluation of Field Total Petroleum Hydrocarbon (TPH) Systems. J Haz Mat 2001;65. 9. Fingas MF, Kyle DA, Lambert P, Wang Z, Mullin JV. Analytical Procedures for Measuring Oil Spill Dispersant Effectiveness in the Laboratory. AMOP 1995;339. 10. Index to EPA Test Methods, April 2003 revised edition, http://epa.gov/, accessed 2010. 11. Lambert P, Goldthorp M, Fieldhouse B, Wang Z, Fingas M, Pearson L, et al. A Review of Oil-in-Water Monitoring Techniques. IOSC 2001;1375. 12. Wang ZD, Fingas M, Li K. Fractionation of ASMB Oil, Identification and Quantitation of Aliphatic Aromatic and Biomarker Compounds by GC/FID and GC/MSD (Part I). J Chromatogr Sci 1994;361.

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13. Blomberg J, Schoenmakers PJ, Brinkman UA. Gas Chromatographic Methods for Oil Analysis. J Chromatogr 2002;137. 14. Beens J, Brinkman UA. The Role of Gas Chromatography in Compositional Analyses in the Petroleum Industry. TrACdTrend Anal 2000;260. 15. Wang Z, Fingas M, Sigouin L. Using Multiple Criteria for Fingerprinting Unknown Oil Samples Having Similar Chemical Composition. Environ Forens 2002;251. 16. Wang Z, Fingas M. Oil Spill Fingerprinting. J Int Soc Environ Forens 2002;3/4. 17. Wang Z, Fingas M, Yang C, Christensen JH. Crude Oil and Refined Product Fingerprinting: Principles, Chapter 16. In: Morrison Robert D, Murphy Brian L, editors. Environmental Forensics; Contaminant Specific Guide, 339. Amsterdam: Academic Press/ Elsevier; 2006. 18. Wang Z, Yang C, Hollebone BP, Fingas M, Lambert P, Landriault M. Characterization and Identification of Spill Samples from Recent Spill Incidents. AMOP 2006;113. 20. Daling PS, Faksness LG, Hansen AB, Stout SA. Improved and Standardized Methodology for Oil Spill Fingerprinting. Environ Forens 2002;263. 21. Stout SA, Uhler AD, Naymik TG, McCarthy KJ. Environmental Forensics: Unravelling Site Liability. Environ Sci Techn 1998;260A. 22. Stout SA, Uhler AD, McCarthy KJ, Emsbo-Mattingly S. Chapter 6: Chemical Fingerprinting of Hydrocarbons. In: Murphy BL, Morrison RD, editors. Introduction to Environmental Forensics, 137. London: Academic Press; 2002. 23. Wang ZD, Yang C, Fingas M, Hollebone B, Peng XZ, Hansen AB, et al. Characterization, Weathering, and Application to Source Identification of Spilled Oils. Environ Sci Technol 2005;8700. 24. ASTM standards, http://www.astm.org. 25. API test methods, http://www.api.org/Publications. 26. Index to EPA Test Methods, April 2003 revised edition, http://www.epa.gov. 27. CCME test methods, http://www.ccme.ca/publications. 28. Wang ZD, Fingas M. Study of the Effects of Weathering on the Chemical Composition of a Light Crude Oil Using GC/MS and GC/FID. J Microcolumn Sep 1995;617. 29. Wang ZD, Fingas M, Sergy G. Chemical Characterization of Crude Oil Residues from an Arctic Beach by GC/MS and GC/FID. Environ Sci Techn 1995;2622. 30. Wang ZD, Fingas M, Blenkinsopp S, Sergy G, Landriault M, Sigouin L, et al. Comparison of Oil Composition Changes Due to Biodegradation and Physical Weathering in Different Oils. J Chromatogr 1998;89. 31. Douglas GS, Bence AE, Prince RC, McMillen SJ, Butler EL. Environmental Stability of Selected Petroleum Hydrocarbon Source and Weathering Ratios. Environ Sci Technol 1996;2332. 32. Wang Z, Fingas M, Yang C, Hollebone B, Peng X. Biomarker Fingerprinting: Applications and Limitations for Source Identification and Correlation of Oils and Petroleum Products. AMOP 2004;103. 33. Wang Z, Yang C, Fingas M, Hollebone B, Yim U, Oh J. Petroleum Biomarker Fingerprinting for Oil Spill Characterization and Source Identification, Chapter 3. In: Wang Z, Stout S, editors. Oil Spill Environmental Forensics: Fingerprinting and Source Identification, 73. Amsterdam: Academic Press; 2007. 34. Prince RC, Elmendorf DL, Lute JR, Hsu CS, Haith CE, Senius JD, et al. 17_(H), 21_(H)Hopane as a Conserved Internal Marker for Estimating the Biodegradation of Crude Oil. Environ Sci Techn 1994;142. 35. Peters KE, Moldowan JW. The Biomarker Guide: Interpreting Molecular Fossils in Petroleum and Ancient Sediments. Old Tappen, NJ Englewood Cliffs, NJ: Prentice Hall; 1993.

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36. Kvenvolden KA, Hostettler FD, Rosenbauer RW, Lorenson TD, Castle WT, Sugarman S. Hydrocarbons in Recent Sediment of the Monterey Bay, National Marine Sanctuary. Marine Geology 2002;181:101e13. 37. Kaplan IR, Galperin Y, Lu S, Lee RP. Forensic Environmental Geochemistry Differentiation of Fuel-types, Their Sources, and Release Time. Org Geochem 1997;289. 38. Volkman JK, Holdsworth DG, Neill GP, Bavor Jr HJ. Identification of Natural, Anthropogenic and Petroleum Hydrocarbons in Aquatic Environments. Sci Total Environ 1992;203. 39. Wang Z, Yang C, Fingas M, Hollebone B, Peng X, Hansen AB, et al. Characterization, Weathering and Application of Sesquiterpanes to Source Identification of Spilled Lighter Petroleum Products. Environ Sci Techn 2005;8700. 40. Stout SA, Uhler AD, McCarthy KJ. Middle Distillate Fuel Fingerprinting Using Drimanebased Bicyclic Sesquiterpanes, Environ. Forensics 2005;6:241e51. 41. Yang C, Wang ZD, Hollebone B, Peng X, Fingas M, Landriault M. GC/MS Quantitation Analysis of Diamondoid Compounds in Crude Oils and Petroleum Products. Environ Forensics 2006;7:292. 42. Yang C, Wang ZD, Hollebone BP, Fingas M, Peng X, Landriault M. GC/MS Quantitation of Diamondoid Compounds in Crude Oils and Petroleum Products. AMOP 2006;91. 43. Wang Z, Yang C, Hollebone B, Fingas M. Forensic Fingerprinting of Diamondoids for Correlation and Differentiation of Spilled Oil and Petroleum Products. Environ Sci Techn 2006;5636. 44. Yang C, Wang ZD, Hollebone BP, Peng X, Fingas MF, Landriault MA. GC/MS Quantitation of Diamondoid Compounds in Crude oils and Petroleum Products. Forensics 2006;370. 45. Dahl JE, Liu SG, Carlson RMK. Isolation and Structure of Higher Diamondoids, Nanometersized Diamond Molecules. Science 2003;96. 46. Grice K, Alexander R, Kagi R. Diamondoid Hydrocarbons as Indicators of Biodegradation in Australian Crude Oils. Org Geochem 2000;67. 47. Stout SA, Douglas GS. Diamondoid Hydrocarbons-Application in the Chemical Fingerprinting of Natural Gas Condensate and Gasoline. Environ Foren 2004;225.

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Chapter 6

Oil Spill Remote Sensing: A Review Merv Fingas and Carl E. Brown

Chapter Outline 6.1. Introduction 6.2. Visible Indications of Oil 6.3. Optical Sensors 6.4. Laser Fluorosensors 6.5. Microwave Sensors 6.6. Slick Thickness Determination 6.7. Acoustic Systems 6.8. Integrated Airborne Sensor Systems

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6.9. Satellite Remote Sensing 6.10. Oil under Ice Detection 6.11. Underwater Detection and Tracking 6.12. Small Remote-controlled Aircraft 6.13. Real-time Displays and Printers 6.14. Routine Surveillance 6.15. Future Trends 6.16. Recommendations

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6.1. INTRODUCTION Large spills of oil and related petroleum products in the marine environment can have serious biological and economic impacts. Public and media scrutiny is usually intense following a spill, with demands that the location and extent of the oil spill be determined. Remote sensing is playing an increasingly important role in oil spill response efforts. Through the use of modern remote-sensing instrumentation, oil can be monitored on the open ocean around the clock. With knowledge of slick locations and movement, response personnel can more effectively plan countermeasures in an effort to lessen the effects of the pollution. In recent years, there has been a strong interest in detection of illegal discharges, especially in view of the large seabird mortality associated with such discharges.1 Even though sensor design and electronics are becoming increasingly sophisticated and much less expensive, the operational use of remote-sensing Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10006-1 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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equipment lags behind the technology. In remote sensing, a sensor, other than the eye or conventional photography, is used to detect the target of interest at a distance. The most common forms of oil spill surveillance and mapping are still sometimes carried out with simple still or video photography. Remote sensing from an aircraft is still the most common form of oil spill tracking. Attempts to use satellite remote sensing for oil spills continue, although success is not necessarily as claimed and is generally limited to identifying features at sites where known oil spills have occurred or for mapping discharges or known spills. It is important to divide the uses of remote sensing into the end use or objective, as the utility of the sensor or sensor system is best defined that way. Remote-sensing systems for oil spills used for routine surveillance certainly differ from those used to detect oil on shorelines or land. A single tool does not serve for all functions. For a given nation and several functions, many types of systems may, in fact, be needed. Furthermore, it is necessary to consider the end use of the data. The end use of the data, be it location of the spill, enforcement, or support to cleanup, may also dictate the resolution or character of the data needed. Several general reviews of oil spill remote sensing have been prepared.2-7 These reviews show that although progress has been made in oil spill remote sensing, this progress has been slow. Furthermore, these reviews show that specialized sensors offer advantages to oil spill remote sensing. Off-the-shelf sensors have very limited application to oil spills.

6.2. VISIBLE INDICATIONS OF OIL Under many circumstances oil on the surface is not visible to the eye.8 Other than the obvious situations of nighttime and fog, in many situations oil cannot be seen. A very common situation is that of thin oil, such as from ship discharges, or

FIGURE 6.1 An example of problems in detecting slicks visually. There is no oil in this image. The differences in water color are caused by mineral fines at the top of the pictures and the meeting of darker water from the open ocean.

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FIGURE 6.2 Another example of confusion in the visible region. This anomaly is caused by the front between a river and seawater. Again there is no oil in this image.

FIGURE 6.3 An image of Herring “milk” on the water surface. This is often mistaken for oil in various sensors, and again there is no oil in this image.

the presence of materials, such as sea weed, ice, and debris, that mask oil presence. Often there are conditions on the sea that may appear like oil, when indeed there is no oil. These include wind shadows from land forms, surface wind patterns on the sea, surface dampening by submerged objects or weed beds, natural oils or biogenic material, and oceanic fronts. In the case of large spills, the area may be too great to be mapped visually. Several of these cases are illustrated in Figures 6.1 to 6.12. All of these factors dictate that remotesensing systems be used to assist in the task of mapping and identifying oil. In many cases, aerial observation and remote sensing are necessary to direct cleanup crews to slicks. Figure 6.13 shows a case where no aerial direction

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FIGURE 6.4 This image again shows no oil and shows open seawater at a front with mineralladen bay water.

FIGURE 6.5 An image of the Exxon Valdez tanker at Naked Island. The apparent oil is actually reflections from clean water and some wind ruffles on the sea. There is no oil in this image.

was given and a skimmer crew is missing the slick by about half a kilometer. Figure 6.14 shows a skimmer crew that was directed to the thicker slick in the area.

6.3. OPTICAL SENSORS 6.3.1. Visible The use of human vision alone is not considered remote sensing; however, it still represents the most common technique for oil spill surveillance. In the

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FIGURE 6.6 An image looking into a bay. The foreground material is oil; however what appears somewhat like oil further into the bay are actually surface wind calms.

FIGURE 6.7 An image of sheen from a major spill. One can see sheen to a distance of about 30 km and about 10 km wide. Large areas like this are hard to map without the aid of remote sensing.

past, major campaigns using only human vision were mounted with varying degrees of success.9 Optical techniques, using the same range of the visible spectrum detection, are the most common means of remote sensing. Cameras, both still and video, are common because of their low price and commercial availability. In recent years, visual or camera observation has been enhanced by the use of GPS (Global Positioning Systems).10 Systems are now available to directly map remote-sensing data onto base maps. In the visible region of the electromagnetic spectrum (approximately 400 to 700 nm), oil has a higher surface reflectance than water, but shows limited nonspecific absorption tendencies. Oil generally manifests throughout the

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FIGURE 6.8 An image of water from an airplane during foggy conditions. There is no oil in this image.

FIGURE 6.9 A visible image of a slick that had just been illegally discharged from a ship. The multiple colors are due to the light path interference and indicates a thickness of about 1 mm.

entire visible spectrum. Sheen shows up silvery and reflects light over a wide spectral region down to the blue. As there is no strong information in the 500 to 600 nm region, this region is often filtered out to improve contrast.11 Overall, however, oil has no specific characteristics that distinguish it from the background.12 Taylor studied oil spectra in the laboratory and the field and observed flat spectra with no usable features distinguishing it from the background.13 Therefore, techniques that separate specific spectral regions do not increase detection capability. Some researchers noted that while the oil spectra is flat, the presence of oil may slightly alter water spectra.14 It has been suggested that

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FIGURE 6.10 A visible image of a cleanup operation. Notice the various false indications of oil further away from the scene. Photography by Environment Canada.

FIGURE 6.11 An infrared image of a slick as taken in 1981. Note the annotation providing essential times and positions.

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FIGURE 6.12 A visible image of the same slick and at the same time as the one shown in Figure 6.11. This illustrates the higher capability that infrared imaging has under these specific conditions.

FIGURE 6.13 A visible image of a cleanup crew missing a slick by at least a half kilometer. The actual slick is noted on the image. Aerial direction of cleanup crews is not only desirable but necessary in many cases. Photography by Environment Canada.

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FIGURE 6.14 A visible image of a cleanup crew aiming toward the thickest slicks in the area as directed by an aerial surveillance team.

the water peaks are raised slightly at 570 to 590, 780 to 710, and 810 to 710 nm. At the same time there are depressions or troughs at 650 to 680 nm and 740 to 760 nm. It has been found that high contrast in visible imagery can be achieved by setting the camera at the Brewster angle (53 degrees from vertical) and using a horizontally aligned polarizing filter that passes only that light reflected from the water surface.15 This is the component that contains the information on surface oil.11 It has been reported that this technique increases contrast by up to 100%. Filters with band-pass below 450 nm can be used to improve contrast. View angle is important, and some researchers have noted that the thickness changes the optimal view angle.16 On land, hyperspectral data (use of multiple bands, typically 10 to 100) has been used to delineate the extent of an oil well blowout.17 The technique used was spectral reflectance in the various channels, as well as the usual black coloration. Video cameras are often used in conjunction with filters to improve the contrast in a manner similar to that noted for still cameras. This technique has had limited success for oil spill remote sensing because of poor contrast and lack of positive discrimination. Despite this, video systems have been proposed as remote-sensing systems.18 With new light-enhancement technology (low lux), video cameras can be operated even in darkness. Tests of a generation III night vision camera shows that this technology is capable of providing imagery in very dark night conditions.19,20 Scanners were used in the past as sensors in the visible region of the spectrum. A rotating mirror or prism sweeps the field-of-view (FOV) and directs the light toward a detector. Before the advent of CCD (charge-coupled device) detectors, this sensor provided much more sensitivity and selectivity than a video camera. Another advantage of scanners was that signals were

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digitized and processed before display. Recently, newer technology has evolved, and similar digitization can now be achieved without scanning by using a CCD imager and continually recording all elements, each of which is directed to a different FOVon the ground. This type of sensor, known as a pushbroom scanner, has many advantages over the older scanning types. It can overcome several types of aberrations and errors, the units are more reliable than mechanical ones, and all data are collected simultaneously for a given line perpendicular to the direction of the aircraft’s flight. Several types of scanners were developed. In Canada, the MEIS (Multidetector Electro-optical Imaging Scanner) and the CASI (Compact Airborne Spectrographic Imager) have been developed, and in the Netherlands, the Caesar system was developed.11, 21, 22 Digital photography has enabled the combination of photographs and the processing of images. Locke et al. used digital photography from vertical images to form a mosaic for an area impacted by an oil spill.23 It was then possible to form a singular image and to classify oil types by color within the image. The area impacted by the spill was also carried out. Video cameras are often used in conjunction with filters to improve the contrast in a manner similar to that noted for still cameras. This technique has had limited success for oil spill remote sensing because of poor contrast and lack of positive discrimination. The detection or measurement of oil in water has never been successfully accomplished using remote visible technology. There may be potential for light scattering technology. Stelmaszewski and coworkers measured the light scattering of crude oil in water emulsions and noted that scattering increases with wavelength in the UV range and decreases slightly with the wavelength of visible light.24 The use of visible techniques in oil spill remote sensing is largely restricted to documentation of the spill because there is no mechanism for positive oil detection. Furthermore, there are many interferences or false alarms. Sun glint and wind sheens can be mistaken for oil sheens. Biogenic material such as surface seaweeds or sunken kelp beds can be mistaken for oil. Oil on shorelines is difficult to identify positively because seaweeds look similar to oil and oil cannot be detected on darker shorelines. In summary, the usefulness of the visible spectrum for oil detection is limited. It is, however, an economical way to document spills and provide baseline data on shorelines or relative positions.

6.3.2. Infrared Oil, which is optically thick, absorbs solar radiation and reemits a portion of this radiation as thermal energy, primarily in the 8 to 14 mm region. In infrared (IR) images, thick oil appears hot, intermediate thicknesses of oil appear cool, and thin oil or sheens are not detected. The thicknesses at which these transitions occur are poorly understood, but evidence indicates that the transition between the hot and cold layer lies between 50 and 150 mm and the minimum

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detectable layer is between 10 and 70 mm.25-28 The reason for the appearance of the "cool" slick is not fully understood. A plausible theory is that a moderately thin layer of oil on the water surface causes destructive interference of the thermal radiation waves emitted by the water, thereby reducing the amount of thermal radiation emitted.8 This may be analogous to the appearance of the rainbow sheen, which is explained in Section 6.2. The cool slick would correspond to the thicknesses as observed above because the minimum destructive thickness would be about two times the wavelength, which is between 8 and 10 mm. This would yield a destructive onset of about 16 to 20 mm to about 4 wavelengths or about 32 to 40 mm. The destructive area is usually only seen with test slicks, which is explained by the fact that the more rapidly spreading oil is more transparent than the remaining oil. The onset of the hot thermal layer would in theory then be at thicknesses greater than this or at about 50 mm. IR devices cannot detect emulsions (water-in-oil emulsions) under most circumstances.29 This is probably a result of the high thermal conductivity of emulsions as they typically contain 70% water and thus do not show a temperature difference. IR cameras are now very common, and commercial units are available from several manufacturers. In the past, scanners with IR detectors were largely used. A disadvantage of the older type of IR detector, however, is that they required cooling to avoid thermal noise, which would overwhelm any useful signal. Liquid nitrogen, which provides about 4 hours of service, had traditionally been used to cool the detector. Some, smaller sensors use closed-cycle or Sterling coolers, which operate on the cooling effect created by expanding gas. While a gas cylinder or compressor must be transported with this type of cooler, refills or servicing may not be required for days at a time.30 In recent times, uncooled detectors are commonplace and have entirely replaced the older, cooled detectors. Most IR sensing of oil spills takes place in the thermal IR at wavelengths of 8 to 14 mm. A slightly different sensor, which is designed as a fixed-mounted unit, uses the differential reflectance of oil and water at 2.5 and 3.1 mm.31 Tests of a mid-band IR system (3.4 to 5.4 mm) over the Tenyo Maru oil spill showed no detection in this range, but ship scars were visible.32-34 Specific studies in the thermal IR (8 to 14 mm) show that there is no spectral structure in this region.35 Tests of a number of IR systems show that spatial resolution is extremely important when the oil is distributed in windrows and patches, emulsions are not always visible in the IR, and cameras operating in the 3 to 5 mm range are only marginally useful.36 Nighttime tests of IR sensors show that there is detection of oil (oil appears cold on a warmer ocean), however, the contrast is not as good as during daytime.36-38 The relative thickness information in the thermal IR can be used to direct skimmers and other countermeasure equipment to thicker portions of the slick. Figures 6.11, 6.12, 6.15, and 6.16 illustrate the utility of IR oil imaging. Oil

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FIGURE 6.15 An image of an oil slick formed from a composite of infrared and ultraviolet images. The red represents the thermal infrared and the thickest oil. The darker spots are intermediate thicknesses. The light blue area represents thin oil or sheen and is taken from the ultraviolet image.

FIGURE 6.16 A composite image of the infrared and ultraviolet images of a slick similar to that in Figure 6.11. The outlined areas are from the infrared sensor and represent the thicker oil. Areas of the infrared and ultraviolet sensors are also annotated.

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detection in the IR is not positive, however, as several false targets can interfere, including seaweed, shoreline, and oceanic fronts.39 IR is reasonably inexpensive, however, and is currently the prime tool used by the spill remote-sensor operator.

6.3.3. Ultraviolet Ultraviolet (UV) sensors can be used to map sheens of oil as oil slicks display high reflectivity of UV radiation even at thin layers (<0.1 mm). Overlaid UV and IR images are often used to produce a relative thickness map of oil spills. This has been illustrated in Figures 6.15 and 6.16. UV cameras, though inexpensive, are not often used in this process, however, as it is difficult to overlay camera images.30 Data from IR scanners and derived from push-broom scanners can be easily superimposed to produce these IR/ UV overlay maps. UV data are also subject to many interferences or false images such as wind slicks, sun glints, and biogenic material. Since these interferences are often different from those for IR sensing, combining IR and UV can provide a more positive indication of oil than using either technique alone.

6.4. LASER FLUOROSENSORS Laser fluorosensors are sensors that take advantage of the fact that certain compounds in petroleum oils absorb UV light and become electronically excited. This excitation is rapidly removed through the process of fluorescence emission, primarily in the visible region of the spectrum. Since very few other compounds show this tendency, fluorescence is a strong indication of the presence of oil. Natural fluorescing substances, such as chlorophyll, fluoresce at sufficiently different wavelengths than oil to avoid confusion. As different types of oil yield slightly different fluorescent intensities and spectral signatures, it is possible to differentiate between classes of oil under ideal conditions.40-50 Readers are referred to a separate subsection in this book for a review of laser fluorosensors. This section on remote sensing will just give a brief introduction. Most laser fluorosensors used for oil spill detection employ a laser operating in the UV region of 300 to 355 nm.40,50-52 With this wavelength of activation, there exists a broad range of fluorescent response for organic matter, centered at 420 nm. This is referred to as Gelbstoff or yellow matter, which can be easily annulled. Chlorophyll yields a sharp peak at 685 nm. The fluorescent response of crude oil ranges from 400 to 650 nm with peak centers in the 480 nm region. The use of laser fluorosensors for chlorophyll and other applications has been well documented.53 One laser fluorosensor operating at 488 nm from an Argon ion laser was successful in detecting oil from a ship platform.54

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Another phenomenon, known as Raman scattering, involves energy transfer between the incident light and the water molecules. When the incident UV light interacts with the water molecules, Raman scattering occurs. This involves an energy transfer between the incident light and the water molecules. The water molecules absorb some of the energy as rotational-vibrational energy and emit light at wavelengths, which are the sum or difference between the incident radiation and the vibration-rotational energy of the molecule. The Raman signal for water occurs at 344 nm when the incident wavelength is 308 nm (XeCl laser). The water Raman signal is useful for maintaining wavelength calibration of the fluorosensor in operation, but it has also been used in a limited way to estimate oil thickness because the strong absorption by oil on the surface will suppress the water Raman signal in proportion to thickness.55,56 The point at which the Raman signal is entirely suppressed depends on the type of oil, since each oil has a different absorption coefficient. The Raman signal suppression has led to estimates of sensor detection limits of about 0.05 to 0.1 mm.57 The principle of fluorescence can also be used on a smaller scale. A handheld UV light has been developed to detect oil spills at night at short range.58 Another related instrument is the Fraunhofer Line Discriminator, which is essentially a passive fluorosensor using solar irradiance instead of laser light.11 This instrument was not very successful because of the limited discrimination and the low signal-to-noise ratio. Laser fluorosensors have significant potential as they may be the only means to discriminate between oiled and unoiled seaweed and to detect oil on different types of beaches. Tests on shorelines show that this technique has been very successful.59 Algorithms for the detection of oil on shorelines have been developed.60 Work has been conducted on detecting oil in the water column, such as occurs with the product, Orimulsion.61-65 The fluorosensor is also the only reliable means of detecting oil in certain ice and snow situations. Operational use shows that the laser fluorosensor is a powerful tool for oil spill remote sensing.19,43

6.5. MICROWAVE SENSORS 6.5.1. Radiometers Microwave radiometers detect the presence of an oil film on water by measuring an interference pattern excited by the radiation from free space. The apparent emissivity factor of water is 0.4 compared to 0.8 for oil.11,66 This passive device can detect this difference in emissivity and could therefore be used to detect oil. In addition, as the signal changes with thickness, in theory, the device could be used to measure thickness. This detection method has not been very successful in the field, however, as several environmental and oilspecific parameters must be known. In addition, the signal return is dependent

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on oil thickness but in a cyclical fashion. A given signal strength can imply any one of two or three signal film thicknesses within a given slick. Microwave energy emission is greatest when the effective thickness of the oil equals an odd multiple of one quarter of the wavelength of the observed energy. Biogenic materials also interfere, and the signal-to-noise ratio is low. In addition, it is difficult to achieve high spatial resolution (might need resolution in meters rather than the typical tens of meters for a radiometer).67 The Swedish Space Agency has carried out work with different systems, including a dual-band, 22.4- and 31-GHz device, and a single band 37-GHz device.68 Skou, Sorensen, and Poulson describe a two-channel device operating at 37.5 and 10.7 GHz.69 Mussetto and coworkers at TRW described the tests of 44-94-GHz and 94-154-GHz, two-channel devices over oil slicks.70 They showed that correlation with slick thickness is poor and suggest that factors other than thickness also change surface brightness. They suggest that a singlechannel device might be useful as an all-weather, relative-thickness instrument. Tests of single-channel devices over oil slicks have also been described in the literature, specifically a 36-GHz and a 90-GHz device.71,72 A new method of microwave radiometry has recently been developed in which the polarization contrasts at two orthogonal polarizations are measured in an attempt to measure oil slick thickness.73 A series of frequency-scanning radiometers have been built and appear to have overcome the difficulties with the cyclical behavior.74,75 In summary, passive microwave radiometers may have potential as allweather oil sensors. Their potential as a reliable device for measuring slick thickness, however, is uncertain at this time.

6.5.2. Radar Capillary waves on the ocean reflect radar energy, producing a “bright” image known as sea clutter. Since oil on the sea surface dampens capillary waves, the presence of an oil slick can be detected as a “dark” sea or one with an absence of this sea clutter.76 Unfortunately, the oil slick is not the only phenomenon detected in this way. There are many interferences or false targets, including freshwater slicks, wind slicks (calms), wave shadows behind land or structures, seaweed beds that calm the water just above them, glacial flour, biogenic oils, and whale and fish sperm.77-81 As a result, radar can be ineffective in locations such as Prince William Sound, Alaska where dozens of islands, freshwater inflows, ice, and other features produce hundreds of such false targets. Despite these limitations, radar is an important tool for oil spill remote sensing because it is the only sensor that can be used for searches of large areas and it is one of the few sensors that can “see” at night and through clouds or fog. Figures 6.17 to 6.23 illustrate the many slick look-alikes that appear in radar displays.

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FIGURE 6.17 Airborne radar image of a small test slick attended by two boats. Note that the boats cast a radar shadow on both their sides. A ship is passing to the top right of the image, and the ship’s wake also casts a radar shadow.

FIGURE 6.18 A satellite Radarsat-I image of a large area of sea during the raising of the Irving Whale barge. Note that the area to the left that appears darker is caused by wind shadows and low winds. Only the small areas noted are actually slicks. One might have to know beforehand where the slicks were before interpreting this image.

The two basic types of imaging radar that can be used to detect oil spills and for environmental remote sensing in general are Synthetic Aperture Radar (SAR) and Side-Looking Airborne Radar (SLAR). SLAR is an older but less expensive technology that uses a long antenna to achieve spatial resolution. SAR uses the forward motion of the aircraft to synthesize a very long antenna, thereby achieving very good spatial resolution, which is independent of range, with the disadvantage of requiring sophisticated electronic processing. Though inherently more expensive, the SAR has greater range and resolution than the

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FIGURE 6.19 A close-up of the area shown in Figure 6.18 from radar satellite. These dark areas are actually oil, as confirmed by ground observation. The white spots in the center are ships.

FIGURE 6.20 An image of the source of the oil shown in Figure 6.19. The ships shown here appear as white spots in the radar image in Figure 6.19. Photography by Environment Canada.

SLAR. In fact, comparative tests show that SAR is vastly superior.82-84 Search radar systems, such as those frequently used by the military, cannot be used for oil spills because they usually remove the clutter signal, which is the primary signal of interest for oil spill detection. Furthermore, the signal processing of this type of radar is optimized to pinpoint small, hard objects, such as periscopes. This signal processing is very detrimental to oil spill detection.

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FIGURE 6.21 A radar satellite image of a coastline. There is no oil in this image. The track through the image is the wake of a vessel. It should be noted that all ship wakes leave a shadow like this, making it very hard to use radar to detect ship discharges. The dark areas near the coastline are low-wind areas, probably caused by the coast wind shadows.

FIGURE 6.22 A view of an area near ships and platforms. A possible slick is pointed out; however, as it is very near a major low-wind area, it is difficult to say whether or not this is really a slick.

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FIGURE 6.23 A view of the track of a vessel. Despite the interpretation that there was a slick behind the vessel, the black line may be simply a ship wake. Note also the other dark areas from low winds and coast wind shadows.

SLAR has predominated airborne oil spill remote sensing, primarily because of the lower price.85,86 There is some recognition among the operators that SLAR is very subject to false hits, but solutions are not offered. Experimental work on oil spills has shown that X-band radar yields better data than L- or C-band radar.87,88 It has also been shown that vertical antenna

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polarizations for both transmission and reception (VV) yield better results than other configurations.82,89-91 The ability of radar to detect oil is also limited by sea state. Sea states that are too low will not produce enough sea clutter in the surrounding sea to contrast to the oil, and very high seas will scatter radar sufficiently to block detection inside the troughs. Indications are that minimum wind speeds of 1.5 m/s (~3 knots) are required to allow detectability, and a maximum wind speed of 6 m/s (~12 knots) will again remove the effect.92-94 The most accepted limits are 1.5 m/s (~3 knots) to 10 m/s (~20 knots). This limits the environmental window of application of radar for detecting oil slicks. Gade et al. studied the difference between extensive systems from a space-borne mission and a helicopter-borne system.95 They found that at high winds, it was not possible to discriminate biogenic slicks from oil. At low-wind speeds, it was found that images in the L-band showed discrimination. Under these conditions, the biogenic material showed greater damping behavior in the L-band. Okamoto et al. studied the use of ERS-1 using an artificial oil (oleyl alcohol) and found that an image was detected at a wind speed of 11m/s, but not at 13.7 m/s.96 SAR can be polarimetric imaging that is horizontal-horizontal (HH), vertical-vertical (VV), and cross combinations of these. Several researchers have shown that VV is best for oil spill detection and discrimination.97-100 Migliaccio et al. showed that the co-polarized phase differencedfor example, the difference between the HH and VV phases can be used to discriminate oil FIGURE 6.24 An HH polarized view of the sea surface.

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131 FIGURE 6.25 A VV polarized view of the same area of sea surface. Note that this polarization yields a slightly clearer image of sea-surface details than shown in Figure 6.24.

slicks from biogenic slicks.97 A larger standard deviation for the slick, compared to the sea, typically indicates that it is oil. Figures 6.24 and 6.25 show the difference between a VV and HH polarization. Radar has also been used to measure currents and predict oil spill movements by observing frontal movements.101 Work has shown that frontal currents and other features can be detected by SAR.102 Shipborne radar has similar limitations and the additional handicap of low altitude, which restricts its range to between 8 and 30 km, depending on the height of the antenna. Ship radars can be adjusted to reduce the effect of sea clutter deenhancement. Shipborne radar successfully detected a surface slick in the Baltic Sea from 8 km away and during a trial off the coast of Canada at a maximum range of 17 km.103 During the Prestige spill, a Netherlands vessel successfully used this technique to guide a recovery vessel into slicks. The technique is, however, very limited by sea state, and in all cases where it was used, the presence and location of the slick were already known or suspected. Recently, researchers have carried out work on improving the imaging of slicks from shipborne radars.104 Today there are some commercial products that enhance the images from shipborne radar to enable some oil imaging. Gangeskar has proposed an automatic system that can be mounted on oil drilling platforms.105 This system would use standard X-band ship navigation units and would provide an alert if an oil spill was present. The system includes

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an extensive postprocessing system to provide both a user-friendly GUI and an automatic detection and alert system. The system has not been fully tested to date. In summary, radar optimized for oil spills is useful in oil spill remote sensing, particularly for searches of large areas and for nighttime or foul weather work. The technique is highly prone to false targets, however, and is limited to a narrow range of wind speeds. Because of the all-weather and daynight capability, radar is now the most common means of remote sensing.

6.5.2.1. Radar Processing Because radar detection of oil spills is so highly susceptible to false images, much work has taken place on means to differentiate oil slicks and false targets, often called look-alikes. These look-alikes include: low-wind areas, areas sheltered by land, rain cells, organic films, grease ice, wind fronts, up-welling zones, oceanic fronts, algae blooms, current shear zones, and so on.106 The discussion in this subsection is relevant to both satellite and airborne SAR systems. Several “automatic” systems have been designed for slick detection.107 Limited testing with actual satellite output has shown that many false signals are present in most locations.108,109 Extensive effort on data processing appears to improve the chances of oil detection.110 In recent years, automatic systems have given way to systems involving smart algorithms that are manipulated by operators.111-113 The most common way to eliminate wind-origin look-alikes is to map the wind fields in the same coordinates as the radar data.110,114 The most common slick look-alikes are low-wind areas. One group of researchers used radar wind data calibrated to wind data from an ocean buoy to map oil seeps in the southern Gulf of Mexico.114 Most researchers used some form of neural networks or fuzzy logic to assist in the discrimination of look-alikes and the intended targets.115-118 Others used various forms of models such as range dependence models.119 Topouzelis and coworkers developed several series of mathematical networks for differentiating slicks from look-alikes.120-123 The basis of these networks is the idea that generally oil slicks are imaged through a complex series of processes and conditions. Thus imaging is not a simple statistical manipulation. The same group developed a fuzzy classification to differentiate look-alikes from oil spills. The methodology involved four procedures. The first is the segmentation of the image into large image segments with different statistical values. In the second procedure, a detailed scale segmentation is carried out, and statistical values of each segment are compared to the threshold of the large segment from which it came. Third, the dark portions are classified according to the properties of the surrounding areas. Finally, the dark areas are classified using knowlege bases. The group also examined the use of

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forward-feed neural networks to discriminate slicks from look-alikes.120,124 Several topologies of forward-feed neural networks were examined, and none were better than others. The networks yielded classification accuracies as high as 91.3 to 93.6% for the given example. A recent work by Topouzelis used the inputs of shape texture, asymmetry, mean difference to neighbours, and power to the mean images in a neural network.106 The workers used forward-feed neural networks. It was found that the classification accuracy was 99.4% for the MLP network in the test case. Later, Topouzelis and co workers used a similar method to test a data set of 69 oil spills and 90 look-alikes.122 They found a combination of 11 features out of a possible 25 features. The 11 features found to be best for discrimination are perimeter, shape factor object mean value, ratio of the power to mean ratios, local area contrast ratio, mean border gradient, maximum border gradient, standard deviation border gradient, maximum border gradient, mean difference to neighbors, and spectral texture. Use of these factors resulted in classification accuracies of 85.3% for oil spills and 84.4% for look-alikes. A similar approach is to use a classification scheme that incorporates some of the same input parameters. Karantzalos and Argialas proposed a classification scheme involving processes and then a classification scheme. The first processing step involves filtering and levels.125 The second step is segmentation of the images to include all suspected slicks. The final step is to classify the potential slicks according to area, perimeter, shape complexity eccentricity, orientation, segment mean border gradient, inside segment standard deviation, and outside segment standard deviation. Several researchers have used Geographic Information System (GIS) databases to assist in the interpretation of SAR imagery.125-131 The technique divides the area of interest into segments and notes data such as currents, proximity to land, wind, and sea lanes. These parameters are then correlated to the SAR images. For example, oil spills are much more likely under the correct wind conditions, in sea lanes, and far from land. Tahvonen used data sets including wind speed and direction, sea-surface temperature, heavy rain, and location of algae blooms to assist in the discrimination.126 Muellenhoff proposed a data set consisting of wind information, sea-surface temperature, chlorophyll-a concentration, geostrophic currents, wave information, contextual background information, and existing oil spill databases.129 The assigned influences were wind speedd30%; wind directiond12%; sea-surface temperatured14%, chlorophyll-a concentrationd10%; oil portsd10%; and main traffic linesd20%. Wave and current direction only accounted for 2% each. Migliaccio and group studied the processing of SAR images from an aircraft-based sensor.132-134 It was noted that the main obstacle to analysis was speckle in the images. Speckle is caused by stray reflectances, such as from rough seas. Speckle is also caused by random constructive and destructive interference. Since speckle is temporary, multi-look imaging is one way to decrease speckle by a large amount. Further processing can then be achieved by

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combining multi-look data with wind data, best obtained from satellite scatterometers. The technique proposed for multi-look data is to divide the SAR imagery into subbands and then generate lower-resolution imagery. Then the images are averaged. This results in reduction of speckle. To process singlelook data with high speckle content, filters are used. First speckle is removed, and then an ROA (ratio of average) filter is used. In both techniques, edge detection is used to find the actual limits of the slicks or look-alikes. Marghany and co workers used a fractal method to analyze SAR data.135 The images are broken into fractals, and these fractals have dimensions that are different for oil spills and look-alikes. A further study under different wind speeds showed that there were differences only in the wide beam mode for lowwind zones and current shear features between real oil slicks.136 Danisi et al. utilized a similar approach.137 Another method employed by researchers to separate oil slicks from lookalikes is to use textural analysis.138,139 Direct statistical methods are also employed. Tello et al. noted that an algorithm characterizing the border between oil spill candidates and the surrounding sea allows for good classification.139 Lounis et al. used a measure of similarity between the local probability density function of clean water and of the dark area to be examined.140 Comparing the two values is said to result in discrimination between oil and look-alikes. Pelizzari employed a similar technique using graph cuts to estimate a smoothness factor.141 Ferraro et al. describe the development of an operational system for the Mediterranean Sea and show a procedure for identifying oil spills as (1) isolation and contouring of all dark signatures, (2) extraction of shape and backscattering contrast signatures, (3) test of these values against standard values, and (4) calculation of the probabilities of each patch.142-144 Another series of techniques involves the use of two streams of information. Several researchers used both SAR and visible information from the MODIS (Moderate Resolution Imaging Spectroradiometer) satellites to discriminate between look-alikes and oil slicks.145 The visible imagery is subject to false images, but not the same ones as satellites, and thus discrimination can be achieved to a degree. Similarly, Sipelgas used visible imagery from the MODIS satellite to assist in discrimination of false images from oil slicks in the Gulf of Finland.146 Adamo et al. used three streams for informationdSAR data, MODIS, and MERIS datadto discriminate look-alikes from actual spills.145

6.5.3. Microwave Scatterometers A microwave scatterometer is a device that measures the scattering of radar energy by a target. One radar scatterometer was flown over several oil slicks and used a low-power transmitter operating in the Ku band (13.3 GHz).11 The scatterometer detected the oil, but discrimination was poor. The “Heliscat,” a device with five frequencies, has been used to investigate capillary wave

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damping.92 The advantage of a microwave scatterometer is that it has an aerial coverage similar to optical sensors and it can look at several incident angles. The main disadvantages include the lack of discrimination for oil and the lack of imaging capability.

6.5.4. Surface Wave Radars It is possible to send radio waves along the sea using high frequency. The conductivity of the sea acts as a form of wave guide. These radars can be used to detect ships as far out as 500 km.147 Since these are surface wave phenomena, only targets above the surface are detected; thus slicks may not be detected by this technique.148 Modeling of the technique does not show whether there is potential for this method.149

6.5.5. Interferometric Radar Radars can be used to measure height, currents, and other surface elevation phenomena using interferometric techniques. Some radar systems on aircraft are fitted for this application, such as the government of Canada Convair 580. This can also be carried out in space using two satellites traveling in tandem. One research group employed the tandem satellite pairs of ERS-2 and ENVISAT to carry out such work, but there are no reports on the use on oil spills.150

6.6. SLICK THICKNESS DETERMINATION There has long been a need to measure oil slick thickness; this need has been expressed both within the oil spill response community and among academics in the field. There are presently no reliable methods, either in the laboratory or in the field, for accurately measuring oil-on-water slick thickness. The ability to do so would significantly increase understanding of the dynamics of oil spreading and behavior. Knowledge of slick thickness would make it possible to determine the effectiveness of certain oil spill countermeasures, including dispersant application and in-situ burning. Indeed, the effectiveness of individual dispersants could be determined quantitatively if the oil remaining on the water surface following dispersant application could be accurately measured.151,152

6.6.1. Visual Thickness Indications A very important tool for working with oil spills has been the relationship between appearance and thickness. Careful study of the literature on this relationship and comparison of this to field experience shows that there is limited potential to scale thicknesses to visual appearance.8 The only physical-based appearances that occurs are thicknesses of about 0.7 to 2.5 mm

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TABLE 6.1 Relationship of Thickness to Appearance Visibility Thresholds (mm)

Typical thickness

Darkening Minimum Silvery Rainbow Colors

Dull Colors

Dark

0.09

2.7

8.5

0.1

0.6*

0.9

*Note this is the only physical-based appearance factor

FIGURE 6.26 A rainbow sheen above a sunken vessel. The appearance of a rainbow sheen is the only strong visible indicator of slick thickness, and thickness may be between about 0.7 and 2.5 mm. Photography by Environment Canada.

at which the rainbow colors appear as a result of multiple constructive and destructive interferences by light. Table 6.1 presents a summation of the best knowledge on this phenomenon. Figures 6.26 and 6.27 show typical rainbow sheens for which we can estimate that the thickness is about 1 mm. This is the only color appearance that has a physical slick thickness associated with it.

6.6.2. Slick Thickness Relationships in Remote Sensors A number of investigators tried to correlate slick thickness with appearance in various remote-sensing instruments. Hollinger and Mennella conducted a series of eight controlled oil spills off Virginia to investigate the use of microwave radiometry to delineate oil spills.153 They used 19.4 and 69.8 GHz radiometers on the spills. Measurements using sorbents were used to calibrate the

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FIGURE 6.27 A rainbow sheen above another sunken vessel. The appearance of a rainbow sheen is the only strong visible indicator of slick thickness, and thickness may be between about 0.7 and 2.5 mm. Photography by Environment Canada.

radiometer. It was noted that the sheens typically had a thickness of 2 to 4 mm. It was found that 90% of the oil was in 10% of the slick area and that the microwave threshold was about 0.1 mm (100 mm). A series of experiments was carried out in 1979 to evaluate IR and SLAR for oil spill detection.154 The imagery was correlated against visual and sorbent measurements, which were used to derive a thickness estimate. It was concluded that the IR threshold was between 25 and 50 mm and for SLAR 100 nm. Furthermore, manipulation of data showed that a mass balance could be achieved if the thickness at which the IR showed oil to be colder at the sea occurred at 100 mm and for the heated portion of the oil at 1,000 mm. The United Kingdom conducted Isowake Experiments in 1982.155,156 On the basis of estimations and calculations, it was concluded that the lowest detectable slick thickness for IR was between 10 and 50 mm, whereas hot spots in the IR image could be as much as 1,000 mm. MacDonald et al. used photography from the space shuttle to define up to 124 slicks in an area of the Gulf of Mexico, offshore Louisiana.157 Similarly, a thematic image from Landsat showed at least 66 slicks in one large area. Some of the thickness relationships were based on unpublished experimental data from Duckworth. Brown et al. conducted experiments to measure the visibility of oil slicks. The observers and a visible UV camera were mounted in a crane basket 30 m over the slick.12,158,159 It was found that the detection ability decreased by over 50% for most oils and for the cameras when the angle was changed from 90 to 55 degrees from the horizontal (equivalent incidence angle of 0 to 35 degrees). Detectability degraded to 70% and sometimes to nil as the viewing angle was

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decreased past 55 through 35 degrees. Brown et al. conducted several experiments to ascertain the relationship between thickness of slicks and the density (or intensity) of the IR image.39 The thicknesses varied between 1 and 10 mm, and thicknesses were measured using an acoustic system. No relationship between slick thickness and IR brightness was found.

6.6.3. Specific Thickness Sensors The suppression of the water Raman peak in laser fluorosensor data has not been fully exploited or tested. This technique may work for thin slicks, but not necessarily for thick ones, at least not with a single excitation frequency. Attempts have been made to calibrate the thickness appearance of IR imagery, but also without success. It is suspected that the temperatures of the slick as seen in the IR are highly dependent on oil type, sun angle, and weather conditions. If so, it may not be possible to use IR as a calibrated tool for measuring thickness. Because accurate ground-truth methods do not exist, it is very difficult to calibrate existing equipment.160,161 The use of sorbent techniques to measure surface thickness yields highly variable results.151 As noted in the section on microwave radiometers, the signal strength measured by these instruments can imply one of several thicknesses. This methodology does not appear to have potential other than for measuring relative oil thickness. A variety of electrical, optical, and acoustic techniques for measuring oil thickness have been investigated.161,162 Two promising techniques were pursued in a series of laboratory measurements. In the first technique, known as thermal mapping, a laser is used to heat a region of oil, and the resultant temperature profiles created over a small region near this heating are examined using an IR camera.163 The temperature profiles created are dependent on the oil thickness. A more promising technique involves laser acoustics.164,165 The Laser Ultrasonic Remote Sensing of Oil Thickness (LURSOT) sensor consists of three lasers, one of which is coupled to an interferometer to accurately measure oil thickness.160,165-168 The sensing process is initiated with a thermal pulse created in the oil layer by the absorption of a powerful CO2 laser pulse. Rapid thermal expansion of the oil occurs near the surface where the laser beam was absorbed, which causes a steplike rise of the sample surface as well as an acoustic pulse of high frequency and large bandwidth (~15 MHz for oil). The acoustic pulse travels down through the oil until it reaches the oilewater interface where it is partially transmitted and partially reflected back toward the oileair interface, where it slightly displaces the oil’s surface. The time required for the acoustic pulse to travel through the oil and back to the surface again is a function of the thickness and the acoustic velocity of the oil. The displacement of the surface is measured by a second laser probe beam aimed at the surface. Motion of the surface induces a phase or frequency shift (Doppler shift) in the reflected probe beam. This phase or frequency modulation of the probe beam can then be demodulated with an interferometer.169 The thickness

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FIGURE 6.28 The signal from a 3-laser-thickness sensor. The time corresponds to a thickness of about 6 mm. This was measured by a prototype sensor mounted in an aircraft and flying over bins with various thicknesses of oil on water.

can be determined from the time of propagation of the acoustic wave between the upper and lower surfaces of the oil slick. This is a very reliable means of studying oil thickness and has great potential. Laboratory tests have confirmed the viability of the method, and a test unit has been flown to confirm its operability.160 Figure 6.28 shows the first airborne measurement of slick thickness. Several attempts have been made to measure thickness by using visible spectral imaging. As there are no visual indications other than the rainbow sheen area around 0.8 mm, these efforts are wasted.8,170

6.7. ACOUSTIC SYSTEMS Pogorzelski has shown that acoustic means can be used to measure oil viscosities on the surface.171 A directional acoustic system employing highfrequency forward specular scattering was used in the laboratory and at sea. Signals scattered are related to the rheological film properties. It is not known at this time if the system is scalable or exactly what the limitations are.

6.8. INTEGRATED AIRBORNE SENSOR SYSTEMS Increasingly, a number of different types of airborne oil spill remote sensors are being consolidated into sensor systems. The reason for this integration is to take advantage of the different information provided by each of the specific sensors and combine the information to provide a more complete and comprehensive

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information product. Although each of the individual sensors has specific inherent weaknesses such as false detections, these false detections are often different for each sensor type; hence a consolidation of information can help resolve and remove some of the uncertainties that exist from a single data source. Furthermore, additional information such as the relative thickness of the oil slick can be deduced from the overlaying of imagery from several sensor types. Although the absolute thickness of an oil slick remains the subject of continued research and scientific opinion, the ability to locate the thicker portions of the slick is essential in terms of operational spill cleanup and response. In addition to the integration of a number of remote sensors into a sensor system, information from other sources such as marine vessel traffic surveillance systems (i.e., automatic identification system, AIS) can be integrated and can play an essential role in identifying the source of the marine pollution. Two commercially available airborne marine oil spill remote-sensing systems are the MEDUSA and the MSS 6000.172-174 MEDUSA incorporates a number of sensor technologies such as laser fluorosensors, IR/UV line scanners, forward-looking IR sensors, microwave radiometers, SLAR systems, and camera systems, as well processing software into a flexible realtime data acquisition and processing system. The data from the various sensors are geo-referenced and fused with information from Airborne Information Systems (AIS) and marine surveillance radars into a GISdbased display output format. The processing software is known as the Oil Spill Scene Analysis System (OSSAS) and allows for the extraction of features such as the area of oil coverage, including areas of intermediate and thicker portions of the slick. The MSS 6000 Maritime Surveillance System is comprised of a flexible suite of sensors such as SLAR systems, IR/UV line scanners, forward-looking IR sensors, microwave radiometers, and camera systems, along with data processing and mission management software in order to perform the oil spill remote-sensing surveillance task. The MSS 6000 also focuses on sensor integration and includes AIS and marine search radar inputs. All sensor data, imagery, slick targets, vessels, and the like are annotated using navigation data from a single source to form an integrated part of a GIS). Both the MEDUSA and MSS 6000 can distribute their data in neardreal time via direct downlink or satellite communications to vessels or shore-based communications centers. A large number of maritime nations are now employing integrated airborne sensor systems.174,175

6.9. SATELLITE REMOTE SENSING The use of optical satellite remote sensing for oil spills has been attempted several times. The slick from the IXTOC I well blowout in Mexico was detected using GOES (Geostationary Operational Environmental Satellite) and by the AVHRR (Advanced Very High Resolution Radiometer) on the

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LANDSAT satellite.11 A blowout in the Persian Gulf was subsequently detected. The massive Exxon Valdez slick was detected on SPOT (Satellite Pour l’Observation de la Terre) satellite data.176 Oiled ice in Gabarus Bay resulting from the Kurdistan spill was detected using LANDSAT data.177,178 Several workers were able to detect the Arabian Gulf War Spill in 1991.179-182 The Haven spill near Italy was also monitored by satellite.183 A spill in the Barents Sea was tracked using an IR band on NOAA 10.184 It is significant to note that, in all these cases, the position of the oil was known and data had to be processed to actually see the oil, which usually took several weeks. Newer findings show that the ability to detect oil may be a complex function of conditions, oil types, and view angles.185-187 Figure 6.29 shows a visible satellite image of an area in Russia in which there was a massive pipeline spill. As noted in the caption for this image, the oil is not visible; however, a round lake in the image was mistaken for oil. Figure 6.30 shows an oiled ice area off Canada in which sediment and oil appear alike. There are several problems associated with relying on satellites operating in optical ranges, for oil spill remote sensing. The first is the timing and frequency of overpasses and the absolute need for clear skies to perform optical work.188 The chances of the overpass and the clear skies occurring at the same time give

FIGURE 6.29 A SPOT satellite visible image of an area in Russia where a large oil spill occurred. The oil spill is shown by the arrows. The black round objects are lakes. This illustrates that satellite visible imagery is difficult to interpret.

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FIGURE 6.30 A satellite visible image of an area off the east coast of Canada where an oil spill had occurred. Some of the black stripes in the white ice are oil mixed with sediment; others are sediment. The black on the right is land and the black on the left is sea. This image also illustrates the lack of discrimination of targets using visible satellite imagery.

a very low probability of seeing a spill on a satellite image. This point is well illustrated in the case of the Exxon Valdez spill.189 Although the spill covered vast amounts of ocean for over a month, there was only one clear day that coincided with a satellite overpass, and that was on April 7, 1989. Another disadvantage of satellite remote sensing is the difficulty in developing algorithms to highlight the oil slicks and the long time required to do so. For the Exxon Valdez spill, it took over two months before the first group managed to “see” the oil slick in the satellite imagery, although its location was precisely known. Recently, several workers have attempted to use MODIS visible data to detect oil spills.190,191 To be successful, these techniques generally rely on ancillary data such as suspected position or other satellite data. There is some information on slicks available from angular information. For example, Chust and Sagarminaga used the Multi-angle Imaging SpectroRadiometer (MISR) sensor aboard a satellite to detect oil spills on Lake Maracaibo, Venezuela.192 This sensor uses nine push-broom cameras at fixed angles from nadir to 70.5o to examine particular surfaces. A comparison of this angular sensor shows that better contrast was obtained than a simple nadir camera on another satellite. Data analysis showed that oil spills appear in

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greater contrast in those view angles affected by sun glitter because of the presence of oil. Recently, IR data from satellite has been used to map the land oil pollution in Kuwait.193 It was found that the old hydrocarbon-contaminated areas showed as much as 10oC difference from the surrounding land. Ground-truthing was used extensively in compiling the data. Casciello et al. also made an attempt to use IR imagery from the thermal IR region of the AVHRR satellite to locate known oil spills.194 Radar satellites, including ERS-1 and -2, Radarsat-1 and -2, and ENVISAT, are useful in detecting large offshore spills and in spotting anomalies.195-198 Radarsat has been used for detecting oil seeps and smaller spills resulting from an oil barge.199,200 The relative location of these smaller slicks was known before the detection. A novel application of Radarsat has been the study of oil lakes in the deserts of Kuwait.201,202 A number of nations now use radar satellites routinely to provide imagery for larger spills and to give indications of ship discharges. ERS-1 and 2 have been used for mapping oil spills in the Caspian Sea.202 Fortuny et al. describe the use of ERS-2 and ENVISAT to provide imagery during the Prestige incident off Spain.203 Torres Palenzuela and co workers used two ASAR (Advanced SAR) images from the Envisat satellite to study the Prestige spill off Spain.204 Using several techniques that were readily-available, such as filtering and comparison to GIS data of the areas, several slicks were identified. These slicks were confirmed by recorded sightings from helicopters and ships. Several countries have instituted satellite monitoring systems for oil pollution.205,206 Many of these countries use processing methods as described above. Extensive programs are in place in the Baltic Sea, North Sea, and English Channel.143 There are now beginning programs in the Black, Caspian, and Azov seas.206,207 Canada has had a program in place for several years.205 The Mediterranean Sea has had such a program for a long time.141,142 A constellation of monitoring satellites is proposed for the Mediterranean sea. In recent years, a number of new satellite-borne SAR sensors have been launched; see Table 6.2. While one of these sensors, Radarsat-2, operates in the traditional Cdband, TerraSARdX and Cosmos Skymed operate in the Xdband, while the PALSAR sensor on ALOS operates in the Ldband. As noted above, Xdband is the preferred band for oil spill remote sensing in terms of Bragg scattering. All four of these new SAR satellites have polarimetric imaging modes (some are experimental vs. operational modes) and much higher spatial resolution (down to 3 m), which may have application for oil spill remote sensing. Radarsat-2, like its predecessor, is an operational commercial satellite that can be tasked to respond to emergency situations such as major oil spills. The time required to task Radarsat-2 in emergency mode is now 4 hours, which is a large improvement from the 12 hours required to task its predecessor. As noted above, VV polarization provides a superior clutter-to-noise ratio (CNR) over HH polarization for oil spill detection. Radarsat-2 is fully

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TABLE 6.2 Current and Future Satellite-Borne SAR Sensors Satellite

Launch Date

Owner/Operator

Band

ERS-2

1995

European Space Agency

C

RADARSAT-1

1995

Canadian Space Agency

C

RADARSAT-2

2007

Canadian Space Agency

C

ENVISAT (ASAR)

2002

European Space Agency

C

ALOS (PALSAR)

2006

Japan Aerospace Exploration Agency

L

TerraSAR-X

2007

German Aerospace Centre

X

Tandem -X

tbd

German Aerospace Centre

X

Cosmos Skymed-1/2

2007

Italian Space Agency

X

TecSAR

2008

Israel Aerospace Industries

X

Sentinel-1

2012

European Space Agency

C

RADARSAT-Constellation (3-satellites)

2014

Canadian Space Agency

C

polarimetric, and there is interest in investigating whether a dual polarization ScanSAR mode utilizing VV/VH polarizations will work for oil and ship detection, respectively, as part of the Integrated Satellite Tracking of Pollution (ISTOP) program.208 The increased number of SAR satellites, as well as the plans to operate constellations of small satellites such as Cosmos (Constellation of Small Satellites for Mediterranean basin Observation), will provide increased temporal coverage with revisit times down to a few hours in some circumstances. The opportunity for increased frequency of image collection should prove useful to the oil spill response community. Figures 6.31 to 6.36 show the use of radar satellites and the look-alikes to oil that sometimes appear in the images.

6.10. OIL UNDER ICE DETECTION The difficulties in detecting oil in or under ice are numerous. Ice is never a homogeneous material but rather incorporates air, sediment, salt, and water, many of which may present false oil-in-ice signals to the detection mechanisms. In addition, snow on top of the ice or even incorporated into the ice adds complications. During freeze-up and thaw in the spring, there may not be distinct layers of water and ice. There are many different types of ice and

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FIGURE 6.31 A satellite radar image of a known spill off the Galapagos Islands. Note that most of the image consists of slick look-alikes.

different ice crystalline orientations. A separate subsection in this book provides a review of oil in and under ice.

6.11. UNDERWATER DETECTION AND TRACKING Many different techniques have been tried for underwater oil detection. First, the division should be made between oil in the water column or floating on a pycnocline, and oil on the bottom. Quite different physics and conditions can apply to these different situations. Several parties have tried to use standard sonars to detect submerged oil on the bottom. Oil on the bottom can appear as a softer surface than ordinary bottom sediment.209 The problem arises in that vegetation on the bottom also appears similar, and thus many false positives arise. In the water column, sonar can be useful as it can locate intermediate oil on pycnoclines; however, there is

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FIGURE 6.32 A satellite radar image of the large Sea Empress spill off the United Kingdom. The dark areas near the shore are calm areas. Note that the slick and these calm areas blend so that there is no delineation between them near the shoreline.

FIGURE 6.33 A Radarsat-1 image of the large Sea Empress spill off the United Kingdom. Similar features as in Figure 6.32 are noted.

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FIGURE 6.34 A third satellite radar image of the large Sea Empress spill off the United Kingdom. This image was taken a few days after the images in Figures 6.32 and 6.33. It appears that the oil slick has separated and some has moved to the bottom of the photograph and part toward the shore. This was never confirmed, and the “slick” at the bottom of the photograph may have indeed been oceanographic features.

no unique signature, and there are often weeds and other debris on pynoclines. Wendelboe et al. report on tests using a 200 and 400 kHz (dual-frequency) multibeam system.210 The contributing signal is the lower acoustic reflectivity of the oil than typical bottom geological formation or the better reflection than weed beds. Wendelboe et al. used the backscatter signals from several tests to develop algorithms for oil detection. This was tested in a tank with a 90% success rate and a 23% false detection rate. Oil on the bottom has successfully been mapped by underwater cameras, often mounted on sleds.210-213 The problems with this technique are the bottom visibilityd which is often insufficient to discriminatedand the difficulty in towing the camera vehicle as slow as 1 knot, the necessary speed. Pfeifer et al. were successful in employing mosaics of photographs to determine the aerial extent of oil on the seafloor.212-213 A low-technology approach had been historically employed. Heavy oil, oil such as would sink, often adheres to oil snares or pom-poms, which are polypropylene strips mounted much as a cheerleader’s pom-pom. These can be mounted on a beam and towed over the bottom and then raised periodically to see if oil has adhered.210 Alternatively, they can be mounted on an anchor with

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FIGURE 6.35 A radar image of the Nakhodka oil spill off the west coast of Japan (Radarsat-1). Only the black features on the lower half of the photograph and near the shoreline have been confirmed as oil. The remainder of the black areas are oceanographic features.

a marker buoy. These are then raised periodically to check whether the subsurface oil has contacted them. Camilli et al. have successfully applied mass spectrometry to the detection of sunken heavy oil (Fuel Oil #6).214 Using the small and enclosed mass spectrometer, TETHYS, the low-molecular-weight hydrocarbons coming from sunken oil masses are monitored. The mass spectrometer is mounted in a submersible that is driven over the seafloor. The exact position of the submersible is monitored closely using an acoustic positioning system on the surface. Signals then can be correlated closely to the position on the seafloor. Three ion peaks of m/z 43, 41, 27 are monitored to establish hydrocarbon

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FIGURE 6.36 A satellite radar image of an oil slick in the North Sea. This slick was confirmed by aerial observation.

presence. Tests show that the ion peaks provide sensitivity as low as 0.4 ppb. This is fully sufficient to monitor sunken oil. Tests were conducted in a test tank and later over actual spills in the Gulf of Mexico. The technique was able to find concentrations of sunken oil and place the locations within 1 meter. The tests in the Gulf of Mexico were conducted at depths of 200 meters and confirmed by using cameras on the submersible.

6.12. SMALL REMOTE-CONTROLLED AIRCRAFT Several parties have suggested using remote-controlled aircraft to provide more economical solutions for response personnel.215,216 In fact, remote-controlled aircraft have been used by a number of parties for monitoring a variety of pollutants since the 1970s.217 Belgium employs an Unmanned Aerial Vehicle (UAV) of the B-Hunter class to routinely monitor its portion of the North Sea.216 This is a large UAV that has visible and IR camera systems aboard. The unit has a 10-hour endurance over the targets. A variety of commercial platforms are now available that can carry small sensors such as visible and IR cameras. Furthermore, automatic navigation technology has now made these units, especially helicopters, very much easier to fly than in previous years.

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6.13. REAL-TIME DISPLAYS AND PRINTERS A very important aspect of remote sensing is the production of data so that operations people can quickly and directly use it. Real-time displays are important, so that remote sensor operators can adjust instruments directly in flight and provide information quickly on the location or state of the spill. A major concern of the client is that data be rapidly available.218 An additional concern is that the data from various sensors be available in a combined or fused form.85 Furthermore, there is a need to correct this data for aircraft motion and to annotate the data with time and position. At this time, existing hardware and software must be adapted as commercial off-the-shelf equipment for directly outputting and printing sensor data is not yet available. The displays and operators of a remote sensing aircraft are shown in Figure 6.37.

6.14. ROUTINE SURVEILLANCE One application of oil spill remote-sensing equipment is to detect and map slicks resulting from illegal discharges of oil from ships and offshore platforms. Historically, this task has always been performed using visual techniques, but in the past decade it has increasingly been turned over to aircraft with some

FIGURE 6.37 The interior of a remote sensing aircraft showing operators and displays. Photography by Environment Canada.

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instrumentation. Typical instrumentation includes a SLAR, IR/UV scanner, and cameras. This sensor package is economical compared to more ideal packages and greatly improves capability beyond just visual observation. Limitations include limited ability to ‘look into’ ship wakes, limited night operations, and inability to positively identify oil slicks. Recent additions such as improved SLAR systems, better display systems, and nighttime cameras have added to the capability but do not overcome these limitations. Figure 6.38 shows pilots overflying the stern of a ship to ascertain whether it is discharging oil. Many efforts have been made to perform surveillance of illegal discharges. Most existing operative remote systems are dedicated to this function. These are estimated to be around 35, most of these being around Europe.219 There are intensive programs in some areas, for example, in the North Sea. Carpenter reports on the 18-year program of surveillance in the North Sea.220 Some interesting statistics are noted. In 2004, 418 unidentified slicks were found, 65 slicks from oil rigs, and 57 slicks from ships. In 2004, 3,314 hours were flown in daylight and 594 in darkness. In the same year 91 slicks were found in the darkness and 449 in daylight. Ferraro et al. describe a routine surveillance program using satellite and aircraft data for the Mediterranean Sea.142 Future work in the Mediterranean Sea proposes a cluster of radar satellites to constantly monitor oil pollution.221 A word about aircraft is suitable here. A variety of aircraft are deployed as remote-sensing aircraft. Typically, different types are deployed for routine surveillance and for remote-sensing research. The latter requires flexibility in mounting sensors and in access to the outside of the aircraft. Figures 6.39 to 6.42 show some remote-sensing aircraft and highlight the modifications necessary.

FIGURE 6.38 A ship viewed from the cockpit of a remote sensing airplane. The ship will be overflown to ascertain whether it is discharging oil. Photography by Environment Canada.

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FIGURE 6.39 A view of a remote-sensing aircraft. The extensive airframe modifications are not visible in this photograph. The aircraft has extensive modifications in the interior to provide racks for equipment.

FIGURE 6.40 The bottom of the aircraft shown in Figure 6.39. This particular aircraft has 4 onemeter ports and one half-meter port. The direct opening in the one port is for a laser beam exit. Photography by Environment Canada.

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FIGURE 6.41 A view of another remote-sensing aircraft. This aircraft carries experimental radars, and one of the radomes is visible under the aircraft. Such modification can cost millions of dollars and take two years to complete.

6.15. FUTURE TRENDS Advances in sensor technology will continue to drive the use of remote sensors as operational oil spill response tools in the future. Cameras and thermal IR cameras that offer high sensitivity are cheap and plentiful. This improvement not only reduces the size and complexity of the sensor, but also the cost. In the next decade, advances in solid-state laser technology, in particular diodepumped solid-state lasers, will greatly reduce the size and energy consumption of laser-based remote sensors. This will promote the use of these sensors in smaller, more economical aircraft within the budget of many more regulatory agencies and maritime countries. Rapidly improving computer capabilities will allow for true real-time processing. At the present time and for the foreseeable future, there is no single “Magic Bullet” sensor that will provide all the information required to detect, classify, and quantify oil in the marine and coastal environment. An example of the improvement in recent years is that of the night-vision camera. It is now possible to use this sensor to visualize oil at night. An illustration of this appears in Figure 6.43. It will require the combined advances in sensor technologies and computer capabilities to gather, integrate, and merge several sources of data into a realtime format, usable by response crews in the field. If this type of information can be made available to response crews in a short enough timeframe following

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FIGURE 6.42 A view of the other side of the aircraft shown in Figure 6.41. This shows a lateral radome on the side of the aircraft as well as the radome on the underside. This aircraft also has extensive modifications in the interior to provide racks for equipment and power to sensors. Photography by Environment Canada.

a spill incident, then it can be used to lessen the potentially disastrous effects of a major oil spill on the marine ecosystem. As technology in remote-controlled systems evolve, it is possible to employ such technology in oil spill remote sensing. First efforts in the deployment of remote-controlled sensing aircraft have posted success and will, no doubt, be expanded in the future.222

6.16. RECOMMENDATIONS Recommendations are based on the above considerations and include economy as a major factor. Table 6.3 shows the considerations related to the development state, cost, and use of the sensor, and Table 6.4 shows the applicability of the sensor to various functions. The laser fluorosensor offers the only potential for discriminating between oiled and unoiled weeds or shoreline, and for positively identifying oil pollution on ice, among ice, and in a variety of other situations. This instrument, however, is large and expensive. A cheap sensor recommended for oil spill work is an IR camera. This is the cheapest undiscriminating device. This is the only piece of equipment that can be purchased off-the-shelf.

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FIGURE 6.43 A night-vision display. The annotation shows the various features of the image. Photography by Environment Canada.

All other sensors require special order and, often, development. Radar, though low in priority for purchase, offers the only potential for large area searches and foul weather remote sensing. Most other sensors are experimental or do not offer good potential for oil detection or mapping. Any sensor package should include a real-time printer and display, and a downlink. In order to respond effectively to major marine oil spills, a combination of airborne and satellite-borne sensor systems is recommended. Improvements in the resolution of satellite-based systems, particularly SAR systems combined with the increased number of such systems and the ability to steer them to image the area of the oil spill, will lead to their increased use in a tactical role. Being capable of imaging vast areas of the open ocean will ensure that satelliteborne sensors will also continue to be used in a strategic manner. There are a number of commercially available airborne sensor systems that provide near real-time information on oil slick location and indications of thicker areas of the pollution in an easily interpretable graphical manner. These airborne sensor systems are currently being employed by a large number of maritime nations in conjunction with satellite-based sensor systems. Historically, satellite sensors suffered from problems of low resolution and the low frequency of scene observation. These inadequacies are now being addressed by higher resolution systems with multiple imaging modes and the

156

TABLE 6.3 Attributes for Airborne Sensor Selection Specific to Oil

Immunity to False Targets

Typical Coverage (km)

Acquisition Cost Range k$

Aircraft Physical Requirements

Still Camera

High

High

Poor

Poor

0.25 to 2

1 to 5

no

Video

High

High

Poor

Poor

0.25 to 5

1 to 10

no

Night Time Vision Camera

Medium

Medium

Poor

Poor

0.25 to 2

5 to 20

no

IR Camera (8e14 mm)

High

Medium

Medium

Medium

0.25 to 2

20 to 50

no

UV Camera

Medium

Medium

Poor

Poor

0.25 to 2

4 to 20

no

MultiSpectral Scanner

Medium

Medium

Poor

Poor

0.25 to 2

100 to 200

Radar

High

High

Medium

Poor

5 to 50

1200 to 8000

yes-Dedicated

Microwave Radiometer

Medium

Medium

Medium

Medium

1 to 5

400 to 1000

yes-Dedicated

Laser Fluorosensor

Medium

Limited

Good

Good

0.01 to 0.1

300 to 1000

yes-Dedicated

some

Oil Analysis and Remote Sensing

Amount of Experience in Use

PART | III

Sensor

State of Development

Night & Fog Operation

Detection of Oil with Debris

Oiled Shoreline Survey

Spill Mapping

Ship Discharge Surveillance

Enforcement and Prosecution

Still Camera

2

n/a

1

2

2

2

2

Video

2

n/a

1

2

2

2

2

Night Time Vision Camera

3

4

1

n/a

2

2

2

IR Camera (8e14 mm)

4

2

1

n/a

3

3

3

UV Camera

2

n/a

n/a

n/a

3

2

1

UV/IR Scanner

4

2

1

n/a

4

3

3

Multi-Spectral Scanner

1

n/a

n/a

1

2

1

1

Radar

n/a

4

n/a

n/a

4

3

2

Microwave Radiometer

1

3

n/a

n/a

2

2

1

Laser Fluorosensor

4

3

5

5

1

5

5

Oil Spill Remote Sensing: A Review

Sensor

Support for Cleanup

Chapter | 6

TABLE 6.4 Sensor Suitability for Various Missions

Key: n/a ¼ not applicable; numerical values represent a scale from 1 ¼ poorly suited to 5 ¼ ideally suited

157

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ability to steer the sensor to look in the direction of the target of interest. There are an increasing number of satellite-borne SAR and optical sensors, some of which currently or soon will operate in constellations to provide increased coverage of the Earth’s surface. These enhanced capabilities will allow for the possible use of these sensors in a tactical mode of operation. In spite of these increased capabilities, there remains an essential role for airborne oil spill remote-sensing platforms. The ability to collect and deliver real-time oil slick location information will ensure the continued use of airborne systems in spite of their high operational costs. If this type of real-time oil spill remote-sensing information can be made available to response crews in a short enough timeframe following a spill incident, the information can be used to mitigate the potentially disastrous effects of a major oil spill on the marine ecosystem.

ACKNOWLEDGMENTS The authors acknowledge the many parties who contributed to this chapter, including the Canada Centre for Remote Sensing, and the Canadian Space Agency. In particular, they acknowledge Environment Canada for the many photographs in this chapter.

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29. Bolus RL. Airborne Testing of a Suite of Remote Sensors for Oil Spill Detecting on Water, Proceedings of the Second Thematic International Airborne Remote Sensing Conference and Exhibition, ERIM, 1996;III 743. 30. Goodman RH. Simple Remote Sensing System for the Detection of Oil on Water, Environmental Studies Research Fund Report Number 98, 1988. 31. Seakem Oceanography, Remote Sensing Chronic Oil Discharges, Environment Canada Report EE-108, 1988. 32. Kennicutt MC, MacDonald IR, Rogne T, Giammona C, Englehardt R. The Tenyo Maru Oil Spill: A Multi-Spectral and Sea Truth Experiment. AMOP 1992;349. 33. Rogne T, Macdonald I, Smith A, Kennicutt MC, Giammona C. Multi-Spectral Remote Sensing and Truth Data from the Tenyo Maru Oil Spill, Proceedings of the First Thematic Conference on Remote Sensing for Marine and Coastal Environments, ERIM 37 [also published in Photogramm Eng Rem Sens, 1993, 1992;391. 34. Rogne TJ, Smith AM. Tenyo Maru Oil Spill Remote Sensing Data Analysis. Washington, D.C: Marine Spill Response Corporation; 1992. MSRC Technical Report Series 92-003. 35. Salisbury JW, D’Aria DM, Sabins FF. Thermal Infrared Remote Sensing of Crude Oil Slicks. Remote Sens Environ 1993;225. 36. Hover GL. Testing of Infrared Sensors for U.S. Coast Guard Oil Spill Response Applications, Proceedings of the Second Thematic Conference on Remote Sensing for Marine and Coastal Environments: Needs, Solutions and Applications, ERIM 1994;I-47. 37. Grierson IT. Use of Airborne Thermal Imagery to Detect and Monitor Inshore Oil Spill Residues During Darkness Hours. Environ Manage 1998;905. 38. Shih W-C, Andrews AB. Infrared Contrast of Crude-Oil-Covered Water Surfaces. Opt Lett 2008;3019. 39. Brown HM, Baschuk JJ, Goodman RH. The Limits of Visibility of Spilled Oil Sheens. AMOP 1998;805. 40. Brown CE, Fingas MF. Review of the Development of Laser Fluorosensors for Oil Spill Application. Mar Pollut Bull 2003;477. 41. Brown CE, Fruhwirth M, Wang Z, Lambert P, Fingas M. Airborne Oil Spill Sensor Test Program, Proceedings of the Second Thematic Conference on Remote Sensing for Marine and Coastal Environments: Needs, Solutions and Applications, ERIM, 1994;I-19. 42. Brown CE, Fingas MF, An J. Laser Fluorosensors: A Survey of Applications and Developments of a Versatile Sensor. AMOP 2001;485. 43. Brown CE, Nelson R, Fingas MF, Mullin JV. Airborne Laser Fluorosensing: Overflights During Lift Operations of a Sunken Oil Barge, Proceedings of the Fourth Thematic Conference on Remote Sensing for Marine and Coastal Environments, ERIM 1997;I 23. 44. Brown CE, Marois R, Fingas MF, Choquet M, Monchalin J-P, Mullin J, et al. Airborne Oil Spill Sensor Testing: Progress and Recent Developments. IOSC 2001;917. 45. Brown CE, Fingas MF. Review of the Development of Laser Fluorosensors for Oil Spill Application. Mar Pollut Bull 2003;477. 46. Hengstermann T, Reuter R. Lidar Fluorosensing of Mineral Oil Spills on the Sea Surface. Appl Optics 1990;3218. 47. Balick L, DiBenedetto JA, Lutz SS. Fluorescence Emission Spectral Measurements for the Detection of Oil on Shore, Proceedings of the Fourth Thematic Conference on Remote Sensing for Marine and Coastal Environments, ERIM 1997;I 13. 48. Sarma AK, Ryder AG. Comparison of the Fluoresence Behaviour of a Biocrude Oil and Crude Petroleum Oils. Energy & Fuels 2006;783.

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212. Pfeifer CE, Brzozowski R, Markian, Redman R. Quantifying Percent Cover of Submerged Oil Using Underwater Video Imagery. IOSC 2008;269. 213. Pfeifer CE, Brzozowski R, Markian, Redman R. Long-Term Monitoring of Submerged Oil in the Gulf of Mexico Following the T/B DBL 152 Incident. IOSC 2008;275. 214. Camilli R, Bingham B, Reddy CM, Nelson RK, Duryea AN. Method for Rapid Localization of Seafloor Petroleum Contamination Using Concurrent Mass Spectrometry and Acoustic Positioning. Mar Pollut Bull 2009;1505. 215. Lehr WJ. The Potential Use of Small UAS in Spill Response. IOSC 2008;431. 216. Donnay E. Use of Unmanned Aerial Vehicle (UAV) for the Detection and Surveillance of Marine Oil Spills in the Belgian Part of the North Sea. AMOP 2009;771. 217. Li K, Fingas MF, Pare´ JRP, Boileau P, Beaudry P, Dainty E. The Use of Remote-Controlled Helicopters for Air Sampling in an Emergency Response Situation, in. AMOP 1994;139. 218. Goodman RH. Overview and Future Trends in Oil Spill Remote Sensing. Spill Sci Techn 1994;11. 219. Huisman J. Use of Surveillance Technology to Support Response Decision Making and Impact Assessment. Interspill 2006. 220. Carpenter A. The Bonn Agreement Aerial Surveillance Programme: Trends in North Sea Oil Pollution: 1986e2004. Marine Pollution Bulletin 2007;149. 221. De Dominicis M, Pinardi N, Coppini G, Tonani M, Guarnieri A, et al. Interspill 2009. 222. Allen J, Walsh B. Enhanced Oil Spill Surveillance, Detection and Monitoring through the Applied Technology of Unmanned Air Systems. IOSC 2008;113.

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Chapter 7

Laser Fluorosensors Carl E. Brown

Chapter Outline 7.1. Principles of Operation 171 7.2. Oil Classification 175 7.3. Existing Operational 179 Units

7.4. Aircraft Requirements 7.5. Cost Estimates 7.6. Conclusions

180 182 182

7.1. PRINCIPLES OF OPERATION 7.1.1. Active versus Passive Sensors Passive sensors are those that measure naturally available energy such as that produced by the sun.1 Passive sensors can only be used when the naturally occurring energy is available, that is, during periods of daylight when the sun is illuminating the earth. Passive sensors cannot therefore be used during periods of darkness, which is at night. Some naturally emitted energy such as thermal infrared energy can be detected during the day or night, providing there is enough energy to be detected. Active sensors, on the other hand, provide their own energy or source of excitation for illumination. The sensor illuminates or excites the target to be investigated. The energy or radiation reflected from that target is then detected and measured by the active sensor. The main advantage of active sensors is the ability to obtain measurements anytime day or night. Furthermore, active sensors can be used at wavelengths that are not provided by the sun, such as the microwave region. It should be noted that active remote sensors require the generation of a large amount of energy in order to adequately illuminate the targets. Examples of active remote sensors include synthetic aperture radars (SARs) and laser fluorosensors.

7.1.2. Sensor Features Laser fluorosensors are the only sensors that detect a primary characteristic of oil, namely, the unique oil fluorescence spectral signature. Other generic sensors rely Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10007-3 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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on secondary characteristics of oil such as the reflection of light of various wavelengths, scattering of microwaves, and emission of infrared energy. Laser fluorosensors are active sensors that take advantage of the fact that certain compounds in petroleum oils absorb ultraviolet light and become electronically excited. This excitation is rapidly removed through the process of fluorescence emission, primarily in the visible region of the spectrum. Since very few other compounds show this tendency, fluorescence is a strong indication of the presence of oil. Natural fluorescing substances, such as chlorophyll, fluoresce at sufficiently different wavelengths than oil to avoid confusion. As different types of oil yield slightly different fluorescent intensities and spectral signatures, it is possible to differentiate between classes of oil under ideal conditions.2-10

7.1.2.1. Excitation Source and Wavelength Selection Most laser fluorosensors used for oil spill detection employ a laser excitation source operating in the ultraviolet region of 300 to 355 nm.4 The fluorescence response of crude oil when excited with an ultraviolet laser ranges from 400 to 650 nm, with peak centers in the 480 nm region. A typical laser fluorosensor system with excimer laser and scanner is shown in Figure 7.1. These excitation wavelengths are a compromise in that they excite all three classes of oil with reasonable efficiency (shorter wavelength lasers would excite lighter oils efficiently but would be rather poor at exciting crude and heavy refined oils). There FIGURE 7.1 Scanning Laser Environmental Airborne Fluorosensor (SLEAF). (Environment Canada)

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are several reasonably priced, commercially available ultraviolet lasers in the 300e355 nm region, including the XeCl excimer laser (308 nm), the nitrogen laser (337 nm), the XeF excimer laser at 351 nm, and the frequency-tripled Nd:YAG at 355 nm. With excitation in this wavelength region, there exists a broad organic matter fluorescent return, centered at 420 nm. This is referred to as Gelbstoff or yellow matter, which must be accounted for. While Gelbstoff disappears if the oil thickness is greater than 10e20 mm (i.e., where the oil is optically thick), it can be an interfering signal when attempting to detect thin films of light oils on water. Chlorophyll yields a sharp peak at 685 nm. Another phenomenon, known as Raman scattering, involves energy transfer between the incident light and the water molecules. When the incident ultraviolet light interacts with the water molecules, Raman scattering occurs. The water molecules absorb some of the energy as rotational vibrational energy and emit light at wavelengths that are the sum or difference between the incident radiation and the vibration rotational energy of the molecule. The Raman signal for water occurs at 344 nm when the incident wavelength is 308 nm (XeCl laser). The water Raman signal is useful for maintaining wavelength calibration of the fluorosensor in operation, but has also been used in a limited way to estimate oil thickness because the strong absorption by oil on the surface will suppress the water Raman signal in proportion to thickness,11 where transmittance ¼ EXP ( thickness absorption coefficient). The point at which the Raman signal is entirely suppressed depends on the type of oil, since each oil has a different absorption coefficient. The Raman signal suppression has led to estimates of sensor detection limits of about 0.05 to 0.1 mm.12 Details of the use of Raman scattering to measure oil slick thickness can be found in the early work of Hoge and Swift13 and the recent studies by Patsayeva et al.14

7.1.2.2. Detection System The detection systems in most laser fluorosensor systems usually involve the collection of laser-induced fluorescence by a telescope and the focusing of the fluorescence onto the entrance slit of a grating spectrometer and then onto either photomultiplier tubes or intensified diode-arrays. The fluorescence spectrum is then recorded at a number of selected wavelengths or over a wide spectral range covering the ultraviolet through the visible. 7.1.2.3. Range-Gating The majority of modern laser fluorosensors are equipped with range-gated detection systems. Range-gating is simply the turning on of the detection system at precisely the time at which the laser-induced fluorescence is expected to return to the laser fluorosensor. This is accomplished by turning the detection system on and off at a precise time based on the known altitude. To accomplish this, the timing of the laser pulse is monitored prior to exiting the aircraft and the elastic backscatter from the surface is then monitored to determine the

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precise aircraft altitude, which is then used to control the range-gating electronics. This allows the detector to observe only the fluorescence induced by the excitation laser and neglect the majority of the background solar radiation.

7.1.2.4. Field of ViewdFixed versus Scanning Systems As noted earlier, active sensors need to deliver sufficient energy to the target, the surface of the earth containing oil contamination, to excite sufficient fluorescence to allow for the detection and classification of the oil. With most airborne laser fluorosensor systems, this means illuminating a field of view (FOV) of about 1 3 mrad, giving a footprint on the surface of about 0.1 m 0.3 m at 100 m altitude. This does not allow for a large amount of the surface to be interrogated by each laser pulse. With higher-powered ultraviolet lasers, one can fly at higher altitudes and enlarge the footprint of the sensor. The repetition rate of the laser and the ground speed of the aircraft are also major factors in the sampling of the surface where the oil contamination is being examined. At ground speeds of 100e140 knots (nautical miles) at a laser repetition rate of 100 Hz, a fluorescence spectrum is collected approximately every 60 cm along the flight path (at 100 m altitude). Some laser fluorosensors only “look” directly below the aircraft and collect fluorescence spectra in a straight line; this is referred to as a “fixed” FOV system. As spilled oil often piles up in narrow bands at the high-tide line, detection of this oil with a fixed FOV system is not optimal. This means that the oil might not be detected because the sensor is striking the surface of the earth on either side of the high-tide line. To compensate for this tendency of the oil to accumulate in a narrow band, it is preferable to change the laser FOV by employing a scanner. The scanner can either be moved in a conical (circular) fashion or back and forth across the surface to increase the likelihood of striking the oil contamination. There are conical scanning laser fluorosensor systems that have been developed in Germany15 and Canada.16 An example of a conical scanner is shown in Figure 7.2.

7.1.3. Pros/Cons Laser fluorosensors are capable of detecting oil and related petroleum products in complex marine, coastal, and terrestrial environments. These sensors are extremely sensitive and can discriminate between oiled and unoiled naturally occurring substances such as kelp and seaweed. It is under these circumstances that the laser fluorosensor can aid in the direction of oil spill countermeasures by discriminating between contaminated and clean areas in the marine and terrestrial environment. Laser fluorosensors are the only sensors that detect a primary characteristic of oil, namely, the unique oil fluorescence spectral signature. Other generic sensors rely on secondary characteristics of oil such as the reflection of light of various wavelengths, scattering of microwaves, and emission of infrared energy.

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FIGURE 7.2 Scanner unit (narrow/wide swath) SLEAF system. (Environment Canada)

At the current time, laser fluorosensors are very large, heavy, and powerhungry systems. These characteristics necessitate the use of large multiengined aircraft to house the systems. These conditions will remain until much smaller diode-pumped solid-state lasers are developed in the ultraviolet region of the electomagnetic spectrum. This development has lagged behind that of solid-state lasers in the visible region and might be another decade in coming to fruition.

7.2. OIL CLASSIFICATION 7.2.1. Real-Time Analysis One of the benefits of modern laser fluorosensors is the ability to detect and classify oil contamination in real time. This availability of real-time oil contamination is essential for rapid oil spill response and environmental damage mitigation. A recent analysis of oil spill detection algorithms for laser fluorosensors has been undertaken by Jha et al.17 In earlier fluorosensors like the LEAF system, Pearson correlation coefficients were calculated to determine the presence of oil contamination and to broadly classify the petroleum products.18 Standard reference fluorescence spectra for light refined, crude, and heavy refined classes of oil, along with a standard water reference spectrum, were stored in the LEAF data analysis computer. Correlation coefficients were calculated for the live spectrum versus the three broad classes of petroleum products and water at the rate of 100 Hz. When the value of the correlation coefficient versus a class of petroleum product was above a certain level and greater than the correlation with the water spectrum, the live spectrum was identified as being of that class of petroleum.

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With modern computer technology, it is now possible to analyze a large amount of laser fluorosensor data in real time. For example, with the Scanning Laser Environmental Airborne Fluorosensor (SLEAF), it is possible to analyze fluorescence data at a rate of nearly 400 Hz and display oil detections along with the flight path of the aircraft on a geo-referenced map output.8,19 With the SLEAF system, fluorescence spectra are analyzed in real time to determine the presence or lack of oil in the sensor field-of-view. Principal component analysis20 is used to classify the oil class as light, medium, or heavy and to estimate the extent of oil coverage in the field of view as clean, light, moderate, or heavy.

7.2.2. Sensor Outputs As noted earlier, a high volume of fluorescence spectral data can be analyzed in real time. In most laser fluorosensor systems, the fluorescence data is georeferenced (i.e., the location of the oil contamination is well known) and the data can be presented in either spectral or map display outputs. While displays of spectral data are important for the sensor operator to verify the proper operation of the sensor, they are of little use to the spill responder. What is essential for the spill responder is knowledge of the location of the oil contamination so that spill response equipment can be rapidly deployed to the spill scene and cleanup operations undertaken. The positive identification of oil contamination afforded through the use of laser fluorosensors is one of their main advantages.

7.2.2.1. Spectral Data The display of spectral data is essential for the effective operation of modern laser fluorosensors. Laser fluorosensor display monitors often include a representation of sensor parameters such as laser pulse energy, operating altitude, laser backscatter energy, reference spectra, and live or real-time fluorescence spectra. The observation of each of these parameters is extremely useful to the sensor operator. In particular, real-time spectra are useful for providing an indication of the interaction of the laser beam with the surface. By observing the live spectrum, the operator has an indication of the water clarity through observation of the water Raman scattering spectrum. A trained sensor operator can easily recognize the presence of oil contamination by the characteristic spectrum of light refined, crude, or heavy refined petroleum products. Figure 7.3 shows typical laser-induced fluorescence spectra of a crude oil. The lack of a proper spectral signature can indicate a problem with the fluorosensor system such as low laser power, low laser backscatter signal, incorrect rangegate timing, or laser misalignment. It is impossible to display all of the spectral data collected with a high sampling rate laser fluorosensor system; a subsample of the spectral data is all that is needed for an experienced operator to monitor system operations.

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FIGURE 7.3 Laser-induced fluorescence spectradlight crude oildSLEAF system.

7.2.2.2. Map Display An efficient map display of oil contamination location(s) is essential for the rapid mitigation of the environmental effects of spilled oil. Displays of oil contamination superimposed over aircraft flight lines are useful for spill responders who participate in oil spill remote sensing overflights. Figure 7.4 shows the operator’s

FIGURE 7.4 Operator’s monitor for, sensor parameters, and map display of SLEAF system. (Environment Canada)

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FIGURE 7.5 Oil contamination indicated with colored bars perpendicular to aircraft flight path on SLEAF system map display. (Environment Canada)

display from Environment Canada’s SLEAF system. Figure 7.5 shows the operator’s display with areas of oil contamination illustrated as colored bars perpendicular to the flight path. Similar information is presented in Figure 7.6, which overlays the scanner pattern on the flight path along with the oil

FIGURE 7.6 Scanner pattern superimposed on aircraft flight path; colors are an indication of oil classification, SLEAF system. (Environment Canada)

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contamination information (different colors for clean, light, medium, or heavy oil classifications). Spill response organizations and personnel are not interested in sensor parameters or spectral data. What is needed are geo-referenced maps showing oil locations. These maps, or at least the geo-referenced oil contamination locations, should be in a format that can be transmitted electronically and be compatible with commonly used geographical information systems (GIS). These maps will help in the rapid and efficient deployment of spill response resources and equipment to the location(s) where oil contamination is the heaviest and the cleanup of contamination is most needed.

7.3. EXISTING OPERATIONAL UNITS 7.3.1. Airborne There are a number of operational airborne laser fluorosensor units operating around the globe. Some of these are research and development units that have progressed to become operational spill response sensors such as the SLEAF system.21 Other laser fluorosensors have been combined with other sensors in commercially available sensor packages, while others are standalone systems or remain as research instruments. There are a number of recent reviews of airborne laser fluorosensor systems in the literature, including those by Samberg,10 as well as Brown and Fingas.18, 22 There are a number of commercially available airborne laser fluorosensors in the marketplace and a few examples are provided here. The first is the Fluorescent LiDAR Spectrometer (FLS-AU) developed by Laser Diagnostics Instruments International Incorporated. The FLS series of LiDARs is designed for pollution monitoring of terrestrial, river, lake, and ocean targets, oil and gas pipeline leak detection, and oil exploration.23 The second example is the laser fluorosensor system developed by Optimare Sensorsysteme AG as part of the MEDUSA system.24 MEDUSA is a flexible real-time data acquisition and processing system that combines a number of sensor technologies for the detection, mapping, quantification, and classification of marine pollution. MEDUSA incorporates a number of unique sensor systems, for example, laser fluorosensors, infrared/ ultraviolet (IR/UV) line scanners, microwave radiometers, radar systems, camera systems, as well as the corresponding processing software. The final example is the Swedish Space Corporation’s MSS 6000 Maritime Surveillance System that can be tailored to integrate with a number of sensors, including a selection of side-looking airborne radar (SLAR), IR/UV cameras, microwave radiometers, forward-looking infrared (FLIR), and laser fluorosensors.25

7.3.2. Ship-Borne A small number of ship-borne laser fluorosensors have been developed. Most ship-borne laser fluorosensors are research and development technologies, although there have been recent commercial developments. Two examples of

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ship-borne laser fluorosensors are the FLIDAR (Fluorescence Lidar) developed by the research group at the Istituto di Ricerca sulle Onde Elettromagnetiche “Nello Carrarra” IROE-CNR26 and the compact lidar system developed by the Japanese Ship Research Institute.27 The FLIDAR system incorporates an XeCl excimer laser, a 12 spectral channel detection system, and a conical scanner to direct the ultraviolet laser beam onto the surface of the ocean alongside the marine vessel onto which the system is mounted. The compact lidar system at the Japanese Ship Research Institute is a frequency-tripled Nd:YAG laser coupled to an intensified CCD camera and uses a series of optical band-pass filters. One commercially available ship-borne laser fluorosensor system is the FLS-S (Fluorescence LiDAR SystemeShip-borne) developed by Laser Diagnostics Instruments International Incorporated. The FLS-S is designed to detect, measure, and map natural Dissolved Organic Matter (DOM), oil pollution, photosynthetic algae, and other contaminants in water.23

7.4. AIRCRAFT REQUIREMENTS The combination of large-size, heavyweight, and demanding power requirements for the ultraviolet lasers detailed below necessitate the use of midsized fixed-wing propeller or turboprop aircraft for laser fluorosensor system installation. Typical aircraft housing laser fluorosensors have included the Dornier 228-212 (see Figure 7.7), Douglas DC-3, CASA C-295, P-3B, and Beech B-99.18

7.4.1. Power The high-powered excimer lasers often employed in airborne laser fluorosensors for oil spill detection require a significant amount of power. This power is typically supplied in the form of 3-phase 208 VAC at 400 Hz for the excimer laser. Additional power is required for systems such as the laser

FIGURE 7.7 Dornier 228-212 twin turboprop aircraft.

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scanner head in the form of 28 VDC and for sensor-controller electronics at 220 VAC, 60 Hz. These power requirements necessitate the use of heavy-duty aircraft power generators and a number of power invertors to supply the energy in the proper voltage, phase, and frequency.

7.4.2. Weight Most laser fluorosensors for oil spill detection employ an ultraviolet excitation laser. In order to deliver enough laser pulse energy and a sufficient repetition rate for use in a fixed-wing aircraft, an excimer laser is usually required. Laser fluorosensor systems that employ excimer lasers such as the XeCl laser operating at 308 nm, capable of producing 150 mJ/pulse at a repetition rate of 400 Hz (such as that used in the SLEAF system shown in Figure 7.8),21 are large and heavy, weighing over 450 kg. Smaller systems are possible with the use of frequency-tripled Nd:YAG lasers operating at 355 nm; however, these lasers are unable to produce the high laser pulse energies and repetition rates to fly at higher altitudes with sufficient areal coverage. These systems are more suitable for helicopter-based platforms that can fly low and slowly and hover over a location for an extended period of time.

7.4.3. Operational Altitude Operational altitudes for laser fluorosensors are entirely dependent on the output energy of the excitation laser and field of view of the system optics. Typical operating altitudes for lasers operating in ultraviolet would be approximately 100 m for a system with 10 mJ/pulse of laser power up to

FIGURE 7.8 Lambda Physik Excimer LaserdSLEAF System. (Environment Canada)

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approximately 500 m for a laser output power of 150 mJ/pulse. The operational altitude will also determine the swath width achieved with a conical scanner; for details refer to Brown and Fingas.18

7.5. COST ESTIMATES The cost of a laser fluorosensor system is significant, partially due to the low production volume of these unique sensors. Cost estimates have been reported by Tebeau et al. for three laser fluorosensor systems ranging from $150,000 to $500,000 $US.28

7.6. CONCLUSIONS Laser fluorosensors capable of detecting oil and related petroleum products in complex marine, coastal, and terrestrial environments have been developed at a number of locations around the world. These sensors are extremely sensitive and can discriminate between oiled and unoiled naturally occurring substances such as kelp and seaweed. It is under these circumstances that the laser fluorosensor can aid in the direction of oil spill countermeasures by discriminating between contaminated and clean areas in the marine and terrestrial environment. Laser fluorosensors are the only sensors that detect a primary characteristic of oil, namely, the unique oil fluorescence spectral signature. Other generic sensors rely on secondary characteristics of oil such as the reflection of light of various wavelengths, scattering of microwaves, and emission of infrared energy. Advances in the fields of lasers, solid-state electronics, and computer operating hardware/software continue to fuel the development of advanced laser fluorosensors. While many of the current systems are large and require dedicated aircraft, the unique data sets available from these laser fluorosensors will ensure their continued development for years to come. Wide acceptance of laser fluorosensors as viable spill response tools will not be achieved until the size of the systems is reduced to a point where they can be flown routinely on small twin-engine aircraft. This reduction in size will come about when highpower, high-repetition rate, diode-pumped solid-state lasers are available.

REFERENCES 1. NRCan, http://www.ccrs.nrcan.gc.ca/resource/tutor/fundam/chapter1/06_e.php, 2010. 2. Brown CE, Fingas MF, Gamble RL, Myslicki GE. The Remote Detection of Submerged Oil, In: Proc. Third R&D Forum on High-Density Oil Spill Response. International Maritime Organization; 2002;46. 3. Brown CE, Marois R, Myslicki G, Fingas MF. Initial Studies on the Remote Detection of Submerged Orimulsion with a Range-Gated Laser Fluorosensor. AMOP 2002;773. 4. Brown CE, Marois R, Myslicki G, Fingas MF, MacKay R. Remote Detection of Submerged Orimulsion with a Range-Gated Laser Fluorosensor. IOSC 2003;779.

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5. Brown CE, Marois R, Gamble RL, Fingas MF. Further Studies on the Remote Detection of Submerged Orimulsion with a Range-Gated Laser Fluorosensor. AMOP 2003;279. 6. Brown CE, Fingas MF, Marois R. Oil Spill Remote Sensing: Laser Fluorosensor Demonstration Flights off the East Coast of Canada. AMOP 2004;317. 7. Brown CE, Fingas M, Marois R, Fieldhouse B, Gamble RL. Remote Sensing of Water-in-Oil Emulsions: Initial Laser Fluorosensor Studies. AMOP 2004;295. 8. Brown CE, Fingas MF, Marois R. Oil Spill Remote Sensing Flights in the Coastal Waters Around Newfoundland. In: Proc. Eighth Intern. Conf. Remote Sensing for Marine and Coastal Environments. Ann Arbor, MI: Altarum; 2005. 9. Hengstermann T, Reuter R. Lidar Fluorosensing of Mineral Oil Spills on the Sea Surface. Appl Opt 1990;3218. 10. Samberg A. The State-of-the-Art of Airborne Laser Systems for Oil Mapping. Can J Rem Sens 2007;143. 11. Piskozub J, Drozdowska V, Varlamov V. A Lidar System for Remote Measurement of Oil Film Thickness on Sea Surface. In: Proc. Fourth Inter. Conf. Remote Sensing for Marine and Coastal Environments. Ann Arbor, MI: Environmental Research Institute of Michigan; 1997; 1:386. 12. Goodman R, Brown CE. Oil Detection Limits for a Number of Remote Sensing Systems. In: Proc. Eighth Inter. Conf. Remote Sensing for Marine and Coastal Environments. Ann Arbor, MI: Altarum Conferences; 2005. 13. Hoge FE, Swift RN. Oil Film Thickness Measurement Using Airborne Laser-Induced Water Raman Backscatter. Appl Opt 1980;3269. 14. Patsayeva S, Yuzhakov V, Varlamov V, Barbini R, Fantoni F, Frassanito C, et al. Laser Spectroscopy of Mineral Oils on Water Surface. EARSeL eProceedings; 2000;. 1:106. 15. Zielinski O, Andrews R, Go¨bel J, Hanslik M, Hunsa¨nger T, Reuter R. Operational Airborne Hydrographic Laser Fluorosensing. In: Proc. Fourth EARSel Workshop, Lidar Remote Sensing of Land and Sea. Dresden; 2001. 16. Brown CE, Marois R, Fingas MF. Preliminary Testing of the Scanning Laser Environmental Airborne Fluorosensor. AMOP 2000;519. 17. Jha NM, Gao Y, Levy J. An Analysis of Oil Spill Detection Algorithms Using Laser Fluorosensor Data. AMOP 2008;741. 18. Brown CE, Fingas MF. Review of the Development of Laser Fluorosensors for Oil Spill Application. Mar Pollut Bull 2003;477. 19. Brown CE, Fingas MF, Marois R. Oil Spill Remote Sensing Flights Around Vancouver Island. AMOP 2006;921. 20. James RTB, Dick R. Design of Algorithms for the Real-Time Airborne Detection of Littoral Oil Spills by Laser-Induced Fluorescence. AMOP 1996;1599. 21. Brown CE, Marois R. Laser Fluorosensor Demonstration Flights over Newfoundland Coastal Waters. AMOP 2007;437. 22. Brown CE, Fingas MF. The Latest Developments in Remote Sensing Technology for Oil Spill Detection. INTERSPILL; 2009. 23. LDI3, http://www.ldi3.com/index.php?main¼16, 2010. 24. Optimare, http://www.optimare.de/cms/en/divisions/fek.html, 2010. 25. Swedish Space Corporation, http://www.ssc.se/filearchive/7/7729/MSS%206000%20pamphlet %20.pdf, 2010. 26. Niccolai F, Bazzani M, Cecchi G, Innamorati M, Massi L, Nuccio C, Santoleri R. A Study for the Remote Monitoring of Organic Matter in the Ocean. In: Proc. EUROPTO Conf. Remote

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Sensing of the Ocean and the Sea Ice V, Remote Sensing for Earth Science, Ocean, and Sea Ice Applications. SPIE 1999;3868:567. 27. Yamagashi S, Hitomi K, Yamanouchi H, Yamaguchi Y. Determination of a Lidar Signal from Images of Backscattered Natural Light on Water Surface. IOSC 2001;929. 28. Tebeau PA, Hansen KA, Fant JW, Terrien MM. Assessing the Long-term Implementation Costs versus Benefits Associated with Laser Fluorosensor Spill Response Technology. AMOP 2007;451.

Part IV

Behaviour of Oil in the Environment and Spill Modeling

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Chapter 8

Introduction to Spill Modeling Merv Fingas

Chapter Outline 8.1. Introduction 8.2. An Overview of Weathering

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8.1. INTRODUCTION When oil is spilled, whether on water or land, a number of transformation processes occur; many of these processes are referred to as the behavior of the oil. The first process is weathering, a series of processes whereby the physical and chemical properties of the oil change after the spill, of which the most important are evaporation and emulsification.1-4 A second group of processes are related to the movement of oil in the environment. Spill modeling combines the knowledge of both these sets of processes and provides the user with information on future locations of the oil as well as information on the state of the oil.5-8 Weathering and movement processes can overlap, with weathering strongly influencing how oil is moved in the environment and vice versa. All processes depend very much on the type of oil spilled and weather conditions during and after the spill.

8.2. AN OVERVIEW OF WEATHERING The specific behavior processes that occur after an oil spill determine how the oil should be cleaned up and its effect on the environment. For example, if an oil evaporates rapidly, cleanup is less intense, but the hydrocarbons in the oil enter the atmosphere. An oil slick could be carried by surface currents or winds to the vicinity of a bird colony or to a shore where seals or sea lions are breeding and severely affect the wildlife and their habitat. On the other hand, a slick could be carried out to sea where it disperses naturally and has less direct effect on the environment. Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10008-5 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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The fate and effects of a particular spill are determined by the behavior processes, which in turn are almost entirely determined by the type of oil and the environmental conditions at the time of the spill. Spill responders need to know the ultimate fate of the oil in order to take measures to minimize the overall impact of the spill. Oil spilled on water undergoes a series of changes in physical and chemical properties that in combination are termed weathering. Weathering processes occur at very different rates but begin immediately after oil is spilled into the environment. Weathering rates are not consistent throughout the duration of an oil spill and are usually highest immediately after the spill. Both weathering processes and the rates at which they occur depend more on the type of oil than on environmental conditions. Most weathering processes are highly temperature-dependent, however, and will often slow to insignificant rates as temperatures approach zero degrees. The processes included in weathering are evaporation, emulsification, natural dispersion, dissolution, photo-oxidation, sedimentation, adhesion to materials, interaction with mineral fines, biodegradation, and the formation of tarballs. These processes are listed in order of importance in terms of their effect on the percentage of total mass balance, that is, the greatest loss from the slick in terms of percentage, and what is known about the process.

8.2.1. Evaporation Evaporation is usually the most important weathering process.9 It has the greatest effect on the amount of oil remaining on water or land after a spill. Over a period of several days, a light fuel such as gasoline evaporates completely at typical ambient temperatures, whereas only a small percentage of a heavier Bunker C oil evaporates. The rate at which an oil evaporates depends primarily on the oil’s composition. Figure 8.1 shows the differential evaporation of several typical oils. The more volatile components an oil or fuel contains, the greater the extent and rate of its evaporation. Many components of heavier oils will not evaporate at all, even over long periods of time and at high temperatures. A separate section on evaporation appears in this section of the book. Oil and petroleum products evaporate in a slightly different manner than water, and the process is much less dependent on wind speed and surface area. Oil evaporation can be considerably slowed down, however, by the formation of a “crust” or “skin” on top of the oil. This happens primarily on land or in calm areas where the oil layer does not get mixed. The skin or crust is formed when the smaller compounds in the oil are removed, leaving the larger compounds, such as waxes and resins, at the surface. This crust then seals off the remainder of the oil and slows evaporation. Stranded oil from old spills has been reexamined over many years, and it has been found that when this crust has formed, there is no significant evaporation in the oil underneath. When this

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40

Time in Hours FIGURE 8.1 Oil evaporation curves for several typical oilsddata from experiments.

crust has not formed, a similar oil could be weathered to the hardness of wood over the same amount of years. The rate of evaporation is very rapid immediately after a spill and then slows considerably. About 80% of evaporation that does take place occurs in the first two days after a spill. The evaporation of most oils follows a logarithmic curve with time. Some oils such as diesel fuel, however, evaporate as the square root of time, at least for the first few days. This means that the evaporation rate slows very rapidly in both cases after a few days. This can be seen in Figure 8.1.

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The properties of an oil can change significantly with the extent of evaporation. If about 40% (by weight) of an oil evaporates, its viscosity could increase by as much as a thousandfold. Its density could rise by as much as 10% and its flash point by as much as 400%. The extent of evaporation can be the most important factor in determining properties of an oil at a given time after the spill and in changing the behavior of the oil.

8.2.2. Emulsification Emulsification is the process by which one liquid is dispersed into another one in the form of small droplets.10 Water droplets can remain in an oil layer in a stable form, and the resulting material is completely different. These waterin-oil emulsions are sometimes called mousse or chocolate mousse, as they resemble this dessert. In fact, both the actual version of chocolate mousse and butter are common examples of water-in-oil emulsions. The mechanism of emulsion formation is not yet fully understood, but it probably starts with sea energy forcing the entry of small water droplets, about 10 to 25 mm (or 0.010 to 0.025 mm) in size, into the oil. If the oil is only slightly viscous, these small droplets will not leave the oil quickly. On the other hand, if the oil is too viscous, droplets will not enter the oil to any significant extent. Once in the oil, the droplets slowly gravitate to the bottom of the oil layer. Asphaltenes and resins in the oil will interact with the water droplets to stabilize them. Depending on the quantity of asphaltenes and resins, as well as other conditions, an emulsion may be formed. The conditions required for emulsions of any stability to form may only be reached after a period of evaporation. Evaporation increases the viscosity to the critical value and increases the resin and asphaltene percentage in the oil. Further discussion on emulsion formation is found in a separate subsection following this introduction.10 Water can be present in oil in four ways. First, some oils contain about 1% water as soluble water. This water does not significantly change the physical or chemical properties of the oil. The second way is called entrainment, whereby water droplets are simply held in the oil by its viscosity to form an unstable emulsion. These are formed when water droplets are incorporated into oil by the sea’s wave action and there are not enough asphaltenes and resins in the oil. Unstable emulsions break down into water and oil within minutes or a few hours, at most, once the sea energy diminishes. The properties and appearance of the unstable emulsion are almost the same as those of the starting oil, although the water droplets may be large enough to be seen with the naked eye. Semi- or meso-stable emulsions represent the third way water can be present in oil. These emulsions are formed when the small droplets of water are stabilized to a certain extent by a combination of the viscosity of the oil and the interfacial action of asphaltenes and resins. These emulsions generally break down into oil and water or sometimes into water, oil, and stable emulsion within a few days. Meso-stable emulsions are viscous liquids that are reddish-brown in color.

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The fourth way that water exists in oil is in the form of stable emulsions. These form in a way similar to meso-stable emulsions except that the oil contains a sufficient amount of resins and asphaltenes to stabilize the water droplets. The viscosity of stable emulsions is 500 to 800 times higher than that of the starting oil, and the emulsion will remain stable for weeks and even months after formation. Stable emulsions are reddish-brown in color and appear to be nearly solid. Because of their high viscosity and near solidity, these emulsions do not spread and tend to remain in lumps or mats on the sea or shore. The formation of emulsions is an important event in an oil spill. First, and most importantly, it substantially increases the actual volume of the spill. Emulsions that contain about 70% water triple the volume of the oil spill. Even more significantly, the viscosity of the oil increases by as much as 1,000 times, depending on the type of emulsion formed. For example, an oil that has the viscosity of motor oil can triple in volume and become almost solid through the process of emulsification. These increases in volume and viscosity make cleanup operations more difficult. Emulsified oil is difficult or impossible to disperse, to recover with skimmers, or to burn. Emulsions can be broken down with special chemicals in order to recover the oil with skimmers or to burn it. It is thought that emulsions break down into oil and water by further weathering, oxidation, and freezethaw action. Meso–or semi-stable emulsions are relatively easy to break down, whereas stable emulsions may take months or years to break down naturally, if they ever do break down. Emulsion formation also changes the fate of the oil. It has been noted that when oil forms stable or meso-stable emulsions, evaporation slows considerably. Biodegradation also appears to slow down. The dissolution of soluble components from oil may also cease once emulsification has occurred.

8.2.3. Natural Dispersion Natural dispersion occurs when fine droplets of oil are transferred into the water column by wave action or turbulence. Small oil droplets (less than 20 mm or 0.020 mm) are relatively stable in water and will remain so for long periods of time. Large droplets tend to rise, and larger droplets (more than 50 mm) will not stay in the water column for more than a few seconds. Depending on oil conditions and the amount of sea energy available, natural dispersion can be insignificant or it can remove the bulk of the oil. In 1993, the oil from a stricken ship, the Braer, dispersed almost entirely as a result of high seas off Scotland at the time of the spill and the dispersible nature of the oil cargo.11 Natural dispersion is dependent on both the oil properties and the amount of sea energy.12 Heavy oils such as Bunker C or a heavy crude will not disperse naturally to any significant extent, whereas diesel fuel and even light crudes can disperse significantly if the saturate content is high and the asphaltene and resin

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contents are low. In addition, significant wave action is needed to disperse oil. In 40 years of monitoring spills on the oceans, those spills where oil has dispersed naturally have all occurred in very energetic seas. The long-term fate of dispersed oil is not known, although it may degrade to some extent as it consists primarily of saturate components. Some of the dispersed oil may also rise and form another surface slick, or it may become associated with sediment and be precipitated to the bottom.

8.2.4. Dissolution Through the process of dissolution, some of the soluble components of the oil are lost to the water under the slick.13,14 These include some of the lowermolecular-weight aromatics. As only a small amount, usually much less than a fraction of a percent of the oil, actually enters the water column, dissolution does not measurably change the mass balance of the oil. The significance of dissolution is that the soluble aromatic compounds are particularly toxic to fish and other aquatic life. If a spill of oil containing a large amount of soluble aromatic components occurs in shallow water and creates a high localized concentration of compounds, then significant numbers of aquatic organisms can be killed. Gasoline, diesel fuel, and light crude oils are the most likely to cause aquatic toxicity. A highly weathered oil is unlikely to dissolve into the water. On open water, the concentrations of hydrocarbons in the water column are unlikely to kill aquatic organisms. Dissolution occurs immediately after the spill occurs, and the rate of dissolution decreases rapidly after the spill as soluble substances are quickly depleted. Some of the soluble compounds also evaporate rapidly.

8.2.5. Photo-oxidation Photo-oxidation can change the composition of an oil.15-18 It occurs when the sun’s action on an oil slick causes oxygen and carbons to combine and form new products that may be resins. The resins may be somewhat soluble and dissolve into the water, or they may cause water-in-oil emulsions to form. It is not well understood how photo-oxidation specifically affects oils, although certain oils are susceptible to the process, whereas others are not. For most oils, photo-oxidation is not an important process in terms of changing their immediate fate or mass balance after a spill.

8.2.6. Sedimentation, Adhesion to Surfaces, and Oil-Fines Interaction Sedimentation is the process by which oil is deposited on the bottom of the sea or other water body. While the process itself is not well understood, certain

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facts about it are. Most sedimentation noted in the past has occurred when oil droplets reached a higher density than water after interacting with mineral matter in the water column. This interaction sometimes occurs on the shoreline or very close to the shore. Once oil is on the bottom, it is usually covered by other sediment and degrades very slowly. In a few well-studied spills, a significant amount (about 10%) of the oil was sedimented on the seafloor. Such amounts can be very harmful to biota that inevitably come in contact with the oil on the sea bottom. Because of the difficulty of studying sedimentation, data are limited. Oil is very adhesive, especially when it is moderately weathered, and binds to shoreline materials or other mineral material with which it comes in contact. A significant amount of oil can be left in the environment after a spill in the form of residual amounts adhering to shorelines and man-made structures such as piers and artificial shorelines. As this oil usually contains a high percentage of aromatics and asphaltenes with high molecular weight, it does not degrade significantly and can remain in the environment for decades. Oil slicks and oil on shorelines sometimes interact with mineral fines suspended in the water column, and the oil is thereby transferred to the water column.19 Particles of mineral with oil attached may be heavier than water and sink to the bottom as sediment or the oil may detach and refloat. Oil-fines interaction does not generally play a significant role in the fate of most oil spills in their early stages, but can have an impact on the rejuvenation of an oiled shoreline over the long term.

8.2.7. Biodegradation A large number of microorganisms are capable of degrading petroleum hydrocarbons. Many species of bacteria, fungi, and yeasts metabolize petroleum hydrocarbons as a food energy source.20,21 Bacteria and other degrading organisms are most abundant on land in areas where there have been petroleum seeps, although these microorganisms are found everywhere in the environment. As each species can utilize only a few related compounds at most, however, broad-spectrum degradation does not occur. Hydrocarbons metabolized by microorganisms are generally converted to an oxidized compound, which may be further degraded, may be soluble, or may accumulate in the remaining oil. The aquatic toxicity of the biodegradation products is sometimes greater than that of the parent compounds. The rate of biodegradation depends primarily on the nature of the hydrocarbons and then on the temperature. Generally, rates of degradation tend to increase as the temperature rises. Some groupings of bacteria, however, function better at lower temperatures, and others function better at higher temperatures. Indigenous bacteria and other microorganisms are often the best adapted and most effective at degrading oil as they are acclimatized to the temperatures and other conditions of the area. Adding “superbugs” to the oil does not necessarily improve the degradation rate.

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The rate of biodegradation is greatest on saturates, particularly those containing approximately 12 to 20 carbons. Aromatics and asphaltenes, which have a high molecular weight, biodegrade very slowly, if at all. This explains the durability of roof shingles containing tar and roads made of asphalt, as both tar and asphalt consist primarily of aromatics and asphaltenes. On the other hand, diesel fuel is a highly degradable product, for it is largely composed of degradable saturates and lower aromatics. Light crudes are also degradable to a degree. While gasoline contains degradable components, it also contains some compounds that are toxic to some microorganisms. These compounds generally evaporate more rapidly, but in almost all cases, most of the gasoline will evaporate before it can degrade. Heavy crudes contain little material that is readily degradable, and Bunker C contains almost none. The rate of biodegradation is also highly dependent on the availability of oxygen. On land, oils such as diesel can degrade rapidly at the surface, but very slowly if at all only a few centimeters below the surface, depending on oxygen availability. In water, oxygen levels can be so low that degradation is limited. It is estimated that it would take all the dissolved oxygen in approximately 400,000 L of seawater to completely degrade 1 L of oil. The rate of degradation also depends on the availability of nutrients such as nitrogen and phosphorus, which are most likely to be available on shorelines or on land. Finally, the rate of biodegradation also depends on the availability of the oil to the bacteria or microorganism. Oil degrades significantly at the oil-water interface at sea and, on land, mostly at the interface between soil and the oil. Biodegradation can be a very slow process for some oils. It may take weeks for 50% of a diesel fuel to biodegrade under optimal conditions and years for 10% of a crude oil to biodegrade under similar conditions. For this reason, biodegradation is not considered an important weathering process in the short term.

8.2.8. Sinking and Overwashing If oil is more dense than the surface water, it may sometimes actually sink. Some rare types of heavy crudes and Bunker C can reach these densities and sink. When this occurs, the oil may sink to a denser layer of water rather than to the bottom. Less dense layers of water may override these denser layers of water. This occurs, for example, when seas are not high and warmer fresh water from land overrides dense seawater. The fresh water has a density of about 1.00 g/mL and the sea water a density of about 1.03 g/mL. An oil with a density greater than 1.00 but less than 1.03 would sink through the layer of fresh water and ride on the layer of salt water. The layer of fresh water usually varies in depth from about 1 to 10 m. If the sea energy increases, the oil may actually reappear on the surface, as the density of the water increases from 1.00 to about 1.03.

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It is important to note that sinking of any form, whether to the bottom or to the top of a layer of dense sea water, is rare. When oil does sink, it complicates cleanup operations as the oil can be recovered only with underwater suction devices or special dredges. Overwashing is another phenomenon that occurs quite frequently and can hamper cleanup efforts. At moderate sea states, a dense slick can be overwashed with water. When this occurs, the oil can disappear from view, especially if the spill is being observed from an oblique angle, as would occur if someone is observing a slick from a ship. Overwashing causes confusion about the fate of an oil spill as it can give the impression that the oil has sunk and then resurfaced.

8.2.9. Formation of Tarballs Tarballs are agglomerations of thick oil less than about 10 cm in diameter. Larger accumulations of the same material ranging from about 10 cm to 1 m in diameter are called tar mats. Tar mats are pancake-shaped rather than round. Their formation is still not completely understood, but it is known that they are formed from the residuals of heavy crudes and Bunker C. After these oils weather at sea and slicks are broken up, the residuals remain in tarballs or tar mats. The re-formation of droplets into tarballs and tar mats has also been observed, with the binding force being simply adhesion. The formation of tarballs is the ultimate fate of many oils.19 These tarballs are then deposited on shorelines around the world. The oil may come from spills, but it is also residual oil from natural oil seeps or from deliberate operational releases such as from ships. Tarballs are regularly recovered by machine or by hand from recreational beaches. Figure 8.2 shows such a tarball on a beach.

FIGURE 8.2 Tarball on a beach. This is the fate of spills on the sea, if not cleaned up.

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8.3. MOVEMENT OF OIL AND OIL SPILL MODELING 8.3.1. Spreading

Area (square kilometres)

Oil spreads to a lesser extent and more slowly on land than on water. Oil spilled on or under ice spreads relatively rapidly but does not spread to as thin a slick as on water.21 On any surface other than water, such as ice or land, a large amount of oil is retained in depressions, cracks, and other surface irregularities. After an oil spill on water, the oil tends to spread into a slick over the water surface. This is especially true of the lighter products such as gasoline, diesel fuel, and light crude oils, which form very thin slicks. Heavier crudes and Bunker C initially spread to slicks several millimeters thick. Heavy oils may also form tarballs and tar mats and thus may not go through progressive stages of thinning. The area of spreading for different types of oil is illustrated in Figure 8.3. Oil spreads horizontally over the water surface even in the complete absence of wind and water currents. This spreading is caused by the force of gravity and the interfacial tension between oil and water. The viscosity of the oil opposes these forces. As time passes, the effect of gravity on the oil diminishes, but the force of the interfacial tension continues to spread the oil. The transition between these forces takes place in the first few hours after the spill occurs. As a general rule, an oil slick on water spreads relatively quickly immediately after a spill. The outer edges of a typical slick are usually thinner than the inside of the slick at this stage so that the slick may resemble a “fried egg.” After a day or so of spreading, this effect diminishes.

10

Crude oil Diesel

1

Bunker C

0.1 Gasoline

0.01 1

10

100

Time (minutes)

1000 1 day

10000 7 days

FIGURE 8.3 The spreading of several oils on the sea, less the amount evaporated. This is taken over a time period of one week. Gasoline initially spreads rapidly, and then its area shrinks because of rapid evaporation.

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Winds and currents also spread the oil out and speed up the process. Oil slicks will elongate in the direction of the wind and currents and, as spreading progresses, take on many shapes depending on the driving forces. Oil sheens often precede heavier or thicker oil concentrations. If the winds are high (more than 20 km/h), the sheen may separate from thicker slicks and move downwind. A slick often breaks into “windrows” on the sea under the influence of either waves or zones of convergence or divergence. Oil tends to concentrate between the crests of waves simply because of the force of gravity. There are often vertical circulation cells in the top 20 m of the sea. When two circulation cells meet, a zone of convergence is formed. When two currents diverge, it forms a zone of divergence. Oil moving along these zones is alternately concentrated and spread out by the circulation currents to form ribbons or windrows of oil rather than continuous slicks. In some locations close to shore, zones of convergence and divergence often occur in similar locations so that oil spills may appear to have similar trajectories and spreading behavior in these areas.

8.3.2. Movement of Oil Slicks In addition to their natural tendency to spread, oil slicks on water are moved along the water surface, primarily by surface currents and winds. If the oil slick is close to land and the wind speed is less than 10 km/h, the slick generally moves at a rate that is 100% of the surface current and approximately 3% of the wind speed. In this case, wind does not generally play an important role. If the wind is more than about 20 km/h, however, and the slick is on the open sea, wind predominates in determining the slick’s movement. Both the wind and surface current must be considered for most situations. The movement resulting from both wind and current inputs is illustrated in Figure 8.4. When attempting to determine the movement of an oil slick, two factors affect accuracy. The more significant factor is the inability to obtain accurate wind and current speeds at the time of a spill. The other, very minor factor is a phenomenon commonly known as the Coriolis effect, whereby the Earth’s rotation deflects a moving object slightly to the right in the northern hemisphere and to the left in the southern hemisphere.

3% of wind component

Resulting movement

Resulting movement

Current component

3% of wind component Current component

FIGURE 8.4 The effect of different wind and current directions on the resulting movement of an oil slick.

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8.3.3. Spill Modeling Spill response personnel need to know the direction in which an oil spill is moving in order to protect sensitive resources and coastline. To assist them with this, computerized mathematical models have been developed to predict the trajectory or pathway and fate of oil. Outputs of one such spill model are shown in Figure 8.5. Today’s sophisticated spill models combine the latest information on oil fate and behavior with computer technology to predict where the oil will go and what state it will be in when it gets there. Their major limitation to accurately predicting an oil slick’s movement is the lack of accurate estimates of water current and wind speeds along the predicted path. This is likely to remain a major limitation in the future. In addition to predicting the trajectory, these models can estimate the amount of evaporation, the possibility of emulsification, the amount of dissolution and the trajectory of the dissolved component, the amount and trajectory of the portion that is naturally dispersed, and the amount of oil deposited and remaining on shorelines. Accurate spill modeling is now a very important part of both contingency planning and actual spill response.

Spil source Current vectors

Net movement of slick

Path traveled by slick

Present location of oil parcels Scene 1 - About 10 hours after spill

Red shows shoreline hit

Scene 3 - About one day after spill

Scene 2 - About 10 hours after spill - with current vectors shown

Oil moves back into main channel from shoreline

Scene 4 - About three days after spill

FIGURE 8.5 Illustration of the outputs of a spill trajectory model.

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Spill models operate in a variety of modes. The most typical is the trajectory mode, which predicts the trajectory and weathering of the oil. The stochastic mode uses available data to predict a variety of scenarios for the oil spill, which includes the direction, fate, and property changes in the oil slick. In another mode, often called the receptor mode, a site on the shore or water is chosen and the trajectory from the source of the oil is calculated. Increasingly, statistically generated estimates are added to oil spill models to compensate for the lack of accurate knowledge of winds and currents.

REFERENCES 1. Boehm PD, Page DS, Brown JS, Neff JM, Bragg JR, Atlas RM. Distribution and Weathering of Crude Oil Residues on Shorelines 18 Years after the Exxon Valdez Spill. Env Sci Techn 2008;9210. 2. Wardlaw GD, Arey JS, Reddy CM, Nelson RK, Ventura GT, Valentine DL. Disentangling Oil Weathering at a Marine Seep Using GCxGC: Broad Metabolic Specificity Accompanies Subsurface Petroleum Biodegradation. Env Sci Techn 2008;7166. 3. Dı´ez S, Jover E, Bayona JM, Albaige´s J. Prestige Oil Spill. III. Fate of a Heavy Oil in the Marine Environment. Env Sci Techn 2007;3075. 4. Short JW, Irvine GV, Mann DH, Maselko JM, Pella JJ, et al. Slightly Weathered Exxon Valdez Oil Persists in Gulf of Alaska Beach Sediments after 16 Years. Env Sci Techn 2007;1245. 5. French-McCay DP. Modeling Impacts of Oil and Chemical Releases. Sea Techn 2006;21. 6. French-McCay DP. Modeling as a Scientific Tool in NRDA for Oil and Chemical Spills. IOSC; 2008. 7. Etkin DS, Michel J, McCay DF, Boufadel M, Li H. Development of a Practical Methodology for Integrating Shoreline Oil-Holding Capacity into Spill Modeling. AMOP 2008;564. 8. French-McCay D, Rowe J, Etkin DS. Transport and Impacts of Oil Spills in San Francisco BaydImplications for Response. AMOP 2008;159. 9. Fingas M. Evaporation Modeling, Chapter 9 in the present work; 2010. 10. Fingas M. Models for Water-in-Oil Emulsion Formation, Chapter 10 in the Present Work; 2010. 11. Lunel T. The Braer spill: Oil fate Governed by Dispersion. IOSC 2005;790. 12. Farwell C, Reddy CM, Peacock E, Nelson RK, Washburn L, Valentine DL. Weathering and the Fallout Plume of Heavy Oil from Strong Petroleum Seeps Near Coal Oil Point, CA. Env Sci Techn 2009;3542. 13. Danchuk S, Willson CS. Numerical Modeling of Oil Spills in the Inland Waterways of the Lower Mississippi River Delta. IOSC 2008;887. 14. Faksness L-G, Brandvik PJ. Distribution of Water Soluble Components from Arctic Marine Oil SpillsdA Combined Laboratory and Field Study. Cold Regions Sci Techn 2008;97. 15. Taghvaei Ganjali S, Nahri Niknafs B, Khosravi M. Photooxidation of Crude Petroleum Maltenic Fraction in Natural Simulated Conditions and Structural Elucidation of Photoproducts. Iranian J Env Health Sci Eng 2007;37. 16. Fernandez-Varela R, Gomez-Carracedo MP, Fresco-Rivera P, Andrade JM, Muniategui S, Prada D. Monitoring Photooxidation of the Prestige’s Oil Spill by Attenuated Total Reflectance Infrared Spectroscopy. Talanta 2006;409. 17. Plata DL, Sharpless CM, Reddy CM. Photochemical Degradation of Polycyclic Aromatic Hydrocarbons in Oil Films. Environ Sci Techn 2008;2432.

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18. Plata D, Reddy CM. Photochemical Degradation of Select Polycyclic Aromatic Hydrocarbons: First-Order Disappearance Rates and Primary Degradation Mechanisms in OilContaminated Coastal Zones. ACS Nat Meet Book of Abstr 2005;230. 19. Khelifa A, Gamble L. Prediction of Tar Ball Formation. AMOP 2006;79. 20. Lepo JE, Cripe CR, Kavanaugh JL, Zhang S, Norton GP. The Effect of Amount of Crude Oil on Extent of Its Biodegradation in Open waterdand Sandy BeachdLaboratory Simulations. Envir Techn 2003;1291. 21. Spaulding ML. A State-of-the-Art Review of Oil Spill Trajectory and Fate Modeling. Oil Chem Poll 1988;39.

Chapter 9

Evaporation Modeling Merv Fingas

Chapter Outline 9.1. Introduction 9.2. Review of Theoretical Concepts 9.3. Development of New Diffusion-Regulated Models 9.4. Complexities to the Diffusion-Regulated Model

201 205 212 229

9.5. Use of Evaporation Equations in Spill Models 9.6. Comparison of Model Approaches 9.7. Summary

233

235 240

9.1. INTRODUCTION Evaporation is a very important process for most oil spills. In a few days, typical crude oils can lose up to 40% of their volume.1 Most oil spill behavior models include evaporation as a process and in the output of the model. Despite the importance of the process, relatively little work has been conducted on the basic physics and chemistry of oil spill evaporation.2 The difficulty with studying oil evaporation is that oil is a mixture of hundreds of compounds and this mixture varies from source to source and even over time. Much of the work described in the literature focuses on “calibrating” equations developed for water evaporation.2 Furthermore, very little empirical data on oil evaporation was published until a decade ago. An important concept in understanding evaporation is to understand the mechanisms that regulate evaporation. If there were no regulation, evaporation would proceed nearly instantly. Figure 9.1 shows a schematic of the airboundary-layer regulated mechanism. The liquid would evaporate at a very high rate if it was not for the regulation caused by the slow transfer of vapor through the air boundary layer. The most common example of this type of regulation is applicable to water, and this concept enters into most people’s common view of evaporation. Evaporation of water can be increased by spreading it out or by increasing the wind speed. Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10009-7 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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Evaporation limited by diffusion rate into the air therefore air-boundary-layer regulated Air Air boundary layer

Liquid

FIGURE 9.1 Illustration of the air-boundary-layer regulation mechanism. The diffusion into the air layer is the limiting factor and serves to regulate the evaporation rate. This rate is affected by turbulence in the air, which will increase the transfer of the molecules across the boundary layer. This regulatory mechanism is true for pure liquids that have a high evaporation rate. Water is an example of such a liquid and is the most common concept held.

Many liquids are not air-boundary-layer regulated primarily because they evaporate too slowly to have the vapors saturate the air boundary layer above them. Many mixtures are often regulated by the diffusion of molecules inside the liquid to the surface of the liquid. This situation is illustrated in Figure 9.2. Such a mechanism is true for many slowly evaporating mixtures of compounds, such as oils and fuels. Some of the outcomes of this mechanism may seem counterintuitive to some people in that increasing the area may not increase the evaporation rate except to a small degree if the initial pool is very thick, such as over about 10 to 20 mm. Also, and perhaps more importantly, increasing wind speed does not increase evaporation. Evaporation limited by diffusion rate through liquid and through surface layer-therefore diffusion regulated Air Liquid surface

Liquid

FIGURE 9.2 Illustration of the diffusion-controlled regulation mechanism. The diffusion through the evaporating liquid is the limiting factor and thus the regulation mechanism. This mechanism is generally true for oils, fuels, and many other mixtures of liquids that both evaporate more slowly than water and are mixtures.

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Scientific and quantitative work on water evaporation is decades old.3,4 The basis for the oil evaporation work in the literature is water evaporation. There are several fundamental differences between the evaporation of a pure liquid such as water and that of a multicomponent system such as crude oil. Most obviously, the evaporation rate for a single-component liquid such as water is a constant with respect to time.3,4 Evaporative loss, by total weight or volume, is not linear with time for crude oils and other multicomponent fuel mixtures.5 Evaporation of a liquid can be considered as the movement of molecules from the surface into the vapor phase above it. The layer of air above the evaporation surface is known as the boundary layer.6 The characteristics of this air layer, or boundary layer, can influence evaporation. In the case of water, the boundary layer regulates the evaporation rate. Air can hold a variable amount of water, depending on temperature, as expressed by the relative humidity. Under conditions where the boundary layer is not moving (no wind) or has low turbulence, the air immediately above the water quickly becomes saturated and evaporation slows or ceases. In practice, the actual evaporation of water proceeds at a small fraction of the possible evaporation rate because of the saturation of the boundary layer. The air-boundary-layer physics are then said to regulate the evaporation of water. This regulation manifests itself in the sensitivity of evaporation to wind or turbulence. When turbulence is weak or absent, evaporation can slow down by orders-of-magnitude. The molecular diffusion of water molecules is at least 103 times slower than turbulent diffusion.6 Evaporation can be viewed as consisting of two components, fundamental evaporation and regulation mechanisms. Fundamental evaporation is that process consisting of the evaporation of the liquid directly into the vapor phase without regulation other than by the thermodynamics of the liquid itself. Regulation mechanisms are those processes that serve to regulate the final evaporation rate into the environment. For water, the main regulation factor is the air-boundary-layer regulation discussed above. Air-boundary-layer regulation is manifested by the limited rate of diffusion, both molecular and turbulent diffusion, and by saturation dynamics. Molecular diffusion is based on exchange of molecules over the mean-free path in the gas. The rate of molecular diffusion for water is about 105 slower than the maximum rate of evaporation possible, purely from thermodynamic considerations.6 The rate for turbulent diffusion, the combination of molecular diffusion and movement with turbulent air, is on the order of 102 slower than that for maximum evaporation. In fact, in the case of water, maximum evaporation is not known and has only been estimated by experiments in artificial environments or by calculation.3 If the evaporation of oil was like that of water and was air-boundary-layer regulated, one could write the mass-transfer rate in semi-empirical form (also in generic and unitless form) as: E K C Tu S

(1)

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where E is the evaporation rate in mass per unit area, K is the mass-transfer rate of the evaporating liquid, presumed constant for a given set of physical conditions, sometimes denoted as kg (gas phase mass-transfer coefficient, which may incorporate some of the other parameters noted here), C is the concentration (mass) of the evaporating fluid as a mass per volume, Tu is a factor characterizing the relative intensity of turbulence, and S is a factor that relates to the saturation of the boundary layer above the evaporating liquid. The saturation parameter, S, represents the effects of local advection on saturation dynamics. If the air is already saturated with the compound in question, the evaporation rate approaches zero. This also relates to the scale length of an evaporating pool. If one views a large pool over which a wind is blowing, there is a high probability that the air is saturated downwind and the evaporation rate per unit area is lower than for a smaller pool. It should be noted that there many equivalent ways of expressing this fundamental evaporation equation. Much of the pioneering work for evaporation studies was performed by Sutton who proposed an equation based largely on empirical work:7 E ¼ K Cs U

7=9

d 1=9 Scr

(2)

where Cs is the concentration of the evaporating fluid (mass/volume), U is the wind speed, d is the area of the pool, Sc is the Schmidt number, and r is the empirical exponent assigned values from 0 to 2/3. Other parameters are defined as above. The terms in this equation are analogous to the very generic equation, (1), proposed above. The turbulence is expressed by a combination of the wind speed, U, and the Schmidt number, Sc. The Schmidt number is the ratio of kinematic viscosity of air (v) to the molecular diffusivity (D) of the diffusing gas in air, that is, a dimensionless expression of the molecular diffusivity of the evaporating substance in air. The coefficient of the wind power typifies the turbulence level. The value of 0.78 (7/9) as chosen by Sutton, represents a turbulent wind, whereas a coefficient of 0.5 would represent a wind flow that was more laminar. The scale length is represented by d and has been given an empirical exponent of 1/9. For water, this represents a weak dependence on size. The exponent of the Schmidt number, r, represents the effect of the diffusivity of the particular chemical, and historically was assigned values between 0 and 2/3.7 This expression for water evaporation was subsequently used by those working on oil spills to predict and describe oil and petroleum evaporation. Much of the literature follows the work of Mackay.8,9 Mackay and co workers adapted the equations for hydrocarbons using the evaporation rate of cumene. Data on the evaporation of water and cumene have been used to correlate the gas phase mass-transfer coefficient as a function of wind speed and pool size by the equation: Km ¼ 0:0292 U 0:78 X 0:11 Sc0:67

(3)

Chapter | 9

Evaporation Modeling

205

where Km is the mass-transfer coefficient in units of mass per unit time and X is the pool diameter or the scale size of evaporating area. Stiver and Mackay subsequently developed this further by adding a second equation:9 N ¼ km AP=ðRTÞ

(4)

where N is the evaporative molar flux (mol/s), km is the mass-transfer coefficient at the prevailing wind (m/s), A is the area (m2), P is the vapor pressure of the bulk liquid (Pascals), R is the gas constant [8.314 Joules/(mol-K)], and T is the temperature (K ). Thus, boundary-layer regulation was assumed to be the primary regulation mechanism for oil and petroleum evaporation. This assumption was never well tested by experimentation, as revealed by a literature search.2 The implications of these assumptions are that evaporation rate for a given oil is increased by: l l l

increasing turbulence increasing wind speed increasing the surface area of a given mass of oil

These factors can then be verified experimentally to test whether oil is boundary-layer regulated.

9.2. REVIEW OF THEORETICAL CONCEPTS Blokker was the first to develop oil evaporation equations for oil evaporation at sea.10 His starting basis was theoretical. Oil was presumed to be a onecomponent liquid. The ASTM (American Society for Testing and Materials) distillation data and the average boiling points of successive fractions were used as the starting point to predict an overall vapor pressure. The average vapor pressure of these fractions was then calculated from the ClausiusClapeyron equation to yield: log

ps qM 1 1 ¼ p 4:57 T Ts

(5)

where p is the vapor pressure at the absolute temperature, T, ps is the vapor pressure at the boiling point, Ts (for ps, 760 mm Hg was used), q is the heat of evaporation in cal/g, and M is the molecular weight. The term qM/(4.57 Ts) was taken to be nearly constant for hydrocarbons (¼5.0 þ/ 0.2), and thus the expression was simplified to: log ps =p ¼ 5:0½ðTs TÞ=T

(6)

From the data obtained, the weathering curve was calculated, assuming that Raoult’s law is valid for this situation giving qM as a function of the percentage

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evaporated. Pasquill’s equation10 was applied stepwise, and the total evaporation time was obtained by summation: t ¼

DhDb X 1 Kev U a PM

(7)

where t is the total evaporation time in hours, Dh is the decrease in layer thickness in m, D is the diameter of the oil spill, b is a meteorological constant (assigned a value of 0.11), Kev is a constant for atmospheric stability (taken to be 1.2 108), a is a meteorological constant (assigned a value of 0.78), P is the vapor pressure at the absolute temperature, T, and M is the molecular weight of the component or oil mass. Thus the model is partially air-boundary-layer regulated. Blokker constructed a small wind tunnel and tested this equation against the evaporation of gasoline and a medium crude oil. The observed gasoline evaporation rate was much higher than was predicted, and the crude oil rate was much lower than predicted. The times of evaporation, however, were somewhat close, and the equation was accepted for further use. The above equations were then incorporated into spreading equations to yield equations to predict the simultaneous spreading and evaporation of oil and petroleum products. Mackay and Matsugu approached the problem by using the classical water evaporation and experimental work.8 The water evaporation equation was corrected to hydrocarbons using the evaporation rate of cumene. It was noted that the difference in constants was related to the enthalpy differences between water and cumene. Data on the evaporation of water and cumene were used to correlate the gas phase mass-transfer coefficient as a function of wind speed and pool size by the equation: Km ¼ 0:0292 U 0:78 X 0:11 Sc0:67

(8)

where Km is the mass-transfer coefficient in units of mass per unit time and X is the pool diameter or the scale size of evaporating area. Note that the exponent of the wind speed, U, is 0.78, which is equal to the classical water evaporation-derived coefficient. Mackay and Matsugu noted that for hydrocarbon mixtures, the evaporation process is more complex, being dependent on the liquid diffusion resistance being present. Experimental data on gasoline evaporation were compared with computed rates. The computed rates showed some agreement and suggested the presence of a liquid-phase masstransfer resistance. This work was subsequently extended by the same group to show that the evaporative loss of a mass of oil spilled can be estimated using a mass-transfer coefficient, as shown above.11 This approach was investigated with some laboratory data and tested against some known mass-transfer conditions on the sea. The conclusion was that this mass-transfer approach could result in predictions of evaporation at sea.

Chapter | 9

Evaporation Modeling

207

Butler developed a model to examine evaporation of specific hydrocarbon components.12 The weathering rate was taken as proportional to the equilibrium vapor pressure, P, of the compound and to the fraction remaining: dx=dt ¼ kPðx=xo Þ

(9)

where x is the amount of a particular component of a crude oil at time, t, xo is the amount of that same component present at the beginning of weathering (t ¼ 0), k is an empirical rate coefficient, and P is the vapor pressure of the oil component. Since petroleum is a complicated mixture of compounds, P is not equal to the vapor pressure of the pure compound, but neither would there be large variations in the activity coefficient as the weathering process occurs. For this reason, the activity coefficients were subsumed in the empirical rate coefficient k. P and k were taken as independent of the amount, x, for a fairly wide range of oils. The equation was then directly integrated to give the fraction of the original compound remaining after weathering as (similar to Henry’s law): x=xo ¼ expðktP=xo Þ

(10)

The vapor pressure of individual components was fit using a regression line to yield a predictor equation for vapor pressure: P ¼ expð10:94 1:06 NÞ

(11)

where P is the vapor pressure in Torr and N is the carbon number of the compound in question. This combined with Equation (10) yielded the following expression: x=xo ¼ exp½ðkt=xo Þexpð10:94 1:06 NÞ

(12)

where x/xo is the fraction of the component left after weathering, k is an empirical constant, xo is the original quantity of the component, and N is the carbon number of the component in question. Equation (12) predicts that the fraction weathered is a function of the carbon number and decreases at a rate that is faster than predicted from simple exponential decay. If the initial distribution of compounds is essentially uniform (xo independent of N ), then the above equation predicts that the carbon number where a constant fraction (e.g., half) of the initial amount has been lost (x ¼ 0.5 xo) is a logarithmic function of the time of weathering: N1=2 ¼ 10:66 þ 2:17 logðkt=xo Þ

(13)

where N1/2 is half the volume fraction of the oil. The equation was tested using data from some patches of oil on shoreline, whose age was known. The equation was able to predict the age of the samples relatively well. It was suggested that the equation was applicable to open water spills; however, this was never subsequently applied in models. It should be noted that this approach is somewhat similar to the model that will be described

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Behaviour of Oil in the Environment and Spill Modeling

later in this paper and also that it is not air-boundary-layer based but is a diffusion-like model based partially on empirical values. Yang and Wang developed an equation using the Mackay and Matsugu molecular diffusion process.13 The vapor phase mass-transfer process was expressed by: Die ¼ km ð pi piN Þ=½RTS

(14)

where Die is the vapor phase mass-transfer rate, km is a coefficient that lumps all the unknown factors that affect the value of Die, pi is the hydrocarbon vapor pressure of fraction, I, at the interface, piN is the hydrocarbon vapor pressure of fraction, I, at infinite altitude of the atmosphere, R is the universal gas constant, and Ts is the absolute temperature of the oil slick. The following functional relationship was proposed: km ¼ aAg eqU

(15)

where A is the slick area, U is the over-water wind speed, and a, q, and g are empirical coefficients. This functional relationship was based on the results of past investigations, including, for instance, those of MacKay and Matsugu who suggested the value of g to be in the range from 0.025 to 0.055.8 Further experiments were performed by Yang and Wang to determine the values of a and q.13 The results were found to be twofold. Experiments showed that a film formed on evaporating oils and that this film severely retarded evaporation. Before the surface film has developed (rt/ro < 1.0078): Kmb ¼ 69A0:0055 e0:42U

(16)

where Kmb is the coefficient that groups all factors affecting evaporation before the surface film has formed and A is the area. After the surface film has developed (rt/ro > 1.0078): Kma ¼ 1=5 kmb

(17)

where ro is initial oil density, rt is weathered oil density at time t, and Kma is the coefficient that groups all factors affecting evaporation after the surface film has formed. The evaporation rate was found to be reduced fivefold after the formation of the surface film. Brighton proposed that the standard formulation used by many workers required refining.14 E ¼ K Cs U 7=9 d1=9 Scr

(18)

His starting point for water evaporation was similar to that proposed by Sutton7 where E is the mean evaporation rate per unit area, K is an empirically determined constant, Cs is the concentration of the evaporation fluid (mass/volume), d is the area of the square or circular pool, and r is an empirical exponent assigned values from 0 to 2/3.

Chapter | 9

209

Evaporation Modeling

Brighton suggested that this equation does not conform to the basic dimensionless form involving the parameters U and Zo (wind speed and roughness length, respectively), which define the boundary-layer conditions. The key factor in Brighton’s analysis was to use a linear eddy-diffusivity profile. This feature implied that concentration profiles become logarithmic near the surface, which is suspected to be more realistic compared to the more finite values previously used. Using a power profile to provide an estimation of the turbulence, Brighton was able to substitute the following identities into the classical relationship: U ¼

u n k

(19)

where u* is the friction velocity, z1 is the reference height above the surface, z0 is the roughness length, and n is the power law dimensionless term. It should be noted that these are applicable to neutrally stable atmospheres. z1 (20) n ¼ In z0 The evaporation equation now becomes: z dX d ku zdX U ¼ z1 dx dz s dz

(21)

where z is the height above the surface, X is the concentration of the evaporating compounds, x is the dimension of the evaporating pool, k is given by K/u)z, and is the von Karman constant, and s is the turbulent Schmidt number (taken as 0.85). Brighton subsequently compared his model with several runs of experimental evaporation experiments in the field and in the laboratory. This included laboratory oil evaporation data.15 The model only correlated well with laboratory water evaporation data, and the reason given was that other data sets were “noisy.” The most frequently used work in spill modeling is that of Stiver and Mackay.9 It is based on some of the earlier work by Mackay and Matsugu, but significant additions were made.8 Additional information is given in a thesis by Stiver.16 The formulation was initiated with assumptions about the evaporation of a liquid. If a liquid is spilled, the rate of evaporation is given by: N ¼ KAP=ðRTÞ

(22)

where N is the evaporative molar flux (mol/s), K is the mass-transfer coefficient under the prevailing wind (ms1), A is the area (m2), and P is the vapor pressure of the bulk liquid. This equation was arranged to give: dFv =dt ¼ KAPv=ðVo RTÞ

(23)

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PART | IV

Behaviour of Oil in the Environment and Spill Modeling

where Fv is the volume fraction evaporated, v is the liquid’s molar volume (m3/mol), and Vo is the initial volume of spilled liquid (m3). By rearranging, we obtain:

or:

dFv ¼ ½Pv=ðRTÞðKAdt=Vo Þ

(24)

dFv ¼ Hdq

(25)

where H is Henry’s law constant and q is the evaporative exposure. The right-hand side of the second to last equation has been separated into two dimensionless groups. The group, KAdt/Vo, represents the time rate of what has been termed the “evaporative exposure” and was denoted as dq. The evaporative exposure is a function of time, the spill area and volume (or thickness), and the mass-transfer coefficient (which is dependent on the wind speed). The evaporative exposure can be viewed as the ratio of exposed vapor volume to the initial liquid volume. The group Pv/(RT) or H is a dimensionless Henry’s law constant or ratio of the equilibrium concentration of the substance in the vapor phase [P/(RT)] to that in the liquid (l/v). H is a function of temperature. The product qH is thus the ratio of the amount that has evaporated (oil concentration in vapor times vapor volume) to the amount originally present. For a pure liquid, H is independent of Fv and Equation 2.26 was integrated directly to give: Fv ¼ Hq

(26)

If K, A, and temperature are constant, the evaporation rate is constant and evaporation is complete (Fv is unity) when q achieves a value of 1/H. If the liquid is a mixture, H depends on Fv and the basic equation can only be integrated if H is expressed as a function of Fv; that is, the principal variable of vapor pressure is expressed as a function of composition. The evaporation rate slows as evaporation proceeds in such cases. Equation (26) was replaced with a new equation developed using data from evaporation experiments: Fv ¼ ðT=K1 Þ Inð1 þ K1 q=TÞ expðK2 K3 =TÞ

(27)

where Fv is the volume fraction evaporated and K1,2,3 are empirical constants. A value for K1 was obtained from the slope of the Fv versus log q curve from pan or bubble evaporation experiments. For q greater than 104, K1 was found to be approximately 2.3T divided by the slope. The expression exp(K2 K3/T) was then calculated, and K2 and K3 were determined individually from evaporation curves at two different temperatures. Variations of all the above equations have been used extensively by many other experimenters and for model application. Brown and Nicholson studied the weathering of a heavy oil, bitumen.17 They compared experimental data using a large-scale weathering tank with two

Chapter | 9

Evaporation Modeling

211

spill model outputs. In the FOOS model, the evaporative exposure concept is used in which the fraction of oil evaporated is given by a variant of the Mackay equation: F ¼ ½InðPÞ þ InðCEÞ þ 1=P=C

(28)

where F is the fraction evaporated, C is an empirical constant, and E is a measure of the evaporative exposure, defined as; E ¼ ðKm AvtÞ=ðRTVo Þ

(29)

Km ¼ 0:0048 U 0:78 Z 0:11 Sc0:67

(30)

where;

and where Km is the mass-transfer coefficient, A is the slick area, v is the oil molar volume, Vo is the initial slick volume, Z is the pool size scale factor, and Sc is the Schmidt number (taken as 2.7). Brown and Nicholson compared the measured evaporation for a 5 ms1 wind at an ambient temperature of 20 C, and evaluation was done with the equation above.17 A spill volume of 100 m3 was assumed. A value of about 105 m3/mol was used for the average molar volume. The model generally described the observed evaporation quite well, particularly during the first few hours. Later, however, the model consistently overpredicted the evaporation rate. A simple method of correcting the equation was implemented by assuming that the vapor phase Schmidt number decreases slightly as the skin on the oil thickens. In response, the evaporative exposure was modified to: Km ¼ ð0:0025 0:000021 tÞ U 0:78

(31)

The predicted evaporation then compared favorably with the measured values. Bobra conducted laboratory studies on the evaporation of crude oils.18 The evaporation curves for several crude oils and petroleum products were measured under several different environmental conditions. These data were compared to the equation developed by Stiver and Mackay.9 The equation used was: Fv ¼ In½1 þ BðTG =TÞ q expðA B To =TÞfT=BTG g

(32)

where FV is the fraction evaporated, TG is the gradient of the modified distillation curve, A and B are dimensionless constants, To is the initial boiling point of the oil, and q is the evaporative exposure as previously defined. The comparison by Bobra et al. showed that the Stiver and Mackay equation predicts the evaporation of most oils relatively well until time exceeds about 8 hours; after that it overpredicted the evaporation. The “overshoot” can be as much as 10% evaporative loss at the 24-hour mark. This is especially true for very light oils. The Stiver and Mackay equation was also found to underpredict or overpredict the evaporation of oils in the initial phases. In addition, it was found that the basic

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assumptions in the bubble experiment as proposed by early researchers, namely, that the air bubbles are saturated with vapor, was not correct.9 Bobra also noted that most oil evaporation follows a logarithmic curve with time and that a simple approach to this was much more accurate than using Equation (32).

9.3. DEVELOPMENT OF NEW DIFFUSION-REGULATED MODELS A review of the theoretical work above reveals that air-boundary-layer concepts are very limited and cannot accurately explain long-term evaporation. Fingas conducted a series of experiments over several years to examine the concepts further.19 The results of the boundary-regulation experiments are presented in the order of the experimental series.

9.3.1. Wind Experiments A major factor in determining whether or not oil evaporation is air-boundarylayer regulated is if the evaporation rate increases with wind as would be predicted by Equations (2) and (8) above. Experiments on the evaporation of oil with and without wind were conducted with ASMB (Alberta Sweet Mixed Blend), gasoline, and water. Water formed a baseline data set since much is known about its evaporation behavior.3 Regressions on the data were performed, and the equation parameters calculated. Curve coefficients are the constants from the best fit equation [Evap ¼ a ln(t)], t ¼ time in minutes, for logarithmic equations or Evap ¼ a Ot, for the square root equations. Oils with few components evaporating at one time have a tendency to fit square root curves.5 While data were calculated separately for percentage of weight lost and absolute weight, the latter is usually used because it is more convenient. The plots of wind speed versus the evaporation rate (as a percentage of weight lost) for each oil type are shown in Figures 9.3 to Figure 9.5. These figures show that the evaporation rates for oils and even the light product gasoline are not increased by a significant amount with increasing wind speed. In most cases, there is a small rise from the 0-wind level to the 1-m/s level, but after that, the rate remains relatively constant. The evaporation rate after the 0-wind value is nearly identical for all oils. This is due to the stirring effect on the oil, which increases the diffusion rate to the surface. The oil evaporation data can be compared to the evaporation of water, as illustrated in Figure 9.5. These data show the classical relationship of the water evaporation rate correlated with the wind speed (evaporation varies as U0.78, where U is wind speed). This, by itself, indicates that the oils studied here are not boundary-layer-regulated, but a small effect is seen in moving from 0-wind to 1 m/s, and not thereafter. This, as noted above, is due to the stirring effect of the wind thus increasing the diffusion rate.

Chapter | 9

213

Evaporation Modeling 50

Percent Evaporated

40

30

20 wind = 0 m/s wind = 1 m/s wind = 1.6 m/s wind = 2.1 m/s wind = 2.6 m/s

10

0

0

500

1000

1500

2000

2500

Time - Minutes FIGURE 9.3 Evaporation of ASMB with varying wind velocities. This figure shows that there is little variation with wind velocity except in going from the 0-wind-level up to the others. This is due to the stirring effect of wind and not air-boundary-layer regulation.

FIGURE 9.4 Evaporation of gasoline with varying wind velocities. This figure also shows that there is little variation with wind velocity except in going from the 0-wind-level up to the others. This again is due to the stirring effect of wind and not air-boundary layer regulation.

100

Percent Evaporated

80

60

40 wind = 0m/s wind =1 m/s wind = 1.6m/s wind = 2.1m/s wind = 2.6m/s

20

0

0

20

40

60

80 100 120 140 160 180

Time - Minutes

214

PART | IV

Behaviour of Oil in the Environment and Spill Modeling

FIGURE 9.5 Evaporation of water with varying wind velocities. This figure shows dramatic differences in the evaporation rate of water with wind velocity. This is typical of air-boundary-layer regulation. Compare Figure 9.5 with oil evaporation in Figures 9.3 and 9.4, which do not show this trend of variance with wind velocity.

100

Percent Evaporated

80

60

40

20

wind = 0 m/s wind = 1 m/s wind = 1.6 m/s wind = 2.1 m/s wind = 2.6 m/s regression line

0 0

20

40

60

80

100 120 140 160 180

Time - Minutes

Figure 9.6 shows the rates of evaporation compared to the wind speed for all the liquids used in this study. This figure shows the evaporation rates of all test liquids versus wind speed. The lines shown are those calculated by linear regression. This clearly shows that water evaporation rate increased, as expected, with increasing wind velocity. The oils, ASMB, and gasoline, do not show any significant increase with increasing wind speed. In any case, they do not show the typical U0.78 relationship that water shows. All the above data show that oil is not boundary-layer-regulated. FIGURE 9.6 Correlation of evaporation rates and wind velocity. The lines are drawn through the data points from experimental values. This clearly shows no correlation of oil evaporation rates with wind velocity and the strong and expected high correlation of water with wind velocity. The water evaporation line is moved to fit on the vertical scale, but otherwise is unaltered.

Evaporation Rate (%/min. or %/ln min.)

25 Gasoline

20

15

10

Water

ASMB

5 FCC Heavy Cycle

0 0

1

Wind Velocity - m/s

2

Chapter | 9

215

Evaporation Modeling

9.3.2. Evaporation Rate and Area Air-boundary-layer regulated liquids evaporate much faster if one increases the area. A small spill of water on the kitchen cupboard can be evaporated quickly by spreading it out on the cupboard. A test of this tendency will also confirm the proposition that oil is diffusion regulated. ASMB was also used to conduct a series of experiments with varying evaporation area. The mass of the oil was kept constant so that the thickness of the oil would also vary. However, the greater the area, the less the thickness, and both factors would increase oil evaporation if it were boundary-layer regulated. The experiments show no correlation between area and evaporation rate. One can conclude that evaporation rate is not highly correlated with area, and thus the evaporation of oil is not air-boundary-layer regulated.

9.3.3. Study of Mass and Evaporation Rate Air-boundary-layer liquids show no correlation between the mass of oil evaporated and the evaporation rate; however, diffusion-regulated liquids do. ASMB oil was again used to conduct a series of experiments with volume as the major variant. Alternatively, thickness and area were held constant to ensure that the strict relationship between these two variables did not affect the final regression results. Figure 9.7 illustrates the relationship between evaporation rate and volume of evaporation material (also equivalent to mass of evaporating material). This figure illustrates a strong correlation between oil mass (or volume) and evaporation rate. This again proves that there is no boundary-layer regulation.

FIGURE 9.7 Correlation of oil mass with evaporation rate. The plots are the equation factors from the evaporation equation, which is approximately equivalent to evaporation rate. This shows a direct relationship between evaporation rate of oil and mass of oil. It indicates that oil is diffusion regulated.

Evaporation Rate - g/ln min.

5

4

3

2

1

0 0

20

40

60

80

Weight - Grams

100

120

140

216

PART | IV

Behaviour of Oil in the Environment and Spill Modeling

9.3.4. Study of the Evaporation of Pure Hydrocarbonsdwith and Without Wind A study of the evaporation rate of pure hydrocarbons was conducted to test the classic boundary-layer evaporation theory as applied to the hydrocarbon constituents of oils. The evaporation rate data are illustrated in Figure 9.8. This figure shows that the evaporation rates of the pure hydrocarbons have a variable response to wind. Heptane (hydrocarbon number 7) shows a large difference between evaporation rate in wind and no wind conditions, indicating boundarylayer regulation. Decane (carbon number 10) shows a lesser effect, and dodecane (carbon number 12) shows a negligible difference between the two experimental conditions. This experiment shows the extent of boundary regulation and the reason for the small or negligible degree of boundary regulation shown by crude oils and petroleum products. Crude oil contains very little material with carbon numbers less than dodecane, often less than 3% of its composition. Even the more volatile petroleum products, gasoline and diesel fuel, only have limited amounts of compounds more volatile than decane, and thus are also not strongly boundary-layer regulated, if at all. 0.6

Evaporation Rate - g/min.

0.5

0.4

Wind

0.3

0.2

0.1

No Wind

0.0 6

8

10

12

14

16

Hydrocarbon Number FIGURE 9.8 Evaporation rate of pure hydrocarbons. This shows that hydrocarbons up to about C12 (dodecane) show some air-boundary-regulated behavior, whereas those above show no airboundary-regulated behavior. As most compounds in oil are higher than dodecane, the bulk oil would not show air-boundary-regulated behavior.

Chapter | 9

217

Evaporation Modeling

9.3.5. Other Factors Another evaluation of evaporation regulation is that of saturation concentration, the maximum concentration soluble in air. The saturation concentrations of water and several oil components are listed in Table 9.1.20 This table shows that saturation concentration of water is less than that of many common oil components. The saturation concentration of water is, in fact, about two orders of magnitude less than the saturation concentration of volatile oil components such as pentane. This further explains why even light oil components have little boundary-layer limitation. Further, the saturation concentration of water is so regulating that with a high relative humidity, there is little that can be added to the air.

9.3.6. Temperature Variation and Generic Equations Using Distillation Data Comparing the evaporation data with temperature, one finds that the evaporation equations for oils show some differences. The resulting finding that unique

TABLE 9.1 Saturation Concentration of Water and Hydrocarbons Substance

Saturation Concentration* in g/m3 at 25 C

water

20

n-pentane

1689

hexane

564

cyclohexane

357

benzene

319

n-heptane

196

methylcyclohexane

192

toluene

110

ethybenzene

40

p-xylene

38

m-xylene

35

o-xylene

29

*Values taken from Ullmann’s Encyclopedia20

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PART | IV

Behaviour of Oil in the Environment and Spill Modeling

equations may be needed for each oil is a significant disadvantage to practical end use, and a way to accurately predict evaporation using other readilyavailable data is necessary. Findings show that distillation data can be used to predict evaporation. Distillation data are very common and are often the only data used to characterize oils. This is because the data are crucial in operating refineries. Crudes are sometimes priced on the basis of their distillation data. New procedures to measure distillation data are very simple, fast, and repeatable. Further, it was noted that oils and fuels evaporated as two distinct typesd those that evaporated as a logarithm of time and those that evaporated as a square root of time.5 Most oils typically evaporated as a logarithm (natural) with time. Diesel fuel and similar oils, such as jet fuel, kerosene, and the like, evaporate as a square root of time. The reasons for this are simply that diesel fuel and the like have a narrower range of compounds that evaporate at similar yield rates, which are a summation of a square root.5 The empirically measured parameters at 15 C were correlated with both the slopes and the intercepts of the temperature equations. Full details of this correlation are given in the literature.22,23 For the variation with temperature, the resulting equation is: Percentage evaporated ¼ ½B þ 0:045ðT 15Þ InðtÞ

(33)

where B is the equation parameter at 15 C, T is temperature in degrees Celsius, and t is the time in minutes. Distillation data were directly correlated to the evaporation rates determined by experimentation. The distillation data used were the type that are stated as the temperature at which a fixed amount of material is lost. The optimal point, or point at which the regression coefficient is maximum, was found to be 180 C by using peak functions. The percent mass distilled at 180 degrees was used to calculate the relationship between the distillation values and the equation parameters. The equations used were derived from correlations of the data. The data from those oils that were better fitted with square root equationsddiesel, Bunker C light, and Fluid Catalytic Cracker (FCC) Heavy Cycledwere calculated separately. The equations derived from the regressions are as follows: For oils that follow a logarithmic equation: Percentage evaporated ¼ 0:165ð%DÞ InðtÞ

(34)

For oils that follow a square root equation: pﬃ Percentage evaporated ¼ 0:0254ð%DÞ t where %D is the percentage (by weight) distilled at 180 C.

(35)

Chapter | 9

219

Evaporation Modeling

These equations can be combined with the equations generated in previous work as shown in Equation (33) above to account for the temperature variations: For oils that follow a logarithmic equation: Percentage evaporated ¼ ½:165ð%DÞ þ :045ðT 15Þ lnðtÞ

(36)

For oils that follow a square root equation:

pﬃ Percentage evaporated ¼ ½:0254ð%DÞ þ :01ðT 15Þ t 180 C.

(37)

where %D is the percentage (by weight) distilled at In addition, a large number of experiments were performed on oils to directly measure their evaporation curves. The empirical equations that result are given in Table 9.2.

TABLE 9.2 Equations for Predicting Evaporation Oil Type

Equation

Adgo

%Ev ¼ (.11 þ .013T)/t

Adgo e long term

%Ev ¼ (.68 þ .045T)ln(t)

Alaminos Canyon Block 25

%Ev ¼ (2.01 þ .045T)ln(t)

Alaska North Slope (2002)

%Ev ¼ (2.86 þ .045T)ln(t)

Alberta Sweet Mixed Blend

%Ev ¼ (3.24 þ .054T)ln(t)

Amauligak

%Ev ¼ (1.63 þ .045T)ln(t)

Amauligak e f24

%Ev ¼ (1.91 þ .045T)ln(t)

Anadarko H1A-376

%Ev ¼ (2.66 þ .013T)/t

Arabian Medium

%Ev ¼ (1.89 þ .045T)ln(t)

Arabian Heavy

%Ev ¼ (1.31 þ .045T)ln(t)

Arabian Heavy

%Ev ¼ (2.71 þ .045T)ln(t)

Arabian Light

%Ev ¼ (2.52 þ .037T)ln(t)

Arabian Light

%Ev ¼ (3.41 þ .045T)ln(t)

Arabian Light (2001)

%Ev ¼ (2.4 þ .045T)ln(t)

ASMB e Standard #5

%Ev ¼ (3.35 þ .045T)ln(t)

ASMB (offshore)

%Ev ¼ (2.2 þ .045T)ln(t)

Av Gas 80

%Ev ¼ (15.4 þ .045T)ln(t)

(Continued )

220

PART | IV

Behaviour of Oil in the Environment and Spill Modeling

TABLE 9.2 Equations for Predicting Evaporationdcont’d Oil Type

Equation

Avalon

%Ev ¼ (1.41 þ .045T)ln(t)

Avalon J-34

%Ev ¼ (1.58 þ .045T)ln(t)

Aviation Gasoline 100 LL

ln(%Ev) ¼ (0.5 þ .045T)ln(t)

Azeri e long term

%Ev ¼ (1.3 þ .045T)ln(t)

Azeri e short term

%Ev ¼ (0.09 þ .013T)/t

Barrow Island

%Ev ¼ (4.67 þ .045T)ln(t)

BCF-24

%Ev ¼ (1.08 þ .045T)ln(t)

Belridge Crude

%Ev ¼ (.01 þ .013T)/t

Bent Horn A-02

%Ev ¼ (3.19 þ .045T)ln(t)

Beta

%Ev ¼ (0.08 þ .013T)/t

Beta e long term

%Ev ¼ (0.29 þ .045T)ln(t)

Boscan

%Ev ¼ (0.15 þ .013T)/t

Brent

%Ev ¼ (3.39 þ .048T)ln(t)

Bunker C e Light (IFO~250)

%Ev ¼ (.0035 þ .0026T)/t

Bunker C e long term

%Ev ¼ (.21 þ .045T)ln(t)

Bunker C (2002)

%Ev ¼ (0.16 þ .013T)/t

Bunker C (short term)

%Ev ¼ (.35 þ .013T)/t

Bunker C Anchorage

%Ev ¼ (0.13 þ .013T)/t

Bunker C Anchorage (long term)

%Ev ¼ (0.31 þ .045T)ln(t)

California API 11

%Ev ¼ (0.13 þ .013T)/t

California API 15

%Ev ¼ (0.14 þ .013T)/t

Cano Limon

%Ev ¼ (1.71 þ .045T)ln(t)

Canola Oil

Litte

Carpenteria

%Ev ¼ (1.68 þ .045T)ln(t)

Cat Cracking Feed

%Ev ¼ (0.18 þ .013T)/t

Chavyo

%Ev ¼ (3.52 þ .045T)ln(t)

Cold Lake Bitumen

%Ev ¼ (0.16 þ .013T)/t

Combined Oil/Gas

%Ev ¼ (0.08 þ .013T)/t

Chapter | 9

221

Evaporation Modeling

TABLE 9.2 Equations for Predicting Evaporationdcont’d Oil Type

Equation

Compressor Lube Oil -New

%Ev ¼ (0.68 þ .045T)ln(t)

Cook Inlet e Granite Point

%Ev ¼ (4.54 þ .045T)ln(t)

Cook Inlet e Swanson River

%Ev ¼ (3.58 þ .045T)ln(t)

Cook Inlet New Batch

%Ev ¼ (3.1 þ .045T)ln(t)

Cook Inlet Trading Bay

%Ev ¼ (3.15 þ .045T)ln(t)

Corrosion Inhibitor Solvent

%Ev ¼ (0.02 þ .013T)/t

Crude Castor oil

Litte

Cusiana

%Ev ¼ (3.39 þ .045T)ln(t)

Delta West Block 97

%Ev ¼ (6.57 þ .045T)ln(t)

Diesel e Anchorage e long term

%Ev ¼ (4.54 þ .045T)ln(t)

Diesel e Anchorage e short term

%Ev ¼ (.51 þ .013T)/t

Diesel e long term

%Ev ¼ (5.8 þ .045T)ln(t)

Diesel Mobile1997

%Ev ¼ (0.03 þ .013T)/t

Diesel (2002)

%Ev ¼ (0.02 þ .013T)/t

Diesel (regular stock)

%Ev ¼ (.31 þ .018T)/t

Diesel fuel e Southern e long term

%Ev ¼ (2.18 þ .045T)ln(t)

Diesel fuel e Southern e short term

%Ev ¼ (0.02 þ .013T)/t

Diesel Fuel 2002

%Ev ¼ (5.91 þ .045T)ln(t)

Diesel Fuel 2002 short term

%Ev ¼ (0.39 þ .013T)/t

Diesel Mobile 1997 long term

%Ev ¼ (0.02 þ .013T)/t

Dos Cuadros

%Ev ¼ (1.88 þ .045T)ln(t)

Ekofisk

%Ev ¼ (4.92 þ .045T)ln(t)

Empire Crude

%Ev ¼ (2.21 þ .045T)ln(t)

Endicott

%Ev ¼ (0.9þ .045T)ln(t)

Esso Spartan EP-680 Industrial Oil

%Ev ¼ (0.66 þ .045T)ln(t)

Eugene Is. 224-condensate

%Ev ¼ (9.53 þ .045T)ln(t)

Eugene Island Block 32

%Ev ¼ (0.77þ .045T)ln(t)

(Continued )

222

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Behaviour of Oil in the Environment and Spill Modeling

TABLE 9.2 Equations for Predicting Evaporationdcont’d Oil Type

Equation

Eugene Island Block 43

%Ev ¼ (1.57 þ .045T)ln(t)

Evendell

%Ev ¼ (3.38 þ .045T)ln(t)

FCC Heavy cycle

%Ev ¼ (.17 þ .013T)/t

FCC Light

%Ev ¼ (0.17 þ .013T)/t

FCC Medium cycle

%Ev ¼ (.16 þ .013T)/t

FCC-VGO

%Ev ¼ (2.5 þ .013T)/t

Federated

%Ev ¼ (3.47 þ .045T)ln(t)

Federated (new-1999)

%Ev ¼ (3.45 þ .045T)ln(t)

Fuel Oil #5

%Ev ¼ (0.14 þ .013T)/t

Garden Banks 387

%Ev ¼ (1.84 þ .045T)ln(t)

Garden Banks 426

%Ev ¼ (3.44 þ .045T)ln(t)

Gasoline

%Ev ¼ (13.2 þ .21T)ln(t)

Genesis

%Ev ¼ (2.12 þ .045T)ln(t)

Green Canyon Block 109

%Ev ¼ (1.58 þ .045T)ln(t)

Green Canyon Block 184

%Ev ¼ (3.55 þ .045T)ln(t)

Green Canyon Block 200

%Ev ¼ (3.11 þ .045T)ln(t)

Green Canyon Block 65

%Ev ¼ (1.56þ .045T)ln(t)

Greenplus Hydraulic Oil

%Ev ¼ (0.68 þ .045T)ln(t)

Greenplus Hydraulic Oil

%Ev ¼ (0.68 þ .045T)ln(t)

Gulfaks

%Ev ¼ (2.29 þ .034T)ln(t)

Heavy Reformate

%Ev ¼ (0.17 þ .013T)/t

Hebron MD-4

%Ev ¼ (1.01 þ .045T)ln(t)

Heidrun

%Ev ¼ (1.95 þ .045T)ln(t)

Hibernia

%Ev ¼ (2.18 þ .045T)ln(t)

High Viscosity Fuel Oil

%Ev ¼ (0.12 þ .013T)/t

Hondo

%Ev ¼ (1.49 þ .045T)ln(t)

Hout

%Ev ¼ (2.29 þ .045T)ln(t)

IFO-180

%Ev ¼ (0.12 þ .013T)/t

Chapter | 9

223

Evaporation Modeling

TABLE 9.2 Equations for Predicting Evaporationdcont’d Oil Type

Equation

IFO-30 (Svalbard)

%Ev ¼ (0.04 þ .045T)ln(t)

IFO-300 (old Bunker C)

%Ev ¼ (0.15 þ .013T)/t

Iranian Heavy

%Ev ¼ (2.27 þ .045T)ln(t)

Issungnak

%Ev ¼ (1.56 þ .045T)ln(t)

Isthmus

%Ev ¼ (2.48 þ .045T)ln(t)

Jet 40 Fuel

%Ev ¼ (8.96 þ .045T)ln(t)

Jet A1

%Ev ¼ (.59 þ .013T)/t

Jet Fuel (Anch)

%Ev ¼ (7.19 þ .045T)ln(t)

Jet Fuel (Anch) short term

%Ev ¼ (1.06 þ .013T)/t

Komineft

%Ev ¼ (2.73 þ .045T)ln(t)

Lago

%Ev ¼ (1.13 þ .045T)ln(t)

Lago Treco

%Ev ¼ (1.12 þ .045T)ln(t)

Lucula

%Ev ¼ (2.17 þ .045T)ln(t)

Main Pass Block 306

%Ev ¼ (2.86 þ .045T)ln(t)

Main Pass Block 37

%Ev ¼ (3.04 þ .045T)ln(t)

Malongo

%Ev ¼ (1.67 þ .045T)ln(t)

Marinus Turbine Oil

%Ev ¼ (0.68 þ .045T)ln(t)

Marinus Valve Oil

%Ev ¼ (0.68 þ .045T)ln(t)

Mars TLP

%Ev ¼ (2.18 þ .045T)ln(t)

Maui

%Ev ¼ (0.14 þ .013T)/t

Maya

%Ev ¼ (1.38 þ .045T)ln(t)

Mayan crude

%Ev ¼ (1.45 þ .045T)ln(t)

Mississipi Canyon Block 807

%Ev ¼ (2.28 þ .045T)ln(t)

Mississippi Canyon Bk. 72

%Ev ¼ (2.15 þ .045T)ln(t)

Mississippi Canyon Block 194

%Ev ¼ (2.62 þ .045T)ln(t)

Mississippi Canyon Block 807

%Ev ¼ (2.05 þ .045T)ln(t)

Morpeth

%Ev ¼ (1.58 þ .013T)/t

(Continued )

224

PART | IV

Behaviour of Oil in the Environment and Spill Modeling

TABLE 9.2 Equations for Predicting Evaporationdcont’d Oil Type

Equation

Nektoralik

%Ev ¼ (0.62 þ .045T)ln(t)

Neptune Spar (Viosca Knoll 826)

%Ev ¼ (3.75 þ .045T)ln(t)

Nerlerk

%Ev ¼ (2.01 þ .045T)ln(t)

Ninian

%Ev ¼ (2.65 þ .045T)ln(t)

Norman Wells

%Ev ¼ (3.11 þ .045T)ln(t)

North Slope - Middle Pipeline

%Ev ¼ (2.64 þ .045T)ln(t)

North Slope - Northern Pipeline

%Ev ¼ (2.64 þ .045T)ln(t)

North Slope - Southern Pipeline

%Ev ¼ (2.47 þ .045T)ln(t)

Nugini

%Ev ¼ (1.64 þ .045T)ln(t)

Odoptu

%Ev ¼ (4.27 þ .045T)ln(t)

Olive Oil

Litte

Oriente

%Ev ¼ (1.32 þ .045T)ln(t)

Oriente

%Ev ¼ (1.57 þ .045T)ln(t)

Orimulsion 400 e dewatered

%Ev ¼ (3.6)ln(t) (at 15oC)

Orimulsion plus water

%Ev ¼ (3 þ .045T)ln(t)

Oseberg

%Ev ¼ (2.68 þ .045T)ln(t)

Panuke

%Ev ¼ (7.12 þ .045T)ln(t)

Petronius VK981A

%Ev ¼ (2.27 þ .013T)/t

Pitas Point

%Ev ¼ (7.04 þ .045T)ln(t)

Platform Gail (Sockeye)

%Ev ¼ (1.68 þ .045T)ln(t)

Platform Holly

%Ev ¼ (1.09 þ .045T)ln(t)

Platform Irene e long term

%Ev ¼ (0.74 þ .045T)ln(t)

Platform Irene-short term

%Ev ¼ (0.05 þ .013T)/t

Point Arguello-comingled

%Ev ¼ (1.43 þ .045T)ln(t)

Point Arguello Heavy

%Ev ¼ (0.94 þ .045T)ln(t)

Point Arguello Light

%Ev ¼ (2.44 þ .045T)ln(t)

Point Arguello Light e b

%Ev ¼ (2.3 þ .045T)ln(t)

Chapter | 9

225

Evaporation Modeling

TABLE 9.2 Equations for Predicting Evaporationdcont’d Oil Type

Equation

Polypropylene Tetramer

%Ev ¼ (0.25)(t) (at 15oC)

Port Hueneme

%Ev ¼ (0.3 þ .045T)ln(t)

Prudhoe Bay e old stock

%Ev ¼ (1.69 þ .045T)ln(t)

Prudhoe Bay (new stock)

%Ev ¼ (2.37 þ .045T)ln(t)

Prudhoe stock b

%Ev ¼ (1.4 þ .045T)ln(t)

Rangely

%Ev ¼ (1.89 þ .045T)ln(t)

Sahara Blend

%Ev ¼ (0.001 þ .013T)/t

Sahara Blend (long term)

%Ev ¼ (1.09 þ .045T)ln(t)

Sakalin

%Ev ¼ (4.16 þ .045T)ln(t)

Santa Clara

%Ev ¼ (1.63 þ .045T)ln(t)

Scotia Light

%Ev ¼ (6.87 þ .045T)ln(t)

Scotia Light

%Ev ¼ (6.92 þ .045T)ln(t)

Ship Shoal Block 239

%Ev ¼ (2.71 þ .045T)ln(t)

Ship Shoal Block 269

%Ev ¼ (3.37 þ .045T)ln(t)

Sockeye

%Ev ¼ (2.14 þ .045T)ln(t)

Sockeye (2001)

%Ev ¼ (1.52 þ .045T)ln(t)

Sockeye Comingled

%Ev ¼ (1.38 þ .045T)ln(t)

Sockeye Sour

%Ev ¼ (1.32 þ .045T)ln(t)

Sockeye Sweet

%Ev ¼ (2.39 þ .045T)ln(t)

South Louisiana

%Ev ¼ (2.39 þ .045T)ln(t)

South Louisiana (2001)

%Ev ¼ (2.74 þ .045T)ln(t)

South Pass Block 60

%Ev ¼ (2.91 þ .045T)ln(t)

South Pass Block 67

%Ev ¼ (2.17 þ .045T)ln(t)

South Pass Block 93

%Ev ¼ (1.5 þ .045T)ln(t)

South Timbalier Block 130

%Ev ¼ (2.77 þ .045T)ln(t)

Soybeam oil

Litte

Statfjord

%Ev ¼ (2.67 þ .06T)ln(t)

(Continued )

226

PART | IV

Behaviour of Oil in the Environment and Spill Modeling

TABLE 9.2 Equations for Predicting Evaporationdcont’d Oil Type

Equation

Sumatran Heavy

%Ev ¼ (0.11 þ .013T)/t

Sumatran Light

%Ev ¼ (0.96 þ .045T)ln(t)

Taching

%Ev ¼ (0.11 þ .013T)/t

Takula

%Ev ¼ (1.95 þ .045T)ln(t)

Tapis

%Ev ¼ (3.04 þ .045T)ln(t)

Tchatamba Crude

%Ev ¼ (3.8 þ .045T)ln(t)

Terra Nova

%Ev ¼ (1.36 þ .045T)ln(t)

Terresso 150

%Ev ¼ (0.68 þ .045T)ln(t)

Terresso 220

%Ev ¼ (0.66 þ .045T)ln(t)

Terresso 46 Industrial oil

%Ev ¼ (0.67 þ .045T)ln(t)

Thevenard Island

%Ev ¼ (5.74 þ .045T)ln(t)

Troll

%Ev ¼ (2.26 þ .045T)ln(t)

Turbine Oil STO 90

%Ev ¼ (0.68 þ .045T)ln(t)

Turbine Oil STO 120

%Ev ¼ (0.68 þ .045T)ln(t)

Udang

%Ev ¼ (0.14 þ .013T)/t

Udang (long term)

%Ev ¼ (0.06 þ .045T)ln(t)

Vasconia

%Ev ¼ (0.84 þ .045T)ln(t)

Viosca Knoll Block 826

%Ev ¼ (2.04 þ .045T)ln(t)

Viosca Knoll Block 990

%Ev ¼ (3.16 þ .045T)ln(t)

Voltesso 35

%Ev ¼ (0.18 þ .013T)/t

Waxy Light and Heavy

%Ev ¼ (1.52 þ .045T)ln(t)

West Delta Block 143

%Ev ¼ (2.18 þ .045T)ln(t)

West Delta Block 30 w/water

%Ev ¼ (0.04 þ .013T)/t

West Texas Intermediate

%Ev ¼ (2.77 þ .045T)ln(t)

West Texas Intermediate

%Ev ¼ (3.08 þ .045T)ln(t)

West Texas Sour

%Ev ¼ (2.57 þ .045T)ln(t)

White Rose

%Ev ¼ (1.44 þ .045T)ln(t)

Zaire

%Ev ¼ (1.36 þ .045T)ln(t)

Chapter | 9

227

Evaporation Modeling

70

Percent Evaporated

60

Diesel at 20 degrees

50

Diesel at 5 degrees

40

North Slope at 20 degrees

30 20

North Slope at 5 degrees

10 0

0

20

40

60

80

100

120

Time in Hours FIGURE 9.9 Comparison of evaporation curves for diesel and Alaska North Slope oils at two different temperatures.

Since the equations described above require only time and temperature (or at the very worst, the percentage of oil distilled at 180 C), it is relatively simple to apply these forms of equations. They can also be applied in models as increments where t, the time, becomes the total time and the previous evaporation is subtracted. For example, if one was modeling the evaporation of ASMB oil in the time step from 12 to 15 hours. The equation is (from Table 9.2): Percentage evaporation ¼ ð3:24 þ :054TÞ InðtÞ

(38)

Substituting for the temperature of 15 C and with a time of 12 hours or 720 minutes, we get a percentage of 26.65. With 18 hours, we get a percentage of 27.72 with a difference of 1.07%, the amount evaporated in the interval between 15 and 18 hours. The variation of evaporation is illustrated in Figure 9.9, which shows the evaporation of two oils, diesel fuel and North Slope Crude, at two temperatures.

9.3.7. A Simplified Means of Estimation This section will present another simple means to calculate the evaporation rate or parameter B in Equation (33).24 This method is not as accurate as the empirical equations such as are presented in Table 9.2. However, the exact evaporation data may not be available. The evaporation parameters (before temperature correction) are the simplest way to proceed. From the work described above, these parameters are given as parameter B above and e0.675 for oils that follow a logarithmic curve and e0.195 for oils that follow a square

228

PART | IV

Behaviour of Oil in the Environment and Spill Modeling

root curve.1 Data on a number of oil evaporation rates, gathered experimentally and basic properties of oil were collected, primarily from a previous paper, and also from literature sources.24-26 While it is known that density and viscosity are not necessarily good indicators of other oil properties, these may be the only data available at the site of a spill, at least until some time passes.21,26 The data show that the general trends of correlation of evaporation parameters with density and viscosity are shown, with significant variance that is only captured by specific oil experiments. The evaporation equation parameters were measured in specific experiments and often are the result of several repeat experiments. The data were correlated with the evaporation parameter in order to derive a simplified model using oil density and viscosity or Saturates, Aromatics, Resins and Asphaltenes (SARA) data.24 The curve-fitting exercise with the logarithmic evaporation data and density and viscosity data resulted in a best-fit simplest equation: Evap ¼ 15:4 14:5 density þ 2:58=viscosity

(39)

where Evap is the evaporation equation parameter and as in Equation (33) is Be0.675 to compensate for the temperature parameter as explained above. Similarly, the data for those oils that evaporate as a square root with time were correlated with density and viscosity. The equation for predicting those oils that evaporate as a square root of time is: Evap ¼ 2:3 1:47 density 0:073 InðviscosityÞ

(40)

where Evap is the evaporation equation parameter or B in Equation (33), but for the square root equivalent. Other data that may be available are SARA data. Statistical analysis shows that only the saturate content correlates, and this does not so well (r2 < 0.6). The addition of the other SARA data only marginally assists in the correlation. However, an equation for the prediction of the evaporation parameter using SARA data is: Evap ¼ 0:048 S þ 0:006 A 0:025 R 0:0003As þ 0:27

(41)

where Evap is the evaporation equation parameter or Be0.675 as in (33) above: S is the saturate content in percent, A is the aromatic content in percent, R is the resin content in percent, and As is the asphaltene content in percent. It is important to understand that such simplified predictions are much less accurate than empirical data such as those shown in Table 9.2.

Chapter | 9

229

Evaporation Modeling

9.4. COMPLEXITIES TO THE DIFFUSION-REGULATED MODEL 9.4.1. Thickness of the Oil Studies show that under diffusion regulation very thick slicks (much more than 5 mm) evaporate slower than other slicks due to the increased path length that volatile components must diffuse in a thicker slick. This can certainly be confused with air-boundary-layer regulation. Figure 9.10 shows the evaporation rate of various thicknesses of oil by the volume to thickness ratio. As can be seen, there is very little difference in this standard presentation. However, one can exaggerate the thickness by a volume factor and this is presented in Figure 9.11. This figure shows that there is a small difference beginning at about 6 mm to about 10 mm. The difference amounts to about 10% slower at 10 mm compared to the rate at about 2 mm. There are few data at very great thicknesses, so this phenomenon requires further investigation. In any case, actual slicks at sea would never reach this thickness. Figure 9.12 shows the concept of slower evaporation with increased path length, that is, increased oil thickness. As noted, there are insufficient data to fully evaluate this at this time, but there is not much motivation as slicks at sea do not reach this thickness.

9.4.2. The Bottle Effect Another confusing phenomenon encountered in trying to understand evaporation is the bottle effect. This effect is illustrated in Figure 9.13. If all the 6.0

Evaporation Rate (%)

5.5 5.0 4.5 4.0 3.5 3.0 2.5

5

10

15

20

Volume to Thickness Ratio FIGURE 9.10 The relationship of volume over thickness (area) to evaporation rate (given as the equation parameter) for one light crude oil. This shows that there is little relationship. Volume largely dictates the evaporation rate; however, for very thick slicks of thickness more than about 10 mm, the evaporation rate slows due to the increased diffusion distance through the liquid.

230 (Volume/Thickness)/Evaporation Rate

PART | IV

Behaviour of Oil in the Environment and Spill Modeling

4.5 4.0 3.5 3.0 2.5 2.0 0

2

4

6

8

10

Thickness mm FIGURE 9.11 A plot of the exaggerated evaporation rate (equation factor, raised by the volume factor) versus oil thickness for one light crude oil. The exaggeration is about an order of magnitude. This shows that evaporation slows somewhat after 6 mm and is slowed more at 10 mm. The effect is only about 10% at 10 mm. This is due to the increased diffusion length through the slick. Typical oil spills are much thinner than about 2 mm, and thus this effect would not be important.

evaporating oil mass is not exposed, such as in a bottle, more oil vapors than can readily diffuse through the air layer at the bottle mouth may yield a partial air-boundary-layer regulation effect. This air-boundary-layer regulatory effect may end when the evaporation of the oil mass lowers past the rate at which the vapors can readily diffuse through the opening. Such effects could occur in reality in situations such as oil under ice, partially exposed to air or when a thick skin forms over parts of the oil, blocking evaporation. During a recent experiment in the Arctic, it was noted that the evaporation rate varied with the amount of exposure to the air.27 This phenomenon was probably caused by a combination of the bottle effect and partially as a result of the increased thickness in the more confined ice situations.

9.4.3. Skinning Several workers have noted that some crude oil and petroleum products form “skins” on their surfaces.28,29 These are largely due to the accumulation of compounds such as resins on the surface, some possibly created by photo oxidation. These can retard the evaporation of the compounds to a great extent. Figure 9.14 shows the results of some evaporation experiments carried out on two oils, Terra Nova crude and Statfjord crude. Simultaneous experiments were carried out on the oils, one of which was stirred, the other not.1 As can be seen in Figure 9.14, the stirred oils evaporated to a greater extent than the unstirred oils. The relevance of this effect at sea may not be as great as wind and waves

Chapter | 9

231

Evaporation Modeling Evaporation limited by diffusion rate through liquid and through surface layer - therefore diffusion regulated Air

Liquid surface

Liquid

Air Liquid surface

In very thick layers, evaporation limited by diffusion rate through liquid but after about 20 to 40 mm, diffusion slows significantly

Liquid

FIGURE 9.12 An illustration of the effect of very great thicknesses of oil. The evaporation rate is slower because of the longer diffusion difference. The difference becomes measurable after about 6 to 10 mm of oil thickness. This is much greater than typical slicks at sea.

may accomplish; the stirring and skin formation may thus be prevented or retarded. It should be noted that during these experiments, one could see the skin formation on the unstirred oil, and this skin developed more toward the end of the 200-hour experiments. Grose used the Mackay and Matsugu equations with some modification and also to account for the skinning factor:30 =ðRKÞ Pi Sk Mi L ¼ C U 0:78 D0:11 (42) o

232

PART | IV

Behaviour of Oil in the Environment and Spill Modeling

More vapor than can easily diffuse through opening - therefore partially air-boundary layer regulated Opening

Air Air

Liquid surface Evaporation limited by diffusion rate through liquid and through surface layer Liquid

FIGURE 9.13 An illustration of the bottle effect. If all the evaporating oil mass is not exposed, more oil vapors than can readily diffuse through the air layer at the bottle mouth may yield a partial air-boundary-layer regulation effect. This regulatory effect may end when the evaporation of the oil mass lowers past the rate at which the vapors can readily diffuse through the opening.

stirred

% Evaporated

40

Statfjord crude

not stirred

stirred

30 not stirred Terra Nova crude

20 Terra Nova Terra Nova - stirred Statfjord Statfjord - stirred

10

0 0

50

100

150

200

Time (Hours) FIGURE 9.14 Results of an experiment to show the effect of “skinning” on oil evaporation. The upper curve in each case is the evaporation of the oil shown with stirring, thus preventing or retarding skin formation. The lower curve is the evaporation without stirring. The effect of skinning for these two oils amounts to several percent differential in evaporation over 200 hours. At sea, wind and waves may mix the oil sufficiently to minimize the skinning effect.

Chapter | 9

Evaporation Modeling

233

where L is the mass of oil evaporated with time (kg/s), C is the environmental transfer constant, U is the wind speed at the surface (m/hr), Do is the diameter of the oiled area (m), K is the oil temperature in Kelvin, Pi is the vapor pressure of the particular component, Sk is the skin factor, and Mi is the molecular-weight equivalent of the particular oil fraction. The skin factor, Sk, ranges from 0.1 to 8 and accounts for the effect of skinning (the formation of a semipermeable surface layer). Yang and Wang suggested a value of Sk ¼ 0.2 after the density of their test oils had increased by 0.78%.13 A value of 1.0 was used in testing the model. In addition, the massloss rate depends on the vapor pressure, Pi, and the molecular weight, MWi, of each fraction. C is a dimensionless environmental transfer constant whose magnitude depends on the units used. The value used for C (0.00024) includes the constant 0.015 after Mackay and Matsugu.8

9.4.4. Rises from the 0-Wind Values Experimentation shows that studies of oil evaporation at absolutely no turbulence or air flow show a slight decrease in evaporation rate from those experiments carried out with slight air movement such as are found in an ordinary room.19 This is due to the slight stirring in the oil mass which increases the diffusion rate somewhat. Tests of this phenomena show that further increases in evaporation rate do not occur with increased air movement or turbulence, thus confirming that this is a phenomenon only at 0-wind or turbulence conditions. These are seen only during capped vessel experiments, and the “jump” in the evaporation rate is seen when the restriction is removed.

9.5. USE OF EVAPORATION EQUATIONS IN SPILL MODELS Evaporation equations are the prime physical change equations used in spill models. This is because evaporation is usually the most significant change that occurs in an oil’s composition. Many models after 1984 have used the Stiver and Mackay approach.9 The equations developed by Mackay and co workers can be implemented in a variety of ways. Often the difference in models is the manner in which the models are applied. Mackay and co workers developed an extensive oil spill model incorporating a number of process equations including evaporation.31 The earlier work of Leinonen and Mackay was used with the modification proposed by Yang and Wang.13,32 The process includes dividing the oil into a number of different fractions and analyzing each fraction for evaporation loss. The mass-transfer function used is the familiar one proposed by Mackay and Matsugu.8 These equations can be solved to obtain V and ci as functions of time. Solutions were developed by assuming a five-component crude oil that spreads on the water surface according to the correlations for the area.

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Payne and co workers developed an oil spill model using the pseudocomponent approach.33-35 Given the boiling point (1 atm) and API gravity of each cut (or pseudocomponent), the vapor pressure of the cut as a function of temperature was calculated. First, the molecular weight and critical temperature of the cut were calculated according to the following correlation: y ¼ C1 þ C2 X1 þ C3 X2 þ C4 X1 X2 þ C5 X12 þ C6 X22

(43)

where y is the vapor pressure of the cut, X 1 is the boiling point (oF) at one atmosphere, X2 is the API gravity, and C16 are constants empirically determined. Similarly, the critical temperature was calculated from the same equation form using the calculated and empirical constant values. Next, the equivalent paraffin carbon number, Nc, was calculated according to: Nc ¼ ðM 2Þ=14

(44)

where M is the molecular weight assigned to the particular cut. The critical volume, Vc, was then calculated according to: Vc ¼ ð1:88 þ 2:44Nc Þ=0:044

(45)

and the critical pressure, Pc, was calculated from: Pc ¼

20:8 Tc þ P0c ðVc 8Þ

(46)

where Tc is the critical temperature and Pc0 correction factor for critical pressure. The factor Pc0 was set to 10 to correct the critical pressure correlation from a strictly paraffinic mixture to a naphtha-aromatic-paraffin mixture. Next the parameter, b, was calculated according to:

where:

b ¼ b0 0:02

(47)

b0 ¼ C1 þ C2 Nc þ C3 Nc2 þ C4 Nc3

(48)

and the values of the constants C 1 to C 4 were calculated and tables of the values are available.19 A final parameter designated as A is then calculated according to: A ¼

Tr b ½log10 ðPrb Þ þ expð20ðTrb bÞ2 Þ Tr b 1

(49)

where A is an intermediary parameter, Trb is the reduced temperature at the normal boiling point, Prb is the reduced pressure at the normal boiling point, and b is an intermediary parameter determined in (48) above.

Chapter | 9

Evaporation Modeling

235

The vapor pressure equation that can be used down to 10 mm Hg can be expressed in terms of A and b as: log10 Pr ¼

Að1 Tr Þ exp½20ðTr bÞ2 Tr

(50)

where Pr is the reduced pressure and Tr is the reduced temperature. A, b, Tc and Pc were determined from the normal boiling point and API gravity of the cut. The temperature at which the vapor pressure is 10 mm Hg was obtained by the root-finding algorithm of Newton-Raphson.34 Below 10 mm Hg, the vapor pressure between two temperatures, Tr1 and Tr2, was calculated according to the Clausius-Clapeyron equation as follows: Z Tr 0:38 2 ð1 T Þ P2 lo r In ¼ dTr (51) P1 RTc Tr1 Tr2 where P1 is the vapor pressure at temperature 1, P2 is the vapor pressure at temperature 2, l0 is the heat of vaporization at 0 K, and Tc is the critical temperature. This was based on the fact that the ratio of the heat of vaporization, l, to (1 e T )0.38 is a constant at any temperature. The latent heat of vaporization was calculated from the slope of the natural log of the vapor pressure equation with respect to the temperature where the vapor pressure is 10 mm Hg. Thus, in the above equation, P2 is the 10 mm Hg vapor pressure at the temperature, Tr, previously determined. Variations of the Payne model were used in older oil spill models. Several models had used the pseudocomponent approach but with the Mackay evaporation method.36 Currently, there are a number of oil spill models using the empirical equations of Fingas.25

9.6. COMPARISON OF MODEL APPROACHES The comparison of air-boundary-layer models with the empirical equations lead to some interesting conclusions on their applicability. Figure 9.15 shows a comparison of the prediction of evaporation of diesel fuel using an air-layerboundary model and an empirical curve. The 0-wind diesel evaporation calculated using an air-layer-boundary model comes closest to the empirical curve. However, prediction is of the wrong curvature. The prediction of diesel evaporation using the wind levels shown results in prediction errors as great as 100% over about 200 hours. Figure 9.16 shows a comparison of the evaporation of Bunker C using two air-layer-boundary models and an empirical curve. The 0-wind evaporation air-boundary-layer prediction comes closest to the empirical curve. As most comparisons show, the evaporation rate up to about 10 hours is similar to the empirical curve. The prediction of Bunker C evaporation

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Percent Evaporated

80

Behaviour of Oil in the Environment and Spill Modeling

Traditional with varying winds

60 Traditional no wind

40 Trad. no wind Trad. 10 m/s Trad. 20 m/s Empirical curve Trad. B. no wind Trad B. 10 m/s Trad. B. 20 m/s

Empirical curve

20

0 0

20

40

60

80

100

120

140

160

Time in Days FIGURE 9.15 A comparison of the evaporation of diesel fuel using an air-layer-boundary model and an empirical curve. The 0-wind diesel evaporation calculated using an air-layer-boundary model comes closest to the empirical curve, but it is of the wrong curvature. The prediction of diesel evaporation using the wind levels shows errors as great as 100% over about 200 hours.

using the wind levels shown results in prediction errors as great as 400% over about 200 hours. These high values of Bunker C evaporation as predicted by air-boundary-layer models with wind conditions are completely impossible, as shown by extensive experimentation and field measurements.19 Figure 9.17 shows a comparison of the evaporation of Prudhoe Bay crude using two airlayer-boundary models with an empirical curve. The 0-wind evaporation prediction using air-boundary-layer methods comes closest to the empirical curve. The evaporation rate calculated by most means up to about 10 hours is similar to the empirical curve. The prediction of Prudhoe Bay evaporation using the wind levels shown results in prediction errors as great as 100% over about 200 hours. These high values of Prudhoe Bay evaporation as predicted by air-boundary-layer models with wind conditions are not realistic. The importance of evaporation modeling can be shown in Figures 9.18 and 9.19. The fate of oil spills is often dictated by evaporation. Accurate modeling of evaporation then becomes of key importance to the useful prediction of oil fate. Thus there are three major errors resulting from the use of air-boundarylayer models. First and most important is that they cannot accurately deal with long-term evaporation; second, the wind factor results in unrealistic values; and finally, they have not been adjusted for the different curvature for diesel-like evaporation. Some modelers have adjusted their models using air-boundary-layer models to avoid very high values at long evaporation times

Chapter | 9

Trad. 0 m/s Trad. 10 m/s Trad. 20 m/s Trad. 40 m/s Trad. 80 m/s Empirical Trad. B 0 m/s Trad. B 10 m/s Trad. B 20 m/s Trad. B 35 m/s

20

Percent Evaporated

237

Evaporation Modeling

15

10 Empirical curve

5

Empirical curve

0 0

20

40

60 80 Time (Hours)

100

120

140

FIGURE 9.16 A comparison of the evaporation of Bunker C using two air-layer-boundary models and an empirical curve. The 0-wind evaporation prediction comes closest to the empirical curve. The prediction of Bunker C evaporation using the wind levels shown results in prediction errors as great as 400% over about 200 hours. These high values of Bunker C evaporation as predicted by air-boundary-layer models with wind conditions are completely impossible. As most comparisons show, the evaporation rate calculated by most means up to about 10 hours is similar to the empirical curve.

by setting a maximum evaporation value. This does avoid very unrealistic high values after a point in time, but does so artificially. Most models of any type will require that one sets a maximum rate to avoid overprediction or values over 100%, for example. This can be best illustrated using a long-term example. A spill in northern Alberta of Pembina oil was sampled 30 years after its spill. Analysis shows that this was weathered to the extent of 58%.37,38 Figure 9.20 shows the comparison of the actual value, the empirical projection, and the air-boundary-layer predicted value. This shows that the air-boundary-predicted value overshoots the estimate by over 60%, despite using only two low wind values of 2 and 7 m/s. Use of higher wind values increases the evaporation to well over 100%.

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Percent Evaporated

40

30

Empirical curve

20

Trad. 0 m/s Trad. 10 m/s Trad. 20 m/s Empirical Curve Trad. B. 0 m/s Trad. B. 10 m/s Trad. B. 20 m/s

Empirical curve

10

0 0

50

100

150

200

250

300

Time (Hours) FIGURE 9.17 A comparison of the evaporation of Prudhoe Bay crude using two air-layerboundary models and an empirical curve. The 0-wind evaporation prediction using air-boundarylayer methods comes closest to the empirical curve. The evaporation rate up to about 10 hours is similar to the empirical curve. The prediction of Prudhoe Bay evaporation using the wind levels shown results in prediction errors as great as 100% over about 200 hours. These high values of Prudhoe Bay evaporation as predicted by air-boundary-layer models with wind conditions are not realistic.

FIGURE 9.18 Highly-evaporated oils can form tar balls that typically strand on beaches. This shows a typical-size tar ball stranded along with other debris.

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Evaporation Modeling

FIGURE 9.19 This shows highly evaporated Bunker C oil, which has just arrived on a beach. In this case, evaporation is a very important factor dictating how an oil spill can be cleaned up.

100 Air-boundary-layer model 7 m/s wind

Percent Evaporated

80

Air-boundary-layer model 2 m/s wind

60 Empirical curve

Analysis value at 30 years

40

Empircal curve Actual analytical Air-Bound., 2 m.s wind Air-Bound. 7 m.s wind

20

0

1 year

0.0

5.0e+4

6 years

1.0e+5

15 years

1.5e+5

2.0e+5

30 years

2.5e+5

Time - Hours FIGURE 9.20 A comparison of the evaporation of Pembina crude using an air-layer-boundary model, an actual analysis after 30 years, and an empirical curve. The evaporation rate up to about 100 hours is similar to the empirical curve. The prediction of long-term evaporation using even small wind levels shown results in prediction errors as great as 60% over about 10 years. These high values of evaporation as predicted by air-boundary-layer models with wind conditions are not realistic.

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9.7. SUMMARY A review of the physics of oil evaporation shows that oil evaporation is not strictly air-boundary-layer regulated. The results of the following experimental series have shown the lack of boundary-layer regulation. 1. A study of the evaporation rate of several oils with increasing wind speed shows that the evaporation rate does not change past the 0-level wind. Water, known to be boundary-layer regulated, does show the predicted increase with wind speed, U (Ux, where x varies from 0.5 to 0.78, depending on the turbulence level). 2. Increasing area does not change the oil evaporation rate. This is directly contrary to the prediction resulting from boundary-layer regulation. 3. The volume or mass of oil evaporating correlates with the evaporation rate. This is a strong indicator of the lack of boundary-layer regulation because with water, volume (rather than area) and rate do not correlate. 4. Evaporation of pure hydrocarbons with and without wind (turbulence) shows that compounds larger than nonane and decane are not boundarylayer-regulated. Most oil and hydrocarbon products consist of compounds larger than these two and thus would not be expected to be boundarylayer-regulated. The fact that oil evaporation is not strictly boundary-layer-regulated implies that a simplistic evaporation equation will suffice to describe the process. The following factors do not require consideration: wind velocity, turbulence level, area, thickness, and scale size. The factors important to evaporation include time and temperature. A comparison of the various models used for oil spill evaporation shows that air-boundary-layer models result in erroneous predictions. There are three issues: air-boundary-layer models cannot accurately deal with long-term evaporation; second, the wind factor results in unrealistic values; and finally, they have not been adjusted for the different curvature for diesel-like evaporation. Modelers have made some effort to adjust air-boundary-layer models to be more realistic for longer-term evaporation, but these may be artificial and result in other errors such as underestimation for long-term prediction. A diffusion-regulated model has been presented along with many empirically developed equations for many oils. The equations are found to be of the form: Percentage evaporated ¼ ½B þ 0:045ðT 15Þ InðtÞ

(52)

where B is the equation parameter at 15 C, T is temperature in degrees Celsius, and t is the time in minutes. It is also noted that with diesel fuel and similar oils, the curve is different and follows a generic curve, such as: pﬃ Percentage evaporated ¼ ½B þ 0:01ðT 15Þ t (53)

Chapter | 9

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Evaporation Modeling

The most accurate predictions are carried out using the empirical equations as noted in Table 9.2. If these are not available, the parameters can be estimated using distillation data, such as: For oils that follow a logarithmic equation: Percentage evaporated ¼ ½:165ð%DÞ þ :045ðT 15ÞlnðtÞ

(54)

For oils that follow a square root equation:

pﬃ Percentage evaporated ¼ ½:0254ð%DÞ þ :01ðT 15Þ t

(55)

180 C,

where D is the percentage distilled at T is the temperature in Celcius, and t is the time in minutes. Equations are also given that allow estimation of evaporation from density, viscosity, or SARA data; however, these are much less accurate than the direct empirically-derived equations.

REFERENCES 1. Fingas MF. The Evaporation of Oil Spills: Development and Implementation of New Prediction Methodology. IOSC 1999;281. 2. Fingas MF. A Literature Review of the Physics and Predictive Modelling of Oil Spill Evaporation. J Haz Mat 1995;157. 3. Jones FE. Evaporation of Water. Chelsea, Michigan: Lewis Publishers; 1992. 4. Brutsaert W. Evaporation into the Atmosphere. Dordrecht, Holland: Reidel Publishing Company; 1982. 5. Fingas MF. Studies on the Evaporation of Crude Oil and Petroleum Products: I. The Relationship between Evaporation Rate and Time. J Haz Mat 1997;227. 6. Monteith JL, Unsworth MH. Principles of Environmental Physics. London: Hodder and Stoughton; 1990. 7. Sutton OG. Wind Structure and Evaporation in a Turbulent Atmosphere. P Royal Society of London 1934;701. 8. Mackay D, Matsugu RS. Evaporation Rates of Liquid Hydrocarbon Spills on Land and Water. Can J Chem Eng 1973;434. 9. Stiver W, Mackay D. Evaporation Rate of Spills of Hydrocarbons and Petroleum Mixtures. Env Sci Tech 1984;834. 10. Blokker PC. Spreading and Evaporation of Petroleum Products on Water. Proceedings of the Fourth International Harbour Conference, 1964;911. 11. Goodwin SR, Mackay D, Shiu WY. Characterization of the Evaporation Rates of Complex Hydrocarbon Mixtures under Environmental Conditions. Can J Chem Eng 1976;290. 12. Butler JN. Transfer of Petroleum Residues from Sea to Air: Evaporative Weathering. In: Windom HL, Duce RA, editors. Marine Pollutant Transfer, 201. Toronto: Lexington Books; 1976. 13. Yang WC, Wang H. Modelling of Oil Evaporation in Aqueous Environments. Water Res 1977;879. 14. Brighton PWM. Further Verification of a Theory for Mass and Heat Transfer from Evaporating Pools. J Haz Mat 1990;215. 15. Brighton PWM. Evaporation from a Plane Liquid Surface into a Turbulent Boundary Layer. J Fluid Mech 1995;323. 16. Stiver W. Weathering Properties of Crude Oils wWhen Spilled on Water, Master of Applied Science Thesis, Department of Chemical Engineering and Applied Chemistry. Toronto: University of Toronto; 1984:4,110,132.

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17. Brown HM, Nicholson P. The Physical-Chemical Properties of Bitumen. AMOP 1991;107. 18. Bobra M. A Study of the Evaporation of Petroleum Oils, Manuscript Report Number EE-135. Ottawa, ON: Environment Canada, 1992. 19. Fingas MF. Studies on the Evaporation of Crude Oil and Petroleum Products: II. Boundary Layer Regulation. J Haz Mat 1998;41. 20. Ullmann Encyclopedia. Hamburg: Ullmann Publishing; 1989-2005. 21. Jokuty PS, Whiticar S, Wang Z, Fingas MF, Fieldhouse B, et al. Properties of Crude Oils and Oil Products. Environment Canada Manuscript Report EE-165, Ottawa, ON 1999. 22. Fingas MF. The Evaporation of Oil Spills: Prediction of Equations Using Distillation Data. Spill Sci Tech Bull 1996;191. 23. Fingas MF. The Evaporation of Oil Spills: Prediction of Equations Using Distillation Data. AMOP 1997;1. 24. Fingas MF. Estimation of Oil Spill Behaviour Parameters from Readily-Available Oil Properties. AMOP 2007;1. 25. Fingas MF. Modeling Evaporation Using Models That Are Not Boundary-Layer Regulated. J Haz Mat 2004;27. 26. Oil Catalogue, http://www.etc-cte.ec.gc.ca/databases/spills/oil_prop_e.html, accesssed April, 15 2010. 27. Brandvik PJ, Faksness L-G. Weathering Processes in Arctic Oil Spills: Meso-Scale Experiments with Different Ice Conditions. Cold Reg Sci Technol 2009;160. 28. Bobra M, Tennyson EJ. Photooxidation of Petroleum. AMOP 1989;129. 29. Garrett RM, Pickering IJ, Haith CE, Prince RC. Photooxidation of Crude Oils. Environ Sci Technol 1998;3719. 30. Grose PL. A Preliminary Model to Predict the Thickness Distribution of Spilled Oil, Proceedings of a Workshop on The Physical Behaviour of Oil in The Marine Environment, Princeton University, 1979. 31. Mackay D, Buist I, Mascarenhas R, Paterson S. Oil Spill Processes and Models, EE-8. Ottawa, ON: Environment Canada, 1980. 32. Leinonen PJ, Mackay D. A Mathematical Model of Evaporation and Dissolution from Oil Spills on Ice, Land, Water, and Under Ice, Proceedings Tenth Canadian Symposium 1975: Water Pollution Research Canada, 1975;132. 33. Payne JR, McNabb Jr GD, Hachmeister LE, Kirstein BE, Clayton Jr JR, et al. Development of a Predictive Model for the Weathering of Oil in the Presence of Sea Ice, Outer Continental Shelf Environmental Assessment Program, vol. 59, NOAA, 1988. 34. Payne JR, Kirstein BE, McNabb Jr GD, Lambach JL, Redding R, et al. Multivariate Analysis of Petroleum Weathering in the Marine EnvironmentdSubarctic, U.S. Department of Commerce, NOAA, OCSEAP, vol. 21, 1984. 35. Payne JR, McNabb Jr GD. Weathering of Petroleum in the Marine Environment, Marine Technology Society Journal, Washington, DC, 1984;24:18. 36. Buist I, Belore R, Guarino A, Hackenberg D, Dickins D, Wang Z. Empirical Weathering Properties of Oil in Ice and Snow. AMOP 2009;56. 37. Wang Z, Fingas M, Yang C, Hollebone B, Peng X. Biomarker Fingerprinting: Applications and Limitations for Source Identification and Correlation of Oils and Petroleum Products. AMOP 2004;103. 38. McIntyre CP, Harvey PM, Ferguson S, Wressnig AM, Snape I, George SC. Determining the Extent of Weathering of Spilled Fuel in Contaminated Soil Using the Diastereomers of Pristane and Phytane. Org Geochem 2007;2131.

Chapter 10

Models for Water-in-Oil Emulsion Formation Merv Fingas

Chapter Outline 10.1. Introduction 10.2. Early Modeling of Emulsification 10.3. First Two Model Developments 10.4. New Model Development

243 249 251

10.5. Development of an Emulsion Kinetics Estimator 10.6. Discussion 10.7. Conclusions

260

260 269

253

10.1. INTRODUCTION Water-in-oil emulsions sometimes form after oil or petroleum products are spilled. These emulsions, often called chocolate mousse or mousse by oil spill workers, make the cleanup of oil spills very difficult.1 When water-in-oil emulsions form, the physical properties and characteristics of oil spills change dramatically. For example, stable emulsions contain from 60 to 90% water, thus expanding the spilled material from 2 to 5 times the original volume. Most significantly, the viscosity of the oil typically changes from a few hundred mPa.s to about 100,000 mPa.s, an increase of 500 or more. A liquid product is changed into a heavy, semisolid material. These emulsions are difficult to recover with conventional spill recovery equipment. Recently, Fingas and Fieldhouse published a paper on emulsion formation as it relates to spilled oil.2 They found that four clearly defined water-in-oil types are formed by oil and petroleum products when mixed with water. This was shown by water resolution over time, by a number of rheological measurements, and by the water-in-oil product’s visual appearance, both on the day of formation and one week later. Some emulsions were observed for over a year, with the same results. The types are named stable water-in-oil Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10010-3 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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emulsions, mesostable water-in-oil emulsions, entrained, and unstable waterin-oil emulsions. The differences among the four types are quite large and are based on at least two water-content measurements and five rheological measurements. More than 300 oils or petroleum products were studied. Fingas and Fieldhouse carried out tests of several indices of stability, a single value that could provide good discrimination between water-in-oil types even on day one.2 It was found that all of these indices could be used to some extent to differentiate the four water-in-oil types. One index of stability was the ratio of the complex modulus of the product on the first day divided by the starting oil viscosity. This index was named stability A. Stability B was the elastic modulus on the first day divided by the starting oil viscosity. Stability C was a combination of these two indices, the log of the cross product of stability A and B. Another index, the viscosity increase, the ratio of the oil viscosity after mixing divided by the starting oil viscosity, was also evaluated. Another test, first day water times stability A, was a simple composite of the first day water content times stability A. The last two parameters evaluated were the tan delta on the day of formation and the change in tan delta over one week. The index called stability C proved to be the index that best differentiated all four water-in-oil types. Scientists reported that asphaltenes were a major factor in water-in-oil emulsions more than 40 years ago.3 The specific roles of asphaltenes in emulsions have not been defined until recently. The basics of water-in-oil emulsification are now understood to a much better degree.2,4-6 The basic principle is that water-inoil emulsions are stabilized by the formation of high-strength viscoelastic asphaltene films around water droplets in oil. Resins also form emulsions, but they do not form stable emulsions, and they actually aid in asphaltene emulsion stability by acting as asphaltene solvents and by providing temporary stability during the time of the slow asphaltene migration. In all, a wide spectrum of researchers have found out that oil composition is a key factor to water-in-oil emulsion formation and that several key factors include the asphaltene, resin, and saturate contents as well as the density and viscosity of the starting oil. McLean and Kilpatrick studied asphaltene aggregation in model emulsions made from heptane and toluene.7 The asphaltenes were extracted using heptane and the resins using open-column silica columns. Although some emulsions could be generated using resins, they were much less stable than those generated by asphaltenes. It was also found that the concentration of asphaltenes and the availability of solvating resins were important. McLean and Kilpatrick put forward the thesis that asphaltenes were most effective in stabilizing emulsions when they are near the point of incipient precipitation.8 It was noted that there are specific resineasphaltene interactions because differing combinations yielded different results in the model emulsions. The most effective emulsion resin and asphaltene stabilizers were the most polar and the most condensed. McLean and Kilpatrick concluded that the most significant factor in emulsion formation is the solubility state of asphaltenes.

Chapter | 10 Models for Water-in-Oil Emulsion Formation

245

Subsequently, several workers reviewed emulsions and concluded that the asphaltene content is the single most important factor in the formation of emulsions.9-11 Even in the absence of any other possibly-synergistic compounds such as resins, asphaltenes were found to be capable of forming rigid, cross-linked, elastic films that are the primary agents in stabilizing waterin-crude oil emulsions. The exact conformations by which asphaltenes organize at oilewater interfaces and the corresponding intermolecular interactions have not been elucidated. McLean and colleagues suggest that the intermolecular interactions must be either p-bonds between fused aromatic sheets; H-bonds mediated by carboxyl, pyrrolic, and sulfoxide functional groups; or electron donoreacceptor interactions mediated by porphyrin rings, heavy metals, or heteroatomic functional groups.9 Workers studying only crude oil emulsions concluded that water-in-oil emulsions are exclusively stabilized by asphaltenes.12 Even though the emulsions contain inorganic solids, waxes, and other organic solids, the main stabilization comes from asphaltenes. Other workers have noted that solid particles, such as clays, when present, can stabilize or contribute to the stabilization of emulsions.13 This is true of emulsions formed by clay-containing bitumens. These clay-stabilized emulsions may have differences from the crude oil and petroleum product emulsions noted in this subchapter. Asphaltenes are defined by their precipitation from oil in pentane, hexane, or heptane. The specific structure of asphaltenes is unknown; however, the molecular weight averages about 750, and there is a planar aromatic structure surrounded by alkane groups, some with heteroatoms, S, N, and O.14 Studies of the time dependency of film strength by viscosity measurements showed that the complex modulus increased about twofold between 2 and 4 hours. This indicates an increased film strength, probably due to asphaltene aggregation and cross-linking. The mechanism by which emulsions form begins when asphaltenes migrate to the oilewater interface, a process that is regulated by the diffusion of the soluble asphaltenes. At the interface, the asphaltenes selfassemble to produce an elastic, rigid, stable film.5,15,16 The absorption of asphaltenes at the watereoil interface proceeds for a long time and may still proceed after a year.17 This implies that the absorption at the interface lowers the net energy of the system and thus is favored thermodynamically. The bulk concentration of asphaltenes is important and drives the amount that is absorbed at the interface. Asphaltenes have their greatest tendency to absorb and make the strongest interfacial film at their limit of solubility. Several workers noted that there were differences in the stability of emulsions, depending on the fractions of asphaltenes taken and also by the amount of asphaltene aggregation present.18,19 Asphaltene aggregation may be an important topic in emulsion stability. Asphaltenes may self-associate in a manner that is oligimerization rather than simple stacking. Several researchers studied the role of resins in water-in-oil formation.2,12 They noted that the main role appears to be solvation of the asphaltenes in the

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oil solution. They conducted experiments showing that the addition of resins at ratios of 2:1 (resins:asphaltenes) could increase the stability of the water-in-oil emulsions by as much as twice. Others have noted that resins and asphaltenes are somehow tied together in emulsion stability. Some researchers noted that with increasing asphaltene:resin ratio, the emulsions in wellheads were more stable.20 The interfacial properties of asphaltenes in several Norwegian offshore crude oils were studied.21 Asphaltenes were shown to be the agent responsible for stabilizing the crude oils tested; however, the resins were also noted as being important. Some effect from naphthenic acids was also observed.22 Sjo¨blom and coworkers noted that many of the stability differences in emulsions can be explained by the interactions between asphaltenes and resins.23 They stated that asphaltenes are believed to be suspended as colloids in the oil with stabilization by resins. Each particle is believed to consist of one or more sheets of asphaltene monomers and absorbed resins to stabilize the suspension. Under certain conditions, the resins can desorb from the asphaltenes, leading to increased asphaltene aggregation and precipitation of the larger asphaltene aggregates. Several workers then noted that there is significant interplay between asphaltenes and resins and that resins solvate the asphaltenes.24,25 The availability of methodologies to study emulsions is very important. In the past 15 years, dielectric methods and rheological methods and many other methods have been exploited to study formation mechanisms and stability of emulsions.5,15 Standard chemical techniques, including nuclear magnetic resonance (NMR), chemical analysis techniques, near-infrared spectroscopy (NIR), microscopy, interfacial pressure, and interfacial tension, are also being applied to emulsions. These techniques have largely confirmed findings noted in the dielectric and rheological mechanisms. The use of high-pressure NIR has been used by one group to study asphaltene aggregation of live crude oils.23,26,27 Further NIR information on the amount of asphaltenes and resins was tied to the emulsion stability.27 Many of the measurements can now be intercorrelated. Most researchers studied the stability of emulsions by measuring the amount of water resolved with time.10,12,28-32 This certainly is the absolute means. Some researchers also subjected the emulsions to centrifugation to assess stability. Dielectric spectroscopy has been used to study emulsions. The electrical permittivity of the emulsion can be used to characterize an emulsion and assign a stability.5,22,25,33,34 The Sjo¨blom group has measured the dielectric spectra using the time domain spectroscopy (TDS) technique. A sample is placed at the end of a coaxial line to measure total reflection. Reflected pulses are observed in time windows of 20 ns and Fourier transformed in the frequency range from 50 MHz to 2 GHz. Many studies on the rheology of emulsions have been performed.35-37 Emulsions stabilized by surfactant films (such as resins and asphaltenes)

Chapter | 10 Models for Water-in-Oil Emulsion Formation

247

behave like hard-sphere dispersions and display viscoelastic behavior. Relaxation time can be determined for the system, which increases with the volume fraction of the discontinuous phase. It has been noted that the emulsion stability is highly dependent on the rheological properties of the water/oil interface and that a high elasticity will increase the level of stability.6 Several workers in the field have used the interface forces on single droplets to study emulsions. One group used an oscillating pendant drop apparatus and correlated this to asphaltene solubility as measured by NIR.38 Yarranton et al. report on the use of interfacial rheology to study emulsion coalesence.39 Asphaltenes from Athabasca Bitumen were mixed with a solvent and injected into an optical cuvette and the droplet was monitored by camera. Interfacial tension was measured from static measurements on the droplet. Elasticity was measured by manipulating the droplet so that sinusoidal oscillations occurred and the elasticity was measured using Fourier analysis. The findings were that the interfacial modulus was a function of asphaltene content and reached a maximum at an asphaltene concentration of about 1 kg/m3. The modulus increased as the interface aged. The data were found to be consistent with the gradual formation of a cross-linked asphaltene network on the interface. Moran et al. studied emulsions using a micropipette technique in which individual emulsion drops are elongated into a cantilever for force measurements.40 The stress-strain measurements are converted to interfacial rheological behavior. Khristov et al. studied emulsions as a film with toluene dilution and the thin liquid film-pressure balance technique.41 Many researchers studied emulsification by using model oils or modified crude oils. Other researchers studied emulsions as thin layers or by droplets.8,42 Hemmingston et al. studied the water-in-oil emulsions formed from 27 crude oils of different origins.43 They found an increase in stability as viscosity increases. Viscosity also correlated with the SARA (Saturates, Aromatics Resins, and Asphaltenes) data taken on the crude oil. Sjo¨blom et al. studied 16 crudes from the North Sea and 5 from North Africa.34 Stability was measured using the results from an electric field cell. A voltage was applied to the cell until coalescence was observed using a microscope. The value of the voltage at the critical point was taken as a measure of stability. The findings of Fingas and Fieldhouse, studying over 400 crudes and petroleum products, point to four groups of emulsions formed by crude oils and petroleum products: stable, mesostable, entrained, and unstable.2 Stable emulsions are reddish-brown solid-like materials with an average water content of about 80% on the day of formation and about the same one week later. Stable emulsions remain stable for at least 4 weeks under laboratory conditions. All of the stable emulsions studied remained so for at least one year. The viscosity increase over the day of formation averages a multiple of 400 and one week later averages 850. The average properties of the starting oil required to form a stable emulsion are: density 0.9 g/mL; viscosity 300 mPa.s; resin content 9%; asphaltene content 5%; and asphaltene-to-resin ratio 0.6.

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Mesostable water-in-oil emulsions are reddish-brown viscous liquids with an average water content of 64% on the first day of formation and less than 30% one week later. Mesostable emulsions generally break down fairly completely within one week. The viscosity increase over the day of formation averages a factor of 7 and one week later averages 5. The average properties of the starting oil required to form a mesostable emulsion are: density 0.9 g/mL; viscosity 1300 mPa.s; resin content 16%; asphaltene content 8%; and asphaltene-to-resin ratio 0.5. The greatest difference between the starting oils for stable and mesostable emulsions are the ratio of viscosity increase (stable 400, first day and 850 in one week; mesostable 7, first day and 5 in one week) and resin content (stable e9%; mesostable e16%). Entrained water-in-oil types are black viscous liquids with an average water content of 45% on the first day of formation and less than 28% one week later.2 The viscosity increase over the day of formation averages a multiple of two and one week later still averages two. The average properties of the starting oil required to form entrained water are: density 0.97 g/mL; viscosity 60,000 mPa.s; resin content 18%; asphaltene content 12%; and asphaltene-to-resin ratio 0.75. The greatest differences between the starting oils for entrained water-in-oil compared to stable and mesostable emulsions are the viscosity of the starting oil (entrained starting oil averages 60,000 mPa.s compared to 200 mPa.s for stable emulsions and 1300 mPa.s for mesostable emulsions) and the ratio of viscosity increase (entrained ¼ 2, first day and 2 in one week; stable 400, first day and 850 in one week; mesostable 7, first day and 5 in one week). Entrained water-in-oil types appear to be applicable to viscous oils and petroleum products, but not extremely viscous products. Unstable water-in-oil emulsions are characterized by the fact that the oil does not hold significant amounts of water. There is a much broader range of properties of the starting oil than for the other three water-in-oil states. For example, viscosities are very low or very high. Included in this group are light fuels such as diesel fuel and very heavy, viscous oil products. The data suggest that the water-in-oil types are stabilized by both asphaltenes and resins, but that, for greater stability, resin content should exceed the asphaltene content slightly.2 Excess resin content (A/R > about 0.6) apparently destabilizes the emulsion. This does not consider the question of different types of asphaltenes or resins. A high asphaltene content (typically > 10%) increases the viscosity of the oil such that a stable emulsion will not form. Viscous oils will only uptake water as entrained water and will slowly lose much of this water over a period of about one week. Viscous oils (typically >1000 mPa.s) will not form stable or mesostable emulsions. Oils or low viscosity or without significant amounts of asphaltenes and resins will not form any water-in-oil type and will retain less than about 6% water. Oils of very high viscosity (typically > 10,000 mPa.s) will also not form any of these water-in-oil types and thus are classified as unstable. This is probably due to the inability of water droplets to penetrate the oil mass.

Chapter | 10 Models for Water-in-Oil Emulsion Formation

249

Several new models for the prediction of water-in-oil emulsions were recently developed.44-48 These models were the first available to calculate the formation of emulsions using a continuous function and employing the physical and chemical properties of oil. Since this initial model was developed, the emulsification properties of more oils were measured, and the properties of some of the oils in the existing set oils have been remeasured. Some of these data were found to be deficient and were eliminated. This enables the models to be recalculated with sound data on over 316 oils out of over 400 studied. The basis of these models is the result of the knowledge demonstrated abovednamely, that models are stabilized by asphaltenes, with the participation of resins. Other components of oil, especially aromatics, may actually interfere with this process. Findings of this group and other groups show that the entire SARA (Saturates, Aromatic, Resins, and Asphaltene) component affects the formation of emulsions as the prime stabilizers; asphaltenes, and secondarily resins, are available for emulsion formation only when the concentration of the saturates and aromatics are at a certain level and when the density and viscosity are correct.2 The very early emulsion formation modeling equations at that time did not use specific knowledge of emulsion formation processes.44 In the past, the rate of emulsion formation was assumed to be first-order with time. This was then approximated with a logarithmic (or exponential) curve. Although not consistent with the knowledge of how emulsions formed, this assumption has been used extensively in oil spill models. The processes outlined in the introduction above were not discovered until many years after the simple assumptions were proposed. Furthermore, the presence of different water-in-oil states dictates that one simple equation is not adequate to predict emulsion formation. The stability of an emulsion, as represented by stability C, was correlated with starting oil properties to start model development. The different waterin-oil types could be differentiated by correlating individually with starting oil viscosity, density, saturate content, asphaltene content, resin content, or asphaltene/resin ratio. Combinations of these oil properties yielded even greater differentiation between water-in-oil types. Examples of good separation of water-in-oil types were achieved by plotting asphaltene content times asphaltene/resin ratio, along with starting oil viscosity and stability. Other correlations with similar input also yielded differentiation between water-in-oil types.

10.2. EARLY MODELING OF EMULSIFICATION The emulsification processes described above were not apparent until about 15 years ago and have since been translated into modeling equations. Furthermore, the presence of different water-in-oil states dictates that one simple equation is not adequate to predict formation. Information on the kinetics of formation at sea and other modeling data was less abundant in the past. It is now known that emulsion formation is a result of surfactant-like behavior of the polar

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asphaltene and resin compounds. While these are similar compounds that both behave like surfactants when they are not in solution, asphaltenes form much more stable emulsions. Emulsions begin to form when the required chemical conditions are met and when there is sufficient sea energy. Furthermore, as pointed out above, three different water-in-oil types are producedddepending on the oil type and its state of weathering. In the past, the rate of emulsion formation was assumed to be first-order with time. This can be approximated with a logarithmic (or exponential) curve. The physical assumption is that all oils uptake water on a first-order basis. Although not consistent with the knowledge of how emulsions formed, this assumption has been used extensively in oil spill models. As will be shown later, this does not yield correct results. Most models that incorporate the phenomenon use the estimation technique of Mackay and co workers or a variation of this technique.49-51 Mackay suggested the following equation to model water uptake: DW ¼ Ka ðU þ 1Þ2 ð1 Kb WÞDt;

(1)

where DW is the water uptake rate, W is the fractional water content, Ka is an empirical constant, U is the wind speed, Kb is a constant with the value of approximately 1.33, and t is time. Because Equation (1) predicts that most oils will form emulsions rapidly given a high wind speed, most users have adjusted the equation by changing constants or the form slightly. Mackay and Zagorski proposed two relationships to predict the formation of emulsions on the sea. They proposed that the stability could be predicted as follows:51 S ¼ Xa ga exp½Kao ð1 xa xw Þ2 þ Kaw x2w exp½0:04ðT293Þ ;

(2)

where S is the stability index in relative units, high numbers indicate stability, xa is the fraction of asphaltenes, ga is the activity of asphaltenes, Kao is a constant which here is 3.3, xw is the fraction of waxes, Kaw is a constant which is 200 at 293 K, and T is the temperature in kelvin. Water uptake was given as: DWT ¼ DWL þ DWS ¼ DT½kf k1 W1 ;

(3)

where DWT is the total change in water content, DWL is the change in water content for large droplets, DWs is the change in water content for small droplets, DT is time, kf is the rate constant for formation, typically 1 h1, kl is the rate constant for large droplet formation and is about 3 h1, and Wl is the fraction of large droplets, which is typically 3 to 4. Kirstein and Redding used a variation of the Mackay equation to predict emulsification:52 ð1 k2 WÞ exp

2:5W ¼ exp ðk5 k3 tÞ; 1 k1 W

(4)

Chapter | 10 Models for Water-in-Oil Emulsion Formation

251

where k2 is a coalescing constant that is the inverse of the maximum weight fraction water in the mixture, W is the weight fraction water in the mixture, k1 is the Mooney constant that is 0.62 to 0.65, k5 is the increase in mousse formation by weathering, k3 is the lumped water incorporation rate constant and is a function of wind speed in knots, and t is the time in days. The change in viscosity due to emulsion formation was given by: m ¼ m0 exp

2:5W ; 1 k1 W

(5)

where m is the resulting viscosity, m0 is the starting oil viscosity, and the remainder are identical to the above. Reed used the Mackay equations in a series of models.53 The constants were adjusted to correspond to field observations: dFwc Fwc ¼ 2 105 ðW þ 1Þ2 ð1 Þ; dt C3

(6)

where dFwc/dt is the rate of water incorporation, W is the wind speed in m/s, Fwc is the fraction of water in oil, and C3 is the rate constant equal to 0.7 for crude oils and heavy fuel oils. The viscosity of the emulsion was predicted using the following variant of the Mooney equation: m 2:5Fwc ¼ exp ; 1 0:65Fwc m0

(7)

where m is the viscosity of the mixture, m0 is the oil starting viscosity, and Fwc is the fraction of water in oil. The effect of evaporation on viscosity was modeled as: m ¼ m0 expðC4 Fevap Þ;

(8)

where m is the viscosity of the mixture, m0 is the viscosity of the starting oil, C4 is a constant that is 1 for light fuels and 10 for heavy fuels, and Fevap is the fraction evaporated from the slick. All of the above work has a basis in the Mackay equations, which were developed before extensive work on emulsion physics took place. It is now known that both the formation and the characteristics of emulsions could be predicted with orders of magnitude more accurately using empirical data as described below.

10.3. FIRST TWO MODEL DEVELOPMENTS The approaches to model development were implemented and are detailed in the literature.44,45 The approaches used empirical data. One approach was to curve fit the physical and content data to the “stability” index, which was at that time the complex modulus of the water-in-oil product divided by the starting oil

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viscosity. Then this stability factor was used in turn to predict a class (stable, mesostable, entrained, or unstable). Another approach was to predict the class directly from the data which approach was later used in an “improved” model. It is important to note that the class was assigned an arbitrary numerical value, which was later adjusted to optimize the fit. This contrasts very much with the new approach described in this chapter, which uses a newly developed stability index. The empirical data were used to develop mathematical correlation.46 The value for each parameter was correlated in a series of models using DataFit (Oakdale Engineering), which calculates linear models. A two-step process is necessary as DataFit is not able to calculate the specific mathematical function with more than two variables, due to the large number of possibilities. Thus, the functions (e.g., linear, square, log) were calculated using a two-way regression (TableCurve), and these functions were in turn used in developing a predictor model for emulsification. The model that predicts class directly will be summarized here. The steps to produce the model are summarized in an earlier paper.45,46 First, the parameters available were correlated one at a time. Regression coefficients were optimized by adjusting the class criteria from a starting value of 1 to 4 and recalculating these class values several times until they remained relatively stationary. The resulting criteria were: 0.608 is unstable; 0.686 is entrained; 0.657 is mesostable; and 0.674 is stable. The input parameters were density, viscosity, saturates, resins, asphaltenes, a/rdthe asphalteneeresin ratio, and the aromatic content. Several of these parameters can have a zero value, which causes calculation problems. If this is the case, the zero is adjusted either to delete these values or to adjust it to the typical high value for the parameter. A second transformation is performed to adjust the data to a singular increasing or decreasing function. Most parameters have an optimal value with respect to class; that is, the values have a peak function with respect to stability or class. After this correction is made to the values, the regression coefficient increases. Arithmetic was used to convert values in front of the peak to values behind the peak, thus yielding a singular declining or increasing function. The optimal value of this manipulation is found by trial and error, beginning with the estimated peak from the first correlation. The arithmetic to perform this manipulation is as follows: if the initial value is less than the peak value, then the adjusted value is the peak value less the initial value; and if the initial value is more than the peak value, the adjusted value is the initial value less the peak value. The values were adjusted by trial and error until a maximum regression coefficient for the whole model was achieved. The values of the second round of calculations were then correlated using the multiparameter regression package, DataFit. The best model was one that included only four input parameters: density, viscosity, resins, and asphaltenes. It was found that the regression coefficients of class with aromatic content, asphaltene/resin ratio, and waxes were too low to include in the model.

Chapter | 10 Models for Water-in-Oil Emulsion Formation

253

Saturates were eliminated in this new round as it was found that this parameter did not contribute to the overall model. There are some problems with the fundamental process of categorizing water-in-oil states at the onset. Some crude oils are enhanced by the addition of emulsion preventors (also called asphaltene suspenders) directly at the wellhead. This is because they are very emulsion prone. Thus, some emulsion-prone oils may not form emulsions during the laboratory or field tests because of the addition of these emulsion-preventing materials. Although attempts are made to receive oils that do not contain these emulsion-preventing materials, it is impossible to know this fact in every case. Several models were achieved. The best value obtained is 0.996 for the revised model; this was a significant improvement over the old value of 0.51. The fit of the class of water-in-oil type was over 70% correct. Oils that form the entrained state generally have densities over 0.96 and viscosities exceeding 10,000 mPa.s. This can be used to discriminate the entrained states from the other states, which may overlap.

10.4. NEW MODEL DEVELOPMENT The older modeling method as noted in Section 10.3, used an assigned number for each water-in-oil type, and then this was regressed with the various oil starting properties. Further, the functional relationship (square, log, exponential, etc.) of the starting oil properties was determined beforehand and then correlated with a multiparameter linear method to yield a predictor model. Since a stability index has been established, this can be used as the target of the correlation.2 This new modeling has a different approach than the old one. Furthermore, this new approach used a multiregression program directly, using various multifunctional transformations of the input oil property data. This will allow the software of the regression model to assign portions of the functions necessary to achieve the highest correlation factor. Other differences are also that the transformations are automated using a peak function fit, yielding slightly different transformation values than the old values; use of a newer data set; and incorporation of several functional input parameters, dependent on the statistics of the model, into the final equation. A transformation is needed to adjust the data to a singular increasing or decreasing function. Regression methods will not respond correctly to a function that varies both directly and inversely with the target parameter. Most parameters have an optimal value with respect to class; that is, the values have a peak function with respect to stability or class. This is illustrated in Figure 10.1 and Figure 10.2. The resin content without any adjustment is plotted against the stability in Figure 10.1. The stability as shown in these figures is Stability C, as described above. As can be seen in this figure, the values of stability peak at about 5% resins. After this correction is made to the values, the regression coefficient increases. The modified distribution is shown

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30

20

Index

10

0

–10

–20

–30 0

10

20

30

Resins FIGURE 10.1 Graph of resin content (uncorrected) versus stability parameter C. The curve fit is the calculated peak. This is typical of the scatter associated with multiple parameter fits, where each parameter only accounts for a small amount of the variance.

in Figure 10.2. The arithmetic converts values in front of the peak to values behind the peak, thus yielding a singular declining function. The optimal value of this manipulation is found by using a peak function as shown by the line in Figure 10.1. This peak function fit is available from TableCurve, regression software. In the past this was achieved by trial and error, beginning with the estimated peak from the first correlation. The accuracy of the new method is obviously much greater. It is important to note that the scatter observed in Figures 10.1 and 10.2 are typical of scatter observed for a single parameter when a large number of parameters are operative. If one plotted the total number of parameters simultaneously (e.g., in multidimensions), then a singular function would appear with much less scatter. The arithmetic to perform the transformation is as follows: if the initial value is less than the peak value, then the adjusted value is the peak value less the initial value; and if the initial value is more than the peak value, then the adjusted value is the initial value less the peak value. The values found for the transformations are listed in Table 10.1. It should be noted that the exponential of density was used along with the natural log of the viscosity. Previous modeling work had shown that these mathematical changes are necessary to achieve higher correlations.

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Chapter | 10 Models for Water-in-Oil Emulsion Formation

30

20

Index

10

0

–10

–20

–30 0

5

10

15

20

25

Resins FIGURE 10.2 Graph of corrected resin content versus stability parameter C. The curve fit is the best fit. This amount of scatter is typical of multiple parameter fits, where each parameter accounts for only a small amount of the variance.

Having the transformed values, the new model proceeds directly to fit a multiple linear equation to the data. The choice of functions was achieved by correlating the stability function directly with the data and taking the best of the functions (e.g., square, log, etc.) further into the regression process. The functionalities of square, logarithmic or exponential curves are

TABLE 10.1 Values Used to Correct Oil Property Input Parameters Parameter

Form

Correction Value

Density

Exponential

2.5

Viscosity

Natural Logarithm

5.8

Saturates

Standard %

45

Resins

Standard %

10

Asphaltenes

Standard %

4

Asphaltene/Resin Ratio

Standard

0.6

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achieved by correlating the straight value of the input properties plus their expanded values, taken here as the cube of the starting parameter as well as the square of the exponential of the starting value; and their companded values, the natural log (ln), and the logarithm (base 10) of the parameter divided by the square of the value. Thus each parameter is correlated with the stability C index in five sets of mathematical statements. This is similar to the standard Gaussian expansion regression technique.54 In this method the regression is expanded to functionalities above and below linear until the entire entity is optimized. For example, a linear function would be included, then a square, and then a square root and so on until tests of the complete regression show that there are no more gains in increased expansions. Using this technique, six input parametersdexponential of density, ln of viscosity, saturate content, resin content, asphaltene content, and the A/R ratiod were found to be optimal. Thus with four transformations and the original values of these input parameters, there are six times five, or 30, input combinations. Using Datafit, a multiple regression software, a maximum of 20 of these could be taken at a time to test the goodness-of-fit. Values that yield Prob(t) factors of greater than 0.9 were dropped until all remaining factors could be calculated at once. The Prob(t) is the probability that input can be dropped without affecting the regression or goodness-of-fit. Over 20 regressions were carried out until the resulting model was optimal. The r2, the regression coefficient, was 0.75, which is quite high considering the many potential sources of error, and so on. The statistics on the new model are shown in Table 10.2, along with the parameters to create the model. Table 10.2 shows that the 14 remaining parameters all contribute to the accuracy of the final result and that none of them can be cut without affecting the outcome of the model. The procedures for using the new model are given below. The first step is to transform the input data so that it forms a continuous declining or increasing function. Density: take the exponential of the density. If the exponential of density is less than 2.5, then the density parameter is 2.5 less the density and if it is greater than 2.5, it becomes the density less 2.5. The value used in the equation is this transformed value. (9) Viscosity: take the natural logarithm (ln) of the viscosity. If the natural log of the viscosity is less than 5.8, then the viscosity parameter is 5.8 less the viscosity natural log, and if it is greater than 5.8, it becomes the natural log of viscosity less 8.7. The value used in the equation is this transformed value. (10) Saturate content: if the saturate content is less than 45, then the saturate content parameter is 45 less the saturate content, and if it is greater than 45, it becomes the saturate content less 45. The value used in the equation is this transformed value. (11)

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Chapter | 10 Models for Water-in-Oil Emulsion Formation

TABLE 10.2 Regression Results Regression Variable Results

Variable

Value

Standard Error t-ratio

Prob(t)

Input Variable

a

0.259

0.015

16.81

0.0

Saturates

b

1.605

0.098

16.43

0.0

Resins

c

17.198

2.215

7.76

0.0

A/R

d

0.050

0.003

19.17

0.0

ln viscosity

e

0.002

0.000

8.63

0.0

Resins

f

0.001

0.000

4.54

0.00001

Asphaltenes

g

8.505

3.348

2.54

0.01

A/R

h

1.159

0.143

8.11

0.0

ln viscosity

i

0.700

0.170

4.11

0.00004

Resins

j

2.971

0.386

7.70

0.0

A/R

k

0.00000006 0.000

10.90

0.0

ln viscosity A/R

l

1.956

0.663

2.95

0.00

m

0.000004

0.000

10.24

0.0

Exp density

n

0.000146

0.000

2.70

0.01

A/R

1.600

7.69

0.0

o

12.305

Math Applied

Cubed

ln

Exp squared

log/ square x

Contant

Resin content: if the value of the resins is zero, then set this value to 20. If the resin content is less than 10, then the resin content parameter is 10 less the resin content, and if it is greater than 10, it becomes the resin content less 10. The value used in the equation is this transformed value. (12) Asphaltene content: if the value of the asphaltene content is zero, then set the value to 20. If the asphaltene content is less than 4, then the asphaltene content parameter is 4 less the asphaltene content, and if it is greater than 4, it becomes the asphaltene content less 4. The value used in the equation is this transformed value. (13) A/R or asphaltene/resin ratio: this is taken as the direct value of the asphaltene content in percent (untransformed) divided by the resin content in percent (again untransformed). If A/R is less than 0.6, then the A/R parameter is

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0.6 less the A/R, and if it is greater than 0.6, it becomes the A/R less0.6. The value used in the equation is this transformed value. (14) The class of the resulting emulsion is then calculated as follows: Stability C ¼ 12:3 þ 0:259 St 1:601 Rt 17:2 A=Rt 0:50 Vt3 þ 0:002 Rt3 þ 0:001 At3 þ 8:51 A=Rt3 1:12 ln Vt þ 0:700 lnRt þ 2:97 lnA=R þ 6:0108 ExplnVt2 1:96 ExpA=Rt2 4:0106 logExpDt=expDt2 1:5104 logA=Rt=A=Rt2

(15)

where Class is the Stability C of the resulting water-in-oil type, St is the transformed saturate content as calculated in Equation (11), abbreviated A here, Rt is the transformed resin content as calculated in Equation (12), abbreviated B, A/Rt is the transformed asphaltene/resin ratio as calculated in Equation (14), abbreviated C, Vt3 is the cube of the transformed ln viscosity as calculated in Equation (10), abbreviated D, Rt3 is the cube of the transformed resin content as calculated in Equation (12), abbreviated E, At3 is the cube of the transformed asphaltene content as calculated in Equation (13), abbreviated F, A/Rt3 is the cube of the transformed A/R ratio as calculated in Equation (14), abbreviated G, lnVt is the natural logarithm (ln) of the transformed viscosity as calculated in Equation (10), abbreviated H, lnRt is the natural logarithm (ln) of the transformed resin content as calculated in Equation (12), abbreviated I, lnA/R is the natural logarithm (ln) of transformed asphaltene/resin ratio as calculated in (14), abbreviated J, ExplnVt2 is the exponential of the transformed viscositydsquareddas calculated in Equation (10), abbreviated K, ExpA/Rt2 is the is the exponential of the A/R ratio e squareddas calculated in Equation (14), abbreviated L, logExpDt/expDt2 is the is the logarithm (base 10) of exponential of the densityddivided by the square of the transformed densityd the transformed density as calculated in Equation (9), abbreviated M, logA/Rt/A/Rt2 is the logarithm (base 10) of exponential of the A/R ratioddivided by the square of the A/R ratiodthe transformed A/R ratio as calculated in Equation (14), abbreviated N.

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Chapter | 10 Models for Water-in-Oil Emulsion Formation

A simplified version of the equation is then: Stability C ¼ 12:3 þ 0:259A 1:601B 17:2C 0:50D þ 0:002E þ 0:001E þ 8:51G 1:12H þ 0:700l þ 2:97J þ 6:0108 K 1:96L 4:0106 M 1:5104 N (16) where the parameters A to N are defined as above. The Stability C of the resulting product is calculated using the rheological measurements of the water-in-oil product formed.2 The basic uncorrected Stability C or cross product is: Xpr ¼ Complex Modulus Starting Oil ViscosityðStability AÞ Elastic Modulus Starting Oil ViscosityðStability BÞ

(17)

The corrected stability C is: Stability C ¼ In ðXpr XprÞ=1000

(18)

where the Xpr is the value from Equation (17). Or, equivalently, the Stability C can be calculated from: Stability C ¼ InðStab A Stab BÞ2 =1011

(20)

The values of Stability C that are assigned to each class are given in Table 10.3. The viscosity of the resulting product can be taken as the average of the types at a given time as shown in Table 10.4.

TABLE 10.3 Conditions for Type Calculations Calculated C Stability Minimum

Maximum

2.2

Other Conditions

State

Error (%)

15

Stable

0

12

0.7

Mesostable

9

18.3

9.1

density >0.96 viscosity > 6000

Entrained

7

7.1

39.1

density <0.85 or >1.0 viscosity<100 or >800000 Asphaltenes or Resins <1%

Unstable

10

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TABLE 10.4 Viscosity Increases From Starting Oil Viscosity Increase On First Day

Week

Year

Entrained

1.9

1.9

2.1

Mesostable

7.2

11

32

Stable

405

1054

991

Unstable

0.99

1.0

1.0

10.5. DEVELOPMENT OF AN EMULSION KINETICS ESTIMATOR The kinetics of emulsion formation have been studied, and data are available to compute the time to formation.45,46 This kinetics study has shown that the times to formation for stable emulsions is particularly rapid and that of entrainment is also rapiddboth in a matter of minutes. This study yielded data in terms of relative formation time and energy (rpm) of the mixing apparatus. A study in a large test-tank has also yielded data on the formation time of the various water-in-oil states. The data of the relative formation times and the wave height are available. The average data over 25 runs were used to calculate the formation time, which was taken as that time at which 75% of the maximum stability measured occurs. The conditions under which these tests took place and the measurements taken are described in the literature.55,56 The wave height for each experiment was measured and used to indicate relative sea energy, taken for a fully developed sea. The laboratory data was converted from relative rotational energy to wave height by equating formation times and then using this multiplier to calculate the equivalent wave height. Formulae were fitted to each of the three categories, and the common formula among all three relevant classes was found to be 1/x1.5 (24), as shown in Table 10.5. The regression coefficients for this formula are also given. Application of the equations in Table 10.5 will then provide a user with a time to formation of a particular water-in-oil state, given the wave height.

10.6. DISCUSSION The first point to be discussed here will be the error or goodness-of-fit. Table 10.2 shows the specific regression statistics by fit parameter. The first column is the value that is used in the predictor equations. The data in the Standard Error column are the estimates of the standard deviations of the fitted regression parameters. The third column is the t-ratio, which is the ratio of the estimated parameter value to the estimated parameter standard deviation. The larger the ratio is, the more significant the parameter is in the regression model. This is

261

Chapter | 10 Models for Water-in-Oil Emulsion Formation

TABLE 10.5 Wave Height Prediction equation y ¼ a þ b/x1.5(24)

Resulting Equation Predictor

a

b

R2

Stable

27.1

7520

0.51

Mesostable

47

49100

0.95

Entrained

30.8

18300

0.94

x is wave height in cm y ¼ time to formation in minutes

a test statistic to determine if the actual parameter value is zero. If the value were zero, then it should not be included in the equation. As can be seen in Table 10.2, the t-ratios are very high; thus, all remaining input parameters are valid. This exercise had begun with 30 input parameters, and only 14 remained that are highly significant. The fourth column is the Prob(t), which is the probability that a parameter can be dropped without losing significance to the model. If Prob(t) ¼ 0.95, there is a 95% chance that the actual parameter value is zero. In cases like the latter, the parameter in question can usually be removed from the model without affecting the regression accuracy. As can be seen from Table 10.2, all the 14 values are highly significant and should not be dropped. Table 10.3 shows the error percentage by water-in-oil type. There is little error for more stable types, but more error for the unstable types. This was noted in past modeling as well.45,46 It is suspected that the reasons for this are as follows: 1. Unstable types generally consist of three widely separate classes of oils or fuels, very light oils such as the fuels that have little or no resins or asphaltenes; those very heavy oils that are so viscous that they will not uptake water; and those oils that have the incorrect ratio or amounts of resins or asphaltenes. It is difficult to mathematically incorporate all three of these variances into one grouping. 2. Some of the oils may be able to form different water-in-oil types, but emulsion inhibitors or asphaltene suspenders have been added to the products. These types of oils make prediction very difficult as they mislead the regression process. 3. There are many different asphaltenes, some of which make much more stable emulsions than other. Recent work has shown that there are hundreds of asphaltene subcomponents varying very much in composition and molecular size.14 Thus the percent of asphaltenes (or resins) certainly does not tell the whole story about the emulsion-stabilizers in the emulsions. It is important to recognize the properties and behaviors of the four waterin-oil types; they are very different from each other. Table 10.6 shows the

262

TABLE 10.6 Average Properties of the Four Water-in-Oil Types Rheological Properties on Day of Formation Viscosity Increase From Starting

Complex Modulus (mPa)

Elasticity Modulus (mPa)

tan delta (V/E)

Complex Viscosity (mPa.s)

Appearance

Entrained

Viscous Black

44.5

27.5*

1.9

829750

514010

1.73

132305

Mesostable

Viscous Reddish

64.3

29.6*

7.2

132780.5

107294.5

1.7

21219.9

Stable

Solid Reddish

80.7

77.4

405

749991.4

710445.9

0.7

119683.2

Unstable

Oil-Like

6.1

6.85*

0.0

10965637.5

3367562.5

2.4

1828062.5

Rheological Properties One Week After Formation

Appearance

Viscosity Increase From Starting

Complex Modulus Change

Elasticity Modulus Change

Tan Delta Change

Complex Viscosity Change

Entrained

Viscous Black

1.9

0.8

0.6

1.7

1.3

Mesostable

Broken

5.4

0.6

0.5

2.2

0.5

Stable

Solid Reddish

859

1.1

1.1

1.1

1.2

Unstable

Oil-Like

0.0

3.8

2.9

1.7

3.6

(Increase is shown as number larger than 1.00) *These water content values are high as most were not measured as they were obviously low.

Behaviour of Oil in the Environment and Spill Modeling

Averages

PART | IV

Week Water Content (%w/w)

Day Water Content (%w/w)

263

Percent Water Loss (Day–1) per Starting Value

Chapter | 10 Models for Water-in-Oil Emulsion Formation 3.0 Entrained Mesostable Stable Unstable

2.5 2.0 Unstable

1.5 1.0 0.5 Stable

0.0

Entrained

Mesostable

e–1

e0 1

e1

e2

7

e3

e4

e5

e6 1 Year

Time (Days) FIGURE 10.3 Graph of water loss as a rate over time for the four water-in-oil types.

different average properties of the four water-in-oil types. It should be noted that on the day of formation, only mesostable and stable may be somewhat similar, this similarity disappears after one week when the mesostable emulsions break down. The change in water content with time is portrayed in Figure 10.3. As can be seen, the unstable type loses the most water in the first few days. The water content itself is shown in Figure 10.4. As the figure shows, the water content of the four types is very different at the start and especially after one week. Figures 10.3 and 10.4 show that the rate of water loss and the amount of water are indeed different aspects of these water-in-oil types. The other significant point in these figures is that the change in water content of the entrained types is the slowest of all. Another comparison of the four water-in-oil types is shown in Figures 10.5 and 10.6 and relates to the viscosities of types. The rate of change in viscosity is quite different for the four types as seen in Figure 10.4. The rise of viscosity for the mesostable types is more than expected and is due to weathering of the oil, which proceeds more rapidly without water content. The apparent viscosity of the four water-in-oil types is shown in Figure 10.5. As the viscosity axis is logarithmic, the differences are very significant between the four types. In summary, the four water-in-oil types differ by as much as orders-of-magnitude in viscosity and water content at one day, one week, and one year. A question that remains is, how good is this model compared to other models? Table 10.7 shows a comparison for several oil types. These oil types were chosen as common types that are in commerce or as they are well known for their properties. The first six columns give the oil identification and its

264

PART | IV

Behaviour of Oil in the Environment and Spill Modeling

80

Stable

70

Mesostable

Water Content %

60

Entrained Mesostable Stable Unstable

50 40

Entrained

30

A

20

Unstable

10 0

e0

e1

e2

e3

e4

e5

e6

ln Time (Days) FIGURE 10.4

Graph of absolute water content of the four water-in-oil types.

Log Rate of Change in Viscosity

3.5 3.0

Stable

2.5

Entrained Mesostable Stable Unstable

2.0 1.5 1.0 Mesostable

0.5

Entrained

0.0 –0.5

Unstable

e-1

FIGURE 10.5

e0 1

e1

e2

e3 7 Time (Days)

e4

e5

1 Year

e6

Graph of the change in viscosity for the four water-in-oil types.

actual properties of water content and viscosity on the first day of formation. The first model compared shows the traditional exponential water uptake as predicted using the equations presented in Section 10.2. The shaded and boxed values are those predictions in error. A criterion was set for at least 25% in

Chapter | 10 Models for Water-in-Oil Emulsion Formation

T

265

D

FIGURE 10.6 Graph of the apparent viscosity of the four water-in-oil types with time.

water content or incorrect typedif predicted. The number of cases predicted correctly are given at the bottom, and the average orders-of-magnitude are different from the actual value. Table 10.7 shows that the old exponential water uptake model predicted the correct water content only 7% of the time in this set of oils and the order of magnitude of the magnitude of viscosity was over two order-of-magnitudes from the actual viscosity on the day of formation. This comparison would indicate that exponential water uptake models are not useful and are, in fact, misleading. The second model compared in Table 10.7 is that of ADIOS, a widely available model from National Oceanic and Atmospheric Administration (NOAA). The water content is predicted within about 25% in about 49% of cases, and the viscosity averages about 1.6 orders-of-magnitude in error from the actual value. The third model compared is the older model by the present author. It predicted the water content correctly in 72% of cases as well the correct water-in-oil type. The last model compared is the one presented for the first time in this chapter. This model was excellent and predicted the water content and type 100% correct for all types and the viscosity error average 0.2 orders-of-magnitude. The prediction capability of the models is illustrated in Figures 10.7 and 10.8. Figure 10.7 shows the percent correctness in assigning state (by water content in the case of the older models). Figure 10.8 shows the ordersof-magnitude in errors for the water content and the viscosity for the models. As can be seen by these figures, the old exponential model predicts so few correctly that it is probably misleading.

266

TABLE 10.7 Comparison of Predictions of Various Models

%

Actual

Oil

Actual

Water

Starting

Day

Viscosity

Water

Viscosity

Water

Viscosity

Water

Viscosity

(mPa.s)

Content

(mPa.s)

Content

(mPa.s)

Content

Content Viscosity

Adios2

Old Exp. Uptake1

First Two State Models3 Type

New Model In This Paper Viscosity

Water

(mPa.s)

Content

Type

Stability

(%w/w)

(mPa.s)

(mPa.s)

0.0

Entrained

57.9

12610

42000

2853140

90

25000

0

50400

44

Entrained

24000

42.5

Entrained

Belridge Heavy

2.7

Entrained

59.6

17105

47000

3870180

90

25000

0

68400

44

Entrained

32500

42.5

Entrained

Bunker C (1987)

0.0

Entrained

26.4

45030

110000

10188510

90

8000

0

180100

44

Entrained

85600

42.5

Entrained

Bunker C (Anchorage)

0.0

Entrained

34.7

8706

28000

1969820

90

25000

0

34800

44

Entrained

16500

42.5

Entrained

High Viscosity Fuel Oil

0.0

Entrained

47.6

13460

73626

3045470

90

40000

0

53800

44

Entrained

25600

42.5

Entrained

IFO - 180

7.8

Entrained

58.4

27280

149617

6172380

90

2000

0

109100

44

Entrained

51800

42.5

Entrained

IFO - 300

0.0

Entrained

52.3

14470

96610.5

3273990

90

200000

0

57900

44

Entrained

27500

42.5

Entrained

Carpenteria

14.9

Meso

54.3

3426

29000

775170

90

400000

70

13700

44

Entrained

24700

64.6

Meso

Dos Cuadras

20.3

Meso

68.6

741

9800

167660

90

20000

47

33300

67

Meso

5300

64.6

Meso

North Slope (Middle Pipeline)

30.5

Meso

61.9

900

2600

203630

90

80000

0

40500

67

Meso

6500

64.6

Meso

North Slope (Northern Pipeline) 31.1

Meso

69.8

748

1400

169240

90

80000

0

33700

67

Meso

5400

64.6

Meso

North Slope (Southern Pipeline) 29.6

Meso

53.5

961

1900

217440

90

80000

0

43200

67

Meso

6900

64.6

Meso

Arabian Light

12.0

Stable

88.9

33

46000

7470

90

1200000

87

18915000

74

Stable

13400

74.7

Stable

Arabian Light

24.2

Stable

84.7

94

48000

21270

90

1200000

87

25658000

74

Stable

38100

74.7

Stable

Cook Inlet - Swanson River

39.7

Stable

81.5

152

29000

34390

90

250000

90

67545000

74

Stable

61600

74.7

Stable

Point Arguello Comingled

0.0

Stable

82.3

533

180000

120600

90

2000000

82

13059000

74

Stable

215900

74.7

Stable

Point Arguello Light

0.0

Stable

93.1

22

67000

4980

90

4000000

93

20190000

74

Stable

8900

74.7

Stable

Point Arguello Light

10.2

Stable

88.8

76

280000

17200

90

4000000

93

40920000

74

Stable

30800

74.7

Stable

Point Arguello Light

19.0

Stable

85.5

183

270000

41410

90

4000000

93

21705000

74

Stable

74100

74.7

Stable

Point Arguello Light

28.3

Stable

79.8

671

140000

151820

90

4000000

93

5139000

74

Stable

271800

74.7

Stable

Prudhoe Bay (1995)

9.3

Stable

85.1

55

46117.95

12440

90

4000000

93

1112000

74

Stable

22300

74.7

Stable

Sockeye

0.0

Stable

86.5

45

685395

10180

90

450000

87

100

6

Unstable

18200

74.7

Stable

Sockeye

12.5

Stable

80.7

163

201945.375

36880

90

450000

87

1122000

74

Stable

66000

74.7

Stable

Sockeye

22.1

Stable

79.1

628

249183.75

142090

90

450000

87

1442000

74

Stable

254300

74.7

Stable

Sockeye Sweet

26.9

Stable

75.5

321

47956.5

72630

90

450000

87

50000

74

Stable

130000

74.7

Stable

(%w/w)

(%w/w)

(%w/w)

(%w/w)

Takula

0.0

Stable

84.8

110

44678.66763

24890

90

1000000

79

141000

74

Stable

44600

74.7

Stable

Takula

11.0

Stable

81.3

844

83238.125

190960

90

1000000

79

228000

74

Stable

341800

74.7

Stable

Behaviour of Oil in the Environment and Spill Modeling

Evap. Belridge Heavy

PART | IV

Oil

Actual Day

0.0

Unstable

3.7

1

7

0

10

1

0

45

67

value problem

1

6.1

Barrow Island

0.0

Unstable

3.7

2

2

0

10

4000

90

100

67

value problem

2

6.1

Unstable

Brent

0.0

Unstable

3.7

6

6

1360

90

160000

90

300

67

value problem

6

6.1

Unstable

Bunker C (Anchorage)

8.4

Unstable

6.0

280000

63352920

90

25000

0

420000

6

Unstable

277200

6.1

Unstable

Diesel (Anchorage)

0.0

Unstable

3.7

2

2

0

10

6.5

0

100

67

value problem

2

6.1

Unstable

Eugene Island Block 32

0.0

Unstable

3.7

10

10

2260

90

160000

90

450

not done

10

6.1

Unstable

Garden Banks 387

4600

29

6.1

Unstable

Green Canyon 200

2.8E+05

Unstable

0.0

Unstable

3.7

29

29

6560

90

37

1305

6

Unstable

19.1

Unstable

3.7

39

39

8820

90

4000

69

1800

67

mesostable

39

6.1

Unstable

Gulfaks

0.0

Unstable

3.7

13

13

2940

90

90000

90

585

not done

13

6.1

Unstable

Jet A1

0.0

Unstable

3.7

2

2

0

10

45

0

100

67

value problem

2

6.1

Unstable

Malongo

0.0

Unstable

3.7

63

63

14250

90

400000

43

2800

67

mesostable

100

6.1

Unstable

Ship Shoal Block 269

26.0

Unstable

3.7

18

18

4070

90

220000

90

810

not done

18

6.1

Unstable

South Louisiana

0.0

Unstable

3.7

8

8

1810

90

160000

90

400

67

mesostable

8

6.1

Unstable

Taching

0.0

Unstable

3.5

5138000

1162526170

90

100000

81

7707000

6

Unstable

5086600

6.1

Unstable

Viosca Knoll 826

0.0

Unstable

1.7

16

3620

90

120000

90

700

67

mesostable

16

6.1

Unstable

West Texas (2000)

0.0

Unstable

3.7

9

1950

90

12000

90

400

67

mesostable

9

6.1

Unstable

Zaire

23.0

Unstable

5.3

533100

120619440

90

120000

38

799700

6

Unstable

527800

6.1

Unstable

1.64

49 1.17

1.26

72 0.40

0.28

100 0.12

Comparison Statistics

5.1E+06 16 9 5.3E+05

% of cases predicted correctly Average orders-of-magnitude from actual value 2.28

Shaded and boxed values highlight incorrect values 1 Calculated by Old Exponential Model as described in this paper 2 Calculated using ADIOS (NOAA) 3 Calculated Using Earlier State Model (Fingas and Fieldhouse, 2005)

7 0.52

Chapter | 10 Models for Water-in-Oil Emulsion Formation

Aviation Gasoline 100LL

267

268

PART | IV

Behaviour of Oil in the Environment and Spill Modeling

Percent Correct in Assigning State

120 100 80 60 40 20 ADIOS

0

0

1 Old Exponential

Early State

2

3

New

4

5

Model

FIGURE 10.7 Graph of the percent correct predictions of the four models compared.

Average Orders of Magnitude Error

2.5

2.0 Viscosity

1.5 Water Content

1.0

0.5

0.0

0

1 Old Exponential

2

3

4

ADIOS

Early State

New

5

FIGURE 10.8 Graph of the amount of error in predictions of the four models compared.

Chapter | 10 Models for Water-in-Oil Emulsion Formation

269

FIGURE 10.9 An emulsion beginning to form at sea. This emulsion is still fluid and thus is probably a mesostable emulsion.

FIGURE 10.10 An emulsion from a spill in the Arabian Gulf. Note that the thin sheen portion of the oil did not form an emulsion. A minimum thickness, probably the size of a few drops or about 0.5 mm, is necessary for an emulsion to form.

Figures 10.9 and 10.10 show typical emulsions at sea. Emulsion formation is important to actions to deal with spills. Therefore, it is important to correctly predict their formation.

10.7. CONCLUSIONS The knowledge that water-in-oil types exist and that a new scheme to classify their stability, herein called Stability C, enables the development of new and much more accurate emulsion formation models. In this chapter, the

270

PART | IV

Behaviour of Oil in the Environment and Spill Modeling

development of a new modeling scheme was described. The density, viscosity, asphaltene, and resin contents are used to fulfill a regression equation to Stability C, which in turn predicts either an unstable or an entrained waterin-oil state or a mesostable or stable emulsion. A prediction scheme is also given to estimate the water content and viscosity of the resulting water-in-oil state and the time to formation given a sea wave-height. The new model can provide accurate prediction of class about 90% of the time. The major inaccuracy lies with the unstable types because of the fact that there are three distinct types of oils or fuels in this class, each very different, and because of the possible presence of emulsion breakers or asphaltene suspenders in the oils. The new model uses only resin, saturate, asphaltene, viscosity, and density data as input. These data are readily available for most oils. The predictions were compared to the actual data from some common oils and against an old model from the present author. Also compared were an old exponential water uptake model dating from the 1980s and the ADIOS model. It was found that the old exponential water uptake model was incorrect most of the time and would not be considered useful.

REFERENCES 1. NAS. Oil in the Sea III, Inputs, Fates, and Effects. Washington, DC: National Research Council, National Academies Press; 2002. 2. Fingas M, Fieldhouse B. Studies on Crude Oil and Petroleum Product Emulsions: Water Resolution and Rheology. Colloids Surf A 2009;67. 3. Berridge SA, Dean RA, Fallows RG, Fish A. The Properties of Persistent Oils at Sea. J Instit of Petr 1968;300. 4. McLean JD, Spiecker PM, Sullivan AP, Kilpatrick PK. The Role of Petroleum Asphaltenes in the Stabilization of Water-in-Oil Emulsions. In: Mullins OC, Sheu EY, editors. Structure and Dynamics of Asphaltenes, 377. New Jersey: Plenum Press; 1998. 5. Sjo¨blom J, Aske N, Auflem IH, Brandal O, Havre TE, Saether O, et al. Our Current Understanding of Water-in-Crude Oil Emulsions: Recent Characterization Techniques and High Pressure Performance. Adv Colloid and Interfac 2003;399. 6. Sjo¨blom J, Hemmingsen PV, Kallevik H. The Role of Asphaltenes in Stabilizing Waterin-Crude Oil Emulsions. In: Mullins OC, Sheu EY, Hammami A, Marshall AG, editors. Asphaltenes, Heavy Oils and Petroleomics, 549. Amsterdam: Springer Publications; 2007. 7. McLean JD, Kilpatrick PK. Effects of Asphaltene Solvency on Stability of Water-in-Oil Emulsions. Colloid Interface Sci 1997;242. 8. McLean JD, Kilpatrick PK. Effects of Asphaltene Aggregation in Model Heptane-Toluene Mixtures on Stability of Water-in-Oil Emulsions. Colloid Interface Sci 1997;23. 9. McLean JD, Spiecker PM, Sullivan AP, Kilpatrick PK. The Role of Petroleum Asphaltenes in the Stabilization of Water-in-Oil Emulsion. In: Mullins, Sheu, editors. Structure and Dynamics of Asphaltenes, 377. New Jersey: Plenum Press; 1998. 10. Gu G, Xu Z, Nandakumar K, Masliyah JH. Influence of Water-Soluble and Water-Insoluble Natural Surface Active Components on the Stability of Water-in-Toluene-Diluted Bitumen Emulsion. Fuel 2002;1859.

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11. Yarranton HW, Hussein H, Masliyah JH. Water-in-Hydrocarbon Emulsions Stabilized by Asphaltenes at Low Concentrations. Colloid Interface Sci 2000;52. 12. Kilpatrick PE, Spiecker PM. Asphaltene Emulsions. In: Sjoblom J, editor. Encyclopedic Handbook of Emulsion Technology, 707. Amsterdam: Marcel Dekker; 2001. 13. Sztukowski DM, Yarranton HW. Characterization and Interfacial Behaviour of Oil Sands Solids Implicated in Emulsion Stability. J Disp Sci Technol 2004;299. 14. Groenzin H, Mullins OC. Asphaltene Molecular Size and Weight by Time-Resolved Fluorescence Depolarization. In: Mullins OC, Sheu EY, Hammami A, Marshall AG, editors. Asphaltenes, Heavy Oils and Petroleomics, 17. Amsterdam: Springer Publications; 2007. 15. Zhang LY, Lopetinsky R, Xu Z, Masliyah JH. Asphaltene Monolayers at a Toluene/Water Interface. Energy Fuels 2005;1330. 16. Lobato MD, Pedrosa JM, Hortal AR, Martinez-Haya B, Lebron-Aguilar R, Lago S. Characterization and Langmuir Film Properties of Asphaltenes Extracted from Arabian Light Crude Oil. Colloids Surf A 2007;72. 17. Fingas MF, Fieldhouse B. A Review of Knowledge on Water-in-oil Emulsions. AMOP 2006;1. 18. Spiecker PM, Gawrys KL, Kilpatrick PK. Aggregation and Solubility Behavior of Asphaltenes and Their Subfractions. Colloid Interface Sci 2003;178. 19. Yang X, Hamza H, Czarnecki J. Investigation of Subfractions of Athabasca Asphaltenes and Their Role in Emulsion Stability. Energy Fuels 2004;770. 20. Ali MF, Alqam MH. The Role of Asphaltenes, Resins and Other Solids in the Stabilization of Water in Oil Emulsions and Its Effects on Oil Production in Saudi Oil Fields. Fuel 2000;1309. 21. Nordli KG, Sjo¨blom J, Stenius P. Water-in-Crude Oil Emulsions from the Norwegian Continental Shelf: 4. Monolayer Properties of the Interfacially Active Crude Oil Fraction. Colloids Surf A 1991;83. 22. Havre TE, Sjo¨blom J. Emulsion Stabilization by Means of Combined Surfactant Multilayer (D-phase) and Asphaltene Particles. Colloids Surf A 2003;131. 23. Sjo¨blom J, Hemmingsen PV, Kallevik H. The Role of Asphaltenes in Stabilizing Waterin-Crude Oil Emulsions. In: Mullins OC, Sheu EY, Hammami A, Marshall AG, editors. Asphaltenes, Heavy Oils and Petroleomics, 549. Amsterdam: Springer Publications; 2007. 24. Spiecker PM, Gawrys KL, Trail CB, Kilpatrick PK. Effects of Petroleum Resins on Asphaltene Aggregation and Water-in-Oil Emulsion Formation. Colloids Surf A 2003;9. 25. Sjo¨blom J, Skodvin T, Jakobsen T, Dukhin SS. Dielectric Spectroscopy and Emulsions: A Theoretical and Experimental Approach. J Disp Sci Technol 1994;401. 26. Kallevik H, Kvalheim OM, Sjo¨blom J. Qualitative Determination of Asphaltenes and Resins in Solution by Means of Near-Infrared Spectroscopy: Correlations to Emulsion Stability. Colloid Interface Sci 2000;494. 27. Kallevik H, Hansen SB, Saether Ø, Kvalheim OM, Sjo¨blom J. Crude Oil Model Emulsion Characterized by Means of Near Infrared Spectroscopy and Multivariate Techniques. J Disp Sci Technol 2000;245. 28. Song M-G, Jho S-H, Kim J-Y, Kim J-D. Rapid Evaluation of Water-in-Oil (W/O) Emulsion Stability by Turbidity Ratio Measurements. Colloid Interface Sci 2000;213. 29. Dicharry C, Arla D, Sinquin A, Graciaa A, Bouriat P. Stability of Water/Crude Oil Emulsions Based in Interfacial Dilational Rheology. Colloid Interface Sci 2006;785. 30. Xia L, Lu S, Cao G. Stability and Demulsification of Emulsions Stabilized by Asphaltenes or Resins. Colloid Interface Sci 2004;504. 31. Sztukowski DM, Yarranton HW. Oilfield Solids and Water-in-Oil Emulsion Stability. Colloid Interface Sci 2005;821.

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32. Yarranton HW, Urrutia P, Sztukowski DM. Effect of Interfacial Rheology on Model Emulsion Coalescence: II Emulsion Coalesence. Colloid Interface Sci 2007;253. 33. Midttun Ø, Kallevik H, Sjo¨blom J, Kvalheim OM. Multivariate Screening Analysis of Waterin-Oil Emulsions in High External Electric Fields as Studied by Means of Dielectric Time Domain Spectroscopy. Colloid Interface Sci 2000;262. 34. Aske N, Kallevik H, Sjo¨blom J. Water-in-Crude Oil Emulsion Stability Studied by Critical Electric Field Measurement: Correlation to Physico-Chemical Parameters and Near-Infrared Spectroscopy. J Petr Sci Eng 2002;1. 35. Tadros ThF. Fundamental Principles of Emulsion Rheology and Their Applications. Colloids Surf A 1994;39. 36. Johnsen EE, Rønningsen HP. Viscosity of "Live" Water-in-Crude-Oil Emulsions: Experimental Work and Validation of Correlations. J Petr Sci Eng 2003;23. 37. Spiecker PM, Kilpatrick PK. Interfacial Rheology of Petroleum Asphaltenes at the Oil-Water Interface. Langmuir 2004;4022. 38. Aske N, Orr HR, Sjo¨blom J. Interfacial Properties of Water-Crude Oil Systems Using the Oscillating Pendant Drop. Correlations to Asphaltene Solubility by Near Infrared Spectroscopy. J Disp Sci Technol 2004;263. 39. Yarranton HW, Sztukowski DM, Urrutia P. Effect of Interfacial Rheology on Model Emulsion Coalescence: I Interfacial Rheology. Colloid Interface Sci 2007;246. 40. Moran K, Yeung A, Masliyah J. The Viscoplastic Properties of Crude Oil-Water Interfaces. Chem Eng Sci 2006;6016. 41. Khristov K, Taylor SD, Czarnecki J, Masliyah J. Thin Liquid Film Technique: Application to Water-Oil-Water Bitumen Emulsion Films. Colloids Surf A 2000;183. 42. Yang X, Czarnecki J. The Effect of Naphtha to Bitumen Ratio on Properties of Water in Diluted Bitumen Emulsions. Colloids Surf A 2002;213. 43. Hemmingston PV, Silset A, Hannisdal A, Sjo¨blom J. Emulsions of Heavy Crude Oils. I: Influence of Viscosity, Temperature and Dilution. J Disp Sci Technol 2005;615. 44. Fingas MF, Fieldhouse B. Formation of Water-in-Oil Emulsions and Application to Oil Spill Modelling. J Haz Mat 2004;37. 45. Fingas MF, Fieldhouse B. Modelling of Water-in-Oil Emulsions. AMOP 2004;335. 46. Fingas MF, Fieldhouse B. An Update to the Modelling of Water-in-Oil Emulsions. AMOP 2005;923. 47. Fingas MF, Fieldhouse B. A Review of Knowledge on Water-in-Oil Emulsions. AMOP 2006;1. 48. Fingas MF. A New Generation of Models for Water-in-Oil Emulsion Formation. AMOP 2009;577. 49. Mackay D, Buist IA, Mascarenhas R, Paterson S. Oil Spill Processes and Models. Environment Canada Manuscript Report EE-8; 1980. 50. Mackay D. A Mathematical Model of Oil Spill Behaviour. Environment Canada Manuscript Report EE-7; 1980. 51. Mackay D, Zagorski W. Studies of Water-in-Oil Emulsions. Environment Canada Manuscript Report EE-34; 1982. 52. Kirstein BE, Redding RT. Ocean-Ice Oil-Weathering Computer Program User’s Manual. Outer Continental Shelf Environmental Assessment Program, vol. 59. Seattle, WA: NOAA; 1988. 53. Reed M. The Physical Fates Component of the Natural Resource Damage Assessment Model System. Oil Chem Poll 1989;99. 54. Araki Y, Konishi S, Kawano S, Matsui H. Functional Regression Modeling via Regularized Gaussian Basis Expansions. Ann I Stat Math 2008;1.

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55. Fingas MF, Fieldhouse B, Noonan J, Lambert P, Lane J, Mullin J. Studies of Water-in-Oil Emulsions: Testing of Emulsion Formation in OHMSETT, Year II. AMOP 2002;29. 56. Fingas MF, Fieldhouse B. Water-in-Oil Emulsions and Application to Oil Spill Modelling, Proceedings of the Fifth International Marine Environmental Modelling Seminar. Sintef 2001;339.

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Chapter 11

Oil Spill Trajectory Forecasting Uncertainty and Emergency Response Debra Simecek-Beatty

Chapter Outline 11.1. Introduction: The 275 Importance of Forecast Uncertainty 11.2. The Basics of Oil Spill 276 Modeling

11.3. Trajectory Model Uncertainties 11.4. Trajectory Forecast Verification 11.5. Summary and Conclusions

280 292 295

11.1. INTRODUCTION: THE IMPORTANCE OF FORECAST UNCERTAINTY Winds and currents play an important role in oil spill transport; and, occasionally, oil moves in a direction that results in unexpected outcomes. One of the most dramatic examples of the latter phenomenon occurred during the 1984 explosion and subsequent breakup of the T/V Puerto Rican. The accident resulted in more than 5,678,000 liters of oil spilling into the Gulf of the Farallones in California. Initially, the oil slick moved southerly as forecasted, thereby avoiding the large seabird and mammal colonies at the Farallone Islands. Oil protection and recovery equipment were deployed to the south, leaving the Farallone Islands and the northern California shoreline unprotected and exposed. On day 5 of the spill, the slick made a sudden and remarkable reversal, and overnight, the oil moved northward approximately 50 km from its location on the previous day. The trajectory forecast completely missed the reversal. Oiled birds and shoreline oiling were reported on the Farallone Islands.1 By day 10, the spill made landfall along the northern California coast Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10011-5 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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at Point Reyes.2 Oil observations and trajectory forecasts were a critical factor in forming daily operational oil recovery and protection decisions. In this instance, the consequences of an inaccurate trajectory forecast were devastating. An in-depth analysis of the meteorological and oceanographic data collected during the T/V Puerto Rican incident suggested that a reversal in the outer continental shelf current transported the oil rapidly to the north. This “dramatic” reversal was likely related to the onset of the Davidson Current or other larger-scale phenomena, which was not predictable with the available oceanographic measurement data.3 Given these sparse real-time environmental data, today’s models would still have difficulty accurately forecasting the current reversal, particularly in the short period required during an emergency response. The difference, however, is that current-day modelers now include uncertainty as part of the trajectory forecast. Today, emergency responders are briefed with both the estimate of the oil movement and alternative possibilities that could present a significant threat to valuable resources. Most decision makers understand that forecasting is imperfect. The physical processes acting on the oil spill are chaotic and complex, and trajectory forecast uncertainty is inevitable. As shown in the T/V Puerto Rican incident and countless other oil spills, there are good practical reasons for disseminating trajectory uncertainty and ensuring that the response community understands the consequences of uncertainty. Figure 11.1 shows a rough representation of the actual and predicted oil movement for the T/V Puerto Rican incident on the fifth day of the spill. The circle is a hypothetical boundary and introduced here for demonstration. The circle represents the possible errors in the model input data and plausible variations in the transport processes. This includes a possible scenario of surface current reversal. In this instance, the area is especially complex and difficult to model so that the level of forecast uncertainty is high. The large bounded area provides a visual cue to the response community about the limitation of the spill model(s). If a high-value resource is within the uncertainty but not within the “best estimate,” responders should seriously consider protecting the resource from oil impact. This example demonstrates that communicating uncertainty information can avoid misrepresenting the capability of oil spill modeling, better convey “what we do know” and “what we don’t know,” and help responders make more informed decisions and avoid problems.4 This is “a minimum regret” approach to protecting high-value resources.

11.2. THE BASICS OF OIL SPILL MODELING Responders, particularly those interested in the operational aspects of a spill, are often in need of a quick, “back-of-the-envelope” estimate of the spill’s trajectory. They have a general idea about oil behavior and understand that wind and current are important factors in a trajectory forecast. The technique

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FIGURE 11.1 Actual and predicted oil movement for the T/V Puerto Rican spill on day 5. Bounding circle represents uncertainty.6

depicted below is a learning tool. It can be very difficult to get a feel for oil spill modeling due to the complicated interactions of the various processes. The main characteristic of a “back-of-the-envelope” trajectory is the use of simplified assumptions for computational simplicity. In this type of estimate, there is no oil weathering, oil spreading, or mixing, and the current is assumed steady and persistent over time. Before using this type of approach, be mindful of these assumptions and recognize that this “best estimate” of the slick movement can have significant errors when extrapolating too far out in time. The calculation is explained in Figure 11.2 and involves plotting the wind drift and surface vectors on a nautical chart. The sum of the two vectors, the

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resultant vector, is the distance traveled by the spill (Figure 11.3). Oil drifts with the surface current at 100% of the current speed, but only at a fraction of the wind speed. Perhaps one of the best known rules of thumb in oil spill modeling is the “3% rule.”6,7 This rule has some theoretical basis and has

1. Plot the last known location of the spill on a nautical chart. Note the time of the observation. 2. Determine the direction and velocity of the surface current. Using oceanographic convention, the surface current is reported as the direction ‘to’. 3. Calculate the length of the surface current vector by multiplying the velocity by hours of drift. The hours of drift will be the total duration of the trajectory forecast period. For example, if the surface current velocity is 5 cm/s and the forecast period (hours of drift) is 3 hours, then the length of the surface current vector 0.6 km. 4. Draw a line on the chart extending from the last known location of the spill in the direction of the surface current. Use the compass rose on the chart to orient the line. The length of the line is the length of the surface current vector. In the example, the length of the line would be 0.3 nautical miles. To properly scale the line, use either the scale on the chart or use the latitude as a scale (1degree of latitude equals approximately 111 km). 5. Using the following table, collect the wind data. Time

Wind Period

No. of Hours

Wind Direction

Wind Velocity

*Leeway (0.03)

Vector Contribution km km km km

The time field is time of the observation (or forecast); wind period is start and end time for wind speed and direction; number of hours is duration in hours; wind direction is direction the wind is coming from; wind velocity is wind speed in miles per hour. For these calculations, 3% of the wind speed (0.03) is the leeway or wind drift factor for an oil spill. Multiply wind velocity by 0.03 and enter the value in *leeway field. The vector contribution is the length of the wind vector. It is calculated by multiplying *leeway by number of hours (similar to step 3). 6. Returning to the nautical chart, draw a line extending from the end of the surface current vector (from step 4) in the direction and distance of the first entry in the vector contribution field. At the end of this vector, draw a line in the direction and distance of the second entry in the vector contribution field. Continue this process until all wind vectors are plotted on the chart. 7. The predicted location of the slick is at the end of the last vector plotted. The time for the predicted location is the sum of the number of hours added to the time of the last reported location of the slick. Remember, the surface current is assumed constant for this time period

FIGURE 11.2 A simple prediction of the oil slick movement using vector addition of the components due to wind and current. Modified from USCG.16

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FIGURE 11.3 The sum of the surface current and wind drift vectors are the resultant oil movement.

been verified in the field and laboratory experiments.8,9 The 3% rule has been successfully used as wind drift factor or leeway for most fresh oil spills. Uncertainty can be calculated by considering other possible factors. For instance, suppose the spilled oil is a viscous residual fuel oil. The 3% rule represents average conditions, but the actual factor ranges from 1 to 6%.10 Viscous oils are often subject to overwash by waves. While submerged, viscous oils will only drift at the speed of the water current and, hence, will have a net lower drift speed than that given by the 3% rule. On the other hand, oil caught in the convergences in windrows will move faster than the average 3%.11 To use uncertainty in the rough estimate, do the calculation with 1% and then 6% of the wind speed. For a 6-hour forecast at a constant 7.7 m/s wind speed, the oil will travel between 1.6 km at 1% and 10 km at 6%. The resulting forecast will be a best guess of a 5 km (3%) displacement with an uncertainty spanning 1.6 km, 1%, to 10 km, 6%. Similar calculations could be employed for uncertainty in the location and direction and speed of the current and wind. Rather quickly, rough calculations using simple vector addition become unwieldy. At this point, serious consideration should be given to applying a more sophisticated approach to the problem. But what oil spill model(s) should be used? Without a grasp of the underlying principles and assumptions, the mere use of a model does not necessarily lead to a good or better answer. Depending on the spill incident, more than one model may be used because a particular model may perform better in certain situations. Performance varies because models assume different things, represent the physics in different ways, have different resolutions, are initialized differently, and often solve the equations in different ways. Therefore, one model’s simulation of a particular aspect of the spill fate and behavior may be rigorous, but it is likely to be weaker in other aspects. A key point to remember is that a model’s uncertainty will vary over time as environmental conditions change, and also spatially due to resolution and boundary limitations. Discussions of the strengths and weaknesses of oil spill models can be found in the literature.12-15 In general, oil spill models use a combination of Eulerian and Lagrangian methods to simulate oil behavior. The velocity field for winds and currents are derived using Eulerian techniques and are represented as individual velocity

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FIGURE 11.4 Examples of current velocity field (A) and particles (B).

vectors at fixed points in the model domain (Figure 11.4A). Oil patches are represented as individual particles that may be referred to as Lagrangian elements (Le’s), spillets, or splots.17,18 The paths of the particles are tracked as they move along the map (Figure 11.4B). Algorithms may vary but most models will need to account for winds, currents, turbulence, and spill details as input data to initialize and move the particles. In most instances, these processes are parameterized from other models or submodels, and they all come with their own uncertainty.

11.3. TRAJECTORY MODEL UNCERTAINTIES Oil spill models are very sensitive to errors in the initial input data, such as the details of the release and the wind and current forecasts. Furthermore, the mathematical calculations used to simulate oil movement are likely based on empirical approximations and assumptions and are subject to time step and grid limitations. Trajectory model uncertainty refers to changes in the forecast as a result of these errors. Unfortunately, quantitative assessment of the errors in trajectory modeling is difficult and limited. In addition, oil spills are notorious for occurring in areas where the environmental data are temporally and spatially incomplete. This leads to a forecast process that often relies on the forecaster’s subjective judgment and approximated input. The ranking of uncertainty as low, medium, and high for trajectory forecasts and the model inputs presented here are subjective. But the forecaster’s subjective judgment can be an invaluable resource, and, at least as anecdotal data suggest, it may be better than a model alone at estimating errors. The fact that the initial estimates are inaccurate and the model itself has inadequacies leads to forecast errors that grow over time. For this reason shortrange forecasts usually have less error than long-range forecasts (Table 11.1). For larger spill events, the model input data should contain fewer errors due to better field observations, such as remote sensing and visual overflights of the spill. The result is that the multiple forecasts produced daily should actually

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TABLE 11.1 Uncertainty for Trajectory Forecasts Oil Spill Trajectory Forecast

Uncertainty

24-hrs

Low e Medium

24 to 48-hrs

Medium

48 to 72-hrs

Medium e High

72þ hrs

High

improve over time. On the first day of a big spill, the uncertainty for the initial forecast will likely range from low to high. On the second day, with more onscene observations, the uncertainty typically ranges from low to medium. By the third day, the uncertainty should be lower. A sophisticated model with extensive data input requirements does not necessarily produce a better forecast. There are an optimal number of input parameters that will determine the total model uncertainty. The model output is only as good as the largest error input. This is the reason that the performances of complex models are often no better, and sometimes worse, than the predictions of the simpler models. The back-of-the-envelope calculation in Section 2 used only a one-time surface current measurement with a constant speed and direction lasting for a few hours. This approach has serious limitations in regard to time and spatially varying currents. The advantage is that the results can be quickly passed on to the decision maker. In contrast, an oil spill model that uses forecast currents from a hydrodynamic model with extensive input data requirements (e.g., real-time salinity and temperature data at various depths) may not yield a successful result or be as useful because, for most emergency spill incidents, the input data to initiate a three-dimensional hydrodynamic model is not available in a timely manner. In fact, the three-dimensional model may have to rely on historical data rather than input conditions specific to the spill event. Complex models work well only when the extensive data requirements are satisfied, which rarely can be fulfilled at an oil spill response.

11.3.1. Release Details In 1987, the barge Hana encountered rough seas while transporting Bunker C fuel oil to the Maui power plant in Hawaii. On the southwest side of Molokai Island, the barge reported spilling approximately 11,360 liters of oil. At the time of the incident, the wind forecast was northeast at 13 to 15 m/s for the next 24 hours. Using this information, the trajectory forecast did not indicate any beaching of the oil and indicated the slick would move to the southwest and out to sea. The next day, “a lot of oil” came ashore on Oahu. How could the

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TABLE 11.2 Uncertainties for Oil Spill Release Details Release Details

Uncertainty

Location

Low e Medium

Time

Low e Medium

Day

Low

Night

Low e Medium

Oil Properties

Medium e High

Potential Spill Volume

Low e Medium

Actual Spill Volume

High

Leak Rate

High

trajectory be so wrong? First, the trajectory forecaster was given incorrect information about the release. In fact, the location of the actual release site was off by 18.5 km. Second, the spill volume was later determined to be over 227,000 liters of oil and not 11,360 liters as initially reported. The larger spill volume affected the trajectory as more oil was spread out over a larger area. Third, the overnight winds were actually from the east and not the northeast as initially forecasted. Unfortunately, there is no reliable way to quantify the errors related to the details of a release. Table 11.2 provides uncertainty for oil spill releases based on decades of experience. If the spill occurs during daylight and there is an experienced overflight observer who can provide coordinates for the spill with a description of the slick, confirmation about the likely spill volume, and a source, then the uncertainty is relatively low. Conversely, release details for a spill occurring at night during a storm or in fog without confirmation from an experienced observer will likely carry a high uncertainty.

11.3.2. Wind Discussions with the local meteorologist can provide valuable insight about the availability of atmospheric models for a specific area and the model limitations. Ideally, time-dependent and spatially varying wind field from an atmospheric model is imported directly into the oil spill model. However, careful consideration is needed before bringing in the wind forecast. Localized phenomena, which are at a smaller scale than the resolution of the atmospheric model, may have a great influence on the oil spill trajectory. Oil spills spread out quickly, but, even for the larger spills, the slick dimensions are frequently smaller than

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283

the resolution of many atmospheric models. This means, for instance, that the wind at the source of the spill could be different from the wind at the leading edge of the slick. A coarse-resolution atmospheric model may have only one wind vector to represent the entire spill area, much like the back-of-theenvelope calculation in Section 2. Table 11.3 provides examples of typical atmospheric model resolutions. Nested grid systems use a low-resolution, global weather model to provide boundary conditions for high-resolution, regional models. A review of a specific atmospheric model will likely reveal qualitative errors. The other challenge is the time resolution of models. The oil trajectory model may have time steps of 15 minutes, but the wind model may be resolving winds at every hour. For most spills in estuaries, the regional models are suited for oil spill trajectory modeling. But even with regional models, local effects, such as the landesea breeze, may not be sufficiently resolved. This can wreak havoc with a trajectory forecast. Shoreline oiling is enhanced with an onshore wind and a falling tide (Figure 11.5A); accurately forecasting the onshore wind is important to getting the trajectory forecast correct. As the tide ebbs, the intertidal areas are exposed, and, if the wind is blowing onshore, the oil adheres and smears down the beach face (Figure 11.5B). An example of the landesea breeze phenomenon and the difficulty forecasting the timing of shoreline oiling occurred during the 1990 T/V American Trader incident. The vessel ran over its anchor, punctured the hull, and spilled over 1.5 million liters of North Slope crude oil. The spill occurred about 1.5 km off Huntington Beach, California. The net oil slick drift was small due to light winds and a weak surface current. The trajectory forecast repeatedly missed the timing of the shoreline oiling due to the interaction of the landesea breeze and tide. For a few days, the tides and winds were synchronized such that the falling tide coincided with an offshore wind due to the sea breeze. The oil floated up the beach face with the rising tide, but the oil did not adhere as an offshore wind (land breeze) pushed the oil out to sea. This pattern continued for several days

TABLE 11.3 Grid Resolutions of Atmospheric Models (Modified from Kalnay19) Atmospheric Models

Grid Resolution

Climate

Several hundred kilometers

Global weather

50e100 km

Regional meso-scale

10e50 km

Storm scale

1e10 km

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FIGURE 11.5 Falling tide and onshore wind (A), and shoreline oiling due to falling tide and onshore wind (B).

until the tides and land breeze were no longer synchronized, and then the oil stranded on the beach. When local details are important, a higher spatial resolution model should be used and the uncertainty should be carefully conveyed. If a suitable atmospheric model is unavailable, the marine forecaster can provide details about the wind forecast and its likely error bounds. This requires a good verbal briefing by the meteorologist. The meteorologist can provide information about wind shift timing, the strength of the pressure gradient, location of high/low fronts, and local effects. The result can be a wind data file containing the meteorologist’s best estimate and error estimate, which can then be fed directly into the model. As an example, the wind forecast may indicate wind from the south at 7.7 m/s for 12 hours, becoming southwest at 5 m/s. This data is used to compute the best estimate of the wind and is entered into the spill model. If the meteorologist indicates that the forecast wind shift could be off by 3 hours, the wind direction off by 20 degrees, and the speeds by 2.5 m/s, the original wind file is modified or an additional file is created with this data. This represents uncertainty in the wind forecast. The accuracy of the forecast depends, among other things, on special weather features, length of the forecast period, and ability of the forecasters to localize their prediction to the spill site (Table 11.4). Optimum wind forecast periods are usually between 6 and 24 hours. For a wind forecast beyond five days, serious consideration should be given to using climatological winds and generating a probability guidance product as a trajectory forecast.

11.3.3. Current In some regions, oil spill modelers have the capability to import time and spatially varying surface current forecasts from ocean circulation models. These models are updated every few hours in a manner similar to atmospheric models. Figure 11.6 shows the expected movement of a hypothetical spill from a continuous release of oil. In this scenario, there are no winds, or turbulent

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285

TABLE 11.4 Uncertainty for the Surface Wind Forecast Surface Wind Forecast

Uncertainty

24-hr

Low e Medium

48-hr

Medium

72-hr

Medium e High

96þhr

High

mixing processes. There are only surface currents from five different sources: the Global Navy Coastal Ocean Model,20the Global Navy Layered Ocean Model,21 the Global Hybrid Coordinate Ocean Model,22 California High Frequency Radar,23 and the Global Sea Surface Height (SSH 2010) model.24 The NCOM, NLOM, and HyCOM models have similar physics but were initialized with different data, have different grid resolutions, and different numerical methods. The HFR and SSH model forecast currents from observations. It is interesting to note that the HyCOM and NLOM circulation models move the spill in opposite directions, whereas in the short term, a consensus

FIGURE 11.6 Particle tracking of a hypothetical spill using multiple current models.

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begins to take shape with the HFR, SSH, and NCOM forecasts as the oil is moved offshore. The five-model runs display the uncertainty in the trajectory forecast using just the surface currents from different sources. Further exploration by the forecaster is needed to seek out an explanation of why the model runs differ. Another word of caution: because a model yields results that compare favorably with observations one day or one week, doesn’t mean it will do well another day or week. For example, the model may perform better if the surface wind speed is within a specific range. In addition, a model that does well in a certain region may not do well in another region. In coastal areas without a regional circulation model, simulating the current may become a challenge. Three-dimensional hydrodynamic models will require extensive oceanographic data for input. In a spill response situation, acquiring relevant real-time data is highly unlikely. To work around this problem, modelers may use a combination of real-time observations (e.g., overflights), astronomical tidal predictions, and historical data for the ocean currents, along with a simplified approach to generating currents. All of this takes time to collect and enter into a model. In an emergency response, decision makers need a forecast quickly. Typically, simplified two-dimensional and one-dimensional models can be more easily calibrated to fit the actual movement of the oil from day to day. It is not unusual that these simple approaches that calibrate currents to daily observations provide better results than large sophisticated models that are difficult to adjust and calibrate. Large, complicated models are often calibrated with historical records that are often short and are collected under environmental conditions very different from those of the spill. Table 11.5 provides a subjective assessment of the uncertainty in the surface circulation of various water bodies. Closer inspection of a specific hydrodynamic model will likely reveal quantitative error assessment. Many rivers are gauged and controlled by locks and dam systems, so that the uncertainty in the predicted flow is generally low. If the river forecaster provides uncertainty in the flow, this information can be included in the analysis. For spills that occur in tidal-driven estuaries or an ungauged river system, the uncertainty in direction is relatively low (Table 11.5), but the strength of the current may not be accurately known; hence, the overall uncertainty is low to medium. A few coastal areas in the United States have the Physical Oceanographic Real-Time System network that combines real-time monitoring of the water level and meteorological conditions with numerical circulation models for water-level forecasting. The inner continental shelf extends from the shoreline to where the depth increases to about 120 m. In this area, most of the oil releases result in shoreline impacts, and the uncertainty, unfortunately, is medium to high (Table 11.5). Currents in this zone are dominated by long-shore winds, freshwater runoff, and tides. In the 2002 oil recovery operation of the sunken vessel SS Jacob Luckenbach, all of these forces were apparent over the course of the oil removal. The vessel sank in 1953, approximately 30 km southwest of the

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TABLE 11.5 Uncertainties in Surface Current Surface Current

Uncertainty

River Gauged

Low

Un-gauged

Low e Medium

Lake

Low e Medium

Shallow water lagoon

Low e Medium

Tidally dominated estuary

Medium

Inner continental shelf

Medium e High

Deep ocean (off continental shelf)

High

Under ice cover

High

Golden Gate Bridge, San Francisco, California. During the course of the operations, when the winds were particularly light, smaller slicks moved to the south and, a few hours later, moved to the north with a weak tide. Without a dominant mechanism forcing the circulation, it became difficult to predict the overall transport of the oil. In contrast to the T/V Puerto Rican incident, the inability to predict strong, large-scale forces responsible for the abrupt changes in the current direction and speed resulted in an erroneous forecast on the scale of a few kilometers over the time span of a few hours. The deep ocean, off the continental shelf, is dominated by drifting oceanic eddies. These density-driven currents have a slow net drift and typically do not affect the currents on the inner shelf. Therefore, their uncertainty is of less importance for most oil spills unless they occur where the shelf is short or nonexistent (e.g., Hawaii). Figure 11.7 shows a snapshot of the SSH-derived currents with large oceanic eddies with current velocity ranging from 5 to 13 cm/s.

11.3.4. Turbulent Diffusion To the spill modeler, processes smaller than the resolution of the model and timescale motions are most often represented as turbulent mixing and present a challenging problem in oil transport. Virtually all oil spill models use simplified formulas to simulate the horizontal and vertical “mixing” of oil. This term could also be considered the “ignorance coefficient” because it represents the effects of mechanisms that are poorly understood and represented.26 A common approach is to represent turbulence using a constant diffusion

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FIGURE 11.7 SSH derived currents. Modified from CoastWatch.24

coefficient,26 but there are other options.27,28 The effects of turbulence will mask small errors in the surface circulation and winds and smooth out the effects of subgrid-scale processes (e.g., Langmuir circulation and convergence zones). The consequence of this turbulent diffusion approach is a loss of resolution that increases over time.

11.3.5. Oil Weathering The rate and degree with which an oil weathers affects its wind-drift factor (or leeway) and hence, its trajectory. As oil weathers, its chemical properties change. Density will increase as the light fractions evaporate, and both viscosity and density will increase if the oil emulsifies. These property changes will affect wind drift and the oil’s ability to disperse. Uncertainty in weathering predictions is generally lower for spills of light refined products, which rapidly dissipate and do not form stable emulsions (e.g., gasoline and diesel). A few crude oils have also been studied, both in the lab and in field trials for weathering behavior. This extra information makes prediction about their behavior more reliable. For other types of oils, such as intermediate fuel oils, where the available data only vaguely characterizes their weathering characteristics, uncertainty is high for the transport, fate, and effects of the oil, and the uncertainty grows over time. For the best estimate trajectory, the modeler may select the oil in the model that best represents the product spilled. To define uncertainty bounds, the oil can be modeled as a conservative quantity, which is neither evaporated nor dispersed into the water column. Field observations can be used to help calibrate weathering of the oil, which in turn will help improve trajectory estimates. The slick drift factor or leeway changes over time because, initially, the spill appears as a large cohesive film but eventually tears apart into smaller patches or tarballs. Table 11.6 shows different wind drifts for various oils and the

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TABLE 11.6 Wind Drift Uncertainty and Distance Traveled for Various Oils Oil Type

No. of Hours

Wind Velocity (m/s)

Wind Drift or Leeway (%)

Vector Contribution (km)

Gasoline

24

7.7

3 to 4

22e30

Diesel

24

7.7

3 to 4

22e30

Fresh IFO

24

7.7

3

22

Fresh crude oil

24

7.7

3 to 4

22e30

Weathered IFO

24

7.7

2 to 3

13e22

Emulsified oil

24

7.7

1 to 2

5.5e13

Scattered tarballs

24

7.7

0.5 to 2

3.7e13

distance likely to travel with a 7.7 m/s wind for 24 hours. The drift factors are estimates based on the modeler’s experience matching visual observations of the slick with the trajectory forecast. For oils with ranges, like the scattered tarballs, this represents the uncertainty in the wind drift and can be modeled by randomly selecting a slick drift between 0.5 and 2% of the wind speed for each patch of oil at each model time step. Since the wind speed is not likely constant, this modeling technique can also simulate wind gusts. Weathering of oil will also determine the type and severity of impacts expected from the oil spill and, consequently, the amount of response personnel and equipment. For example, if the expected impact from a spill were scattered coin-sized tarballs every 10 m along the shoreline, the cleanup response effort would be very different than that for a spill resulting in a 2-m-wide band of emulsified oil. Therefore, it is important to not only forecast where and when oil will go but what type of impact to expect. Any uncertainty related to the fate of the oil should be conveyed with the trajectory forecast.

11.3.6. Ensemble Forecasting The 1976 Argo Merchant grounding off Nantucket Island, Massachusetts, was one of the most studied oil spills in history with over 200 scientists participating in the response effort. Five independent research teams provided operational forecasting of the oil distribution.29,30 The on-scene commander was presented with five forecasts; each displaying different trajectories. This was the beginning of ensemble forecasting in spill response. Ensemble forecasting involves generating a collection of forecasts based on varying initial conditions, model parameters, and physics. The forecasts can be a compilation of outputs from different models31 or from the same model using different boundary conditions

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and data choices32,33. Ensemble forecasting has developed into the primary means of presenting trajectory forecast uncertainties. The results of ensemble forecasting must be communicated so that the decision maker can interpret and understand the information. Figure 11.8A shows an example a visual graphic of the trajectory forecast that uses the best available input data. Here, particles simulating oil movement are converted so that darker contours indicate a higher concentration of particles.4 The forecast provides only one prediction of the future, with no information about uncertainty. Decision makers are likely to move much of the available oil recovery and protection resources to the area where the contour contacts the shoreline. This is often the type of forecast requested by emergency responders to support operational decisions, even though it is not the complete picture needed for optimum response. Figure 11.8B shows a visual representation of ensemble forecasting. The confidence limit represents the output from a series of trajectory forecasts. In addition to output from multiple models, the forecaster may have used his or her subjective judgment and considered other plausible, what-if, scenarios. The scenarios may have included what if the weather forecast of a frontal passage is off by 12 hours; the release time is off by 1 hour, and the surface current speed off by 20 cm/ s? How would this affect the oil movement? The confidence limit is a visual cue to the decision maker that represents the boundary of the output from multiple models and/or output from multiple runs from one model. The product conveys the likely locations of oil and provides responders with not only a best estimate trajectory, but also other possibilities that could result in a significant threat.

FIGURE 11.8 tainty (B).

Examples of a trajectory forecast without uncertainty (A) and with uncer-

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11.3.7. Communicating Trajectory Forecast Uncertainty Communicating the uncertainty of the trajectory forecast is critical to users. It allows them to make decisions based on the reliability of the forecast and the consequences from inaccuracies in the forecast. The general public is familiar with probabilities associated with forecasts thanks in large part to National Oceanic and Atmospheric Administration’s (NOAA’s) National Weather Service producing forecasts for hurricanes, tornadoes, and precipitation in terms of probabilities. However, for spill movement, it is not possible to compute the uncertainty probabilities for where and when the oil will come ashore. The number of spills with adequate field observations is not sufficient for statistical analysis. Well-documented marine oil spills with robust data sets are the exception, and experimental spills in the ocean are quite few in number. Ocean-surface current drifter studies cannot provide probabilities of the oil movement for any given day, under any given condition. Given the environmental variability and model shortcomings, there is not enough data to generate probabilities for oil spill trajectory forecast. As a result, the oil spill trajectory forecast uncertainty must be conveyed in a way other than with probabilities. Galt proposed a digital standard that presents uncertainty of the trajectory forecast that alleviates the “language of probabilities” problem.4 The trajectory model is first used with the best available input data. It is then run a second time to set the uncertainty or confidence bounds. In the uncertainty model run, each of the particles can be thought of as a centroid of an independent spill and is assigned its own wind and current data. The resultant spread of the particles represents an ensemble of spills. The distribution is not related to oil concentration but represents an ensemble of different spills. However, to make this work, the expert forecaster needs to specify uncertainty bounds for the currents, winds, and other various inputs parameters. A standardized method does not exist, and the approach relies on the forecaster’s subjective judgment. Figure 11.9 shows an example of the NOAA standard for visually representing uncertainty. The graphic is designed to express the amount of complexity and uncertainty in a particular forecast without presenting probabilities. Postprocessing software, independent of the oil spill model, was used to generate the graphic. The product includes a base map, contoured particles, and an outer confidence limit. The bottom of Figure 11.8 contains a scale with eight patterns of oil distribution. By looking at the scale bar, emergency responders can quickly determine how the light, medium, and heavy contours relate to the oil distribution observed on-scene and, from this, develop response options. Regardless of the way uncertainty is expressed to the decision maker, it needs to be done. To do this successfully, the forecaster realistically expresses uncertainty for every input parameter as well as the numerical uncertainty inherent with the model. This is a daunting task, particularly for estimating uncertainty with oil type, oil volume, spill location, spill time, and oil slick observational data.

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FIGURE 11.9 Sample trajectory forecast product.

11.4. TRAJECTORY FORECAST VERIFICATION How accurate are oil spill models? The question is an obvious one but difficult to answer. The back-of-the-envelope calculation presented in Section 2 is a good place to start. For demonstration purposes, the hypothetical calculation

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or forecast indicates that the oil spill remains offshore. Field observation data is needed for verification, and for this demonstration, the location of every piece of oil is known. Suppose the field data indicates the bulk of the oil remained offshore and only a small amount of oil came ashore. Was the model or, in this case, the calculation accurate? The skills of a trained forecaster in this process are important. The forecaster can make multiple calculations or multiple models runs and include uncertainty. If the small amount of oil onshore was within the uncertainty of the calculation, then the forecast was accurate. Model errors can occur for various reasons and are not consistent over time or space; therefore, it is important to have a skilled forecaster verify the model output. Oil spill models cannot precisely predict the movement of every patch of oil. Some models may perform better than others under different conditions, but, inevitably, oil spill models will be wrong. Quantifying the model’s error is not easy due to the constraints found at most oil spill incidents (e.g., observations of surface oil that are both temporally and spatially incomplete). This contrasts with forecasting in other fields. For example, NOAA’s National Hurricane Center has precise metrics to measure hurricane forecasts versus observations. At this time, precise metrics to measure oil spill trajectory forecasts do not exist. Ideally, a formal methodology would be developed for the comparison of the trajectory forecast with observed field data. Such a comparison would provide a means for assessing the model’s performance relative to other spill models. A challenge for the oil spill trajectory forecaster is determining whether a model, despite its uncertainties, can be used to make a useful forecast. The challenge for decision makers is to determine how to use the forecast and its inherent uncertainties to make an informed decision. This section provides a brief description within which a forecaster and decision maker can determine a model’s performance for accurately predicting the oil movement. Field observation data are the basis of model verification. However, collecting data from field experiments and during an emergency response is not simple. It is extremely difficult and often illegal or impossible to stage experimental oil spills in the open ocean. If permission is granted, the experiments are small-scale and conducted over a short time period: usually hours, not the days needed for characterizing a specific set of conditions. This makes it difficult to test models against field data due to the varying environmental conditions and a mismatch between model scales and experiment scales. Attempts to use data from emergency response are always problematic because the on-scene observations of the oil distribution contain significant errors. It is not always known how much of the oil was spotted by the observer or what part of the slick was seen. Overflights of the spill may not be conducted due to poor weather or aircraft availability resulting in large time gaps between observations. Observational errors can also result from observers reporting “false positives” such as kelp beds, silt plumes, algae, and jellyfish, to name but a few. Remote-sensing techniques are imperfect as well because of limitations of the

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sensor, availability of assets (aircraft and satellite), and weather conditions. Due to these constraints, other approaches need to be developed to evaluate the performance of oil spill models. A common approach for evaluating an oil spill model’s performance is a hindcast. In a hindcasting, the release details of wind and current data at the time of the incident are entered into a model to see how well the output matches the reported location of oil. If the hindcast accurately shows the oil movement as known to have occurred, the model is considered successful. The comparison between the hindcast and observations mostly consist of visual inspection rather than statistical evaluation due to the problems with collecting oil observation data.34-37 Hence, there is a need for an experienced forecaster who understands the uncertainty associated with oil fate and observations. Oil observations can be used to make model adjustments so that the hindcast matches the observed distribution of the oil. This is model calibration, and an example can be found in Turrell.38 Parameters within the model are calibrated to match the movement of the spill. Again, the process is subject to error due to problems in collecting field observations and requires a knowledgeable forecaster who knows which model parameters to modify for a best fit. Other approaches are to compare model estimates and measurements to field data on a spill-by-spill basis and then calibrate a model with that comparison.17,39 However, caution is needed in this approach to avoid using a calibrated model for different geographic locations and environmental conditions. Every spill is a unique event, and every location has its own environmental challenges. The remaining technique for evaluating oil spill model performance that appears in the literature is validation. Oil spill trajectory models can never be conclusively validated because they never completely simulate reality.40 In general, validated models are those that have shown correspondence to experimental data. A more accepted approach is a model evaluation process in which the results of the model are determined to be sufficient and, that despite the uncertainties, can be used in decision making.41 In all cases, the model’s documentation should provide clear understanding of why and how the model can be used.

11.4.1. Diagnostic Verification Forecast verification is an integral part of the forecast process in an emergency response as the spill situation and environmental conditions can change very rapidly. As an example, the vessel(s) involved in the accident may be unstable. A submerged pipeline may have a small continuous leak with a potential for a much larger release of oil. The weather is constantly changing, and the currents are changing with tides and coastal events. Therefore, the model results need to be continuously compared to observed data by a skilled forecaster during a spill response. The forecaster needs to compare the predictions with field reports and decide if the model parameters are sufficiently correct or

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require modifications to match the field data. Calibrating the model(s) with the previous day’s overflight observations does not ensure that the forecast will match the next day’s overflight, but it will give the forecaster an idea of which model parameters to monitor. During the T/V Puerto Rican incident, discussed in Section 1, daily adjustments were made to the model, but the forecasters never anticipated a reversal in the surface current, not even with a predicted wind shift. The more serious the consequence of forecast error, the more important monitoring and collection of field data. Essentially, the forecaster is calibrating the model to the spill during the response. Figure 11.10A shows an example of a map of the oil distribution for an oil spill. The map was used to verify the spill model. The model is run from the start of the spill and stopped at the time of the overflight observation. Since no model can simulate reality perfectly, visual inspection of the overflight map and the model run likely indicates differences in the oil location. Adjustments are likely made to model parameters so that the model matches the overflight map. The calibrated model can then be used to generate a forecast (Figure 11.10B). In a spill, forecast verification is an integral part of the forecast process.

11.5. SUMMARY AND CONCLUSIONS In this chapter, the fundamentals of uncertainty related to oil spill fate and transport forecasting were presented. The T/V Puerto Rican incident was used as an example of the importance of uncertainty in the trajectory forecast. This event showed that an estimate of the uncertainty in the forecast provides more information than a single best estimate that uses the initial model input data. Decision makers, who only consider the single best estimate and largely ignore the forecast uncertainty, tend to make less than optimal decisions. If an incident similar to the T/V Puerto Rican were to occur today, close monitoring of the spill by field observations (e.g., overflights, surface current buoys, and remote sensing) and communicating the trajectory forecast uncertainty will help responders make more informed decisions and avoid problems. Presenting both the best estimate and the uncertainty in the trajectory forecast provides the decision maker the opportunity to support a minimumregret decision-making strategy.42 At nearly every spill, there is always a limited amount of resources available for shoreline protection and cleanup. With both the best estimate and uncertainty, decision makers can weigh the wisdom of directing the cleanup toward the most likely spot for oil as opposed to defending less likely but more environmentally important locations.43,44 Overflight operations can conduct more intelligent surveillance, using uncertainty or confidence forecast boundaries to determine their flight paths and prevent any oil from sneaking past the response efforts. The public can be provided with a more realistic representation of what is known about the slick location, avoiding false expectations concerning trajectory accuracy.

296 PART | IV Behaviour of Oil in the Environment and Spill Modeling

FIGURE 11.10 Map of oil distribution (A) and oil spill trajectory forecast (B).

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297

The conclusions from this chapter are simple but important. Oil spill fate and transport forecasting contains errors and, under certain circumstances very large errors. As a result, it is important to convey uncertainty bounds with the forecast. Good field data and a skilled forecaster are needed to adequately calculate, portray, and communicate the uncertainty in the predictions.

ACKNOWLEDGMENTS The findings and conclusions in this chapter are those of the author and do not necessarily represent the views of the National Oceanic and Atmospheric Administration (NOAA). This chapter arose from a series of training conducted by NOAA for the U.S. Coast Guard. We hope this chapter performs the function of introducing relevant principles of modeling uncertainty to the next generation of spill responders. The author would like to acknowledge Glen Watabayashi, Dr. Alan Mearns, and Mark Dix for their assistance in preparing this chapter. Thanks also to Jeffery Lankford for kindly providing Figure 11.1.

REFERENCES 1. PRBO (Point Reyes Bird Observatory). The Impacts of the T/V Puerto Rican Oil Spill on Marine Bird and Mammal Populations in the Gulf of Farallones. 2. FMSA (Farallones Marine Sanctuary Association), Coastal Ecosystem Curriculum: Oil Spills. http://www.farallones.org/documents/education/oilspills.pdf, 2002. 3. Breaker LC, Bratkovich A. CoastaldOcean Processes and Their Influences on the Oil Spilled of San Francisco by the M/V Puerto Rican. Mar Environ Res 1993;1003. 4. Galt JA. Uncertainty Analysis Related to Oil Spill Modeling. Spill Sci Techn Bull 1998;231:4. 5. Lehr WJ. Personal Communication to Debra Simecek-Beatty; February 8, 2010. 6. Smith CL. Determination of the Leeway of Oil Slicks. In: Wolfe DA, Anderson JW, Button DK, Malins DC, Roubal T, Varanasi U, editors. Fate and Effects of Petroleum Hydrocarbons in Marine Ecosystems and Organisms, 351. New York: Pergamon Press; 1976. 7. Huang J. A Review of the State-of-the-art of the Oil Spill Fate/Behavior Models. IOSC 1983;313. 8. Wu J. Sea-Surface Drift Currents Induced by Wind and Waves. J Phys Oceanogr 1983;1441. 9. Fallah MH, Stark RM. Random Drift of an Idealized Oil Patch. Ocean Eng 1976;89. 10. Lehr WJ, Simecek-Beatty D. The Relation of Langmuir Circulation Processes to the Standard Oil Spill Spreading, Dispersion and Transport Algorithms. Spill Sci Tech Bull 2000;247. 11. Leibovich S. Surface and Near-surface Motion of Oil in the Sea, Contract 14-35-0000130612, Minerals Management Service, U.S. Department of Interior; 1997. 12. Yapa PD, Shen HT. Modeling River Oil-SpillsdA Review. J Hydr Res 1994;765. 13. ASCE Task Committee on Oil Spills. State-of-the-Art Review of Modeling Transport and Fate of Oil Spills. J Hydraulic Eng 1996;594. 14. Cekirge HM, Palmer SL. Mathematical Modeling of Oil Spilled into Marine Waters. In: Brebbia CA, editor. Oil Spill Modeling and Process. Southhampton, UK: WIT Press; 2001. 15. French-McCay DP. Oil Spill Impact Modeling: Development and Validation. Environ Toxicol Chem 2004;2441. 16. USCG, United States Coast Guard National Search and Rescue Manual, Vol. II: Planning Handbook; 1991.

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17. French-McCay D. Development and Application of Damage Assessment Modeling: Example Assessment for the North Cape Oil Spill. Mar Poll Bull 2003;341. 18. Beegle-Krause CJ. Advantages of Separating the Circulation Model and Trajectory Model: GNOME Trajectory Model Used with Outside Circulation Models. AMOP 2003;825. 19. Kalnay E. Atmospheric Modeling, Data Assimilation, and Predictability. Cambridge, UK: Cambridge Univ. Press 2003. 20. NCOM (Navy Coastal Model), Naval Research Laboratory. http://www7320.nrlssc.navy.mil/ global_ncom, 2010. 21. NLOM (Global Navy Layered Model), Naval Research Laboratory. http://www7320.nrlssc. navy.mil/global_nlom, 2010. 22. HyCom (Global Hybrid Coordinate Ocean Model), National Ocean Partnership Program. http://www.hycom.org/, 2010. 23. HFR (California High Frequency Radar), Southern California Coastal Ocean Observing System. http://sccoos.org/data/hfrnet, 2010. 24. CoastWatch. http://coastwatch.noaa.gov/, 2010. 25. NRC (National Research Council). Principles for Evaluating Chemicals in the Environment. National Academy of Sciences; 1975. 26. Okubu A. Diffusion and Ecological Problems: Mathematical Models. Dordrecht, Holland: Springer-Verlag; 1980. 27. Elliot AJ, Dale AC, Proctor R. Modeling the Movement of Pollutants in the UK Shelf Seas. Mar Poll Bull 1992;614. 28. Thibodeaux L. Chemodynamics: Environmental Movement of Chemicals in Air, Water, and Soil. New York, NY: John Wiley & Sons; 1979. 29. Grouse PL, Mattson JS. The Argo Merchant Oil Spill, National Oceanic and Atmospheric Administration. Boulder, CO: Environmental Research Laboratory; 1977. 30. Pollack AM, Stolzenbach KD, Investigations in Response to the Argo Merchant Oil Spill, Sea Grant Program, Report No. MITSG 78-8. Cambridge, MA: Crisis Science; 1978. 31. Daniel P, Dandin P, Josse P, Skandrani C, Benshila R, Tiercelin C, et al. Towards Better Forecasting of Oil Slick Movement at Sea Based on Information from the Erika. In: Proc. Third R&D Forum on High-Density Oil Spill Response. Brest, France: Int’l. Maritime Org; 2002. 32. Sebastiao P, Guedes Soares C. Uncertainty in Predictions of Oil Spill Trajectories in a Coastal Zone. J Mar Sys 2006;257. 33. Sebastiao P, Guedes Soares C. Uncertainty in Predictions of Oil Spill Trajectories in Open Sea. Ocean Eng 2007;576. 34. Venkatesh S. Model Simulations of the Drift and Spread of the Exxon Valdez Oil Spill. Atmosphere-Ocean 1990;90. 35. Venkatesh S, Crawford WR. Spread of Oil from the Tenyo Maru, off the Southwest Coast of Vancouver Island. Natural Hazards 1993;75. 36. Proctor R, Elliot AJ, Flather RA. Forecast and Hindcast Simulations of the Braer Oil Spill. Mar Pollut Bull 1994;219. 37. WDOE (Washington Department of Energy), Puget Sound Trajectory Analysis Planner (TAP) Technical Documentation. Spill Prevention, Preparedness, and Response Program, Publication#03-08-007; 2003. 38. Turrell WR. Modeling the Braer Oil SpilldA Retrospective view. Mar Pollut Bull 1994;4. 39. Vethamony PK, Sudheesh MT, Babu S, Jayakumar R, Manimurali AK, Saran LH, et al. Trajectory of an Oil Spill of Goa, Eastern Arabian Sea: Field Observations and Simulations. Environ Pollut 2007;438.

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40. Anderson MG, Bates PD. Model Validation Perspectives in Hydrological Science. New York, NY: John Wiley & Sons; 2001. 41. Pascual P, Stiber N, Sunderland E. Draft Guidance on the Development, Evaluation, and Application of Regulatory Environmental Models. U.S. Environmental Protection Agency, http://www.epa.gov/crem/knowbase; 2003. 42. Galt JA. The Integration of Trajectory Models and Analysis into Spill Response Information Systems. Spill Sci Tech 1997;23. 43. Wirtz KW, Liu X. Integrating Economy and Uncertainty in an Oil-Spill. DSS: The Prestige Accident in Spain. Estuar Coast Shelf Sci 2006;525. 44. Wirtz KW, Baumberger N, Adam S, Liu X. Oil Spill Impact Minimization Under Uncertainty: Evaluating Contingency Simulations of the Prestige Accident. Ecolog.l Econ 2007;417:61.

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Part V

Physical Spill Countermeasures on Water

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Chapter 12

Physical Spill Countermeasures Merv Fingas

Chapter Outline 12.1. 12.2. 12.3. 12.4.

Containment on Water 303 Skimmers 315 Sorbents 325 Manual Recovery 329

12.5. 12.6. 12.7. 12.8.

Temporary Storage Pumps Separation Disposal

330 332 334 335

12.1. CONTAINMENT ON WATER Containment of an oil spill is the process of confining the oil, either to prevent it from spreading to a particular area, to divert it to another area where it can be recovered or treated, or to concentrate the oil so that it can be recovered, burned, or otherwise treated. Containment booms are the most frequently used piece of equipment for containing an oil spill on water. Booms are generally the first equipment mobilized at a spill and are often used throughout the operation. This portion of text covers the types of booms, their construction, operating principles and uses, as well as how they sometimes fail. It also covers ancillary equipment used with booms, sorbent booms, and special-purpose and improvised booms. The topic of fire-resistant booms for use when burning oil on water is covered in the subsection on in-situ burning.

12.1.1. Types of Booms and Their Construction A boom is a floating mechanical barrier designed to stop or divert the movement of oil on water. Booms resemble a vertical curtain with portions extending above and below the water line. Most commercial booms consist of four basic components: a means of flotation, a freeboard member (or section) to prevent oil from flowing over the top of the boom, a skirt to prevent oil from being swept underneath the boom, and one or more tension members to support the entire boom. Booms are constructed in sections, usually 15 or 30 m long, with connectors installed on each end so that sections of the boom can Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10012-7 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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be attached to each other, towed, or anchored. A section of a typical boom is shown in Figure 12.1. Some typical commercial booms are illustrated in Figure 12.2. The floats determine the buoyancy of the boom and the level above the water surface. Floats are located along the center line, outboard, on one side, or on outriggers. Booms either have solid floats or the boom itself is inflatable. Solid floats are usually made of a plastic foam such as expanded polyurethane or polyethylene and are segmented or flexible so that the boom can ride the surface of the waves. Inflatable booms are either self-inflating or are inflated using a powered air source. They require little storage space but are generally less rugged than booms with fixed floats. The freeboard member is the portion of the boom above the water, which prevents oil from washing over the top of the boom. The term freeboard is also used to refer to the height from the water line to the top of the boom. The skirt is the portion of the boom below the floats, which helps to contain the oil. It is usually made of the same types of fabric as the freeboard member and the covering of the floats. Typical materials include polyvinyl chloride (PVC), polyester, nylon, or aramid, sometimes coated with a spray-on protector or another covering such as PVC, polyester, polyurethane, nitrile, and polyether urethane to resist degradation from oil.1 Most booms are also fitted with one or more tension members that run along the bottom of the boom and reinforce it against the horizontal load imposed by waves and currents. Tension members are usually made of steel cables or chains but sometimes consist of nylon or polyester ropes. The boom fabric itself is not strong enough to withstand the powerful forces to which booms are subjected, except in protected waters. For example, the force on a 100-m long section of

Means of Flotation

rd

boa

Free

Weighted Ballast

Skirt Tension Member

FIGURE 12.1 Basic boom construction.

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305

FIGURE 12.2 Typical commercial containment booms.

boom could be as much as 10,000 kg, depending on sea conditions and the construction of the boom.2 Booms are sometimes constructed with ballast or weights designed to maintain the boom in an upright position. Lead weights have been used for this, but steel chain in the bottom of the boom often serves as both ballast and a tension member. A few booms also use a chamber filled with water as ballast. Many booms nowadays are constructed without ballast, however, and their position in the water is maintained by balancing the forces on the top and bottom of the boom. Another construction feature common in larger booms is the addition of stiffeners or rigid strips, often consisting of plastic or steel bars, which are designed to keep the boom in an upright position. The three basic types of booms are fence, curtain booms, which are most common, and external tension member booms, which are relatively rare. Booms are also classified according to where they are used, that is, offshore, inshore, harbor, and river booms, based on their size and ruggedness of construction. The fence boom is constructed with a freeboard member above the float. Though relatively inexpensive, these booms are not recommended for use in high winds or strong water currents. Curtain booms are constructed with a skirt below the floats and no freeboard member above the float. Curtain

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booms are most suitable for use in strong water currents. External tension member booms, which are constructed with a tension member outside the main structure, are used in strong currents and in water containing ice or debris. The characteristics of booms that are important in determining their operating ability are the buoyancy-to-weight ratio or reserve buoyancy, the heave response, and the roll response. The buoyancy-to-weight ratio or reserve buoyancy is determined by the amount of flotation and the weight of the boom. This means that the float must provide enough buoyancy to balance the weight of the boom with the force exerted by currents and waves, thereby maintaining the boom’s stability. The greater a boom’s reserve buoyancy, the greater its ability to rise and fall with the waves and remain on the surface of the water. The heave response is the boom’s ability to conform to sharp waves. It is indicated by the reserve buoyancy and the flexibility of the boom. A boom with good heave response will move with the waves on the surface of the water and not be alternately submerged and thrust out of the water by the wave action. The roll response refers to the boom’s ability to remain upright in the water and not roll over.3

12.1.2. Uses of Booms Booms are used to enclose oil and prevent it from spreading, to protect harbors, bays, and biologically sensitive areas, to divert oil to areas where it can be recovered or treated, and to concentrate oil and maintain an sufficient thickness so that skimmers can be used or other cleanup techniques, such as in-situ burning, can be applied. Booms are used primarily to contain oil, although they are also used to deflect oil. When used for containment, booms are often arranged in a U-, V-, or J-configuration. The U-configuration is the most common and is achieved by towing the boom behind two vessels, anchoring the boom, or combining these two techniques. The U-shape is created by the current pushing against the center of the boom. The critical requirement is that the current in the apex of the U does not exceed 0.5 m/s or 1 knot, which is referred to as the critical velocity. This is the speed of the current flowing perpendicular to the boom, above which oil will be lost from the boom. In open water, the U-configuration can also be achieved by allowing the entire boom system to move downcurrent so that the velocity of the current, as opposed to that of the boom, does not exceed the critical velocity. If this velocity is exceeded, first small amounts of oil and then as the relative velocity increases, massive amounts will be lost. This leads to several types of boom failure that are described in the next section. Figure 12.3 shows failure of a U-configuration. If used in areas where the currents are likely to exceed 0.5 m/s or 1 knot, such as in rivers and estuaries, booms are often used in the deflection mode. The boom is then deployed at various angles to the current, shown in Table 12.1, so

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FIGURE 12.3 A U-configuration that is failing. The current here is too high, and thus entrainment failure is occurring.

that the critical velocity is not exceeded. The oil can then be deflected to areas where it can be collected or to less sensitive areas as shown in Figure 12.4. If strong currents prevent the best positioning of the boom in relation to the current, several booms can be deployed in a cascading pattern to progressively move oil toward one side of the watercourse. This technique is effective in wide rivers or where strong currents may cause a single boom to fail. The deflection is intended to be in a straight line, but usually cusps form in the boom as a result of the current. When booms are used for deflection, the forces of the current on the boom are usually so powerful that stronger booms are required and they must be anchored along their entire length.

TABLE 12.1 Deflection Angles and Critical Current Velocities Angle (degrees)

Critical Velocity of Perpendicular Current*

90

0.5

75

0.5

60

0.6

45

0.7

35

0.9

15

1.9

*The current that would be encountered if the boom was perpendicular to the current

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Boom Secured by Anchor or Boat

Anchor Current

Recovery Operation Oil Diverted to Shore Area

FIGURE 12.4 Diagram showing how a deflection boom is used.

The U-configuration is also used to keep oil from spreading into bays or other sensitive areas, as well as to collect oil so that cleanup measures can be applied. The J-configuration is a variation of the U-configuration and is usually used to contain oil as well as to deflect it to the containment area. The V-configuration usually consists of two booms with a counterforce such as a skimmer at the apex of the two booms. Figure 12.5 shows a V-configuration used to direct oil to a skimmer. Encirclement is another way that booms can be used for containment. Stricken ships in shallow waters are often encircled or surrounded by booms to prevent further movement of oil away from the ship. Oil losses usually still occur because the boom’s capacity is exceeded or strong currents may sweep the oil under the boom. In many cases, however, this is all that can be done to prevent further spillage and spreading of the oil. Encirclement is often used as a preventative measure at tanker loading and unloading facilities. Because these facilities are usually situated in calm waters, oil from minor spills can often be contained using this technique. Booms are also used in fixed systems attached to docks, piers, harbor walls, or other permanent structures with sliding-type connectors that allow the boom to move up and down with the waves and tide. Their purpose is to protect certain areas from an oil spill. They are also used to enclose an area where oil is frequently loaded or unloaded or to provide backup containment for operations such as oil/water separators on shore. As these booms are often in place for 10 years before replacement, special long-lasting booms are usually used. Booms are also used in a “sweep” configuration to either deflect oil or contain it for pickup by skimmers. The sweep is held away from the vessel by

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FIGURE 12.5 A boom V-configuration used to direct oil to a skimmer.

a fixed arm, and the boom is allowed to form a U shape, as shown in Figure 12.6. A skimmer is usually placed in the U or is sometimes fixed in the vessel’s hull, and the oil is deflected to this position. Special vessels are required that can maneuver while moving slowly so that the boom does not fail. The various configurations in which booms can be deployed are shown in Figure 12.6.

12.1.3. Boom Failures A boom’s performance and its ability to contain oil are affected by water currents, waves, and winds.3-6 Either alone or in combination, these forces often lead to boom failure and loss of oil. Eight common ways in which booms fail are discussed here. Some of these are illustrated in Figure 12.7. Entrainment FailuredThis type of failure is caused by the speed of the water current and is more likely to happen with a lighter oil. When oil is being contained by a boom in moving water, if the current is fast enough, the boom acts like a dam and the surface water being held back is diverted downward and accelerates in an attempt to keep up with the water flowing directly under the boom. The resulting turbulence causes droplets to break away from the oil that has built up in front of the boom, referred to as the oil headwave, pass under the boom, and resurface behind it. The water speed at which the headwave becomes unstable and the oil droplets begin to break away is referred to as the critical velocity. It is the speed of the current flowing perpendicular to the boom, above which oil losses occur. For most booms riding perpendicular to the

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Skimmer

U-Configuration

V-Configuration

Leaking tanker

Encirclement

J-Configuration

Bay

Sweep

Exclusion

Anchored booms

Current

Current Recovery area

Diversion

Cascade

FIGURE 12.6 An illustration of various configurations used in boom deployment.

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Water current Water current

Entrainment

Drainage Failure

Water current

Splashover

Water current

Submergence

Critical Accumulation

Water current

Planing

FIGURE 12.7 An illustration of several modes of boom failure.

current, this critical velocity is about 0.5 m/s (about 1 knot). Figure 12.3 shows a boom that is losing oil by entrainment failure. At current speeds greater than the critical velocity, this type of boom failure can be overcome by placing the boom at an angle to the current or in the deflection mode. Since currents in most rivers and many estuaries exceed the critical velocity of 0.5 m/s (1 knot), this is the only way the oil can be contained. The approximate critical velocities for booms riding at other angles to the current are listed in Table 12.1. Drainage FailuredSimilar to entrainment, this type of failure is related to the speed of the water current, except that it affects the oil directly at the boom. After critical velocity is reached, large amounts of the oil contained directly at the boom can be swept under the boom by the current. Both entrainment and drainage failure are more likely to occur with lighter oils. One or both of these

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FIGURE 12.8 Drainage failure occurring on a boom.

two types of failure can occur, depending on the currents and the design of the boom. Figure 12.8 shows this type of boom failure. Critical AccumulationdThis type of failure usually occurs when heavier oils, which are not likely to become entrained in water, are being contained. Heavier oils tend to accumulate close to the leading edge of the boom and are swept underneath the boom when a certain critical accumulation point occurs. This accumulation is often reached at current velocities approaching the critical velocities listed in Table 12.1, but can also be reached at lower current velocities. SplashoverdThis failure occurs in rough or high seas when the waves are higher than the boom’s freeboard and oil splashes over the boom’s float or freeboard member. It can also occur as a result of extensive oil accumulation in the boom compared to the freeboard. Submergence FailuredThis type of failure occurs when water goes over the boom. Often the boom is not buoyant enough to follow the wave motion, and some of the boom sinks below the water line and oil passes over it. Submergence failure is usually the result of poor heave response, which is measured by both the reserve buoyancy and the flexibility of the boom. Failure due to submergence is not that common as other forms of failure, such as entrainment, usually occur first. PlaningdPlaning occurs when the boom moves from its designed vertical position to almost a horizontal position on the water. Oil passes over or under a planing boom. Planing occurs if the tension members are poorly designed and do not hold the boom in a vertical position or if the boom is towed in currents far exceeding the critical velocity. Figure 12.9 shows this type of failure. Structural Failure dThis failure occurs when any of the boom’s components fail and the boom lets oil escape. Sometimes structural failure is so

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FIGURE 12.9 Boom failure due to planing.

serious that the boom is carried away by the current. This does not happen often in normal currents and conditions. Floating debris, such as logs and ice, can contribute to structural failure. Shallow Water BlockagedThis type of failure occurs when rapid currents form under a boom when it is used in shallow waters. With the boom acting like a dam, the flow of water under it increases and oil is lost in several of the ways already described. Shallow water is probably the only situation in which a smaller boom might work better than a larger one. It should be noted, however, that booms are not often used in shallow water.

12.1.4. Ancillary Equipment A wide variety of ancillary equipment is used with booms. Hand-holds are often installed on smaller booms that can be lifted by hand and lifting points are installed on larger booms for lifting by crane. Without such provision for lifting, booms must often be lifted using ropes or cables placed around the boom; such lifting can cause damage. All booms have some form of end connector for joining them to other booms or to other pieces of hardware for towing or anchoring. While there are some standard connectors, they also vary among different manufacturers of booms, which can complicate the hookup. Towing bridles and towing paravanes are pieces of equipment that are designed to be attached to the boom so that it can be towed without being submerged or stressed. Booms are usually towed to the site of a spill in a straight line and must withstand stresses associated with this mode of transport. Anchors, anchor attachments, and lines are also available for use with booms.

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Booms are often stored on reels or in special containers designed for fast and efficient deployment. This is particularly important with heavier fireresistant booms as a 50-m section of such a boom could weigh hundreds of kilograms.

12.1.5. Sorbent Booms and Barriers Sorbent booms are specialized containment and recovery devices made of porous sorbent material such as woven or fabric polypropylene, which absorbs the oil while it is being contained. Sorbent booms are used when the oil slick is relatively thin, that is, for the final “polishing” of an oil spill, to remove small traces of oil or sheen, or as a backup to other booms. Sorbent booms are often placed off a shoreline that is relatively unoiled or freshly cleaned to remove traces of oil that may recontaminate the shoreline. They are not absorbent enough to be used as a primary countermeasure technique for any significant amount of oil. Sorbent booms require considerable additional support to prevent breakage under the force of strong water currents. They also require some form of flotation so that they won’t sink once they are saturated with oil and water. Oil sorbent booms must also be removed from the water carefully to ensure that oil is not forced from them and the area recontaminated. Figure 12.10 shows the use of a sorbent boom to contain a small spill.

12.1.6. Special-Purpose Booms A variety of special-purpose booms is available. A tidal seal boom floats up and down, but forms a seal against the bottom during low tide. These are often used

FIGURE 12.10 Use of a sorbent boom to contain a small spill.

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315 FIGURE 12.11 Illustration of the bubble barrier concept.

Oil

Entrained Water Air Inlet

Perforated Pipe

to protect beaches or other stretches of shoreline from oiling. An ice boom is used to contain or divert oil in ice-infested waters. It is not used to contain or divert ice. An ice boom usually has slots at the water line so that oil and water can pass through but ice cannot. A bubble barrier consists of an underwater air delivery system, which creates a curtain of rising bubbles that deflect the oil. Bubble barriers are occasionally used at fixed facilities such as harbors and loading platforms where the water is generally calm. The concept of bubble barriers is illustrated in Figure 12.11. High-pressure air or water streams can also be used to contain and deflect oil. Because of their high-power requirements, they are usually used only to deflect oil in front of skimmers or fixed separator systems. Chemical barriers use chemicals that solidify the oil and prevent its spread. Large amounts of chemicals are required, however, and the potential for containment is low. Net booms made from fine nets are used to collect viscous oils, tarballs, and oiled debris without having the large hydrodynamic forces of a solid boom. Oil trawls are similar to net booms, but are made in the shape of a U so that oil is contained in the net pocket.

12.2. SKIMMERS Skimmers are mechanical devices designed to remove oil from the water surface. They vary greatly in size, application, and capacity, as well as in recovery efficiency.7,8 Skimmers are sometimes classified according to the area where they are used, for example, inshore, offshore, in shallow water, or in rivers, or sometimes by the viscosity of the oil they are intended to recover, that is, heavy or light oil. Often skimmers are classified by the operating principle for example, disk, brush or weir skimmers. Skimmers are available in a variety of forms, including independent units built into a vessel or containment device and units that operate in either a stationary or mobile (advancing) mode. Some skimmers have storage space

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for the recovered oil, and some of these also have other equipment such as separators to treat the recovered oil. The effectiveness of a skimmer is rated according to the amount of oil that it recovers, as well as the amount of water picked up with the oil. Removing water from the recovered oil can be as difficult as the initial recovery. Effectiveness depends on a variety of factors including the type of oil spilled, the properties of the oil such as viscosity, the thickness of the slick, sea conditions, wind speed, ambient temperature, and the presence of ice or debris. Most skimmers function best when the oil slick is relatively thick, and most will not function efficiently on thin slicks. The oil must therefore be collected in booms before skimmers can be used effectively. The skimmer is placed in front of the boom or wherever the oil is most concentrated in order to recover as much oil as possible. Skimmers are often placed downwind from the boom, so that the wind will push the oil toward them. Small skimmers are usually attached to light mooring lines so that they can be moved around within the slick. Weather conditions at a spill site have a major effect on the efficiency of skimmers. Most skimmers work best in calm waters. Depending on the type of skimmer, most will not work effectively in waves greater than 1 m or in currents exceeding 1 knot. Most skimmers do not operate effectively in waters with ice or debris such as branches, seaweed, and floating waste. Some skimmers have screens around the intake to prevent debris or ice from entering, conveyors or similar devices to remove or deflect debris, and cutters to deal with sea weed. Very viscous oils, tarballs, or oiled debris can clog the intake or entrance of skimmers and make it impossible to pump oil from the skimmer’s recovery system. Skimmers are also classified according to their basic operating principles: oleophilic surface skimmers; weir skimmers; suction skimmers or vacuum devices; elevating skimmers; submersion skimmers; and vortex or centrifugal skimmers. Each type of skimmer has distinct advantages and disadvantages, which are discussed in this section. Other miscellaneous devices used to recover oil are discussed after the skimmers are covered.

12.2.1. Oleophilic Surface Skimmers Oleophilic surface skimmers, sometimes called sorbent surface skimmers, use a surface to which oil can adhere to remove the oil from the water surface. This oleophilic surface can be in the form of a disc, drum, belt, brush, or rope, which is moved through the oil on the top of the water. A wiper blade or pressure roller removes the oil and deposits it into an onboard container or the oil is directly pumped to storage facilities on a barge or on shore. The oleophilic surface itself can be steel, aluminum, fabric, or plastics such as polypropylene and polyvinyl chloride. Oleophilic skimmers pick up very little water compared to the amount of oil recovered, which means they have a high oil-to-water recovery ratio. They therefore operate efficiently on relatively thin oil slicks. They are not as

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susceptible to ice and debris as the other types of skimmers. These skimmers are available in a range of sizes and work best with light crude oils, although their suitability for different types of oil varies with the design of the skimmer and the type of oleophilic surface used. The operating principles of oleophilic skimmers are illustrated in Figure 12.12. The disc skimmer is a common type of oleophilic surface device. The discs are usually made of either polyvinyl chloride or steel. Disc skimmers work best with light crude oil and are well suited to working in waves and among weeds

FIGURE 12.12 Illustration of the principles of oleophilic surface skimmers.

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FIGURE 12.13 A disc skimmer under test.

or debris. These skimmers are usually small and can be deployed by one or two people. Disadvantages are that the recovery rate is slow and they work poorly with light fuels or heavy oils. Figure 12.13 shows a disc skimmer undergoing testing. The drum skimmer is another type of oleophilic surface skimmer. The drums are made of either a proprietary polymer or steel. The drum skimmer works relatively well with fuels and light crude, but is ineffective with heavy oils. Drum skimmers are often smaller in size like the disc skimmer. Figure 12.14 shows a dual drum skimmer. Belt skimmers are constructed of a variety of oleophilic materials ranging from fabric to conveyor belting. Most belt skimmers function by lifting oil up

FIGURE 12.14 A dual drum skimmer.

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from the water surface to a recovery well. As the motion of the belt through the water drives oil away from the skimmer, oil must be forced to the belt manually or with a water spray. Belt skimmers have been designed to overcome this problem, including one that pumps the oily water through a porous belt and the inverted belt skimmer that carries the oil under the water. The oil is subsequently removed from the belt by scrapers and rollers after the belt returns to a selected position at the bottom of the skimmer. Belt skimmers of all types work best with heavier crudes, and some are specially constructed to recover tarballs and very heavy oils. Belt skimmers are large and are usually built into a specialized cleanup vessel. Figure 12.15 shows a belt skimmer. Brush skimmers use tufts of plastic attached to drums or chains to recover the oil from the water surface. The oil is usually removed from the brushes by wedge-shaped scrapers. Brush skimmers are particularly useful for recovering heavier oils, but are ineffective for fuels and light crudes. Some skimmers include a drum for recovering light fuels and a brush for use with heavier oils. These skimmers can also be used with limited amounts of debris or ice. Brush skimmers are available in a variety of sizes, from small portable units to large units installed on specialized vessels or barges. Figure 12.16 shows a brush skimmer. Rope skimmers remove oil from the water surface with an oleophilic rope of polymer, usually polypropylene. Some skimmers have one or two long ropes that are held in the slick by a floating, anchored pulley. Others use a series of small ropes that hang down to the water surface from a suspended skimmer body. The rope skimmer works best with medium viscosity oils and is particularly useful for recovering oil from debris- and ice-laden waters. Rope skimmers vary in size from small portable units to large units installed on specialized vessels or barges. Figure 12.17 shows a rope skimmer.

FIGURE 12.15 An oleophilic belt skimmer.

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FIGURE 12.16 A brush skimmer under test.

FIGURE 12.17 A rope skimmer in use in a heavily oiled situation.

12.2.2. Weir Skimmers Weir skimmers are a major group of skimmers that use gravity to drain the oil from the surface of the water into a submerged holding tank. The configurations of weir skimmers are illustrated in Figure 12.18. In their simplest form, these devices consist of a weir or dam, a holding tank, and a connection to an external or internal pump to remove the oil. Many different models and sizes of weir skimmers are available. A weir skimmer at work is shown in Figure 12.19. A problem with some older weir skimmers is their tendency to rock back and forth in choppy water, alternately sucking in air above the slick and water

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Pump to Storage

Oil Slick

Weir-Type Skimmer

Side View

to External Pump

FIGURE 12.18 Illustration of the weir skimmer concept.

below. This increases the amount of water and reduces the amount of oil recovered. Some models include features for self-levelling and adjustable skimming depths so that the edge of the weir is precisely at the oilewater interface, minimizing the amount of water collected. Weir skimmers do not work well in ice and debris or in rough waters, and they are not effective for very heavy oils or tarballs. Weir skimmers are economical, however, and they can have large capacities. They are best used in calm, protected waters. Weir skimmers have also been built into booms and have been moderately successful in providing high recovery rates of lighter crudes.

12.2.3. Suction or Vacuum Skimmers Suction or vacuum skimmers use a vacuum or slight differential in pressure to remove oil from the water surface. Often the “skimmer” is only a small floating

FIGURE 12.19 A weir skimmer at work.

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FIGURE 12.20 Illustration of suction skimmer concepts. Oil Slick Side View

Suction Skimmer Oil Slick

to External Pump Intake Tubes

Suction Skimmer

Top View

head connected to an external source of vacuum, such as a vacuum truck. The head of the skimmer is simply an enlargement of the end of a suction hose and a float. The principle of operation of a suction skimmer is shown in Figure 12.20. Suction skimmers are similar to weir skimmers in that they sit on the water surface, generally use an external vacuum pump system such as a vacuum truck, and are adjusted to float at the oilewater interface. They also tend to be susceptible to the same problems as weir skimmers. They are prone to clogging with debris, which can stop the oil flow and damage the pump. They also experience the problem of rocking in choppy waters, which causes massive water intake, followed by air intake. Their use is restricted to light to medium oils. Figure 12.21 shows the use of a vacuum truck and suction hose to clean a beach. Despite their disadvantages, suction skimmers are the most economical of all skimmers. Their compactness and shallow draft make them particularly useful in shallow water and in confined spaces. They operate best in calm water with thick slicks and no debris. Very large vacuum pumps, called air conveyors, and suction dredges have been used to recover oil, sometimes directly without a head. Both of these adaptations, however, have the same limitations as smaller suction skimmers.

12.2.4. Elevating Skimmers Elevating skimmers or devices use conveyors to lift oil from the water surface into a recovery area as illustrated in Figure 12.22. A paddle belt or wheel or

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FIGURE 12.21 Use of a vacuum truck and suction hose to clean up oil on a beach.

a conveyor belt with ridges is adjusted to the top of the water layer, and oil is moved up the recovery device on a plate or another moving belt. The operation is similar to removing liquid from a floor with a squeegee. The oil is usually removed from the conveyor by gravity. When operating these skimmers, it is difficult to maintain the conveyor at the water line. In addition, they cannot operate in rough waters or in waters with large pieces of debris, and they cannot deal with light or very heavy oils. Elevating skimmers work best with medium to somewhat heavy oils in calm waters. They are generally large and are sometimes built into specialized vessels. Figure 12.23 shows an elevating skimmer at work.

12.2.5. Submersion Skimmers Submersion skimmers use a belt or an inclined plane to force the water beneath the surface. The belt or plane forces the oil downward toward a collection well where it is removed from the belt by a scraper or by gravity. The oil then flows upward into the collection well and is removed by a pump. Submersion skimmers move faster than other skimmers and can therefore cover a large area, making them suitable for use at larger spills. They are most effective with light oils with a low viscosity and when the slick is relatively thin. Disadvantages include a poor tolerance to debris compared to other skimmers, and they cannot be used in shallow waters. Submersion skimmers are larger than other types of skimmers and are usually mounted on a powered vessel.

12.2.6. Skimmer Performance A skimmer’s performance is affected by a number of factors including the thickness of the oil being recovered, the extent of weathering and emulsification

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Moving Paddles or Scrappers

Oil Slick Fixed Inclined Plane

Collection Well

Movement of Vessel

Squeegee or Roller Collection Well Oil Slick Rotating Belt

Movement of Vessel

FIGURE 12.22 Illustration of elevating skimmer concepts.

of the oil, the presence of debris, and weather conditions at the time of recovery operations. A skimmer’s overall performance is usually determined by a combination of its recovery rate and the percentage of oil recovered. The maximum amount of oil that a skimmer could recover is called the Nameplate Recovery Rate and is typically provided by the manufacturer of a skimmer.9-11 A similar definition is the Effective Daily Recovery Capacity, which is the amount that a skimmer could recover in daylight hours under ideal conditions. The recovery rate is the volume of oil recovered under specific conditions. It is measured as volume per unit of time, for example, m3/h, and is usually given as a range. If a skimmer takes in a lot of water, it is detrimental to the overall efficiency of an oil spill recovery operation. The results of performance testing on various types of skimmers are given in Table 12.2.1,7,9-11

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FIGURE 12.23 An elevating skimmer at work.

In addition to these characteristics, other important measures of a skimmer’s performance include the amount of emulsification caused by the skimmer, its ability to deal with debris, ease of deployment, ruggedness, applicability to specific situations, and reliability.

12.2.7. Special-Purpose Ships Special-purpose ships have been built specifically to deal with oil spills. Some ships have been built with a hull that splits to form a V-shaped containment boom with skimmers built into the hull, although this requires very expensive design features so that the ship can withstand severe weather conditions. Other ships have been built with holes in the hull to hold skimmers, with sweeps mounted on the side to direct oil to the skimmer area. Many small vessels have been custom-built to hold skimmers.

12.3. SORBENTS Sorbents are materials that recover oil through either absorption or adsorption. They play an important role in oil spill cleanup and are used in the following ways: to clean up the final traces of oil spills on water or land; as a backup to other containment means, such as sorbent booms; as a primary recovery means for very small spills; and as a passive means of cleanup. An example of such passive cleanup is when sorbent booms are anchored off lightly oiled shorelines to absorb any remaining oil released from the shore and prevent further reoiling of the shoreline. Sorbents can be natural or synthetic materials. Natural sorbents are divided into organic materials, such as peat moss or wood products, and inorganic

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TABLE 12.2 Performance of Typical Skimmers Recovery Rate (m3/hr) for given oil type*

Skimmer Type

Diesel

Light Crude

Heavy Crude

Oleophilic Skimmers small disc 0.4 to 1

0.2 to 2

large disc

10 to 20

10 to 50

0.5 to 20

0.5 to 2

brush

0.2 to 0.8

large drum small drum large belt

0.5 to 5 1 to 5

inverted belt

large weir

80 to 95

1 to 20

3 to 20

3 to 10

0.5 to 5

2 to 10 2 to 20

5 to 25

Elevating Skimmers paddle conveyer

1 to 10

1 to 20

Submersion Skimmers large 0.5 to 1

1 to 80

1 to 20

0.3 to 1

0.3 to 2

large trawl unit

2 to 40

large vacuum unit

3 to 20

Vortex/Centrifugal Skimmers centrifugal unit 0.2 to 0.8

0.2 to 10

75 to 95 85 to 95

5 to 30

1 to 10

80 to 95

0.5 to 5

5 to 10

Suction Skimmers small

0.5 to 2

80 to 95

30 to 100

advancing weir

80 to 95

10 to 30

2 to 20 0.2 to 10

Percent Oil** 80 to 95

10 to 30

rope Weir Skimmers small weir

Bunker C

20 to 80 3 to 5

50 to 90 30 to 70

1 to 5

10 to 40 70 to 95 3 to 10 20 to 90

3 to 10

10 to 80 2 to 20

*Recovery rate depends very much on the thickness of the oil, type of oil, sea state, and many other factors **This is the percentage of oil in the recovered product. The higher the value, the less the amount of water and thus the better the skimmers’ performance

materials, such as vermiculite or clay. Sorbents are available in a loose form, which includes granules, powder, chunks, and cubes, often contained in bags, nets, or socks. Sorbents are also available formed into pads, rolls, blankets, and pillows. Formed sorbents are also made into sorbent booms and sweeps. One

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type of plastic sorbent is formed into flat strips or “pom-poms.” which are particularly useful for recovering very heavy oils. The use of synthetic sorbents in oil spill recovery has increased in the last few years. These sorbents are often used to wipe other oil spill recovery equipment, such as skimmers and booms, after a spill cleanup operation. Sheets or rolls of sorbent are often used for this purpose. Synthetic sorbents can often be reused by squeezing the oil out of them, although extracting small amounts of oil from sorbents is sometimes more expensive than using new sorbent. Furthermore, oil-soaked sorbent is difficult to handle and can result in minor releases of oil between the regeneration area and the area where the sorbent is used. The capacity of a sorbent depends on the amount of surface area to which the oil can adhere as well as the type of surface. A fine porous sorbent with many small capillaries has a large amount of surface area and is best for recovering light crude oils or fuels. Sorbents with a coarse surface would be used for cleaning up a heavy crude oil or Bunker. Pom-poms intended for recovering heavy Bunker or residual oil consist of ribbons of plastic with no capillary structure. General-purpose sorbents are available that have both fine and coarse structure, but these are not as efficient as products designed for specific oils. Some sorbents are treated with oleophilic (oil-attracting) and hydrophobic (water-repelling) agents to improve the ability of the material to preferentially absorb oil rather than water. As natural sorbents often recover large amounts of water along with the oil, they can be treated to prevent water uptake. This type of treatment usually increases the ability of certain sorbents to remain afloat. The performance of sorbents is measured in terms of total oil recovery and water pickup, similar to skimmers. “Oil recovery” is the weight of a particular oil recovered compared to the original weight of the sorbent. For example, highly efficient synthetic sorbent may recover up to 30 times its own weight in oil, and an inorganic sorbent may recover only twice its weight in oil. The amount of water picked up is also important, with an ideal sorbent not recovering any water. Some results of performance testing of typical sorbents with various types of oils are given in Table 12.3.11-14 A number of precautions must be considered when using sorbents. First, the excessive use of sorbents at a spill scene, especially in a granular or particulate form, can compound cleanup problems and make it impossible to use most mechanical skimmers. Sorbents may cause plugging in discharge lines or even in the pumps themselves. Second, sorbents that sink should not be used as they could be harmful to the environment. Sinking is a problem with many sorbents, such as untreated peat moss, most inorganic sorbents, and many wood products. Many countries do not allow the use of sorbents that sink in applications on water, as the oil will usually be released from the sorbent over time and both the oil and the sorbent are very harmful to benthic life.

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TABLE 12.3 Performance of Some Sorbents Typical Oil Recovery with Oil Type (weight:weight)*

Sorbent Type

Diesel

Light Crude

Heavy Crude

Bunker C

Percent Oil**

Synthetic Sorbents polyester pads

7

9

12

20

90þ

polyethylene pads

25

30

35

40

90þ

polyolefin pom-poms

2

2

3

8

90þ

polypropylene pads

6

8

10

13

90þ

polypropylene pom-poms

3

6

6

15

90þ

polyurethane pads

20

30

40

45

90þ

Natural Organic Sorbents bark or wood fibre

1

3

3

5

70

bird feathers

1

3

3

2

80þ

peat moss

2

3

4

5

80þ

treated peat moss

5

6

8

10

80þ

straw

2

2

3

4

70

vegetable fibre

9

4

4

10

80þ

Natural Inorganic Sorbents clay (kitty litter) 3

3

3

2

70

treated pearylite

8

8

8

9

70

treated vermiculite

3

3

4

8

70

Vermulite

2

2

3

5

70

*Recovery depends very much on the thickness of the oil, type of oil, surface type and many other factors **This is the percentage of oil in the recovered product. The higher the value, the less the amount of water and thus the better the sorbent’s performance

Finally, recovery and disposal of the oiled sorbent material must be considered. As oiled sorbent is most often burned or buried, the sorbent must retain the oil long enough so that it is not lost during recovery operations or in transport to disposal sites. The excessive use of sorbents is illustrated in Figure 12.24. A sorbent used for heavy oil is illustrated in Figure 12.25.

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FIGURE 12.24 The excessive use of particulate sorbent on a spill. Sorbents are best used in a polishing role.

FIGURE 12.25 A sorbent for heavy oil spill polishing. This type of sorbent is sometimes called a pom-pom as it resembles those used by cheer leaders.

12.4. MANUAL RECOVERY Small oil spills or those in remote areas are sometimes recovered by hand. Heavier oils are easier to remove this way than lighter oils. Spills on water close to shorelines are sometimes cleaned up with shovels, rakes, or by cutting the oiled vegetation. Hand bailers, which resemble a small bucket on the end of a handle, are sometimes used to recover oil from the water surface. Manual recovery is tedious and may involve dangers such as physical injury from falls

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FIGURE 12.26 Manual cleanup near a shoreline.

on the shore. Much shoreline cleanup is usually done manually. Figure 12.26 shows manual cleanup near a shoreline.

12.5. TEMPORARY STORAGE When oil is recovered, sufficient storage space must be available for the recovered product. The recovered oil often contains large amounts of water and debris that increase the amount of storage space required. Figure 12.27 shows a massive collection of drums that are used as temporary storage after a successful manual cleanup. Several types of specially built tanks are available to store recovered oil. Flexible portable tanks, often constructed of plastic sheeting and a frame, are the most common type of storage used for spills recovered on land and from rivers and lakes. These are available in a range of sizes from approximately 1 to 100 m3 and require little storage space before assembly. Most of these types of tanks do not have a roof, however, so rain or snow can enter the tank and vapors can escape. Figure 12.28 shows a flexible portable tank being used for oil recovery. Rigid tanks, which are usually constructed of metal, are also available but are less common than flexible tanks. Pillow tanks, constructed of polymers and heavy fabrics, are usually used to store oil recovered on land. These are placed on a solid platform so that rocks cannot puncture the tank when full. Pillow tanks are also sometimes used on the decks of barges and ships to hold oil recovered at sea. Oil recovered on land is often stored in stationary tanks built for other purposes, and in dump trucks and modular containers, lined with plastic. Recovered oil can also be temporarily stored in pits or berms lined with polymer sheets, although this open type of storage is not suitable for volatile oils. Towable, flexible tanks, usually bullet-shaped, are also used to contain oil recovered at sea. Their capacity varies, but they can hold up to several tons.

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FIGURE 12.27 An illustration of a successful cleanup with little bulk temporary storage available.

These tanks are also constructed of polymers, with fabric materials sometimes used as a base. Since most oils are less dense than water, these tanks will float throughout the recovery process. When full, these tanks can be difficult to maneuver, however, and they can be difficult to empty, especially if the oil is viscous and contains debris. Oil recovered at sea is often temporarily stored in barges. Many cleanup organizations have barges that are used solely for storing recovered oil and lease barges for use at larger spills. Recovered oil is also stored in the holds of ships, usually using older vessels. This is more economical than using designated tanks on land, especially when the recovered oil has to be stored for long periods of time until a final disposal method is found. Drums, small tanks,

FIGURE 12.28 A portable tank used for spilled oil recovery.

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livestock watering troughs, and even bags have also been used to contain oil from smaller spills, both on land and at sea.

12.6. PUMPS Pumps play an important role in oil spill recovery. They are an integral part of most skimmers and are also used to transfer oil from skimmers to storage tanks. Pumps used for recovered oil differ from water pumps in that they must be capable of pumping very viscous oils and dealing with water, air, and debris. The three basic types of pumps used for pumping oil recovered from spills are centrifugal pumps, vacuum systems, and positive displacement pumps. The operating principles of some pumps are shown in Figure 12.29.

Centrifugal Pumps Centrifugal pumps have a spinning vane that moves the liquid out of a chamber by centrifugal force. These pumps, which are regularly used for pumping water and wastewater, are not designed for use with oil and are generally not capable of dealing with material more viscous than light crudes. Centrifugal pumps

Inlet

Outlet

Inlet

Wiper

Outlet

Centrifugal

Screw or Auger

Inlet

Inlet valve Piston

Air Outlet valve

Piston

Outlet

Diaphragm

FIGURE 12.29 The operating principle of some common oil recovery pumps.

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cannot typically deal with debris. They are economical and universally available, however, and are often used in oil spill cleanup operations.

Vacuum Systems Vacuum systems consist of vacuum pumps and tanks mounted on a skid or truck. The vacuum pump creates a vacuum in the tank and the oil moves directly through a hose or pipe to the tank from the skimmer or the source of the oil. The oil does not go through the pump, but moves directly from its source into the tank. Vacuum systems can handle debris, viscous oils, and the intake of air or water. The vacuum tank requires emptying, however, which is usually done by opening the entire end of the tank and letting the material move out by gravity. Positive Displacement Pumps Positive displacement pumps are often built directly into skimmers to recover more viscous oils. These pumps have a variety of operating principles, all of which have some common schemes. Oil enters a chamber in the pump where it is pushed by a moving blade, shoe, or piston to the exit of the pump. The oil and other material with it must move through the chamber because there is no alternative passagedthus the name positive displacement. The screw or auger pump is a common type of positive displacement pump. The oil drops into part of the screw and is carried to an output. Wiper blades remove oil from the auger flights to prevent it from remaining on the auger shaft. The screw pump can deal with very viscous oils and is often built into skimmers. A gear or lobe pump uses gears or lobes mounted on a shaft to accomplish the positive displacement of oil through a chamber. Neither of these pumps can handle debris or highly viscous oil. The diaphragm pump uses a flexible plate or diaphragm to move oil from a chamber. This type of pump usually requires a valve, which limits its use to material that can pass through the valve, making it unsuitable for oil containing debris. A vane pump, which uses a movable metal or polymer plate to move oil in a chamber, functions in a manner similar to a centrifugal pump, but with positive displacement. The peristaltic pump uses a hose that is progressively squeezed by rollers moving along the top of its surface. As the oil never comes into contact with any material other than the hose, this pump is suitable for use with a variety of hazardous materials. Both the vane pump and peristaltic pump can handle medium viscosity oils and small debris. A piston-like plunger in the sliding shoe pump moves oil along between the input and output ports. This pump does not require valves, although certain models do include them. The piston pump is similar to the sliding shoe pump except that oil is simply pushed out of the cylinder from the input valve to the output valve. Both sliding shoe and piston pumps can handle viscous oils, but generally cannot handle debris.

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Finally, the progressive cavity pump uses a rotating member inside a molded cylinder that together form a cavity that moves from input to output as the centre is rotated. This pump can handle very viscous oils and debris, but is heavy and more expensive than other types of pumps.

12.6.1. Performance of Pumps The performance of pumps is usually measured in terms of the volume displaced per unit of time at a given viscosity, suction head, and pressure head.15-17 The suction head is the maximum height that a pump can draw the target liquid, and the pressure head is the maximum height that a pump can push the target liquid. These heads are not important in most pump applications in oil spill recovery. It is important, however, that pumps used for pumping oil are selfpriming rather than requiring that a flow of liquid be established before the pump is functional. Other important factors to consider are the pump’s ability to deal with emulsions and debris and the degree of emulsion formation that takes place in the pump itself.

12.7. SEPARATION As all skimmers recover some water with the oil, a device to separate oil and water is usually required. The oil must be separated from the recovery mixture for disposal, recycling, or direct reuse by a refinery. Sometimes settling tanks or gravity separators are incorporated into skimmers, but separators are more often installed on recovery ships or barges. Portable storage tanks are often used as separators, with outlets installed on the bottom of the tanks so that water that has settled to the bottom of the tank can be drained off, leaving the oil in the tank. Vacuum trucks are also used in this way to separate oil and water. Screens or other devices for removing debris are sometimes incorporated into separators. A gravity separator is the most common type of separator. In its simplest form, it consists of a large holding tank in which the oil and water mixture is held long enough for the oil to separate by gravity alone. This is referred to as the residence time and varies from minutes to hours. When inflow volumes are large, it can be difficult to find large enough separators to provide the long residence times required. Oil refineries have large separators that may cover several hectares and are used for treating refinery waste and are sometimes also used to treat oil recovered from spills. Separators are often made with baffles or other interior devices that increase the residence time and thus the degree of separation. The parallel plate separator is a special model of gravity separator. Many parallel plates are placed perpendicular to the flow, creating areas of low water turbulence where drops of oil can re-coalesce from the water and rise to the surface. Centrifugal separators have spinning members that drive the heavier water from the lighter oil, which collects at the center of the vessel. These separators are very efficient but have less capacity than gravity separators and cannot

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handle large debris. They are best suited to constant amounts of oil and water. Sometimes centrifugal separators are used in tandem with gravity separators to provide an optimal system. As emulsions are not broken down in separators, emulsion-breaking chemicals are often added to the recovered mixture before it enters the separator. Heating the emulsions to 80 or 90 C usually results in separation, and the water can then be removed, although this process uses a lot of energy. Separator performance is measured by the water-removal efficiency and the throughput volume. Important factors affecting performance include the ability to handle small debris (larger debris is usually removed) and a wide variety of oil and water ratios, with oil content and flow rate sometimes changing suddenly.

12.8. DISPOSAL Disposing of the recovered oil and oiled debris can be the most difficult aspects of an oil spill cleanup operation.18-20 Any form of disposal is subject to a complex system of local, provincial or state, and federal legislation. Unfortunately, most recovered oil consists of a wide range of contents and material states and cannot be classified as simply liquid or solid waste. The recovered oil may contain water that is difficult to separate from the oil and many types of debris, including vegetation, sand, gravel, logs, branches, garbage, and pieces of containment booms. This debris may be too difficult to remove, and thus the entire bulk material may have to be disposed of. Spilled material is sometimes directly reused either by reprocessing in a refinery or as a heating fuel. Some power plants and even small heating plants such as those in greenhouses can use a broad spectrum of hydrocarbon fuels. Often the equipment at refineries cannot handle oils with debris, excessive amounts of water, or other contaminants and the cost of pretreating the oils can far exceed the value that might be obtained from using them. Heavier oils are sometimes sufficiently free of debris to be used as a road cover when mixed with regular asphalt. Recovered material from cleaning up beaches can be used in this way. If the material is of the correct consistency, usually sand, the entire mixture might be mixed with road asphalt. Incineration is a frequent means of disposal for recovered oil, as large quantities of oil and debris can be disposed of in a relatively short time. Disadvantages are the high cost, which may include the cost of transporting the material to the facility. In addition, approval must be obtained from government regulatory authorities. Local emission guidelines for incinerators may preclude simply placing the material into an incinerator. Spill disposal is sometimes exempt from regulations, or special permits are available. Several incinerators have been developed for disposing of either liquid or solid materials, but these all require special permits or authority to operate. In remote locations, it may be necessary to burn oiled debris directly on the recovery sites without an incinerator because it is too bulky to transport to the nearest incinerator.

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Contaminated beach material is difficult to incinerate because of the sand and gravel content. Special burners have been constructed to process these materials, and the beach material can then be returned to the original site. There are also machines to wash oily sand or gravel. The oil recovered from this process must be separated from the wash water and then disposed of separately. Similarly, heat treatment devices remove oil from sand or gravel without burning. The resulting vapors are trapped, condensed, and the oil is disposed of. This method is not common as it requires large amounts of heat energy. Figure 12.30 shows bags of mixed debris from shoreline cleanup. This material was put into a special landfill. Incineration should be differentiated from in-situ burning, which involves burning the material directly on site without the use of a special device. This is usually only applied to lightly oiled driftwood, and special permission must be obtained from the appropriate authorities. Oiled debris, beach material, and sorbents are sometimes disposed of at landfill sites. Legislation requires that this material not contain free oil that could migrate from the site and contaminate groundwater. Some governments have standard leachability test procedures that determine whether the material will release oil. Several stabilization processes have been developed to ensure that free oil does not contaminate soil or groundwater. One process uses quick lime (calcium oxide) to form a cement-like material, which can be used on roads as a dust-inhibitor. Land-farming is the application of oil and refinery waste to land where it degrades. This practice is now banned in most jurisdictions since many oil components do not break down, and contaminants, such as metals and polyaromatic hydrocarbons, are carried away from the site, often in groundwater. Lightly contaminated water from skimmers, less than 15 parts-per-million (ppm) by weight of oil, can usually be returned to the water body from where it

FIGURE 12.30 Bags from shoreline cleanup. These are typically disposed of in special landfills.

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came. More contaminated water may require further treatment in separators or at a municipal wastewater treatment plant.

ACKNOWLEDGMENTS Environment Canada is acknowledged for the use of photographs and other materials in the preparation of this document.

REFERENCES 1. Fingas MF. The Basics of Oil Spill Cleanup. 2nd ed. Boca Raton, FL: CRC Press; 2000. 2. Potter S, McCourt J, Smith R. Estimation of Towing Forces on Oil Spill Containment Booms. AMOP 1999;825. 3. Castro A, Iglesias G, Carballo R, Fraguela JA. Floating Boom Performance Under Waves and Currents. J Haz Mat 2010;226. 4. Amini A, Bollaert E, Boillat J-L, Schleiss AJ. Dynamics of Low-Viscosity Oils Retained by Rigid and Flexible Barriers. Ocean Eng 2008;1479. 5. Muttin F. Oil Spill Boom Modelling by the Finite-Element Method. WIT Trans Ecol Environ 2008;67. 6. Muttin F. Structural Analysis of Oil-Spill Containment Booms in Coastal and Estuary Waters. Appl Ocean Res 2008;107. 7. Schulze R. Oil Spill Response Performance Review of Skimmers, ASTM Manual Series. ASTM 1998. 8. Schwartz SH. Performance Tests of Four Selected Oil Spill Skimmers. AMOP 1979;493. 9. Fingas MF. Weather Effects on Oil Spill Countermeasures. This Work; 2010:339. 10. Meyer P, Schmidt W, Delgado J-E, DeVitis D, Potter S, Haugstad E, et al. Application of the American Society of Testing and Materials (ASTM) New Skimmer Test Protocol. AMOP 2009;323. 11. Potter S. The Use of Consensus-Based Standards to Improve Oil Spill Equipment Testing and Selection Protocols. IOSC 2008;427. 12. Cooper D, Gausemel I. Oil Spill Sorbents: Testing Protocol and Certification Listing Program. IOSC; 2005:393. 13. Cooper D, Dumouchel A, Brown CE. Multi-Track Sorbent Boom and Sweep Testing. AMOP 2005;393. 14. Carmody O, Frost R, Xi Y, Kokot S. Surface Characterisation of Selected Sorbent Materials for Common Hydrocarbon Fuels. Surf Sci 2007;2066. 15. Potter S, Bronson M, Thompson E, Majors L. Testing of Various Options for Improving the Pumping of Viscous Oils and Emulsions. AMOP 2007;387. 16. Drieu MD, Nourse PC, MacKay R, Cooper DA, Hvidbak F. Latest Update of Tests and Improvements to US Coast Guard Viscous Oil Pumping System. Mar Pollut Bull 2003;470. 17. Cooper DW, MacKay R. Assisted Pumping of Extremely Viscous Oils. AMOP 2001;373. 18. Richardson C. Waste Management in Major Marine Oil Spills: The Importance of Its Strategy. International Conference on Health, Safety, and Environment in Oil and Gas Exploration and Production 2004;1065. 19. Jones MT, Najafi FT. The Disposal of Used Oil, Spilled Crude Oils, and Their Associated Sorbent Materials. Annual ConferencedCanadian Society for Civil Engineering 2002;2723. 20. Davies G. The Management of Oily Waste. Interspill 2000;151.

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Chapter 13

Weather Effects on Oil Spill Countermeasures Merv Fingas

Chapter Outline 13.1. Introduction 339 13.2. Review of Literature on 343 Spill Countermeasures and Weather 13.3. Development of Models 383 for Effectiveness of Countermeasures

13.4. Overview of Weather Limitations 13.5. Summary and Conclusions

405 407

13.1. INTRODUCTION Weather has been recognized as one of the most important factors in predicting oil spill fate and behavior.1,2 Weather has not, however, been well recognized in designing oil spill countermeasures.1,3 Bad weather is usually recognized as a condition that hinders or stops effective oil spill countermeasures.4 The traditional concept of “windows of opportunity” began with the topic of dispersants in about the mid-1990s. This concept largely related to the window of opportunity for dispersal as time progressed and the oil became more weathered and less dispersible. As time progresses, the window of opportunity to disperse closes.5 Thus, the prime variable for generating the window was weathering with time. Subsequently, some of the same concepts, but only including the same parameters, were extended to physical recovery and containment.6-10 The windows of opportunity for Alaska North Slope oil, based on weathering only, were stated by Champ et al. to be 0 to 36 hours for burning, 0 to 36 hours for dispersing, 0 to 18 hours for oilewater separator, and 26 to 120 hours for reduced dispersant effectiveness.9 It is important to note that outside of dispersion, the windows of opportunity concept, in actual fact, has little relevance. Before the publication of the window of opportunity concept, it was not included in logistic planning, nor was weather considered an essential part in Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10013-9 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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planning oil spill countermeasures.11 Historically, most reference to windows of opportunity were to the time factor. The biggest concern was the evaporation of the oil, which leads to large increases in viscosity and therefore increased difficulty in recovery and other countermeasures. Another concern was the emulsification of the oil. The secondary time window is that of spreading. A typical crude oil can spread over dozens of square kilometers in the first day after the spill.12,13 Furthermore, once spreading progresses, the thickness approaches or is less than 1 mm, a thickness that cannot be dealt with by any form of countermeasure. Oil that had been at sea for a period of time was sometimes thought to be lost, and countermeasures were hopeless.14 Only recently has it been recognized that many of these problems do not occur with heavy oils.15 Currently, weather is sometimes incorporated into contingency plans. Some countries have even incorporated weather and its effects into shoreline mapping.16 The presence of ice, though not strictly a weather condition, is weather related and can severely affect the recovery of standard equipment.17 The ability to perform multiple tasks at sea is typically recognized, although the ability to use chemical dispersants and mechanical recovery are not compatible with one another and in-situ burning is incompatible with both of these.18 The costs of spills have not been evaluated in terms of weather conditions.19-21 There is insufficient information in the literature with which to judge the effect of weather conditions on the costs and general progress of oil spill cleanup. Harper et al. reviewed costs and did not include the effects of weather.22 They also noted that the costs of offshore cleanup are less than shoreline cleanup by a factor of 2.5 to 4. In-situ burning is estimated to be about 5 times cheaper than offshore recovery and 10 times cheaper than shoreline cleanup. Recently, Robertson and Kumar prepared a “response gap” analysis for Prince William Sound and the Hitchinbrook Entrance.23 They placed cut-off values for wind, wave height, temperature, and visibility and then used actual weather buoy data to evaluate the operability of physical countermeasures. The criteria are shown in Table 13.1 and the resulting cut-off values in Table 13.2. One point that should be noted is that Arctic conditions, particularly in winter, are much more extreme than others and should bear special consideration.24-26 Many documents on Arctic oil spills exist, and thus Arctic countermeasures per se will not be covered here.

13.1.1. Spreading Compared to Weathering Spreading, which is a function of time and oil properties, will result in thin slicks, which may not be recoverable, burnable, or dispersible.27 Oceanic processes including Langmuir circulation and the presence of ocean fronts may result in the collection of material, thus reversing the effects of spreading to a certain degree.28-31 Initial spreading equations such as those by Fay do not consider weather factors such as transport by wind and waves and, consequently, underpredict the spreading when wind is a factor.32

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TABLE 13.1 Robertson and Kumar’s Response Physical Countermeasures Limits Environmental Factor

Green Response Not Impaired

Yellow Response Impaired

Red Response Not Possible/Effective

Wind (speed in Knots) (m/s)

0 to <21 (0 to <10 m/s)

21 to <30 (10 to <15 m/s)

> 30 (>15 m/s)

Sea State (waves in metres)

<1 if wave steepness considered

1 to <2 also considered wave steepness

>2 also considered wave steepness

Temperature ( C)

> 3 C

8 C to 3 C and wind speed >12 knots (6 m/s)

<8 C and wind speed >5 knots (3 m/s)

Visibility (km)

>0.8 (day light)

0.4 to 0.08

<0.4

not present

Red any factor is red if two or more are yellow

Combination of Factors Green if all factors are green if only one factor yellow

13.1.2. Important Components of Weather A review of weather factors that are relevant to the effectiveness of countermeasures at sea shows that wind speed and the resulting wave heights are the most important factor. Current or speed of water movement is not usually the result of changing weather, but will be covered briefly in this chapter. Temperature affects countermeasures such as dispersion but is not as significant in terms of other countermeasures. Temperature can be significant if it results in icing. The relevant temperature changes at sea are only from 5 to 20 C. This spread in water temperature does not cause viscosity changes that are significant as it relates to skimmers and especially not to booms. On land, however, much wider temperature differences exist. Wind is the component that generates waves and by itself can cause significant changes in oil behaviour.33 Wind can also change the rate of surface drift of oil. Youssef and Spaulding found that the drift factor (normally taken as 3.5%) varies with wind. In shallow water, the drift factor increases with increasing wind speed.34 The deflection angle, however, was found to be insensitive to variations in depth, but increases slightly as wind speed increases. For waves, the most important component to consider is the type of wave.35,36 A regular wave does not impose as great a constraint on performance

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TABLE 13.2 Robertson and Kumar’s Response Limits Applied to Prince William Sound Environmental Factor

Green Response Not Impaired

Yellow Response Impaired

Red Response Not Possible/Effective

Wind (speed in Knots) (m/s)

0 to <21 (0 to <10 m/s)

21 to <30 (10 to <15 m/s)

>30 (>15 m/s)

Sea State (waves in metres)

<1 if wave steepness considered

1 to <2 also considered wavesteepness

>2 also considered wave steepness

Temperature ( C)

>3 C

8 C to 3 C and wind speed > 12 knots (6 m/s)

<-8 C and wind speed > 5 knots (3 m/s)

Visibility (km)

>0.8 (day light)

0.4 to 0.08

<0.4

Green if all factors are green if only one factor yellow

Red any factor is red if two or more are yellow

Combination of Factors

Results Location Central Prince William Sound

Percent of Time

Percent of Time

Entire year

87.4

12.6

Summer (April to September)

95.8

4.2

Winter (October to March)

76.9

23.1

Location Hitchinbrook Entrance

Percent of Time

Percent of Time

Entire year

61.5

38.5

Summer (April to September)

83.8

16.2

Winter (October to March)

33.9

66.1

as does an irregular wave. A typical wave situation that can cause countermeasures difficulty is shown in Figure 13.1. At sea, many different types of wave energies have been recognized. For example, breaking waves display more energy than nonbreaking waves.37,38 Goodman noted that wave energy was a most important factor, but one that was not understood.39 Cheng et al. designed waves for a test tank and noted that wave shape was an important factor.40 Payne et al. studied the weathering of the Exxon Valdez oil in the field and in test tanks.41 They note that weather, especially the waves, is an important factor in

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FIGURE 13.1 A ship in distress and leaking oil; however, the waves are such that it is difficult to apply spill countermeasures.

the fate and behavior of the oil. Simecek-Beatty et al. developed a model of chemical dispersion and use the fact that the mixing layer is 1.5 times the wave height.42 This shows that wave height is a strong predictor of dispersion amount. Some observers state that weather is a very important factor as it relates to spill countermeasures effectiveness.43,44 The resolution of the data is also very important. Elliot and Jones review the prediction of oil spill behavior and fate during the Sea Empress incident and note that the use of coarse grid, nonoperational data resulted in prediction errors.45 They maintain that accuracy could be improved by using high-quality and high-resolution weather data.

13.1.3. Oil Properties Regardless of Weathering Oil properties play a large role in the behavior and fate of oil at sea, including how the oil relates to changes in the weather. Buist et al. studied waxy crudes from eastern Canada and found that, from a countermeasures perspective, they behaved differently than other oils, regardless of small differences in temperature.46 Fingas et al. noted that the dynamics of orimulsion were changed by variations in temperature.47 The lower the temperature, the more orimulsion surfaces.

13.2. REVIEW OF LITERATURE ON SPILL COUNTERMEASURES AND WEATHER 13.2.1. A Priori Decision Guides A number of a priori guides have been issued; these guides are based on logic and not on specific tests. A classic guide described by Al Allen in 198848 was

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Physical Spill Countermeasures on Water

meant to serve as an intermediate in calculating volume rates for each countermeasure analyzed. The logic that Allen uses is summarized here. For burning, it was assumed that a sufficient thickness (2 to 3 mm) is needed for oil to burn and that ignition cannot be carried out at winds greater than about 10 m/s (20 knots) but that, once ignited, burns can be sustained much past this value. Allen notes that mechanical cleanup techniques typically work best on thick oil layers in calm seas and that this drops off quickly at winds of 7 to 10 m/s (Beaufort 3 to 4). The thickness relationships are also crucial, as assumed earlier. High-seas skimming equipment may have an extended envelope, but this is not defined. Allen notes that, as short-period wind-waves build to 0.6 to 0.9 m, booms will suffer significant losses due to entrainment and splashover. The lower bound of dispersant use was estimated to be a wind of about 5 m/s (Beaufort 2) on the basis of the mixing required. The upper limit of dispersant application was estimated to be about 12 to 14 m/s wind (Beaufort 5 to 6) on the basis of the benefits compared to natural dispersion, which should be great at this sea level. Allen combines these weather options with a volume recovery versus spill thickness to provide an assessment basis for offshore countermeasures.48 Exxon Mobil lists the weather limitations (upper limit) for dispersant application as: work boats (tugboat type)dwind speed 3 to 11 m/s (7 to 21 knots), significant wave height 0 to 3 m; single-engine airplanesdwind speed 8 to 11 m/s (17 to 21 knots), significant wave height 2 to 3 m; medium-sized helicoptersdwind speed 9 to 11 m/s (17 to 27 knots, significant wave height 2 to 8 m); and large multiple-engine airplanesdwind speed 15 to 18 m/s (30 to 35 knots), significant wave height 9 to 12 m.49 DeCola presented a survey of world guidelines and decision trees for dispersant use.50 Of the about 30 guides or decision trees presented, only two decision trees note restrictions on weather conditions. The US Environmental Protection Agency (EPA) Region 6 guideline indicates an upper limit of 13 m/s (25 knots) on dispersant use, and the Washington/Oregon guidelines specify a lower limit of a sea state of 1 and an upper sea state of 4 (1 to 10 m/s winds). The latter guideline also specifies an upper limit of 0.5 m/s current for mechanical countermeasures. Koops and Huisman give a priori limits of Beaufort 6 for skimmers and other mechanical recovery, a limit between 2 and 8 Beaufort (2 to 20 m/s wind) for dispersion, and a lower threshold of greater than 3 Beaufort for natural dispersion.51 Koops gives the limit of skimmers as 1.5 m wave heights and notes that swell has no effect on the capability to mechanically recover.52 The Mechanical Equipment Calculator, part of National Oceanic and Atmospheric Administration (NOAA’s) Spill Tools on the Internet, does not include the effects of weather on containment and recovery, although effectiveness is calculated in the program.53 The program includes primarily the inputs of slick thickness and efficiency. Etkin and coworkers describe modeling of countermeasures to include the effect of currents.54 Dempsey suggests a limit of a wind speed of 12 m/s (25 knots) and a sea state with a wave height not exceeding 3 m for offshore work.55

Chapter | 13 Weather Effects on Oil Spill Countermeasures

345

Reed described the OSCAR spill model and noted that the mechanical recovery efficiencies in the model were set as 80% with a 5 m/s wind and 60% with a 10 m/s wind.56-58 It is important to note that most of the above estimates are not based on quantitative results. Quantitative results are presented in the remainder of this subsection.

13.2.2. General Countermeasures Most authors presume low weather limits for at-sea countermeasures. The presumption is typically that countermeasures cannot be conducted if the sea is not dead calm.59,60 Steen et al. suggest a limit of 1 m waves, while at the same symposium, Koops and Huisman suggest a limit of five times that amount.51,60 Det Norske Veritas, in cooperation with the Norwegian Pollution Authority, has developed standards for the certification of oil spill recovery technologies.61 The certification focuses on test methods specifically geared to smaller test tanks as exist in Norway and not on developing minimum specifications for such equipment. Weather conditions have not been included.

13.2.3. Booms Schulze and coworkers reviewed the performance of booms and summarized 20 years of testing.62,63 They note that it is important to relate first loss velocity as well as test oil viscosity, freeboard, boom draft, and the boom buoyancy-toweight ratio. Much of the boom testing was conducted in OHMSETT. The results of boom testing in OHMSETT have varied over the years. Devitis and Hannon note that the results of testing have gone up over the years; that is, the first loss tow velocity has increased.64 Specifically, Devitis and Hannon report that there was a jump between the 1982 and 1992 results. During that period, no testing was conducted in OHMSETT, and when it resumed the first loss failures jumped from about 0.5 to 0.6 m/s. However, Devitis and Hannon state first that the range of results is about the same and that the differences may stem from the fact that the earlier results were conservative and second that boom designs have improved somewhat. The results of testing from 1975 to 1982 and the procedures for offshore testing for oil spill containment booms were reviewed by Nash and Hillger.65 The first loss speed ranged from 0.1 to 0.57 m/s for a calm situation and from 0 to 0.56 m/s for regular waves and 0 to 0.38 m/s for chop. Testing results from OHMSETT are summarized in Table 13.3. The classic failure of oil spill containment booms at currents of about 0.4 m/s (0.8 knots) is well established by hydrodyamic models and tests. Much of this theory was established by Wicks.67 Milgram and van Houten summarized the classic theories and demonstrated these in a test tank.68 Delvigne described boom failure by critical accumulation of viscous oils.69 Delvigne also noted

TABLE 13.3 Tests of Boom Performance with Changing Weather Conditions Current/Tow Speed

Boom

Reference

Year of Test

First Loss Speed m/s

Typical booms Fence - catenary

62

1977

0.2

Fence - catenary

62

1977

0.23

Fence - diversionary

62

1977

0.6

Fence - diversionary

62

1977

0.7

Fence - diversionary

62

1977

0.5

Fence - catenary

62

1991

Fence - catenary

62

Fence - catenary

Critical Speed m/s

Wave Height Summary Speed/ Wave/s

Oil Viscosity mPa. S

Number of Tests

Wave Height m

Wave Conditions

300

8

calm or 0.3

long regular waves

300

0.6

short regular waves

300

calm

0.7

300

0.3

long regular waves

1.3

300

0.6

short regular waves

0.45

64

calm

1991

0.5

64

calm

62

1991

0.6

64

calm

Curtain - catenary

62

1977

0.45

333

Curtain - catenary

62

1977

0.25

Curtain - diversionary

62

1977

0.6

Curtain - diversionary

62

1977

0.4

Curtain - catenary

62

1977

0.45

Curtain - catenary

62

1977

0.35

Curtain - diversionary

62

1977

0.4

Curtain - diversionary

62

1977

0.45

0.17

1.3

1.3

0.7

0.3

Oil Type

16

calm or 0.3

long regular waves

333

0.6

short regular waves

1462

calm or 0.3

long regular waves

1462

0.6

short regular waves

230

calm

230

0.3

336

calm

336

0.3

long regular waves

long regular waves

Curtain - diversionary

62

1977

0.38

Curtain - catenary

62

1977

Curtain - diversionary

62

Curtain - catenary

0.5

336

0.6

0.4

649

calm, or short or long reg waves

1977

0.4

333

calm, or short or long reg waves

62

1977

0.45

97

calm, or short or long reg waves

Curtain - diversionary

62

1977

0.7

235

calm, or short or long reg waves

Curtain EF- catenary

62

1977

0.35

194

calm, or short or long reg waves

Curtain EF- diversionary

62

1977

0.45

134

calm, or short or long reg waves

Self-inf - catenary

62

1977

0.25

300/177

calm

Self-inf - catenary

62

1977

0.3

300/177

0.3

long regular waves

Self-inf - catenary

62

1977

0.4

300/177

0.6

short regular waves

Self-inf - catenary

62

1977

0.2

300/10

calm or 0.3

long regular waves

Self-inf - catenary

62

1977

0.35

300/10

0.6

short regular waves

Self-inf - diversionary

62

1977

0.75

300/238

calm

Self-inf - diversionary

62

1977

0.5

0.85

300/238

0.3

long regular waves

Self-inf - diversionary

62

1977

.6-.8

0.15

300/238

0.6

short regular waves

Self-inf - diversionary

62

1977

0.2

1

300/238

0.3

harbour chop

0.35

0.5

short regular waves

(Continued )

TABLE 13.3 Tests of Boom Performance with Changing Weather Conditionsdcont’d Current/Tow Speed

Boom

Reference

Year of Test

First Loss Speed m/s

Self-inf - catenary

62

1980

.4/.55

Self-inf - catenary

62

1980

0.45

Self-inf - catenary

62

1980

.4/0.57

Self-inf - catenary

62

1991

Press-inf - diversionary

62

Press-inf - diversionary

Critical Speed m/s

Wave Height Summary Speed/ Wave/s

Wave Height m

Wave Conditions

1026/3000

0.2

long regular waves

1026/3000

0.2

long regular waves

1026/3000

0.4

long regular waves

0.5

10/64

calm

1993

.5/.7

100/370

calm

62

1993

0.7/0.9

100/9300

calm

Press-inf - diversionary

62

1993

0.7/0.65

0.55

Press-inf - diversionary

62

1993

0.8/0.9

0.25

Press-inf - diversionary

62

1993

0.7/0.8

0.25

Press-inf - diversionary

62

1993

0.62/0.8

Press-inf - diversionary

62

1993

0.5/0.8

Press-inf - diversionary

62

1993

0.6/0.8

Press-inf - diversionary

62

1993

0.6/0.7

Press-inf - diversionary

62

1993

Press-inf - diversionary

62

Press-inf - diversionary

62

0.13

Oil Type

Oil Viscosity mPa. S

Number of Tests

0.3

long regular waves

100/9900

0.6

short regular waves

100/9900

0.3

harbour chop

100/9900

calm

900/7500

0.3

900/10400

calm

900/3600

0.6

0.72/0.88

100/850

calm

1993

0.63/0.7

300/870

calm

1993

0.65/0.8

300/870

0.3

0

0.2

0.15

harbour chop

short regular waves

long regular waves

Press-inf - diversionary

62

1993

0.63/0.85

Press-inf - diversionary

62

1993

0.6/0.7

Press-inf - diversionary

62

1993

0.5/0.62

Press-inf - catenary

62

1991

Press-inf - catenary

62

Press-inf - catenary

0.35

300/630

0.3

harbour chop

300/1050

calm or 0.3

long regular waves

300/1050

0.3

harbour chop

0.6

10/64

calm

1991

0.45

10/64

calm

62

1991

0.75

10/64

calm

Fence

62

1997

0.5

0.63

600/3000

calm

Fence

62

1997

0.35

0.45

0.63

600/3000

0.24

regular waves

Fence

62

1997

0.55

0.65

0.17

600/3000

0.3

long regular waves

Fence

62

1997

0.48

0.55

0.07

600/3000

0.2

harbour chop

Fence

62

1997

0.48

0.66

500/2900

calm

Fence

62

1997

0.37

0.53

0.46

500/2900

0.24

regular waves

Fence

62

1997

0.48

0.6

0

500/2900

0.3

long regular waves

Fence

62

1997

0.5

0.53

0.07

500/2900

0.2

harbour chop

Fence

62

1999

0.45

0.6

400/200

calm

Fence

62

1999

0.38

0.45

0.29

400/200

0.24

regular waves

Fence

62

1999

0.45

0.6

0

400/200

0.3

long regular waves

Fence

62

1999

0.45

0.6

0

400/200

0.2

harbour chop

0.35

Fire-resistant booms

(Continued )

TABLE 13.3 Tests of Boom Performance with Changing Weather Conditionsdcont’d Current/Tow Speed

Boom

Reference

Year of Test

First Loss Speed m/s

Critical Speed m/s

Intern foam

62

1999

0.48

0.63

Intern foam

62

1999

0.42

0.55

Intern foam

62

1999

0.55

Intern foam

62

1999

Press inflat

62

Press inflat

Wave Height Summary Speed/ Wave/s

Oil Type

Oil Viscosity mPa. S

Number of Tests

Wave Height m

Wave Conditions

360/1940

calm

0.25

360/1940

0.24

regular waves

0.74

0.23

360/1940

0.3

long regular waves

0.53

0.65

0.19

360/1940

0.2

harbour chop

1997

0.45

0.61

500/1730

calm

62

1997

0.4

0.21

500/1730

0.24

regular waves

Press inflat

62

1997

0.54

0.3

500/1730

0.3

long regular waves

Press inflat

62

1997

0.5

0.17

500/1730

0.2

harbour chop

Exterior tension

62

1999

0.45

0.63

360/2064

calm

Exterior tension

62

1999

0.3

0.48

360/2064

0.24

regular waves

Exterior tension

62

1999

0.5

0.65

360/2064

0.3

long regular waves

Exterior tension

62

1999

0.35

0.55

360/2064

0.2

harbour chop

Ceramic

66

1982

1.1

heavy

1300

calm

Ceramic

66

1982

1.1

0

heavy

1300

0.2

Ceramic

66

1982

0.9

0.5

heavy

1300

0.4

Ceramic

66

1982

0.7

2

heavy

1300

0.2

harbour chop

Chapter | 13 Weather Effects on Oil Spill Countermeasures

351

that the classical droplet breakaway failure varied as a square of the current velocity. Tedeschi reviews booms and notes that the typical failure is at winds of 8 to 9 m/s (15 to 18 knots).70 Fitzmaurice reviews containment and failure modes and suggests that multiple boom configurations might be used to avoid critical accumulation.71 Several workers utilized models to study failure modes.72-82 Although most did not include waves as a failure mode, Castro included waves and boom shape in physical model study.83 Chen also reviews containment and proposed to raise containment limits by using porous nets in front of the booms to slow the currents.84 Johnston et al. identified a boom failure mechanism just before critical accumulation occurs with heavy oils. This mode is characterized by a surging under the boom.85 Zhu and Strunin propose a new containment model utilizing the Froude number submergence depth and the amount of oil trapped by the barrier.86 The effect of waves has been studied by Van Dyck and Bruno.87 They conducted a series of tow tank tests showing that short-wavelength waves are the most difficult sea conditions for a floating boom to follow, even at optimum tow speeds or relative currents. Wave height was found not to be the limiting parameter, provided the wavelength/height ratio is 12:1 or greater. Short length/ height ratios lead to breaking waves where the height of the breaker must not exceed the available freeboard of the floating boom or there will be significant oil loss. Optimum catenary tow speeds are verified to be near 0.5 knot full scale for all wave sizes tested. Lee and Kang review the performance of booms in currents and waves.88 They suggest that the effect of waves is to increase the horizontal current velocity. They present a graphical algorithm to predict the failure resulting from symmetrical waves. Kordyban developed a model to examine the effect of waves on boom failure.89 His approach is similar to Lee and Kang, and a sinusoidal wave increases the effective velocity. Marks et al. analyzed the forces on a boom and calculated that the total force was directly related to the wave amplitude as well as 12 other factors.90 Milgram reviewed the specific mechanical design features of booms.91 He derived the following relationship to predict fabric tearing force as: fr ¼ ðCr rgðd þ bÞ2 1H 1=3 Þ=10

(1)

where the factors of interest to this paper are: fr ¼ tearing force, and H ¼ the significant wave height Milgram also notes that fabric tearing is the most significant type of physical damage to the boom and that it relates to the one-third power of the significant wave height. Several workers have noted that the wave period is a serious factor in determining boom capabilities in waves.92 Oebius noted that a height-to-period ratio of 0.04 is optimal for boom containment, but that shorter periods such as 0.056 would result in loss of containment.92

352

PART | V

Physical Spill Countermeasures on Water

Potter et al. studied the towing forces on booms.93 The first formulation that they review has the wave height as a direct and linear factor. The second formulation has the wave height as a constant that varies with boom and wave type. A typical constant for wave height is about 2 for a calm condition, 3.5 for regular waves, and 4 for harbor chop. Allen-Jones reviewed the towing forces and suggested that the direct use of significant wave height might be appropriate.94 Schulze and Potter subsequently conducted a series of tests in OHMSETT to measure the tow forces.95 This resulted in a new estimator of tow force, which includes the tension caused by the force of water being directly proportional to the significant wave height. Several attempts have been made to increase the containment capability of booms in fast waters using energy dissipative devices.96-99 Wong and Witmer used an elliptical shape to increase containment capability.100 Fang and Wong used a ramp and a series of vertical barriers to create a calm recovery area.77 Sloan et al. and Nordvik et al. tested several booms offshore in the New York/New Jersey area.101-103 Findings included the result that many of the booms tested were not suitable for the conditions encountered in offshore waters and that the wave height was only one of the factors that caused an excess of tow forces for the boom designs. It was also noted that a strong relationship existed between tow speed submergence initiation and reserve buoyancy. Also, it was found that the calculation methods for tow force underestimated the tow force. It was suggested that this might be a result of not adding the second tow vessel’s acceleration. Nash and Molsberry discuss offshore testing and report that the size of the system is a factor.104 They observed that larger booms performed better in an offshore environment. Suzuki et al. tested booms in ice and found that the ice presence actually increased the critical tow speed.105 The critical tow speed with ice present generally increased from 0.4 to 0.5 m/s, depending on a variety of conditions.

13.2.3.1. Typical Booms Yazaki described the Japanese government’s requirements for two types of booms as being able to contain oil in winds of 10 or 20 m/s (type C, small harbor, or type D, larger, boom); wave heights of 1 and 1.5 m, and 0.25 and 0.5 m/s current.106 Brown et al. noted that booms would fail at tow velocities of 0.25 m/s if the oil was heavier.107 13.2.3.2. Special and High-Current Booms Getman reported on the tests of three fast current oil recovery devices: the Shell ZRV skimmer, the Seaward streaming fibre skimmer, and the French Cyclonet 050.108 Getman stated that the Shell ZRV performed well in a high

Chapter | 13 Weather Effects on Oil Spill Countermeasures

353

current and in a wave train and that the other two devices performed poorly in a wave train. Bitting reported on the testing of the NOFI Vee-Sweep system, observing that this device retains oil at higher speeds than most other devices.109 Hansen measured the performance of a number of devices including sorbent booms in fast water.110-111 The JBF 6001 and Current Buster worked up to 3 and 3.5 m/s currents, respectively. Hansen described a series of tests to measure the performance of fast water booms and deflectors.112 Brekne et al. described a boom designed to work in up to 2.5 m significant wave height and 20 m/s winds (50 knots).113 This new specialized boom, known as the Uniboom, uses a net for the lower portion of the skirt and is self-inflating. No subsequent data was actually provided on measured performance. Williams and Cooke studied and tested bubble barriers for containing and burning oil.114 They found that the depth of slick contained varied as the square of the current velocity. For example, in 8 to 10 m/s wind, the floating bubble barrier held a 3.2 cm slick several meters away. Eryuzlu and Hauser describe the use of floating deflectors to move oil out of currents to calm areas.115 A prototype deflector was tested in currents from 0.8 to 2.1 m/s and successfully deflected oil simulant to a calm area. Folsom and Johnson describe a streamlined boom that was claimed to contain or deflect oil up to 3 m/s.116 Nash and Johnson report on the use of plunging water jets to converge oil slicks. They found that by using this technology they could converge slicks at current speeds of up to 3 m/s.117 Brown et al. report on the study and testing of several high-speed containment concepts, including vertical cylinders, vertical slats with and without a back wall, vertical walls with fins at an angle, a hydrofoil, and horizontal structures including inclined screens and a variety of filters.107,118 Several of these innovations improved the containment ability, but no single system was recommended. Swift et al. reported on tests of an inclined submergence bow plane device that retained oil at currents up to 1.03 m/s.119 Wong et al. describe new booms for high-current application.120,121 Cooper et al. describe a modified boom to contain heavy oil.122

13.2.4. Skimmers Extensive testing of skimmers has been conducted in the OHMSETT facility. Tests from the 1970s are summarized by Smith and Lichte and by Farlow and Griffiths.123,124 Additional data are given by Lichte et al.125,126 These tests are summarized again in Schulze.127 The book by Schulze is used as the prime source of data here, as summarized in Table 13.4. New testing is described in several papers but quantitative results are not given.128-130

TABLE 13.4 Tests of Skimmer Performance with Changing Weather Conditions Current/Tow Speed Summary

Skimmer

Wave Height Summary

Year Slope

ORR

Slope Slope Slope

ORR

of

ORR

Slope

TE

Slope TE

RE

Oil

Viscosity Thick.

# of Speed Height Wave

ORR TE

RE

m2s/h

%s/m

%s/m %s/m m2/h

%/m

%/m

Type

mPa. S

mm

Tests m/s

m

m3/h %

%

200

120

3

0.25

calm

58.2

56

Reference Test

RE

ORR

Slope Slope %/m

Oil

Slick

Wave Conditions

Harbour/Small Skimmers Skimming barrier

127

1977

Skimming barrier

127

1977

200

120

5

0.25

0.3

47.4

34.5

Skimming barrier

127

1977 115.4

198.3

134.6

36

61.9

71.7

200

120

2

0.38

calm

harbour chop

73.2

73.5

Skimming barrier

127

1977 57.6

99

12.8

200

120

6

0.5

calm

72.6

59.2

Skimming barrier

127

1977

18

30.9

41.3

200

120

2

0.38

0.3

63.6

43.6

Skimming barrier

127

1977

45

77.3

23.7

200

120

4

0.5

0.3

regular

71.7

48.9

Skimming barrier

127

1977

0

0

50.3

200

120

4

0.5

0.3

regular

58.2

40.9

Skimming barrier

127

1977

15.2

26.1

49.4

200

120

1

0.25

0.5

regular

50.6

31.3

Skimming barrier

127

1977

12.6

27.8

34.6

200

120

4

0.5

0.5

regular

66.3

41.9

Skimming barrier

127

1977

18.8

17.2

38.8

200

120

4

0.5

0.5

regular

63.2

39.8

Skimming barrier

127

1977

25.3

43.5

46.7

200

120

2

0.25

0.6

harbour chop

43

28

Skimming barrier

127

1977

85

8

60.2

200

120

3

0.38

0.6

harbour chop

61

37.4

Skimming barrier

127

1977

30

10.3

40.7

200

120

6

0.5

0.6

harbour chop

54.6

34.8

Skimming barrier

127

1977

30.7

11.5

41.5

200

120

6

0.5

0.6

harbour chop

54.2

34.3

Sirene skimming barrier

127

1979

545

3.1

1

0.38

calm

18

100

23

Sirene skimming barrier

127

1979 87.5

486.1

175

158.3

545

3.3

1

0.5

calm

28.5

79

42

Sirene skimming barrier

127

1979 41.6

231.1

288

104

545

3.2

1

0.63

calm

28.4

28

49

Sirene skimming barrier

127

1979 5.9

33

240.5

8.1

Sirene skimming barrier

127

1979

1

5.6

Sirene skimming barrier

127

1979

35.8

Sirene skimming barrier

127

1979

545

3

1

0.75

calm

15.8

11

26

18.2

545

3.2

1

0.38

0.6

harbour chop

18.6

99

31

199.1 85

48.5

545

3.3

1

0.63

0.6

harbour chop

39.5

49

71

25.7

142.6 115

26.8

545

2.6

1

0.75

0.6

harbour chop

33.4

31

58

1.7

Sirene skimming barrier

127

1979

23.3

129.6

306.7

86.3

545

2.7

2

1

0.3

harbour chop

11

8

16

Sirene skimming barrier

127

1979

3.2

17.8

2

29.8

545

3.2

1

0.38

0.5

regular

16.4

99

27

Sirene skimming barrier

127

1979

35.4

196.7 94

26.2

545

2.7

1

0.63

0.5

regular

35.7

53

55

Sirene skimming barrier

127

1979

178

3.1

1

0.38

calm

16.6

99

22

Sirene skimming barrier

127

1979 155

933.7

258.3

183.3

178

3.3

1

0.5

calm

35.2

68

44

Sirene skimming barrier

127

1979 16

96.4

244

80

178

3.1

1

0.63

calm

12.6

38

42

Sirene skimming barrier

127

1979 7

42.3

237.8

5.4

178

2.6

1

0.75

calm

14

11

24

Sirene skimming barrier

127

1979

1.8

10.8

2

178

3.2

1

0.38

0.5

regular

15.7

99

21

Sirene skimming barrier

127

1979

46.4

279.5 96

74

178

3.1

1

0.5

0.5

regular

39.8

51

59

Sirene skimming barrier

127

1979

21.6

130.1 158

44

178

3.5

1

0.63

0.5

regular

27.4

20

44

Sirene skimming barrier

127

1979

1.6

9.6

170

14

178

2.5

1

0.75

0.5

regular

15.8

14

29

Sirene skimming barrier

127

1979

1.3

7.7

0

4.3

178

3.1

1

0.38

0.7

harbour chop

15.7

99

25

Sirene skimming barrier

127

1979

4

24.1

82.9

17.1

178

2

1

0.5

0.7

harbour chop

19.4

41

34

Sirene skimming barrier

127

1979

11.4

68.8

61.4

64.3

178

3.3

1

0.63

0.7

harbour chop

24.6

56

67

Sirene skimming barrier

127

1979

0

0

122.9

10

178

2.9

1

0.75

0.7

harbour chop

16.6

13

29

0

(Continued )

TABLE 13.4 Tests of Skimmer Performance with Changing Weather Conditionsdcont’d Current/Tow Speed Summary

Skimmer

Wave Height Summary

Year Slope

ORR

Slope Slope Slope

ORR

of

ORR

Slope

TE

Slope TE

RE

Oil

Viscosity Thick.

# of Speed Height Wave

ORR TE

RE

m2s/h

%s/m

%s/m %s/m m2/h

%/m

%/m

Type

mPa. S

mm

Tests m/s

m

m3/h %

%

Reference Test

RE

ORR

Slope Slope %/m

Oil

Slick

Wave Conditions

Lori brush skimmer

127

1979

med. oil 600

ns

1

0.75

calm

0.31

60

Lori brush skimmer

127

1979 0.6

182.8

86.7

med. oil 600

ns

1

1.05

calm

0.48

86

Lori brush skimmer

127

1979 0.8

258.1

40

med. oil 600

ns

1

1.3

calm

0.75

82

Lori brush skimmer

127

1979 0.9

279.6

24

med. oil 600

ns

1

1.5

calm

0.96

78

82.9

5.7

Lori brush skimmer

127

1979 0.3

med. oil 600

ns

1

1.8

calm

0.58

66

Lori brush skimmer

127

1979

0.3

80.6

131.3

med. oil 600

ns

1

0.75

0.16

regular

0.35

81

Lori brush skimmer

127

1979

2.6

842.3

83.3

med. oil 600

ns

1

1

0.18

regular

0.78

75

Lori brush skimmer

127

1979

2.5

821.1

72.7

med. oil 600

ns

1

1.3

0.22

regular

0.87

76

Lori brush skimmer

127

1979

2

645.2

56

med. oil 600

ns

1

1.5

0.25

regular

0.81

74

Lori brush skimmer

127

1979

1.1

349.5

33.3

med. oil 600

ns

1

1.8

0.24

regular

0.57

68

Scoop weir skimmer

127

1978

heav. oil 1000

ns

2

0.25

calm

Scoop weir skimmer

127

1978 6.9

75.3

0

heav. oil 1000

ns

1

0.38

calm

10.1

100

87

Scoop weir skimmer

127

1978 13.6

147.8

220

heav. oil 1000

ns

3

0.5

calm

5.8

45

100

Scoop weir skimmer

127

1978 13.4

145.9

176.3

heav. oil 1000

ns

4

0.63

calm

4.1

33

Scoop weir skimmer

127

1978

heav. oil 1000

ns

1

0.38

0.3

10.6

91

4.7

50.7

30

9.2

regular

100

57

Scoop weir skimmer

127

1978

7.5

81.5

71.7

heav. oil 1000

ns

1

0.25

0.6

harbour chop

4.7

57

Scoop weir skimmer

127

1978

6.3

68.8

53.3

heav. oil 1000

ns

3

0.38

0.6

harbour chop

5.4

68

100

Scoop weir skimmer

127

1978

4.2

45.3

51.7

heav. oil 1000

ns

3

0.5

0.6

harbour chop

6.7

69

Scoop weir skimmer

127

1978

7.5

81.5

118.3

heav. oil 1000

ns

2

0.63

0.6

harbour chop

4.7

29

Disc skim. - flat -CCG tests

127

1993

lt. crude 5 to 50

10

0

calm

Disc skim. - flat -CCG tests

127

1993

85

lt. crude 5 to 50

10

0

0.4

regular

65

Disc skim. - flat -CCG tests

127

1993

63.8

lt. crude 5 to 50

10

0

0.8

harbour chop

48

Disc skim. - flat -CCG tests

127

1993

lt. crude 5 to 50

25

0

calm

Disc skim. - flat -CCG tests

127

1993

32.5

lt. crude 5 to 50

25

0

0.4

regular

83

Disc skim. - flat -CCG tests

127

1993

38.8

lt. crude 5 to 50

25

0

0.8

harbour chop

65

Disc skim. -T-disk -CCG 127 tests

1993

lt. crude 5 to 50

10

0

calm

Disc skim. -T-disk -CCG 127 tests

1993

47.5

lt. crude 5 to 50

10

0

0.4

regular

46

Disc skim. -T-disk -CCG 127 tests

1993

51.3

lt. crude 5 to 50

10

0

0.8

harbour chop

24

Disc skim. -T-disk -CCG 127 tests

1993

lt. crude 5 to 50

25

0

calm

Disc skim. -T-disk -CCG 127 tests

1993

lt. crude 5 to 50

25

0

0.4

37.5

95

99

96

99

100

regular

85

(Continued )

TABLE 13.4 Tests of Skimmer Performance with Changing Weather Conditionsdcont’d Current/Tow Speed Summary

Skimmer

Wave Height Summary

Year Slope

ORR

Slope Slope Slope

ORR

of

ORR

Slope

TE

Slope TE

RE

Oil

Viscosity Thick.

# of Speed Height Wave

ORR TE

RE

m2s/h

%s/m

%s/m %s/m m2/h

%/m

%/m

Type

mPa. S

Tests m/s

m3/h %

%

67.5

lt. crude 5 to 50

25

heav. oil 1900

Reference Test

RE

Disc skim. -T-disk -CCG 127 tests

1993

Paddle skimmer

127

1977

Paddle skimmer

127

1977

Rope mop stationary

127

1977

Rope mop stationary

127

1977

Rope mop stationary

127

1977

Rope mop stationary

127

1977

Rope mop stationary

127

1977

Rope mop stationary

127

1977

Rope mop towed single

127

1978

Rope mop towed single

127

1978 4.2

90.9

1.8

Rope mop towed single

127

1978 0.5

7.2

105

Rope mop towed single

127

1978

Rope mop towed single

127

1978 3.1

53.3

Rope mop towed single

127

1978 5.5

73.3

ORR

23

1.5

244.7

57.7

Slope Slope %/m

105

330

35

1.7

53.8

15

7

225.8

10

Oil

Slick mm

Wave m

Conditions

0

0.8

harbour chop

26

0

calm

heav. oil 1900

26

0

0.2

lt. crude 6

20

0

calm

regular

harbour chop

46

9.4

91

84

4.8

70

18

2.6

89

3.5

68

3.1

79

4.1

70

10

98

7.3

73

lt. crude 6

20

0

0.6

lt. crude 14

20

0

calm

lt. crude 14

20

0

0.6

lt. crude 79

20

0

calm

lt. crude 79

20

0

0.6

med. oil 793

5

0.75

calm

4.6

55

med. oil 793

5

1.3

calm

6.9

56

harbour chop

harbour chop

med. oil 793

5

1.5

calm

6.8

35

8

173.9

40

med. oil 793

5

0.75

0.15

regular

5.8

61

14.5

4

58

20

med. oil 793

5

1.3

0.15

regular

7.5

53

10

2.7

39.2

133.3

med. oil 793

5

1.5

0.15

regular

6.4

55

Rope mop towed single

127

1978

Rope mop towed single

127

1978 5.1

59.9 61.4

6.5

141.3

3.3

med. oil 793

5

0.75

0.6

harbour chop

8.5

53

7.3

2

29

11.7

med. oil 793

5

1.3

0.6

harbour chop

5.7

49

15

3

44.1

18.3

med. oil 793

5

1.5

0.6

harbour chop

lt. crude 65

4 ave

1.25

calm

7

36

23

Rope mop towed single

127

1978 3.5

Oil mop ZRV

127

1976

Oil mop ZRV

127

1976 0

0

84

0

lt. crude 65

4 ave

1.5

calm

7

15

23

Oil mop ZRV

127

1976 0.6

8.6

18

2

lt. crude 65

4 ave

1.75

calm

7.3

27

24

Oil mop ZRV

127

1976

lt. crude 65

4 ave

1.5

0.6

4.8

21

10

Oil mop ZRV

127

1977

heav. oil 3000

3

3

0.5

calm

4.3

71

52

Oil mop ZRV

127

1977 7.2

167.4

44

50

heav. oil 3000

3

6

1

calm

7.9

49

77

Oil mop ZRV

127

1977 8.5

197.7

7

23

heav. oil 3000

3

2

1.5

calm

12.8

64

75

Oil mop ZRV

127

1977

heav. oil 3000

3

4

0.5

0.6

10

80

35

Oil mop ZRV

127

1977

lt. crude 3

3

9

1

calm

9.4

65

66

Oil mop ZRV

127

1977 8.1

86.2

2

4

lt. crude 3

3

2

2

calm

17.5

67

62

Oil mop ZRV

127

1977 3

31.9

14.7

12

Oil mop ZRV

127

1977

Oil mop ZRV

127

1977 3.5

Oil mop ZRV

127

1977

3.7

9.5

37.2

16

13

52.4

10

220.9 15

21.7

28.3

harbour chop

harbour chop

5

46

lt. crude 3

3

3

2.5

calm

13.9

43

48

0

0

11.7 20

lt. crude 3

3

4

1

0.6

harbour chop

9.4

72

54

7.7

43.8

18.3

35

lt. crude 3

3

5

2

0.6

harbour chop

12.9

56

41

5

28.6

2.5

21.3

lt. crude 3

3

2

2

0.8

regular

13.5

65

45

Marco belt skimmer

127

1976

heav. oil 837

8 to 11

6

0.5

calm

11.5

85

57

Marco belt skimmer

127

1976 24.2

210.4

10

18

heav. oil 837

8 to 11

5

1

calm

23.6

90

66

Marco belt skimmer

127

1976 9.1

79.1

23

19

heav. oil 837

8 to 11

4

1.5

calm

harbour chop

20.6

62

76

Marco belt skimmer

127

1976

heav. oil 837

8 to 11

1

0.5

0.6

harbour chop

10.7

76

74

1.3

11.6

15

28.3

(Continued )

TABLE 13.4 Tests of Skimmer Performance with Changing Weather Conditionsdcont’d Current/Tow Speed Summary

Wave Height Summary

Year Slope

ORR

Slope Slope Slope

ORR

of

ORR

Slope

TE

Slope TE

RE

Oil

Viscosity Thick.

# of Speed Height Wave

ORR TE

RE

m2s/h

%s/m

%s/m %s/m m2/h

%/m

%/m

%/m

Type

mPa. S

mm

Tests m/s

m

Conditions

m3/h %

%

RE

ORR

Slope Slope

Oil

Slick

Wave

Skimmer

Reference Test

Marco belt skimmer

127

1976 2.4

22.4

62

46

19.5

82.6

75

25

heav. oil 837

8 to 11

1

1

0.6

harbour chop

11.9

45

51

Marco belt skimmer

127

1976 1.8

16.8

48

37

13.5

65.5

56.7

65

heav. oil 837

8 to 11

1

1.5

0.6

harbour chop

12.5

28

37

Marco belt skimmer

127

1976

20.8

18.3

heav. oil 837

8 to 11

1

0.5

1.2

harbour chop

.

60

35

Marco belt skimmer

127

1976

41.7

26.7

heav. oil 837

8 to 11

1

1

1.2

harbour chop

9.9

40

34

heav. oil 784

3

1

0.25

calm

3

74

87

heav. oil 784

3

22

0.5

calm

6.1

71

79

heav. oil 784

6

1

0.5

calm

9.9

71

84

40

2

12

32

Marco belt skimmer

127

1977

Marco belt skimmer

127

1977 12.4

Marco belt skimmer

127

1977

Marco belt skimmer

127

1977 8.8

293.3

12

2

heav. oil 784

3

5

0.75

calm

7.4

68

88

Marco belt skimmer

127

1977 25.2

254.5

8

16

heav. oil 784

6

1

0.75

calm

16.2

69

88

Marco belt skimmer

127

1977 6.9

231.1

29.3

8

heav. oil 784

3

31

1

calm

8.2

52

81

Marco belt skimmer

127

1977 17.4

175.8

20

4

heav. oil 784

6

1

1

calm

18.6

61

86

Marco belt skimmer

127

1977 2.6

85.3

40

12

heav. oil 784

3

8

1.5

calm

6.2

24

72

Marco belt skimmer

127

1977

0.8

27.8

43.3

61.7

heav. oil 784

3

5

0.5

0.6

harbour chop

3.5

48

50

Marco belt skimmer

127

1977

1.2

38.9

71.7

63.3

heav. oil 784

3

1

0.75

0.6

harbour chop

3.7

31

49

Marco belt skimmer

127

1977

9.5

96

95

65

heav. oil 784

6

2

1

0.6

harbour chop

4.2

14

45

413.3

Marco belt skimmer

127

1977

0.5

16.7

35.8

34.2

heav. oil 784

3

2

0.5

1.2

harbour chop

2.4

31

46

Marco belt skimmer

127

1977

0.3

8.3

38.3

33.3

heav. oil 784

3

1

0.75

1.2

harbour chop

3.3

28

47

Fixed submersion plane

127

1978

lt. oil

19

3

2

0.75

calm

14.8

51

Fixed submersion plane

127

1978 40

270.3

36

lt. oil

19

3

2

1

calm

24.8

78

Fixed submersion plane

127

1978 31.7

214.4

20.8

lt. oil

19

3

3

1.5

calm

38.6

77

Fixed submersion plane

127

1978 13.1

88.6

1.1

lt. oil

19

3

5

2

calm

31.2

49

Fixed submersion plane

127

1978 5.8

39.4

10.7

Fixed submersion plane

127

1978

Fixed submersion plane

127

1978 1.6

18.2

28

lt. oil

19

3

2

2.5

calm

25

27

20

135.1

56.7

lt. oil

19

3

2

0.75

0.3

harbour chop

8.8

34

52

209.7

170

lt. oil

19

3

2

1

0.3

harbour chop

9.2

27

Fixed submersion plane

127

1978 9.6

109.1

2.7

75.3

195.2

150

lt. oil

19

3

5

1.5

0.3

harbour chop

16

32

Fixed submersion plane

127

1978 14.3

162.7

6.4

15

48.1

23.3

lt. oil

19

3

4

2

0.3

harbour chop

26.7

42

Fixed submersion plane

127

1978

11.2

75.5

18.3

lt. oil

19

3

1

0.75

0.6

harbour chop

8.1

40

Fixed submersion plane

127

1978

17.6

118.9

52

lt. oil

19

3

1

0.75

0.5

regular

6

25

Fixed submersion plane

127

1978 8.4

140

4

33.4

134.7

108

lt. oil

19

3

1

1

0.5

regular

8.1

24

Fixed submersion plane

127

1978 1.2

20

20

67

173.6

134

lt. oil

19

3

1

1.5

0.5

regular

5.1

10

Fixed submersion plane

127

1978

heav. oil 1230

10

1

1

calm

87.8

90

Fixed submersion plane

127

1978 217.2

heav. oil 1230

10

2

1.25

calm

33.5

87

247.4

12

Fixed submersion plane

127

1978 107.8

122.8

36

heav. oil 1230

10

2

1.5

calm

33.9

72

Fixed submersion plane

127

1978 51.2

58.3

29

heav. oil 1230

10

4

2

calm

36.6

61

Fixed submersion plane

127

1978

heav. oil 1230

3

1

0.5

calm

3.2

8

Fixed submersion plane

127

1978 18.8

heav. oil 1230

3

3

1.38

calm

19.7

77

585.9

78.4

(Continued )

TABLE 13.4 Tests of Skimmer Performance with Changing Weather Conditionsdcont’d Current/Tow Speed Summary

Wave Height Summary

Year Slope

ORR

Slope Slope Slope

ORR

of

ORR

Slope

TE

Slope TE

RE

Oil

Viscosity Thick.

# of Speed Height Wave

ORR TE

RE

m2s/h

%s/m

%s/m %s/m m2/h

%/m

%/m

Type

mPa. S

Tests m/s

m3/h %

%

Skimmer

Reference Test

Fixed submersion plane

127

1978 46.6

Fixed submersion plane

127

1978

Fixed submersion plane

127

1978 28.4

355

60

Fixed submersion plane

127

1978 16.3

203.3

20

RE

ORR

Slope Slope %/m

1456.3 148

Fixed submersion plane

127

1978

Fixed submersion plane

127

1978 37.2

516.7

104

Fixed submersion plane

127

1978 3.5

48.1

24

38

16.7

143.4

62.9

116.7

45

Oil

Slick mm

Wave m

Conditions

heav. oil 1230

3

3

1

calm

26.5

82

heav. oil 1230

3

1

0.75

0.3

harbour chop

8

32

heav. oil 1230

3

2

1

0.3

harbour chop

15.1

47

heav. oil 1230

3

1

1.5

0.3

harbour chop

20.2

47

heav. oil 1230

3

1

0.75

0.6

harbour chop

7.2

29

heav. oil 1230

3

1

1

0.6

harbour chop

16.5

55

heav. oil 1230

3

1

1.5

0.6

harbour chop

4.6

11

Fixed submersion plane

127

1978

heav. oil 1230

3

2

0.75

0.5

regular

4.3

20

Fixed submersion plane

127

1978 4.7

109.8

6.4

heav. oil 1230

3

1

2

0.5

regular

10.2

28

Fixed submersion plane

127

1978 0.9

21.7

16

heav. oil 1230

3

1

1.5

0.5

regular

3.6

8

DIP 2001

127

1973

Alberta crude

8

.7 ave

1

1.3

calm

2.7

88

30

DIP 2001

127

1973

Alberta crude

8

.7 ave

1

1.6

0.6

3.5

49

20

DIP 2001

127

1975

Arab crude

24

1

1

0.5

calm

1.1

94

96

DIP 2001

127

1975 0.4

Arab crude

24

0.5

1

1

calm

0.9

77

94

1.3

36.4

34

49.4

65

regular

DIP 2001

127

1975

DIP 2001

127

1975 1.8

Stationary skim. - Manta 127 Ray

1975

Stationary skim. - Manta 127 Ray

1975

Stationary skim. - skim pak

127

1980

Stationary skim. - skim pak

127

1980

Stationary skim. - skim pak

127

1980

Stationary skim. - skim pak

127

1980

Stationary skim. - skim pak

127

1980

Stationary skim. - skim pak

127

1980

Slurp skimmer

127

1975

Slurp skimmer

127

1975

Slurp skimmer

127

1975

Slurp skimmer

127

1975

Slurp skimmer

127

1975

200

6

0

0

10

Arab crude

24

1

1

0.5

0.4

natural

0.9

81

95

2.3

250

7.5

Arab crude

24

1

1

1

0.4

natural

1.8

78

96

DOP

79

20

6

calm

DOP

79

20

1

0.6

medium 200

7

3

calm

medium 200

7

1

0.26

medium 200

23

2

calm

medium 200

29

3

0.26

medium 200

16

3

calm

medium 200

16

1

0.19

crude

24

1

1

calm

crude

24

1

1

0.2

crude

24

5

1

calm

crude

24

8.2

1.9

2.7

4.2

1

0.1

40.6

76.9

67.3

50.1

558.8

10.9

8.3

3.8

15.4

15.8

30

0

Emulsion 3500

5

1

0.2

5

1

calm

harbour chop

regular

regular

regular

natural

natural

20.1

27

15.2

22

2.5

8

2

7

4

31

3.3

27

8.4

29

7.6

28

0.17

5

0.36

11

0.46

15

0.47

15

0.49

25

(Continued )

TABLE 13.4 Tests of Skimmer Performance with Changing Weather Conditionsdcont’d Current/Tow Speed Summary

Wave Height Summary

Year Slope

ORR

Slope Slope Slope

ORR

of

ORR

Slope

TE

Slope TE

RE

Oil

Viscosity Thick.

# of Speed Height Wave

ORR TE

RE

m2s/h

%s/m

%s/m %s/m m2/h

%/m

%/m

Type

mPa. S

mm

Tests m/s

m3/h %

%

1

Skimmer

Reference Test

Slurp skimmer

RE

ORR

0.4

71.4

Slope Slope %/m

55

Oil

Slick

Wave m

Conditions

0.2

natural

127

1975

Emulsion 3500

5

0.42

14

Harbour Mate weir skim. 127

1993

Diesel

4.5

10

calm

0.2

5

Harbour Mate weir skim. 127

1993

Diesel

4.5

25

calm

1.3

28

Harbour Mate weir skim. 127

1993

3.5

1750

5

Diesel

4.5

10

0.4

regular

1.6

3

Harbour Mate weir skim. 127

1993

0.3

19.2

10

Diesel

4.5

25

0.4

regular

1.2

24

Harbour Mate weir skim. 127

1993

0

0

2.5

Diesel

4.5

10

0.8

harbour chop

0.2

3

Harbour Mate weir skim. 127

1993

0.6

48.1

22.5

Diesel

4.5

25

0.8

harbour chop

0.8

10

Harbour Mate weir skim. 127

1993

crude

50 to 300 10

calm

0.08

1

Harbour Mate weir skim. 127

1993

crude

50 to 300 25

calm

1.3

21

Harbour Mate weir skim. 127

1993

0

31.3

0

crude

50 to 300 10

0.4

regular

0.09

1

Harbour Mate weir skim. 127

1993

2

153.8

32.5

crude

50 to 300 25

0.4

regular

0.5

8

Harbour Mate weir skim. 127

1993

0

31.3

1.3

crude

50 to 300 10

0.8

harbour chop

0.1

2

Harbour Mate weir skim. 127

1993

0.3

19.2

2.5

crude

50 to 300 25

0.8

harbour chop

1.1

19

Destroil weir skimmer

127

1979

heavy

810

5

5

calm

16.2

69

Destroil weir skimmer

127

1979

10

61.7

21.3

heavy

810

5

2

0.47

harbour chop

11.5

59

Destroil weir skimmer

127

1979

24.2

149.4

78.9

heavy

810

5

2

0.19

regular

11.6

54

18.1

111.6

Destroil weir skimmer

127

1979

Destroil weir skimmer

127

1979

Destroil weir skimmer

127

1979

GT-185

127

1988

GT-185

127

1988

GT-185

127

1988

GT-185

127

1988

1.7

5.6

GT-185

127

1988

37.5

125

Walosep

127

1988

Walosep

127

1988

Veegarm towed weir

127

1980

Veegarm towed weir

127

1980 28

254.5

0

Veegarm towed weir

127

1980 7

63.6

Veegarm towed weir

127

1980 22.7

206.1

Veegarm towed weir

127

1980

Veegarm towed weir

127

1980 56

509.1

0

Veegarm towed weir

127

1980 10

90.9

Veegarm towed weir

127

1980 26.7

Veegarm towed weir

127

1980 17

Veegarm towed weir

127

1980 4.8

34.2

15

186

71.4

92.3

123.1

heavy

810

5

1

0.26

light

9

5

2

calm

light

9

5

1

0.26

Bunker C 11700

calm

Bunker C 11700

0.4

Terra Nova

100-600

calm

26.7

Terra Nova

100-600

0.3

125

Terra Nova

100-600

0.4

65

Bunker C >100k 70

184.2

0

regular

regular

0.4

93

18.4

77

9.5

45

21

76

15

50

30

100

regular

29.5

92

regular

15

50

38

2

regular

calm

Bunker C >100k

20.9

regular

10

2

1

0.25

calm

11

100

8

48

1

0.5

calm

18

100

20

8

10

1

1.25

calm

18

92

18

0

5.3

1

1

calm

28

100

12

2

0.25

calm

11

100

18

16

2

0.5

calm

25

100

22

18

10

2

1.25

calm

21

82

28

242.4

30.7

13.3

2

1

calm

31

77

28

154.5

50

6

2

1.25

calm

28

50

24

43.6

56

3.2

2

1.5

calm

17

30

22

(Continued )

TABLE 13.4 Tests of Skimmer Performance with Changing Weather Conditionsdcont’d Current/Tow Speed Summary

Wave Height Summary

Year Slope

ORR

Slope Slope Slope

ORR

of

ORR

Slope

TE

Slope TE

RE

Oil

Viscosity Thick.

# of Speed Height Wave

ORR TE

RE

m2s/h

%s/m

%s/m %s/m m2/h

%/m

%/m

Type

mPa. S

Tests m/s

m3/h %

%

RE

ORR

Slope Slope %/m

Oil

Slick mm

Wave m

Conditions

Skimmer

Reference Test

Veegarm towed weir

127

1980

5

0.25

calm

18

100

35

Veegarm towed weir

127

1980 80

444.4

0

20

5

0.5

calm

38

100

40

Veegarm towed weir

127

1980 5

27.8

22

5

5

1.25

calm

23

78

40

Veegarm towed weir

127

1980 24

133.3

50.7

5.3

5

1

calm

36

62

39

Veegarm towed weir

127

1980

light

9

2

0.25

calm

5.4

100

5

Veegarm towed weir

127

1980 4.8

88.9

0

0

light

9

2

0.5

calm

4.2

100

5

Veegarm towed weir

127

1980 1.4

25.9

70

1

light

9

2

1.25

calm

4

30

4

Veegarm towed weir

127

1980 0.3

4.9

90.7

1.3

light

9

2

1

calm

5.6

32

4

Veegarm towed weir

127

1980

heavy

1300

2

0.25

calm

14

100

9

Veegarm towed weir

127

1980 8

57.1

0

4

heavy

1300

2

0.5

calm

16

100

8

Veegarm towed weir

127

1980 6

42.9

18

2

heavy

1300

2

1.25

calm

8

82

7

Veegarm towed weir

127

1980

Veegarm towed weir

127

1980 8

80

8

8

Veegarm towed weir

127

1980 4

40

40

2

Veegarm towed weir

127

1980

Veegarm towed weir

127

1980 12

80

0

16

0.5

4.8

31.6

6.8

0.25

1.9

regular

10

40

5

6.8

27.4

30.5

7.9

0.5

1.9

regular

12

42

7

0.75

1.9

regular

8

20

6

20

181.8 0

25

0.25

0.2

regular

15

100

13

35

140

25

0.5

0.2

regular

18

100

17

0

Veegarm towed weir

127

1980 12

80

20

14

Veegarm towed weir

127

1980 6.7

44.4

34.7

5.3

55

177.4

15

55

0.75

0.2

regular

21

90

20

1

0.2

regular

20

74

17

Veegarm towed weir

127

1980

2.1

39

210.5

0

light

9

2

0.25

0.19

harbour chop

5

60

5

Veegarm towed weir

127

1980 2

40

152

0

1.6

37.6

410.5

0

light

9

2

0.5

0.19

harbour chop

4.5

22

5

Veegarm towed weir

127

1980 2

40

96

2

0

0

94.7

0

light

9

2

0.75

0.19

harbour chop

4

12

4

Veegarm towed weir

127

1980 0

0

64

1.3

3.2

56.4

105.3

0

light

9

2

1

0.19

harbour chop

5

12

4

Veegarm towed weir

127

1980

4.2

30.1

26.3

0

heavy

1300

2

0.25

0.19

harbour chop

13.2

95

9

Veegarm towed weir

127

1980 7.6

57.6

140

4

4.7

29.6

210.5

0

heavy

1300

2

0.5

0.19

harbour chop

15.1

60

8

Veegarm towed weir

127

1980 0.6

4.5

138

4

28.9

361.8 294.7

0

heavy

1300

2

0.75

0.19

harbour chop

13.5

26

7

Veegarm towed weir

127

1980

12.5

89.3

12.5

2.5

heavy

1300

2

0.25

0.4

harbour chop

9

95

10

Veegarm towed weir

127

1980 14

155.6

200

16

26.3

164.1

137.5

5

heavy

1300

2

0.5

0.4

harbour chop

5.5

45

6

Veegarm towed weir

127

1980 8

88.9

154

12

7.5

93.8

160

7.5

heavy

1300

2

0.75

0.4

harbour chop

5

18

4

Veegarm towed weir

127

1980

2.2

41.2

60.3

0

light

9

2

0.25

0.63

harbour chop

4

62

5

3.7

86.9

101.6

1.6

light

9

2

harbour chop

6.5

36

Veegarm towed weir

127

1980 10

RST Advancing weir

127

1992

RST Advancing weir

127

1992

Transrec

128

19951998

Transrec

128

19951998

Transrec

128

19951998

250

104

4

50

211

0.5

0.63

medium 380

6

0.38

calm

medium 380

7

0.38

0.27

various

2

5

1

80

1.3

various

2

5

1.5

78

5

various

2

5

2

70

0

11.1

regular

4

23.7

97

10.2

94

Offshore skimmers

(Continued )

TABLE 13.4 Tests of Skimmer Performance with Changing Weather Conditionsdcont’d Current/Tow Speed Summary

Wave Height Summary

Year Slope

ORR

Slope Slope Slope

ORR

of

ORR

Slope

TE

Slope TE

RE

Oil

Viscosity Thick.

# of Speed Height Wave

ORR TE

RE

m2s/h

%s/m

%s/m %s/m m2/h

%/m

%/m

Type

mPa. S

Tests m/s

m

m3/h %

%

2

2.5

65

Skimmer

Reference Test

Transrec

128

19951998

RE

ORR

Slope Slope %/m 6

Oil

various

Special skimmers

Slick mm

Wave

5

Conditions

2 to 5

USCG HSS

112

1999

27

Sundex

3 to 4

calm

98 to 18

USCG HSS

112

1997

10

Sundex

2 to 4

calm

69 to 79

NOFI

112

1999

8

Sundex

2 to 5

calm

98 to 90

UNH FS

112

2000

17

Sundex

3 to 4

calm

98 to 46

USCG ZRV

112

1977

11

Sundex

2 to 4

calm

72 to 61

LPI fixed plane

112

1978

6

Sundex

3 to 5

calm

82 to 61

Fasflo

112

1999

14

Sundex

2 to 5

calm

72 to 45

USCG HSS

112

1997

18

Hydrocal

2 to 5

calm

83 to 29

USCG HSS

112

1999

22

Hydrocal

2 to 3

calm

72 to 6

USCG HSS

112

2000

11

Hydrocal

2 to 3.5 calm

72 to 61

NOFI

112

1999

0

Hydrocal

2 to 5

calm

91 to 91

USCG ZRV

112

1977

6

Hydrocal

2 to 3

calm

66 to 49

High Speed Circus

112

1999

Stream Stripper

112

2000

Sorbent booms

L/m

40

Hydrocal

12

Hydrocal

2 to 4

calm

90 to 50

calm

80 to 66

1

7

Boom 1

111

2000

1

calm

8

Boom 1

111

2000

1.5

calm

14

Boom 1

111

2000 3

1

calm

12

Boom 1

111

2000

1

calm

14

Boom 2

111

2000

1

calm

10

Boom 2

111

2000 3

1

calm

13

Boom 2

111

2000 0

1.7

calm

10

Boom 2

111

2000 7

1.7

calm

11

Boom 2

111

2000 7

2.5

calm

10

Boom 2

111

2000 9

2.5

calm

6

Boom 2

111

2000

1

calm

13

Boom 3

111

2000

1

calm

6

Boom 3

111

2000 7

1.7

calm

7

Boom 3

111

2000 8

2.5

calm

6

Boom 3

111

2000 11

2.5

calm

6

Boom 3

111

2000 11

370

PART | V

Physical Spill Countermeasures on Water

Watkins notes that a measure of the effectiveness of a skimmer is the ability to recover the most oil in the least time.131 Suzuki et al. tested model skimmers at scale models and described the flow mathematically.132 Similar work was carried out by Brekne.113 Guenette and Buist reported on extensive testing of the Lori brush skimmer, as did Cooper and coworkers on a brush skimmer.133,134 Similarly, Broje and Keller analyzed a disk skimmer.135-137 Similar work was also carried out on a cold climate skimmer.138 While it is acknowledged that skimmers may have similar limits as booms (about 0.5 m/s (1 knot)), these limitations can be overcome by several means, most typically by moving the skimmer at a lesser relative velocity to the oil on the sea. Several workers have proposed skimmer designs to overcome these limitations. Several earlier works used air herding or sheltering of the recovery area.139-142 Clauss and Ku¨hnlein proposed and have demonstrated the use of massive wave-shielding hulls and energy-absorbing designs to allow at-sea recovery.143 Ueda et al. tested a model skimmer that avoids the effects of waves by diverting oil into a calm area.144 Hara et al. proposed to use a moon pool inside a vessel to increase the wave limit from 1 to 2 or 3 m wave height.145 Akahoshi et al. suggest that the current limit of sea recovery is a wave height of 2.5 m and propose using a compensating float-pump system to deal with motion of the recovery platform.146 Hvidbak and Gunter note that heavy oil imposes additional restrictions on recovery at sea.147 Provant described the capabilities of the recovery equipment for the weather conditions of Prince William Sound.148 Provant provides tables of expected wave heights with winds in the sound. The degradation of performance of skimmers is given as follows: sea height up to 0.9 m, 80%; 1 to 2 m, 70%, 2.1 to 2.7 m, 50%; and over 2.8 m, 10%. Nordvik described modifications of the Transrec oil recovery system to improve its recovery efficiency and to enable high seas recovery.128 The unit recovered 15 to 85% of the oil presented to it during individual tests in 1.5 m waves and was thought to be capable of operating in waves up to 4 m. Nordvik suggested limits for windows of opportunity for skimmers based on increase in viscosity.6 Nordvik suggested a limit of 3 to 10 hours for a disc skimmer and 10 hours for a brush skimmer for the heavy oil BCF 17. For BCF 24, the window was estimated to be 2 to 3 days for a disk skimmer and after 3 days for a brush skimmer. These limits were based on the viscosity number generated from an oil viscosity model. A test of skimmers and booms in cold weather conditions showed no differences from warmer weather tests of the same skimmers.149 Shum and Borst tested a rope-mop skimmer in a test tank with ice and found that the recovery rates were not affected by up to 50% ice concentration.150 After 50% ice concentration, the mouth of the skimmer became jammed with ice. These tests show that the most significant factor in temperature is the formation of ice. Gates and Corradino described a test of a weir skimmer in a test tank.151 The recovery did not deteriorate significantly when waves were increased from 0.18 to 0.47 meters.

Chapter | 13 Weather Effects on Oil Spill Countermeasures

371

13.2.4.1. Harbor/Small Skimmers The standard specifications for a harbor skimmer are that they should be able to achieve the specified performance with a 0.3 m wave.152 Velocity of the skimming surface is important, and studies have shown that significant performance improvements in a skimmer can be achieved if the rotation speed is slowed.153 Yazaki noted that the government of Japan specified that the small skimmer must be able to operate at winds of 10 m/s and up to 0.5 m wave height and larger skimmers at winds of up to 15 m/s and wave heights of up to 1.2 m.106 13.2.4.2. Offshore/Larger Skimmers Nordvik noted successful recoveries on the open seas at up to 10 to 13 m/s winds and in waves up to 2.5 m/s.6 Peigne reports on the test of the Sirene and ESCA offshore skimming systems.154 Both systems were able to recover oil during offshore tests in winds up to 10 m/s and with accompanying waves of 1 to 2 m. Leigh described efforts to build and test two skimming devices to withstand sea state 5 (equivalent to winds of 10 to 14 m/s and wave heights of about 2 m).155 The two devices were a disc-drum skimmer and a weir basin that sheltered the basin face from oncoming waves. Wilson reported on the testing of a high-seas weir boom and noted that high recoveries were obtained in seas with up to 3 m waves and winds of up to 15 m/s. Up to 7,500 tons of oil or emulsion was collected in high seas.156 13.2.4.3. Special/High-Current Skimmers Schwartz describes some of the first tests on higher-speed skimmers, noting the performance decrease with both waves and tow speed.157 Hansen described a series of tests to measure the performance of fast water skimmers.112 The “Ocean Buster” skimmer, a unit using a weir and calm area behind the weir, has been successfully tested at tow speeds up to 2 m/s (4 knots).113 The same skimmer was tested in seas up to 3 m significant wave height at a tow speed of 0.8 m/s (1.5 knots). Coe describes a similar effort in which the United States Coast Guard (USCG) high-speed skimmer capability was increased up to 3 m/s (6 knots) by using a deflector.158 Many of these data have not been verified by other workers. 13.2.4.4. Skimming Ships Several Dutch efforts have taken place over the past 20 years to use dredger vessels with their systems for the recovery of oil.159 Recent efforts have focused on modifications to the input system to allow the dredge vessels to use their own pumps, thereby utilizing this enormous capacity. The heart of the system is the floating unit known as a dredge skimmer, which replaces the regular draghead. This skimmer follows the wave movements, and the suction pipeline is kept in position about 2 m under the water level by the suction tube gantries. A sweeping arm is connected to the skimmer through a double hinge, allowing the arm freedom of movement horizontally and vertically. Koops et al. describe the use of

372

PART | V

Physical Spill Countermeasures on Water

the earlier versions of these skimming vessels to recover the heavy oil during the Katina oil spill.160 The modified dredges recovered oil up to waves of 2 m, at which point the sweeping operation was stopped to avoid damage. Recent versions of the vessel were used during the Prestige spill and recovered up to 13,000 L of pure heavy oil during a three-month operation period.161

13.2.5. Dispersants Over 20 years ago, neither weathering of the oil nor weather itself was considered in planning for dispersant application.162 More recently, dispersant applications have been assessed using only weathering and not weather as a criterion for results.163-167 Nordvik proposed a weathering-based window of 26 hours for ANS crude and 2 hours for Bonnie Light.6 A period of reduced dispersibility was estimated to be 26 to 120 hours for ANS crude and 2 to 4 hours for Bonnie Light. After 4 hours, Bonnie Light was deemed not dispersible. Several workers noted that the weathering of the oil itself was a major factor in dispersant effectiveness.168-172 If one calculates both the time as it relates to spreading and the viscosity change of most oils as they weather, dispersability for most oils is severely diminished after 12 to 36 hours.173-175 Most heavy oils are barely, if at all, dispersible only in the first 12 hours.173-175 In past years, temperature was thought to be unimportant, but as time progressed, most researchers found more significant effects. Martinelli and Lynch reviewed the factors affecting chemical dispersion and found that the most two important factors are the oil composition and sea energy. Martinelli and Lynch concluded that temperature was semi-important, and several other factors were not investigated.176 Farmwald and Nelson tested the effect of temperature on dispersibility on Prudhoe Bay crude and found a variable temperature effect.177 Daling and Brandvik et al. measured dispersant effectiveness in the laboratory and found that, as temperature was lowered, effectiveness fell by as much as 20%.178-180 The researchers also noted that photolysis of the oil resulted in less effectiveness. Lunel and Lewis proposed that the bottom threshold for dispersibility be established as 15% for moderate sea conditions and 30% for calm sea conditions.181 Lunel et al. suggested that winds of 0 to 5 m/s be classified as low energy and that winds of 6 to 10 m/s be classified as high energy.182 The natural dispersion on a medium fuel oil was 0.8% at low energy and 3% at high energy. The dispersion for the medium fuel oil for Slickgone was 8% at low energy and 17% at high energy. Scholz et al. suggest a minimum threshold of energy of a sea state of 1 to 5 (corresponding to winds of 2.5 to 12 m/s and waves of 0.1 to 2 m).163 At higher sea states, many crude oils will disperse naturally. Most of the oil spilled during the Braer incident, which was a Gulfaks crude oil, dispersed naturally.182-184 Lunel noted that the winds were of force 8 to 10 (16 to 26 m/s, yielding waves of about 6 to 12 m and gusts of wind up to 35 m/s) during that incident. It is important to state that the oil, Gulfaks, was dispersible and that

Chapter | 13 Weather Effects on Oil Spill Countermeasures

373

the same conditions applied to a Bunker C, for example, would not result in significant dispersion. Lunel also stated that natural dispersion is slower and moves only to about 1 m depth. This had been stated earlier by Cormack and Nichols.185 Fuentes et al. studied natural dispersion in a turbulent laboratory apparatus and found that natural dispersion increased with increased oil weathering.186 The oil was a lighter Arabian crude. The winds during the Sea Empress incident were up to 20 m/s, and thus much of the dispersion that occurred during that incident may have been natural.187 Natural dispersion has been studied and described by several other workers.58,188 Mackay et al. described the natural dispersion of oil as:189 Fraction dispersed ¼ 0:11ðW þ 1Þ2 ð1 þ 50m1=2 dst Þ 1

(2)

where W is the wind speed in m/s, m is the viscosity in mPa.s, d is the slick thickness in cm, and St is the oil-water interfacial tension in dyne cm1. Most recent models use the equations of Delvigne and Sweeney:190 Q ¼ CD0:57 S F d0:7 Dd

(3)

where Q is the entrainment rate of oil droplets, C is an empirical constant dependent on oil type, D is the dissipated breaking wave energy, S is the fraction of the sea surface covered by the oil, F is the fraction of the sea hit by breaking waves, d is the oil particle diameter, and Dd is the oil particle diameter interval. The wave energy, D, is given by: D ¼ 0:0034rgH 2

(4)

2

where D is the energy in J/m , r is the density of seawater, g is the gravitational constant, and H is the rms value of wave height. Thus in both the Mackay and the Delvigne formulation, the amount of oil that enters the water varies as the square of the wave height. Delvigne and Hulsen subsequently developed a small laboratory method to measure the dispersibility of an oil.191 Koops also presents a formulation for natural dispersion:52 Vdisp ¼ Voð1 e7:6105 Ht=Vo0:62 Þ where Vdisp is the volume of oil dispersed naturally, Vo is the initial oil volume, H is the significant wave height, and t is the time.

(5)

374

PART | V

Physical Spill Countermeasures on Water

In the Koops formulation, the oil dispersion varies linearly with the wave height. Mackay later developed a relationship for breaking waves only, and the parameter that determined the rate of dispersion was only the amount of dispersant applied.192 The effectiveness of Corexit 9500 and Corexit 9527 was tested on Alaska North Slope crude oil at various salinities and temperatures representative of conditions found in southern Alaskan waters.193 The oil was weathered to different degrees. Tests were conducted in a swirling flask at temperatures of 3, 10, and 22 C with salinities of 22 and 32%/. Analysis was by GC. The authors concluded that, at the common temperatures found in the estuaries and marine waters of Alaska, the dispersants were largely ineffective. They also found an interactive effect between temperature and salinity. A high effectiveness for “emulsion,” an uncharacterized mixture of oil and water, was attributed to “osmotic shock” because of the difference in the salinity of preparation (33% / oo) and the test salinity. Later, Fingas et al. studied this same mixture and concluded that this was a matter of ionic strength that varies as both salinity and temperature.194 Deposition of dispersant droplets depends on the droplet sizes discharged from the nozzles. Lindblom and Cashion presented a relationship that describes the droplet sizes:195 VMD ¼ kðma sb rc V d De Þ

(6)

where VMD is the droplet volume mean diameter, m is the dispersant viscosity, s is the surface tension, r is the density of the dispersant, V is the exit velocity relative to the surrounding airstream, D is the nozzle diameter, and k, a, b, c, d, e are empirical constants. It should be noted that d varies from e0.6 to e1.3 depending on dispersant; thus the effect of increasing wind velocity is to decrease the droplet diameter discharged. Smedley studied the deposition of dispersants from DC-4 and Canadair spray aircraft. Smedley noted that droplets less than 100 mm and sometimes up to 500 mm may be entrained in aircraft vortices and may not be deposited near the intended target. Tests also showed that crosswinds cause poor deposition.196 Fay reported on a series of tests on the MASS spray system at Crosbytown, Texas,197 and found that 20 to 80% of the dispersant was lost and did not hit the targeted area. The results of these tests are shown in Table 13.5. Giammona et al. conducted a major campaign to measure the deposition of dispersant from several aircraft platforms near Alpine, Texas.198 These data have been used here to provide prediction of the relation of wind to deposition efficiency and thus weather cut-offs.

Altitude ft

Wind Speed (kn)

Cross Wind

Deposition % **

Droplet Information Average (sm)

(mm) Maximum

Approximate VMD*

Dispersant

Spray System

Gallons Sprayed

Litres Sprayed

Ground Speed (kn)

9527

ADDS

45

171

140

50

13

9

68

104

969

300

9527

ADDS

45

171

140

100

9

8

15

162

1108

450

9527

ADDS

45

171

140

100

13

9

59

78

630

300

9527

ADDS

45

171

140

150

17

12

48

116

758

300

9527

ADDS

45

171

140

120

17

13

73

120

671

250

9527

ADDS

45

171

140

50

18

15

66

68

671

200

9527

ADDS

45

171

140

100

14

12

75

68

888

300

9527

ADDS

45

171

140

150

15

15

56

93

687

400

9527

ADDS

56

212

140

50

8.5

2

46

35

544

400

9527

ADDS

45

171

140

100

9.3

1

78

93

630

300

9527

ADDS

60

227

140

150

6

0

38

76

778

450

9527

ADDS

30

114

140

120

10.2

7

52

137

646

350

9527

ADDS

38

144

140

50

13

1

50

70

758

400

9527

ADDS

41

155

140

120

9.5

9

75

96

785

250

375

(Continued )

Chapter | 13 Weather Effects on Oil Spill Countermeasures

TABLE 13.5 Dispersant Spray Trials at Alpine, Texas

376

TABLE 13.5 Dispersant Spray Trials at Alpine, Texasdcont’d

Cross Wind 5

Deposition % **

Droplet Information Average (sm)

(mm) Maximum

Approximate VMD*

33

101

689

400

42

87

639

150

Spray System

Gallons Sprayed

Litres Sprayed

9527

ADDS

56

212

140

150

12

9527

MASS

116

440

200

100

2

9527

MASS

59

224

200

100

2

38

61

1018

200

9527

MASS

41

155

200

100

31

76

838

250

9527

MASS

40

152

200

100

29

85

903

150

9527

MASS

40

152

200

100

19

81

656

150

9527

MASS

52

197

200

100

6

4

86

94

809

200

9527

MASS

41

155

200

100

7

4

40

105

510

200

9527

MASS

36

136

200

100

9.5

1

49

55

879

250

9527

MASS

60

227

200

100

7

1

44

52

506

150

9527

MASS

93

352

200

100

4.5

1

54

56

796

150

9527

MASS

65

246

200

100

7

2

23

94

810

200

1

Physical Spill Countermeasures on Water

Dispersant

PART | V

Altitude ft

Wind Speed (kn)

Ground Speed (kn)

MASS

113

428

200

100

12

5

20

91

832

100

9527

DC-4

32

121

136

50

17

15

31

60

317

150

9527

DC-4

0

0

136

50

9554

MASS

52

197

200

100

3.5

3

56

67

842

150

9554

MASS

48

182

200

100

3.5

0

44

76

918

150

9527

MASS

71

269

200

100

2.5

1

47

30

348

100

9527

DC-3

37

140

115

50

46

50

594

150

9527

DC-3

33

125

115

50

4.5

1

53

83

690

300

9527

DC-4

38

144

115

50

6.5

0

20

54

316

200

9527

DC-4

43

163

136

50

5.5

1

22

57

591

150

9527

DC-4

71

269

136

50

5.5

2

34

57

591

150

9527

DC-4

81

307

136

50

9

2

13

49

405

150

9527

Air Tr.

0

0

119

15

2.5

8

40

31

711

100

9527

Air Tr.

0

0

119

15

2.5

1

35

38

488

200

1

74

9527

Air Tr.

0

0

119

30

2.5

2

9527

Air Tr.

0

0

119

30

7

4

31

377

150

42

405

150

Chapter | 13 Weather Effects on Oil Spill Countermeasures

9527

*where volume hits 50% in middle of distribution. **calculated in this work.

377

378

PART | V

Physical Spill Countermeasures on Water

Lewis calibrated a helicopter bucket system, finding that the standard conditions of 30 m/s (60 knots) forward speed and altitude of 14 m resulted in about 70% deposition.199 A forward speed of 8 m/s (15 knots) and 6 m resulted in better or optimal deposition, although the ground effect of the helicopter rotors was extreme. A deposition of about 3 to 6 mL/m2 was obtained at the standard conditions, with a loss of about 20% of the material due to wind drift under the prevailing weather conditions of 2 to 5 m/s winds. At this wind speed the deposition was about 3.4 mL/m2 (about 3.5 US gal/acre) with a swath width of about 21 m. Reducing the air speed to 15 m/s (30 knots) and an altitude of 7 m increased the dosage rate to 14 mL/m2 (about 14 US gal/acre) with a deposition rate of at least 70%. Brandvik et al. tested a new helicopter bucket but did not gauge the effect of wind.200 Payne et al. studied the use of dispersant on the Pac Baroness and noted that winds of 7 to10 m/s caused problems in deposition.201 Furthermore, it was impossible to tell if the dispersant hit the slick or was blown off by the crosswind. Payne et al. also studied the test application of dispersant on the Mega Borg spill and noted that there was significant wind drift of the dispersants.202 Lunel noted in several sea trials that winds of 5 to 10 m/s were not a problem for aerial application, although targeting is a problem and that this is best done with the aid of remote sensing.203-213 Guyomarch et al. describe a field experiment in which the wind ranged from 3 to 20 m/s. This wind was not noted as a factor.214 Several workers noted that dispersion using spray booms on vessels was relatively unaffected by winds up to 15 m/s.215

13.2.5.1. Other Agents Pope et al. tested surface collecting agents and evaluated them over a range of temperatures.216 The efficiencies of the agents only decreased slightly with air temperatures down to less than 0 C. The effect of wind of 2 to 3 m/s was to assist in herding.

13.2.6. In-Situ Burning Several workers have reviewed the use of burning in various weather conditions.217 Buist et al. studied the burn rates and conditions of some Alaskan oils with and without ice.218 This data has been used for prediction purposes in Table 13.6. Buist discusses the windows of opportunity for in-situ burning.219 He proposes that the maximum wind speed for successful ignition is 10 to 12 m/s, although no basis for this is given. Later in the paper, Buist also proposes a series of weathering percentages and water content for which oils would or would not burn or where efficiency is severely hampered. Further limitations discussed include operational limits and the fact that VFR flying rules for the helicopter would require greater than 4 km visibility and a minimum 300 m ceiling. Buist et al. studied in-situ burning in a test tank on the North Slope of

TABLE 13.6 Tests of Burning Performance with Changing Weather Conditions

Burn

Reference

Year of Test

Rate Change mm/min

Burn Rate mm/min

Oil Type

Oil Weathering %

Test Condition

0.9

ANS

0

open water

0.8

ANS

0

frazil

1.5

Northstar

0

open water

0.8

Northstar

0

frazil

1

Northstar

33.8

open water

0.6

Northstar

33.8

frazil

1

Northstar

43.8

open water

0.4

Northstar

43.8

frazil

1.6

Pt. McIntyre

0

open water

Change with Frazil/Slush Ice Alaska mid-scale

Buist 2003

2002

Alaska mid-scale

Buist 2003

2002

Alaska mid-scale

Buist 2003

2002

Alaska mid-scale

Buist 2003

2002

Alaska mid-scale

Buist 2003

2002

Alaska mid-scale

Buist 2003

2002

Alaska mid-scale

Buist 2003

2002

Alaska mid-scale

Buist 2003

2002

Alaska mid-scale

Buist 2003

2002

0.1

0.7

0.4

0.6

average

0.45

Change with Brash Ice Buist 2003

2002

0.6

0.3

ANS

0

Brash

Alaska mid-scale

Buist 2003

2002

1.1

0.4

Northstar

0

Brash

Alaska mid-scale

Buist 2003

2002

0.8

0.2

Northstar

33.8

Brash

Alaska mid-scale

Buist 2003

2002

0.7

0.3

Northstar

43.8

Brash

Alaska mid-scale

Buist 2003

2002

1.3

0.3

Pt. McIntyre

0

Brash

average

0.8

379

Alaska mid-scale

Chapter | 13 Weather Effects on Oil Spill Countermeasures

Rate Summary

380

PART | V

Physical Spill Countermeasures on Water

Alaska and found that the wave steepness reduced both the burn rate and effectiveness.220 Bech et al. found that increasing wave action reduced burn efficiency.221 Thornborough described a series of in-situ burns conducted off the United Kingdom in 1996.222 The trial was specifically designed to examine the limits of ignition and combustion under sea conditions. Burn 1 was ignited using a small hand-held unit with a sea state of 4/5 (waves of 1 to 2 m), wind of 10 to 13 m/s (20 to 25 knots), and a current speed of 0.9 m/s (1.8 knots). The boom and the ignition were successful and were not significantly hampered by the prevalent weather conditions. The second burn was ignited using a Helitorch at sea state of 4 (waves about 1.5 m), wind of 10 m/s (20 knots), current of 0.9 m/s (1.8 knots), and again at 120 degrees from the current direction and that of the towing vessel. The second burn involved oil containing 25% water. The burning fuel from the Helitorch reached the sea surface from a height of 60 to 70 ft (20 to 25 m) and a helicopter speed of 10 to 13 m/s (20 to 25 knots). Above this height and speed, the gelled gasoline did not stay ignited. Nordvik et al. reviewed windows of opportunity for burning, noting that the lower flammability limit and weathering of the oil are important.6,223 This paper also proposes an upper wind limit of 10 to 12 m/s (20 knots) for the ignition of the oil. The source of this limit, other than a related report, is not given. A weathering diagram generated from the IKU model is given as the means for estimating the weathering time at which the flash point is reasonable, given a certain wind velocity. Earlier, Nordvik had proposed a window based on formation of emulsion for ANS crude of 36 hours and of 1 hour for Bonnie Light crude.6

13.2.6.1. Ignition Farmwald and Nelson tested the effect of temperature on flammability and ignition of Prudhoe Bay crude and found temperature had little effect.177 Guenette and Wighus reported that ignition was difficult when winds exceeded 10 m/s.224 Bech et al. found that ignition was difficult with emulsified oils.221 D’Atri and King conducted a burn in cold conditions and found that gelled gasoline did not work; however, a propane weed-burner worked well.225 Guenette and Thornborough reported on the use of two types of igniters used off the coast of the United Kingdom.226 Burn 1 was ignited using a small handheld unit with a sea state of 4/5 (waves of 1 to 2 m), wind of 10 to 13 m/s (20 to 25 knots), and a current speed of 0.9 m/s (1.8 knots). The boom and the ignition were successful and not significantly hampered by the prevalent weather conditions. The second burn was ignited using a Helitorch at sea state of 4 (waves about 1.5 m), wind of 10 m/s (20 knots), a current of 0.9 m/s (1.8 knots), and again at 120 degrees from the current direction and that of the towing vessel. The hand-held unit consisted of a jar of gelled gasoline and a flare. The unit was floated out to the oil after lighting the flare; the flame from the flare melted the wall of the plastic and then ignited the gelled gasoline. The second

Chapter | 13 Weather Effects on Oil Spill Countermeasures

381

device used a modified Helitorch in which the fluid included an emulsion breaker as well as the usual gelled fuel. Moffat and Hankins tested a flare-type igniter specially built for oil spills.227 The flares showed a temperature of 1370 C at the center, and this was maintained for a 3-minute burn. The igniter was used to ignite diesel fuel in ambient temperatures of 3 C with winds of 8 to 10 m/s.

13.2.6.2. Fire-Resistant Boom Meikle reported on the test of a ceramic fire-resistant boom.66 Measurements on the loss rate versus tow speed were taken, as well as the rate of burning at different tow speeds. These are reported in Table 13.3. Buist et al. also reported on the testing of a fire-resistant boom.228 The boom was successfully tested in a towing mode up to wave heights of 4 m and contained oil in currents up to 0.4 m/s. Several workers reported on the tests on fire-resistant booms as containment booms.229,230 Many of the booms showed performance near that of conventional booms. The first loss and critical failure velocities were reported. McCourt et al. tested a series of fire-resistant booms for ruggedness while exposed to a propane fire and found that most booms could tolerate the propane fires.231

13.2.7. Others Pumps and transfer devices are not really limited by the weather, but are affected significantly by viscosity, which increases as the oil weathers or at low temperatures. Lower temperatures would, of course, increase viscosity somewhat and make pumping more difficult. Cooper and Mackay, and Hvidbak and Gunter review viscous pumping technologies.232,233 Nordvik proposed a window of opportunity limit for using sorbents based on weathering and increased viscosity of oil.5 Nordvik suggested that a viscosity of 15,000 mPa.s would constitute a reasonable upper limit. The window of opportunity for heavy oil such as BCF-17 and BCF-24 became 4 and 10 days, respectively. The effectiveness was felt to be reduced to 50% after 36 hours. Nordvik also proposed a window of opportunity limit for centrifugal separators based on the closing density gap between oil and seawater.5 This limit was calculated to be 18 hours for ANS and 24 hours for Bonnie Light. Provant studied the effects of wave height on separation by decanting.148 Provant rated the decrease in performance with wave height as follows: wave height up to 0.9 m, 0.8 decanting factor (eg. 80% effective); waves of 1 to 2 m, 0.8; waves of 2.1 to 2.7 m, 0.7; and over 2.8 m, 0.6. McCourt and Shier studied the sediment interaction on the Yukon River and found in laboratory experiments that there were temperature and energy relationships.234 The mean oil loading was 0.006 goil/gsolids at an arc (shaking angle) of 4 degrees, 0.1 at 7 degrees, and 0.11 at 10 degrees. This is explained by increasing contact and coalescence. The loading went from the 0.11 noted at 15 C up to 0.26 goil/gsolids at 2 C.

382

PART | V

Physical Spill Countermeasures on Water

13.2.8. Ice Conditions While it was not one of the purposes of this study to examine the cleanup efficiencies with ice inasmuch as this is more than a factor of weather, somedata were found that make it possible to calculate the degradation of certain

FIGURE 13.2 Recovery of oil under ice using a rope mop skimmer. This type of Arctic cleanup is not covered in this subsection. FIGURE 13.3 Extreme snow cover can hamper oil spill countermeasures. Although this type of situation is relevant to land spill situations, little study has been carried out.

Chapter | 13 Weather Effects on Oil Spill Countermeasures

383

recovery techniques with increasing ice concentrations.235 Abdlenour et al. summarized tests of a water-spray boom/weir combination in increasing ice conditions.236 Shum and Borst tested a rope mop in ice-infested conditions and found a sharp drop-off in effectiveness.150 Figure 13.2 shows oil-in-ice recovery, a topic not covered here, and Figure 13.3 covers heavy snow conditions, a situation that may be relevant here but is not often studied. Several workers have noted that ice, not temperature, is an issue.235,237 Tsang and Vanderkooy described the development of an ice boom that shows the capability of deflecting ice floes on rivers and allowing oil to pass through.238 The boom was successfully tested in heavy ice concentrations and with currents up to 0.2 m/s.

13.3. DEVELOPMENT OF MODELS FOR EFFECTIVENESS OF COUNTERMEASURES 13.3.1. Overall The basic procedure to develop a model for countermeasure effectiveness was to use literature data on testing of the particular countermeasure and then to correlate this data with the weather factor to form a model. The main advantage of this method is that it yields a relatively realistic outlook on the actual relationship between performance and the weather factor under consideration. Its main disadvantage is that often there are no data on the performance of oil spill countermeasures at high winds, waves, or extremes in temperature. Thus, to a certain extent, the existing quantitative data must be extrapolated past the typical measurement points.

13.3.2. Booms The quantitative data obtained for boom performance with weather is summarized in Table 13.3. The variance of critical velocity and wave height can be seen in the table. Figures 13.4 to 13.6 illustrate boom failures. An analysis of the variation of critical loss rate and wave height shows some correlation. This allows one to use the values presented in Table 13.3 directly to predict the decrease in first loss and critical velocities. Figure 13.2 shows the decrease in first loss and critical tow velocities with increasing wave height using the averages of all booms and then the average of fire-resistant booms. The decrease in performance of booms with increasing wave height as shown in Figure 13.7 is expected and has been relatively well known for several years. Table 13.7 shows the correlation between various performance parameters. As can be seen, there is a poor correlation between the oil viscosity, wave height, and first loss speed.

13.3.3. Skimmers The quantitative data obtained for skimmer performance with weather is summarized in Table 13.4. These data come largely from Schulze and represent

384

PART | V

Physical Spill Countermeasures on Water

FIGURE 13.4 The rollover failure of an oil spill containment boom.

FIGURE 13.5 Typical failure of a boom due to droplet breakaway under the contained slick. This typically occurs at about 0.35 m/s (0.7 knots).

data collected over 25 years of skimmer testing.127 Table 13.4 shows the three most important values of skimmer performance, ORR, TE, and RE. The oil recovery rate (ORR) is the quantitative rate in volume per unit time, usually m3/hour, and is corrected for water recovery. The throughput efficiency (TE) is applicable only to advancing skimmers. It is the percentage of oil presented to a skimmer versus that recovered, in percent. The recovery efficiency (RE) is the percent of oil recovered out of the total oil and water recovered. Table 13.8 shows the calculations of the rate of change of the ORR, TE, and RE with increasing current and wave height. These are calculated directly from the data shown in Table 13.4. The rate of change is taken when other parameters of the test, including viscosity and oil type, tow rate, and wave height and type, are held constant.

385

Chapter | 13 Weather Effects on Oil Spill Countermeasures

FIGURE 13.6 Closeup of boom failure; this one is also due to droplet breakaway under the contained slick but is accelerated by the waves present.

Critical or First Loss Speed (m/s)

1.0

Average boom - critical speed Average boom - first loss Fire boom - critical speed Fire boom - first loss

0.8

0.6

0.4

0.2

0.0 0.0

0.5

1.0

1.5

2.0

2.5

Wave Height m FIGURE 13.7 Effect of waves on boom performance.

The following points must be made about skimmer test data. 1. The most important point is that most skimmers show unique data and response to current or tow speed. It is difficult to generalize about skimmers without making the point that there are many exceptions. In this report,

386

PART | V

Physical Spill Countermeasures on Water

TABLE 13.7 Correlation of Performance and Test Parameters for Booms First Loss Speed

Critical Speed/Wave

Oil Viscosity

Wave Height

First Loss Speed

1.00

0.01

0.39

L0.40

Critical/wave

0.01

1.00

0.55

0.05

Oil Viscosity

0.39

0.55

1.00

0.13

Wave height

L0.40

0.05

0.13

1.00

–those items noted in bold show possible, but not significant correlation.

2.

3. 4.

5.

6.

7.

some generalizations are made, but the author is fully aware of the difficulty of doing so. The test data presented in Tables 13.4 and 13.8 are summarized from a variety of literature sources. The accuracy of these sources is unknown in every case, although Schulze is known to be a highly accurate summary.127 Several of the literature sources behind this reference were checked, and no errors were noted. It should also be recognized that the accuracy and precision of some of the data behind the collection are questionable. Furthermore, many data points were collected in the 1970s. The variability of the data may no doubt be due to the variability in test conditions and also in the capability to measure the necessary parameters. Some of the data summarized here are actually estimates. It will be noted very readily that the change rate of skimmer effectiveness, particularly ORR, will usually increase with increasing tow speed. Schulze had noted this.127 The reason, as Schulze also noted, is no doubt the increased oil encounter rate when tow speed increases. This complicates calculations of the “decrease” in ORR with increasing tow speed. The effect noted in point 4 above also occurs with some increasing wave activity. The same reason is probably pertinent here. This also complicates calculations for decline in recovery with wave height; however, as the wave increases, the performance generally falls and one can use these values separately. Some skimmers may show unusually high or low performance in these data. This is largely due to the test conditions. For example, if a skimmer is not tested at a high tow speed or a high wave, its performance may appear to be very good compared to a similar skimmer that is tested under more rigorous conditions. There is no easy way to deal with these variances. The effect of ice on performance is shown in Table 13.9. The average ORR declines somewhat with increasing ice percentage. Both TE and RE appear, on average, to be unaffected by ice concentration.

Current/Tow Speed Summary

Wave Height Summary

Skimmer

% ORR/ TE/ RE/ %ORR/ curr % curr % curr % wave s/m s/m s/m %/m

Overall Average

L112

Skimming barrier Sirene skimming barrier

62

L26

L54

148.7

73.7

0.7

246.5 240.6

89.9

62.2

39.1

547.7

Lori brush skimmer 200.9 Scoop weir skimmer

72.8

132.1

45.3

RE/ wave %/m

%ORR/ ORR TE RE wave m3/h % % %/m

TE/ wave %/m

RE/ wave %/m

%ORR/ wave %/m

TE/ wave %/m

RE/ wave %/m

59

17

12

64 50 L80.1

53.1

16.1

15.3

90.8

22.2

45.4

60

43 21.2

39.7

26.9

13.8

23

53 38 74.3

20

46.5

115.5

75.3

1

77.3

81.1

92.5

65

7 53

Paddle skimmer 23.2

Rope mop towed single

9.6

Oil mop ZRV

75.6

26

21.7

43.5

6.6

19.2

Harbour Chop

TE/ wave %/m

Disc skimmers e flat and T

Rope mop stationary

Regular Waves

105

3.2

106.5

75 547.7 66 88 50.7

81 51

78.3

5

80

8.5

7

51 64.2

25.3

10

52 45 28.6

6.2

75.3 30

71 7

54.8

50.6

2.5

56.7

68.9

32.9

51.1

56.2

7.5

21.3

41.6

4.6

Chapter | 13 Weather Effects on Oil Spill Countermeasures

TABLE 13.8 Summary Skimmer Performance with Changing Weather Conditions

26.3

387 (Continued )

388

TABLE 13.8 Summary Skimmer Performance with Changing Weather Conditionsdcont’d Current/Tow Speed Summary

Skimmer

Wave Height Summary

% ORR/ TE/ RE/ %ORR/ curr % curr % curr % wave s/m s/m s/m %/m 7.1

TE/ wave %/m

RE/ wave %/m

%ORR/ ORR TE RE wave m3/h % % %/m

24.7

49.3

36.4

10

54 63

Fixed submersion plane

187.6 14.8

129.7

87.4

19

44

DIP 2001

81.8

99.8

20.8

2

78 72 149.7

20

142.4

TE/ wave %/m

RE/ wave %/m

98

10.8

8

22 64.8

11.7

Slurp skimmer

166.1

8.3

0.4

14 166.1

12.5

Harbour Mate weir skimmer

196.5

9.2

1

10 402.1

Weir skimmers, Destroil, GT-185

84

43.5

19

59 87.1

7.7

14

68 14 33.6

25.7

73

4.1

Transrec Various high speed skimmers

4.7

13.2

111.9 4

13

75

TE/ wave %/m

RE/ wave %/m

24.7

49.3

36.4

124.3

82.9

40.6

8.3

15.8

12

6.6

54.4

61.7

21.3

23.9

5.2

152

2.3

Physical Spill Countermeasures on Water

58.7

53.4

%ORR/ wave %/m

20.8

Stationary skimmer - skim pak

Veegam towed weir 79.5

Harbour Chop

PART | V

Marco belt skimmer 178.2 25.8

Regular Waves

Positive Values Only Regular Waves

Average

Harbour Chop

Regular Waves

Harbour Chop

%ORR/ wave %/m

TE/ wave %/m

RE/ wave %/m

%ORR/ wave %/m

TE/ wave %/m

RE/ wave %/m

%ORR/ wave %/m

TE/ wave %/m

RE/ wave %/m

%ORR/ wave %/m

TE/ wave %/m

RE/ wave %/m

Overall Average

90.8

54.9

50

67.4

96.7

32.5

5.4

54

33.1

41.4

93.8

27.4

Skimming barrier

26.1

39.7

38.6

54.8

2.5

39.7

32.8

0

54.8

Sirene skimming barrier

12.7

15.9

68.7

52.3

30.8

2.1

11.1

115.5

23.1

77.3

81.1

106.5

115.5

106.5

273.9

Lori brush skimmer Scoop weir skimmer

30

Disc skimmers e flat and T

77.3

25.4

81.1

50.6

30

56.7

e

e

e

e

Rope mop stationary

244.7

105

330

61.9

32.9

122.4

Rope mop towed single

39.2

20

29

7.5

12.5

Oil mop ZRV

28.6

21.3

48.1

26.3

28.6

e

18.3

0 50.6

Paddle skimmer

2.5

37.7

56.7

e 52.5

2.5

165

3.5

0

32.9

15.6

13.6

0

7.5

21.3

3.3

6.9

26.3

389

(Continued )

Chapter | 13 Weather Effects on Oil Spill Countermeasures

Calculated and Summarized Values

390

TABLE 13.8 Summary Skimmer Performance with Changing Weather Conditionsdcont’d Calculated and Summarized Values Positive Values Only Regular Waves %ORR/ wave %/m

TE/ wave %/m

RE/ wave %/m

Fixed submersion plane

142.4

%ORR/ wave %/m

TE/ wave %/m

RE/ wave %/m

54.5

49.3

43.6

124.3

82.9

36.3

Stationary skimmer e skim pak

64.8

11.7

Slurp skimmer

71.4

55

Harbour Mate weir skimmer

86.5

15.8

33.7

Weir skimmers, Destroil, GT-185

120.3

83.7

61.7

Veegam towed weir

87.4

23.9

67.9

Transrec

25.7 4.1

40.6

8.3

152

Regular Waves %ORR/ wave %/m

TE/ wave %/m

142.4

98

74.9

28.6

RE/ wave %/m

Harbour Chop %ORR/ wave %/m

TE/ wave %/m

RE/ wave %/m

39.6

49.3

40

124.3

82.9

64.8

11.7

40.6

8.3

47.4

33.8

0

0

9.2

157.8

15.8

22.9

7.9

21.3

103.7

69.1

61.7

21.3

4.7

60.5

23.9

36.6

25.7 4.1

152

3.5

Physical Spill Countermeasures on Water

DIP 2001

98

Harbour Chop

PART | V

Marco belt skimmer

Average

Performance in Ice Slope of ORR m3/h %

ORR Slope %/%

Slope of TE %/%

Conditions

Slope of RE %/%

Ice Conc. %

Oil Type

Oil Viscosity mPa. S

Slick Thick mm

Number of Tests

ORR m3/h

TE %

0

medium

460

6 ave

4

1.2

6.8

RE %

Skimmer

Reference

Year of Test

Skimming bow

236

1984

Skimming bow

236

1984

0.01

0.5

0.1

30

medium

460

10 ave

3

1.03

9

Skimming bow

236

1984

0.01

0.8

0

50

light/ medium

22/460

6 ave

5

0.7

8

Skimming bow

236

1984

0.01

0.9

0.1

70

light/ medium

22/460

8 ave

9

0.46

11

Rope mop

127

1984

0

light

17

4

1

2.9

53

50

Rope mop

127

1984

0.02

0.7

0.6

0.1

25

light

17

3

2

2.4

68

47

Rope mop

127

1984

0.05

1.8

0.2

0.6

25

light

17

8

2

4.2

49

66

Rope mop

127

1984

0.03

1.1

0.1

0.3

50

light

17

3

2

1.3

58

67

Rope mop

127

1984

0.04

1.3

0.7

0.7

75

light

17

3

1

0

0

0

Rope mop

127

1984

0

light

17

3

2

2.7

59

29

Rope mop

127

1984

0

light

17

8

1

4.9

41

50

391

(Continued )

Chapter | 13 Weather Effects on Oil Spill Countermeasures

TABLE 13.9 Tests of Skimmer Performance with Changing Ice Conditions

392

TABLE 13.9 Tests of Skimmer Performance with Changing Ice Conditionsdcont’d Performance in Ice

Conditions

ORR Slope %/%

Slope of TE %/%

Slope of RE %/%

Ice Conc. %

Oil Type

Oil Viscosity mPa. S

Slick Thick mm

Number of Tests

ORR m3/h

TE %

RE %

Reference

Rope mop

127

1984

0.03

1.2

1.7

0.2

12.5

light

17

3

1

3.1

80

32

Rope mop

127

1984

0.1

2.1

1.2

0.2

12.5

light

17

8

1

6.2

56

52

Rope mop

127

1984

0.01

0.4

0.5

0.1

25

light

17

3

4

2.4

72

31

Rope mop

127

1984

0.06

1.2

1.2

0.4

25

light

17

8

3

6.4

70

59

Rope mop

127

1984

0.02

0.6

0.3

0.1

37.5

light

17

3

1

2.1

71

26

Rope mop

127

1984

0.03

1.2

0.2

0.3

50

light

17

3

1

1.1

49

15

Rope mop

127

1984

0.04

0.7

0.2

0.2

50

light

17

8

1

3.1

51

41

average

0

0.14

L0.35

L0.04

Physical Spill Countermeasures on Water

Skimmer

PART | V

Slope of ORR m3/h %

Year of Test

Chapter | 13 Weather Effects on Oil Spill Countermeasures

393

8. Many other factors influence oil recovery for a skimmer, including oil viscosity and thickness of oil presented to a skimmer. These factors were kept constant throughout this exercise by taking the same conditions with only the interest, tow speed, or wave height as a variable. The cross-correlation matrix for all skimmers in this study is given in Table 13.10, for the Marco belt skimmer in Table 13.11, and for the Veegarm system, an advancing weir, in Table 13.12. These tables show that combining data such as is done in Table 13.10 results in little, if any, correlation between different factors. The reason for this is that different factors influence different skimmer systems differently. For example, an increasing viscosity positively affects the ORR of the Marco skimmer (as can be seen in Table 13.11) and negatively affects a disk skimmer. These correlations show that many of the common-sense relationships do hold true if individual skimmers or skimming principles are examined. Another question that arises is the relationship between the decrease in performance and the parameter that is being examined. As with booms described above, it was found that the general relationship with performance and waves is one of a square root type. A typical analysis is shown in Figure 13.8. Models then used to predict the performance of skimmers were based on a square root function and the decreases in performance from empirical data as summarized in Table 13.8. Figure 13.9 shows the ORR change for groups of skimmers and the average of all the skimmer data. This shows that the recovery is significantly decreased by harbor chop more than by regular waves. Figure 13.10 shows the ORR for a variety of specific skimmers. It can be seen from this figure that ORR changes significantly between specific skimmers. Similarly, the changes in TE and RE are shown in Figures 13.11 and 13.12, respectively. The differences between individual units will again be noted. The change in the performance indicators with increasing current or tow speed were also examined. As was noted earlier and can be seen in Tables 13.4 and 13.8, often the ORR increases with increasing tow speed. This is because the oil encounter rate is increased, at least up to the point that the skimmer can handle the increased velocity. Often skimmers show an increase up to a point and then a decrease. This was handled in averaging the decrease in performance with current by looking at the positive values (decrease in performance only). The change in ORR with increasing current or tow speed cannot be shown because generally it is an increase. The TE does generally decrease with increasing tow speed as seen in Figure 13.13. One sees a significant difference in the throughput efficiency of the different types of skimmers with the changing speed or current. Recent efforts have shown that suction skimmers can remove oil even in high seas.161,239 A good example of this is the use of suction skimmers to recover over 10,000 tons of oil during the Prestige incident. The process,

394

TABLE 13.10 Cross-Correlation Matrix for Factors Influencing Performance for All Skimmers in this Study TE/ curr

RE/ curr

ORR/ wave

Parameter %ORR/ TE/ wave wave

RE/ wave

Oil Visc

Slick mm

Tow m/s

ORR/curr

1.00

0.61

0.03

0.71

0.21

0.11

0.31

0.35

0.19

0.26

0.28

%ORR/curr

0.61

1.00

0.32

0.58

0.11

0.06

0.31

0.29

0.08

0.01

TE/curr

0.03

0.32

1.00

0.47

0.41

0.26

0.59

0.53

0.11

RE/curr

0.71

0.58

0.47

1.00

0.04

0.06

0.03

0.37

ORR/wave

0.21

0.11

0.41

0.04

1.00

0.39

0.01

%ORR/wave

0.11

0.06

0.26

0.06

0.39

1.00

TE/wave

0.31

0.31

0.59

0.03

0.01

RE/wave

0.35

0.29

0.53

0.37

Oil Visc

0.19

0.08

0.11

Slick mm

0.26

0.01

Tow m/s

0.28

Wave m

0.06

ORR

Wave m

ORR

TE

RE

0.06

0.31

0.13

0.11

0.15

0.14

0.28

0.35

0.27

0.08

0.37

0.09

0.14

0.40

0.15

0.06

0.26

0.34

0.19

0.44

0.18

0.21

0.35

0.02

0.04

0.19

0.11

0.17

0.11

0.15

0.03

0.38

0.06

0.04

0.03

0.09

0.07

0.12

0.13

0.03

1.00

0.03

0.03

0.01

0.13

0.18

0.00

0.58

0.32

0.35

0.38

0.03

1.00

0.17

0.26

0.32

0.05

0.12

0.05

0.18

0.06

0.02

0.06

0.03

0.17

1.00

0.18

0.02

0.06

0.04

0.18

0.11

0.08

0.26

0.04

0.04

0.01

0.26

0.18

1.00

0.27

0.12

0.68

0.11

0.06

0.15

0.37

0.34

0.19

0.03

0.13

0.32

0.02

0.27

1.00

0.16

0.05

0.16

0.08

0.14

0.09

0.19

0.11

0.09

0.18

0.05

0.06

0.12

0.16

1.00

0.06

0.26

0.18

0.31

0.28

0.14

0.44

0.17

0.07

0.00

0.12

0.04

0.68

0.05

0.06

1.00

0.25

0.06

TE

0.13

0.35

0.40

0.18

0.11

0.12

0.58

0.05

0.18

0.11

0.16

0.26

0.25

1.00

0.09

RE

0.11

0.27

0.15

0.21

0.15

0.13

0.32

0.18

0.11

0.06

0.08

0.18

0.06

0.09

1.00

Values in bold are significant cross-correlation factors.

Physical Spill Countermeasures on Water

%ORR/ curr

PART | V

ORR/ curr

ORR/ curr

%ORR/ curr

TE/ curr

RE/ curr

% ORR/ ORR/ wave wave

TE/ wave

ORR/curr

1.00

0.56

0.78

0.63

1.00 1.00

%ORR/curr

0.56

1.00

0.82

0.22

TE/curr

0.78

0.82

1.00

RE/curr

0.63

0.22

ORR/wave

1.00

%ORR/wave

Oil Visc

Slick mm

Tow m/s

Wave m

ORR

1.00 1.00

0.50

0.13

0.55

0.55

0.43 L0.74 0.69

1.00 1.00

1.00 1.00

0.75

0.73

0.85

0.65

0.37

0.65

1.00

1.00

1.00

0.19

0.67

0.53

0.53

0.65

0.12 0.81

L0.80

0.65

1.00

1.00

1.00

0.93

0.29

0.27

0.08

0.02 0.35

0.48 0.44

0.53

1.00

1.00

1.00

1.00

0.87

0.54

0.09

0.65

0.75

0.76

0.40

0.72

0.16

0.28

1.00

1.00

1.00

1.00

0.87

1.00

0.53

0.04

0.46

0.69

0.66

0.25

0.52

0.28

0.25

TE/wave

1.00

1.00

1.00

0.93

0.54

0.53

1.00

0.68

0.31 0.13 0.56

0.52

0.07 0.72

0.20

RE/wave

1.00

1.00

0.19

0.29

0.09

0.04

0.68

1.00

0.54 0.47 0.44

0.24

0.39 L0.80 0.55

Oil Visc

0.50

0.75

0.67

0.27

0.65

0.46

0.31 0.54

1.00

0.90

0.32

0.37

0.50

0.06

0.43

Slick mm

0.13

0.73

0.53

0.08

0.75

0.69

0.13 0.47

0.90

1.00

0.33

0.25

0.69

0.11

0.31

Tow m/s

0.55

0.85

0.53

0.02 0.76

0.66

0.56

0.32

0.33

1.00

0.16

0.50

0.48

0.13

Wave m

0.55

0.65

0.65

0.35

0.52 0.24

0.37

0.25

0.16 1.00

0.39 0.50

L0.89

ORR

0.43

0.37

0.12

0.48 0.72

0.07 0.39

0.50

0.69

0.50

0.39

1.00

0.38

0.33

TE

L0.74 L0.75

L0.81 0.44 0.16 0.28

0.72 L0.80 0.06

0.11

0.48 0.50

0.38

1.00

0.70

RE

0.69

L0.80 0.53 0.28 0.25

0.20 0.55

0.43 0.31 0.13 0.89

0.33

0.70

1.00

0.72

0.52

0.44

TE

RE

L0.75 L0.72

395

Values in bold are significant cross-correlation factors.

0.40 0.25

RE/ wave

Chapter | 13 Weather Effects on Oil Spill Countermeasures

TABLE 13.11 Cross-Correlation Matrix for Factors Influencing Performance for the Marco Belt Skimmer

396

TABLE 13.12 Cross-Correlation Matrix for Factors Influencing Performance for the Veegarm System ORR/ curr

%ORR/ curr

TE/ curr

RE/ curr

ORR/ wave

%ORR/ wave

TE/ wave

RE/ wave

Oil Visc

Slick mm

Tow m/s

Wave m ORR TE

ORR/curr

1.00

0.94

0.48

0.64

0.12

0.09

0.38

0.33

0.15

0.38

0.20

0.23

L0.78 0.53 0.66

%ORR/curr

0.94

1.00

0.48

0.64

0.06

0.23

0.31

0.13

0.20

0.19

0.17

0.18

L0.71 0.50 0.56

TE/curr

0.48

0.48

1.00

0.65

0.38

0.23

0.70

0.51

0.21

0.10

0.15

0.04

0.50 0.71 0.45

RE/curr

0.64

0.64

0.65

1.00

0.32

0.11

0.42

0.47

0.61

0.02

0.08

0.14

0.53 0.57 0.53

ORR/wave

0.12

0.06

0.38 0.32 1.00

0.87

0.38 0.62

0.17

0.28

0.05 0.32

%ORR/wave

0.09

0.23

0.23 0.11 0.87

1.00

0.37 0.27

0.02

0.08

0.04

TE/wave

0.38

0.31

0.70

0.37

1.00

0.11

0.18

0.31 0.37 0.56 0.47

RE/wave

0.33

0.13

0.51 0.47 0.62

0.27

0.42 1.00

0.27

0.33

0.07 0.69

0.40

0.80

Oil Visc

0.15

0.20

0.21

0.02

0.11 0.27

1.00

0.11

0.01 0.74

0.34

0.78

Slick mm

0.38

0.19

0.10 0.02

0.01

0.17 0.45

0.11

0.71

Tow m/s

0.20

0.17

0.15 0.08

0.28

0.08

0.18

0.11 0.01

1.00

0.26 0.29

0.31 0.28

Wave m

0.23

0.18

0.04

0.05

0.04

0.31 0.07

0.01 0.17

0.26

1.00

ORR

L0.78

L0.71

0.50 0.53 0.32

0.04

0.37 0.69

0.74

0.45

0.29

0.29 1.00

0.44

0.85

TE

0.53

0.50

L0.71 0.57 0.30

0.20

0.56 0.40

0.34

0.11

0.31

0.40 0.44

1.00

0.42

RE

0.66

0.56

0.45 0.53 0.54

0.21

0.47 0.80

0.78

0.71

0.28

0.35 0.85

0.42

1.00

0.14

Values in bold are significant cross-correlation factors.

0.17

0.42

1.00 0.33

0.54

0.04 0.20

0.21

0.29 0.40 0.35

Physical Spill Countermeasures on Water

0.61

0.38

0.30

PART | V

0.42

RE

397

Chapter | 13 Weather Effects on Oil Spill Countermeasures

FIGURE 13.8 Relationship between ORR (oil recovery rate) and wave height (m).

Oil Recovery Rate (from maximum)

100 All skimmers - reg. waves All skimmers - harbour chop Average skimmer - reg. waves Average skimmer - harbour chop

80

60

40

20

0 0

1

2

3

4

Wave Height m FIGURE 13.9 Effect of waves on skimmer performance.

however, involves recovering large amounts of surface material and then separating this water and oil on board the vessel. In conclusion, use of the average decrease in performance (ORR, TE, or RE) with increasing current appears to yield a reasonable estimate of performance with increased wave energy.

398

PART | V

Physical Spill Countermeasures on Water

Oil Recovery Rate (from maximum)

100

ZRV 80

Sirene 60

Skimming barrier

40

Skimming Barrier Sirene Scoop weir Oil Mop ZRV Marco belt Fixed Sub. plane Skim pack Harbor Mate Weir Skimmers, GT. Veegam moving weir

Weir skimmers 20

0 0

1

2

3

4

5

Wave Height m FIGURE 13.10 Effect of waves on specific skimmers. 100

ZRV

Through put Efficiency

80

Marco belt skimmer 60

40

Average of all Skimming barrier Scoop weir Oil mop ZRV Marco belt Fixed sub. plane Veegarm

20

0 0.0

0.5

1.0

1.5

2.0

2.5

Wave Height m FIGURE 13.11 Effect of waves on throughput efficiency.

13.3.4. Dispersants The variance of dispersant effectiveness with wind speed is a complex function.240 It is known from the literature that effectiveness goes down with

399

Chapter | 13 Weather Effects on Oil Spill Countermeasures 100

Veegarm

Recovery Efficiency %

80

Weir skimmers

Skimming barrier, ZRV and towed rope mop

60

40

20

average 0 0.0

0.5

1.0

1.5

2.0

2.5

Wave Height m Average skimmer Skimming barrier Sirene Disc skimmers Rope mop stationary Rope mop towed

Rope mop ZRV Marco Skim Pak Harbor Mate Weir skimmers Veegarm

FIGURE 13.12 Effect of waves on recovery efficiency. 100

Relative Effectiveness %

High speed skimmer 80 Ave skimmer ZRV Offshore arm High speed skimmer Boom critical Boom first loss

60

40

20

Average skimmer

Boom critical and first loss speed

ZRV Offshore arm

0 0.5

1.0

1.5

2.0

2.5

3.0

Current or Tow Speed m/s FIGURE 13.13 Effect of tow or current speed on recovery efficiency.

400

PART | V

Physical Spill Countermeasures on Water

decreasing dispersant but goes up with increasing energy. The deposition is known to vary with wind speed.198 The empirical data in Table 13.5 from various sources, but mainly Giammona et al., was correlated to observe whether simple relationships could predict the relationship between wind and deposition.198 Included in the correlation were aircraft speed, head wind, cross wind, measured droplet diameters, and altitude with the deposition percentage. Surprisingly, it was found that altitude had little relation to the deposition percentage, but the other factors, such as wind, did. Dropping all parameters except wind speed and the particle average volume diameter, it was found that a relatively simple relationship could be established for deposition with wind speed. This relationship is shown in Figure 13.14. This figure shows the threeway correlation between volume mean diameter (VMD), wind, and the percent deposition. VMD here is the actual value less the optimal diameter of 300 mm. The correlations had shown that the best deposition was obtained with this VMD and that lesser VMD would result in poorer deposition. The correlation achieved was 0.54, which is rather good considering the many variables in deposition, including those mentioned earlier. From this a simple correlation for deposition with wind relationship was derived: Depositionð%Þ ¼ ð80 3X Wind SpeedÞ

(7)

This was used in subsequent calculations for relative dispersant effectiveness.

FIGURE 13.14 Correlation of wind, droplet size, and deposition. The VMD is the particle size smaller than 300 mm, and the three-dimensional view also shows the fit surface. The circles above and below the fit surface show data scatter.

Chapter | 13 Weather Effects on Oil Spill Countermeasures

401

The final model to be achieved should conceptually consist of the deposition times the decrease in dispersion caused by the decrease in deposition, then times the increase in dispersion caused by the increasing wave energy. The next step is to separate natural and chemical dispersion so that the effect of dispersants alone can be estimated. The first step is to calculate the fall-off in deposition with wind speed, which was done with the formula developed from the analysis shown in Figure 13.15. Then the drop in chemical dispersion effectiveness with decreasing dispersant amount was calculated using the square root function as determined from empirical data as illustrated in Figure 13.15.240 Next the natural dispersion was calculated using the Delvigne and Mackay natural dispersion approximations in which the natural dispersion varies as the square of the wave height. It is presumed that a light oil would disperse naturally almost completely by the wave height of about 25 m or a wind of about 25 m/s as was observed during the Braer incident. See Section 13.5 for discussion of this issue. Figure 13.16 shows the standard wind-wave conversion.241 Using this conversion, the total dispersant effectiveness model was created as shown in Figure 13.17. It is important to stress that what is shown here is relative effectiveness, that is, the rationalized effectiveness with the maximum set to 100%. The value typically measured in laboratory tests or other such similar effectiveness tests is absolute effectiveness. Thus if one wanted to know the effectiveness percent at a particular wind or wave condition, then the relative effectiveness is multiplied by the absolute effectiveness. For example, if a dispersant has a value of 40% in the laboratory, then at a wind speed of about 12 m/s (25 knots) the relative effectiveness is 60% and the effectiveness then becomes the two factors multiplied or 0.4 X 0.6 or 24%.

FIGURE 13.15 Correlation of dose (dispersant to oil ratio) and dispersant effectiveness.

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Physical Spill Countermeasures on Water

FIGURE 13.16 Correlation of wind speed and wave height.

Relative Percent Effectiveness

100

Deposition Natural Dispersion Chemical Dispersion Total Dispersion

80

Total Dispersion

60

Chemical Dispersion

40

Natural Dispersion

Deposition

20

Chemical Dispersion

0 0

5

10

15

20

25

30

Wind Speed m/s FIGURE 13.17 Model of dispersion of various types with wind speed.

The dispersion model will be described in greater detail in this section. The natural dispersion follows Delvigne and Mackay approximations, specifically: Natural dispersionfðwave height þ 1:2Þ2 =5

(8)

403

Chapter | 13 Weather Effects on Oil Spill Countermeasures

5 degrees C 15 degrees C 25 degrees C Moles 9527 3 deg Moles 9527 10 deg Moles 9527 22 deg Moles 9500 3 deg Moles 9500 10 deg Moles 9500 22 deg

70 60

Effectiveness%

50

Fingas 2006 5 deg 10 deg

40

Moles 9527 - 22 deg

30 Moles tests

20 10

Fingas 2006 25 deg C

0

0

10

20

30

Salinity o/oo FIGURE 13.18 The effectiveness of test dispersions with temperature and salinity.

Chemical dispersion is modeled using a four-step process. The first step is to calculate the loss in effectiveness with deposition. The deposition was calculated as above using empirical data as shown in Figure 13.14. This value is rationalized then to be a relative number, that is, starting from a maximum of 100%. The next step is to bring in the wave height as well as the wind with a Delvigne-like relationship. Relative dispersionfðloss with windÞ2 wave height

(9)

The relative dispersion was then averaged over immediate increments to ensure that it went in smoother increments with increasing wind and wave height. Chemical dispersion is also known to vary with temperature.193,194 The graph of the temperature versus effectiveness is shown in Figure 13.18. On average, the effectiveness decreases as the square root of the temperature between 3 and 22 C.

13.3.5. In-Situ Burning The relation between burning and weather conditions involves several components. If containment is involved, the limitations are those of the

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containment boom, already discussed under booms above. The relationships are shown in Figure 13.7. Whether or not containment is required, there are two factors important to burning: the ability to ignite and the ability to maintain burning in a wind. The second factor, the ability to maintain burning in wind, is probably not of concern. The limitation on burning may be the ability to ignite in a wind. The section above on burning noted that no specific tests were conducted on ignition limits. However, there are some pieces of information that can be used to make an estimate on igniting using current techniques. It should be noted that techniques that involve some form of sheltering may increase the limits of ignition in wind. Thornborough noted a success in ignition at 13 m/s (25 knots) winds.222 If this is assigned a probability of 0.8, and 10 m/s is assigned a probability of 1, since this has been performed several times, one can extrapolate a probability of ignition using a linear form as shown in Figure 13.19. The burning of oil in ice reduces the efficiency somewhat.218 This data can be used to show the decrease in effectiveness. Table 13.8 shows that, on average, Frazil or slush ice slows burning by 0.45 mm/min and brash ice by 0.8 mm/min.

13.3.6. Others Provant rated the decrease in performance of decanting (gravity separation) with wave height as: wave height up to 0.9 m, 0.8 decanting factor (e.g., 80% effective); waves of 1 to 2 m, 0.8; waves of 2.1 to 2.7 m, 0.7; and over 2.8 m, 0.6.148 These data result in a simple nomogram as shown in Figure 13.20.

Probability of Ignition

100

80

60

40

20

0

10

12

14

16

18

20

22

24

Wind Speed m/s FIGURE 13.19 The probability of ignition with wind speed.

26

405

Chapter | 13 Weather Effects on Oil Spill Countermeasures

Success in Decanting %

100

80

60

40

1

2

3

4

5

Wave Height m FIGURE 13.20 The ability to decant with wind speed.

13.4. OVERVIEW OF WEATHER LIMITATIONS The changes in the effectiveness of countermeasures with waves are shown in Figure 13.21. This figure shows the plots of typical skimmers, booms, and the decanting estimation. Thus there is a wide discrepancy between the capability of various skimmers to deal with wave height but the sea performance of booms is less variable and has limitations at the lower end of the wave scale. Figure 13.22 summarizes the wind speed limitations of several countermeasures. The waves have been equated to wind for this diagram.242,243 This shows how booms are limited by wind speed (and the resulting waves) to a low wind speed of about 3 m/s. Harbor skimmers are limited to similar wind/wave regimes. High-speed skimmers can deal with great wind/wave systems. Chemical dispersion peaks at winds of about 12 m/s as this is the point at which decreasing deposition is matched by increasing sea energy. The probability of ignition persists throughout the diagram to yield a lower probability at winds of about 25 m/s. Figure 13.23 shows the current or tow speed limitations. The average skimmer and boom is limited to below about 1 m/s, while high-speed and zero relative velocity skimmers (ZRVs) have potentially much greater potentials. Figure 13.24 shows an overall view of the effect of wind on several countermeasures. Figure 13.24 The relative performance of countermeasures with wind speed. The first (yellow) bar shows the point at which the effectiveness is at 50%, and the final (green) bar shows the where the performance is decreased to 25%. Temperature does not limit most physical recovery or burning. It does, however, limit chemical dispersion.

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All skimmers reg. waves All skimmers harbour chop Average Skimmer reg. waves Average Skimmer habour chop All booms Critical velocity All booms first loss Decanting

Relative Performance %

100

80

Booms critical velocity

60

Average skimmer regular waves

40

20

All skimmers in harbour chop

0 0

1

2

3

4

5

Wave Height m FIGURE 13.21 Relative performance of countermeasures with wave height.

Dispersant deposition Chemical dispersion Boom Critical failure Boom first loss Ave. Skimmer - reg. waves Ave. Skimmer - harbour chop High speed skimmer Probability of ignition

100

Probability of ignition Relative Effectiveness %

80

High speed skimmer 60

Chemical dispersion

Skimmers 40

Booms Dispersant deposition

20

0 0

5

10

15

20

25

30

Wind Speed m/s FIGURE 13.22 Relative performance of countermeasures with wind speed.

407

Chapter | 13 Weather Effects on Oil Spill Countermeasures 100

Relative Effectiveness%

High speed skimmers 80 Ave skimmer ZRV Offshore arm High speed skimmer Boom critical Boom first loss

60

40

ZRV and offshore arm

20

Booms critical Average skimmer or first loss

0 0.5

1.0

1.5

2.0

2.5

3.0

Current or Tow Speed m/s FIGURE 13.23 Relative performance of countermeasures with current or tow speed.

45

Wind Speed m/s

40 35

25% value 50% value

30 25 20 15 10

Ignition (probability of ignition)

Chemical dispersion

Fast current skimmers

Offshore skimmers

Typical booms

0

Harbour skimmers

5

FIGURE 13.24 The relative performance of countermeasures with wind speed. The first (yellow) bar shows the point at which the effectiveness is at 50%, and the final (green) bar shows the where the performance is decreased to 25%.

13.5. SUMMARY AND CONCLUSIONS Spill countermeasures are affected by weather conditions, and, in some cases, they cannot continue under adverse weather conditions. Although the literature did not show any quantitative guides for the performance of countermeasures under varying weather conditions, many a priori estimates are available. These

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a priori guides may not be useful because they lack quantitative backing. Data could be extracted from a number of papers to enable assessment of changes in the performance of countermeasures related to weather conditions. Many estimates or traditional limits are found in the literature, but these vary considerably and may not be useful. Table 13.13 summarizes the many limits found in the literature, and the numerical findings of this report. Table 13.13 shows the high scatter of the a priori limits around the 25 and 50% performance limits developed in this report. The total countermeasures performance is shown in Figure 13.25. Note that this is relative effectiveness compared to a nominal 100% effectiveness at no wind or in the case of chemical dispersion at high energy or wind. The most important factors influencing the performance of countermeasures are the wind and wave height. These two factors are related and, given a typical sea, can be interconverted. These factors must sometimes be considered separately, however, so that specific weather effects can be examined. Other weather conditions affecting countermeasures include currents and temperature. Currents are important in that they become the critical factor for certain countermeasures such as booms. Temperature primarily affects dispersants and has been shown to have only minimal effect on other countermeasures. Booms are the countermeasures most susceptible to weather conditions. Booms will fail at a current of 0.5 m/s (1 knot) regardless of design or other conditions. This is due to inherent hydrodynamic limitations. There is waveassociated degradation of this value, and this is dependent on design. Nomograms are given for some typical booms. Skimmers show degradation of recovery potential with increasing wave height and also with relative current. Skimmer performance is very individual, and a number of skimmer performance curves have been developed for this study. Some skimmers can only function effectively in absolutely calm waters, while others have recovered oil in sea states of up to 5 or 6 (wave heights of up to 3 m with corresponding winds of up to 15 m/s or 30 knots). Sufficient data exist to predict performance with waves and currents for over 30 specific skimmers and 10 generic types. Advancing skimmers generally show an increase in oil recovery with increasing current or tow speed because this presents more oil to them or increases the encounter rate. The weather affects dispersant application and effectiveness in three ways: the amount of dispersant that contacts the target is highly wind-dependent; the amount of oil dispersed on the surface is very dependent on ocean turbulence and energy; and the amount of oil remaining in the water column is dependent on the same energy. Nomograms for effectiveness have been created. At highsea energies, many lighter oils can disperse naturally. The weather affects in-situ burning in two ways: the ability to ignite oil in a given wind and the ability to sustain ignition in a given wind. While there are few data on these, estimates of ignition success were made based on prior experience.

TABLE 13.13 Summary of Weather Limits or Functions Noted in This Report Variable Limits

Countermeasure Reference

Type

Booms

first loss

This work

critical velocity

Wind

m/s

25%

50% 25%

3

4

Wave

1.2

m

Current

50% 25%

2

0.5

A Priori Limits m/s

Wind

50% m/s

Other

Wave

Current

Wind

Wave

Current

m

m/s

m/s

m

m/s

Notes

0.5 to .06

measured

0.4

typical

0.7

Yazaki 1983

government specification

10

1

0.25

spec for type C boom

Yazaki 1983

government specification

20

1.5

0.5

spec for type D boom

Williams and Cooke 1985

bubble barrier critical velocity

8 to 10

Brekne et al. 2003

critical velocity

20

Tedeschi 1999

critical velocity

8 to 9

Nash and Hillger

first loss

0.1 to 0.6

measured calm

Nash and Hillger

first loss

0 to 0.6

measured regulaqr waves

Nash and Hillger

first loss

0 to 0.38

measured harbour chop

Van Dyck and Bruno

catenary tow optimal

0.5

Marks et al. 1971

total force on boom

Function

oil held several m away

2.5

design for new boom

varies directly as wave height

(Continued )

TABLE 13.13 Summary of Weather Limits or Functions Noted in This Reportdcont’d Variable Limits

Countermeasure Reference

Type

Wind

m/s

25%

50% 25%

Wave

m

Current

50% 25%

A Priori Limits m/s

Wind

50% m/s

Other

Wave

Current

Wind

Wave

Current

m

m/s

m/s

m

m/s

Notes

Function

Milgram 1977

fabric tearing strength

one-third power of wave height

Potter et al. 1999

towing force

varies directly as wave height

Schulz and Potter 2002

towing force

varies directly as wave height

Suzuki et al. 1985

critical velocity

Brown et al. 1993

critical velocity

0.25

if oil was heavy oil

Hansen 2001

critical velocity

3

test for JBF 6001

Hansen 2001

critical velocity

3.5

test for Current Buster

Eryuzlu and Hausser 1977

floating deflector

0.8 to 2.1

successful deflection

Folsom and Johnson 1981

critical velocity

3

claim for boom

Nash and Johnson

critical velocity

3

test for plunging jet

Swift et al. 2000b

critical velocity

1.03

containment for submerged bow plane

increased in ice from 0.4 to 0.5

Skimmers

Meikle 1983

fire resistant boom test

1

Buist et al. 1983

fire resistant boom test

This work

typical harbour

7

10

1.5

2

0.6

1

typical offshore

7

10

2.5

5

4

7

fast current

2

4

10

15

5

8

4

0.4

in towing mode primarily

Reed 1995

mechanical recovery efficiencies

5

80% efficiency

Peigne 1985

successful recovery

10

Reed 1995

mechanical recovery efficiencies

10

Wilson 1981

tests

15

3

weir boom tests

Nordvik 1995

successful recovery

10 to 13

2.5

successful recovery

Leigh 1973

design objectives

10 to 14

1.2

drum skimmer and weir basin objectives

Koops 1985

successful recovery

2

skimming vessel recovery

Brekne et al. 2003

tests

3

Gates and Gordiano 1985

effect of waves

0.18 to 0.47

1 to 2

Sirene and ESCA tests 60% efficiency

0.8

Ocean Buster tests no decrease for wave increase

(Continued )

TABLE 13.13 Summary of Weather Limits or Functions Noted in This Reportdcont’d Variable Limits

Countermeasure Reference Hara et al. 2002

Skimmers

Type

Wind

m/s

25%

50% 25%

Wave

m

Current

50% 25%

A Priori Limits m/s

Wind

50% m/s

Other

Wave

Current

Wind

Wave

Current

m

m/s

m/s

m

m/s

increase in capability

from 1 to 2 or 3

Notes increase in capability by moon pool

Allen 1988

mechanical cleanup

6

0.8

Dempsey 2002

offshore work generally

12

3

Koops and Huisman 2002

skimmers generally

13

Decola 2003

Wash./Or. Guide mechanical cleanup

Koops 1988

skimmers generally

1.5

Steen 2002

general limit

1

Koops and Huisman 2002

general limit

5

Akahoshi et al. 2002

sea recovery limit

2.5

Provant 1992

degradation in performance

0.9

80% effective

Provant 1992

degradation in performance

1 to 2

70% effective

Provant 1992

degradation in performance

2.1 to 2.7

50% effective

0.5

Function

Chemical dispersion

Provant 1992

degradation in performance

over 2.8

10% effective

Nordvik 1995

Transrec performance

1.5

15 to 85% TE

Nordvik 1995

Transrec limitations

4

expected limits of operation

Tech. Serv. Br. 1984

temperature limitations

temperature no difference

Shum and Borst 1985

ice limitations

50% ice caused no difference

Hansen 20021

tests

3

Ocean Buster tests

Coe 1999

tests

3

USCG high speed skimmer

This work

typical rising/falling

10 to 18

22

Decola 2003

Wash./Or. Guide

Koops and Huisman 2002

natural dispersion

1 to 10

Allen 1988

general dispersion

12

Decola 2003

EPA region size guide

13

Exxon Mobil 2000

application - large aircraft

15 to 18

Koops and Huisman 2002

chemical dispersion

2 to 20

3

minimum

5

minimum

3

9 to 12

(Continued )

TABLE 13.13 Summary of Weather Limits or Functions Noted in This Reportdcont’d Variable Limits

Countermeasure Reference

Type

Wind

m/s

25%

50% 25%

Wave

m

Current

50% 25%

A Priori Limits m/s

Wind

50% m/s

Other

Wave

Current

Wind

Wave

Current

m

m/s

m/s

m

m/s

Notes

Exxon Mobil 2000

application e workboat

3 to 11 0 to 3

Exxon Mobil 2000

application e single-engine aircraft

8 to 11 2 to 3

Exxon Mobil 2000

application e helicopters

9 to 11 2 to 8

Daling 1988

dispersion and temperature

20% fall off with lower temperature

Lunel and Lewis 1999

lower sea threshold

15% for low sea, 30% for calm

Lunel et al. 1995a

classification of energy

0 to 5 m/s ¼ low; 6 to 10 m/s high energy

Scholz et al. 1999

lower energy threshold

winds 2.5 to 12 m/s waves 0.1 to 2 m

Lunel 1995a

Braer sea energy

16 to 26 m/s waves 6 to 12 m; winds gusts up to 35 m/s

Mackay et al. 1980

natural dispersion

Function

directly with square of wind

Chemical dispersion

Burning

Delvigne and Sweeney 1988

natural dispersion

directly with square of wind

Koops 1988

natural dispersion

directly with wave height

Moles et al. 2001

temperature effects

Lindblom 1983

aerial application droplet size

Lewis 1995

helicopter bucket deposition

speed of 7 m/s caused 30% deposition

Lewis 1995

helicopter bucket deposition

wind of 2 to 5 m/s caused 20% loss

Payne et al. 19991b

deposition with wind

wind of 7 to 10 m/ s caused loss of deposition

This work

probability of ignition

Thornborough 1997

actual ignition

10

1.5

0.9

Helitorch

Thornborough 1997

actual ignition

10 to 13

1 to 2

0.9

hand held igniter

Moffat and Hankins 1997

ignitor test

8 to 10

Allen 1988

effectiveness decreased with lowering temperature directly with wind velocity

18

24

11

Nordvik 2002

ignition limit

10 to 12

Buist et al. 2003b

ignition limit

1o to 12

1.1

successful test

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Ignition of oil Chemical dispersion Boom Critical failure Boom first loss Ave. Skimmer - reg. waves Ave. Skimmer - harbour chop High speed skimmer Probability of ignition

Relative Effectiveness %

100

80

60 boom boom critical loss first loss ave skimmer

40

chemical dispersion

Ignition of oil

regular waves high speed skimmer

20 ave. skimmer harbour chop 0 0

5

10

15

20

25

30

Wind Speed m/s FIGURE 13.25 The overall effect of wind on oil spill countermeasures. Note that this is relative effectiveness, compared to a nominal 100 % effectiveness at no wind or in the case of chemical dispersion at high energy or wind.

ACKNOWLEDGMENTS The Prince William Sound Regional Citizens Advisory Council is acknowledged for sponsoring an earlier study on weather aspects of countermeasures. Some of the data here is used from that study.

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Chapter | 13 Weather Effects on Oil Spill Countermeasures

417

8. Nordvik AB, MA, Bitting KR. In: Ornitz BE, Champ MA, editors. Oil Spills First Principles: Prevention and Best Response. Review of the Processes for Estimating Time Windows for InSitu Burning of Spilled Oil at Sea, 573. Amsterdam: Elsevier Publishing; 2002. 9. Champ MA, Nordvik AB, Simmons JK. Utilization of Technology Windows of Opportunity in Marine Oil Spill Contingency Planning, Response and Training. IOSC 1997;993. 10. Champ MA. In: Ornitz BE, Champ MA, editors. Oil Spills First Principles: Prevention and Best Response. The Technology Windows-of-Opportunity Oil Spill Response Strategy, 289. Amsterdam: Elsevier Publishing; 2002. 11. Hann RW. Unit Operations, Unit Processes, and Level of Resource Requirements for the Cleanup of the Oil Spill from the Supertanker Amoco Cadiz. IOSC 1979;147. 12. Jeffery PG. Large-Scale Experiments on the Spreading of Oil at Sea and Its Disappearance by Natural Factors. IOSC 1971;469. 13. Thalich P, Xizobo C. Accurate Simulation of Oil Slicks. IOSC 2001;1133. 14. Beynon LR. Codes of Practice for Dealing with Oil Spills at Sea and on Shore: A European View. IOSC 1969;617. 15. Dicks B, Ansell DV, Guenette CC, Moller TH, Santner RS, White IC. A Review of the Problems Posed by Spills of Heavy Fuel Oils, Proceedings of the Third Research and Development Forum on High-Density Oil Spill Response, IMO; 2002. 16. Kokkonen T, Ihaksi T, Jolma A, Kuikka S, Dynamic Mapping of Nature Values to Support Prioritization of Coastal Oil Combating. Environ Model Soft, 2020;248. 17. Lamp HJ. Lake Champlain: A Case History on the Cleanup of #6 Fuel Through Five Feet of Solid Ice at Near-Zero Temperatures. IOSC 1971;579. 18. Harris C. The Sea Empress Incident: Overview and Response at Sea. IOSC 1999;177. 19. Etkin DS. Estimating Cleanup Costs for Oil Spills. IOSC; 1999. 20. Etkin DS. Comparative Methodologies for Estimating on-Water Response Costs for Marine Oil Spills. IOSC 2001;1281. 21. Etkin DS, Tebeau P. Assessing Progress and Benefits of Oil Spill Response Technology Development since Exxon Valdez. IOSC; 2003. 22. Harper J, Godon A, Allen AA. Costs Associated with the Cleanup of Marine Oil Spills. IOSC; 1995. 23. Robertson TL, Kumar SA. Estimating the Response Gap for Two Operating Areas in Prince William Sound, Alaska. IOSC 2008;615. 24. Oskins CJ, Bradley D. “Extreme” Cold Weather Oil Spill Response Techniques and StrategiesdIce and Snow Environments. IOSC 2003;1128. 25. Hazel III WE, Raunchily MR. Health and Safety Issues During Cold Weather Oil Spill Responses. IOSC 2003;109. 26. Kowalski T. Oil Spill Cleanup in Severe Weather and Open Ocean Conditions. IOSC; 2001. 27. Lasted M, Martinson EJ, Currents Computed with a Barotropic Ocean Model: Application to Simulation of Oil Slick Movements in Actual Weather Conditions, Mechanics of Oil Slicks, vol. 133. Paris: Ancient Editions; 1981. 28. Thorpe SA. Langmuir Circulation and the Dispersion of Oil Spills in Shallow Seas. Spill Sci Techn Bull 2000;213. 29. McWilliams JC, Sullivan PP. Vertical Mixing by Langmuir Circulations. Spill Sci Techn Bull 2000;225. 30. Lehr WJ, Simecek-Beatty D. The Relation of Langmuir Circulation Processes to the Standard Oil Spill Spreading, Dispersion, and Transport Algorithms. Spill Sci Techn Bull 2000;247. 31. Simecek-Beatty D, Lehr WJ. NOAA-MMS Joint Langmuir Circulation and Oil Spill Trajectory Models Workshop. AMOP 2000;601.

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136. Broje V, Keller AA. Interfacial Interactions Between Hydrocarbon Liquids and Solid Surfaces Used in Mechanical Oil Spill Recovery. J Coll Interface Sci 2007;286. 137. Broje V, Keller AA. Improved Mechanical Oil Spill Recovery Using an Optimized Geometry for the Skimmer Surface. Env Sci Techn 2006;7914. 138. Keller AA, Clark K. Oil Recovery with Novel Skimmer Surfaces under Cold Climate Conditions. IOSC 2008;667. 139. Ayers RR, Fraser JP, Kazmierczak LJ. Developing and Open-Seas Skimmer. IOSC 1975;401. 140. Freestone FJ, Anderson RA, Trentacoste NP. United States Environmental Protection Agency Research in High-Speed Devices for the Recovery of Thin-Film Oil Spills. IOSC 1975;409. 141. Neal RW, Bianchi RA, Johanson EE. The Design and Demonstration of a RemotelyControlled High-Seas Oil Recovery System. IOSC 1975;395. 142. Widawsky A. Development of Harbor Oil Spill Removal-Recovery Systems: Phase I. IOSC 1975;379. 143. Claus GF, Ku¨hnlein WL. Efficiency of Selected Oil Skimming Systems in Irregular Seas. IOSC 1991;115. 144. Ueda K, Yamanouchi H, Hikida K. Recovery of Spilled Oil in Waves. AMOP 2001;275. 145. Hara S, Yamakawa K, Hoshino K, Yukawa K, Hikida K, Kagemoto H, et al. Improvement of Performance on Multi-purpose Work Vessel, Proceedings of the Third Research and Development Forum on High-Density Oil Spill Response, IMO; 2002. 146. Akahoshi S, Ono S, Iwasaki T, Kobayashi E. Study of Large Oil Recovery System for Use Under Rough Sea Weather Conditions, Proceedings of the Third Research and Development Forum on High-Density Oil Spill Response, IMO; 2002. 147. Hvidbak F, Gunter PA. Preparation for Recovery of Heavy Oil Spills, with Emphasis on Mechanical Feeder Skimmers, Proceedings of the Third Research and Development Forum on High-Density Oil Spill Response, IMO; 2002. 148. Provant SG. Assessment of the Transrec-350 Mechanical Recovery Capacity of the Oil Spill Response Equipment of the Oil Spill Response Equipment in Prince William Sound. AMOP 1992;219. 149. Technical Services Branch. A Winter Evaluation of Oil Skimmers and Booms. Environment Canada Report EPS 4-EP-84-1; 1984. 150. Shum JS, Borst M. OHMSETT Tests of a Rope-Mop Skimmer in Ice-Infested Waters. IOSC 1985;31. 151. Gates DC, Corradino KM. OHMSETT Tests of the Toscon Weir Skimmer and Gravity Differential Separator. IOSC 1985;35. 152. Smith JBH, McLellan C, Pintler LR. Development of An Oil Skimming System to Meet Navy Specifications. IOSC 1989;91. 153. Christodoulou MS, Turner JT. Experimental Study and Improvement of the Rotating Disc Skimmer. IOSC 1987;101. 154. Peigne G. Ecumoire II: Evaluation of Three Oil Recovery Devices Offshore. IOSC 1985;13. 155. Leigh JT. Oil Recovery on the High Seas. IOSC 1973;351. 156. Wilson HB. Development and Testing of a Weir Boom for Oil Recovery at Sea. IOSC 1981;643. 157. Schwartz SH. Performance Tests of Four Selected Oil Spill Skimmers. AMOP 1979;493. 158. Coe T. Control of Oil Spills in Fast Water CurrentsdA Technology Assessment. IOSC; 1999. 159. Ouwerkerk MR, Verbeek PRH, Schut T. A New Tool for Large-Scale Oil Combat. IOSC; 1995. 160. Koops W, Sanders FJ, Gubbens JM. The Katina Oil Spill 1982, Combatting Operation at Sea. IOSC 1985;299.

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161. Huisman S. Private Communication 2008. 162. Lindstedt-Siva J. Advance Planning for Dispersant Use. IOSC 1987;329. 163. Scholz DK, Kucklick JH, Pond R, Walker AH, Bostrom A, Fischbeck P. A Decision-Maker’s Guide to Dispersants: A Review of the Theory and Operational Requirements. American Petroleum Institute, Publication Number 4692; 1999. 164. Lewis A, Aurand D. Putting Dispersants to Work: Overcoming Obstacles. Technical Report IOSC-004, API; 1997. 165. Aurand D. The Application of Ecological Risk Assessment Principles to Dispersant Use Planning. Spill Sci Techn Bull. 1995;241. 166. Trudel K, Ross S, Belore R, Buffington S, Rainey G. Technical Assessment of the Use of Dispersants on Spills From Drilling and Production Facilities in the Gulf of Mexico Outer Continental Shelf. AMOP 2001;531. 167. Trudel K, Ross S, Belore R, Buffington S, Rainey G, Ogawa C, et al. Technical Assessment of Using Dispersants on Marine Oil Spills in the U.S. Gulf of Mexico and California. IOSC 2003;1. 168. Lewis A, Daling PS, Kristiansen TS, Singsaas I, Fiocco RJ, Nordvik AB. Chemical Dispersion of Oil and Water-in-Oil Emulsions: A Comparison of Bench Scale Test Methods and Dispersant Treatment in Meso-Scale Flume. AMOP 1994;979. 169. Lewis A, Daling PS, Strom-Kristiansen T, Brandvik PJ. The Behaviour of Sture Blend Crude Oil Spilled at Sea and Treated with Dispersant. AMOP 1995;453. 170. Lewis A, Daling PS, Nordvik AB. The Effect of Oil Weathering on the Laboratory Determined Effectiveness of Oil Spill Dispersants, Marine Spill Response Corporation Workshop. MSRC; 1995. 171. Lewis A, Crosbie A, Davies L, Lunel T. Large Scale Field Experiments Into Oil Weathering at Sea and Aerial Application of Dispersants. AMOP 1998;319. 172. Lewis A, Crosbie A, Davies L, Lunel T. The AEA ‘97 North Sea Fields Trials on Oil Weathering and Aerial Application of Dispersants. In: Dispersant Application in Alaska: A Technical Update, 78. Cordova: Prince William Sound Oil Spill Recovery Institute (OSRI); 1998. 173. Fingas MF. A Practical Guide to Chemical Dispersion for Oil Spills, Chapter 16 in this work; 2010. 174. Fingas MF. Models of Oil Spill Dispersion Stability. AMOP; 2010. in press. 175. Fingas MF. Oil Spill Dispersants: A Technical Summary, Oil Spill Science and Technology 2010:435. 176. Martinelli FN, Lynch BWJ. Factors Affecting the Efficiency of Dispersants. LR 363 (OP), Warren Spring Laboratory, Stevenage; 1980. 177. Farmwald JW, Nelson WG. Dispersion Characteristics and Flammability of Oil under Low Ambient Temperatures Conditions. AMOP 1982;217. 178. Daling PS. A Study of the Chemical Dispersability of Fresh and Weathered Crude Oils. AMOP 1988;481. 179. Daling PS, Brandvik PJ, Singsaas I. Weathering of Oil and Use of Dispersants: Methods for Assessing Oils’ Properties at Sea and the Feasibility of Oil Spill Dispersants. NOSCA Seminar on Oil Pollution Control; 1995. 180. Brandvik PJ, Daling PS, Aareskjold K. Chemical Dispersability Testing of Fresh and Weathered OilsdAn Extended Study with Eight Oil Types. Report No. 02.0786.00/12/90, IKU SINTEF Group, Norway; 1991. 181. Lunel T, Lewis A. Optimisation of Oil Spill Dispersant Use. IOSC 1999;187. 182. Lunel T. Dispersant Effectiveness at Sea. IOSC 1995;147. 183. Thomas D, Lunel T. The Braer Incident: Dispersion in Action. AMOP 1993;843.

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184. Lunel T. The Braer Spill: Oil Fate Governed by Dispersion. IOSC; 1995. 185. Cormack D, Nichols JA. The Concentrations of Oil in Sea Water Resulting from Natural and Chemically Induced Dispersion of Oil Slicks. IOSC 1977;381. 186. Fuentes HR, Jaffe R, Tsihrintzis VA, Boye D. In-Water Natural Dispersion. Water Res 1995;638. 187. Lunel T, Davies L. Dispersant Effectiveness in the Field on Fresh Oils and Emulsions. AMOP 1996;1355. 188. Sebastiao P, Soares CG. Modeling the Fate of Oil Spills at Sea. Spill Sci Techn Bull 1995;121. 189. Mackay D, Buist I, Mascarenhas R, Petersen S, Oil Spill Processes and Models, Manuscript Report EE-8, Environment Canada; 1980. 190. Delvigne GAL, Sweeney CE. Natural Dispersion of Oil. Oil Chem Poll 1988;281. 191. Delvigne GAL, Hulsen LJM. Simplified Laboratory Measurement of Oil Dispersion CoefficientdApplication in Computations of Natural Oil Dispersion. AMOP 1994;173. 192. Mackay D. Effectiveness of Chemical Dispersants Under Breaking Wave Conditions, The Use of Chemicals in Oil Spill Response, STP 1252. ASTM 1985;310. 193. Moles A, Holland L, Short J. The Effectiveness of Corexit 9527 and 9500 in Dispersing Fresh, Weathered and Emulsion of Alaska North Slope Crude Oil Under Subarctic Conditions. Anchorage: Prince William Sound Regional Citizens’ Advisory Council; 2001. 194. Fingas MF, Fieldhouse B, Wang Z. The Effectiveness of Oil Spill Dispersants on Alaskan North Slope Crude Oils Under Various Temperature and Salinity Regimes. AMOP 2006;821. 195. Lindblom GP, Cashion BS. Operational Considerations for Optimum Deposition Efficiency in Aerial Application of Dispersants. IOSC 1983;53. 196. Smedley JB. Assessment of Aerial Application of Oil Spill Dispersants. IOSC; 1981. 197. Fay RR. Measuring the Aerial Application of Oil Dispersant from Very Large Aircraft at Moderate Altitude. AMOP 1993;1057. 198. Giammona C, Binkley K, Fay R, Denoux G, Champ M, Geyer R, et al. Aerial Dispersant Application: Field Testing Research Program, Alpine, Texas, MSRC Technical Report Series 94-019; 1994. 199. Lewis A. Calibration and Use of a Helicopter Bucket to Apply Oil Spill Dispersants. AMOP 1995;505. 200. Brandvik PJ, Lewis A, Daling PS, Strøm-Kristiansen T. On-Land and Offshore Testing of a New Helicopter Bucket for Dispersant ApplicationdResponse 3000D. AMOP 1997;499. 201. Payne JR, Clayton JR, Phillips CR, Robinson JU, Kennedy D, Talbot J, et al. Dispersant Trials Using the Pac Baroness, A Spill of Opportunity. IOSC 1991;427. 202. Payne JR, Reilly TJ, Martrano RJ, Lindblom GP, Kennicutt MC, Brooks JM. Spill-ofOpportunity Testing of Dispersant Effectiveness at the Mega Borg Oil Spill. IOSC 1993;791. 203. Lunel T. Dispersion of a Large Experimental Slick by Aerial Application of Dispersant. AMOP 1994;951. 204. Lunel T. Field Trials to Determine Quantitative Estimates of Dispersant Efficiency at Sea. AMOP 1994;1011. 205. Lunel T. Research Requirements to Determine Dispersant Effectiveness at Sea, Second International Oil Spill Research and Development Forum. IMO 1995;271. 206. Lunel T. Understanding the Mechanism of Dispersion Through Oil Droplet Size Measurements at Sea, The Use of Chemicals in Oil Spill Response, STP 1252. ASTM 1995;240. 207. Lunel T, Baldwin G, Merlin F. Comparison of Meso-Scale and Laboratory Dispersant Tests with Dispersant Effectiveness Measured at Sea. AMOP 1995;629.

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208. Lunel T, Davies L, Brandvik PJ. Field Trials to Determine Dispersant Effectiveness at Sea. AMOP 1995;603. 209. Lunel T, Wood P. A Laboratory Dispersant Effectiveness Test Which Reflects Dispersant Efficiency in the Field. AMOP 1996;461. 210. Lunel T, Russin J, Bailey N, Halliwell C, Davies Louise. A Successful at Sea Response to the Sea Empress Spill. AMOP 1996;1499. 211. Lunel T, Rusin J, Bailey N, Halliwell C, Davies L. The Net Environmental Benefit of a Successful Dispersant Operation at the Sea Empress Incident. IOSC 1997;185. 212. Lunel. T. Sea Empress Spill: Dispersant Operations, Effectiveness, and Effectiveness Monitoring, Dispersant Application in Alaska: A Technical Update. Cordova: Prince William Sound Oil Spill Recovery Institute (OSRI); 1998; 59. 213. Lunel T. Dispersant Pre-Approvals: Best Practice. IOSC 2001;441. 214. Guyomarch J, Mamaca E, Champs M, Merlin F-X. Oil Weathering and Dispersibility Studies: Laboratory, Flume, Mesocosms, and Field Experiments, In: Proceedings of the Third Research and Development Forum on High-Density Oil Spill Response, IMO 2002;166. 215. Lichtenthaler RG, Daling PS. Dispersion of Chemically Treated Crude Oil in Norwegian Offshore Waters. IOSC 1983;7. 216. Pope P, Allen A, Nelson WG. Assessment of Three Surface Collecting Agents During Temperature and Arctic Conditions. IOSC; 1985. 217. Fingas MF, An Overview of In-Situ Burning, Chapter 23 in this work; 2010. 218. Buist I, Majors L, Linderman K, Dickins D, Mullin J, Owens C. Tests to Determine the Limits of In-Situ Burning of Thin Oil Slicks in Brash and Frazil Ice. AMOP 2003;629. 219. Buist IA. Window-of-Opportunity for In-Situ Burning. Spill Sci Techn Bull 2003;341. 220. Buist I, McCourt J, Mullin J, Glover N, Hutton C, McHale J. Mid-Scale Tests of In-Situ Burning in a New Wave Tank at Prudhoe Bay, AK. AMOP 1998;399. 221. Bech C, Sveum P, Buist I. The Effect of Wind, Ice, and Waves on the In-Situ Burning of Emulsions and Aged Oils. AMOP 1993;735. 222. Thornborough J. United Kingdom In-Situ Burn Trials, Lowenstoft. IOSC 1996;131:1997. 223. Nordvik AB, Champ MA, Bitting KR. Estimating Time Windows for Burning Oil at Sea: Processes and Factors. Spill Sci Techn Bull. 2003;347. 224. Guenette CC, Wighus R. In-Situ Burning of Crude Oil and Emulsions in Broken Ice. AMOP 1996;895. 225. D’Atri B, King T. Flicking Your Bic at 25 Below. AMOP 1993;669. 226. Guenette CC, Thornborough J. An Assessment of Two Off-Shore Igniter Concepts. AMOP 1997;795. 227. Moffatt C, Hankins P. Results of Experiments with Flare Type Igniters on Diesel Fuel and Crude Oil Emulsions. AMOP 1997;1197. 228. Buist IA, Pistruzak WM, Potter SG, Vanderkooy N, McAllister IR. The Development and Testing of a Fireproof Boom. IOSC 1983;43. 229. Bitting KR, Coyne PM. Oil Containment Tests of Fire Booms. AMOP 1997;735. 230. Hansen KA. Second Phase Evaluation of Fire Resistant Booms: Containment Performance. AMOP 2000;429. 231. McCourt J, Buist I, Pratte B, Jamieson W, Mullin J. Testing Fire Resistant Booms in Waves and Flames. AMOP 1997;823. 232. Cooper D, Mackay R. Assisted Viscous Oil Pumping. AMOP 2002;143. 233. Hvidbak F, Gunter PA, The Development and Test of Techniques for Emergency Transfer of Extreme Viscosity Oil (Refloated Bitumen), In: Proceedings of the Third Research and Development Forum on High-Density Oil Spill Response, IMO; 2002.

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234. McCourt J, Shier L. Interaction between Oil and Suspended Particulate Material in the Yukon River. AMOP 1998;79. 235. Grenon S. How to Prioritize Numerous Environmental Issues? Case Study of the HavreSaint-Pierre Spill. AMOP 2000;943. 236. Abdelnour R, Johnstone T, Howard D. Laboratory Testing of an Oil Skimmer Boom in Broken Ice Fields. AMOP 1985;131. 237. Arita M, Yamaguchi M, Narita S, Koyama K, Ueda K, Izumiyama K. Countermeasures for Oil Spills in Cold WaterdIn the Case of Japan. AMOP 1998;265. 238. Tsang G, Vanderkooy N. Development of a Novel Ice Oil Boom for Flowing Waters. IOSC 1979;377. 239. Ono S, Yamaga H, Kato Y, Shigeiri Y, et al. Research and Development of Oil Skimmer for Stormy Weather. Proceedings of the International Offshore and Polar Engineering Conference, 2001;374. 240. Fingas MF. In: Laurier L, Schramm, editors. Surfactants: Fundamentals and Applications to the Petroleum Industry. Use of Surfactants for Environmental Applications, Chapter 12, 461. Cambridge University Press; 2000. 241. Hunt LM, Groves DG. A Glossary of Ocean Science and Undersea Technology Terms. New York: Compass Publications; 1976. 242. Barker CH, Wesley D. Modeling Potential Skimmer and Booming Strategy Effectiveness. AMOP 2004;397. 243. Chrastansky A, Gallies U. Model-Base Long-Term Reconstruction of Weather-Driver Variations in Chronic Oil Pollution Along the German North Sea Coast. Mar Pollut Bull 2009;967.

Part VI

Treating Agents

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Chapter 14

Spill-Treating Agents Merv Fingas

Chapter Outline 14.1. Introduction 14.2. Dispersants 14.3. Surface-Washing Agents 14.4. Emulsion Breakers and Inhibitors

429 429 430

14.5. 14.6. 14.7. 14.8.

Recovery Enhancers Solidifiers Sinking Agents Biodegradation Agents

431 431 431 432

430

14.1. INTRODUCTION Treating the oil with specially prepared chemicals is another option for dealing with oil spills. An assortment of chemical spill-treating agents are available to assist in cleaning up or removing oil. It should be noted, however, that approval must be obtained from the appropriate authorities before these chemical agents can be used. In addition, these agents are not always effective, and the treated oil or the treating chemical may be toxic to aquatic and other wildlife.

14.2. DISPERSANTS Dispersant is a common term used to label chemical spill-treating agents that promote the formation of small droplets of oil that “disperse” throughout the top layer of the water column. Dispersants contain surfactants, chemicals like those in soaps and detergents, that have molecules with both a water-soluble and oil-soluble component. Depending on the nature of these components, surfactants cause oil to behave in different ways in water. Surfactants or surfactant mixtures used in dispersants have approximately the same solubility in oil and water, which stabilizes oil droplets in water so that the oil will temporarily disperse into the water column. Two major issues associated with the use of dispersantsdtheir effectiveness and the toxicity of the resulting oil dispersion in the water columndhave generated controversy in the last 40 years. There is an extensive section on dispersants following this introduction. Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10014-0 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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14.3. SURFACE-WASHING AGENTS Surface-washing agents, or beach cleaners, are different from dispersants. Surface-washing agents are effective in some situations, but they have not been widely accepted partially because of this confusion with dispersants. While toxicity has been a problem with some dispersants in the past, testing has shown that the better surface-washing agents have very little aquatic toxicity and their use could prevent damage to shoreline species. While both products contain surfactants, those in dispersants are equally soluble in both water and oil, whereas in surface-washing agents, the surfactants are more soluble in water than in oil. Surface-washing agents operate by a different mechanism than dispersants. This mechanism is known as detergency and is similar to the use of detergents for washing clothes. In fact, dispersants and surface-washing agents may be quite different. Testing has shown that a product that is a good surface-washing agent is often a poor dispersant and vice versa. Dispersants and surface-washing agents are used for quite different purposes. Rather than causing the oil to disperse, surface-washing agents are intended to be applied to shorelines or structures to release the oil from the surface. During low tide, the oil is sprayed with the surface-washing agent, which is then left to soak for as long as possible. It is washed off with a lowpressure water stream in an area that has been isolated using booms and skimmers. Laboratory- and field-scale tests have shown that these agents substantially reduce the adhesion of the oil so that as much as 90 to 95% of the oil can be released from rocks or other surfaces. There is an extensive section on oil spill surface washing agents in this chapter.

14.4. EMULSION BREAKERS AND INHIBITORS Emulsion breakers and inhibitors are agents used to prevent the formation of water-in-oil emulsions or to cause such emulsions to revert to oil and water. Several formulations can perform both functions. Water-in-oil emulsions can seriously complicate a cleanup operation by increasing the amount of material to be recovered, disposed of, and stored by up to three times. Water-in-oil emulsions are so viscous that skimmers and pumps often cannot handle them. There are different types of emulsion breakers and inhibitors, some of which are best used when little water is present, referred to as a closed system, and others that are best used on the open water, referred to as an open system. For example, some contain surfactants that are very soluble in water and are best used in closed systems so that they are not lost to the water column. Others contain polymers that have a low water solubility and thus are best used on open water. The aquatic toxicity of the products also varies widely. The effectiveness of emulsion breakers and inhibitors is measured as the minimum dose required to break a stable emulsion or prevent one from

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forming. As with dispersants, the use of emulsion breakers or inhibitors is subject to rules and regulations in most countries. Only a few agents have passed both the effectiveness and toxicity criteria, and permission is required to use them. Similar legislation exists in many countries, especially for the use of these products on open waters. Emulsion breakers are not often used on open water or in cleanup operations in general.

14.5. RECOVERY ENHANCERS Recovery enhancers, or viscoelastic agents, are formulations intended to improve the recovery efficiency of oil spill skimmers or suction devices by increasing the adhesiveness of oil. These agents can increase the recovery rate of sorbent surface skimmers for products such as diesel fuel by up to ten times. These products are not useful, however, with normally adhesive products such as heavy crude oils and Bunker C. One recovery enhancer consists of a nontoxic polymer in the form of microsprings, or coiled molecular forms, which increase the adhesion of one portion of the oil to the other.

14.6. SOLIDIFIERS Soldifiers are intended to change liquid oil to a solid compound that can be collected from the water surface with nets or mechanical means. They are sometimes referred to as gelling agents or collecting agents. Collecting agents are actually a different category of agent that are the opposite of dispersants and are not yet fully developed. Solidifiers consist of cross-linking chemicals that couple two molecules or more, or polymerization catalysts that cause molecules to link to each other. Solidifiers usually consist of powders that rapidly react with and fuse the oil. Depending on the agent, about 10 to 40% by weight of the agent is required to solidify the oil, under ideal mixing conditions. An extensive section on solidifiers follows this introduction. Solidifiers have not been used in the past for a number of reasons. Most importantly, if oil is solidified at sea, it makes recovery more difficult as skimming equipment, pumps, tanks, and separators are built to deal with liquid or very viscous liquid. Second, such a large amount of agent is required to solidify oil that it would be impossible to treat even a moderate spill. Third, the faster solidifiers react with the oil, the less likely the oil is to become solidified because the oil initially solidified forms a barrier that prevents the agent from penetrating the remaining oil. Trials at sea have shown that solidifiers often do not solidify the oil mass even when large amounts of treating agents are used.

14.7. SINKING AGENTS Sinking agents are any material, usually minerals, that absorbs oil in water and then sinks to the bottom. The use of sinking agents is banned in almost all countries, however, due to serious environmental concerns. These agents can

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jeopardize bottom-dwelling aquatic life, and the oil is eventually released to reenter the water column in the original spill area.

14.8. BIODEGRADATION AGENTS Biodegradation agents are used to accelerate the biodegradation of oil in the environment. They are used primarily on shorelines or land. They are not effective when used at sea because of the high degree of dilution and the rapid movement of oil. Many studies have been conducted on biodegradation and the use of these agents. Hundreds of species of naturally occurring bacteria and fungi have been found that degrade certain components of oil, particularly the saturate component, which contains molecules with 12 to 20 carbon atoms. Some species will also degrade the lower-molecular-weight aromatic compounds. Hydrocarbondegrading organisms are abundant in areas where there is oil, such as near seeps on land or in water. Studies have shown that many of these native microorganisms, which are already thriving in the local climatic and soil conditions, are better at degrading oil than introduced species that are not yet acclimatized to local conditions. Different types of oil have different potential for biodegradation, based primarily on their saturate content, which is the most degradable component. For example, diesel fuel, which is almost 95% saturates, will degrade readily under the right conditions. However, some types of Bunker C that contain few saturates will not degrade to any extent under any circumstances. This explains why asphalt, the asphaltene, and heavy aromatic fraction of oils that does not degrade is often used in building roads and in roofing shingles. Biodegradation agents include bioenhancement agents that contain fertilizers or other materials to enhance the activity of hydrocarbon-degrading organisms, bioaugmentation agents that contain microbes to degrade oil, and combinations of these two. Studies have shown that adding bioenhancement agents to oil spilled on land can enhance the removal rate of the saturate and some of the aromatic fraction of the oil, so that as much as 40% of the oil is degraded in time periods from one month to a year. It is most important to recognize that one cannot ever degrade all the oil, especially if it is a heavier type. Much of the oil will remain undegraded and relatively unaltered, even years later. Furthermore, it may be difficult to distinguish between oil removed by biodegradation and other weathering processes. It has been found that the agents are most effective when added at an oilto-nitrogen-to-phosphorus ratio of 100:10:1. Fertilizers that maintain the soil at a more neutral level are best for degrading oil. Fertilizers that make the soil acidic usually slow biodegradation. Fertilizers that are more oil-soluble and less water-soluble are most effective as they are not as likely to be washed away.

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Bioaugmentation agents are not used as extensively as bioenhancement agents at oil-contaminated sites. This is because bioaugmentation agents add new microorganisms, which is not usually as effective as stimulating existing bacteria. There are strict government regulations about introducing new, nonindigenous, and possibly pathogenic species to an area. All types of biodegradation agents are subject to government regulations and approval before use. It should be noted that, while biodegradation does remove the saturates and some aromatic fractions of the oil, it can take weeks or even years to remove the degradable fraction, even under ideal conditions. Furthermore, the undegradable components of the oil, which constitute the bulk of heavier crudes, remain at the spill site, usually as a tarry mat often called asphalt pavement. It has been found that biodegradation is useful for treating oil on grasslands or other land not used to grow crops where the undegraded asphaltenes, resins, aromatics and other undegradable components are not likely to pose a problem.

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Chapter 15

Oil Spill Dispersants: A Technical Summary Merv Fingas

Chapter Outline 15.1. Introduction 15.2. The Basic Physics and Chemistry of Dispersants 15.3. The Basic Nature of Dispersions or Oil-inWater Emulsions 15.4. Effectiveness

435 437

440

15.5. Monitoring 15.6. Physical Studies 15.7. Toxicity 15.8. Biodegradation 15.9. Other Information 15.10. Summary and Conclusions

481 500 519 535 539 562

451

15.1. INTRODUCTION The use of dispersants still generates debate four decades after the Torrey Canyon incident. Some of the same issues predominate.1 The motivations for using dispersants are the same: reduce the possibility of shoreline impact, lessen the impact on birds and mammals, and promote the biodegradation of oil. The issues surrounding dispersants also remain the same: effectiveness, toxicity, the effect of dispersants on biodegradation, and long-term considerations. Recently, the National Academy of Sciences released its study of the use of chemical dispersants in the United States.1 This report is particularly instructive and provides some useful assessments of the situation. Their assessments and recommendations will be summarized in the applicable sections of this chapter. The prime motivation for using dispersants has been stated to be reduction of the impact of oil on shorelines. To accomplish this reduction, the dispersant application must be highly successful and effectiveness high. As some oil would still come ashore following treatment, there is much discussion on what effectiveness is required to significantly reduce the shoreline impact.2 A major issue that remains is the actual effectiveness during spills so that these values Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10015-2 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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can be used in estimates and models in the future. A significant physical fact must also be considereddthat is, the lifetime of the dispersion. Because not all dispersions are stable and will degrade to surface slick and some residual dispersion, the utility of dispersants in any case should consider this fact. The second motivation for using dispersants is to reduce the impact on birds and mammals on the water surface. As the National Academy of Sciences (NAS) committee on dispersants states, little or no research on this matter has been carried out anytime since the 1980s. In their report (p. 274) they note the following: Of additional concern is the effect of dispersed oil and dispersants on the waterproof properties of feathers and their role as thermal insulators. One of the recommendations of the NRC (1989) report was that studies be undertaken to “assess the ability of fur and feathers to maintain the water-repellency critical for thermal insulation under dispersed oil exposure conditions comparable to those expected in the field.” This recommendation is reaffirmed because of the importance of this assumption in evaluating the environmental trade-offs associated with the use of oil dispersants in nearshore and estuarine systems because it has not been adequately addressed.1

The third motivation for using dispersants is to “promote the biodegradation of oil in the water column.” The effect of dispersants on biodegradation is still a matter of dispute. A number of papers state that dispersants do not promote biodegradation, whereas others indicate that dispersants suppress biodegradation. The most recent papers, however, confirm that promotion or suppression is a matter of the surfactant in the dispersant itself and the factors of environmental conditions. More details of recent findings will appear in the subsequent discussion. What is very clear at this time is that the surfactants in some of the current dispersant formulations can either suppress or have no effect on biodegradation. Further, there are issues about the biodegradability of the surfactants themselves, and this fact can confound many tests of dispersed oil biodegradation. Several questions remain unanswered, however. An important issue that never comes up is that it is known that oil-degrading bacteria largely live on the water surface, where they would feed on natural hydrocarbons in the absence of spills. Would not putting oil in the water column then remove it from these bacteria? However, in the case of oil seeps or oil-contaminated sediments, there are microbial colonies associated at depth. Another serious question is that of timescale. Biodegradation takes place over weeks, months, and years. Dispersion half-lives are 12 to 24 hours. This author prepared a review of dispersants in 2002 and covered the period to 1997.2 Another review covered the period from 2002 to mid-2008.3 The latter review was combined with the earlier review to provide coverage from 1997 to 2008.4 The comprehensive review contained over 450 references. Literature not covered in this present summary is covered in the reviews.5 Another bibliographic search was published during this time as well but did not contain a review.6 Previous reviews covered the various oil spill dispersant topics.7 All these are reviews of the literature, and most cover similar topics as this review.

Chapter | 15 Oil Spill Dispersants: A Technical Summary

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15.1.1. What Are Dispersants? Many surfactant mixtures for treating oil spills have been promoted in the past four decades to overcome the extensive problems and costs of physical recovery. Of particular interest in this section are dispersants; these are formulations containing surfactants as active ingredients. Surfactants have varying solubilities in water and varying actions toward oil and water.8 The parameter used to characterize surfactants is the hydrophiliclipophilic balance (HLB). HLB is determined using theoretical equations that relate the length of the water-soluble portion of the surfactant to the oil-soluble portion of the surfactant. A surfactant with an HLB between 1 and 8 promotes the formation of water-in-oil emulsions and one with an HLB between 12 and 20 promotes the formation of oil-in-water emulsions. A surfactant with an HLB between 8 and 12 may promote either type of emulsion, but generally promotes oil-in-water emulsions. Dispersants have an HLB in this range. Dispersants are formulated to “disperse” oil slicks into the sea or another water body. Surface-washing agents, or beach cleaners as they are sometimes called, are surfactant formulations designed to remove oil from solid surfaces such as beaches. Emulsion breakers and inhibitors are intended to break waterin-oil emulsions or to prevent their formation. Although many of these treating agents have been promoted, few are still being produced. More than 100 dispersants have been tested for toxicity and effectiveness by Environment Canada, but only 2 remain on the department’s list of accepted products.9 The compendium of oil spill treating agents prepared by the American Petroleum Institute in 1972 lists 69 dispersants and 43 surfacewashing agents, most of which are also listed as dispersants.10 Only two of these are commercially available today, each being produced in a different formulation. More than 300 surface-washing agents have been sold in the North American market, but only about 36 of these are still commercially available. There were 26 surface-washing agents on the U.S. National Contingency Plan List in 2010. It is estimated that approximately 600 dispersants have been sold worldwide, of which only about 200 were ever tested in the lab or field, even in a limited way. The abundance of products makes it difficult for potential buyers and environmentalists to discriminate between effective products and those that are ineffective or could actually cause more damage than if the oil were left without intervention.

15.2. THE BASIC PHYSICS AND CHEMISTRY OF DISPERSANTS 15.2.1. Formulations Dispersants are oil spill treating agents formulated to disperse oil into water in the form of fine droplets. Typically, the HLB of dispersants ranges from 9 to 11. Ionic surfactants can be rated using an expanded scale and have HLBs ranging from 25 to 40. Ionic surfactants are strong water-in-oil emulsifiers, very soluble in water, and relatively insoluble in oil, which generally work from the water

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onto any oil present. Such products disappear rapidly in the water column and are not effective on oil. Because they are readily available at a reasonable price, however, many ionic surfactants are proposed for use as dispersants. These agents are better classified as surface-washing agents. Some dispersants contain ionic surfactants in small proportions, yielding an average HLB more toward 15 than 10. Studies on the specific effect of this mixing on effectiveness or mode of action have not been done. A typical dispersant formulation consists of a pair of nonionic surfactants in proportions to yield an average HLB of 10 and some proportion of ionic surfactants. Studies have been done on this mixture, one of which used statistical procedures in an attempt to determine the best mixture of the three ingredients.11 An improvement in performance was claimed by adjusting the three ingredients. Several patents are held on dispersants.12-14 The typical ingredients, from patents, are listed in Table 15.1. Some dispersants listed for use in Canada, the United States, and Europe are listed in Table 15.2.

15.2.2. Nature of Surfactant Interaction with Oil Surfactants interact with oil and oil droplets to yield a temporary lower-energy statedgiven many conditions and circumstances. 15-18 The disperse state is often called an emulsion, and in the oil spill trade it is known as a dispersiondto distinguish these oil-in-water emulsions from water-in-oil emulsions (called emulsions and sometimes mousse). Some surfactants will align along slick and droplet interfaces and thus promote the temporary stabilization of droplets in water. This droplet stabilization is enhanced by the presence of surfactants at the interface TABLE 15.1 Contents of Dispersants (patent information) Type

Surfactants and Solvents

Hydrocarbon-based -1

Sorbitan monooleate Ethoxylated monooleate Na dioctyl sulfosuccinate Solvent - hydrocarbon and butyl cellosolve

Hydrocarbon-based-2

Sorbitan monooleate Ethoxylated sorbitan monooleate Ethoxylated sorbitan trioleate Na tridecyl sulfosuccinate Solvent - hydrocarbon and butanols

Hydrocarbon-based-3

Mixtures of polyethylene glycol monoleate Solvent- hydrocarbon

Aqueous-based-1

Tall oil esters (35%), ethyl dioxitol (47%) Sorbitan monolaurate (7%), water (10%) Calcium Sulfonate (1%)

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Chapter | 15 Oil Spill Dispersants: A Technical Summary

TABLE 15.2 Listed Dispersants in Various Countries (lists may not be complete due to changes with time) Product

Manufacturer/Origin

United Canada States

Corexit 9500 (now EC9500A)

Exxon, Houston

U

U

Corexit 9527 (now EC9527A)

Exxon, Houston

U

U

Enersperse xx

BP, Britain (old stocks)

U

Biodispers

USA, Newport, NH

U

Dispersit SPC 1000

Polychem, Chestnut Ridge, NY

U

Finasol OSR 62

Total Fluides, France

U

JD (109, 2000)

Globemark, Houston, TX

U

Mare Clean (20, 200, 505)

Taiho, Japan

U

NEOS AB-300

Neos, Japan

U

Nokomis (3-AA, 3-F4)

Mar-Len, Hayward, CA

U

Saf-Ron Gold

Sus. Env. Tech., Mesa, AZ

U

Sea Brat #4

Alabaster, Pasadena, TX

U

ZI-400

Studio City, CA

U

Agma DR 379, OSD 569

Agma, UK

U

Caflon OSD

Univar, UK

U

Dasic Slickgone LS

Dasic, UK

U

Emulsol LW

Arrow Chemicals, UK

U

Gard Slicksol

Larragard, UK

U

NU CRU

Ara Chem, San Diego, CA

U

OD 4000, OSR 4000

Innospec, UK

U

OSD/LT

Ashland Chem., Boonton, NJ

U

Britain France U

U

Radiagreen OSD, OSD-2B Oleon NV, Belgium

U

Seacare Ecosperse, 52, OSD

U

Unitor Chemicals, Norway

U

U

U

U

(Continued )

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TABLE 15.2 Listed Dispersants in Various Countries (lists may not be complete due to changes with time)dcont’d United Canada States

Product

Manufacturer/Origin

Britain France

Super-dispersant 25

Oil Slick Dispersants, UK

U

Veclean Oil Dispersant

Westchem B.V., NL

U

W-2096

Baker Petrolite, UK

U

BIOREICO R93

France

U

Disper 12 M

France

U

Disperep 12

France

U

Dispolene 36s

France

U

Emulgal C-100

France

U

Inipol IP 80, IP 90, IPC

France

U

Neutralex C

France

U

Oceania 1000

France

U

OD 4000 (PE 998)

France

U

15.3. THE BASIC NATURE OF DISPERSIONS OR OIL-IN-WATER EMULSIONS It is well known that most emulsions are not stable and will break down into their constituent parts. This effect is due to a large number of forces, as will be described in this section, but also to the fact that the stabilizers or surfactants act using weak forces. It is also known that chemically dispersed oil destabilizes after the initial dispersion. There is an extensive body of literature on surfactants and interfacial chemistry, which includes an abundance of experimental data on the topic as well as many theoretical approaches to it. This report will summarize both the data and the theory. The phenomenon of resurfacing oil is the result of two separate processes: destabilization of an oil-in-water emulsion and desorption of surfactant from the oil-water interface. Almost every paper on the topic of the stability of emulsions notes that emulsions are not stable.15-20 There are also many books on the topic.21-24 It is noted that emulsions are not thermodynamically stable, but may be kinetically stable depending on the timescale considered. In the case of kinetic stability, emulsions are not stable in terms of years, and the scale of time considered typically relates to consumer products and may be months. In terms of oil spill dispersions, half-life may be only a matter of hours. The destabilization of

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oil-in-water emulsions such as chemical oil dispersions is a consequence of the fact that emulsions are not thermodynamically stable. Natural forces move the emulsions to a stable state, which consists of separated oil and water. What is important is the rate at which this occurs. An emulsion that stays sufficiently stable until long past its practical use consideration may be said to be kinetically stable. There are several forces and processes that result in the destabilization and resurfacing of oil-in-water emulsions such as chemically dispersed oils. These include gravitational forces, surfactant interchange with water and subsequent loss of surfactant to the water column, creaming, coalescence, flocculation, Ostwald ripening, and sedimentation.

15.3.1. Forces of Destabilization 15.3.1.1. Droplet Separation The most important force in resurfacing oil droplets from an oil-in-water emulsion is gravitational separation.25 Droplets in an emulsion tend to move upward when their density is lower than that of water. This is true for almost all crude oil and petroleum dispersions as they usually have droplets with a density lower than that of the surrounding water. Dense or heavy oils are poorly, if at all, dispersible. The rate at which oil droplets will rise due to gravitational forces is dependent on the difference in density of the oil droplet and the water, the size of the droplets (Stokes’s Law, as will be described in Section 15.3.2), and the rheological properties of the continuous phase. The rise rate is also influenced by the hydrodynamical and colloidal interactions between droplets, the physical state of the droplets, the rheological properties of the dispersed phased, the electrical charge on the droplets, and the nature of the interfacial film. Creaming is a process that is simply described by the appearance of the starting dispersed phase at the surface.25 Creaming is the process that might be described in the oil spill world as resurfacing. Robins describes creaming at length, noting that it is a very important phenomenon in the food-processing business.19 As much as 40% of the cost of developing a new food emulsion involves the long-term testing related to creaming. Examples of this include yogurt, whipped cream, jam, and many other types of food. Sedimentation is the reverse of creaming and occurs when the dispersed phase is denser than water. Coalescence is the joining of two or more droplets to form a larger droplet. Coalescence is an important destabilization process in oil spills. Changes in droplet size resulting in coalescence have been monitored as an emulsion destabilizes. Ostwald ripening may be an understated mechanism in the destabilization of oil-in-water emulsions.25 Basically, Ostwald ripening is the growth of larger emulsion droplets by absorption of soluble components from the water column. The effect is to remove soluble material from the water column and smaller droplets, resulting in an increased growth of the larger droplets. The

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phenomenon occurs because the soluble components of the dispersed phase are more soluble in the larger droplets than in the water and the smaller droplets. Although the Ostwald ripening phenomenon has not been investigated with oilin-water emulsions to the same extent as other phenomena, it is believed to be quite important. Studies of undecane, hexadecane, benzene, and octane-inwater emulsions have shown that Ostwald ripening is an important factor in destabilization.25 Flocculation is another process that occurs when two particles come together to form an agglomerate of particles, but the particles do not coalesce.

15.3.1.2. Surfactant Separation It is well known that there is an exchange of surfactants between the target droplet and the surrounding water.18 This promotes destabilization of the emulsion. When the water is in a large ratio to the droplet concentration, surfactant is largely lost and destabilization is relatively rapid. In laboratory tests, a small ratio of oil-to-water then becomes important in simulating the conditions at sea. Surfactants will distribute between the bulk phase (water) and the interface to achieve equilibrium between the two phases. This equilibrium depends on the watereoil solubility characteristics of the surfactant. In a closed system, this equilibrium is achieved rapidly with little loss of surfactant. In an open system, however, equilibrium is never achieved, the surfactant leaches into the water, and over a period of hours, little surfactant is left in the oil droplets. The Marangoni effect is an important phenomenon in terms of surfactant stability and dynamics.26 This effect is due to the tendency of surfactant concentrations to quickly distribute over an interface. If there is a deficit in surfactant concentration on one side of a droplet, the surfactant quickly moves to restore the equilibrium concentration over the droplet. The restoration of equilibrium is known as Marangoni stabilization. Marangoni instability arises as a result of this surfactant flow because the flow continues and results in areas of greater and lesser surfactant concentration over the droplet interface. Some researchers have noted that Marangoni instability was periodic and was about on the order of 1000 seconds for one particular system.27 It was noted that convective instability periodically switched between a slow and a more rapid transport regime. During a convective stage, fast absorption of surfactant occurred with rapid inflow of surfactant to the interface. During a diffusive stage, desorption occurred and gradients built up until the system became unstable again. Several studies have shown, both experimentally and theoretically, that small surfactants will displace larger surfactants or polymers at the interface. Although studies have shown that mixed surfactant systems yield more stable emulsions as a rule, the size difference between surfactants is critical to this. A mixed surfactant system with large and small surfactants will essentially be more stable than one stabilized by the small surfactants alone, as these small surfactants will displace the larger surfactants at the interface. This condition is

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Chapter | 15 Oil Spill Dispersants: A Technical Summary

Marangoni circulation Surface tension Sub-layer viscosity

Radius

Surfactant concentration Surfactant diffusion Absorption Desorption Surfactant type Surfactant chain length Steric stabilization Surfactant precipitation

Ostwald ripening

Dissolution

Doublet formation

Van der Waals force Brownian movement

Bulk diffusivity Micelle formation

Oscillatory structure Interactions

Surface deformation force

Film strength Film thinning Film (Gibbs) elasticity Film thickness Film viscosity

Electrostatic force Steric forces

Capillary force Velocity of approach

Legend Force Flux or movement Influence

FIGURE 15.1

Capillary wave Thermal fluctuation Pulse

Flocculation Depletion flocculation

Hydrodynamic forces

The forces and influences on two droplets approaching each other.

predicated on the fact that the concentration of surfactants at the interface is great and there actually is interference between surfactants. Several additional forces have been described and are summarized in the literature.25 These are depicted graphically in Figure 15.1.

15.3.2. The Science of Stabilization The basis for much of the physics and chemistry surrounding emulsion stability is that emulsions are not thermodynamically stable.15 One view of this is that two immiscible liquids are combined or one immiscible liquid is dispersed into another immiscible liquid. Since the interfacial tension between these two

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liquids will always be greater than zero despite the amount or type of surfactants, there is a force or energy leading toward destabilization. Furthermore, the interfacial energy is vastly increased by increasing the area between the two liquids through the process of increasing the number of droplets. This results in an energy imbalance that will tend to force the two media to separate. Kinetic stability is another consideration when describing an emulsion. An emulsion is said to be kinetically stable when significant separation, usually considered to be half or 50% of the dispersed phase, occurs outside of the usable time. Therefore, if the time of use is one day, an emulsion with a half-life of more than one day may be considered to be usable. In food emulsions, this stability would be well past the stated shelf life. It should be noted, however, that food emulsions are poor examples for crude oil-in-water emulsions because their stability can be controlled in closed systems by adding enough surfactants and gelling the water media, thereby negating coalescence and suppressing surfactant loss. The function of any emulsifying agent or surfactant is to stabilize (somewhat) an otherwise unstable system. The emulsifying agent does so by absorption at the liquideliquid interface as an oriented interfacial film. This oriented film performs two functions: (1) it reduces the interfacial tension between the two liquids and consequently the thermodynamic instability of the system resulting from the increase in the interfacial area between the two phases, and (2) it decreases the rate of coalescence of the dispersed liquid droplets by forming mechanical, steric, and/or electrical barriers around them. The steric and electrical barriers inhibit the close approach of one droplet to another. The mechanical barrier increases the resistance of the dispersed particles to mechanical shock and inhibits them from coalescing when they do collide. When emulsions form, the emulsifying agents or surfactants reduce the amount of work required for formation. Stability can be defined as the resistance of the droplets to coalescence.15 Creaming, or standard gravity separation, was not considered to be destabilization in classical terms because it occurs with or without emulsifier stabilization. The classic destabilization processes were considered to be coalescence, flocculation, and phase inversion. The rate of coalescence was stated to be the only quantitative measure of emulsion stability. These factors have now changed to encompass broader areas, as shown in the present review. It has been found that the rate at which the droplets of a macroemulsion coalesce from larger droplets depends on a number of factors: the physical nature of the interfacial film, the existence of an electrical or steric barrier on the droplets, the viscosity of the continuous phase, the size distribution of the droplets, the phase volume ratio, and the temperature. These factors are dealt with in greater detail in this section. The physical nature of the interfacial film is important. The droplets of dispersed liquid in an emulsion are in constant motion and frequently collide. If the interfacial film surrounding the two colliding droplets in an emulsion ruptures, the droplets will coalesce to form a larger droplet, and eventually the

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emulsion will separate and break. The strength of the film then becomes an important factor in emulsion stability. Highly purified surfactants tend to form weak interfacial films, whereas mixtures of different types of surfactants tend to form stronger films, although there is evidence that smaller surfactants displace larger ones at the interface. Mixtures of a water-soluble and an oil-soluble surfactant are often used in oil spill dispersants, for example, a mixture of Span and Tween surfactants. As these surfactants may be of different sizes, there may be a problem with destabilization. The presence of an electrical charge on the dispersed droplets can create an electrical barrier, preventing two particles from closely approaching each other. While ionic surfactants are sometimes used in oil spill dispersants for this purpose, these surfactants will rapidly partition to the water phase in dilute systems such as at sea. Nonionic surfactants, such as those that typically constitute the bulk of oil spill dispersants, have a lesser charge and pose a weak electrical barrier to coalescence. The viscosity of the continuous phase is an important factor in dispersion stability. An increase in the viscosity of the continuous phase reduces the diffusion of the droplets and thus the frequency of collisions. This is given by the classic equation:25 D ¼

kT 6pha

(1)

where D is the diffusion rate, k is the Boltzmann constant, T is the absolute temperature, h is the viscosity of the liquid continuous phase, and a is the radius of the droplets. It is obvious from this equation that the diffusion occurs inversely to the viscosity of the continuous phase. This is very important for oil spill dispersion as the viscosity of the continuous phase is that of water and is, in fact, very low. Therefore, there is a high diffusion rate, high collision rate, and potential for coalescence. This contrasts with many food emulsions in which the continuous phase is deliberately rendered viscous to reduce coalescence and thus increase stability. Equation (1) predicts that oil spill dispersions will not be as stable as many other emulsions. Another factor influencing the rate of coalescence of the droplets is the size distribution of the droplets. The smaller the range of sizes, the more stable the emulsion. The larger particles have less surface area for the volume and thus are more thermodynamically stable and tend to grow at the expense of the smaller droplets. As this process continues, the emulsion destabilizes. An emulsion with a fairly uniform size distribution is more stable than one with a wide distribution of particle sizes. This factor is also significant when discussing oil spill dispersions. Oil spill dispersions have wide distribution of droplet sizes because of the nature of crude oil and the wide distribution of compounds

446

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in it.1 Oil spill dispersions are therefore less stable by nature than many other types of emulsions. Temperature is an important factor in emulsion stability, for a change in temperature causes changes in interfacial tension between the two phases. Temperature can also cause differential changes in other factors such as the relative solubility of the surfactant in the two phases and in the diffusion in the system. Emulsifying agents are usually most effective when near the point of minimum solubility in the solvent in which they are dissolved because at this point they are most surface-active. Since the solubility of the emulsifying agent usually changes with temperature, the stability of the emulsion also changes with temperature. The classic equation to describe this is by Smoluchowski:15 dn ¼ 4pDrn2 dt

(2)

where dn dt is the rate of diffusion-controlled coalescence, D is the diffusion, r is the collision radius (distance between centres when coalescence begins), and n is the number of particles per cm3. Combining this equation with diffusion equations yields an expression for the rate of coalescence of particles and thus for the stability of the emulsion: dV 4 Vkt E=kT ¼ AeE=kt ¼ e dt 3 h

(3)

where dV dt is the rate of the coalescence of droplets or the stability of the emulsion, V is the volume of the dispersed phase, for example, volume per unit volume, k is the Boltzmann constant, T is the absolute temperature, E is the energy barrier to coalescence, h is the viscosity of the liquid continuous phase, and A is the collision factor as defined by the left portion of the equation. This is the most important equation in describing the stability of oil-inwater emulsions, for it shows that volume and the viscosity of the continuous phase (e.g., water) are critical parameters in describing stability or increased coalescence. In other words, oil spill dispersions will always have low stability. Further, this shows that the effect of temperature is exponentiald that is, collisions are increased with temperaturedor emulsions are actually more stable at lower temperaturedthat is, from the collision point of view only. The forces between particles or droplets are an important physical consideration in describing stability.15 The stronger the force between particles, if opposite sign, the greater the stability of an emulsion. These forces might be considered to be of four types: soft or electrostatic forces, hard sphere, van der Waals, and steric forces.

Chapter | 15 Oil Spill Dispersants: A Technical Summary

447

The soft or electrostatic forces and van der Waals interparticle forces are described in the well-established theory of the stability of dispersions by Derajaguin and Landau (in 1941) and Verwey and Overbeek (in 1948); thus this theory is now called the DLVO theory.15 The theory presumes a balance between the repulsive and attractive potential energies of interaction between the dispersed particles or droplets. Repulsive interactions are due to either the similarly charged electrical double layers surrounding the particles or to solvent-particle interactions. Attractive interactions are believed to be mainly due to the van der Waals forces between particles. For dispersion to occur, the repulsive forces must be larger than the attractive forces. Stokes’s rising rate e The classic Stokes’s equation is: s ¼

2Drga2 9h

(4)

where s is the rise rate, Dr is the density difference between the disperse and droplet phases, g is the gravitational constant, a is the droplet radius, F(F0) is a volume dependent correction factor and is 1 for dilute solutions, and Dh is the difference between the viscosity of the disperse and droplet phases. This equation is very important in terms of understanding the resurfacing of oil spill dispersions. It shows that for the smallest droplets at 1 m below the slick, the rise rate would be about a year (or forever) and for the largest droplets immediately below the slick, rise rate is a few seconds. Several researchers have shown that surfactants do not affect the base rise rate, but others question whether the Stokes’s rate is far too slow.25,27 Many researchers have shown that the rise rate predicted by the Stokes’s equation is far too slow compared to experimental measurements. These might be explained by the destabilization processes described in this report, namely, coalescence, flocculation, and Ostwald ripening. All of these processes serve to increase particle diameter and thus significantly increase the rise rate. A doubling of a droplet radius results in a quadrupling of the rise rate for that particular droplet.

15.3.3. Oil Spill Dispersions There are some measurements of the half-lives of oil and hydrocarbon emulsions in the literature.25 Some of these papers presented data from which the half-life of the particular emulsion could be calculated.25 This is shown in Table 15.3. The half-life data for crude oil emulsions are all very similar with an average half-life of about 12 hours. Resurfacing has been noted during several large tank tests as well.28 Sterling et al. studied the coalescence of Arabian crude oil emulsions with the dispersant Corexit 9500.29 For the range of pH from 4 to 10 and salinity, 10%,

448

TABLE 15.3 Oil Spill Dispersion Half-Lives from the Literature Summary

Literature Data

Oil Type

Dispersant/ Surfactant

Average Half-Life (hours)

Nominal

Arabian Crude

Corexit 9500

4.5

Arabian Crude

Corexit 9500

Arabian Crude

Lower Range

Upper Range

Units

Other Factors

4.5

Hours

Shear rate 5 s1

4

4

Hours

Shear rate 10 s1

Corexit 9500

2.5

2.5

Hours

Shear rate 20 s1

Alaska North Slope

Corexit 9500

15

10

20

Hours

Alaska North Slope

Corexit 9527

15

10

20

Hours

Alberta Sweet Mixed Blend

Corexit 9500

18

10

25

Hours

Alberta Sweet Mixed Blend

Corexit 9527

18

10

25

Hours

Milling Lubricant

Surfact mix

24

Kerosene

Various

3

0.5

5

Hours

Gesium Crude

Various

40

0.5

96

Hours

Crude Oil

Surfact & polyacrylamide

1.5

1

2

Hours

Crude Oil

Natural surfactants

0.2

0.01

0.5

Hours

Hydrocarbons

Average

12

Decane and Decanol

SDS

0.4

0.25

0.5

Hours

Toluene

Ionic

10

5

15

Hours

Tetradecane

SDS

3

0.1

6

Hours

Tetradecane

Tween 20

24

24

Treating Agents

Hours

Closed system

PART | VI

24

Hours

Chapter | 15 Oil Spill Dispersants: A Technical Summary

449

30%, and 40%, the z potentials range from e3 to e10 mV. This potential would not be sufficient to produce significant resistance to coalescence. Coalescence kinetics of the premixed crude oil and dispersant were determined with a range of shear rates and salinity. It was found that increasing shear rate increases coalescence as predicted by the extensive body of literature on the topic. Sterling and coworkers found that the dispersed oil fraction decreased with increasing coalescence and especially with time. The half-life extrapolated from the data implies that the half-life of the Arabian crude oil emulsion with Corexit 9500 dispersant was about 5 hours for a shear rate of 5 s1, about 4.5 hours for 10 s1, about 4 hours for 15 s1, and about 3.5 hours for a shear rate of 20 s1. It is important to emphasize that, although increased turbulence enhances coalescence, increased turbulence at the sea surface may also result in redispersion. The two processes do not appear to balance off because in experiments, it was noted that maintaining energy only decreased the resurfacing rate by about 10% over time periods of 8 to 96 hours.25

15.3.4. Significance of Emulsion Stability Crude oil-in-water dispersions are similar to many other types of emulsions in that they are stable under some conditions for a period of hours. During this time, destabilization processes are underway that result in oil resurfacing. Because of movement of the slick, from which the dispersion occurred and because the water column may have differential movement from the slick, resurfacing oil will likely appear in areas outside the residual slick. As resurfacing is a slow process and goes on for many hours, most of the oil will not be visible on the surface unless processes such as Langmuir cells were to reconcentrate the oil into slicks or unless there was no relative movement between the surface slick and the water column. There is a vast body of information and experimentation and a broad consensus on the stability of such emulsions. The stability and resurfacing of crude oil emulsions are influenced by the following forces. 1. Natural stabilization/destabilization forces The most important force is gravity. As most oils are less dense than water, their emulsion droplets are also less dense than water and will rise. The reappearance of oil on the surface is known as creaming. There are many destabilizing forces to emulsions such as chemically dispersed oil, including coalescence, flocculation, Ostwald ripening, and phase inversion. It is known that coalescence of droplets is the most important destabilization process for emulsions similar to dispersed crude oil emulsions. 2. Standard tendency of emulsions to instability There are many repulsive forces and attractive forces between droplets. The net result of these forces is to destabilize the droplet after some period of time.

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PART | VI

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3. Instability of interfacial film with surfactants The interfacial films stabilized by surfactants are subject to a number of destabilization processes, including Marangoni circulation, hydrodynamic destabilization, oscillatory forces, pulsing, thermal instabilities, surfactant desorption, and others. These forces weaken the interfacial film and consequently destabilize the emulsion. 4. Loss of surfactant In addition to the mechanisms of interfacial stability reduction noted in point 3, there is a net loss of surfactant in dilute emulsions such as oil spill dispersions. This net loss is caused by the tendency of the surfactants to equilibrate between the water bulk phase and the oil droplet interface. As crude oil emulsions are continually being diluted, surfactant movement from the interface to achieve equilibrium constitutes a loss of surfactant to the system. This loss of surfactant accelerates the destabilization of the emulsion. 5. The heterogeneous mixture of compounds in oil Oil consists of dozens of major constituents, most of which are very different in size and properties. This results in the formation of very different droplet sizes. In addition, the effect of surfactant is quite different on the various fractions of the oil. 6. Wide distribution of droplet sizes Because crude oil dispersions have a wide distribution of droplet sizes with much of the volume in the micron-sized area, the emulsions have a lower stability. It has been demonstrated that emulsions of micron-sized droplets are less stable. It has also been shown that the presence of even a few larger droplets will destabilize an emulsion, as this triggers destabilization processes such as Ostwald ripening. 7. Low viscosity of water Because the viscosity of water is low, destabilization processes are more prevalent in water than in other bulk fluids. The low viscosity of water increases coalescence and the diffusion of surfactants away from oil droplets in oil-in-water emulsions. 8. Increasing dilution of the emulsion For dilute emulsions, surfactant desorption becomes surfactant loss. Further surfactant absorption would not occur. As crude oil dispersions or emulsions are dilute and become increasingly dilute with time, they destabilize through surfactant loss and through many of the other processes noted in this report. Crude oil dispersions would be considered less stable than most other emulsions typically studied. 9. Effect of sea energy or turbulence Increased sea energy or turbulent energy increases the amount of coalescence that occurs, resulting in greater resurfacing. However, increased turbulence also causes redispersion, thus offsetting the effect of the recoalescence somewhat.

451

Chapter | 15 Oil Spill Dispersants: A Technical Summary

60 Typical redispersion 2%/hour redispersion

Effectiveness (%)

50

40

30 Typical re-dispersion

20

10

2%/hour additional redispersion

0 0

200

400

600

Time (minutes) FIGURE 15.2 The results of a typical series of runs of dispersion model with a 60% effectiveness as a start and a 50% redispersion effectiveness. This figure shows the typical decline in oil in the water column as time proceeds. The two curves shows the difference in assumptions, the first with typical redispersion and the second with an additional 2%/hour decline in effectiveness.

Thus in summary, dispersions are at best a transient phenomenon. The effectiveness value is a changing value at a given point in time. To illustrate this, a model was developed, based on the stability equations above, to look at the implications of these physics for the effectiveness and half-lives of emulsions.30 Figure 15.2 illustrates the typical effectiveness change over a period of time. Figure 15.3 shows the change in half-life with increase depth of mixing. as indicated by the wave height.

15.4. EFFECTIVENESS Effectiveness remains a major issue with oil spill dispersants. It is important to recognize that many factors influence dispersant effectiveness, including oil composition, sea energy, state of oil weathering, type of dispersant used and amount applied, temperature, and salinity of the water. The most important of these factors is the composition of the oil, followed closely by sea energy and the amount of dispersant applied.1 It is equally important to recognize that the only thing that really counts is effectiveness on real spills at sea. More emphasis should be put on monitoring this real effectiveness so that there is real information for assessment and modeling. Effectiveness issues are confounded by the simple fact that many tests, regardless of scale, show highly different results depending on how they are constructed and operated. Detailed scientific examination of most of these tests

452

PART | VI

Treating Agents

160

Half Life (min.)

140

Change in half-life typical redispersion

120

100

80 Change in half-life reduced redispersion (2%/hr.)

60

40 0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Wave Height (m) FIGURE 15.3 Plot of the half-lives of the dispersions with the two models of redispersion. It can be seen that half-lives are not affected greatly by which model of redispersion is chosen, because redispersion is much more an influence after about 120 minutes and model consideration here is about 48 hours.

shows major deficiencies in procedure or analytical methods. Further, testers should recognize the fact that effectiveness changes with time, and this factor should be built into testing procedures. More emphasis is needed on looking at the real results from real spills. Another major issue is that of the toxicity of dispersants and dispersed oil, an issue that will be discussed later. Another issue to keep in mind is that of long-term effects. The long-term effects of chemically dispersed oil have not been well studied and therefore remain largely a topic for speculation. On a community level, there have been very few studies such as the TROPICS study; however, no molecular-level studies were undertaken on any of these studies.1,31 These issues will be discussed later and form a “cluster” of major concerns on oil spill dispersants.

15.4.1. Introduction to Effectiveness Dispersant effectiveness is typically defined as the amount of oil that the dispersant puts into the water column compared to the amount of oil that remains on the surface. Many factors influence dispersant effectiveness, including oil composition, sea energy, state of oil weathering, type of dispersant used and the amount applied, temperature, and salinity of the water. The most important of these is the composition of the oil, followed closely by sea energy and the amount of dispersant applied.

Chapter | 15 Oil Spill Dispersants: A Technical Summary

453

One of the major confusions that persist is the relationship of effectiveness to viscosity. There is a certain belief that a “viscosity cut-off” of effectiveness for dispersants exists.4 In fact, certain components of oil, such as resins, asphaltenes, and larger aromatics or waxes, are barely dispersible, if at all. Oils that are made up primarily of these components will disperse poorly when dispersants are applied. On the other hand, oils that contain mostly saturates, such as diesel fuel, will readily disperse both naturally and when dispersants are added. The additional amount of diesel dispersed when dispersants are used compared to the amount that would disperse naturally depends primarily on the amount of sea energy present. In general, less sea energy implies that a higher dose of dispersant is needed to yield the same degree of dispersion as when the sea energy is high. This should not be attributed to viscosity alone, but primarily to oil composition. Oils that typically contain a larger amount of resins, asphaltenes, and other heavier components are typically more viscous and less dispersible. Viscosity, however, does not track composition very well and thus is only an indicator of dispersibility. A “viscosity cut-off” does not exist. While it is easier to measure the effectiveness of dispersants in the laboratory than in the field, laboratory tests may not be representative of actual conditions. Important factors that influence effectiveness, such as sea energy and salinity, may not be accurately reflected in laboratory tests. Results obtained from laboratory testing should therefore be viewed as representative only and not necessarily reflecting what would take place in actual conditions. When testing dispersant effectiveness in the field, it is very difficult to measure the concentration of oil in the water column over large areas and at frequent enough time periods. It is also difficult to determine how much oil is left on the water surface as there are no methods available for measuring the thickness of an oil slick and the oil at the subsurface often moves differently than an oil slick on the surface. Any field measurement at this time is best viewed as an estimate. The NAS committee on dispersants reviewed effectiveness testing.1 It noted that as the physical scale of the effectiveness increases, the cost and realism increase, but the degree to which factors that affect dispersion can be controlled and the ability to quantitatively measure effectiveness decrease. The committee also states that when modeling or prediction is carried out, viscosity is an insufficient predictor of dispersion efficiency. The chemical composition of oil is important, and several factors of composition have been shown to correlate well with dispersant effectiveness. Two other factors relating to dispersant effectiveness are the dispersant-to-oil ratio and the oil-to-water ratio, but the most important factor may be the energy applied, energy dissipation rate, or mixing energy. In reviewing testing, the NAS committee notes that several important principles of experimental design are often ignored, including systematic errors that affect the outcome in one direction and random errors. Common systematic errors in dispersant effectiveness measurement included ignoring the evaporation of volatile compounds, poor analytical methods, and

454

PART | VI

Treating Agents

incomplete recovery of floating oil. These three errors, as an example given in the NAS report, introduce a positive bias in the estimates of dispersant effectiveness.

15.4.2. Field Trials Previous workers and reviews have put forward discussion on field trials.1,32 Field tests can provide opportunities to test and train on full-scale application equipment as well as to develop and test full-scale monitoring equipment and to verify oil fate and transport models. Field tests, however, are subject to high costs, and legal issues may impede the carrying out of these tests. A major limitation on field trials is the limited data set that can be obtained from one given trial. The experimental design of field trials is an issue, and a primary objective should be to obtain an unbiased estimate of the variation that exists between two experimental slicks. Another major limitation of field trials is the inability to measure remaining oil slick thickness. NAS or most scientists do not believe sorbent testing to be an accurate method. Measurement of oil in the water column is also fraught with difficulties; use of fluorometers, it has been observed, only gives a relative measurement. The output of fluorometers also changes with time, aromatic composition, and so on. Visual observation has been used, but a suggestion to improve visual results is to use ‘blind’ observers who are not aware of the particular treatment applied. Visual observation is subject to many variables including position of the sun, cloud cover, and viewing angle. The NAS committee notes that results from field trials are generally lower than those obtained in the laboratory, suggesting that the energy regimes in the laboratory are higher than those encountered in field trials.1 Mass balances should be attempted on field trials. In conclusion, the complexities and costs of carrying out meaningful field trials suggest that more effort be placed on improving bench-scale and mesocosm research projects. As a recommendation, the NAS committee stated that future field-scale work should be based on systematic and coordinated bench-scale and wave-tank testing. Many field trials have been conducted in the past to assess the effectiveness of dispersants. Several papers have assessed the techniques used to measure effectiveness in these tests.33 There is no general consensus that effectiveness and other parameters can actually be measured in the field using some of the current methodologies. The effectiveness determined during field trials varies significantly. Recent results, which may be more reliable, claim that dispersants removed about 10 to 40% of the oil to the subsurface.1,33 The purpose of these tests were: 1. To quantify the effectiveness of dispersants on a given oil in a given application situation 2. To demonstrate the effectiveness of dispersants and/or application techniques

Chapter | 15 Oil Spill Dispersants: A Technical Summary

455

3. To measure concentrations of oil in the subsurface as a result of dispersant use 4. To determine dispersibility conditions and relationships between factors 5. To quantify application factors, such as effect of application rate and droplet size Table 15.4 shows the tests conducted in the past.35-62 Several papers have assessed the techniques used to measure effectiveness in these tests.33,63 The effectiveness determined during these trials varies significantly. The validity of the older results is even more questionable because of both the analytical methodology, which is now known to be incorrect, and data treatment methods.1,33,34,63,64 Most tests relied heavily on developing a mass balance of oil in the water column and that left on the surface.33 In early tests, samples from under the oil plume were analyzed in a laboratory using colorimetric methods. Colorimetric methods are not valid for this type of analysis and are no longer used. Fluorometry has recently been used, but this method is also unreliable because it measures only a small and varying portion of the oil (middle aromatics) and does not discriminate between dissolved components and oil that actually dispersed. Furthermore, it is impossible to calibrate fluorometers for whole oil dispersions in the laboratory without using accurate techniques such as extraction and gas chromatographic analysis. It is known that the aromatic ratio of the oil changes as a result of the dispersion process.33 In early tests, it was not recognized that the plume of dispersed oil forms near the thicker oil in the tail of the slick and that this plume often moves off in a separate trajectory from the slick.63 Many researchers tried to measure the hydrocarbon concentrations beneath the slick and then integrated this over the whole slick area. As the area of the plume is always far less than this area, the amount of hydrocarbons in the water column was greatly exaggerated. Since the colorimetric techniques used at the time always yield some value of hydrocarbons, the effectiveness values were significantly increased. When effectiveness values from past tests were recalculated using only the area where the plume was known to be, those values decreased by factors as much as 2 to 5.33,63 Although no applications of dispersants on freshwater spill have been found, one field test was carried out in fresh water.65 Effectiveness was not measured. The ASTM standards on the use of dispersants in fresh water such as lakes and rivers suggest that they not be used in fresh water primarily because most lakes and rivers are used as sources of drinking water.66-68 In summary, testing in the field is difficult because effectiveness values depend on establishing a mass balance between oil in the water column and on the surface. Because this mass balance is difficult to achieve, results are questionable. All tests relied heavily on developing a mass balance between oil in the water column and that left on the surface. In early tests, samples from under the oil plume were analyzed in a laboratory using colorimetric methods,

TABLE 15.4 Dispersant Field Tests Location/ Identifier

Reference Year

Number Oil Type

Amount, m3 Dispersant

Application Method

Rate, D: 0

Sea Effectiveness State Claimed % unless noted otherwise

North Sea Great Britain

North Sea- Norway

North Sea Great Britain

35

36

37

1997

1995

1995

136

Forties Crude - Weathered 50

Corexit 9500

airplane

1:19

3-4

good

135

Forties Crude - Weathered 50

Slickgone NS

airplane

1:19

3-4

good

134

Alaska North Slope Weathered

30

Corexit 9500

airplane

1:30

good

133

Troll - Weathered

15

Corexit 9500

helicopter

1:20

1-2

good

132

Troll - Weathered

15

Corexit 9500

ship

1:20

1-2

good

131

Troll - Weathered

15

Corexit 9500

control

control

1-2

130

Medium Fuel Oil

continuous 50L/min

OSR 5

boat

1:20

>2

33%

129

Medium Fuel Oil

continuous 50L/min

Corexit 9527

boat

1:20

>2

32

128

Medium Fuel Oil

continuous 50L/min

Slickgone NS

boat

1:20

>2

23

127

Medium Fuel Oil

continuous 50L/min

BP 1100X

boat

1:20

>2

10

126

Medium Fuel Oil

continuous 50L/min

LA 1834

boat

1:20

>2

9

125

Medium Fuel Oil

continuous 50L/min

Control

boat

1:20

>2

4

North Sea -Norway

North Sea - Great Britain

North Sea - Great Britain

124

Forties Crude

continuous 50L/min

Slickgone NS

boat

1:20

>2

16

123

Forties Crude

continuous 50L/min

Control

boat

1:20

>2

6

122

Medium Fuel Oil

continuous 50L/min

Slickgone NS

boat

1:20

<2

10.5

121

Medium Fuel Oil

continuous 50L/min

Control

boat

1:20

<2

1.5

120

MFO Emulsion

continuous 50L/min

Corexit 9527

boat

1:20

<2

4

119

MFO Emulsion

continuous 50L/min

Slickgone NS

boat

1:20

<2

6

118

MFO Emulsion

continuous 50L/min

Control

boat

1:20

<2

0.2

117

Sture Blend Crude

20

Corexit 9500

helicopter

1:12

4-5

good

116

Sture Blend Crude

20

control then-Corexit 9500

helicopter - next day

control then 1:20

4-5

good

115

MF/GO (Medium Fuel Oil/ Gas Oil)

20

Dasic Slickgone NS

airplane

1:10

2-3

good

114

MF/GO

20

Control

113

MF/GO (Medium Fuel Oil/ Gas Oil)

continuous 50L/min

OSR 5

boat

!:20

5-6

29.5

41

112

MF/GO

continuous 50L/min

Slickgone NS

boat

!:20

5-6

17

42

111

MF/GO

continuous 50L/min

BP 1100X

boat

!:20

5-6

10

38

39

40

1994

1993

1993

2-3

(Continued )

TABLE 15.4 Dispersant Field Testsdcont’d Location/ Identifier

North Sea - Great Britain

Beaufort Sea - Canada

North Sea Haltenbanken

Reference Year

43

44

45

1992

1986

1985

Norway

Brest, Protecmar VI

46

1985

Number Oil Type

Amount, m3 Dispersant

Application Method

Rate, D: 0

Sea Effectiveness State Claimed

110

MF/GO

continuous 50L/min

Control

boat

Control

5-6

1.6

109

Forties Crude

12.3

LA 1834 then Dasic LTSW

airplane

1:100, 1:28

4-5

good

airplane

1:100

108

Forties Crude

12.3

LA 1834

107

Forties Crude

12.3

Control

4-5

106

Topped Federated Crude

2.5

control

.

.

105

Topped Federated Crude

2.5

Corexit CRX-8

helicopter

1:1

2-3

poor

104

Topped Federated Crude

2.5

BP MA700

helicopter

1:1

2-3

poor

103

Topped Federated Crude

2.5

BP MA700

helicopter

1:10

2-3

102

Topped Federated Crude

2.5

control

.

.

101

Topped Statfjord Crude

12.5

Alcopol

premixed

250 ppm

101

Topped Federated Crude

2.5

control

.

.

100

Topped Statfjord Crude

12.5

control

.

.

1-2

99

Topped Statfjord Crude

12.5

Finasol

premixed, 3m below surface

1:50

1-2

.

98

Topped Statfjord Crude

12.5

control

.

.

1-2

.

97

Fuel Oil

part of below Dispolene 355

ship-aerosol

1:9

1

.

4-5

1-2

France

Norway

Halifax, Canada

Holland

96

Fuel Oil

part of below Dispolene 355

ship-spray

1:9

1

.

95

Fuel Oil

28

Dispolene 355

helicopter

1:9

1

.

94

Fuel Oil

5

control

control

.

1

93

Statfjord

10

Corexit 9527

airplane

1:50

-

-

92

Statfjord

12

Corexit 9527

premixed

1:33

2

.

91

Statfiord

10

Corexit 9527

airplane

l:80

2

.

90

Statfjord

10

control

control

.

2

.

89

Statfjord

10

Corexit 9527

airplane, Islander

1:75

1

.

88

Statfiord

10

control

control

.

1

87

ASMB

2.5

control

control

.

2-3

7

50

86

ASMB

2.5

BP MA700

helicopter

1:10

2-3

10-41

51

85

ASMB

2.5

control

control

.

1

1

84

ASMB

2.5

Corexit 9550

helicopter

1:10

1

1.3

83

ASMB

2.5

control

control

.

1

1

82

ASMB

2.5

Corexit 9527

helicopter

1:20

1

2.5

81

Statfjord

2

Finasol OSR-5

airplane

1:10-30

1-2

2

80

Statfjord

2

Finasol OSR-5

airplane

1:10-30

1-2

2

79

Light Fuel

2

control

control

.

2-3

2

78

Statfjord

2

Finasol OSR-5

premixed

1:20

2-3

100

77

Light Fuel

2

Finasol OSR-5

airplane

1:10-30

1

2

47

48

49

52

1984

1983

1983

(Continued )

TABLE 15.4 Dispersant Field Testsdcont’d Location/ Identifier

Reference Year

Mediterranean Protecmar V

47

France

53

North Sea, Britain

49

1982

1982

54

Norway

55

1982

Number Oil Type

Amount, m3 Dispersant

Application Method

Rate, D: 0

Sea Effectiveness State Claimed

76

Statfjord

2

Finasol OSR-5

airplane

1:10-30

1

2

75

Statfjord

2

control

control

.

1

2

74

Light Fuel

2

control

control

.

1-2

2

73

Statfjord

2

control

control

.

1-2

2

72

Light Fuel

5

control

control

.

2

71

Light Fuel

2

premixed

premixed

1:20

1-2

40-50

70

Light Fuel

4

Dispolene 325

helicopter

1:2.9

1-2

.

69

Light Fuel

3.5

Dispolene 325

ship

1:2.6

1-2

.

68

Light Fuel

5

Dispolene 325

airplane, CL215

1:2.8

2

.

67

Light Fuel

5

Dispolene 325

ship

l:2.8

2

.

66

Light Fuel

5

Dispolene 325

airplane, CL215

1:2.4

3

.

65

Light Fuel

3

10% Dispolene

ship

1:2

3

.

64

Arabian

20

Corexit 9527

airplane, Islander

1:4

1

63

Arabian

20

Corexit 9527

airplane, Islander

1:2

1

62

Arabian

20

control

control

.

1

61

Statfjord

0.2

10% Corexit 9527

ship

1:13

2-3

.

2

Newfoundland

56

Mediterranean, Protecmar III

57

France

47

Mediterranean, Protecmar II

47

France

57

1981

1981

1980

60

Statfjord

0.2

10% Corexit 9527

ship

1:18

2-3

22

59

Statfjord

0.2

10% Corexit 9527

ship

1:17

2-3

1.9

58

Statfjord

0.2

control

control

.

2-3

2.6

57

Statfjord

0.2

10% Corexit 9527

ship

1:10

2-3

1.7

56

Statfjord

0.2

10% Corexit 9527

ship

1:10

2-3

6

55

Statfjord

0.2

control

control

.

2-3

0.6

54

ASMB

2.5

Corexit 9527

airplane, DC-6

1:10

1

.

53

ASMB

2.5

control

control

.

1

52

Light Fuel

6.5

control

control

.

1-2

.

51

Light Fuel

6.5

Shell

airplane, CL215

1:3

2-3

.

50

Light Fuel

6.5

Dispolene 325

airplane, CL215

1:3

1-2

50

46-49

9527

45

5 Corexit

CL215

44

Finasol OSR-

airplane

43

Mediterranean, Protecmar I France

47

1979

BPIIOOWD

various and

42

Light Fuel

1-5.5

BPIIOOX

ship, helicopter,

.

1-3

.

28-41

Light Fuel

3 each

BPIIOOX

ship, helicopter,

.

1-3

.

32

9527

(Continued )

TABLE 15.4 Dispersant Field Testsdcont’d Location/ Identifier

Reference Year

Number Oil Type

Amount, Dispersant m3

31

5 Corexit

CL215

30

Finasol OSR-

airplane

29 Long Beach, USA

Victoria, BC, Canada

Southern California, USA

58

59

60

61

1979

1978

1978

Application Method

Rate, D: 0

Sea Effectiveness State Claimed

BPIIOOWD

various and

27

Prudhoe Bay

1.6

2% Corexit 9527

ship

1:11

2-3

62

26

Prudhoe Bay

1.6

2% Corexit 9527

ship

1:11

2-3

11

25

Prudhoe Bay

3.2

conc.

airplane, DC-4

1:27

2-3

60

24

Prudhoe Bay

1.6

control

control

.

2-3

1

23

Prudhoe Bay

1.6

conc.

airplane, DC-4

1:25

2-3

45

22

Prudhoe Bay

3.2

conc.

airplane, DC-4

1:20

2-3

78

21

Prudhoe Bay

1.6

2% Corexit 9527

ship

1:67

2-3

5

20

Prudhoe Bay

1.6

2% Corexit 9527

ship

1:67

2-3

8

19

Prudhoe Bay

1.6

control

control

.

2-3

0.5

18

North Slope

0.2

10%, 9527

ship, WSL

1:1

I

.

17

North Slope

0.4

10%, 9527

ship, WSL

1:1

1

.

16

North Slope

0.2

10%, 9527

ship, WSL

1:1

2

.

15

North Slope

0.6

Several, demonstration

Several, demonstration .

1-2

.

Wallops Island, USA

60

1978

61

North Sea, Britain

49 62

1976

14

North Slope

0.8

BPI IOOWD

ship, WSL

>1:5

1-2

.

13

North Slope

0.8

Corexit 9527

ship

> 1:5

0-1

.

13

North Slope

0.8

Corexit 9527

ship

>1:5

1-2

.

12

North Slope

3.2

Corexit 9527

airplane, Cessna

> 1:5

1-2

.

10

North Slope

0.8

BPI IOOWD

ship, WSL

> 1:5

0-1

.

9

North Slope

1.7

Recovery þ

helicopter

> 1:5

0-1

.

8

North Slope

3.2

Corexit 9527

airplane, Cessna

> 1:5

0-1

.

7

North Slope

1.7

Control later Corexit 9527

control then helicopter > 1:5

0-1

.

6

La Rosa

1.7

Corexit 9527

helicopter

1

50

1:11

5

Murban

1.7

Corexit 9527

helicopter

1:11

I

100

4

La Rosa

1.7

Corexit 9527

helicopter

1:5

1

.

3

Murban

1.7

Corexit 9527

helicopter

1:5

1

.

2

Kuwait

10% BP 1100

ship, WSL

1:20

2-3

100

1

Ekofisk

10% BP 1100

ship, WSL

.

I

.

0.5

464

PART | VI

Treating Agents

which are notoriously inaccurate. Fluorometry has recently been used, but this method is also unreliable because it measures only a small and varying portion of the oil (middle aromatics) and does not discriminate between dissolved components and oil that actually dispersed. There is further discussion on analytical techniques in a later section of this report. The points raised in Section 15.4: Tank Tests are valid for field tests as well. In summary, testing in the field is fraught with measurement difficulties; however most of the past tests showed poor effectiveness, and the overall average of those that assigned values was 16%.

15.4.3. Laboratory Tests Many different types of procedures and apparatus for testing dispersants are described in the literature. Fifty different tests or procedures are described in one paper.69 Only a handful of these are now used, however, including the Labofina, Warren Springs, or rotating flask test; the swirling flask test; and the baffled flask test. Most of these procedures are used only on occasion for special studies. Some are used for regulatory purposes to screen dispersants for effectiveness prior to national approval. Some common tests are listed in Table 15.5. Several investigators have reported results of apparatus comparison tests conducted in early years.70-76 In the several papers reviewed, all authors concluded that the results of the different tests do not correlate well, but some conclude that some of the rankings are preserved in different tests. Generally, the more different types of oil tested, the less the results correlate. It has been shown that laboratory tests can be designed to give a comparable value of oil dispersion if the parameters of turbulent energy, oil-to-water ratio, and settling time are set at similar valuesdbut most importantly if correct analytical procedures are applied.73 In the literature, different protocols are sometimes described for the same apparatus. The testing protocol used can sometimes change the data more than the actual physical test. Fingas measured, calculated, or estimated energy and work in several laboratory vessels and compared to estimates of energy/work at sea.77-79 Some measurements completed by particle image velocimetry (PIV) and anemometry were compared to these calculated values. The initial measurements and estimates indicate that the energy in several laboratory vessels is similar and that it may be equivalent to those encountered at sea under moderate wind and wave conditions. Two techniques have been initiated to measure energy. The measurement technique chosen to do this is PIV. In this method, seed particlesdwhich could be oil dropletsdare put into the fluid and the fluid is illuminated with a laser. The movement of a particle in a given cell is measured as a function of time. This can occur as fast as 30 to 200 Hz, depending on the apparatus. Turbulent energy can be calculated at each point in the image frame. The other method used is hot wire anemometry. Although this method can yield data similar to PIV, it requires the intrusion of a probe into the area. The

TABLE 15.5 Apparatus for Laboratory Testing of Dispersant Effectiveness Alternate Names (s)

Energy Source

Water Volume (L)

Prime Use

Where Used

Swirling Flask

ASTM

vessel movement

0.12

regulatory general

ASTM, Canada USA, others

vessel movement

0.12

general

USA

Baffled Flask LABOFINA

Warren Springs Rolling Flask

vessel rotation

0.25

regulatory general

Britain

Mackay

MNS Mackay-Nadeau-Steelman

air stream

6

regulatory general

Norway

High-Energy

moving vessel

5

experimental

Canada

EXDET

wrist-action shaker

0.25

experimental

Exxon

IFP

French Standard

oscillating hoop

16

regulatory general

France

SET

Simulated Environmental Test Tank

circulating pump

119

regulatory

not used at present

Cascading Weir

Flume

fall over weir

constant flow 0.5 L/s

experimental

not used at present

fall down tube

1 e flowing

experimental

not used at present

water flow

constant flow (~0.05 L/s)

experimental

not used at present

Flowing Column

Concentric Tube

Bobra

Oscillating Hoop

35

experimental

rarely used

South African BP Sunbury

moving plates

30

regulatory general

not used at present

Spinning Drop

Interfacial

water movement

<0.05

experimental

not used at present

propeller

1.5

experimental

not used at present

Blender

465

oscillating hoop

Wave-Plate Tank

Chapter | 15 Oil Spill Dispersants: A Technical Summary

Test Name

466

PART | VI

Treating Agents

methods are compared in several laboratory vessels under several energy conditions. Kaku and Boufadel have conducted similar measurements in some laboratory apparatuses.80,81 The laboratory apparatuses compared are the swirling flask and the baffled flask. Some of these laboratory data were compared to the field data by Lunel and coworkers, and the results are shown in Table 15.6.1,75,76,82 While the data correlate somewhat to the field data, with a wide spread in effectiveness numbers and the few data points, this correlation should not be overstated. Another interesting point is that the effectiveness values obtained in the field are lower than the data obtained in the laboratory, indicating that the energy levels may be much higher in laboratory tests than those in the field conditions described here. Furthermore, all of the laboratory tests yield effectiveness values much higher than field values. This is contrary to what was thought in previous years. The results of a number of dispersant effectiveness tests taken from published laboratory results were compared in one study.8 The correlation among tests varies from high to low. This may be due to errors associated with the measurement, such as errors in measurement of volumes and variances in energy of the apparatus. It was also noted that the ranking of effectiveness is generally consistent; that is, those oils and dispersants that show the highest or lowest effectiveness do so in all tests. A lot of work has been done recently on the new Environmental Protection Agency (EPA) test entitled the baffled flask. 83-86 This apparatus has been TABLE 15.6 Intercomparison of Laboratory and Field Effectiveness Results Effectiveness Results in Percent Field Test SF SF [16e17] GC CA

IFP

WSL WSL Lab 1 Lab 2 Exdet

Medium Fuel Oil Corexit 9527

26

54

50

91

42

42

67

Medium Fuel Oil Slickgone NS

17

49

46

94

29

23

50

Medium Fuel Oil LA 1834/Sur

4

2

2

50

16

11

38

Forties Crude

Slickgone NS

16

47

65

95

28

25

60

Forties Crude

LA 1834/Sur

5

2

2

61

15

12

53

0.54 0.87

0.94

0.41

0.35 0.19 0.56

0.62

0.27

Oil Type

Dispersant

2

Correlation with field test (R )

0.89 0.7

Ratio Lab test/field test

0.4

Legend: SF ¼ Swirling Flask, GC ¼ analysis by Gas Chromatography, CA ¼ Colorimetric Analysis, IFP ¼ French Institute for Petroleum test, WSL ¼ Warren Springs Laboratory Test, EXDET e an Exxon test.

Chapter | 15 Oil Spill Dispersants: A Technical Summary

467

studied extensively including energy studies, variation with temperature, salinity, and operational parameters. This test is a high-energy test and uses an obsolescent colorimetric analytical method. More description of this will be given in an analytical section below. Reviews of testing have noted several conclusions on laboratory testing.1,8 Bench-scale testing is widely used to evaluate the performance of dispersants and the physical and chemical mechanisms of oil dispersion. A major disadvantage is, of course, that it is difficult to scale the results of these tests to predict performance in the field. Several factors that are difficult to extrapolate include energy regimes, dilution due to horizontal and vertical advection, and turbulent diffusion. Bench-scale tests are very useful for determining the effectiveness of various dispersanteoil combinations, salinity, temperature effects, effects of oil composition, and effects of oil weathering. It has also been noted that the conditions for some tests are not realistic and result in unrealistically high effectiveness values. Many operators of these tests are not using valid analytical techniques.

15.4.4. Tank Tests There has been high interest in tank tests recently. The U.S. National Academy of Sciences focused much attention on tank testing in its recent report.1 It notes that the physical characteristics of wave tanks imply that the encounter probability of the dispersant with the oil slick will be higher than can be achieved during a real spill response. Thus, wave-tank tests provide upper limits on operational effectiveness. There is concern that wave-tank tests may also not count for the skinning of oil that often occurs with weathering. Skinning occurs when heavier components of the oil, typically resins, float to the top and coat the rest of the oil so that penetration from either side is slowed. Another concern is that the dispersant application system should simulate the droplet-size distributions and impact velocities in real application systems. The wave energies used in tanks should be scalable to actual sea states. It is also noted that coalescence and resurfacing of dispersed oil droplets occur and that wave-tank experiments should include investigation of these phenomena. In summary, the advantage of wave tanks is to investigate operational effectiveness components and observe diffusion of droplets more like those at sea. The dispersant droplet size generation in tanks may be an important factor. The committee feels that the measurement of effectiveness should also include the measurement of dispersed oil droplet size. Further, factors such as mass balance and analytical methods require careful consideration. 1,87 The EPA and the Canadian Department of Fisheries constructed a new test tank at Bedford Nova Scotia. Extensive calibration, wave, and energy measurement were carried out at this facility.88-92 In recent times, more extensive testing has been carried out, and quantitative relationships have developed between energy dissipation rate and dispersion.90 Recent testing

468

PART | VI

Treating Agents

showed effectiveness amounts ranging from 53 to 95%, depending on conditions and dispersants. In a related test, effectiveness was found to be 21 to 36% under regular waves and 42 to 62% under breaking waves.91 This is very similar to the findings at other well-controlled facilities such as at the Texas A&M facility and the Imperial Oil facility. The energy factor under breaking waves in the Bedford Tank created much smaller droplet sizes as would be expected. In a related study, a model was created for droplet sizes produced under breaking waves based on tank test results.92 OHMSETT, a government-run test tank in New Jersey, has continued work on dispersant tank testing.93-100 The facility is still working on the recommendations for analytical methods. Tank testing began with the Imperial test tank facility in Calgary, Alberta. 101 Workers at this facility were pioneers in measuring mass balance, energy, and other essential parameters to tank dispersant testing. The range of effectiveness achieved was generally from 20 to 60% in a few hours and 10 to 30% over one day. Texas A&M followed up with a new test facility near Corpus Christi.102 This facility advanced the art of measuring mass balance, energy, and other tank testing parameters. The effectiveness they measured was similar to that of the Imperial tank crew. The author and coworkers prepared extensive studies on tank testing.103-106 The following presents 17 critical factors that need to be considered and included in any test for measuring the effectiveness of dispersants in a tank or in the field in order for that test to be valid. 1. Mass balance The measurement of effectiveness should include the determination of mass balances.87 It is noted that in tanks where this is attempted, accounted-for mass balances typically vary from 50 to 75%. It is recommended that mass balance should be calculated in all wave-tank studies of dispersant effectiveness. Mass balance remains a large issue. Several testing groups were able to establish mass balances in their tanks to enable more accurate assessments of dispersant effectiveness. Bonner et al. developed a materials balance approach in conducting petroleum experiments at the Shoreline Emergency Research Facility (SERF).107-109 The SERF facility is located on land outside Corpus Christi, Texas, and is run by Texas A&M University. The first attempt at a materials balance was during a 1998 study on the fate/ effects of dispersant use on crude oil. Both water column and beach sediment samples were collected. For the materials balance, the defined environmental compartments for oil accumulation were sediments, water column, and the water surface, while the discharge from the tanks was presumed to be the primary sink. The factors that required development included a need to quantify oil adhesion to the tank surfaces. This was resolved by adhering strips of the polymer tank lining to the tank sides so

469

Chapter | 15 Oil Spill Dispersants: A Technical Summary

that the strips could be later removed and extracted for oil. A water-surface oil slick quantification protocol was developed, using solid-phase extraction disks. Initially the group was able to account for only 10 to 33% of the oil originally placed in the tank. After considerable effort, the mass balance was improved to about 50 to 75%. This illustrates the problems of attaining a mass balance. Mass balance is very difficult to achieve in large test tanks, especially in full-scale field tests. Brown et al. reported on tank tests of dispersant effectiveness.101,110 Effectiveness was measured in two ways: by accumulating the concentrations of oil in the water column by fluorometric measurements and by removing and weighing oil on the surface. The results of these two measurements, the amount of oil unaccounted for, and the difference between the two measurements, are shown in Table 15.7. These data show that between 0 and 68% of the oil in the tank can be unaccounted for. Furthermore, in two cases (2 and 3 in the table), the amount of oil was overcalculated. This shows the difficulty in attaining a mass balance, even in a confined test tank. Brown et al. observed that the problem was accentuated by the heterogeneities in oil concentration in the tank.101 Some of the unaccounted oil may have been in regions where the concentrations of oil were higher than average. It should also be noted that surface removal exaggerated the amount of oil dispersed from a factor of 1 to 8, with an average of 4 times. Mass balance is very important in test situations because it relates directly to the reliability of the data. If the mass balance is not accounted for, the TABLE 15.7 Results of Effectiveness Tests in The Imperial Tank Results of Effectiveness by Different Methods

Dispersant Oil Combination

Water Column e 3 Hour

Surface Removal

Percentage Unaccounted For

Percent Difference Between Methods

1

9

53

38

44

2

24

77

1

53

3

33

77

10

44

4

9

76

15

67

5

11

39

50

28

6

14

43

43

29

7

16

16

68

0

470

PART | VI

Treating Agents

numbers are meaningless. The above examples show that mass balance losses, even in the more controlled tank tests, can vary from a few percent and higher. If the measurement made does not account for the discrepancies in mass balance, then very high errors result. A typical example of this is using only the oil remaining on the surface as an indicator of dispersant effectiveness. In a very highly controlled test series, this number can be from 0 to 67% greater than the oil actually dispersed (factors of 1 to 8 times the amount recovered). The experiences of Bonner et al. show that there are major losses of oil in three areas that historically have not been considered in performing a mass balance.107-109 These are adhesion to walls, adhesion to sediments, and formation of invisible slicks. These three losses can account for over 50% of the oil loss in certain cases. Methods for the measurement of each of these oil losses were developed and applied. The adhesion to the walls was measured by placing strips of wall material into the test tank and later removing and quantifying the oil on these strips. It was noted that the age and conditions of these strips were important as the more weathered tank would hold more oil than the newer, unweathered strips. Bonner and coworkers noted that the sediment (even that from the apparently clean tank bottom) must be collected and oil content measured.107109 Oil in thin slicks was measured using a solid-phase extraction disk held by vacuum to retain both the disk and oil adhered to the disk. A question that must be dealt with is, as in the title of the Brown et al. paper, “where has all the oil gone?” 110 In summary, the mass balance problems revolve around analytical problems; loss of oil through thin, invisible sheens; calculation difficulties; inability to recover surface oil after dispersant applied; and loss to tank walls and also in the presence of large heterogeneities in oil concentrations in the water column. 2. Proper controls A proper control experiment is needed in order to accurately assess a dispersant tank test or a field trial. The control slick must be treated equally to the test slick in every respect except for the application of dispersant. The measurement of any factor of the dispersant slick should then be compared to the same measured factor of the control. 3. Analytical methods Few analytical methods can be used in field situations even in a test tank. Very early in the tank testing program, fluorometers, particularly Turner fluorometers, were used. In early years before Global Positioning Systems (GPS), it was difficult to assess the position at which samples were taken if the sampling probes were not fixed to the tank. Now accurate GPS data coupled directly to fluorometer data can provide reasonable positional data for the fluorometric readings. Some of the earlier trials used grab samples that were subsequently taken for analysis by Ultraviolet (UV) or Infrared (IR) absorption.63,103 These

Chapter | 15 Oil Spill Dispersants: A Technical Summary

471

methods are notoriously inaccurate and scientifically incorrect and have long since been replaced by gas chromatography methods. A further problem is that of sample preservation. Samples must be chilled immediately and treated to prevent bacteria growth and hydrocarbon loss. Standard procedures are available, but in early trials these were not applied. The use of fluorometry for oil measurement has been examined in detail.94-97 These studies show that fluorometry is a sensitive, but not necessarily accurate, means of oil determination. A fluorometer uses UV or near UV to activate aromatic species in the oil. The UV activation energy is more sensitive to the naphthalenes and phenanthrenes, whereas the near UV is more sensitive to large species such as fluorenes. The composition of the oil changes with respect to aromatic content as it weathers and is dispersed, with the concentration of aromatics increasing. Thus, the apparent fluorescent quantity increases in this process. Studies then showed that because the amount and distribution of PAHs, the target compound for fluorometers, change with time during the course of a chemical dispersion event, a fluorometer can never be truly “calibrated” for a particular oil and dispersant combination.111-114 The composition of the oil changes with respect to aromatic content as it weathers and is dispersed, with the concentration of aromatics increasing. A fluorometer reading will always remain a relative value and even with careful calibration can only give indications that are as much an order of magnitude from the true value. Efforts continue on fluorescent measures, but there needs to be more recognition that this method will always be relative and highly prone to error.115 Even with good calibration and taking samples directly from the output of a fluorometer, there are significant differences because the target compounds of the PAHs have different distributions and concentrations with time, conditions, and weathering of the oil. Figure 15.4 shows the lack of relation between the total petroleum hydrocarbon (TPH) measured by Gas Chromatography-Flame Ionization Detection (GC-FID) and the reading of the fluorometer. Samples for analysis were taken directly from the output of the fluorometer, and readings were recorded for comparison. Figure 15.4 shows that the correlation between readings is poor. The calibration of fluorometric readings is critical, but one should bear in mind that an exact reading is impossible, as pointed out earlier.113-116 The most important factor is how the oil is introduced to the fluorometer and the subsequent readings made. The physical factors that influence how much of the oil the fluorometer sees are the solubility and dispersibility of the particular oil and the subsequent evaporation or volatilization of the oil. A typical procedure is to add oil and dispersant to a container (e.g., a bucket) and then pump this through a flow-through fluorometer. Most often, that amount of oil added is taken as the amount of oil read by the fluorometer. The problem with this method is that most of the

472

PART | VI

Treating Agents

100

140

35 30

TPH (ppm)

25 20 15 10 5 0

0

20

40

60

80

120

160

Fluorometer Reading (relative units) FIGURE 15.4 Comparison of fluorometer readings compared to actual readings. These results were taken from an experiment in a test tank.

oil is not dispersed into the water column and that some large amounts of soluble species are present, which would not be the case in the sea. Tests of these types of methods show that the fluorometer calibration curve is generally between 5 and 10 times greater than is the actual case. Thus, a reading of 15 ppm in the field is actually a reading of somewhere between 1.5 and 3 ppm. As this was generally the case in a few testtank trials, the actual ppm readings provided are far too high and cannot simply be converted into actual values. A somewhat better method of calibrating a fluorometer is to use weathered oil (to about the percentage expected in the field) and introduce this to a closed container. After about 15 minutes of pumping, take a sample and analyze it by a standard gas chromatography (GC) method.114 Then the addition continues, one increment at a time, with sampling and analysis at each increment. After the numbers are collected, this will form a relatively good calibration curve. But because of the differences in chemical composition, this calibration curve could also give results as high as twice that of actual concentration. The most reliable method of calibrating a fluorometer is to perform the above calibration procedure, but repeat it throughout the actual experiment. Almost simultaneous samples are relatively easy to collect from the fluorometer as the flow from the output of the fluorometer can be captured and preserved for later analysis. This is generally done when the fluorometer reading is

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relatively stable to ensure correspondence between the sample and the fluorometric value. The actual values and the previously prepared calibration curve can be compared to examine the differences in composition. It should be noted that this method was followed in some of the past test-tank work. This is the case for the data illustrated in Figure 15.4. One must remember that, in fact, the aromatic concentrations in the dispersed plume are a composite of dispersed and dissolved aromatics and this total concentration is changing with time. The effects of running probes into the water column have not been fully examined. Several devices have been created in the past to examine the subsurface water column; however the standby usually ends up being weighted hose. Tests show that there is significant retention on Tygon tubing and that pumping for up to one hour may be required to clear this line to the point of background measurements. Teflon tubing appears to show a smaller effect, although less testing has been conducted on this. There may be a serious effect on measurements, depending on how the tubes or sampling devices are deployed. Some test-tank work used fixed probes with Teflon tubing. Another complication to sampling is the retention of surface oil on the sampling tubes, weights, and pumps that are lowered into the water. As the equipment goes through the surface slick, which is present over greater areas than the in-water plume, some of the surface oil will be retained on the sampling equipment and will be read as oil concentration at that depth. Although some experimenters have dragged the submerged sampling train to the next sample point to avoid this problem, this action may also drag oil on the outside of the sampling gear. In summary, fluorometry is a technique sometimes used for measuring relative concentrations of oil in the water column at test tanks. It must be noted that fluorometers cannot truly be calibrated for the oil as there are many variables, as explained earlier. The errors encountered all increase the apparent value of the oil concentration in the water column. Incorrect calibration procedures can distort concentration values up to 10 times their actual value, or even more. Correct analytical methods involve performing accurate GC measurements both in the laboratory and in the field during the actual experiment. Furthermore, water sampling gear must be deployed in such a way as to avoid disturbing the underwater plume or carrying oil from one level or area to another. Fixed probes and sampling after a period of time may assist in minimizing this disturbance problem. 4. Time lag and length of time plume is followed There are certain time characteristics of the dispersion process that must be understood. First, the time to visible action after the dispersant application varies from 15 to 90 minutes. Fast action is herding and not dispersion. The visible action is generally taken as the appearance of a yellow-to-coffeecolored plume in the water. The second item of timing to note is that the

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dispersant may continue to act for up to an hour after application. Third, the movement and dispersion of the plume are generally slow, although the plume is generally visible for about 3 hours and is never visible after about 8 hours. Finally, the oil in the plume will resurface slowly over the next several days. It is important to take measurements as long as possible. The Beaufort Sea experiment is a good example. Three slicks were laid and two left as controls.44 Two days later, three slicks were found at sea, and each had the same orientation and geometry as one on the first day of the experiment. The largest slick, in area, was the dispersed slick, although the oil content was not known. The interpretation of the results would have been quite different if the slick had not been followed for 2 days. Brown et al. noted that they had to measure their test tank after 24 hours to yield a reasonable result. Measurements before about 6 hours were found to be of little value.110 In summary, as the oil concentration in the water is constantly changing, any value should be expressed as a function of time and place. Further, since the dynamics of the dispersion process change rapidly in the first few hours, values should only be used after about 6 hours. 5. Mathematics of calculation and integration Several examples of the effects of integrating and averaging incorrectly are given in a past paper.63 This effect is exacerbated if nonzero oil concentration values are measured in areas outside of the plume. These errors are illustrated in Figure 15.5. Methods of integration and handling background values can easily change the values by as much as threefold, even for the identical case.33 Another concern regarding the mathematics is that related to the use of fixed water column concentration values to determine effectiveness. Although this method has not been used in recent years, it was thought to be a reliable means of estimating effectiveness. The assumption that is made is that the slick is evenly distributed in 1, 2, or 3 meters. Then once the concentration is measured, an effectiveness is assigned. Table 15.8 illustrates the variances in using this type of scheme. This shows that one concentration could yield a wide range of effectiveness values depending on what assumption one makes. Because one cannot make oil thickness measurements and because the depth of mixing is not simply a fixed depth, this type of procedure is not a valid method for determining effectiveness. 6. Lower and upper limits of analytical methods The lower and upper limits of the analytical methods applied are another important factor, especially in field situations. If the measurement is less than the lower limit, use of these values can result in serious errors, as shown above. The lower analytical limit should be taken as twice the standard deviation, or about 0.3 ppm for an older fluorometer or about 0.1 ppm for a newer unit. Use of double the standard deviation is standard

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Case 1 Actual situation 2

2 2

4

Area dimensions

Concentrations

4 5 10 5 10 0

Integration First part = 2 x 4 x 5 = 40 Second part = 2 x 4 x 5 = 80 Third part = 2 x 4 x 5 = 40 Remaining part = 10 x 10 -(4 x 6) x 0 = 0 Sum = 40 + 80 + 40 = 160

Case 2 Illustration of taking non-zero values 2

2 2

4

4 5 10 5 10 0.5

Integration First part = 2 x 4 x 5 = 40 Second part = 2 x 4 x 5 = 80 Third part = 2 x 4 x 5 = 40 Remaining part = 10 x 10 -(4 x 6) x 0.5 = 38 Sum = 40 + 80 + 40 + 38 = 198

Case 3 Illustration of averaging values 10 Integration Total =10 x 10 x 4.1 = 410 4.1

10

FIGURE 15.5 Illustration of the effect of integration and averaging techniques on the final values e A 2-d example.

laboratory practice, and, in fact, newer practices advocate three times the standard deviation. Values below this should be taken as no-detect levels and not zero, but for calculation purposes, zero is the only choice. The upper limit is equally important since the amount of oil in the water column could exceed the upper limit of some analytical procedures. If this were to occur in practice, the effectiveness would be underestimated. Fluorometers are nonlinear in concentrations approaching or exceeding about 100 ppm oil-in-water; therefore very high concentrations might be missed, although such high concentrations have never been measured in the field or lab. 7. Thickness measurements Several researchers have tried to estimate the amount of oil remaining on the surface by estimating thickness. One of the most common means to do so was by touching the surface with a sorbent. The amount of oil in the sorbent was determined by a number of means such as colorimetric or

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TABLE 15.8 Illustration of the Use of Concentration Values and Mixing Assumptions Assumptions 1 mm slick

3 mm slick

10 mm slick

mixed in mixed in mixed in mixed in mixed in mixed in 1m 3m 1m 3m 1m 3m Concentration Found in Water ppm

Value of Effectiveness %

Value of Effectiveness %

Value of Effectiveness %

1

0

0

0

0

1

0

5

1

0

2

1

5

1

10

1

0

3

1

10

1

15

2

1

5

2

15

2

20

2

1

6

2

20

2

25

3

1

8

3

25

3

30

3

1

9

3

30

3

40

4

1

12

4

40

4

50

5

2

15

5

50

5

75

8

3

23

8

75

8

IR analysis. This was then presumed to relate directly to the oil thickness. Careful laboratory tests of these techniques have shown that they do not yield a good quantitative thickness result.109,117 The removal of oil from the surface is not necessarily total for several reasons. The edges of the sorbent may trap more oil, it may not be possible to calibrate the sorbents in the laboratory, and there may be poor extraction from the sorbent. Sorbents cannot be “calibrated” in the laboratory because it is very difficult to get a uniform thickness of oil in a vessel in the lab. Oil often does not spread uniformly and can form “blobs” interconnected by sheen. Oil will be herded to one side even by the minimal air circulation in the laboratory. Also, most oils will form a concave or convex lens with more oil on either the edge or the middle. The use of sampling tubes and similar devices is fraught with similar difficulties. In summary, the thickness of oil on the surface of the test tank cannot be measured. Therefore, thickness cannot be measured as one

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way to determine dispersant effectiveness. Recent work by Bonner et al. has resulted in thin slick estimation methods as a means of examining mass balance.107,109 Goodman and Brown have successfully developed acoustics in the Imperial test tank to measure the thickness of the oil, given thicknesses of 4 or more mm. 8. Behavior of oil with surfactant content Oil behavior that is strongly affected by surfactant content other than dispersion includes lesser containment capability and lower adhesion. These also affect the ability to measure oil remaining on the surface. If the oil were to be contained, dispersant applied, and the remaining oil measured, errors as large as an order of magnitude would occur because the oil would pass under the boom. The value that is important is the critical velocity of containment. The critical velocity of containment is the velocity at which oil is lost under the boom through several failure mechanisms. The critical velocity of containment can be given by Lee and Kang:118 Ucr ¼ f2½gTo=w ðr ro Þ1=2 ðr þ ro Þ=ðrro Þg1=2

(5)

where: Ucr is the critical velocity, To/w is the interfacial tension between oil and water, r is the water density, and ro is the oil density. A very low ratio of dispersant or surfactant to oil (about 1:100) will lower the interfacial tension to about half its previous value.8 Thus, according to the equation, this would lower the critical velocity to about 0.7 of the previous value. If an experiment were set up that measured the oil left behind a containment boom where the oil was being held close to critical velocity, even a small amount of dispersant would release the oil. If the oil left were measured as the effectiveness of the dispersant, this effectiveness value would be highly exaggerated and would represent containment failure and not dispersion. The other factor changed by adding dispersant to oil is the adhesion of the oil. While quantitative studies have not been performed on this, practical tests have shown that it is difficult, if not impossible, to remove the remaining oil after dispersant application using a sorbent surface skimmer.110 Such a skimmer relies on the adhesion of the oil to remove it from the water surface. Again, because of the effect of the dispersant, the oil remaining on the surface is likely to be underestimated, leading to an increase in the apparent effectiveness of the dispersant. While this effect is not felt to be as large as that of containment failure, it is significant nevertheless. The combination of errors resulting from using contained oil slicks and lack of mass balance is at least a factor of 4, as noted in Brown and coworkers, and is possibly as large as no dispersion at all, even though the surface appears to be clear.110

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9. Surfactant stripping It is relatively well known that an exchange of surfactants takes place between the target droplet and the surrounding water.18 This results in destabilization of the emulsion. In situations where the water is a large ratio to the droplet concentration, surfactant is largely lost and destabilization is relatively rapid. In laboratory tests, the ratio of the oil to water then becomes important in simulating the conditions at sea. In the swirling flask test, the oil-to-water ratio is 1:1200, which may be somewhat representative of a more open situation. Some other laboratory tests use only 1:50. The relationship of the energy, the dilution, and other factors in the laboratory test to open water conditions is not well understood at this time. Chemically dispersed oil has been known to destabilize due to the loss of surfactants to the water column. Once droplets lose a critical amount of surfactant, they are less likely to remain in the water column. 10. Recovering surface oil Some experimenters have tried to recover surface oil in an attempt to directly determine effectiveness by presuming that the entire remainder is dispersed. This is incorrect because the loss from the surface includes the amount evaporated, the amount in very thin slicks, the amount that is physically unrecoverable, oil adhered to booms or other surface objects, errors in the amounts of all the oil compartments, and oil that is simply unaccounted for. Controlled tests in a test tank have shown that the difference between oil accounted for in the water column and the amount on the surface can vary from 0 to 80%.101,110 This again represents the typical error of trying to perform a surface-only measurement. Once oil is treated with dispersant, it becomes less adhesive and therefore much more difficult to recover from the surface using typical skimmers and sorbents. This fact can contribute to the error. Some experimenters have recovered surface oil.107-109,119 While a typical experimental procedure, it should be noted, for the reasons described earlier, that this surface oil number is fraught with error and great care must be taken to ensure good recovery as well as subsequent interpretation of the results. 11. Background levels of hydrocarbons The background level of hydrocarbons is important for several reasons, some of which have been discussed. A good background value is needed first to subtract concentration values and second to know when to terminate integration of the spill. It is suggested that the same techniques, along with the grab samples for calibration, be applied in the area before dispersant application and also after, if practical, to determine the range of background values in the area. These values can then be judged for use in correcting the values and for ending integration. Another problem associated with the background levels is that hydrocarbons will adhere to sample tubes and equipment. This will result in higher

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than background values at the end of a run through the plume. There is no easy solution to the problem. One solution is to examine the values and look at where the signal drops off significantly, probably at the end of the plume, and use this value as a “corrected” background. Some experimentation at the scene of the measurements can be used to define the carry-through of hydrocarbons in the system. It should be noted that, if the carry-through is not corrected for, gross errors could occur in the amount of oil calculated. 12. Fluorescence of the dispersant While the dispersant mixtures per se should not fluoresce, most of them show a significant signal when placed in a Turner Fluorometer.113 The reason for this fluorescence is the reflection of UV and other light into the detection path and the actual fluorescence of small amounts of fluorescent material in the dispersant or picked up through the system. Most experimenters have ignored the fluorescence of the dispersant in the past because it was presumed that there was no contribution. Furthermore, in an actual application or experiment, the pickup of even a small amount of oil by the dispersant will result in a significant signal. While this is difficult to correct for, one way is to correct all the readings to accurate GC analytical results. 13. Herding Herding is the phenomenon that occurs when the oil is pushed aside by the dispersant.120 Herding takes place because the spreading pressure of the dispersant can be more than that of the oil slick, especially when the oil slick is thin. The dispersant must directly contact the water surface in order to cause herding. This readily occurs with thin oil slicks because aerially applied droplets are generally 300 to 1200 mm in size, while the oil slick could easily be as thin as 100 mm (appearing as a thick slick).120 There are several problems associated with herding, the major one being that often little dispersion occurs if the oil is herded. The larger droplets will land on the surface first and cause herding if the conditions are correct, and then much of the dispersant that follows in smaller droplets can land directly on the water. A problem in test tanks is that herding could be interpreted as dispersant effectiveness. 14. Heterogeneity of the slick and plume As slicks are rarely homogeneous in thickness, the dispersant applied may be insufficient in areas or may break through and cause herding in other areas.120,121 Furthermore, slick heterogeneities will result in heterogeneities in the dispersant plume, which will again result in difficulties integrating the plume. Using peak values will result in overestimating the dispersant effectiveness and vice versa. This difficulty can be mitigated by integrating very small areas of the subsurface plume. In tanks, this can be overcome somewhat by continuing circulation for 24 hours and then measuring.110

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15. True analytical standards There exist certified laboratories that use certified petroleum hydrocarbon measurement techniques. These techniques should be used for tank studies. One of the most serious difficulties in older field and tank trials occurred when inexperienced staff tried to conduct chemical procedures. Analytical methods are complex and cannot be conducted correctly without chemists familiar with the exact procedures. Furthermore, field instrumentation such as fluorometers require calibration using standard procedures and field samples during the actual test-tank trial. These samples must be taken and handled by standard procedures. Certified standards must be used throughout to ensure good Quality Assurance/Quality Control (QA/QC) procedures. In this era, it is simply unacceptable not to use certified methods, laboratories, and chemists. 16. Weathering of the oil Dispersant effectiveness decreases with weathering of the oil. The weathering trend is characteristic of that oil, but every oil shows this decrease.122 The oil used for any dispersant test should be weathered to an extent that it would represent a realistic situation, for example, equivalent to about 1 day. The weathering of the oil will also assist in maintaining a more correct mass balance. 17. Other issues It is important during any experiment to alter only one variable at a time. Otherwise, the outcome may be a result of the combination of the inputs, leading to confusion as to what the effect was of a given variable. Another distinct issue is that of scaling wave energy.107 Dispersant effectiveness is largely affected by energy inputs, and therefore scaling and control of energy in a test tank is an important factor. In the laboratory, energy input to the dispersant/oil mixture can be very tightly controlled, but in a test tank it could be highly variable and subject to influences such as winds. Bonner et al. provide mathematical tests of energy scaling and means to estimate wave reflection, which is another source of variability.107

15.4.5. Analytical Means Analytical means in any test system continues to be a major concern. It should be made very clear that only careful GC/FID or MS techniques produce a true answer.111-115 Few analytical methods can be used outdoors or in field situations. Very early in the field testing program, fluorometers, particularly Turner fluorometers, were used. Some of the earlier trials used grab samples that were subsequently taken for analysis by UV or IR absorption. These methods are notoriously inaccurate and have long since been replaced by gas chromatography methods. A further problem is that of sample preservation. Samples must be chilled immediately

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and treated to prevent bacterial growth and hydrocarbon loss. Standard procedures are available, but in early trials these were not applied. Another analytical issue in the field of effectiveness measurement is the use of colorimetric measures. The basic science of the issue is as follows: To be a valid colorimetric measurement, the analyte must have a chromophore or color-absorbing center and the system must obey the Beer-Lambert law (linear absorption over broad range of concentrations).115 Oil does neither of these two things. Oil is a mixture of dozens to hundreds of compounds, none with a chromophore, or visible light-absorbing center. Furthermore, what occurs in an oil-in-solvent system is simply light blockage. In analytical chemistry, colorimetry is never used, even when valid, because of the many problems, interferences, and inaccuracies. Only gas chromatography and detection by mass spectrometry or flame ionization are considered valid techniques.

15.5. MONITORING 15.5.1. Introduction to Monitoring An important aspect of the whole dispersant issue is the actual effectiveness in the field. This aspect has not been measured in the past except at a very few spills. Much of the discussion on dispersant effectiveness could have been saved had dispersant effectiveness been monitored more closely during actual applications. While it is easier to measure the effectiveness of dispersants in the laboratory than in the field, there are few standard testing procedures and tests may not represent actual conditions. For example, important factors that influence effectiveness, such as sea energy and salinity, may not be accurately reflected in laboratory tests. However, dispersant effectiveness at sea is very difficult to measure and such measurements are subject to many types of errors. When testing dispersant effectiveness in the field, it is very difficult to measure the concentration of oil in the water column over large areas and at frequent enough time intervals. It is also difficult to determine how much oil is left on the water surface as there are no methods available for measuring the thickness of an oil slick and the oil at the subsurface often moves differently from the oil on the surface. The quantitative method is not used in modern monitoring practices. Instead, a relative measure of dispersant effectiveness is made. Several papers have assessed the techniques used to measure effectiveness in field tests.123,124 There is no general consensus that effectiveness and other parameters can actually be measured in the field using some of the current methodologies. Many historical tests relied heavily on developing a mass balance of oil in the water column and that left on the surface.123,124 Fluorometry has recently been used, but this method is also quantitatively unreliable,

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for it measures only a small and varying portion of the oil (aromatics with two to five rings) and does not discriminate between dissolved components and oil that actually dispersed. Furthermore, it is difficult to calibrate fluorometers for whole oil dispersions in the laboratory without using accurate techniques such as extraction and gas chromatographic analysis. It is known that the aromatic ratio of the oil changes as a result of the dispersion process. In early tests, it was not recognized that the plume of dispersed oil forms near the heavy oil in the tail of the slick and that this plume often moves off in a separate trajectory from the slick.124 Many researchers “measured” the hydrocarbon concentrations beneath the slick and then integrated this over the whole slick area. As the area of the plume is always far less than this area, the amount of hydrocarbons in the water column was greatly exaggerated. In recent years, many of these factors have been recognized, and monitoring is being instituted to simply determine whether or not a dispersant application has any measurable effectiveness. Most of the current monitoring protocols do not try to quantify the effectiveness of dispersants. Furthermore, the purpose of the monitoring is to derive this limited indication of effectiveness because it is also now recognized that there is a potential to have little or no dispersion in actual situations. In summary, dispersant effectiveness testing in the field is necessary to indicate whether or not the dispersant was effective to some degree. Quantitative measures are difficult because effectiveness values depend on establishing a mass balance between oil in the water column and on the surface. Furthermore, it is difficult to quantify the oil at sea. Because this mass balance and oil concentration values are difficult to achieve, specific quantitative results are questionable. Recent protocols have focused on developing relative measures to simply ascertain whether there is some relative effectiveness as compared to little or no effectiveness.

15.5.2. Review of SMART Protocol The most common monitoring protocol in the United States is SMART (Special Monitoring of Applied Response Technologies).125-127 SMART is a nonregulatory protocol promulgated by the United States Coast Guard, the National Oceanic and Atmospheric Administration (NOAA), the U.S. EPA, and Minerals Management Service (MMS). The purpose of the protocol is to provide information for decision making. It is supposed that if the dispersant application were found to be ineffective, further dispersion would not be carried out. The SMART protocol proposes three tiers of monitoring: Tier I is visual monitoring only. Tier II includes fluorometer monitoring of the underwater dispersed oil plume. Tier III includes fluorometer monitoring at several depths and the possibility of performing other in-situ water analysis.

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Sampling the water from the fluorometer and subsequent laboratory analysis is suggested, although no protocols or standards are given for the laboratory analysis. Detailed procedures are given for on-site work. For the visual surveillance recommended for all tiers, the SMART protocol suggests that a visual aid observer such as the NOAA Dispersant Application Observer Job Aid be used to provide the user with imagery comparison.128,129 The protocol also suggests that thermal infrared imaging would provide “a higher degree of sensitivity” l in determining dispersant effectiveness. Tier II is the use of a continuous-flow fluorometer and the output from this on a relative basis. The suggestion is that a reading of about 5 times the background level indicates that the dispersant is working. The data is to be collected at three locations: in a clean area to provide background; under the oiled slick before dispersant was applied; and then after the oil has been treated with dispersants. Data are to be collected both electronically and some manually in a provided form. Positions are to be recorded with a GPS. Water samples are taken from the fluorometer output, preserved on ice, and analyzed later. No procedures are given for the subsequent analysis, although sampling procedures are given in detail. Tier III monitoring has two alternatives: multiple depths with one fluorometer or a transect at 1 and 5 m (or other depths as negotiated) with two fluorometers. Data are treated as before. When one fluorometer is used, the instrument is to be positioned where a high reading is obtained and then readings are taken down as far as 10 m. The data are to be used only as an indication of the difference between the oil-only and dispersed levels. A level of 5 times is suggested as indicating dispersant effectiveness. The protocol suggests that an s-shaped passage be made though the slick to perform measurements as shown in Figure 15.6, as drawn from the SMART protocol. The protocol also suggests strong links between the command post and the field sampling and observation platforms as shown in Figure 15.7. The protocol recommends that the subsurface dispersed oil plume be tracked using a Davis Drifter. Figures 15.8 and 15.9 show the suggested deployment of Davis Drifters. SMART also advocates a box coordinate method in which coordinates of the target are provided from the monitoring aircraft. The SMART protocol also recommends that in Tier III monitoring, the concentration be measured from 1 to 10 m. This is illustrated in Figure 15.10. It should be noted that Tier III has never been used and there only has been limited use of Tier II.

15.5.3. The SERVS Protocol The Ship Escort Response Vessel System (SERVS) of the Alyeska Pipeline Service Company (APSC) has published its own extensive monitoring system.130 The protocol is detailed and includes visual monitoring and

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FIGURE 15.6 Sample path as recommended in the Smart document.

FIGURE 15.7 Illustration of the communication between field and command post.

FIGURE 15.8 Suggested initial deployment of Davis Drifter.

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FIGURE 15.9 Deployment of a second Davis Drifter.

FIGURE 15.10 Concept of SMART monitoring with a fluorometer.

on-water monitoring by taking samples as well as by collecting fluorometric data. As with SMART, the procedures are not intended to quantify the amount of dispersant effectiveness or to yield a mass balance. The SERVS protocol is intended to answer the question of whether the application dispersed oil and to provide data for future use, including for scientific purposes. After the application of dispersant, a vessel held in the vicinity moves to place drogues or markers at the upcurrent and at the downcurrent areas of the dispersed area. Drogues are initially to be rigged to follow currents at the 2-m depth. The sampling vessel moves to a standby position upwind and upcurrent of the dispersant target and outside the oil. Background water samples are taken at this location, as are fluorometer data. This location is also marked with a drogue. The locations are marked using the drogues as reference points. The sampling vessel then moves to sample the area under the first dispersant application area. Samples are also taken under the untreated slick. Guidance is

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provided from the spotter aircraft as well as by reference to the drogues. Detailed instructions are given for each move and operations at each sample point. The fluorometer is specified as a Turner model 10 with a short-wave light kit. A tube is used to sample at depths of between 0.5 and 5 m. The 2-m depth is recommended for the initial transit. The fluorometer is used to give relative results. The fluorometer is to be calibrated in continuous flow mode before and after each survey. A bench calibration procedure is also prescribed, and this includes detailed procedures using Alaska North Slope (ANS) crude oil. Very detailed operation and decontamination procedures are given for the fluorometer. The water grab samples are collected from the outflow port of the fluorometer. Vertical samples are also taken using a Valskon sampler at stations from 10, 5, and 1 m. Two types of samples are prepared: total petroleum hydrocarbon samples and volatile aromatic samples. The former are preserved at 4 C without acid and the latter with acid. Large numbers of samples are taken, and up to 30 coolers must be provided to hold these samples. The Volatile Organic Compound (VOC) samples are measured by purge and trap and injection into a GC/MS. The PHC analysis is conducted by EPA method 602 and 610. This includes TPH and PAH results. Documentation procedures are given on sampling and fluorometer datataking. Neither the airborne visual monitoring nor analytical procedures are described in detail.

15.5.4. Review of Other Protocols Most jurisdictions in the United States recommend the use of SMART protocols. 131-135 The SMART protocol has been used in two dispersant applications in the Gulf of Mexico.134,135 A survey of dispersant regulations in most countries shows that they do not include monitoring protocols.136 The author could find only the SMART protocol in the United States, the SERVS protocol, and a protocol in the New Zealand dispersant policy. The New Zealand protocol includes provisions for monitoring.137,138 The protocol is short and consists mostly of a monitoring report form. Two types of monitoring are proposed: visual and fluorometer. Neither guidelines nor values are given for the fluorometer. The visual guidelines are that a coffee-colored plume indicates effectiveness and a white plume indicates excessive dispersants. Much of the recent monitoring techniques evolves from earlier British field trials.139,140 Lunel advocates the dual type of monitoring such as is described in SMART; however, the specifications and procedures are somewhat different. Lunel recommends visual monitoring of the dispersed plume (coffee-colored) and notes that a white plume indicates excess dispersant use. Such monitoring methods are hinted at in Australian documentation but are not required.141

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15.5.5. Review of Goodman Analysis of SMART A critique of the SMART protocol was published in the 2003 AMOP Proceedings.142 The first point raised is the question of why dispersants and burning, of all the possible countermeasures possible, are the only ones to require monitoring. The second question is that of the possible delay caused by selecting, mobilizing, and deploying the team. Goodman notes that, even though the document states that such activities should not hold up the dispersant operation, it inevitably will. The third question raised is that of the purpose of effectiveness versus toxicity. Goodman supposes that the main issue is toxicity and notes that SMART does not address this question. It is also noted that the SMART protocol would not give a realistic measure of dispersant effectiveness. Goodman explains that SMART does not cover three areas mentioned in the “Dispersant Application Observer Job Aid”: (1) time delay in dispersion after application; (2) dispersed oil plume variations; and (3) the occurrence of overand underdoses of dispersant.128 Goodman also points out that neither the job aid nor SMART describes how the suggested still and video photography should be done. According to Goodman, the prescription of a water-sampling protocol complicates the issue. The extra time, logistical support, and arrangements may not result in any improvement in determining dispersant effectiveness. Goodman states that the problems of interpreting oil concentrations is very difficult in view of the dynamic nature of the slicks and dispersed oil plume, and because of the heterogeneities observed, and the short time of a traverse. The results are that these noisy data may not lead to a correct interpretation of effectiveness. Goodman also notes that fluorometric measures on the open ocean are quite complex and subject to many problems and variations and thus may be unreliable. According to Goodman, the illustrations in the SMART document portray unrealistic scenarios of the whole slick being treated and the whole slick turning into a dispersed oil plume that is the same size as the oil slick. He also observes that the dispersed plume and the undispersed surface slick may not separate under some circumstances and thus may be missed in the sampling process. Goodman states that the SMART protocol makes no provision for compensating for the Eckman spiral, which is the effect of the Coriolis force on the water flow from the direction of the wind at the surface 90 to the right in the northern hemisphere. (Simply stated, this is the effect in the northern hemisphere that wind influences curve to the right due to the Earth’s rotation.) Goodman notes that Tier II sampling at various depths does not solve any problems or limitations of sampling at a single depth. As Goodman points out, SMART should have addressed the following three major problems: 1. The net environmental benefit of dispersant use i. Impact on surface organisms ii. Impact on subsurface organisms

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iii. Relative environmental importance of surface and subsurface organisms and their population dynamics 2. The perceived and actual public acceptance of dispersant use i. Fishery concerns in terms of catch, tainting, and fishing gear contamination ii. The concern of the public and environmentalists about adding another chemical to the ecosystem iii. The cheap factor 3. The effectiveness of dispersant use compared to other response techniques i. The amount of oil treated in a given time period ii. The reduction of surface oil and oiling of shorelines iii. The response time iv. The area of the slick covered v. The effectiveness of dispersing the oil Goodman notes that SMART covers only item 3(v). He suggests that Tier I, visual monitoring, is adequate for this purpose.

15.5.6. Considerations for Monitoring in the Field 15.5.6.1. Behavior of the Slick or Plume The dispersed oil plume can move in a different direction than the surface slick.124 Furthermore, the plume’s geometry generally has no relation to the surface slick. Almost any combination of movement and geometry is possible, depending on the differential between surface and subsurface currents and wind speeds. A major problem is therefore created in locating sample boats and later in trying to quantify the oil in the plume, whose extent is unknown. The best solution to this problem is to perform good aerial surveillance, preferably from a helicopter, or have a series of aerial photographs taken with good time stamps. The samplers will require direction from a helicopter platform to ensure that measurements are conducted on representative portions of the underwater plume. Generally, the plume can be seen better from the air. The underwater plume can initially be seen from the surface and the air as a yellow-colored mass, but later it is difficult to see from the surface or air. If the plume moves with the surface slick, neither surface nor airborne observers can see it, and it is difficult to develop an accurate measurement and calculation plan to determine the amount of oil in the plume. 15.5.6.2. Safety A prime consideration should be the safety of the operation. The crew in a small sample boat is at risk when an aircraft application is going on and a rapid change in weather is possible. As suggested in SMART or similar protocols, sampling is feasible only in small boats. These small boats should therefore be launched from large, safer vessels that remain in the vicinity while sampling is

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being done. A compromise to this might be to perform sampling from larger, more seaworthy vessels.

15.5.6.3. Purpose and Objectives The prime purpose and objective of monitoring processes such as SMART should be to determine whether or not a particular dispersant is relatively effective. Some users appear to misinterpret the protocol as actually yielding an effectiveness value. As this report will show, there are many nuances to a dispersant application, and thus it is impossible to simply say whether or not a particular application was effective. It might be more appropriate to rate the application as somewhat effective, slightly effective, or apparently ineffective. These are probably the three most accurate things that could be said about a particular application. Goodman has raised the question of whether there is any need for monitoring the dispersant application.142 This report will show that there are many false indications, both from a visual and an analytical point of view. These false indications point to a strong need to properly monitor a dispersant application to see whether there was effectiveness. Other spill countermeasures do not have false indications such as this and thus do not need the same type of monitoring. 15.5.6.4. Misleading Indications There are many visual and other indications that may be misleading in determining the effectiveness or lack of effectiveness in some particular applications. These indications are discussed in this section. 15.5.6.5. Visual Indications That Show More Effectiveness Than Actually Occurred HerdingdHerding is the phenomenon whereby the oil is pushed aside by the dispersant.120 This effect occurs because the spreading pressure of the dispersant can be more than that of the oil slick, especially in thin oil slicks. In order to cause herding, the dispersant must directly contact the water surface. This readily occurs with thin oil slicks because aerially applied droplets are generally 300 to 1200 mm in size, while the oil slick could easily be as thin as 100 mm (appearing as a thick slick).120 Herding presents several problems, the major one being that often little dispersion occurs if the oil is herded. If the conditions for herding are present, the larger droplets will land on the surface first and cause herding, and then much of the dispersant that follows in smaller droplets will land directly on the water. The appearance of open water leads some to believe that dispersion and not herding has occurred. Furthermore, the remaining dispersant appears as a white plume in the open water and can also lead to misimpressions.

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Dispersant-only plumedDispersant can run off more viscous oil or can land directly on the water as noted in the description of herding. Once in the water, dispersant forms a whitish plume until it mixes to a greater extent with the water. Such plumes could be mistaken for dispersed oil as opposed to dispersant only. Herding into smaller unseen stripsdHerding does not necessarily occur in a broad swath. Oil is often herded into small strips that are not visible from the air. These will re-spread after a period of time. Spreading dOne of the side effects of dispersants is to reduce the oil’s interfacial tension and thus increase its tendency to spread. This has been observed at several field trials.143 The result is that the surface slick may be spread to thicknesses that are not visible or at least are not visible under the conditions that apply. This can lead to the assumption that the oil is dispersed into the water column, while it has actually been spread out over a much larger area. Lacing dAnother phenomenon that has been observed is the formation of “lace.” This is a sheen of oil with “holes” in it. The holes are caused by smaller drops of dispersant leading to herding. The lace is usually visible only from the surface and not from the air. Thus what appears to be sheen disappears after dispersant application, but actually portions of it have been herded by dispersant droplets.

15.5.6.6. Visual Indications That Show Less Effectiveness Than Actually Occurred A number of visual indications would lead one to conclude that little or no dispersion is occurring, when in fact there is some or even significant dispersion. These indications are as follows. Plume under remaining slickdThe dispersed oil plume may move under the remaining slick. As the surface is never 100% clear of oil under the dispersant application path, the dispersant operation appears to have had no effect. This is unlikely to last for a long time as the plume could emerge from under the remaining slick within about one hour depending on the size of the slick and the plume. Plume not developed at time of observationdThe dispersed oil plume can take 15 to 60 minutes to develop to a maximum. Observation may take place before the plume is fully developed, leading to a conclusion that there is no plume. This and many other points raised here emphasize the need for good and continual surveillance during the first few hours after a dispersant application and for at least one hour after a trial dispersion. Poor visibility conditionsdThe dispersed plume is not highly visible and can be obscured by haze and some fog. It is unlikely, however, that a test application would be conducted under such conditions.

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15.5.6.7. Fluorescent Indications That Show More Effectiveness Than Actually Occurred There are also indications using fluorometers that can be misleading in terms of the effectiveness of a particular dispersant. These indications are discussed next. Resurfacing after measurementdResurfacing of dispersed oil occurs in every case.25,30 The phenomenon was described earlier in this chapter. The point here is that, if the fluorometry measurement is taken before much resurfacing takes place, the calculated effectiveness is lower. Repeatedly measuring one part of the plumedThe surface sampling crew does not have a good fixed frame of reference to guide them, and it is very easy to repeatedly sample the same small dispersed oil plume. This is true even with high-resolution GPS data. This re-measurement of the same area will lead to a large overestimation of the amount of dispersed oil in the area and can be prevented by good aerial directions and can be documented by plotting the course of the small boat using good GPS data and the plumes after the operation is completed. Dispersant-only plumedWhen aerially applied dispersant lands on heavier or emulsified oils, the dispersant generally runs off without much dispersant penetrating the oil and without any measurable effect on the oil. As mentioned earlier, the dispersant begins to mix with the water and forms a milky mixture that may be mistaken for dispersant effectiveness. This should be noted by direct surface observation to ensure that runoff is not mistaken for dispersant effectiveness. Although the dispersant mixtures per se should not fluoresce, most of them show a significant signal when placed in a Turner Fluorometer.113,114 The reason for this fluorescence is the reflection of UV and other light into the detection path and the actual fluorescence of small amounts of fluorescent material in the dispersant or picked up through the system. Most experimenters have ignored the fluorescence of the dispersant in the past because it was presumed that there was no contribution. In an actual application or experiment, the pickup of even a small amount of oil by the dispersant will result in a significant signal. Although this is difficult to correct for, one way is to correct all the readings to quality GC analytical results. Dissolved aromaticsdAfter an oil spill occurs, a significant plume of aromatics forms. These aromatics are the prime target of a fluorometer and will give significant readings. A dissolved aromatic plume will be as significant as a dispersed oil plume under certain circumstances. There is no way to distinguish this in the field and even in the lab without special analytical procedures. Other fluorescent material in areadFluorometers do not discriminate between sources of fluorescence. Fluorometers operating at long wavelengths will readily pick up organic material and those at short wavelengths, less so.113,114 During a survey of Vancouver harbor several years ago, this author encountered a large submerged plume of fluorescent material using a Turner

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fluorometer. Sample analysis and contact with a local refinery showed that this was aromatic material that had been inadvertently released by the refinery. Dispersant and aromatics onlydA probable occurrence is that dispersants and aromatics from the oil are in an area and these fluoresce and could be mistaken for dispersed oil.

15.5.6.8. Fluorescent Indications That Show Less Effectiveness Than Actually Occurred Fluorometer misses plumedIt is very easy to miss the dispersed oil plume with a surface-sampling rig. As noted before, there are few points of reference for the surface sampling team and their field of view is very narrow. This again points to the need for good aerial support at this type of operation. Misdirected by aerial observerdThe surface sampling team could be misdirected by the aerial observers through a series of errors. This is more likely with a fixed-wing aircraft as overpasses might occur at about 15-minute intervals and the aerial observers can easily lose track of where the surface crew was in the past sequence. Measurement before plume developsdCertain time characteristics of the dispersion process must be understood. First, the time to visible action after the dispersant application varies from 15 to 40 minutes. Fast action is herding and not dispersion. The visible action is generally taken as the appearance of a yellow-to-coffee-colored plume in the water. The second item of timing to note is that the action of the dispersant may continue for up to an hour after application. Third, the movement and dispersion of the plume are often slow, although the plume is generally visible for about 3 hours and is never visible for more than about 8 hours. Finally, the oil in the plume can resurface slowly over several days. Since the resurfaced oil is usually thinner than the visibility limits, this will not be noticed unless there is little differential movement between the slick and the dispersed plume. It is important to track and follow the undispersed oil, control slick, and dispersed plumes for as long as possible. The Beaufort Sea experiment is a good example. Three slicks were laid and two were left as controls.143 Two days later, three slicks were found at sea, and each had the same orientation and general geometry as on the first day of the experiment. The largest slick was the dispersed slick, although the oil content was not known. The interpretation of the results would have been quite different if the slick had not been followed for days.

15.5.7. Visual Surveillance Visual surveillance has been a standard tool for examining the effectiveness of dispersants. The primary indicators are the visual appearance of a yellow-tocoffee-colored plume in the water from dispersed oil. Indicators of poor effectiveness are the appearance of herding or dispersant-only plumes in the water (whitish).

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A very important tool for working with oil spills has been the relationship between the appearance and thickness of the oil. This relationship is occasionally used to estimate the amount of oil before or after dispersion. Present thickness charts actually date from 1930. Before this date, it was already recognized that slicks on water had consistent or nearly consistent appearances. A series of experiments conducted at that time resulted in charts that are still used today. Only a few experiments have been done in recent years. These appearance factors are very important because they provide the only means of estimating the amount of oil in thin sheens on the sea. There are no means for estimating the amount of thick slicks on the sea. The literature is in general agreement that the lower limit of oil visibility ranges from 0.03 to 1.6 mm with a typical average of 0.1 mm.144 Below this average of 0.1 mm, oil is simply not visible to the human eye, and light is transmitted through these thin slicks. Often oil spill observers presume that, if they do not see a slick or sheen, no oil is present. After spreading, which is enhanced by dispersant application, a significant portion of the oil can reside in the “invisible” sheen. This is another reason that surface measurements may be unreliable. These very thin sheens cannot be recovered, seen, or measured at this time.

15.5.8. Remote Sensing Although remote sensing can be useful to assess dispersant trials, some of the data can be misinterpreted. Careful use must be made of data, and recognition must be given to the physical basis of these data. Very importantly, it should be recognized that no capability exists to measure oil thickness using current airborne sensors. There was once a popular myth that infrared sensors could be used to “measure” oil thickness, but theory and tests have shown otherwise.117 Furthermore, attempts were made to use sorbent tests to “calibrate” infrared imagery, and this too was shown to be incorrect.117 The only thickness information available to the oil spill worker is the fact that the rainbow appearance has a thickness of between 0.15 and 0.8 mm, as described above.144 This occurs because of multipath interferences in visible light and is well understood on a physical basis. After the slick becomes thicker, the black/brown appearance has no thickness associated with it. Remote sensing is thought to be a necessary tool for measuring the extent of the surface slick and of the dispersed plume.145,146 While color photography with good time marks is essential, nadir-looking, spatially corrected color imagery is much better. Infrared (IR) photography can give a picture of the relative thickness, but can be misled by the presence of a dispersed oil plume. Infrared photography was to be the prime measure of effectiveness in the Beaufort Sea trials in 1986.143 A computer device had been built to directly yield areas of thick slicks (i.e., IR “hot” area). As the trial progressed, the area of the dispersed slick grew

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rapidly, far beyond that of the two control slicks. While the naive conclusion would be that dispersants were very ineffective and actually increased the amount of oil on the water surface, the actual fact was that the dispersant increased the area of oil on the surface and the dispersed plume was also hotter than the surrounding water due to the absorption of IR radiation. Several reviews of remote-sensing technology and of sensors can provide useful imagery.147,148

15.5.9. Tracking of Oil on Surface Because the long-term effectiveness of the dispersant should be understood as well as the short-term effectiveness (in terms of hours), sea trials should include an appropriate plan to track and sample the slick, the plume, and resurfaced oil. Technologies exist to monitor the surface slick.149-151 Tracking is essential to ensure that the geometries and positions of both the plume and surface slick are well established for the airborne and surface crews. Tracking resurfaced oil might be difficult because it is not highly visible. The use of GPS can now accurately locate the position of the entire surface track. GPS information can be noted at each sampling station, along with the exact GPS time. Software now exists to readily plot these points onto maps.

15.5.10. Tracking of Oil Underwater While technologies to track the underwater plume are not as well tested as those to track oil on the surface, success has been recorded using drogued buoys such as the Davis Drifter.126,145,146 Both the resurfaced oil and the plume should be tracked using remote sensing or drogue and sampling techniques. Tracking is essential to ensure that the geometries and positions of both the plume and the surface slick are well established for the airborne and surface crews. Sampling of the subsurface plume should be guided by airborne crews as well as by observing the plume and the drogued buoys in the plume. Misplaced sampling can result in underestimation of the dispersed amount or in large overestimations if the extent of the plume is overestimated. The dispersed oil plume spreads out over time and becomes increasingly more difficult to track. Eventually it becomes invisible to surface and aerial observation, at which time it can be tracked using fluorometer probes and drogued buoys. The buoys may require repositioning based on fluorometry information as noted in the SMART protocol.

15.5.11. Mass Balance The SMART protocol and other monitoring protocols do not purport to establish a percentage of effectiveness, nor should they. To achieve a percentage effectiveness, the experiment would have to establish a mass balance. Mass

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balance is very difficult to achieve in open field tests. In the 1993 North Sea dispersant trials, the dispersed oil in the water column measured shortly after the dispersant treatment accounted for only 1.8 to 3.5% of the initial volume of the oil released.39,40 Similarly, only 0.1 to 0.2% could be accounted for under the control slick, so the difference between the two was emphasized, for example, 16 to 27 times the amount of oil. Even in enclosed test tanks, it is very difficult to establish a mass balance. Several examples of this are given above.

15.5.12. Use of Undispersed Slick(s) as a Control In order to properly assess a dispersant field test, a proper control slick is needed. The control must be treated equally to the treated slick in every respect except for the application of dispersant. The SMART protocol suggests that the slick before treatment be used as the control. The importance of using a control slick can be illustrated by two field dispersant trials, treatment of emulsified oil from the Exxon Valdez and the Beaufort Sea Trial. Both were attended by the author of this chapter. In the Exxon Valdez test of dispersant application to an emulsified oil slick, two slicks were chosen in the Gulf of Alaska, south of Seward. One was left as a control, and the other was treated with large amounts of dispersant. Sampling was conducted from a ship and aircraft, some equipped with remote-sensing gear, from which the slicks were observed for about 6 hours. The dispersant failed to break the emulsion and did not disperse the oil. Coincidentally, the control slick broke up somewhat after about 5 hours. This was probably due to its great exposure to waves as it was up-sea of the treated slick. Without a control, the experimental results could be interpreted differently. Use of the same slick as a control as the target slick requires further analysis. The control would in this case act only to compare fluorometric readings on an initial basis. Some smaller slick should be left as a control for comparison over a longer term if the dispersant application is continued.

15.5.13. Background Levels of Hydrocarbons The background level of hydrocarbons is important for several reasons, some of which are mentioned above. A good background value is needed, first to subtract concentration values and second, to know when to terminate integration of the spill. The background of hydrocarbons in the sea varies widely.121,152-154 This is especially true in estuarine and riverine outputs into the sea. These areas are often the same areas that were used for dispersant experiments in the past and possibly also the areas where dispersant may be applied. It is suggested that the same techniques, along with the grab samples for calibration, be applied in the area before dispersant application as well as after, if practical, to determine the range of background values in the area. These values can then be judged for use in correcting the values and for ending integration.

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Another problem associated with background levels is that hydrocarbons will adhere to sample tubes and equipment. This will result in higher than background values at the end of a run through the plume. There is no easy solution to the problem. One of the solutions is to examine the values and look at where the signal drops off significantly, probably the end of the plume, and use this value as a “corrected” background. Some experimentation at the scene of the measurements can be used to define the carry-though of hydrocarbons in the system. It should be noted that if the carry-through is not corrected for, gross errors could occur in the amount of oil calculated.

15.5.14. Using and Computing Values SMART and its other counterparts are not intended to result in percentage effectiveness. Nevertheless, users will inevitably try to use these values to “calculate” effectiveness. This should not be done as it will lead to errors, as described above. Another issue is the use of a sampling protocol to determine effectiveness on a trial application. Though a useful concept, this author suggests that it is not practical. The cost of mounting a dispersant operation, be it a trial or not, is too great to stop it after it has begun. In a typical situation, it would not be acceptable to leave the slick with no countermeasures during decision time or to delay countermeasures for further decisions. It may be much more advantageous to obtain a sample of the oil and perform one of the quick bottle tests on the oil as it now is in the field. This would form a better decision point in view of the costs and acceptability of approach.

15.5.15. Recommended Procedures for Monitoring Dispersant Applications 15.5.15.1. Overall In view of what has already been covered in this chapter, it should be apparent that there are many nuances to monitoring the effectiveness of a dispersant application. Furthermore, use of a trial aerial application as a decision point for continuance is questionable in most circumstances. It is suggested that a field test be conducted on a small sample of the oil instead. The aerial application is too expensive to stop if it is not effective. The trial application should only proceed if there is reasonable certainty that the oil is dispersible. It should be noted that the procedures described in this section will not lead to a quantitative value of effectiveness. 15.5.15.2. Field Pretest It is recommended that a small pretest of effectiveness be carried out rather than relying on monitoring as described above. Several tests have been developed and

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are summarized in Table 15.9. The prime purpose of these tests is to screen the effectiveness before application proceeded. No test or agency recommending them, however, suggested any level of effectiveness (even relative) that should be achieved before full application proceeded. The advantage of a pretest is that, before application proceeds, a screen is carried out. This screening takes little logistics and does not interfere with other operations or organization for an actual dispersant application. If the screen test shows that there is potential for dispersant effectiveness, then planning for the next stage can proceed. The last row of Table 15.9 shows a recommended test.124 The concept behind this is that a very simple test would suffice. The procedure for this test is that a sample of the actual spilled oil and a sample of the water in the area are obtained. As soon as practical after the samples are obtained, about 1 L of the water sample is placed into a bottle with a narrower neck (to exaggerate the oil measurement) and filled to the start of the neck. A line is placed at the top of the water level to indicate where the oil would start. This can be done with an etching tool or a special marker. About 1 mL (about 5 drops) of the dispersant to be used is added to 10 mL of oil, is mixed briefly, and is then poured into the test vessel. A mark is placed at the top of the oil. The test vessel is vigorously shaken for 1 minute and left standing for 10 minutes, and a mark is placed at the top of the new oil level. The criterion suggested is that about half of the oil should be dispersed before proceeding with full-scale dispersant application. For information purposes, the oil and dispersant laboratory effectiveness result could be obtained and compared to this value.

15.5.15.3. Visual Surveillance It is suggested that visual surveillance is a prime method for determining whether or not the initial spray had any effect. The many factors noted in this report must be considered, and a good field guide is also needed. At least one experienced person should be employed for the visual surveillance to be effective. It is recommended that buoys be used to track the plume and the remaining slick. Davis Drifters can be used to track the plume, and spill tracker buoys can be used to track the remaining slick. Further visual surveillance on the slicks is necessary for at least one day. The visual surveillance requires documentation by photography. Good quality digital still pictures are the best. The color quality must be good in order to be able to distinguish between white (dispersant only) and yellow-to-brown (dispersed oil) plumes. All images require time-coding. 15.5.15.4. Measurements From the Surface The measurements from the surface, such as by using fluorometry, may provide little additional information over pretesting and visual surveillance. The basic question that any monitoring protocol should ask is: “Is there significant dispersant effectiveness or not?” Surface monitoring may result in confusing

498

TABLE 15.9 Field Tests for Screening Effectiveness Oil to Water Ratio

Dispersant Added (mL)

Dispersant to Oil

battery tester 2 cm d 21 cm long

50

1

1:50

0.2 premixed

1:20

156

1-litre flask

1000

10

1:100

1

1:10

US EPA test

157

test tube

5 cm in 1 cm tube (~6 mL)

10 drops (~2 mL)

~1:3

1 drop (~0.2 mL)

~1:10

Fina Spill Test Kit

158

graduated cylinder

100

2

1:50

0.1 0.2

1:10 1:20

Pelletier Screen Test

159

25 mL vial

20

0.1

1:200

0.05

2

Suggested

124

wine bottle or similar

~1000

~10 (50 drops)

~1:100

~1 (5 drops)

~1:10

Vessel

American Petroleum Institute

155

Environment Canada

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Oil Added (mL)

Reference

PART | VI

Water Capacity (mL)

Test Sponsor

Shake Time (min.)

Settling Time (min)

American Petroleum Institute

end over end 0.5/second

2

Environment Canada

rotated to 140 30 times

US EPA test

Measurement Description

Effectiveness Criteria

5

extraction by toluene colorimetric comparison

none

~15

3

visual measurement of oil height

none

vertical 2/second

1

10

height-O-ring movement light obscuration

none

Fina Spill Test Kit

shaking

0.17

0.5

colour comparison to scale provided

none

Pelletier Screen Test

vortex with magnetic stirrer 2000 rpm

1

1

visual estimation

none

Suggested

stopper flask and shake

1

10

height of lines on bottles top, bottom, after settling of oil

>~40% of oil gone (about half)

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information that is not directly relevant to this question. Therefore, from a strictly monitoring point of view, surface monitoring is not recommended as a prime method. For scientific and documentation purposes, however, it is suggested that water column sampling would be extremely useful. Good quality data from surface monitoring could be very useful for future purposes. For this purpose, the protocols as proposed for SERVS are recommended.130 These field procedures and the accompanying lab procedures require updating.

15.6. PHYSICAL STUDIES 15.6.1. Energy Traditionally, the effectiveness of a dispersant was viewed as simply a result of interfacial phenomena, that is, the lowering of the surface tension of the oil by the use of surfactants.160 It is now apparent that many factors influence the effectiveness of dispersants, the most important of which are the basic physics of dispersion, sea energy, the composition of the oil, the type of dispersant and the amount applied, temperature, and salinity of the water.8,30,162 Given a certain type of oil and salinity, the important considerations are the sea energy and the amount of dispersant. In the past, some experiments focused on determining the relationship between energy and dispersant effectiveness. An energy-dispersant amount diagram for Alberta Sweet Mixed Blend, a common oil in North America, is shown in Figure 15.11. The diagram is based on older experimental data.161 Energy is indicated by the rotational rate

% Dispersion 100

100

80

80

60

60

40

40

20 0 400 350 300 250 200 150 100 Relative Energy

20 0 1/12.5 1/25

50

0

0

1/50 1/100 1/200 Dispersant to Oil Ratio 1/400

FIGURE 15.11 Typical relationship between energy, amount of dispersant, and the effectiveness of dispersion.

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of the shaker unit, which shows that there is a predictable relationship between the three factors of effectiveness, energy, and dispersant quantity. While the figure shows that energy is a very important factor, the same dispersant effectiveness can be achieved at several different energy-dispersant combinations. This older work did not quantify energy. New work shows more specifically what the energy is and at what scales it operates in the test vessel or the sea.

15.6.1.1. Theoretical Basis An important aspect of oil spill processes is the energy applied to the oil on the water surface. As it turns out, sea energy is a very important part of the amount of dispersion. The energy and work applied are known to affect the kinetics of water-in-oil emulsion.77 Furthermore, it has been found that energy is critical in understanding the effectiveness of chemical dispersion of oil.162 The kinetic energy and turbulence in small laboratory apparatuses have recently been studied because turbulent energy is felt to be the most important form of energy related to emulsion formation and dispersion. Turbulence is the fluctuation of velocity.163 If a velocity assemblage is viewed, the description of the overall velocity is given as: U ¼ U þ u0

(6)

where U is the overall velocity component, U is the average or constant velocity, and u0 is the fluctuating component or turbulence The intensity of turbulence is given by: I ¼ ðu2 þ v2 þ w2 Þ1=2

(7)

where I is the turbulence intensity and, u, v, and w are the average turbulence in the x, y, and z directions. The turbulent kinetic energy can be given by: k ¼ 1=2m ðu2 þ v2 þ w2 Þ

(8)

where k is the kinetic energy, m is the mass, typically one unit in the Standard International Units (SIU) system, u, v, and w are the average turbulent velocity components in the x, y, and z directions, and Average turbulence is the average standard deviation in velocity. Turbulence in natural systems decays as the force that initiated is no longer applied. Kolmogorov developed the classic decay law:164 u2 wt10=7 where u is the turbulence in a particular vector, and t is time.

(9)

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The work imparted by wind can be estimated as:165 W ¼ rair gV 2 =2p

(10)

where W is the work rair is the density of the air, g is gravity, and V) is wind stress, the actual impact of wind on a surface. The energy dissipation rate per unit surface area can be estimated from:165 3 ¼ 15 V 3

(11)

where 3 is the dissipation rate and, V is the wind speed. Mellor describes the relationship between wave energy and amplitude as:166 E ¼ g a2 =2

(12)

where E is the wave energy per unit area, g is the gravitational constant, and a is the wave amplitude. A classic method of presenting energy and turbulence energy and decay is in the form of a power density spectrum or density function.167 In this type of presentation, the energy or dissipation of energy is presented versus a logarithm of wave number. The classic decrease in energy with wave number is 5/3. This is said to be a “natural” decay or energy distribution as it is found in many natural systems. The turbulent and kinetic energies of several natural systems have been measured. Horne et al. measured the turbulent energy and dissipation rates of five sites on Georges Bank using a shear probe array.168 The vertically integrated dissipation or energy production was measured as ranging from 0.007 to 0.91 W/m2. The average measured dissipation rate ranged from 2.3 to 46 X 107 W/kg seawater. Lough and Mountain also measured turbulence on Georges Bank.169 Dissipation rates were 1011 to 107 W kg1 but at the surface was 1 to 2 orders of magnitude higher. Sterling et al. report that energy dissipation in an estuary ranges from 101 to 100 W/m3 and for open water, 100 to 101W/m3.170 Barbarosa and Metais describe ocean energies, noting that storms can initiate strong downward velocities of up to 10 cm s1 and surface energy losses as great as 1,000 W/m2.171 Maar et al. measured the turbulence in cruises off Denmark and Greece and found that there was a large range in turbulent diffusion (0.2 to 250 cm2 s1).172 Stocker and Imberger measured the horizontal transport and dispersion on a lake, Kinneret, in Israel, finding that the mean horizontal diffusion dispersion coefficient was 17.1 m2 s1 while the vertical dispersion was negligible.173

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15.6.1.2. Velocity, Energy, and Work Measurement Thermal Anemometry Thermal anemometers can be used to measure fluid velocity by sensing the changes in heat transfer from a small, electrically heated element immersed in the fluid.174 In one form of the instrument, the constant temperature anemometer, the cooling effect produced by fluid flowing over the element is balanced by the electrical current to the element. The change in current is measured as voltage change and forms the anemometer output. The anemometer output is typically coupled to a computer where that data can be collected and analyzed. An important feature of thermal anemometers is the ability to measure very rapid changes in velocity. Frequency changes up to 30,000 Hz or fluctuations as short as 30 microseconds can be measured. This high frequency is accomplished by coupling very fine sensing elements such as a wire of 4 to 6 micrometers in diameter or a platinum thin-film deposited on a quartz substrate. This size also makes the probe less obtrusive than older design probes. The probe will still interfere with fluid flow. Several side effects have been classified and procedures developed to deal with these side effects.175 Particle Image Velocimetry In PIV, the flow as marked by micron-sized seeder particles is illuminated by a light sheet.176 Two images of each particle are recorded in a short time interval. Processing the two images yields a local velocity vector by tracking individual particles. As the time interval is small compared to the flow timescales, PIV can deliver instantaneous velocity maps in a plane. Illumination is typically accomplished using a laser. Common lasers are Nd:YAG and argon ion lasers. The laser can easily produce a very thin light sheet, thus avoiding problems of multiple targets. A light sheet is created using a cylindrical lens or series of lenses. Most modern systems use Charge-coupled Device (CCD) cameras gated to the pulse repetition frequency of the laser. The advantage of using PIV for the applications in oil spill is that surface seeding can be employed. This then results in data relevant only to the surface of the water, such as would be true for an oil slick. Furthermore, this type of data can result in a depiction of surface flow, an important first step in studying the energy of a particular apparatus. Laser Doppler Anemometry The laser doppler anemometer uses laser transmitters and receivers to interrogate a small volume of water or air.177 The transmitter produces periodic short laser pulses. Ambient scatterers such as bubbles or seeding material scatter a portion of the laser light. The receiver detects these scattered laser pulses. The frequency of the returned laser pulses is doppler shifted by the

504

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Treating Agents

speed of the scattering particles. The return signals can then be demodulated to calculate speeds within the defined sample volume. Acoustic Doppler Velocimetry The acoustic doppler velocimeter uses focuses on acoustic transmitters and receivers to interrogate a small volume of water.178 The transmitter produces periodic short acoustic pulses. Ambient scatterers such as bubbles or seeding material scatter a portion of the acoustic energy. The receiver detects these scattered acoustic pulses in the defined sample volume. The frequency of the returned acoustic pulses is doppler shifted by the velocity of the scattering particles. The return acoustic signals can then be used to calculate velocities within the defined sample volume. Calculation by Energy Imparted Brocart et al. developed a method for online water-in-oil emulsification. The route to energy calculation is typical:179 The velocity can be split into two parts: the constant, slow changing component and turbulence: U ¼ Ua þ u0

(13)

where U is the total velocity, Ua is the average or slow-moving velocity component, and u0 is the rapidly changing component or turbulence. The power density (z) is the primary energy term that can be used to calculate droplet size and other mixing parameters. Brocart et al. calculated the power density of a propeller mixing system as:179 z ¼

kinetic energy rV 3 ¼ 4c application time

(14)

where 3 is the power density for a rotor-stator mixer, r is the fluid density, V is the tip velocity of the rotor, and c is the number of teeth on the rotor. Bocart et al. (2002) noted that the power density for this rotor-stator system ranged between 108 and 1010 W/m3, which is higher than other calculation methods. Fingas and coworkers calculated the energy and work of a rotating emulsification apparatus where the motion is end over end. The total kinetic energy in each bottle was given by:180 KE ¼ 1=2MV2 where KE is the total energy in ergs,

(15)

Chapter | 15 Oil Spill Dispersants: A Technical Summary

505

M is the mass being agitated in grams, here approximately 620 g of water and oil, and V is the velocity in cm/s, which is 2prdwhich is rpm/60 7.5 cm. Kinetic energy by this formula is then 196 x rpm2 ergs. Ergs were used in this study because they are a much more convenient unit than the SIU Joules at these low energy levels. This simple formulation was used to assign an energy level to each rotational velocity. Again, it is important to note that the energy estimated here was the total energy input to the system, and not turbulent energy, which may be the prime factor in emulsion formation. Work can be defined by looking at the force applied to the system by gravity. Since F ¼ ma (16) where F ¼ force applied to the system in Newtons, m ¼ mass, which here is 0.62 kg, a ¼ the acceleration due to gravity, which is 9.8 m/s2, and thus F ¼ 6.08 Newtons. Work ¼ F D

(17)

where F ¼ the force in Newtons ¼ 6.08, D ¼ distance through which the force moves, which here is the average height through which the water falls, which is 15/2 cm or 0.075 m. Thus, work is 6.08 0.075 J per revolution of the apparatus, or 0.456 J per revolution of the apparatus. Saiz and coworkers calculated the energy dissipation rate in a grid-stirred laboratory vessel as:181 3 ¼ 8:5 104 freq3:003 (18) where 3 is the dissipation rate in cm2 s0.3 and freq is the frequency of the grid stroke. Camp and Stein developed a relationship to calculate energy imparted to a system with paddles as:182 W ¼ C A V 2 =2

(19)

where W is the work, C is the drag coefficient, A is the area of the paddle normal to the movement, and V is the velocity of the paddles with respect to the liquid. The levels of turbulence, velocity, and other factors for the swirling flask, septum flask, a variant of the swirling flask without the spout, and a 300-L tank with a central stirring propeller can be calculated. Testing shows that the velocity, energy, and other similar factors increase as the rpm is increased; however, there is some noise. This noise is caused by the change in flow patterns with changing velocity and with random motions in the vessels as well as small-scale turbulence. Calculation shows that the energy dissipation varies in a nonlinear manner with rotational speed in the swirling flask, but closer to

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Treating Agents

linear for the 300 L tank. Placement of the probe affects the results. Comparison of placing the probe at the funnel location compared to opposite the funnel location in the swirling flask does change the values. The energy rises faster with increasing rpm at the location directly by the funnel or spout location as there is an increased flow at this location. Fingas carried out dual or cross-wire probe measurements in three vessels.77-79 This probe simultaneously measures the velocity and turbulence components in the U direction, in this case the horizontal component, and in the V direction, in this case in the vertical or vessel depth component. The U and V data were mathematically processed to provide an equation so that a smoothed value was used at the rotational speeds at which the vessels are normally operated. The flow patterns change as the vessel rotation speed changes, and the probes may no longer be directly facing the flow origin as they were at low speeds. In the large 300-L tank, a downward flow developed further with increased rpm, and thus the flow pattern changed significantly. The U component (horizontal flow) is very high compared to the V component in the swirling flask compared to the V componentdin fact, about 40 times higher as an average in some vessels. This indicates that vertical mixing is much lower in the swirling flask than in the large tank. Thus, simply stated, the turbulence energy in the horizontal direction is about 5 times the energy in the vertical direction. Several laboratory vessels were examined on the basis of the energy and work calculations. These data are shown in Table 15.10 along with the experimental values noted above. The work and energy associated with agitation are calculated using the calculation equations noted. It is interesting to note that once the work and energy are adjusted for the volume of water present in the vessel, the energy level and work input are similar and within about an order of magnitude of one another. The energy and work input are also similar to that noted for wind and wave equivalents. All the same, caution should be noted in making this comparison, as all the calculated values are based on simple assumptions. Table 15.10 shows that all of the laboratory apparatuses studied have energy levels similar to those of low-wind and sea states. Furthermore, Table 15.10 shows that there are variances in energy levels, but that the agreement between experimental methods and calculated energy levels is generally within an order of magnitude. A comparison of the calculated energies between the vessels and waves shows that overall energies in some of the apparatuses are similar to those encountered at sea but that some vessels have very high energies, much greater than at sea.

15.6.2. Composition of Oil In the distant past, viscosity was thought to be the only quality of an oil that influenced the effectiveness of a dispersant.183 It soon became apparent, however, that the chemical constituents of oil had a major influence on the effectiveness of dispersants. Later, studies correlating effectiveness and oil

TABLE 15.10 Work, Energy, and Turbulence Levels of Various Laboratory Apparatuses Compared to Calculated Sea Levels Adjusted for Volume /L

Experimental Dual Probe

Near Surface Energy by Single Thermal Probe

Energy Application

Typical rpm Setting rpm

Calculation Calculated Equation Water Work from Volume Input this mL Joules/min Paper

Calculated Calculated Work Energy Input Level Joules/ Joules Lmin

Calculated Energy Level Joules/L

Energy Dissipation (U and V sum)

PIV Data Turbulence Total Turbulence Turbulence % Joules % %

Apparatus

Use

Swirling Flask

Dispersant screening

moving table

150

120

0.35

10, 12

3.50E-05

2.9

2.92E-04

6.50E-04

360

1.40E- 105 04

Septum Flask

Dispersant screening

moving table

150

120

0.17

10,12

3.50E-05

1.4

2.92E-04

5.67E-04

781

1.00E- 70 04

Standard Beaker

Various

moving table

150

400

1.2

10,12

1.20E-04

3

3.00E-04

Emulsion Unit

Emulsion formation

end-over-end rotation

50

600

22.8

10, 12

0.05

38

8.33E-02

Labofina Unit

Dispersant screening

end-over-end rotation

50

250

4.56

10, 12

0.01

18.2

4.00E-02

High Energy Unit

Dispersant physics

moving table

100e250 150 average

5000

294

10, 12

8.22E-03

58.8

1.64E-03

Tank

Large-scale testing

agitator

120 240 480

300000 33 300000 66 300000 132

14 14 14

0.28 1.1 4.5

0.11 0.22 0.44

9.33E-04 3.67E-03 1.50E-02

90

8.22E-03 1.23E-02 1.77E-02

376 467 322

90

80

5.90E- 40 02 5 2.00E- 38 01 6.00E01

(Continued )

TABLE 15.10 Work, Energy, and Turbulence Levels of Various Laboratory Apparatuses Compared to Calculated Sea Levelsdcont’d Adjusted for Volume /L

Apparatus

Use

Tank

Large-scale testing

Energy Application

Typical rpm Setting rpm

Calculation Calculated Equation Water Work from Volume Input this mL Joules/min Paper

Calculated Calculated Work Energy Input Level Joules/ Joules Lmin

Calculated Energy Level Joules/L

oscillating hoop

60 strokes

300000 18

0.9

3.00E-03

13

0.06

The following are approximations based on estimation equations given in reference 77-79 Wind Equivalent

comparison

over cubic metre of water

5 m/s 10 m/s 20 m/s 30 m/s 40 m/s

1000 1000 1000 1000 1000

1.2 4.9 20 44 78

5 5 5 5 5

0 0 0 0 0.01

1.2 4.9 20 44 78

1.00E-04 2.00E-04 4.00E-04 1.60E-03 6.40E-03

Wave Height Equivalent

comparison

per metres wave height

0.5 1 2 3 4

1000 1000 1000 1000 1000

1.2 4.9 20 44 78

7 7 7 7 7

0 0 0 0 0.01

1.2 4.9 20 44 78

1.00E-04 2.00E-04 4.00E-04 1.60E-03 6.40E-03

Experimental Dual Probe

Energy Dissipation (U and V sum)

Near Surface Energy by Single Thermal Probe

PIV Data Turbulence Total Turbulence Turbulence % Joules % %

509

Chapter | 15 Oil Spill Dispersants: A Technical Summary

1.0

Regression Coefficient

0.8

disperses

0.6 0.4 0.2 0.0 -0.2

hinders dispersion

-0.4 -0.6 -0.8

12

14

16

18

20

22

24

26

Carbon Number FIGURE 15.12 Diagram of the effectiveness values for specific hydrocarbons.

composition revealed that the most important factor was the amount of saturates in the oil.184 It was also found that the effectiveness of dispersants decreases with increasing amounts of resins and asphaltenes in the oil. Furthermore, it was found that effectiveness could be predicted using a simple model of saturates, less the other components of the oil, including resins, asphaltenes, and aromatics. In the past decade more precise laboratory effectiveness data and compositional data have enabled correlation with higher precision. Thirteen models for the prediction of chemical dispersibility have been developed.185,186 The models range widely in terms of input parameters and statistical quality. These models can be used to predict the chemical dispersibility of oils, given the required input parameters. Table 15.11 shows the models, statistics on the fits, and parameters used to predict effectiveness. The development of these models reveals essentials of chemical dispersion.185 The results show that small n-alkanes are prone to dispersion and that this ends at about C20. Hydrocarbons as large as C26 resist dispersion, as is illustrated in Figure 15.12 in which the regression coefficients (R2) or the correlation with effectiveness are plotted against the n-alkane carbon number. It can be seen that there is a steady progression downward beginning at C12 and crossing 0 at about the C20 carbon number. The aromatic component may show a similar tendency, but sufficient data were not available to provide details. The naphthalene component showed a high regression coefficient (R2 ¼ 0.76), and the total PAHs were relatively high (R2 ¼ 0.67). This indicates that the larger PAHs are relatively indispersible and that the smaller ones (naphthalenes) are highly dispersible.

510

TABLE 15.11 Models to Predict Effectiveness Using Oil Composition Parameters Variable Variable

Variable

Variable

Variable Variable

Number Description

Variables

R2

1

2

3

4

5

1

High correlators only

5

0.98

lnC12 -3.19

Napthalene PAH2 0 -7.62

c12-c182 0.01

BP<250 0.79

-11.1

parameter value

2

Best plus boiling point

6

0.98

lnC12 -2.75

Napthalene 1/C26 0 0.11

PAH2 -7.48

c12-c182 BP<250 0.01 0.76

-10.65

parameter value

3

Best plus viscosity

6

0.94

lnC12 -1.29

Napthalene 1/C26 0 -0.02

PAH2 -8.65

c12-c182 1/viscos 0.01 100

-2.93

parameter value

4

Two-way density and viscosity

2

0.71

Model Z ¼ a þ be-density þ c/viscosity0.5

5

Two-way density and BP<250

2

0.7

-7.78

parameter value

Number of

c ¼ 60

5

0.68

c ¼ 0.0787 ½

Saturates Aromatics 0.32 3.44

lnResins -4.32

lnAsphaltenes 1/viscos -1.81 58.9

Treating Agents

Groups plus viscosity

8

Model Z ¼ a þb/density1.5 þ cBP1.5

a ¼ -68.8 b ¼ 67.4 6

Variable Variable Constant 7

PART | VI

a ¼ -77.6 b ¼ 214

6

Groups plus low HC

5

0.95

Saturates Aromatics½ lnResins -18.2 -33.6 -1.86

lnAsphaltenes c12-c182 -9.03 0.01

296

parameter value

8

Groups plus VOCs

5

0.71

Saturates Aromatics½ lnResins -0.03 -2.24 -12.2

lnAsphaltenes VOCs -4.87 0

73.4

parameter value

9

Groups alone

4

0.57

Saturates Aromatics½ lnResins -0.1 -0.68 -13.3

lnAsphaltenes -4.38

62.7

parameter value

10

Composition components

13

1

Saturates Aromatics½ lnResins -15.4 -42.6 -2.25

lnAsphaltenes VOCs -14 0

C16-17

1/C26 0.82

Napthalene 0

PAH2 0

Saturates -7.09

Aromatics½ -72.6

lnResins -69.7

lnAsphaltenes -11.6

lnC12 11.4

lnC14 2.8

1/C26 0.3

Napthalene 0

11

Smallest complete set

14

1

C18 8.87

1/density 1/viscos 855 -250 BP<250 4.96

c12-c182 -0.02

12

Physical data less pp

4

0.71

1/density 1/viscos 90 22.9

BP<200 -0.44

BP<250 0.86

13

Physical data

5

0.69

1/density Pour point2 1/viscos 121 0 15.3

BP<200 -0.49

BP<250 0.73

c12-c182 0.07

368

lnC12 -1.71

lnC14 8.34

parameter value parameter value

VOCs 0

BP<200 -6.82

parameter value parameter value

-95.6

parameter value

-124

parameter value

Chapter | 15 Oil Spill Dispersants: A Technical Summary

7

511

512

PART | VI

Treating Agents

The development of the models shows that certain parameters are very good predictors of chemical dispersibility. These include the specific chemical composition indicators such as the n-alkane values of C12, C14, naphthalenes, and so on. The group composition indicators such as SARA are poor predictors. The physical properties are poor predictors of chemical dispersibility. Some properties have no or very little dispersibility prediction indication, and these include wax content, interfacial tension, and flash point.

15.6.3. Amount of Dispersant Although several workers have noted the decline in the amount of dispersion with decreasing dosages of dispersant, few have actually measured this decline.161,187 The relationship of the amount of dispersion that occurs and the dosage of dispersant used as conducted in a series of laboratory experiments are shown in Figure 15.13, taken from older data.161 The dosage is given as the ratio of dispersant to oil, 1/x where x is the amount of dispersant relative to one volume of oil. Thus 1/5 represents a dosage of 1/5 the volume of dispersant versus the volume of oil or a ratio of 1:5 dispersant:oil. These results are typical in that they show an exponential decline in effectiveness with dispersant amount.

15.6.4. Temperature Several workers have reported that dispersant effectiveness declines with temperature.71,161,188 Some have suggested, however, that it is difficult to distinguish between the effect of viscosity and other factors and the effect of 100 COREXIT CRX-8 COREXIT 9527 ENERSPERSE 700 EXPERIMENTAL A EXPERIMENTAL B EXPERIMENTAL C

Effectiveness %

80

60

40

20

0 0

10

20

30

40

Ratio of Dispersant to Oil 1/x

50

FIGURE 15.13 Effect of the amount of dispersant.

513

Chapter | 15 Oil Spill Dispersants: A Technical Summary

40

EFFECTIVENESS %

30

20

10

0 0

10

20

30

40

50

TEMPERATURE IN CELCIUS FIGURE 15.14 Effect of temperature.

temperature. A typical decline in effectiveness with temperature is shown in Figure 15.14.161

15.6.5. Salinity Several workers have noted that conventional dispersants did not function well in waters of low salinity. In earlier studies Belk and coworkers found that effectiveness decreases as salinity decreases and that effectiveness is minimal in absolute fresh water.189 One freshwater dispersant showed limited effectiveness in “hard” water with a high ionic content. Brandvik and coworkers tested the effectiveness of dispersants at both low temperature and low salinity conditions and found that most dispersants dropped by as much as a factor of 100 and typically about 1/5 in going from the salinity of 33 to 5%.188 Both series of tests were conducted at 0 C. It was concluded that new formulations of dispersants would have to be developed for use in the Arctic because of both the lower temperatures and salinities of Arctic waters. Similarly, Erkisson and Moet and coworkers tested dispersants in a modified Warren Springs apparatus and found that effectiveness decreased sharply with time (settling time) and temperature, and decreased somewhat when oil was weathered.190,191 Most

514

PART | VI

60 COREXIT 9527

Treating Agents

FIGURE 15.15 Traditional effect of salinity.

ENERSPERSE 700

EFFECTIVENESS %

50

40

30

20

10

0 0

10 20 30 40 50 60 70 80 90 100 110

SALINITY o/oo

authors found that effectiveness declined sharply with salinity similar to that shown in Figure 15.15.161 In more recent times, the effectiveness of dispersion at different temperatures and salinity has been measured using various tests. It has been found that there is a joint effect between temperature and salinity. Blondina et al. measured the effectiveness of dispersing Prudhoe Bay crude at 20 C and 20% as 23% for Corexit 9500 and 13% for Corexit 9527, using the EPA swirling flask method.192,193 The results also show that, for the same tests, the use of colorimetry as an analytical technique as much as doubled the apparent effectiveness. It was concluded that the chromatographic method showed less bias to oils as dependent on their compositions. These results are consistent with previously measured results, namely, that dispersant effectiveness is less with lower salinity. Blondina et al. also measured the effectiveness of the dispersants Corexit 9527 and Corexit 9500 on several oils.194 These researchers concluded that the interaction between the salinity of the receiving water and the ability of surfactant-based dispersants to enhance petroleum accommodation into the water column can be both oil- and dispersant-specific. They found that Corexit 9500 was more effective than Corexit 9527 on most oils at most salinities, but the opposite was true in some cases. Corexit 9500 maintained its effectiveness over a wider range of salinities. Blondina et al. concluded that decisions should

Chapter | 15 Oil Spill Dispersants: A Technical Summary

515

be made on a specific situation based on the oil, the dispersant, and the salinity of the receiving water.194 Moles et al. conducted a series of measurements on ANS oil at lower temperatures and lower salinity.195,196 For Corexit 9500 at a temperature of 10 C and 22%, the effectiveness was 8% for fresh ANS and 2% for weathered ANS. Under the same conditions, Corexit 9527 showed an effectiveness of 10% for the fresh ANS and 5% for the weathered ANS. The effectiveness of Corexit 9500 and Corexit 9527 was tested on ANS crude oil at various salinities and temperatures representative of conditions found in Southern Alaskan waters. The oil was weathered to different degrees. Tests were conducted in a swirling flask at temperatures of 3, 10, and 22 C with salinities of 22 and 32%. Analysis was by GC. The authors concluded that, at the common temperatures found in the estuaries and marine waters of Alaska, the dispersants were largely ineffective. They also found that there was an interactive effect between temperature and salinity. A high effectiveness for “emulsion,” an uncharacterized mixture of oil and water, was attributed to “osmotic shock” because of the difference in the salinity of the preparation (33%) and the test salinity. At the combinations of temperature and salinity such as might be typical for Alaska, dispersant effectiveness in the test was less than 10%. The results generally show the decrease in effectiveness with decreasing salinity. There may be a relationship between temperature, salinity, and effectiveness as shown in these data. The Moles data were tested for ability to form a consistent relationship between temperature and salinity. This test was carried out by correlating the three-dimensional factors of effectiveness, salinity, and temperature. The results show a high correlation for the fresh ANS and less so for the weathered and emulsified products. These results will be discussed in a later portion of this chapter. Fingas et al. studied the effect of resurfacing of dispersed oil.197 As part of this study, a series of standard tests were conducted with Alberta Sweet Mixed Blend (ASMB) and ANS crude oils and the dispersants Corexit 9527 and Corexit 9500. The same tendencies as Moles et al. (2001, 2002) found for ANS were found in this study, namely, that the effectiveness of Corexit 9500 with ANS increases as salinity increases and that of Corexit 9527 generally does as well, but this is variable. The effectiveness of Corexit 9527 appears to peak at a salinity of 25%. It is not yet known why ANS has shown this tendency in these studies. The ASMB and most other crudes show throughout this study that the effectiveness is Gaussian, with the peak in this case being about 20%. Sterling et al. studied the coalescence of dispersed oil droplets.29 Theoretical studies were conducted using DLVO theory, and kinetic studies were conducted using a laboratory apparatus. Sterling et al. came to the following conclusions: 1. For salinity and pH values found in natural waters, the z-potential values of chemical dispersed crude oil were slightly negative. The z-potential is

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PART | VI

Treating Agents

a measure of charge between particles and is relevant to dispersants in that a higher z-potential indicates a more stable particle and could imply a higher effectiveness. For a fixed pH value, z-potential values become marginally more negative with increased water salinity. Using DLVO theory, no significant electrostatic energy barrier to droplet coalescence was present. This implies that oil dispersions (including those with dispersants) are unstable over time. 2. Within the tested experimental conditions, the collision efficiency parameter, a (the probability of successful particleeparticle collision) was significantly greater than 0. This result suggests that coalescence kinetics were important in estimating dispersant efficiency in laboratory-scale protocols and may be important in coastal spills. The shear rate was the dominant parameter in estimating observed coalescence rates and dispersant efficiencies. This finding implies that the effectiveness is very dependent on shear rate, but that the resulting emulsions will also be unstable, and in fact coalescence occurs faster under some energetic conditions. 3. Salinity had a variable influence on effectiveness values measured in this study. Sterling et al. suggest that salinity has a strong overall effect and, thus, because salinity shows a lesser effect on coalescence, salinity must have a greater effect on initial droplet formation. Surfactants are the active ingredient in dispersants. Surfactants work to sustain oil droplets in the water by maintaining a portion of the molecule in the oil (lipophilic) and in the water (hydrophilic). The ratio of lipophilic to hydrophilic depends on the ionic strength of the water, which relates directly to the salinity. The hydrophilic portion of the surfactant is more soluble in water with a higher salinity. As salinity rises past a certain point, the surfactant becomes too soluble in the water and has a stronger tendency to partition to the water phase completely. Thus, in theory, the surfactant is more lipophilic in fresh water and increases in hydrophilicity as the salinity rises. The stability of the resulting droplets also depends on salinity due to the increasing ionic strength of the water as salinity rises. This increasing ionic strength results in greater molecular force. Again, as the salinity rises above a certain point, this point being dependent on the particular type of surfactant, this increased force results in more surfactant molecules leaving the oil drop entirely. There is a theoretical scale of HLB. This is calculated by the type of surfactant present. A surfactant with an HLB of 10 is a dispersant; that is, the force of the molecule is equally balanced between hydrophilic and lipophilic tendencies. A surfactant of much greater than 10 is said to form oil-in-water emulsions (dispersions), and one of much lower than 10 can promote the formation of water-in-oil emulsions. The HLB of a surfactant changes with salinity. A low salinity lowers the HLB and vice versa. Thus, it is theoretically possible to design a dispersant with surfactants for lower salinity waters. While this possibility exists, it should be noted that the stability of dispersions is less

517

Chapter | 15 Oil Spill Dispersants: A Technical Summary

in less saline waters. Furthermore, there are no recent measurements on freshwater dispersants, indicating that the industry has not pursued this avenue. Wrenn et al. tested several surfactants directly on fresh water but used only an optical estimation technique for effectiveness; thus the results cannot be compared directly to others noted here.198 However, it was found that lower HLB values (8 to 10) provided better dispersion in fresh water than higher HLBs. The only conclusion one could draw is that the current commercial dispersants would not be optimal for fresh water. Newer testing is marked by the use of chromatography for analysis and very strict protocols in operating the dispersant tests. These tests are marked by having standard deviations of less that 10% and often less than 5%. These are less than an order of magnitude of standard deviations in previous testing. The following are the conclusions of the authors of these newer studies. a) In waters with a salinity of 0%, most dispersants have a very low effectiveness or are sometimes even completely ineffective. b) Dispersant effectiveness peaks in water with a salinity from 20 to 40%. This may depend on the type of dispersant used. Corexit 9500 appears to be less sensitive to salinity, but still peaks at about 35%. Corexit 9527 is more sensitive to salinity and appears to peak at about 25% with some oils and at about 35% with others. c) There is a relatively smooth gradient of effectiveness with salinity both as the salinity rises to a peak point of effectiveness and as it exceeds this value. The curves for this salinity appear to be Gaussian, as shown by a typical curve in Figure 15.16. d) While there is some evidence for a temperatureesalinity interaction as noted in the data of Moles et al. (2002)196 there is not enough data to 18 16

Effectiveness %

14 12 10 8 6 4 2 0

10

20

30

40

50

60

Salinity o/oo FIGURE 15.16 Dispersant Effectiveness Data for Corexit 9527 and a Light Arabian Crude (Data from Moet et al., 1995).191

518

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make solid conclusions, so further studies were carried out. This joint relationship will be described in a following section. e) Recent data are almost exclusively measured using Corexit 9527 and Corexit 9500, and, since these have the same surfactant packages, there is a concern that the results may be more relevant to these formulations than to many other formulations. f) The values found in recent tests are much lower than the older tests, but the trends are the same. The general surfactant literature was reviewed for salinity effects on surfactants and surfactant phenomena.200 A body of literature exists on the use of surfactants for secondary oil recovery. There are several commonalities among the many findings. Recovery efficiency falls off at both high and low salinities. The salinity at which surfactant efficiency peaks is very dependent on the structure of the specific surfactant. Several studies on the interaction of specific hydrocarbons and surfactants were reviewed. The consensus of these papers is that the solubility of the hydrocarbon increases with increasing salinity and decreases at low salinities. The interfacial tension of water and oil changes with surfactant and salinity. The interfacial tension is higher at lower salinities. The optimal interfacial tension is generally achieved at salinities of between 25 and 35%. A number of physical systems involving surfactants and salinity changes are reported in the literature. Included in these works is the finding that the stability of microemulsions is greater at salinities of 25 to 35%. Some workers found that the stability of systems was very low in fresh water or waters of salinities of <10%. Similar effects were found with gels, polymer thickeners, and linkermolecule solubilization.200 Some field studies of dispersant application were conducted in the freshwater environment. While effectiveness was not specifically measured, both series of studies showed that effectiveness may have been low. In the one study, the investigators found that the surfactants had poor effectiveness and stability. In this particular case, the dispersion lasted only about an hour and the dispersion was limited to a few centimeters. In another case, it was noted that in the dispersed pond, there was oil around the edges within a short time of dispersant application. Effects were monitored in both cases, but could not be compared and were not compared to similar applications at sea. Some effects studies were conducted under varying salinity conditions. In one study, naphthalene and a,b napthol sulphate uptake were studied under different salinity conditions. There were no significant differences for different salinities, although naphthalene uptake was somewhat higher under low salinity conditions. Another study examined the induction of hsp60 protein in goldenbrown algae. It was found that greater salinity reduced the effects of the simulated oil spills to the algae.

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Dispersant No-Dispersant

Counts

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0

3

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27

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Particle Size (m) FIGURE 15.17 Particle size distribution of an oil dispersion.

15.6.6. Particle or Droplet Size In the past, researchers believed that dispersants created smaller droplets that were obviously more stable in the water column.72 Several researchers found that droplet sizes did not change with the amount of dispersion used, but that more dispersant simply created a larger amount of droplets of relatively the same size.71,161,200 A typical distribution of droplet sizes, with and without the use of dispersant, is shown in Figure 15.17, which is adapted from Lunel.70 Extensive droplet size measurement in the laboratory using various instruments notes that most oils yield a volume mean diameter (VMD) of 18 mm.30,161 Mukherjee and Wrenn proposed a model that relates effectiveness and droplet size.201 A recent work shows that the droplet size is very crucial to the half-life of dispersion at sea.30

15.7. TOXICITY An important issue that arises when we discuss dispersants is toxicity, both of the dispersant itself and of the dispersed oil droplets. Acute toxicity became an important issue in the late 1960s and early 1970s when application of toxic products resulted in substantial loss of sea life. For example, the use of dispersants during the Torrey Canyon episode in Great Britain in 1968 caused massive damage to intertidal and subtidal life.8 Since that time, dispersants have been formulated with less aquatic toxicity. The issue may not be the toxicity of the dispersant itself but the large increase in the oil droplets in the water and the large increase in PAHs in the water column as a result of dispersant use. A standard toxicity test is to measure the acute toxicity to a standard species such as the rainbow trout. The LC50 of a substance is the Lethal Concentration to 50% of a test population, usually given in mg/L, which is approximately equivalent to parts per million. The specification is also given with a time period, which is often 96 hours for larger test organisms such as fish. The smaller the LC50

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number, the more toxic the product. The toxicity of dispersants used in the early 1970s ranged from about 5 to 50 mg/L measured as an LC50 to the rainbow trout over 96 hours. Dispersants available today vary from 200 to 500 mg/L (LC50) in toxicity and contain a mixture of surfactants and a less toxic solvent. Today, the oil itself is more toxic than the dispersants, with the LC50 of diesel and light crude oil typically ranging from 20 to 50 mg/L, for either chemically or naturally dispersed oil. The natural or chemical dispersion of oil in shallow waters can result in a mixture that is toxic to sea life. For example, a spill in 1996 from the North Cape in a shallow bay on the Atlantic coast caused massive loss of benthic life without the use of dispersants.202 Another significant factor in terms of the impact of this spill was the proximity to shore, which caused a high concentration of hydrocarbons in the water. Similar toxicity could also result if dispersants were applied close to shore. Dispersant acute toxicity was reviewed extensively in terms of toxicity, particularly in an earlier review by the National Academy of Sciences published in 1989.12 The data and references will not be repeated here because many of the toxicity and analytical techniques have been improved and the data is changing. The major issues have changed since this 1989 review was published. First, the concern over the exposure regimes has subsided. In the last decade, concern was voiced that the time-dose applied to test organisms was not relevant to the regime that the same organisms would be exposed to in an actual dispersant application. New methods for testing aquatic toxicity have enabled more realistic dosing. Furthermore, many of the methods used in the past were questionable. Toxicity testing is more accurate today due to new analytical techniques. Results of older aquatic toxicity studies of the ubiquitous dispersant Corexit 9527, produced by Exxon, show that the 96-hour acute toxicity to many fish averages 100 mg/L (approximately equivalent to parts per million) and approximately 10 mg/L to more sensitive life forms.12 Many of these results are obtained from screening tests, which are aquatic toxicity tests designed to determine whether a dispersant meets minimum acceptability criteria. Since the 1989 NAS study, several researchers have studied the aquatic toxicity of oil, dispersants, and dispersed oil. Some of the older studies are summarized here and the studies are presented in the approximate order of the year of the first study summarized: Gulec and Holdway studied the toxicity of oil and the dispersant Corexit 9527 to the amphipod, Allorchestes compressa.203 They found that the mean acute 96-hour LC50 for A. compressa exposed to Corexit 9527 was 3 mg/L, for dispersed crude oil it was16.2 mg/L, and for the water-accommodated fraction of Bass Strait crude oil it was 311,000 mg/L. Sublethal effects were also measured for a 30-minute exposure. The EC50 (threshold for sublethal effects) was found to be 50.2 mg/L for Corexit 9527, 64.4 mg/L for Corexit 9527, 65.4 mg/L for dispersed crude oil, and 190,000 mg/L for the water-accommodated fraction of Bass Strait crude oil.

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Singer and coworkers also found that the dispersed fraction was more toxic than the oil or dispersant alone.204-206 This group tested the toxicity of Prudhoe Bay oil and Corexit 9527 to red abalone (Halliotis rufescens), a kelp forest mysid (Holesimysis costata), and the topsmelt (Atherinops affinis). The dispersed oil showed much higher toxicological responses; in fact, no responses were noted with the water-accommodated fraction (WAF) itself. The toxicity of the dispersant and dispersed oil ranged from 28.6 to 74.7 mg/L, for the mysid, 10.5 to 16.8 mg/L for the topsmelt, and 17.8 to 32.7 mg/L for the abalone. Similarly, Midlaugh and Whiting reported on tests to embryonic inland silversides, Menidia beryllina.207 Effects were ranked in terms of toxicity observed at the percentage of the No. 2 fuel oil WAFs, with and without Corexit 7664 and Corexit 9527. Dispersants were also tested alone. Embryos exposed to the No. 2 fuel oil in 20% salinity water showed responses only at the 100% WAF concentration. Corexit 7664 alone elicited response at 10% WAF, and when combined with fuel oil at 1% WAF. Corexit 9527 and fuel oil elicited responses at 10% WAF. The acute toxicity of physically and chemically dispersed crude oil to the estuarine mysid, Mysidopsis bahia, and the kelp forest mysid, Holesimysis costata, was evaluated in continuous and spiked exposure conditions.208 The continuous exposure LC50 for M. bahia was about 0.65 mg/L for chemically dispersed oil and was similar for the physically dispersed oil. Continuous exposure LC50 for H. costata was 0.17 mg/L for the chemically dispersed oil and 0.10 mg/L for the physically dispersed oil. No toxicity for physically dispersed oil was observed for either species in the spiked-exposure tests, but the chemically dispersed oil showed a toxicity of 13 to 25 mg/L for M. bahia and 1 to 5 mg/L for H. costata. It was concluded that only spiked-exposure tests should be used because this is the type of exposure occurring during oil spills and dispersant usage. Fucik and coworkers tested the toxicity of dispersant and oil (Western and Central Gulf oils) and dispersant (Corexit 9527) to several indigenous species from the Gulf of Mexico.209 The 96-hour LC50 of oil alone to shrimp (both Penaeus aztecus and Penaeus setiferus) was around 12 mg/L and of oil, and dispersant was from 14 to 15 mg/L. The LC50 of dispersant alone for the blue crab (Callinectes sapidus) ranged from 78 to 80 mg/L, and for dispersant and oil it was 20 to 91 mg/L. The LC50 of dispersant alone for the eastern oyster (Crassostrea virginica) was 5 mg/L, and for dispersant and oil, 4 to 11 mg/L. The LC50 of dispersant alone for inland silverside larvae (Menidia beryllina) ranged from 43 to 47 mg/L, and for dispersant and oil it was 59 to 100 mg/L. The LC50 of dispersant alone for inland silverside embryos (Menidia beryllina) was over 100 mg/L and the same for dispersant and oil. The LC50 of dispersant alone for Atlantic menhaden (Brevoortia tyrannus) was 42 mg/L, and for dispersant and oil it was 22 to 65 mg/L. The LC50 of dispersant alone for the Spot (Leiostomus xanthurus) was 27 mg/L, and for dispersant and oil, 50 to 68 mg/L. The LC50 of dispersant alone for the red drum (Sciaenops

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ocellatus) ranged from 52 to over 100 mg/L, and for dispersant and oil, over 100 mg/L. Burridge and Shir evaluated the toxicity of oil and dispersants to marine algae.210 They found that sometimes germination was enhanced and sometimes there was little effect, depending on dispersant/oil combinations. The 48-hour EC50 for dispersant alone was 10,500 mL/L in the case of Corexit 7664, 27,000 mL/L for Corexit 8667, 0.7 mL/L for Corexit 9500, and 30 mL/L for Corexit 9527. The EC50 for the dispersant/oil mixture (Bass Strait crude) was 130 mL/L for the crude alone, 4,000 mL/L for Corexit 7664, 2,500 mL/L for Corexit 8667, 20 mL/L for Corexit 9500, and 200 mL/L for Corexit 9527. Wolfe et al. studied dispersants to a primary producer, algae, Isochrysis galbana, and a primary consumer, a rotifer, Brachionus plicatilis.211 Results showed that the uptake of naphthalene increased significantly in the presence of dispersant in algae and also in the rotifer via trophic transfer. Unsal studied aquatic toxicity to the prawn, Palaemon elegans, and found the 24-hour LC50 for oil alone (Turkish crude) was 83.5 mL/L, for dispersant (Spillwash) 0.0112 mL/L, and for the oil dispersant mixture 1.1 mL/L.212 Some researchers studied the effects of dispersants on whole ecosystems and not on individual species.213,214 The ASTM guides on dispersants are prepared for whole systems.66-68 The advantages of this approach are that often users think in terms of their ecosystem as a whole and also because of the many links between trophic levels in a given ecosystem. The disadvantages are that studies may not be applicable to other ecosystems and certain important species may not be studied in a given system, simply because they were not considered. Several researchers studied tropical ecosystems focusing on corals, sea grasses, and mangroves.214-217 Knap, Ballou, and coworkers reviewed the fate and effects of oil on tropical ecosystems. It was noted that different researchers found different effects of oil and dispersants together and oil alone. Some found that oil and dispersed oil had severe and irreversible effects on coral systems, and others found exactly the opposite. The application of dispersants to a tropical ecosystem was studied by applying oil to separate areas containing sea grass, mangrove, and coral habitats. One site was treated with a dispersant, Corexit 9527, and the sites were monitored over a 2-year period. It was found that in the short term, the chemically dispersed oil caused the number of invertebrates, including corals, to decline, but the effects disappeared over the long term. Fresh, untreated oil had several long-term effects on the survival of the mangrove and associated fauna, but only minor effects on sea grasses, corals, and associated organisms. Updates to some of these studies will be given later in this chapter. Thorhaug and coworkers tested the toxicity of dispersants to corals, mangrove, sea grasses, and selected Jamaican fish species.218,219 It was found that the mortality of mangroves exposed for 10 hours to 1250 ppm of dispersed oil varied from 0 to 80%, with 20% being a typical value. The other species were exposed to 125 ppm of dispersed oil for 6 hours. Mortality for the fish ranged from 0 to 100%, with 100% being the most typical value. The corals and

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sea grasses showed similar mortality trends at the same concentrations. When the fate and effects of dispersants and oil were studied in a freshwater lake, it was found that dispersants reduced the overall impact of the oil by reducing the adhesion of the oil to grasses and reeds around the lake.220 The effects of oil, dispersant and oil, and dispersant were examined at a salt marsh in Nova Scotia.221 After 4 years, it was concluded that the effects of the oil ranged from minimal but persistently negative in the creek-edge and highmarsh zones to negative but short-lived in the mid-marsh zone. The effects of the dispersant ranged from slightly positive in the creek-edge to acutely negative but short-lived in the mid- and high-marshes. The effects of the oil and dispersant together ranged from slightly positive in the creek-edge to slightly negative in the mid- and high-marsh zones. In a project carried out in an intertidal zone in Maine, oil was released into a cove, and its fate was monitored over a 2-year period.212,223 It was concluded that the dispersed oil had less impact than undispersed oil. A major project to evaluate the fate, effects of, and countermeasures for dealing with oil spilled in the Arctic was conducted over several years beginning in 1980.223 Dispersants were applied in one bay, and the fate of the oil and effects on the ecosystem were monitored for several years. The dispersed oil narcotized benthic life in the first day, although within one week, the bay recovered. The oil was deposited in sediment to a degree, but was largely carried away, and traces could be found in sediment up to 2 km away, the furthest extent of sampling. The fate of oil in this bay was compared to that of an adjacent bay in which the same amount of oil was released and recovered to some extent with skimmers and the remainder left. The remaining oil also diminished with time and had little impact. Another group of researchers assessed the use of dispersants in cold water in a large outdoor test vessel.224 Several series of tests were conducted using Forties crude oil and a dispersant composed of Brij 92 and Brij 96 in salt water at e1.6 C. The effectiveness of the dispersant was greatly reduced compared to when used in warmer water. The biodegradation of the dispersant-treated oil was reduced compared to that of the control, and the population of heterotrophs initially decreased in all tanks, but soon recovered. The 2006 U.S. National Academy of Sciences report on dispersants had many discussions on toxicity.1 The report states several times that there is insufficient understanding of the fate of dispersed oil in aquatic systems, particularly interaction with sediment particles and subsequent effects on the biotic components. The relative importance of different routes of exposured that is, the uptake and associated toxicity of oil as dissolved components compared to oil droplets and as mineral particle-associated dropletsdis poorly understood. Many exposure models and studies do not consider these differences either. The new trends in ecotoxicology, that is, population and community-level approaches, are gaining wider acceptance in general and hopefully will be more accepted in the oil spill community in the future.

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The committee also summarizes testing procedures, noting that the standard short-term lethal toxicity test data, though abundant, may not be sufficient to assess the potential risk of dispersed oil.1 These short-term tests are also inadequate to assess potential delayed effects due to oil metabolism, bioaccumulation, and photoenhanced toxicity. Some protocols for producing dispersed and chemically dispersed oil are reviewed. Toxicity testing using common procedures varies the dose of the solution compared to an alternate procedure of diluting test procedures. The advantages of both common procedures are discussed. It is also noted that better exposure quantification is required, and testing should move away from “nominal doses” or simply calculating on the basis of added material. The difference in solubility of the materials can result in orders of magnitude errors when using nominal dosage methods. Better testing methods have used TPH or total petroleum hydrocarbon analysis. Advanced methods presently use and will continue to use quantification by classes such as alkanes, BTEX, and PAHs. Many studies have quantified as many as 50 PAHs in the toxicants. The 2006 committee noted that the 1989 dispersant report concluded that the acute lethal toxicity of chemically-dispersed oil is primarily associated with the dispersed oil and dissolved oil constituents. However, several studies are noted in which this conclusion is not valid and the conclusion should be reexamined. Sensitivity to dispersants and dispersants varies significantly by species and life stage. Embyronic and larval stages are more sensitive than adults to both dispersants and dispersed oil. Excellent tables of acute toxicity results are given in this chapter in which these conclusions are shown. In addition to acute toxicity, dispersant may have more subtle effects that influence health of organisms. As an example, dispersants have been reported to affect the uptake of oil constituents. It should be noted, that there is a dearth of longer-term studies on the toxicity of dispersants themselves. The toxicity of dispersed oil has been examined in a number of studies, as summarized by the NAS.1 Because oil consists of many classes of compounds and hundreds of individual compounds, aquatic organisms are potentially exposed to many toxicants with different modes of action and via different exposure routes. The actual toxicity of dispersed oil in the environment depends on many factors: effectiveness of the dispersion, mixing energy, oil type, weathering of the oil, dispersant type, temperature, salinity, exposure duration, and light penetration into the water column. In actual practice, some weathering (several hours) would occur after the spill, resulting in the loss of many volatiles and enriching the oil in PAHs. PAH toxicity is primal; however, several studies have noted that other components in the oil account for much of the toxicity as well. For some organisms, dispersed droplets are also an important route of exposure, either through droplet/gill interactions or through ingestion. Studies show that some organisms accumulate PAHs differently via particulate or dissolved routes. Organisms may also be exposed to oil by contamination of their food. Many oil constituents, such as the monoaromatics

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and PAHs, are narcoticsdthat is, substances that cause a state of arrested activity of protoplasmic structures. Several laboratory studies as summarized by NAS indicate that PAH toxicity increases (from about 12 to about 50,000 times) in exposures conducted with UV light present as it would be in nature in shallow waters.1 Photoenhanced toxicity consists of two mechanisms, but the most important one is photosensitization. This occurs when a PAH absorbs energy from the light and then transfers it to dissolved oxygen. The result is enhanced toxicity to many organisms. The literature reviewed up to the committee’s period of writing indicated that there was no consensus on the relative toxicities of chemically and physically dispersed oil.1 Many studies found that the PAH concentration is much higher in chemically dispersed oil than for physically dispersed oil. Several researchers have recently noted higher toxicities of chemically dispersed oil. Some studies have also found that the PAH bioaccumulation kinetics are increased in chemical dispersions. Depuration rates either increased or decreased, depending on the organism. A useful table of chemically dispersed and physically dispersed toxicity is given in the report. The NAS comments on fresh water as well,1 stating that the amount of literature related to effects on freshwater organisms is low. This is attributed to the fact that most common U.S. dispersants have low freshwater efficacy and the use of dispersants in fresh water is unlikely since most water bodies provide a source of drinking water. Little is known about the effects of dispersant or dispersed oil on wildlife. The report speculates that while chemical dispersants may lower the amount of oil to which a bird or an aquatic mammal is exposed, potentially there may be a loss of insulation through reduction of surface tension at the feather/furewater interface. Since this is a very important factor, more research on this aspect is needed. Toxicity issues related to microbes have not been well studied and may be confounded by a number of side phenomena, some of which are described in the report.1 Coral reefs have been found to be very sensitive to oil or dispersants because the tissue over the skeleton is very thin and because oil droplets adhere to the surface of the organism. The committee makes a number of recommendations for further studies, notably: quantify the weathering and fate of chemically dispersed oil compared to undispersed oil; obtain data on dissolve-phase PAH and particulate/oil-droplet phase PAH concentrations in test tanks or ideally, at spills-of-opportunity; assess the ability of fur and feathers to maintain water repellency under dispersed oil exposure conditions; and conduct a series of focused toxicity studies to provide data on photoenhanced toxicity, estimate the contributions of dissolved and particulate oil phases to toxicity, and expand toxicity tests to include delayed effects.1Of particular concern is the actual toxicity of the dispersed oild compared to physically dispersed oil. Several current studies and peer-reviewed examples of this are as follows.

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A study of benzo(a)pyrene type (BaP) and naphthalene-type metabolite elimination in Australian bass after exposure to Bass Strait crude oil and chemically dispersed crude oil was carried out by Cohen and coworkers.225 Chemically dispersing the crude oil resulted in five times higher concentrations of TPH in the water column, compared to the water-soluble fractions alone. There was only a slightly higher amount of the PAH bilary metabolic concentrations after four days in the dispersed samples. This difference disappeared after 12 days depuration, and the oil-only had very slightly higher levels. This slight difference was attributed to the fact that the dispersed crude increased metabolic activity and caused a higher degree of sublethal stress. Cohen et al. again studied Australian bass exposure to the water-accommodated fractions of Bass Strait crude oil or dispersed crude oil to assess the sublethal effects of oil spill remediation techniques on fish.226 Fish were exposed to these treatments for 16 days either through the water column or through a preexposed diet of an amphipod. Fish gills, liver, and white muscle were sampled, and cytochrome C oxidase and lactate dehydrogenase activities were quantified. In all treatments of fish exposed by way of the water column, aerobic activity increased in the gills, whereas a decrease of this enzymic activity was observed in the liver and white muscle. Exposures by way of the food pathway indicated similar trends. Anaerobic activity increased in the gills, liver, and white muscle after water-borne exposures. Stimulation in anaerobic activity also occurred in the liver and white muscle of fish after exposure to contaminated food. Oxidase activity in the gills was the most sensitive biomarker when monitoring waterborne exposures to petroleum hydrocarbons. In the gills, the dispersed oil treatment resulted in the most pronounced biological response, suggesting that in the short term the use of dispersants on an oil slick might cause the most perturbations to fish metabolism. Couillard et al. exposed newly hatched mummichog in a 96-h static renewal assay to water-accommodated fractions of dispersed crude oil (DWAF)(dispersed water-accommodated fraction) or crude oil WAF to evaluate if dispersant-induced changes in aqueous concentrations of PAHs affected larval survival, body length, or ethoxyresorufin-O-deethylase (EROD) activity.227 Weathered Mesa light crude oil and filtered seawater with or without the addition of Corexit 9500 were used to prepare DWAF and WAF, respectively. At 0.2 g/L, the addition of dispersant caused a two- and fivefold increase in the concentrations of total PAH and high-molecular-weight PAH (HMWPAH) with three or more benzene rings. The highest mortality rates (89%) were observed in larvae exposed to DWAF. A reduction in body length was correlated with increased levels of SPAH and not with HMWPAH. The EROD activity increased linearly with HMWPAH and not with SPAH. Chemical dispersion increased both the SPAH concentrations and the proportion of HMWPAH in WAF. Dispersed HMWPAH were bioavailable, as indicated by a significantly increased EROD activity in exposed mummichog larvae.

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Fuller et al. evaluated the relative toxicity of oil, dispersant, or both substances, on both a continuous and a declining concentration over time.228 Two fish species and a shrimp, were used. Microbial toxicity was evaluated using Microtox. The results suggested that the oil and dispersant mixtures had about the same or less toxicity than the oil mixtures alone. The continuous exposures yielded more toxicity than the declining exposure conditions. Unweathered oil fractions were more toxic than the weathered fractions of the same oil. Toxicity appeared to be largely a result of the soluble oil components. Georgiades et al. examined exposure to oil-derived products and results from countermeasures on the behavior and physiology of the Australian 11armed asteroid. Asteroids were exposed to dilutions of WAF of Bass Strait stabilized crude oil, dispersed oil, or burnt oil for 4 days, and prey localization behavior was examined immediately after exposure, as well as following 2, 7, and 14 days depuration in clean seawater. 229 The prey localization behavior of asteroids exposed to WAF and dispersed oil was significantly affected, though recovery was apparent following 7 and 14 days depuration, respectively. Behavioral impacts were correlated with the total petroleum hydrocarbon concentrations (C6eC36) in each exposure solution, WAF (1.8 mg /L), dispersed oil (3.5 mg/L), and burnt oil (1.14 mg/L), respectively. The total microsomal cytochrome P450 content was significantly lower in asteroids exposed to dispersed oil than in any other asteroids, while asteroid alkaline phosphatase activity was not significantly affected. Khan and Payne studied the influence of dispersant, Corexit 9527, and dispersed oil on mature members of Capelin, Atlantic Cod, Longhorn Sculpin, and Cunner. Exposure was for 96 hours.230 The acute studies showed that mortality was greater in both cod and sculpin exposed to dispersant-WAF mixtures than for any other group. Both the dispersant and the WAF also caused mortality in the cod, but not to the cunner. Examination of gill lesions in the same species showed that epithelial separation and rupture of the secondary lamellae of the gills were observed in fish following exposure to any of the three challenges. The percentage of gill lesions was generally greater with the dispersed oil. The authors note that the increase in gill lesions was probably a result of dispersant-enhanced toxicity. Koyama and Kakuno studied the toxicity of three dispersants and heavy fuel oil to a marine fish, red sea bream.231 The mean lethal oil concentration of the water-accommodated oil fraction was 325 mg/L. Mixtures of oil and dispersant were more toxic than dispersant or oil alone. Use of a dispersant-to-oil percentage of 20%, which is recommended by the manufacturer because of its efficiency in oil emulsification and dispersion, yielded higher 24-h oil concentrations and resulted in a higher mortality rate than did the use of higher percentages of dispersant. Liu et al. conducted a field investigation on a Louisiana Spartina shoreline to evaluate the toxic effects of crude oil (ANS crude oil) and dispersed oil

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(ANS þ dispersant Corexit 9500) on three aquatic species indigenous to the Gulf of Mexico: Gulf killifish, Eastern oyster, and white shrimp.232 Results indicated that total hydrocarbon concentration value in oiled treatments decreased rapidly in 3 h and was below 1 ppm at 24 h after initial treatment. Corexit 9500 facilitated more ANS fractions to dissolve and disperse into the water column. The shrimp showed short-term sensitivity to the ANS and ANSC þ 9500 at 30 ppm. However, most test organisms of each species survived well after 24-h exposure to the treatments. Laboratory tests conducted concurrent with the field investigation indicated that concentrations of crude oil higher than 30 ppm were required for any significant toxic effect on the juvenile organisms tested. Long and Holdway investigated the effects of acute exposure to crude and dispersed crude oil and a reference toxicant on recently hatched octopus.233 The water-accommodated fraction (WAF) of Bass Strait crude oil was prepared using a ratio of one part crude oil to nine parts filtered seawater and mixing for 23 h. Dispersed-WAF was prepared using a ratio of one part Corexit 9527 to 50 parts crude oil and an oil to water ratio of 1:9 and mixing for 23 h. The 48-h LC50 values were similar for WAF, dispersed-WAF, and the reference toxicant. Yoshida et al. studied the fate of PAHs with and without dispersants in 500 L tanks with seawater.234 Samples of water and particles were analyzed for 38 PAHs. Low-molecular-weight PAHs (with less than three rings) disappeared rapidly, generally within 2 days. High-molecular-weight PAHs (with more than four rings) remained in the water column for longer times, up to 9 days. Significant portions (10 to 94%) of the high-molecular-weight PAHs settled to the bottom and were caught in the sediment trap. The addition of chemical dispersant accelerated the biodegradation of PAHs but amplified the amount of PAHs found in the water column. The water column enrichment factor caused by dispersants was up to 6 times. The increased PAHs appeared to overwhelm the biodegradation, and thus higher concentrations were observed in the dispersanttreated tanks throughout the experiment. The dispersant appeared to reduce the amount of heavy PAHs sedimented and put these into the water column. Ramachandran et al. conducted an experiment to measure whether oil dispersion increases or decreases the exposure of aquatic species to the toxic components of oil.235-237 To evaluate whether fish would be exposed to more polycyclic aromatic hydrocarbons (PAHs) in dispersed oil relative to equivalent amounts of the water-accommodated fraction (WAF), measurements were made of CYP1A induction in trout exposed to the dispersant, Corexit 9500, WAFs, and the chemically enhanced WAF (CEWAF) of three crude oils. The crude oils comprised the higher viscosity Mesa and Terra Nova and the less viscous Scotian Light. Total petroleum hydrocarbon and PAH concentrations in the test media were determined to relate the observed CYP1A induction in trout to dissolved fractions of the crude oil. CYP1A induction was 6:1,100-fold higher in CEWAF treatments than in WAF treatments, with Terra Nova having the greatest increase, followed by Mesa and Scotian Light. Mesa had the

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highest induction potential with the lowest EC50 values for both WAF and CEWAF. The dispersant Corexit was not an inducer, and it did not appear to affect the permeability of the gill surface to known inducers such as bnapthoflavone. These experiments suggest that the use of oil dispersants will increase the exposure of fish to hydrocarbons in crude oil. Mielbrecht et al. investigated the influence of a chemical dispersant on the uptake, biotransformation, and depuration of a model hydrocarbon, [14C]phenanthrene ([14C]PHN), by larval topsmelt.238 Exposure was via aqueousonly or combined dietary and aqueous routes from a WAF of Prudhoe Bay Crude Oil or a WAF of Corexit 9527-dispersed Prudhoe Bay Crude Oil (PBCO). Trophic transfer was measured by incorporating into exposure media both a rotifer, as food for the fish, and a phytoplankton, as food for the rotifers. Shortterm (~4 h) bioconcentration of PHN was significantly decreased in topsmelt when oil was treated with dispersant, but differences diminished after 12 hours. When trophic transfer was incorporated, PHN accumulation was initially delayed, but after 12 h it attained similar levels. Dispersant use also significantly decreased the proportion of biotransformed PHN (as 9-phenanthrylsulfate) produced by topsmelt. Chemical dispersant use in oil spill response may reduce short-term uptake but not long-term accumulation of hydrocarbons such as PHN in pelagic fish. Otitoloju evaluated the toxicities of a Nigerian crude oil, dispersants, Biosolve and OSD 9460, and their mixtures, based on ratios 9:1, 6:1 and 4:1 (v/v), against the juvenile stage of a prawn in laboratory bioassays.239,240 On the basis of the derived toxicity indices, crude oil with 96-h LC50 value of 0.28 ml/L was found to be about six times more toxic than the Biosolve dispersant (96-h LC50 1.9 ml/L) when acting alone against the prawn. Toxicity evaluations of the mixtures of crude oil and dispersant revealed that the effects of the crude oil/dispersant mixtures varied, depending largely on the proportion of addition of the mixture components. The interactions between mixture of crude oil and Biosolve dispersant at the test ratios of 9:1 and 4:1 were found to conform with the model of synergism, while the interactions between the mixture prepared based on ratio 6:1 conformed with the model of antagonism, based on the concentration addition model. Interactions between the dispersant OSD 9460 and the crude oil at test ratio 12:1, however, conformed to the model of antagonism, indicating that the mixture was less toxic than crude oil acting alone. Furthermore, the mixtures prepared based on ratios 9:1 and 6:1 were found to be less toxic than crude oil when acting singly against the prawn while the mixture prepared based on ratio 4:1 was found to have similar toxicity with crude oil when acting singly, based on the derived synergistic ratio values. Perkins et al. tested the toxicity of oil and dispersed oil to a cold-water species, Tanner crab larvae, and compared the result to two standard warmwater test species, the saltwater mysid and fish larvae.241 The method of reporting the exposure dose: loading rate, volatile organic analytes (VOA, C6eC9), TPHs (TPH C10eC36), or their summation, total hydrocarbon

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concentrations (THC C6eC36), would result in different conclusions. These differences were found to be important with the water-accommodated fraction in cold water, and significant when reporting the chemically enhanced wateraccommodated fraction, dispersed oil. The differences are chiefly due to the greater accommodation of VOA in the colder water. Ramachandran et al. studied the induction of cytochrome P-4501A (CYP1A) enzymes of fish to test the effect of salinity on PAH availability. Freshwater rainbow trout and euryhaline mummichog were exposed to water-accommodated fractions and chemically enhanced water accommodated fractions at 0%, 15%, and 30% salinity.237 For both species, PAH exposure decreased as salinity increased, whereas dispersant effectiveness decreased only at the highest salinity. Risks to fish of PAH from dispersed oil are concluded to be the greatest in coastal waters where salinities are low. The use of chemical oil dispersants causes a transient increase in hydrocarbon concentrations in water, which increases the risk to aquatic species if toxic components become more bioavailable. The risk of effects depends on the extent to which dispersants enhance the exposure to toxic components, such as PAHs. Increased salinities can reduce the solubility of PAH and the efficiency of oil dispersants. Shafir et al. employed a nubbin assay on more than 10,000 coral fragments to evaluate the short- and long-term impacts of dispersed oil fractions from six commercial dispersants, the dispersants and water-soluble-fractions of Egyptian crude oil, on two Indo Pacific branching coral species.242 Survivor status and growth of nubbins were recorded for up to 50 days following a single, short (24-hour) exposure to toxicants in various concentrations. Manufacturerrecommended dispersant concentrations proved to be highly toxic and resulted in mortality for all nubbins. The dispersed oil and the dispersants were significantly more toxic than crude oil WSFs. As corals are particularly susceptible to oil detergents and dispersed oil, the authors noted that the results of these assays rule out the use of any oil dispersant in coral reefs and in their vicinity. The ecotoxicological impacts of the various dispersants on the corals could be rated on a scale from the least to the most harmful agent, as follows: Slickgone > Petrotech > Inipol > Biorieco > Emulgal > Dispolen. Rowe et al. exposed snapping turtle (Chelydra serpentina) eggs to two concentrations of chemically or physically dispersed water-accommodated fractions of weathered Arabian light crude oil (0.5 to 10 g oil/L water).243 Test solutions were passed through nest substrate to simulate hydrocarbon alterations in composition during percolation to egg depth. Hatchlings were raised for 13 months, during which numerous measurements were taken. Prior to percolation, total PAH (the sum of 52 PAHs) in physically dispersed oil fractions was similar (43 to 67 mg/L). Following percolation, Total Petroleum Aromatic Hydrocarbons (tPAH) was also similar in physically dispersed fractions (14 to 24 mg/L). Addition of dispersant increased tPAH prior to percolation in the high treatment (302 mg/L) relative to low (13 mg/L), but percolation resulted in nearly equal concentrations in both treatments (High, 30;

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Low, 22 mg/L) due to physical trapping of dispersed oil by the nest substrate. In both chemically and physically dispersed fractions, percolation reduced lowmolecular-weight (MW) compounds such that embryos were exposed to primarily mid- to high-MW compounds. Total PAH in eggs differed 15-fold between the chemically-dispersed high and physically-dispersed high treatments (560 and 36 mg/kg, respectively), the former characterized by higher MW compounds than the latter. While eggs accumulated up to 560 mg/kg tPAH, there were no effects on hatching success or hatchling/juvenile traits. The results demonstrate that PAH profiles are altered during percolation, suggesting that experiments with subsurface organisms should be designed to account for compositional changes that occur as the solutions percolate through the substrate Jung and coworkers exposed the ovoviviparous rockfish, Sebastes schlegeli, to hydrocarbons in the water-accommodated fraction of crude oil, in the presence or absence of oil dispersants.244 Concentrations of CYP1A and levels of its catalytic activity ethoxyresorufin O-de-ethylase (EROD) in rockfish exposed to WAF at concentrations of 0.1% and 1% were significantly increased by the addition of a dispersant, Corexit 9500, after 48-h exposure. After 72-h exposure, the levels of CYP1A and EROD activity were significantly increased in 0.1% and 0.01% chemically enhanced WAF (CEWAF) (Corexit 9500 and Hiclean II dispersant). Bile samples from fish exposed to WAF alone had low concentrations of hydrocarbon metabolites, exemplified by 1-hydroxypyrene. After 72-h exposure, hydrocarbon metabolites in bile from fish exposed to WAF in the presence of either Corexit 9500 or Hiclean II were significantly higher compared with fish exposed to WAF alone or control fish. These experiments confirm that the use of oil dispersants will increase the exposure of ovoviviparous fish to hydrocarbons in oil. Schien and coworkers studied the bioavailability and chronic toxicity of hydrocarbons dissolved into water from floating diesel (WAF) and chemically dispersed diesel (chemically enhanced WAF) by measuring the extent of EROD induction in juvenile rainbow trout and by the severity of blue sac disease in embryos.245 The WAF of floating diesel was nontoxic to embryos at nominal concentrations up to 1 mg/L, causing only small weight changes. Chemical dispersion increased the bioavailability and toxicity of diesel to trout by 100fold. Diesel chemically enhanced water-accommodated fraction induced EROD activity, caused blue sac disease, and impaired development and growth of embryonic trout at nominal concentrations as low as 10 mg/L; 88% mortality occurred at 100 mg/L. Thus, dispersion of oil by any means increased the bioavailability and apparent toxicity of diesel to fish embryos without changing the toxicity of its components. Hannam and coworkers studied the impact of dispersed oil exposure on immune endpoints in the Arctic Scallop, Chlamys islandica, using a combination of cellular and humoral biological responses. Laboratory exposures of C. islandica to sublethal dispersed oil concentrations (0.06 and 0.25 mg L1) were conducted over 15 days, followed by a 7-day recovery period in clean seawater.

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Cellular endpoints were significantly altered following dispersed oil exposure: haemocyte counts and protein levels were significantly elevated, while cell membrane stability and phagocytosis demonstrated a significant reduction. While these results indicate alteration in the immune endpoints measured, this appears to be reversible upon removal of the contaminant stress. However, the impact of long-term continuous exposure and high-level acute exposure to oil is still unknown and may have consequences for disease resistance and survival.246 Of the recent toxicity studies, most researchers (about 90%) found that chemically dispersed oil was more toxic than physically dispersed oil. About half of these studies found that the cause for this finding was the increased PAHs (typically about 5 to 10 times) in the water column. Others noted the increased amount of total oil in the water column. Still others observed that dispersion simply increased the bioavailability. Two researchers described the damage to fish gills caused by the increased amount of droplets. Almost no researchers found that chemically dispersed oil was roughly equivalent to physically dispersed oil. Some studies depart from the traditional lethal aquatic toxicity assay, and some focus on the longer-term effects of short-term exposures. There is a need to leave the traditional lethal assays and use some of the newer tests for genotoxicity, endocrine disruption, and so on, as data for these types of studies is absent.

15.7.1. Toxicity of Dispersants Bhattacharyya et al. carried out toxicity studies in freshwater-marsh microcosms containing South Louisiana Crude (SLC) or diesel fuel and treated with a cleaner (Corexit 9580) or dispersant (Corexit 9500) using Chironomus tentans (benthic invertebrate), Daphnia pulex (water flea), and Oryzias latipes (fish).247 Bioassays used microcosm water or soil slurry taken 1, 7, 31, and 186 days after treatment. The crude was less toxic than diesel, chemical additives enhanced oil toxicity, the dispersant was more toxic than the cleaner, and toxicities were greatly reduced by day 186. Toxicities were higher in the bioassay with the benthic species (Chironomus) than in those with the two water-column species. Freshwater organisms, especially benthic invertebrates, thus appear seriously effected by the toxicants under the worst-case scenario in the test microcosms. Koyama and Kakuno studied the toxicity of three dispersants and heavy fuel oil to a marine fish, red sea bream.231 The 24-h LC50 of all three dispersants were at least 1,500 mg/L; these dispersants appeared to be relatively less toxic to marine fish than others studied in the past. Scarlett et al. compared the toxicity of the two dispersants, Corexit 9527 and Superdispersant-25 (SD-25), to a range of marine species representing different phyla occupying a wide range of niches: A marine sediment-dwelling amphipod, a mussel, the snakelocks anemone, and a sea grass.248 Organisms

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were exposed to static dispersant concentrations for 48 h, and median lethal concentration, median effect concentration, and lowest-observable-effect concentration (LOEC) values were obtained. The sublethal effects of 48-h exposures and the ability of species to recover after 72 h after exposure were quantified relative to the 48-hr endpoints. Results indicated that the anemone lethality test was the most sensitive with LOECs of 20 ppm, followed by mussel feeding rate, seagrass photosynthetic index, and amphipod lethality, with mussel lethality being the least sensitive with LOECs of 250 ppm for both dispersants. The results were consistent with the hypothesis that dispersants act physically and irreversibly on the respiratory organs and reversibly, depending on exposure time, on the nervous system. Superdispersant-25 was found overall to be less toxic than Corexit 9527, and its sublethal effects were more likely to be reversible following short-term exposure. The results of dispersant toxicity testing are similar to those found in previous yearsdnamely, that dispersants vary in their toxicity to various species. However, dispersant toxicity is typically less than the toxicity of dispersed oil, by whatever tests. There are no studies departing from the traditional lethal aquatic toxicity assay and none that focus on the longer-term effects of short-term exposures. There certainly is need for more of these types of studies. There is also a need to leave the traditional lethal assays and to use some of the newer tests for genotoxicity, endocrine disruption, and others.

15.7.2. Photoenhanced Toxicity Several researchers have noted that oil and especially dispersed oil has greater toxicity when exposed to UV or UV components of natural sunlight. Baron et al. studied the photoenhanced toxicity of weathered ANS crude on the eggs and larvae of Pacific Herring with and without the dispersant, Corexit 9527.249 The oil alone was toxic to larvae at concentrations below 50 mg/L (approximately equivalent to 50 ppb) total PAH. Toxicity decreased with time after initial oil exposure. Brief exposure to sunlight of about 2.5 hours/day for 2 days increased toxicity from 1.5 to 48-fold over control lighting. Photoenhanced toxicity only occurred when oil was present in larval tissue and increased with increasing PAH content in the tissue. Ultraviolet A (UVA) treatments caused a lesser effect than natural sunlight, but UVA plus sunlight caused greater toxicity than sunlight alone. The toxicity of chemically dispersed oil was similar to oil alone in control and UVA treatments, but oil and dispersant treatments were significantly more toxic in the sunlight treatments. The dispersant may be accelerating PAH dissolution into the aqueous phase, resulting in more rapid toxicity. The authors proposed the hypothesis that weathered ANS oil is phototoxic and that UV is a factor in the mortality of the early life stages of herring exposed to oil and chemically dispersed oil. Kirby et al. studied the effects of oil on Pacific oyster larvae.250 Results show that Kuwait crude oil, both mechanically and chemically dispersed,

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demonstrated significant levels of photoenhanced toxicity. The mechanically dispersed oil WAF demonstrated toxic effects at 50% dilution under normal laboratory conditions, but effects were evident at concentrations as low as 10% under UV conditions. When dispersed oil was tested, effects were apparent at 25 and 5% dilutions under the room and UV conditions, respectively. Comparisons of the no-observed effect concentrations suggest that UV illumination lowers the concentration of the onset of WAF toxicity of Kuwait crude by up to five times and that with dispersed oil the UV-mediated effects are at a point approximately 10 times lower. The impact of UV-light on WAF toxicity is also shown by the calculated LC50s, with the results showing a two- and fourfold increase in toxicity with mechanically and chemically dispersed oil, respectively. These results indicate that the use of chemical dispersants on oil increases the toxicity of the WAF and augments the magnitude of the UV-mediated toxicity. The few tests of photoenhanced toxicity clearly show that oil and especially dispersed oil is increased by UV light. Increases of 1.5 to 4 were found for physically dispersed oil and increases of about 4 to 48 times for chemically dispersed oil. This photoenhanced toxicity is particularly applicable to dispersant application in shallow waters. A question then arises as to the validity or the field relationship of a laboratory test where the light does not contain UV.

15.7.3. Testing Protocols A group of scientists developed protocols known as CROSERF (Chemical Response to Oil Spills: Ecological Research Forum). The CROSERF aquatic testing protocols were developed with the objective of standardizing test methods and reducing interlaboratory variability. The purpose of CROSERF was to provide state, federal, and international agencies, industry, academic researchers, and consultants engaged in research on the ecological effects of oil spill response chemicals, especially dispersants, with a forum for the exchange of ideas and coordination of research.251 As one of the main objectives of CROSERF, the laboratory researchers evaluated ways to improve such tests, and ultimately they developed a new set of protocols for conducting toxicity tests, focused on providing consistent detailed analytical chemistry, environmentally realistic exposure regimes, and standard methods for solution preparation. These protocols offer a baseline set of standard procedures that other laboratories may use to develop comparable data sets. Barron and Ka’aihue reviewed these protocols as they relate to subarctic conditions. A number of refinements were recommended to adapt the protocols to testing with subarctic species with the expected longer oil persistence.252,253 These refinements include: testing fresh and moderately weathered oil under conditions of moderate mixing energy; preparing toxicity test solutions using variable duration of tests from 4 to 7 days; quantifying approximately 40 PAHs and their alkyl homologues; assessing the potential for photoenhanced toxicity;

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and incorporating a bioaccumulation endpoint by measuring tissue concentrations of PAHs. Refinements in the preparation of oil dosing solutions, exposure and light regimes, and analytical chemistry should increase the utility of the test results for interpreting the toxicity of chemically dispersed oil in subarctic conditions. A number of discussions have been held on toxicity testing protocols:1 Notably, the protocols in the oil spill field have not kept pace with the researchers in the field; and there are many protocols in the literature, but the field of oil spill research appears to still use old protocols that are largely focused on acute lethal assays.

15.8. BIODEGRADATION The U.S. National Academy of Sciences reviewed the biodegradation of dispersed oil, noting that the effect of dispersants on biodegradation is a very important topic inasmuch as one of the stated objectives of using dispersants is to increase biodegradation.1 The effects of surfactants and oil dispersants on the rate and extent of biodegradation of crude oil and individual hydrocarbons have been extensively investigated with mixed results. Some studies showed biodegradation to be stimulated, many others pointed to inhibition, and yet others observed no effects with the addition of dispersants or surfactants. The effect of surfactants and dispersants depends on the chemical characteristics of the dispersants, the hydrocarbons, and the microbial community. Other factors such as nutrient concentrations, oilewater ratios, and mixing energy also affect the observed biodegradation rate. Many of the older studies that observed stimulation may have been confounded by the growth on the dispersants themselves, as some of the surfactants are readily biodegradable. The effect of the dispersants on the oil biodegradation rate is most sensitive to the characteristics of the dispersant itself, even if all other factors are kept constant. In one study, several specific surfactants were shown to inhibit the biodegradation of some classes of hydrocarbons. Only a few surfactants stimulated biodegradation in a culture taken from refinery sludge. NAS noted that other studies have shown complex interactions of oil, surfactant. and conditions. One study showed that the ionic surfactant in Corexit 9527 and 9500 inhibited cultures of alkane-degrading bacteria. The nonionic surfactants in the same mixture stimulated biodegradation. The variable effects of dispersants and surfactants on oil biodegradation are probably due to their effect on microbial uptake of hydrocarbons. It is clear that surfactants can interfere with the attachment of hydrophobic bacteria to oil droplets, making the process very complex to understand. The study concludes that no systematic and reproducible effects of chemical dispersion on the biodegradation rate of crude oil have been demonstrated. The study also notes that the older experimental systems used to investigate these effects might be inappropriate to represent the environment because they applied high mixing

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energy in an enclosed, nutrient-sufficient environment and allowed sufficient time for microbial growth. Microbial growth on open ocean slicks is likely to be nutrient limited and may be slow relative to processes that lead to the formation of water-in-oil emulsions, which are resistant to biodegradation. In addition, the study reported that the most toxic components of the oil, the biodegradation of PAHs, have never been shown to be stimulated by dispersants. The study concludes that only PAH mineralization can be equated with toxicity reduction and that stimulation of alkane biodegradation would not be meaningful in the overall toxicity of oil spills.1 Lindstrom and Braddock examined the effects of Corexit 9500 and sediment on microbial mineralization of specific aliphatic and aromatic hydrocarbons found in crude oil.254 The gross mineralization of crude oil, dispersed crude oil, and dispersant by a marine microbial consortium in the absence of sediment was also measured. When provided as carbon sources, the chosen consortium mineralized Corexit 9500 the most rapidly, followed by fresh oil, and finally weathered oil or dispersed oil. However, mineralization in shortterm assays favored particular components of crude oil (2-methyl-naphthalene > dodecane > phenanthrene > hexadecane > pyrene) and was not affected by the addition of nutrients or sediment. Adding dispersant inhibited hexadecane and phenanthrene mineralization but did not affect dodecane and 2-methyl-naphthalene mineralization. Thus, the effect of dispersant on biodegradation of a specific hydrocarbon was not predictable by class, but included inhibition of biodegradation. Page et al. conducted an experiment at a wetland research facility to investigate the behavior and effects of chemically dispersed oil (CDO) using Corexit 9500.255 The replicated treatments included oiled control, ‘‘high-dose’’ CDO (1:10 dispersant-to-oil ratio (DOR)), low-dose CDO (1:20 DOR), as well as an unoiled control. Known amounts of oil or dispersed oil were added to the respective plots. Sediment samples were taken over a 99-day period using a 5-cm-diameter coring device. The GC/MS results for both total target saturate hydrocarbons and total target aromatic hydrocarbons were measured, and data were modeled using nonlinear regression. The overall (including abiotic and biotic) petroleum loss rates for the dispersed oil treatments were not statistically different when compared to the oiled control. However, the initial concentrations for the dispersed oil treatments were statically lower than those for the oiled control. From this, it can be inferred that the dispersed oil was more prone to flush off the sediments, as was visually observed. Biodegradation rates were also determined for all treatments; it was concluded that there were no differences when comparing each dispersed oil treatment to the oiled control. The sediments from each plot were also analyzed for microbial population numbers and acute toxicity. Statistical analyses for both sets of data found no significant differences for the dispersed oil treatments when compared to the oiled control. MacNaughton et al. studied the degradation of crude oils, with and without dispersant, in two separate experiments, without replication.256 In one

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experiment Forties crude was mixed with a dispersant, Corexit 9500, and nutrients and was incubated for 27 days at 15 C. In another experiment, ANS, treated similarly, was incubated at 8 C for 35 days. All results were compared to a “killed” control with no nutrients added. A third test was carried out in which only seawater was added and there was no dispersant. The test vessel was similar to the Mackay dispersant apparatus with a high air flow. The amount of total alkanes was measured in the samples. In both studies microbial colonies started after 4 days as well as the formation of neutrally buoyant clusters consisting of oil, bacteria, protozoa, and nematodes. By day 16, the sizes of the clusters increased and sank to the bottom of the test flask. In the “killed” controls, no bacteria were observed. The TPH measurements in all three tests showed similar end results, with the dispersant one being slightly lower in the Forties case but not in the Alaska oil case. No biodegradation was observed in the Alaska oil, but some was apparent in the Forties oil. Martha and Mulligan carried out a comparison involving biodegradability of oil with dispersants or biosurfactants.257 A Brent crude, Corexit 9500 and a biosurfactant were used. The biosurfactant, rhamnolipid, is a metabolic by-product of Pseuomonas aeruginosa. The commercial product, JBR 425, in a 25% solution, was used. The EPA biodegradation protocol using a 250 mL flask was employed. Five treatments were compared for total GC/MS TPH and microbial counts over the 35-day experiment. The treatments were oil only, chemical dispersant, biodispersant, biological agent (seeded solution), and biodispersant with the biological agent. The most biodegradation occurred with the biodispersant and biological agent mixed, then the biological agent alone, then the bio-dispersant, then oil only, and then finally the dispersant only. The measurement of microbial counts showed about the same order of populations. It was concluded that use of the rhamnolipid biosurfactant promoted biodegradation, whereas the chemical dispersant always suppressed biodegradation. Yoshida et al. studied microbial responses to the addition of oil with or without a chemical dispersant in mesocosm and microcosm experiments by using denaturing gradient gel electrophoresis of bacterial ribosomal DNA and direct cell counting.234 When a water-soluble fraction of oil was added to seawater, increases in cell density were observed in the first 24 h, followed by a decrease in abundance and a change in bacterial species composition. After addition of an oil-dispersant mixture, increases in cell density and changes in community structure coincided, and the amount of bacteria remained high. These phenomena also occurred in response to the addition of only dispersant. These results suggest that the chemical dispersant may be used as a nutrient source by some bacterial groups and may directly or indirectly prevent the growth of other bacterial groups. Thus overall, the effect of dispersant overall may be to slow biodegradation, depending on the type of bacteria present. Nyman et al. set up microcosms to measure the effects of chemical additives on hydrocarbon fate in freshwater marshes.258 The test microcosms received no hydrocarbons, South Louisiana crude, or diesel; and no additive, a dispersant,

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or a cleaner. Oil fate was determined by the concentration of four total petroleum hydrocarbon (TPH) measures and 43 target hydrocarbons in water and sediment fractions 1, 7, 31, and 186 days later. Disappearance was distinguished from biodegradation via hopane-normalization. After 186 days, TPH disappearance ranged from 24 to 97%. There was poor correlation among the four TPH measures, which indicated that each quantified a different suite of hydrocarbons. Hydrocarbon disappearance and biodegradation were unaltered by these additives under worse-case scenarios. There was generally no benefit in increased biodegradation, nor was there a significant decline in degradation, The authors conclude that use of these additives must generate benefits that outweigh the lack of effect on biodegradation demonstrated in this report, and the increase in toxicity that they reported earlier. Venosa and Holder conducted laboratory experiments to study the biodegradability of oil after dispersants were applied.259 Two experiments were conducted, one at 20 C and the other at 5 C. In both experiments, only the dispersed oil fraction was investigated. Each experiment included treatment flasks containing 3.5% artificial seawater and crude oil previously dispersed by either Corexit 9500 or JD2000 at a dispersant-to-oil ratio of 1:25. Two different concentrations of dispersed oil were prepared, the dispersed oil then transferred to shake flasks, which were inoculated with a bacterial culture and shaken on a rotary shaker at 200 rpm for several weeks. Periodically, triplicate flasks were removed and sacrificed to determine the residual oil concentration remaining at that time. Oil compositional analysis was performed by gas chromatography/mass spectrometry to quantify the biodegradability. Dispersed oil biodegraded rapidly at 20 C and less rapidly at 5 C. After time, the rate of biodegradation of the undispersed oil was about the same as dispersed oil. Al-Sarawi et al. used water samples from the Kuwait coast to count and isolate bacteria capable of growth on low-molecular-weight organic compounds known to be released by picocyanobacteria.260 The compounds tested were potassium acetate, sodium pyruvate, fumaric acid, succinic acid, sodium citrate, and glycerol. For comparison, the bacterial numbers on glucose and Tween 80 and crude oil (Tween 80 is a surfactant related to those sometimes used in dispersants), as sole sources of carbon and energy, were also determined. Sodium pyruvate was, in most cases, the carbon and energy source most commonly utilized by the cultivable surface water bacteria. Four common cultivable bacterial genera and three less common bacterial genera were identified on the test carbon sources. Quantification of heterotrophic bacteria associated with cultures of local picocyanobacterial strains, originally isolated from the Gulf surface water, also revealed that the carbon source most commonly utilized by cultivable bacteria was sodium pyruvate. Bacteria were not countable on the oil or Tween, indicating that these were not a preferred source of carbon and would be degraded after sodium pyruvate, if at all.

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Zolfaghari et al. carried out the flask test on various oils and dispersants and found that there was a large difference in dispersants and that dispersants themselves biodegraded before the oil.261 After 24 hours there were no differences between any of the samples. These measurements were carried out by optical density and thus are qualitative. Saeki et al. prepared a biosurfactant by spray-drying the sterilized culture broth of Gordonia sp. strain JE-1058, and the agent was designated as JE1058BS.262 On testing by the baffled flask test, the biosurfant showed potential to be applied as an oil spill dispersant. It also showed some stimulation of biodegradation when applied to ANS crude oil. Overall many of the experimental systems used to investigate these effects might be seen as being inappropriate to represent the environment because they applied high mixing energy in an enclosed, nutrient-sufficient environment and allowed sufficient time for microbial growth. Microbial growth on open ocean slicks is likely to be nutrient limited and may be slow relative to other fate processes, many of which are resistant to biodegradation. It is of note that the most toxic components of the oil, the biodegradation of PAHs, have never been shown to be stimulated by dispersants.1 The study concludes that only PAH mineralization can be equated with toxicity reduction; stimulation of alkane biodegradation would not be meaningful in the overall toxicity of oil spills. Of the recent studies mentioned earlier, over half of the researchers found inhibition of oil biodegradation by dispersants, and the remainder reported that biodegradation rates were about the same.

15.9. OTHER INFORMATION 15.9.1. Component Separation It has long been known that some oil component separation takes place with the use of dispersants.263 Abdallah et al. noted this separation for a light Middle East crude and four different dispersants.264 The Abdallah study of dispersion and analysis by gas chromatography showed that the lower n-alkanes are much more dispersed than are other components, including the larger n-alkanes.

15.9.2. Dispersant Use The use of dispersants remains a controversial issue. In most jurisdictions, special permission is required to use them, whereas in other jurisdictions, their use is banned. In Canada, for example, use requires special permission from Environment Canada, through the Regional Environmental Emergencies Team (REET).265 Similarly, in the United States, special permission to use dispersants is required from the U.S. Coast Guard and the Environmental Protection Agency, and in waters close to shore, permission is also required from the state.266 In both Canada and the United States, products must pass standard test procedures for toxicity and effectiveness before they can be used. Only about

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30 dispersants of approximately 200 proposed products are approved for use (Table 15.2). Countries that allow dispersants to be used do so only outside of a specific distance from shore. The toxicity associated with the use of dispersants is caused by the dispersed droplets and by the increased deposition of toxic aromatic compounds. As there is not enough capacity for dilution closer to shore, in most countries where dispersants are allowed, they can only be used at a specific distance, that is, 1 to 10 km, from shore. Many jurisdictions also specify that the water must be at least 10 to 30 m deep before dispersants can be used, which means that dispersants are generally used in offshore ocean waters. Dispersants are seldom used in fresh water. Many countries restrict such use since fresh water is often a source of drinking water.66-68 Formulations designed for use in salt water are not effective in fresh water, although a few dispersants are specifically formulated for fresh water. The use of dispersants varies around the world, and their use has been declining steadily. In Canada, dispersants were used freely in the late 1970s and early 1980s; however, almost all stockpiles and equipment have now been sold. It is thought that dispersants were last used in Canada in about 1984. In the United States, dispersants have been used about three times per decade in the last 30 years. Dispersants have rarely been used in North America in the past 10 years and then only in the Gulf of Mexico.267 Dispersants are not used in Europe, except in some countries such as Great Britain and occasionally in France and potentially in Norway, Italy, and Spain. Britain has the longest history of dispersant use and has well-documented procedures for its use.268 Dispersants are occasionally used in Africa, especially in South Africa and Nigeria. In the Middle East, dispersants are used around the Arabian Gulf. India permits the use of dispersants and in the Far East, they are used in Singapore, Malaysia, and Indonesia. Japan permitted dispersant use in the past. Australia also allows the use of dispersants. An analysis of the potential for the use of dispersants in United States waters was conducted by Kucklick and Aurand.269 Data was obtained on 138 refined and 69 crude oil spills. Using the given criteria, it was found that dispersants could have been used at approximately 25% of the large spills of crude oil and 7% of the large spills of refined oil that have occurred in the past 20 years. This compares to about 45% of the same sample of crude oil spills and 25% of spills of refined products at which burning could have been conducted. This would indicate that dispersants are rarely used in the United States on spills where conditions might be suitable. Information available in the literature on the use of dispersants over the last 30 years is provided in Table 15.12. The table was largely based on literature as well as contacts with organizations such as ITOPF, which maintained their own records.270-289 Some large-scale uses were probably not documented or noted in the literature, whereas many uses, even of a smaller nature, are not documented anywhere. The rate of reporting can be estimated from the use situation

TABLE 15.12 Use of Dispersants on Spills e 1966e2009

Country

Date

Location

Name

Volume of Oil

Oil Type

Dispersant Used

Effectiveness

Reported Effects

Reference(s)

Australia

2009

offshore Australia

West Atlas rig blowout

440 bbls/day

Motara light crude

Slickgone

not visibly effective

no reports

270-272

Egypt

2009

Suez Canal area

YM Inception

7 tons

HFO

Korean

2007

near shore

Hebei Spirit

900 tons

fuel oil

unkown

not effective

no reports

270,273

United Kingdom

2007

near shore

MSC Napoli

200 tons

IFO

Slickgone

not visibly effective

no reports

270,274

Philippines

2006

near shore

MT Solar I

2000 tons

IFO

unknown

poor

no reports

270,275,276

not effective

270

India

2006

near Karwar

Ocean Seraya

390 tons

fuel oil

unknown

unknown

no reports

270,277

Japan

2006

near shore

Eastern Challenger

75 tons

HFO

NEOS and Unizol

not effective

no reports

270

Saudi Arabia

2006

near shore

Titan Mercury

250-1500 tons

Arabian heavy crude

unknown

270

Chile

2005

Eider

<1000 tons

IFO-180

effective

270

China

2005

Jubilee Glory

3000 tons oily water

oily water/IFO380/ Diesel oil

unknown

270

Iran

2005

Astro Lupus

560 tons

Kuwait export crude

Slickgone (3000L)

not effective

270

Colombia

2005

Saetta

27 tons

IFO 380

Corexit 9527

unknown

270

China

2005

GC-Chemist

unknown

Diesel MDO Bunkers

not effective

270

Kenya

2005

Ratna Shalini

150-180 tons

Murban crude

Corexit 9527 & Slickgone NS

effective

270

Suez Canal

2004

Al Samidoon

900 tons

Kuwait Medium crude

effective

270

Japan

2004

London Express

10 tons

IFO 380 bunkers

unknown

270

United States

2004

Main Pass pipeline

1200 tons

light crude

Offshore, LA

Corexit 9500

unknown

no reports

278

(Continued )

TABLE 15.12 Use of Dispersants on Spills e 1966e2009dcont’d Reported Effects

Country

Date Location

Name

Volume of Oil

Oil Type

Dispersant Used

Effectiveness

Colombia

2003

Alma Ata

168 tons

Coal and HFO 380

Corexit 9500 and 9580

Unknown

Reference(s) 270

Pakistan

2003

Tasman Spirit

30,000 tons

Iranian cude

Partial

270

China

2002

Tasman Sea

160-350 tons

Brunei Crude Oil

Effective

270

Singapore

2002

Neptank VII

300 tons

IFO 380

Unknown

270

Japan

2002

Ai Ge

115 tons

Heavy Bunker oil & LFO

Not effective

270

Singapore

2002

Agate

128 tons

Waxy Indonesian Crude

Unknown

270

Thailand

2002

Eastern Fortitude

240 tons

IFO180

Not effective

270

India

2001

Luc Nam

<100 tons

IFO180, marine diesel & lube

Effective

270

UK

2000

Randgrid

12-15 tons

Heidrun crude

Effective

270

Singapore

2000

Natuna Sea

7000 tons

Nile Blend crude

Unknown

270

Greece

2000

Nordland

110 tons

IFO 180

S Africa

2000

Treasure

200 tons

fuel and lube oils

UAE

2000

Al Jaziah

100-200 tons

Fuel oil (?)

United States

2000

Offshore, LA

Poseidon pipeline

400 tons

light crude

Nanga Parbat

India

2000

Mangalore

Sri Lanka

1999

near shore

OSE 750

Corexit 9527 - 14 tons

Partial

270

Partial

270

Unknown

270

successful

no reports

278 279

unknown

fuel oil

unknown

unknown

no reports

unknown

fuel oil

unknown

unknown

massive fish kill 280

United States

1999

Galveston, TX

Blue Master

20 tons

IFO 180

Corexit 9500 - 3 tons

unknown

no reports

278

Chile

1999

Irish Sea

40-100 tons

IFO

Not effective

270

Philippines

1999

Mary Anne

711 tons

IFO

Unknown

270

Japan

1998

Chun IL

15 tons of each

Diesel and HFO

Unknown

270

Philippines

1998

Princess of the Orient

600 tons?

Fuel oil (mostly HFO)

Unknown

270

United States

1998

Offshore

Undersea Pipeline

115-355 tons

light crude

Corexit 9527 - 11.4 tons

effective

no reports

281 (OSIR 29 Jan 98), 278

United States

1998

Offshore

Red Seagull

64 tons

light crude

Corexit 9500

effective

no reports

281 (OSIR 29 Jan 98), 278

United States

1998

Offshore

undersea pipeline

71 tons

medium crude

Corexit 9527 -

effective

no reports

281 (OSIR 22 Jan 98), 278

United Kingdom

1997

Offshore

Production Platform 685 ton

North Sea crude

Corexit 9500

somewhat

no reports

281 (OSIR 16 Oct 97)

Singapore

1997

Offshore

Evoikas/Orapin Global

25-30 k tons

Heavy Fuel Oil

various

no effective

no reports

281 (OSIR 16 Oct 97)

Japan

1997

Offshore

Nakhodka

27,000 tons

Medium Fuel Oil

various - limited amounts

ineffective

no reports

281 (OSIR 17 Jul 97)

Korea

1997

Nearshore

No. 3 O Sung

500-1200 tons

Bunker C

various - 112 tons

ineffective

no reports

281 (OSIR 24 Apr 97)

Uruguay

1997

Offshore

San Jorge

4500 tons

medium crude

various

ineffective

no reports

281 (OSIR 13 Feb 97)

Indonesia

1997

Mutiara

40-150 tons

Sangatta crude

Unknown

270

France

1997

Katja

190 tons

HFO

Not effective

270

Japan

1997

Diamond Grace

500 tons

Umm Shaif (Abu Dhabi) light

Unknown

270

Rep. of Korea

1997

Osung No.3

1700 tons on board

HFO

Unknown

270

(Continued )

TABLE 15.12 Use of Dispersants on Spills e 1966e2009dcont’d

Country

Date

Uruguay

Location

Dispersant Used

Effectiveness

Reported Effects

Name

Volume of Oil

Oil Type

1997

San Jorge

5000 tons

Canadon Seco crude

Effective

Reference(s) 270

Japan

1997

Nakhodka

6200 - 8000 tons

IFO 180

Not effective

270

S Korea

1996

Taiyoung Jasmin

<160 tons

HFO, marine diesel & lube

Not effective

270

Greece

1996

Kriti Sea

20-30 tons

Arabian Light Crude

Unknown

270

Saudi Arabia

1996

Liverpool Bay

257 tons

HFO

United Kingdom

1996

Estuary

Sea Empress

76,000 tons

Forties Crude Oil

Corexit, Dasic - 444 tons

Partial

unknown

270,271,283

South Korea

1996

Offshore

Hang Chang No. 8

100,000 gal

Fuel Oil

unknown

unknown

unknown

281 (OSIR, XIX/ [25])

Greece

1996

Estuary (dock)

Kriti Sea

>10,000 gal

Arabian Light Crude?

unknown

some oil hit beaches

unknown

281 (OSIR, XIX/ [31])

South Korea

1996

Estuary (at pier)

Barge Yung Jung No. 1

unknown

Bunker C and Marine Diesel

3,200 gallons - dispersant

no reports

unknown

281 (OSIR, XIX/ [32])

Singapore

1996

Nearshore

unknown

unknown

unknown

Chernkleen and Corexit 9500

effective

unknown

281 (OSIR, XIX/ [32])

S Korea

1995

Yeo Myung

40 tons

HFO

Australia

1995

Nearshore

Iron Baron

450 tons

Heavy Fuel

BP AB & Androx 6120

Not effective

unknown

270,281(OSIR 3 Aug 95)

Korea

1995

Nearshore

Sea Prince

1400 tons

Bunker C

unknown

Not effective

unknown

270,281 (OSIR 13Jul 95), 282

Korea

1995

Nearshore

Honum Sapphire

1000 tons

Arabian Heavy

unknown

unknown

unknown

270,282

Unknown

270

Unknown

270

United States

1995

Offshore

West Cameron 198 500-700 bbls

Light Natural gas condensate

unknown

unknown

unknown

278,282

Thailand

1994

Offshore

Visahakit

106,000 gal

Diesel Oil

unknown

unknown

unknown

282

South Africa

1994

Offshore

Sunken vessel

Leaking oil

unknown

Chemserve OSE 750

unknown

unknown

282

Singapore

1994

Offshore

Honum Pearl

3000-30,000 gal

Slop Oil

Shell VDC & Corexit 9527 unknown

unknown

282

South Africa

1994

Nearshore

Appollo Sea

763,000 gal

Fuel Oil, Gasoline (49,000 gal)

Chemserve OSE 750

unknown

unknown

284

India

1994

Embayment?

Maharishi Dayanand

30,000 gal

Crude Oil

unknown

unknown

unknown

282

United Kingdom

1993

Nearshore

Braer

25 million gal

Gulfaks Crude

Dasic-LTSW (95 tons), Dispolene-345 (15 tons),

ineffective

no reports

282

India

1993

Offshore

Maersk Navigator

unknown

unknown

unknown

unknown

unknown

282

Argentina

1993

Bay/Estuary

Two tankers

10,000 gal/6000 gal

Crude Oil

unknown

unknown

unknown

282

India

1993

Offshore

Pipeline

1.5-1.8 million gal

Crude Oil

unknown

unknown

unknown

282

Japan

1993

Bay/Estuary

Taiko Maru

100,000 gal

Heavy Oil

unknown

unknown

unknown

282

Korea

1993

Bay/Estuary

Barge Keumdong No. 5

376,000 gal

Heavy Fuel Oil

unknown

unknown

unknown

282

Korea

1993

Offshore

Sambo No. 11

1200 gal

Bilge

unknown

unknown

unknown

282

France

1993

Nearshore

Lyria

800,000 gal

Iranian/Saudi Heavy Crude

unknown

no reports

no reports

284

South Africa

1993

Nearshore

Fishing trawler

32,000 gal

Diesel and Blended Fuel

unknown

unknown

unknown

284

Greece

1992

Offshore

Geroi Cheromorya

400,000 gal

Light Crude

unknown

unknown

unknown

282

United States

1992

Offshore

Cook Inlet spill

8000 gal

medium crude

Corexit 9527

ineffective

no reports

281 (OSIR 9 Jan 92)

United Kingdom

1992

Nearshore

Russian factory

8000 gal

Diesel Oil

Enersperse 1583

unknown

unknown

282

Australia

1992

Estuary?

Era

87,000 gal

Light Crude

unknown

unknown

unknown

282

(Continued )

TABLE 15.12 Use of Dispersants on Spills e 1966e2009dcont’d

Country

Date Location

Name

Volume of Oil

Oil Type

Dispersant Used

Effectiveness

Reported Effects

Reference(s)

Greece

1992

Offshore

Unknown slick

500 x 3.2 km

unknown

unknown

unknown

unknown

282

Egypt

1992

Nearshore?

Soheir

21,000 gal

Fuel oil

unknown

unknown

unknown

282

Argentina

1992

Estuary

President Arturo Umberto Ulia

184,000 gal

Crude

unknown

unknown

unknown

282

Nevis (France)

1991

Nearshore

barge Vista Bella

550,000 gal

No. 6 Fuel Oil

Finasol OSR-7, OSR-52

variable reports

unknown

285,286

Australia

1991

Nearshore

Sanko Harvest

150,000-180,000 gal

Fuel Oil

BP A-B, Arderox B1 20

unknown

unknown

285

Japan

1991

Estuary

Scan Alliance

150 x 50 mi. slick

Heavy Fuel Oil

unknown

unknown

unknown

282

Australia

1991

Offshore

Kirki

6 million gal

Light Crude Oil

unknown

unknown

unknown

282

Japan

1991

Offshore

Aiko Maro

34,000 gal

Diesel

unknown

unknown

unknown

282

United Kingdom

1991

Estuary

Pipeline in Thames River

unknown

Crude Oil

unknown

unknown

unknown

282

Japan

1991

Offshore

South Korean container ship

17,000 gal

Light Fuel Oil

unknown

unknown

unknown

282

United Kingdom

1990

Estuary

British Resolution

minor

Crude

unknown

no information

no reports

285

United Kingdom

1990

Nearshore

Rosebay

1100 tonnes

Iranian Light Crude

110 tonnes of concentrate

75% dispersed

no reports

55

United Kingdom

1990

Nearshore

Kondor

not specified

Diesel and lubes

unknown (6 tons)

appeared successful

no reports

285

Greece

1990

Bay

Nalkratis

1200 gal

Iraqui Crude Oil

unknown

unknown

no reports

285

United States

1990

Offshore

Mega Borg

45-150 tons (12,00040,000 gal)

Light Crude

Corexit 9527

effective

minimal

285

Greece

1990

Nearshore

Happy Leader

large amounts

Crude Oil

unknown

unknown

no reports

285,286

Greece

1990

Offshore

Unknown

unknown

unknown

unknown

partially successful

minimal

285

Spain

1990

Offshore

Sea Spirit/Hesperus 11,400 tons (3 million Fuel Oil gal)

unknown

appeared successful

no reports

285,286

Hong Kong

1990

Nearshore

barge Hoi Fung

100 tons

Waste Oil

unknown (26,000 gal)

appeared successful

no reports

285

United Kingdom

1990

Estuary

barge Portfield

large amounts

Medium Fuel Oil

unknown (15-20 tons)

unknown

unknown

285

UAE

1989

Nearshore

Tropical Lion

unknown

unknown

unknown

no information

no information 285

Japan

1989

Offshore

Otake Maru/ Taiho Maru

unknown

Diesel Fuel

unknown (700 L)

no information

no information 285

United States

1989

Nearshore

Exxon Valdez

11 million gal (258,000 Alaska North Slope bbls) Crude

Corexit 9527

ineffective

no reports

287

United Kingdom

1989

Nearshore

Phillips Oklahoma/ 800 to 900 tons Fiona

no reports

285

British Maureen crude Dasic Slickgone LTSW (70 appeared successful tons)

Japan

1989

Nearshore

Mansion Trader

minor

Fuel Oil

unknown

unknown

no reports

285

Uruguay

1989

Bay

Presidente Rivera

90,000 gal (340 tons)

Fuel Oil

unknown

unknown

no reports

285

United Kingdom

1989

Estuary

Texaco Westminster 15,000 gal (57 tons)

Light Fuel Oil

Enersperse

unknown

no reports

285

United Kingdom

1988

Offshore

Piper Alpha Platform

unknown

Crude

unknown

successful on small patch

unknown

285

United States

1987

Offshore

PacBaroness

30 bbls/day

Possibly diesel

Corexit 9527

appeared successful

no reports

285,286

Panama

1986

Nearshore

Texaco Refinery

20,000-30,000 bbls

Mixture, Mexican & Venezuelan

Corexit 9527 (72 drums)

effective?

no reports

285,286

Singapore

1986

Nearshore

Bunkering barge

< 100 metric tons

unknown

Locally manufactured

unknown

unknown

285

Lube Oil & additives

United States

1984

Offshore

Puerto Rican

100,000 bbls

Corexit 9527 (2000 gal)

initially effective

no reports

285,286

South Africa

1983

Offshore

Castillo de Bellver

160,000-190,000 tons unkown

Solvent-based & concentrates

unknown

no evidence

285

United Kingdom

1983

Estuary

Sivand

6000 tons

BP 1100, Dasi, Disp. 34S (28,500 gal)

estimated 1/6 to 1/2

no reports

285,286

Nigerian Forcados crude

(Continued )

TABLE 15.12 Use of Dispersants on Spills e 1966e2009dcont’d

Country

Date Location

Name

Volume of Oil

Oil Type

Dispersant Used

Effectiveness

Reported Effects

Reference(s)

Ireland

1979

Bay

Betelgeuse

3-5 tons per day after fire

Saudi Arabian crude

BP 1100 WD

effective

no reports

285,286

Denmark

1979

Nearshore

Thumtank 3

2800 bbls (400 tons)

Heavy Fuel Oil

unknown

start only

no reports

285

South Korea

1979

Bay

Continental Friendship

unknown

Bunker C

unknown

no information

no information 285

Egypt

1979

Bay (Suez Canal)

Skyron II

14,000 bbls (2,264 tons)

Crude

unknown

no information

no information 285

Greece (Crete)

1979

Nearshore

Messiniaki Frontis

35,000-70,000 bbls (5000-10,000 tons)

Libyan Crude

unknown

no information

no information 285

Mexico

1979

Offshore

Ixtoc I - platform

20,000 bbls/day (Total Crude Oil 3,750,000 bbls)

Corexit 9527

questionable

no reports

285

United States

1978

Nearshore

Barge Pennsylvania 881 bbls (126 tons)/ 143 bbls (20 tons)

No. 6 Fuel Oil/ No. 2 Fuel Oil

Corexit 9527 (2000 gal)

effective

unknown

285,286

United Kingdom

1978

Nearshore

Christos Bistas

14,500-22,000 bbls (2000-3000 tons)

Iranian Crude

several types (70,000 gal)

poor

no reports

285

United Kingdom

1978

Offshore

Eleni V

56,000 bbls

Heavy Fuel Oil

6800 bbls of BP11OOD and 10% Dasic LTD

ineffective

no reports

12

Saudi Arabia

1978

Nearshore

Hasbah 6 platform

105,000 bbls

Heavy Crude Oil

unknown

ineffective

no reports

12

France

1978

Nearshore

Amoco Cadiz

220,000 tons

Heavy Crude Oil

various (2500 tons)

ineffective

no reports

12

Spain

1976

Nearshore

Urqiola

100,000 tons

Heavy Oil

various (2400 tons)

ineffective

some reports

288

United Kingdom

1975

Offshore

Olympic Alliance

2000 tons

Iranian Light Crude

BP 11 OOX & Dasic LT 2 (200 tons)

some noted

no reports

285

Portugal

1975

Nearshore

Jakob Maersk

88,000 tons

Heavy Oil

various (110 tons)

ineffective

no reports

288

Singapore

1975

Nearshore

Showa Maru

15,000 tons

Heavy Oil

various (500 tons)

ineffective

no reports

288

Spain

1971

Bay

Polycommander

100,000 bbls (14,500 tons)

Crude

Corexit 7664

effective

no evidence

285

United States

1970

Nearshore

Delian Apollon

unknown

No. 6 Fuel Oil

Corexit 8666 and 7664

no reports

no reports

285

United States

1970

Offshore

Chevron Main Pass Block 41

35,000-65,000 bbls (5000-9300tons)

GOM Crude

mostly Corexit 7664 (2000 drums)

unknown

no evidence

285,286

Canada

1970

Nearshore

Arrow

5000 tons

Bunker C

various - 12 tons

ineffective

no reports

288

United Kingdom

1970

Nearshore

Pacific Glory

6300 tons

Heavy Oil

various

mixed reports

mixed reports

288

Saudi Arabia

1970

Bay (Tarut)

Pipeline Spill

unknown

Light Arabian Crude

unknown

unknown

no evidence

285

South Africa

1969

Offshore

World Glory

322,000 bbIs (46,000 tons)

Kuwait Crude

unk. up to 20,000 gallons /day for 20 days

no reports

no reports

285,286

United States

1969

Nearshore

Barge Florida

175,000 gal (550 tons)

No. 2 Fuel Oil

unknown

not effective

severe shore impacts

289

United States

1969

Nearshore

Well A-21, Santa Barbara

77,000 bbIs (12,000 tons)

Santa Barbara Crude

ARA Gold Crew Bilge Cleaner (37,500 gal)

no estimates

no reports

285

Bahamas

1968

1 km offshore on coral reef

General Colocotronis

19,370 bbIs (2600 tons)

Bunker C

Corexit 7664, Magnus Oil Spill Disperser, Ameroid

reportedly worked

none?

286,286

Puerto Rico

1968

Nearshore

Golden Eagle

12000 tons

Heavy Oil

various - 60 tons

ineffective

no reports

288

South Africa

1968

Nearshore

Esso Essen

105,000 bbls (115, 000 tons)

Arabian Heavy

Corexit 7664 (15.6 m 3)

unknown

no benthic effects

284

United Kingdom

1967

Nearshore

Torrey Canyon

105,000 bbls

Kuwait Crude Oil

10,000 tons of toxic degreasers/detergents

variable reports

intertidal mortalities

12

Germany

1966

Offshore - Elbe

Anne Mildred Brovis 118,900 bbls

Iranian Crude

Moltoclar, Asca Super, A-11, Slix/Navee,

mixed reports

no reports

285,267

Gamlen, BP-1002, Ameroid-Drew

550

PART | VI

Treating Agents

in Canada. It is known by the author that dispersants were used on a small scale at 23 spills on the east coast of Canada in the 1980s, although not one of these uses appears in the literature cited in Table 15.12. The applications listed in the table therefore probably represent the larger ones and only a few smaller ones. From the information in Table 15.12, the following conclusions can be drawn about dispersant use. 1. Given that the table is as complete as it can be, either dispersants are used infrequently or their use is poorly documented. Information on their use is certainly sketchy in the literature. 2. The large-scale use of dispersants appears to be declining. 3. Only a few countries have used dispersants on a large scale in the past. 4. Most applications of dispersants do not involve scientific assessment of their effectiveness. 5. Dispersants do not appear to have been used on fresh water in the past. A Further explanation is needed on the entries in Table 15.12. The effectiveness is highly subjective. There is no doubt that the operators would usually declare a dispersant application to be successful. Furthermore, there was very little scientific assessment on any of the cases noted. The same goes for the effects column. Unless there was a massive fish kill, no effects were noted and indeed, actually assessed. Dispersants are used so infrequently in some locations that stockpiles are sometimes in place for as long as 20 years before use. In Great Britain, the government studied the aging of dispersants by testing effectiveness.290 The laboratory performed both long-term tests and short-term accelerated tests in various containers and at 20 and 30 C. The tests did not show dispersant deterioration, as indicated by the effectiveness values. In summary, dispersant use in recent times is not well-documented, or it is in fact, decreasing. Scientific assessment of dispersant effectiveness at spill scenes is often not carried out. In recent years some document reviews of dispersant use have been issued. Henry reviewed the seven spills in the Gulf of Mexico between the years of 1995 and 2005 which were treated with dispersants.278 The spills are: West Cameron 198 Pipeline spill, 1995; High Island Pipeline system Oil Spill, 1998; T/V Red Sea Gull spill, 1998; Mississippi Canyon 109 Pipeline Spill, 1998; M/V Blue Master, 1999; Poseidon Pipeline Oil Spill, 2000; and Main Pass 69 Pipeline Spill, 2004. Although these applications appeared to be successful, little measurement or documentation took place. Payne and Allen conducted laboratory tests with the Santa Barbara seep oil. Results from those tests indicated that the 11 API gravity seep oil from the Monterey Formation was not amenable to treatment with dispersants (0% dispersion), but similar tests on nearby Platform Holly produced oil (also from the Monterey Formation) indicated a possible dispersion of up to 70%.291 A limited set of in-situ field tests (using a hand-held spray bottle with less than

Chapter | 15 Oil Spill Dispersants: A Technical Summary

551

one pint of Corexit 9500) were completed on the seep oils in June 2003 in order to determine whether the earlier laboratory results were an artifact of the seep oil collection and shipment or some other unknown factor. The field tests convincingly demonstrated that the natural seep oils were not amenable to treatment with Corexit 9500. Gilson reports on the use of dispersants on the Exxon Valdez spill. Within hours of its occurrence, the United States Coast Guard (USCG) discussed dispersant use with Alyeska and others.287 A trial run performed on the first day of the spill was determined to be ineffective. Massive herding was observed by the application crew. The effectiveness of two subsequent drops was inconclusive because of poor light and mechanical problems. The fourth drop had increased wave action that theoretically could have helped mix the dispersant. Increased winds hampered the fifth and sixth drops, and it was determined that the window for effectiveness had closed. The remaining four experimental applications in Blying Sound on April 2 and April 13 off Seward were ineffective due to the emulsification of the oil. Chapman et al. reviewed the use of dispersants on oil spills that occurred over the 10-year period in Europe between 1995 and 2005 and reported that only on a relatively few occasions were dispersants used in response to incidents in European waters.268 The fact that dispersants were not used appears to be chiefly due to unfavorable circumstances for dispersants to work effectively. Of the 77 incidents attended by ITOPF in Europe during the period under review, six involved the use of dispersants at sea (8%): one in France, one in Cyprus, two in Greece and two in the UK. Two of the six incidents were spills of heavy fuel oil. Steen and Findlay’s review of the published literature on dispersant use around the world shows 213 documented uses since 1968 and 38 in the last decade.292 Overall, about 50% of the events were noted as being effective and the other half about equally ineffective or inconclusive, or undocumented. Use is now highest in Africa and Asia. The reporting of use is noted as being inconsistent and in some cases, absent.

15.9.3. Application of Dispersants To be effective on an oil spill, dispersant must be applied as soon as possible after the spill before the slick thins out too much or the oil weathers excessively. Thin slicks have been found to disperse poorly, as does highly weathered oil. Dispersants were first applied on oil spills using boat-mounted spray systems. Early in the 1970s, however, it was realized that such systems, usually with a spray width of about 10 m, did not provide adequate coverage of a spill. Large systems for larger boats and small ships were developed, but the dispersant had to be mixed with seawater, requiring extra equipment to control dilution and application rates. Use of smaller vessels for applying dispersant is not common today.

552

PART | VI

Treating Agents

TABLE 15.13 Dispersant Spray Equipment Typical Characteristics

Platform

Dispersant Load (L)

Coverage Per Hour (Ha)

Coverage Per Day (Ha)*

Speed

small boat

1000

10

80

6

small ship

3000

20

160

6

supply ship

10,000

30

240

6

small helicopter

700

170

280

50

large helicopter

2000

280

800

50

Agriculture spray plane

400

170

270

100

DC-3

4500

540

2400

120

DC-4

8000

840

4800

150

DC-6

11,000

1010

7330

150

C-130 (Hercules)

13,000

1010

8670

180

*Presuming a working day of 8 hours and typical sorties 50 km from base, and a target dosage of 15 L/Ha.

Aerial spraying, which is done from small and large fixed-wing aircraft, as well as from helicopters, is the most popular application method today. This method allows the dispersant to be applied neat, which is thought to be best because, when diluted in water, dispersants may not repartition to the oil phase and could be lost to the water column. The other benefit of aerial spray systems is that they have the potential to cover a large area. The aerial coverage that can be achieved from various types of aircraft as well as from different sized vessels is shown in Table 15.13.293 As can be seen, the best coverage is obtained when spraying from large transport aircraft. Dispersants must be applied through a system designed specifically for that purpose. For example, the spray volume of pesticide spraying equipment is generally 10 to 50 times less than a dispersant spray system. In addition, pesticide spraying equipment is designed to apply pesticide as a fine spray or mist, with droplet sizes of about 50 to 200 mm. It is believed that dispersants are best applied in larger droplets, 400 to 700 mm in size, so that the droplets will not blow away and an adequate amount of dispersant will be deposited onto the oil slick. The essential elements in applying dispersant successfully are to supply enough dispersant to a given area in droplets of the correct size and to ensure that the dispersant comes into direct contact with the oil. Several tests of aerial application systems have been carried out in the past, and a new set of studies

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has been conducted. Giammona and coworkers report on tests of aerial application of dispersants to determine the effectiveness of applying dispersants at different altitudes, in varying flows, and several other parameters.294,295 It was found that the important factors affecting the effective application of dispersants are altitude, wind speed and direction, major droplet characteristics, rate of flow of dispersant, boom configuration, deposition, and the width and patterns of the spray swath. Based on several tests of equipment, including the ADDSPAK (an aerial application package designed specifically for dispersants) in a Hercules and a DC-3; a U.S. Air Force MASS (systems for general spray purposes) system in a Hercules and an Air Tractor; and a DC-4 spray system, it was concluded that, while altitude did not change the amount of dispersant applied, it did affect the spray pattern to a certain extent. The deposited droplets were sometimes in the desired range of 400 to 700 mm, although many of the flights did not result in droplets in that size range. It was also found that many of the flights did not achieve the targeted 5 gpa (gallons per acre) dosage on the ground. Past studies on the desired droplet size were based on the premise that droplets ranging from 400 to 700 mm in size were best for an effective application.296,297 The impact of droplets of this size range on oil spills has not been determined. Oil spills spread rapidly, and the oil thicknesses in the slick are often in this size range or smaller within hours.298 It is known that slicks often spread out to a 100-mm thickness within hours of the spill. Earlier researchers of aerial trials suggested that the mean droplet diameter should be about half of the slick thickness.299 Another important consideration when applying dispersants is the concept of windows-of-opportunitydthat is, appropriate time periods after a spill during which conditions are correct for the use of dispersants. One group of researchers estimated such windows-of-opportunity for dispersant use, based primarily on viscosity data and laboratory tests.300 It was found that the prime window of opportunity for the use of dispersants on ANS oil was during the first 26 hours after a spill. It was estimated that a reduced effectiveness window would last from 26 to 120 hours after the spill. After this time, the oil would not be considered “treatable.” The most effective time for dispersing Bonnie Light crude oil was during the first 2 hours after the spill, and the time period for reduced dispersibility was 2 to 4 hours. As above, the oil would be considered untreatable after 4 hours. The formation of water-in-oil emulsions was a factor, and it was suggested that the treatment time could be increased by using emulsion-breaking agents.

15.9.4. Assessment of the Use of Dispersants The NAS committee on the study of dispersants has commented on dispersant assessment overall.1 The committee discusses the context of dispersants within oil spill countermeasures. Dispersants might be used if: (a) an oil slick threatens

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a sensitive coastal area and mechanical recovery is not feasible, (b) there is sufficient wave energy to break up the surface slick and mix the oil droplets into the water column, (c) the oil is of a type known to be dispersible, (d) there is sufficient potential for rapid dilution of the dispersed oil, and (e) in the course of spraying, dispersants are not applied directly to birds or mammals. The committee indicates that there is insufficient scientific information for making decisions about the likely benefits and consequences of dispersant use as an oil spill countermeasure. The committee report also alludes to a disagreement about how to interpret the results of laboratory, mesocosm, and limited field tests to date, because of the difficulty of simulating an adequate range of realistic exposure conditions. Further, the report notes that certain basic issues need to be resolved before dispersants can gain fuller acceptance as a response tool. Examples of these unresolved issues include the high variability of dispersant effectiveness to environmental factors and oil properties. This change cannot be accurately predicted with sufficient consistency to support decision making over a variety of conditions. Another example given is that the acute and chronic toxicity of dispersed oil has not been adequately studied under realistic conditions to support decision making and risk balancing. With respect to nearshore dispersion, more information will have to be gathered regarding the effectiveness and potential effects over a wide range of conditions found in nearshore areas before a policy decision on such use can be made. The committee also reviewed the decision-making process in the United States.1 Three approval processes in the United States are case-by-case approval, quick approval, and preapproval. In each case, the use of dispersant would require the federal on-scene commander to have approval from the regional response team. Before decisions are made, three basic questions need to be asked: will dispersants work?, can the spill be treated effectively?, and what are the environmental trade-offs? A major consideration in decision making would also include the preparedness to apply dispersants in adequate quantity. New U.S. Coast Guard rules require the ability to apply dispersants within 12 hours after an oil release within 50 nautical miles of shore. Considerations should also include adequate supply of dispersants and the ability to apply at a dispersant:oil dosage of 1:20. The risk framework includes three phases: problem formulation or definition, analysis, and risk characterization. The problem definition phases include identifying habitats and resources of concern; stressors and response options; and resource interactions. The analysis phase includes use of a trajectory model to predict what habitats might be impacted, assessment of scientific literature, discussion on estimates and preparation of a risk square, and a tool to weight the various risks and options. This analysis should take place before any spill occurs, and the information would be available to the parties requiring it. Because spill conditions may deviate from the set of scenarios used, real-time decision making may be necessary. Further questions might be asked: Will a mechanical response be sufficient? Is the spilled product known to be

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dispersible? Are sufficient chemical response assets available to treat the spill? Are the environmental conditions conducive to successful application and effectiveness? Will the effective use of dispersant reduce the impacts of the spill to shoreline and water-surface resources without significantly increasing impacts to water column and benthic resources? The resurfacing of oil should be considered. If the plume and the surface slick are both going to a resource that requires protecting, there is no benefit to chemical spill dispersion. There would only be a benefit if the subsurface plume went in a different direction where there are fewer resources to be protected. Several manuals have been issued on dispersant application, and they include decision trees on when to use dispersants.301-303

15.9.5. Spills-of-Opportunity Research The U.S. National Academy of Sciences notes that spills-of-opportunity may provide a good opportunity to conduct needed research.1 Its report recommends the following: detailed plans, target areas on the surface need to be identified by smoke bombs or other markers, dispersant to be applied into the wind, good photo and video documentation, water column concentrations measured with fluorometers and grab samples by GC/MS, and use of remote-sensing techniques. It is also recommended that both dissolved-phase and particulate oil droplets be sampled. The disadvantages of spills-of-opportunity studies include the fact that needed resources are often tied up in response; thus scientific operations may not be possible. Good data from real spills would be most useful in making assessments and inputs for spill models. Essential data needs include the following: concentrations under the water column, effectiveness values, diffusion and transport values with currents and winds, separation between dissolved and droplet components, long-term data, and detailed component analysis of the dispersed oil with time. Some of the recommended procedures appeared in the monitoring section above.

15.9.6. Interaction with Sediment Particles The NAS report maintains that not much is known about the long-term fate of oil and suspended particulate matter (SPM) in the water column.1 Once formed, oilemineral aggregates appear to be very stable structures, and the buoyancy will depend on the oil to mineral ratio. In one study, more oil settled to the bottom in the absence of dispersants than with dispersants. A study also noted that increased clay concentrations were needed to form aggregates as the salinities increased. Dispersant treatment results in greater numbers of oil droplets and thus greater numbers of interactions with SPM and greater number of agglomerates. The greater number of mineral particles results in larger and more aggregates. It should be noted that large amounts of research have been

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conducted on oileSPM interaction since the NAS report was completed, and there are many findings, notably that oileSPM particles will often settle to the bottom. Khelifa et al. studied aggregation between suspended oil droplets and suspended particulate matter (SPM), which leads to the formation of oileSPM aggregates (OSAs).304 A laboratory study was conducted to measure the size, density, and settling velocity of OSAs formed under various mixing conditions. Both physically and chemically dispersed oils were tested using Standard Reference Material 1941b prepared by the National Institute of Standards and Technology, Arabian Medium and South Louisiana crude oils, and Corexit 9500 dispersant. Two sediment-to-oil ratios of 0.5 and 1 were used. At a sediment-to-oil ratio of 0.5, the results showed that oileSPM interaction leads to formation of abundant negatively buoyant OSAs that settle at an average rate of 1 mm/s; their average effective density is about 60 g/L; and their size varies from 30 to about 350 mm. The minimum effective density and settling velocity of OSAs measured in this study were 34 g/L and 0.3 mm/s, respectively. Slightly denser OSAs were obtained with chemically dispersed oil. Less difference was obtained between physical properties of OSAs and those of sediment flocs when the sediment-to-oil ratio was increased from 0.5 to 1. Both Stokes’s Law and a modified one overestimate the settling velocity of OSAs and are not recommended for use in oil spill modeling. Li et al. conducted a wave-tank study to investigate the effects of chemical dispersants and mineral fines on the dispersion of oil and the formation of oilmineral-aggregates (OMAs) in natural seawater.305 The results of ultraviolet fluorometry and GC-FID analysis indicated that dispersants and mineral fines, either alone or in combination, enhanced the dispersion of oil into the water column. Measurements taken with a laser in-situ scattering transmissometer showed that the presence of mineral fines increased the total concentration of the suspended particles from 4 to 10 mL/L, whereas the presence of dispersants decreased the particle size (mass mean diameter) of OMAs from 50 to 10 mm. Observation with an epifluorescence microscope indicated that the presence of dispersants, mineral fines, or both in combination significantly increased the number of particles dispersed into the water. In summary, the interaction of droplets, particularly chemically dispersed droplets appears to be an important facet of oil fate. Although much more research is needed, it appears that high concentrations of sediment will have significant effect on dispersed oil droplets and the formation of stable OMAs. These OMAs will sink slowly and sediment on the bottom.

15.9.7. Modeling Oil and Dispersed Oil Behavior and Fate The U.S. Academy committee conducted 14 model runs using two different oil spill models to assess the sensitivity and effect of various input parameters on various outputs including fate, trajectory, and encounter with a shoreline.1

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Although the scenarios were found to be instructive, the need to specify dispersant effectiveness as a model input was the weakest part of the dispersant assessment. Unfortunately, the dispersant effectiveness is one of the most important input parameters. The results of the exercise indicate that without models, it is very difficult to integrate all interacting (and perhaps competing) transport and fate process, oil properties, and dispersant use to predict the oil in various compartments and in various areas. It is concluded that transport and fate models should be used to assist in making decisions during an actual spill. This is especially the case in the nearshore where there are even more complex flow fields. Models require improvement, and efforts should be made to improve and validate models. This includes undertaking research at laboratory and mesoscale to define the parameters that control oil dispersibility. Several efforts have been carried out to predict overall response costs, effects, and resource damage with various levels of dispersant effectiveness.306-311 The limitations of this modeling, as noted by the committee, are as follows: effectiveness must be assumed and input, effectiveness with time is not calculated, and inputs for various fates and effects are not necessarily available. The exercises are useful, however, to understand the various facets of response, resource assessment, and costs.

15.9.8. Separation of Dispersants from Water After a dispersant test, much of the applied dispersant is in the test water and oil can be removed by surface methods. In large test tanks, the water cannot be replaced, so means are needed to remove excess surfactants. Cooper et al. showed that this can be carried out using membrane or reverse osmosis techniques; this method is not very economical, however.312 SLR also showed that activated carbon works for this purpose, and this is the method now used.97

15.9.9. Dispersant Breakthrough Oil Slicks It is known that dispersant droplets can break through oil slick and then herd the oil. To date, no test has been conducted of the droplet sizes to break through typical oils that might be dispersed. Ebert et al. carried out a test on IFO-380 and found that 1,000 mm droplets did not break through a thin slick of this material.313 But since IFO-380 is highly elastic and not considered to be dispersible, tests on dispersible, in-elastic oils are needed.

15.9.10. Overall Effects of Weather on Dispersion Fingas and Ka’aihue studied how oil spill countermeasures are affected by weather.314 A literature review was carried out to determine whether there were data related to the performance of all countermeasure techniques under varying weather conditions. Although the literature did not provide any quantitative guides for the performance of countermeasures under varying weather

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conditions, data could be extracted to enable assessment of changes in their performance related to weather conditions. The most important factors influencing countermeasures are wind and wave height. These two factors are related and, given sufficient time for the sea to become “fully-arisen,” can be interconverted. These factors must sometimes be considered separately so that specific weather effects can be examined. Other weather conditions affecting countermeasures include currents and temperature. Currents are important as they become the critical factor for certain countermeasures such as booms. Temperature primarily affects the performance of dispersants and has been shown to have only minimal effect on other countermeasures. The weather affects dispersant application and effectiveness in three ways: the amount of dispersant that contacts the target is highly wind-dependent; the amount of oil dispersed is very dependent on ocean turbulence and other energy; and the amount of oil remaining in the water column is dependent on the same energy. At high-sea energies, natural dispersion is very much a factor for lighter oils. Nuka Research carried out a study on weather windows for Prince William Sound, and this study indicates that:315 l

l

l

l

l

l

Dispersant application in the Central Sound is not possible 75% of the time year-round, mostly because of darkness and conditions too calm for dispersant mixing. Dispersant application at Hinchinbrook Entrance is not possible 80% of the time year-round, mostly because of darkness, conditions too rough for application, or too calm for mixing. These were compared with the results of the mechanical response gap estimate for the same two operating areas of Prince William Sound, concluding: When all technologies are considered together, some type of response can be mounted in Central Prince William Sound 90% of the time and 70% of the time at Hinchinbrook Entrance. Mechanical response is a more robust response technology than either dispersants or in-situ burning in both operating areas. Mechanical response is the response method least likely to be precluded by environmental conditions in both the Central Sound and Hinchinbrook Entrance areas. Overall, response in either area is more likely to be precluded by environmental factors in winter than in summer.

In summary, weather including temperature, winds, and waves are an important consideration for oil spill dispersion. The weather “window” for effective dispersant use may be small in northern areas.

15.9.11. Joint Effect of Temperature and Salinity on Effectiveness Fingas et al. studied dispersion effectiveness for ANS oil at different temperatures, and salinity.316 The results of this study were compared to a historical test reported in the literature, in which both the temperature and salinity were

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5 degrees C 15 degrees C 25 degrees C Moles 9527 3 deg Moles 9527 10 deg Moles 9527 22 deg Moles 9500 3 deg Moles 9500 10 deg Moles 9500 22 deg

70 60

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50 40

FingasWork 5 deg 10 deg

Moles 9527 - 22 deg

30 Moles tests

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Fingas Work 25 deg C

0

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Salinity o/oo FIGURE 15.18 Effectiveness data from Fingas,316 along with Moles data.195

varied over a range of values. The finding of this study is that there is an interaction between salinity and effectiveness for ANS crude oil. The results appear to be surprising at first, especially in that the maximum effectiveness is obtained at a temperature of 10 C and at a salinity of 25%. Expectations are that the greatest effectiveness would be at the highest temperature and the highest salinity.199 Explanations of this finding are not obvious, but may include the fact that temperatureesalinity effects may indeed be a three-way trade-off, with the salinity effect peaking at a select value depending on specific surfactant content; the temperature increasing effectiveness; and the ionic strength match with the polarity of the surfactants in the dispersant. The match between ionic strength and its relation to the surfactant polarity may be the factor that causes this apparent reversal of results. The salinity effect alone is consistent with findings in many previous studies. These studies show that effectiveness peaks at values between about 20 and 30%, depending on the given surfactant formulation. Few independent temperature and effectiveness studies have been conducted to yield a consistent set of values, although they generally show an increase with rising temperature. A regression equation was found for the particular oil and dispersant.316 Some of the results are shown in Figure 15.18. In summary, there appears to be an interaction between salinity and temperature for oil spill dispersant effectiveness. Effectiveness apparently peaks at about 15 C and about 25%. Further study in other test apparatuses is suggested.

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15.9.12. Dispersibility of Biodiesels Hollebone et al. examined natural and chemically enhanced dispersion of biodiesel in both low- and high-energy conditions.317 Biodiesels were found to have significant differences with petroleum diesels in water chemistries and in potential ecological impacts. All organisms tested show that biodiesels have less acute toxicity than petroleum diesels. It remains unclear which components of the biodiesels are the most water-soluble and have the greatest potential for adverse effects on aquatic ecosystems. Neat biodiesels were found to be much more dispersible in high-energy conditions than petroleum diesel.

15.9.13. Application Systems Some recent work on application systems was carried out. Motolenich and Clark reviewed vessel dispersant application systems.318 Three types of vessel application systems are spray arm systems, fire monitor systems, and singlenozzle neat application systems. Salt et al. reviewed new strategies for the deployment of dispersants using aircraft.319 The development of alternative small-aircraft packages are summarized. Nedwed et al. discussed the use of icebreakers to mix oil spill dispersions in ice conditions.320 Testing of this concept was carried out in a basin with ice present and shows that effective dispersion occurred. The mixing extends up to 20 m below the icebreaker. Nedwed et al. described a new dispersant that is a gel.321 The dispersant has up to 90% active ingredient compared to 40 to 50% for traditional dispersants. The underlying concept is that the buoyant gel will float and mix with the oil, rather than being washed off as many traditional dispersants. Preliminary testing with the dispersant showed that it is more effective on more viscous oils and is effective at lower dispersant:oil ratios. Further, aerial application is thought to be more successful with less drift. There are several ASTM standards on dispersant application.296,297 Of most significance in recent years is the new standard on single-nozzle neat application systems.322

15.9.14. Accelerated Weathering For many years, several researchers have maintained that oil treated with chemical dispersants weathers at a much more rapid rate than untreated oil.161 Researchers have found that accelerated weathering ranges from 0 to 30%, with an average of 11% at times of about ½ hour.161 These results show that an average of 11% of the mass is removed over a short time by the action of dispersants. Untreated oil would ultimately lose this mass by evaporation over a much longer time depending on temperature. The accelerated weathering of oil was examined by GC analysis.161 A computer program was used to analyze the relative amounts of n-alkanes and

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then to draw comparisons between compositions in the three fractions, oil in the water column, oil on the surface, and untreated oil. The weathering of oils was particularly enhanced in the C9 to C13 portion of the oil content. The amount of these compounds present in either the undispersed oil remaining on the top or in the water column is on average less than that in the starting oil. Each compound, up to C13 is about 5% less abundant than in the starting oil. This analysis shows that accelerated weathering is taking place. The gas chromatograms also show that the light aromatics are almost totally evaporated from the oil during the dispersion process. This accelerated weathering presents a complication in studying the effectiveness of a dispersant on a light oil in that the oil weathers progressively as the experiment proceeds. This effect has been described for many years in compiling data for dispersants.121 The first stage weathered sample for a light oil, typically representing a loss of 10% , displays a higher effectiveness than heavier fractions. This is a result of the loss of oil components such as BTEX, which would not be measured in the water after a dispersant experiment because they would have largely evaporated. So if these light components are abundant, the dispersibility appears to increase at the first weathering stage after the fresh oil experiment, as illustrated in Figure 15.19 based on a laboratory experiment.121 Figure 15.19 shows a typical curve of effectiveness with time. The initial value is high, and then there is a drop; at about 17 to 20 hours weathering there is a rise and then a slow steady decline with time. The reason for the sag or drop in effectiveness before the 17- to 20-hour peak is probably due to the 60

50

Effectiveness %

Gap in effectiveness due to loss from weathering Curve peaks at 17 to 20 hours

40

Remainder of curve shows normal decline

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Time (hours) FIGURE 15.19 Effect of Weathering on the effectiveness curve (ASMB with Corexit 9527).

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60

Probable curve with no weathering

Effectiveness %

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Smoothed curve calculated through data

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Time (hours) FIGURE 15.20 Effect of weathering on effectiveness curve e same as Figure 15.19 as above, but with untreated oil curve shown.

accelerated weathering. This is always seen on light oils. It should be noted that the standards for these experiments were prepared by weathering for the same length of time as the dispersed samples, so the specific effect of weathering is compensated for, but not the loss of components through accelerated volatilization by dispersant action. The latter occurs as a result of accelerated loss of components after the dispersion process occurs. Figure 15.20 shows the effect of calculating a smoothed curve through the existing data and the calculated drop-off curve if there were no weathering effect.

15.10. SUMMARY AND CONCLUSIONS The literature on oil spill dispersants is extensive. For example, between 1997 and 2009 more than 450 papers were found. The results of this literature are appraised and summarized here along with older and classic literature. The basic nature of dispersants, like any other surfactant, is the resulting product, or the dispersion in the water column is not stable and over time the dispersed oil will resurface to an oil slick. This is the ultimate stable state. The half-lives of oil spill dispersions are estimated to vary between 12 to 24 hours. The prime motivation for using dispersants is to reduce the impact of oil on shorelines. To accomplish this reduction, the dispersant application must be highly successful and effectiveness high. As some oil would come ashore and much would resurface within a few hours, there is much discussion on what

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effectiveness is required to significantly reduce the shoreline impact. A major issue that remains is the actual effectiveness during spills so that these values can be used in estimates for assessment and models. The second motivation for using dispersants is to reduce the impact on birds and mammals on the water surface. As the NAS committee on dispersants notes, little or no research on this matter has been carried out since the 1980s.1 The benefits or deleterious effects of using dispersants to reduce impacts on wildlife still remain unknown. The third motivation for using dispersants is to promote the biodegradation of oil in the water column. The effect of dispersants on biodegradation is still a matter of discussion. There are a number of contradictory papers stating that dispersants inhibit biodegradation, whereas others indicate that dispersants have little effect on biodegradation. The most recent papers, however, confirm that the surfactants in some of the current dispersant formulations can either inhibit or leave biodegradation unaffected. No recent study has shown that dispersants clearly enhanced biodegradation. Furthermore, there are issues about the biodegradability of the surfactant themselves, and this fact can confound many tests of dispersed oil biodegradation. As the NAS committee pointed out, older tests that may have shown enhanced biodegradation with dispersants were flawed in that they were conducted under high nutrient conditions and in times that were not representative of oceanic conditions.1 An important issue that is rarely discussed is that oil-degrading bacteria largely live on the water surface, where they would feed on similar natural hydrocarbons in the absence of spills. Another serious question is that of timescale. Biodegradation takes place over weeks, months, and years compared to dispersion half-lives of 12 to 36 hours.

15.10.1. Effectiveness Testing Overall Effectiveness remains a major issue associated with oil spill dispersants. It is important to recognize that many factors influence dispersant effectiveness, including oil composition, sea energy, state of oil weathering, type of dispersant used and the amount applied, temperature, and salinity of the water. The most important of these factors is the composition of the oil, followed closely by sea energy and the amount of dispersant applied. It is equally important to recognize that the only thing that really matters is effectiveness on real spills at sea. More emphasis might be put on scientifically monitoring actual effectiveness so that the world has the real information for assessment and modeling. Effectiveness issues are confounded by the fact that various tests show highly different results depending on how they are constructed and operated. Detailed scientific examination of most effectiveness tests shows major deficiencies. Emphasis should be on real results from real spills.

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15.10.2. Laboratory Effectiveness Tests Bench-scale testing continues to be widely used to evaluate the performance of dispersants and the physical and chemical mechanisms of oil dispersion. A major disadvantage is that it is difficult to scale the results of these tests to predict performance in the field. Several factors that are difficult to extrapolate include energy regimes, dilution due to advection, and turbulent diffusion. Bench-scale tests are very useful for determining the effectiveness of various dispersanteoil combinations, salinity, temperature effects, effects of oil composition, and effects of oil weathering. It has been noted that many of the current tests are too energetic, for they yield results well above those obtained in older field tests.

15.10.3. Tank Testing Tank testing continued at high levels during the review time period. Tank testing technology still lags the many recommendations put forward by the NAS committee and others. Since these recommendations were not followed, reviews of these particular tests were not given here.

15.10.4. Analytical Methods for Effectiveness Analytical means continues to be a major concern for effectiveness testing. It is very clear that only careful GC/MS techniques produce a correct result answer. Few analytical methods can be used outdoors or in field situations. Very early in the field testing program, fluorometers were used. Studies then show that because the amount and distribution of PAHs, the target compound for fluorometers, change with time during the course of a chemical dispersion event, a fluorometer can never be truly “calibrated” for a particular oil and dispersant combination. The invalid colorimetric analytical method also continues to be used in a few cases for laboratory tests.

15.10.5. Toxicity of Dispersed Oil and Dispersants The results of dispersant toxicity testing are similar to those found in previous years, namely, that dispersants vary in their toxicity to various species. However, dispersant toxicity is less than the toxicity of dispersed oil, by whatever tests. In recent toxicity studies of dispersed oil, most researchers found that chemically dispersed oil was more toxic than physically dispersed oil. About half of these researchers found that the cause for this difference was the increased PAHs (typically about 5 to 10 times) in the water column. Others noted the increased amount of total oil in the water column. Some researchers observed damage to fish gills caused by the increased amount of droplets. Few researchers found that chemically dispersed oil was roughly equivalent to physically dispersed oil.

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The reasons for the change in findings in recent years might be attributed to better analytical techniques, both biological and chemical, as well as the use of newer tests. The increase in the toxicity of chemically dispersed oil can be attributed to the increase (~5 times) in PAHs in the water column as a result of dispersant action; the large increase in number of droplets, conveying more oil into the water column; the detected action of droplets on fish gills; and the increased partitioning of more toxic oil components from surface or sediment into the water column. Some studies depart from the traditional lethal aquatic toxicity assay, and some focus on the longer-term effects of short-term exposures. There certainly is a need for more of these types of studies. There is also a need to shift from the traditional lethal assays to some of the newer tests for genotoxicity, endocrine disruption, and similar tests.

15.10.6. Biodegradation of Oil Treated by Dispersants Of the recent studies noted, most researchers focused on inhibition of oil biodegradation by dispersants, and some found that biodegradation rates were about the same. No researcher in recent times has found enhanced biodegradation as a result of dispersant use. The NAS committee notes in commenting on some of the old studies that overall one might consider the experimental systems used to investigate biodegradation to be inappropriate for representing the environment because they applied high mixing energy in an enclosed, nutrient sufficient environment and allowed sufficient time for microbial growth. Microbial growth on open ocean slicks is likely to be nutrient limited and may be slow relative to other fate processes, many of which are resistant to biodegradation. The NAS also suggested that the most toxic components of the oil, the biodegradation of PAHs, has never been shown to be stimulated by dispersants.1 The NAS study concludes that only PAH mineralization can be equated with toxicity reduction; stimulation of alkane biodegradation would not be meaningful in the overall toxicity of oil spills.

15.10.7. Spill-of-Opportunity Research Accurate and precise data from real spills would be most useful in making assessments and inputs for spill models. Essential data needs include: concentrations under the water column, effectiveness values, diffusion and transport values with currents and winds, separation between dissolved and droplet components, long-term data, and detailed component analysis of the dispersed oil with time.

15.10.8. Monitoring Dispersant Applications Effectiveness monitoring at actual dispersant operations could provide very useful information for future assessment, modeling, and basic understanding of

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chemical dispersion. Emphasis must be placed on obtaining accurate and precise data.

15.10.9. Dispersant Use in Recent Times Dispersant use in recent times is not well documented or is in fact decreasing. Scientific assessment of dispersant effectiveness at spill scenes is usually not carried out.

15.10.10. Interaction with Sediment Particles The interaction of droplets, particularly chemically dispersed droplets, appears to be an important facet of oil fate. Although much more research is needed, it appears that high concentrations of sediment will have a significant effect on dispersed oil droplets and the formation of stable OMAs. OMAs appear to be stable over time and sink slowly and sediment on the bottom.

15.10.11. Stability of Dispersions and Resurfacing with Time Oil spill dispersions are not stable, and dispersed oil will destabilize and rise to the surface. Half-lives of dispersions may be between 4 and 24 hours. More study on this aspect is needed; this consideration requires incorporation into dispersant effectiveness studies.

15.10.12. Fate of Dispersed Oil There are few, if any, thoughts on the long-term fate of dispersed oil.

15.10.13. Application Technology and Issues Some work was done on application issues. Of particular significance was the development of single-point delivery systems. ASTM standards now cover these systems. Some preliminary work was carried out on gelled dispersants.

15.10.14. Correlation of Oil Properties with Effectiveness Studies show good correlation with oil properties and dispersant effectiveness. The more specific the chemical property, the better the correlation.

ACKNOWLEDGMENTS The author acknowledges several parties for their help in this compilation including the Prince William Sound Regional Citizens Advisory Council for their support of dispersant reviews, which preceded this summary, and Environment Canada for their data, which I have summarized here. Several persons, such as Helen Chapman of ITOPF, were gracious in supplying data for Table 15.12.

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264. Abdallah SZ, Mohamed, Ahmed FM. Effect of Biological and Chemical Dispersants on Oil Spills. Pet Sci Technol 2005;463. 265. Lumley TC, Harrison S, Hollebone BP. Evaluation of Methods for Assessing Effectiveness of Oil Spill Treating Agents. AMOP 2007;117. 266. Environmental Protection AgencydNational Contingency Plan Product Schedule. United States Environmental Protection Agency (U.S. EPA); 2009. 267. Etkin DS. Factors in the Dispersant Use Decision-Making Process: Historical Overview and Look to the Future. AMOP 1998;281. 268. Chapman H, Purnell K, Law RJ, Kirby MF. The Use of Chemical Dispersants to Combat Oil Spills at Sea: A Review of Practice and Research Needs in Europe. Mar Pollut Bull 2007;827. 269. Kucklick JH, Aurand DV. An Analysis of Historical Opportunities for Dispersant and In-Situ Burning Use in the Coastal Waters of the United States, Except Alaska, MSRC Technical Report 95-005. Washington, DC: Marine Spill Research Corporation; 1995. 270. Chapman H, ITOPF, ITOPF Internal Data Base, Private Communication, September 2009. 271. Straitimesdhttp://www.straitstimes.com/BreakingþNews/World/Story/STIStory_420360.html, December 2009. 272. http://www.theaustralian.news.com.au/story/0, 25197, 25997360e12377,00.html, accessed, December 2009. 273. Wikipedia, http://en.wikipedia.org/wiki/2007_Korea_oil_spill, accessed, December 2009. 274. Colcomb K. The NAPOLI Incident, Devon UK 2007dThe Formal NCP Environment Group. IOSC 2008;103. 275. ITOPF, http://www.itopf.com/information-services/data-and-statistics/case-histories/slist.html, 2009. 276. Visayas, http://www.inquirer.net/specialfeatures/visayasoilspill/view.php?db¼1&article¼ 20060925-22853, December 2009. 277. Hindu 2, http://www.hindu.com/2006/06/03/stories/2006060303360300.htm, December 2009. 278. Henry C. Review of Dispersant Use in U.S. Gulf of Mexico Waters Since the Oil Pollution Act of 1990. American Petroleum Institute, Washington, DC: IOSC; 2005. 279. Hindu, http://www.hindu.com/2000/06/25/stories/0425210p.htm, December 2009. 280. EnviroNEWs, September 1999, Soapy Soup from Sri Lanka Spill Kills Fishery, oohttp://ens. lycos.com/ens/sep99/1999L-09-23-01.html, December 1999. 281. OSIR. Oil Spill Intelligence Report. Arlington, MA: Cutter Information Corporation; 1989e1999 (Issue numbers and dates listed in Table 12). 282. Fiocco R, Communication to Lewis A, Aurand D, 1996. 283. Lunel T, Rusin J, Bailey N, Halliwell C, Davies L. The Net Environmental Benefit of a Successful Dispersant Operation at the Sea Empress Incident. IOSC 1997;184. 284. Welsh J. International Oil Spill Statistics: 1994, Oil Spill Intelligence Report. Arlington, MA: Cutter Information Corporation; 1994. 285. Exxon Mobil. Exxon Mobil Research and Engineering Dispersant Application Guidelines. Florham Park, NJ: Exxon Mobil Publishing; 2008. 286. National Oceanic and Atmospheric Administration (NOAA), Oil Spill Case Histories 19671991: Summaries of Significant U.S. and International Spills, Report No. HMRAD 92e11, NOAA Hazardous Materials Response and Assessment Division, Seattle, WA, 1992. 287. Gilson D. Report on the Non-Mechanical Response for the T/V Exxon Valdez Oil Spill. Anchorage, Alaska: Prince William Sound Regional Citizens’ Advisory Council (PWSRCAC), http://www.pwsrcac.org/projects/EnvMonitor/dispers.html; 2006.

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307. French-McCay D, Rowe JJ, Whittier N, Sankaranarayanan S, Etkin DS, Pilkey-Jarvis L. Evaluation of the Consequences of Various Response Options Using Modeling of Fate, Effects, and NRDA Costs of Oil Spills into Washington Waters. IOSC 2005. 308. French McCay D, Nordhausen W, Payne JR, Rowe JJ. Modeling Potential Impacts of Effective Dispersant Use on Aquatic Biota. AMOP 2006;855. 309. French-McCay D, Mueller C, Payne J, Terrill E, Otero M, Kim SY, et al. Dispersed Oil Transport Modeling Calibrated by Field-Collected Data Measuring Fluorescein Dye Dispersion. IOSC 2008;527. 310. Reed M, Daling P, Lewis A, Ditlevsen MK, Brørs B, Clark J, Aurand D. Modelling of Dispersant Application to Oil Spills in Shallow Coastal Waters. Environ Modell Softw 2004;681. 311. Schmidt-Etkin DS, French-McCay D, Rowe J, Whittier N, Sankaranarayanan S, Pilkey-Jarvis L. Impacts of Response Method and Capability on Oil Spill Costs and Damages for Washington State Spill Scenarios. IOSC 2005. 312. Cooper D, Volchek V, Cathum S, Peng H, Lane J. Trace Dispersant Detection and Removal. AMOP 2003;799. 313. Ebert TA, Downer R, Clark J, Huber CA. Summary of Studies of Corexit Dispersant Droplet Impact Behavior into Oil Slicks and Dispersant Droplet Evaporation. IOSC 2008;797. 314. Fingas MF, Ka’aihue L. Weather Windows for Oil Spill Countermeasures. AMOP 2004;881. 315. Nuka. Non-Mechanical Response Gap Estimate for Two Operating Areas in Prince William Sound. Anchorage, AK: Prince William Sound Regional Citizens’ Advisory Council (PWSRCAC), http://www.pwsrcac.org/projects/EnvMonitor/dispers.html; 2008. 316. Fingas MF, Fieldhouse B, Wang Z. The Effectiveness of Oil Spill Dispersants on Alaskan North Slope Crude Oils Under Various Temperature and Salinity Regimes. AMOP 2006;821. 317. Hollebone BP, Fieldhouse B, Landriault M, Doe K, Jackman P. Aqueous Solubility, Dispersibility, and Toxicity of Biodiesels. IOSC 2008;929. 318. Motolenich KM, Clark JR. Vessel Dispersant Application in Oil Spill Response. IOSC 2005. 319. Salt D, Stockham R, Byers S. Technical Innovation in Light Aircraft Dispersant Application Systems. IOSC 2003. 320. Nedwed T, Belore R, Spring W, Blanchet D. Basin-Scale Testing of ASD Icebreaker Enhanced Chemical Dispersion of Oil Spills. AMOP 2007;151. 321. Nedwed T, Clark JR, Canevari GP, Belore R. New Dispersant Delivered as a Gel. IOSC 2008;121. 322. ASTM 2465. Standard Guide for Oil Spill Dispersant Application Equipment: Single-Point Spray Systems. West Conshohocken, PA: American Society for Testing and Materials; 2007.

Chapter 16

A Practical Guide to Chemical Dispersion for Oil Spills Merv Fingas

Chapter Outline 16.1. Introduction and 583 Decision Making 16.2. How Dispersants 591 Are Used 16.3. Safety and 598 Postdispersion Actions

Appendix A. Specific Spill Scenarios and Dispersion Strategies Appendix B. Nomograms to Calculate Spreading and Viscosity with Time

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16.1. INTRODUCTION AND DECISION MAKING Dispersants are recognized as an alternative countermeasure for controlling oil spills on water. When used properly, with certain oils, and under the right conditions, chemical dispersants can rapidly reduce the oil on the surface or divert surface oil from following undesirable trajectories. Chemical dispersion can shorten the response time to an oil spill, thus reducing the chances that the oil will move further on the water surface and thereby protecting sensitive areas. Rapid dispersion of oil can prevent the oil from reaching shorelines, which are difficult to clean and where the greatest environmental damage caused by oil spills occurs. Dispersants are surfactant formulations that create small oil droplets that move into the water column. They are applied to achieve an approximate dispersant-to-oil ratio of 1:15 to 1:25, although slick thickness is hard to judge and no measurement technique is available. Although boats and ships have historically been used for this purpose, their ability to treat large areas is very restricted. Today, dispersants are usually applied from low-flying aircraft. Spray units have been designed for many platforms and are available as either permanent or temporary installations on whatever platform is available. As Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10016-4 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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dispersants are applied undiluted from aircraft and are usually diluted with seawater when sprayed from boats, quite different equipment is required for the two application platforms. Effectiveness is a primary concern when using dispersants. It has been found that their effectiveness depends primarily on the type of oil being dispersed and then on the amount of sea energy at the time of the dispersal operation. The primary factor affecting the ability of an oil to disperse is its composition. The lighter the oil, the better it disperses. Heavier components such as resins, asphaltenes, and waxes do not disperse. Heavy residual oils such as Bunker C, which consist mostly of these heavier components, disperse little, if at all. A minimum of sea energy is required before dispersants function. The higher the sea energy, the more effective is the dispersant. As oil weathers, its more dispersible content decreases and its viscosity increases, making it more difficult for the dispersants to mix with the oil. Heavy oils and highly weathered oils may not disperse at all under certain conditions. Light oils will disperse well and, if left untreated, may also disperse naturally. It is important to recognize that not all oil that is treated will disperse; there will always be some residual slick. This certainly must be weighed in considering response options. It is also very important to recognize that the dispersants are a temporary measure. Much of the oil dispersed will resurface within 12 hours. Thus if the trajectory of the surface slick is the same as the subsurface slick, the overall benefits of dispersant treatment will be nullified. The use of dispersants is a trade-off between a number of factors, such as protecting shorelines and birds versus possibly adversely affecting fish. In most countries, the use of dispersants is tightly regulated by government agencies. The decision process involves assessing the current situation and the protection priorities such as fish, shoreline types, and special habitats. Other factors that must be assessed include the probable effectiveness of the dispersant on the type of oil spilled, the temperature and salinity of the waters, and the ability to disperse significant amounts of oil with the equipment and dispersant available. The steps involved in chemical dispersion are shown in Figure 16.1. How dispersion decision making proceeds is outlined in Figure 16.2. These figures will be highlighted in the discussion that follows.

16.1.1. An OverviewdHow, When, and Where Dispersants Are Used Dispersants are considered an alternative countermeasure for oil spills, along with the many other countermeasures available. Often, several countermeasures should be applied at one time. Dispersants are a control tool and do not remove oil from the environment. Thus they are used when oil spills are approaching sensitive areas that require quick protection. When considering the use of dispersants, the proximity of the dispersant application to sensitive

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Oil spill occurs Chemical chosen as a response option

Obtain regulatory approvals

Choose targets

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Sensitive areas would benefit Oil is dispersible Sea energy is sufficient Plans are in place Equipment is obtainable

Dispersant Spray equipment

Set operation

Target sites Weather/time windows

Implement equipment deployment plans

Protection priorities

Implement health and safety plans

Brief all personnel on deployment and health and safety plans

Transport supplies and personnel

Begin dispersant operation

Monitor dispersant operation Conclude operation Return equipment

Assess and report results

FIGURE 16.1 Steps in chemical dispersion.

marine environments, such as mangrove forests, sea grasses, marshes, and corals, is an important factor. Decisions about the use of dispersants must be based on a net environmental benefit analysis of use versus nonuse of dispersants as discussed in Section 16.1.2. The potential environmental impact of the trajectory of the dispersed oil plume should be considered in addition to the environmental impact of the undispersed oil plume.

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Yes

Yes

No

wind <20 m/s (40 knots), wave height <3 m , but > 0.6 m and no other conditions unsuitable for dispersant operations

emulsification does not occur thickness > 1mm , and viscosity < 5000 mPa.s

No

Begin the implementation of the dispersant operation according to plan FIGURE 16.2 Decision flowchart for chemical dispersion.

Many jurisdictions impose regulatory limitations on the water depth to which dispersants can be applied (3 to 30 m). Dispersants are best applied in deep waters and not close to sensitive resources. Applying dispersants to prevent oil from entering the sensitive habitats should be considered to minimize environmental impact. Dispersants should not be used, however, to remove oil

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adhering to mangroves or shorelines. Instead, shoreline cleaners or surfacewashing agents should be considered. It is important to carry out the preplanning noted in this document before applying dispersants. The following are the minimum conditions that should be met when using dispersants: 1. Fundamental conditions a) There must be a positive potential benefit to using dispersants. b) There must not be sensitive environments that could be impacted. c) The operation should be feasible, with enough equipment and dispersant to produce a beneficial result. d) The oil should be dispersible and in dispersible condition, for example, not highly weathered or in the form of a stable emulsion. e) The oil should be heading toward an area or environmental habitat that needs to be protected. f) The water should be of sufficient salinity (>25%) to allow for effective dispersion. g) The effectiveness should be considered, as well as the effects of the remaining oil on the surface, which will always be present. h) The inevitable resurfacing of the dispersed oil must also be considered. 2. Environmental considerations a) The habitat in which dispersion will occur is not sensitive to hydrocarbons in the water column. b) The dispersed oil plume will not come into contact with sensitive water environments, including coral reefs and beds of sea grass, within the next 12 hours. c) The dispersion will result in a net environmental benefit as described in Section 16.1.2. Dispersants are generally applied when the above conditions exist. They are applied directly to the oil using application equipment either from boats, ships, aircraft, or helicopter buckets. Plans for the application must be developed in advance to ensure safety and the efficiency/effectiveness of the operation. The items to be considered in this preplanning stage are listed in Table 16.1.

16.1.2. Net Environmental Benefit Analysis A Net Environmental Benefit Analysis or NEBA is used to evaluate the decision to use oil spill dispersants. The concept is that the total benefit of applying dispersants is evaluated compared to the potential damage that would occur if they were not applied. It is important to stress that at this time NEBA is more of a concept than a developed tool. The NEEBA, or Net Environmental and Economics Benefit Analysis, is a variation on this theme and adds the concept of economics to the vector. It should be stressed that this concept has been even less developed as a tool than the basic NEBA.

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TABLE 16.1 Preplanning for Dispersant Application 1 Environmental Resources Sensitivity mapping coral reefs mangroves shallow areas endangered species species at risk

3 Oil Types Tests with oil types Effectiveness scenarios Weathering profiles Time windows

2 Dispersants and Equipment Dispersant stocks Equipment for this Dispersion planning Dispersion scenarios

4 Preplanning Preplanned NEBA Preplanned conditions

The sequence of analysis is intended to proceed from the concentrations of oil expected under the slick, the toxicity of these diluted fractions to the local flora and fauna, and a comparison of this with the distribution and fate of the oil if not treated. It is currently proposed that models be used to generate this type of information and sometimes even the economic analysis that flows with it. The following is the scenario for a full NEBA/NEEBA analysis. 1. Generate the dispersant application and countermeasures scenarios. This is typically carried out using computer analysis and includes: l Spread, thickness, and geographical prediction of oil deposition, including weathering and chemical composition; l Application scenario, including dosage of the various amounts, prediction of effectiveness, and deposition of unburned fractions; l Very importantlydconcentrations of the oil under the slicks and their fate and movement; l Effectiveness of mechanical and other countermeasure scenarios; and deposition and movement of the oil if no countermeasures were carried out. A NEEBA analysis would include the economics of the three componentsd dispersant application, no-countermeasures, and the normal mechanical removal efforts. The dilution of dissolved and dispersed hydrocarbons can be calculated. Dispersant scenarios should be calculated with the variances in the dispersibility of the oil. It is typical to calculate all the dispersant scenarios, with effectiveness half of the predicted amount and some percentage above to yield three scenarios. 2. Generate ecological-impact scenarios for mechanical countermeasures only, other forms of countermeasures that may be considered or applieddin suites or separatelyddispersant-only, and no countermeasures.

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Again, economics can be included to yield a cost analysis. The impact scenarios will include the toxic effects on key species in the affected areas, the variances in trajectories, and a sensitivity analysis of the predicted oil concentrations under the slick. The predicted recovery of species is also modeled. 3. The outputs of the total process include information on the effects for each countermeasure scenario, including the effects of undispersed oil or oil that was not subject to the dispersant process. These effects can then be evaluated in terms of their ecological value. The social costs and benefits are also evaluated at this stage. A NEEBA analysis would include an evaluation of the economic costs and the benefits of each countermeasure scenario. The sequence of NEBA planning is listed in Table 16.2.

16.1.3. Scenarios For Which Dispersants Might Be Used It is important that scenarios for dispersant application be developed for the regions of concern. Typical scenarios for situations in which dispersants might be used are listed in Appendix A.

16.1.4. Planning Process and Checklists Planning begins with assessing the environmental resources in the area as listed in Table 16.1. After the sensitive areas are mapped, focus is then on the available dispersants and application equipment, which will dictate the capability to chemically disperse oil slicks. If the equipment is available, planning then proceeds to scenarios such as illustrated in Appendix A. This is tied together with the NEBA analysis as summarized in Table 16.2. It is important to set the priorities for chemical dispersion in line with the priorities for environmental protection. Planning then continues with examination of the oil types that may require dispersion in the region. Effectiveness scenarios are set for the oils, along with the weathering profiles, and the resulting time windows for effective chemical dispersion. This is readily accomplished by referring to Appendix B. This appendix provides tables and nomograms that give values or estimations of the spreading area, thickness, oil viscosity, dispersant needed, and the hours of operation for several dispersant application platforms for 100, 1000, and 10,000 ton scenarios and for 12, 24, and 48 hours. The final step is to compile all the information into preplanned NEBA and preplanned scenarios so that decisions can be made quickly. Oil spilled on water undergoes several changes with time, and this should be taken into account when planning dispersant operations. The processes that cause these changes include emulsification, evaporation, oxidation, spreading, and natural dispersion. In order to determine the effectiveness of a dispersant

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TABLE 16.2 Sequence of Analysis in NEBA Sequence Number

Information Input

Analysis

Output

1

Basic spill information

Trajectory modelling

Direction of surface slick

Amount

Fate modelling

Direction of plume/ dispersed oil

Dispersant available

Dispersant modelling

Dispersed oil concentrations

Dispersant operation information

Countermeasure modelling

Amount dispersed

3

Area resources

Effects modelling

Effect of dispersed/ undispersed oil

4

NEBA

NEBA

Total effects of dispersed oil

Location Oil type Weather and predicted weather Oceanographic information 2

Undispersed oil and residual oil

5

Economic model

Social analysis

Social costs and benefits of each scenario

NEEBA

Costs of alternatives

operation for a particular oil slick, it is important to understand how these processes change the properties of spilled oil and ultimately affect the oil’s ability to disperse. As time progresses, the slick becomes increasingly thinner on the water. A light crude oil will be an average of 0.5 mm thinner after about 48 hours, a thickness that is nearly impossible to treat with dispersants. For practical purposes, 1 mm will be taken as the practical limit in this guide.

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The formation of emulsions significantly changes the properties and characteristics of oil spills. Stable emulsions contain from 60 to 80% water, thus expanding the original volume of spilled material by two to five times. Most significantly, the dynamic viscosity of the oil typically changes from a few hundred mPa.s to about 100,000 mPa.s, a typical increase of 1000. A liquid product is thus changed to a heavy, semisolid material. For practical purposes, once an emulsion has formed, the oil is considered to be nondispersible.

16.2. HOW DISPERSANTS ARE USED The primary method for applying dispersants is to spray the dispersant onto the slick as soon as possible after the spill. The dispersant must be applied onto slicks before they become too thin and before the oil weathers excessively. Studies have been done on the application of dispersants directly into leaking tanks. This has been largely abandoned because analysis of case histories shows that very little opportunity for such application actually exists. Furthermore, implementing such a method with a stricken tanker would probably be more difficult than to conduct a spray operation. Dispersants were first applied on oil spills using boat-mounted spray systems. In the early 1970s, it was realized that small boats with a spray width of about 10 m could not deal with a very large amount of oil. Both large systems for larger boats or small shipsdthe size of supply boatsdand spray systems for aircraft were developed. Smaller vessels are rarely used today for application. While there are spray systems for applying pesticides, spray systems for dispersants must be designed quite differently as spray volume is generally 10 to 50 times greater. Most pesticide systems are designed to apply pesticide as a fine spray or mist with droplet sizes from about 50 to 200 mm, whereas dispersants are best applied at 400 to 700 mm. These droplets are large enough to result in good deposition rather than being blown away and small enough that the dispersant droplets do not break through the oil slick. The physics of the system is such that dispersants must be diluted in order to be sprayed from a slow-moving ship, whereas they are applied “neat” from aircraft. Applying dispersants in neat form is thought to be best because, when diluted with water, dispersants may not repartition to the oil phase and could be lost to the water column. Mixing seawater on vessels requires apportioning pumps or devices to ensure a consistent mixture of oil and water. There are several practical references and standards on the design and calibration of such systems. The advantage of aerial spray systems is that, in theory, they can cover a large area. A concern is that of the desired droplet size. All past work was based on the premise that a 400 to 700 mm droplet size was best for deposition. The effect of droplets in this size range on spills has not been determined. Spills spread rapidly and are often at this size range or thinner within hours. It is known that slicks will often spread down to a 100 mm (0.1 mm) thickness

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within hours. Researchers at earlier aerial trials have suggested that the mean droplet diameter should be about half of the slick thickness.

16.2.1. Dispersion Spray Equipment Dispersants are best applied either “neat” (undiluted or diluted with water). Aerial spraying, which is done from small and large fixed-wing aircraft, as well as from helicopters, is the most popular application method. Spray systems on small aircraft used to spray pesticides on crops can be modified to spray dispersants. Such aircraft can carry about 250 to 1000 L of dispersant and can perform many flights in one day in diverse conditions. Some spray systems and their aerial coverages are listed in Table B2 in Appendix B. As can be seen in the table, large spray systems on large aircraft are attractive from the aerial coverage point of view. Spray systems are available for boats, which vary in size from 10‑ to 30‑mwide spray booms to tanks from 1000 to 10,000 L. As dispersant is almost always diluted with seawater to maintain a proper flow through the nozzle, extra equipment is required on the vessel to control dilution and application rates. About 10,000 to 100,000 L of dispersant can be applied in a day, which would cover an area of 1 million m2 or 1 km2. As this is substantially less than could be sprayed from a single aircraft, spray boats are rarely used for a large spill. A spray system operating from a vessel is shown in Figure 16.3. When spraying dispersant, it is important to deliver fine droplets (400 to 700 Fm) to the slick at sufficient dosage to produce results. The dispersant-to-oil ratio is generally taken to range from 1:15 to 1:25. It is also essential to ensure that the dispersant comes into direct contact with the oil. Droplets larger than 1000 Fm will break through the oil slick and cause the oil to collect in small ribbons, which is referred to as herding. This can be detected by the rapid clearance of the oil in the dispersant drop zone without the formation of the usual white-to-coffee-colored plume in the water column. This is very

FIGURE 16.3 A spray system from a boat in operation (note the underlapping spray pattern).

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detrimental and wastes the dispersant. Herding can also occur on thinner slicks when the droplets of dispersant are smaller. Dispersants must always be applied with a system designed specifically for the purpose. If pesticide spray equipment is used, small droplets form that may blow away and not enough dispersant is deposited onto the oil slick. The distribution of smaller droplets of dispersant is not desirable, especially when spraying from the air as small droplets will blow away with the wind and probably not land on the intended oil slick. Unless suitably modified, fire monitors or regular hoses from ships may not produce correct droplet sizes or quantities of dispersant per unit area. Furthermore, the high velocity of the water/dispersant mixture can herd the oil away, resulting in loss of dispersant to the water column, where it has little effect on oil floating on top of the water. New single-point application nozzles have been developed that provide relatively good distribution of correctly sized droplets. It is very difficult with aerial equipment to spray enough dispersant on a given area to yield a dispersant-to-oil ratio of 1:15 to 1:25. The rate at which the dispersant is pumped and the resulting droplet size are critical, and a slick must often be underdosed with dispersant rather than creating very small droplets. Tests have shown that reapplying dispersant to the same area several times is one way of ensuring that enough dispersant is applied to the oil. The nozzle and flow calibration procedure is done in four steps. First, the equipment is inspected, and any defects are corrected before further calibration. The second step is the calibration of the flowmeter, and third is calibration of the unit by catching water spray from each nozzle. The fourth step is the preparation of a calibration curve. Spray equipment should be maintained and periodically calibrated. Procedures and standards for design, maintenance, and calibration are given in the literature listed in Section 16.4.

16.2.2. Spray Aircraft The required dispersant load and coverage obtained by the various dispersant delivery platforms are given in Appendix B. As discussed, aerial spraying is done from both small and large fixed-wing aircraft as well as from helicopters. Transport aircraft with internal tanks can carry from 4000 to 12,000 L of dispersant. Large transport aircraft such as Hercules fitted with portable spray systems can carry about 20,000 L, which could treat 400,000 L of oil at a dispersant-to-oil ratio of 1:20. At a thickness of 0.5 mm, this oil would cover about 400,000 m2 or 0.4 km2. This treatment could be applied in as little as an hour after loading the dispersant and as many as eight flights could be flown in a day, depending on the distance from the airport to the spill. Figure 16.4 illustrates a Hercules spraying dispersant in a test over land. When using large aircraft, however, it can be difficult to obtain the required amount of dispersant. A co-op typically stores 100 drums or about 20,000 L of

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FIGURE 16.4 A large aircraft applying dispersant.

dispersant, which could be sprayed in one flyover. Further flights would have to wait for the arrival of more dispersant from other co-ops or production sources. An entire country’s supply of dispersant can easily be used up in one day if spraying with large aircraft. Flying at an altitude of 15 to 30 m, the optimal spray altitude, the pilot of the spray aircraft cannot see the slick. When dispersant is being sprayed from an aircraft, a spotter aircraft must therefore precede the spray aircraft to provide instructions for the setup of lines, when to turn the spray on and off, and small directional corrections. When using helicopters, spray buckets are available in many sizes from about 500 to 2000 L. If applied at a dispersant-to-oil ratio of 1:20, 10,000 to 40,000 L of oil could be treated. If the slick is 0.5 mm thick, this would cover about 10,000 to 40,000 km2 (or about 0.01 to 0.04 km2). It would take about 1 to 2 hours to fill and spray each bucket over the oil. As a spill countermeasure, this rapid coverage of such a large area is appealing. Figure 16.5 shows a helicopter applying dispersants from a bucket.

16.2.3. Spray Nomograms and Calculations It is important to calculate the feasibility of performing the dispersant operation. To this end, a series of simple nomograms have been created and are provided in Appendix B. Figures B1 to B3 shows the calculated areas, slick thickness, and viscosity with weathering for spills of 100, 1000, and 10,000 tons. Figure B1 can be used to estimate the area of slicks at the three sizes of spills. Figure B2 can be similarly used to calculate the thickness of the oil slick. Oil slicks less than about 1 mm will be hard to treat with dispersants. Figure B3 shows the increase in viscosity over time for a very light crude oil. After 48 hours, the viscosity of this light oil is such that it may not be treatable with dispersants. The nomogram for the increase in viscosity for a medium crude oil is shown in

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FIGURE 16.5 A helicopter spray system in operation.

Figure B3. It can be seen that, after about 24 hours, the oil will not be amenable to dispersants. Similarly, the nomogram for treating a heavy crude oil is shown in Figure B5. This figure shows that heavy oils are only amenable to treatment by dispersants in the first few hours. After the viscosity of the oil reaches 1000 mPa.s or cSt, the oil is poorly dispersible and the upper limit at which any dispersion occurs is about 5000 mPa.s. Figure 16.6 shows the dispersant runoff that occurs after application of dispersant to viscous oil. In such a situation, almost none of the oil would be dispersed.

FIGURE 16.6 Dispersant running off a heavy oil patch.

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16.2.4. Monitoring, Sampling, and Analytical Equipment The purpose of monitoring protocols is first to determine whether or not dispersant applications are effective and second to estimate their relative effectiveness. Dispersant effectiveness is defined as the amount of oil that the dispersant puts into the water column compared to the amount of oil that was spilled. In the field, effectiveness is visually indicated by the formation of a yellow-to-coffee-colored plume of dispersed oil in the water column which may be visible from ships and aircraft. This is shown in Figure 16.7. Dispersant effectiveness is primarily monitored by visual surveillance or insitu measurements of oil concentrations. When testing dispersant effectiveness in the field, it is very difficult to measure the concentration of oil in the water column over large areas and at frequent enough time periods. It is also difficult to determine how much oil is left on the water surface as there are no methods available for measuring the thickness of an oil slick and the oil at the subsurface often moves differently than the oil on the surface. The quantitative method is not used in modern monitoring practices. Instead, a relative measure of dispersant effectiveness is made. Quantitative measures are difficult because effectiveness values depend on establishing a mass balance between oil in the water column and that left on the surface. Insitu fluorometry can be used to give an indication of the relative concentration of the oil in the water column. Some protocols to do this have been developed, e.g., SMART (Special Monitoring of Advanced Response Technologies) protocol.

16.2.5. Equipment Availability A large amount of dispersant and application equipment is required to mount an operation for a large spill. This must be preplanned, as described in Section

FIGURE 16.7 View of a dispersant test showing the yellow-to-coffee-colored plume from effective dispersiondnote the remaining oil.

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16.1.4. Depending on the jurisdiction, equipment and dispersant can be obtained by prior agreement from various organizations including the Marine Spill Response Corporation (MSRC), Clean Harbors Environmental Services, Inc., Clean Caribbean and Americas (formerly Clean Caribbean Cooperative), Clean Bay Incorporated, National Response Corporation, Marine Pollution Control, and FOSS Environmental & Infrastructure in the United States. Some of these organizations are able to assist for a fee or can lease equipment and operators. Another important factor to consider is the time required to deliver additional dispersant and equipment to the site, especially considering the short time windows. For most scenarios, the time window is less than 48 hours as calculated using Appendix B. Significant amounts of dispersant and dispersant application equipment must therefore be prepositioned close to potential spill sites.

16.2.6. Equipment Checklist The process that should be followed for preplanning has been laid out in Section 16.1.4. An equipment checklist should be developed for the specific operation to be carried out in the plan. This will vary from scenario to scenario, with different types of oil and local conditions. It must be ensured that a process such as that outlined in Figures 16.1 and 16.2 can be implemented once a spill occurs.

16.2.7. Conducting the Operation In the early stages of spill management, questions may arise as to whether or not a dispersant application will be effective. A simple test as described here can answer that question. The suggested procedure is to obtain a sample of the actual spilled oil and a sample of the water in the area. As soon as practical after the samples are obtained, about 1 L of the water sample is placed into a bottle with a narrower neck (to exaggerate the oil measurement) and filled to the start of the neck. Using an etching tool or special marker, a line is placed at the top of the water level to indicate where the oil would start. About 1 mL (or 5 drops) of the dispersant to be used is added to 10 mL of oil. This is mixed briefly and then poured into the test vessel. A mark is placed at the top of the oil. The test vessel is shaken vigorously for 1 minute and let stand for 10 minutes and the top of the new oil level is marked. About half the oil should be dispersed before proceeding with full-scale dispersant application. For information purposes, the oil and dispersant laboratory effectiveness result should be obtained and compared to this value. If this test is positive or the oil is known to be dispersible, the dispersant operation will proceed. When applying dispersant, the best tactic is to apply the chemical to the thickest portions of the oil. This is generally done visually, although infrared cameras can greatly assist by identifying the heavy portions of the oil. Personnel in the spotter aircraft will give the required directions. The operation

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is continued for as long as the oil is thick and effectiveness is being noted as described in Section 16.2.4. The operation should be stopped if any of the following conditions are noted: lack of effectiveness, change in spill trajectory, a longer time than the precalculated time window, deteriorating weather conditions for flying, lack of wave energy, or any interferences to safe operations.

16.3. SAFETY AND POSTDISPERSION ACTIONS 16.3.1. Worker Health and Safety Precautions Worker safety should be a prime consideration during the dispersant operation. All personnel involved in a dispersant operation should complete a 40-hour hazmat course or the equivalent course in the relevant country. Personnel involved in a dispersant operation should be familiar with the technology and procedures in this guide. It is recommended that experienced operations staff attend at least a oneday course on the use of spray equipment and that an additional day be spent practicing spray operations and any emergency procedures. Personnel who are not totally familiar with equipment deployment and operations should spend at least one week in training and practice. All members of the helibucket operating team require extensive training. This training should be provided only by a highly experienced lead person, such as the helibucket supervisor. Operators and ground support personnel should generally participate in at least three days of training, including several practice runs. The size, structure, and navigational equipment of any vessels used must be suited to the wind, sea state, carrying requirements, and visibility conditions expected during the dispersant operation. For operations on the open water, vessels should have a reliable positioning system, such as a GPS, compass, or gyrocompass, working radar, working depth sounder, HF radio, VHF radio, and telephone. Under the relevant regulations in the country, each vessel is legally required to have the appropriate safety equipment in accordance with the size and type of vessel and the type of operation being undertaken. This includes life jackets, survival suits, life boats, life rafts, life-saving rings, flares, firefighting equipment, and navigation lights. Any chartered vessel should possess a valid Coast Guard inspection certificate or equivalent certificate for the country in which the operation will be carried out. Before chartering a vessel, a survey by a qualified ship surveyor or naval architect is recommended. All flying operations must be carried out in accordance with federal flight regulations. All aircraft to be used for applying dispersant should be carefully chosen to suit the required tasks. Flight plans must take into consideration all relevant weather conditions, such as wind, visibility, cloud types and height, the presence or forecasted presence of fog, precipitation, and sea state.

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For helibucket operations, the helicopter must have sufficient lift capacity to carry a pilot, co-pilot, and a helibucket full of dispersant and be equipped with a cargo hook able to sling the helibucket as well as jettison it. The pilot must test the jettison mechanism before each operation. For safety reasons, twin-engine helicopters are preferred, particularly for offshore operations, as they are more powerful than single-engine machines and can gain altitude faster. If a singleengine helicopter is used, it must be equipped with floats to facilitate emergency landings. The helicopter must comply with the relevant regulations regarding helicopter maintenance and the operation being undertaken. When arranging for helicopter services, it is recommended that the performance capability of the aircraft and its suitability for its intended use be confirmed with the helicopter pilot and/or helicopter operator. Only the pilot and co-pilot, or one other person if required for the spray activation, should ride in the helicopter during the helibucket operation, and all should wear a survival suit. During nearshore operations, updraft and downdraft winds against cliffs must be considered. In case of mechanical difficulty, emergency landing locations for the helicopter should be identified in advance through site surveillance. The public should not be exposed to sprayed dispersant exceeding the recommended human health concern levels. The most concern would be the exposure to overspray or drip from the nozzles during overflight. People who may be affected by the dispersant operation, even if only remotely, must be briefed about the operation. An important part of the safety program for a dispersant operation is establishing minimal safety zones. The safety zones established for the environmental issues should be sufficient for human populations as operations should not take place nearshore. Safety zones on the sea around the dispersant operation should be on the order of 0.5 km to avoid interfering with vessel traffic and to prevent spray from landing on surface vessels or workers in the area.

16.3.2. Follow-Up Monitoring It has been proposed that dispersant application be monitored to determine whether or not the initial spray had any effect. The protocols currently consist of some visual criteria and often a surface monitoring program consisting of using in-situ fluorometers to gauge the relative effectiveness of a dispersant application. The current published methods including the SMART (Special Monitoring of Advanced Response Technologies) and the SERVS (Shoreline Environmental Research Facility) protocols do not assure that effectiveness is gauged accurately. There is still potential for answers that are completely opposite to the actual situation. Furthermore, the current protocols are limited by basic physical and chemical problems so that at best they are estimates of whether the dispersant application is completely ineffective or somewhat effective.

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Monitoring oil concentrations in the water column would provide useful scientific information, although this information may not be useful to the incident commanders because of the complexities of the measurements. Visual surveillance is at this time the primary means of determining the effectiveness of the dispersant application. At least one experienced person should be employed for the visual surveillance to be effective. It is also recommended that buoys be used to track the plume and the remaining slick. Davis Drifters can be used to track the plume, and slick tracker buoys can be used to track the remaining slick. Further visual surveillance of the slicks is necessary for at least one day. The visual surveillance should be documented with photographs. Good quality digital still pictures are the best. The color quality must be good in order to distinguish between white (dispersant only) and yellow (dispersed oil) plumes. All images require timecoding. And finally, in conducting the visual surveillance, it must be recognized that there are a large number of false positives and negatives. These are summarized here.

16.3.2.1. Visual Indications That Show More Effectiveness Than Actually Occurred The following visual indications could create the impression that dispersion has occurred when in fact there is little or no dispersion. HerdingdThis is the phenomenon whereby the oil is pushed aside by the dispersant, resulting in a clear path behind the application vehicle. A dispersant application in which the oil was herded without any apparent effectiveness is shown in Figure 16.8. Dispersant-only plumedOnce in the water, dispersant forms a whitish plume until it mixes to a greater extent with the water. Such plumes could

FIGURE 16.8 View of a dispersant application where herding has occurred. This photo does not show any visible effectiveness.

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FIGURE 16.9 View of a dispersant application where dispersant-only plumes are seen. Part of this is caused by dispersant ineffectiveness on the heavy oil coming from the ship.

be mistaken for dispersed oil as opposed to dispersant only. Figure 16.9 shows a situation in which the dispersant has largely run off heavy oil. A closeup of this is shown in Figure 16.6. Herding into smaller, unseen stripdOil is often herded into small strips that are not visible from the air. SpreadingdDispersants increase the tendency of the oil to spread. The surface slick may spread out to thicknesses that are not visible. Lacingd“Lace” is a sheen of oil with “holes” in it that are caused by smaller drops of dispersant leading to herding. The “lace” is usually visible only from the surface and not from the air.

16.3.2.2. Visual Indications That Show Less Effectiveness Than Actually Occurred The following visual indications could create the impression that little or no dispersion is occurring when in fact there is some or significant dispersion. Plume under remaining slickdThe dispersed oil plume may move under the remaining slick. Plume not developed at time of observationdThe dispersed oil plume can take 15 to 60 minutes to develop to a maximum. Poor visibility conditionsdThe dispersed plume is not highly visible and can be obscured by haze and fog. It is unlikely, however, that a test application would be conducted under such conditions.

ADDITIONAL INFORMATION ASTM Guide for Oil Spill Dispersant Application Equipment; Boom and Nozzle Systems, F-141307. West Conshohocken, PA: American Society for Testing and Materials; 2007.

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ASTM Standard Test Method for Determination of Deposition of Aerially-Applied Oil Spill Dispersants, F-1738e07. West Conshohocken, PA: American Society for Testing and Materials; 2007. ASTM, Guide for Ecological Considerations for the Use of Oilspill Dispersants in Freshwater and Other Inland Environments, Lakes, and Large Water Bodies, STP F 1210e08. Philadelphia, PA: American Society for Testing and Materials; 2008. ASTM, Guide for Ecological Considerations for the Use of Oilspill Dispersants in Freshwater and Other Inland Environments, Rivers, and Creeks, STP F 1231e08. Philadelphia, PA: American Society for Testing and Materials; 2008. ASTM, Guide for Ecological Considerations for the Use of Oilspill Dispersants in Freshwater and Other Inland Environments, Ponds, and Sloughs, STP F 1209e2008. Philadelphia, PA: American Society for Testing and Materials; 2008. ASTM, 2465, Standard Guide for Oil Spill Dispersant Application Equipment: Single-Point Spray Systems. West Conshohocken, PA: American Society for Testing and Materials; 2007. Cedre, Merlin F. In: Using Dispersants to Treat Oil Slicks at Sea, www.cedre.fr; December 2009. Committee on Understanding Oil Spill Dispersants. Efficacy and Effects (National Research Council of the National Academies)(NAS), Oil Spill Dispersants: Efficacy and Effects. Washington, DC: National Academies Press; 2006. Exxon Mobil. Dispersant Guidelines. Reston, Virginia: Exxon Mobil Corporation; 2008. Fingas MF. A Review of Literature Related to Oil Spill Dispersants, 1997‑2008. Anchorage, Alaska: Prince William Sound Regional Citizens’ Advisory Council (PWSRCAC) Report; 2008. Fingas MF. Oil Spill Dispersants: A Technical Summary, Chapter 15; 2010. IPIECA. Net Environmental Benefit Analysis. London, UK: International Petroleum Institute for Environmental Consultation; 1993. IPIECA. Chemical Dispersion. London, UK: International Petroleum Institute for Environmental Consultation; 1993. Lewis A, Merlin F, Daling P, Reed M, Applicability of Oil Spill Dispersants: Part I, Overview. European Maritime Safety Agency, EMSA, London, 2009.

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APPENDIX A. SPECIFIC SPILL SCENARIOS AND DISPERSION STRATEGIES

Scenario 1 Dispersion at Sea Location: At sea Position: Offshore Proximity of Oil to Resources: A large slick of oil well away from the shore but heading to shore. Condition of Oil: The oil is light or medium crude slick and is more than 1 mm thick, fresh, and not emulsified. Weather and Sea State: Seas of 0.5 to 2 m Protection Target: Birds and mammals nearshore, shoreline.

Scenario 2 Dispersion at Sea Location: At sea Position: Offshore Proximity of Oil to Resources: A large slick of oil well away from the shore but heading to sea (with a probability of it heading to shore in the future). Condition of Oil: The oil is light or medium crude slick and is more than 1 mm thick, fresh, and not emulsified.

Strategy General This is the absolutely ideal condition for dispersion. Verify wind and current direction to ensure that dispersing the slick will not affect people, property, or environmentally sensitive areas. As a first response, as much of the slick as possible can be dispersed. Ensure that sufficient resources are available as soon as possible to deal with at least the leading edge of the slick. If the pre-test or data show that the oil is marginally dispersible, continue operation but stop if effectiveness is not seen. Dispersant Strategy Focus attention on the thick leading portion of the slick. The slick should be approached from downwind. Monitoring Aircraft overflights should be carried out to ensure that the slick is being dispersed and that the plume is not heading toward sensitive areas. A standby boat could be used to take water samples or conduct fluorometry. The dispersant operation should be stopped if it is seen that it is not effective.

Strategy General This is an ideal condition for dispersion, however protecting shoreline amenities is less of a priority. Verify wind and current direction to ensure that dispersing the slick will not affect people, property, or environmentally sensitive areas. As a first response, as much of the slick as possible can be dispersed. Ensure that sufficient resources are available as soon as possible to deal with at least the leading edge of the slick. If the pre-test or data show that the oil is marginally dispersible, continue operation but stop if effectiveness is not seen. Dispersant Strategy Focus attention on the thick leading portion of the slick. (Continued )

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Scenario 2 Dispersion at Sea Weather and Sea State: Seas of 0.5 to 2 m Protection Target: Birds and mammals nearshore, shoreline if the oil changes its offshore trajectory.

Scenario 3 Dispersion at Sea Location: At sea Position: Offshore Proximity of Oil to Resources: A large slick of oil well away from the shore but heading to shore. Condition of Oil: The oil is light or medium crude slick and is more than 1 mm thick, fresh, and not emulsified. Weather and Sea State: Seas greater than 2 m but currently less than 4 m, winds >20 m/s or 40 knots. Protection Target: Birds and mammals nearshore, shoreline.

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Strategy The slick should be approached from downwind. Monitoring Aircraft overflights should be carried out to ensure that the slick is being dispersed and that the plume is not heading toward sensitive areas. A standby boat could be used to take water samples or conduct fluorometry. The dispersant operation should be stopped if it is seen that it is not effective.

Strategy General This is a marginal condition for dispersion. Verify that the operation can be done safely before proceeding. Verify wind and current direction to ensure that dispersing the slick will not affect people, property, or environmentally sensitive areas. As a first response, as much of the slick as possible can be dispersed. Ensure that sufficient resources are available as soon as possible to deal with at least the leading edge of the slick. If the pre-test or data show that the oil is marginally dispersible, continue operation but stop if effectiveness is not seen. Dispersant Strategy Focus attention on the thick leading portion of the slick. The slick should be approached from downwind. Monitoring Aircraft overflights should be carried out to ensure that the slick is being dispersed and that the plume is not heading toward sensitive areas. The dispersant operation should be stopped if it is seen that it is not effective.

Scenario 4 Dispersion in a Bay

Strategy

Location: Bay Proximity of Oil to Resources: A large slick of oil well away from the shore but heading to sea. Condition of Oil: The oil is light or medium crude slick and is more than 1 mm thick, fresh, and not emulsified.

General This is a marginal condition for dispersion. Verify wind and current direction to ensure that dispersing the slick will not affect people, property, or environmentally sensitive areas. Verify that the depth for at least 5 km is above 10 m or the local restriction. As a first response, as much of the slick as possible can be dispersed.

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Scenario 4 Dispersion in a Bay Weather and Sea State: Seas of 0.5 to 2 m Protection Target: Birds and mammals nearshore, shoreline if the oil changes its offshore trajectory. Water Depth: More than 10 m (or local restriction) for at least 5 km.

Strategy Ensure that sufficient resources are available as soon as possible to deal with at least the leading edge of the slick. If the pre-test or data show that the oil is marginally dispersible, continue operation but stop if effectiveness is not seen. Dispersant Strategy Focus attention on the thick leading portion of the slick. The slick should be approached from downwind. Monitoring Aircraft overflights should be carried out to ensure that the slick is being dispersed and that the plume is not heading toward sensitive areas. A standby boat could be used to take water samples or conduct fluorometry. The dispersant operation should be stopped if it is seen that it is not effective.

APPENDIX B. NOMOGRAMS TO CALCULATE SPREADING AND VISCOSITY WITH TIME TABLE B1 Calculation of Spreading and Viscosity Change Spill Size Area (sq km) at Time Type

tons

1 hour

12 hours

24 hours

48 hours

light crude

100

1

2

4

7

1000

9

49

85

149

10000

312

1205

2041

3508

100

1

2

4

7

1000

9

49

84

146

10000

302

1200

2040

3492

100

1

3

4

8

1000

7

49

84

146

10000

249

1144

2067

3773

medium crude

heavy crude

(Continued )

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TABLE B1 Calculation of Spreading and Viscosity Changedcont’d Slick Thickness (mm) Type

tons

1 hour

12 hours

24 hours

48 hours

light crude

100

2.2

1

0.7

0.5

1000

6.7

2.4

1.7

1

10000

12

5.1

3.6

2.4

100

2.2

1

0.8

0.5

1000

6.7

2.4

1.7

1

10000

12

5.1

3.7

2

100

2.3

1

0.8

0.6

1000

7

2.6

1.9

1.2

10000

12

5.5

4

2.7

medium crude

heavy crude

Viscosity mPa.s Type

tons

1 hour

12 hours

24 hours

48 hours

light crude

100

46

196

347

1220

1000

28

125

226

810

10000

22

88

155

550

100

310

1300

2300

6700

1000

198

830

1500

4500

10000

163

590

1070

31,100

100

1460

2900

4600

30,000

1000

1390

2300

3500

220,000

10000

1380

2000

2900

170,000

medium crude

heavy crude

Rules of thumb e slick thickness should be greater than 2 mm e viscosity should be less than 5000 mPa.s italics shows situations where effective dispersion is unlikely.

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TABLE B2 Spray Coverage and Hours for Different Spill Sizes Hours operation to disperse (within 24 hours time window) Dispersant Coverage Coverage 100 1000 Load (L) per hour (Ha) per day (Ha)) tons tons

10,000 tons

small boat

1000

10

80

40

850

20410

small ship

3000

20

160

20

425

10205

supply ship

10,000

30

240

13.3 283

6803

small helicopter

700

170

280

2.4

50

1201

large helicopter

2000

280

800

1.4

30

729

Agricultural spray plane

400

170

270

2.4

50

1201

DC-3

4500

540

2400

0.7

16

378

DC-4

8000

840

4800

0.5

10

243

DC-6

11,000

1010

7330

0.4

8

202

C-130 (Hercules)

13,000

1010

8670

0.4

8

202

tons of dispersant

5

50

500

drums of dispersant

25

250

2500

Hours operation to disperse (within 48 hours time window) Dispersant Coverage Coverage Load (L) per hour (Ha) per day (Ha))

100 1000 tons tons

10,000 tons

small boat

1000

10

80

70

1490

35080

small ship

3000

20

160

35

745

17540

supply ship

10,000

30

240

23.3 497

11690

small helicopter

700

170

280

4.1

2060

88

(Continued )

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TABLE B2 Spray Coverage and Hours for Different Spill Sizesdcont’d Hours operation to disperse (within 48 hours time window) Dispersant Coverage Coverage Load (L) per hour (Ha) per day (Ha))

100 1000 tons tons

10,000 tons

large helicopter

2000

280

800

2.5

53

1250

Agricultural spray plane

400

170

270

4.1

88

2060

DC-3

4500

540

2400

1.3

28

650

DC-4

8000

840

4800

0.8

18

420

DC-6

11,000

1010

7330

0.7

15

350

C-130 (Hercules)

13,000

1010

8670

0.7

15

350

tons of dispersant

5

50

500

drums of dispersant

25

250

2500

* Presuming the maximum number of hours of operation and daylight, per vehicle.

10000 10,000 tons

Area (sq. km)

1000

100 1000 tons

10 100 tons

1

100 tons 1000 tons 10,000 tons

0.1 0

10

20

30

40

Time (Hours) FIGURE B1 Nomogram for calculating slick area with spill size.

50

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100 tons 1000 tons 10,000 tons

12

Thickness (mm)

10 10,000 ton

8 6 1000 ton

4 2

Practical thickness limit

0 0

10

20

30

40

50

Time (Hours) FIGURE B2 Nomogram for calculating slick thickness with spill size and time.

100 ton 1000 ton 10,000 ton

Viscosity (mPa.s)

10000

increasing difficulty to disperse

1000

100

10 0

10

20

30

40

50

Time (Hours) FIGURE B3 Nomogram for estimating oil vicosity time e light crude.

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100 ton 1000 ton 10,000 ton

1e+5

Viscosity (mPa.s)

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limit of practical dispersion

1e+4

1e+3 increasing difficulty to disperse

1e+2 0

10

20

30

40

50

Time (Hour) FIGURE B4

Nomogram for estimating oil vicosity with time e medium crude.

100 ton 1000 ton 10,000 ton

Viscosity (mPa.s)

1e+5

10,000 ton

100 ton limit of practical dispersion

1e+4

increasing difficulty to disperse

1e+3 0

10

20

30

40

50

Time (Hours) FIGURE B5 Nomogram for estimating oil vicosity with time e heavy crude.

Chapter 17

Procedures for the Testing and Approval of Oil Spill Treatment Products in the United KingdomdWhat They Are and Considerations for Development Mark Kirby

Chapter Outline 17.1. Background and Introduction 17.2. Toxicity Testing Procedures 17.3. Test Description

611 613 615

17.4. Testing with Heavy Fuel Oils 17.5. The 2007 Uk Scheme Review 17.6. Conclusions

619 620 626

17.1. BACKGROUND AND INTRODUCTION The United Kingdom is characterized by a relatively long and diverse coastline for the size of the country. The UK government regards the protection and sustainable use of the marine environment as a high priority and has a long history of developing legislation to control potentially damaging human activities. The latest of these is the Marine and Coastal Access Bill which received royal assent in November 2009. It seeks to promote marine spatial planning and sustainable use of marine resources, and to put in place strong regulatory schemes to monitor and control activities. The UK also acknowledges the importance of marine-based commerce and transport to the national economy and is surrounded by some of the busiest Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10017-6 British Crown Copyright Ó 2011.

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shipping lanes in the world. With this activity inevitably comes a higher risk of marine accidents and subsequent marine damage from the spillage of oil and other cargoes. The response to oil spills in UK marine waters is undertaken by the Maritime and Coastguard Agency (MCAdan executive agency of the UK Department of Transport) which, along with commercial partners, have at their disposal a wide array of options to tackle spills in order to mitigate their impacts. The ability to treat oil spills with treatment products is regarded as a powerful option during response scenarios. The use and approval of spill treatment products, such as chemical dispersants, is controlled in the UK by the Marine Management Organisation (MMO e an executive non-departmental public body of UK government) using powers available to them under the Marine and Coastal Access Act 2009 (previously under the Food and Environment Protection Act 1985).1 The Marine and Coastal Access Act requires a license to be issued for the deposit of any substance or article in the sea. Exemptions to the act allow, that a license is not required for the deposit of a substance for the purpose of treating oil on the surface of the sea, subject to certain conditions. The MMO is the licensing authority under the Act and requires that all oil treatment products for use in waters over which they have jurisdiction must be approved. This paper explains the approval process and gives an overview of the toxicity testing procedures. Under the UK approval scheme, there is a need to assess and approve all types of oil spill treatment products. At present four different groups are recognized: dispersants, sorbents, bioremediation agents, and miscellaneous. Depending on the type of product, a range of testing is required with respect to both efficacy and toxicity, and only if products pass the appropriate assessments can they be considered for use in UK waters. However, two types of toxicity assessment, the Sea Test and the Rocky Shore Test, are compulsory for all products. Product approvals are reviewed, and renewed if appropriate, every five years (more frequently for bioremediation products).

17.1.1. Preassessment Requirements The testing and approval procedures in the UK have been in place for nearly 30 years and form a well-established statutory scheme. More details of the scheme can be found at the MMO website (www.marinemanagement.org.uk). Applicants for a product approval need to fill out a comprehensive application form before any testing is initiated. Information such as manufacturer identification, manufacturers’ recommended application rates, and chemical constituents are all required before the application proceeds. The proposed product labeling is also reviewed under the scheme. All chemical dispersants need to undergo efficacy testing procedures before toxicity assessment. The current test specification for dispersants in the UK is LR448.2 Efficacy testing is not currently required for sorbent or miscellaneous

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(e.g., gelling agents, demulsifiers, herders, surface cleaners, etc.) products, although the licensing authorities will request appropriate documentary evidence on a case-by-case basis and may review this situation at a later date. Bioremediation products will also require an efficacy assessment before they are toxicity tested. In addition to efficacy and toxicity testing, bioremediation agents require more extensive assessment than other products due to the greater concern expressed with regard to the addition of biological agents or microbial activity enhancing agents to the natural environment. This will include a basic microbiological hazard assessment (if appropriate) to ensure that the microbial strains present do not constitute a pathogenic risk to humans, fish, or shellfish. Only once the appropriate information is provided and efficacy conditions are met will a product be submitted for further toxicity testing.

17.2. TOXICITY TESTING PROCEDURES 17.2.1. Reference Oil The oil used in all toxicity tests is Kuwait crude. This medium crude oil has been used extensively in toxicity studies on the effects of dispersants for many years at the Cefas Laboratories, so a good reference base of results exists.3-6 On reception, a fresh batch of test oil is decanted into smaller air-tight storage containers that are filled to the brim to avoid loss of volatile fractions during storage. They are stored in a cool area, and a new container is used for each test. New oil batches are chemically analyzed by gas chromatography-flame ionization detector (GC-FID) or gas chromatography-mass spectrometry (GC-MS), and the chromatogram is examined to confirm that no loss of volatiles has occurred. Such a loss of volatile components (weathering) can result in a dramatic reduction in oil toxicity. Figure 17.1 shows chromatograms of whole (Figure 17.1a) and weathered (Figure 17.1b) Kuwait crude oil. The chromatograms in Figure 17.1 were produced with the following gas chromatograph set up: Hewlett Packard 5890a GC coupled to a Hewlett Packard 7673 auto-injector, on-column injector, and hydrogen gas carrier. The column was a fused silica capillary column, 25 m by 0.3 mm internal diameter, coated with SE-54 type phase. Sample volumes of 1 ml were injected at 60 C and held for one minute. Oven program was set at 60e320 C, with hold for 7 minutes and a runtime of 60 minutes. Detection was by flame ionization (FI) or mass-spectrometer (MS). Any equivalent GC setup will suffice.

17.2.2. Test water The water used for maintenance of test animals in stock tanks and in all toxicity tests is natural seawater taken from a site known to be relatively free of

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FIGURE 17.1 Gas chromatographs showing spectra of whole (a) and weathered (b) Kuwait crude oil.

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industrial, agricultural, and sewage pollution. It should be filtered to 10 mm and brought to the test temperature of 15 C (þ 1 C) prior to use. The salinity must be in the range of 28 to 35&.

17.2.3. The Sea Test This test is compulsory for all oil treatment products.

17.2.3.1. Rationale This Sea Test is based on the premise that if oil treatment products are correctly applied to an oil slick at sea, marine organisms will be exposed to a mixture of oil and product rather than to a suspension or solution of product alone. The test therefore compares the toxicity of oil dispersed under standard conditions of mechanical agitation with that of the same amount of oil treated with the product in question under the same conditions of mechanical agitation. Research has shown that concentrations of oil (especially dispersed oil) under slicks reduce rapidly in the first few hours.6,7 It was, however, technically difficult and unrealistic in a routine and reproducible laboratory test to reproduce this phenomenon. Therefore, it was decided to base the test on the exposure of a marine organism to a fixed concentration for a fixed period. 17.2.3.2. Test Species The test species is the brown shrimp (Crangon crangon). They should be between 50 and 70 mm total length and caught from an area known to be relatively free of contamination. They are acclimated in well-aerated, gently flowing seawater for 4 to 5 days prior to use in a test. They are not fed during this acclimation period.

17.3. TEST DESCRIPTION Developmental work showed that exposure of shrimp to 1,000 ppm of Kuwait crude oil produced a measurable mortality during the Sea Test procedure, and this concentration was therefore adopted. The concentration of oil used in the test is very high compared to those that might be observed in the field, and thus includes a safety factor for species more sensitive than shrimp to the acute toxic effects of oil. Briefly, the Sea Test involves the exposure of shrimp to either mechanically or chemically dispersed oil (Kuwait crude oil) in 18 liter cylindrical tanks (20 shrimp per tank). In all, 18 ml (1,000 ppm) of oil is added, and dispersion is facilitated by a propeller mounted within a central column and driven via a magnetic coupling to a pneumatic motor. Shrimp are exposed to the dispersed oil for 100 minutes before being removed to recovery tanks of clean flowing seawater for 24 hours. There are five replicate tanks for each

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FIGURE 17.2 The statutory Sea Test rig setup as used for the toxicity assessment of oil spill treatment products in the United Kingdom.

treatment. After the recovery period, mortalities are determined, and statistical comparisons are made between the results gained by mechanical and chemical dispersion. The premise of the test is that products will be deemed to fail (and therefore not be eligible for a UK approval) if the toxicity of treatment oil under these conditions is significantly greater than the toxicity of the oil alone (see Section 17.3.5 for an explanation of significance determination). Figure 17.2 shows the Sea Test rig set up, and Figure 17.3 displays a Sea Test in progress, clearly showing different levels of oil dispersion within the tanks. Full details of the test procedure can be found in a published protocal.8

17.3.1. The Rocky Shore Test The Rocky Shore Test is compulsory for all dispersants, bioremediation agents and “nonrecoverable” miscellaneous products. It will also be required for “recoverable” sorbents or miscellaneous products if they are to be used in a rocky shore environment or stand any chance of reaching such an environment after usage. A Rocky Shore Test should only be carried out if the candidate product has already passed the compulsory Sea Test.

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FIGURE 17.3 A standard Sea Test in process. The difference can clearly be noted between mechanically dispersed oil (left) and chemically dispersed oil (right).

17.3.2. Rationale The intertidal zone is of great value both in amenity and ecological terms. Detrimental effects of using oil treatment products (dispersant spraying, etc.) on shorelines are likely to have only limited impact on adjacent commercial fisheries (e.g., cockles) if applied on sandy beaches and will be relatively benign on dynamic pebble beaches where there is good drainage and a relatively impoverished species community. Therefore, for these environments (i.e., sandy/pebble amenity beaches) it is assumed that a product passing the Sea Test will be of an acceptably low risk. However, the death of grazing organisms (e.g., winkles and limpets) that inhabit rocky shores can lead to a much more significant deleterious ecological change due to extensive uncontrolled growth of seaweed. Consequently, a toxicity test was developed using a typical intertidal grazing organism, the common limpet (Patella vulgata). When products are used to clean oil from beaches, animals are exposed to very different conditions to that experienced at sea. Both oiled and unoiled animals may be exposed to neat product and left exposed until they are washed by the next incoming tide or the use of water hoses. The Rocky Shore toxicity test for all dispersants and bioremediation agents has therefore been based on these exposure conditions. Preliminary tests in the laboratory showed that the mortality of limpets exposed to oil is high and the detection of a toxic effect due to the product over and above that of the oil would be difficult and less accurate than determination of the effect of the product alone. In addition, a product is likely to be applied

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over wide areas of shore and the evaluation of a particular product should also take into account the effect of the product on those parts that are unoiled as well as those that are oiled. Therefore, the test finally adopted was designed to assess the effect of application of the product on unoiled limpets. The amounts of product applied to the test organism were based on the density of application likely to be encountered in practice. Similarly, the test sought to simulate the initial exposure to a product for an average period of 6 hours followed by successive tidal rinsing. In order to compensate for seasonal variations in the susceptibility of the test species, the effects of a standard oil alone were also assessed. Granular sorbents and some miscellaneous products have been shown in preliminary tests to express a different type of deleterious effect than that of direct toxicity: that of physical adhesion interference. This phenomenon also appears to be much more acute when the product is sorbed with oil; therefore, the Rocky Shore Test for these products is slightly modified to take this into account.

17.3.3. Test Species The test species is the common limpet, Patella vulgata of 30e40 mm shell width. The limpets should be collected from a relatively uncontaminated beach. In order to avoid damage, the limpets should be taken from a beach with chalk boulders from which they can be carefully removed with an oyster knife without breaking or chipping their shells. They should be kept as cool as possible and returned to the laboratory immediately. They are placed, shell uppermost, in polyethylene stock tanks lined with polyethyene sheeting to facilitate subsequent removal. The animals are maintained in well-aerated, gently flowing seawater and subjected to intermittent immersion (about 18 h immersed and 6 h dry) to simulate tidal action. The limpets should be acclimated to laboratory conditions (i.e., 15 C 1 C air and water temperature) for at least 96 h before use. They are not fed during their stay in the laboratory.

17.3.4. Test Description Briefly, the Rocky Shore Test involves the introduction of limpets onto Perspex plates (20 limpets per plate) (Figure 17.4) on which they are exposed to oil or dispersant at a dose of 0.8 ml of per limpet (0.4 l m2 equivalent under these test conditions), applied as a spray from a hand-held spray bottle. The limpets are left in air exposed to the dispersant or oil for 6 hours prior to being rinsed with clean seawater and the plates being placed horizontally in tanks of clean flowing seawater. The mortality of the limpets are monitored over a further 72 hours during which tanks are drained daily and the limpets are left in air for a period of 6 hours to simulate a tidal cycle. After this period, mortalities are statistically compared between five treatment (dispersant only) and five control (oil only) exposures. The premise of the test is that products will be deemed to

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619

FIGURE 17.4 The common limpet (Patella vulgata) is used in the standard Rocky Shore Test. Here the test organisms are seen on the Perspex plate prior to oil or product treatment.

fail (and therefore not be eligible for a UK approval) if the mortality observed in the product exposures significantly exceeds that gained with the oil alone. Full details of the test procedure can be found in a published protocol.8

17.3.5. Test Validity and Pass/Fail Assessment The tests described above allow for assessments on the basis of comparing the mortalities occurring in five replicate “controls” against those in five replicate “treatments.” Each set of five replicates must be subject to statistical analysis to ensure that the set is homogeneous. If this is not the case for treatment or control, the test is invalid. Once it has been confirmed that the replicate groups are homogeneous, the two sets are compared statistically (Student’s t-test, F variance ratio) for differences in their mean. If the oil toxicity is significantly ( p < 0.05) greater in the treatment than in the controls and also results in a designated percentage increase in mortality, then the product is deemed to have failed the assessment and will not be granted an approval for use in UK waters. The regulatory authority retains the right to decide on pass/fail in borderline cases after taking scientific expert advice.

17.4. TESTING WITH HEAVY FUEL OILS The original suite of test procedures developed in the UK uses a standard crude oil as the surrogate oil for those that could be encountered during real scenarios. The rationale behind this was twofold: (1) spills of crude oil were considered the greatest threat and the most likely candidate for successful treatment, and (2) only medium to light oils were likely to be amenable to dispersion by the generation of dispersants available at that time.

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More recently, it has been acknowledged that, while spills of lighter oils remain a risk, a more regular threat comes from spills of heavy or intermediate fuel oils that virtually all vessels of a certain size carry. Some larger vessels carry thousands of tons of fuel oil alone. Therefore, it is regarded beneficial for spill responders to have treatment options appropriate to tackle fuel oil spills, and several modern dispersant formulations have been proven to be effective in the treatment of heavy fuel oils under certain circumstances. This issue was considered a high priority during a recent review (2007) of the UK testing and approval scheme, and as a result an amended toxicity test assessment, based on the current Sea Test, is being developed at the Centre for Environment, Fisheries, and Aquaculture Science. The new test procedure was finalised in 2010 and could become part of the statutory approval scheme by 2011. The exact way in which the new protocol may be introduced into the approval scheme is still under review but the introduction of this assessment will allow certain products to have an additional designation on their approvals to allow them to be used on heavy fuel oil spills.

17.5. THE 2007 UK SCHEME REVIEW 17.5.1. Review and Improvement Essential as regulatory approval schemes are considered to be, their basis and mechanisms need to be reviewed regularly to ensure that they are taking account of new developments and that they remain fit for purpose. The MMO, the UK regulator, has been aware of this need and conducted an original review of the use and approval of dispersants in 1993.9 This report made a number of recommendations, the most significant of which was that all approved products should be made to pass both the Sea and the Rocky Shore Test assessments before being granted an approval. Previously, products that failed the Rocky Shore Test could be approved for offshore use only. This decision was based on the application of the precautionary principle in order to avoid products designed for use offshore from being applied on coasts and vice versa. There was no direct scientific justification for the decision as it was considered that, if used correctly, products designed for use “at sea” could still be used safely away from shorelines. In 2007, the UK government conducted a second scheme review that considered in much greater detail whether the testing methods and approval processes are appropriate for modern products and whether they take into account any significant operational considerations.

17.5.2. Specific Issues 17.5.2.1. Sea and Rocky Shore Test Assessment? The need for products to pass both toxicity test procedures was reassessed. The original requirement, brought in over 10 years ago, had the required effect in

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that it resulted in an approved list that consisted of products that could be used safely in all marine environments. However, this also meant that manufacturers had to produce products that could pass both tests and therefore this somewhat stifled the development of specialist products for use in offshore or near-shore scenarios, and removed from the list some products that were particularly effective when treating heavy oils. Concerns have been raised that the general reduction in the number of products approved for use in the UK and the lack of ‘specialist’ products has limited the product options for responders. On balance, the review considered that it was prudent to maintain that standard products should pass both Sea and Rocky Shore Tests to gain approval. However, it is likely that new approvals for products to treat heavy fuel oils (see above) will only need to gain approval against the newly developed Sea Test for Heating Fuel Oils (HFOs).

17.5.2.2. Type 2 versus Type 3 Testing The majority of modern dispersants can be used as a type 2 (water-diluted concentrate) or a type 3 (concentrate used neat) product. As such, they are designated type 2/3 dispersants. In the current testing protocols it is stipulated that type 2/3 dispersants only have to pass toxicity assessments as a type 2 dispersant to get approval as a type 2/3. This was introduced on the basis that early products appeared to show less efficacy differentiation whether applied as a type 2 or 3. However, we now have limited evidence to suggest that results from the standard Sea Tests can differ depending on whether the product is applied as a type 2 or 3. Furthermore, in the majority of cases, it is apparent that the toxicity increase is greater when tested as a type 3 (Figure 17.5). The

FIGURE 17.5 A selection of comparative brown shrimp (Crangon crangon) mortality results obtained during Sea Test exposures when a dispersant is applied as either a type 2 or a type 3 product.

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majority of dispersants in any large-scale response are used in the undiluted type 3 mode (from aircraft), and there is some concern that products are approved for use as a type 3 product, although their approval was given on the basis of testing as a type 2 product. It is uncertain how significant this is, and certainly most type 3 uses will be offshore where there is a high potential for dilution. Nevertheless, the review concluded that products should undergo testing for both type 2 and type 3 uses, if the applicant requests.

17.5.2.3. Different Oils It is recognized that significant marine oil spills are increasingly likely to involve heavy and very heavy fuel oils, which can be carried in the 1000s of tons by large ocean-going vessels as bunker fuels alone. Furthermore, the volume of heavy and residual fuel oils transported through UK waters from Russia and the former Soviet Union states continues to grow, and the increased risk of spills of heavy fuel oils has been recognized following recent incidents involving the product tankers Prestige and Erika. The need to ensure that there are products available specifically approved for use on heavier oils has been one of the most high-profile debates in the current scheme review, and it seems likely that a new category of approval will be introduced to approve dispersants for use against these types of oil. Any new approval will be based on a product passing appropriate efficacy and toxicity tests using a representative heavy oil, but the appropriate pass/fail levels will need to be established. 17.5.2.4. Product:Oil Ratios In the current UK Sea Test all dispersant products are tested at a dispersant:oil ratio of 1:10. This is a higher ratio than most manufacturers recommended application rates (1:20e1:30) but allows for a safety margin in the event that excess dispersant is applied during a real incident. Nevertheless, the manufacturers of modern dispersants claim that they are highly efficacious and can work effectively at oil:dispersant ratios as low as 1:100, and, therefore, the 1:10 test ratio is too stringent. Preliminary evidence (Figure 17.6) using three different dispersants at a range of dispersant:oil ratios in the Sea Test shows a reduction in total mortality at lower ratios. In certain cases the change in mortality would have been enough to affect whether a product passed or failed the approval process. This implies that, providing a product could demonstrate proven efficacy at lower ratios, certain efficacious products could be approved with ratio use limitations. The review considered this aspect very carefully but concluded that lower ratios should not be incorporated into the statutory testing procedures while there remain uncertainties about how dose ratios could be operationally

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FIGURE 17.6 Mortalities of brown shrimp (Crangon crangon) during a standard Sea Test when three selected dispersants are applied at reducing product:oil ratios.

controlled and concerns about possible over-application. In the future it is possible that the current tests could be modified such that a dilution element is introduced during the test exposure period (100 minutes), so that dispersed oil concentrations reduce quicker over the exposure period for more efficacious products.

17.5.2.5. Physical Conditions It is known that certain physical conditions can have a significant impact on dispersant efficacy and hence toxicity. The UK tests are based on standard conditions of 15 C and 30e35&. This is representative of most offshore summer conditions in the UK, but the question has been raised regarding whether products should be tested under differing physical conditions to ascertain their effectiveness and environmental acceptability in spill scenarios in other waters. In general, it is well appreciated that increases in temperature tend to result in higher levels of toxicity for most pollutants with most test species. Preliminary data proves this also to be true with the toxicity of Kuwait crude oil under Sea Test conditions (Figure 17.7). This relationship has also been seen in assessments of toxicity in dispersants.10 However, it also needs to be considered that oil viscosity generally reduces with increased temperature, and therefore a greater range of oils may be amenable to dispersion under these conditions.11 Converse to that is the fact that one would expect the oil to weather faster at higher water temperatures, and therefore the window of opportunity for successful dispersant treatment might be reduced. The impact of temperature on dispersant effectiveness is complex, leading some researchers to conclude that dispersant efficiency does not follow a general trend with increase in temperature and is different for each oil, depending on its properties.12

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FIGURE 17.7 The relationship between test temperature and final mortality levels of brown shrimp (Crangon crangon) exposed to Kuwait crude oil during the standard Sea Test.

Salinity is a very significant factor in the effectiveness of dispersants. All the major commercially available dispersants have been formulated for use in normal marine salinities of 30 &þ, and it has been well documented that the effectiveness of dispersants generally decreases at lower salinities.12,13 The reason for this is not fully understood. However, the effectiveness of a dispersant is, in part, a function of how much of the surfactant component of the formulation is available to interact and mix with the oil and thus reduce the oilewater interfacial surface tension. As salinity decreases, the surfactant effectively becomes more soluble, and thus less is available to interact with the oil. Sterling et al. discovered only a limited influence on dispersant effectiveness by changes in salinity when the oil and dispersant were premixed, and no significant impact was noted with respect to droplet size or subsequent coalescence kinetics under these conditions.14 The evidence suggests that the salinity effect on dispersant effectiveness is therefore primarily due to how this affects solubility, which is not such an issue when the oil and dispersant are premixed. Because premixing is not an option during real response scenarios, some research has been conducted to take this into account by increasing the salt content (by addition of calcium chloride) of the dispersant formulation and thus reducing its initial solubility on application.15 Toxicity is closely related to the solubility and bioavailability of toxic oil components (e.g., polycyclic aromatic hydrocarbonsdPAH). Solubility is much greater at lower salinities; therefore, the potential for toxicological impact of oil spills is, in general, lower in high-salinity environments. This effect is demonstrated for dispersed oil toxicity under Sea Test conditions (Figure 17.8). This increased solubility holds true for oil components whether or not dispersants are used, but is enhanced by the use of dispersants almost

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FIGURE 17.8 The mortality of brown shrimp (Crangon crangon) when exposed to chemically dispersed Kuwait crude oil in varying salinity conditions.

certainly as a result of decreased droplet size, which is also known to increase toxicity.16,17 Therefore, high-salinity environments could result in increased dispersion but lower solubility of toxic components, the combined impacts of which are a complex issue to extrapolate to the environment.18 This short review confirms that the issue of temperature and salinity is complex; therefore, it was not considered appropriate to attempt to incorporate these factors into the statutory testing process. However, it does highlight the fact that oil treatment products used in areas of high temperature/salinity (e.g., the Arabian Gulf) or low temperature/salinity (e.g., the Baltic Sea) may need to be assessed under specific test conditions in order to obtain the best list of approved products.19

17.5.2.6. Combined Toxicity/Efficacy Currently, the UK scheme uses distinct and separate assessments for toxicity and efficacy. This approach has worked well, and therefore it seems unlikely that it will change substantially. It has, however, been acknowledged that the various efficacy tests used globally tend to provide a similar ranking of products. Therefore it was considered whether efficacy results generated by other established methods can be used to support approval applications in the UK. The rationale underpinning the toxicity assessment in the UK is, however, quite distinct and, for the Sea Test, is heavily based on how a product application affects the toxicity of the oil rather than any assessment of the inherent toxicity of the product itself. The review has shown strong continued support for this approach and the protection it affords. The relationship between efficacy and toxicity is not straightforward and is still not well understood. While we continue to assess these elements in

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isolation, the statutory test process (which provides the greatest bulk of information in the UK) will not inform this debate further. As such, some consideration has been given to introducing a combined efficacy/toxicity testing procedure. The current Sea Test toxicity assessment incorporates an environment with a standard and reproducible mixing/energy regime from which an efficacy assessment could easily be derived. This would allow the direct comparison of efficacy and toxicity from the same test. However, because current standard guidelines are considered sufficient, the review did not support such a change to the test procedures.

17.5.2.7. Products Other Than Dispersants The current Sea and Rocky Shore Test procedures were designed specifically with the assessment of oil dispersants in mind and have been used or modified for the assessment of other products as required. In general, this has worked well, with the tests being fully suitable for the assessment of other types of products designed to be applied to oil directly on the sea surface (e.g., sorbents, etc.). Surface cleaners, however, are not designed to be added directly to oil slicks on the sea surface and therefore the current test procedures are perhaps less suitable for these products. Cefas has developed a specific testing approach to address the assessment of surface cleaners.8 In essence, this approach requires the development of a standard procedure for the oiling and weathering of surfaces, followed by a test procedure that will allow the surface to be treated with a given technique or product and all the runoff collected. The subsequent assessment will then be based on three pillars: (1) Efficacyddetermination of the success of oil removal from the surface via chemical analysis; (2) Oil Recoverabilitydvolumetric determination of the oil floating in the runoff tank; and (3) Toxicitydtoxicological assessment of the runoff water from the treatment. These three elements will enable an assessment of efficiency versus potential impact for a given coastal environment for a given approach. At the time of the review, relatively few surface cleaners were being submitted for formal approval; therefore, the development of a new test procedure was not felt to be a priority by the review. However, it is known that recreational and small users in ports and marinas not covered by the scheme are regularly using a variety of commercial surface cleaners (from domestic detergents to garage forecourt cleaners). Efforts to bring the need to use environmentally acceptable products to the attention of recreational users may result in changes in the future.

17.6. CONCLUSIONS The government-conducted review of the scheme was driven by an increased awareness that a number of issues needed to be considered to ensure the scheme remained “fit for purpose.” These issues had been raised by scientists,

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manufacturers, conservationists, and responders, and the review was designed as a wide consultation that would offer all the opportunity to comment on a broad range of relevant topics. The review considered the need for the scheme to be flexible and responsive to the manufacturers’ needs while addressing the needs and concerns of the conservationists and regulators. Presently, the scheme applies stringent testing for both efficacy and toxicity using limited oil types and conditions that result in an approved product list that can be applied to all oils and under all conditions (subject to permission). While it was acknowledged during the review that the current list of approvals did not allow a responder to make a choice of the most appropriate product for a range of scenarios based on scientific assessment, it was considered inappropriate to “overcomplicate” the tested process unnecessarily. The final conclusions of the review recognized the significance of all the issues raised to the use of oil spill treatment products in the marine environment. However, only two primary recommendations, which would require research to implement, were taken forward: 1. In recognition of the increased likelihood of fuel oil or heavy oil spills, it was recommended that a new test be developed to enable the toxicity testing of products designed for use on these types of oil. 2. In recognition of data that provide strong evidence that dispersant products elicit higher toxicity in the Sea Test when added as a type 3 (neat) as opposed to a type 2 (water diluted), it was recommended that the practice to approve products as type 2/3 on the basis of a type 2 test only should cease. Further research will be required to establish the type 2 versus type 3 toxicity differences and new pass/fail criteria for each test type. At the time of writing research is currently being initiated to address these issues.

REFERENCES 1. The Marine and Coastal Access Act 2009. London, UK: The Stationary Office; 11/2009 439546 19585. 2. Morris PR, Martinelli FNA. A Specification for Oil Spill Dispersants, Report No. LR 448 (OP). Stevenage: Warren Spring Laboratory (now part of AEA Technology); 1983. 3. Portmann JE, Connor PM. The Toxicity of Several Oil-Spill Removers to Some Species of Fish and Shellfish. Mar Biol 1968;322. 4. Dicks B. Some Effects of Kuwait Crude Oil on the Limpet, Patella Vulgata. Environ Pollut 1973;219. 5. Wilson KW. Toxicity Testing for Ranking Oil Dispersants. In: Beynon CR, Cowell EB, editors. Ecological Aspects of Toxicity Testing of Oils and Dispersants, 11. London: Applied Science Publishers; 1974. 6. Cormack D. Oil Pollution. Chem Ind 1977;605.

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7. Lunel T, Swannell R, Rusin J, Wood P, Bailey N, et al. Monitoring the Effectiveness of Response Operations During the Sea Empress Incident: A Key Component of the Successful Counter-Pollution Response. Spill Sci Techn Bull 1995;99. 8. Kirby MF, Matthiessen P, Rycroft R. Procedures for the Approval of Oil Spill Treatment Products in the UK. Lowestoft: DFR Fisheries Research Technical Report Series; 1996 (102): ISSN 0308e5589. 9. Rycroft RJ, Matthiessen P, Portmann JE. MAFF Review of the UK Oil Dispersant Testing and Approval Scheme. Lowestoft, United Kingdom: Directorate of Fisheries Research Publication; 1994. 10. George-Ares A, Clark JR. Aquatic Toxicity of Two CorexitÒ Dispersants. Chemosphere 2000;897. 11. Wei QF, Mather RR, Fotheringham AF. Oil Removal from Used Sorbents Using a BioSurfactant. Bioresource Techn 2005;331. 12. Chandrasekar S, Sorial GA, Weaver JW. Dispersant Effectiveness on Oil SpillsdImpact of Salinity. ICES J Mar Sci 2006;1418. 13. Blondina GJ, Singer MM, Lee I, Ouano MT, Hodgins M, et al. Influence of Salinity on Petroleum Accommodation by Dispersants. Spill Sci Techn Bull 1999;127. 14. Sterling MC, Bonner JS, Ernest ANS, Page CA, Autenreith RL. Chemical Dispersant Effectiveness Testing: Influence of Droplet Coalescence. Marine Pollution Bulletin 2004;48:969. 15. George-Ares A, Lessard RR, Becker KW, Canevari GP, Fiocco RJ. Modification of the Dispersant Corexit 9500 for Use in Freshwater. IOSC 2001;1209. 16. Ramachandran SD, Sweezey MJ, Hodson PV, Boudreau M, Courtenay SC, Lee K, et al. Influence of Salinity and Fish Species on PAH Uptake from Dispersed Crude Oil. Mar Poll Bull 2006;1182. 17. Norton MG, Franklin FL. In: Research into Toxicity Evaluation and Control Criteria of Oil Dispersants, 1. Lowestoft, MAFF: Fisheries Research Technical Report No. 57; 1980. 18. Riazi MR, Al-Enezi GA. Modelling of the Rate of Oil Spill Disappearance from Seawater for Kuwaiti Crude and its Products. Chem Eng J 1999;161. 19. Chapman H, Purnell K, Law RJ, Kirby MF. The Use of Chemical Dispersants to Combat Oil Spills at Sea: A Review of Practice and Research Needs in Europe. Mar Poll Bull 2007;827.

Chapter 18

Formulation Changes in Oil Spill Dispersants: Are They Toxicologically Significant? Mark F. Kirby, Paula Neall, Jennifer Rooke, and Heather Yardley

Chapter Outline 18.1. Introduction 629 18.2. Materials and Methods 630

18.3. Results 18.4. Discussion

633 638

18.1. INTRODUCTION The potential impact of oil spills on the marine environments and shorelines of the United Kingdom (UK) remains highly significant. Historically, illinformed usage of early dispersant products to tackle spills, such as the Torrey Canyon in the English Channel, resulted in detriment to the impacted shorelines and marine areas.1 This contributed to the development of further legislation to protect the marine environment from damage caused by deposits of a range of substances.2 To underpin this legislation, appropriate research was conducted, and schemes were developed to provide an approval process for chemical usage or other activities that could affect the marine environment. The scheme enables the assessment and approval of marine oil spill treatment products and the associated approval process began operating in the late 1970s and involved a combined assessment of efficacy and toxicity. The Marine Management Organisation (an executive non-departmental public body of UK government) is the current regulator of the scheme, under the Marine and Coastal Access Bill 2009, to issue approvals to all products used for the treatment of oil on the surface of the sea.2 From the point of view of environmental protection, the crucial part of the assessment is toxicity testing, which ensures that only products that are environmentally Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10018-8 British Crown Copyright Ó 2011.

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acceptable gain an approval. The standard toxicity testing procedures used in the scheme were developed and amended by The Centre for Environment, Fisheries and Aquaculture Science (Cefas) and comprise two distinct assessments, the Sea Test and the Rocky Shore Test.3,4 Once a product passes through the scheme successfully, it is issued an approval for use that is valid for five years. After this time, an applicant can renew the approval by simply completing an appropriate application form, which includes a section to enable reconfirmation that the formulation is the same as that originally tested. However, due to the longevity of the scheme, some products have been through three to four approval renewal assessments, and, as a result of changes in their chemical suppliers over that period, minor changes to their formulation have been requested. Formulation amendments are generally small changes (1 to 2% by volume) to one constituent, with an appropriate increase or decrease in a second to compensate. Acceptance decisions are informed by advice from an expert marine ecotoxicologist. However, as products can remain approved for many years, the potential for formulation differences, compared to that which was originally tested becomes greater. As a result, the assessment becomes more difficult without sound toxicological evidence to underpin it. As the approval scheme matured, both scientific advisors and regulators recognized that the “scientific judgment” approach inevitably allows for greater uncertainty in the advice. The consequences of doing nothing could lead to a situation where products are put on the market for which the potential environmental impacts are unknown. Hence, Defra commissioned Cefas to undertake basic research to investigate the toxicological properties of common dispersant constituents and to use these data to produce risk assessment guidelines that will allow the environmental effects of “formulation creep” to be assessed using a scientifically sound approach.

18.2. MATERIALS AND METHODS 18.2.1. General Approach l

l

l

l

Determine the inherent toxicity of a number of common constituents found in dispersant formulations using the Tisbe battagliai (a marine harpacticoid copepod) standard acute bioassay. Determine how increases in the proportion of certain constituents affect the inherent toxicity of the dispersant formulation. Using the standard suite of UK statutory tests (the Sea Test and Rocky Shore Test), determine how changes in formulation affect the ultimate result of the test. Use the data from the tests to develop risk assessment options that can be applied to the assessment of future requests for constituent change.

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631

18.2.2. Dispersants and Constituents Dispersant formulations are made up of three to seven individual constituents (e.g., surfactants, solvents, wetting agents, and other additives). Cefas hold a confidential database of dispersant constituent makeup, which was used to select a range of common dispersants and constituents for investigation. Although all approved dispersants have their own unique recipe, a number of constituents are commonly found in a range of products. Six constituents were selected for further research on the basis of their frequent usage in commercial dispersant formulations: monopropylene glycol (MPG); sorbitan monooleate (SMO); sodium dioctyl sulphosuccinate (SDS); 2-Butoxyethanol (2-B)(ethylene glycol monobutyl ether); polyethylene glycol monooleate (PEGMO); and dearomatized kerosene (DK). However, a further 20þ constituents are currently found in UK-approved dispersants. Both the constituents and dispersants were sourced directly from the dispersant manufacturers. Toxicity information on the constituent chemicals of currently approved dispersants was extracted from the material safety data sheets as supplied by the manufacturers and the literature where available. A summary of their aquatic toxicity is shown in Table 18.1.

18.2.3. Toxicity Tests 18.2.3.1. Tisbe battagliai The Tisbe battagliai (copepod) bioassay is a routinely used and internationally accepted method and was conducted as described by Hutchinson and Williams.6-8 A stock solution of the test chemical was prepared in filtered seawater extracted from the River Crouch, Essex, UK. The stock solution was vigorously shaken or stirred on a magnetic stirrer for one hour to ensure that the chemical was in solution or had reached maximum solubility. All solutions were prepared in stoppered volumetric flasks to avoid possible loss of volatiles. A solvent carrier, acetone, was used for assays with poorly soluble chemicals. The final concentration of acetone was 1 ml L1 in the final test solutions. From the stock solution, five concentrations selected from a log scale were prepared via serial dilutions, plus a seawater control. Exposures were conducted at 20 C (1). Mortalities were checked after a 48-hr exposure and median lethal concentrations (LC50s), and 95% confidence limits were calculated using Toxcalc (Tidepool Scientific Software, USA) by the maximum likelihood probit method. Reference tests using zinc sulphate were carried out alongside every batch of tests to ensure that the procedures met test validity criteria. 18.2.3.2. Sea Test The Cefas Sea Tests were carried out in strict accordance with the statutory protocol.4 Test organisms, brown shrimp (Crangon crangon), were obtained via

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TABLE 18.1 The aquatic toxicity of selected dispersant constituent chemicals. Values are median lethal concentrations (LC50s) in mg L1 (test duration in parentheses) sourced directly from the supplied material safety data sheets or literature.5 (nd ¼ no data) Chemical

CAS No.

Fish

Crustacean

Algae

2-Butoxyethanol (Ethylene glycol monobutyl ether)

111-76-2

1650 (24 H) Carassius auratus 1490 (96 h) Lepomis macrochirus

600-1000 (48 h) Crangon crangon1600 (48 h) Daphmia magna

>1000 (72 h) Unspecified

Monopropylene glycol

57-55-6

23,800 (96 h) Cyprinodon variegatus

>43,500 (48 h) Daphmia magna

>19,000 (72 h) Unspecified

Sorbitan monooleate

1338-43-8

>1000 (96 h) Oncorhynchus mykiss

nd

nd

Polyethylene glycol monooleate

9004-96-0

nd

nd

nd

26.1 (96 h) Oncorhynchus mykiss

7.1 (48 h) Daphmia magna

nd

nd

nd

nd

Sodium dioctyl sulphosuccinate Dearomatised kerosene

577-11-7

64742-47-8

trawl from the River Crouch, Essex, UK. They were acclimated to laboratory conditions for at least four days prior to testing. Briefly, the Sea Test involves the exposure of shrimp to either mechanically or chemically dispersed oil (Kuwait crude) in 18 liter cylindrical tanks (20 shrimps per tank). A total of 18 ml (1,000 ppm) of oil is added, and dispersion is facilitated by a propeller mounted within a central column and driven via a magnetic coupling to a pneumatic motor. Shrimp are exposed to the dispersed oil for 100 minutes before being removed to recovery tanks of clean flowing seawater for 24 hours. There are five replicate tanks for each treatment. After the recovery period, mortalities are determined, and statistical comparisons are made between the results gained by mechanical and chemical dispersion. The premise of the test is that products will be deemed to fail (and therefore not be eligible for a UK approval) if the toxicity of treatment oil under these conditions is significantly greater than the toxicity of the oil alone.

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18.2.3.3. Rocky Shore Test The Cefas Rocky Shore Test is a second toxicity test assessment that oil spill treatment products have to undertake to gain approval for use in UK waters. Along with the Sea Test, it is currently a compulsory requirement. All tests were carried out in accordance with the UK statutory protocol.4 Common limpets (Patella vulgata) were collected from the shore at Peacehaven, Sussex, UK (grid ref. 417 005) and acclimated under laboratory conditions for at least four days prior to use. Briefly, the Rocky Shore Test involves the introduction of limpets onto Perspex plates (20 limpets per plate) on which they are exposed to oil or dispersant at a dose of 0.8 mL of oil/dispersant per limpet (0.4 L m2 equivalent under these test conditions). The limpets are left in air exposed to the dispersant/oil for 6 hours prior to being rinsed with clean seawater and the plates being placed horizontally in tanks of clean flowing seawater. The mortality of the limpets is monitored over a further 72 hours during which tanks are drained daily and the limpets left in air for a period of 6 hours to simulate a tidal cycle. After this period, mortalities are statistically compared between five treatment (dispersant only) and five control (oil only) exposures. The premise of the test is that products will be deemed to fail (and therefore not be eligible for a UK approval) if the mortality gained in the product exposures significantly exceeds that gained with the oil alone.

18.2.4. Testing Schedule The study progressed through a logical sequence of testing. Initial tests were conducted using the Tisbe battagliai bioassay to determine the inherent toxicity of the selected constituents and a range of approved dispersants. The next stage of testing focused on the production of modified dispersant formulations in which the proportion by % weight of selected constituents was increased by between 0 and 32% (with a concomitant reduction in the constituent of lowest toxicity). The modified dispersants were then assessed alongside the original formulations using the statutory Sea and Rocky Shore Tests to determine whether the formulation changes would result in different performance under these test conditions. Finally, the modified dispersant formulations were tested for their toxicity to the harpacticoid copepod, Tisbe battagliai, and compared to the original formulations to determine the potential for percentage increases in specific chemical constituents to affect the inherent toxicity of the dispersant formulation.

18.3. RESULTS 18.3.1. Inherent Toxicity of Constituent Chemicals and Dispersants Table 18.2 shows the range of toxicity results obtained using the Tisbe bioassay for the tested constituents and dispersant formulations. Ranges are provided

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TABLE 18.2 The toxicity of selected oil spill dispersants and formulation constituents to the harpacticoid copepod, Tisbe battagliai. Values are ranges of median lethal concentrations (LC50’s) obtained from several test samples. Chemical

No of Samples Tested

48 h LC50 (mg L1)

95% Confidence Limits

2-Butoxyethanol

4

211e1007

103e1219

Monopropylene glycol

4

7139e11783

5985e13944

Sorbitan monooleate

6

>1000

e

Polyethylene glycol monooleate

3

671e1220

572e1394

Sodium dioctyl sulphosuccinate

9

2.8e4.2

2.2e4.8

Dearomatised kerosene

6

>10000

e

Dispersant formulations

16

15.4e>250

4.1e>250

because they cover the spread of results obtained with the supplied chemicals from several different manufacturing sources. Likewise, the range given for dispersant formulations covers the results obtained for all dispersants tested (some 16 different formulations). All are based on nominal concentrations and have not been analytically verified. The most toxic constituent was SDS, with an LC50 ranging between 2.8 and 4.2 mg L1. This product was supplied as a solution in either monopropylene glycol or petroleum distillate, and this toxicity relates to the mix. However, because the solvents themselves are known to be of much lower toxicity, it can be concluded that the vast majority of the toxicity came from the SDS. The low toxicity associated with dearomatized kerosene and sorbitan monooleate is almost certainly because of their low water solubility and, in the case of DK, volatility. Even when added with a miscible solvent (acetone), they could not be held in solution long enough to elicit a toxic response.

18.3.2. Toxicity of Reformulated Dispersants in the Sea Test Several candidate dispersants were reformulated either by the manufacturers or mixed in the laboratory. The reformulations consisted of making up exactly the same formulation for all components by percentage weight but increasing one constituent by 2%. The final percentage of a constituent in the reformulation depended on its amount in the original product. For example, if dispersant x had

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635

5% SDS and dispersant y had 10%, their reformulations for increased SDS would be 7% and 12%, respectively. In all, 12 different reformulated dispersants were tested alongside the original products using the Sea Test. The results were found to be variable with 9 of the reformulations demonstrating a greater ability to increase the toxicity of dispersed oil in comparison to the original formulation. However, none of the reformulations resulted in significantly (p < 0.05 1 way ANOVA) increased toxicity in the Sea Test (i.e., the reformulations did not significantly (p < 0.05) increase the toxicity of dispersed oil to a greater extent than did the original formulation). Even when limited tests were done on reformulations with 4%þ increases in one constituent, the assessment was inconclusive. Although the Sea Test is perfectly acceptable for determining whether use of a particular oil treatment product can greatly increase the toxic effect of the oil, it does not appear to be sensitive enough to detect small changes in the toxicity of the dispersant.

18.3.3. Toxicity of Reformulated Dispersants in the Rocky Shore Test Two sets of Rocky Shore Tests were conducted using a range of reformulations of the same original dispersant in which SDS and then MPG had their percentage proportions increased in a range between 2 and 10% and the water component in the formulation decreased by a similar amount. Percentage mortality of the limpets from the reformulations was compared to that gained with the original formulation. The results showed a strong relationship between raised levels of SDS in the formulation and increased mortality, with 2e7% increase in SDS resulting in 10e15% increases in limpet mortality and a 10% increase in SDS causing >30% mortality rises. However, increases in MPG showed no discernible increase in toxicity.

18.3.4. Inherent Toxicity of Reformulated Dispersants The final phase of testing concentrated on the assessment of how these formulation changes affected the inherent toxicity of the final product using the Tisbe assay. In order to do this, a set concentration was selected at which mortalities could be expected from the range of dispersants that would be tested. On the basis of the inherent toxicity tests described earlier, a concentration of 30 mg L1 was selected as the standard dispersant concentration at which to do the test comparisons. Under our test conditions, this concentration was found to give a mortality range of between 5 and 75% after 48 hours for the broad range of dispersants tested. Figure 18.1 shows the results of toxicity tests on three different dispersants with an increase in the proportion of SDS. The SDS used was dissolved in MPG for all three dispersants. In all cases an increase in SDS results in increased

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FIGURE 18.1 Percent mortality of Tisbe battagliai after 48h at 30 mg L1 for reformulations of three dispersants with an increased range of 210% in sodium dioctyl sulphosuccinate (SDS) dissolved in monopropylene glycol (MPG) (error bars ¼ 1 SD).

mortality. Mortality of 95e100% was produced by all dispersants tested at þ10% SDS. Percentage increase in polyethylene glycol (PEG) was tested in three dispersants (Figure 18.2). PEG increase in one of the tested dispersants only showed a slight increase in percentage mortality over a range of þ2e32% PEG

FIGURE 18.2 Percent mortality of Tisbe battagliai after 48h at 30 mg L1 for reformulations of three dispersants with an increased range of 2e32% in polyethylene glycol monooleate (PEG) (error bars ¼ 1 SD).

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FIGURE 18.3 Percent mortality of Tisbe battagliai after 48h at 30 mg L1 for a reformulation of an oil spill dispersant with an increased range of 2e32% in monopropylene glycol (MPG) (error bars ¼ 1 SD).

(Figure 18.2). However, increasing the PEG content in a different dispersant resulted in a gradual rise in percentage mortality. The increase was up to þ10%; however, this appeared to be the point at which the mean percentage mortality was beginning to level off. In all of the dispersant reformulations tested mean percentage mortality did not exceed 50%. An increase in the percentage of MPG in a selected dispersant showed a gradual increase in mortality over the þ2 to 32% MPG range (Figure 18.3). The largest change in mortality occurs up to a 5% MPG increase where the mortality increases by approximately 20%. At between 5 and 32% increase, the mean percentage mortality begins to level off, and the increase over this range is approximately 15%. An increasing percentage of SMO was tested in a selected dispersant, and no increase in mean percentage mortality was shown over a range of up to þ32% SMO (Figure 18.4). In fact, a decrease was observed in comparison to the original product in all reformulations with increased SMO. A change in percentage of dearomatized kerosene was tested in two dispersants. Mean mortality of the original formulation of one of the dispersants was already high (77%), and therefore the full effect of increased DK may have been masked, as 100% mortality was shown at only a 4% increase (Figure 18.5). The second dispersant tested had a considerably lower mortality for the original formulation (<10%). There was no increase in mortality at 2%; however, a rapid rise (increase to 70%) in mortality was observed at between a 2 and 8% increase of DK in the formulation. Other constituents, such as 2-butoxyethanol, showed no discernible change in mortality even when increased up to 10% in a selected dispersant.

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FIGURE 18.4 Percent mortality of Tisbe battagliai after 48h at 30 mg L1 for a reformulation of an oil spill dispersant with an increased range of 2-32% in sorbitan monooleate (SMO) (error bars ¼ 1 SD).

FIGURE 18.5 Percent mortality of Tisbe battagliai after 48h at 30 mg L1 for reformulations of two dispersants with an increased range of 2-10% in dearomatised kerosene (DK) (error bars ¼ 1 SD).

18.4. DISCUSSION 18.4.1. Do Formulation Changes Matter? The key question for regulators, responders, and environmental advisers is: “Do small formulation changes matter?” This study has provided important scientific evidence on this matter, but its use in a regulatory framework will need to

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take account of political and commercial issues, as well as the environmental concerns framed by the precautionary principle. Toxicity assessments have their predictive limitations, and it is impossible to simulate the exposure conditions and interactions between oil, dispersant, biota, and physical environment in the laboratory. Nevertheless, the potential consequences of getting a formulation change assessment wrong and allowing an environmentally unacceptable product to be used could result in deserved criticism of any approval scheme.

18.4.2. Sea Test The approval of oil spill dispersants in the UK has, as its core element, the Sea Test.4 The premise of this assessment is that a dispersant when applied to an oil spill should not cause significantly elevated toxicity over that which would have been caused by mechanically dispersed oil alone. It is well recognized that the greatest toxicological risk during a spill comes from the oil itself. Modern dispersants are much less toxic than most crude oils, but they have the ability to shift the impacts of the oil from one environmental compartment to another (i.e., surface to water column).9,10 The statutory Sea Test represents an enclosed system, and therefore this toxicity shift is not significant and so the direct toxicity of the oil itself remains the main factor in exposures with or without dispersant. The results suggest that toxicity changes caused by modest dispersant formulation amendments are being masked by the toxicity of the oil in the Sea Test.

18.4.3. Rocky Shore Test The Rocky Shore Test is the second compulsory toxicity test element in the UK scheme. This test uses a different approach from that of the Sea Test in that it compares the effects of crude oil alone to that of the dispersant alone. This approach reflects the fact that rocky shore organisms are more likely to be sprayed with neat dispersant during a shoreline cleanup operation. The pass/fail criteria work on the premise that an oil spill dispersant should not be more toxic than the oil alone under the test conditions. The Rocky Shore Test assessments in this study looked at the effects of large changes (up to 10% increases) in SDS and MPG and showed that increases of 2% or more of SDS can result in significantly higher limpet mortality but increases of up to 10% of MPG do not. This suggests that this test can differentiate between formulation changes of different constituents probably because the masking effect of the oil seen in the Sea Test does not occur. However, because of its limited applicability to a specific coastal environment and its expense, the Rocky Shore Test is not recommended as a standard test procedure on which to base a formulation change assessment process.

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18.4.4. Are Specific Constituents of Concern? The question of environmental significance remains difficult to ascertain with the standard suite of UK statutory tests. As a result, supplementary research was conducted using the Tisbe bioassay to more thoroughly investigate impacts on inherent toxicity. The most toxic component routinely used in dispersant formulations was established as SDS. This came in a number of variations depending in which solvent it was dissolved, but it gave a 48-hr LC50 value of 2.8e4.2 mg L1 to Tisbe. In contrast, other constituents had 48-hr LC50 values of up to 10,000 mg L1, and others were unobtainable due to their insoluble nature (Table 18.2). Dispersant formulations had 48-hr LC50 values from 12 to >200 mg L1, suggesting that certain constituents, especially those that were poorly soluble, are contributing significantly to the overall toxicity of the formulation. Mean percentage mortalities after 48 hours at a standard dispersant concentration (30 mg L1) were observed for a range of original and reformulated dispersants. The aim was to categorize certain key or common constituents in terms of their ability to contribute to the overall inherent toxicity of the formulation. It was demonstrated that SDS increased dispersant toxicity significantly in three separate products when its percentage volume in the formulation was only modestly increased. For example, increases of 2 and 4% SDS resulted in subsequent percentage mortality increases of 15e30% and 20e40%, respectively, across this range of dispersants (Figure 18.1). These results agree with the fact that SDS was also the most toxic individual constituent tested. Other constituents that showed an ability to increase formulation toxicity were MPG and DK. Modest (<5%) increases in the percent volume of each of these constituents resulted in ~20% increase in Tisbe mortality under the test conditions (Figures 18.3 and 18.5). These results are in contrast to their individual toxicities, which were 7,000e12,000 mg L1 for MPG and above the solubility point for DK. These constituents represent those whose contribution to toxicity is only apparent when in a formulation where the presence of surfactants and solvents make them biologically available. In contrast to those constituents mentioned above, certain constituents were shown to have no consistent impact on formulation toxicity, such as PEG (Figure 18.2) or 2-butoxyethanol; others, SMO and polyoxyethylene sorbitan monooleate (POESMO) (results not shown here), reduced the overall toxicity of formulations when their percentage volume was increased (Figure 18.4). This study has allowed the differentiation of dispersant constituents into basic categoriesdfor example, those that increase the toxicity of formulations (e.g., SDS) and those that are benign or reduce the toxicity (e.g., SMO).

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This information could inform a basic scheme for assessing formulation change on the inherent toxicity of dispersant products. The extent to which increases of a given constituent affect the toxicity of the formulation is a function of the initial proportion in which it was present and will vary depending on the interactions with the other constituent chemicals. For example, further scrutiny of Figure 18.2 shows that for one product an increase in PEG appears to increase formulation toxicity, but for the other two an increase has a little effect. Examination of the formulations reveals that PEG makes up only 6% of the first product but 17.4% and 20% for the latter two. Therefore, modest increases of 2e4% of the overall contribution of PEG meant a proportionately greater increase in PEG in one than for the others, which may explain the differences.

18.4.5. Significance of Inherent Toxicity Changes of Formulations? The investigations described in this study have made two clear discoveries: (1) The presence of crude oil in the statutory Sea Test masks any toxicity differences observed as a result of modest formulation change, and (2) individual dispersant constituents can be categorized in terms of their ability to change the inherent toxicity of the formulation when their own proportion is increased. The natural extrapolation of these statements to an environmental context means that when a dispersant is in contact with crude oil, the formulation changes make little difference in terms of toxicity; but where dispersant alone is present, the formulation changes may result in a greater impact than would have been associated with the original formulation. The issue that needs to be debated by regulators, scientists, and the industry is whether constituent amendments that might increase the toxicity of a formulation should, in principle, be allowed. Application of the precautionary principle would suggest that they should not, but a pragmatic view may not see the potential for increased environmental impacts as significant.

ACKNOWLEDGMENTS The authors would like to thank the UK Department for Environment, Fisheries, and Rural Affairs (Defra) for funding this study under project AE0818.We are also indebted to several dispersant manufacturers with UK approvals for the supply of dispersants and chemical constituents. We have ensured that the commercially confidential information about their products has been maintained in this chapter. The following suppliers have agreed to allow their name to be associated with the study: Agma Ltd., Arrow Chemicals, Baker Petrolite, Dasic International Ltd., Drew Marine (Division of Ashland Inc.), Innospec Ltd., Total Fluides (TOTAL Group), and Univar UK Ltd. Our thanks go to all for their cooperation, interest, and comments.

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REFERENCES 1. Southward AJ, Southward EC. Recolonization of Rocky Shores in Cornwall after Use of Toxic Dispersants to Clean up the Torrey Canyon Spill. J Fish Res Bd Can 1978;682. 2. The Marine and Coastal Access Act 2009. London, UK: The Stationary Office; 11/2009 439546 19585. 3. Blackman RAA, Franklin FL, Norton MG, Wilson KW. New Procedures for the Toxicity Testing of Oil Slick Dispersants in the United Kingdom. Mar Pollut Bull 1978;234. 4. Kirby MF, Matthiessen P, Rycroft RJ, Procedures for the Approval of Oil Spill Treatment Products, Fish. Res. Tech. Rep. 102, MAFF (now Cefas), Lowestoft, UK. ISSN 0308e5589, 1996. 5. Royal Society of Chemistry (RSC). In: Richardson ML, editor. The Dictionary of Substances and Their Effects. United Kingdom: Royal Society of Chemistry; 1992. 6. Thomas KV, Benstead R, Thain JE, Waldock MJ. Toxicity Characterisation of Organic Contaminants in UK Estuaries and Coastal Waters. Mar Pollut Bull 1999;925. 7. Thain JE, Allen Y, Kirby S, Reed J, The Use of Sediment Bioassays in Monitoring and Surveillance Programs in the UK: A Preliminary Assessment, International Council for the Exploration of the Sea (ICES), ICES CM 2000/S:11, 2000. 8. Hutchinson TH, Williams TD. The Use of Sheepshead Minnow (Cyprinodon variegates) and a Benthic Copepod (Tisbe battagliai) in Short-Term Tests for Estimating the Chronic Toxicity of Industrial Effluents. Hydrobiologica 1989;567. 9. Mitchell FM, Holdaway DA. The Acute and Chronic Toxicity of the Dispersants Corexit 9527 and 9500, Water Accommodated Fraction (WAF) of Crude Oil and Dispersant Enhanced WAF (DEWAF) to Hydra viridissima (green hydra). Wat Res 2000;343. 10. Fingas MF. A Review of Literature Related to Oil Spill Dispersants Especially Relevant to Alaska. Anchorage: Report for Prince William Sound Regional Citizens’ Advisory Council; 2002.

Chapter 19

Environment Canada’s Methods for Assessing Oil Spill Treating Agents Carl E. Brown, Ben Fieldhouse, Trevor C. Lumley, Patrick Lambert and Bruce P. Hollebone

Chapter Outline 19.1. Introduction 643 19.2. Toxicity and 645 Effectiveness of Treating Agents for Oil Spills 19.3. Approval for Use 662 of Treating Agents in Canadian Waters

19.4. Challenges to Current Toxicity Test Protocols 19.5. Conclusions

662 666

19.1. INTRODUCTION Spill-treating agents (STAs) is the term used to describe the broad class of chemical and biological agents used to mitigate the environmental damage caused by spilled oil.1 The most commonly discussed treating agents are dispersants, a class of chemicals that are intended to stabilize oil droplets in the water column.2 Several other types of STAs are sometimes proposed for use during spill response or later remediation: shoreline-washing agents (SWAs), herding agents, demulsifiers, solidifiers, biodegradation enhancers, and sinking agents. When any spill takes place in Canada, the decision to use treating agents is evaluated by the environmental specialists at all levels of government, represented by the Regional Environmental Emergency Teams (REETs).3 Several acts of Parliament limit or restrict the use of treating agents, including the Fisheries Act, the Canadian Environmental Protection Act, and the Migratory Birds Convention Act.3 The potential impact of treating agents on the environment is first estimated by assessing their in-vitro toxicity to sensitive or sentinel organisms. The most Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10019-X Copyright Ó 2011 Elsevier Inc. All rights reserved.

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commonly used endpoint in animal exposure models is acute lethality (LC50), which is the concentration that will be fatal to 50% of a test population.4 However, it is generally understood that evaluation methods that employ sublethal endpoints should also be considered. Sublethal effects are potentially devastating to local fauna populations and are typically consequences of genotoxicity or endocrine-disrupting capacity that can lead to transgenderification within populations, mutagenic effects, or teratogenic effects in individuals and their offspring. The decision to allow use of an STA is guided by one concern: there must be a reasonable expectation of a net environmental benefit. Environmental damage caused by an agent or by the impact of oil-agent mixtures must not be worse than damage from the untreated spill or other countermeasure alternative. Consequently, two criteria must be met before an STA is considered for use. First, an STA must demonstrate a high degree of effectiveness under laboratory conditions and with specific reference to their intended use. Dispersants, for example, must be able to break a sufficient amount of oil into small droplets that persist long enough in that state to be carried away from the original slick; surface-washing agents (SWAs) must be able to “release” oil bound to surfaces. Second, the toxicity of an STA or STA-oil mixture, as estimated under laboratory conditions, must not be greater than the estimated threat to the environment of the untreated oil. The procedure for Environment Canada (EC) has been to evaluate both the toxicity and effectiveness of treating agents to ensure that these products will provide a positive net environmental benefit. Although they are well known, dispersants are not the only chemical method of treating oil spills. Treating agents fit into categories based on their mode of action. l

l

l

l

l

l

l

l

Dispersants are used to break up an oil slick into smaller droplets to remove it from the surface and to break up the slick or to change its trajectory. Surface washing agents (SWAs), also called shoreline-washing agents, facilitate the removal of the oil from solid surfaces. Demulsifiers and emulsion inhibitors break down oilewater emulsions in order to improve the efficiency of oil recovery. Herding agents are insoluble surfactants that collect oil by reducing slick size. Recovery agents increase the oil’s adhesiveness in order to make it easier to collect with skimmers. Solidifiers irreversibly bind spilled oil into a rubberlike substance that can be recovered readily by mechanical means. Gelling agents work in a similar fashion by partially solidifying spilled oil into a gel for easier removal by manual means. Biodegradation agents are additives that encourage microbial action, either in the form of nutrients (biostimulation) or actual living organisms (bioaugmentation).

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l

Sinking agents bind to oil to make it descend in the water column.

This chapter will summarize the work done by the Emergencies Science and Technology Section (ESTS) of EC to assess the toxicity and effectiveness of treating agents. Much of the acute toxicity evaluation, primarily 96-hour rainbow trout and D. magna LC50, and suppression of bioluminescence using the Microtox test for IC50, has been done to satisfy the requirements set forth in the 1984 guidelines on dispersant use.5-9 Toxicity information for other treating agents is also included with a summary of toxicology data generated to date by EC.

19.2. TOXICITY AND EFFECTIVENESS OF TREATING AGENTS FOR OIL SPILLS 19.2.1. Dispersants Toxicity has been one of the primary concerns with the use of dispersants. Although some dispersants demonstrate fairly low toxicity in-vitro, the suspended oil droplets in the water column may be toxic to some species. Oil-dispersant mixtures may be equally or less toxic over time than the oil alone, and there is evidence that dispersant may increase the toxicity of the portions of petroleum products that are water-soluble.10,11 Dispersant use was discouraged after incidents in the 1960s and 1970s when their use caused substantial loss of sea life. Acute toxicities for several dispersants from the EC test program can be found in Table 19.1. Dispersant formulations in current use, such as Corexit

TABLE 19.1 Dispersant Acute Toxicity Testing Dispersant

Organism

96-hour LC50 (mg/L)

Corexit 9500

Oncorhynchus mykiss

354

Corexit 9500

Photobacterium phosphoreum (30 min IC50)

0.065%

Corexit 9527

Daphnia magna

37

Corexit 9527

Daphnia magna

31

Corexit 9527

Daphnia magna

40

Corexit 9527

Daphnia magna

42

Corexit 9527

Daphnia magna

34

Corexit 9527

Daphnia magna

42

(Continued )

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TABLE 19.1 Dispersant Acute Toxicity Testingdcont’d Dispersant

Organism

96-hour LC50 (mg/L)

Corexit 9527

Gasterosteus aculeatus

103

Corexit 9527

Gasterosteus aculeatus

104

Corexit 9527

Gasterosteus aculeatus

24

Corexit 9527

Oncorhynchus mykiss

108

Finasol OSR-52

Salmo gairdneri

71

Neos AB3000

Gasterosteus aculeatus

320

Neos AB3000

Salmo gairdneri

>¼320

Nokomis 3

Salmo gairdneri

>¼110

Enersperse 700

Daphnia magna

52

Enersperse 700

Daphnia magna

45

Enersperse 700

Daphnia magna

40

Enersperse 700

Daphnia magna

60

Enersperse 700

Daphnia magna

51

Enersperse 700

Daphnia magna

52

Corexit CRX-8

Daphnia magna

0.6

Corexit CRX-8

Daphnia magna

<1

Corexit CRX-8

Daphnia magna

<1

Corexit CRX-8

Daphnia magna

24

Corexit CRX-8

Daphnia magna

37

Corexit CRX-8

Daphnia magna

30

Dispersant G.E.

Oncorhynchus mykiss

35

Dispersant G.P.

Oncorhynchus mykiss

200

Dispersant G.T.

Oncorhynchus mykiss

8

Dispersant G.W.

Oncorhynchus mykiss

2

Dispersant G.Y.

Oncorhynchus mykiss

0.71

Pennyworth

Salmo gairdneri

44

Shell Dispersant

Salmo gairdneri

71

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9500, are much less acutely toxic than first-generation dispersants by a factor of 10 or more.12

19.2.1.1. Bench-Scale Dispersant Testing In the laboratory, dispersant effectiveness is estimated using a number of different tests.2,13 The most commonly used protocols around the world include the swirling flask test (SFT), the baffled flask test (BFT), and the Warren Spring end-over-end flask test. All bench-scale tests share the common advantages that they are inexpensive in terms of time and equipment, and thus allow a large number of samples to be analyzed in a short period of time. Variables such as temperature, dispersant-to-oil ratio (DOR), salinity, and energy dispersion can be easily controlled, allowing for very specific and detailed testing. Bench-scale tests also share a number of disadvantages. The most problematic is the great difficulty in relating the bench-scale systems to open ocean conditions. The most common approach to this is to relate the energy available in the turbulent motion of the test flask, the energy dispersion, to the energy dispersed by wave motion in ocean conditions.14,15 Most of the laboratory tests rank dispersants in relative order of effectiveness. Laboratory tests are designed primarily to screen candidate dispersants against a standard oil. In addition, laboratory tests offer an easy means of evaluating the effect of various parameters such as salinity, temperature, and oil type on the effectiveness. 19.2.1.2. Swirling Flask Test The SFT is used to rank the effectiveness of dispersants on different types of oil spilled in typical energy conditions. Dispersant may be premixed with oil or added to oil in a modified Erlenmeyer flask containing simulated seawater. Dispersant oil ratios (DORs) of 1:25 and 1:10 are both used for the SFT. The flask is placed on an orbital shaker table and swirled gently. After 20 min of shaking, the vessel contents are allowed to settle for 10 min, after which a sample is drawn from the water below the slick by a side spout on the Erlenmeyer flask. The amount of petroleum hydrocarbon detected by gas chromatography is used to calculate the efficacy of the dispersant by comparison with a set of calibration samples. This test (at DOR 1:25) is the current standard test for dispersant effectiveness used by EC. Pros of the Swirling Flask Test The swirling flask test has been widely used and is an American Society for Testing and Materials (ASTM) standard method; a large database of dispersant efficacy testing using this method has accumulated.16 Different oils and different dispersants can be compared under identical conditions. As is shown in Table 19.2, results of this test correlated most highly with at sea-tests. The small scale and relatively low cost of the SFT allow a broad range of products and conditions to be tested. A highly standard gas chromatography analytical

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TABLE 19.2 Intercomparison of Laboratory and Field Effectiveness Results Effectiveness Results in Percent

Oil type Dispersant

Field Test [16e17] SF GC SF CA IFP

WSL WSL Lab 1 Lab 2 Exdet

Medium fuel oil

Corexit 9527

26

54

50

91

42

42

67

Medium fuel oil

Slickgone NS 17

49

46

94

29

23

50

Medium fuel oil

LA 1834/Sur

2

2

50

16

11

38

Forties crude

Slickgone NS 16

47

65

95

28

25

60

Forties crude

LA 1834/Sur

2

2

61

15

12

53

Correlation with field test (R2)

0.89

0.7

0.54 0.87

0.94

0.41

Ratio lab test/field test

0.4

0.35

0.19 0.56

0.62

0.27

4

5

Legend: SF ¼ Swirling Flask, GC ¼ analysis by Gas Chromatography, CA ¼ Colorimetric Analysis, IFP ¼ French Institute for Petroleum test, WSL ¼ Warren Springs Laboratory test.

FIGURE 19.1 A swirling flask test vessel after a test. This particular oil-dispersant combination would not have been highly effective, yielding an effectiveness value of about 10%.

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FIGURE 19.2 Laboratory personnel perform the analysis of dispersion testing using gas chromatography. This is the only standard method approved for testing oil in water.

technique has been prescribed. A test vessel and the analysis procedure are shown in Figures 19.1 and 19.2, respectively. Cons of the Swirling Flask Test Swirling flask dispersant effectiveness percentages may not be applicable directly to full-scale spill situations. The relative rankings of dispersants tested with the swirling flask effectiveness transfer to a real-world scale, but the values provided by the test may not be representative of dispersal potential in the real world. Testing has in fact shown that the test appears to be more energetic than actual field conditions.17 Table 19.2 shows field effectiveness tests completed by a consortium of agencies in the North Sea showing that the swirling flask test is still higher than tests at sea, but the lowest of the common test apparatuses.2,18-20

19.2.1.3. Baffled Flask Test This method was designed to correct the perceived inadequacies of the swirling flask method, specifically the relatively low mixing energy. For the BFT, simulated seawater is put into baffled flasks (trypsinizing flasks with a port added to the bottom of the flasks), after which oil is applied to the water surface and dispersant is applied to the middle of the slick (DOR 1:10). The flask is then shaken on an orbital shaker for 10 min, followed by 10 min of settling time. Samples are collected from the spout near the bottom of the flask. The sample is extracted and analyzed by fluorometry.21 Under test conditions, the BFT

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provides 30 times the mixing energy of the SFT.22 The developers contend that the BFT best simulates the breaking wave conditions where dispersants are most effective.14 The BFT is currently proposed as the standard dispersant effectiveness test used by the U.S. Environmental Protection Agency (EPA). Pros of the Baffled Flask Test Similar in scale to the SFT, the BFT is low cost and rapid to perform, and many products and conditions can be tested. This test makes much more mixing energy available to the oil and dispersant and is said to better simulate breaking wave conditions.14 Cons of the Baffled Flask Test This test shares many of the same limitations as the SFT, providing ranks rather than absolute effectiveness numbers. The test is not yet standard in any jurisdiction. Many scientists argue that this test overestimates the effectiveness of dispersants by making an unrealistically large amount of energy available to the mixture and that real ocean waves have much less energy available to force the dispersion.17 Since the swirling flask is already about five times more energetic than similar sea conditions, this test is unrealistically energetic, as noted in Table 19.2 where even the SFT is five times the field result. Further, no approved analytical method has yet been chosen for this test.

19.2.1.4. Warren Springs Laboratory/Labofina End-Over-End Flask Method In the United Kingdom and some other jurisdictions, dispersant effectiveness is evaluated with a test developed at the Warren Springs Laboratory (WSL).23 Dispersant is added to a flask containing seawater and a medium fuel oil at a DOR of 1:50. The mixture is allowed to rest for 1 min, and then it is rotated end-overend for 2 min. After mixing, it is left to settle for 1 min. A sample of the water is collected and, after extraction, analyzed by colorimetry, which is not a method acceptable in chemical analytical circles. A dispersant is considered effective if the dispersion is greater than 60%. A dispersant is approved for use in the UK if it has passed the WSL test. Storage, selection, and use of dispersants are outlined in The Approval and Use of Oil Dispersants in the UK.24 Pros of the Warren Springs Laboratory End-Over-End Flask Model This method minimizes the number of variables by using only one oil type at a predetermined temperature and viscosity. Small volumes are used, which facilitates cleanup and makes efficient use of limited lab space. The energy of the test appears to be closer to field results than most tests (see Table 19.2). Cons of the Warren Springs Laboratory End-Over-End Flask Model Since all tests use a medium fuel oil with standard viscosity at 10 C, the results may not apply to dispersants that may perform differently depending on

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temperature and viscosity. Effectiveness is also very dependent on flask geometry and can be hard to reproduce. The high oil-to-water ratio used in the test tends to favor coalescence, which may underestimate dispersant effectiveness.2

19.2.1.5. Wave Tank Testing for Oil Dispersants Wave tanks are expensive to operate and difficult to characterize, but provide a much more realistic scale for testing oil STAs than laboratory bench-scale testing. At the same time, they allow for much more frequent testing than on open water, with no concern over permitting issues. The analytical problems abound, however, and parameters may be as difficult to control or measure as at sea. 1. Environmental Protection Agency (EPA)/Fisheries and Oceans (DFO) Wave Tank at the Bedford Institute of Oceanography This tank, located in Dartmouth, Nova Scotia, Canada, was recently constructed primarily for testing oil treating agents. The tank is currently 32 m long, 0.6 m wide, and 1.2 m deep, with a working volume of 16.4 m3. The water used is natural seawater drawn from Halifax Harbour. Water can be changed twice a day to allow for very rapid testing. The wave generation paddle can produce acyclic waves to simulate a wide variety of wave conditions. A wide range of hydrodynamic regimes can be studied in the tank due to the highly customizable wave generator.25 2. OHMSETT The Oil and Hazardous Materials Simulated Environmental Test Tank (OHMSETT) in New Jersey is a large test tank, 203 m long, 20 m wide, and 3.4 m deep, and typically contains 9700 m3 of natural seawater, but at lower salinity. It was designed to simulate a marine environment for the purpose of testing spill remediation methods. Dispersants have been tested at OHMSETT since 2002. The facility allows for a wide variety of testing, including both operational and hydrodynamic variables. A paddle wave-maker allows for testing in regular periodic waves. In this test environment, temperature, wave action (length, height, and period), salinity, and slick depth can be controlled to a certain degree. 3. SERF The Shoreline Environmental Research Facility (SERF) near Corpus Christi, Texas, has nine wave tanks for simulating tides and waves, with the option to recycle water or to draw clean fresh or seawater for the duration of the test. The tanks are each 33.5 m long, 2.1 m wide, and 2.4 m deep. Customized wave patterns can be generated from a computerized paddle to simulate a wide range of nonperiodic wave conditions.26 SERF is unique among the tanks listed here in that it was designed to test tidal and nearshore conditions, which allows for oil and sediment interaction to be studied, as well as open ocean conditions. Test protocols at SERF account for mass balance. For analytical purposes, the test tanks are divided into

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“compartments”dsurface water, water column, and tank wallsdeach of which is measured for the oil mass balance.27 4. S.L. Ross Environmental Research The wave tank operated by S.L. Ross Environmental Research Ltd., located in Ottawa, Ontario, Canada, has been used for dispersant effectiveness testing for more than 10 years.28 The tank is 10 m long, 1.2 m wide, 1.2 m deep, and is usually filled with about 10 m3 of salt or fresh water, depending on the test. The salt water is prepared from fresh water with sodium chloride added to a concentration of 30 to 33 parts-per-thousand. Periodic waves can be generated by a mechanical paddle and are dissipated by an artificial beach to minimize reflection. Dispersant is applied using the same nozzle systems widely used on ship-mounted dispersant application systems. A “bubble curtain” can be used to promote mixing and dispersion in the middle of the tank. Pros of Wave Tank Testing In contrast to laboratory- or bench-scale testing, which is very difficult to relate to use in the open ocean, dispersant testing in full-scale wave tanks allows for effectiveness to be tested with much greater realism.29 Not only is the hydrodynamic scale much closer to ocean conditions, but test tanks use much more realistic waves for mixing, instead of the small-scale turbulence in the flask tests. In addition, the operation and engineering of the application configuration of the dispersant may also be tested in some wave tank facilities. Mass balance is possible, but difficult to achieve in tanks, while much harder to achieve in open ocean testing.30 Cons of Wave Tank Testing The primary difficulties of wave tank studies are similar to other tests and relate to the increased difficulty of taking any type of analytical measurements. In terms of simulating ocean environments, the limitations of wave tanks can be mostly related to the finite size of the tanks. Spills in test tanks are confined by the walls of the tanks. Dispersant is usually applied in an optimal way, with controlled droplet size and application rates. Effectiveness measured in wave tanks should thus be considered an upper limit to real-world conditions.2 Experiments in test tanks can overestimate the effectiveness of dispersants by as much as five times the actual value because of the adhesion to walls and extra evaporation as well as other mass balance issues.31 Second, wave tanks are not a perfect hydrodynamic simulation of open ocean conditions because of wall effects. Compensating for these effects in treating agent testing requires difficult and time-consuming hydrodynamic characterization of the test tanks. This has only been accomplished for a few test tanks. Mass balance is a difficult problem in wave tanks and must be measured carefully. Samples taken below the surface may not be representative as the

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surface slick in no way represents the movement or shape of the belowsurface dispersion plume.30 When there are below-average light levels due to weather conditions, it can be hard to see the plume of dispersed oil below the water’s surface.32 Oil also tends to adhere to the container and instruments, and can be lost by evaporation. In the past, this loss was assumed to be a result of dispersion.30,31 Mass balance problems can also occur when oil escapes over or under a containment boom due to wind and wave action.32

19.2.1.6. Testing of Dispersants in Natural Environments Dispersant effectiveness has been tested in controlled spills, at spills of opportunity, and on natural oil seeps. This testing has been reviewed extensively.2,28,29 Testing dispersants in real conditions requires a lot of equipment, needs extensive permitting, and is limited by seasonal conditions. Because of the costs and time required, such tests are not suitable for routine evaluations of products, but are useful to “ground truth” the laboratory and wave tank testing described earlier. Based on the results of both field studies and actual spills, it is clear that there is difficulty in correlating laboratory effectiveness tests to what happens at sea.29 Table 19.2 shows the best effort to date using an at-sea test in the North Sea. The difficulty in correlating is probably due primarily to several factors. The mixing energies and the energy dispersion are quite different in the laboratory vessels compared to those encountered by a slick at sea.15 The physics of droplet formation and coalescence in the mixing vessels and the tanks are key parameters in designing effectiveness tests.33 Calculation of mass balance is very important to control for variability of transport. A “compartmentalization” of the oil fate in the test vessel or tank can be very useful in accounting for variabilities in mass balance.27 The design of any dispersant effectiveness test must be evaluated with reference to real-world data, whether from experimental releases, spills of opportunity, or case studies of incidents. The three factors discussed aboved energy dispersion, oil droplet size and formation, and mass balancedmust all be carefully considered in order to judge the utility of a laboratory or wave tank test for evaluating products.

19.2.2. Shoreline-Washing Agents Shoreline Surface washing agents (SWAs) are used to facilitate the removal of oil from contaminated surfaces, such as shorelines or vessel hulls. SWAs include surfactants to increase the effectiveness of water washing.36 Treatment makes the oil float so that it can be flushed toward absorbent/containment booms by spraying the treated area with low-pressure water. In contrast to dispersants, washing agents are formulated not only to remove oil from surfaces, but also to allow oil to coalesce quickly on the water surface to permit easy removal. A good SWA is usually a poor dispersing agent and vice versa.1

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The toxicity of shoreline washing agents, sometimes known as beach cleaners, is often less than that of the oil. Laboratory testing often assumes a higher concentration of washing agent than there would be present in the environment after remediation efforts. Washing agents that cause little or no dispersion of oil have less effect on the water column.34 Perhaps the most commonly used shoreline cleaning agent, Corexit 9580, has been the subject of several toxicity studies. It appears that the harm it causes to the shoreline is comparable to the effects of the oil alone.35 Sample acute toxicity testing results for selected SWAs from the EC test program can be found in Table 19.3. Surface washing agents (SWAs) are generally much less acutely toxic than dispersant products, but several products have been found to have significant toxicities.

TABLE 19.3 Surface-Washing Agent Acute Toxicity Testing Results Surface Washing Agent

Organism

96-hour LC50 (mg/L)

Corexit 9580

Oncorhynchus mykiss

>10000

Corexit 9580

Oncorhynchus mykiss

>1000

BG CLEAN 401

Oncorhynchus mykiss

88

BG CLEAN 401

Photobacterium phosphoreum (5 min IC50)

0.0033%

Biosolve

Oncorhynchus mykiss

9

Corexit 7664

Salmo gairdneri

851

Petrotech PTI-25

Oncorhynchus mykiss

701

Petrotech PTI-25

Photobacterium phosphoreum (15 min IC 50)

0.009355%

Simple Green

Oncorhynchus mykiss

205

PES-51

Oncorhynchus mykiss

14

PES-51

Photobacterium phosphoreum (30 min IC50)

0.018272%

d-Limonene

Salmo gairdneri

76

d-Limonene Type ’0’

Salmo gairdneri

50

Formula 2067

Oncorhynchus mykiss

11

Citrikleen 1850

Salmo gairdneri

18

Citrikleen 1855

Salmo gairdneri

55

Citrikleen Fc 1160

Salmo gairdneri

75

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TABLE 19.3 Surface-Washing Agent Acute Toxicity Testing Resultsdcont’d Surface Washing Agent

Organism

96-hour LC50 (mg/L)

Citrikleen Xpc

Salmo gairdneri

34

Formula 861

Oncorhynchus mykiss

24

BP1100 WD

Gasterosteus aculeatus

85

BP1100 WD

Gasterosteus aculeatus

280

BP1100 WD

Gasterosteus aculeatus

195

BP1100 WD

Gasterosteus aculeatus

268

BP1100 WD

Gasterosteus aculeatus

85

BP1100 WD

Gasterosteus aculeatus

70

BP1100 WD

Gasterosteus aculeatus

90

BP1100 WD

Gasterosteus aculeatus

90

BP1100 WD

Salmo gairdneri

120

BP1100 WD

Salmo gairdneri

120

BP1100 WD

Salmo gairdneri

158

BP1100 WD

Salmo gairdneri

150

Reentry KNI (C-9963)

Oncorhynchus mykiss

8

Palmolive

Salmo gairdneri

13

Breaker-4

Artemia salinas

340

Con-Lei

Oncorhynchus mykiss

70

Sunlight

Salmo gairdneri

13

Bioversal

Oncorhynchus mykiss

110

Mr Clean

Oncorhynchus mykiss

30

Gran Control O

Oncorhynchus mykiss

75

CRX-8-LT

Salmo gairdneri

20

Formula 730

Oncorhynchus mykiss

33

Lestoil

Oncorhynchus mykiss

51

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19.2.2.1. Inclined Slope Test for Surface-Washing Agents Effectiveness Environment Canada (EC) has evaluated a variety of methods for testing the effectiveness of SWAs. The test that has had the most replicable results is the inclined trough test. A heavy oil is placed in a stainless steel trough and allowed 10 min to spread. The troughs are then weighed. The SWA is applied to the surface of the oil. After 10 min, the troughs are placed on an inclined support. The troughs are then rinsed with water and weighed again. The difference in weights is the amount of oil removed by the SWA. Effectiveness is measured in terms of the percentage, by weight, of oil removed from the trough. This test is the current method for ranking SWA effectiveness used by EC. A photograph of this test trough appears in Figure 19.3. Pros of the Inclined Slope Test Of all the methods evaluated, the results of the inclined slope test on a stainless steel substrate proved to be the most reproducible. The small scale minimizes waste and space requirements. It is simple in design and execution, which reduces the likelihood of errors.

FIGURE 19.3 repeatability.

A view of the inclined trough test for surface-washing agents. This test has a high

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Cons of the Inclined Slope Test Potential problems with this method arise from the material used for the troughs. Stainless steel seems to be the only surface for which consistent results can be achieved after its first use. Also, the amount of oil deposited on the trough may be disproportionate to the area of the substrate, which could result in a greater depth, with a smaller exposed surface area than a spread-out slick. The volume of treating agent may also have to be altered depending on the properties of the test oils. Water is used to rinse the troughs after the oil is allowed to react with the SWA for 10 min. The amount of water used may not be adequate to remove the SWA and oil, depending on the properties of the oil used.

19.2.3. Demulsifiers and Emulsion Inhibitors Emulsion-breaking products are designed to break water-in-oil emulsions.13 Emulsions can increase the amount of waste material to be collected by up to three times the volume of oil spilled.36 They are usually more soluble in water than in oil, although the commercial products available have a wide range of solubility. The amount of demulsifier required depends on the product, the type of oil, and the quantity of oil. Some demulsifiers are more toxic than modern dispersants.35 These products are not commonly used since the formation of stable emulsions is not common.37 Sample results of acute toxicity screening for selected demulsifiers from the EC test program can be found in Table 19.4. Environment Canada (EC) has tested very few demulsifiers. Demulsifiers are effective at lower concentrations where there is greater mechanical mixing force such as wave action.38-41 Separation of the oil and water phases helps reduce the amount of water collected with cleanup efforts. Collected water greatly reduces the amount of oil that can be collected offshore since storage on sea vessels is limited.38-41 Emulsion inhibitors reduce the amount of collected water by pulling oil out of the emulsified state. Emulsion breakers have not been widely used on spills in open water.13 Demulsifiers are tested by EC on an emulsion prepared from a standard medium crude oil. The demulsifier is applied to the emulsion according to the manufacturer’s directions and agitated. The emulsion is considered broken if

TABLE 19.4 Demulsifier Acute Toxicity Testing. Demulsifier

Organism

96-hour LC50 (mg/L)

Alcopol 60 Breaker-4

Oncorhynchus mykiss Oncorhynchus mykiss

62 340

Brand S Demoussifier Vytac DM

Oncorhynchus mykiss Oncorhynchus mykiss

>3200 >6400

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the remaining oil phase contains 30% less water than the original emulsion based on a KarldFischer titration. Emulsion inhibitors prevent water-in-oil emulsions from forming. No product has ever been marketed as an emulsion inhibitor. However, dispersants have been considered by some for this purpose.

19.2.4. Herding Agents Herding agents, also called collecting agents, are used to limit the spread of oil slicks on water. They cause little oil dispersion at low energies, so toxicity focuses on the agent itself on water surface organisms and shoreline vegetation.35 The purpose is to force the slick into a smaller area and thicken the slick to facilitate removal either by mechanical collection or in-situ burning.41 This treatment works best on thinly spread oils in calm weather conditions.36 Recently, there has been some interest in using herding agents to enhance in-situ burning in ice-infested water. S.L. Ross Environmental Research has reported success in preliminary testing of herding agents in simulated ice conditions in test tanks.42 The efficacy of herding agents is still the subject of research. Many considerations remain unresolved, including the means of timely application of the agent, the duration of the window for burning after application of the agent, and how wave and wind conditions limit use. Environment Canada (EC) currently does not test the effectiveness of herding agents. Past testing did not show great potential for these agents.

19.2.5. Recovery Agents Recovery agents are used to facilitate physical removal of an oil slick with a skimmer. They can cause a tenfold increase in the removal of products like diesel fuel.1 One such agent is a nontoxic polymer that exists in the form of microsprings that cause the oil to bind to itself.1 Information is sparse because these are rarely used, especially on heavier oils that are already relatively adhesive. Recovery agents are not extensively used by the response industry. Environment Canada (EC) currently does not have a routine test for effectiveness of recovery agents as several different mechanisms are operative. Past testing showed great potential for enhancing recovery using elasticity enhancers, but significant problems were encountered such as high cost and the potential for overdosing. Figure 19.4 shows a skimmer recovering oil treated with a recovery agent.

19.2.6. Solidifiers and Gelling Agents Solidifiers and gelling agents cause oil spills to become more solid. These agents are not popular because the volume required is very large and removal of the

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FIGURE 19.4 A skimmer recovering oil treated with a recovery agent. Note that the skimmer is recovering excess oil; thus, the oil is accumulating at the top of the skimmer sump.

solidified slick is logistically difficult and costly. However, these products are used in easily confined areas such as harbors where thick fuel slicks can be trapped. Treated oil that is not collected can smother shoreline plants and fauna. There may also be effects to plants as a result of the adhesion.43 In terms of toxicity, solidifiers and gelling agents are perhaps one of the most innocuous choices. Many are considered nontoxic, with LC50 values greater than 10,000 ppm.35 A summary of EC testing is shown in Table 19.5. Figure 19.5 shows EC’s test for this type of agent. The type and quantity of a solidifying agent depend on the oil’s composition and temperature.44,45 Tests at sea have shown that the amount of solidifier needed typically exceeds what can be transported to the site of the spill.44 This makes it difficult to store and transport the cleanup material and results in a much larger amount of oily waste to be collected and disposed of.46 Gelling agents work in a similar fashion by partially solidifying spilled oil into a gel for easier removal. Gelling can be reversed to get liquid oil.36 Operationally, their use is linked to situations with high natural containment such as harbors and artificial catchments. The effectiveness of solidifiers and gelling agents is tested by EC. Solidifiers and agents are stirred into an oil slick over water. Treatment is considered complete when no free oil remains on the water surface. The effectiveness of the agent is calculated as a percentage, by weight, of solidifier required to treat a specific weight of oil.

19.2.7. Biodegradation Agents The addition of microbes to aid in the natural decomposition of oil has limited usefulness. According to the United States’ National Response Team, it is difficult to add bacteria to obtain levels higher than what would occur

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TABLE 19.5 Environment Canada Testing of Solidifiers AGENT

PERCENT1 TO SOLIDIFY

TOXICITY2 (AQUATIC)

A610 PETROBOND

13

>5600

RAWFLEX

16

>5600

ENVIROBOND 403

18

>5600

NORSOREX

19

>5600

JET GELL

19

>5600

GRABBER A

21

>3665

RUBBERIZER

24

>5600

ELASTOL

26

>5600

CI Agent

26

>10,000

OIL BOND 100

33

>5600

OIL SPONGE

36

>5600

PETRO LOCK

44

>5600

MOLTEN WAX

109

>5600

POWDERED WAX

278

>5600

1 2

Values are the average of at least 3 measurements, average standard deviation is 6. Values are LC50 to Rainbow Trout in 96 hours.

FIGURE 19.5 A view of the Environment Canada solidifier test. The white powder is a solidifier that is about to be added to the oil in the test vessel.

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naturally.47 This is in part an effect of the available surface area of the slick. Bacterial proliferation is dependent on the food supply. Degradation of a thick slick will not be hastened by adding bacteria unless mechanical procedures are also in place for increasing the oil’s surface area. It also appears that added bacteria compete poorly with indigenous species.48 This is convenient in terms of long-term consequences, since it suggests that bacterial additions will not have any lasting effects on the ecosystem. Nutrient and/or bacterial additions in areas with little water circulation may trigger eutrophication; therefore, treatment plans should include nutrient and oxygen-level monitoring.43 A simulated wetland oil spill experiment in Quebec, Canada showed no improvement in oil dissipation or decrease in toxicity with the use of bioremediation agents.49 Sample acute toxicity screening results for selected biodegradation agents from the EC test program can be found in Table 19.5. Agents used to promote biodegradation are generally not acutely toxic to most organisms. However, surfactants added to products to enhance dispersion during treatment will introduce much greater toxicity. Effectiveness testing for oil spill biodegradation agents (OSBAs) is based on the percentage removal and rate of degradation of petroleum hydrocarbons. Water-accommodated fractions of oil are spiked with a culture of microorganisms and incubated at controlled temperatures for several weeks. Gas chromatography is used to determine the rate and amount of degradation of total petroleum hydrocarbons, five homologous series of alkylated polycyclic aromatic hydrocarbons, and terpenoid petroleum biomarkers.50 Percentage removals are calculated for each analyte, as some compounds, such as the n-alkanes, will degrade much more quickly than others, such as the terpenoid petroleum biomarkers. Biodegradation rates are estimated by fitting first- or second-order decay curves to the time series data.

19.2.8. Sinking Agents Sinking agents are used to submerge spilled oil into the water column and ultimately to sink it to the bottom. The simplest sinking agents are materials such as sand, clay, chalk, and cement. Sinking agents increase the persistence of oil pollution since natural degradation is slower at depth than on the water’s surface. This further complicates remediation and toxicity studies. Toxicity to benthic organisms cannot be expressed in general terms because of their rich diversity. Sinking agents are banned in many countries, including Canada, due to environmental concerns.1 The benefits of sinking agents is debatable, especially due to the lack of study of the ocean floor after their use. Responders to the 1978 sinking of the Amoco Cadiz tanker used chalk as a sinking agent and for weeks afterwards, a large number of dead sea organisms washed ashore.51 Large amounts of oil were sunk with chalk after the Torrey Canyon spill with apparent success, but the seafloor was not examined.52 The use of talc for the Santa Barbara was

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completely unsuccessful.52 In such situations, the oil is likely to be gradually rereleased into the area of the original spill.1

19.3. APPROVAL FOR USE OF TREATING AGENTS IN CANADIAN WATERS Response to an oil spill in Canadian waters is the responsibility of the polluter, with oversight by a federal agency for the particular jurisdictiondusually the Canadian Coast Guard or National Energy Board in offshore waters. The Regional Environmental Emergency Team (REET) is convened to provide advice and recommendations on environmental aspects to the response oversight agency. The REET is composed of federal, provincial, and territorial agencies with an interest in the spill and its potential environmental impact, (co-)chaired by EC. The REET is a forum for the many agencies to provide their input, determine overall recommendations by consensus, and speak with a single voice to the oversight agency. Several acts of Parliament limit or restrict the introduction of hazardous materials into waterways, including the Fisheries Act, the Canadian Environmental Protection Act, and the Migratory Birds Convention Act. The legislative restrictions apply equally to STAs. A proposed treatment plan that includes the use of STAs is vetted by the REET to ensure reasonable expectation of net environmental benefit. The decision is made on a case-by-case basis, taking the full context of the spill scenario into account. Consideration must be given not only to the merits of a particular chemical countermeasure, but also to the qualities of the individual products. Environment Canada (EC) has had a program dedicated to spill emergencies for over three decades, within the mandate of the ESTS. Product evaluation is not limited to the standard tests outlined previously.5,53-55 The purpose is not usually to determine whether the product meets performance thresholds against a regulatory backdrop, as is the case in many other jurisdictions, but rather to provide baseline information for establishing product behaviors and comparisons to inform the REET. Additional testing using novel methods to evaluate particular behaviors of products with oil, and specific physical conditions, are often performed to address spill considerations and concerns that evolve over time. The collective internal testing by ESTS is combined with research documented by other sources to provide a composite of available knowledge for REET consideration. A benefit of this approach over a rigid screening protocol is that while baseline data is available for direct product comparison, the evaluation can be readily expanded to address product innovation, differentiation, or emerging concerns.

19.4. CHALLENGES TO CURRENT TOXICITY TEST PROTOCOLS Most of the literature available on this subject is based on research conducted prior to 1990. Dispersants that have been approved for use under specific

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conditions can be found on a list of approved treatments provided by the federal government. The laboratory work that supports these recommendations is outdated and needs to be reexamined. So-called current methodologies are not very current. The trout method is complex and time-consuming and does not represent many species, marine environments, or trophic levels. Furthermore, many toxicology experiments with dispersants have been conducted with fresh oil. The composition of oil changes with time due to the forces of nature, a multitude of physical processes grouped under the name “weathering”. Oil becomes more viscous with weathering as the volatile components are removed. This changes the ratio of volatile components to residual components, which in turn affects the physical properties of the slick. A further problem with existing research is the tendency to regard oil as a single, uniform, and homogeneous substance.56 In reality, oil can contain thousands of different components, each of which will have an effect on the slick’s environmental impact.56-58 This is further reason to regularly incorporate several species into toxicity testing methodologies as opposed to a single representative. The scientific and first-response communities are beginning to recognize the need for an updated toxicity test protocol. Recognition of the need for a standardized approach to dispersant efficacy and toxicity testing has resulted in a proposed outline for future experimentation by some scientists.59 These scientists did not suggest a specific experimental design, but rather a list of criteria that need to be addressed when creating a test method. The Chemical Response to Oil Spills: Ecological Research Forum (CROSERF) has promoted research on test methodology standardization since the mid-1990s.60-63 CROSERF has especially focused attention on the preparation of the chemically enhanced water-accommodated fraction (CEWAF). If it is truly desired to test a single species, simpler and more modern methods are available such as a minnow short-term reproduction assay.64 Every species has different sensitivities, so it is a gross oversimplication to depend on the toxicity results for a single type of animal. Current methods provide little insight into the effects of a dispersant-oil-water mixture on an ecosystem. Trout and a complex experimental setup are used to evaluate the toxicity of the dispersant alone, with no oil present.5 There are more modern alternatives to using fish such as the E-screen and A-screen, invertebrate bioassays, organic extraction of artificial substrate samples, and reproduction studies.65-74 Some organizations are choosing to use invertebrates for ethical as well as economic reasons. For smaller organisms, the size of the test tank is relatively much larger and therefore is a better representation of reality. Larger-scale experiments are ideal and were popular years ago. A Canadian example is a study conducted at Pointe-au-Pe`re, Quebec, where experiments took place during autumn, winter, and spring, and lasted from two weeks to two months.75 This allowed the researchers to evaluate natural degradation by bacteria and zooplankton under different weather conditions.

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Although single-species testing is more suited to quantifying the impact of a spill on a specific economically important organism, testing of treating agents for potential impact on all affected organisms is impractical and prohibitively expensive.76 Consequently, sensitive or “sentinel” species may be selected to act as surrogate or representative for assessing toxicity. The importance of testing oil-dispersant mixtures in realistic proportions has been recognized in several recent studies.77-81 There is also a need for shoreline testing and consideration of oil-mineral aggregates. Also, there is a gap where fresh water and soil contamination should be addressed. The current pass/fail system may be easier to understand, but the oversimplification of toxicity testing may inhibit informed decisions about which product is best in a given set of circumstances.

19.4.1. Endocrine-disrupting Capacity Certain chemicals either mimic or antagonize reproductive hormones. The effects manifest as a reduced quantity or quality of reproductive cells, deformation of reproductive organs, or transgenderification in affected individuals or populations. In humans, data indicate that endocrine-disrupting chemicals can lower sperm quality and quantity, increase spontaneous abortion rates, or lower overall fertility.82,83 These so-called xenoestrogens come from a variety of sources, including lotions, plasticizers, dyes, pesticides, food preservatives, lubricants, adhesives, and surfactants. A number of tests are available for assessing chemicals for endocrinedisrupting capacity. Animal assays with rodents have been used, with variations in vaginal cornification or uterine wet weight as endpoints. The E-screen assay measures an induced increase in the number of human breast MCF-7 cells and essentially relies on the same metabolic pathways as the live rodent assay. The E-screen, however, removes the handling difficulties inherent in live animal testing and allows for screening that is more applicable to environmental exposure than delivery of a test chemical orally or by injection. Exposing fish or other marine or aquatic fauna to potential endocrine disruptors has also proven useful. For this type of assay, the endpoint is chosen to reflect known or probable changes in sex cells or organs specific to the test organism. Very little is known about the potential for endocrine disruption by STAs in aquatic species.

19.4.2. Genotoxicity Toxicity data is sparse because of the number of contributing variables. Oil comes in many forms and each has a distinctive water-soluble fraction. Heavy crude oils have a very small soluble portion, but are more likely to cause suffocation. Values also depend on the exposure duration, any chemical treatments used in cleanup, food chains, and potential alternative sources of

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food that the test organism may choose when a primary source becomes contaminated. Genotoxicity is relative to the species tested and the proximity to the spill site.84 Three species of fish were tested years after the Haven oil spill in 1991. Hepatic cells of the test subjects were examined under the microscope for necrosis and micronuclei, which are present in greater quantities in response to xenobiotics.84 This method may be useful for monitoring the long-term effects of a spill in a relatively easy and noninvasive manner. A similar study in the Baltic and North Seas found that the quantity of micronuclei found in flounder erythrocytes and blue mussel gill cells was relative to the degree of pollution. Ecogenotoxicological monitoring is important since a significant amount of the human food supply comes from the oceans. However, results vary according to age, sex, season, feeding habits, temperature, reproduction, tissue sample origin, and level of dissolved oxygen in the water.85 Fish research has led the way to mammalian studies. Mussels from the coast of France after the 1999 Erika oil spill were fed to rats daily for two and four weeks. The effects of the contaminated mussels were examined in the rats’ liver, bone marrow, and blood. Genotoxicity was greatest in rats fed mussels from the most contaminated sites. Encouragingly, there was evidence of DNA repair at low exposure levels.86 Interestingly, the contamination did not appear to affect the rats’ growth. Although such studies are useful for monitoring individual cases, caution must be taken when attempting to predict the consequences of future spills because each environment and oil is unique.

19.4.3. Sublethal Effects Most toxicology studies of STAs have focused on the acute lethality of the agents and their mixtures with oil. These tests often do not consider the harmful effects that may not immediately cause death. There are many established test methods for measuring harm expressed in manifestations other than direct mortality. Sublethal toxicity can be measured in terms of an organism’s growth and development when exposed to a pollutant.87 This type of study involves careful examination of the early life stages of an exposed organism. Different concentrations of the CEWAF are correlated to the degree of mortality and morbidity in the test population. For example, the effects of polycyclic aromatic hydrocarbons (PAHs) leached from heavy Alberta bitumen on fathead minnow larvae include retarded embryonic growth, failure to hatch, premature or late hatching, death while partially hatched, edema, craniofacial malformations, altered pigmentation, spinal deformities, and hemorrhage.87 Other tests such as the ethoxyresorufin-O-deethylase (EROD) assay of the gills or liver can show that an organism has been exposed to certain types of

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water-borne pollutants such as PAHs and polychlorinated biphenyls (PCBs), including those that are a result of spilled oils.88-92 This test is based on the induction of the cytochrome P450 1A (CYP1A) enzyme that occurs in response to exposure to a pollutant. CYP1A mediates EROD activity. The EROD response from the examined tissue is a measure of an organism’s metabolic response to the pollutant. Therefore, the EROD response is correlated to the concentration of the pollutant as well as the duration of exposure.89,90 For example, a Canadian study of EROD assays from the livers of fish exposed to the water-accommodated fraction (WAF) WAF of oil and dispersed oil showed greater EROD activity in rainbow trout exposed to the WAF of the dispersed oil than those exposed to the WAF of the same oil without dispersant.93 A similar method was used to measure the response of rainbow trout to PAHs from industrial effluents. It was established that some contaminants have a synergistic effect that results in a much higher EROD response than expected.91 The authors conclude that studies of pollutant mixtures are more accurate in predicting toxic effects than traditional studies that have focused on a single component of a pollutant. This supports the move to test oil STAs of all types in combination with the oils they are meant to treat. EROD activity can be measured in almost all parts of the test organism. For example, the intestinal epithelial cells may be used when the route of exposure is ingestion.92 However, it is important to note that the induction of CYP1A varies between species and tissue type, so results cannot be compared between different species or between different sample tissues. The EROD test is sometimes complemented with the enzyme-linked immunosorbent assay (ELISA).94 ELISA detects the presence of a specific protein, especially antibodies or antigens, in a sample. In some cases, one assay works better than the other because of the nature of the pollutant. For example, some PCBs can inhibit rather than induce EROD activity and heavy metals may have a more pronounced effect on EROD activity than on CYP1A content results from ELISA.95,96

19.5. CONCLUSIONS Oil STAs are an option only under specific circumstances in Canada, determined case by case based on a net environmental benefit analysis. Assessment of the effectiveness and toxicity of treating agents is generally limited to laboratory testing, which sometimes does not directly correlate to open water conditions and profoundly limits the scope of potential impacts. However, laboratory testing offers an inexpensive and repeatable way of assessing the effectiveness and potential impacts of products designed as treating agents. Researchers at EC and elsewhere continue to study STAs to better inform decision-makers about the overall benefit of their use.

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REFERENCES 1. Fingas MF. The Basics of Oil Spill Cleanup. 2nd ed. Boca Raton, FL: Lewis Publishers, CRC Press; 2000. 2. Committee on Understanding Oil Spill Dispersants: Efficacy and Effects (National Research Council of the National Academies). Oil Spill Dispersants: Efficacy and Effects. Washington, DC: The National Academies Press; 2006. 3. Lambert P, Fieldhouse B, Fingas MF. A Discussion on the Use of Oil Spill Treating Agents in Canada. AMOP 2006;1077. 4. Canadian Environmental Protection Act (CEPA), Canada Gazette Part III, 22:3, Chapter 33, 1999. 5. Abbott FS. Guidelines on the Use and Acceptability of Oil Spill Dispersants, 2nd ed. Ottawa, ON: Environment Canada, EPS 1-EP-84-1; 1984. 6. Environmental Protection Service (EPS), Standard Procedure for Testing the Acute Lethality of Liquid Effluents, Ottawa, ON: Environment Canada, EPS 1-WP-80-1; 1980. 7. Environmental Protection Service (EPS), Biological Test Method: Reference Method for Determining Acute Lethality of Effluents to Rainbow Trout, http://www.etc-cte.ec.gc.ca/ organization/bmd/bmd_publist_e.html, EPS Report 1/RM/13, 2nd ed., Ottawa, ON; 2000. 8. Environmental Protection Service (EPS), Biological Test Method: Reference Method for Determining Acute Lethality of Effluents to Daphnia Spp., http://www.etc-cte.ec.gc.ca/ organization/bmd/bmd_publist_e.html, EPS Report 1/RM/14; 2000. 9. Environmental Protection Service (EPS), Biological Test Method: Toxicity Test Using Luminescent Bacteria, http://www.etc-cte.ec.gc.ca/organization/bmd/bmd_publist_e.html, Ottawa, ON: EPS Report 1/RM/24; 1992. 10. Otitoloju AA. Crude Oil Plus Dispersant: Always a Boon or Bane? Ecotox Environ Safety 2005;198. 11. ESPIS, Technical Summary: MMS Publication 94-0021. Dispersed Oil Toxicity Tests with Species Indigenous to the Gulf of Mexico, http://mms.gov/itd/abstracts/94-0021a.html; 1994. 12. Fingas MF. Use of Surfactants for Environmental Applications, Chapter 12. In: Schramm Laurier L, editor. Surfactants: Fundamentals and Applications to the Petroleum Industry, 461. Cambridge, UK: Cambridge University Press; 2000. 13. Fingas MF, Kyle DA, Laroche ND, Fieldhouse BG, Sergy G, Stoodley RG. The Effectiveness Testing of Spill Treating Agents, The Use of Chemicals in Oil Spill Response, ASTM STP 1252, Peter Lane, editor. ASTM 1995;286. 14. Kaku VJ, Boufadel MC, Venosa A. Evaluation of the Mixing Energy in the EPA Flask Tests for Dispersant Effectiveness. In: Oil Spills 2002, 1211. Southampton, UK: Wessex Institute of Technology; 2002. 15. Fingas MF. Energy and Work Input in Laboratory Vessels. IOSC 2005;663. 16. ASTM F 2059-06. Standard Test Method for Laboratory Oil Spill Dispersant Effectiveness Using the Swirling Flask. ASTM; 2006. 17. Fingas MF. Oil Spill Dispersants: A Technical Summary, Chapter 15 in this volume, 2010. 18. Nordvik AB, Hudon, TJ. Interlaboratory Calibration Testing of Dispersant Effectiveness, Phase I, MSRC Technical Report Series Report 93e003.1. Washington, D.C.: MSRC; 1993. 19. Nordvik AB, Osborn HG. Interlaboratory Calibration Testing of Dispersant Effectiveness, Phase II, MSRC Technical Report Series Report 935e003.2. Washington, D.C.: MSRC; 1993. 20. Lunel T, Baldwin G, Merlin F. Comparison of Meso-Scale and Laboratory Dispersant Tests with Dispersant Effectiveness Measured at Sea. AMOP 1995;629.

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21. Sorial G, Chandrasekar S, Weaver JW. Characteristics of Spilled Oils, Fuels, and Petroleum Products: 2a. Dispersant Effectiveness Data for a Suite of Environmental ConditionsdThe Effects of Temperature, Volatilization, and Energy. EPA/600/R-04/119; 2004. 22. Kaku VJ, Boufadel MC, Venosa AD. Evaluation of Mixing Energy in Laboratory Flasks Used for Dispersant Effectiveness Testing. J Envir Engrg 2006;93. 23. Lewis A. Determination of the Limiting Oil Viscosity for Chemical Dispersion at Sea. London, UK: MCA Project MSA 10/9/180; 2004. 24. Department for Environment, Food, and Rural Affairs (DEFRA). The Approval and Use of Oil Dispersants in the UK. London, UK: Marine Safety Authority; 2006. 25. Li Z, Boufadel MC, Venosa AD, Lee K. A Wave Tank Facility to Assess Chemical Oil Dispersant Effectiveness as a Function of Energy Dissipation Rate. Interspill; 2006. 26. Page CA, Bonner JS, McDonald TJ, Autenrieth RL. Behavior of a Chemically Dispersed Oil in a Wetland Environment. Water Res 2002;3821. 27. Bonner JS, Page CA, Fuller CB. Meso-Scale Testing and Development of Test Procedures to Maintain Mass Balance. Mar Pollut Bull 2003;406. 28. S.L. Ross Environmental Research, A Review of Dispersant Use on Spills of North Slope Crude Oil in Prince William Sound and the Gulf of Alaska, Report No. C634.956.1, PWSRCAC. Anchorage, AK: Prince William Sound Regional Citizens Advisory Council; 1997. 29. Fingas MF, Ka’aihue L. Dispersant Field TestingdA Review of Procedures and Considerations. AMOP 2004;1003. 30. Fingas MF. A White Paper on Oil Spill Dispersant Effectiveness Testing in Large Tanks, PWSRCAC, Anchorage, AK: Prince William Sound Regional Citizens Advisory Council; 2002. 31. Brown HM, Goodman RH, Canevari GP. Where Has All the Oil Gone? Dispersed Oil Detection in a Wave Basin and at Sea. IOSC 1987;307. 32. Belore R. Large Wave Tank Dispersant Effectiveness Testing in Cold Water. S.L. Ross Environmental Research Ltd, http://www.slross.com/publications/IOSC/2003_217-Large_ Tank_DE_Testing_In_Cold_Water.pdf; 2003. 33. Sterling MC, Bonner JS, Ernest ANS, Page CA, Autenreith RL. Chemical Dispersant Effectiveness Testing: Influence of Droplet Coalescence. Mar Pollut Bull 2004;969. 34. ASTM F1872-05. Standard Guide for Use of Chemical Shoreline Cleaning Agents: Environmental and Operational Considerations. Conshohocken, PA: ASTM; 2005. 35. Walker AH, Kucklick JH, Michel J. Effectiveness and Environmental Considerations for NonDispersant Chemical Countermeasures. Pure Appl Chem 1999;67. 36. Walker AH, Kucklick JH, Michel J, Scholz DK, Reilly T. Chemical Treating Agents: Response Niches and Research and Development Needs. IOSC 1994;211. 37. Fingas MF, Fieldhouse B. Studies on Crude Oil and Petroleum Product Emulsions: Water Resolution and Rheology. Colloids Surf A 2009;67e81. 38. Buist I, Lewis A, Guarino A, Lane J. Extending Temporary Storage Capacity with Emulsion Breakers, Herndon, VA: MMS Report; 2002. 39. Buist I, Lewis A, Guarino A, Mullin J. Examining the Fate of Emulsion Breakers Used for Decanting, Herndon, VA: MMS Report; 2005. 40. Buist I, Lewis A, Guarino A, Devitis D, Nolan K, Smith B, et al. Extending Temporary Storage Capacity with Emulsion Breakers. AMOP 2002;139. 41. Marine Spill Response Corporation (MSRC), Chemical Oil Spill Treating Agents, MSRC Report 93e105, Washington, D.C.: Marine Spill Research Corporation; 1995. 42. Buist I, Potter S, Meyer P, Zabilansky L, Mullin J. Mid-Scale Test Tank Research on Using Oil Herding Surfactants to Thicken Oil Slicks in Pack Ice-An Update. AMOP 2006;691.

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43. Northwest Area Committee, Northwest Area Shoreline Countermeasures Manual and Matrices, http://www.rrt10nwac.com/files/nwacp/9640.pdf; 1995. 44. Fingas MF, Fieldhouse B. Review of Solidifiers, Chapter 22 in this volume, 2010. 45. Ghalambor A. The Effectiveness of Oil Solidifiers for Combating Oil Spills, Baton Rouge, LA: Louisiana State Government, Louisiana OSDRAP; 1996. 46. EPA, Gelling Agents, http://www.epa.gov/oilspill/gelagents.htm; May 2006. 47. US NRT, Fact Sheet: Bioremediation in Oil Spill Response. An Information Update on the Use of Bioremediation, http://www.nrt.org/production/NRT/NRTWeb.nsf/AllAttachmentsByTitle/ A-78bioremedFS/$File/bioremed_FS.pdf?OpenElement, NRT; 2000. 48. Tagger S, Bianchi A, Juillard M, LePetit J, Roux B. Effect of Microbial Seeding of Crude Oil in Seawater in a Model System. Mar Biol 1983;13. 49. Johnson BT, Petty JD, Huckins JN, Lee K, Gauthier Joanne. Hazard Assessment of a Simulated Oil Spill on Intertidal Areas of the St. Lawrence River with SPMD-TOX. Environ Tox 2004;329. 50. Wang Z, Fingas MF, Blenkinsopp S, Sergy G, Landriault M, Sigouin L, et al. Comparison of Oil Composition Changes due to Biodegradation and Physical Weathering in Different Oils. J Chromat 1998;89. 51. ITOPF, Technical Information Paper: The Use of Chemical Dispersants to Treat Oil Spills, http://www.ipieca.org/downloads/oil_spill/AAOP/itopf_tip4.pdf, ITOPF; 2004. 52. Boesch DF, Hershner CH, Milgram JH. Oil Spills and the Marine Environment: Papers Prepared for the Energy Policy Project of the Ford Foundation, http://www.fordfound.org/ eLibrary/documents/0216/096.cfm; 1974. 53. Lumley TC, Fieldhouse B, Hollebone BP, Harrison S. Evaluation of Methods for Assessing Effectiveness of Oil Spill Treating Agents. AMOP 2007;117. 54. Lumley TC, Hollebone BP, Harrison S. Evaluation of Methods for Assessing Toxicity of Oil Spill Treating Agents. AMOP 2007;133. 55. Environmental Protection Service (EPS), Standard Procedure for Testing the Acute Lethality of Liquid Effluents, Ottawa, ON: Environment Canada, EPS 1-WP-80-1; 1980. 56. Mills MA, McDonald TJ, Bonner JS, Simon MA, Autenrieth RL. Method for Quantifying the Fate of Petroleum in the Environment. Chemosphere, 1999;2563. 57. Sterling Jr MC, Bonner JS, Page CA, Fuller CB, Ernest ANS, Autenrieth RL. Partitioning of Crude Oil Polycyclic Aromatic Hydrocarbons in Aquatic Systems. Environ Sci Techn 2003;4429. 58. Barron MG, Podrabsky T, Ogle S, Ricker RW. Are Aromatic Hydrocarbons the Primary Determinant of Petroleum Toxicity to Aquatic Organisms? Aquat Toxicol 1999;253. 59. Mearns AJ. Elements to Be Considered in Assessing the Effectiveness and Effects of Shoreline Countermeasures. Spill Sci Technol Bull 1995;5. 60. Coelho G, Aurand D. Proceedings of the Seventh Meeting of the Chemical Response to Oil Spills: Ecological Effects Research Forum. Lusby, MA: Ecosystem Management & Associates, Inc., EM&A Report 97e02 ; 1997. 61. Singer MM, Aurand D, Coelho G, Bragin GE, Clark JR, Jacobson S, et al. Making, Measuring, and Using Water-Accommodated Fractions of Petroleum for Toxicology Testing. IOSC 2001;1269. 62. Clark JR, Bragin GE, Febbo RJ, Letinski DJ. Toxicology of Physically and Chemically Dispersed Oils Under Continuous and Environmentally Realistic Exposure Conditions: Applicability to Dispersant Use Decisions in Spill Response Planning. IOSC 2001;1249. 63. Rhoton SL, Perkins RA, Braddock JF, Behr-Andres C. A Cold-weather Species’ Response to Chemically Dispersed Fresh and Weathered Alaska North Slope Crude Oil. IOSC 2001;1231.

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64. Ankley GT, Kahl MD, Jensen KM, Hornung MW, Korte JJ, Makynen EA, et al. Evaluation of the Aromatase Inhibitor Fadrozole in a Short-Term Reproduction Assay with the Fathead Minnow (Pimephales promelas). Toxicol Sci 2002;121. 65. Adams GG, Klerks PL, Belanger SE, Dantin D. The Effect of the Oil Dispersant OmniCleanÒ on the Toxicity of Fuel Oil No. 2 in Two Bioassays with the Sheepshead Minnow. Cyprinodon variegates Chemosphere 1999:2141. 66. Barron MG, Ka’aihue L. Critical Evaluation of CROSERF Test Methods for Oil Dispersant Toxicity Testing Under Subarctic Conditions. Mar Pollut Bull 2003;1191. 67. Barron MG, Carls MG, Short JW, Rice SD. Photoenhanced Toxicity of Aqueous Phase and Chemically Dispersed Weathered Alaska North Slope Crude Oil to Pacific Herring Eggs and Larvae. Environ Toxicol Chem 2003;650. 68. Bhattacharyya S, Klerks PL, Nyman JA. Toxicity to Freshwater Organisms from Oils and Oil Spill Chemical Treatments in Laboratory Microcosms. Environ Pollut 2003;205. 69. Coˆte´ C, Blaise C, Michaud J-R, Me´nard L, Trottier S, Gagne´ F, et al. Comparisons between Microscale and Whole-Sediment Assays for Freshwater Sediment Toxicity Assessment. Environ Toxicol Water Qual 1998;93. 70. Cotou E, Castritsi-Catharios I, Moraitou-Apostolopoulou M. Surfactant-Based Oil Dispersant Toxicity to Developing Nauplii of Artemia: Effects on ATPase Enzymatic System. Chemosphere 2001;959. 71. Duke TW, Petrazzuolo G, editors. Oil and Dispersant Toxicity Testing, Proceedings of a Workshop on Technical Specifications Held in New Orleans January 17e19, 1989, Herndon, VA: OCS Study MMS 89-0042, Contract No. 14-12-0001-30447; 1989. 72. Klerks PL, Nymann JA, Bhattacharyya S. Relationship Between Hydrocarbon Measurements and Toxicity to a Chironomid, Fish Larva, and Daphnid for Oils and Oil Spill Chemical Treatments in Laboratory Freshwater Marsh Microcosms. Environ Pollut 2004;345. 73. Soto AM, Sonnenschein C, Chung KL, Fernandez MF, Olea N, Serrano FO. The E-Screen Assay as a Tool to Identify Estrogens: An Update on Estrogenic Environmental Pollutants. Environ Health Perspect Suppl 1995;103. 74. Soto AM, Sonnenschein C, Calabro J, Rudel R, Brody J. Methods for Determining Estrogenic (E-screen) and Androgenic (A-screen) Activity of Chemicals Using Cell Proliferation Assays, http://caat.jhsph.edu/programs/workshops/testsmart/endocrine2001/proceedings/soto.htm; 2001. 75. Siron R, Pelletier E, Brochu C. Environmental Factors Influencing the Biodegradation of Petroleum Hydrocarbons in Cold Seawater. Arch Environ Contam Toxicol 1995;406. 76. Eisler R, Kissil GW. Toxicities of Crude Oil-Dispersant Mixtures to Juvenile Rabbitfish, Siganus rivulatus. T Am Fish Soc 1975;571. 77. Fuller C, Bonner J, Page C, Ernest A, McDonald T, McDonald S. Comparative Toxicity of Oil, Dispersant, and Oil Plus Dispersant to Several Marine Species. Environ Tox Chem 2004;2941. 78. Koyama J, Kakuno A. Toxicity of Heavy Fuel Oil, Dispersant, and Oil-Dispersant Mixtures to a Marine Fish, Pagrus major. Fisher Sci 2004;578. 79. Page CA, Bonner JS, Sumner PL, McDonald TJ, Autenrieth RL, Fuller CB. Behavior of a Chemically-Dispersed Oil and a Whole Oil on a Near-Shore Environment. Water Res 2000;2507. 80. Tjeerdema RS, Lin CY. Acute and Chronic Effects of Crude and Dispersed Oil on Pre-Smolt Stage Chinook Salmon. A Research Preproposal for the Oiled Wildlife Care NetworkdApril 2005, http://www.vetmed.ucdavis.edu/owcn/pdfs/05-06Tjeerdema.pdf; 2005. 81. Singer MM, George S, Lee I, Jacobson S, Weetman LL, Blondina G, et al. Effects of Dispersant Treatment on the Acute Aquatic Toxicity of Petroleum Hydrocarbons. Arch Environ Contam Toxicol 1998;177.

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82. Gwicercman A, Carlsen E, Keiding N, Skakkebaek NE. Evidence for Increasing Incidence of Abnormalities of the Human Testis: A Review. Environ Health Pers; 1993:65e71. 83. Sharpe RM, Skakkebaek NE. Are Oestrogens Involved in Falling Sperm Count and Disorders of the Male Reproductive Tract? Lancet 1993;1392. 84. Pietrapiana D, Modena M, Guidetti P, Falugi C, Vacchi M. Evaluating the Genotoxic Damage and Hepatic Tissue Alterations in Demersal Fish Species: A Case Study in the Ligurian Sea (NW-Mediterranean). Mar Pollut Bull 2002;238. 85. Barsien_ J, Lazutka J, Syvokiene J, Dedonyt V, Rybakovas A, Bagdonas E, et al. Analysis of Micronuclei in Blue Mussels and Fish from the Baltic and North Seas. Environ Tox 2004;387. 86. Lemiere S, Cossu-Leguille C, Bispo A, Jourdain MJ, Lanhers MC, Burnel D, et al. DNA Damage Measured by the Single-Cell Gel Electrophoresis (Comet) Assay in Mammals Fed With Mussels Contaminated by the Erika Oil-Spill. Mutat Res 2005;581:11. 87. Colavecchia MV, Backus SM, Hodson PV, Parrott JL. Toxicity of Oil Sands to Early Life Stages of Fathead Minnows (Pimephales promelas). Environ Tox Chem 2004;1709. 88. Jo¨nsson M, Brandt I, Brunstrom B. A Gill Filament-Based EROD Assay for Monitoring Waterborne Dioxin-Like Pollutants in Fish. Environ Sci Techn 2002;3340. 89. Matsuo AYO, Woodin BR, Reddy CM, Val AL, Stegman JJ. Humic Substances and Crude Oil Induce Cytochrome P450 1A Expression in the Amazonian Fish Species Colossoma marcropomum (Tambaqui). Environ Sci Technol 2006;2851. 90. Mdegela R, Myburgh J, Correia D, Brathen M, Ejobi F, et al. Evaluation of the Gill FilamentBased EROD Assay in African Sharptooth Catfish (Clarias gariepinus) as a Monitoring Tool for Waterborne PAH-type Contaminants. Ecotox 2006;51. 91. Basu N, Billiard S, Fragoso N, Omoike A, Tabash S, Brown S, et al. Ethoxyresorufin-ODeethylase Induction in Trout Exposed to Mixtures of Polycyclic Aromatic Hydrocarbons. Environ Tox Chem 2001;1244. 92. Woodin BR, Smolowitz RM, Stegman JJ. Induction of Cytochrome P4501A in the Intertidal Fish Anoplarchus purpurescens by Prudhoe Bay Crude Oil and Environmental Induction in Fish from Prince William Sound. Environ Sci Technol 1997;1198. 93. Ramachandran SD, Hodson PV, Khan CW, Lee K. Oil Dispersant Increases PAH Uptake by Fish Exposed to Crude Oil. Ecotox Environ Safety 2003;300. 94. Stagg RM, Rusin J, McPhail ME, McIntosh AD, Moffat CF, Craft JA. Effects of Polycyclic Aromatic Hydrocarbons on Expression of CYP1A in Salmon (Salmo salar) Following Experimental Exposure and After the Braer Oil Spill. Environ Tox Chem 2000;2797. 95. Bru¨schweiler BJ, Wu¨rgler FE, Fent K. An ELISA Assay for Cytochrome P4501A in Fish Liver Cells. Environ Tox Chem 1996;592. 96. Bru¨schweiler BJ, Wu¨rgler FE, Fent K. Inhibitory Effects of Heavy Metals on Cytochrome P4501A Induction in Permanent Fish Hepatoma Cells. Arch Environ Contam Toxicol 1996;475.

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Chapter 20

The United States Environmental Protection Agency: National Oil and Hazardous Substances Pollution Contingency Plan, Subpart J Product Schedule (40 Code of Federal Regulations 300.900) William J. Nichols

Chapter Outline 20.1. Introduction 20.2. Why Is There a Product Schedule? 20.3. Authorities for a Product Schedule 20.4. Information Requested from Manufacturers 20.5. Agency Activities 20.6. Practical Utility of the Data

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20.7. Authorities for Use 20.8. Federal Agencies’ Role within the Regional Response Team 20.9. Does Listing Mean the Environmental Protection Agency Approves and Endorses a Product? 20.10. Conclusions

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20.1. INTRODUCTION The National Oil and Hazardous Substances Pollution Contingency Plan, more commonly called the National Contingency Plan or NCP, is the United States federal government’s blueprint for responding to both oil spills and Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10020-6 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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hazardous substance releases. The National Contingency Plan is the result of our country’s efforts to develop a national response capability and promote overall coordination among the hierarchy of responders and contingency plans. Subpart J of the NCP applies to navigable waters of the United States and adjoining shorelines, the waters of the contiguous zone, and the high seas beyond the contiguous zone in connection with activities under the Outer Continental Shelf Lands Act, activities under the Deepwater Port Act of 1974, or activities that may affect natural resources belonging to, appertaining to, or under the exclusive management authority of the United States, including resources under the Magnuson Fishery Conservation and Management Act of 1976 (40 CFR 300.900). The authority to use alternative countermeasures on oil spills is granted to the U.S. federal government within the National Contingency Plan (NCP) under section 300.910.

20.2. WHY IS THERE A PRODUCT SCHEDULE? In 1967 the Torrey Canyon broke apart off the coast of England, oiling many prime holiday beaches as 95,000 tons (593,750 barrels) of oil were released into the ocean. A total of 10,000 tons (66,000 barrels) of chemicals were used to attempt to remove the oil from the impacted shorelines. Many of these chemicals were actually degreasing agents containing over 60% aromatic solvents. Both the solvents and the surfactants were highly toxic to marine life.1 Kenneth Biglane, then the director of the U.S. Oil and Special Materials Control Division, flew to the spill site and witnessed what can be described, and confirmed by many in the oil spill response community, as severe misuse of chemical cleaning agents. Biglane stated that anyone who was able to carry hoses, back pumps, and portable pumps was pressed into service. Biglane saw unprecedented damage to the biota. Coastal hotels were approached by salesmen encouraging them to use these materials on their oil-contaminated beachesdmuch to the hotel owners’ regret as these materials helped cause erosion of those very beaches. In June of 1968, President Lyndon Johnson directed the secretaries of Department of Defense (DOD), Department of Interior (DOI), and Department of Transportation (DOT) and the director of the U.S. Office of Science and Technology to assume special responsibilities to complete a multiagency contingency plan in order to strengthen the nation’s preparedness to act in the event of an oil spill pollution emergency along the coasts and waterways. Chemical dispersants were being highly touted by industry, and each week DOT, DOD, and DOI were besieged by chemical salesmen, who wandered in off the street or were sent by congressmen and showed up on-scene at most spills. Newspapers would report on a “marvelous potion” and spend many hours interviewing the few federal experts who knew about the compounds. The Environmental Protection Agency (EPA) was not opposed to the proper use

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of these chemicals, but hoped that situations such as the Torrey Canyon spill response would indeed become rare events. In April 1970, Congress passed the Federal Water Pollution Control Act, which called for an NCP. Further, Congress called for preparing a schedule of chemicals for use on spills. At that time Kenneth Biglane convened a task force at the EPA, including six state water pollution control administrators, to establish the NCP Product Schedule.2 Today it is a fact that dispersants and some other chemical countermeasures are far less toxic than their predecessors. However, at times the EPA is still inundated with salespeople seeking the agency’s endorsement or approval of their products. Vendors often base their request on their product’s low toxicity, but seldom provide product data to substantiate their claims. While the EPA encourages the prudent and effective use of oil spill mitigating products, it is imperative that manufacturers follow the proper procedures within Subpart J of the NCP in order to have their products listed and, in turn, used properly. Several countries have copied the EPA’s regulations and product testing protocols. Some have established their own product schedule, while most just adopt the EPA’s Schedule.

20.3. AUTHORITIES FOR A PRODUCT SCHEDULE The use of dispersants, other chemical agents, and bioremediation agents to respond to oil spills in U.S. waters is governed by Subpart J of the NCP (40 CFR 300.900). The EPA’s regulation, which is codified at 40 CFR 300.00, requires that the EPA prepare a schedule of “dispersants, other chemicals, and other spill mitigating devices and substances, if any, that may be used in carrying out the NCP.” The Product Schedule (hereafter referred to as the Schedule) is required by Section 311(d)(2)(G) of the Clean Water Act (CWA), as amended by the Oil Pollution Act of 1990 (OPA). Under Subpart J, respondents wishing to add a product to the Schedule must submit technical product data specified in 40 CFR 300.915 to the EPA. The EPA places oil spill mitigating products on the Schedule if all the required data are submitted. The Schedule is available to Federal OnScene Coordinators (OSCs), Regional Response Teams (RRTs), industry, states, oil spill response companies, hazardous materials response teams, and Area Committees for determining the most appropriate products to use in various spill scenarios. Products currently listed on the Schedule are divided into five basic categories: dispersants, surface-washing agents, surface-collecting agents, bioremediation agents, and miscellaneous oil spill control agents.

20.4. INFORMATION REQUESTED FROM MANUFACTURERS Under Subpart J, manufacturers who wish to list a product on the Schedule must report the items specified below for the appropriate category. Dispersants Those chemical agents that emulsify, disperse, or solubilize oil into the water column or promote the surface spreading of oil into the water column.

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1. Name, brand, or trademark, if any, under which the dispersant is sold 2. Name, address, and telephone number of the manufacturer, importer, or vendor 3. Name, address, and telephone number of primary distributors or sales outlets 4. Special handling information and worker precautions for storage and field application, including maximum and minimum storage temperatures 5. Shelf life 6. Recommended application procedures, concentrations, and conditions for use 7. Results of the effectiveness test set forth in Appendix C of the NCP 8. Results of the toxicity test set forth in Appendix C of the NCP 9. Physical properties covered by the American Society for Testing and Material’s reference standards 10. Dispersing agent components 11. The concentrations or upper limits of any heavy metals, cyanide, and chlorinated hydrocarbons 12. The identity of the laboratory that performed tests, the qualifications of the laboratory’s staff, and laboratory experience with similar tests Under the NCP Subpart J, respondents must have dispersant products tested for effectiveness and toxicity and provide the results to the EPA’s Office of Emergency Management Regulatory and Policy Development Division. Dispersants are required to demonstrate a 50% (5%) effectiveness level or greater in order to be placed on the Schedule. Only those dispersants that meet or exceed the effectiveness acceptability threshold are eligible to be listed on the Schedule and need be tested for toxicity. RRTs may require an additional swirling flask test using a type of oil other than that specified in Subpart J Appendix C (Alaska North Slope Crude and South Louisiana Crude). An RRT may require a toxicity test using an invertebrate species other than that specified in Appendix C (Menidia beryllina and Mysidopsis bahia). This authority is not intended to make the preauthorization of certain technologies more difficult and does not authorize the RRTs to establish more stringent effectiveness and toxicity criteria, but will enable them to make more informed decisions by providing them with additional site- or area-specific data. Individual states, however, may require other tests and more stringent toxicity requirements. Although there is no toxicity threshold for dispersants, the EPA feels that when making decisions on the use of dispersants, or any other product, spill responders should use the least harmful products that have been proven effective under the standardized laboratory conditions and actual field use. The EPA explicitly reserves the right to request additional documentation regarding both tests and conduct verification testing of the effectiveness test results.

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Surface-Washing Agents (SWAs): Any product that removes oil from solid surfaces, such as beaches and rocks, through a detergency mechanism and does not involve dispersing or solubilizing the oil into the water column. In addition to the information and data required for dispersants, a surface-washing agent’s components must be provided. The EPA will be conducting research on developing a test method and may specify an effectiveness protocol for SWAs. This category generates the most confusion due to SWAs’ action on removing oil from an impervious surface. SWAs are designed to break up and lift the oil, allowing it to float on water and be collected for removal using sorbents, vacuum trucks, skimmers, or other mechanical means. They are not supposed to emulsify or disperse the oil in any large degree, as this makes the recovery of the oil more difficult. Dispersants and SWAs are therefore opposite in action and purpose. However, the EPA is concerned that these products are often used to achieve the same result, and this practice leads to misuse of the products. SWAs have been used on open water spills, while dispersants have been used to wash oil from sandy beaches, driving the oil deeper into the substrate. Both misuses may cause further harm to the environment than the oil alone. SWAs are not allowed to be discharged into or applied directly onto a water body, but should always be recovered along with the oil. As often reported by state and federal authorities, SWAs have been used to expedite cleanup with little concern for preventing runoff from reaching waterways. Runoff has caused fish kills and oil accumulation in storm drains, creating explosion hazards. Fire departments may use an SWA to quickly dissipate fumes and fuel from a vehicle accident to prevent fire and explosion hazards. OSCs may authorize their use to prevent harm to human life, even if the product is not listed on the Schedule. The EPA encourages recovery of the oil or gas in all cases. Surface-Collecting Agents: Those chemical agents that form a surface film to control the layer thickness of oil. Test results distinguishing a surface-collecting agent from other chemical agents is required. The protocol for this test requires that a small amount of the product is added to a beaker of water to determine whether the product sinks or is contained at the surface. If the major portion of the chemical added, 75%, is at the water surface as a separate and easily distinguished layer, the product is a surface-collecting agent (a/k/a herding agent).There were no surfacecollecting agents on the list as of August 2010. Bioremediation Agents: Microbiological cultures, enzyme additives, or nutrient additives that are deliberately introduced into an oil discharge and that will significantly increase the rate of biodegradation to mitigate the effects of the discharge. For microbiological cultures, a listing of all microorganisms by species, including percentages and special nutrients additions is required. For enzyme

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additives, information on their source and operating conditions must be listed. Miscellaneous Oil Spill Control Agents: Any product, other than those defined above that can enhance oil spill cleanup, removal, treatment, or mitigation. Examples of these agents are sorbents impregnated with chemical or biological ingredients, elasticity modifiers, emulsion treating agents, and solidifiers. Due to the nature of this category, the EPA reserves the right to require further testing of products that do not meet strict definitions of defined product categories. Some products may qualify as a “mixed product,” in which case the criteria to be listed may include combinations of the requirements listed above. Note that the miscellaneous category is not a “catch-all” for manufacturers wishing to market a product they claim will perform all the actions described in other categories. An example is an SWA that also acts like a dispersant when used in a neat form or a bioremediation agent that also contains enough surfactant to disperse the oil into the water column. The EPA reserves the right to closely examine the method of action for every product and makes corrections to manufacturer application language when necessary. Some latitude may be granted, but it is important for the integrity of the Schedule and its usefulness to the oil spill community that manufacturers not market a product as a comprehensive one-size-fits-all agent able to perform any oil spill-related task. Under Subpart J, the respondent must also notify the EPA of any changes in the composition, formulation, or application of the dispersant, surface-washing agent, surface-collecting agent, bioremediation agent, or miscellaneous oil spill control agent. If the change is likely to alter the effectiveness or toxicity of the product, the EPA may require retesting. If the EPA decides that retesting is necessary, the submitter must have the product tested in a state certified laboratory and forward the data, along with the qualifications of the laboratory staff, to the EPA.

Special Note on Sorbents The term sorbent means essentially inert and insoluble materials that are used to remove oil and hazardous substances from water through adsorption, in which the oil or hazardous substance is attracted to the sorbent surface and then adheres to it; absorption, in which the oil or hazardous substance penetrates the pores of the sorbent material; or a combination of the two. Sorbents are generally manufactured in particulate form for spreading over an oil slick or as sheets, rolls, pillows, or booms. Sorbents are not required to be listed under the NCP Product Schedule. However, sorbents that contain chemical or biological components, especially when made in loose form, may be required to be listed. Manufacturers that produce sorbent materials that

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consist of materials other than those listed in paragraph (g)(1) of 300.915 shall submit to the EPA the technical product data specified for miscellaneous agents. Materials listed under (g)(1) include organic materials such as peat moss and bird feathers, mineral compounds including volcanic ash and vermiculite, and synthetics such as polypropylene and polyester. If the EPA determines that the sorbent may cause a deleterious effect on the environment, the product needs to be listed under the miscellaneous category. Examples of sorbents that are required to be on the Schedule include loose cellulose materials that contain nonindigenous microbes, chemical solidifiers, or any other product that does not meet the definition of sorbents as stated in 300.915 (g). EPA is aware that the 1994 Subpart J list of sorbent materials is dated and does allow for broader interpretation of what sorbent is to accommodate newer materials.

20.5. AGENCY ACTIVITIES Under Subpart J, EPA will perform activities when a manufacturer applies to have a product listed on the Product Schedule. Once the technical product data required by the rule are submitted, the EPA must perform the following activities: l l l

l

Receive and process the data Review the data for completeness and procedural accuracy Notify the respondent of the decision on listing the product on the Schedule If approved, place the product on the Schedule, store the data, and supply the data upon request

The EPA’s decision to place a product on the Schedule is based on the completeness of the information presented; however, the product will be evaluated for its effects on water quality as prescribed in the CWA section 311. The EPA reserves the right to request further documentation of a lab’s test results. The EPA also reserves the right to verify test results and consider those results in determining whether a product meets listing criteria. The EPA has 60 days to notify the manufacturer of its decision to list a product on the Schedule, or request additional information, and/or a sample of the product in order to review and/or conduct validation sampling.

20.6. PRACTICAL UTILITY OF THE DATA If all of the required data are submitted, the EPA places oil spill mitigation products on the Schedule. The Schedule is available for use by OSCs, RRTs, and Area Committees in determining the most appropriate products to use in various spill scenarios. Under 40 CFR 300.910(a), RRTs and Area Committees are required to address the desirability of using the products on the Schedule in

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their Regional Contingency Plans and Area Contingency Plans, respectively. The required information is needed from the respondent so that the OSCs, RRTs, and Area Committees can make informed decisions to safely employ chemical countermeasures to control oil discharges. Correct product use is critical in emergency situations. While OSCs and Area Committees, along with RRTs, make the decisions to use or not use alternative methods, there are certain guidelines and national policies that apply. The EPA’s policy that draws some attention and disagreement is that freshwater use of dispersants is not authorized for waters of the United States. Shallow marine water use is also discouraged. This policy is in agreement with the National Academy of Sciences and other research efforts. There are exceptions, but due to the nature of dispersants, the environmental conditions, and the requirements to use them effectively, the EPA will not allow general or preauthorized use of dispersants in the inland waters of the United States.

20.7. AUTHORITIES FOR USE Section 311(d)(2)(G) of the CWA, as amended by the OPA, requires that the NCP include a schedule identifying “dispersants, other chemicals, and other spill mitigating devices and substances, if any, that may be used in carrying out” the NCP. The authority of the President to implement the CWA is currently delegated to the EPA by Executive Order 12777 (56 FR 54757, October 18, 1991). The Schedule is available for use by OSCs, RRTs, and Area Committees in determining the most appropriate products to use in various spill scenarios. For spill situations that are not addressed by the preauthorization plans, OSCs, with the concurrence of the EPA representative to the RRT and, as appropriate, the concurrence of RRT representatives from the states with jurisdiction over the navigable waters threatened by the spill, and in consultation with the Department of Commerce (National Oceanic and Atmospheric Administration, NOAA), and the DOI natural resource trustees, when practicable, may authorize the use of chemical or biological agents on the oil. State environmental agencies and the responsible party may also be consulted.

20.8. FEDERAL AGENCIES’ ROLE WITHIN THE REGIONAL RESPONSE TEAM The EPA OSCs are available for inland spills. Every coastal region establishes its jurisdictional boundaries with the local Coast Guard Sectors. As per 40 CFR Section 300.120, the United States Coast Guard (CG) is the predesignated OSC and has the overall responsibility for oil spill response management in the coastal zone and for incidents under its jurisdiction, including alternative countermeasure activity. The CG, in conjunction with the RRT, will be directly involved in a dispersant application and use of any

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listed products, and may be responsible for assigning tasks to each participating agency during the response. The EPA, with its expertise, may act as a technical adviser to the OSC. This includes advising the OSC on the ability of a particular bioremediation agent to degrade oil in the environment safely and at a rate that is significantly higher than the natural rate of oil degradation. The NOAA maintains extensive information on ocean and atmospheric conditions. This information can be used to assist in the selection of a particular countermeasure technology. The NOAA has both a biological assessment team and support contractors, who understand how products may be used in conjunction with more conventional cleanup strategies. The DOI manages certain areas of the U.S. coastline and most federal inland areas. During a response and during planning stages, the Fish and Wildlife Service provides consultation for Endangered Species protection for any spill within the areas managed by DOI response activities. The DOI federal land managers are consulted by the OSC regarding response actions that are compatible with the management philosophy for the area. The use of any products may conflict with the land management objectives of the DOI agencies.3

20.9. DOES LISTING MEAN THE ENVIRONMENTAL PROTECTION AGENCY APPROVES AND ENDORSES A PRODUCT? No. The listing of a product on the Schedule does not constitute approval of the product. To avoid possible misinterpretation or misrepresentation, any label, advertisement, or technical literature that refers to the placement of the product on the NCP Product Schedule must either reproduce in its entirety the EPA written statement that it will list the product on the Schedule under 40 CFR 300.920(a)(2) or include the disclaimer shown below.4 Failure to comply with these restrictions or any other improper attempt to demonstrate the approval of the product by any NRT or other U.S. government agency shall constitute grounds for removing the product from the Schedule. Disclaimer: [PRODUCT NAME] is on the U.S. Environmental Protection Agency’s NCP Product Schedule. This listing does NOT mean that EPA approves, recommends, licenses, certifies, or authorizes the use of [PRODUCT NAME] on an oil discharge. The listing means only that data have been submitted to EPA as required by Subpart J of the National Contingency Plan, 300.915

The EPA makes no claim that any of the listed products work exactly as they are supposed to. At this time the only thresholds that must be met are for the Dispersant Swirling Flask Test and the Bioremediation 28-Day Effectiveness Test.

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20.10. CONCLUSIONS 20.10.1. Proper Uses and Lessons Learned The EPA encourages industry, OSCs, state and local agencies, the international response community, oil spill response organizations, fire departments, and the entire oil spill community to communicate with the EPA and each other. OSCs and first responders play a vital role in deciding when to use a product by their participation on the RRT. RRT representatives may be called on more often to concur with in-situ burning, chemical, and biological countermeasures for marine and inland spills. It is invaluable that experiences, lessons learned, and best practices be shared with the U.S. NRT, which in turn can evaluate and distribute this information. Providing lessons learned will assist in understanding the appropriate uses and limitations of alternative countermeasures like the products listed on the NCP Product Schedule. In 2010, the EPA will be proposing changes and improvements to Subpart J and the product listing process. We welcome diverse participation in this process. which will be announced in the U.S. Federal Register. For more information about listing products on the NCP Product Schedule, contact the EPA’s NCP Information Line at (202) 260-2342, or write to: U.S. Environmental Protection Agency Office of Emergency Management (5104A), 1200 Pennsylvania Ave., Washington, DC 20460. Packages must be sent to the EPA Product Schedule Manager (5104A), U.S. EPA, 1200 Pennsylvania Ave. NW, Washington, DC 20460.

REFERENCES 1. American Petroleum Institute, A Decision Maker’s Guide to Dispersants, A Review of the Theory and Operational Requirements, Health and Environmental Sciences Department, Publication Number 4692; 1999. 2. Biglane, K, Director Oil and Special Materials Control Division. Memo to the EPA Record Subject: Oil Spill Dispersant Chemicals; 1976. 3. Caribbean Regional Response Team, Bioremediation Spill Response Plan, Response Technology Committee, Bioremediation Subcommittee Region II EPA; 1995. 4. United States Environmental Protection Agency, 40 Code of Federal Regulations Part 300, National Oil and Hazardous Substances Pollution Contingency Plan, Final Rule, Federal Register; 1994.

Chapter 21

Surface-Washing Agents or Beach Cleaners Merv Fingas and Ben Fieldhouse

Chapter Outline 21.1. Introduction to 683 Surface-Washing Agents 21.2. Review of Major 686 Surface-Washing Agent Issues

21.3. Other Issues

697

21.1. INTRODUCTION TO SURFACE-WASHING AGENTS Surface-washing agents (SWAs) or beach cleaners are formulations of surfactants designed to remove oil from solid surfaces such as shorelines. In some countries they are also used on solid surfaces such as roads. Since they are intended to remove oil rather than to disperse it, SWAs contain surfactants with higher hydrophilic-lipophilic balance (HLB) than those in dispersants. Most SWAs are formulated not to disperse oil into the water column, but to release oil from the surface where it floats. Higher water flushing energy will typically result in some dispersion. SWAs are a recent phenomenon. Agents have been classified as SWAs rather than dispersants in the past 20 years, with most of the newer products promoted after the Exxon Valdez spill in 1989. Before that, dispersants were assessed on shorelines, with mixed results.1,2 In the oil spill industry, the new specially designed products may still be called dispersants by some. As with dispersants, effectiveness and toxicity are the main issues with SWAs, although the level of concern is not as great. There are several reasons for this. First, SWAs have not been used on a large scale anywhere in the world. Unlike dispersants, they are not a universally applicable agent, but are used in specific cases of supratidal or intertidal oiling. Second, no adverse incidents have been documented using SWAs, such as the killing of aquatic life when dispersants were used after the Torrey Canyon spill.3 Finally, many SWAs can be relatively effective and much less toxic than dispersants. Removing oil from Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10021-8 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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a surface appears to be easier than dispersing it from the sea surface. Furthermore, some of the surfactants used in SWAs have far less aquatic toxicity than those used for dispersants. There is some concern about whether SWAs can result in appreciable amounts of dispersed oil. Some products currently listed as surface-washing agents do disperse the oil when exposed to moderate agitation or sea energies. Tests of products at high-sea energies show that they do disperse the oil to a degree. If this occurs, the situation can be similar to that with dispersants.4 At this time, the only product approved by Environment Canada as an SWA is Corexit 9580 from Nalco.5 The U.S. Environmental Protection Agency (EPA) has approved 30 agents as listed in Table 21.1.6

TABLE 21.1 Environmental Protection Agency List of Surface Washing Agents Product Name AQUACLEAN BG-CLEAN 401 BIOSOLVE HYDROCARBON MIGRATION TECHNOLOGY CLEAN SPLIT (see SPLIT DECISION SC) CN-110 COREXIT EC7664A (formerly COREXIT 7664) COREXIT EC9580A (formerly COREXIT 9580 SHORELINE CLEANER) CYTOSOL DO-ALL #18 DUO-SPLIT (see SPLIT DECISION SC) ENVIROCLEAN (formerly ENVIRO CLEAN 165) E-SAFE F-500 GOLD CREW SW MICRO CLEAN (see NATURE’S WAY HS) NALE-IT NATURE’S WAY HS NATURE’S WAY PC (see NATURE’S WAY HS)

(Continued )

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685

TABLE 21.1 Environmental Protection Agency List of Surface Washing Agentsdcont’d Product Name PETRO-CLEAN PETRO-GREEN ADP-7 (formerly D-14) POWERCLEAN (see NATURE’S WAY HS) PETROTECH 25 PREMIER 99 SC-1000 SHEEN-MAGIC SIMPLE GREEN SPILLCLEAN (SW-36) or SPILLCLEAN ["Concentrate"] (a/k/a FIREMAN’S BRAND SPILLCLEAN) SPLIT DECISION SC (formerly SPLIT DECISION) SUPERALL #38 (see TOPSALL #30) SX-100 TOPSALL #30 (From National Contingency Plan Product Listdas of July 2009 http://www.epa.gov/OEM/content/ ncp/product_schedule.htm.)

21.1.1. Motivations for Using Surface-Washing Agents The major motivations for using SWAs on shorelines is to remove as much of the oil as possible without the incumbent disruption that often occurs with physical removal techniques. The procedure for using an SWA on a shoreline is to apply the agent, let it soak (typically ½ to 4 hours or as much as possible), and rinse off the surface with low pressure and cool water. The oil is then recovered, typically with skimmers. This can result in minimal disturbance to the shoreline and recovery of much of the oil. The motivations for using SWAs on impermeable surfaces are similar; however, there are few uses on impermeable surfaces. The use of SWAs on permeable surfaces such as soil is not recommended. Potential users are advised to consult the American Society for Testing and Materials (ASTM) Guides on these products.7-9

21.1.2. Surface Washing Agent Issues The issues associated with SWAs are the effectiveness of the products on aged oils on surfaces, the dispersion of the oil with higher energies, the toxicity of the

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product, and resulting remobilized oil and possible movement of oil down into the shoreline or subsurface. Many countries have regulations and tests for acceptability of these agents.10-12

21.1.3. Surface-Washing Agent Chemistry Little information is available on specific formulations for SWAs because the formulations vary extensively and many are not patented. Several basic types of formulations are: 1. Nonionic or anionic surfactants with HLBs of more than 11 in a lowaromatic hydrocarbon solvent 2. d-Limonene in various solvents 3. Surfactants mixed with various solvents 4. Surfactants in glycol-type solvents similar to dispersants 5. Detergents with little or no solvent 6. Solvent mixtures Several papers have been written on the development of SWAs.13-17 Many of the agents were developed after the Exxon Valdez spill in 1989. The following three products were tested on oiled shorelines resulting from the Exxon Valdez spill: Corexit 7664, Corexit 9580, and PES-51. Most products functioned as expected, and Corexit 9580 appeared to be most successful.

21.2. REVIEW OF MAJOR SURFACE-WASHING AGENT ISSUES 21.2.1. Effectiveness Field Trials. Several tests of the effectiveness of SWAs have been conducted at actual spills. The results of some of these tests are listed in Table 21.2.1,15,18-27 Although effectiveness was not quantified in any of these field tests, in every case, except where dispersants were used in earlier years, the tests were declared to be successful. The earlier dispersant trials showed variable effectiveness and, where penetration was measured, indicated that dispersants promoted penetration of the oil into the subsediments.27 Little and Baker reported on field and laboratory studies of the use of dispersants in nearshore areas or on shorelines.27 Tests showed that some dispersant treatments can increase the penetration of oil into sediment and that the oil may be retained in the subsurface. The nature of the shoreline or sediment was the main factor determining whether the penetration was enhanced by dispersant. On some shorelines it was shown that natural removal can be enhanced by dispersant usage. It was also found that dispersant-enhanced toxicity of oil could pose a problem, and it was suggested that work be done on defining an effective minimum dispersant-to-oil ratio. While field evaluation methods have not been fully developed for SWAs, field screening kits for evaluating both effectiveness and toxicity have been

Country Date

Location

Name

Volume of Oil

Oil Type

Canada

1999

Quebec

Havre St. Pierre

~10 tons

Bunker C

Canada

1999

Nova Scotia

Canso

~1 ton

United States

1998

Alaska

Exxon Valdez

United States

1997

Maine

Uruguay

Mar-97

Uruguay

Mar-97

United States

Agent Used

Effectiveness

References Cited

Corexit 9580

successful

2

Bunker C

Corexit 9580

successful

2

test only

North Slope

PES 51

not known

18

Julie N.

test only

Bunker C

Corexit 9580

50% removed

19

shoreline

San Jorge

test only

Corexit 9580

successful

[20] OSIR 6 mar 97

shoreline

San Jorge

test only

Enviroclean

successful

[20] OSIR 6 mar 97

6-Oct-96 Maine

Julie N.

test only

Bunker C

Corexit 9580

varied

[20] OSIR, 3 Oct 96, 17 Oct 96

New Zealand

late 96

Wellington

Sydney Express/ Maria Luisa

8 tonnes

Diesel

OSD 9

successful

[20] OSIR, 5 Jun 97

United States

1994

Puerto Rico

Morris J. Berman test only

Bunker C

Corexit 9580

successful

21, 22

687

(Continued )

Chapter | 21 Surface-Washing Agents or Beach Cleaners

TABLE 21.2 Use of Surface-Washing Agents and Major Field Tests

688

TABLE 21.2 Use of Surface-Washing Agents and Major Field Testsdcont’d Name

Volume of Oil

Oil Type

Agent Used

Effectiveness

References Cited

United States

1994

Puerto Rico

Morris J. Berman test only

Bunker C

PES 51

successful

21, 22

United States

1994

Texas

San Jacinto River small amount

Crude

Corexit 9580

successful

23

United States

1994

Louisiana

oil marsh

small amount

Crude

Corexit 9580

successful

23-25

United States

1993

Alaska

Exxon Valdez

test only

North Slope

PES 51

successful

15,27

Great Britain

1987

Fokestone

test

test only

Fuel Oils and emulsion

dispersants

variable

1

Great Britain

1985-88

Wales

test

test only

Fuel Oils and crude

dispersants

variable

28

United States

1970

Florida

Delian Appollan

test only

Bunker C

Corexit 8666

variable

21

Treating Agents

Location

PART | VI

Country Date

Chapter | 21 Surface-Washing Agents or Beach Cleaners

689

developed and tested. Clayton and coworkers reported on the development of test kits for evaluating the effectiveness and aquatic toxicity of SWAs.28-31 The test was evaluated using natural substrates, including gravel, rock fragments, and eelgrass. It was concluded from laboratory tests that the field test would be an appropriate indicator of effectiveness in the field. Four field-applicable methodologies for testing the aquatic toxicity of SWAs were tested, including the Microtox unit, echinoderm fertilization, byssal thread attachment in mussels, and righting and water-escaping ability in periwinkle snails. While all methodologies were able to detect differences in toxicity, the Microtox and echinoderm fertilization showed greater sensitivity and/or precision. Laboratory Testing. Laboratory tests for SWAs were first developed by Environment Canada.32 After evaluating about 25 testing methods, including troughs, surfaces, and coupons in flasks, the trough was found to be the most repeatable and a close simulator of field processes. A coupon is a small wafer of material such as brick or stone. A close-up of the sloped-trough test is shown in Figure 21.1. A heavy oil such as Bunker C was placed on a small metal trough, agent applied, and then the oil was flushed away with water. Quantitation is by weight. The U.S. EPA subsequently evaluated a number of test methods and then evaluated several products with a trough test similar to that used by Environment Canada.33,34 In recent times, the U.S. EPA has worked on a revised gravel-washing test.35,36 This new test is summarized in the Appendix. The French government laboratory developed a small coupon test to screen products for acceptability.37 Initial findings were that the SWA dosage, applied as a dilution, was a factor in the removal. However, effectiveness did not increase once the ratio of agent to oil was 1:1. A variety of agents, including dispersants, have been extensively tested by Environment Canada using the trough test.4,38,39 The results of some of these tests are shown in Table 21.3. Included in this table are effectiveness results from the trough test for both fresh water and salt water and effectiveness as a dispersant using the swirling flask test and Alberta Sweet Mixed Blend crude oil. These test results show that products that are effective as a dispersant are not effective as an SWA, and vice versa. This effect, which was noted in FIGURE 21.1 A close-up of the Environment Canada test trough showing the oil deposition.

690

TABLE 21.3 Surface-Washing Agent Test Results Percent Oil Removed Saltwater

Toxicity

Effectiveness as a Dispersant (%)

Corexit 9580

69

53

>10,000

0

D-Limonene

51

52

35

0

Penmul R-740

49

44

24

9

Limonene ’0’

38

43

35

0

TRL-900

50

40

7

0

Formula 2067

41

39

11

0

Ecologic 5M10MB10

24

38

62

0

Citrikleen XPC

37

36

34

2

ECP 99 Oil Eater

34

36

16

7

Oriclean

32

70

0

Ultrasperse II

41

32

57

14

Formula 861

32

32

24

0

Core Tech 2000x

31

27

Corexit 7664

25

27

22 850

2

Treating Agents

Freshwater

PART | VI

Product Name

20

26

57

6

Neutro Gold

18

26

50

7

Core Tech 2000

26

25

325

21

Pronatur Extra

19

25

9

0

Superall

22

24

Bioorganic

23

18

0

BP 1100 X AB

28

23

2900

0

AutoScrub Gold

15

22

57

7

BP 1100WD

30

21

120

6

Tesoro Pes 51

23

21

14

0

Ecologic BF-104

35

20

62

0

Champion JS10-232

27

20

1060

0

COR 7664/Isopar

17

20

1500

1

Biosurf

15

20

42

0

Champion JS10-242

27

19

380

<5

Tesoro Pes 41

22

19

9

0

ERA 369

21

19

10

10

Chapter | 21 Surface-Washing Agents or Beach Cleaners

ECP Responder SW

691

(Continued )

692

TABLE 21.3 Surface-Washing Agent Test Resultsdcont’d Percent Oil Removed Saltwater

Toxicity

Effectiveness as a Dispersant (%)

Oil Gon

20

19

134

0

Tierra Q-100

34

17

177

0

Pronatur

23

17

75

0

Re-Entry

17

17

8

0

Biocat 145

14

17

104

0

Sea Spray

26

16

420

0

Palmolive

14

16

13

9

Per 4m

14

16

566

0

ESP Pro

6

16

80

0

ERA 369X

15

15

Topsall

14

354

0

Aquaquick 2000

12

14

870

0

Breaker-4

17

13

340

0

M.X. #1

13

13

90

6

15

Treating Agents

Freshwater

PART | VI

Product Name

13

13

110

Oil Lift

13

13

not done

6

Ecologic 5M5B4

11

13

46

0

Ortec

0

13

123

0

Simple Green

24

12

205

Sunlight

16

12

13

9

Citrikleen 1855

14

12

55

0

Inprove

14

12

78

0

Citrikleen FC1160

10

12

75

0

Con-Lei

8

12

70

0

Alcopol 60

11

62

18

Ecologic 10M10B10

19

11

23

0

Pyprr

12

11

650

0

Bioversal

8

11

120

0

Oil Spill Eater

5

11

135

0

Icoshine

12

10

40

0

Oil Lift (repeat test)

12

10

not done

6

Chapter | 21 Surface-Washing Agents or Beach Cleaners

Nokomis 3

693

(Continued )

694

TABLE 21.3 Surface-Washing Agent Test Resultsdcont’d Percent Oil Removed Saltwater

Toxicity

Effectiveness as a Dispersant (%)

Ecologic BF-102

25

9

46

0

F-500

15

9

0.6

9

Envirosperse OSD

0

9

108

<5

Green Unikleen

13

8

165

11

ZI-808

7

8

179

59

Siallon Emulsifier

6

8

375

0

PC-100 (petro controller)

8

7

12,000

0

Ecologic BF-103

7

7

71

0

IDX 20

6

7

140

0

Mr Clean

13

6

30

0

Gran Control

5

6

75

0

Envirowash 1000

20

5

1650

0

Corexit CRX8

14

5

20

45

SX-100 Oil Dispersant

10

5

5

0

Treating Agents

Freshwater

PART | VI

Product Name

3

5

33

0

ZI-800

16

4

221

55

Cytosol

8

4

1770

0

Corexit 9527

13

3

108

33

Balchip 215

8

3

157

0

Tornado

8

3

1350

0

Firezyme

4

3

521

0

BG Clean 401

3

3

88

0

Equisolve

0

3

60

0

Jansolve

25

2

57

0

Citrickleen 1850

24

2

18

11

Super Dispersant

6

2

337

18

Value 100

4

2

4250

0

Biosolve

2

2

9

0

Lestoil

9

1

51

0

Enersperse 700

1

1

50

32

Corexit 9500

26

0

354

36.3

Chapter | 21 Surface-Washing Agents or Beach Cleaners

Formula 730

695

(Continued )

696

TABLE 21.3 Surface-Washing Agent Test Resultsdcont’d Percent Oil Removed Freshwater

Saltwater

Toxicity

Effectiveness as a Dispersant (%)

Brady Non-Butyl Degreaser

5

0

433

0

Oil Dissolver

5

0

40

0

Inipol EAP-22

0

0

17

9

Petrotech

0

0

1460

0

Microat S

2795

0

PPL L1094

467

0

Slickgone NS

100

30

Green Unikleen (diluted)

10

Dispersit SPC 1000

not done 2

32

Treating Agents

(Effectiveness results from a test using a sloped trough; Toxicity values are 96-hour Rainbow Trout LC-50 results; Dispersant effectiveness values are from the Swirling Flask test, using the readily-dispersable ASMB.)

PART | VI

Product Name

Chapter | 21 Surface-Washing Agents or Beach Cleaners

697

previous studies, is thought to be due to the difference in HLB needed for a dispersant (HLB ~ 10) and for an SWA (HLB > 10).40 For comparison purposes, the table also includes household products and other products that are not intended for use on oil spills. Guenette et al. tested a number of agents for effectiveness using the Environment Canada test as described in the Appendix.41 The standard oils, Bunker C and orimulsion bitumen, were used. The latter was the primary target of testing. Results are summarized in Table 21.4. It was found that the removal of both oils was greatly enhanced by the use of the treating agents. D-Limonene was the best agent, but several agents yield similar results. The product effectiveness was highly influenced by temperature, and some removed little at 5 C. It was also noted that household cleaning products and dispersants were not effective in removing oils and were frequently toxic to fish.

21.2.2. Toxicity The acute lethal toxicity of many SWAs is shown in Table 21.3.40,42 Unlike dispersants, the aquatic toxicity of SWAs varies from nontoxic (>1000 mg/L) to highly toxic (<50 mg/L). Toxicity does not correlate with effectiveness. In fact, the most effective product noted in Table 21.3, Corexit 9580, is also the least toxic as measured on the Rainbow Trout. Shigenaka et al. found no adverse biological effects of Corexit 9580 during an application to a saltwater marsh.43 Pezeshki and coworkers studied the effects of Corexit 9580 on sea grasses and also found no adverse effects.23,25 Similarly, Teas et al. studied the use of Corexit 9580 on mangroves and found benefits and no toxicity.44 Hoff et al. reviewed PES-51, which consists primarily of d-Limonene, and found its aquatic toxicity to be relatively high.15 Michel et al. reviewed the toxicity of various SWAs.45 A summary of these data is given in Table 21.5.

21.3. OTHER ISSUES 21.3.1. Application SWAs are applied directly on the stranded oils and left to penetrate for at least 15 to 30 minutes.7,17 The oil is then flushed with water to remove the oil and direct it to a cleanup area. From there, the oil is generally removed with a conventional skimmer system. Since the SWAs are typically applied to a small expanse of oil at the upper or intertidal zone, they are applied manually using hand-held or backpack sprayers or using large-vehicle or vessel-mounted sprayers. Such an application is illustrated in Figure 21.2. It would be difficult to apply the agent using airborne spray systems, and much product would be lost. On shorelines, the product must be applied during low tide and the oil removed before the tide rises and the oil is no longer accessible. No extensive research or testing of application methods for SWAs have yet been done.

698

TABLE 21.4 Test of Surface-Washing Agents Percent Oil Removed Orimulsion

Bunker C

5 C

22 C

5 C

Product Description

Aquatic Toxicity Rainbow Trout 96 hr LC50 (mg/L)

D-Limonene

36

20

56

32

natural product in citrus peels

35

PES-51

32

23

42

30

SWA

14

Corexit 9580

27

15

57

24

SWA

>10,000

Oriclean

27

14

35

19

SWA

70

BP1100X

23

10

44

12

dispersant

2900

Champion JS19-232

0

4

27

1

SWA

1060

Simple Green

0

household cleaner

205

Palmolive

1

dish detergent

13

Corexit 9500

1

dispersant

354

Corexit 9527

1

dispersant

33

Citrikleen 1850

2

SWA

18

Blank (water)

0

blank

SWA ¼ surface washing agent. After Guenette et al., 1999.41

Treating Agents

22 C

PART | VI

Product

Parameter

Aquaclean

Biosolve

Agent CN-110

Corexit 7664

Toxicity

Mummichug 71 mg/L, 96 h brine shrimp 12 mg/L, 48 hr

Rainbow Trout 9 mg/L, 96h Fathead minnow >750 96 h

Rainbow Trout 1460 mg/L, 96h Mummichug 4,830 mg/L, 96 h

Rainbow Trout 850 mg/L, 96h Mummichug >1000 mg/L, 96 h

Toxicity Atlantic Silversides mg/L 96 h

71

6.4

52,200

87

Myside shrimp

33

3.6

12,300

584

water solubility

100%

100%

Corexit 9580

Cytosol

Toxicity

Rainbow Trout >10,000 mg/L, 96h Mummichug >10,000 mg/L, 96 h

Nature’s Way

PES-51 Rainbow Trout 14 mg/L, 96h Mummichug 1425 mg/L, 96 h

Toxicity Atlantic Silversides mg/L 96 h

87

736

Myside shrimp

32

124

insoluble

14 ppm, fresh, 7 ppm sea

water solubility

100%

Chapter | 21 Surface-Washing Agents or Beach Cleaners

TABLE 21.5 Summary Toxicity Data on Surface-Washing Agents

45

699

After Michel et al. 2001.

700

PART | VI

Treating Agents

FIGURE 21.2 Application of surface-washing agents after the Sea Empress spill in the United Kingdom using a backpack sprayer. The two hoses were used to flush the oil to a recovery area.

21.3.2. Dispersion with Higher Applied Energy It has been known that SWAs will disperse oil if high energy is applied.2 Fieldhouse performed tests on dispersion using a modified method that applied higher energy.4 Test results are shown in Table 21.6 and illustrated in Figure 21.3. The findings of this study are as follows: (a) At the high mixing energies noted, all three products tested, Corexit 9580, PES-51, and Cytosol, dispersed the oil to a large degree. (b) Only Corexit 9580 dispersed the oil significantly at 5 C and 15 and 25 C; PES-51 and Cytosol dispersed the oil as well. (c) The salinity of the water had only a minor effect on the dispersion. (d) The untreated oils dispersed to the extent of about 40% in saline water and up to about 30% in fresh water. (e) All dispersions were unstable over a 24-hour period, but were stable in the first few minutes. The implications of this study are that, to avoid dispersion, low-energy flushing must be used. Similar findings are noted by Je´ze´quel.46

21.3.3. Assessment of the Use of Surface-Washing Agents Several parties have assessed the use of SWAs for use on both fresh and saltwater shorelines.47,48 In summary, SWAs are recommended for use where: weathered or heavy oil is stranded on beach or similar surface, where adequate soaking time can be achieved, and where the oil can be flushed to a recovery system using low-pressure water. In some countries SWAs are used to clean oil from surfaces such as roads.

Bunker C tests

Vol. % Oil Dispersed

Other Oil Tests Vol. % Oil Dispersed

Dose Ratio (SWA:Oil)

Temp ( C)

Salinity (NaCl)

Settling Time

Corexit 9580

PES

0.4

5

3.30%

1min

96.2

0.4

5

3.30%

5min

0.4

5

3.30%

0.4

5

0.4

Oil Type

Dose Ratio (SWA:Oil)

Salinity (NaCl)

Settling Time

Corexit 9580

36.8

ASMB

1:10

3.30%

1min

93.2

90.4

33.8

ASMB

1:10

3.30%

5min

73.7

30min

67

13.9

ASMB

1:10

3.30%

30min

27.1

3.30%

3hr

27.9

6.7

ASMB

1:10

3.30%

3hr

11.4

5

3.30%

24hr

9

ASMB

1:10

Fresh

1min

91.1

0.4

15

3.30%

1min

100.4

58.5

54

ASMB

1:10

Fresh

5min

68.1

0.4

15

3.30%

5min

87.5

51.7

46.4

ASMB

1:10

Fresh

30min

23.9

0.4

15

3.30%

30min

66.3

16.3

25.8

ASMB

1:10

Fresh

3hr

12

0.4

15

3.30%

3hr

35.5

7.5

17.8

ASMB

Untreated

Fresh

1min

30.3

0.4

15

3.30%

24hr

8.8

3.2

ASMB

Untreated

3.30%

1min

36.6

0.4

15

Fresh

1min

98.7

78.9

47.2

ASMB

Untreated

Fresh

5min

16.8

0.4

15

Fresh

5min

82

67.8

35.5

ASMB

Untreated

3.30%

5min

20.1

Cytosol

701

(Continued )

Chapter | 21 Surface-Washing Agents or Beach Cleaners

TABLE 21.6 Summary of High-Energy Tests of Surface-Washing Agents

702

TABLE 21.6 Summary of High-Energy Tests of Surface-Washing Agentsdcont’d

Bunker C tests

Vol. % Oil Dispersed

Other Oil Tests Vol. % Oil Dispersed

Salinity (NaCl)

Settling Time

Corexit 9580

PES

Cytosol

Oil Type

Dose Ratio (SWA:Oil)

Salinity (NaCl)

Settling Time

Corexit 9580

0.4

15

Fresh

30min

61.5

25.1

28.2

ASMB

Untreated

Fresh

30min

4.4

0.4

15

Fresh

3hr

33.7

9.7

25.4

ASMB

Untreated

3.30%

30min

6.2

0.4

15

Fresh

24hr

14.6

3.7

ASMB

Untreated

Fresh

3hr

1.4

0.4

25

3.30%

1min

95.6

54.3

92.9

ASMB

Untreated

3.30%

3hr

0.5

0.4

25

3.30%

5min

91.7

35

86

AHC

0.14

3.30%

1min

81.1

0.4

25

3.30%

30min

81.9

26.1

66.6

AHC

0.14

3.30%

5min

63.2

0.4

25

3.30%

3hr

52

10.7

30.9

AHC

0.14

3.30%

30min

35.7

0.4

25

3.30%

24hr

12.4

5

4.9

AHC

0.14

3.30%

3hr

25.5

0.2

15

3.30%

1min

84.6

AHC

0.14

3.30%

24hr

1.4

0.2

15

3.30%

5min

78.2

AHC

Untreated

3.30%

1min

9.6

0.2

15

3.30%

30min

42.3

AHC

Untreated

3.30%

30min

4.3

Treating Agents

Temp ( C)

PART | VI

Dose Ratio (SWA:Oil)

15

3.30%

3hr

28.4

AHC

Untreated

3.30%

24hr

0.5

0.2

15

3.30%

24hr

2.2

HSC

0.14

3.30%

1min

81

0.2

15

Fresh

1min

81.6

HSC

0.14

3.30%

5min

77.1

0.2

15

Fresh

5min

75.7

HSC

0.14

3.30%

30min

40.2

0.2

15

Fresh

30min

43.6

HSC

0.14

3.30%

3hr

24.9

0.2

15

Fresh

3hr

35

HSC

0.14

3.30%

24hr

2

0.2

15

Fresh

24hr

8.2

HSC

Untreated

3.30%

1min

1.6

HSC

Untreated

3.30%

30min

1.3

HSC

Untreated

3.30%

24hr

0.1

Oils: ASMB ¼ a light crude, AHC ¼ Arabian Heavy Crude, HSC ¼ heavy synthetic crude. After Fieldhouse, 2008.3

Chapter | 21 Surface-Washing Agents or Beach Cleaners

0.2

703

704

PART | VI

C 9580 5 deg PES 5 deg 9580 15 deg PES 15 deg Cytosol 15 deg C 9580 fresh PES fresh Cytosol fresh C 9580 25 deg PES 25 deg Cytosol 25 deg

100 Agents at 25 deg and in fresh water 80

Percent Dispersion

Treating Agents

agents at 15 deg 60

40 agents at 5 deg 20

0

1

5

30

e0

e1

e2

3 hours e3

e4

e5

24 hours e6

e7

Settling Time in Minutes FIGURE 21.3 The dispersant percentage of various surface-washing agents with amounts of settling time. Higher temperatures increase the amount of dispersion, but over time (e.g., 24 hours) most dispersions are destabilized.

REFERENCES 1. Morris PR, Thomas DH. Evaluation of Oil Spill Dispersant Concentrates for Beach Cleaningd1987 Trials. Warren Springs, UK: Warren Spring Laboratory Report LR 624(OP); 1987. 2. Fingas MF. Use of Surfactants for Environmental Applications, Chapter 12. In: Schramm Laurier L, editor. Surfactants: Fundamentals and Applications to the Petroleum Industry, 461. Cambridge, UK: Cambridge University Press; 2000. 3. Etkin DS. Factors in the Dispersant Use Decision-Making Process: Historical Overview and Look to the Future. AMOP 1998;281. 4. Fieldhouse B. Dispersion Characteristics of Oil Treated with Surface Washing Agents for Shoreline Cleanup. AMOP 2008;371. 5. Environment Canada Standard List of Approved Treating Agents. Ottawa, ON: Environment Canada; 2009. 6. Environmental Protection AgencydNational Contingency Plan Product Schedule, United States Environmental Protection Agency (U.S. EPA), http://www.epa.gov/OEM/content/ncp/ product_schedule.htm, accessed July, 2009. 7. ASTM, ASTM 1872. Use of Chemical Shoreline Cleaning Agents: Environmental and Operational Considerations. West Conshohocken, PA: American Society for Testing and Materials; 2004.

Chapter | 21 Surface-Washing Agents or Beach Cleaners

705

8. ASTM, ASTM 1279. Ecological Considerations for the Use of Oilspill Dispersants in Freshwater and Other Inland Environments, Permeable Surfaces. West Conshohocken, PA: American Society for Testing and Materials; 2008a. 9. ASTM, ASTM 1280. Ecological Considerations for the Use of Oilspill Dispersants in Freshwater and Other Inland Environments, Impermeable Surfaces. West Conshohocken, PA: American Society for Testing and Materials; 2008b. 10. Kirby M, Devoy B, Law RJ. Ensuring the Most Appropriate Oil Spill treatment of Products Are AvailabledA Review of Toxicity Testing and Approval Issues in the UK. IOSC 2008;829. 11. Nichols WJ. The U.S. Environmental Protection Agency: National Oil and Hazardous Substances Pollution Contingency Plan, Subpart J Product Schedule (40 CFR 300.900). IOSC 2001;1479. 12. Lumley TC, Harrison S, Hollebone B. Evaluation of Methods for Assessing Effectiveness of Oil Spill Treating Agents. AMOP 2007;117. 13. Fiocco RJ, Canevari GP, Wilkinson JB, Jahns HO, Bock J, Robbins M, et al. Development of Corexit 9580-A Chemical Beach Cleaner, American Petroleum Institute, Washington, DC. IOSC 1991;395. 14. Canevari GP, Fiocco RJ, Lessard RR, Fingas MF. Corexit 9580 Shoreline Cleaner: Development, Application, and Status. In: Lane Peter, editor. The Use of Chemicals in Oil Spill Response, ASTM STP 1252, 227. Philadelphia, PA: American Society for Testing and Materials; 1995. 15. Hoff R, Shigenaka G, Yender R, Payton D. Chemistry and Environmental Effects of the Shoreline Cleaner PES-51, HAZMAT Report No. 942. Seattle, WA: National Oceanic and Atmospheric Administration; 1994. 16. Clayton JR, Tsang S-F, Frank V, Marsden P, Chau N, Harrington J. Chemical Surface Washing Agents for Oil Spills. U.S. Environmental Protection Agency Report, EPA/600/SR-93/113; 1993. 17. Fiocco RJ, Lessard RR, Canevari GP. Improved Oiled Shoreline Cleanup with Corexit 9580. Proceedings of 1996 Petro-Safe Conference 1996;276. 18. Adec, Private Communication with Alaska Department of Environmental Conservation, 1998. 19. Michel J, Lehmann SM, Henry CB. Oiling and Cleanup Issues in Wetlands, M/T Julie N Spill, Portland, ME. AMOP 1998;841. 20. OSIR, Oil Spill Intelligence Report, Cutter Information Corporation, Arlington, MA. (Issue numbers and dates listed in Table 21.12). 21. Clayton JR, Michel J, Snyder BJ, Lees DC. Utility of Current Shoreline Cleaning Agent Tests in Field Testing, MSRC Technical Report Series Report 95-004. Washington, DC: Marine Spill Research Corporation; 1995. 22. Michel J, Benggio BL. Testing and Use of Shoreline Cleaning Agents During the Morris J. Berman Spill. IOSC 1995;197. 23. Tomblin TG. San Jacinto River Incident, Report to Federal On-Scene Commander, Use of Corexit 9580 for Shoreline Cleanup in Mitchell Bay. Reston, Virginia: Exxon Report; 1994. 24. Pezeshki SR, DeLaune RD, Nyman JA, Lessard RR, Canevari GP. Removing Oil and Saving Oiled Marsh Grass Using a Shoreline Cleaner. IOSC 1995;203. 25. Pezeshki SR, DeLaune RD, Nyman JA. Investigation of Corexit 9580 for Removing Oil From Marsh Grass. Baton Rouge, LA: Technical Report submitted to Exxon Research and Engineering from Louisiana State University; 1994. 26. Rog S, Owens D, Pearson L, Tumeo M, Braddock J, Venator T. PES-51 Shoreline Restoration of Weathered Subsurface Oil in Prince William Sound, Alaska. AMOP 1994;607.

706

PART | VI

Treating Agents

27. Little DI, Baker JM. The Role of Dispersants in the Persistence and Fate of Oil in Sediments. In: Dicks B, editor. Ecological Impacts of the Oil Industry, 169. Chichester: John Wiley and Sons; 1989. 28. Clayton JR, Stransky BC, Schwartz MJ, Lees DC, Michel J, Snyder BJ, et al. Development of Protocols for Testing Cleaning Effectiveness and Toxicity of Shoreline Cleaning Agents (SCAs) in the Field, MSRC Technical Report Series Report 95-020.1. Washington, DC: Marine Spill Research Corporation; 1995. 29. Clayton JR, Stransky BC, Adkins AC, Lees DC, Michel J, Schwartz MJ, et al. Methodology for Estimating Cleaning Effectiveness and Dispersion of Oil with Shoreline Cleaning Agents (SCAs) in the Field: Data Report. AMOP 1996;423. 30. Clayton JR, Stransky BC, Adkins AC, Lees DC, Michel J, Schwartz MJ, et al. Methods for Calculating Cleaning Effectiveness and Dispersion of Oil with Shoreline Cleaning Agents in the Field. AMOP 1995;454. 31. Clayton JR, Stransky BC, Schwartz MJ, Lees DC, Michel J, Snyder BJ, et al. Development of Protocols for Testing Cleaning Effectiveness and Toxicity of Shoreline Cleaning Agents (SCAs) in the Field: Data Report, MSRC Technical Report Series Report 95-020.2. Washington, DC: Marine Spill Research Corporation; 1995. 32. Fingas MF, Stoodley G, Harris G, Hsia A. Evaluation of Chemical Beach Cleaners, in Proceedings of the Workshop on the Cleanup of Beaches in Prince William Sound Following the Exxon Valdez Spill, Anchorage, Alaska, sponsored by National Oceanic and Atmospheric Administration, Seattle. NOAA 1989;5. 33. Sullivan D, Sahatjian KA. Evaluation of Laboratory Tests to Determine the Effectiveness of Chemical Surface Washing Agents. IOSC 1993;511. 34. Clayton JR, Renard EP. Statistical Assessment: Two Laboratory Tests for Estimating Performance of Shoreline Cleaning Agents for Oil Spills. AMOP 1994;877. 35. Luedeker CC, Koran KM, Venosa A. Effect of Variables on Performance of Surface Washing Agents Under a Newly-Developed Testing Protocol. IOSC 2008;843. 36. Koran KM, Venosa A, Luedeker CC. Evaluation of Detergency, Interfacial Tension and Contact Angle for Five Surface Washing Agents. IOSC 2008;785. 37. Merlin FX, Le Guerroue P. The New French Approval Procedure for Shoreline Cleaning Agents; AMOP 1994;943. 38. Fingas MF, Kyle DA, Laroche ND, Fieldhouse BG, Sergy G, Stoodley RG. Oil Spill Treating Agents. Spill Technology Newsletter 1993;18:1. 39. Fingas MF, Kyle DA, Laroche ND, Fieldhouse BG, Sergy G, Stoodley RG. The Effectiveness Testing of Spill Treating Agents. In: Lane Peter, editor. The Use of Chemicals in Oil Spill Response, ASTM STP1252. T, 286. Philadelphia: PA, American Society for Testing and Materials; 1995. 40. Fingas MF, Kyle DA, Wang Z, Handfield D, Ianuzzi D, Ackerman F. Laboratory Effectiveness Testing of Oil Spill Dispersants. In: Lane Peter, editor. The Use of Chemicals in Oil Spill Response, ASTM STP 1252, 3. PA, Philadelphia: American Society for Testing and Materials; 1995. 41. Guenette CC, Sergy GA, Fieldhouse B. Removal of Stranded Bitumen From Intertidal Sediments Using Chemical Agents, Phase I: Screening of Chemical Agents. Environmental Protection Service, Ottawa, ON: Environment Canada, Manuscript Report EE-162, 1998. 42. Fingas MF, Kyle DA, Wang Z, Ackerman F, Mullin J. Testing of Oil Spill Dispersant Effectiveness in the Laboratory. AMOP 1994;905. 43. Shigenaka G, Vicente VP, McGehee MA, Henry CB. Biological Effects Monitoring During an Operational Application of Corexit 9580. IOSC 1995;177. 44. Teas HJ, Lessard RR, Canevari GP, Brown CD, Glenn R. Saving Oiled Mangroves Using a New Non-Dispersing Shoreline Cleaner. IOSC 1993;147.

Chapter | 21 Surface-Washing Agents or Beach Cleaners

707

45. Michel J, Walker AH, Scholz D, Boyd J. Surface-Washing Agents. IOSC 2001;805. 46. Je´ze´quel R. Influence of Weathering of Heavy Fuel Oil on High-Pressure Washing Efficiency with and Without Cleaning Agent. AMOP 2009;177. 47. Walker AH, Michel J, Canevari G, Kucklick J, Scholz D, Benson CA, et al. Chemical Oil Spill Treating Agents: Herding Agents, Emulsion Treating Agents, Solidifiers, Elasticity Modifiers, Shoreline Cleaning Agents, Shoreline Pre-Treatment Agents and Oxidation Agents. MSRC Technical Report Series Report 93-015. Washington, DC: Marine Spill Research Corporation; 1993. 48. Robertson DR, Maddox JH. Shoreline Surface Washing Agent Test and Evaluation Protocol for Freshwater Use in the Great Lakes Region. American Chemical Society, Division of Petroleum Chemistry Preprints 2003;48:31. 49. Fingas MF, Fieldhouse B. A Review of Knowledge on Water-in-Oil Emulsions. AMOP 2006;1. 50. Fingas M, Fieldhouse B, LeRouge L, Lane J, Mullin J. Studies of Water-in-Oil Emulsions: Energy and Work Threshold as a Function of Temperature. AMOP 2001;65. 51. Koran KM, Venosa AD, Luedeker CC, Dunnigan K, Sorial GA. Development and Testing of a New Protocol for Evaluating the Effectiveness of Oil Spill Surface Washing Agents. Marine Pollution Bulletin; 2009:1903.

APPENDIX 21.1. ENVIRONMENT CANADA’S TEST METHOD 33,39 Summary The method uses a stainless-steel trough that is placed at a specified angle. Heavy oil, or the target oil, is placed on an area on the trough. The treating agent is applied in droplets to the surface of the oil and after 10 minutes at 5-minute intervals, rises of water are applied to the trough. After drying, the trough is weighed and the removal calculated by weight loss. Repeatability is within 5%.

Method Measure the oil to be used in test using a positive-displacement pipette. Set the pipette to 150 microliters (mL). Aspirate the oil (the target or Environment Canada sets aside an aliquot of 1987 Bunker C as a standard), which has been previously stirred, into the pipette, making sure no air bubbles are present. Wipe the end of the pipette tip off to ensure that the oil inside the tip is flush with the end. Place the clean trough on the balance and allow the reading to become steady. Record the weight. Return to work area with trough. Dispense the oil onto the trough in a slick of even thickness along its length. The slick is positioned along the fold of the trough commencing approximately 160 millimeters from the trough’s lower end and moving upward in an evenflowing motion for about 45 to 50 millimeters. Any remaining oil on the tip of the pipette can be removed by wiping the tip on the trough (at a point just below the beginning of the slick). Start the time. Place the oiled trough on

708

PART | VI

Treating Agents

the balance. While waiting for a steady reading, start the clock/stopwatch/ timer. Record the weight of the oiled trough and stand vertically after weighing. At t ¼ 9:30 minutes, aspirate the dispersant or SWA into the pipette. The pipette is set to 30 microliters (mL). At t ¼ 10:00 minutes, place the trough horizontal and apply washing agent onto the now lengthened slick. This is accomplished by depressing the plunger of the pipette until a drop protrudes about halfway out of the tip. This drop is then touched to the oil slick. Repeat this technique in order to get a thin and even coating over the slick. Record the weight and place the trough horizontally for a 10-minute SWA soaking. At t ¼ 19:45 minutes, set up the trough in the stand at a 45 angle at a height such that a collection beaker can be placed under the lower end. A 30 mL syringe with an 18-gauge needle is positioned over the center of the trough so that the water will run down the trough approximately 5e10 millimeters before encountering the oil slick. The lower end of the trough will just clear the tip of the 240 milliliter pyrex waste beaker that is set up to catch the runoff. The point of impact of the water rinse stream is in the center of the trough’s fold and 205 millimeters from the lower end of the trough. Aspirate the water into the “Oxford” pipette. At t ¼ 20 minutes, place 5 milliliters of fresh or salt water in the rinse-dispensing syringe body. The water should then drip out of the needle onto the trough, thereby rinsing away the oil/ dispersant/SWA mixture. At t ¼ 29:45 minutes, aspirate 5 milliliters of water, again using the pipette. At t ¼ 30 minutes, repeat the rinse procedure. At t ¼ 40 minutes, visually examine the trough to determine how much water remains on or in the oil slick (the water is fairly obvious). Nonlinting laboratory issue is used to absorb excess water; blot up the remaining water without removing any of the oil that is on the trough. To blot up the water that is on the oil, it is best to place the end of the dampened roll into a droplet that is in the middle of the slick. This usually results in absorption of the water droplet without absorbing much of the oil at the same time. Once all the water has been removed, the trough can be weighed and the weight recorded. Calculations: Equation 1: Amount of Oil Deposited ¼ Trough Weight (freshly oiled) Weight of Clean, Dry Trough Equation 2: Amount of Oil Removed ¼ Trough Weight (freshly oiled) Weight of Rinsed, Blotted Trough Equation 3: Percentage of Oil Removed ¼ (Equation 2 / Equation 1) 100% Notes Blanks should be run using the same procedure with minimal changes. The SWA would not be applied at t ¼ 10 minutes; however, rinses would still be run

Chapter | 21 Surface-Washing Agents or Beach Cleaners

709

at t ¼ 20 and t ¼ 30 minutes. All the weighings should be identical with the exception that the amount of SWA applied would not be weighed. Elevated temperature-rinsing runs are the same except the rinse water is warmed to elevated temperatures, for example, 50 C. Different gauge needles, with smaller internal diameters, may be used to give lengthened rinse times due to smaller flow rates. After the final weighing is completed, the trough is cleaned using small pieces of a polypropylene oil-sorbent mat. These pieces are approximately 20 by 20 millimeters and are held using needle-nose pliers. The excess oil is then wiped off. The trough is then rinsed with dichloromethane to dissolve and carry away the remaining oil film. A final rinse with acetone followed by a wipe with a towel finishes the cleaning procedure.

EPA DRAFT PROTOCOL35,36,51 Summary Oil is applied to sand or gravel in a mesh basket. Diluted SWA is applied to the oil. This is allowed to soak for 15 minutes, and then the basket is immersed in a beaker with water. This is shaken for 5 minutes and then removed and drained. The oil in the rinse water is extracted and analyzed. A standard analytical method was not yet described. Method: Wire mesh baskets are loaded with 15 mL of either gravel or sand. For wet test the substrate is placed in water. The applied oil is weathered for 18 hours. The diluted treating agent (either 100 or 50% diluted) is applied. The system is allowed to weather for 15 minutes. The baskets are then placed into a 600 mL flask and 100 mL water is added. This is placed on a shaker and shaken for 5 minutes at 150 rpm. The baskets are allowed to drain for 5 minutes. The wash is extracted with three 5 mL aliquots of dichloromethane. The remaining oil on the substrate is extracted with two 20 mL aliquots of dichlormethane. These should be analyzed by a standard method, and the amount of oil calculated in each to determine the oil washed off and remaining.

Fieldhouse High-Energy Protocol4 The apparatus selected for generating dispersions was the end-over-end rotational mixer with 2.2 L fluorinated HDPE bottles.50 The oil and surfacewashing agent rotation was to the direction of the closure of a wide-mouthed bottle containing wash water. The test apparatus and energy profile have been detailed elsewhere.50 For this test, the total force on the cap end each rotation is 9.8 newtons, the work per revolution is 0.735 J, and the total work over the mixing time is 162 J. The SWA product was premixed with the target oil to limit variation between tests, as well as to accommodate the short soak time of one product compared to the other two products. This also offers greater

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homogeneity of the test matrix during the washing process, limiting the effects of SWA application at the oil surface. The volume of water added to the bottle was 1 L, a compromise between turbulent energy considerations during mixing (greater water volume produces lower energy input as the head of water falls a shorter average distance on the down cycle) and the need to provide sufficient water volume for sampling at several time points. The volume of product/oil premix was set at a ratio of 1:1000. The primary test oil selected for evaluation was the Environment Canada SWA standard oil (see first method above). The ratio of SWA to oil was set at 2:5 for Corexit 9580, which is the manufacturer’s recommended dosage, and required approximately 2 minutes at a 55 RPM mixing rate to fully remove the oil, the highest setting for the mixer. At the same dosage of PES-51, a time of 4 minutes was required. Full cleaning was not achieved by the Cytosol product at this dosage for times up to 10 minutes; however, 4 minutes mixing later proved sufficient in the higher temperature test at 25 C. The test condition of 4 minutes at 55 RPM was adopted to enable direct comparison of Corexit 9580 with PES-51. Quantification by gas chromatography with flame ionization detector (GC-FID) was used rather than the alternative gravimetric analysis to provide greater precision for the anticipated low oil volumes. All reagents and equipment are left overnight in a temperature-controlled room to thermally equilibrate at the test temperature, 0.5 C. A 1 L volume of water of specified salinity is transferred to a 2.2 L wide-mouthed bottle and inserted upright into a rotary agitator with variable speed motor, by Associated Design (www.AssociatedDesign.com). The test oil and SWA are premixed in a glass vial at the designated volumetric ratio for the specific test, weighing before and after each addition for verification. The premix is thoroughly stirred until homogeneous. A 1 mL volume of the mixture is distributed across the inner surface of a polypropylene bottle closure using a positive displacement pipette. The oil is allowed to spread for 2 minutes. The closure is then inverted and secured onto a bottle containing the wash water. The mixer is rotated for 4 minutes at a rate of 55 RPM, with the cap end leading the rotation. The bottles are then removed and the contents transferred in their entirety to a 1 liter separatory funnel. Samples of 150 mL volume are collected at 1, 5, and 30 minutes and 3 and 24 hours post-transfer. The collected samples are extracted with 3 volumes of 25 mL dichloromethane in 250 mL separatory funnels. It is helpful to add clean, concentrated brine to the freshwater samples to assist phase resolution of the water and solvent. The extracts are collected in a 100 mL mixing cylinder and corrected to 75 mL. Quantitation is by GC-FID using 5-a-androstane as the internal standard. Blanks are run before and after sample sets to quantify the baseline for blank subtraction. The relative response factor (RRF) of 15 alkanes in the C9 to C36 range is determined by averaging the response from triplicate injections bracketing the sample analysis. The total oil volume of the samples is calculated from the GC response in the C16 to C36 range corrected by proportionality to the response of prepared oil standards of

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711

the test oil for the same range. The oil standards are prepared in triplicate by adding 150 mL of target oil to a volume of water and extracted by the same method as the samples, then analyzed. The GC response for 100% oil in the appropriate range is determined, then adjusted to correspond to the change in oil volume due to SWA dosing. The variables in test parameters were varied as indicated for SWA product, water salinity, temperature, and oil type.

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Chapter 22

Review of Solidifiers Merv Fingas and Ben Fieldhouse

Chapter Outline 22.1. Introduction to Solidifiers 22.2. Review of Major Solidifier Issues 22.3. Other Issues 22.4. Summary

713 717 728 730

Appendix 22.1. Testing Procedures from Environment Canada Brief Description of the Test Equipment and Supplies Calculation

732

733 733 733

22.1. INTRODUCTION TO SOLIDIFIERS The use of solidifiers was never widespread from the 1960s, when the concept started. Solidifiers are used to recover oil from smaller areas quickly, to prevent the spread of slicks, to recover thin sheens, and to protect areas and wildlife on a rapid basis. The issues surrounding solidifiers also remain the same: their effectiveness, problems involved in mixing the solidifier with the oil, long-term considerations, and possible toxicity. The most important issue of all is that solidifying the oil precludes the use of most other countermeasures. It is an important point to recognize that most other countermeasures, especially booms and skimmers, are designed to recover liquid oil. Oil weathering and oil becoming more viscous and even solid are major problems in the oil spill business. So unless solidified oil can be recovered easily and quickly, solidification will compound the oil spill problem. This, and other factors, may restrict the use of solidifiers to small, thin, and nearshore spills. Serious research gaps exist that have not been addressed during the 40 years since solidifiers were first proposed. This limits the widespread use of the products.

22.1.1. Motivations for Using Solidifiers The prime motivation for using solidifiers is to reduce the spread of oil and protect wildlife and receptor areas. To accomplish this objective, the solidifier Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10022-X Copyright Ó 2011 Elsevier Inc. All rights reserved.

713

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Treating Agents

application must be highly successful and its effectiveness high. Furthermore, the recovery of the solidified oil must occur rapidly and efficientlydbefore the oil leaves the immediate vicinity. The second motivation for using solidifiers is to reduce the impact on birds and mammals on the water surface. No research at all has been carried out on this aspect of treating agent use. This gap is remarkable considering this is one of the prime motivations for use.

22.1.2. Solidifier Issues Utility remains a major issue with oil spill solidifiers. If solidifiers are used, this precludes the use of other mechanical countermeasures. It is important to recognize that booms and skimmers are meant to deal with liquid oil. The big problem associated with these recovery methods is the weathering of oil or dealing with heavier oils. More viscous and heavy oils are a major problem. Solidifying the oil without recovering it immediately can cause major problems. Thus solidifiers must never be used on large spills or where the oil cannot be recovered immediately. Another major issue is the completeness of solidification and mixing of the solidifier with the oil mass. Large-scale tests point to two situations where this issue arises.1 A solidifier can potentially react with the oil with which it first comes into contact, leaving the remaining oil untreated. Mixing of the agent is always an issue, and the resulting “solidified” oil is often a heterogeneous mixture.2,3 The last issue to be raised in this chapter is that of long-term fate and effects. The long-term effects of treated or partially treated oil have not been well studied and therefore remain largely a topic for speculation.

22.1.3. Solidifier Chemistry There are several different kinds of solidifiers, and it is important to understand how they all work. Some of them form chemical bonds, whereas others work only by adsorbency into polymer chains. Because the exact details of most products are proprietary, only a general presentation can be made here.

22.1.3.1. Polymer Sorbents The polymer sorbent is currently the most common type of solidifier. This type is sometimes called a supersorbent, but would be best called a polymer sorbent. Strictly speaking, these products are not solidifiers but sorbents. There is no chemical bonding; instead, van der Waals forcesdweak attraction forces between moleculesdhold the oil between polymer strands. Figure 22.1 shows a scheme of how these work. Many polymers have spaces between them that can hold oil. The oil can be adsorbed into these spaces. The oil is held into these spaces by van der Waals forces. If there was little solidifier of some types, the oil could be removed by applying pressure to the completed solid. The success

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Chapter | 22 Review of Solidifiers

(C) (A)

Adsorbed Oil

(B)

FIGURE 22.1 Schematic of the Process of Polymeric Adsorption. (A) shows a schematic of a typical polymer which on a microscale has spaces. If added to oil, these polymers start absorbing oil as shown in (B). The final product is shown in (C), where the polymer matrix swells with the absorbed oil.

of this reversal would depend on the time, as the solidified oil becomes more stable with time. Many polymers are capable of this action. Generally, the block co-polymers are more efficient and hold oil better. Currently, the most commonly used materials are styrene-butadiene and related polymers. Others that have been used in the past include polytertiary-butylstyrene, polyacrylo-nitrile butadiene, polyisoprene (rubber), polyethylene and polypropylene, poly isobutylene, and related polymers. These types of sorbents have the advantages that they are relatively simple, probably of low toxicity, and slower to react and thus mix betterdgiven a similar density to oil. Furthermore, these products do not link to other materials such as booms, docks, organic material, or stone. The disadvantages of these types of solidifiers are that they are more like sorbents and oil can be released from these products, especially under some pressure.

22.1.3.2. Cross-Linking Agents Cross-linking agents are chemical products that chemically form bonds between two hydrocarbons to solidify the oil. The reaction is a chemical one and typically can release a small amount of heat or absorb that amount of heat depending on the chemical used. When solidifiers were popular in the 1980s, cross-linking agents were more commonly used than polymer sorbents. One must therefore be careful about interpreting some of the literature, for some of the tests may refer only to crosslinking agents or to polymer sorbents or products that are a combination of both, as will be described in the next section. The schematic of how these products function is shown in Figure 22.2. This figure shows that the starting reagent, shown as Xs, mixed with the black oil to form the cross-links as shown by the jagged line. Also, it might be noted that with thick oil, the cross-linking product reacts mostly with the first oil with

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PART | VI

(A) XXXXXXXXXX XXXXXXXXXX

(B)

Treating Agents

(C)

X X XX X XX X

FIGURE 22.2 Schematic of the Process of Cross-Linking. (A) shows a schematic of oil with the Xs being the cross-linking agent. If added to oil, these agents start to cross-link various oil components as shown in (B) by the jagged lines. The final product is shown in (C) where the agent has cross-linked a portion of the oil.

which it comes into contact. Most cross-linking agents react quickly and thus do not penetrate very thick oil. Cross-linking agents that have been used include norbornene and anhydrides. Pelletier and Siron made a new series of oil-treating agents that solidify oil.4 These agents were prepared by reacting surfactants, alcohols, or carboxylic acids with alkychlorosilanes in light hydrocarbon solvents. The advantages of cross-linking agents are that the final product is truly solidified (if mixed before the product reacts completely). If fully solidified, the product leaches little oil and forms a durable mat that is easy to recover. The disadvantages of this technology is that it is difficult to get complete solidification, especially of a thicker slick as the product is reactive and reacts with the first hydrocarbon with which it comes into contact. Cross-linking agents also have the disadvantage of linking with other hydrocarbons such as those in containment booms, docks, and organic matter.

22.1.3.3. Cross-Linking Agents and Polymeric Sorbents Combined This type of agent combines a polymeric sorbent with a cross-linking agent. Often the cross-linking agent is attached to a polymer end. The purpose of this combination is to gain the advantages of both types of agent. A schematic of how this agent type works is shown in Figure 22.3. The polymers used are those described above, while the cross-linking agents are typically anhydrides. British Petroleum’s (BP’s) product called RigidOil, which was an agent of this type, is of interest because the composition was widely disclosed.5 The agent consisted of two liquids that were generally mixed shortly before applying to the oil. The one liquid consisted of a 10% maleinized polybutadiene of molecular weight 8000, with 50% of odorless kerosene plus ester as a diluent. The other liquid consisted of a cross-linking agent, zinversate diethanolamine, also in 50% kerosene/ester (9:1). Extensive testing was carried out on this product as reported in this chapter.

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Chapter | 22 Review of Solidifiers

(A)

Cross-linking sites on polymer agent

(B)

X X X

X

X

X

X

X

X

X X

X

X

X

X X

(C) X

X

X

X X

X

X X

X

X

X

X X

X

X

FIGURE 22.3 Schematic of the Process of Polymeric Sorption Combined with Cross-Linking. (A) shows a schematic of oil with the Xs being the cross-linking agent on the ends of polymers. If added to oil, these agents start to adsorb oil and cross-link various oil components as shown in (B) by the jagged lines. The final product is shown in (C) where the agent has adsorbed and crosslinked a portion of the oil.

This type of solidifier agent has two chief advantages: the product mixes with oil better than cross-linking agent alone, and solidification, if achieved, is better than for polymeric sorbents alone. The disadvantages of this type of agent are that generally it has two components that must be mixed immediately before application and that solidification may be difficult to achieve because the product may form a crust with the oil on the top. This type of agent may also adhere to booms, docks, and other carbon-containing materials.

22.2. REVIEW OF MAJOR SOLIDIFIER ISSUES This section will explore the subtopics of solidifier use. Information is drawn from the papers summarized in the back of this chapter, with emphasis on the reviewed literature.

22.2.1. Effectiveness Solidifier effectiveness is defined as the amount of agent that is required to solidify oil under standard conditions. Many factors may influence solidifier effectiveness, including oil composition, sea energy, state of oil weathering, type of solidifier used, and the amount applied. The most important of these factors is the composition of the oil, but there is very little data on testing with these factors. Although it is easier to measure the effectiveness of solidifiers in the laboratory than in the field, laboratory tests may not be representative of actual conditions. Important factors that influence effectiveness, such as sea energy and mixing, may not be accurately reflected in laboratory tests. Results obtained from laboratory testing should therefore be viewed as representative only and not necessarily reflecting what would take place in actual conditions. However, laboratory testing is useful in establishing chemical and physical relationships, and phenomena.

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22.2.1.1. Field Trials Several field trials were carried out on BP’s product, RigidOil.6 In 1981, 11 tests were carried out using RigidOil on 205 L light fuel oil and topped crude. The product was applied using spray booms. The North Sea was choppy throughout the tests and thus promoted mixing. Several tests resulted in what appeared to be completed solidified oil. Some tests, however, resulted in partially solidified oil with some free oil floating beside the mass of solidified oil. In two tests the oil emulsified with water after the solidifier was applied. In that same time period, a trial of RigidOil was carried out on oil under ice in the Canadian Beaufort Sea.6 The application resulted in some solidification and some free oil, which was thought to have been caused by the lack of mixing. A test on oil on the shoreline was carried out at BIOS (Baffin Island Oil Spill) Study.6 The agent was mixed and then applied with a hand sprayer. This resulted in the formation of a crust with little solidification of oil under the crust. It was judged that this application had little benefit. The cause was felt to be a too-rapid reaction of the agent and lack of mixing. In the mid-1980s, the BP agent was tested on a larger scale by the Canadian Coast Guard and the Canadian oil industry offshore of Newfoundland.7 In these large-scale tests, even more agent was required to partially solidify the oildin fact, up to 40% of the actual volume of the oil itself. This is double the laboratory requirement. Both requirements were deemed to be far in excess of what was actually practical in the event of a real spill. Crude oil was released, and a ship with spray booms applied the solidifier to the oil, which was partially contained in a boom. The agent again reacted with the oil on the surface, and when the oil was sampled at a later time, it was soft with some portions almost liquid. Apparently, the surface solidified and was later mixed by waves with the liquid oil underneath. It was concluded that this technology was not practical for offshore oil spills. Delaune et al. tested the solidifier product, Nochar A 650, by putting the granular product on oiled test plots near a shoreline.8 Four days after the application, the oil was removed by hand. The findings were that the solidifier did react with the South Louisiana crude, forming a cohesive solid mass with no dripping. The solidified oil had a rubberlike consistency that retained its shape and could be removed either mechanically or manually. The recovery of oil in the three plots ranged from 70 to 76%. The findings from the field tests are that more solidifier was required to achieve the end result than from laboratory tests. Furthermore, in many cases, complete solidification was not achieved. This appears to be particularly the case when the oil was thick and when there was insufficient mixing energy. Nearshore tests or use appeared to be more successful, especially when the slicks were thin and mixing was achieved. Caution must be used, however, in translating the test findings of one type of solidifier to another type, as the three types of solidifiers behave somewhat

Chapter | 22 Review of Solidifiers

719

differently. Polymeric sorbents are less likely than the other two types to form a crust and thus inhibit further solidification. Cross-linking agents are the most likely to form a crust.

22.2.1.2. Laboratory Tests Laboratory tests were carried out by Environment Canada over several years, by Exxon, Rea, Pelletier, and Ghalambor. Most companies used a procedure similar to that noted in Appendix A, with the endpoint being the disappearance of free oil. Some tested with penetrometers and viscometers; however, no consistent results were found. Fingas et al. reported on the testing of three solidifiers: BP’s Rigid Oil, which consisted of polymer in deodorized kerosene and a cross-linking agent; a Japanese product consisting of an amine that forms a polymer; and the solidification agent proposed by Professor Bannister of the University of Lowell, an agent that used liquefied carbon dioxide and an activating agent.9 During tests conducted in the laboratory, all three agents functioned, but required large amounts of agent to effectively solidify the oil (that is, render the oil to a viscosity of greater than 1 million cSt). In some situations, the oil became a viscous semisolid that would not aid in recovery. The BP agent worked better than the other agents and was tested on a larger scale by the Canadian Coast Guard and the Canadian oil industry. In these large-scale tests even more agent was required to solidify the oildin fact, up to 40% of the actual volume of the oil itself. This is double the laboratory requirement. Both requirements were deemed to be far in excess of what was practical in the event of a real spill. A standard test was developed to assess new solidifiers. The test consists of adding solidifier to an oil while being continuously stirred until the oil is solid.9 The test results were found to be repeatable within 5%, despite the fact that visual observation was used. The results of testing some solidifiers are given in Table 22.1, with the procedures outlined in Appendix 22.1. The aquatic toxicity of these products was measured and, in all cases for the products listed, exceeded the maximum test value. In other words all products listed were relatively nontoxic to aquatic species. It should be noted that some products, such as the wax, are poor sorbents and solidifiers and have little interstitial spaces in which sorption can occur. This is why such products require over 100% of the material to solidify. Rea tested seven pure polymer or cross-linking chemicals with diesel fuel.10 Mixing was carried out, and then the products were tested with a penetrometer and also tested for diesel fuel vaporization as well as leachability. The products tested were norbornene (in two forms), styrene-ethylene butylene-styrene block copolymer (in two forms), and styrene-butadiene block co-polymer in three forms. The testing was carried out over 3000 hours, with the properties of the gelled substance tested at each point and either 5 or 10% of the polymer added. There was little differentiation between the various polymers in terms of

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TABLE 22.1 Environment Canada’s Testing of Solidifiers AGENT

PERCENT1 TO SOLIDIFY

TOXICITY2 (AQUATIC)

A610 Petrobond (Nochar)

13

>5600

Rawflex

16

>5600

Envirobond 403

18

>5600

Norsorex

19

>5600

Jet Gell

19

>5600

Grabber A

21

>3665

Rubberizer

24

>5600

SmartBond HS

25

>5600

Elastol

26

>5600

CI Agent

26

>5600

Gelco 200

29

>5600

Oil Bond100

33

>5600

Oil Sponge

36

>5600

Spill Green LS

43

>10000

Petro Lock

44

>5600

SmartBond HO

45

>5600

Molten wax

109

>5600

Powdered wax

278

>5600

1

Values are the average of at least 3 measurements, average standard deviation is 6 Values are LC50 to Rainbow Trout in 96 hour this shows that all are insoluble and less than can be measured 2

penetrometer data over the time. Among the findings, it was shown that the gelled fuel continued to solidify over time but eventually approached a constant level. The ratio of solidification was proportional to the mass of agent added. All the gelled fuels emitted volatile organics at a declining rate over time. The leachability of BTEX, however, was lowered by gelation. Test results are summarized in Table 22.2. Ghalambor tested 21 available solidifiers:11 Elastol 1, Elastol 2, Envirobond # 403, Nochars A 610, Nochars A 650, OARS, OSSA, Omni-Zorb #2000, Omni-Zorb # AZ1N, Omni-Zorb # BZ, Omni-Zorb # PZ, Petro-Lock, Rubberizer, Seamated3mm, Seamated4 mm, Seamate fine, SPI particulate

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Chapter | 22 Review of Solidifiers

TABLE 22.2 Agents Used in Rea’s Solidifier Testing

Active Agent

Type e According to This Report

Apparent Physical Density Description g/mL

Relative Effectiveness*

A

Norbornene

cross-linker

green clumped flakes

0.2

10

B

Norbornene (with solvents)

cross-linker

white powder

0.32

7

C

Styrene-ethylene butylene-styrene block copolymer

polymeric sorbent

white small flakes

0.22

1

D

Styrene-butadiene block copolymer

polymeric sorbent

off-white powder

0.4

3

E

Styrene-butadiene block copolymer

polymeric sorbent

white rough flakes

0.18

3

F

Styrene-butadiene block copolymer

polymeric sorbent

white large flakes

0.31

no data

G

Styrene-ethylene butylene-styrene block copolymer

polymeric sorbent

white powderflakes

0.21

2

Designation

* The author (Rea) did not have a table of Effectiveness, these are values calculated approximately from the graphs using the reciprocal of the penetration times the percentage used, a bigger number is better

1, SPI particulate 2, Spill Gel (Fractech), Waste-set PS # 3200, and Waste-set PS # 3400. It should be noted that there are only 13 unique types; the remainder are variations of the same product. It might also be observed that some of these products are elasticizers or sorbents. The results of testing did not reveal the product names. Various test oils were used. The laboratory test was similar to that noted in Appendix 22.1, with somewhat different quantities of water, and the endpoints were chosen to be the same. The “consumption level” of the solidifier or the quantity of agent needed to solidify varied from 25 to 120%. The viscosity of the resulting products varied from about 1000 Poise to about 8000 Poise. Calorimetry was carried out on the reactions, and the heat of reaction varied from 0.9 to 4.3 Cal/g. Values less than 1 would indicate an endothermic reaction and values greater than 1 would be an exothermic, or heat-releasing, value. Values very close to 1 could

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PART | VI

Treating Agents

be considered as neither endothermic or exothermic. All three types of reactions were found. The Exxon laboratory test included application of solidifier to oil until no visible oil remained on the water surface.12 The oils tested were gasoline, diesel, Bunker C, and three different crude oils. Although most of the products were able to solidify some of the oils into a firm mat, none of the solidifiers formed a firm, solid mat with all of the oils tested. The solidifiers used ranged from a ratio of about 1:5 to about 1:20. Dahl et al. also report on the testing of several agents.13 The laboratory test included a modification of the Environment Canada test (described in Appendix 22.1) and included application of solidifier to oil until no visible oil remained on the water surface. The 14 solidifiers tested were Micro-Set, SPI, Omni-Zorb, Inipol, Nochar A-610, GTS-modified Elastol, Seamate, MWE, Envirobond, Petrosorb, Petro-Lock, PetroGuard, Rubberizer, and Petro-Capture. The salt level did not have an effect on solidification. Pelletier and Siron tested their new silicone solidifier using a light crude oil, Brent. A procedure similar to that in Appendix 22.1 was used.14 The ratio needed to solidify was 1:7, agent to oil. The solidified oil contained water up to 85% by weight of the total mass. These agents are prepared by reacting surfactants, alcohols, or carboxylic acids with alkychlorosilanes in light hydrocarbon solvents. A trichlorosilane of a general formula, Cl3SiR, where R is H or CH3, is used as the primary reactant. The reaction proceeds as: Cl3 SiR þ R-OH / SiOR þ HCI Two silanes, octadecyltrichlorosilane (CH3(CH2)17SiCL3) and trimethyoxysilane ((CH2))3SiH), are added to the solution along with a surfactant, silicone grease, and a petroleum ether solvent. The mixture of the final solution was a ratio, by molar weights, of one part Brij 76, the surfactant, one part of trichlorosilane, 5 parts of the octadodecyltrichlorosilane, 5 parts of the trimethoxysilane, and 0.05 g/mole of silicone grease in petroleum ether. The treatment solution is rapidly sprayed over the surface. Laboratory testing was carried out using a light crude oil, Brent. The ratio needed to solidify was 1:7, agent to oil. The solidified oil contained water up to 85% by weight of the total mass. It was found that the silicone coated solid surfaces and rendered them less adhesive to oil. The solidification process was found to be independent of temperature and salinity effects. The solidifier could easily be reformulated as an oil herder as well. The product was thought to be nontoxic, but no tests were carried out. The application of this solidifier was thought to be useful for application to very small spills and not to larger spills. Use of the petroleum ether as a solvent rendered this mixture flammable, but a substitute solvent was found. Fieldhouse and Fingas tested a number of agents for effectiveness using the method outlined in the Appendix, and also using rheology.3 The test results and observations are summarized in Table 22.3. The conclusions from

723

Chapter | 22 Review of Solidifiers

TABLE 22.3 Recent Testing by Environment Canada Product

Oil Thickness (mm)

Dose (%w/w)

Description

0.1

222

Excess product, separate

1

79

Clumps

10

42

Incomplete, oil released

10

46

Overnight, cohesive layer

0.1

273

Excess product

1

92

Clumps

2

68

Cohesive layer

5

50

Cohesive layer, res. sheen

10

42

Cohesive layer, res. sheen

10

37

Cohesive layer, res. sheen

Arab Heavy 2

60

Cohesive layer, brittle

Fuel Oil #5 1

31

Crust

0.1

129

Clumps

1

44

Cohesive layer

10

30

Additional

10

32

Overnight, cohesive

0.1

129

Clumps

0.5

59

Clumps

1

49

Cohesive layer

2

38

Cohesive layer

5

38

Cohesive layer

10

28

Cohesive layer, res. sheen

10

25

Cohesive layer, excess oil

2

51

Cohesive layer, brittle

2

23

Cohesive layer

Arab Heavy

2

45

Cohesive layer, brittle

2

20

Clumps, res. slick

Sockeye

2

32

Sits on top, brittle, res. slick

Oil

SmartBond Diesel HO

ASMB

SmartBond Diesel HS

ASMB

Arab Light

(Continued )

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Treating Agents

TABLE 22.3 Recent Testing by Environment Canadadcont’d Product

Oil

Oil Thickness (mm)

Dose (%w/w)

Description

CI Agent

Diesel

0.1

117

Clumps

1

40

Cohesive layer

10

24

Cohesive layer, sags

0.1

91

Clumps

1

52

Cohesive layer, brittle

2

47

Cohesive layer

5

29

Cohesive layer, res. sheen

10

19

Cohesive layer, res. slick

10

19

Cohesive layer, res. slick

50

Cohesive layer, brittle

-5

77

Separate grains

-5

56

Clumps

0

79

Clumps

-5

52

Clumps

-5

30

Clumps

ASMB

0

50

Cohesive layer, brittle

Diesel

-5

47

Cohesive layer

ASMB

-5

35

Clumps

ASMB

0

56

Cohesive layer, brittle

ASMB

Arab Heavy 2 Temperature ( C) SmartBond Diesel HO ASMB ASMB SmartBond Diesel HS ASMB

CI Agent

this part of the study are that the optimum oil layer thickness for ASMB and marine diesel is between 2 and 5 mm. In this range, the product treatment was virtually complete, and the treated oil could be recovered as a single mat. Below 1 mm, the layer is not sufficiently thick to provide contact between product grains to remain cohesive; this is true below 2 mm for some agents that are more granular. At 100 mm, the treating agent must be applied in excess, and the individual grains or small agglomerations tend to repel each other. At 10 mm, the endpoint is misleading as the treatment is still

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incomplete, especially for the more granular, floating, and reactive agents. Some agents have a tendency to crust at the surface and are only driven down by the weight of additional product on top. Some products more easily entered the oil layer, especially those that are denser than the oil, and thus there were fewer issues with incomplete treatment. Allowing the sample to sit overnight greatly improved recovery, but the resulting mat was less firm and tended to flow. The effect of oil complex modulus and dosage required to solidify is illustrated in Figure 22.4. Fieldhouse and Fingas also tested at laboratory scales, Two of the agents were tested on marine diesel and ASMB at a thickness of 2 mm in d5 C conditions and at 0 C on ASMB only at laboratory scales.3 Results are also provided in Table 22.3. One of the products was far less cohesive at the lower temperatures, but dose rates were similar. Another product appeared to be less affected, perhaps due to smaller grain size. Only one of the treatment combinations had an outcome similar to the test result at 15 C. It appears that temperature is a limiting factor for generating a cohesive mass. It is interesting that when moved to room temperatures, the treated material adhered and became a cohesive mass. Another issue identified during these tests is the density of the solidifier. If the agent was lighter than the oil (which is the case with most agents), the top surface of the oil was solidified and the agent did not penetrate the remaining oil. Mixing of the agent with the oil was always the issue, and the resultant solidified masses were often quite heterogeneous.

FIGURE 22.4 Plot of the Complex Modulus versus Percent Solidifier Added. This figure shows that heterogeneity of the solidified product causes the increase in complex modulus to be nonlinear. Thus viscosity measurements of effectiveness may not be accurate.

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Throughout this testing, few endpoints other than the disappearance of free oil were used. Measurement of viscosity and penetration was used, but an acceptable procedure was not found. This is probably because of the heterogeneity of the solidified mass. Sampling error may also be a cause. It should be noted that all researchers felt that the disappearance of free oil method did result in good repeatability. This matter will be discussed further in the analytical section below.

22.2.1.3. Tank Tests Only one tank test was carried out, that by Exxon in 1995.13 Field application studies were carried out in the Imperial tank, and a specialty insulation blower was used. The oils tested were gasoline, diesel, Bunker C, and three different crude oils. The primary purpose was to assess the overall applicability of the technology on a larger scale. The findings of the field application were as follows: the blower performed well; the application rate was about 1:1; waves of about 12 to 20 cm had little effect but the material broke into clumps; solidification increased with time and if the leading edge was treated and approached the shore, little retention on the shore was noted. Tests of recovery were carried out, and fish netting was found to work well; containment booms also worked, and the solidified oil could be removed to drums using shovels or wire-screen nets. Disposal was found to be an issue, solidified diesel was still flammable, and vapors were released from the solidified oils. 22.2.1.4. Actual Use One of the producers of a microsorbent product provides recent use on its website.15 These results are summarized in Table 22.4. 22.2.1.5. Analytical Methods Analytical means in any test system is a major concern. As noted, almost all tests were carried out using visual meansdthat is, noting the presence of liquid oil. Most researchers also stated that standard statement in science meaning that one can do the same experiment again and get same results. It was probably for this reason that this means continued. Several researchers used penetrometers and viscometers to try to determine an endpoint.7,10 These methods did not yield consistent results. One problem with these methods is that a sample must be removed for analysis, disrupting the test. Furthermore, sampling a heterogeneous material often results in varying results. The method adopted by Environment Canada (see Appendix 22.1) uses visual testing, and repeatability within less than 5% has been found. It has also been found, however, that changing operators initially results in a slightly greater discrepancy, but this problem is remedied with practice. This situation is unsatisfactory, however, inasmuch as a test should always be operator

Waterway

Place

Product

CI used

Product Removed

Approx. Ratio*

Time**

McAlpine Dam

Louiseville, KY

hydraulic oil

25 gals

35 gal

0.3

4 hr

Ohio River

Louiseville, KY

oily sludge

962 lbs

534 gals sludge

0.2

6 hr

unidentified

Clewiston, FL

diesel fuel

55 lbs

55 gals

0.5

3 hr

manhole

Mid-Atlantic

vault oil

70 lbs

35 gals

0.2

2 hr

Creek

New Town Creek, NY

unspecified

boom

sheen only

Juniper Beach

Louisville, KY

diesel fuel

30 lbs

15 gal

Channel

Jacksonville, FL

diesel fuel

boom

sheen only

na

Channel

St. Petersburg, FL

gasoline

boom

sheen only

na

Storm drain

Louisville, KY

diesel fuel

70 lbs plus booms

40 gals

0.2

3 hr

Highway

Jeffersonville, IN

diesel fuel

60 lb

40 gals

0.2

4 hr

Drain

Simpsonville, KY

hydraulic oil

35 lbs plus boom

15 gals

0.3

2 hr

Retention pond

Shelbyville, KY

diesel fuel

40 lb plus boom, pads

150 gals

0.1

8 hr

Channel

Reddington Shores, FL

diesel fuel

1 lb plus booms

sheen only

1 hr

Cooling Tower

Albama

lube oil

filter

reduce discharge

na

Secondary Containment

London, Ohio

transformer oil

containment

0.2

3 hr

na

727

* Ratio estimated by this author using the data on web site. ** Given on the web site as the time to clean up.

na

Chapter | 22 Review of Solidifiers

TABLE 22.4 Uses of CI Agent (from CIAGENT website)

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independent. Research on other endpoints were unsuccessful, although more effort could be applied.7 Rea noted similar findings.10

22.2.2. Toxicity The second issue important in any discussion of solidifiers is toxicitydboth of the solidifier itself and of the treated oil. A standard aquatic toxicity test is to measure the acute toxicity to a standard species such as the rainbow trout. The LC50 of a substance is the “Lethal Concentration to 50% of a test population,” usually given in mg/L, which is approximately equivalent to parts per million. The specification is also given with a time period, which is often 96 hours for larger test organisms such as fish. The smaller the LC50 number, the more toxic the product. The aquatic toxicity of solidifiers has always been low (LC50 << 1000) or not measurable as the products are not water soluble. Some studies depart from the traditional lethal aquatic toxicity assay, and also some focus on the longer-term effects of short-term exposures. There certainly is a need for more of these types of studies. There is also a need to abandon the traditional lethal assays and use some of the newer tests for genotoxicity, endocrine disruption, and others.

22.2.2.1. Toxicity of Solidifiers The results of solidifier toxicity testing are similar to those found in previous years, namely, that solidifiers have no aquatic toxicity. No studies depart from the traditional lethal aquatic toxicity assay, and none focuses on the longer-term effects of short-term exposures. Further, there is a need to test the effects of the solidifier and treated oil on wildlife that may come into contact with the products. Of particular concern is the potential for enhanced adhesion of the product. 22.2.2.2. Toxicity of the Treated Oils No studies of the toxicity of solidifier-treated oils were found.

22.2.3. Biodegradation No studies of the biodegradability of solidifiers or of solidifier-treated oil were found.

22.3. OTHER ISSUES 22.3.1. Spill Size A review of the limited work to date shows that solidifiers appear to work only on very small and thin spills.9,12 This is because the solidifiers mix poorly on large and thick spills. Further, it is difficult to apply solidifiers at controlled rates on larger spills and to provide adequate mixing.

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22.3.2. Solidifier Use in Recent Times Because of the preauthorization of use in USA Environmental Protect Agency (EPA) region 4, several uses in that area have occurred.15,16 These uses have limited documentation and no independent reviews. All of the spills have been very small, as is the specification of the preauthorization.

22.3.3. Solidifiers or Sorbents One of the serious issues that must be dealt with is the difference between true solidifiers and sorbents.16 Many of the products on the market today are polymer sorbents, as noted earlier. It may not be satisfactory to classify these as solidifiers; however, there is a very fine line between these and similar products. These form a continuum to regular sorbents, such as polypropylene pads and peat moss. Regulatory authorities need to address this question because the leachability of the oil and disposal issues are quite different at the opposite ends of the sorbent spectrum. One of the specifications might be the oil leachability using a specific test.

22.3.4. Potential for Sinking There are concerns that solidified oil might sink.16 No studies of the density of the final products have been performed, although no instance of sinking has been observed in the limited testing and use to date.

22.3.5. Modeling Solidifier and Solidified Oil Behavior and Fate There are no models that incorporate solidification, nor are there any algorithms to incorporate into models. Since the use of solidifiers may be restricted to very small spills, this may not be an issue.

22.3.6. Solidified Oil Stability No studies of the long-term stability of solidified oil have been made. Rea studied the solidified oil for 160 days but did not conclude anything in particular about the stability of these products.10

22.3.7. Fate of Unreacted Solidifier No studies of the fate of unreacted solidifier have been carried out. Concerns are not that great, however, with many of the current polymer sorbents.

22.3.8. Recovery of Solidified Oil In recent uses, most solidified oil was recovered using hand tools such as shovels, ranks, and pool nets. Dahl et al. suggest the use of fishing nets or nets that were developed for the recovery of heavy oil. Recovery is another factor that may restrict the use of solidifiers to small, nearshore spills.13

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22.3.9. Solidification Time Solidification time is very important and is partially dependent on the reactivity of the treating agent itself. If the reaction time is very fast, crusting occurs and the oil will not be completely solidified. If the reaction time is too slow, the product is not useful. It is suggested that solidification time might best occur between 10 and 60 minutes to have optimal use on typical small spills.

22.3.10. Application Systems Only Dahl et al. developed systems to apply solidifier by modifying an insulation blower. Since current applications are to small, nearshore spills, manual application is carried out.13

22.3.11. Reduction of Flash Point Limited testing by some researchers showed that fuel flash points were not reduced by solidification.10,13 There is no chemical or physical reason to assume that flash points would be altered by the use of typical solidifiers.

22.3.12. Assessment of the Use of Solidifiers Several authors have assessed the use of solidifiers from a nontechnical perspective.17-25 The general conclusions of these documents are that solidifiers could be safely used on small spills. None of the documents addressed the operational definition of solidifiers.

22.3.13. Disposal Methods or Recycling Little work has been carried out on the disposal of used solidifiers and the solidified mass of oil. Leachate testing carried out on some products reacted with oil suggest that these products could be safely disposed of in a landfill. Incineration is also possible in some jurisdictions. Recycling has not been tried or at least has not been mentioned in the literature.

22.4. SUMMARY Solidifiers have not been used or studied to the extent that operational considerations or uses can be definitively stated. Considerations include the following: l

l

l

Solidifiers may be useful on very small spills, close to shore where product can be recovered. The long-term fate of solidifiers and solidified oil in the environment has not been studied. Some of the products currently touted as solidifiers are actually sorbents.

Chapter | 22 Review of Solidifiers

l

l

l

731

The mixing of solidifiers with oil is very difficult due to high reactivity with first oil encountered and density difference problems. There is no reduction of flash point or other inherent chemical properties of the oil. There are generally few data on all aspects of solidifiers.

ACKNOWLEDGMENTS The author acknowledges the Prince William Sound Regional Citizens Advisory Committee, which funded an earlier study on solidifiers. Some of this data is drawn from this study.

REFERENCES 1. Walker AH, Michel J, Canevari G, Kucklick J, Scholz D, Benson CA, et al. Chemical Oil Spill Treating Agents: Herding Agents, Emulsion Treating Agents, Solidifiers, Elasticity Modifiers, Shoreline Cleaning Agents, Shoreline Pre-treatment Agents, and Oxidation Agents. Washington, DC: Marine Spill Response Corporation; 1994. Technical Report Series 93d015. 2. Fingas MF. A Review of Literature Related to Oil Spill Solidifiers, 1990d2008. Anchorage, Alaska: Prince William Sound Regional Citizens’ Advisory Council (PWSRCAC) Report; 2008. 3. Fieldhouse B, Fingas MF. Solidifier Effectiveness: Variation Due to Oil Composition, Oil Thickness, and Temperature. AMOP 2009;337. 4. Pelletier E, Siron R. Silicone-Based Polymers as Oil Spill Treatment Agents. Environ Tox Chem 1999;18:813. 5. Meldrum IG, Fisher RG, Plomer AJ. Oil Solidifying Additives for Oil Spills. AMOP 1981;325. 6. McGibbon G, Fisher RG, Meldrum IG, Plomer AJ. Further Developments in Oil Spill Solidification. AMOP 1982;199. 7. Fingas MF, Kyle DA, Laroche ND, Fieldhouse BG, Sergy G, Stoodley RG. The Effectiveness Testing of Spill Treating Agents. In: Lane Peter, editor. The Use of Chemicals in Oil Spill Response, ASTM STP 1252, 286. Philadelphia: American Society for Testing and Materials; 1995. 8. Delaune RD, Lindau CW, Jugsujinda A. Effectiveness of “Nochar” Solidifier Polymer in Removing Oil from Open Water in Coastal Wetlands. Spill Sci Tech Bull 1999;5:357. 9. Fingas MF, Stoodley R, Laroche N. Effectiveness Testing of Spill-Treating Agents. Oil Chem Poll 1991;7:337. 10. Rea B. Analyses of Solidification and Fixation Parameters of Diesel FuelWhen Blended with Chemical Polymer Gelling Agents. Las Cruces, NM: New Mexico State University; 1991. 11. Ghalambor A. The Effectiveness of Solidifiers for Combatting Oil Spills. Louisiana Applied and Educational Oil Spill Research and Development Program; 1996:68. 12. Dahl W, Lessard RR, Cardello EA, Fritz DE, Norman FS, Twyman JD, et al. Solidifiers for Oil Spill Response, Proceedings of the Society of Petroleum Engineers Conference on Health Safety and Environment, SPE paper No. 35860, 1996;803. 13. Dahl WA, Lessard RR, Cardello EA. Recent Research on the Application and Practical Effects of Solidifiers. IOSC 1997;391. 14. Pelletier E, Siron R. Silicone-Based Polymers as Oil Spill Treatment Agents. Environ Tox Chem 1999;18:813. 15. CI Agent Website, http://www.ciagent.com, accessed December, 2009.

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16. Michel J, Keane P, Benggio B. Pre-Authorization for the Use of SolidifiersdResults and Lessons Learned. IOSC 2008;345. 17. Scholz D, Boyd J, Walker AH, Michel J. Using the Selection Guide for Spill Countermeasures Technologies in Response Decision Making and Planning. IOSC 2001;797. 18. Walker AH, Kucklick JH, Steen A, Fritz D. Oil Spill Chemicals in Freshwater Environments: Technical Issues. IOSC 1995:373. 19. Walker AH, Kucklick JH, Michel J. Effectiveness and Environmental Considerations for NonDispersant Chemical Countermeasures. Pure Appl Chem 1999;71:67. 20. RRT Team IV, Regional Response Team IV, Pre-Authorization Policy for the Use of Solidifiers, Regional Response Team IV, 2006. 21. Walker AH, Michel J, Canevari G, Kucklick J, Scholz D, Benson CA, et al. Chemical Oil Spill Treating Agents: Herding Agents, Emulsion Treating Agents, Solidifiers, Elasticity Modifiers, Shoreline Cleaning Agents, Shoreline Pre-treatment Agents, and Oxidation Agents. Washington, DC: prepared for the Marine Spill Response Corporation; 1994. Technical Report Series 93d015. 22. Workshop Proceedings on The Use of Chemical Countermeasures Product Data for Oil Spill Planning and Response, Xerox Document University and Conference Center, Leesburg, VA, 1995. 23. Walker AH, Pond RG, Kucklick JH. Using Existing Data to Make Decisions About Chemical Countermeasure Products. IOSC 1997;403. 24. Walker AH, Scholz D, Boyd JN, Levine E, Moser E. Using the Pieces to Solve the Puzzle: A Framework for Making Decisions About Applied Response Technologies. IOSC 2001;503. 25. Walker AH, Kucklick JH, Michel J, Scholz D, Reilly T. Chemical Treating Agents: Response Niches and Research and Development Needs. IOSC 1995:211.

APPENDIX 22.1. TESTING PROCEDURES FROM ENVIRONMENT CANADA Solidifier Test Procedures Used in Early Years 1.a. Equipment: Stirrer stop watch analytical balance 1.b. Supplies: Jar ASMB (Alberta Sweet Mixed Blend) standard oil salt water spatula 1.c. Procedure: 200 mL of seawater is placed into jar, and 20 mL of the standard oil is weighed and placed on the water. A stirrer (Labline model 200 or equivalent) is placed at the oilewater interface and is turned on. After one minute, quantities of the solidification agent are added at 1-minute intervals from a pre-weighed container. A plastic spatula is used to test the solidity of the oil. When the oil is solid as determined by a viscosity of 1 million or the visual equivalent, the weight of solidifier added and the weight of the oil are used to calculate the percentage required to solidify.

Oil Solidifier Effectiveness Test Used 1998 to Present PurposedThe purpose of the test is to determine the effectiveness of a solid spill treating agent (STA) in solidifying a standard oil under specific laboratory conditions. This allows for the assessment of an STA product as a spill countermeasure, as well as comparison with other products of the same class.

Chapter | 22 Review of Solidifiers

733

BRIEF DESCRIPTION OF THE TEST The product is added in weighed increments to a known mass of standard oil with mixing. The endpoint is reached when the oil mass no longer moves freely and the exposed water surface lacks a sheen of oil. The effectiveness value is reported as the percentage required to solidify.

EQUIPMENT AND SUPPLIES 500 mL 3.3% (w/v) sodium chloride solution 20 mL standard oil 1 liter beaker, 10 cm ID Mixer with 3-blade impeller, 1.5 cm width and 3 cm radius Balance, min. 10 mg accuracy Weighing boat Scoop or spoon Timer

Procedure 1. All materials are allowed to reach room temperature prior to starting. The oil is mixed thoroughly, and the agent is homogenized as required. 2. Add 500 mL of 3.3% sodium chloride solution to a 1-liter beaker. 3. Weigh a syringe containing 20 mL of standard oil. Carefully add the 20 mL of oil to the surface of the salt water. Weigh the empty syringe to determine the mass of oil. 4. Insert a 3-blade mixer into the beaker, adjusting such that the impellers are just at the surface. Begin mixing at 75 RPM and continue for 1 minute. 5. Weigh 1.0 g of solidifier agent into a weighing boat. Record the mass to at least two decimal places. 6. Add the solidifier agent to the oil slick between the mixing blades and the beaker walls and observe. 7. Continue adding solidifier agent in 1.0-g increments at 1-minute intervals until there is a significant change in oil properties. 8. Continue adding solidifier agent in 0.1-g increments at 1-minute intervals until the end point is reached. 9. The endpoint is defined by an immobile oil slick and the lack of a sheen on exposed water surfaces. 10. The contents are continuously stirred for a minimum 20-minute period, regardless of the time required to reach the end point.

CALCULATION The sum total of solidifier agent added is divided by the initial mass of the oil to provide the ratio of solidifier-to-oil. The result of the test is reported in percentage form.

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Part VII

In-Situ Burning

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Chapter 23

An Overview of In-Situ Burning Merv Fingas

Chapter Outline 23.1. Introduction 23.2. An Overview of in-situ Burning 23.3. Assessment of Feasibility of Burning 23.4. EquipmentdSelection, Deployment, and Operation

737 737 758

23.5. Possible Spill Situations 858 23.6. Post-burn Actions 870 23.7. Health and Safety 878 Precautions during Burning

811

23.1. INTRODUCTION In-situ burning is the oldest technique applied to oil spills and is also one of the few techniques that has not been explored in scientific depth until recently. This is because burning, though easy to apply, is far more complex than initially appears. Furthermore, burning oil on water is not intuitive, and thus many people do not pursue this course of action. In-situ burning has been used to deal with land spills ever since land spills first occurred. There is little documentation on this method, and this trend continues. Of the few documented cases, most were successful and resulted in little environmental damage.

23.2. AN OVERVIEW OF IN-SITU BURNING 23.2.1. The Science of Burning The fundamentals of in-situ burning are similar to those of any fire, namely, that fuel, oxygen, and an ignition source are required.1,2 Fuel is provided by the vaporization of oil. The vaporization of the oil must be sufficient to yield a steady-state burningdthat is, one in which the amount of vaporization is about the same as that consumed by the fire. Once an oil slick is burning, it Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10023-1 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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burns at a rate of about 0.5 to 4 mm per minute. This rate is limited by the amount of oxygen available and the heat radiated back to the oil. The oil burn rate is a function of the oil type as well as conditions such as ice present. The steady-state burning implies that the conditions noted above are met.3 If not enough vapors are produced, the fire will either not start or will be quickly extinguished. The amount of vapors produced is dependent on the amount of heat radiated back to the oil. This has been estimated to be about 2 to 3% of the heat from a fire for a pool fire.4,5 If the oil slick is too thin, some of this heat is conducted to the water layer below it. Since most oils have the same insulation factor, most slicks must be about 0.5 to 3 mm thick to yield a quantitative burn. Once burning, the heat radiated back to the slick and the insulation are usually sufficient to allow combustion down to about 1 mm of oil. Chatris and coworkers noted that burns of diesel fuel and gasoline went through a three-phase process.6 In the first phase the burn spreads over the whole pool and then increases to the maximum value. The second step is when the fire burns at a relatively constant rate over the entire pool. In the third step, the fire falls back and the rate decreases until the fire is extinguished. If greater amounts of fuel are vaporized than can be burned, more soot is produced as a result of incomplete combustion, fuel droplets are released downwind, or, more typically, small explosions or fireballs occur.7,8 The lastnamed phenomenon is often observed when gasoline or light crudes are burning. It has been shown that diesel fuel burns differently than other fuels, with a tendency to atomize rather than vaporize. This results in an obviously heavier soot formation.9 Soot formation is an issue that has been studied by several scientists over many years.10-17 Soot formation occurs by several processes. One common process is the aggregation of molecular species into larger compounds, and another process is the partial combustion of fuels such as diesel fuels. Diesel fuels and kerosene are known to burn with more soot than most other fuels.18-22 This is for several reasons; diesel fuel and kerosene can form droplets under heat, and these droplets will often only burn partially, leaving carbonaceous material on the inside or even whole fuel with carbonaceous material or soot on the outside. Most other fuels will evaporate under the influence of heat and do not form significant amount of droplets such as diesel, kerosene, or jet fuel. The amount of oil that can be removed in a given time period depends on the fuel and on the area covered by the oil. As mentioned above, most oil pools burn at a rate of about 1 to 4 mm per minute, which means that the depth of oil is reduced by that value of millimeters per minute. As a rule of thumb, the oil burn rate is about 2000 to 5000 L/m2$day. Several tests have shown that this does not vary significantly with oil weathering but varies with oil type.23 Emulsified oil may burn slower as its water content reduces the spreading rate and increases the heat requirement. Chatris and coworkers carried out a study on the burning rates of gasoline and diesel fuel and found that diesel fuel burned at a rate of 0.57 kg/ m2/s or 2.9 mm/min and gasoline burned at 3.5 mm/min.6 Burn rate depends on wind velocity to a small degree.24 The burn rate for gasoline was 0.002 g/cm2.s

Chapter | 23 An Overview of In-Situ Burning

739

(equivalent to a pool regression rate of about 2 mm/min) at no wind velocity, and this increased slightly and then returned to about the same rate at a wind velocity of 3 m/s. Fingas measured the small-scale burn rate of several heavy fuels and found that burn rates for heavy fuels varied from 0.5 to 3 mm/min.25 Buist et al. found that the burn rate for many crude oils in ice was between 1 and 2 mm/min, typically half of the rate when ice was not present.26 Historically, it was thought that the burn rates depended on scale size. The early work proposed a cyclic relationship between burn rate and pan diameter.4 This theory was based on propositions about flame characteristics in the laminar flow region (0 to 10 cm), to the transition zone (10 to 100 cm), through to the turbulent flow regime (>100 cm). Since most tests and actual burns are greater than 100 cm in diameter, this theory may not be relevant to in-situ burning. Some authors have reported an increase in burn rate with wind speed.4 Buist et al. reported an increase equal to 0.15 times the wind speed multiplied by the quiescent burn rate.4 This translates into about a twofold increase in burn rate for a tenfold increase in wind speed. Many studies have focused on flame dynamics and flame propagation.27-32 Studies conducted in the last 10 years have shown that the type of oil is relatively unimportant in determining how an oil ignites and burns, except for heavier or emulsified oils. However, heavy oils require longer heating times and a hotter flame to ignite than lighter oils and may often require a primer such as kerosene or diesel fuel. Earlier studies appeared to indicate that heavier oils and oils with water content required greater thicknesses to ignite. However, recent testing has shown this position to be incorrect.25 Several workers have tested various oils to determine their ignitability, with the general result that most oils are similar without stable emulsion formation.33,34 Burn efficiency is the initial volume of oil before burning, less the volume remaining as residue, divided by the initial volume of the oil. The amount of soot produced is usually ignored in calculating burn efficiency. Efficiency is largely a function of oil thickness. For example, a slick of 2 mm burning down to 1 mm yields a maximum efficiency of 50%. A pool of oil 20 mm thick burns to approximately 1 mm, yielding an efficiency of about 95%. Current research has shown that other factors such as oil type and low water content only marginally affect efficiency. Most, if not all, oils will burn on water if slicks are thick enough and if sufficient vapors can be produced by the ignition and subsequent fire. Except for light refined products, different types of oils have not shown significant differences in burning behavior. Weathered oil requires a longer ignition time and somewhat higher ignition temperature.35 Alternatively, weathered or heavy oils can be ignited with the addition of a primer.25 At the time of the Torrey Canyon spill (1967), it was not known that the thickness of the oil would be a limitation. Glassman and Hansel conducted studies shortly after this incident and concluded that the slicks that did not ignite were below minimum thickness.36 Maybourn studied oil ignition thicknesses and found that slicks that

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In-Situ Burning

were 3 and 6 mm thick burned.37 Twardus conducted preliminary tests of minimum burning thicknesses and proposed that all fuels burned at the 5 mm initial thickness tried.35,38 Bunker C required longer heating times and the addition of a primer. Further testing on light crudes showed that the minimum thickness for ignition was 0.58 to 0.62 mm and the residues varied between 0.35 and 0.58 mm.38 This was compared to unconfined fresh oil thicknesses of 0.5 to 0.6 mm at 0oC, 0.2 to 0.25 mm at 5oC, and 0.5 mm at 10oC. Aged oil showed limiting spreading thicknesses of 1.90 to 3.0 mm at 0oC, 1.2 to 2 mm at 5oC, and 1.2 to 1.3 mm at 10oC. Fingas et al. showed that thicknesses greater than about 0.5 mm burned for all types tested.39,40 Arai et al. studied burn rates of various crudes and found that rates decreased at thicknesses from 18 to 1 mm, but most oils could be ignited at 1 to 2 mm.41 It was thought that the initial burn thickness depended on variances in the thermal conductivity of the starting oil. Elam et al. measured the thermal conductivity of three crude oils as being 130 mW/m K over a 50 K temperature range.42 Little difference was found for oil type or temperature. Overall, many workers have concluded that the rule of thumb is that the minimum ignitable thickness of oil is 1 to 3 mm. However, most did not test thin thicknesses or establish minimums. Fingas showed that even heavy oils at thicknesses of 0.5 mm and above could be ignited, sometimes with the aid of diesel as a primer.25 Some studies have been conducted of the final thickness of burning oil on water before it is extinguished. Buist et al. reviewed a large number of cases in which oil burn residue, or the thickness of the oil at the end of the burn, was measured.4 They found that the average final thickness was 1 mm and that the residue ranged in thickness from about 0.5 to 2 mm. Thus, it was proposed that 1 mm be adopted as the rule of thumb for final burn thickness. It is uncertain whether oil that is completely emulsified with water can be ignited. Oil containing some emulsion can be ignited and burned.43 During the successful test burn of the Exxon Valdez oil, some patches of emulsion were present (probably less than 20%). While it did take longer to ignite the burn (>5 minutes), it did not affect the efficiency of the burn.44 It is suspected that fire breaks down unstable water-in-oil emulsion, and thus water content may not be a problem if the fire can be started. There is inconclusive evidence at this time on the water content at which emulsions can still be ignited. One test suggested that a heavier crude would not burn with about 10% water, another oil burned with as much as 50% water, and still another with about 70% water.35,43 Twardus noted that mixtures containing less than 20% water ignited readily but required preheating.35 Mixtures of oil with 30 to 50% water required a powerful igniter and a still longer preheating time. Three mixtures containing about 70% water burned with a long preheating time and a powerful igniter. One study indicated that emulsions may burn if a sufficient area is ignited.45 Further studies indicated that stable emulsions will not burn, but oil containing less than 25% water can be ignited. The burning of emulsions may be related to their stability class.46,47 It should be noted that the emulsion stability was not measured in any of the

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741

previous studies. Emulsions may not be a problem because chemical deemulsifiers could be used to break enough of the emulsion to allow the fire to start. Once started, it is believed that most emulsions would burn. The residue from oil spill burning is largely unburned oil, with some lighter or more volatile products removed. When the fire ceases, unburned oil is left that is simply too thin to sustain combustion. In addition to unburned oil, oil is also present that has been subjected to high heat and is thus weathered. Finally, heavier particles are reprecipitated into the fire. Highly efficient burns of some types of heavy crude oil may result in oil residue that sinks in seawater. Soot is formed in all fires. The amount of soot produced is not precisely known because there is no direct means of measuring soot from large fires. It is believed that the amount of soot is about 0.3 to 3% for crude oil fires and about 3 to 8% for diesel fires.17,48 An additional consideration is that the soot precipitates out at a rate equal to approximately the square of the distance from the fire. Thus a constant percentage of soot for a whole fire may be irrelevant. A recent study shows that soot percentage is most probably between 0.3 and 1% for a light crude.17 Soot consists of agglomerates of spherical particles. Nelson measured several soot agglomerates and found that the individual spheres had radii of 5 to 25 nm (1 nm ¼ 1000 mm).49 Soot particles were aggregates of 50 to 250 spheres and the aggregation could be described as a fractal dimension of 1.7 to 1.9. Sorensen and Feke studied soot particles and found that the aggregates ranged from 50 nm to 400 mm with a fractal dimension of 1.8.50 The primary particle size was found to be 5 nm with the smallest typical aggregation being 10 to yield the smallest typical diameter of 50 nm. A recent study of soot particles noted that small spherical particles are formed ranging in size from 200 nm to about 3 mm.51 These are called plerospheres. These small particles contain large amounts of trace metals as found in the originating oils. X-ray analysis shows that metal concentration increases as the dimension decreases. The total heat radiated by a given burn has been measured as 1.1 MW/m2.52 Evans calculated that the heat required to vaporize the oil was 6.7 KW/m2 and that the heat lost from conduction through the slick to the underlying water was 2.5 KW/m2. The fraction of heat released that was radiated back to the pool was about 0.02 at the rim of the pool and 0.045 at the center. Other researchers report a reradiated heat fraction between 0.01 and 0.02 (1 to 2%).4 Garo et al. calculated that 1% of heat was radiated back to the surface.53 Thermal radiation is always an issue with fires; in the past several models for predicting radiation from hydrocarbon fires were developed.54,55 McCourt et al. reported on the total heat radiated by various fires.56 Alaska North Slope oil showed a heat release rate of 176 KW/m2, diesel fuel 230 KW/m2, and propane, 70 KW/m2. The heat radiated by a liquid propane fire enhanced by air flow and increased pressures was 180 KW/m2. The heat flux on booms as a result of these fires was reported as 140 to 250 KW/m2 for crude oils, 120 to 160 KW/m2 for diesel fuel, 60 to 100 KW/m2 for propane, and 100 to 160 KW/ m2 for enhanced propane burning.

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Flame spreading rates have been measured at several fires.4,57 Flame spreading rates do not vary much with fuel type, but do vary significantly with wind, especially as this relates to up and down wind. Flame spreading rates range from 0.01 to 0.02 m/s (0.02 to 0.04 knots). Downwind flame spreading rates range from 0.02 to 0.04 m/s (0.04 to 0.08 knots), and up to 0.16 m/s (0.3 knots) for high winds. Wu et al. measured flame velocities as a function of external heat fluxes and found these to vary from 0.01 to 0.16 m/s (0.02 to 0.3 knots), depending on the heat flux.58,59 Higher heat fluxes yielded high-flame spread rates. Flame velocities did not change when oil was thicker than 8 mm. Fingas et al. measured the flame spread rates in burning several heavy oils and orimulsion and found that the rate was an average of 0.045 m/sec.57 These rates ranged from 0.003 to 0.14 m/sec. It should be noted that all these rates are for fires on the ground and not through vapor clouds. It has been noted that, at spills of gasoline in hot climates, fires have been noted to spread through vapor clouds as fast as 100 km/hour. This is typical of flame spread through vapor clouds. Flame heights have been measured by several authors.4 While data vary significantly, a rule of thumb could be that the flame height of a small fire less than 10 m in diameter is about twice that of the diameter of the fire. The flame height approaches the diameter of the pool up to about 100 m in diameter. Thus, an estimate of flame height for a fire in a boom with a radius of about 10 to 20 m is about 1.5 times the diameter, or 15 to 30 m. Several workers reported on findings that there is a vigorous burn phase near the end of a burn on water.4 This is caused by increasing heat transfer back to the water surface with decreasing slick thickness. Significant amounts of heat are transferred to water near the end of a burn when slick thickness approaches 1 mm, and this heat ultimately causes the water to boil. The boiling injects steam and oil into the flame, giving rise to a “vigorous” burn with the production of steam. This phenomenon occurs only in shallow test-tanks because there is little movement of water under the slick to carry the heat away. During the NOBE burn at sea, no vigorous burning was observed, and thermocouple measurements in the water showed no increase in the water temperature.60 This is due to two factors: the movement of the slick over the water and the vast amount of water under the burn. Thus, the phenomenon of the rapid or vigorous burn phase is not relevant to the at-sea situation. Some workers have studied a related phenomenon, sometimes known as boil-over, which occurs when water is entrained in the oil during combustion.61,62 Boilover typically occurs when a fuel layer is thin and is on a water layer. Heat transfer from the boiling liquid and/or flame can heat the water to boiling. When this occurs, the burning fuel is ejected and the turbulence of the fire is increased. Ferrero et al. studied this phenomenon with gasoline and diesel fuel and found that it occurs only with diesel fuel. A related phenomenon is when water is entrained in the fuel layer. The entrained water droplets will explode if rapidly heating, thus causing what appears to be rapid boiling or even more

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violent behavior. This can occur with many oils, but particularly with emulsified oils. Several parties have studied the dynamics of burning and observed the above burn behaviors.58,59,62-67 Pilewskie and Valero measured the radiative effect of the Kuwait oil fires at a point about 100 km downwind of the fires.68 They found that the smoke plume absorbed about 78% of the solar radiation and that about 8% was transmitted to the land surface. The smoke reached a maximum height of 4.5 km, with little penetrating the stratosphere, which indicates that self-lofting did not occur. Self-lofting is a phenomenon that may occur if a plume maintains or increases its buoyancy as a result of heat absorption from the sun. Table 23.1 summarizes the burnability of several types of oils. The history of the science of in-situ burning is filled with interesting theories and suppositions. There are several reviews on older theories.4,71 In summary, much of the older data may be irrelevant to burning per se, simply because newer studies have shown many of the factors or possible burn parameters to be less important than was once thought.

23.2.2. Summary of In-Situ Burning Research and Trials The first reference in the literature to the burning of oil on water was the use of a log boom to burn oil on the Mackenzie River in 1958.72 Failed attempts to ignite the oil spilled from the Torrey Canyon in 1968 were widely known.73 Extensive research on in-situ burning of oil spills began in the late 1970s and was carried out in North America by Environment Canada, the U.S. Coast Guard (USCG), the U.S. Minerals Management Service (USMMS), and the U.S. National Institute of Standards and Technology (NIST). Over the years, research into in-situ burning has included laboratory-, tank-, and full-scale test burns. In the late 1970s several burn tests and studies were carried out in Canada by a consortium of government and industry agencies. Figure 23.1 shows that oil resurfaced on ice, and Figure 23.2 shows the Beaufort Sea Burn carried out in 1975. Some tests in the early 1980s were performed by ABSORB (now Alaska Clean Seas) and USMMS to evaluate the burning of oil in ice-covered areas. This research covered environmental and oil conditions such as sea state, wind velocities, air and water temperatures, ice coverage, oil type, slick thickness, and degree of oil weathering and emulsification.74 Several tests have also been performed in an oil spill test-tank at the USMMS OHMSETT Facility in New Jersey. Since the early 1990s, several meso-scale burns have been performed at the USCG Fire and Safety Detachment in Mobile, Alabama. Figure 23.3 shows one of the burns at Mobile. Table 23.2 lists some of the tests and burns since the first recorded use of oil spill burning on water. The largest and most extensive offshore test burn took place off the coast of Newfoundland, Canada in August 1993.60,75-79 The Newfoundland Offshore

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TABLE 23.1 Burning Properties of Various Fuels Ease of Ignition

Flame Spread

Burning Rate (mm/min)

Sootiness of Flame

Efficiency Range (%)

Reference (s)

Gasoline

very high

very easy

rapid - through vapours

3.5

medium

95-99

69,70

Diesel Fuel

high

easy

moderate

2.9

very high

90-98

6,69

Light Crude

high

easy

moderate

3.5

high

85-98

69

Medium Crude

moderate

easy

moderate

3.5

medium

80-95

69

Heavy Crude

moderate

medium

moderate

3

medium

75-90

69

Weathered Crude

low

difficult, add primer

slow

2.8

low

50-90

69

Light Fuel Oil

low

difficult, add primer

slow

2.5

low

50-80

69

Heavy Fuel Oil

very low

difficult, add primer

slow

2.2

low

40-70

69

Lube Oil

very low

difficult, add primer

slow

2

medium

40-60

69

Waste Oil

low

difficult, add primer

slow

2

medium

30-60

69

Emulsified Oil

low

difficult, add primer

slow

1 to 2

low

30-60

69

In-Situ Burning

Burnability

PART | VII

Fuel

Chapter | 23 An Overview of In-Situ Burning

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FIGURE 23.1 Oil that has resurfaced from an under-ice experiment in Balaena Bay, Beaufort Sea, Canada. The oil was released under the ice in 1974 and resurfaced through first-year ice in 1975.

Burn Experiment (NOBE) involved 25 agencies from Canada and the United States. Two 50,000 L batches of oil were released and burned within a fireresistant boom. During this test, more than 2000 parameters were evaluated using various sampling methods. Figures 23.4 and 23.5 show the NOBE burn. The major findings were that all emission and pollutant levels measured 150 m away from the burn were below health concern levels and that at 500 m from the burn, these levels were difficult to detect. In many cases, pollutants in the

FIGURE 23.2 Burning of the oil on the ice as shown in Figure 23.1.

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FIGURE 23.3 A view of one of the test burns at the USCG facility at Mobile, Alabama, in 1991. Diesel fuel is being burned here as witnessed by the heavy, black smoke plume. There are many instruments measuring emissions under the smoke plume.

smoke plume were less than detected in the original unburned oil. The results also showed that the emission levels from this large burn were lower than found during the mesoscale burns. A test of emissions from fires were carried out by a consortium of industry and government agencies at a test facility in Calgary Alberta.80 Figure 23.6 shows one of these test burns. Tests of various aspects of burning were conducted at the USCG facility in Mobile Bay, Alabama in 1991, 1992, and 1994. More than 35 burns were conducted using crude oil and diesel fuel. Physical parameters were measured as well as emission data. Fireboom test evaluations using diesel fuel were conducted in 1997 and 1998 by the NIST and sponsored by the USCG Research and Development Center and the USMMS.81,82 Five booms were evaluated in 1997 and six in 1998. The test evaluations were conducted in a wave tank designed specifically for evaluating fire-resistant containment booms located at the USCG Fire and Safety Test Detachment facility in Mobile Bay, Alabama. The wave tank was designed to accommodate a nominal 15-m boom section, forming a circle approximately 5 m in diameter. Figure 23.7 shows a boom undergoing a fire test, and Figure 23.8 depicts a boom under the influence of waves, without fire present. The test cycle consisted of three one-hour burning periods with two one-hour cool-down periods between the burning periods, in accordance with the draft American Society of Testing and Materials (ASTM) F-20 Committee standard.83 Four of the six booms evaluated in 1998 were shipped to the OHMSETT facility for post-burn oil containment and tow tests based on

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Chapter | 23 An Overview of In-Situ Burning

TABLE 23.2 Summary of Burns or Tests Year

Country

Location/Incident

Description

1958

Canada

Mackenzie River, NWT

First recorded use of in-situ burning, on river using log booms

1967

Britain

TORREY CANYON

Cargo tanks difficult to ignite with military devices

1969

HOLLAND Series of experiments

Igniter KONTAX tested, many slicks burned

1970

Canada

ARROW

Limited success burning in confined pools

1970

SWEDEN

OTHELLO/KATELYSIA

Oil burned among ice and in pools

1970

Canada

Deception Bay

Oil burned among ice and in pools

1973

Canada

Rimouskidexperiment

Several burns of various oils on mud flats

1975

Canada

Balaena Baydexperiment Multiple slicks from underice oil ignited

1976

U.S.A.

ARGO MERCHANT

Tried to ignite thin slicks at sea

1976

Canada

Yellowknifedexperiment

Parameters controlling burning not oil type alone

1978-82 Canada

Series of experiments

Studied many parameters of burning

1979

MidAtlantic

ATLANTIC EMPRESS/ AEGEAN CAPTAIN

Uncontained oil burned at sea after accident

1979

Canada

IMPERIAL ST. CLAIR

Burned oil in ice conditions

1980

Canada

McKinley Baydexperiment

Several tests involving igniters, different thicknesses

1981

Canada

McKinley Baydexperiment

Tried to ignite emulsions

1983

Canada

EDGAR JORDAIN

Vessel containing fuels and nearby fuel ignited

1983

U.S.A.

Beaufort Seadexperiment Oil burned in frazil ice

1984

Canada

series of experiments

1984-5

U.S.A.

Beaufort Seadexperiment Burning with various ice coverages tested

1984-6

U.S.A.

OHMSETTdexperiments

Tested the burning of uncontained slicks

Oil burned among ice but not with high water content Ice concentration not important, Emulsions don’t burn

(Continued )

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TABLE 23.2 Summary of Burns or Testsdcont’d Year

Country

Location/Incident

Description

1985

Canada

Offshore Atlanticdexperiment

Oil among ice burned after physical experiment

1985

Canada

EssodCalgaryd experiments

Several slicks in ice leads burned

1986

Canada

Ottawadexperiments/ analysis

Analyzed residue and soot from several burns

1986

U.S.A.

Seattle and Deadhorsedexperiments

Test of the Helitorch and other igniters

1986-91 U.S.A.

NISTdexperiments

Many lab-scale experiments

1986-91 Canada

Ottawadanalysis on above

Analyzed residue and soot from several burns

1989

U.S.A.

EXXON VALDEZ

Test burn performed using a fire-proof boom

1991

U.S.A.

First set of Mobile experiments

Several test burns in newly-constructed pan

1992

U.S.A.

Second set of Mobile burns

Several test burns in pan

1992

Canada

Several test burns in Calgary

Emissions measured and Ferrocene tested

1993

Canada

Newfoundland Offshore burn

Successful burn on full scale off shore

1994

U.S.A.

Third set of Mobile burns

Large scale diesel burns to test sampler

1994

U.S.A.

North Slope burns

Large scale burn to measure smoke

1994

Norway

Series of Spitzbergen burns

Large scale burns of crude and emulsions

1994

Norway

Series of Spitzbergen burns

Try of uncontained burn

1996

Britain

Burn test

First containment burn test in Britain

1996

U.S.A.

Test burns in Alaska

Igniters and boom tested

1997

U.S.A.

Fourth set of mobile burns Small scale diesel burns to test booms

1997

U.S.A.

North Slope tank tests

Conducted several tests on waves/ burning

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Chapter | 23 An Overview of In-Situ Burning

TABLE 23.2 Summary of Burns or Testsdcont’d Year

Country

Location/Incident

Description

1998

U.S.A.

Fifth set of mobile burns

Small scale diesel burns to test booms

2001

U.S.A.

Boom tests in OHMSETT

Small scale propane tests of test booms

2002

U.S.A.

Small scale tests in Alaska Tested burning in frazil and brash ice

2003

Canada

Small scale tests on heavy Tested procedures to burn heavy and oils emulsified fuels

2004

Canada

Small scale tests on heavy Tested procedures to burn heavy and oils emulsified fuels

2008

Svalbard, Norway

Burns in ice

Tested burning in frazil and brash ice

ASTM suggestions. In general, there was some degradation of materials in all of the booms. More tests were conducted in 1996 and 1997 by S.L. Ross Environmental Research Ltd., sponsored by the USMMS and the Canadian Coast Guard.33,34 These tests evaluated firebooms using propane rather than the smoke-producing fuels such as diesel or crude oil. The propane test evaluations were conducted in

FIGURE 23.4 A distant view of the Newfoundland Oil Burn Experiment (NOBE) in 1991. Most of the vessels behind the burn are associated with emission measurements.

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FIGURE 23.5 A closer view of the burn at NOBE. The three-point boom tow is partly visible. The helicopter is used for observation and filming.

a wave tank located at the Canadian Hydraulic Centre, National Research Council of Canada in Ottawa. The heat flux measured in the 1997 tests with airenhanced propane was comparable to fluxes measured in the diesel fuel fires. Two separate fireboom test evaluations using air-enhanced propane were conducted in the fall of 1998 by MAR, Inc. and S.L. Ross Environmental Research Ltd.56,84 Both tests were conducted at the OHMSETT facility in Leonardo, New Jersey. The first test was sponsored by the USMMS and the U.S. Navy Supervisor of Salvage (SUPSALV). Three candidate fire protection systems were tested and evaluated. Each consisted of a water-cooled blanket designed to be draped over existing oil boom to protect its exposure to an in-situ oil fire. In the second fireboom evaluation, a prototype stainless steel PocketBoom was tested and evaluated using the air-enhanced propane system. The PocketBoom was a redesign of the Dome boom originally developed for use in Arctic seas. Liquid propane from a storage tank was heated to create gaseous propane and piped to an underwater bubbling system. The test protocol was similar to the ASTM draft method noted above. The booms generally survived the tests and showed less degradation than previous models of the same booms.

23.2.3. How Burns at Sea Are Conducted Several burn guidance documents have appeared in the past 10 years.85-88 This subsection attempts to combine all the points made in the past few years as far as operational knowledge on in-situ burning is concerned.

Chapter | 23 An Overview of In-Situ Burning

751 FIGURE 23.6 A burn test conducted in 1990 in Calgary to run preliminary emission studies. A sampling package was suspended by crane into the smoke plume. The crane boom is visible in the middle foreground. Sample stations, covered in foil, are also visible downwind of the fire.

There are several distinct steps involved in burning oil spills at sea, all of which are discussed in detail in this book. The basic steps are summarized in Figure 23.9. When an oil spill occurs, the situation is examined and analyzed for possible countermeasures. The type of oil, its thickness, and its state at the time burning could be applied are reviewed. The questions to be asked before deciding to use in-situ burning at a particular spill situation are outlined later. If burning is possible and the response organization is prepared for burning, planning will then begin. A plan is formulated using preestablished scenarios, checklists, and safety procedures. In most cases, containment will be required either because the slick is already too thin to ignite or will be too thin within hours. Personnel and equipment are then transported to the site. In most cases, a fire-resistant boom is deployed downwind of the spill and a tow is begun. When the oil collected in the boom is thick enough, it is ignited using an igniter. The boom tow is resumed and continued until the fire is extinguished or the tow is stopped for operational reasons. The burning and progress of the tow are monitored by personnel on aircraft or on a larger ship from which an overview

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FIGURE 23.7 A stainless steel boom undergoing fire tests at Mobile, Alabama. Note that this boom is leaking a considerable amount of oil.

FIGURE 23.8 A fire-resistant boom being tested at Mobile, Alabama. The boom is currently undergoing a cool-down period under waves with no fire present.

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Oil spill occurs In-situ burning chosen as response option Obtain regulatory approvals Notify public Select personnel

! containment booms (if required) ! ignition devices

Select equipment

! treating agents (if required) ! support vessels/aircraft

Implement equipment deployment plans

! monitoring, sampling, analytical devices

Implement health and safety Brief all personnel on deployment and health and safety plans Choose exact time and location for in-situ burning Transport equipment and personnel to burn site Deploy containment boom (if required) Ignite slick Conduct and monitor burn operation Terminate in-situ burn Recover residue (if required) Assess burn and report results FIGURE 23.9 Steps in in-situ burning.

of the slick and conditions is possible. The monitoring crew can also direct the boom tow vessels to slick concentrations upwind. During the burn, monitoring normally includes estimating the area of oil burning at specific time intervals so that the total amount burned can be estimated. The amount of residue is

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similarly estimated. Particulate matter downwind might be monitored to record the possible exposure levels. The burn could be stopped in an emergency by releasing one end of the boom tow or by speeding up the tow so that oil is submerged under the water. If the burning stops because there is not enough oil in the boom, the tow can be resumed going downwind and then turning around into the wind before reigniting. After the burn operation is finished, for the day or for the single burn, the burn residue must be removed from the boom. As the burn residue is very viscous, a heavy-oil skimmer may be required if there is a large amount of material. A small amount of residue can be removed by hand using shovels or sorbents. During the cleanup of the Exxon Valdez spill in 1989, 137 m of boom and 152-m-long tow lines were used in a U-configuration to concentrate several patches of slightly emulsified oil. An estimated 57,000 to 114,000 L of oil were collected. The collected oil was then towed to an area away from the surrounding slick and set on fire by igniting a small plastic bag of gelled gasoline and throwing it toward the slick from one of the tow boats. Figure 23.10 shows this burn, which took place at night. During the burn, the fire’s intensity was controlled by adjusting the speed of the tow vessels. Slowing down the tow speed increased the size of the burn area and moved it toward the opening of the U. Increasing the tow speed increased the concentration of the oil in the apex of the boom. The burn lasted 1 hour and 15 minutes, with the most intense part of the burn lasting about 45 minutes. The residue from the burn was a thick tarlike material that was easily recovered. The

FIGURE 23.10 A controlled burn during the Exxon Valdez spill. About 50,000 L of oil was pulled away from the main oil slick and burned in a fire-resistant boom.

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755

total volume of residue was approximately 1,100 L, resulting in an estimated burn efficiency of greater than 98%.44 Oil can also sometimes be burned without containment and by using natural containment features such as oceanic fronts, ice, or shorelines to contain oil. Details on the use of booms and other techniques are provided below.

23.2.4. Advantages and Disadvantages In-situ burning has some distinct advantages over other spill cleanup methods. These advantages include: l l l l l

Rapid removal of large amounts of oil from the water surface Significantly reduced volume of oil requiring disposal High efficiency rates Less equipment and labor required May be only cleanup option in some situations, for example, oil-in-ice conditions89

The most significant of these advantages is the capacity to rapidly remove large amounts of oil. When used at the right time, that is, early in the spill before the oil weathers and loses its flammable components, and under the right conditions, in-situ burning can be very effective at rapidly eliminating large amounts of spilled oil, especially from water. This can prevent oil from spreading to other areas and contaminating shorelines and biota. Compared to mechanical skimming of oil, which generates a large quantity of oil and water that must be stored, transferred, and disposed of, burning generates a small amount of burn residue. This residue is relatively easy to recover and can be further reduced by repeated burns. Although the efficiency of a burn varies with a number of physical factors, removal efficiencies are generally much greater than those for other response methods such as skimming and the use of chemical dispersants. During the NOBE conducted off the coast of Newfoundland in 1993, efficiency rates of 98 and 99% were achieved. Figure 23.11 shows the small amount of residue remaining after the first burn. In ideal circumstances, in-situ burning requires less equipment and labor than other techniques. It can be applied in remote areas where other methods cannot be used because of distances and lack of infrastructure. Often not enough of these resources is available when large spills occur. Burning is relatively inexpensive in terms of equipment needed and actually conducting the burn operations. In-situ burning also has disadvantages, some of which are the following: l

l l

Large black smoke plume created and public concern about toxic emissions to the air and water Limited time frame in which the oil can be ignited Oil must be a minimum thickness in order to ignite and burn and must usually be contained to achieve this thickness

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FIGURE 23.11 The remaining oil after burning 50 tons of crude oil during NOBE. This amount is estimated to be less than 1% of the starting oil. l l

Risk of fire spreading to other combustible materials Burn residue must be disposed of89

The most obvious disadvantage of burning oil is the large black smoke plume that is produced and public concern about emissions. Figure 23.12 shows one such large plume. Extensive studies have recently been conducted to measure and analyze these emissions. The results of these studies are discussed below. The second disadvantage is that the oil will not ignite and burn unless conditionsdsuch as thicknessdare right. Most oils spread rapidly on water, and the slick quickly becomes too thin for burning to be feasible. Fire-resistant booms can be used to concentrate the oil into thicker slicks so that the oil can be burned. While this obviously requires equipment, personnel, and time, concentrating oil for burning requires less equipment than collecting oil with skimmers. And finally, burning oil is sometimes not viewed as an appealing alternative to collecting the oil and reprocessing it for reuse. It must be pointed out, however, that recovered oil is usually incinerated as it often contains too many contaminants to be economically reused. Furthermore, reprocessing facilities are not readily accessible in most parts of the world.

23.2.5. Comparison of Burning to Other Response Measures In-situ burning is most often compared with the use of dispersants as a countermeasure. Dispersants are chemical spill-treating agents that promote the formation of small droplets of oil that ‘disperse’ throughout the water column. Dispersants contain surfactants, chemicals like those in soaps and detergents,

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757

FIGURE 23.12 The smoke plume from the second NOBE burn. Analysis of the plume material shows that it is about 0.5% of the amount of oil burned by weight and that over 90% of the material is carbon.

that have both a water-soluble and an oil-soluble component. Surfactants or surfactant mixtures used in dispersants have approximately the same solubility in oil and water, which stabilizes oil droplets in water so that the oil will disperse into the water column. This could be helpful when an oil slick is threatening a bird colony or a particularly sensitive shoreline. Two major issues associated with the use of dispersantsdthe toxicity of the resulting oil dispersion in the water column and their effectivenessdhave generated controversy in the last 30 years. The toxicity associated with dispersant use relates to the toxicity of the dispersed oil as well as the additional toxicity caused by the dispersion. In shallow or confined waters, dispersed oil could be toxic to aquatic life. For this reason, dispersants are not used close to shore. Special permission is necessary in most countries to use dispersants. Effectiveness is influenced by many factors, including the composition and degree of weathering of the oil, the amount and type of dispersant applied, sea energy, salinity of the water, and water temperature. The composition of the oil is the most important of these factors, followed closely by sea energy and the amount of dispersant applied. Dispersion is not likely to occur when oil has spread to thin sheens so that the oil in thinner portions of the spill will not disperse when dispersants are applied. Further chemical dispersions do not last long. Significant amounts of oil resurface with time. A chemical dispersion half-life may be as short as 12 hours.

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A significant disadvantage of dispersants is that either they do not work at all or they do not work well on weathered oil, emulsified oils, heavy oils, and thin sheens. Dispersants work best on light crude oils and not at all on residual oils. There is a narrow window of opportunity after a spill during which dispersants can be applied, which can be as short as a few hours or a day. After a period of time, the oil becomes too weathered or emulsified with water. In-situ burning is also compared to mechanical recovery of oil spills. In open waters, burning has advantages over mechanical recovery. Mechanical recovery includes the use of booms and skimmers to physically contain the oil and remove it from the water. Booms are limited to waters where the currents, relative to the boom, are less than 0.4 m/s, or they must be used in diversionary mode. On the other hand, while recovery using booms and skimmers is slower than removal by in-situ burning or dispersants, the oil is recovered without the potential for air and water pollution. Mechanical recovery works well in sheltered waters such as harbors and marinas where burning should not be conducted, but is impossible in high currents and waves over 2 m. On land, burning has significant advantages over most techniques. Unless the oil is very thick, pumping is very limited. Any process that takes a lot of time will allow oil to penetrate the soil. In some marine spill situations, the best cleanup strategy involves a combination of mechanical recovery techniques and burning for various portions of a spill. For example, burning can be applied in open water, and oil that has already moved closer to shore can be recovered with booms and skimmers. Burning could also be used on open water after the window of opportunity closes for effective use of dispersants. Burning does not preclude the use of other countermeasures on other parts of the slick. When combining different cleanup techniques, the objective should be to find the optimal mix of equipment, personnel, and techniques that results in the least environmental impact of the spill.

23.3. ASSESSMENT OF FEASIBILITY OF BURNING 23.3.1. Burn Evaluation Process When an oil spill occurs, information must be obtained on the spill location, weather conditions, and any other relevant conditions at the site. The necessary questions to be asked before deciding to use in-situ burning are outlined in Figure 23.13. A more detailed Burn Evaluation Sheet, which also includes information on response equipment, is provided in Table 23.3.

23.3.2. Areas Where Burning May Be Prohibited Burning may be prohibited within a specified distance of human habitation, for example, within 1 km and within a specified distance of the shoreline, of

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759

FIGURE 23.13 Decision flowchart for in-situ burning.

petroleum-loading, production, or exploration facilities; or of a nature preserve, bird colony, or national or state/provincial parks. Burning may also be prohibited over a marine park or preservation area and over areas designated as military target areas or former areas of munitions dumping.

760

PART | VII

In-Situ Burning

TABLE 23.3 In-Situ Burn Evaluation Sheet Form completed by ___________________________Date ___________ Time ________ Name of incident (e.g., tanker, platform, or location name) __________________________ Date of incident __________________Time of incident ___________________ Type of incident:

tanker grounding ___ tanker transfer ___

tanker collision ___

tanker explosion ___ blow out ___ other ____________________ Spill location:

latitude _______________longitude __________________

Type of product released ____________________________________________ Estimated volume of product released ____________________ Estimated area covered by the slick ________________ Is source still releasing product?: yes ___ If yes, at what estimated flowrate ____

no ___

Is source and/or slick burning on its own?:

yes ___

no ___

Condition of the oil Current

24-hour forecast 48-hour forecast

date and time thickness range emulsification (% of slick and water content) weathering (%) type of slick (check one) one large slick large patches several small patches thin strips other Description of estimated trajectory of spill (also attach maps showing current, 24-hour and 48-hour estimated positions) ___________________________________________________________________________ ___________________________________________________________________________

761

Chapter | 23 An Overview of In-Situ Burning

TABLE 23.3 In-Situ Burn Evaluation Sheetdcont’d ________________________________________________________ Location of nearest land to the spill site _________________________________________ Distance from spill site _________ Location of land area(s) expected to be oiled by slick within the first 48 hours after spill incident Distance from spill

Est. date and time of oiling

____________________________

Location

_______________

___________________

____________________________

_______________

___________________

____________________________

_______________

___________________

____________________________

_______________

___________________

Name and location of communities near the spill site [within 100 km (60 miles)] Name of community

Location

______________________

_____________________ _______________

Distance from spill

______________________

_____________________ _______________

______________________

_____________________ _______________

______________________

_____________________ _______________

______________________

_____________________ _______________

Name and location of inhabited sites near the spill site [within 100 km (60 miles)] Name of inhabited site

Location

______________________

_____________________ _______________

Distance from spill

______________________

_____________________ _______________

______________________

_____________________ _______________

______________________

_____________________ _______________

Location and type of environmentally sensitive area(s)/population(s) [within 100 km (60 miles)] Type of area or population Location Distance from spill ______________________

_____________________ _______________

______________________

_____________________ _______________

______________________

_____________________ _______________

______________________

_____________________ _______________

______________________

_____________________ _______________

Location and type of other areas that could be effected (e.g., parks, archeological sites, anthropogenic structures) [within 100 km (60 miles)] Type of area

Location

______________________

_____________________ _______________

Distance from spill

______________________

_____________________ _______________

______________________

_____________________ _______________

(Continued )

762

PART | VII

In-Situ Burning

TABLE 23.3 In-Situ Burn Evaluation Sheetdcont’d Weather and sea conditions Current

24-hour forecast 48-hour forecast

date and time air temperature water temperature wind speed wind direction skies (check those that apply): clear partially cloudy overcast rain fog storm tide (check one) slack incoming outgoing dominant current speed dominant current direction sea state (check one) calm choppy swell waves (check one) < 0.3 m (1 ft) 0.3 - 1 m (1 to 3 ft) > 1 m (3 ft) Tidal projection Next high tide at _____________ (date) ___________ (time) Next low tide at _____________ (date) ___________ (time) Location of nearest oil spill response equipment depot Location __________________________Distance from spill ________________

763

Chapter | 23 An Overview of In-Situ Burning

TABLE 23.3 In-Situ Burn Evaluation Sheetdcont’d Location of specific response equipment (indicate if specific equipment will not be required) Equipment

Description and number required

Location

Time required for deployment

vessels remote sensing aircraft helicopters tug boats fire-resistant boom conventional boom igniters skimmers sorbent

23.3.3. Regulatory Approvals The regulatory approvals required for in-situ burning vary among different jurisdictions. In general, the legal constraints and liabilities associated with insitu burning are not well defined. The situation is aggravated by the fact that the public is reluctant to accept regulations that allow any kind of burning. The public must be provided with information about the issues associated with insitu burning in order to accept regulations allowing it. This information must include a comparison of the risks of burning with the risks associated with other cleanup options and the results of simply leaving the spilled oil and not treating it at all.90 In general, regulatory agencies are most concerned with how the burn will affect air quality.90 Most jurisdictions stipulate air quality levels that cannot be exceeded no matter what is being burned. Some jurisdictions have modified the air quality limits for special cases, such as in-situ burning of oil during an emergency. When using in-situ burning on the open ocean, international laws governing activities at sea must be observed, particularly the 1996 Protocol to the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other

764

PART | VII

In-Situ Burning

Matter, 1972, referred to as the 1996 Protocol to the London Convention. Several countries have signed this Convention, including Canada and the United States, which means that they must incorporate the terms of the 1996 Protocol into their domestic law. In Canada, these laws are incorporated into the Canadian Environmental Protection Act (CEPA). In the United States, they are being incorporated into new acts promulgated by the Environmental Protection Agency (U.S. EPA). It is recommended that anyone involved in the decision-making process associated with in-situ burning should obtain legal advice on how the terms of the Protocol should be applied and how these terms affect in-situ burning in their particular situation(s) and jurisdiction. General observations on how the Protocol relates to in-situ burning are outlined here. Article 5 of the 1996 Protocol prohibits “incineration at sea.” In Article 1, Section 5 incineration at sea is defined as the combustion on board vessels, aircraft, platforms or other man-made structures of wastes or other matter for the purpose of their deliberate disposal by thermal destruction. “Incineration at sea” does not include the incineration of wastes or other matter on board vessel, aircraft, platform or other man-made structure at sea if such wastes or other matter were generated during the normal operation of that vessel, platform or other man-made structure at sea.

Based on this definition, in-situ burning of an oil slick on water would not be considered incineration because the oil is not “on board a vessel, aircraft, platform or other man-made structure.” However, other methods related to insitu burning as discussed in some sections of this chapter would be considered incineration at sea under the first part of this definition. An example would be lifting oil from the water using a partially submerged barge and then burning the oil. On the other hand, it could be argued that if a vessel was designed specifically to lift the oil from the water and burn it on board the vessel, it could be interpreted as the “normal operation of that vessel” as defined in the second part of the definition and therefore not considered to be incineration. Regardless of whether burning spilled oil is considered incineration at sea, in Article 8, Section 1 of the Protocol, the prohibition on incineration is lifted when it is necessary to secure the safety of human life or of vessels, aircraft, platforms or other man-made structures at sea . . . if dumping (incineration) appears to be the only way of averting the threat and if there is every probability that damage consequent upon such dumping will be less than would otherwise occur. Such dumping (incineration) shall be conducted so as to minimize the likelihood of damage to human or marine life and shall be reported forthwith to the Organization (International Maritime Organization).

It could be argued that these conditions apply in many spill situations. In addition, under Article 8.2 of the Protocol, an emergency permit can be issued

Chapter | 23 An Overview of In-Situ Burning

765

for incineration at sea “in emergencies posing an unacceptable threat to human health, safety or the marine environment and admitting of no other feasible solution. In the United States, ocean disposal/incineration permits are issued by the EPA. Environment Canada issues these permits for use in Canada.

23.3.4. Environmental and Health Concerns The primary environmental and health concern related to in-situ burning is the emissions produced by the fire. The measurement of emissions and calculations using equations developed from emission data have revealed several facts about the quantity, fate, and behavior of the basic emissions from burning. Overall, emissions are now understood to the extent that emission levels and safe distances downwind can be calculated for fires of various sizes and types. A typical crude oil burn (500 m2) would not exceed health limits for emissions beyond about 500 m from the fire. The emissions produced by in-situ burns are discussed below. People and the environment can be protected by ensuring that the burn is kept the minimum distance away from populated and sensitive areas. Procedures for calculating these safe distances are given later in this chapter as well.

23.3.4.1. Safety of Response Personnel During in-situ burn operations, all response personnel must be fully trained in the operational and health and safety procedures associated with any equipment or operation being used. Personnel involved in the planning stage of the operation and for the deployment of vessels, barriers, and ignition devices must also be well trained. General health and safety guidelines are discussed below. These guidelines should be used to develop site-specific plans once it has been decided that in-situ burning will take place. 23.3.4.2. Public Health In general, depending on weather conditions, in-situ burning should not be carried out within 1 km of heavily populated areas. Weather conditions to be considered include the presence or absence of an inversion and the wind direction. According to monitoring of oil fires done up until 1994, groundlevel emissions from crude oil fires have never exceeded 25% of established human health concern levels more than 1 km away from the fire.89 Therefore, if no significant air turbulence or ground-level atmospheric inversions occur, burning can be conducted close to populated areas. In sparsely populated areas, it may be best to evacuate residents close to the burn site. Methods are now available for calculating emission concentrations and safe distances downwind from in-situ oil burns, and these are summarized below.

766

PART | VII

In-Situ Burning

23.3.4.3 Air Quality The major barrier to acceptance of in-situ burning of oil spills is the lack of understanding of the resulting combustion products and the belief that it is just transferring pollution to the sky. It should be noted that emissions from oil fires are much smaller than typical emissions from other types of burning, for example, biomass burning.91 Several types of emissions are formed and released when oil is burned. The atmospheric emissions of concern include the smoke plume, particulate matter precipitating from the smoke plume, combustion gases, unburned hydrocarbons, organic compounds produced during the burning process, and the oil residue left at the burn site. Although consisting largely of carbon particles, soot particles contain a variety of absorbed and adsorbed chemicals. Complete analysis of the emissions from a burn has involved measuring all these components. The emphasis in sampling has been on air emissions at ground level as these are the primary human health concern and the regulated value. This section will focus on these emissions. The monitoring of emissions conducted at past burns was as comprehensive as possible, and the best field samplers and instrumentation available at the time were used (Figures 23.14 and 23.15). Measurement techniques have progressed over the years, however, and continue to improve. In addition, the data from these burns are so extensive that not even encapsulating

FIGURE 23.14 A sampling station for emissions at Mobile, Alabama in 1997. This station was set up, and analysis was carried out as a joint venture between Environment Canada and the U.S. Environmental Protection Agency.

Chapter | 23 An Overview of In-Situ Burning

767

FIGURE 23.15 A series of sampling stations set up at Mobile in 1994.

summaries can be provided here. The summarized data appears in the References section of this chapter, and qualitative statements about that data will be made here. The smoke from fires might be considered as toxins themselvesdas a bulk group. Neviaser and Gann calculated that the LC50 value for smoke to rats is 30 g/m3 for a 30-minute exposure to various smokes.92 If the conditions are characterized by poor ventilation, a value of LC50 of 15 g/m3 is suggested. Extensive measurement of burn emissions began in 1991 with several burns conducted in Mobile, Alabama to measure various physical facets of oil burning.93 Analysis of the data from these burns showed several interesting facts, as well as some gaps in the data. In 1992, two further series of burns were monitored for emissions.80,93 In 1993, two major burns were conducted at sea specifically to measure emissions, although many other measurements were also taken.76-79 Further tests were conducted in 1994 and 1997.93-100 Heavy oil burning emissions tests were carried out in 2003 and 200425,40,57,101 These tests and the number of burns monitored are summarized in Table 23.4. Particulate Matter/SootdAll burns, especially those of diesel fuel, produce an abundance of particulate matter, which is the primary emission from an oil fire that exceeds recommended human health concern levels. Concentrations of particulates in emissions from burning diesel are approximately four times that from similar-sized crude oil burns at the same distance from the fire. Particulate matter is distributed exponentially downwind from

768

TABLE 23.4 Summary of Studies Used to Measure In-Situ Burn Emissions Year

Number of Burns

Number Monitored Oil Type

Prime Purpose

Burn Area Time of Number of Number of Target Range (m2) Burns (min.) Instruments Compounds

Mobile

1991

14

14

Louisiana crude

physics

37 to 231

20 to 60

30

70

Mobile

1992

6

6

Louisiana crude

physics

36 to 231

20 to 60

30

70

Calgary

1992

20

3

crude, diesel

emissions

37

20 to 70

25

40

Newfoundland

1993

2

2

crude (ASMB)

emissions

467 to 600

60 to 90

200

400

Mobile

1994

3

3

diesel

physics

199 to 231

60 to 80

95

400

Mobile

1997

9

8

diesel

boom tests

25

60

95

400

Mobile

1998

12

9

diesel

boom tests

25

60

76

400

Ottawa

2003

8

8

heavy oils, orimulsion

burnability

0.5 to 3

4 to 36

6

200

Ottawa

2004

10

10

heavy oils, orimulsion

burnability

1 to 4

4 to 36

6

200

In-Situ Burning

Note: above values are approximate or rounded-off.

PART | VII

Location

Chapter | 23 An Overview of In-Situ Burning

769

the fire. Concentrations at ground level (1 m) can still be above normal health concern levels (150 mg/m3) as far downwind as 500 m from a small crude oil fire. Of greatest concern are the smaller or respirable particulates. The PM-10 fraction, or particulates less than 10 mm, are generally about 0.7 of the total particulate concentration (TSP) of all particulates measured. The PM-2.5 fraction is currently the subject of particular concern at this time.102 Currently, the fine particles are coming under increasing scrutiny as health problems. Polyaromatic Hydrocarbons (PAHs)dCrude oil burns result in polyaromatic hydrocarbons (PAHs) downwind of the fire, but the concentration on the particulate matter, both in the plume and the particulate precipitation at ground level, is often an order of magnitude less than the concentration of PAHs in the starting oil. This includes the concentration of multiringed PAHs, which are often created in other combustion processes such as low-temperature incinerators and diesel engines. There is a slight increase in the concentration of multiringed PAHs in the burn residue. When considering the mass balance of the burn, however, most of the five- and six-ringed PAHs are destroyed by the fire. When diesel fuel is burned, the emissions show an increase in the concentration of multiringed PAHs in the smoke plume and residue, but a net destruction of PAHs is still found. Volatile Organic Compounds (VOCs)dVolatile organic compounds are organic compounds that have high enough vapor pressures to be gaseous at normal temperatures. When oil is burned, these compounds evaporate and are released. The emission of volatile compounds was measured at several test burns. One-hundred and forty-eight volatile organic compounds have been measured from fires and evaporating slicks. The concentrations of VOCs are relatively low in burns compared to an evaporating slick. Concentrations appear to be below human health levels of concern even very close to the fire. Concentrations appear to be highest at the ground [1 m (3.3 ft)] and are distributed exponentially downwind from the fire source. VOCs, though present, do not constitute a major human or environmental threat. Dioxins and DibenzofuransdDioxins and dibenzofurans are highly toxic compounds often produced by burning chlorine-containing organic material. Particulates precipitated downwind and residue produced from several fires have been analyzed for dioxins and dibenzofurans. These toxic compounds were at background levels at many test fires, indicating no production by either crude or diesel fires. CarbonylsdOil burns produce low amounts of partially oxidized material, sometimes referred to as carbonyls or by their main constituents, aldehydes (formaldehyde, acetaldehyde, etc.) or ketones (acetone, etc.). Carbonyls from crude oil fires are at very low concentrations and are well below health concern levels even close to the fire. Carbonyls from diesel

770

PART | VII

In-Situ Burning

fires are somewhat higher but also below concern levels. The burning of alcohol-containing fuels might result in the release of more carbonyls. Carbon DioxidedCarbon dioxide is the end result of combustion and is found in increased concentrations around a burn. Normal atmospheric levels are about 300 ppm, and levels near a burn can be around 500 ppm, which presents no danger to humans. The three-dimensional distributions of carbon dioxide around a burn have been measured. Concentrations of carbon dioxide are highest at the 1 m level and fall to background levels at the 4 m level. Concentrations at ground level are as high as 10 times that in the plume, and distribution along the ground is broader than for particulates. Carbon MonoxidedCarbon monoxide levels are usually at or below the lowest detection levels of the instruments and thus do not pose any hazard to humans. The gas has only been measured when the burn appears to be inefficient, such as when water is sprayed into the fire. Carbon monoxide appears to be distributed in the same way as carbon dioxide. Sulphur DioxidedSulphur dioxide per se is usually not detected at significant levels or sometimes not even at measurable levels in the area of an in-situ oil burn. Sulphuric acid, or sulphur dioxide that has reacted with water, is detected at fires, and levels, though not of concern, appear to correspond to the sulphur content of the oil. Other GasesdAttempts were made to measure oxides of nitrogen and other fixed gases. None was measured in about 10 experiments. Other CompoundsdThere is a concern when burning crude oil about any “hidden” compounds that might be produced. In one study conducted several years ago, soot and residue samples were extracted and “totally” analyzed in various ways. While the study was not conclusive, no compounds of the several hundred that were identified were of serious environmental concern. The soot analysis revealed that the bulk of the material was carbon and that all other detectable compounds were present on this carbon matrix in abundances of parts-per-million or less. The most frequent compounds identified were aldehydes, ketones, esters, acetates, and acids, which are formed by incomplete oxygenation of the oil. Similar analysis of the residue shows that the same minority compounds are present at about the same levels. The bulk of the residue is unburned oil without some of the volatile components. Lemieux et al. used some of the data from the burns referenced here to calculate emission factors for various compounds.103 Data were calculated from Fingas et al. 1996, 1998; these are summarized in Table 23.5. These authors noted that emissions of PAHs were much higher when polymers were burned rather than oils. 23.3.4.3.1. Calculation of Emission Concentrations Downwind Sufficient data are now available to assemble emission data and correlate the results with spatial and burn parameters. The correlations are summarized in a reference.86 Although many correlations were tried, it was found that

771

Chapter | 23 An Overview of In-Situ Burning

TABLE 23.5 Emissions of Organic Compounds Calculated by Lemieux et al.* Emissions From Pool Fire (mg/kg Burned)

Class of Compound

Compound

Diesel Fuel

Crude Oil

VOC’s

Benzene

1020

250

Toluene

40

Ethylbenzene

10

Xylenes

25

Nonane

13

Ethyltoluenes

22

Formaldehyde

300

140

Acetaldehyde

63

32

Acrolein

39

11

Acetone

35

20

Methylethylketone

13

7

Benzaldehyde

104

44

Isovaleraldehyde

17

5

Methylisobutylketone

11

2,5-dimethlybenzaldehyde

13

Naphthalene

160

44

Acenapthylene

99

4

Acenaphthene

10

Fluorene

1

0.5

1-Methylfluorene

26

0.2

Phenanthrene

13

6

Anthracene

15

1

Fluoranthene

20

4

Pyrene

2

5

Benzo[a,b]fluorine

4

0.3

Benzo[a]anthracene

5

1

Carbonyls

PAHs

(Continued )

772

PART | VII

In-Situ Burning

TABLE 23.5 Emissions of Organic Compounds Calculated by Lemieux et al.*dcont’d

Class of Compound

Emissions From Pool Fire (mg/kg Burned) Compound

Diesel Fuel

Crude Oil

Chrysene

9

1

Benzo[b&k]fluoranthene

7

2

Benzo[a]pyrene

5

1

Indeno[1,2,3-cd]pyrene PCDDs/Fs

HpCDD

7 e-5

OCDD

1.3 e-4

TCDF

2.1 e-4

HxCDF

1.9 e-5

Total PCDD/F

4.3 e-4

*Values have generally been rounded off to 2 or 3 significant figures.103

atmospheric emissions correlated relatively well with distance from the fire and the area covered by the fire. This information was used to develop prediction equations for each pollutant, using the data gathered from the 30 test burns conducted to date. Sufficient data were available to calculate equations for over 150 individual compounds and for all the major groups. In some cases, however, the data are insufficient to yield high-correlation coefficients and low errors. These correlations will significantly increase understanding of in-situ burning in the areas of assessing the importance of specific emissions and classes, predicting a “safe” distance for burning, and predicting concentrations at a given point from the fire. These predictions are based solely on actual data and therefore may be more accurate than theoretical-based predictions. This increased accuracy applies to situations where the conditions are the same as those under which the emissions data were collected. The data were collected with winds between 2 and 5 m/s (4 to 10 knots) and with no inversions present. Table 23.6 gives the prediction equations for several common emission groupings and specific compounds, and Table 23.7 for diesel fuel. These data were then used to calculate the difference between the regulated level (typically the time-weighted average recommended exposure to a substance) and the calculated amount of the substance for several burns.

Distance From Fire Taken at 300 m Values When Burn Area Taken as 200 m2

Equations to Calculate Equation Parameters

Substance

Concentration (mg/m3)

% of Limit

Safe Distance (m)

Total particulates

<0

<0

60

0.2

12.7

0.03

4.79

PM-10

<0

<0

60

0.15

12.7

0.03

4.79

PM-2.5

<0

<0

60

0.04

12.7

0.03

4.79

Total VOCs

6

3

210

161,990.6

PAHs

0

22

90

188.4

Fixed Gases

160

1

0

10,120

Carbonyls

0

0

0

630

Normal Threshold Limit (mg/m3)

a

b

c

Chapter | 23 An Overview of In-Situ Burning

TABLE 23.6 Emission Calculations and Values for Crude Oil Burns

Equations

Conc. ¼ a þ b)size c)ln(distance) Concentration is mg/m3 for particulates Concentration is mg/m3 for gases and organics size is area of fire in m2 distance is distance from edge of fire in m.

773 (Continued )

TABLE 23.6 Emission Calculations and Values for Crude Oil Burnse(cont’d) 774

Calculated Values Summations of Organic Chemicals and Gases (mg/m3)

(mg/m3)

(mg/m3)

Burn Area Taken as 2

2

2

Fixed Gases

200 m

400 m

800 m

Sulphur Dioxide

0

0

11

Carbon Dioxide

160

264

474

Carbon Monoxide

0

0

Acetaldehyde

0

Acetone Formaldehyde

(mg/m3)

Equations to Calculate

Normal Threshold Limit (mmg/m3)

Equation Parameters a

b

c

20

19.4

0.03

5.29

10,000

520

0.52

81.5

0

100

7.72

0

1.56

0

42

200

23.3

0.12

12.9

0

0

18

170

11.3

0.04

5.11

0

0

26

260

58.4

0.1

20.1

1-Methylnaphthalene

0

1

2

20

1.01

0

0.38

1-Methylphenanthrene

0

0

0

0.12

0

0.02

2,3,5-Trimethylnaphthalene

0

0

0

10

0.29

0

0.08

2,6 -Dimethylnaphthalene

0

0

1

30

0.61

0

0.25

2-Methylnaphthalene

0

0

2

20

1.4

0

0.46

Acenaphthene

0

0

0

5

0.07

0

0.01

Carbonyls

0.3

PART | VII

PAHs

In-Situ Burning

0

0

0

2

0.07

0

0.01

Anthracene

0

0

0

0.2

0.32

0

0.07

Benz(a)anthracene

0

0

0

0.2

0.14

0

0.4

Benzo(a)pyrene

0

0

0

0.2

0.62

0

0.15

Benzo(b) fluoranthene

0

0

0

0.2

0.11

0

0.02

Benzo(e)pyrene

0

0

0

0.2

0.11

0

0.02

Benzo(g,h,i)perylene

0

0

0

0.1

0.23

0

0.05

Biphenyl

0

0

0

1.3

0.51

0

0.07

Chrysene

0

0

0

0.2

0.12

0

0.03

Dibenz(a,h)anthracene

0

0

0

0.2

0.02

0

0

Dimethylnaphthalenes

0

1

1

1.75

0

0.26

Fluoranthene

0

0

0

0.2

0.85

0

0.15

Fluorene

0

0

0

5

0.3

0

0.07

Indenol(1,2,3-cd)pyrene

0

0

0

0.2

0.16

0

0.04

Methylphenanthrenes

0

0

0

0.3

0.32

0

0.08

Naphthalene

0

1

1

1.86

0

0.39

Perylene

0

0

0

0.2

0.07

0

0.02

Phenanthrene

0

0

0

0.2

0.79

0

0.14

30

52

775

(Continued )

Chapter | 23 An Overview of In-Situ Burning

Acenaphthylene

776

TABLE 23.6 Emission Calculations and Values for Crude Oil Burnsdcont’d Calculated Values Summations of Organic Chemicals and Gases (mg/m3)

(mg/m3)

(mg/m3)

Burn Area Taken as 2

2

2

Fixed Gases

200 m

400 m

800 m

Pyrene

0

0

0

Trimethylnaphthalenes

0

0

0

1,2,3-Trimethylbenzene

0

1

1,2,4-Trimethylbenzene

1

1,3,5-Trimethylbenzene

(mg/m3)

Equations to Calculate

Normal Threshold Limit (mmg/m3)

Equation Parameters a

b

c

0.54

0

0.12

10

0.86

0

0.21

5

123

11.4

0.01

2.53

6

15

123

22.4

0.02

4.58

0

1

8

123

17.3

0.02

4.28

1,4-Diethylbenzene

0

1

3

260

4.66

0.01

0.95

2,2,3-Trimethylbutane

0

0

3

2850

25

0.03

7.49

2,2,4-Trimethylpentane

0

1

6

1230

5.41

0.01

1.66

2,2,5-Trimethylhexane

0

0

0

925

8.49

0.01

2.58

2,2-Dimethylbutane

0

0

35

1550

61

0.11

19.3

2,2-Dimethylpentane

0

0

22

1440

52.3

0.08

16.5

2,2-Dimethylpropane

0

0

2

1500

25.2

0.03

7.93

0.2

VOCs

PART | VII In-Situ Burning

0

0

8

1230

14

0.02

4.53

2,3-Dimethylbutane

0

0

89

1550

168

0.31

57

2,3-Dimethylpentane

0

0

84

1445

173

0.29

56.8

2,4-Dimethylhexane

0

0

30

1230

72.2

0.11

22.7

2,4-Dimethylpentane

0

0

48

1445

99

0.16

32

2,5-Dimethylhexane

0

0

22

1230

40.5

0.08

14.3

2-Ethyltoluene

0

1

4

123

5.98

0.01

1.47

2-Methylbutane

0

0

1202

1500

2221

4.58

821

2-Methylheptane

0

0

106

1230

240

0.38

77.4

3-Methylhexane

0

0

245

1445

526

0.9

175

3-Methylpentane

0

0

399

1550

822

1.41

272

4-Ethyltoluene

1

2

4

2850

4.79

0.01

0.85

4-Methylheptane

0

1

27

1230

30.1

0.06

9.44

Benzene

0

1

11

72

0.02

14.1

Butane

0

0

903

1900

1700

3.31

604

c-1,3-Dimethylcyclohexane

0

7

91

2000

82.4

0.21

28

c-1,4/t-1,3-Dimethylcyclohexane

0

9

34

2000

22.4

0.06

6.74

c-2-Butene

0

0

4

1100

4.73

0.01

1.6

Cyclohexane

0

0

410

1030

726

1.43

256

1.6

Chapter | 23 An Overview of In-Situ Burning

2,3,4-Trimethylpentane

777 (Continued )

778

TABLE 23.6 Emission Calculations and Values for Crude Oil Burnsdcont’d Calculated Values Summations of Organic Chemicals and Gases (mg/m3)

(mg/m3)

(mg/m3)

Burn Area Taken as 2

2

2

200 m

400 m

800 m

Cyclopentane

0

0

148

Decane

0

0

Dodecane

0

Ethylbenzene

Equations to Calculate

Normal Threshold Limit (mmg/m3)

Equation Parameters b

c

1720

262

0.53

93.8

29

935

97

0.09

24.5

0

14

740

27.1

0.04

7.43

0

2

18

434

25

0.04

6.69

Heptane

0

0

576

1640

1170

2.11

400

Indan (2,3-Dihydroindene)

0

1

2

83

2.64

0

0.56

Isobutane (2-Methylpropane)

0

0

313

1670

414

1.05

165

Iso-Butylbenzene

0

0

2

260

3.48

0.01

1.06

Isoprene (2-Methyl-1,3-Butadiene)

0

0

11

13

17.4

0.03

5.51

Iso-Propylbenzene

0

0

0

246

21.4

0.02

6.41

In-Situ Burning

a

PART | VII

Fixed Gases

(mg/m3)

0

14

57

434

88.6

0.11

20.8

Methylcyclohexane

0

0

827

1610

1660

3.03

571

Methylcyclopentane

0

0

343

2687

2090

2.9

713

Naphthalene

0

0

4

52

5.92

0.01

1.7

n-Butylbenzene

0

0

1

260

3.28

0

0.81

Nonane

0

0

92

1050

232

0.33

70.5

n-Propylbenzene

0

1

4

246

6.85

0.01

1.52

Octane

0

0

210

1400

513

0.78

162

o-Xylene

0

3

10

434

26

0.02

5.38

p-Cymene (1-Methyl-4-isopropylbenzene)

4

5

7

140

2.52

0.01

0.01

Pentane

0

0

1383

1770

2590

5.05

920

Propane

0

0

18

4508

733

0.79

236

Propene

0

0

24

2615

21.8

0.06

8.28

Total

0

0

7332

13,400

24

4430

Undecane

0

0

21

50

0.05

12.4

100,000 830

Chapter | 23 An Overview of In-Situ Burning

m,p-Xylene

779

780

TABLE 23.7 Emission Calculations and Values for Diesel Fuel Burns Distance From Fire Taken at 300 m Values When Burn Area Taken as 200 m2

Substance

Concentration (mg/m3)

% of Limit

Safe Distance (m)

Total particulates

<0

<0

90

PM-10

0.14

32

PM-2.5

0.07

91

Equations to Calculate Normal Threshold Limit (mg/m3)

Equation Parameters a

b

c

0.25

2

0.01

0.64

140

0.15

1.02

0.01

0.33

320

0.04

1.44

0.01

0.41

Summations of Organic Chemicals (mg/m3)

(mg/m3)

21

3

80

1110

PAHs

0

0

30

10

Fixed Gases

86

0

0

3370

Carbonyls

110

8

0

280

Equations

In-Situ Burning

Conc.¼ a þb)size - c)ln(distance) Concentration is mg/m 3 for particulates Concentration is mg/m3 for gases and organics size is area of fire in m2 distance is distance from edge of fire in m.

PART | VII

Total VOCs

Calculated Values

(mg/m3)

(mg/m3)

(mg/m3)

Burn Area Taken as

(mg/m3)

Equations to Calculate Equation Parameters

Fixed Gases

200 m2

400 m2

800 m2

Normal Threshold Limit (mmg/m3)

Sulphur Dioxide

0

0

0

20

0.53

0

0.17

Carbon Dioxide

86

131

220

10000

14.9

0.22

-4.56

Carbon Monoxide

0

0

0

100

0.87

-48.5

88.4

Acetaldehyde

0

0

0

200

0.5

0.03

18.4

Acetone

4

16

39

170

14.7

0.06

3.84

2-butanone

102

111

127

350

115.1

0.04

3.64

Butyraldehydes

0

4

18

350

22.5

0.03

5.68

Formaldehyde

4

26

69

260

35.4

0.11

9.18

Proprionaldehyde

0

7

22

350

19.6

0.04

4.85

1-Methylnaphthalene

0

0

2

20

1.79

0

0.59

1-Methylphenanthrene

0

0

1

0.3

0.7

0

0.24

2,3,5-Trimethylnaphthalene

0

1

10

10

9.51

0.02

3.05

a

b

c

Carbonyls

Chapter | 23 An Overview of In-Situ Burning

Summations of Organic Chemicals and Gases

PAHs

781 (Continued )

782

TABLE 23.7 Emission Calculations and Values for Diesel Fuel Burnsdcont’d Calculated Values Summations of Organic Chemicals and Gases (mg/m3)

(mg/m3)

(mg/m3)

Burn Area Taken as

(mg/m3)

Equations to Calculate Equation Parameters

400 m2

800 m2

2,6 -Dimethylnaphthalene

0

0

3

30

2.87

0.01

0.92

2-Methylnaphthalene

0

0

2

20

2.37

0.01

0.78

Acenaphthene

0

0

6

5

5.67

0.01

1.88

Acenaphthylene

0

0

10

2

11.3

0.02

3.65

Anthracene

0

0

4

0.2

4.22

0.01

1.39

Benz(a)anthracene

0

0

0

0.2

0.32

0

0.11

Benzo(a)pyrene

0

0

0

0.2

0.38

0

0.14

Benzo(b) fluoranthene

0

0

1

0.2

0.54

0

0.18

Benzo(k) fluoranthene

0

0

0

0.2

0.01

0

0

Benzo(e)pyrene

0

0

0

0.2

0.21

0

0.08

a

b

c

In-Situ Burning

200 m2

PART | VII

Fixed Gases

Normal Threshold Limit (mmg/m3)

0

0

0

0.1

0.33

0

0.11

Biphenyl

0

0

2

1.3

1.86

0

0.6

Chrysene

0

0

0

0.2

0.33

0

0.11

Dibenz(a,h)anthracene

0

0

0

0.2

0.38

0

0.11

Dimethylnaphthalenes

0

0

2

30

1.62

0

0.52

Fluoranthene

0

0

2

0.2

1.95

0

0.65

Fluorene

0

0

0

5

0.1

0

0.03

Indenol(1,2,3-cd)pyrene

0

0

0

0.2

0.26

0

0.09

Methylphenanthrenes

0

0

0

0.3

0.28

0

0.09

Naphthalene

0

0

2

52

2.01

0.01

0.67

Perylene

0

0

0

0.2

0.05

0

0.02

Phenanthrene

0

0

2

0.2

1.62

0

0.53

Pyrene

0

0

2

0.2

1.99

0

0.66

Trimethylnaphthalenes

0

0

1

10

0.8

0

0.27

1,2,3-Trimethylbenzene

0

0

2

123

2.99

0

0.85

1,2,4-Trimethylbenzene

13

34

76

123

15.3

0.11

4

1,2-Diethylbenzene

0

1

2

123

0.89

0

0.25

Chapter | 23 An Overview of In-Situ Burning

Benzo(g,h,i)perylene

VOCs

783

(Continued )

784

TABLE 23.7 Emission Calculations and Values for Diesel Fuel Burnsdcont’d Calculated Values Summations of Organic Chemicals and Gases (mg/m3)

(mg/m3)

(mg/m3)

Burn Area Taken as

(mg/m3)

Equations to Calculate Equation Parameters

400 m2

800 m2

1,3,5-Trimethylbenzene

0

0

1

123

5.55

0

1.45

1,3-Butadiene

0

3

13

400

6.49

0.02

2.27

1,3-Diethylbenzene

0

0

1

260

0.62

0

0.13

1,4-Diethylbenzene

0

0

0

260

3.57

0

0.84

1-Butene/2-Methylpropene

2

10

26

500

7.5

0.04

2.43

1-Heptene

2

6

14

1500

2.14

0.02

0.72

1-Hexene/2-Methyl-1-Pentene

0

1

2

1500

1.01

0

0.23

1-Methylcyclohexene

0

1

3

1500

1.13

0.01

0.39

1-Methylcyclopentene

0

0

1

1500

0.24

0

0.04

1-Nonene

0

0

4

1500

4.09

0.01

1.33

1-Octene

0

0

0

1500

0.78

0

0.16

1-Pentene

3

8

18

1500

1.55

0.02

0.64

a

b

c

In-Situ Burning

200 m2

PART | VII

Fixed Gases

Normal Threshold Limit (mmg/m3)

0

0

1

1230

0.69

0

0.21

2,2,4-Trimethylpentane

0

0

1

1230

3.23

0

0.8

2,2,5-Trimethylhexane

0

1

2

1230

1.09

0

0.31

2,2-Dimethylbutane

0

0

1

1230

1.69

0

0.48

2,2-Dimethylpropane

0

0

1

1230

0.34

0

0.09

2,3,4-Trimethylpentane

0

0

1

1230

1.92

0

0.54

2,3-Dimethylbutane

0

3

10

1230

3.35

0.02

1.1

2,3-Dimethylpentane

0

0

6

1230

7.62

0.01

2.33

2,4-Dimethylhexane

0

0

2

1230

2.23

0

0.65

2,4-Dimethylpentane

0

0

2

1230

3.26

0.01

1.02

2,5-Dimethylhexane

0

0

1

1230

1.12

0

0.3

2-Ethyltoluene

0

0

1

123

3.32

0

0.86

2-Methyl-1-Butene

0

0

1

1230

0.95

0

0.28

2-Methyl-2-Butene

0

0

2

1230

1.67

0

0.53

2-Methylbutane

0

0

29

1230

43.1

0.08

13.2

2-Methylheptane

0

2

10

1230

7.87

0.02

2.45

2-Methylhexane

0

4

20

1230

13.4

0.04

4.44

2-Methylpentane

0

7

21

1230

15.7

0.04

4.17

785

(Continued )

Chapter | 23 An Overview of In-Situ Burning

2,2,3-Trimethylbutane

786

TABLE 23.7 Emission Calculations and Values for Diesel Fuel Burnsdcont’d Calculated Values Summations of Organic Chemicals and Gases (mg/m3)

(mg/m3)

(mg/m3)

Burn Area Taken as

(mg/m3)

Equations to Calculate Equation Parameters

400 m2

800 m2

3,6-Dimethyloctane

0

3

13

1230

-0.03

0.03

1.27

3-Ethyltoluene

0

0

1

434

5.74

0

1.44

3-Methylheptane

0

1

6

1230

4.9

0.01

1.51

3-Methylhexane

0

0

36

1230

34.1

0.09

12.2

3-Methylpentane

0

1

6

1230

7.11

0.01

2.09

4-Ethyltoluene

0

0

1

1230

2.84

0

0.72

4-Methylheptane

0

1

4

1230

1.62

0.01

0.49

Benzene

0

7

33

1.6

27.4

0.06

8.15

Butane

0

0

11

1900

19.6

0.03

5.55

c-1,3-Dimethylcyclohexane

0

3

12

2000

5.81

0.02

1.95

c-1,4/t-1,3-Dimethylcyclohexane

0

1

4

2000

2.46

0.01

0.84

a

b

c

In-Situ Burning

200 m2

PART | VII

Fixed Gases

Normal Threshold Limit (mmg/m3)

0

1

2

1100

0.67

0

0.21

c-2-Heptene

0

0

0

1100

2.02

0

0.53

c-2-Hexene

0

0

2

1100

1.91

0

0.7

c-2-Pentene

0

1

1

1100

0.6

0

0.18

Cyclohexane

0

2

12

1030

8.27

0.02

2.74

Cyclohexene

0

0

2

600

1.55

0

0.48

Cyclopentane

0

1

3

1720

2.6

0.01

0.81

Cyclopentene

1

1

1

1030

0.23

0

0.01

Decane

0

0

0

2000

23.1

0.01

6.05

Dodecane

0

0

7

2000

139

0.12

40.1

Ethylbenzene

0

0

3

434

6.53

0.01

1.69

Heptane

0

8

47

1640

32.2

0.1

10.9

Hexylbenzene

0

0

4

600

4.55

0.01

1.38

Indan (2,3-Dihydroindene)

0

0

1

83

0.76

0

0.19

Indene

0

0

1

123

0.31

0

0.1

Isobutane (2-Methylpropane)

0

0

0

1610

7.22

0

1.58

m,p-Xylene

0

2

20

434

29.7

0.05

8.13

787

(Continued )

Chapter | 23 An Overview of In-Situ Burning

c-2-Butene

788

TABLE 23.7 Emission Calculations and Values for Diesel Fuel Burnsdcont’d Calculated Values Summations of Organic Chemicals and Gases (mg/m3)

(mg/m3)

(mg/m3)

Burn Area Taken as

(mg/m3)

Equations to Calculate Equation Parameters

400 m2

800 m2

Methylcyclohexane

0

6

39

1610

27.9

0.08

9.44

Methylcyclopentane

0

2

7

2687

5.21

0.01

1.55

Naphthalene

0

0

5

52

10.8

0.01

3.05

n-Butylbenzene

0

0

0

260

1.63

0

0.43

Nonane

0

0

10

1050

19.6

0.03

5.68

n-Propylbenzene

0

0

1

246

1.77

0

0.44

Octane

0

6

22

1400

13.9

0.04

4.31

o-Xylene

0

0

13

434

20.9

0.04

6.3

p-Cymene (1-Methyl-4-isopropylbenzene)

0

0

0

140

1.02

0

0.28

a

b

c

In-Situ Burning

200 m2

PART | VII

Fixed Gases

Normal Threshold Limit (mmg/m3)

0

1

24

1770

29.2

0.06

9.1

Propane

0

0

0

4508

19.5

0

4.5

Propene

0

9

27

2615

10.2

0.04

3.25

Propyne

0

0

1

1000

0.87

0

0.24

sec-Butylbenzene

0

0

1

123

0.88

0

0.25

Styrene

0

5

13

123

3.96

0.02

1.37

t-1,2-Dimethylcyclohexane

0

2

6

1600

2.86

0.01

0.93

t-2-Butene

0

0

1

1600

0.9

0

0.28

t-2-Heptene

0

0

2

1600

1.89

0

0.55

t-2-Hexene

0

4

17

1600

0.38

0.03

1.53

t-2-Octene

0

23

68

1600

4.58

0.11

4.67

t-2-Pentene

0

2

5

1600

2.24

0.01

0.68

t-3-Heptene

0

0

0

1600

85.4

0.07

25.7

tert-Butylbenzene

0

0

1

123

1.37

0

0.41

Toluene

0

11

39

123

34.6

0.07

8.94

Chapter | 23 An Overview of In-Situ Burning

Pentane

789

790

PART | VII

In-Situ Burning

Results of a simple exercise of this type are shown in Tables 23.6 and 23.7. These tables show that emissions, especially of particulate matter, are significantly higher from a diesel fire than from a crude oil fire, as had been noted in several studies of particulate emissions.9,48,94,95 Other emissions of concern are similar for diesel and crude oil, although the PAHs are somewhat higher when diesel burns. This calculation confirms that particulate matter is the greatest concern, followed by the PAHs on the particulate matter and the total VOCs. Analysis of the VOC data shows these data to be close to being a matter of concern. However, it should be noted that the level of VOCs is much higher (as much as three times higher as measured in some tests) when oil is evaporating in the absence of burning than when burning. Carbonyls are another emission of concern, although they are significantly below health concern levels for the scenarios in Table 23.6 and 23.7. The level of concern is the percentage of the regulated level attained by the emission. For example, if a regulated level is 75 mg/m3 and the calculated value is 150, then the level of concern is given as 200%. There is no health concern for fixed gases such as carbon dioxide or carbon monoxide at levels measured at burns to date. Safe distances downwind from a crude oil burn (based on PM-10 concentrations) can be calculated as: 12:5 þ 0:0347 X fire size ðm2 Þ Safe DistanceðmÞ ¼ exp 4:79 Safe distances downwind from a diesel fire can be calculated as 1:44 þ 0:0052 X fire size ðm2 Þ Safe DistanceðmÞ ¼ exp 0:412 Note: To convert feet to meters, multiply by 0.3048. To convert meters to feet, multiply by 3.28084. A final point should be made that the level of PM-2.5 measured for diesel emissions is the same as the PM-10 level or exceeds it. This indicates that most of the matter consists of PM-2.5. As PM-2.5 is the emission of highest concern, this becomes the most important factor for calculating safe distances. Based on these data, safe distances have been calculated for a variety of fire sizes for diesel fuel and crude oil. These are given in Table 23.8.

23.3.4.4. Water Quality Research has shown that in-situ burning of oil does not release any more oil components or combustion by-products into the water column than are present if the oil is left unburned on the water surface.89 Water samples from underburning oil have been analyzed, and no organic compounds were detected.75,79,104 Only low levels of hydrocarbons have been found, at concentrations

791

Chapter | 23 An Overview of In-Situ Burning

TABLE 23.8 Safe Distance Calculations Type and Area

Burn Area Hectares (Acres)

Safe Distance in Kilometres

Safe Distance in Miles

0.25 (.6)

0.09

0.06

0.5 (1.2)

0.5

0.3

0.75 (1.9)

3.2

2

0.25 (.6)

0.8

0.5

0.5 (1.2)

20

12.4

Crude Oil Burns small area 250 m2 full boom pull 500 m

2 2

large boom pull 750 m Diesel Burns small area 250 m2 full boom pull 500 m

2

Based on PM-2.5 concentrations.

that would not result in fish mortality, even in a confined body of water. No PAHs have been detected in water samples from underburning oil. Toxicity tests of the water column were also conducted, and no toxicity was noted. The burning process leaves a residue, however, that is composed primarily of oil, with little removed other than some of the more volatile materials.96,97 The residue contains a large amount of PAHs, though usually less than the original oil and though it may also contain a slightly higher concentration of metals. The residue consists of unburned oil, oil depleted of volatiles, reprecipitated soot, and partially burned oil. It appears to be similar to weathered oil of the same type and is typically viscous and dense. Several tests have shown that burn residue is no more aquatically toxic than other weathered oils and, in fact, is much less toxic than fresh oils of the same type. There is evidence that the metals contained in the original oil (usually 10 to 40 ppm of vanadium, chromium, and nickel) become concentrated in the burn residue.89 The density of this residue depends on how heavy the original oil is and the completeness of the burn, although it will never be denser than the heaviest hydrocarbon found in the original oil. Figure 23.16 shows the residue from the NOBE burn number 2. Figure 23.17 shows a residue from a heavy oil burn. A very efficient burn of a heavier crude oil will produce a dense residue that may sink and pose a threat to benthic species. Sinking is very rare, however, and has been recorded in only 2 of about 200 burns worldwide. Aquatic toxicity tests performed on samples of residue have shown very low toxicity.76 Residues can be collected in a backup boom using sorbents, or a skimmer can be used to collect lighter residues.

792

PART | VII

In-Situ Burning

FIGURE 23.16 Residue from the second NOBE burn. The residue is dense and as can be seen has a small film of water over it.

FIGURE 23.17 Residue from burning a heavy oil. Note that this residue is so solid that it can be removed as a sheet.

Chapter | 23 An Overview of In-Situ Burning

793

Another concern is that burning will raise the water temperature below the oil, as extreme temperature changes can affect marine species.76 Measurements during burn trials, however, show no significant increase in water temperature, even during some burns in shallow, confined test-tanks. Thermal transfer to the water is limited by the insulating oil layer and is actually the mechanism by which the combustion of thin slicks is extinguished.

23.3.4.5. Effects on Land Where possible, every effort should be made to prevent spilled oil from reaching a shoreline, as removing oil from sand, rocks, and vegetation is difficult and costly. In-situ burning is a rapid response method that can be used effectively to protect shorelines from spilled oil. To prevent the deposit of soot on shorelines, however, burning should be conducted at least 1 km away from the shoreline, if this is possible. If burning on land, there are some precautions that should be taken, as noted later in this chapter. 23.3.4.6. Effects on Birds and Other Species Wildlife on land is generally not affected if burning is conducted more than 1 km away from shore or sensitive areas. It has also been observed that birds will avoid the burning site and therefore are unlikely to be affected by the burn. Similarly, marine species should not be affected as the water column normally does not become contaminated and the water temperature does not change within a few centimeters below the slick. Benthic species may be affected by the sinking of heavy burn residue. 23.3.4.7. Infrastructure Concerns Oil slicks should not be burned close to infrastructure such as buildings, docks, lighthouses, oil platforms, and vessels that originally contained the oil.

23.3.5. Oil Properties and Conditions Oil spilled on water undergoes several changes with time. The processes that cause these changes include emulsification, evaporation, oxidation, spreading, dispersion, sedimentation, dissolution, and biodegradation. In order to determine the effectiveness of in-situ burning for a particular oil slick, it is important to understand how these processes change the properties of spilled oil and ultimately affect the oil’s ability to ignite and sustain burning.

23.3.5.1. Slick Thickness Over the years, a wide variety of oils has been burned in tests and at actual spills. Research has shown that virtually all oils will burn on water if the slick is thick enough. In general, slicks must be at least 0.5 to 3 mm thick in order to be ignited and to sustain quantitative burning, and a burn will be extinguished once

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the slick becomes less than approximately 0.5 to 1 mm thick.86 This thickness is required for heat transfer to take place. It should be noted that this thickness is not as binding a rule as was once thought. As the slick becomes very thin, the heat generated by burning is lost to the water below the slick, resulting in insufficient available heat to vaporize the constituents of the oil required to sustain combustion.89 An oil spill containment boom or other containment method is often used to increase a slick’s thickness or to maintain it at the thickness required for burning. In some circumstances, for example, on dry sand or grass, oil can sometimes be ignited at lower thicknesses.

23.3.5.2. Oil Weathering/Volatile Content As a rule, the greater the percentage of volatile compounds in an oil, the more easily it will ignite and continue to burn. It can therefore be difficult to ignite weathered oils and heavy crude oils (No. 5 and above) and higher ignition temperatures, primers, and/or longer ignition exposure times may be required.86,105 During one burn test, it was found that weathered oils actually burned with an average 7% greater efficiency than fresh oils.74 23.3.5.3. Heavy Oils Heavy oils were thought to burn poorly, if at all; however, results in recent years show that these will burn quite well under most circumstances.57 Studies in the past decade have shown much more potential for burning these oils than was previously thought.86 Burning tests of bitumen, a very heavy oil, along with water have been conducted and have shown useful removal potential. The burning of heavy oils has been studied by Environment Canada over a period of five years.25,39,40,57,101 Figure 23.18 shows one such burn, and Figure 23.19 shows the remaining residue. Figure 23.20 illustrates the ignition of a heavy oil. Heavy oils such as Bunker C burn quite well but yield a highly viscous residue. Figures 23.21 and 23.22 illustrate heavy oil burn residues. This highviscosity residue has a high asphaltene and resin content. There is no evidence of the presence of soluble components; thus the residue should exhibit low aquatic toxicity. Examination of the SARA content shows that the values of SARA for the residue can be used to predict burn efficiency. There appears to be a consistent reduction of saturate and aromatic content in an oil with increasing burn efficiency. This is based on values from 10 burn experiments and 4 oil types. The prediction equation is: Burn Efficiencyð%Þ ¼ 23000 þ 230 Aromatic% þ 227 Saturate%ð1Þ þ 254 Resin% þ 218 Asphaltene% Several types of oils were used, as shown in Table 23.9. The results of two series of burning are shown in this table as well. It is interesting to note that

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FIGURE 23.18 A burn of Bunker C. The efficiency of this burn was about 60%. The horizontal objects are thermal probes.

FIGURE 23.19 The residue from the burn in Figure 23.18. Note that it is so solid that it can be picked up as a single sheet.

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FIGURE 23.20 The ignition of a heavy oil. This is easiest carried out by adding a small amount of primer such as diesel fuel (about 20 mL) and adding a small wick such as cardboard or paper towel.

FIGURE 23.21 The residue of a heavy oil burn. The residue has solidified into chunks with brittleness of taffy.

orimulsion burning efficiency averages about 40 to 60% (excluding the water content of 30%), bunker C burning averages about 65%, and burning bitumen averages about 12%. Orimulsion has certain peculiar burning characteristics such as popping when the water is explosively released.106,107 It is suggested

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FIGURE 23.22 Another residue of a heavy oil burn. This residue may be moved as a sheet and parts are brittle.

that the burning of orimulsion actually takes place as a two-step process: first vaporization and water release and second, the actual combustion. Extremely weathered oils such as the bunker test oil would not burn, and analysis of this oil showed that its calculated burn efficiency as per the equation above was calculated to be about zero. The burn rate for orimulsion was found to be between 0.5 and 2 mm/min.57,101 Fingas et al. found that the burn rates for heavy oils varied from 1 to 2 mm/min.57,101 Emissions from these heavy oil burns showed very low emissions compared to crude oils, and in particular there were few volatiles and few PAHs measured in the air. The residues from all the burns were highly viscous. When cooled, all residues were solid and even “glassy” in some cases as shown in Figures 23.19, 23.21, and 23.22. Analysis of the residues showed some concentration of higher-molecular-weight pyrogenic PAHs.

23.3.5.3. Oil Emulsification In general, unstable oil emulsions can be ignited and will sustain burning because the emulsion is quickly broken down during the burning process.108 By contrast, stable oil emulsions are difficult to ignite because a large amount of energy is required to heat the water and therefore, additional energy is required to vaporize the oil in the emulsion before the burning is sustained. Test burns have shown that once an emulsified oil is ignited and has burned long enough, the heat from the burn sometimes breaks down the emulsion and allows the slick to continue to burn.45

798

TABLE 23.9 Heavy Oil Burning Oil Viscosity (mPa.s)

Burn Conditions

Efficiency %

Burn Rate mm/min

Flame Height m

Peak Height m

1m

ESTD Bunker

15330

normal

64.8

1.2

1.5

2

1.5 m

ESTD Bunker

15330

normal

63.8

1

1

1.5

1m

Test Oil

16,273.33333

would not burn

2

no volatiles remaining

1.5 m

Test Oil

16,273.33333

would not burn

2

no volatiles remaining

1m

Orimulsion)

254.7

normal

65.6

1.7

3

8

1.5 m

Orimulsion)

254.7

normal

61.3

2.3

1.5

4

1m

ESTD Bunker

15,330

normal

65.9

1.1

3

4

1.5 m

ESTD Bunker

15,330

normal

70

1

1.5

3

1m

Bitumen

4,038,333.333

normal

12.3

1

1.5

2

1.5 m

Bitumen

4,038,333.333

normal

12.9

0.9

1

1.5

Overall Average

39.3

1.5

1.7

3.3

42

1

1.6

2.6

1, 1.5

)

1

Orimulsion)

254.7

30% water content 1 average of 17 burns.

variable

In-Situ Burning

Oil Type

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Pan Size

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Strictly speaking, all unstable emulsions can either be broken down by mechanical means or will break down on their own over time. Based on the commonly accepted definition of stable emulsionsdan emulsion that persists for at least five days at 15 Cdstudies have shown that stable and unstable emulsions have different characteristics.47 The two most obvious characteristics relate to color and viscosity. Stable emulsions are reddish brown, whereas unstable emulsions are black. The viscosity of stable emulsions is usually more than three orders of magnitude greater than the oil from which the emulsion was made, whereas the viscosity of an unstable emulsion is less than one order of magnitude greater than the original oil. There is also a middle form or mesostable emulsion that usually is brownish in color and has a viscosity about 50 times that of the starting oil. Some typical properties of water-in-oil states are given in Table 23.10.47 The literature has shown that the stability of an emulsion depends on the concentration of ashphaltenes and, to a lesser extent, resins in the oil. These compounds form a viscoelastic film at the oilewater interface. As well, oil will not create a stable emulsion with a very low (<30%) or very high (>90%) water content. In general, the water content of stable emulsions ranges from 60 to 75%, although there is no correlation between water content and stability of an emulsion within this range.47

23.3.6. Weather and Ambient Conditions Weather conditions such as wind speed, gusts, shifts in wind direction, wave height and geometry, and water currents can all jeopardize the safety and effectiveness of a burn operation. Strong winds can make it difficult to ignite the oil during in-situ burning. Once the oil is ignited, high winds can extinguish the fire or make it difficult to control. In general, oil can be successfully ignited and burn safely at wind speeds less than 20 m/s (40 knots).89,109 Tank tests have shown that at wind speeds greater than 15 m/s (30 knots), the flames would not propagate upwind .87 During a test in England, however, oil burned in winds up to 25 m/s (50 knots).110 Although the effects of air and water temperatures on the ability to ignite and burn oil slicks is not well documented, tank tests have shown that air temperatures of e11 to 23oC and water temperatures of e1 to 17oC did not affect the ability of a slick to burn.74 While no testing has been done on the effect of rain on burning, rain would probably lower the efficiency of the burn due to the cooling effect of the water. High-sea states can make it difficult to contain oil. Waves higher than 1 m can cause the oil to splash over the containment boom.89 High waves can also contribute to the emulsification of oil, which could make it more difficult to ignite. Tests in ice-covered areas have shown that ice coverage has a minimal effect on the ability of a slick to burn.74 In fact, ice is typically used as a natural method to contain oil for burning. More details on ice situations are presented in a special section below.

800

TABLE 23.10 Average Properties of the Four Water-in-Oil Types Rheological Properties on Day of Formation

Averages

Appearance

Day Water Content (%w/w)

Entrained

viscous black

44.5

27.5*

1.9

8.30Eþ05

5.14Eþ05

1.73

1.3Eþ05

Mesostable

viscous reddish

64.3

29.6*

7.2

1.33Eþ05

1.07Eþ05

1.7

2.1Eþ04

Stable

solid reddish

80.7

77.4

405

7.50Eþ05

7.10Eþ05

0.7

1.2Eþ05

Unstable

oil-like

6.1

6.85*

0.0

1.10Eþ07

3.37Eþ06

2.4

1.8Eþ06

Week Water Content (%w/w)

Viscosity Increase Complex from Modulus Starting (mPa)

Elasticity Modulus (mPa)

Tan Complex Delta Viscosity (V/E) (mPa.s)

Rheological Properties One Week After Formation Complex Modulus Change

Elasticity Modulus Change

Tan Delta Change

Complex Viscosity Change

Entrained

viscous black

1.9

0.8

0.6

1.7

1.3

Mesostable

broken

5.4

0.6

0.5

2.2

0.5

Stable

solid reddish

859

1.1

1.1

1.1

1.2

Unstable

oil-like

0.0

3.8

2.9

1.7

3.6

(Increase is shown as number larger than 1.00). *These water content values are high as most were not measured as they were obviously low.

In-Situ Burning

Viscosity Increase From Starting

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Appearance

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Burning can only be done safely at night if oil conditions, weather conditions, and sea conditions are well known. Towing booms at night would be unsafe under most conditions. Burning at night would be a relatively safe choice in the case of a thicker, uncontained spill at sea, especially if the spill is offshore and its extent is well known. Some nearshore spills and spills in marshes have been burned at night, which is a relatively safe practice because the concentrations and location of the oil are known and precautions can be taken to ensure that the fire does not spread to surrounding areas.

23.3.7. Burning in Special Locations There is only limited experience in the application of burning in a variety of special locations. Summary information on the use of burning at locations other than on open waters using fire-resistant boom is provided in this section.

23.3.7.1. Marshes Several marsh burns have been conducted around the world, including recent well-documented burns in Louisiana and Texas. These burns were largely successful and provided important information on protecting the marsh plants and the best time of year to burn. The roots of marsh plants, which also house the propagation portion of the plants, are sensitive to heat. If burning is conducted at a dry time of year, such as in late summer, these roots could be killed. Flooding is a useful technique for flushing oil out of a marsh while protecting the roots of marsh plants. This can sometimes be accomplished by putting a berm across the drainage ditches or by pumping water into the high areas of the marsh. Care must be taken to use floodwater of similar salinity to that normally present in the marsh and to restore the natural drainage in the marsh after the flood. Often marshes cannot be flooded, however, and thus burning could be conducted when the marsh is wet such as in spring. If a marsh cannot be burned within about one month of oiling, there is usually no benefit to burning because the oil will already have penetrated and severely damaged most of the plant life. When burning in marshes, care must be taken to prevent damage to shrubs and trees that grow in the back and higher areas of the marsh. A fire-break must be available to prevent the fire from spreading outside the marsh and to ensure that wind will not drive the fire into nearby forested areas. Several cases of burning in marshes follow. Copano Bay111 On January 7, 1992, an underground pipeline ruptured by Chiltipin Creek near Copano Bay, Texas, spilling 460 m3 of South Texas light crude oil into a salt marsh. Vacuum trucks, skimmer, pumps, and sorbents were brought to the scene but proved to be only marginally effective. After considering various

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options, a decision was made to burn the oil. The oil was ignited four days after it spilled and burned for 20 hours in various areas. The area was surveyed, and pockets of remaining oil were ignited later. At the time of the burn the marsh was covered with water from recent heavy rainfall, providing protection to plant roots and rhyzomes. A study to monitor marsh plant recovery over a period of five years suggested that plant diversity in the impacted area was reduced, but that total plant biomass was similar to the control area after two growth seasons. Rockefeller Refuge112-114 On March 13, 1995, approximately 6 m3 of condensate oil spilled from a pipeline in the Rockefeller Refuge, Louisiana, affecting 20 ha of brackish marsh. Mechanical cleanup equipment was brought on scene, but was both ineffective at collecting the oil and damaging to the marsh. In-situ burning of marshes is commonly used in that area to reduce organic debris, reduce unwanted fires, and enhance marsh growth. At the time of the spill, the water layer over the marsh soil was 5 to 10 cm thick. In-situ burning of the oiled marsh was approved and conducted four days after the burn, removing the oil from 8 ha of the impacted marsh. Studies conducted three years later concluded that the areas impacted and burned recovered better than the areas impacted but not burned. Three years after the burn, the burned areas attained the same plant density as the reference area. Ruffy Brook115,116 On July 22, 2000, a transfer pipeline near Ruffy Brook, Minnesota, failed and released over 8 m3 of medium Bow River crude oil into a marsh fed by Ruffy Brook. The spill affected approximately 3 acres of freshwater marsh that was covered by water 30 to 100 cm above the marsh soil surface. Mechanical recovery was deemed difficult to deploy and potentially damaging to the marsh, so in-situ burning was conducted the same day of the spill. The burn lasted for three hours, and remaining pockets of oil were ignited over a period of three days. No secondary burning occurred during this operation. It is estimated that 80% of the oil was consumed during the burn. A significant amount of burn residue (in some places 1 cm thick) was left after the fire went out. The residue was picked up by hand three days later. There is no evidence that any residue sank. The marsh was visited a year later and was found to have recovered well, with the exception of willows, a fire-sensitive species. The quick response prevented spreading of the oil and thereby minimized damage to the marsh. Bayou Tank Battery117 On August 17, 2002, a spill occurred at a tank battery in the Sabine National Wildlife Refuge in southwestern Louisiana. The spill of 24 to 50 m3 crude oil

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ran into the adjacent marsh. Salt water spilled together with the oil, spreading the oil over about 1.5 ha of dense marsh. A burn was started on the first day. A survey indicated that most of the oil had been successfully removed from the marsh. The removal of the residue, however, proved to be difficult and took several days to accomplish using sorbents and nets. Soil samples were taken in unaffected and burn areas to assess them for metal content. Analysis of the soil samples for cadmium, chromium, copper, lead, manganese, nickel, vanadium, and zinc showed that the metal contents were relatively the same in the area under the burn and nearby. This indicated that burning, at least in this particular case, did not increase the soil metal content for those metals noted. The burn did show, however, that removal of residue is difficult and requires significant time. Diesel Spill in Wetlands and Salt Flats, Northern Utah118 On January 21, 2000, release of an estimated 16 m3 of diesel occurred from a product transportation pipeline north of Great Salt Lake in Utah. Because of weather (freeze/thaw periods and wind), the product spread over 15 ha of salt flat and wetlands during the next few days. Initial oil containment efforts were successful in reducing the risk of oil impacts in a nearby national migratory bird refuge. However, the risk remained to migratory waterfowl that were expected to arrive at the impacted wetland within approximately 6 weeks. As a result, insitu burning was proposed to remove the free-phase diesel and destroy the oiled vegetation. Upon approval of a site remediation plan and fire management plan, a Helitorch was used on March 10, 2000, to initiate a burn of the most highly impacted 5 ha. The following month (late April), 1.3 ha of remaining lightly oiled vegetation were burned using drip torches and propane wands for ignition. It was estimated that 75 to 80% of the spilled diesel was burned in these operations. Because burning of the oil and impacted vegetation would not remove diesel that had penetrated into the soils, bioremediation techniques were subsequently implemented to further reduce hydrocarbon levels in the soil and attain the regulatory cleanup target of 20 mg/kg total polycyclic aromatic hydrocarbons. Mosquito Bay116,119 On April 5, 2001, 160 m3 condensate spilled in Mosquito Bay, Louisiana, in a remote coastal marsh. The oil spill resulted from the failure of a 20-inch pipeline. The spill oiled a total of 15 ha with heavy oil covering approximately 5 ha. The environmental conditions of the brackish tidal marsh included Distichlis spicata (salt grass), Spartina alternaflora (cord grass), and Spartina Pattens (wire grass). The oil penetrated burrows and root cavities during the low tide. Pre-burn surveys and photo documentation were conducted. The oil was burned on April 12 and 13, approximately 7‑8 days after the spill occurred. Varying daily wind speeds and tidal changes played an

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FIGURE 23.23 Mosquito Bay, Louisiana burn of condensate crude oil on April 12, 2001, seven days post-spill. Photograph by Jacqueline Michel, Research Planning, Inc.

important role in this burn. After the burn, > 40 ha were burned, which was nearly three times the oiled area. Burning was effective in removing surface oil but not subsurface oil. Vegetation died in areas of heavy oiling, but recovery occurred in light and unoiled areas. A photo of the burn is shown in Figure 23.23. Tank Spill Resulting from a Hurricane120-122 On August 29, 2005. Hurricane Katrina made landfall near Buras, Louisiana and caused an oil storage tank to rupture, spilling about 600 m3 of Louisiana Sweet Crude. Most of the oil migrated to the retention pond at the facility. During Hurricane Rita (September 24), approximately 16 to 40 m3 of oil were released into the adjacent marsh environment. A portion of the marsh was heavily oiled or moderately oiled (ca. 2 ha and 6 ha, respectively). A total of 15.5 ha of marsh were covered by the oil. On October 12 to 13, a burn was initiated and covered 7.9 ha of the marsh. Test plots were sampled 9 months and one year after the burn. Regrowth from heavily and moderately oiled plots (28 plots) were compared to two nonoiled and nonburned or reference plots. The plots were monitored for above-ground biomass, plant height, and stem density. Total aboveground biomass, live biomass and dead biomass in the oil, and burned zones were not significantly different from those in the reference areas after one year. Stem heights also showed recovery within one year, and the number of stems of the dominant plant, Scirpus, in the oil and burned areas was equal to, or greater than, that in the reference areas. Complete recovery of the above-ground vegetation occurred within one year after the burn. A photograph of this burn is shown in Figure 23.24.

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FIGURE 23.24 Marsh burn of oil released from a tank farm on the Mississippi River after hurricanes Katrina and Rita. Burn occurred on October 12, 2005, five weeks after the initial release. Photograph by NOAA.

One of the concerns is that burns will affect the environment on a long-term basis. Otitoloju and coworkers studied a mangrove system that was affect both by a spill and a subsequent burn.123 The refined petroleum and fire resulted in a decrease in biodiversity from about 0.8 to about 0.2. About 2½ to 3 months later, there were signs of recovery along with a decrease in hydrocarbon levels from about 3.7 mg/kg to 0.42 mg/kg. The recovery coincided with the loss of hydrocarbons. Lindau and Delaune carried out field studies on the sensitivity of Sagittaria lancifolia, a common marsh plant, to in-situ burning of crude oil.124 Plots (24) were constructed in a fresh marsh, and schemes of control and treatments were set up. Burning was carried out three days after oil application and at a flooding stage of 15 to 25 cm of water. Live stem count and carbon fixation were measured up to 52 weeks after the oil application. It was found that the oil application and burning had only a short-term effect on the Sagittaria. After five to six weeks after the burn, most indications were that the Sagittaria had returned to before oil and burn conditions. The tests also showed that leaving the oil to naturally degrade may also be an option as plant recovery in the unburnt section was similar to the burnt section. The recovery in the burned section may be more rapid. Mendelssohn and coworkers carried out a series of experiments to determine optimum water depth for burning on marsh plants.125-128 Three

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marsh types were collected: a Spartina alterniflora dominated marsh, a Spartina patens and Distichlis spicata codominated brackish marsh, and a Sagittaria lancifolia-dominated marsh. The sods were placed in metal buckets and instrumented with thermocouples. Various control and treatment procedures were applied. After burns, the vessels were returned to a greenhouse where recovery was evaluated. It was found that water depth was a key factor in the recovery of the marsh plants. When the water depth was 2 to 10 cm, the soil temperature did not exceed 40oC and there was little vegetative damage. In those test vessels where the water table was 2 cm below the soil surface, there was significant vegetative damage and the soil temperatures rose to 80 to 100oC. There were different effects on the different species. Spartina patens and Distichlis spicata were less affected by these higher temperatures. The in-situ burned removed about 99% of the oil from the water or soil surfaces. These and other studies have led practitioners to prepare guidelines for marsh burns.129 In the future, this remediation technique may become more routine.130-132

23.3.7.2. Nearshore Burning can be conducted nearshore if there are no people in the area and there is no danger of the fire spreading to plants on the shore. As these two factors cannot always be guaranteed, nearshore burning is not often conducted. The exception to this is in the Arctic where these conditions often exist and where nearshore burning is practiced frequently. Such burns have been very successful, particularly if the oil is contained by the shoreline. If there is also an onshore wind, oil is concentrated against the shoreline. 23.3.7.3. Intertidal Pools When oil is stranded in tidal pools formed during low tide, igniting the oil from above using a helitorch or other air-deployable igniter and conducting a burn may be the only viable cleanup solution. It can be dangerous for response personnel to get to the spilled oil either from the shore or the water between tides, and such attempts are not recommended. The window of opportunity for burning is quite narrow, however, because of the extreme fluctuations between outgoing and incoming tides. It is also difficult to predict the location of the oil pools, and there may not be enough time to conduct aerial surveillance before burning operations. This type of in-situ burn operation would be useful if a spill occurred in an area such as the extensive intertidal flats in the Bay of Fundy in Eastern Canada.

23.3.8. Burning on Land Burning on land is a much older and much more frequently used technique than oil in-situ burning on water.133,134 Many of the same considerations in

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807

this overall burning section apply to land as might apply to burning on water. There are several important differences to consider, however. First, the ease of ignition and minimum burning thickness may not apply if combustible material such as dried grass is available. Burning in cases where there is dried vegetative material or wood in the target area is simply a matter of igniting that material. Both the dried vegetative material and oil will burn, depending on the circumstances. It should be borne in mind that burning is often used on land to remove combustible material as a fire prevention method, as well as to control certain plant species. The effects on land are largely a function of how much heat is transferred into the soil, which is also a function of how quickly the fire passes over and of soil moisture content. Figures 23.25 to 23.28 illustrate burning oil spills on land. One of the concerns associated with burning on land is what effect fire will have on the soil structure. One such study focused on the effects of both a spill and the subsequent burn on the physical properties of the soil.135 A crude oil spill occurred in Nigeria in 2006, and a fire subsequently consumed most of the surface oil. The soil was sample to depth of 5 m, and several measurements were taken: natural moisture content, grain size distribution, consistency (Atterberg) limits, California bearing ratio (CBR), and unconsolidatedundrained triaxial compression. The findings of this study showed that the crude oil spill and subsequent fire did not have a significant impact on the foregoing soil properties. Very little crude oil was observed in the core samples, leading to the conclusion that the fire did not increase oil penetration or increase it significantly.

FIGURE 23.25 Burning of oil on muskeg in Russia. The oil was from a series of pipeline leaks.

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FIGURE 23.26 Burning of oil from a pipeline spill in northern Alberta. The burn removed a large portion of the oil in the low-lying area where it was ignited.

FIGURE 23.27 Burning of a fuel oil spill in a drainage ditch. This is a frequently-used technique to deal with such spillage.

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FIGURE 23.28 A view of the oil fires in Kuwait after the Iraqi invasion. These fires were extensively studied.

Overton and Miles conducted a series of tests in greenhouse pots with upland soil and common Bermuda grass.132 Six treatments including burning, phytoremediation, and lime addition were evaluated in the pots. Soil samples were taken a number of times after treatment up to 300 days. Aromatic and aliphatic hydrocarbon content was measured in the soil samples. Data from the project suggested that there is no significant difference in aromatic and aliphatic hydrocarbon content between oil burning, nonburning and lime addition treatments.

23.3.9. Burning In or On Ice Many test burns have been conducted on or among ice floes. The ice serves as a natural barrier to the spreading of the oil. Much of the early burn work was carried out as a countermeasure for oil in ice.136-141 Hundreds of research papers have been written on this topic, many of these from 1974 to 1986. Figures 23.1 and 23.2 showed the classic Beaufort Sea burn from 1975; Figures 23.29 to 23.31 show some burns carried out on or with ice. More recently, a group of scientists carried out an experiment of oil under and in ice near Svalbard in Norway. The oil was allowed to surface, where it was ignited with gelled hexane.142 The oil was Statfjord crude, 3400 liters, and once weathered 27% was 2480 L. The thickness was calculated to be 35 mm and covered an area of 69 m2. The burn endured for 11 minutes and the 1 mm of residue yielded 106 L of 0.95 g/mL density. This burn reduced the volume by 96%, and the burn rate was 3.1 mm/min.

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FIGURE 23.29 Burning recovered oil from a spill directly on the ice surface.

Majors and McAdams report on the burning of a small spill on the tundra in Alaska. The burn did not remove the bulk of the oil due to the low thickness of the oil.143 Brandvik and Fakness carried out mesoscale experiments on oil in ice and developed a scheme for the burnability of oil on ice dependent on water content.144

FIGURE 23.30 Burning oil in a lead at sea after behavior tests.

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Chapter | 23 An Overview of In-Situ Burning

FIGURE 23.31 Burning of oil on ice at sea.

23.4. EQUIPMENTdSELECTION, DEPLOYMENT, AND OPERATION This section outlines the types of equipment that are used in responding to a spill with in-situ burning and the steps involved in deploying and operating this equipment. This equipment includes containment booms; other containment and burning equipment; igniters; aircraft and response vessels; treating agents; monitoring, sampling, and analytical equipment; and residue recovery equipment. This section is intended to assist response personnel in the proper selection and deployment of equipment for particular response situations.

23.4.1. Burning Without Containment Controlled burning of uncontained slicks is sometimes possible if the slick is thick enough and all other safety factors are considered. Because it takes time to get containment booms to a site, if the oil slick is already fairly thick, it may

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be advisable to ignite and burn as much of the slick as possible as a first response and then bring in containment booms to thicken the remaining parts of the slick for a second burn. Uncontained oil can be ignited with a helitorch at the location where the oil is thickest. When personnel are burning an uncontained slick, they must ensure that there is no direct link between the oil to be burned and the source of the oil, for example, the tanker or platform on the sea, to prevent the fire from spreading to the source. The safest and quickest option is to move the source away from the slick. When the spill originates from a platform or other fixed source, the portion of the slick that is to be burned should be moved away from the source and the slick around the source should be isolated using containment booms. Several oil spills or blowouts have accidentally caught fire while uncontained and have burned well.105 Figures 23.32 to 23.35 show accidental and uncontained burns. While it is not known what conditions are best for burning uncontained oil, emulsified oil may stop or retard the spreading of uncontained oil while it burns.105 In a large burn, large volumes of air are drawn into the fire, which is referred to as a “firestorm.” This may provide enough force to prevent the oil from spreading. In remote areas, natural barriers such as shorelines, offshore sandbars, or ice can sometimes be used to contain oil in order to burn it. The shorelines must consist of cliffs, rocks, gravel, or sandy slopes to resist burning, and there must be a safe distance between the burning oil and any combustible materials, such as wooden structures, forests, or grass cover. On land, containment generally occurs naturally. In populated areas, weather conditions must be such that the

FIGURE 23.32 A ship on fire. Note that the oil is burning on the water without containment.

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FIGURE 23.33 An overview of an offshore platform on fire with oil on the water burning without containment as well.

FIGURE 23.34 A close-up of Figure 23.33 with only the rig burning.

smoke plume will drift away from the populated centers. Zones of convergence on the sea can also be used to contain oil. Local oceanographers must be consulted to determine the location of these zones. The Coast Guard and local fishermen are also familiar with currents in an area.

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FIGURE 23.35 Oil burning on the water without containment from a tanker that is obscured by smoke.

23.4.2. Oil Containment and Diversion Methods As discussed earlier, an oil slick should be at least 0.5 to 3 mm thick in order to quantitatively remove significant amounts of oil. It is not fruitful to burn thin slicks anyway. Several methods for increasing the thickness of a slick to this level or for maintaining a thickness at or above this level are discussed in this section.

23.4.2.1. Fire-Resistant Booms The biggest concern with containment booms for in-situ burning is the ability of the boom’s components to withstand heat for long periods of time. Very few fire-resistant booms are commercially available because the market is small and the cost of production is high. Fire-resistant booms can sometimes cost considerably more than conventional booms. These booms are constantly being tested for fire resistance and for containment capability, and designs are modified in response to test results. The fire resistance of these booms has been extensively tested at the USCG Fire and Safety Test Detachment in Mobile, Alabama. These booms have also been tested for strength, integrity, and oil containment capabilities during tow tests at the Oil and Hazardous Materials Simulated Environmental Test Tank (OHMSETT) facility in Leonardo, New Jersey. The different types of fire-resistant boom are water-cooled booms, stainless steel booms, thermally resistant booms, and ceramic booms. Fire-resistant

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booms require special handling, especially stainless steel booms, because of their size and weight. Thermally resistant booms are similar in appearance and handle like conventional booms, but are built of many layers of fire-resistant materials. (The various types of fire-resistant boom were shown in Figure 23.4.) Fire-resistant booms developed by Environment Canada in the late 1970s consisted of a series of ceramic, stainless steel designs or those that used air or water sprays to contain oil during burning.145,146 Figure 23.36 shows an early ceramic boom being tested at OHMSETT. Environment Canada also worked with conventional booms using water-cooling systems and with log booms. In the early 1980s, Dome Petroleum Ltd. further modified the stainless steel boom developed by Environment Canada. The Dome boom consists of 1.5 m vented stainless steel flotation units with a pentagonal cross section. A stainless steel panel attached to the top of each unit creates the freeboard, and a PVCcoated nylon skirt attached to the bottom of the float provides the draft. The flotation sections are attached using 0.75 m flexible panels constructed of stainless steel mesh encased in a Fibrefax blanket with a PVC-coated nylon skirt. The Dome boom was designed to be used for more than one in-situ burn incident. Fire-resistant booms manufactured today are generally designed to survive several burns at one site, but are then disposed of or refurbished. The only documented use of a fire-resistant boom for burning at a major oil spill is the use of the fireboom at the Exxon Valdez spill.44 This Elastec/American Marine boom with some experimental prototype sections was used during the NOBE in 1993 at which two burns of 50,000 L of oil were conducted. After the first burn, small gaps were found in the Nextel ceramic fabric above the

FIGURE 23.36 The ceramic fire-resistant boom being tested at OHMSETT.

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waterline between the flotation logs, caused by abrasion. The damage was minor enough to allow the boom to undergo a second burn. After the second burn, the stainless steel wire mesh in one of the prototype sections had parted, resulting in the loss of 2-meter-long flotation logs. This was caused by the use of small sections of steel wire mesh during manufacture rather than using full sheets. ASTM has developed a standard to test the durability of fire-resistant booms for in-situ burning.83 The standard is a minimum 5-hour test involving three 1-hour burning periods with two 1-hour cool-down periods between the burning periods. Booms are tested in a test-tank with oil or diesel fuel. Oil is pumped into the center of the boom at a predetermined rate and is burned. The oil is continuously fed into the boom for 1 hour and then is shut off, allowing the burn to die out. The boom then cools for 1 hour and is tested for two additional 1-hour burn/1-hour cooling sessions. At the start of the third burn, oil is pumped into the boom to test for gross leakage. Several booms were tested in this manner. An analogous test was developed using propane and conducted at the OHMSETT test facility.147 The SWEPI fireboom, designed for an ice-infested environment, passed the basic test requirements in 2000, as did four protective covers, including one from Oil Stop and three from Applied Fabric Technologies. Figure 23.37 shows one boom being tested at Mobile, Alabama. In 1994, the Marine Spill Response Corporation (MSRC) conducted atsea towing tests of four fire-resistant booms: the American Marine (3M) Fire Boom, the Applied Fabrics PyroBoom, the Kepner Plastics SeaCurtain FireGard, and the Oil Stop Auto Boom Fire Model.148 The purpose of these tests was to evaluate the relationship between boom performance and buoyancy-to-weight ratio, tow speed, and sea state. The booms were towed in a U-configuration at tow speeds of between 0.25 and 1.25 m/s (0.5 and 2.5 knots). The results of these tests showed that the higher the buoyancy-toweight ratio of the boom, the faster the boom can be towed before it will submerge. In general, fire-resistant booms have a lower buoyancy-to-weight ratio than conventional booms. It was also found that three of the four booms tested exhibited mechanical failure at high tow speeds. The report further concluded that the mechanical integrity, sea-keeping performance, and ease of deployment and recovery of commercially available fire-resistant boom must be improved. The USCG and the USMMS evaluated the containment behavior of the fireresistant booms currently on the market in a test-tank and compared these results with previous at-sea performance results.149,150 These studies determined the tow speeds at which the booms first began to lose oil (“first loss”) and the speed at which a continuous, significant loss occurs (“gross loss”). It also determined the rate of loss of oil at specific tow speeds and the tow speed at which the boom physically failed, that is, became submersed or suffered structural damage. The results of these tests are summarized in Table 23.11.

149

First and Gross Loss Tow Speeds, m/s (knots) Wave Conditions*

Loss Rate Test, L/min @ Tow Speed m/s (knots)

Boom Type

Loss

C

1

2

3

1st loss þ 0.05 m/s (0.1 knots)

1st loss þ 0.15 m/s (0.3 knots)

Critical Tow Speed m/s (knots)

PyroBoom

First Gross

0.51 (1.00) 0.62 (1.20)

0.37 (0.72) 0.48 (0.93)

0.55 (1.07) 0.67 (1.30)

0.49 (0.95) 0.57 (1.10)

246 @ 0.57 (1.10)

534 @ 0.67 (1.30)

1.03 (2.75)

Spill-Tain

First Gross

0.44 (0.85) 0.54 (1.05)

0.21 (0.40) 0.31 (0.60)

0.44 (0.85) 0.54 (1.05)

0.45 (0.88) 0.55 (1.07)

27 @ 0.49 (0.95)

178 @ 0.59 (1.15)

3.08 (>6.00)

American Marine/3M

First Gross

0.44 (0.85) 0.57 (1.10)

0.37 (0.72) 0.46 (0.90)

0.45 (0.87) 0.59 (1.15)

0.46 (0.90) 0.59 (1.15)

64 @ 0.49 (0.95)

303 @ 0.59 (1.15)

1.16 (2.25)

Dome Boom

First Gross

0.49 (0.95) 0.68 (1.32)

0.38 (0.75) 0.54 (1.05)

0.49 (0.95) 0.62 (1.20)

0.52 (1.00) 0.64 (1.25)

32 @ 0.54 (1.05)

151 @ 0.64 (1.25)

1.03 (2.00)

Oil Stop

First Gross

0.46 (0.90) 0.63 (1.22)

0.41 (0.80)

0.55 (1.07)

0.52 (1.00)

74 @ 0.51 (1.00)

286 @ 0.61 (1.20)

1.80 (3.50)

Chapter | 23 An Overview of In-Situ Burning

TABLE 23.11 Performance of Fire-Resistant Containment Booms

*Wave Conditions. C ¼ calm water, no waves generated. 1 ¼ wave #1, regular sinusoidal wave, H1/3 ¼ 25 cm (9.8 in), L ¼ 4.9 m (16 ft). 2 ¼ wave #2, regular sinusoidal wave, H1/3 ¼ 33.8 cm (13.3 in), L ¼ 12.8 m (42 ft). 3 ¼ wave #3, regular sinusoidal wave, H1/3 ¼ 22.6 cm (8.9 in), L not calculated.

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The following are the conclusions of these tests. l

l

l

l

In terms of oil containment, the performance of the fire-resistant booms was similar to that of conventional, non-fire-resistant booms, with first losses occurring at tow speeds of 0.44 to 0.52 m/s (0.85 to 1.0 knots) in calm waters. These losses were relatively unaffected by regular waves and were reduced slightly by short-crested waves. The physical failure of fire-resistant booms was also similar to that of conventional booms with critical tow speeds between 1 and 1.5 m/s (2 and 3 knots), with the exception of the Spill-Tain Boom for which the critical tow speed exceeded 3 m/s (6 knots). The critical tow speeds determined during the at-sea tests were lower by 0.25 to 0.75 m/s (0.5 to 1.5 knots) than the critical tow speeds determined during tank tests. From the limited data available from the in-tank and at-sea tests, an increase in the buoyancy-to-weight ratio of the boom appears to increase the boom’s ability to contain oil at higher than normal tow speeds.

The following is a brief description of the fire-resistant booms currently on the market. Detailed specifications for these booms can be found on the manufacturer’s websites. American Fire Boom (http://www.americanmarine.org/ceramic.html) has flotation sections made of rigid ceramic foam surrounded by two layers of stainless steel knitted mesh, a high temperature-resistant ceramic textile fabric, and a PVC outer cover that also forms the skirt. This boom is normally deployed from a container or tray. This is the boom used at NOBE, as shown in Figure 23.5. Auto Boom Fire Model (Oil Stop - http://www.oilstop.com/fireboom.html) is an inflatable boom with an internal water-cooling system. The flotation chamber is insulated with a ceramic blanket covered with a stainless steel mesh. The skirt is made of a polyurethane fabric. This boom can be stored and deployed from a reel. Before the boom is placed in the water, however, the water-cooling system must be connected on a large, flat area. FESTOP Fire Boom is a stainless steel fireboom available in two sizes that is claimed to withstand temperatures up to 1,260 C. The company is located in France. Figure 23.37 shows this boom after a short demonstration burn. The Hydro-Fire Boom (Elastec/American Marine e http://www. americanmarine.org/hydro.html) is a water-cooled, inflatable boom that is sometimes stored on and deployed from a reel. A 150-m length of boom can be stored on a reel with sections (30 m). Figures 23.38 and 23.39 show this boom before and after the ASTM test burn. PyroBoom (http://www.appliedfabric.com/content/pages/pyroboom.php) (Applied Fabric Technologies) is a fence boom with a freeboard constructed of a patented refractory material and a skirt made of a urethane-coated material. Hemispherical stainless steel floats are attached to either side of the fence portion. This boom can be stored in a container and deployed from a large flat

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FIGURE 23.37 The Festop fireboom shown after a short demonstration fire.

FIGURE 23.38 The Hydro-Fire Boom shown before testing.

area, or it can be deployed from a reel system, which in turn is stored in a container. The boom is shown in Figures 23.40 and 23.41 before and after the burn test. PocketBoom (http://www.appliedfabric.com/content/pages/pocketboom. php) (Applied Fabric Technologies) is a stainless steel boom that is similar

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FIGURE 23.39 The Hydro-Fire Boom shown after the ASTM test.

FIGURE 23.40 The PyroBoom shown before testing.

to the design of the Dome Boom but in a small version. Figures 23.42 and 23.43 show this boom before and after testing. SeaCurtain FireGard (Kepner Plastics) uses a heavy-gauge stainless steel coil covered with a high-temperature refractory material to make up the flotation sections of the boom. The skirt is made of a polyurethane-coated polyester or nylon fabric. The stainless steel coil causes the boom to self-inflate during deployment, but the boom must be manually compacted during recovery. The boom is no longer actively listed. Spill-Tain Fire Proof Boom is a stainless steel boom constructed in sections connected by hinges. Floats, made of stainless steel filled with closed cell glass foam, are located at the midway point of the stainless steel panels, so

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FIGURE 23.41 The PyroBoom shown after the ASTM test.

FIGURE 23.42 The PocketBoom shown before testing.

that the lower half of the panel forms the skirt and the upper half forms the freeboard. This boom is stored and deployed from a folded position. Larger sizes of the boom would require a boat hoist or crane for deployment. This boom is no longer actively listed as an oil spill product. (This boom is shown in Figure 23.7 under the ASTM test.)

23.4.2.2. Conventional Booms Conventional booms cannot usually be used to contain burning oil because the construction materials either burn or melt, compromising the boom’s ability to contain the oil. It is often much quicker to get a conventional boom to a spill site, however, as it is much less expensive and very few fire-resistant booms are stockpiled at spill response depots.

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FIGURE 23.43 The PocketBoom shown after the ASTM fire test.

Conventional booms can be used to corral a slick and contain it until a fireresistant boom can be obtained. These booms can also be used to contain and thicken a slick to an acceptable burning thickness and then burn it, thus sacrificing the boom. The overall burn efficiency of this method is questionable, however, as the boom will not remain intact for very long once the oil is burning. When the boom fails, the slick could spread and quickly become too thin to sustain burning. Logs or other floating material can sometimes be used as temporary booms. In narrow rivers, dams can be constructed across the upper layer of water to contain or divert the oil for burning.

23.4.2.3. Boom Configurations and Towing The size of boom required for an in-situ burn depends on the amount of oil to be burned. Generally, the oil in the boom should fill no more than one-third of the area of the catenary. If the boom is too long, it will be difficult to control, and the stress on the boom may be too great. If the boom is too short, the catenary may not be large enough to contain the burned oil. In general, the length of boom used ranges from 150 to 300 m.75,152 Most commercial booms come in standard lengths of 15 or 30 m. Figure 23.44 shows the various configurations of boom. The relationship between the boom length and the area of oil that can be contained is shown in Figure 23.45. The overall height of the boom should be equal to the maximum expected wave height (short period waves, not swell) from peak to trough. An important factor to be considered when containing oil is the direction and speed at which the boom is being towed. The distance from the burn to the tow vessels should be far enough that the burn does not pose any danger to the tow vessel or to personnel onboard the vessel. Temperature profile tests performed during the NOBE trials showed that the air and water temperature ahead

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FIGURE 23.44 Fire-resistant boom designs.

of the burn levels off very quickly.86 Therefore, unless the tow line was very short (only a few meters), the heat from the fire would not be an issue. As well, since the boom is being towed upwind, the smoke from the burn should not reach the tow vessels.

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Metres 60 m

Slick or Burn Area (m2)

3000 Each curve represents the value of the length of the slick or burn from the apex of the boom

50 m

2000

40 m

30 m 1000 20 m 15 m 10 m 5m

0 0

100

200

300

400

500

Boom Length (m)

Feet

35000

2

Slick or Burn Area (ft )

30000

200 ft

Each curve represents the value of the length of the slick or burn from the apex of the boom

160 ft

25000 130 ft

20000

15000 100 ft 10000 65 ft 50 ft

5000

30 ft 15 ft

0 200

400

600

800

1000

1200

1400

1600

1800

Boom Length (ft) FIGURE 23.45 Nomogram to calculate burn or slick area.

Tow lines from tow boats should generally be at least 75 m long. The boom must always be towed into the wind so that the smoke will go behind it. As tow speeds are measured relative to the current, the boom may have to be towed very slowly or even downwind to maintain a low enough speed relative to the

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current while towing into the wind. If the boom is towed too slowly, however, the burn will begin to move up toward the end of the boom. In general, the boom must be towed at a speed of less than 0.4 m/s (0.7 knots) relative to the current in order to prevent the oil from splashing over the boom or becoming entrained beneath the boom. The towing speed may have to be increased periodically if the burn begins to fill more than two-thirds of the boom catenary.76 If contained oil does become entrained in the water column below the boom or splash over the boom, it will resurface or pool directly behind the apex of the boom. This oil could be reignited by burning oil inside the boom or by oil that splashes over the boom. Another important factor in ensuring that the oil is properly contained for burning is the configuration of the boom. Booms can be towed in various configurations, depending on the equipment available and the weather and seastate conditions. The various conventional configurations for towing oil spill booms are shown in Figure 23.46. The standard configuration is a length of fire-resistant boom connected with tow lines to two vessels at either end of the boom to tow the boom in a catenary or U shape, as shown in Figure 23.46 a. A tether line or cross bridle is often secured to each side of the boom several meters behind the towing vessels to ensure that the boom maintains the proper U shape, as shown in Figure 23.46b. This tether line or cross bridle is very useful in maintaining the correct opening on the boom tow as well as preventing the accidental formation of the J configuration. The tether line can also be attached to the vessels as shown in Figure 23.46c. The advantage of this method is that boat operators can detach the tether line very quickly in case of an emergency. When using the standard U-configuration, it can be difficult to ensure that the two towing vessels maintain the same speed. To overcome this problem and to increase control over the boom configuration, three vessels can be used as shown in Figure 23.46d. One vessel tows the boom by pulling from the center, using tow lines at each end of the U, while the other two vessels pull outward from the ends of the boom to maintain the U shape. This configuration was used during the NOBE tests in 1993. During these tests, 210 m of boom were towed in a modified U-configuration. A 45-m tether line or cross bridle was attached across the ends of the U. One vessel towed the boom using two 120-m lines attached to the ends of the U. The U was kept open by lines towed from two other vessels in an outward direction at an approximately 45 angle. The towing speed was maintained at 0.25 m/s (0.5 knots) throughout the burn. Bitting and coworkers tested a number of these configurations and found that many of the proposed configurations in this subsection were viable.151 If the oil is nearshore, a boom or booms can be used to divert it to a calm area, such as a bay, where the oil can be burned. An example of this method using two booms is shown in Figure 23.46e. Diversion booms must be positioned at an angle relative to the current that is large enough to divert the oil, but

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FIGURE 23.46 Towing boom configurations for in-situ burning.

not too large that the current would cause the boom to fail. The boom must be held in place either by anchors, towing vessels, or lines secured to the shoreline. In nearshore situations, anchors can be used to secure booms in a stationary position. It is important, however, that a proper anchor is used, particularly in high currents, to ensure that the boom will stay in place for the duration of the

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burn. Various types of anchors suitable for anchoring containment booms are available.86

23.4.2.4. Novel Containment Configurations for in-situ Burning A number of boom configurations or containment methods have been proposed in the literature or at workshops. Most of these methods have not been tested or have not been tested quantitatively. Log booms, which are illustrated in Figure 23.47a, have been used several times in northern Canada. In fact, the first documented in-situ burn was conducted successfully using a log boom on the Mackenzie River in 1958.72 Although log booms burn, if the boom maintains its buoyancy ratio, there is sufficient time to conduct a burn lasting several hours. The major problem with log booms is the leakage between sections. The gaps between sections are usually sealed with fire-resistant material such as fiberglass cloth. Booms can also be used to divert oil slicks rather than to contain them. Diversion modes are usually used when the current is too fast for the oil to be contained in a U-configuration, that is, greater than 0.4 m/s (0.75 knots). Conventional booms can be used to divert oil so that the oil is actually burned beyond the boom or contained by a natural barrier, such as the shoreline. One such method involves concentrating and “funneling” the oil through an opening created by two booms as shown in Figure 23.47b, so that the burning takes place mostly behind the boom. As far as is known, this type of configuration has never been tested even in model form. A boom with solid flotation sections would have to be used because any flame impingement on an inflatable boom causes rapid failure. Despite the apparent weaknesses, the proposal has merit in that it would only be used in a situation where complete containment was not necessary and losses, even failures, would not cause major problems. The rear opening would have to be wide enough to avoid buildup of oil in front of the boom and narrow enough to ensure that the oil slick is thick enough to sustain burning even with the re-spreading that would occur behind the boom. A modification of this configuration is the use of paravanesdrigid metal boom-towing sections that attach at the rear mouth of the conventional boom (see Figure 23.7c). This is also an untested concept, but there is an advantage in having relatively fire-resistant paravanes at the mouth of the boom. Thus, if fire does propagate inside the boom, there will be no catastrophic boom failure. The use of corrugated steel sheets as temporary firebooms has also been proposed.152 The corrugated sheets could be fastened to metal stakes in shallow water, as shown in Figure 23.47d, or coupled to drums for application in deeper waters, as shown in Figure 23.47e. As this has never been tested, it is not known how long the corrugated steel would withstand the heat flux of the fire, although it would probably withstand at least a few hours.

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FIGURE 23.47 Untested containment/diversion configurations for in-situ burning.

23.4.2.5. Deployment of Booms for In-Situ Burning The deployment procedures for fire-resistant containment booms depend on the type of boom used. The water-cooled booms are either inflatable or flexible in some way, and, therefore, they can be stored on and deployed

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from a reel. However, these booms sometimes require a large flat area for the proper installation of the water-cooling equipment as the boom is removed from the reel. Stainless steel booms and thermally resistant booms are rigid and therefore must be stored in sections in a container and also require a large flat area to lay out and connect the sections. Because of their rigidity and weight, a winch or crane is normally required to assist in deploying and recovering these booms. After floating in the water for some time, the containment boom becomes waterlogged, making it much heavier than when it was deployed. The vessel used to recover the boom must therefore be stable enough to handle this weight, especially if a crane or winch is being used. See Section 23.4.5 for more information on vessels used for deploying booms. Because of the added difficulty in handling some fire-resistant booms, they may be damaged during deployment and recovery. Care must be taken to ensure that the boom is moved slowly and handled carefully. For example, the cinch and choker attachment of a crane can damage a boom, and it is therefore better to use a web belt to lift the boom. It is also much easier to deploy and recover the boom if a powered reel is used. The containment boom normally comes in sections that are joined by a connector. Many of the commercially available fire-resistant booms are being designed with standard connectors as prescribed by ASTM or to accommodate adapters that fit such standard connectors.153 These connectors allow different types of booms to be joined easily and securely. In any case, if more than one type of boom is used for containment, the connectors on these booms should be checked first to ensure that they can be properly joined. If a burn is to be performed nearshore, that is, within 5 km, the boom can be deployed from shore and then towed out in a straight line. It is for this reason that the ASTM standard for fire-resistant boom indicates that a fire-resistant boom section that is at least 150 m long must be able to withstand towing in a straight line at 2.5 m/s (5 knots) for a period of 2 hours.85 If the burn is to take place too far from shore for the boom to be deployed from the shoreline, the boom must be deployed from a vessel. Again because a fire-resistant boom is quite cumbersome, a large deck area is normally required for boom deployment. The following is a typical procedure for deploying a boom in open water from a vessel using a standard U-configuration. l

l l

l

The deployment vessel situates itself far enough downwind from the oil so that there is enough time to deploy the boom before approaching the oil. The deployment vessel aligns itself so that its bow is facing upwind. Before the first part of the boom is deployed from the deck, a tow line for the towing vessel is attached to the end. The boom is deployed off its stern so that the wind causes the boom to trail behind the vessel.

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When the last section is deployed, the end of the boom is attached with a tow line to the deployment vessel, which now becomes one of the towing vessels. The tow line at the other end of the boom is then attached to a second towing vessel. The second towing vessel heads upwind until the proper U-configuration is formed.

If a tether line or cross bridle is used across the opening of the U (see Figures 23.46b, c, and d), this line should be attached to the end of the boom or tow line closest to the deployment vessel before the last section is deployed. Once the U is formed, a third vessel will have to bring this line across to the other end of the boom or tow line and connect it. If, as shown in Figure 23.6d, a third tow vessel is used for stability, the tow lines for this third vessel should also be attached as the boom is deployed and then attached to the third vessel, which then situates itself in-between and ahead of the other two tow vessels. The method for deploying a diversion barrier in a river (see an example in Figure 23.46e) is very different from deploying a containment boom in a U-configuration in the open ocean. The boom must be held in place at an angle relative to the current that is large enough to divert the oil, but not too large that the current would cause the boom to fail. The boom must, therefore, be secured in place either with lines to the shoreline or towing vessels, or by anchoring the boom on the river bottom. Unless the boom can be fixed to both shorelines, it is normally more secure to use anchors. In fact, the Canadian Petroleum Association has found that two anchors placed in series are usually required to prevent the boom from moving in high-current situations.154 The proper deployment of anchors in order to hold a boom can be difficult, as they must be deployed slowly and systematically in order to properly set in the river bottom. The anchors should be securely in place before the boom is deployed. The Canadian Petroleum Association has developed a detailed guideline for the deployment of anchors and diversion boom in fast-flowing rivers. This guideline is presented in Figures 23.48 and 23.49.

23.4.2.6. Backup Booms A backup boom can be placed 200 to 300 m behind the burn to contain any oil that has been entrained or has splashed over a fire-resistant boom during the burn. A conventional boom that is not fire-resistant can be used, as any burning stray oil would be extinguished on its own or by the fire-extinguishing vessel before it reached this boom. It has also been found that oil escaping from the fire-resistant boom will usually pool directly behind the boom because of eddies formed in this area. This oil usually remains in this area for some time and therefore can become relighted or remain lighted. If this oil escapes from this area, it will spread and

Chapter | 23 An Overview of In-Situ Burning

FIGURE 23.48 River boom deployment schematic (adapted from PROSCARAC, 1992).

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Step 1 Install anchor buoys at upstream and downstream ends of control points

Step 2 Connect two CPA anchors together on work barge deck with appropriate cable, Anchor chains and anchor marker buoys

Step 3

In-Situ Burning

Step 6 After both anchors are in river, hook work boat onto anchor cable marker buoy and start pulling anchors downstream to set them

Step 7 After the CPA anchors are set, tow the river boom to the anchoring cable for attachment

Step 8

Mark approximate location After the river boom is where river boom will be attached to the anchor, deployed using a fixed attach shoreline ropes landmark. Move upstream or cables to the boom approximately 200 feet. Important - Never set anchors out farther than the maximum deflection angle and boom length Step 9 allowed by the current conditions

Step 4 Put out anchor marker buoy, deploy front CPA anchor, once anchor is on bottom work boat slowly drifts down stream - do not get chain or rope into the teeth of anchor

Step 5 As chain from front CPA anchor tightens, start deploying rear CPA anchor. Be careful not to tangle rope or chain into anchor.

After the shoreline ropes or cables are attached, pull the boom toward the shore. Ensure that the angle of the boom doesn’t exceed the critical angle.

Step 10 Burn is conducted once boom is in place. After the burn is completed boom and anchors are removed and all equipment cleaned and returned

Ca

ble

Fire resistant boom

s Burn Area

FIGURE 23.49 River boom deployment procedures (adapted from PROSCARAC, 1992).

become too thin to sustain burning and can therefore be safely collected in the backup boom.

23.4.2.7. Alternatives to Booms A number of ideas have been proposed to replace fire-resistant booms when burning oil on water. Marine Research Associates have proposed the use of modified barges to contain the oil for burning. Some of these barges are shown in Figure 23.50.152 One concept involves cutting the center tanks from a barge or extensively modifying a barge without center tanks, so that only wing tanks remain. The barge would be towed at the apex of a boom and oil contained within the center of the barge as illustrated in Figure 23.50a. A design for a barge with inflatable sides is illustrated in Figure 23.50b, and another design

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FIGURE 23.50 Novel concepts for burning oil on water (adapted from Maritime Research Associates, 1998).

that uses forced air to enhance burning is illustrated in Figure 23.50c. These concepts and several variations of them are analyzed in detail in the Marine Research Associates report to US MMS, which shows that the barge concepts should provide a stable burn platform and a far extended life over fire-resistant

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FIGURE 23.51 Bubble barrier.

boom.152 These concepts are very costly to implement and result in large, heavy devices. Bubble barriers are another concept that has been relatively effective at containing oil when tested in calm waters under actual operation situations, although it has never been used in conjunction with burning. A bubble barrier consists of an underwater air delivery system that creates a curtain of rising bubbles that deflects the oil. This concept is illustrated in Figure 23.51. Work on bubble barriers has shown that the horsepower requirement is high, with a very large compressor needed for barriers longer than about 100 m.152 Testing has also shown that a large blower can power a bubble barrier using a firehose as outlet. The maximum length of the barrier in this case varies from 50 to 150 m.155 Environment Canada has also worked on the development of a water jet barrier that could potentially be used for in-situ burning.156 The design developed consists of high-pressure hoses connected to a water pump. Each arm of the barrier is formed by two hoses, each with four evenly spaced sets of opposing jets. The force from the water jets holds the oil in the V formed by the barrier arms. This containment would allow oil to be safely burned. It was also felt that air entrained by the water jets would increase the efficiency and cleanliness of the burn. Unfortunately, these claims have not been fully tested due to mechanical problems and difficulties in maneuvering the barrier using its current configuration.

23.4.3. Ignition Devices A variety of ignition devices or methods, both commercial and noncommercial, have been used to ignite oil slicks, although the methods of igniting oil on water

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have not been well documented.105,109 Many of the methods used are modifications of ignition devices used for other purposes. In general, an ignition device must meet two basic criteria in order to be effective. It must apply sufficient heat to produce enough oil vapors to ignite the oil and then keep it burning, and it must be safe to use. Safety issues to be considered when operating ignition devices are outlined in a subsequent section. Research has shown that to a certain extent the thicker the slick, the more easily and quickly it will ignite. The main factor, the lighter, that is, the more volatile or less weathered the oil, the more easily it will ignite. For heavy oils, more heating time is required to produce enough ignitable vapors. It is suggested that for heavy oils, a primer, preferably diesel fuel or kerosene, is used to soak in the oil for a few minutes before applying an igniter. As discussed above, unstable emulsions can be ignited, but may require additional energy before burning is sustained. Yet, stable emulsions can be very difficult to ignite because the water in the oil acts as a heat sink and a high amount of energy is required to heat the water and vaporize the oil before burning can be sustained. Primers are quite useful in igniting emulsions. Commonly available devices, such as propane and butane torches, have been used in the past to ignite oil slicks. They are more effective on thick slicks, however, as torches tend to blow the oil away from the flame on thin slicks, thus hampering ignition. Weed burners or torches have also been suggested as an ignition device for in-situ burning. In the late 1970s, research began into developing aerial ignition devices for in-situ burning. The various commercial and noncommercial devices or methods available for igniting oil slicks and the operational procedures for their use are discussed in this section.

23.4.3.1. Helitorches The most sophisticated commercial devices used today for igniting oil slicks are the helitorch igniters. These are helicopter-slung devices that dispense packets or globules of burning, gelled fuel and produce an 800 C flame that lasts up to 6 minutes.109,157 This type of igniter was designed for the forestry industry and is used extensively for forest fire management. Two helicopterbased systems suitable for igniting in-situ burns are the Simplex helitorch manufactured by Simplex Manufacturing of Portland, Oregon, and the Universal Drip Torch available from Universal Helicopters of Deer Lake, Newfoundland, or Canadian Helicopters of Prince George, British Columbia. These helitorches are shown in Figures 23.52 and 23.53. The Simplex helitorch was used effectively during the NOBE in-situ burn exercise off the coast of Newfoundland in 1993.158 Simplex information can be found at http://www. simplexmfg.net/english/brochures/5400_2009%5BConverted%5D.pdf. While the two units are assembled differently, they operate in a similar way. Both have a 205-L fuel barrel connected to a fuel pumping and ignition system. On the Simplex torch, all parts are mounted on an aluminum frame to which the

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FIGURE 23.52 The Simplex Helitorch.

FIGURE 23.53 The Universal Drip Torch.

slinging cables are attached. The pumping and ignition system of the Drip Torch are attached to the fuel transport pipe, which is connected with a hose to the opening of the barrel. The pipe with all the attachments is mounted on top of the barrel with clips, and the whole system is slung by cables running from the pipe. The components of a helitorch are illustrated in Figure 23.54. The fuel used in the helitorch system is a mixture of a powdered gelling agent with either gasoline, jet fuel, or a diesel/gas mixture. SureFire, an aluminum soap, is the most commonly used gelling agent. Alumagel is another type of gelling agent that was used to make Napalm for military purposes. It is currently available only through military surplus. The SureFire powder is more readily available and gels faster than Alumagel. An improved version of SureFire gell, known as SureFire II, is now available. The manufacturer claims that this new product mixes easier, gels faster and at a lower temperature, and

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FIGURE 23.54 Helitorch Components.

remains in suspension longer than the original product. SureFire and SureFire II are available from Simplex Manufacturing in Portland, Oregon. When preparing to operate a helitorch, the gelling agent and fuel must be mixed in a secure area well away from any ignition sources. The first step is therefore to set up a mixing area where the fuel is mixed with the gelling agent and a loading area where the barrels are loaded onto the helitorch system. These two areas should be at least 30 m apart and 150 m away from the helipads and helicopter refueling areas. They should also be well away from any ignition sources and upwind from the burn area. The general setup of these areas is shown in Figures 23.55 and 23.56. These areas must be used solely for the work associated with the helitorch and should not be combined with other helicopter operations or other work associated with the burn. No personnel other than the helitorch crew should be allowed in these areas unless authorized by the helitorch supervisor. The organizational structure for all those involved in operating the helitorch system during an in-situ oil spill burn includes a helitorch supervisor, a safety officer, a hook-up operator, and three personnel to carry out fuel mixing. This is typical of the structure described in helitorch operation manuals, which are written mainly for controlled burning on land, that is, forestry operations that require additional team members. For small spills, where very few drums of gelled fuel are needed, this team could be further simplified to the following three persons: the helitorch supervisor, who would also perform the duties of the safety officer and the hookup operator, one fuel mixer, and the pilot. The mixing of gelling agent and fuel, the loading of the fuel, and the hookup of the helitorch to the helicopter should be done on land unless the burn site is too far from land for the helicopter to ferry the helitorch, that is, more than

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Travel path with full torch Wind direction toward burn

Shoreline

Travel path to drop off empty torch

Loading area Minimum 150 m (500 ft)

Helipads and Helicopter refueling area

(See Figure 23.56 for details of the mixing and loading areas)

Fuel mixing area

FIGURE 23.55 Location of fuel mixing and Helitorch loading areas (adapted from OMNR, 1990).159

20 km. In this case, the fuel and agent should be mixed at a land-based site, and the barrels of gelled fuel should be stored on a ship in an area approved for fuel storage. This area must be above deck in a contained, ventilated area, well away from any ignition sources. A loading area should be set up on the ship, where the barrels of gelled fuel will be loaded onto the helitorch system and hooked

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FIGURE 23.56 Setup of fuel mixing and Helitorch loading areas (adapted from OMNR, 1990).159

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up to the helicopter. In this case, any preliminary testing and preparations for the ignition procedure should be done at a land base. The fuel is mixed with the gelling agent directly in the specialized barrels that come with the helitorch unit, using the raised hatch opening in the barrel. The required ratio of gelling agent to fuel depends primarily on the type of fuel and the air temperature. In general, the lower the flash point of the fuel, the less gelled agent is required. The gelling times of various types of fuel when mixed with the SureFire brand of gelling agent are shown in Table 23.12. In most cases, unleaded gasoline is recommended because it is often the most readily available fuel. The mixing ratios should be determined using the tables provided in Table 23.13. Mixing times at various temperatures are also given in these tables. The amount of fuel needed to ignite an oil spill is primarily related to the number of slicks and the degree of weathering of the oil. The amount of fuel should not normally be related to the amount of oil to be burned. During the NOBE burn test in 1993, 20 L of gelled fuel were used to ignite a slick of 50,000 L. One barrel of gelled fuel containing 180 L could ignite approximately 450,000 L of oil covering the same area as during this trial. Figure 23.57 shows a helitorch being discharged of excess fuel before the helicopter returned to base. The volatility of the type of oil used and the temperature may also affect the amount of gelled fuel required. It should also be noted that the amount of gelled fuel dropped depends on the individual operator, since not every operator holds down the ignition switch for the same amount of time. Using the carrying handles on the barrel, the barrel containing the gelled fuel is transported to the loading area and attached to the helitorch frame or ignition system. The attachment of the helitorch to the helicopter is illustrated in Figure 23.58. The complete system is then attached to the helicopter using slinging cables. The electrical connection runs along one of these cables. For ignition purposes, the torch can be hooked up at right angles to the frame so that the pilot can see the ignition head. If the unit is being transported a long distance, however, it should be hooked up parallel to the frame to reduce the drag on the unit and conserve the helicopter’s fuel. Before the ignition preparation begins, the helicopter should set down on a helipad on a ship near the site to change the position of the torch perpendicular to the frame. Before the helitorch is deployed, wind conditions are checked so that the pilot can approach the burn from an upwind or crosswind direction. Water currents are also checked to ensure that the burning gel will not drift toward any vessels involved in the burn operation. A test drop can be carried out. If this indicates that the gelled fuel is igniting and falling properly, the pilot positions the helicopter over the desired location, fires the torch on a slow pass, and then leaves the area. If igniting a fuel with a high flash point, the pilot may have to hover over the burn area and release multiple balls of burning fuel to concentrate the fire in one location.

Fuel Type

Mixing Time Required to Attain Desired Viscosity (depends on temperature and mixing ratio)

Effect of Air Temperature

Stability of Gelled Fuel

Jet Fuel A

Mixes very slowly (20 to 120 min.)

Recommended when air temperatures are high, because of stability, but longer mixing time is required.

Most stable e lasts 4 to 5 weeks, 2 to 3 days at higher than 20 C (68 F).

Jet Fuel B

Mixes quickly (8 to 18 min.)

Increase in air temperature has little effect on mixing time.

Stable for 2 to 3 weeks or 2 to 3 days at higher than 20 C (68 F).

Regular or Unleaded Gasoline

Mixes fairly quickly (10 to 45 min.)

Recommended for air temperatures below 10oC (50oF) to ensure continuous ignition.

Stable for 2 to 3 weeks or 2 to 3 days at higher than 20 C (68 F).

70% Diesel/30% Gasoline

Mixes slowly (10 to 110 min.)

Increase in air temperature affects mixing time.

Stable for 2 to 3 weeks or 2 to 3 days at higher than 20 C (68 F).

Comments

Chapter | 23 An Overview of In-Situ Burning

TABLE 23.12 Gelling Times of Some Oils (Using SureFire)

Percentage of gasoline should be increased below 10oC (50oF).

841

TABLE 23.13 SUREFIRE Gel Ratios Using the following table select an appropriate mixing ratio, then locate the graph for the type of fuel to be gelled. The time for the gelled fuel to reach the acceptable viscosity can then be determine from the mix type and air temperature. Mixing Ratio (weight of Sure Fire/volume of fuel) Mixture

g/L

lb/U.S. gal

lb/imp. gal.

A

5.9

0.05

0.06

B

7.9

0.07

0.08

C

9.9

0.08

0.1

D

11.9

0.1

0.12

For Air Temperatures in Degrees Celsius

For Air Temperatures in Degrees Fahrenheit

50 45 40 35 30 25 20 15 10 5 0

Unleaded/Regular Gasoline 50 45 40 35 30 25 20 15 10 5 0

Time to Acceptable Viscosity (min.)

Time to Acceptable Viscosity (min.)

Unleaded/Regular Gasoline

0

2

4

6

8 10 12 14 16 18 20 22

30

35

40

80 60 40 20 0

Time to Acceptable Viscosity (min.)

0

2

4

6 8 10 12 14 16 18 20 22 Air Temperature (°C)

Jet Fuel A

140 120 100 80 60 40 20 0 0

2

4

6

8 10 12 14 16 18 20 22

Air Temperature (°C)

Time to Acceptable Viscosity (min.)

100

50

55

60

65

70

70/30 Diesel/Gasoline 120 100 80 60 40 20 0 30

35

40

45

50

55

60

65

Air Temperature (°F)

Time to Acceptable Viscosity (min.)

Time to Acceptable Viscosity (min.)

70/30 Diesel/Gasoline 120

45

Air Temperature (°F)

Air Temperature (°C)

Jet Fuel A

140 120 100 80 60 40 20 0 30

35

40

45

50

55

60

Air Temperature (°F)

65

70

70

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FIGURE 23.57 The helicopter discharging excess gelled igniter before returning to base. This was after igniting the first burn at NOBE.

23.4.3.2. Noncommercial Ignition Devices Simple ignition methods such as oil-soaked paper, rags, or sorbent have been used to ignite oil at actual and test spills.109 For example, gelled fuel in a plastic bag was used to ignite some of the oil from the Exxon Valdez spill. The bag was ignited, thrown toward the slick from a boat, and floated into the slick. It should be noted that diesel oil is preferable to gasoline for soaking materials or as a base for the gelled fuels in hand-held igniters because diesel burns slower, making it safer and supplying more preheat to the slick. As noted earlier, ignition of heavier oils is best carried out using a primer such as diesel fuel and kerosene, and a small wick such as a piece of cardboard or sorbent.40 This enables a start similar to lighting a candle. The flames will then spread to the unprimed oil nearby. An illustration of such an ignition is given in Figure 23.20. In large scale, heavy oil ignition might be accomplished by applying a bit of primer and then using the helitorch. Use of a gelled fuel igniter was found inadequate to directly ignite heavy fuels without the use of an igniter.40 A variety of hand-held igniters have been devised for igniting oil slicks.109 These are meant to be thrown into a slick from a vessel or helicopter. These devices often have delayed ignition switches to allow enough time to throw the igniter and, if required, allow it to float into the slick. These igniters use solid propellants, gelled fuel, gelled kerosene cubes, reactive chemical compositions, or a combination of these, and burn for 30 seconds to 10 minutes at temperatures from 1000 to 2500 C.109 Some igniting devices use reactive metals and therefore do not have to be lit before being deployed. The Kontax igniter is an example of such a self-igniting

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FIGURE 23.58 Mounting configuration of helitorch to helicopter (adapted from OMNR, 1990).159

device that was tested and marketed in the 1970s.109 This device consisted of a metal cylinder filled with calcium carbide with a metal bar coated with sodium metal running through the middle. When the device was thrown into the spill, the sodium metal reacted with the water to produce heat and hydrogen. The calcium carbide reacted with the water to produce acetylene. The hydrogen ignited and in turn ignited the acetylene. The flame from the burning acetylene was sustained long enough to heat the oil and produce vapors that were subsequently ignited. The main concern with this type of device is safety. The

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chemicals must be stored in a very dry place as accidental exposure to water would cause them to ignite. In the late 1970s, during offshore oil exploration activities in the Beaufort Sea, researchers began investigating the use of aerial ignition devices for in-situ burning of oil spills. This work led to the development of two Canadian ignitersdthe DREV Igniter and the Dome Igniter. The DREV igniter was initially designed in the early 1980s by the Canadian Defence Research Establishment in Valcartier, Quebec (DREV), in conjunction with the Environmental Protection Service of Environment Canada.157,160-162 Several configurations of the igniter were built, some of which were intended for deployment on pools of shallow water on ice. This igniter has also been referred to as the EPS Igniter, the AMOP Igniter, the DREV/ABA Igniter, and the Pyroid. It was manufactured by Astra Pyrotechnics, Ltd. (formerly ABA Chemical Ltd.) of Guelph, Ontario, but is no longer in production. The advantage of this type of igniter is that it was built by a licensed pyrotechnic company using approved components and is licensed to be transported by truck or air freight. Figure 23.59 shows this igniter being tested on water. As shown in Figure 23.60, the DREV igniter is an air-deployable igniter with a pyrotechnic device sandwiched between two square flotation pads. Before tossing the device from the aircraft into the slick, the operator pulls the firing switch, which strikes a primer cap. The system has a 10-second delay mechanism that allows time for the device to be thrown and to settle into the slick. After the delay, an initial fast-burning ignition composition is ignited that

FIGURE 23.59 A DREV igniter being tested on open water. This igniter is a pyrotechnic device and is equipped with safety features such as a delay fuse.

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FIGURE 23.60 DREV igniter (adapted from Twardawa & Couture, 1983).162

in turn ignites a rocket motor propellant consisting mainly of 40 to 70% ammonium perchlorate, 10 to 30% magnesium or aluminum metal, and 14 to 22% binder. This produces a ring of fire with temperatures close to 2300 C that burns for 2 minutesdlong enough for the surrounding oil to vaporize and ignite. The Dome igniter was developed by Dome Petroleum Ltd. in Calgary, Alberta in conjunction with Energetex Engineering of Waterloo, Ontario.157,162 It has also been known as the Energetex Igniter or the Tin Can Igniter and was

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FIGURE 23.61 Dome igniter (adapted from Buist et al., 1994).4

intended to be manufactured on site. This unit was not a manufactured unit and was intended to be “home-made.” As shown in Figure 23.61, the wire-mesh fuel basket, which contains a solid propellant and gelled kerosene, is surrounded by two metal floats. An electric ignition system activates a fuse wire allowing about a 45-second delay. The fuse then ignites a thermal igniter wire, which ignites the solid propellant and finally ignites the gelled kerosene. The gelled kerosene burns at temperatures of 1200 to 1300 C for about 10 minutes, allowing the oil to vaporize and burn.

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The drawback of both the DREV and the Dome igniters is that one igniter is required for each slick or part of a slick to be burned. For large oil slicks and oil in melt pools, several igniters may be required, which is costly and time consuming. Another technique for igniting in-situ oil fires is the use of lasers. In the 1980s, Environment Canada sponsored research by Fleet Technology Ltd. (formerly Arctec Canada, Ltd.) and Physical Sciences Inc. of Andover, MA.163,164 This involved testing various laser techniques for igniting a variety of types of oil at different temperatures. The most successful technique in laboratory tests was to use a continuous-wave CO2 laser to heat a localized area of the oil slick. The laser heats the oil to a temperature above its fire point. The heating time varies from a few seconds to more than 30 seconds, depending on the type of oil, degree of weathering, and the oil temperature. The oil vapors are then ignited by a spark produced just above the oil surface by a focused high-power pulse beam from a second laser. A laser-focusing telescope with focusing mirrors is used to aim this second laser. Despite the success of this research, this device was not fully developed due to lack of funding. A hand-held igniter, designed by Simplex and Spiltec, was used during insitu burning tests in 1996 off the shores of Great Britain.110 This igniter consists of a 1-L polyethylene “Nalgene” bottle filled with gasoline gel. The gel was made by mixing 1 L of gasoline with 0.01 kg of SureFire fuel gelling agent, which is the agent used in the helitorch. This bottle and a standard 15-cm marine hand-held distress flare are secured side by side within two polystyrene foam rings. The flare is lit and thrown into the slick, where it burns for approximately 60 seconds before melting the plastic bottle and lighting the gelled gasoline, which in turn lights the oil. Such a device, which is relatively easy to make and to deploy, is shown in Figure 23.62.

FIGURE 23.62 Hand‑held igniter.

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23.4.4. Treating Agents In general, as a burn becomes hotter and thus more efficient, the emissions from the burn are reduced. Work has been done to investigate the use of chemical additives to enhance burning. Although a number of agents can be used, none of these is readily available or has proven to be effective for the task. Agents include emulsion breakers, ferrocene, combustion promoters, and sorbents. Recent Norwegian work showed that combining chemicals that suppress smoke emissions with those that break emulsions and promote combustion is ineffective.105 However, the agents worked well separately. Chemicals could also be added to oil before transport so that it will burn more efficiently if spilled. Oxidizers, such as the chemical ferrocene that is used to solidify rocket fuel, can also be added to oil after spillage. Emulsion breakers and inhibitors are formulated to break water-in-oil emulsions or to prevent them from forming. They have not been used extensively in field trails and rarely in actual spills. Some information is available on specific formulations of these agents, but the formulations vary extensively, and many are not specifically patented. Only three products, Gamelin EB439, Vytac DM, and Breaxit OEB-9, are specifically marketed for oil spills.165 Another product, Alcopol 60, has also been used extensively in field trials in the past. Many products of this type are marketed for use in breaking emulsions that occur in petroleum production, but most have never been applied to oil spills.166 Several tests of emulsion breakers or inhibitors have been conducted. The results of some of these tests may not be useful, however, as they did not focus on the fact that there are several stability classes or water-in-oil states, that is, stable emulsions, mesostable emulsions, unstable emulsions, and entrained water. Furthermore, some testing may not have used proper analytical methods to evaluate the effectiveness. The action required of the product must also be considered when developing effectiveness tests. It has been shown that some products will inhibit emulsification better than they will break an emulsion that is already formed.47 It is therefore appropriate to have two types of tests for each of these functions. In addition, some emulsion breakers are used on the open sea, which is called an open system, and others are used in conjunction with skimmers, tanks, and pumps, with little water present, which is called a closed system. Thus, a total of four different tests are required to test all facets of emulsion treating agents. Environment Canada has evaluated two treating agents in tests that are designed to measure each of the four testing regimes.47,167 Different results were obtained with the same agents in the four different tests. In breaking stable emulsions in open systems, as would be the case in the open sea, the minimum ratio of 1:300 (wt:wt) was needed for Vytac DM and 1:200 for Alcopol 60. In breaking stable emulsions in a closed system such as would be the case with

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a skimmer or a closed vessel, Vytac required a minimum ratio of 1:250 and Alcopol, 1:280. Much less agent is required to inhibit the formation of a waterin-oil emulsion than to break such an emulsion. Furthermore, it was found that mesostable emulsions required much less agent, although this amount was too variable to measure. Tests were also conducted to determine the amount necessary to prevent the formation of emulsions. Buist and coworkers tested several combinations of the oilfield emulsion breaker, EXO 0894, to break emulsions of Alaska North Slope oil before burning.168 It was found that 500 to 5000 ppm of EXO 0894 was sufficient to break emulsions that contained up to 65% water, so that these would burn. Emulsions containing more water would not burn. These laboratory-scale tests also found that at least one hour of mixing time was often required after spraying with the emulsion breaker before the emulsion would break. When used in tests, emulsion breakers have been applied using hand sprayers. In actual situations, it has been proposed that dispersant application equipment would be used. Buist et al. used a herding agent to attempt to thicken oil for burning in pack ice.169-173 The shoreline cleaning agent (EC9580) reduced the area of fluid oils somewhat, but not sufficiently to burn. On thicker oils (perhaps 1 mm) the shoreline cleaner agent was able to increase the thickness to about 2 to 4 mm. The United States Navy herder was found to be best. This was tested at several scales. Outdoor tests showed that the herders were effective at reducing the slicks to burnable areas in pack ice. It should be noted that the herder only worked in calm conditions and that a wind of 1.5 m/s was sufficient to overcome the effect. Ferrocene is a chemical that can reduce or eliminate soot production from burns.173-176 Tests have shown that ferrocene, when mixed with the oil, is highly effective at percentages from 1 to 2%. The problem with ferrocene is that it is more dense than oil and water, so it must be premixed just before burning, which is very difficult to do outside a pan test burn. Ferrocene can now be encapsulated so that it does float and can even be added to the fire once in progress. In the past, several combustion promoters, usually agents that would act as both a wicking agent like a sorbent and an auxiliary fuel, have been tested and shown to be marginally useful.3 None of these agents is currently available. Some have suggested that such agents may be useful in burning uncontained slicks, but further research is required on these agents before they can be applied to actual in-situ burn situations. Sorbents such as peat moss have proven useful in burning by acting as wicking agents.177 It has been shown that such agents could reduce the minimum burning thickness and increase the efficiency of a burn. Sorbents may allow uncontained burning to be conducted in marginal conditions, but again more research is needed. Breitenbeck studied the use of various materials as wicking agents, including bagasse, corn cobs, kenaf, peanut

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hulls, rice hulls, rice straw, and wheat straw.178 It was found that kenaf, a natural fiber similar to jute, was best for the purpose. A study of the shape factor also showed that ellipsoids were best. In burning diesel fuel, the kenaf ellipsoids would enable ignition as low as 0.25 mm and a burn down to 0.08 mm. Even at thicker starting slicks the final thickness was only 0.05 to 0.2 mm. Similar tests on cold water showed similar results; the temperature had little effect. In burning weathered crude oil, using kenaf allowed a burn down to 0.07 to 0.2 mm.

23.4.5. Support Vessels/Aircraft for At-Sea Burns Vessels and aircraft play an important role in a successful in-situ burn operation. Vessels are required to bring equipment and personnel to the burn site and to tow booms, as well as to carry monitoring equipment. Barges and small boats may also be required for standby fire safety operations, monitoring, recovering residue, and storing equipment and residual oil. Tug boats may be required if a tanker must be moved away from the burn area. A sufficient number of vessels must be available to transport and deploy the length of containment boom required at the burn site. The vessels must have a large enough deck to carry the boom as well as any equipment and materials required for handling the boom. They must also be able to move steadily at a slow speed (<0.5 m/s or 1 knot) and have bow-thrusters for easy maneuvering and to quickly move in reverse if required to do so. When containment booms are used in open water, two vessels are required to carry, deploy, recover, and tow each end of the boom, depending on the configuration. For safety reasons, any vessels used in a burn operation must be large and stable enough to carry the necessary equipment in all possible sea states, including storm conditions. A vessel with an onboard crane and one or more tugger winches is recommended for handling equipment on deck and for recovering oil from the water. Separate, smaller tow vessels can be used to tow the boom. Fixed wing aircraft and/or helicopters may also be required to perform surveillance of the spill site, carry monitoring equipment, and perform ignition and extinguishing operations. For safety reasons, twin engine helicopters are recommended for helitorch operations. If a single-engine helicopter must be used, it should be equipped with floats to allow emergency landing on the water. This is not a requirement for twin engine helicopters. When using more powerful twin engine helicopters in ignition operations, however, the oil must be ignited high enough above the slick to ensure that the down draft from the helicopter does not extinguish the burn. For all aircraft operations, reliable air-to-ground communications are essential to coordinate operations. During helitorch operations, this includes communications between the base ship, the helicopter, and the fireboom

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deployment vessels. A safety standby boat having communications with the helicopter may also be desirable under certain circumstances. Any vessel used as a floating base for helicopter operations must have a helideck with a nearby fuel storage area and be equipped for onboard firefighting operations. If using a helitorch or other helicopter-deployed igniter, and the distance from shore is too far for safe helicopter transit from a landbase, another vessel may be required to store the gelled fuel and for helitorch refueling operations. When burning against a shoreline without the use of deflection or containment booms, only one helicopter (preferably a twin engine) is required to carry the helitorch and conduct ignition operations. If booms are needed, vessels or aircraft will be required to transport the equipment to the site. Vessels and aircraft may not be needed to hold the boom in place, however, as this can be done with anchors. A vessel with a low freeboard to allow for easy access to the water surface is recommended for recovering oil residue using skimmers. A seatruck or landing craft used in conventional oil spill response is ideal for access to the water surface. The amount of residue that can be recovered will depend on the displacement of the boat used and the size of tank and cargo that can be safely carried on deck considering vessel stability.

23.4.6. Monitoring, Sampling, and Analytical Equipment Monitoring the emissions during an in-situ burn operation can provide continuous feedback as to whether the burn is progressing properly and safely. A well-planned monitoring program in which data are recorded before, during, and after a burn will also help answer any questions that come up after a burn operation is completed. It is generally recommended that, if possible, the following sampling and monitoring be performed for any in-situ burn operation: l l l

l

Real-time monitoring of PM-10 particulate matter in the smoke Real-time monitoring of volatile organic compound (VOCs) in the smoke Soot sampling for analysis for organic compounds and polyaromatic hydrocarbons (PAHs); and Residue sampling for analysis for organic compounds and PAHs

If it is determined that burning can be done safely and will likely result in the least overall environmental impact, operations should not be delayed because of monitoring and sampling activities.

23.4.6.1. Real-Time Monitoring In general, real-time monitoring of emissions should be performed downwind of the fire and at a point closest to populated areas. Studies of the emissions from in-situ oil burns indicate that the main public health concern is particulate

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matter in the smoke plume, as this is the first emission that normally exceeds recommended health concern levels. For monitoring of particulate matter, it is generally accepted that the concentration of small respirable particles having a diameter of 10 mm or less (PM-10) should be less than 150 mg/m3 for a 24-hour period and PM-2.5 should be less than 35 mg/m3. This is the standard set out by several national authorities, including the National Institute of Occupational Health and Safety (NIOSH), and described in the U.S. Code of Federal Regulations. The second emission of concern is polyaromatic hydrocarbons or PAHs on the particulate matter. Volatile organic carbons or VOCs are a tertiary concern. The devices currently used to carry out real-time monitoring of particulates are the Dustrak, MiniRAM, and DataRAM aerosol monitors, which are capable of detecting the PM-10 and PM-2.5 particulates emitted by a burn. Figure 23.63 shows a cluster of particle-measuring instruments; these are mostly DataRAMs and the old RAMs. It is important to note that the concentrations of particles downwind are very variable over time. A reading can be over the recommended maximum value one instant and then at baseline values the next. Furthermore, the background values must be measured and subtracted from the current value. As both the MiniRAM and DataRAM measure humidity as particulate (which it is), the instructions state that these instruments should not be used in locations where there is high humidity. This certainly applies to locations on boats and near the sea. Experimentation has shown that high humidity can lead to readings as much as five times the maximum exposure value, although the data

FIGURE 23.63 A cluster of particle-measuring instruments that are mostly DataRAMs and the older RAMs. These are set under a test burn.

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can be corrected for this. In both cases, the real-time value on the instrument is noted only for interest. The instrument readings should be electronically recorded and averages calculated from the recorded and corrected data. The DataRAM has an internal recorder. There are no reliable real-time or near real-time methods for monitoring PAHs. There are many methods for sampling particulates using pumps and filter papers, however, and some portable devices are also available. Real-time monitoring of VOCs can be done, but it is fraught with difficulties and inaccuracies. VOCs are sampled in many ways; the use of evacuated metal cylinders, known as Summa canisters, is easy and yields accurate results.

23.4.6.2. Visual Monitoring Visual monitoring is not as effective as monitoring using instruments. Obviously, gases and light concentrations of particulate matter cannot be seen. The trajectory of the smoke plume can be observed, however, and its passage over land, population centers, and other points of concern can be noted, timed, and recorded. This information is necessary if there is ever a question of exposure to emissions after an in-situ burn incident. The prime areas of deposition should be surveyed after a burn to check for soot deposits. If soot is found, it should be sampled for possible analysis if necessary. 23.4.6.3. Sample Collection and Analysis Several methods for collecting and analyzing samples can be used to evaluate the effectiveness of in-situ burning. Not all these methods will be required in an actual emergency burn situation, but depending on the circumstances, regulations, and/or the specific operational plan, some or all of them may be required. The secondary emissions of concern from an in-situ burn are the PAHs associated with the particulate matter. There are several simple methods for collecting these particles for subsequent laboratory analysis. Simple sampling pumps can also be used to confirm particulate counts as well as to trap particles. Analysis of the trapped particles is complex and must be done by a laboratory with the required equipment and experience in PAH analysis. Volatile organic compounds or VOCs are a third emission of concern. These can be sampled using evacuated metal canisters known as Summa canisters, which are opened for a specified time to collect a representative sample of the gas. The compounds must be analyzed by a specialized laboratory with the required equipment and experience in analyzing VOCs from Summa canisters. Figure 23.64 shows Summa canisters along with other basic equipment for monitoring emissions. Full sampling and analysis of chemical spills or situations such as burns is performed regularly by agencies such as the Emergency Response Team (ERT) of the U.S. EPA and the Emergencies Science Division (ESD) of Environment Canada. These organizations may be able to assist in monitoring burns.

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FIGURE 23.64 A collection of instruments and devices for measuring the emissions from burning. The metal canisters are Summa canisters, the instruments are DataRAMs for measuring particulate concentrations, and at the far right of the table are pumps for taking particulates for subsequent PAH analysis. The jars in the front are for sampling the oil and the subsequent burn residue.

Figure 23.65 shows a cluster of instruments put out by Environment Canada and U.S. EPA to monitor a test burn.

23.4.6.4. Data Analysis Analysis should be performed on the electronically recorded real-time particulate data. First, a baseline of background values should be established, which can be done graphically. This background should then be subtracted from the entire data set. This baseline may change throughout the burn, as is evidenced by the data trend moving up or down throughout the monitoring period. If the background does change, which happens frequently, it is more complex to subtract because it changes at each point in time. The background data can be subtracted by using a spreadsheet program that uses the slope of the line to subtract the background at each point in time. Second, the data should be averaged over the time period that the data was taken. Third, the data needs to be corrected to reflect a 24-hour period, which is the time period over which the maximum exposure is usually specified. For example, if the average particulate concentration was 100 mg/m3 over a 6-hour period, the 24-hour value is 25 mg/ m3, assuming there is no other source of particulates.

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FIGURE 23.65 A collection of instruments put out by Environment Canada and the U.S. Environmental Protection Agency to collect emissions and emission data.

Because of these necessary data manipulations, data from real-time monitoring of burn emissions must be regarded with caution and cannot be used to establish that a burn is either safe or unsafe.

23.4.7. Final Recovery of Residue The oil residue left after a burn is usually a heavy, tarlike material that is very viscous and adhesive, similar to a highly weathered oil. The greater the burn efficiency, the higher the density and viscosity of the residue. The burn residue from some types of oil may sink in the water column. This behavior should be determined in advance for common crude and bunker oils being transported in American or Canadian waters. The decision to recover the residue mechanically or leave it to break down biologically depends on the total volume of the residue, whether the residue is

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dense enough to sink, and where it is expected to go if left alone. Other considerations include the immediate availability of equipment and personnel who may be deployed in other recovery efforts. On land residue is readily recovered using mechanical means. At sea, residue is best recovered using a vessel with low freeboard that provides easy access to the water surface. A sea truck or landing craft used in conventional oil spill response is ideal for this purpose. The amount of residue that can be recovered will depend on the displacement of the vessel and the size of tank and other equipment that can be safely carried on the deck. Figure 23.66 shows the collection of burn residue using sorbents. Depending on sea conditions and the dimensions and displacement of the sea truck, such a vessel could carry an estimated 1 to 5 tons of residue. Recovering residue is simplified if the recovery vessel can be operated from a shore base. The vessel can be launched from shore, and the recovered residue can be removed using a vacuum truck on shore. If the residue is too viscous to remove using vacuum devices, it can be removed manually. When conducting a burn on the open ocean, launching and retrieving a boat to recover residue can be difficult. Unless the burn site is within reasonable distance of shore, the residue recovery vessel must be deployed from one of the larger vessels towing the fire boom. This vessel must be equipped with a suitably sized crane to launch and retrieve the residue boat and must have enough tankage or deck space to hold the recovered residue.

FIGURE 23.66 The collection of residue from the last burn at NOBE. The residue is being collected using sorbents.

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Transferring the recovered residue to a larger vessel could be difficult, especially if the larger ship has a high freeboard. The residue tanks should therefore be carried on the ship with the lowest transfer height. Residual oil can also be collected in a backup boom and recovered using sorbents or skimmers suitable for use with heavy oil. Depending on the volume, the residue can be recovered or transferred using either a vacuum suction system or a submersible pump, or it can be manually transferred with shovels and buckets. Residual oil can also be collected in a backup boom and recovered using sorbents or skimmers suitable for use with heavy oil. Depending on the anticipated volume and properties of the residue, the collected residue could be transferred using either a vacuum suction system, a submersible pump such as the many heavy oil pumps now available, or manually using shovels and buckets. Another option is to herd the residue into one area using pumps or water hoses deployed from a small boat. Once herded, it may be possible to reignite the residue or to ignite it with newly collected oil to further reduce the volume of residue to be recovered. Because of the small areas involved, hand-held igniters are more suitable than helitorches for reigniting residue.

23.4.8 Equipment Checklist Before starting any in-situ burn response operation, all the required equipment must be available. To assist in determining the type and specifications of the equipment that may be required for a burn operation, an equipment checklist has been included in Table 23.14. In the United States, the National Oceanic and Atmospheric Administration (NOAA) has developed a software package called SpillTools, which consists of computer-based tools and learning aids designed to help both government and private organizations gain access to information for developing plans for possible spills (http://response.restoration.noaa.gov/index.php). Specifically, the in-situ burn calculator provides oil spill planners and responders with calculations for estimating time and fireboom lengths required for burning oil in either a single release (batch) or a continuous release of oil. This calculator depends on a knowledge of oil slick thicknesses or source release rates. The calculator permits rapid computation for a range of conditions for a burn scenario, which should provide some realistic solutions. The model can assist in selecting and staging appropriate equipment.

23.5. POSSIBLE SPILL SITUATIONS As no two oil spill situations are the same, it is helpful to look at several possible scenarios when developing response techniques for spill situations.

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TABLE 23.14 Burn Equipment Checklist Vessels and Aircraft Tow vessels Command vessel Surveillance aircraft Helicopter for igniter Safety Equipment Fire pump for each tow boat Fire hoses Fire nozzles Fire extinguishers First aid kits Fire blankets for tow boats Extra radios Containment Equipment Full length of fire-resistant boom Extra lengths Towing paravanes Towing cables Bridles Attachment shackles Anchors e if needed Equipment for backup boom if needed Ignition Equipment Hand-held igniters Helitorch and accessories Residue Cleanup Equipment Sorbents Shovels or bailers Drums or other recovery collection containers Heavy oil skimmer e if necessary Pumps and hoses for skimmer General Supplies Burn plan Safety plan Radios Contact lists Helitorch Equipment Helitorch unit Helicopter connecting harness Fuel gellant Fuel mixture Fire extinguishers Hard hat Gloves

(Continued )

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TABLE 23.14 Burn Equipment Checklistdcont’d Goggles Protective clothing Safety boots Respirators Propane bottle Monitoring Equipment RAM and/or DataRAM PAH Sampling pump/filters Summa cannister Recording notebook, pens Personal Protection Equipment Respirators Boots, gloves Special clothing Duct tape for sealing Goggles Personal Cleanup Equipment Sorbents, rags, towels Citrus cleaner Garbage bags Soap, warm water Extra clothing

The following specific spill scenarios and the suggested strategies for dealing with them are described in Table 23.15: burning at sea, burning in a protected bay, burning on a river, burning in melt pools in the Arctic, and burning in an intertidal zone.86 The strategies listed in Table 23.15 can best be implemented by using specific tactics. These tactics are listed in Table 23.16, and each one is illustrated separately in Figures 23.67 to 23.75. Each of these tactics has specific advantages and limitations.86 The well-known tactic of using a towed fireboom to collect and burn oil directly in the boom is shown in Figure 23.67.86 As with all booms, this technique has a relative current limitation of 0.4 m/s (0.7 knots) before oil is lost under or over the boom. This can be overcome on the open ocean by towing at the relative velocity, despite the surface current. This means that if the actual current exceeds 0.4 m/s (0.7 knots), the boom tow could be slipping downcurrent. Another limitation of this method is that the fire could propagate to the source of the oil or endanger the tow boats and their crew. Collecting the oil separately, towing the boom away from a nonburning source, and then burning the oil is shown in Figures 23.68 and 23.69. This approach prevents the fire from spreading to the oil source. Another advantage

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TABLE 23.15 Specific Spill Scenarios and Burning Strategies Scenario 1 Burning at Sea Location: At sea Position: Offshore Proximity of Oil to Source: A large slick of oil well away from the source without any trail leading back to the source Condition of Oil: The oil in the centre of the slick is more than 3 mm (0.12 in.) thick and is not emulsified Weather and Sea State: Calm conditions

Strategy General Verify wind and current direction to ensure that burning the slick will not affect people, property, or environmentally sensitive areas. As a first response, as much of the slick as possible can be burned without using containment. This will require a helicopter with a helitorch. Several ignition points may be required to burn all parts of the slick that are burnable. Depending on the size of the slick and distance from land, a ship stationed near the slick may be required to refuel the helicopter and helitorch. Once the slick will no longer burn, containment can be used to further thicken the remaining oil and attempt to burn it again. Containment Configuration For the second stage of burning, ideally a fireresistant boom should be used in the U-configuration towed by two vessels. If a fireresistant boom is not available, a conventional boom can be used with the understanding that the boom would be sacrificed and that its containment ability will be severely limited as the burn proceeds. Depending on the amount of oil to be burned, manageable sections of the slick (about 1/3 of the boom’s U area) should be carved off from the main slick using the boom and transported away from the slick for burning. The slick should be approached from downwind and the boom should be towed into the wind during burning. Protection Aircraft overflights should be carried out to ensure that burning is under control and that sensitive areas are not being affected. A standby boat should be nearby for helicopter rescue. Aircraft with extinguishing foam or waterbombing capability should be available. During containment operation, towing vessels should have water spray guns ready to protect them from flames. Accident Response During containment operation, tow vessels

(Continued )

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TABLE 23.15 Specific Spill Scenarios and Burning Strategiesdcont’d Scenario 1 Burning at Sea

Strategy disconnect boom towing lines and sail away upwind from the burning oil or they should speed up to entrain oil, thus reducing slick thickness and extinguishing the burn. Notice of a floating hazard is filed to ships in the area. Aircraft with extinguishing foam or waterbombing capability fly over burn.

Scenario 2 Burning at Sea Location: At sea Position: Offshore Proximity of Oil to Source: A large slick of oil with a trail leading back to the tanker from which it was spilled. Condition of Oil: The oil in the centre of the slick is more than 3 mm (0.12 in.) thick and is not emulsified Weather and Sea State: Calm conditions

Strategy General As a first response, send tugs out to the site to move the tanker away from the main part of the slick. Surround the tanker with containment boom to prevent further seepage from the area and fully separate the vessel from the main slick. Water cannons can be used to separate any sheen connecting the tanker to the main part of the slick. Verify wind and current direction to ensure that burning the slick will not affect people, property, or environmentally sensitive areas. As much of the slick as possible can be burned without using containment. A helitorch should be used for ignition. Several ignition points may be required to burn all parts of the slick that are burnable. Depending on size of slick and distance from land, a ship stationed near the slick may be required to refuel the helicopter and helitorch. Once the slick will no longer burn, containment can be used to further thicken the remaining oil and attempt to burn the slick again. Containment Configuration For the second stage of burning, ideally a fireresistant boom should be used in the U-configuration towed by two vessels. If a fireresistant boom is not available, a conventional boom can be used, with the understanding that the boom will be sacrificed and that its containment ability will be severely limited as the burn proceeds. Depending on the amount of oil to be burned, manageable sections of the slick (about a third of the U area) should be carved off from the main

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TABLE 23.15 Specific Spill Scenarios and Burning Strategiesdcont’d Scenario 2 Burning at Sea

Strategy slick using the boom and transported away from the slick for burning. The slick should be approached from downwind and during burning, the boom should be towed into the wind. Protection Aircraft overflights should be carried out to ensure that burning is under control and that sensitive areas are not being affected. Vessels with water sprayers can be situated around the tanker to prevent any flames from reaching it. A standby boat should be situated nearby for helicopter rescue. Aircraft with extinguishing foam or waterbombing capability should be available. During containment operation, towing vessels should be equipped with water spray guns to protect vessels from flames. Accident Response During containment operation, tow vessels should disconnect boom towing lines and sail upwind from the burning oil or they should speed up to entrain oil, thus reducing slick thickness and extinguishing the burn. Notice of a floating hazard is filed to ships in the area. Aircraft with extinguishing foam and/or waterbombing capability fly over burn.

Scenario 3 Burning at Sea

Strategy

Location: At sea Position: Offshore Proximity of Oil to Source: A large slick of oil well away from the source without any trail leading back to the source Condition of Oil: The oil in the slick is less than 2 mm (0.08 in.) thick and some parts of the slick are emulsified Weather and Sea State: Winds approximately 15 m/s (30 knots) and waves occasionally greater than 1 m (3.3 ft.)

General An emulsion breaking treating agent should be applied to the parts of the slick that have stable emulsions. Verify wind and current direction to ensure that burning the slick will not affect people, property, or environmentally sensitive areas. Using containment boom with an overall height of at least 1 m (3.3 ft), small sections of the slick should be pulled away from the main slick and burned. Monitor wave heights and try to burn during times when waves are less than 1 m (3.3 ft) or, if possible, tow contained portion to an area (Continued )

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TABLE 23.15 Specific Spill Scenarios and Burning Strategiesdcont’d Scenario 3 Burning at Sea

Strategy where waves are less than 1 m (3.3 ft) high. Ideally, a helicopter with a helitorch would be required to burn the contained oil. Depending on the size of the slick and distance from land, a ship stationed near the slick may be required to refuel the helicopter and helitorch. Containment Configuration Because several burns will have to take place, a fire-resistant boom in the U-configuration towed by two vessels should be used. Manageable sections of the slick (about a third of the U area) should be carved off from the main slick using the boom and transported away from the slick for burning. The slick should be approached from the downwind side and boom should be towed into the wind during burning. Protection Aircraft overflights should be carried out to ensure that burning is under control and that sensitive areas are not being affected. A standby boat should be nearby for helicopter rescue. Aircraft with extinguishing foam or waterbombing capability should be available. Towing vessels should have water spray guns to protect vessels from flames. Accident Response During containment operation, tow vessels disconnect boom towing lines and sail away upwind from the burning oil or they should speed up to entrain oil, thus reducing slick thickness and extinguishing the burn. Notice of a floating hazard is filed to ships in the area. Aircraft with extinguishing foam and/or waterbombing capability fly over burn.

Scenario 4 Burning in Protected Bay

Strategy

Location: Protected bay Position: Nearshore, close to a small populated area Proximity of Oil to Source: Well away from the source without any trail leading back to the source

General If the shoreline around the bay is too sensitive to allow for burning, the oil should be pulled out of the bay using containment boom and burned away from the shoreline. A helitorch can be used for igniting the burn.

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TABLE 23.15 Specific Spill Scenarios and Burning Strategiesdcont’d Scenario 4 Burning in Protected Bay Condition of Oil: Slick less than 2 mm (0.08 in.) thick Weather and Sea State: Calm conditions

Strategy If combustible materials are well away from the edge of the shoreline or the shoreline can be protected, the oil can be burned within the bay using the shoreline and/or containment booms to concentrate and contain the oil for burning. A helitorch can be used for ignition, but if accuracy is a concern, hand-held igniters should be used, thrown from a boat and allowed to float into the slick. Verify wind and current direction to ensure that burning the slick would not affect people, property, or environmentally sensitive areas. Containment Configuration If oil is to be burned outside the bay, booms should be used in a U-configuration to bring the oil out of the bay and away from the shoreline for burning. If possible, the burning should take place within a fire-resistant boom and the slick should be lighted with a helitorch. Boom should be towed into the wind during burning. If burning is to take place in the bay, boom should be used in a diversion mode to direct the oil towards a calm part of the bay to concentrate it for burning. The slick can be lighted with either a helitorch or an igniter thrown into the slick from a vessel. Protection Aircraft overflights should be carried out to ensure that burning is under control and that sensitive areas are not being affected. A standby boat should be nearby for helicopter rescue, if a helitorch is being used. Aircraft with extinguishing foam or waterbombing capability should be available. For offshore burning, towing vessels should be equipped with water spray guns to protect vessels from flames. Within the bay, burning should take place at low tide, if possible, and the shoreline should be soaked with water before and during the burn. Water sprayers can be located on shore to divert flames from shoreline. If possible, fire trucks should be placed on the shoreline in case flames reach combustible material on the shoreline. Accident Response For offshore burning, tow vessels disconnect boom towing lines and sail upwind from the

(Continued )

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TABLE 23.15 Specific Spill Scenarios and Burning Strategiesdcont’d Scenario 4 Burning in Protected Bay

Strategy burning oil or they should speed up to entrain oil, thus reducing slick thickness and extinguishing the burn. Notice of a floating hazard is filed to ships in the area. Aircraft with extinguishing foam and/or waterbombing capability fly over burn and fire trucks are available on the shoreline.

Scenario 5 Burning on River

Strategy

General Location: River Before burning can take place, the oil should be Position: Nearshore, away from diverted to a calm part of the river (slow current amenities and populated areas Proximity of Oil to Source: Distant - area, a point or bay area) where the shoreline is free of combustible materials or can be protected no trail back to the source from the flame. Condition of Oil: Slick less than Both the shoreline and containment booms 2 mm (0.08 in.) thick should be used to concentrate and contain the oil Weather and Sea State: Calm for burning. conditions, current more than A helitorch can be used for ignition, but if 0.5 m/s (knots) accuracy is a concern, hand-held igniters should be used, thrown from a boat and allowed to float into the slick. Verify wind and current direction to ensure that burning the slick will not affect people, property, or environmentally sensitive areas. Containment Configuration Boom should be used in a diversion mode to direct the oil towards a calm part of the river to concentrate it for burning. If containment boom is required during the burning phase, a fire-resistant boom should be used when possible. Protection Aircraft overflights should be carried out to ensure that burning is under control and that sensitive areas are not being affected. Aircraft with extinguishing foam or water bombs should be available. The shoreline should be soaked with water before and during the burn. Water sprayers can be located on shore to divert flames from shoreline. If possible, fire trucks should be available on the shoreline in case flames reach combustible material on shore.

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TABLE 23.15 Specific Spill Scenarios and Burning Strategiesdcont’d Scenario 5 Burning on River

Strategy Accident Response Aircraft with extinguishing foam and/or water-bombing capability should fly over burn and fire trucks should be available on shore.

Scenario 6 Burning in Melt Pool in Arctic Location: Arctic, slicks of oil in several melt pools Position: Nearshore, away from amenities and populated areas Proximity of Oil to Source: Distant no trail back to the source Condition of Oil: More than 3 mm (0.12 in.) thick and emulsification that has remained stable over several days Weather and Sea State: Calm conditions, wind speeds approximately 20 m/s (40 knots)

Strategy General An emulsion breaking treating agent should be applied to the parts of the slick that have stable emulsions. Verify wind and current direction to ensure that burning the slick will not affect people, property, or environmentally sensitive areas. A helitorch should be used to ignite the oil in each melt pool. Depending on size of slick and distance from land, a ship stationed near the slick may be required to refuel the helicopter and helitorch. Containment Configuration Containment boom should not be required as the melt pools should act as natural containment. Water spray can be used to push oil to one side of the pool during the burn to keep the thickness at a burnable level. Protection Aircraft overflights should be carried out to ensure that burning is under control and that sensitive areas are not being affected. Standby boat should be nearby for helicopter rescue. Aircraft with extinguishing foam or water-bombing capability should be available. Accident Response Aircraft with extinguishing foam and/or waterbombing capability fly over burn.

Scenario 7 Burning in Intertidal Zone

Strategy

Location: Intertidal zone Position: Nearshore Proximity of Oil to Source: Well away from the source without any

General If possible, install temporary sheet metal boom or fire-resistant boom in shallow waters and initiate burn.

(Continued )

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TABLE 23.15 Specific Spill Scenarios and Burning Strategiesdcont’d Scenario 7 Burning in Intertidal Zone trail leading back to the source Condition of Oil: The oil in the slick is less than 2 mm (0.08 in.) thick Weather and Sea State: Calm conditions

Strategy If the shoreline is too sensitive to allow for burning or the containment boom is too close to populated or sensitive areas, the oil should be pulled away from the area using containment boom and burned away from the shoreline. A helitorch can be used for igniting the burn. If combustible materials are well away from the edge of the shoreline or the shoreline can be protected, the oil can be burned against the shore using the shoreline and/or containment booms to concentrate and contain the oil for burning. A helitorch can be used for ignition, but if accuracy is a concern, handheld igniters should be used, thrown from a boat and allowed to float into the slick. Verify wind and current direction to ensure that burning the slick would not affect people, property, or environmentally sensitive areas. Containment Configuration If oil is to be burned away from the area, booms should be used in a U-configuration to bring the oil away from the shoreline for burning. If possible, the burning should take place within a fire-resistant boom and the slick should be lighted with a helitorch. Boom should be towed into the wind during burning. If burning is to take place in the area, boom should be used in a diversion mode to direct the oil towards a calm area to concentrate it for burning. The slick can be lighted with either a helitorch or an igniter thrown into the slick from a vessel. Protection Aircraft overflights should be carried out to ensure that burning is under control and that sensitive areas are not being affected. A standby boat should be nearby for helicopter rescue, if a helitorch is being used. Aircraft with extinguishing foam or waterbombing capability should be available. For offshore burning, towing vessels should be equipped with water spray guns to protect vessels from flames. Burning should take place at low tide, if possible, and the shoreline should be soaked with water before and during the burn. Water sprayers can

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TABLE 23.15 Specific Spill Scenarios and Burning Strategiesdcont’d Scenario 7 Burning in Intertidal Zone

Strategy be located on shore to divert flames from shoreline. If possible, fire trucks should be placed on the shoreline in case of flames reaching combustible material on the shoreline. Accident Response For offshore burning, tow vessels disconnect boom towing lines and sail upwind from the burning oil or they should speed up to entrain oil, thus reducing slick thickness and extinguishing the burn. Notice of a floating hazard is filed to ships in the area. Aircraft with extinguishing foam and/or waterbombing capability fly over burn and fire trucks are available on the shoreline.

is that the oil can be collected using a conventional boom and then transferred to a fire-resistant boom for actual burning. Since fire-resistant boom is more expensive and harder to deploy than conventional boom, this option has some practical and economic benefits. Use of a towed boom to protect amenities from a burning source of oil is shown in Figure 23.70. Using an anchored boom to burn oil is shown in Figure 23.71. This tactic poses no risk to tow boats and their crew. The boom may not maintain correct alignment with the wind and current, however, and the relative velocity of the surface current and the boom are also considerations. Use of an anchored deflection boom to direct oil away from amenities or toward burn areas is shown in Figure 23.72. The burning of oil against shoreline is shown in Figure 23.73; this can only be done if there is no combustible material such as trees and buildings on the shoreline. In addition, highly adhesive oil residue may be left on the shoreline, which may be difficult to remove. Burning oil in ice is illustrated in Figure 23.74. The natural containment of ice can serve to thicken oil sufficiently for ignition and burning to take place. This technique has often been used to burn oil spills in the Arctic. Oil can be contained in shallow water using a temporary steel boom as shown in Figures 23.47 and 23.75 and as described in Section 23.4.2.4. The boom is constructed of corrugated steel sheets and metal stakes. As a portion of

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TABLE 23.16 Tactics for Dealing with Oil in Various Situations Tactic

Applications

Towed boom e burn in tow (shown in Figure 67)

Burning source Separation between source and oil Source separated

Towed boom e collect and burn (shown in Figure 68)

Source of oil is not burning Oil near populated or sensitive areas

Towed boom e source separated (shown in Figure 69)

Source of oil is not burning

Boom used to separate source General or protect amenities (shown in Figure 70) Anchored boom (shown in Figure 71)

Rivers, estuaries, or in shallow water Over subsurface sources or blowouts

Deflection boom (shown in Figure 72)

Oil deflected away from amenities Oil deflected to burn area

Burning against shoreline (shown in Figure 73)

Remote shoreline with no hazards

In ice (shown in Figure 74)

Oil is thick enough to burn

Temporary steel boom (shown in Figure 75)

Oil can be contained in shallows

Un-contained burning (shown in Figure 76)

Oil is thick enough to burn

the corrugated steel is in the water, heat is dissipated, and the sheet metal should remain intact long enough for the oil to be burned. It is important to stress that this method has not been extensively tested; therefore, backups should be in place in case of failure. Finally, burning uncontained oil is shown in Figure 23.76. While this method is simple and economical, the oil must be thick enough to support ignition and burning, which is rare for most uncontained spills of crude oil.

23.6. POST-BURN ACTIONS 23.6.1. Follow-Up Monitoring The site must be surveyed immediately after the burn to ensure that no burning materials remain in the area. This could include thick patches of

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FIGURE 23.67 Use of towed boom to burn oil directly.

FIGURE 23.68 Use of towed boom to collect and burn oil.

escaped oil, parts of the boom, or burning organic matter. After this immediate surveillance, the residue should be recovered quickly before it sinks. Areas where residue may have sunk should be carefully documented because this could adversely affect the benthic environment. The area should be surveyed and the amount of unburned oil remaining should be estimated. This value and the amount of residue are important in estimating the overall mass balance.

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FIGURE 23.69 Use of towed boom to separate source from fire.

FIGURE 23.70 Use of towed boom to protect amenities.

Analysis of particulate matter, PAHs, and VOCs at the downwind locations should be completed if these are sampled, and these results should be included in the final burn report. In the case of the VOCs, a background sample must be collected on a day when burning is not taking place and when the wind is blowing in a similar direction as on the day of the burn. A report on the actions taken during the burn should be prepared at this time to ensure that others can learn from the burn and that a good record remains if there are any questions on efficiency or other issues.

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FIGURE 23.71 Use of anchored fire-resistant boom.

FIGURE 23.72 Fire-resistant boom used in deflection mode.

23.6.2. Estimation of Burn Efficiency Burn efficiency is measured as the percentage of oil removed compared to the amount of residue left after the burn. The burn efficiency, E, can be calculated by the following equation, where voi is the initial volume of oil to be burned and vof is the volume of residual oil remaining after burning (ASTM, 1997):89 voi vof E ¼ voi

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FIGURE 23.73 Burning against shorelines.

In this equation, the initial volume of oil, voi, can be estimated in a number of ways. If the spill source is known, as in the case of a vessel or coastal storage depot, the volume spilled can be estimated from the tank size and the amount of oil remaining in the tank. In the case of an offshore rig, the pumping rate can be used to estimate the initial volume. If the source is unknown or the volume of oil released from the source cannot be estimated, the volume of the slick can be estimated either visually using objects of known dimensions, for example, a response vessel or containment boom, or using timed overflights, aerial photographs, or remote-sensing devices. This

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FIGURE 23.74 Burning on ice.

area, together with an estimate of the average thickness of the oil, performed either visually by taking samples or by remote sensing, can then be used to estimate the volume of the slick. It should be noted that this equation does not take into account the volume of oil lost through soot produced from the burn, which is a small amount and difficult to measure, or any residue that has sunk or cannot be collected. If the residue remains afloat, it can be recovered either by skimmers or sorbents. The volume of residual oil remaining after burning, vof, can be

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FIGURE 23.75 Fire-resistant boom used in deflection mode.

estimated by measuring the volume or weight recovered. If the residue cannot be recovered, the volume of the residue slick can be measured by estimating its area and thickness, in the same way described for estimating the initial volume of oil. The volume of any tarballs in the residue should also be taken into account. If some or all of the residue sinks, which is rare, the amount of oil that burned (voi e vof) can be estimated using the fact that, for most oils and conditions, an oil slick burns at a rate of 1 to 4 mm/min. The amount burned

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FIGURE 23.76 Unconfined burning at sea.

can be estimated using this range, the area of the slick on fire, and the total time of the burn. Research has shown that burn efficiency is not affected by the oil properties, but depends primarily on the thickness of the slick and oil type. Regardless of the initial thickness of the oil, the final thickness will be in the order of 1 to 2 mm. As such, a much greater burn efficiency is achieved when burning a 20mm-thick slick than a 2-mm-thick slick. The burn efficiency also depends on the flame-contact probability. This is a random parameter that can be controlled by proper containment, but is also affected by wind speed and direction. The burn efficiency can be reduced if the thickness of the slick is inconsistent, that is, the flame reaches patches that are too thin to sustain burning or if the slick is not continuous.

23.6.3. Burn Rate It is generally accepted that an oil slick burns at a slick thickness reduction rate of 1 to 4 mm/min. (See Table 23.1 above for rates of specific oils.) This range translates to about 1,000 to 5,000 L/m2$day. During the final stages of burning when the slick becomes very thin, the rate decreases until the slick becomes less than 0.5 mm thick. Like the burn efficiency, the burn rate is somewhat independent of the physical conditions and properties of the oil. Oil emulsification can reduce the burn rate, as does ice in the burn area, because the water in the oil increases the amount of heat required for burning and thus reduces the rate at which the burn spreads.

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23.7. HEALTH AND SAFETY PRECAUTIONS DURING BURNING 23.7.1. Worker Health and Safety Precautions To protect the health and safety of workers involved with in-situ burning, a thorough health and safety plan must be established and be well understood by all personnel involved before the operation begins. As with any operation in which health and safety are issues, workers are responsible for their own safety and for the safety of their coworkers. To assist in the development of proper health and safety plans for in-situ burning, much of the information required can be obtained from firefighting associations.

23.7.1.1. Preventing Unwanted Ignition and Secondary Fires Once the operation begins, the burn must be closely monitored to allow response personnel to determine whether the burn situation must be reassessed, the plan needs to be modified, or the burn must be controlled or terminated. If on the sea, surveillance of the burn area should be arranged to provide such essential information to the tow operators as the thickness and frequency of slicks in the path of the boom tow or containment area, the precise direction of the smoke plume, the area of oil burning, and whether this is increasing or decreasing. If on land, surveillance of the area around the burn, before, during, and after the burn is essential. At sea, two surveillance tactics should be considered: aerial surveillance and surveillance from a larger vessel. The increased visibility from aircraft, particularly helicopters, ensures the safety of the burn operation. However, a larger vessel not only provides a good view of the tow operation from the surface but can also be equipped with extra fire monitors for firefighting capability. This vessel also provides a means of rescue if one of the tow vessels fails. Any potential difficulties in a burn operation, such as encountering thick burnable slicks that could burn out of control, should be anticipated and avoided. The fire could propagate ahead of the tow vessels or to amenities that can be burned. Other difficulties that should be avoided are the loss of significant amounts of burning oil behind the boom. These burning patches could also cause problems downwind. This can be avoided by having an extra fire-resistant boom downwind to catch any burning patches or vessels with fire monitors to extinguish them. Flames spread very rapidly through vaporsdas rapidly as 100 m/s or 200 knots. If burning a highly volatile oil such as a fresh, very light crude, gasoline, or mixtures of these in other oils, vapor flame spread can occur and cause serious injury. This phenomenon is referred to as vapor flashback. It can only be avoided by carefully assessing the properties and characteristics of the oil to be burned. If burning these very light mixtures, it must be ensured that no people

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are in the area. These circumstances are rare because, normally, by the time responders have reached an oil spill, the volatile fraction of the oil has been removed. In any case, all burn personnel should be familiar with the hazards and with the difference between the speed of flames spreading on a pool and through a vapor cloud. Burning should not be attempted on a slick that could flash back to the source of the spill such as a tanker or toward populated areas. This can usually be prevented by removing or isolating the source from the part of the slick to be burned or separating manageable sections of the slick with containment booms and burning these sections within the boom well away from the main source of the slick. In tanker spills, the source can be moved away using tug boats, which can be brought to the site more quickly than containment booms. When this is not possible, containment booms can be used to isolate the main part of the slick from the source. Precautions must also be taken to prevent the fire from spreading to nearby combustible material such as grass cover, trees, docks, buildings, and operational vessels. Perhaps the best way to prevent unwanted or uncontrollable burns is to carve off a manageable section of oil from a large slick and pull it well away from the main slick or other combustible material before igniting it. This oil can be collected using conventional booms and then transferred to fire-resistant booms in an area where it is safe to burn. If oil is close to shore, deflection booms can be used to deflect oil toward a calm area such as a bay where it can be safely burned. Exclusion booms could be used to keep oil away from areas where it is not wanted. A number of techniques can be applied to prevent secondary fires, fire spreading to unwanted areas, and flashback of the fire to workers. If a boom is used, it must be towed properly. It is important to recognize that a boom fails when towed at a speed faster than about 0.4 m/s (0.8 knots) and that the boom should always be towed into the wind. On most oil slicks, flames will not spread across an oil slick at a rate faster than about 0.2 m/s (0.4 knots). Thus, in a typical situation in which the boom is steadily towed at least at the flamespreading speed, flames will not reach the boom tow vessels, even at low winds. Caution should be taken, however, because winds can change rapidly. Burns should not be conducted if the tow boats are actually in thick oil or could pass through it. Operators of a boom tow should be knowledgeable about how to control the area of the burn by increasing or decreasing the tow speed. At excessive tow speeds, the oil will be lost through the boom apex as a result of boom failure, entrainment under the boom, or loss over the top of the boom. At a towing speed that is too slow, the oil, and therefore the fire, will slowly spread to the boom opening, toward the towing vessels. The movement of oil back and forth in the boom is also influenced by the amount of oil encountered. If more oil is encountered than can be burned in the area of the boom, measures will have to be taken to prevent the fire from spreading toward the tow vessels. If no safe

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action is possible, the fire may have to be extinguished or the boom tow dropped. Once the oil is burning, extinguishment may not always be straightforward or easy. Several tow control methods have been suggested to extinguish the fire within a towed fire-resistant boom. The first method is to release one end of the boom tow and let the oil spread until it is too thin to burn.105 Second, if the tow speed is increased to greater than containment velocities (0.4 m/s or 0.8 knots), oil will submerge under the boom and the fire is often extinguished. Since this method has not been tested and may be difficult to carry out, it is not suggested as the primary technique. Another suggested method is to slow down the towing rate, thereby reducing the encounter rate.89 It is recommended that fire extinguishing equipment be available during the burn. One dedicated fire extinguishing equipment vessel should be positioned beside the boom containing the burn. During burn operations at sea, those who must be near the burn such as the tow-boat operators can be protected by ensuring that fire monitors of sufficient capacity are available. These monitors can be left on to guarantee they are ready if needed. Extra fire monitors and experienced crews should be available on the surveillance vessel to assist if a fire spreads. The fire can also be extinguished by using a firefighting foam made for liquid fuel fires and, if available, aircraft with water-bombing capabilities. To ensure safety, at least two of these extinguishing methods should be ready at a burn site. When burning is done close to shore, fire trucks and crews can be stationed at strategic points on land to fight unwanted secondary fires.

23.7.1.2. Boom Handling When booms are being moved and recovered, personnel should avoid cables under tension, such as the boom towing lines or tugger winch cables, when in use. Personnel should also avoid standing in the coil or bight of a rope or cable lying on deck, which could tighten around a leg or foot and drag a person overboard. Crane operations onboard ship are particularly dangerous, as the roll of the ship may cause the load to swing like a pendulum on the crane wire. Anything being lifted by crane should have two handling lines attached to control the load. Only the crane operator, the signal person, and the two persons holding the load control lines should be involved in the operation. All other personnel should stay well away from the load while it is being lifted. The signal person is in charge of the operation. All personnel must maintain visual contact during the work. Hand signals should be reviewed and understood before operations begin. Communications between the vessel bridge and the deck supervisor should be clear. Hand signals should be understood by all participants. It is

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recommended that a trained spill response team leader should supervise the entire operation from a safety point of view to detect any unsafe situations as they arise. Recovering the boom after the burn has been completed is difficult and extremely messy work , for the boom is usually waterlogged and covered with a tarlike residue.179 Workers should wear rain gear with neoprene gloves, rubber boots, and eye goggles. Cuffs should be taped with duct tape. Appropriate decontamination materials are also required for cleaning personnel after the work is completed. Sorbent materials, rags, paper and fabric towels, citrus cleaners, soap and warm water, hand cream, garbage bags, and containers should all be available onboard the vessel. Any cleaning materials used should be collected after the burn for proper disposal.

23.7.1.3. Ignition Operation Safety The following are some general safety issues related to ignition devices.109 l

l l

l

l

The operators must fully understand the operational and safety instructions for the specific device being used. This includes understanding safe operating procedures, training requirements, disposal requirements for spent igniters, and requirements for retrieving and handling igniters that misfire. The device should be protected against accidental activation. Hand-held igniters should have a delay mechanism that postpones the ignition of the device for at least 10 seconds from the time of activation. This delay allows time to activate and throw the device and for it to float into the slick. For helitorch systems, specific helicopter safety precautions must be followed, as well as the specific precautions for helitorch systems outlined in Section 23.7.1. Any device deployed from a helicopter should not require the use of open flames or sparks within the aircraft.

23.7.1.3.1. Helitorch Safety Because the safety aspects associated with helitorch setup and deployment are multifaceted, strict coordination among the various persons involved in the operation is extremely important.86 There are safety issues associated with helicopter operations, shipboard operations (if the fuel is being stored onboard and/or the helitorch is being deployed from a ship), and the storage, mixing, transporting, and loading of flammable liquids. Under no circumstances should any untrained persons be involved in the helitorch operation. In particular, those responsible for preparing, deploying, and igniting the helitorch must be fully trained in helicopter safety and in grounding procedures when transferring fuel. They must also be aware of the

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volatility of the fuel mixtures used and understand that static charges can occur when fueling and moving equipment.159 The helitorch is ignited by the helicopter pilot. The door on the pilot’s side of the helicopter can be removed on some aircraft to give the pilot a clear view of the helitorch. The helitorch control switch (toggle switch) should be mounted directly on the cyclic stick at a point where the pilot can comfortably operate it. The attachment of the helitorch frame to the helicopter is crucial from a safety point of view. The device must remain stable when carried from the helicopter’s cargo-hook, but it must also detach quickly if it needs to be jettisoned in the event of an emergency. If the helitorch is deployed from a ship where space for maneuvering a helicopter is limited, the following precautions should be taken. 1. When the helitorch is ready for pickup and the helipad is clear of equipment, the helitorch supervisor radios the pilot with a request to move into position and pick up the torch. 2. When the helicopter returns for refueling, it hovers over the helipad so that the helitorch can be disconnected. The helicopter then moves away from the ship and assumes the hover position. The helicopter is not permitted to land until the helitorch and all other equipment and obstructions are removed from the helipad. A three-person fire safety crew should be available onboard the ship at all times, as well as a dedicated 68-kg fire extinguisher. Two 9-kg dry chemical fire extinguishers suitable for extinguishing fuel fires, a first-aid burn kit, and a spill cleanup kit for any fuel spills should be available both at the mixing and the loading areas. Personnel must wear fire protective clothing, goggles, a dust mask, and gloves when mixing and dispensing the gelled fuel and testing the system. The helitorch must be maintained in good working order at all times. The valve that prevents the fuel from exiting the torch after the pilot has released the toggle switch can become clogged by dust or grit and remain partially open. The valve should therefore be checked and cleaned if necessary before each flight. As a further precaution, it is also recommended that the valve be thoroughly cleaned after every third or fourth refueling of the helitorch and that the O-ring in the valve be replaced as soon as it shows any sign of degradation. In general, all parts of the helitorch equipment must be cleaned regularly and any faulty parts replaced at the first sign of wear and tear or any other problem. Spare parts for the torch must always be available at the burn site. All personnel involved in operating the helitorch must also be aware of the dangers of dealing with highly flammable gelled fuels. As such, proper grounding procedures must be used during the mixing of the fuels, when the fuel barrels are attached to the torch system, and when the torch is

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attached to the helicopter. It should also be noted that the helicopter picks up static as it flies through the air. The helicopter should therefore also be grounded as soon as it lands, before the torch is unhooked from the cargo hook. The helitorch barrels must be filled using a nonsparking pump in a well-ventilated area to dissipate fumes. If mixing is done by hand, a wooden or an aluminum paddle should be used to prevent sparking. The proper grounding procedures to be followed in the mixing area are shown in Figure 23.77. Before the helitorch is deployed, the water currents and wind conditions should be noted to determine the safest location for the ignition. A preflight test must also be carried out at this time to test the cargo hook, fuel pump, propane discharge, sparkers, and the toggle switch connected to the pilot’s cyclic stick. Before igniting the slick, a predetermined location should be chosen to perform a test drop of a small amount of ignited gelled fuel. Wind and current direction should be checked again to ensure that the burning gelled fuel does not drift toward any of the operational vessels. If the test burn indicated that the gelled fuel is igniting and falling properly, the pilot positions the helicopter over the desired location, fires the torch on a slow pass, and then leaves the area. If igniting a fuel with a high flash point, the pilot may have to hover over the

Ground Cable Fuel Tank

Ground Cable Grounding Rod 1.2 m (4 ft.) into Soil

Barrel Being Filled Bond From Nozzle to Barrel Being Filled

Barrel Being Agitated

Grounding Rod 1.2 m (4 ft.) into Soil

Ground Cable

FIGURE 23.77 Grounding and bonding procedures for mixing helitorch fuel (adapted from OMNR, 1990).159

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burn area and release multiple balls of burning gelled fuel in order to concentrate the fire in one location. When the ignition session is completed, the pilot disengages the helitorch circuit breaker to isolate the toggle switch so that no burning gelled fuel is accidentally dropped. The helicopter then returns to the land- or ship-based helitorch deployment site. When the helicopter lands, the recovery crew should stabilize and secure the helitorch before the helicopter pilot disconnects the cargo hook. This is especially important when the gelled fuel barrel is empty because the torch system can easily be blown off the helipad by the downdraft of the helicopter’s rotors.

23.7.1.4. Exposure of Personnel to Burning Operations Crews in vessels involved in tow operations are in danger of being exposed to fire or flames if the fire should move up the boom. This could occur if thick patches of oil are encountered and the flame spreads along this thicker patch. The flame velocity is about 0.02 to 0.16 m/s. The flames will not spread toward the tow vessels if the boom is moving at a speed of at least 0.4 m/s (0.8 knots) in an upwind direction. Because winds can change rapidly, however, this fact should not be taken as an assurance of safety. In highly variable winds, caution must be taken to ensure that thick concentrations of oil are not encountered at low boom-tow speeds. Any crews working alongside the burn could be exposed to high concentrations of particulate matter, PAHs, and/or VOCs if the wind changes and blows toward them. For this reason, operational vessels should not operate behind the tow-boat positions. On land, fires can move very rapidly if combustible material such as trees and grass is available. A fire break should always be made in the area in advance of ignition. Helitorch personnel are not directly exposed to the dangers of burning operations other than being exposed to small amounts of vapors from the fuel used for gelling. If necessary, respirators can be used to minimize this exposure. The helitorch operator in the helicopter is not physically exposed to any dangers, other than those normally associated with flying. When booms and other equipment are handled, the appropriate personal protective equipment must be worn. This includes safety boots, hard hats, goggles, neoprene gloves, life jackets, chemical-resistant clothing, and foul weather gear. 23.7.1.5. In-Situ Burn Training All personnel involved in a burn in most jurisdictions must complete a 40-hour hazmat course. Personnel involved in a burn should be familiar with the technology and procedures in this section.

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It is recommended that experienced boom operations staff attend at least a one-day course on the use of booms for in-situ burning and that an additional day be spent on practicing towing booms and releasing oil from booms such as might be required in an emergency. Personnel who are not totally familiar with boom deployment and operations should spend at least one week in training and practice. All members of the helitorch operating team require extensive training. Only a highly experienced lead person, such as the helitorch supervisor, should be used to provide training. Operators and ground support personnel should generally participate in at least three days of training, including several practice runs.

23.7.1.6. Vessel Safety The size, structure, and navigational equipment of any vessels used in an in-situ oil burn must be suited to the wind, sea state, carrying requirements, and visibility conditions expected during the burn operation. For operations on the open water, vessels should have a reliable positioning system, such as GPS, a compass or gyrocompass, working radar, working depth sounder, HF radio, VHF radio, and telephone. Under the Canada Shipping Act, each vessel is legally required to have appropriate safety equipment in accordance with the size and type of vessel and the type of operation being undertaken. This includes life boats, life rafts, lifesaving rings, flares, firefighting equipment, life jackets, survival suits, and navigation lights. Any vessel chartered in Canada or the United States should possess a valid Coast Guard inspection certificate. A survey by a qualified ship surveyor or naval architect is recommended before chartering a vessel. The Ship Safety Branch of the Canadian Coast Guard should be consulted for more information about these requirements. 23.7.1.6.1. Burning Directly Inside a Ship There is a special situation if the in-situ burning is to be carried out in a stranded vessel.180 Safety is, of course, the primary criterion. The oil must be accessible to ignition and accessible to air. Explosives or industrial cutting equipment may be used to allow oil to flow from tanks to spaces where it will be burned and to increase ventilation area. This should be conducted by salvage and explosive experts. Typically, the planned burn would take place in the ship’s hold(s), and explosives would be used to open passage from lubrication and fuel tanks to the hold. Lubrication and fuel tanks generally do not have sufficient exposure to the air to allow for burning. Oxygen from air is necessary for burning. Studies have shown that the area of ventilation is a critical regulating factor in the burning of oil directly on ships and in other confined spaces. The rate of burning is generally calculated based on the area of ventilation openings in the case of low

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wind situations. Studies have shown that top and side openings combined will yield better ventilation than top openings alone. The presence of two openings allows for air circulation over the area of fire. Small-scale studies have shown that a minimum of 10% ventilation is needed to prevent extensive coking. The 10% refers to the area of ventilation compared to the surface area of oil available to burn. An area of more than 20% ventilation has been shown to result in little coking during test burns. External winds assist in providing additional ventilation, despite the semiclosed conditions that may exist. One study showed a threefold increase in burn rate with wind increase from 0 to 11 m/s.180 During the burn process, some localized oil may become superheated.180 When the heating is sufficient, flash evaporation of a component of this oil may occur, and the surrounding boiling oil can erupt upward toward the top ventilation port. This could result in oil being splashed onto other parts of the vessel or sea. This phenomenon has been observed in test situations with crude oil. The safety of the proposed operation should be the primary consideration.180 The vessel should be stable and relatively stationary during the preparation and burn phases. The operation should only be contemplated if the operation will not result in flashback to other sources of fuel. The fire should be prevented from spreading to other combustible material in the area, including trees, docks, and buildings. Preparation of the vessel for burning by using explosives and subsequent burning of the oil will weaken the ship’s structure. Burning in ships should be considered only if there is no potential for future salvage of the vessel or if the trade-off between future salvage potential and removing the oil is favorable. The use of preparation and burning may weaken the structure sufficiently to result in breakup of the vessel. A breakup may result in the release of oil. Salvage experts and experts on ship design should be consulted where possible, before proceeding with the preparation for ignition and burn. They should also be consulted after the burn regarding options to deal with the remaining vessel. The vessel may not be seaworthy, towable, or even in condition to allow shipbreaking in place.

23.7.1.7. Aircraft Safety All flying operations must be carried out in accordance with federal flight regulations (Federal Aviation Agency (FAA) in the United States or Transport Canada). All aircraft associated with an in-situ burn should be chosen carefully to suit the required tasks. Flight plans should be well thought out to take into consideration wind, visibility, cloud types and height, the presence or forecasted presence of fog, precipitation, sea state, and other relevant weather conditions. For helitorch operations, the helicopter must have sufficient lift capacity to carry a pilot, copilot, and a helitorch full of fuel and be equipped with

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a cargo hook able to sling the helitorch as well as jettison it. The pilot must test the jettison mechanism before each helitorch operation. For safety reasons, a twin engine helicopter is preferred, particularly for nearshore operations. These helicopters are more powerful than single-engine machines and can therefore gain altitude more quickly. If a single-engine helicopter is used, it must be equipped with floats to facilitate emergency landings. The helicopter must comply with Transport Canada or U.S. Transport regulations regarding helicopter maintenance and the operation being undertaken. Only the pilot and copilot or one other person if required for the ignition activation should ride in the helicopter during the helitorch operation. All persons in the helicopter should wear a survival suit. During nearshore operations, updraft and downdraft winds against cliffs must be considered. Emergency landing locations for the helicopter should be identified in advance through site surveillance in case of mechanical difficulty. It is recommended that when helicopter services are being arranged, the performance capability of the aircraft and its suitability for its intended use be confirmed with the helicopter pilot and/or helicopter operator.

23.7.2. Public Health and Safety Precautions The public should not be exposed to emissions exceeding the recommended human health concern levels. The most concern would be exposure to PM-2.5 particulates greater than 35 mg/m3 over a 24-hour period. This level can be determined by using the formulas provided in Section 23.3.4.3 to calculate minimum safe burn distances and by monitoring the particulate levels using the methods outlined in this chapter. It is important to note that atmospheric inversions can occur that will increase ground-level concentrations to high levels and that the smoke plume itself might drop to ground level at higher elevations further inland. Monitoring must be done to ensure that this situation does not occur. If there is potential of this event occurring, the burn should not be started. If a burn is already started and the plume drops to ground level, the situation should be immediately assessed to determine whether the burn should be stopped, people evacuated, and/or whether the plume could drop again. Any people who may be affected by the burning, even if only remotely, must be briefed so that they are aware of the activity and the possible need to evacuate the area on short notice. If burning is done near land, sufficient personnel must be available on land and be in good communications with the burn command vessel. The land-based personnel will monitor the smoke plume and stay in contact with local weather officials to be informed of any potential changes that could cause the plume to directly affect people on the ground.

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If burning against or very near the shore, additional precautions must be taken to ensure that the fire does not spread from the oil to other combustible material. The fire should be monitored from shore by personnel with the ability to put out any potential fires. Trees and other combustibles near the shore might be wetted down as an extra precaution.

23.7.3. Establishing Safety Zones An important part of the safety program for an in-situ burn operation is establishing minimal safety zones. This has been accomplished in several ways including the use of values larger than the measured hazardous distances, calculated as shown above, and the use of smoke plume modeling. An extensive section on calculating safe distances is given in Section 23.3.4 above. Smoke dispersion modeling has been used frequently in the past decade to establish safe zones and to obtain permits for large industrial sources. Specialized models have been developed that can also be applied to in-situ burning. Although models are not intended to replace monitoring, they provide an important tool for assessing the impact of smoke both before and after a burn. The smoke model ALOFT (A Large Outdoor Fire Plume Trajectory model) was developed by the National Institute for Standards and Technology for the USMMS.181 It is designed to run on a PC and thus could be used as an immediate tool for predicting safety zones. The model has been used to prepare tables of safe distance predictions for typical fires. The model also incorporates the effects of surface roughness and the mixing layer depth that is the depth of atmospheric mixing or the atmospheric boundary layer. It might also be viewed as the height of the clouds. It is important to recognize the limitations of each type of hazard zone estimation. Differing weather conditions can change the concentrations of particulate matter dramatically. In many cases, the plume drops to ground level. Weather officials should be consulted for possible wind changes, atmospheric inversions, and other factors that can change the trajectory and impact of the plume.

23.7.4. Monitoring Burn Emissions A major barrier to the acceptance of in-situ burning of oil spills is the lack of understanding of the resulting combustion products. Several types of emissions are formed and released when oil is burned. The atmospheric emissions of concern include the smoke plume, particulate matter precipitating from the smoke plume, combustion gases, unburned hydrocarbons, organic compounds produced during the burning process, and the oil residue left at the burn site. Although consisting largely of carbon particles, soot

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particles contain a variety of absorbed and adsorbed chemicals. Complete analysis of the emissions from a burn has involved measuring all these components. The emphasis in sampling has been on air emissions at ground level, as these are the primary human health concern and the regulated value. This section focuses on these emissions. Some attempts have been made to monitor emissions remotely. Vocacek et al. were able to monitor biomass burning remotely using a visible detector monitoring the strong emission lines of potassium (K) at 766.5 and 769.9 nm.182 This method was tested using the AVIRIS satellite spectrometer and monitoring a fire on the ground. It should be noted that the monitoring of emissions conducted at past burns was as comprehensive as possible and the best field samplers and instrumentation available at the time were used. Measurement techniques have progressed over the years, however, and continue to improve. In addition, the data from these burns are so extensive that not even encapsulating summaries can be provided here. The summarized data appears in the references cited in this section, and qualitative statements about that data will be made here.

23.7.4.1. Summary of Measurements In general, real-time monitoring of emissions should be performed downwind of the fire and at a point closest to populated areas.99 Studies of the emissions from in-situ oil burns indicate that the main public health concern is particulate matter in the smoke plume, as this is the first emission that normally exceeds recommended health concern levels. For monitoring of particulate matter, it is generally accepted that the concentration of small respirable particles having a diameter of 2.5 mm or less (PM-2.5) should be less than 35 mg/m3 for a 24-hour period. This is the standard set out by many nations, including the National Institute of Occupational Health and Safety (NIOSH), and described in the U.S. Code of Federal Regulations. The devices currently used to carry out real-time monitoring of particulates are the DustTrak, MiniRAM, and DataRAM aerosol monitors, which are capable of detecting the PM-2.5 particulates emitted by a burn.183 It is important to note that the concentrations of particles downwind are highly variable over time. A reading can be over the recommended maximum value one instant and then at baseline values the next. Furthermore, the background values must be measured and subtracted from the current value. As many instruments measure humidity as particulate (which it is), the instructions state that these instruments should not be used in locations where there is high humidity without taking corrective action. This certainly applies to locations on boats and near the sea. Experimentation has shown that high humidity can lead to readings as much as five times the maximum exposure value, although the data can be corrected for this. In both cases, the real-time value on the

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instrument is noted only for interest. The instrument readings should be electronically recorded, and averages calculated from the recorded and corrected data.

23.7.4.2. DataRAM/RAM Summary The DustTrak, MiniRAM, and DataRAM are commercially available pieces of equipment commonly used in the occupational health and safety industry. The portable monitors (MIE Inc., Bedford MA) allow measurement of aerosols and particulates continuously. The advantage of time information is the potential to correlate particulates with specific burn events, such as when the burn is initiated or extinguished. Some of these instruments are shown in Figures 23.63 and 23.64. 23.7.4.3. Sampling Particulates Using Filters Particulate levels from a burn can be most accurately determined by collecting a representative sample on a quartz fiber filter using a high-volume sampling pump.99,183 The accumulation of particulate on the filter can be measured by differential weighing. The concentration can be calculated by dividing the weight collected by the volume of air. An added advantage of this particulate sampling method is that, after weighing, the collected particulates can be analyzed for PAH compounds by gas chromatography, following a solvent extraction procedure. Other burn products of interest, such as metals, could also be analyzed. A high-volume sampler (greater than 200 L/minute capability) is necessary for collecting particulate at a burn site in order to collect enough sample over the relatively short duration of the burn. The flow must be measured in order to calculate the concentration. The flow will decrease as the filter is loaded. For this reason, a flow rate must be recorded at both the initiation and conclusion of sampling, while the filter is in place. The flow rate is usually determined as a function of the back pressure created by the pump, although it is sometimes measured by an inline mass flowmeter. All high-volume samplers operate on AC power due to the current required to run the pump. The unit will either have a power switch or be controlled by AC supply. There is generally a voltage regulator that can be adjusted externally. The frame for the conventional quartz fiber filter is designed to hold either a 4" diameter filter circle or an 8" 10" filter sheet. The frame holds the filter in place, while the pump creates a negative pressure on the bottom side of the filter, creating a flow of air through the filter that allows air to pass through but not the particulate. In most cases, the TSP fraction is being collected, for which a filter with 0.8 micron (m) pore size is used. The collected sample can be used to determine particulate levels by differential weighing and/or can be analyzed for various burn products, usually PAHs.

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There are various types of high-volume samplers capable of collecting TSP samples. The conventional TSP sampler, which has an 8" 10" frame and allweather housing, is the most popular for permanent or semipermanent sampling locations. There are also more portable samplers that have a tripod stand rather than the all-weather housing. These models are preferred when frequent relocation is required, but they are less weather-resistant. For use in isolated areas, compact samplers are available that are carried in one hand, such as the GMW Handi-Vol 2000. Most of the samplers that use an 8" 10" filter frame operate in the range of 500 L/minute. When a 4" filter frame is used, the flow rate is usually closer to 200 L/minute. In some samplers, such as those used for pesticides (PS-1), an additional sample collection medium is employed. After the particulate is collected on the particulate filter, the air passes through a flow-through sorbent medium that collects airborne vapors. These samplers can be effectively used to collect particulate samples, with or without the second sampling medium.

23.7.4.4. Methodology of VOC Sampling Using Summa Canisters The Summa canister is one method used to collect a metered amount of whole air for laboratory analysis.99,184 Air is collected in these evacuated, stainless steel canisters to be analyzed for VOCs. In conventional highvolume sampling methods, the VOCs are lost either during sampling or in transit. By contrast, the Summa canister method ensures that most of the VOCs are captured and remain stable between the sample collection on-site and the subsequent laboratory analysis. The amount of VOCs found in air samples collected close to oil burns varies, depending on several factors including fuel composition and distance from the burn. A precision restrictor valve on the canister provides the controlled flow required when sampling during the course of a burn or pre-burn. The Summa canister is a spherical, polished stainless steel container with a single manually controlled valve. The canister must be cleaned and evacuated by an accredited laboratory before use. A precleaned and precalibrated flow restrictor valve is affixed in order to meter the flow into the canister. No restrictor valve is necessary to collect an instantaneous grab sample. These canisters are most commonly available in sample volumes of 6 L, although 1 L and 20 L sizes, as well as less common sizes, are also available. For accurate time-averaged sampling, flow must remain constant throughout the sample collection period. When using a flow restrictor, air should not be drawn into the canister until ambient pressure is attained, since the flow rate begins to change as the back pressure is reduced. This occurs when the pressure inside the canister is approximately half (0.53) ambient pressure. The time taken to reach this point varies with the flow rate. Since the flow rate does not fall off sharply until close to ambient pressure, sample collection can continue

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until the sample volume (calculated from the flow rate) reaches 75% of the canister capacity without gross variance in actual volume collected. Flow rate should be calculated based on the sampling period. Flow restrictors are calibrated using a dry standard method capable of measuring accurately down to 1 mL/minute. The canister should be located in an area that is representative of the sampling area. To begin sample collection, fully open the valve on the canister. Note the time opened. A grab sample can be collected in less than one minute. For time-averaged sample collection, continue collecting the sample until either the sampling is completed or the maximum calculated volume of the canister (75% of capacity) is reached. Fully close the valve. Record the time closed and calculate the sampling time. Remove the flow restrictor valve carefully and replace the brass cap. Carefully clean (or bake out) the flow restrictor assembly before using the canister again. Both the extraction and VOC analysis of the contents of the Summa canisters should be performed by an accredited laboratory. The canister must then be cleaned and reevacuated before it is used to collect more samples. The main limitation of Summa canisters is that the analysis of the canisters must be done off-site, so there is no on-site indication of the quality of the sample collected. Proper prechecks and precautions do not prevent an occurrence during the sampling period that may compromise the flow of sample into the Summa canister. Because of the adiabatic expansion and resultant cooling effect when air passes through the restricted opening, when sampling in humid ambient conditions at temperatures below 5 C, water vapor could freeze inside the orifice, effectively closing the valve until ambient temperatures rise.

23.7.4.5. Combustion Gas Measurement Combustion gases of concern include carbon dioxide, carbon monoxide, sulphur dioxide, and nitrogen oxides. Carbon DioxidedCarbon dioxide is the end result of combustion and is found in increased concentrations around a burn.99,185 Normal atmospheric levels are about 300 ppm, and levels near a burn can be around 500 ppm, which presents no danger to humans. The three-dimensional distributions of carbon dioxide around a burn have been measured. Concentrations of carbon dioxide are highest at the 1-m level and fall to background levels at the 4-m level. Concentrations at ground level are as high as 10 times that in the plume, and distribution along the ground is broader than for particulates. Carbon dioxide can be measured in a number of ways, real-time instruments generally measure it using an infrared technique, discrete samples can be taken and quantified by gas

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chromatography ,and infrared open-path instruments can provide real-time measurement. Carbon MonoxidedCarbon monoxide levels are usually at or below the lowest detection levels of the instruments and thus do not pose any hazard to humans. The gas has only been measured when the burn appears to be inefficient, such as when water is sprayed into the fire. Carbon monoxide appears to be distributed in the same way as carbon dioxide. Measurements of carbon monoxide can be done using similar techniques as for carbon dioxide. Sulphur DioxidedSulphur dioxide per se is usually not detected at significant levels or sometimes not even at measurable levels in the area of an in-situ oil burn. Sulphuric acid, or sulphur dioxide that has reacted with water, is detected at fires, and levels, though not of concern, appear to correspond to the sulphur content of the oil. Sulphur dioxide itself, though not detected, can be measured using specialized sensor-type instruments or reactive tape instruments. Sulphuric acid aerosols can be measured by titrating caustic solutions through which the sample air was drawn (impinger method) or using a reactive tape instrument.

23.7.4.6. Monitoring Polyaromatic Hydrocarbons on Particulates Polyaromatic Hydrocarbons (PAHs) are aromatic compounds found in crude oil and are often produced as a result of combustion. Many PAHs are toxic to humans and to the environment, particularly the larger PAHs. Crude oil burns result in PAH downwind of the fire, but the concentration on the particulate matter is often an order of magnitude less than the concentration in the starting oil and sometimes several orders of magnitude less. Diesel contains low levels of PAHs with smaller molecular size, but results in more PAHs of larger molecular sizes after burning. Larger PAHs are either created or concentrated by the fire. Larger PAHs, some of which are not even detectable in the diesel fuel, are found both in the soot and in the residue. The concentrations of these larger PAHs are low and often just above detection limits. Overall, studies have shown that more PAHs are destroyed by the fires than are created. The Soxhlet extraction method can be used to extract PAHs from the whole filter sheets more easily than microwave extraction.186 The extracts are dried by filtering through anhydrous sodium sulphate and concentrated to approximately 1-2 mL. The concentrated extracts are then quantitatively transferred to a preconditioned 1.5 g silica gel microcolumn topped with 1 cm anhydrous sodium sulphate for sample cleanup. The eluent is collected in a precalibrated centrifuge tube and concentrated under a stream of nitrogen to appropriate volume. Finally, the concentrated eluent is spiked with an internal standard d14-terphenyl and made up to the accurate preinjection volume (0.5 to 1.0 mL) for Gas Chromatograph analysis.

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The analysis of target PAHs and other hydrocarbons is performed on a gas chromatograph by a qualified laboratory.

23.7.4.7. Carbonyls Carbonyls such as aldehydes and ketones are created by oil fires, but exceed health concern levels only when very close to fires.99,187 Monitoring for carbonyls is conducted using a specialized sorption tube (DNPH) and sampling pump. Analysis is conducted in the laboratory. The methods are detailed and require experienced laboratory personnel, but are not fraught with particular difficulties. Accuracies are ensured by the use of standards and internal standards. The condition of the sample tubes is important, and sample tubes must be kept frozen before use. The particular limitations that have been noted are that the sensitivity of the method depends on the amount of soot collected and small samples often have insufficient material to allow proper detection of PAHs.

ACKNOWLEDGMENTS Environment Canada is acknowledged for its data and photographs from burn studies conducted from 1974 to the present. Much of this chapter derives from this data. This chapter also acknowledges the reference, Fingas and Punt, 2000, which forms the basis of much of the current chapter.86

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98. Fingas MF, Lambert P, Wang Z, Li K, Ackerman F, Goldthorp M, et al. Studies of Emissions from Oil Fires. AMOP 2001;767. 99. Fingas MF, Goldthorp M, Lambert P, Wang Z, Li K, Ackerman F, et al. Monitoring Emissions from the In-Situ Burning of Oil Spills on Water. Ottawa, ON: Environment Canada Manuscript Report Number EE-167; 2001. 100. Fingas MF, Lambert P, Li K, Wang Z, Ackerman F, Whiticar S, et al. Studies of Emissions from Oil Fires. IOSC 2001;539. 101. Fingas MF, Wang Z, Fieldhouse B, Brown CE, Yang C, Landriault M, et al. In-Situ Burning of Heavy Oils and Orimulsion: Analysis of Soot and Residue. AMOP 2005;333. 102. Russel AG, Brunerkreef B. A Focus on Particulate Matter and Health. Environ Sci Technol 2009;4620. 103. Lemieux PM, Lutes CC, Santoianni DA. Emissions of Organic Air Toxics from Open Burning: A Comprehensive Review. Prog Energ Comb 2004;1. 104. Daykin MM, Kennedy PA, Tang A. Aquatic Toxicity from In-Situ Oil BurningdNewfoundland Offshore Burn Experiment (NOBE). Ottawa, ON: Environment Report; 1995. 105. McKenzie B. Report of the Operational Implications Working Panel. In: Jason NH, editor. In-Situ Burning Oil Spill Workshop Proceedings, 11. Gaithersburg, MA: NIST; 1994. 106. Maki T, Miura And K. A Simulation Model for the Pyrolysis of Orimulsion. Energy Fuels 1997;819. 107. Kadota T, Yamasaki H. Recent Advances in the Combustion of Water Fuel Emulsion. Prog Energ Combust 2002;385. 108. Fingas MF, Fieldhouse B, Mullin J. Studies of Water-in-Oil Emulsions: Stability Studies. AMOP 1997;1. 109. Astm F 1990-07. ASTM Standard Guide for In-Situ Burning of Oil SpillsdIgnition Devices. Conshohocken, PA: ASTM; 2007. 110. Gue´nette CC, Thornborough J. An Assessment of Two Off-Shore Igniter Concepts. AMOP 1997;795. 111. Hyde LJ, Withers K, Tunnell Jr JW, Coastal. High Marsh Oil Spill Clean-Up by Burning: Five-Year Evaluation. IOSC 1999;1257. 112. Hess TJ, Byron I, Finley HW, Henry CH. The Rockefeller Refuge Oil Spill: A Team Approach to Incident Response. IOSC; 1997:817e21. 113. Pahl JW, Mendelson IA. The Application of In-Situ Burning to a Louisiana Coastal Marsh Following a Hydrocarbon Product Spill: Preliminary Assessment of Site Recovery. IOSC; 1997:823e8. 114. Pahl JW, Mendelson IA. Recovery of a Louisiana Coastal Marsh Three Years After In‑Situ Burning of a Hydrocarbon Product Spill. IOSC; 1999:1279e82. 115. Dahlin J, Zengel S, Headley C, Michel J. Compilation and Review of Data on the Environmental Effect of In-Situ Burning of Inland and Upland Oil Spills. American Petroleum Institute, Publication Number 4684; 1999. 116. Michel J. 2002. Inland In-Situ Burning Case Histories: Upland and Wetlands. EPA Freshwater Spills Symposium Proceedings; Washington, DC; 2002. 117. Sneddon J, Hardaway C, Bobbadi KK, Beck JN. A Study of Crude Oil Site for Selected Metal Contamination Remediated by a Controlled Burning in Southwest Louisiana. Microchem J 2006;8. 118. Allen A. Use of In-Situ Burning at a Diesel Spill in Wetlands and Salt Flats, Northern Utah, U.S.A: Remediation Operations and 1.5 Years of Post-Burn Monitoring. IOSC 2005:544.

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119. Henry C, Thumm S, Cuty P, Brolin J, Michel J. Application of In Situ Burning During the Mosquito Bay Spill: Observations and Trade‑Off Discussions. IOSC 2003:240. 120. Baustian JJ, Mendelssohn IA, Lin Q, Rapp J, Myers J. Year‑One Recovery of an Intermediate Marsh in South Louisiana after an In-situ Burn for Oil Spill Remediation. AMOP 2007;851. 121. Merten A. Cooperative Efforts to Use In-Situ Burning in Empire, LA, in an Intermediate Marsh Following Hurricane Katrina and Rita. EPA Freshwater Spills Symposium 2006. 122. Ewing JT, Grimes WD, Baccigalopi M, McElroy A. Response Strategies to a Remote Inland Oil Spill and Fuel Transfer After a Hurricane. IOSC 2008;969. 123. Otitoloju AA, Are T, Junaid KA. Recovery Assessment of a Refined-Oil Impacted and Fire Ravaged Mangrove Ecosystem. Environ Monit Assess 2007;353. 124. Lindau CW, Delaune RD. Vegetative Response of Sagittaria Lancifolia, to Burning of Applied Crude Oil. Water Air Soil Pollut 2000;161. 125. Mendelssohn IA, Carney K, Bryner NP, Walton WD. Coastal Marsh Recovery and Oil Remediation after In-Situ Burning: Effects of Water Depth, Soil, and Marsh Type. Louisiana OSRADP, Baton Rouge, LA, 2001. 126. Mendelssohn IA, Lin K, Bryner NP, Walton WD, Twilley WH, et al. In-Situ Burning in the Marshland EnvironmentdRecovery and Regrowth of Spartina alterniflora, Spartina patens and Sagittaria lancifolia Plants. AMOP 2001;785. 127. Bryner NP, Walton WD, DeLauter LA, Twiley WH, et al. In-Situ Burning in the Marshland EnvironmentdSoil Temperatures. AMOP 2000;823. 128. Bryner NP, Walton WD, Twiley WH, Roadarmel G, et al. In-Situ Burning in the Marshland EnvironmentdSoil Temperatures Resulting from Crude Oil and Diesel Fuel Burns. AMOP 2001;729. 129. Astm WK. 17360, Standard Guide for In-Situ Burning of Oil Spills in Marshes. Conshohochen, PA: ASTM; 2010. 130. Merton AA, Henry CB. Decision-Making Process to Use In-Situ Burning to Restore an Oiled Intermediate Marsh Following Hurricanes Katrina and Rita. IOSC 2008;545. 131. Gonzalez MF, Lugo GA. Texas Marsh Burn: Removing Oil from a Salt Marsh Using In-Situ Burning. IOSC 2005;8370. 132. Overton EB, Miles MS. Reevaluation of an In-Situ Burn and Phytoremediation Studies for Onshore Spills. Baton Rouge, LA: Report for Louisiana State University, OSRADP; 1999. 133. Fritz DE. In-Situ Burning of Spilled Oil In Freshwater Inland Regions of the United States. Spill Sci Technol 2003;331. 134. Fritz DE. In-Situ Burning in Inland Regions. Interspill 2006. 135. Youdeowei PO. The Effect of Crude Oil Pollution and Subsequent Fire on the Engineering Properties of Soils in the Niger Delta. Bull Eng Geol Environ 2008;119. 136. Brown HM, Goodman RH. In-Situ Burning of Oil in Ice Leads. AMOP 1986;245. 137. Fingas MF. In-Situ Burning of Oil Spills: Review and Research Priorities, Proceedings of the International Seminar on Oil Spill Research. United States Coast Guard 1992;247. 138. ASTM 2230. Standard Guide In-situ Burning of Oil Spills on Water: Ice Conditions. Conshohochen, PA: ASTM; 2008. 139. Guenette CC, Sveum P. In-Situ Burning of Uncontained Crude Oil and Emulsions. AMOP 1995;997. 140. Purves WF. Techniques for Igniting and Burning Oil on Arctic Ice, 201C-1. Kanata, ON: Arctec Canada; 1977.

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141. Ross SL. Environmental Research Ltd and Energetex Engineering, In-Situ Burning of Uncontained Oil Slicks, EE-60. Ottawa, ON: Environment Canada; 1986. 142. Dickins DF, Brandvik PJ, Bradford J, Fakness L-G, Liberty L, Daniloff R. Svalbard 2006 Experimental Oil Spill Under Ice: Remote Sensing, Oil Weathering Under Arctic Conditions and Assessment of Oil Removal by In-Situ Burning. IOSC 2008;681. 143. Majors L, McAdams F. Responding to Spills in an Arctic Oil FielddLessons Learned. IOSC 2008;689. 144. Brandvik PJ, Fakness LG. Weathering Processes in Arctic Oil Spills: Meso-Sale Experiments with Different Ice Conditions. Cold Reg Sci Technol 2009;160. 145. Meikle KM. An Effective Low-Cost Fireproof Boom. IOSC 1983:245. 146. Buist IA, Pistruzak WM, Potter SG, Vanderkooy N, McAllister IR. The Development and Testing of a Fireproof Boom. AMOP 1983;70. 147. Buist I, McCourt J, Morrison J, Schmidt B, DeVitis D, et al. Fire Boom Testing at OHMSETT in 2000. AMOP 2001;707. 148. Nordvik AB, Simmons JL, Hudon TJ. At-Sea Testing of Fire Resistant Oil Containment Boom Designs. In: Proceedings of the Second International Oil Spill Research and Development Forum 1995;479. London, UK: IMO; 1995. 149. Bitting KB, Coyne PM. Oil Containment Tests of Fire Booms. AMOP 1997;735. 150. Cunneff S, Devitis D, Nash J. Test and Evaluation of Six Fire Resistant Booms at OHMSETT. Spill Sci Technol Bull 2000;353. 151. Bitting K, Gynther J, Drieu M, Tideman A, Martin R. In-Situ Burning Operational Procedures Development Exercises. AMOP 2001;695. 152. Marine Research Associates. Technology Assessment and Concept Evaluation for Alternative Approaches to In-Situ Burning of Oil Spills in the Marine Environment. Herndon, VA: U.S. MMS; 1998. 153. Ross SL. World Catalog of Oil Spill Response Products. 9th ed. SL Ross, http://www.slross. com/WorldCat/WorldCatmain.htm; 2010. date accessed July 2010. 154. PROSCARAC (Prairie Regional Oil Spill Containment and Recovery Advisory Committee), Anchor Design and Deployment Review 1992. 155. Alyeska Pipeline Service Company, Supplemental Information Document #1, Section 8dBurning, Addendum to the Prince William Sound Contingency Plan. Anchorage, AK: Alyeska; 1998. 156. Punt M. The Performance of a Water Jet Barrier in a River. Spill Tech News 1990;1. 157. Allen AA. Alaska Clean Seas Survey and Analysis of Air Deployable Igniters. AMOP 1986;353. 158. Lavers L, Newfoundland Department of Forestry, personal communication, 1997. 159. Ontario Ministry of Natural Resources (OMNR). Specialized Fire Equipment Manual. Toronto, ON: Ignition DevicesdHelitorch; March 1990. 160. Energetex Engineering. Arctic Field Trials of the DREV/AMOP Incendiary Devices. Environment Canada, Ottawa, ON: Environmental Protection Service, Manuscript Report EE-17; 1981. 161. Energetex Engineering. Environmental Testing of Dome Air-Deployable Ignitor. Calgary: Dome Petroleum Ltd.; 1982. 162. Twardawa P, Couture G. Incendiary Devices for the In-Situ Combustion of Crude Oil Slicks. Valcartier: National Defence Research Establishment; 1983. 163. Frish M, Nebolsine P, DeFaccio M, Scholaert H, Kung W, Wong J. Laser Ignition of Arctic Oil SpillsdEngineering Design. AMOP 1986;203. 164. Frish M, Gauthier V, Frank J, Nebolsine P, Laser Ignition of Oil Spills: Telescope Assembly and Testing. Ottawa, ON: Environment Canada Manuscript Report EE-113; 1989.

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165. Walker AH, Michel J, Canevari G, Kucklick J, Scholz D, Benson CA, et al. Chemical Oil Spill Treating Agents: Herding Agents, Emulsion Treating Agents, Solidifiers, Elasticity Modifiers, Shoreline Cleaning Agents, Shoreline Pre-treatment Agents, and Oxidation Agents. Herndon, VA: MSRC Technical Report Series Report 93-015; 1993. 166. Ross SL, Canevari GP, Consultchem. State-of-the-Art Review: Emulsion Breaking Chemicals. Calgary, AB: Canadian Petroleum Association Report; 1992. 167. Fingas MF, Fieldhouse B. Studies of Water-in-Oil Emulsions and Techniques to Measure Emulsion Treating Agents. AMOP 1994;213. 168. Buist IA, Glover N, McKenzie B, Ranger R. In-Situ Burning of Alaska North Slope Emulsions. IOSC 1995;139. 169. Buist I, Morrison J. Research on Using Oil Herding Surfactants to Thicken Oil Slicks in Pack Ice for In-Situ Burning. AMOP 2005;349. 170. Buist I, Potter S, Zabilansky L, Meyer P, Mullin J. Mid-Scale Test Tank Research on Using Oil Herding Surfactants to Thicken Oil Slicks in Pack Ice: An Update. AMOP 2006;691. 171. Buist I, Potter S, Nedwed T, Mullin J. Field Research on Using Oil Herding Surfactants to Thicken Oil Slicks in Pack Ice for In-Situ Burning. AMOP 2007;403. 172. Buist I, Potter S, Nedwed T, Mullin J. Herding Agents Thicken Oil Spills in Drift Ice to Facilitate In-Situ Burning: A New Trick for an Old Dog. IOSC 2008;673. 173. Mitchell JBA. Smoke Reduction from Burning Crude Oil Using Ferrocene and Its Derivatives. Spill Tech. News 1990;11. 174. Mitchell JBA. Smoke Reduction from Burning Crude Oil Using Ferrocene and its Derivatives. Combust Flame 1991;179. 175. Mitchell JBA. Smoke Reduction from Pool Fires Using Ferrocene and Derivatives. AMOP 1992;681. 176. Mitchell JBA. Hydrocarbon Fire Technology Program: Technical Report. Calgary, AB: Esso Resources Canada Ltd; 1993. 177. Coupal B. Use of Peat Moss in Controlled Combustion Techniques. Ottawa, ON: Environment Canada, EPS Report 4-EE-72-1; 1972. 178. Breitenbeck GA. Devices to Support In-Situ Burning of Oil on Water. LSU Report 01e003; 2001. 179. Sloan SL, Pol DF, Nordvik AB. Phase 2: At Sea Towing Tests of Fire Resistant Oil Containment Booms. Herndon, VA: MSRC Technical Report Series 95e001; 1995. 180. ASTM 2533. Guide for In-Situ Burning of Oil in Ships or Other Vessels. Conshohochen, PA: ASTM; 2007. 181. McGrattan KB. Smoke Plume Trajectory Modeling. In: Proceedings of In-Situ Burning of Oil Spills 1999;75. Herndon, VA: U.S. Minerals Management Service; 1999. 182. Vodacek A, Kremens RL, Fordham AJ, Vangorden SC, Luisi D, Schott JR. Remote Optical Detection of Biomass Burning Using a Potassium Emission Signature. Int J Remote Sens 2002;2721. 183. Lambert P, Ackerman F, Fingas M, Goldthorp M, Fieldhouse B, et al. Instrumentation and Techniques for Monitoring the Air Emissions during In-Situ Oil/Fuel Burning Operations. AMOP 1998;529. 184. Li K, Caron T, Landriault M, Pare´ JRJ, Fingas M. Measurement of Volatiles, Semi-Volatiles and Heavy Metals in an Oil Burn Test. AMOP 1992;561. 185. Goldthorp M, Lambert P, Fingas MF, Ackerman F, Schuetz S, Turpin R, et al. Duplicating Conditions for Field Testing of Carbon Dioxide: A Modeller’s Dream Becomes a Technician’s Nightmare. AMOP 1999;13.

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186. Wang Z, Fingas MF, Landraiult M, Sigouin L, Lambert P. Distribution of PAHs in Burn Residue and Soot Samples and Differentiation of Pyrogenic and Petrogenic PAHs from PAHsdthe 1994 and 1997. In Song C, Hsu C, Mochida I, editors. Mobile Burn Study, Diesel Fuels 1999:237. 187. Zervas E. Formation of Oxygenated Compounds from Isooctane/Toluene Flames. Energy Fuels 2005;1865.

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Part VIII

Shoreline Countermeasures

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Chapter 24

Shoreline Countermeasures Edward H. Owens

Chapter Outline 24.1. Introduction 24.2. Shoreline Treatment Decision Process 24.3. Treatment Options

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24.4. Treatment by Shore Type 916 24.5. Waste Generation 919

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24.1. INTRODUCTION A common saying in oil spill response is that “the shoreline is the final boom.” When all other options are impractical or unsuccessful, oil spilled at sea near the coast will most likely be stranded. Similarly, a spill into a lake or river will likely oil the lake shores or river banks. The way in which an oiled shoreline or river bank is treated or cleaned depends on many factors related to the potential effects on the environment, human activities in the area, safety, and practicality. A critical element of the decision process is to establish treatment endpoints so that the response team has an operational target and will know when their assignment has been completed. Oil spilled on water is transported and spread by winds and surface currents, which are often variable and only occasionally can be predicted accurately.1 Consequently, the fate, behavior, and effects of spills on water have a high level of unpredictability and uncertainty. By contrast, oil spilled on land moves relatively slowly and, except in rare circumstances, flows downslope and collects in low areas or enters ditches, streams, and rivers. The rate of downslope movement is a function of the oil viscosity, air and ground temperatures, slope steepness, and the surface condition (roughness, vegetation type, soil type, permeability, etc.). A key objective for a response to a spill on land is to prevent oil from reaching moving waters because of the significant difference in rates of oil transport on land and water. When spills occur on land, the oil generally is static after a short time period, or moves only slowly, so that detection is straightforward and recovery operations generally proceed in an Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10024-3 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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orderly and progressive manner as compared to the more dynamic situations that usually typify river, coastal, or open-water spills. As oil moves from land to rivers to open waters, the sharp increase in the size of the affected area is accompanied by an increase in the number and types of resources at risk and by a decrease in the ability of responders both to protect resources at risk and to recover the mobile oil (Figure 24.1). The response to an oil spill on water can be considered as a series of fallback positions in a source-to-shoreline sequence (Figure 24.2), although some elements of the overall strategy may take place at the same time. The concept of fallback strategies applies equally to land, river, lake, or marine spills.

24.1.1. Control At or Near the Source The primary objective of a spill response operation is to minimize the size of affected area and damage to vulnerable resources. Ideally, this would be achieved by operations launched to contain, recover, and/or eliminate (i.e., disperse or burn) the oil on the water as near to the source as possible (#1 in Figure 24.2).

24.1.2. Control on Water If control at or near the source cannot be achieved due to feasibility, practicality, or safety factors, and if the spilled oil poses a threat to the coastal zone, FIGURE 24.1 Time and space elements for oil spills in different environments.

Chapter | 24 Shoreline Countermeasures

1

Control At/Near Source

2

Control on Water

3

Coastal Protection Strategy

4

Treat Oiled Shoreline

FIGURE 24.2 strategies.

909 Fallback operational response

then a defensive strategy would be implemented to minimize the size of the affected area and prevent oil from reaching the coastal zone (#2 in Figure 24.2). The objective of this strategy would be to prevent oil from reaching vulnerable shoreline area(s) and would involve on-water recovery and/or elimination (dispersion or burning).

24.1.3. Shoreline Protection Strategy In the event that oil cannot be contained, recovered, or eliminated on the open water due to feasibility, practicality, or safety factors, the next line of defense would be at or near the shoreline to protect site-specific vulnerable and sensitive shoreline resources or habitats at risk (#3 in Figure 24.2). The objective of a protection strategy would be to contain and recover oil, divert oil away from the shore, and/or redirect or deflect oil to strand on a shoreline that does not have sensitive resources at risk and where shoreline recovery could be effective.

24.1.4. Shoreline Treatment If all of the first series of control or protection strategies are not completely successful, the final step could be the cleanup of stranded oil (#4 in Figure 24.2), which, typically, is designed to accelerate natural recovery or to minimize further effects of the oil, for example, to prevent wildlife contact. In some cases, natural recovery of an oiled shoreline or section of shoreline may be a preferred strategy (see Section 24.3.1). The objectives, or endpoint criteria, for shoreline cleanup vary within the area affected by a spill depending, in part, on shore type and are set on a segment-by-segment basis. In most spills where oil reaches the coast, shoreline cleanup is the longest and most expensive component of a response operation.

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24.2. SHORELINE TREATMENT DECISION PROCESS The treatment of oiled shorelines typically is based on a decision process that involves: l l l l

A survey and assessment of the shoreline oiling conditions Development of treatment recommendations and priorities Establishment of treatment endpoints A signoff process to determine when sufficient effort has been taken to achieve those endpoints

Shoreline assessment procedures, known as the Shoreline Cleanup Assessment Technique (SCAT) (see Figure 24.3), have been developed that use standard terms and definitions to systematically survey and document the character of an oiled shoreline and of the oil that has been stranded.2 This technique is widely used and has been adapted to rivers and Arctic environments.3 SCAT teams usually include representatives of the various agencies or landowners. The development of a shoreline treatment or cleanup plan involves decisions and recommendations regarding treatment strategies and tactics and the establishment of termination criteria or treatment endpoints for sections of oiled shorelines. Treatment activities are planned to accelerate recovery rates when and where possible. The design and planning of these activities initially involves a knowledge, among other things, of: l l l

Where the oil is located on the coast, lake, or river The shore types that are oiled The character and amounts of oil present at each location

FIGURE 24.3

SCAT team looking for subsurface oil on a pebble-cobble beach.

Chapter | 24 Shoreline Countermeasures

l

l l

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The location of the oil (with respect to tidal, lake, or river water levels; on the surface or penetrated into the substrate, etc.) The potential for oil remobilization The expected persistence of the oil

Much of this information may be obtained as part of SCAT surveys. Once the distribution and character of the oil has been established, a key element of the decision process is to evaluate the likely fate and effects of the oil and the potential effects of treatment activities.4,5 This evaluation typically would take into account the following principles: l

l

l

As Low As Reasonably Practical (ALARP) ALARP is a term used to describe the point beyond which further treatment is no longer practical due to physical or safety reasons or no longer desirable because of NEB considerations. Net Environmental Benefit (NEB) The concept of NEB involves an evaluation of different treatment options, the different levels of treatment or cleanup in terms of concentrations of remaining oil, levels of cleanup effort, and levels of environmental intrusion in terms of the potential effect(s) of the stranded oil and the potential effects of proposed treatment activities. The objective of a treatment activity is to accelerate recovery of an oiled shoreline or river bank as close as possible to the pre-spill condition. At some point in the treatment process, the benefits of continued cleaning activities are offset by potential environmental damage so that further treatment may delay rather than accelerate recovery.6,7 Some shore types, such as salt marshes, wetlands, or tundra, are particularly vulnerable to damage by response operations, and natural recovery may be the preferred option from an environmental perspective. This option should be considered in the context of other factors, such as the potential effect(s) of untreated oil on wildlife and human activities. Waste Minimization Shoreline cleaning generates oily and operational waste that must be packaged, transported, and disposed of in a responsible manner. Greater effort is required. The stricter the treatment of endpoints, the greater is the volume of waste to be managed. Waste minimization is particularly important in remote areas as this reduces effort and secondary effects (including environmental disturbance and carbon emissions). In this context, in-situ shoreline treatment techniques are preferred, when appropriate, as these reduce effort and secondary effects.8

The selection of an appropriate treatment strategy is based initially on the shoreline type and the character and amount of oil on the shoreline segment. Treatment tactics are basically the same for land, river, lake, or marine spills. Recommendations regarding appropriate treatment tactics consider the NEB, waste generation, and the cleanup or completion criteria.

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The shoreline cleanup plan may identify one or more operational phases, each with a set of treatment activities and endpoints. For example, the initial phase of a shoreline response may focus on the removal of bulk or mobile oil that could be recovered easily and/or would be easily remobilized. Once all potentially mobile oil has been removed, the same segment(s) may then be treated to a second endpoint(s) that defines the desired final completion target. One phase in this treatment process may allow for a period of natural weathering during which the objective would be to monitor the reduction of oil concentrations by natural processes, such as wave action and biodegradation. Treatment endpoints, or completion criteria, are established early in the decision process to determine which shoreline or river segments require treatment and to provide field operations teams with cleanup targets for those segments.9 These endpoints are evaluated by the shoreline operations team to ensure that they are practical and feasible. A SCAT survey typically provides the necessary information base for shoreline treatment decisions. If the survey shows that a segment meets the endpoint(s), then no treatment is recommended. If the segment contains oil that is above the endpoints, then treatment options are recommended to achieve that standard. When the operations team considers that they have achieved the endpoint(s), typically an inspection team surveys the segment and if they agree then would recommend to the spill management team that no further treatment is necessary. Additional cleanup may be required if the survey team finds that endpoint(s) have not been achieved. More than one inspection may be necessary if the treatment plan calls for a multistage program with a sequence of endpoints as described above. In this case, the inspections allow the operations teams to progress from one phase to the next.

24.3. TREATMENT OPTIONS Many individual tactics can used to treat or clean shorelines and river banks, and these are described in detail by a number of manuals.10-14 These tactics can be grouped into three basic shoreline response strategies as shown in Table 24.1.

24.3.1. Natural Recovery This strategy leaves the stranded oil to natural oil removal and weathering processes, such as wave action and biodegradation, and allows the oiled shoreline to recover without intervention. This strategy may be appropriate where: l

l l

To treat or clean stranded oil may cause more (unacceptable) damage than leaving the environment to recovery naturally (NEB) Response techniques would not be able to accelerate natural recovery Safety considerations could place response personnel in danger either from the oil (itself) or from environmental conditions (weather, access, hazards, etc.)

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TABLE 24.1 Shoreline Treatment Techniques Natural Recovery Physical Removal l

l

l l l

washing and recovery l flooding (<1.5 bars) l low pressure (<3 bars), ambient temperature l low pressure, warm/hot water temperature l high pressure (4þ bars), ambient temperature l high pressure, warm/hot temperature l sand blasting manual removal l shovels, rakes, etc l vegetation cutting vacuums mechanical removal sorbents

In-situ Treatment l l l l l

mixing, dry or wet sediment relocation burning dispersants or shoreline cleaners bioremediation

24.3.2. Physical Removal Physical removal involves the recovery and disposal of stranded oil. There are a range of tactical options available to remove oil; these options basically involve either flushing or washing, with containment and recovery, or manual or mechanical removal (Table 24.1). Washing moves oil either onto the adjacent water where it can be contained by booms and recovered by skimmers, or toward a collection area, such as a lined sump or trench, where it can be removed by vacuums, sorbents, or skimmers. Simple flooding can remove light or mobile oils, but higher water pressure and/or temperature may be required as oil viscosity increases to mobilize the oil. Flushing or washing often is carried out in combination with flooding to move the remobilized oil to collection areas. Low-pressure washing typically involves hand-held hoses as shown in Figure 24.4. High pressure “spot washing” often is used to remove thin oil or stains from man-made structures. Manual removal includes shovels and rakes (Figure 24.5), as well as the deployment and recovery of passive sorbents to collect oil and cutting or wiping oiled vegetation. Manual removal has the advantage of minimizing waste generation but is labor intensive and relatively slow.

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FIGURE 24.4 Low-pressure washing of an oiled river bank.

Mechanical removal techniques essentially use equipment designed for earth-moving or construction projects (Figure 24.6), although a few commercial devices have been fabricated specifically for shoreline cleanup applications. Mechanical techniques involve minimal labor support and can clean beaches rapidly, but typically generate as much as 10 times more oiled solid waste than manual removal. Scrapers, front-end loaders, and backhoes can

FIGURE 24.5

Manual removal of thick surface oil.

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FIGURE 24.6 Mechanical removal of surface oil layer with a front-end loader.

remove oil materials in a single step, whereas graders and bulldozers only move oil sediments for subsequent removal by other equipment. The removal of oil that has penetrated into coarse sediment or has been buried by sediment movement can involve the generation of large volumes of waste. Manual techniques may be appropriate only for small amounts of subsurface oil so that mechanical removal or in-situ treatment (see below) may be more practical options. No single physical removal technique has all of the four ideal attributes: l l l l

minimal resource requirements, a rapid cleanup rate, a single-step operation, and minimal waste generation

so that the evaluation and selection of removal options typically involves a degree of compromise or trade offs.

24.3.3. In-Situ Treatment An in-situ treatment strategy involves tactics that are conducted on site and thus minimize the generation or recovery of oiled materials that then require transfer and disposal. The range of tactics includes: l l

Mixing (also known as tilling, land farming, or aeration) Sediment relocation (also known as berm relocation or surf washing)

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Burning Dispersants or shoreline cleaners Bioremediation

Mechanical mixing of oiled sediments involves agitation either in the absence of water above the water line (“dry”) (Figure 24.7) or underwater (“wet”) (Figure 24.8). In both cases the intent is to mix, expose, or turn over the sediment in situ. This differentiates mixing from sediment relocation where sediments are purposely moved from one location to another (Figure 24.9). Dry mixing and sediment relocation promote oilefine particle interactions that accelerate weathering and biodegradation. Wet mixing releases oil from the sediment, which can be then contained and recovered on the water surface. The group of chemical or biological tactics involves the addition of agents to facilitate removal of the oil from the shore zone or to accelerate natural in-situ oil removal, degradation, and weathering processes. Only dispersant application and bioremediation are true in situ and standalone techniques, as the other tactics require an additional removal component. Burning, chemical treatment, and biological agents are regulated by government agencies and require appropriate approvals and compliance.

24.4. TREATMENT BY SHORE TYPE The character of the shoreline or river bank is a primary factor that affects the behavior of stranded oil and the selection of treatment strategies and tactics.

FIGURE 24.7 Dry mixing on a sand beach.

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FIGURE 24.8 Wet mixing in a streambed.

A number of cleanup manuals address shoreline treatment in the context of shore types.14-17 A common feature of these response manuals is the use of matrices to relate appropriate treatment tactics to shore types and oil character (Figure 24.10).

FIGURE 24.9 Sediment relocation on a remote coarse mixed-sediment beach.

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FIGURE 24.10 Example of a treatment options matrix for a sand beach.14

There is a fundamental difference between substrate types characterized by sediments and those that do not have sediments. Oil cannot penetrate impermeable substrates such as bedrock, beachrock, or man-made concrete structures but can penetrate coarse sediments (cobble beaches) or be buried by mobile sediments (sand beaches, river point bars, tidal flats, or sabkhas). Vegetated shores, such as mangroves, low-lying tundra, reed beds, or salt marshes, typically are sensitive to treatment and to the cleanup operations.

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Response operations on these shore types involve careful consideration of the effects of the operational activities and the benefits of oil removal or treatment versus natural recovery. Shoreline treatment may involve a phased strategy with the initial recovery of mobile or thick oil by physical washing or by manual or mechanical removal. The objective of this first phase often is to prevent remobilization of the oil. A second, “polishing” phase, may be carried out to remove or clean the residues and could involve further removal, in-situ treatment, and/or bioremediation to achieve the treatment endpoints.

24.5. WASTE GENERATION All oil spill cleanup operations involve the generation of waste materials (Figure 24.11).18,19 There is no correlation between the volume of waste generated and the original amount of spilled oil.8,20 Large spills can generate small amounts of waste, whereas small spills can generate 10 or even 20 times the amount of waste compared to the amount of oil spilled. The majority of waste on response operations is generated by shoreline cleanup, and the amount of waste generated by shoreline operations is primarily a function of the treatment methods that are selected and of treatment endpoints that are established. Mechanical cleanup is a relatively rapid technique but can generate up to 10 times more waste than manual removal. From a waste minimization and disposal perspective, the preferred options are manual

FIGURE 24.11 Waste generated by manual removal on a sand beach.

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techniques that generate small volumes of oily waste or those in-situ techniques that do not generate oil or oily wastes, only operational or logistics waste materials: l l l l l l

Natural recovery Mixing Sediment relocation Burning Dispersants Bioremediation

These in-situ techniques are well suited to remote areas because they are relatively rapid and involve minimal resource requirements and logistics support. As in most cleanup decisions, typically there is trade-off that involves efficiency, practicality, costs, and net environmental benefit.

REFERENCES 1. Murray SP. The Effects of Weather Systems, Currents, and Coastal Processes on Major Oil Spills at Sea. In: Kullenberg G, editor. Pollutant Transfer and Transport in the Sea, Vol. II, Chap. 5. Boca Raton, FL: CRC Press; 1982. 2. Owens EH, Sergy GA. The SCAT ManualdA Field Guide to the Documentation and Description of Oiled Shorelines. 2nd ed. Edmonton AB: Environment Canada; 2000. 3. Owens EH, Sergy GA. The Arctic SCAT ManualdA Field Guide to the Documentation of Oiled Shorelines in Arctic Regions. Edmonton AB: Environment Canada; 2004. 4. IPIECA. Oil Spill Preparedness and ResponsedReport Series Summary. London: International Petroleum Industry Environmental Conservation Association; 2006. 5. Owens EH, Sergy GA. A Shoreline Response Decision-Making Process. IOSC 2008;443. 6. Baker JM. Net Environmental Benefit Analysis for Oil Spill Response. IOSC 1995;611. 7. IPIECA. Choosing Spill Response Options to Minimize DamagedNet Environmental Benefit Analysis, Report Series, vol. 10. London: International Petroleum Industry Environmental Conservation Association; 2000. 8. Owens EH, Taylor E, O’Connell K, Smith C. Waste Management Guidelines for Remote (Arctic) Regions. AMOP 2009;155. 9. Sergy GA, Owens EH. Selection and Use of Shoreline Treatment Endpoints for Oil Spill Response. IOSC 2008;435. 10. CEDRE. Response on LanddTechnical Data Sheets, http://www.cedre.fr/en/response/ response-on-land/cleanup.php. Brest: Centre de Documentation de Recherche et d’Expe´rimentations sur les pollutions accidentelles des eaux; July 2010. 11. Exxon Mobil. Oil Spill Response Field Manual. Fairfax, VA: Exxon Mobil Research and Engineering Co.; 2008. 12. NOAA. Shoreline Countermeasures ManualdTemperate Coastal Environments. Seattle, WA: National Oceanic and Atmospheric Administration, Office of Response and Restoration, Hazardous Materials Response and Assessment Division; 1992. 13. NOAA. Shoreline Countermeasures ManualdTropical Coastal Environments. Seattle, WA: National Oceanic and Atmospheric Administration, Office of Response and Restoration, Hazardous Materials Response and Assessment Division; 1992.

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14. Owens EH, Sergy GA. A Field Guide to Oil Spill Response on Marine Shorelines. Ottawa, ON: Environment Canada; 2010. 15. API-NOAA. Options for Minimizing Environmental Impacts of Freshwater Spill Response, Prepared by E.H. Owens and J. Michel for American Petroleum Institute, Washington, DC, and National Oceanic and Atmospheric Administration, Seattle, WA, American Petroleum Institute Publication No. 4558, 1995. 16. ITOPF. Shoreline Cleanup, http://www.itopf.com/spill-response/clean-up-and-response/shoreline-clean-up/London, July 2009. 17. NOAA. Characteristic Coastal Habitats: Choosing Spill Response Alternatives, http:// response.restoration.noaa.gov/book_shelf/911_coastal.pdf, Seattle, WA: National Oceanic and Atmospheric Administration, Office of Response and Restoration, Hazardous Materials Response Division; July 2001. 18. CEDRE. Oily Waste Management, http://www.cedre.fr/en/publication/waste/waste.php, Brest: Centre de Documentation de Recherche et d’Expe´rimentations sur les pollutions accidentelles des eaux; July 2004. 19. IPIECA. Guidelines for Oil Spill Waste Minimization and Management, Report Series, vol. 12. London: International Petroleum Industry Environmental Conservation Association; 2004. 20. ITOPF. Oil Spill ResponsedDisposal of Oil and Debris, http://www.itopf.com/spill-response/ clean-up-and-response/disposal. London: ITOPF; July 2004.

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Chapter 25

Automated Assessment and Data Management Alain Lamarche

Chapter Outline 25.1. Introduction 923 25.2. Automated Processing 924 and Data Management: Goals and Definition 25.3. Shoreline Observations 929 Data Processing

25.4. Assessment Automation 939 Methods and Tools 25.5. Shoreline Assessment 948 Data Management Issues

25.1. INTRODUCTION Observation of the state of a shoreline following a spill is an essential activity that is at the heart of the response planning effort.1 The aim of shoreline observations is to support response planning by providing a picture of the extent and characteristics of oiling conditions along affected portions of the shoreline. The nature and complexity of shoreline surveys evolve in time with the needs of the response. Early surveys are used for scoping purposes and are usually made from an aircraft. These surveys will provide a rough overview of the extent of the shoreline potentially affected by oil. Video surveys, which essentially involved the videotaping of the affected area and recording of the observed oil cover, are also often used both to get a better estimate of the oil cover and to define operational shoreline segments. Information gathered from aerial overviews and video surveys, along with complementary information from local sources, are then used to start planning the response process and prepare for the full-scale ground surveys.2 Shoreline surveys are making increased use of the Shoreline Cleanup and Assessment Technique (SCAT) approach, a method that is designed to provide unbiased and objective evaluations of the state of oiling and enable selection of cleanup and treatment methods.3 The method has been adopted worldwide and Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10025-5 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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is systematically used in North America, New Zealand, Australia, and many European countries.1,4,5 The amount and precision of the data gathered increases in detail and complexity with the type of survey: from rough estimates (often verbal) of the location of oiled shorelines to precise location of patches of oil along short segments of the shoreline.2 In order to be of any use for planning purposes, survey data must be processed in a timely manner.6 The entire response planning effort greatly benefits from the use of computerized treatment systems that enable the transformation of raw data into useful information, including reports, listings, and maps.6,7 A lot of the material presented in this section can be found in the Shoreline Cleanup Assessment Technique (SCAT) Data Management Manual.2 In addition, many of the shoreline assessment data management methods and issues discussed in this chapter were actually experienced while developing, operating, and perfecting the ShoreAssessÒ dedicated shoreline assessment data management system.8 This Geographic Information Systems (GIS)-based SCAT data management system has been used for the last 10 years in a number of shoreline response intensive incidents.

25.2. AUTOMATED PROCESSING AND DATA MANAGEMENT: GOALS AND DEFINITION 25.2.1. Understanding the Use of Shoreline Assessment Data during a Response Observations gathered from shoreline surveys are used for planning purposes by the entire response, if provided in a timely way. Figure 25.1 demonstrates the process: Field surveyors (SCAT or other) record their observations, which are processed into tables, maps, and lists of recommendations. These are used by tactical planning groups to aid in producing a treatment plan, which includes segment-by-segment cleanup instructions. These instructions are implemented by operations personnel who perform the requested cleanup actions. The figure demonstrates the importance of providing documents derived from survey observation in a timely manner, so that they can be effectively used to develop a response plan. In fact, shoreline surveys act as the “eye and ears” of a response. The data gathered from these surveys are processed and distributed in various formats mainly to provide accurate and unbiased information about the state of oiling along the shoreline. This information is used by the various teams involved in a response, as described in Table 25.1.

25.2.2. The Nature of Shoreline Assessment Data The exact nature of the data gathered by survey teams varies with the type of survey method. The various types of SCAT shoreline survey methods and their

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FIGURE 25.1 The treatment response cycle.

objectives are summarized in Table 25.2 and Figure 25.2. A response can include all or a few of the different survey methods. The following are the three primary survey methods used: Aerial reconnaissance surveys quickly evaluate the extent of the impacted area. The objective is simply to define the geographic distribution of oiled shorelines, to help define the overall scale of the problem, and to develop regional objectives. Aerial videotape/mapping surveys provide detailed information that is used to divide the affected shorelines into segments and to map the oil distribution and shoreline character within each segment. Full-scale ground surveys methodically and systematically document all details of the surface and subsurface oiling conditions within each of the segments determined by the aerial mapping. Additional supplementary surveys include the following: First responder ground surveys are typically conducted by local people to provide an initial ground-view assessment of the nature of the oiling conditions before formal responders arrive on the scene. These surveys provide data similar to that provided by aerial videotape/mapping surveys.

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TABLE 25.1 Uses of Shoreline Assessment Data Within Each Section of Incident Command or Response Management System Planning Define response priorities. Select cleanup or treatment method. Identify the required level of effort for shoreline operations. Define and apply cleanup or treatment end-point criteria. Update the situation status boards. Identify the amounts and types of waste that could be generated at each site. Monitor the progress of the response. Operations Locate the sites to be treated. Use the most appropriate access method. Apply the selected treatment method(s) for each oiled area. Apply the selected waste transfer and disposal method(s). Logistics Estimate the required equipment and personnel and their support requirements. Finance Estimate the cost of the response. Unified or Incident Command Evaluate the scale of the problem and the scope of the response. From Lamarche et al., 2007.2

Spot ground surveys are similar to full-scale ground surveys, but are applied on a few shoreline segments or even on portions of selected shoreline segments. Post-treatment ground surveys are used to monitor the progress of treatment and to determine whether the treatment endpoint criteria have been reached. Long-term monitoring surveys or programs repeat observations and measurements from ground surveys in order to provide a sequential record of change over time. Detailed ground surveys are those that produce the largest amount of data, and also present the most difficult challenge for data processing.6 Field observations are typically recorded on paper in the form of sketches (Figure 25.3) and Shoreline Oiling Summary forms (Figure 25.4). Such documents are produced for each shoreline segment surveyed. Notice that the notion of shoreline segment is central to the SCAT method: shoreline segments are defined as alongshore units within which the shoreline

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TABLE 25.2 Summary of SCAT Survey Methods Survey Methods

Key Objectives

Aerial Reconnaissance

Define overall scale of the problem to develop regional objectives. Mapping or documentation are not required. May result in hand-drawn information on a map/chart and a few photographs.

Aerial Video Survey, First Responder Ground Survey

Systematically document or map to create segments; develop regional strategies and plans; and define locations and lengths of oiled shorelines, including surface oil band width and estimated distribution.

Systematic Ground Survey

Systematically document surface and subsurface shoreline oiling conditions in all segments within the affected area. This category includes full-scale, posttreatment, and long-term monitoring surveys.

Spot Ground Survey

Systematically document surface and subsurface shoreline oiling conditions for selected segments or portions of segments in the affected area.

From Owens and Sergy, 2004.1

character is relatively uniform. Examples of “typical” shoreline segments include: (1) sandy beaches between rocky outcrops or (2) a stretch of rip-rap in a harbor or marina. The two figures also illustrate some of the characteristics of shoreline survey data, which include the following: l l

l

l

Data and textual information reported for each shoreline segment surveyed Within each shoreline segment, reporting of a potentially large number of surface or subsurface oil zones, which may have not only varied amounts of oil, but also be located over different substrate types, and thus need to be treated by different methods More or less uniform substrate types observed along the shoreline segment, in addition to the primary type Large number of annotations and recommendations, which are all generally relevant to the operations teams that will be in charge of treating the area

25.2.3. Practical Use of Shoreline Observations The data and textual information contained within sketches and forms needs to be processed in order to be distributed and used by other teams involved in the response. A set of typical outputs used for response planning follows. The oiling summary table (Table 25.3) indicates the degree of oiling observed for each of the shoreline or substrate types affected by oil. This table

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FIGURE 25.2 SCAT surveys performed during an oil spill response (from Lamarche et al., 2007).2

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FIGURE 25.3 Example of a sketch.

provides an overview of the situation and indicates the amount of effort that will be necessary to correct the situation. The oiling summary map (Figure 25.5) gives an overview of the oiling situation and is used to communicate and plan. The shoreline treatment recommendation transmittal form (Figure 25.6) provides detailed treatment instructions to the cleanup crew. When available, this form can be combined with a sketch so that operations personnel can locate oil patches and subject each one to the appropriate treatment.

25.3. SHORELINE OBSERVATIONS DATA PROCESSING As shown above, shoreline assessment surveys often produce a large amount of data that need to be processed before the next planning cycle in order to be useful for decision making. Data processing is thus one of the central tasks of the shoreline assessment data management process.

25.3.1. Data Processing Organization Within a response organization, the data management team will normally be responsible for the processing that leads to the production of all outputs used by the various teams involved. Figure 25.7 shows how data gathered from the field

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FIGURE 25.4 Example of a filled shoreline oiling summary (SOS) form.

makes its way to its various users within an Incident Command System. The diagram shows that data gathered by field surveyors (within forms and sketches) is processed by the data manager and shoreline assessment (SCAT) coordinator, in order to produce summary maps and tables, as well as treatment recommendations. This information is then further analyzed and refined (particularly treatment recommendations) before being incorporated within action plans and distributed as treatment instructions. Spill response managers within incident command will use summary tables and overview maps to judge the overall state of the situation and will often use

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TABLE 25.3 Example of an Oiling Summary Table Length of Shoreline by Oiling Category (m) Substrate Type

Heavy

Moderate

Light

Very Light

NOO

Bedrock

205

118

3,292

232

7,606

Seawall

0

298

7,992

10,994

51,558

Sand

0

484

2,181

31,599

44,248

Sandy Gravel

498

0

566

145

34,039

Coarse Gravel

0

0

50

300

16,773

Cobble-Pebble

522

1,046

3,897

2,957

9,762

Boulder

60

733

166

0

771

Rip-Rap

562

2,562

4,232

16,888

101,624

Mud

0

0

969

0

6,582

Vegetation

0

90

350

0

118,307

Total

1,847

5,331

23,695

63,115

391,270

detailed segment information to focus on certain “problem areas” for which treatment decisions are needed. Logistics personnel will use the information for support planning of the response effort, including the distribution of personnel and equipment. Operations personnel will make use of treatment instruction and detailed maps in order to apply the approved (and appropriate) treatment method for each oiled area

25.3.2. Responsibilities of the Shoreline Assessment Data Management Team The shoreline assessment data management team operates the system used to manage, process, and distribute shoreline assessment data and information (i.e., summary reports, tables, and maps). The essential role of a shoreline assessment data management team is to ensure that shoreline observations and assessments derived form field observations are available to support the work of all groups involved in the response to a spill. With this role comes distinct responsibilities, some of which involve legal issues. These responsibilities are listed in Table 25.4 and are discussed below.

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FIGURE 25.5 Example of an oiling summary map.

25.3.2.1. Data Integrity Data integrity is the first responsibility of the shoreline assessment data management team. In the spirit of the “Chain of Custody” concept, original field documents received by the management team should not be altered in any way. Any necessary changes, for example, for clarification or to include information that has been inadvertently omitted, should be clearly noted on the document itself and initialed and dated by the person who makes the change(s). 25.3.2.2. Data Preservation and Documentation The shoreline assessment data management team is also responsible for ensuring that all original data and materials produced to support the response effort are preserved and documented. Maintenance of the shoreline assessment database initially involves making copies of all data forms and sketches and storing this material in folders. Computerized files should be backed up daily, so that it should be possible to recover data quickly in the event of computer failure to prevent a break in the workflow. There is no error-free database. Therefore, data used for processing should also be verified at some point during the response, when time permits, in order to detect errors that might have crept into the data files. Data validation techniques include simply comparing the information on the original paper material to the outputs of the digital data

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FIGURE 25.6 Example of a filled shoreline treatment recommendations form.

and developing techniques for detecting “unreasonable data.” Calculating oil volumes can be used for this purpose. A general review of the data is typically performed when all shoreline field survey operations are finished.

25.3.2.3. Data Processing The shoreline assessment data management team is also responsible for the accurate representation of processed data in summary reports, tables, and maps. This requires that personnel responsible for data processing understand the

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FIGURE 25.7 Data flow and teams involved in gathering and processing shoreline assessment data (from Lamarche et al., 2007).2

TABLE 25.4 Responsibilities of the SCAT Data Management Team Data integrity Data preservation and documentation Data processing Data distribution

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precision and limitations of the data. This is important in order to prevent generating misleading or inaccurate information.

25.3.2.4. Data Distribution Finally, the shoreline assessment data management team is responsible for distributing the processing results in a timely manner. This requires that members of the data management team understand the decision-making process and the management cycle, which may vary with each incident. Since response personnel will generally not wait for the available documents in order to carry on with their work, the data management team must organize their workflow so that documents are generated and communicated to those who need them when they need them. Not providing needed information on time results either in parallel processing systems, such as manually skimming through paper Shoreline Oiling Summary forms or failure to use the data at all.6

25.3.3. Data Management Tasks and Processes Data management includes a number of distinct tasks carried out to acquire, validate, document, store, secure, process, and maintain a database of shoreline observations and information. Figure 25.8 presents an overview of all these tasks, which are summarized below.

FIGURE 25.8 Shoreline assessment data management tasks (adapted from Lamarche et al., 2007).2

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SCAT data management can be broken down into two general categories: (1) managing the data and (2) processing and applying the data.

25.3.3.1. Managing SCAT Data Setting-up of the data management system involves preparing a data management system, including personnel and equipment, for implementation and deployment at the incident operations center. In order to ensure efficiency, data management tools should be selected well before any spill occurs and be part of the response preparedness and contingency planning. In addition, providers of data management services should be identified and well trained in operating the selected data management tools. Table 25.5 lists all the steps involved in setting up a data management system. Initial response survey data are performed immediately after the incident in order to evaluate the entire affected area as quickly as possible. The data provide a coarse overview of the oiling characteristics along large portions of the coastline. Data management tasks performed to prepare for data processing (Table 25.6) thus need to focus on a rapid turnover in order to provide data summaries that can be used for planning as quickly as possible. Managing ground survey data (Table 25.7) constitutes the central and typically longest portion of the shoreline assessment data management team’s efforts, since data and material generated by ground surveys are detailed and relate to a range of different elements (e.g., shore type, surface and subsurface oiling conditions, access, staging potential, and ecological constraints). Decisions based on the results of detailed ground surveys have a direct impact on the quality of the response and the level of effort of the shoreline treatment activities. The turnaround time for processing field data is often very short,

TABLE 25.5 Data Management System Setup Tasks Obtain general information about the spill Obtain available cartographic material Obtain any available shoreline characteristics data Prepare all data management tools for transport to the Command Centre Once on site, report to the designated personnel, setup and verify equipment Obtain data describing the incident Obtain the location of operations divisions and enter them in the database Print and distribute general overview maps From Lamarche et al., 2007.2

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TABLE 25.6 Initial Response Survey Data Management Tasks Obtain aerial survey data Examine material Clarify items that may need to be modified Enter data in the database (adjust it if necessary) Produce and distribute summary maps and reports Backup and organise survey data From Lamarche et al., 2007.2

particularly during the early stages of a response where field teams provide new survey information on a daily basis. Data management tasks performed to prepare for data processing therefore need to provide optimal data quality as quickly as possible.

25.3.3.2. Processing and Applying Shoreline Assessment Data Once the data has been captured in the database, it must be processed so that it can be presented in reports, maps, and tables. Three levels of processing can be defined (Figure 25.9). These are summarized below: Evaluating oiling conditions for each oil zone represents the basic and lowest level of processing. This is done for each of the surface or subsurface oil

TABLE 25.7 Ground Survey Data Management Tasks Prepare data capture support documents Distribute document to the ground survey crews Obtain data from the ground survey crews Examine ground survey material Clarify any item that requires modifications/changes and correct omissions Enter data in the SCAT ground survey database Validate the data Produce and distribute summary maps and reports Back-up and organize survey data From Lamarche et al., 2007.2

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FIGURE 25.9 Data processing steps and tasks (from Lamarche et al., 2007).2

zones observed, recorded, and characterized on the Shoreline Oiling Summary form. Oil cover and oiling category are assessed directly from the width, thickness, and distribution of each oil zone. The substrate type is evaluated from the recorded substrate types of each oil zone. Basic processing can also include an estimation of remobilization potential and oil persistence. Summarizing oiling conditions within each shoreline segment is necessary in order to present oiling assessments on a shoreline segment basis. Methods developed to summarize oiling characteristics for each segment must take into account the fact that SCAT surveys may report oiling as multiple parallel oil zones with varied oiling characteristics. The following information can be summarized from the ground survey observations in a single shoreline segment: l l l

Overall substrate type, oil cover, and oiling category Length of shoreline by oiling category Volume of oil

Summarizing data for more than one segment includes all the data manipulations necessary for developing maps and tables used to summarize the information in many segments for entire surveys and/or the entire area affected by a spill. The method selected may vary according to the nature, characteristics, number of segments covered, and complexity of the SCAT data recorded during field surveys.

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25.3.4. Why and When to Establish a Shoreline Assessment Data Management Team Shoreline assessment data management teams are used primarily to prevent potential bottlenecks in the decision-making cycle caused by the need to process the field data (and make sure that field data are actually used in the planning process). This bottleneck may arise because survey teams do not have time to process the data themselves or because the survey coordinator does not have the time to produce shoreline assessment summaries. Shoreline assessment data management teams should be used whenever the data produced by survey activities exceeds the processing power of the field survey coordinator and when field data must be analyzed and summarized for planning purposes. Factors that should be taken into consideration when defining the need for a shoreline assessment data management team are summarized in Table 25.8. An obvious example of the need for a shoreline assessment data management team is when a spill covers tens of kilometers of shoreline and the area is surveyed by three or four teams producing data and information for multiple segments over several days. On the other hand, a spill that affects only one or two shoreline segments would not require a data management team. As a rule of thumb, a data management team is probably not needed if the fieldwork involves a single field survey team and covers seven shoreline segments or less. Even for a smaller spill, however, one individual must be assigned responsibility for the tasks that would be performed by a shoreline assessment data management team to ensure that the information gathered in the field is available for the decision-making process.

25.4. ASSESSMENT AUTOMATION METHODS AND TOOLS While all data management tasks can be performed manually with pencil and paper, computerized tools are more efficient and are often needed to speed up TABLE 25.8 Defining the Need for a Shoreline Assessment Data Management Team Factor

Criteria

Number of shoreline segments

More than 7

Number of SCAT teams

More than 1

Survey frequency

More than twice

Processing time needed to summarize the data

More than 1 hour

From Lamarche et al., 2007.2

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PART | VIII Shoreline Countermeasures

the process and ensure that processing results are provided in a timely fashion. Computerized tools range from simple office applications, such as word processors and spreadsheet programs, to more sophisticated GISs and specialized SCAT data management and processing systems. Some government and private agencies have developed GIS-based computerized pre-spill databases. When such systems are available, they greatly contribute to increase the efficiency of the management process, particularly when links have been developed between shoreline assessment data management tools and the pre-spill database.9 The efficiency of the data management process during a response will greatly increase if the response organization has selected data management tools and trained data management personnel on a regular basis during drills and exercises.

25.4.1. Basic Tools The basic tools for SCAT data management and processing tasks are listed in Table 25.9. Following is a short discussion of their main characteristics, strengths, and weaknesses, and most appropriate use for shoreline assessment data management.

TABLE 25.9 List of Basic Data Management and Processing Tools Tool

Optimal Use

Pencil and paper

Capture of SCAT field observations on forms and sketch maps

Spreadsheet programs

Reports and data processing

Databases systems

Data management (data entry and reports)

Geographic Information Systems (GISs)

Data processing (production of overview and summary maps)

Specialized programs

Data processing (automation of certain types of processing)

Word processors

Organization of processed data (production of comprehensive reports, including tables and other types of outputs)

Web-based applications

Distribution of processed data

Portable applications From Lamarche et al., 2007.

Field data acquisition 2

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25.4.1.1. Pencil and Paper All shoreline assessment data management tasks, from data acquisition to data processing, can be performed manually using pencil and paper. In fact, this has been the traditional approach to shoreline (including SCAT) data management. However, during spills with even moderate amounts of ground survey activitydfor example, data from more than five shoreline segments per daydthe task can quickly become overwhelming when using manual methods.6 Almost all data management tasks can now be done using electronic tools. The use of automation increases performance, particularly in terms of quality of data processing and the speed and quantity in producing decision-making documents.7 Without this processing power, information derived from shoreline survey (SCAT) is often underutilized. Nevertheless, pencil and paper are still the most flexible and reliable method, for they can be used when all else fails. Pencil and paper will probably always be used for field data acquisition, especially for producing sketches. For this reason, shoreline assessment data managers should be able to perform all data management tasks using pencil and paper. 25.4.1.2. Spreadsheet Programs Spreadsheet programs can be used for many SCAT data management tasks and have the following advantages: l l

l

l

l

They can easily create and set up data tables to store survey data. As spreadsheets are basically calculation tools, they can incorporate automated processing programs. They include many functions that enable and simplify the production of formatted tables. They are ideal for various kinds of data analysis, including the production of simple graphics. Spreadsheet-derived tables can easily be incorporated into word processing documents.

Spreadsheet programs are designed primarily for business calculations and analysis and are not data storage and retrieval tools. This leads to the following weaknesses: l l

l

Only a limited amount of data can be stored. There is no simple way to develop data entry forms with data validation rules. They cannot be directly linked to GISs.

As a result, spreadsheet programs are best suited to data processing and formatting. Because of their flexibility, they are ideal for developing and

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implementing data processing systems suitable for the unique situations that occur during larger spills. For example, a spreadsheet-based system was first developed and implemented to manage and process tar ball data during the New Carissa response.10

25.4.1.3. Database Systems Database systems are specifically designed to enable and simplify data storage and retrieval. They include many functions and mechanisms that make them ideal for: l

l l

l l

l

Efficiently developing and creating data storage structures, such as sets of linked tables Ensuring data integrity Providing data entry forms that include many validation tools, such as validation rules and pull-down lists Supporting the production of various types of reports Making it possible to automate data processing through the use of embedded programs Representing data in space through links with GISs

The trade-off when using database systems, however, is the time required to develop the components of the database. This includes creating tables, data entry forms, and reports and developing the programs used for data processing. A sophisticated database system designed for managing shoreline assessment data, which includes validation rules and report-generating mechanisms, requires a small team and several months to develop.

25.4.1.4. Geographic Information Systems Geographic Information Systems (GISs) are designed primarily to support the integration of spatial data through the use of maps. For SCAT data management, these systems are ideally suited to displaying and analyzing summary and overview decision-making support maps, such as those presented in Section 25.2.3. To use GIS technology for a spill response, however, all information must first be assigned a position in space, which is referred to as geo-referencing. This operation can be one of the most time-consuming parts of the data entry process, as each SCAT element, that is, shoreline segments, surface oil zones, and pits/trenches, must be located and entered, often manually. GIS systems often benefit from any type of support for this data entry. It takes time and effort, however, to develop SCAT-specific data entry tools. When data has been geo-referenced, a GIS is particularly valuable for producing summary or overview maps to support the decision-making process. Map production can be very time-consuming without any electronic support, as

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the operator must select a specific data element to map and a scheme to display the data as well as enter labels, scale bars, and North arrows. Automating the map production process greatly enhances the use of a GIS, but also takes time and effort.

25.4.1.5. Specialized Programs Two types of specialized programs can be used to automate assessments and computations: (1) those that implement more complex computation algorithms, for example, calculating total length of oiled segment by surface oiling category, and (2) expert or rule-based systems that use rules to make assessments, for example, assessing surface oiling category. Specialized programs are ideally suited to automating well-defined data processing that is not based on simple computations. These programs are best used as tools hidden or embedded within other programs, such as spreadsheets, GISs, or databases that store the data to be processed. 25.4.1.6. Word Processors Word processors are powerful and flexible tools that are ideal for organizing processed information. They are used to integrate outputs, images, maps, and tables of various origins within a single document. 25.4.1.7. Internet-Based Applications Internet-based applications provide access to information to anyone who is connected to this global network. The Internet is often used during spill response to disseminate processed information, such as overview maps, incident action plans, or overflight images. Some organizations have developed Internet-based data and information systems that incorporate outputs and even validated data produced by the shoreline assessment data management team. 25.4.1.8. Portable Applications Portable applications refer to database or GIS systems designed to function on Personal Digital Assistants (PDAs) or similar small computing devices. PDAbased systems, linked to a Geographic Positioning System (GPS), provide a relatively inexpensive solution to the bottleneck experienced when entering paper-based data within computerized systems. Portable applications for data acquisition are complete systems that may include databases, small GISs, and communication programs. Although they cannot totally replace pencil and paper, particularly for producing sketches, PDA-based systems can greatly reduce data acquisition and processing times.11

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25.4.2. Combining Tools Within a Data Management Support System A shoreline assessment data management support system is composed of an array of tools and processes used to organize data and make it available in the most appropriate form to support the decision-making process. The overall system includes the following components: l l l l

A field data acquisition system Some mechanism for storing data tables, paper files, and GIS Data processing methods and tools Support tools for distributing data

This section focuses on how basic management tools can best support the shoreline assessment process. The main data management tasks are outlined in Figure 25.10 and briefly discussed here. Capturing shoreline assessment data

FIGURE 25.10 SCAT data management system tasks and support tools (from Lamarche et al., 2007).2

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and observations in the field, though not exactly a data management task, is included since this is an important part of the entire system.

25.4.2.1. Data Capture Two basic methods are used to capture SCAT data: (1) pencil and paper to fill in field forms and create sketches and (2) dedicated portable applications. Field personnel also use digital cameras and a GPS to record positions. For small spills, pencil and paper are perhaps the most useful and efficient method for recording ground survey data. Due to the volume of data collected in larger spills, however, this method can cause a bottleneck when transcribing data from hard copy to the data management system. Computerized portable systems, including weatherized PDAs equipped with GPS units, can alleviate such issues as the data is directly uploaded into the SCAT data management system.11 25.4.2.2. Entering Data into the Database Support tools for entering data into a set of computer files (the SCAT database) must be quick and accurate. Electronic forms offer options that can reduce the possibility of mistakes and increase accuracy when entering data from paper material. These methods include: l l

l

Using data entry lists within list boxes for data entry categories Using internal validation programs when data values are incompatible; for example, the top value of a subsurface oil zone cannot be higher than the bottom one, or all data associated with surface oiling should be set to “0” or “nil” if “No Oil” is observed along a segment Automatically providing values to certain data elements, for example, the shoreline segment ID

Some of these methods also increase the speed of data entry. One of the best ways to increase the speed of data entry, however, is to take advantage of the fact that the value of certain data tends to be similar from one entry to the next. For example, oil type generally stays the same for all surface oil zones at the same incident. Similarly, the composition of the SCAT survey team stays the same for all surveys carried out by that team. Electronic forms, which are usually a function of database systems such as Microsoft Access, can also be created to simplify data entry within GIS systems. Data entry forms and additional functions within GIS systems can also be used to increase the speed of data entry. For example, shoreline segments can be delineated faster and easier through a “copy-paste” tool that enables the user to select a portion of a coastline from a “coastline” layer, copy it to memory, and paste it to define the new segment. The use of GPS-equipped field computers offers the ultimate data capture environment. Data captured in electronic format in the field can be quickly

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incorporated in the database and be ready for processing almost instantlydand without the possibility of data entry mistakes and misinterpretation, which is a common issue with paper forms.

25.4.2.3. Data Processing The most appropriate tool for SCAT data processing varies according to the general subtask category. Summary tables are best produced using report generators, which are usually an integral part of database systems, and specialized processing. These systems simplify data formatting to develop reports. The nature of ground survey (SCAT) data requires some specialized processing. Some of this processing is simple, such as the assessment of the Oiling Category from the width, percentage coverage, and thickness of oil (Table 25.10). Others can become a bit complicated, particularly when many oil zones of varying character are observed along a segment (Figure 25.11). This processing can be incorporated within subprograms of database systems, which greatly speeds up the creation of summaries. Summary tables can also be produced using spreadsheet programs. If data is stored in database systems, exporting it to a spreadsheet is usually straightforward. Summary maps are best produced by using the capabilities of GIS systems. Developing GIS-specific programs to automate map production considerably reduces data processing time and also helps to standardize map outputs. The benefits of standardization are that the same types of lines and colors are consistently used for similar categories, and certain important elements of the map, such as the scale bar, incident name, survey code, or the North arrow, are less likely to be omitted. Standardization can also be achieved by using “map templates.” TABLE 25.10 Estimation of Surface Oiling Category Width of Oiled Area

Distribution

Wide (>6 m)

Medium (>3 to 6 m)

Narrow (>0.5 to 3 m)

Very Narrow (<0.5 m)

Continuous 91 to 100%

Heavy

Heavy

Moderate

Light

Broken 51 to 90%

Heavy

Heavy

Moderate

Light

Patchy 11 to 50%

Moderate

Moderate

Light

Very light

Sporadic 1 to 10%

Light

Light

Very light

Very light

Trace <1%

Very light

Very light

Very light

Very light

From Owens and Sergy, 2004.1

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FIGURE 25.11 Step-by-step procedure to summarize oiling category along a shoreline segment (from Lamarche et al., 2007).2

Technical recommendations are best produced by using the expertise of shoreline treatment specialists. The selection of treatment methods can also be supported by using specialized rule-based programs, such as ShoreAssessÒ. In addition, if a standardized description of treatment methods is included in the SCAT data management system, the production of recommendations will be much faster. The treatment specialist can use these basic treatment descriptions as a starting point to write up recommendations using a word processor.

25.4.3. Information Distribution The results of data processing usually take the form of paper outputs and their electronic equivalent. Distributing paper output is straightforward and allows the shoreline assessment data manager to ensure the accuracy of the outputs

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before their release. Some summary or overview maps can be printed, preferably on large paper, and posted on walls. Finally, it is often simpler to create incident action plans by putting together and photocopying (or scanning) paper outputs rather than producing an electronic document. The electronic equivalent of processed data can be distributed in a variety of ways, which should be tested and agreed upon by those who will use them. Some validation process, such as having the outputs scrutinized by the shoreline assessment coordinator, should be developed before distribution. Often, the fastest way to distribute electronic documents is to make them available through a local area network or an FTP site. In this case, the files to be distributed should be given obvious names and be located in a clearly identified directory folder. One way to ensure that outputs are always clearly identified is to regroup them within a single document, such as a word processing file. This method has some added benefits to the data user, who often produces incident action plans with a word processor. Integrating outputs is simplified if it is already in word processing format. The pertinent data can also be e-mailed to the intended user. This is particularly helpful if the user is not part of the spill response local area network. Outputs can also be distributed by copying the information on removable media, such as memory sticks or CD. Processed data and outputs can be posted on a website dedicated to the spill and is a practical way to distribute observations and evaluation results to a large audience. This is feasible, however, only if some personnel are dedicated to maintaining and updating the site. A simple and practical way of distributing the data gathered during ground surveys is to scan them and assemble them into indexed documents such as Adobe pdf files.

25.5. SHORELINE ASSESSMENT DATA MANAGEMENT ISSUES A number of common issues are liable to affect and disturb the data management process, including: l l l l

Equipment failure Software corruption Overwhelming amounts of data Conditions unique to the response

Following is a short discussion of each of these situations, together with suggestions to ensure the continuing support of the data management team.

25.5.1. Equipment Failure Equipment fails. Even with the best possible safeguards, such as having a second computer with a backup of all the software and data, computerized equipment can still be out of service for variable periods of time.

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The data management team should ideally be prepared for the worst and be able to produce at least a minimum amount of data management services using only pencil and paper. These include classification and analysis of field data from forms and sketches, as well as update of summary tables and paper maps while the equipment is down. These tasks would need to be completed in an acceptable amount of time. This, of course, requires that some members of the data management team have a very good understanding of shoreline assessment methods and needs of planning personnel.

25.5.2. Software Corruption Although software corruption is a less severe form of general system failure, it can lead to insidious problems as shoreline assessment data management personnel may not be aware of it immediately. The evidence that something is wrong will often come from strange or unexpected processing results, which is why it is so important to validate outputs. Once it is established that some of the software is not working properly, alternative means should be developed to ensure that the work is completed with an acceptable level of efficiency. This could mean resorting to more rugged programs, developing temporary spreadsheet-based solutions for data processing, or even using pencil and paper to generate the necessary outputs. Training for disaster scenarios should cover work practices that prevent a sudden and complete breakdown and result instead in a gradual degradation of data management performance.

25.5.3. Overwhelming Amounts of Data In the event that the amount of data clearly exceeds the team’s processing capability, team members must learn how to prioritize their activities and develop shortcuts to ensure that the reports and summaries can be made available in an acceptable form to those who need it. The shoreline assessment data management teams should also be involved in full-scale exercises so that members of the response organization understand what to expect from the data management effort. Finally, members of the data management team should understand their tools so that they know how to recover information if the system fails. Team members should also understand the needs of shoreline observations and summaries, so they can provide adequate services even when only pencil and paper are available.

25.5.4. Conditions Unique to the Response No two spills are entirely alike. Even though the shoreline observation and assessment methods (such as SCAT) may be standardized, the unique

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PART | VIII Shoreline Countermeasures

FIGURE 25.12 Classification of customization issues (from Lamarche, 2008).12

conditions specific to shoreline-response intensive incidents directly impact the data management process. Unique spill-dependent conditions can be classified in four major categories:12 l l l

l

Unique local geographic conditions (such as shoreline types) Organization-specific needs (need to accommodate pre-spill information) Complexity of oiling observations or operations (multiband oiling conditions, multiple surveys, or multiple teams for a single survey) Unique conditions specific to a spill, which include the creation of additional descriptors (addition of Oiled Stem Height) or the need to develop new observation and assessment methods (submerged oil, monitoring of minute amounts of oil, tarballs)

Each of these situations will require that the data management team modify its existing tools, or even create new ones (Figure 25.12). Following is a short discussion on how to address each of these issues.

25.5.4.1. Common, Simple Adaptation Common, simple adaptations of the use of the shoreline assessment method are generally necessary to take into account specific geographical particularities or location-specific factors. Obvious and simple examples include the nature of shoreline types, which will vary according to type of environment. Environment Canada, for example, has identified a specific set of forms for the following environments: marine shoreline, inland lakes, rivers, and streams. In order to deal with these common issues, the data management system must easily accommodate changes in shoreline types, backshore character, substrate types, and so on.

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25.5.4.2. Organization-Specific Modifications Organization-specific modifications are due to the nature of standards adopted by an organization, or the wish and necessity to use existing pre-spill shoreline information. This mostly affects the information used to describe various aspects of shoreline segments. Some examples include shoreline classification (the United States, for example, uses NOAA ESI classification as shoreline types, unlike Canada or New Zealand); and specific elements on shoreline treatment recommendations forms (such as the nature and title of the list of people that need to approve the form). Thus, the data management system must easily enable the modification of forms. 25.5.4.3. Oiling Observation Issues Some oiling situations can become complex and are difficult not only to report, but also to record and process within a computerized system. Figure 25.13 provides an extreme example of a multiple-band oil zone situation. The issue associated with the “multiple surface oil bands” situation comes from the need to provide information to operations personnel that will enable the association of each oil zone with the appropriate treatment method. This can be done in a number of ways, the two most common being:

FIGURE 25.13 Example of a complex multiple-band oil zone situation (from Lamarche, 2008).12

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PART | VIII Shoreline Countermeasures

Associating specific substrate type with treatment methods (for example, mechanical removal on sand or manual removal on bedrock) Associating each oil zone with its specific treatment method, as stated in a Shoreline Treatment Recommendation form

The mapping capabilities of modern GIS system can be used to deal with these issues by associating either the description of oiling conditions (as is shown in Figure 25.13) and/or the treatment recommendation for each oil zone within a label pointing to the oil zone, overlaid on a high-resolution georeferenced satellite or aerial image. This method proves to be particularly effective when it is necessary to locate small “patches” of oil that need to be removed manually.9 Other complex issues that have been observed are related to the survey process. A common situation is the resurvey of certain segments within an impacted area. In this case, certain segments will be surveyed only once, and others many times in a particular time interval. This issue can be dealt with by including a routine within the data management software that identifies and “tags” the last survey done for any given segment. This allows the construction of oiling maps that include the latest observations at a given moment, by using the record selection mechanism available in modern GISs. Situations might also arise where different teams, surveying the same areas on the same day, report different observations. In the event that the observer could not agree on the likely oiling characteristics, then two approaches can be used to solve the issue. If oil zones of both observations cover exactly the same areas, then only the most severe oiling conditions would be reported, while the oiling characteristics of the less severe observations would be entered in a note field associated with each oil zone. This method might not do in the case where the oil zone location would not exactly coincide. In this second situation, then both oiling conditions would be reported as different oil zones, again using the “note” field associated with each oil zone to indicate the “double observation” situation.

25.5.4.4. Spill-Specific Customization The simplest case of spill-specific customization arises when a new descriptor (not part of the original shoreline observation set) needs to be taken into account as it becomes part of the response decision process. An example is the “oiled stem height,” which was one of the factors used to determine treatment procedures in a heavy oil spill that affected reed beds and marshes. This issue can be dealt with by simply adding the new descriptor to the shoreline database. More complex adaptations to the shoreline database arise when new observation methods have to be developed to take into account unique spill conditions or response needs. Two cases will be presented to illustrate these situations: the necessity to monitor minute amounts of oil and the necessity to assess and locate submerged oil.

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FIGURE 25.14 Temporal evolution of monthly tarball volume (from Lamarche, 2008).12

In the course of the New Carissa incident, a monitoring program was developed to assess the evolution of tarballs along the impacted and potentially impacted shoreline.13 What was done, in effect, was to develop a survey method that allowed the reporting of minute amounts of oil. To that effect, a new form was developed to record tarball data, and treatment procedures were created to show the temporal evolution of small amounts of oil. The procedures included the computation of tarball volumes based on their average size and the use of graphs with logarithmic scale to show temporal trends (Figure 25.14). In this particular case, all data entry and processing was done using a spreadsheetbased system. Submerged tarballs are not usually an issue in marine spills, but they became a concern in a spill of heavy oil on a large inland lake. A special survey program was developed to record the density of submerged tarballs along the shoreline and within reed beds. The method made use of special “submerged oil survey form” (Figure 25.15), where observed tarball density was recorded and associated with waypoints provided by a GPS. The method led to the development of a representation of the density of submerged tarballs that essentially associated GPS track lines with

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PART | VIII Shoreline Countermeasures

FIGURE 25.15 Portion of a computerized submerged oiling observation form (from Lamarche, 2008).12

point-observation. These representations were used by cleanup personnel to locate and remove tar balls (Figure 25.16). In this case, an entire set of methods needed to be developed to store submerged oil data within a database and partially automate the production of maps.

FIGURE 25.16 Example of a submerged oiling map. Lines represent “GPS track lines”. The map shows a 50-m resolution grid (from Lamarche, 2008).12

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REFERENCES 1. Owens EH, Sergy GA. A SCAT Manual for Arctic Regions and Cold Climates. AMOP 2004;703. 2. Lamarche A, Sergy GA, Owens EH. Shoreline Cleanup Assessment Technique (SCAT) Data Management Manual. Environment Canada: Emergencies Science and Technology Division, Ottawa, ON: Science and Technology Branch; 2007. 3. Owens EH, Teal AR. Shoreline Cleanup Following the Exxon Valdez Oil SpilldField Data Collection Within the SCAT Program. AMOP 1990;411. 4. Lamarche A, Roberts J. Development of a Shoreline Segmentation Database for the Coast of New Zealand. AMOP 2004;751. 5. National Oceanic and Atmospheric Administration (NOAA). Shoreline Assessment Manual, Report 2000-1. HAZMAT; 2000. 6. Lamarche A, Tarpley J. Providing Support for Day-to-Day Monitoring of Shoreline Cleanup Operations. AMOP 1997;1131. 7. Lamarche A, Morris D, Owens EH, Poole S, Tarpley J. The Benefits of Computerized SCAT Data Management Within an Incident Command System. AMOP 1998;157. 8. Lamarche A, Black C, Varanda A-P, Owens EH. The Use of Knowledge Base Software to Identify Shoreline Treatment Options. IOSC 1995;55. 9. Lamarche A, Gundlach E. Use of GIS and Digital Orthoquads to Support Inspection and Operations During Oil Spill Response. IOSC 2003;180. 10. Owens EH, Mauseth GS, Martin CA, Lamarche A, Brown J. Tar Ball Frequency Data and Analytical Results From a Long-term Beach Monitoring Program. Mar Pollut Bull 2002;770. 11. Lamarche A. A Personal Digital Assistant (PDA) System for Data Acquisition During Shoreline Assessment Field Surveys. AMOP 2006;217. 12. Lamarche A. Adaptability and Flexibility, Keys Towards Successful SCAT Data Management. AMOP 2008;601. 13. Owens EH, Lamarche A, Martin CA. Tarball Data from the Oregon Coast. IOSC 2001;1535.

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Part IX

Submerged Oil

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Chapter 26

Submerged Oil Jacqueline Michel

Chapter Outline 26.1. Introduction 26.2. Submerged Oil Characteristics 26.3. Review of Recent Submerged Oil Spills

959 961 965

26.4. Submerged Oil Spill Response Methods and Recommendations for Future Work

975

26.1. INTRODUCTION Spills of submerged oil pose special challenges during all phases of an emergency response. Submerged oils are difficult to track and locate; there are no proven containment methods for either oil suspended in the water column or deposited on the seafloor; underwater recovery methods are complex, expensive, and inefficient; the oil is often viscous, making it difficult to pump; and large volumes of water and/or sediment usually must be handled during recovery and disposal. As is the case for all oil spills, every submerged oil spill is a unique combination of conditions based on oil type and behavior, environmental setting, and physical processes. Terminology is not consistent for describing the different types of oil that do not float on the surface. The following terms are suggested: l l

l l

Submerged: any oil that is not floating on the water surface Overwashed: oil that is floating near the water surface but gets covered by a layer of water by wave action Suspended: oil that is moving in the water column with the currents Sunken: oil that has accumulated on the bottom of the waterbody

According to the National Research Council report on nonfloating oils, oil can become submerged via two primary pathways, as summarized in Figure 26.1.1 In the first pathway, an oil can be lighter than the receiving water Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10026-7 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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PART | IX

Submerged Oil

FIGURE 26.1 Factors that affect the behavior of heavy oils (from NRC, 1999).1

(oilewater density ratio less than one) and initially float. However, the oil can interact with sediments and subsequently become heavier than water, either by (1) stranding on a sandy intertidal substrate, picking up sand, then being eroded from the shoreline; or (2) mixing with sand suspended in the water column by wave action.2 In either case, depending on the amount of sediment mixed into the oil, the oilesediment mixture can become slightly negatively buoyant and become suspended in the water column by currents, or it can be dense enough to sink to the bottom. It is important to note that the oil itself is still buoyant and, if the oil separates from the sediment, it can refloat. In the second pathway, an oil that is denser than the receiving water (oilewater density ratio greater than one) will not float. Figure 26.2 shows the relationship between API gravity and water density, and at what receiving water salinities an oil of a specific API gravity will float or not float. In fresh water, oils with an API gravity less than 10 will not float; in seawater, oils with an API gravity of less than about 6.5 will not float. Evaporation alone can increase the density of oil to cause submergence only for oils that already are close to the density of the receiving water.3,4 Currents also play an important role in the behavior of submerged oil (Figure 26.1). If currents are weak, the oil will sink to the bottom. If the currents are greater than about 0.1 meters per second, the oil will stay suspended in the water column. The oil can eventually settle out in low-flow zones, often over large areas. Oil that has accumulated on the seafloor can be resuspended by currents, including riverine and coastal currents and currents generated by wave action. Therefore, submerged oil spills are those where the oil becomes heavier

Chapter | 26 Submerged Oil

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FIGURE 26.2 The relationship between water density (and API gravity) and salinity at 15 C.

than the receiving water, either because of its original density or increased density because of uptake of sediments.

26.2. SUBMERGED OIL CHARACTERISTICS A search was made of the published literature and oil spill case studies to characterize the types of oil that did not float after release.5,6 The annotated bibliography by Kaperick was a valuable source of spills prior to 1995.7 The National Oceanic and Atmospheric Administration (NOAA) oil spill database was also searched (http://old.incidentnews.gov/incidents/history.htm). Cases where the oil sank after burning were not included because of the effect of extreme heating on oil behavior. Also, not included were spills where the oil slick were reported as floating just below the water surface (making it difficult to track) but eventually stranded onshore. Table 26.1 is a summary of 26 oil spills in which submerged oil was reported. This is not a comprehensive list, but it is representative of the range of conditions where some fraction of the oil submerged. The list includes spills of crude oils, refined products, asphalt, carbon black feedstock, and coal tar oil. The spills are listed in alphabetical order, with information on oil type, the API gravity of the oil if reported, and the conditions that led to submerged oil. There are several common characteristics among the types of oils that became submerged. The only crude oils in Table 26.1 are heavy, viscous crude oils from Venezuela (Merey, Pilon, and Bachaquero crude oils). In these three cases, the oil initially floated (API gravity of 13.6e17.3), stranded thickly on flat, sandy intertidal habitats, picked up sand, then a fraction of the stranded oil was eroded from the shoreline and submerged. The T/V Alvenus spill came ashore on the sand low-tide terrace and sand beaches of Galveston Island, Texas, and an estimated 11e17% of the spilled volume was deposited in the

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Submerged Oil

TABLE 26.1 Summary of Case Studies of Oil Spills That Did Not Float5

Spill Name and Date

Oil Name/API

Floated, Heavier Then Than Sank after Water/Sank Stranding

Floated, Then Sank Without Stranding

T/V Alvenus, 1984

Merey, Pilon Crude/ 13.8, 17.3

T/B Apex 3512, 1995

Slurry oil/ -0.6

X (fresh)

Apex Towing, June 1995

Slurry oil/ 0.5

X (fresh)

M/T Athos 1,2005

Bachaquero Crude/ 13.6

X

T/B Morris J. Berman, 1994

No. 6 fuel oil/ 9.5

X

X

T/B Bouchard 155, 1993

No. 6 fuel oil/ 10.5

X

X

T/B DBL-152, 2005

Slurry oil/ 4.5

X (salt)

Detroit River, 1996

Coal tar oil/ -12.5

X (fresh)

T/B EMC423, 2005

Clarified slurry oil/ <10

X (fresh)

T/V Eleni V, 1978

Heavy fuel oil/ 14.4-19

ESSO Puerto Rico, 1988

Carbon black feedstock/ 2.0

T/V Katina,1982

Heavy fuel oil/ 10.7

M/V Kuroshima, 1997

Bunker C

Lake Wabamun, 2005

No. 6 fuel oil/ 12

Lake Winona,1979

No. 6 fuel oil/ 12

X (fresh)

T/B MM-53, 2006

64-22 asphalt

X (fresh)

X

X X (fresh) X X X

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Chapter | 26 Submerged Oil

TABLE 26.1 Summary of Case Studies of Oil Spills That Did Not Float5dcont’d

Spill Name and Date

Oil Name/API

Floated, Heavier Then Than Sank after Water/Sank Stranding

T/B MCN-5,1988

Heavy cycle gas X (salt) oil/ -1.2

T/V Mobiloil,1984

Industrial/ residual oil/ 5.5e11.3

Floated, Then Sank Without Stranding

X (fresh)

T/V Nissos Amorgos, 1997 Bachaquero Crude/ 16.8?

X

T/V Presidente Rivera, 1989

No. 6 fuel oil/ 17.4

X

T/V Provence, 1996

No. 6 fuel oil/ 6.2

X (salt)

SS Sansinena, 1976

Bunker C/ 7.9

X (salt)

SE Florida Mystery Spill, 2000

Heavy fuel oil

T/B SFI 33, 1990

No. 6 fuel oil/ 6.5

T/V Thuntank 5,1986

No. 6 fuel oil/ ??

T/B Vesta Bella, 1991

No. 6 fuel oil/ 4.6-10

X X (salt) X X

nearshore troughs as a submerged oil:sand mixture.8 The T/V Nissos Amorgos spill stranded on sandy beaches and flats outside of Lake Maracaibo, Venezuela, some of which was quickly buried by clean sand and some (no more than 5%) of which sunk in the nearshore troughs.9 During the M/T Athos 1 spill, the crude oil stranded on the sandy tidal flats of Tinicum Island in the Delaware River below Philadelphia, picked up sand while being reworked by wave action, and some fraction became submerged. Rough estimates were that up to 5% of the spilled oil volume became submerged. River currents kept the oil suspended above the bottom. It seems that the heavy crude oils that picked up sediment and became submerged are particularly viscous and sticky. They have to be transported in

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Submerged Oil

heated tanks to keep the oil pumpable. They form thick deposits onshore, sand adheres to the thick deposits, and the oil:sand mixtures get eroded from exposed shorelines. All of the 13 spills where the oil submerged initially (without picking up sediment) were heavy, refined oil products or coal tar oil that were denser than the receiving water (API gravity from 7.9 to -12.5). It is important to understand the crude oil refining processes used to produce these refined products. The refining process of crude oil usually involves (1) distillation, or separation of the hydrocarbons that make up crude oil so that the heavier products, such as asphalt, are separated from the lighter products, like kerosene; (2) conversion, or cracking of the molecules to allow the refiner to squeeze a higher percentage of light products, such as gasoline, from each barrel of oil; and (3) treatment, or enhancement of the quality of the product, which could entail removing sulphur from such fuels as kerosene, gasoline, and heating oils. The addition of blending components to gasoline is also part of this process. A barrel of 42-U.S. gallons of crude oil yields slightly more than 44 gallons of petroleum products. This “process gain” of volume is due to a reduction in the density during the refining process. In 2004, one barrel of crude oil, when refined, yielded 19.7 gallons of finished gasoline, as well as smaller quantities of many other petroleum products. The amount of residual fuel oil generated per barrel of crude oil was only 1.72 gallons. Improvements in the refining process to produce more gasoline have led to production of a smaller amount of a very heavy residue. Five of the spills in Table 26.1 involved slurry oil, also called heavy cycle gas oil. These oils are the heaviest bottom fraction of the refining of crude oil produced by a fluid catalytic cracker (FCC), used to get additional gasoline product from heavy hydrocarbon fractions. The residue out of an FCC is heavier than the residue from straight crude distillation, so slurry oils often have an API gravity below 10. Common uses are in blending heavy fuel oils (or used neat), as feed for a coker or hydrocracker that can handle these materials, or as carbon black feedstock. This product is called slurry oil because, in its unclarified state, it contains small amounts (<<1%) of both carbon and FCC catalyst solids (mostly silica/alumina). Slurry oils can be filtered to get most of the solids out; then they are called clarified slurry oil. Slurry oil is most often used within a refinery or sold to other refineries for further processing, however, it can also be sold as a fuel. The slurry oil from the DBL-152 was a blended product that was being shipped to an electric utility company. It is difficult to characterize these slurry oils because there is a wide range of residues and diluents used in their production. Also, the term slurry oil is not well-defined as a fuel oil product. It is more of a term used by refineries to describe the residual fractions after catalytic cracking that contains catalyst and carbon solids. It can be treated to remove the solids or not, then blended with a diluent to produce a heavy fuel oil that may or may not be called a “slurry oil.” Fifteen of the spills listed in Table 26.1 involved heavy refined products referred to as No. 6 fuel oil, heavy fuel oil, or heavy industrial fuel oil. The API

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gravity of these oils varied from 19 to 4.6. It is very difficult to chemically characterize heavy refined products today because of the widely varying methods by which they are produced. Current refining methods include more processes to increase the amount of gasoline produced per barrel of oil. Thus, the residual “bottoms” streams are heavier than in the past and tend to have a high percentage of heavy aromatics. Typically, No. 6 fuel oils are the residues from straight distillation of crude oil. It is interesting to note that none of the spills listed in Table 26.1 involved an intermediate fuel oil (IFO). These fuels are blended products, starting with a heavy oil and blended with a lighter oil to meet commercial specifications. The lighter blending oil is usually a product similar to diesel in terms of the carbon number range. However, the blending product would not include additives and other refinement processes used to make commercial-grade diesel. There have been numerous spills of three other types of oils represented in Table 26.1: asphalt, carbon black feedstock, and coal tar oil. These products exhibit very different behaviors when spilled. Asphalt, shipped hot, usually solidifies quickly into a hard, solid material. Carbon black feedstock is a dark, viscous liquid produced as one of the heaviest residues after petroleum cracking and coking, with an API gravity of about e0.5. Coal tar oil, a byproduct of the distillation of coal during the steel-making process, is a viscous, sticky, dense liquid that is composed mostly of aromatic hydrocarbons. Thus, it poses many health and safety risks, as documented by the response to the 1996 release of 13,300 liters to the Detroit River.10

26.3. REVIEW OF RECENT SUBMERGED OIL SPILLS 26.3.1. M/V Athos I At 9:30 P.M. on November 26, 2004, the M/T Athos 1 struck several submerged objects while preparing to dock at the CITGO refinery in Paulsboro, New Jersey, resulting in the release of 1,007,000 liters of Bachaquero Venezuelan crude oil, a heavy crude oil that is heated during transport. The Bachaquero crude oil had a density of 0.973-0.978 g/mL and thus would float in both fresh and seawater. However, oil was reported on the bottom at the collision site. It was determined that this oil had been “injected” into the sediment under the pressure of the release, creating its own trench 2e2.5 m wide, 0.7 m deep, and 13 m long. The oil was immobile due to highly cohesive forces exerted by the viscous oil. This oil was eventually removed by diver-directed pumping. Oil stranded on the sandy intertidal flat on Tinicum Island did not refloat with the rising tide. Instead, the thick oil patches rolled around on the sand, picked up sediment, and were eroded by waves, producing submerged oil that was negatively buoyant and subject to transport by riverine and tidal currents. Operators at utility and industrial water intakes along the river close to the

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spill site reported oil in their water intakes that were drawing water from below the surface to depths of up to 6 m deep, though none reported shutdowns. Downstream, the Salem Nuclear Power Plant shut down because of the threat of oil contamination of the circulation and service water intake systems. This mobile submerged oil also posed risks to shellfish resources in Delaware Bay. Standard sorbent drops, sediment cores, and side scan sonar all proved to be ineffective in detecting the submerged oil. Two other methods proved to be more effective: snare samplers and Vessel-Submerged Oil Recovery System (V-SORS). Snare samplers, consisting of an anchor, 15 m of snare on a rope,

FIGURE 26.3 The M/V Athos I snare sampler (Photograph credit: Mark Ploen).

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and a float (shown in Figure 26.3), were deployed determine where in the water column the oil occurred. The first results showed that the oil stained the snare mostly on the bottom 1 meter or so, indicating that the oil was suspended just above the bottom, though small amounts of oil were present on the snares suspended in the middle and upper water column. The snare samplers north and south of Tinicum Island had the highest amounts of oiling. Eventually, nearly 100 snare samplers were deployed to track the spread of the mobile submerged oil. The samplers were inspected regularly, and the percent oil coverage at different intervals was recorded. Most of the time, the heaviest oiling was on the bottom 1 m. The V-SORS consisted of a 2.4 m carbon steel pipe, 15e20 cm in diameter, rigged in a bridle fashion, attached with several 1.8 to 2.4 m lengths of 1 cm chain (Figure 26.4). Around the chains, snare was tied. The chains keep the sorbents along the bottom. The oil readily adhered to the snares underwater. The system was then towed behind a vessel and dragged along the bottom and somewhat angled through the water column. It was pulled up regularly and inspected for oil. The oil coverage on the snares was roughly estimated.

26.3.2. T/B DBL-152 Shortly before midnight on November 10, 2005, the Tug Rebel and Integrated Tank Barge DBL-152 struck a submerged oil platform damaged by Hurricane Rita about 55 km offshore Cameron, Louisiana. The tug released the barge

FIGURE 26.4 The vessel-submerged oil recovery system (V-SORS) (Photograph credit: DBL152 Response Team Members).

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about 5 km from the platform, once a list in the barge was noticed. The barge drifted for about 15 km until it grounded; 12 days later, the barge capsized. The DBL-152 was carrying a heavy refined oil, called a slurry oil, with an API gravity of about 4. The methods by which the oil was blended turned out to be very important to understanding the behavior of the spilled oil. The barge was loaded with oils from five shore tanks that were “line blended” and spread evenly into the bottom of the barge tanks. All tanks were started at one time, and the flow and volume from each shore tank were regulated to meet the target specifications of the blended oil. This case is typical of very heavy oils in that each shipment is a unique blend. The API and volume of each oil in the blend are as follows. API

Liters

-2.3 3.8 3.9 9.7 24.6

2,475,000 8,092,000 6,695,000 1,644,000 298,000

Eventually, it was determined that 7.22 million liters of oil were released from the DBL-152. The response to this major spill of nonfloating oil posed many challenges to the response team, including a work area 55 km offshore, limited response and salvage resources because of the recent hurricanes, many down days due to weather, submerged oil on the bottom that was sporadically remobilized by storm events, and pipeline safety issues. Figure 26.5 shows photographs of the different types of sunken oil on the sea bed. Multiple techniques for tracking, containing, and recovering the submerged oil were discussed, and many were used (Table 26.2). The most successful approach was: side scan sonar and remotely operated vehicles (ROVs) to identify targets, underwater videocamera and/or divers to confirm the presence of submerged oil and determine if there were recoverable amounts of oil present, V-SORS to determine the spatial extent, and snare sentinels to monitor for spread of the oil. Overall, divers provided the most detailed observations of the quantity of oil at specific sites. Snare sentinels were used as an early warning system of the spread of the oil beyond a known perimeter and to estimate the transport rates over time.11 Modifications included “snare-baited” crab pots, replacing the snare-strung chain on the bottom to provide a better indicator of subsurface migration of tarballs. These detection systems were called snare sentinels. The V-SORS required a vessel with a crane or A-frame and winch system to deploy and retrieve the heavy unit, and there were few such vessels available. The vessel had to slow or stop for retrieval, and it took time to get back on station for redeployment. To address concerns about V-SORS potential snagging and damaging pipelines, a breakaway design was added (weak link on one side) to

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FIGURE 26.5 Photographs of the sunken oil from the T/B DBL-152 (Photograph credits: DBL152 Response Team Members).

reduce snagging. To increase the speed of the surveys, an alternative V-SORS design was developed, called V-SORS Light consisting of a single bundle of 2e3 chains zip-tied together with white snare attached. They could be manually deployed and retrieved, so a V-SORS Light could be set up on both the port and starboard sides of the vessel. One V-SORS Light could be dragged on the bottom for the specified distance, and the second one deployed as the first one was retrieved, so there were no gaps in the coverage and no time lost getting back to the waypoint. Up to 37 km could be surveyed per day. Figure 26.6 shows examples of the systems used to detect the sunken oil.

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FIGURE 26.5 Photographs of the sunken oil from the T/B DBL-152 (Photograph credits: DBL152 Response Team Members) (continued).

Another improvement was the towing of the V-SORS along predesignated transects that were entered as waypoints into the vessel GPS navigational system. The oiling along these transects were called into the command post in near real time; thus, there was no lag in data processing, and the results were immediately available for planning where to deploy divers and/or an ROV.11 Figure 26.7 shows an example of the survey results using the V-SORS and snare sentinels during the response phase. Side scan sonar was thought to be effective early in the spill, with 8 out of 10 targets confirmed as oil (Ploen, M., 2009. personal communication), but less effective after the oil spread out, estimated at 50% two weeks later.11 Thus, the use of side scan sonar was abandoned due to the high rate of false positives, the long lag time for data processing and interpretation, and the need for validation.

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TABLE 26.2 Advantages and Disadvantages of Technologies Used to Detect and Recover Submerged Oil During the DBL-152 Oil Spill Advantages

Disadvantages

Side-scan sonar e detection of oil on the bottom - Good spatial coverage - Not affected by poor visibility - Good visualization of large oil accumulations and other bottom features (e.g., debris piles, pipelines)

- Once the oil spread out, had reduced success at oil identification - Slow turnaround (days) for useful product - Need validation of targets as oil - Limited by sea conditions

RoxAnnÔ seabed classification system e detection of oil on the bottom - Signal is interpreted rather than having to visually interpret it

- Narrow swath (1-2 meters) - Needs confirmation of interpretations - Less accuracy in muddy substrates

Remotely operated underwater video e detection of oil on the bottom - Provides a record for review by others - Could be directed to fly the edge of large accumulations to estimate area/volume - Can vary the height above the seafloor to improve visibility/coverage - Provides more quantitative estimates of frequency and size of oil accumulations, especially useful to calibrate V-SORS data (never done)

- Small survey swath (1 meter) because of low visibility - Use system with umbilical tether; operator would fly a search pattern around the boat, so no exact position of the video image available - Frequent down days because of poor visibility

Snare sentinels e detection of oil in the water column - Effective at detecting oil at various depths in the water column - Time-series data very useful to track trends

- Time and labor intensive for deployment, inspection, and replacement - High loss rates - No calibration of the efficacy of sampling and it might change over time

V-SORS (Heavy) e detection and recovery of submerged oil - Could be towed at up to 2.5 meters per second (5 knots), though usually 1.5-2 meters per second, thus able to cover a large distance - Area swept is about 2.5 meters - Confident that it maintains bottom contact

- Requires larger vessel with crane or A-frame and pulley to deploy/retrieve - Lots of concern about pipeline snagging - Cannot determine where along the trawl the oil occurred; no calibration with actual amount of oil on bottom

(Continued )

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TABLE 26.2 Advantages and Disadvantages of Technologies Used to Detect and Recover Submerged Oil During the DBL-152 Oil Spilldcont’d Advantages - Can vary the length of the trawl to refine spatial extent, to some degree - Good positioning capability with onboard GPS

Disadvantages - Longer transects because of handling difficulty

V-SORS (Light) e detection and recovery of submerged oil - Manually deployed so can be deployed using smaller boats - Can have very short trawls, if needed - Can conduct continuous surveys without stopping, towed at 1.5-2 meters per second

- Narrow swath so less information on patchy oil - Concerns about it losing contact with the bottom with wave action - Cannot determine where along the trawl the oil occurred; no calibration with actual amount of oil on bottom

Diver-directed pumping e oil recovery from the bottom - Divers could learn to minimize water and sediment recovery - Can target individual oil patches - Minimal risk of resuspension of the oil during recovery

- Creates large volumes of water for handling, treatment, and disposal - For offshore work, complex logistics to support dive team and there are many weather delays - Difficult to reposition work platform over oil - Slow recovery rate; mobile oil kept spreading

Diver-directed pumping was selected as the preferred method of sunken oil recovery; however, operations were severely limited by short weather windows and frequent remobilization of the oil, requiring moving recovery operations. Eventually, only 5% of the oil was recovered.12 Table 26.2 lists the advantages and disadvantages of the submerged oil detection and recovery methods used during the T/B DBL-152 spill.

26.3.3. Lake Wabamun Spill On August 3, 2005, an estimated 712,500 liters of a bunker fuel oil were spilled adjacent to Lake Wabamun, Canada as a result of a train derailment, with an estimated 150,000 liters entering the lake. The warm oil initially floated, but within hours some of the oil was observed to be submerged and/or neutrally buoyant. Between the spill and freeze-up of the lake in November, the oil floated, moved up and down in the water column, sank to the lake bottom (in

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FIGURE 26.6 Top e snare sentinels with traps. Bottom dV-SORS Light. (Photograph credits: DBL-152 Response Team Members).

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FIGURE 26.6 Underwater video camera, showing issues with equipment contamination (Photograph credits: DBL-152 Response Team Members) (continued).

accumulations ranging from small tarballs to large “tar logs” up to 5 m in length), and resurfaced as sheens.13 In studies of samples of oil from the Lake Wabamun spill, Fingas et al. found that the tarballs contained extraneous material including grass, insects, sand, coal, and some fine sediment.13 As little as 1% sand was sufficient to make the oil sink in fresh water, and uptake of material was the dominant mechanism by which the oil sank. The laboratory studies showed that the oil changes density faster than water with temperature, but changes in temperature alone during the spill would not have caused the oil to rise or sink in the lake water. The submerged oil posed significant threats to the water intakes of two large power plants located on the lake. The methods attempted to detect submerged oil on the shallow lake bottom and in the fringing reed beds included fish nets, underwater video, sorbents drops and drags, and visual observations including use of viewing tubes. The most effective method was visual. Methods tried during recovery operations included manual removal using rakes and sieves, vacuum, underwater wet tilling, underwater sorbents, and reed cutting. The submerged oil did not adhere to sorbents under water. The most effective methods were manual removal in the shallow lake bottom and reed beds. Oil removal operations continued in 2006, though at the end of the cleanup in 2006, it was evident that a quantity of oil remained in the lake, particularly in the reed beds.

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FIGURE 26.7 Map of the V-SORS and snare sentinels during the T/B DBL-152 response as of December 20, 2005.

26.4. SUBMERGED OIL SPILL RESPONSE METHODS AND RECOMMENDATIONS FOR FUTURE WORK 26.4.1. Methods for Detection of Oil Suspended in the Water Column Three types of systems have recently been used to detect and monitor for the presence of oil suspended in the water column: (1) stationary sorbent systems, (2) trawled sorbent systems, and (3) field fluorometry. Other promising methods that have not been used or evaluated include airborne remote-sensing technologies such as LIght Detection And Ranging (LIDAR) and laser fluorosensors. Stationary sorbent systemsdThese systems are deployed at a location and inspected at some interval. They can consist of a single length of snare on a rope attached to a float and an anchor, snare on a rope with one or more crab or lobster pots stuffed with snare on the bottom (to increase the sampling area of the snare on the bottom), or just bottom pots with a minnow trap or eel pot stuffed with snare at selected water depths. The configuration depends on water depth and where the oil is in the water column. Use of crab or lobster pots sometimes has a special purposedproviding information on the potential for

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contamination of a fishery in the spill area. These systems have been used at the following spills of nonfloating oil: T/V Provence, New Hampshire, T/B Bouchard-120 in Buzzards Bay, Massachusetts, M/T Athos 1, Delaware River, and DBL-152 off Louisiana. White snare (known as “first-run” snare) is required to improve oil detection (and has to be special ordered). However, they have a high loss rate, from both natural processes and vandalism. Construction and deployment techniques to improve survival and reduce maintenance are needed. Trawled detection systemsdFish nets have been trawled to search for and recover oil in the water column, such as the T/V Presidente Rivera in the Delaware River (though the oil in the net could not be removed once it was filled and the net had to be disposed of oil14), and on the bottom as the Lake Wabamun spill in Canada. Sometimes the trawl is stuffed with snare. There is little information on their sampling efficiency. Delvigne conducted laboratory and flume studies to determine leak rates and oil behavior for different mesh sizes, oil viscosities, and flow rates.15 Trawled systems with appropriate materials and mesh size could be useful to provide a quantitative measure of the amount of oil in the water column or and changes over time. Several vendors sell trawl nets for oil spill response to viscous oils and emulsions (e.g., Scantrawl and Jackson trawl net), but there is no information on whether they have been used during actual spills and their performance. Field fluorometrydThis method was used at the M/T Athos 1 spill to monitor for oil in water intakes at a facility and along transects in the Delaware River. All readings were at background, even when there was visible oil on the water surface. Fluorometry may not be an appropriate method because most heavy oils that become submerged have low dissolved fractions of oil and form larger oil droplets that pose difficult calibrations.

26.4.2. Methods for Detection of Oil on the Bottom The technologies used to detect submerged oil on the bottom are as follows. Visual surveysdIn shallow and clear water, submerged oil can be detected visually unless it becomes covered with sediment. At the Morris J. Berman spill in Puerto Rico, the oil patches were readily visible from the air because of the clear water. At the Lake Wabamun spill in Canada, teams used underwater viewing tubes from small boats and kayaks to search for oil on the bottom near shallow wetlands. Standard terminology, photography, and validation sampling are needed for this method to be of value. Diver observations/videodDivers with helmet-mounted video cameras are used in relatively clear water to document the presence of oil on the bottom. They can make their own observations, interact with the oil to demonstrate its condition and thickness, and collect samplesdall recorded on tape and using GPS to record locations. Diver observations are useful for preliminary surveys at a few sites. Improvements are needed in gear in oil-contaminated waters.

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Remotely operated videocameradAt sites where visibility on the bottom is at least 0.5 m, an underwater videocamera has been shown to be a very useful technology. It provides good visual documentation of the distribution of the submerged oil, but only in the 1 m or so field of view. Visibility is one of the most important limiting factors. Most responders do not have much experience in this technology, and they need more information on the different models, configurations, operating conditions, GPS capabilities, postprocessing tools, and so on, to make the best choice. Research on the availability and use of other wavelengths besides visible would resolve the limitations of poor water visibility. Sorbent dropsdAd-hoc systems consisting of a weight with sorbent materials attached are used to bounce or drag for short distances along the bottom. Teams target areas of potential oil accumulation. This method has been used since the first “diaper drops” during the 1984 T/V Mobiloil spill in the Columbia River. It is low tech but uses materials that are readily available at spill responses. Sediment coresdDifferent types of sediment cores have been used in the past. Most of the time, the results have been of limited value because the oil distribution was very patchy and the sampling area of the core too small to be effective. Also, they have not worked well when the oil was so mobile that the oil was pushed away by the wake caused by the impact of the corer on the bottom. They are most successful when the oil is confined to a specific area and thickly pooled, a rare occurrence. Bottom trawl netsdBottom trawling nets, modified by addition of sorbent materials, have been used to generate semiquantitative data on the amount of subsurface oil (e.g., Lake Wabamun spill). Oil type and particle size, bottom sediment type, potential obstructions for snagging, water depth, and other conditions would determine the type of a bottom trawl system and mesh size appropriate for use. Often, the oil is too liquid to be contained by the net, or too viscous that it quickly clogs the net.14 Trawled systems with appropriate materials and mesh size could be useful in providing a quantitative measure of the amount of oil on the bottom and changes over time. Currently, commercial fishnets are used on an ad-hoc basis. Nets designed for optimal retention and detection of oil and cheap enough for frequent replacement are needed. Chain drags/V-SORSdThese systems can vary from a single chain with a few snares to the large V-SORS with an 8-ft pipe and 28 chains with many snares. They have been used at many submerged oil spills to provide information on the location and amounts of oil on the bottom. An operations manual with specifications for fabrication of the different configurations and protocols for their deployment, based on the many recent experiences, would be of value to future response teams. Also, there is a need for strategies to calibrate the degree of oiling on the snares with the amount of oil on the bottom. Currently, it is not possible to determine the particle size, number of particles, or percent of oil cover on the seafloor based on the visual observations of oil on these

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systems. It is not possible to determine whether the snares encountered one large patch along the distance of the drag or multiple small patches. Also, information is needed on the efficiency of oil pickup by the snares and the rate of oil washoff from the snares. Laboratory tests could be conducted to determine oil pickup and washoff rates on snares under water at different flow rates, oil types, and temperatures. Acoustic systemsdSide scan sonar and multibeam sonar systems are frequently considered to map the distribution of submerged oil on the seafloor. They have many benefits, including: (1) they can operate in low or no visibility settings; (2) they provide good visualization of the seafloor contours, which aids in identifying potential accumulation areas; (3) they provide geo-referenced data that can be used to locate targets and estimate volumes; (4) they have a good range of areal coverage; and (5) systems are generally available on short notice. However, insufficient information is available to responders to guide them when this technology may be appropriate and in selection of the best system. Also, the postprocessing of the raw data can be time-consuming. Side scan sonar has been used at several spills, but in most cases its effectiveness was inconclusive (e.g., Apex barge spill in the Mississippi RiverdM/T Athos 1)16. A systematic assessment of acoustic systems should be performed to identify the conditions under which they are likely to be effective for detection of submerged oil on the bottom, and how the technology might be improved to increase their overall performance. Side scan sonar was used extensively during the DBL-152, yet there are little hard data on the operating conditions of the system, how well it performed initially, and what factors led to the change in performance over time (oil breakup into smaller pieces, sediment cover on the oil surface?). This spill is the one case study where there may be enough data to review and evaluate the performance of side scan sonar, over space and time, if the data are available. Airborne remote-sensing technologies such as LIDAR have not been used at any spill of submerged oil because little is known about their potential effectiveness at detecting oil on the seafloor under different conditions of water depth, turbidity, bottom type, oil thickness, and percent of oil cover. Also, little is known about the turnaround time from data acquisition to useful product for different types of sensors. Research into existing above-water remote-sensing technologies to determine which systems have the best potential for use is recommended.

26.4.3. Containment of Suspended Oil/Protection of Water Intakes Several types of filter fences or curtains have been used at spills either to contain oil suspended during recovery of submerged oil from the bottom or to protect water intakes. One design is to attach snare to a frame that is suspended downcurrent of the recovery site, as was done at the coal tar oil spill in the

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Detroit River where the currents reached 2 m per second.10 During the M/T Athos 1 spill, a “snare monster” was constructed with two frames so that snare could be stuffed in between. It was originally built to protect water intakes but was only used to monitor for oil suspension during recovery of oil from the river bottom. Geotextile fabric was used to divert oil from the water intakes at a utility power plant at the Lake Wabamun spill, though there is no information on how well it performed. All of these systems were constructed ad hoc, without the benefit of engineering guidelines on water flow rates, filtration rates, and the like. Pneumatic barriers (air bubble curtains) have been proposed to protect water intakes, and one was used at the Lake Wabamun spill at one of the power plant water intake canals. There are commercially available net booms, though the depth of the net is only 1e2 m below the surface. They are only effective where currents are less than 0.4 m per second (0.75 knots).1 There is an obvious need for improved technologies and engineering guidelines for deployment of systems that will protect water intakes during spills where oil becomes suspended in the water column. Plant shutdowns are expensive and can cause significant hardship and financial loss. Also, similar principles could be used in the design of filter fences, curtains, or air bubble curtains to prevent the spread of oil suspended during recovery operations. This could be a complex project because of the range of conditions; however, designs and guidelines could be developed for a few typical conditions.

26.4.4. Containment of Submerged Oil on the Bottom The only successful containment of oil on the bottom has occurred naturally, where the oil accumulated in low-flow zones or existing depressions on its own. During the DBL-152, the idea of building a berm/trench or filter fence around the larger patches of oil was not feasible because the oil would become suspended 0.5-1 m in the water column during storms and would likely pass over the structure. There have been some experimental bottom booms built that work just like a regular boom with a heavy ballast to seal on the bottom with the “float chamber” suspended off the bottom. The strategy of containing oil on the bottom, under conditions where it can move or is moving, would be similar to those using booms to divert floating oil to recovery devices. Bottom booming strategies would have deal with a wide range of conditions and oil behavior, which usually are poorly understood during the emergency phases of a spill response.

26.4.5. Recovery of Submerged Oil on the Bottom Recovery of submerged oil on the bottom requires multiple systems for picking up the oil, separating the oil, water, and sediments, and treating the waste streams. Different techniques have been used, with varying success.

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Diver-directed pumpingdThis method has been used most often because divers are most efficient when the oil coverage varies in size and thickness, as it often does. Past problems with pumping of viscous oils, freezing of the pumps with debris, and diver decon have been improved through experience. The biggest need is a solution to reduce the amount of water intake during underwater pumping of viscous oils. Another need is new ideas on how to improve the pumping rate. Divers are able to handle hoses of limited size and length. They weigh themselves down and crawl along the bottom to vacuum up the oil. Systems that would allow a diver to direct larger vacuum systems underwater, such as powered sleds that could handle larger hoses and have a mechanism to concentrate the oil towards the nozzle, would greatly increase recovery rates. Remotely operated vehicle pumping systemsdLong-term diving operations are inherently dangerous, and they become more so at increasing depths. ROV technology has expanded to many applications. ROVs were modified to hot-tap the hull of the wreck of the T/V Prestige and pump the oil off at 3500 meters depth, albeit at great cost. The Remotely Operated Lightering System (ROLS), which operates as a diverless hot-tap and pumping system to remotely recover liquid products from the tanks of sunken vessels is a proven technology that could be built upon. Research into the use of ROVs to pump oil from the seafloor at depths beyond those safely conducted by divers is recommended. Such systems would also need methods to reduce the amount of water intake while increasing the amount of oil picked up. DredgesdDifferent types of dredges have been proposed or used to recover oil from the bottom. Where the oil is solidified, environmental clamshell dredges have been used successfully. Hopper dredges have been proposed in the past, but the massive volumes of water and sediment generated, compared to the amount of oil recovered, is a significant factor in the selection process. In fact, a hopper dredge was seriously considered during the DBL-152 because of the need to quickly recover the submerged oil before it spread (though the oil spread before final plans were developed). Modifications using a large duckbill dredge head have been designed to reduce the amount of water and sediment. During the T/B Morris J. Berman spill, two small dredges using centrifugal vane pumps and rotating dredge cutterheads were used to recover submerged oil in two small embayments with good success.17 Large, onshore pools provided the capacity needed for decanting. There will be spills in the future when dredges will be needed for rapid recovery of submerged oil. Research is needed on how existing dredges might be used and what modifications can be quickly made to improve their performance. As with other pumping systems, a particular need is to develop methods to reduce the amount of water and sediment collected during dredging operations. Decanting systemsdDecanting of water collected during underwater oil recovery can become a limiting factor of the overall operation. The decanting systems are usually configured quickly, under-designed, and often modified by trial and error. Guidelines and calculation tools are needed to improve

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decanting systems that consider oil type, droplet size, flow rates, and the like. Designs should be based on readily available equipment because of their need under emergency conditions.

REFERENCES 1. National Research Council. Spills of Nonfloating Oils: Risk and Response. Washington, D.C.: National Academy Press; 1999. 2. Michel J, Galt JA. Conditions Under Which Floating Slicks Can Sink in Marine Settings. IOSC 1995;573. 3. Lee SC, Mackay D, Bonville F, Joner E, Shiu WY. A Study of the Long Term Weathering and Density Increase of Submerged and Over-Washed oils. AMOP 1998:33e60. 4. Fingas MF, Hollebone B, Wang Z, Smith P. The Properties of Heavy Oils and Orimulsion: Another Look. AMOP 2003;43. 5. Michel J. Assessment and Recovery of Submerged Oil: Current State Analysis, U.S. Coast Guard. Groton, CT: Research & Development Center; 2006. 6. Michel J. Spills of Nonfloating Oils: Evaluation of Response Strategies. IOSC 2008;261. 7. Kaperick JA. Oil Beneath the Water Surface and Review of Current Available Literature on Group V Oils: An Annotated Bibliography, Report HMRAD 95e8. NOAA 1995:34. 8. Alejandro AC, Buri JL. M/V Alvenus: Anatomy of a Major Oil Spill. IOSC 1987:27e32. 9. Moller TH. Summary of the T/V Nissos Amorgos Oil Spill. Unpublished document distributed at the NRC Workshop on Nonfloating Oil Spills, on August 20, 1998. London: International Tanker Owners Pollution Federation Limited; 1998. 10. Helland RC, Smith BL, Hazel III WE, Popa M, McCarthy DJ. Underwater Recovery of Submerged Oil during a Cold Weather Response. IOSC 1997;765. 11. Redman R, Pfeifer C, Brzozowski E, Markarian R. A Comparison of Methods for Locating, Tracking, and Quantifying Submerged Oil Used During the T/B DBL 152 Incident. IOSC 2008;255. 12. Pfeifer C, Brzozowski E, Markarian R, Redman R. Long-Term Monitoring of Submerged Oil in the Gulf of Mexico Following the T/B DBL 152 Incident. IOSC 2008;275. 13. Fingas MF, Hollebone B, Fieldhouse B. The Density Behaviour of Heavy Oils in Water. AMOP 2006;57. 14. Wiltshire GA, Corcoran L. Response to the Presidente Rivera Major Oil Spill, Delaware River. IOSC 1991;253. 15. Delvigne GAL. Netting of Viscous Oils. IOSC 1987;115. 16. Weems LH, Byron I, Oge DW, O’Brien J, Lanier R. Recovery of LAPIO from the Bottom of the Lower Mississippi River. IOSC 1997;773. 17. Burns GH, Kelly S, Benson CA, Eason T, Benggio B, Michel J, et al. Recovery of Submerged Oil at San Juan, Puerto Rico 1994. IOSC 1995;551.

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Part X

Effects of Oil in the Environment

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Chapter 27

Effects of Oil in the Environment Gary Shigenaka

Chapter Outline 27.1. Introduction 27.2. Some Definitions 27.3. Size Matters: Seeps vs. Spills 27.4. An “Equation” to Convey Toxic Impact 27.5. Route of Exposure: The Anthrax Example 27.6. Route of Exposure: Oil 27.7. Oil Chemistry, Physical Behavior, and Oil Effects

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27.8. Freshwater/Saltwater Differences 27.9. Tropical Environments 27.10. Arctic Environments 27.11. Ecological Effects of Oil Spills 27.12. The Future of Oil Effects Science 27.13. Summary and Conclusions

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27.1. INTRODUCTION Doull and Bruce write that “Toxicology.is both a science and an art,” with the science defined as the observational or empirical phase, and the art as the predictive phase, with the linkage between the two represented by the need to apply the former to accomplish the latter.1 In this sense, assessment of oil spill effects provides an excellent, sometimes befuddling, and often frustrating example: we empirically observe the behavior and effects of oil in the laboratory, and we can record impacts from an actual oil spill when it occursdbut linking the pieces, predicting the effects of a given release of a given oil potentially impacting a given set of resources in a given area, may be less of an art than it is magic.or wishful thinking. This is to say: we haven’t quite figured it all out yet. But, we seem to be getting closer. A common perception of the effects of oil in the environment is captured in the evocative photographs and footage of oiled wildlife struggling after Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10027-9 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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exposure to a spill. While the impacts represented by this kind of outcome are only a few of the many possible, they are visually compelling, memorable, and by default assumed by many to be diagnostic for what occurs when oil intersects with the environment. With these kinds of images burned into the collective consciousness and id, nearly any elementary school student or viewer of the evening news can tell us, with some certainty, that oil is indeed harmful. The recent (2010) Deepwater Horizon oil spill in the Gulf of Mexico, and its attendant media coverage, have done little to dispel the notion that these events are ecological and human disasters of the first order. The early images of bright red oil emulsions stretching for miles on the water, thousands of response and recovery vessels near the accident site, massive applications of chemical dispersants, plumes of smoke from burning of oil slicks, the inevitable photographs of oiled pelicans and sea turtles, and stories about impacted fishing communities and local and regional economies only serve to underscore the perception that oil spill IMPACTS are profound and far-reaching. Similarly, the scientific literature contains countless studies that document toxicity of petroleum products and their chemical constituents to virtually the entire spectra of plants and animals. But not every oil spill is an environmental catastrophedand even the same spill incident variably affects different organisms in different ways, at a given moment and over time. The empirical view from 40,000 feet suggests that generalizations about impacts may not be appropriatedand we begin to sense the challenges of understanding the effects of oil. Some of these challenges have been articulated by others undertaking the task of rendering at least a portion of the oil impacts universe into something that we can understand: l

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Determining the effects of oil . is complex, and generalizing about effects is difficult. One must remember that specific impacts are very species and situation dependent.2 Because many physical and biological processes in the marine and coastal environment are poorly understood, it is difficult for scientists to measure the full impacts of an oil spill, and sometimes the results appear contradictory.3 Oil spills will have different environmental effects.the environmental effects will depend on factors such as type of oil, different oceanographic conditions, latitude, season, and type of ecosystem.this complicates extrapolation of data in even the most general terms.4 Many spill impacts have been documented in the scientific and technical literature, and although not all the effects of oil pollution are completely understood, an indication of the likely scale and duration of damage can usually be deduced from the information available. However, it can be difficult to present a balanced view of the realities of spill effects.the simple reality is that sometimes significant damage occurs, sometimes not.5

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Oil can kill marine organisms, reduce their fitness through sublethal effects, and disrupt the structure and function of marine communities and ecosystems. While such effects have been unambiguously established in laboratory studies.and after well-studied spills .determining the subtler .effects on populations, communities, and ecosystems.poses significant scientific challenges.6

Petroleum is, of course, a natural material that is extracted like other minerals and then processed and refined into thousands of products applied to a myriad of general and specialized uses. Oil spills are one of the unfortunate consequences of accidents that occur during the extraction, production, or transportation processes, or during end uses. However, oil is also released naturally into both terrestrial and marine environments through seeps, where oil deposits close to the surface of the soil or sediment are exposed. Rather than reflect severe biological impacts from this chronic localized exposure, these natural oil seep areas can be remarkable in their lack of apparent effects. That is, despite the presence of what amounts to be large, continuous oil spills, oil seep areas do not show impacts commensurate with our perceptions of oil as a poison and the results of research that confirm those perceptions. How do we reconcile these disparate notions and observations in order to understand the effects of oil in the environment? In this chapter, we will discuss the characteristics of the substances we consider to be “oil” and describe how these form the basis for a complex formula to be solved in order to understand how oil affects organisms exposed during oil spills. We will summarize the toxicology and research studies that have helped us to understand if and how oil is harmful. Finally, we will consider the implications for oil spill response.

27.2. SOME DEFINITIONS The derivation of the word, “oil” dates to 13th-century Middle English (oile), and stems from Latin (oleum) and Greek (elaion) terms relating, not surprisingly, to olive oil and olives. The official Merriam-Webster definition for oil is “any of numerous unctuous combustible substances that are liquid or can be liquefied easily on warming, are soluble in ether but not in water, and leave a greasy stain on paper or cloth.” The particular oils with which we are concerned for the purposes of this book are those derived from petroleum. Referring again to Merriam-Webster, this takes us to a more focused definition: “an oily flammable bituminous liquid that may vary from almost colorless to black, occurs in many places in the upper strata of the earth, is a complex mixture of hydrocarbons with small amounts of other substances, and is prepared for use as gasoline, naphtha, or other products by various refining processes.”

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A part of this lengthy definitiond“a complex mixture of hydrocarbons”d reflects one of the key concepts relevant to the environmental impacts of petroleum oil spills: oil, specifically petroleum oil, is not a singular substance that is the same from place-to-place, time-to-time, and, for our purposes, from spill-to-spill. As we shall learn, this fact immensely complicates our task of understanding the behavior and effects of oil. Toxicity is another concept about which all of us have some intuitive understanding. A simple but broadly applicable definition for toxicity is “the degree to which a substance is able to damage an exposed organism.” In the case of oil, however, the simplicity of this definition begins to elude us as we dissect it into its component parts and consider it in the context of petroleum; we can use it to preview the actual difficulty of discussing the toxicity of oil. For example: .the degree to which a substance is able to damage an exposed organism. As we noted in the preceding definition, the oil we are considering is not a single substance, but a complex mixture of many substances, or chemicals. This means that our assessment of oil toxicity begins with as many oil constituents or constituent groups as we care to evaluate. .the degree to which a substance is able to damage an exposed organism. What do we mean by the term, “damage?” Does this means only a lethal endpoint? Or does it include sublethal injury from which an organism might recover? Does cellular injury that we cannot link to some observable impairment constitute damage? What about behavioral shifts resulting from exposure? Or shifts in community structure? Given the rather dynamic and elusive elixir that we suspect petroleum to be, we can begin to anticipate the many permutations of impact that will result if we consider multiple substances and multiple endpoints for damage. .the degree to which a substance is able to damage an exposed organism. The definition infers that exposure is a precondition for damage. If a poisonous material does not come into contact with an organism of concern, is it still toxic? This may sound a little bit like the old philosophical riddle, “If a tree falls in the woods and nobody hears it, does it make a sound?” But this is a highly relevant question from the perspective of spill response, because if we accept that reducing exposure reduces impact, we can attempt to implement measures for reducing or preventing oil from coming into contact with a resource of concern. .the degree to which a substance is able to damage an exposed organism. It is a fact of toxicology that there are differences in the way a given toxin or toxic mixture affects different organisms and even different life stages of the same organism. Therefore, consideration of multiple organisms or life

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stages in an assessment of oil effect complicates our already challenging task by an additional possibly daunting factor. We will use the definitions above as a template for discussing the basics of oil effects in the environment and will expand on the challenges they represent to us when we assess and respond to an oil spill.

27.3. SIZE MATTERS: SEEPS VS. SPILLS In its raw form, oil is a natural material that can readily be found, in many parts of the world, above ground or on the water, and is quite visible. The National Research Council estimated that 45% of the oil entering the world’s oceans derives from natural seepage from geologic formations, and Hoefler counted 200 natural underwater oil seeps that have been identified around the world.5,7 One of the best-known of these areas lies offshore from Santa Barbara, California, near Coal Oil Point. These seeps release 20e25 tons of oil each day, ultimately resulting in a degree of nearshore sediment oiling equivalent to 8e80 Exxon Valdez-size spills, as well as countless tarballs on the beaches of the central California coast.8 By any measure, this is a considerable amount of oil in a relatively small portion of the marine environment. This same area is also known as the site of the first major oil spill disaster in U.S. history, the Santa Barbara spill of 1969. However, the seeps and the iconic historical spill are only marginally related. That is, although the oil spilled in 1969 derived from the same source that feeds the seeps (an oil-rich geologic feature called the Venture Avenue Anticline), the seeps themselves were not responsible for the spill. Rather, it was a blowout at a production platform tapped into the submarine oil reservoir: uncompensated pressure increases in a 3500-foot well drilled under Union Oil Platform Alpha split the well casing and then fractured the seafloor around it, allowing oil to leak uncontrollably into the water column directly from the reservoir. By the time the source of the spill had been contained (11 days later), approximately 3 million gallons of oil had been released.9 News reports showed beaches with oil pooled as deeply as 6 inches, along with oiled, dead seabirds and marine mammals. Photographs, film footage, and written accounts of these and other spill-related impacts not only stoked public resentment against oil companies, they also played an important role in fostering the beginnings of the American environmental movement that culminated in the first Earth Day celebration and the passage of landmark U.S. legislation to strengthen environmental protection. As noted by U.S. President Richard Nixon, “The Santa Barbara incident has frankly touched the conscience of the American people.” The Santa Barbara oil seeps and the 1969 oil spill are extreme examples of the same-source crude oil released into the same marine environment, but resulting in very different perceived and documented impacts. The oil seeps

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have been and continue to be generally considered as an inconvenience or nuisance, requiring tar to be cleaned off the feet of beachgoers and blankets; the Santa Barbara spill, on the other hand, was a seminal event in U.S. environmental history whose impacts were seen as devastating and ultimately farreaching. The continuous inputs from the Coal Oil Point seeps and the lack of adverse environmental impact related to them suggest that the marine environment can tolerate some level of exposure to oil; however, the dramatic impacts from the Santa Barbara spill illustrate that an effects threshold can be and was exceeded. How do we account for the range of impacts (or nonimpacts), and how can we apply this insight to other oil spill situations? What are the lessons for oil spill response? More narrowly focused studies of the biology of oil seeps have revealed relatively moderate effects attributable to oil exposure in this setting. For example, Helix summarized the studies of benthic communities around the seeps and did not find the areas to be substantially affected.10 In fact, proximity to natural oil and gas seeps actually increased overall productivity and enhanced fecundity in species like copepods, which are generally considered to be sensitive to hydrocarbon exposure. Spies et al. studied benthic organisms as well as fish around the California seeps and found few indications of adverse impactdalthough fish sampled near the oil sources showed physiological evidence of aromatic hydrocarbon exposure (i.e., enzyme activation) and had higher incidences of gill and liver lesions.11,12 In this case, documented oil exposure did not translate into documented oil effect. Helix attributed the modest incidence of adverse effects to a number of factors: l l

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Seeps are patchy in distribution, and amounts released are quite variable. The oil to which communities are exposed varies in degree of “freshness,” which substantially influences toxicity. Different biological communities have differing tolerances to the different levels of exposure. Some organisms are capable of adapting to the presence of oil, either by accommodating or simply avoiding accumulations of oil.

We can make the same kinds of analytical observations for human-caused oil spills to suggest why more adverse impacts may occur, even when the same oil source as relatively benign seeps is involved: l

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Oil spills are not uniform in distribution of product released (i.e., patchy), so the amounts to which organisms are exposed can vary widely. Spilled oils vary widely in chemical composition, from highly refined fuels to unrefined crude oils and remnants of the refining process. Adding to this complexity is the fact that spilled oil changes, or weathers, once it is released into the environment, and so the same oil days or weeks after a spill occurs is likely to differ substantially from the fresh oil initially released. It

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is essentially a different kind of oil spill, even with a single original source oil. These differences considerably affect the native toxicity of the product, as well as our assessment of that toxicity. Different biological communities have differing tolerances to the different products and different levels of exposure. In an oil spill situation, the sheer volume of oil released into the environment over a relatively short period of time tends to overwhelm any inherent capability of the affected environment (also referred to as “net assimilative capacity” by Overton et al.13) to tolerate or accommodate exposure to the oil.

In the seep versus Santa Barbara spill example, all of the considerations played a role in very different effects profiles. However, the differences in volumes spilled over time probably were the most significant. Although 20-25 tons of oil per day released from seeps is a considerable amount of oild equivalent to around 7000 gallons per daydthe total for an 11-day period (the length of the uncontrolled Santa Barbara spill) would amount to a maximum of around 85,000 gallons. This is far less oil than the estimated 3 million gallons released by the Platform Alpha blowout. Based on the empirical qualitative and quantitative information we have at our disposal, we can make some crude assignments of impact for the ongoing Santa Barbara seep release and the Platform Alpha release: 85,000 gallons/11 days (seep release) ¼ not so bad; 3,000,000 gallons/11 days (Platform Alpha) ¼ bad. It should be abundantly apparent that at this scale, the impact assessment is not quantum mechanics, nor are the results transferable to stone tablets. It could also be argued that a metric of “bad” overstates the broader population or ecological impact represented by the hundreds to thousands of bird and marine mammal mortalitiesdalthough the social/political/cultural/historical significance of the 1969 spill cannot be denied. Also, less debatable is the dubious wisdom of then-Union Oil President Fred L. Hartley’s stated opinion (Clarke and Hemphill9) concerning the singular lens through which he interpreted the impacts of the Santa Barbara spill: “I don’t like to call it a disaster, because there has been no loss of human life. I am amazed at the publicity for the loss of a few birds.”

27.4. AN “EQUATION” TO CONVEY TOXIC IMPACT Our task here does not include factoring in the cultural or social contexts of oil spills in determining overall effect or impact (though we should note that completely ignoring those other contexts would be very foolish indeeddthey simply are to be contemplated elsewhere). That reprieve, however, does not necessarily simplify the challenge of assessing or predicting our more narrowly construed biological impacts. It remains a daunting task.

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How, then, can we begin to sort through the facts of what is known about oil toxicity and the documented effects of a given spill event to make some sense of it all, to extract some pearls of wisdom to take with us to the next oil spill response? First of all, although we suggested above that size (of a release) matters, it is useful to think beyond only bulk amounts of oil introduced into a habitat of concern when assessing effects of that oil. Yes, the amount of oil inflicted on biological communities is important. But additional considerations enter into the calculus of impact. The amount of oil is equivalent to the dose. But the oil also has a unique toxicity signature that results from the complex chemistry we have discussed. Finally, the extent and the characteristics of exposure to organisms and communities of concern is itself the result of a complex series of physical interactions dependent on the chemistry of the oil, the physics of its interaction with receiving waters, and the dynamics of how it is moved and distributed in the environment. We can reduce this to a deceptively simple “equation”: Oil Impact ¼ Dose Toxicity Exposure...or some function thereof. This can be applied to specific oils and to individual organisms as well as to portray potential overall effect of entire spills. We can work through several permutations of this function, with information from actual incidents to understand how it works. A few examples follow. Case 1: High Dose High Toxicity High Exposure (North Cape, 1996) Dose ¼ 828,000 gallons, high dose Toxicity ¼ Home heating oil, similar to diesel, higher acute toxicity Exposure ¼ Storm conditions in nearshore zone of Rhode Island mixed oil throughout water column Impact ¼ High, widespread highly visible mortalities of benthic organisms, some with high intrinsic and cultural value (lobsters) Case 2: High Dose Medium Toxicity Low Exposure (Odyssey, 1988) Dose ¼ 40 million gallons, very high Toxicity ¼ Crude oil, medium toxicity Exposure ¼ Low, tanker broke apart 900 miles off the coast of Newfoundland Impact ¼ Low, limited landfall for spilled oil Case 3: High Dose Low Toxicity Low Exposure (Barge DM932, 2008) Dose ¼ 420,000 gallons, medium Toxicity ¼ #6 fuel oil (“bunker”), lower acute toxicity but higher density and viscosity, potential for submergence and wildlife fouling impacts Exposure ¼ Low, despite downstream transport and stranding along 200 miles of Mississippi River banks Impact ¼ Extensive shoreline fouling, some recreational use impacts in New Orleans, minimal resource impacts Case 4: Low Dose Medium Toxicity Low Exposure (Cosco Busan, 2007)

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Dose ¼ 53,000 gallons, low Toxicity ¼ Intermediate fuel oil, medium acute toxicity Exposure ¼ Low Impact ¼ High; heavily populated urban area, impacted recreational uses; Congressional hearings The difficulties and variability inherent in interpreting the biological impacts of oil spills are not a recent epiphany for researchers. In 1974, Anderson et al. commented on the tremendous variability of documented damages from larger spills to that time.14 They attributed the range of impacts to differences in environmental and geographic conditions at spill sites, and to differences in the spilled oils themselves. In the preceding examples, we have shown only a few different permutations of the many (3 3 3 ¼ 27, if we accept that there are three qualitative levels of low, medium, and high for each of the three components of the impact equation). If we choose to refine the levels to include more nuance beyond high, medium, and low, then correspondingly more combinations are generated. The point of this is the impact and the factors that enter into generating it. There are many paths to the same destinationdwhich may sound like cheap philosophy, but it simply indicates that very different inputs into the impact equation can generate similar results. Or the flip side of the mixed metaphorical coin is that the presence or absence of one or more factors can amplify or negate another factor. Finally, it is impossible to anticipate and account for everything, as in the Cosco Busan example. The metrics of our simple equation alone would have calculated that this spill would be minor in its impact, but public opinion, media coverage, and political interest elevated perceived impact to a much higher level. The dose/toxicity/exposure equation incorporates the information inputs we consider during spill response, that is, how much spilled, what spilled, what can be done to protect valued resources? Of those three considerations in a response, two are relatively easily addressed: how much spilled (dose), and what can we do to contain/divert/collect the spilled material (exposure)? The most difficult piece for us to determine, all other things being equal, is the “what spilled question,” along with its implications. A narrower focus on impacts leads us to pose more questions about details and brings to the fore the questions of what the composition of the spilled material is and what is its toxicity. In the case of oil products, the questions can be slightly rephrased to ask, how do we expect the oil to harm? For a spill responder, the answer to that question then doubles back to considerations of oil behavior, exposure, and the differences implicit in routes of exposure. The petroleum industry often characterizes crude oils according to their geographic source location, for example, Alaska North Slope crude. However, this designation by itself does not provide any insight into fate and effects if the oil is spilled, and it is not very useful for response personnel. That is, oil toxicity,

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physical state, and the changes that occur with time and weathering are not conveyed or distinguished by geographic source names. The U.S. Environmental Protection Agency (EPA) uses the physical characteristics of petroleum oils as a way to consider the many types of oils from a response-oriented perspective; that is, how will the oil behave in the environment, and how will exposed organisms respond? The four U.S. EPA categories are defined as:15 Light, Volatile Oils. These oils are highly fluid, often clear, spread rapidly on solid or water surfaces, have a strong odor, a high evaporation rate, and are usually flammable. They penetrate porous surfaces, such as dirt and sand, and may be persistent in such a matrix. They do not tend to adhere to surfaces; flushing with water generally removes them. Light, volatile oils may be highly toxic to humans, fish, and other biota. Most refined products and many of the highest quality light crudes can be included in this class. Nonsticky Oils. These oils have a waxy or oily feel. They are less toxic and adhere more firmly to surfaces than light, volatile oils, although they can be removed from surfaces by vigorous flushing. As temperatures rise, their tendency to penetrate porous substrates increases and they can be persistent. Evaporation of volatiles may lead to a heavier and more persistent residue oil. Medium-to-heavy paraffin-based oils fall into this class. Heavy, Sticky Oils. These oils are characteristically viscous, sticky or tarry, and brown or black. Flushing with water will not readily remove this material from surfaces, but the oil does not readily penetrate porous surfaces. The density of heavy, sticky oils may be near that of water, and they often sink. Weathering or evaporation of volatiles may produce solid or tarry nonfluid oil. Toxicity is low, but wildlife can be smothered or drowned when contaminated. This class includes residual fuel oils and medium to heavy crudes. Nonfluid Oils. These oils are relatively nontoxic, do not penetrate porous substrates, and are usually black or dark brown in color. When heated, nonfluid oils may melt and coat surfaces that become very difficult to clean. Residual oils, heavy crude oils, some high-paraffin oils, and some weathered oils fall into this class. During an oil spill, these classifications are dynamic and may change for a given product released into the environment, dependent on the effects of weathering or more transient changes such as ambient temperature. As we have noted, these influence the state and behavior of crude oil and refined petroleum products. For example, as volatiles evaporate from a nonsticky oil, it may become a heavier product with different physical characteristics. If a significant temperature drop occurs (e.g., at night), a heavy, but still fluid, oil may solidify. Upon warming, however, it may revert back to its original state. A general rule of thumb for oil spill responders has long been that the refined fractions of crude oil, like gasoline or jet fuels, were the most toxic of

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the oil products we might encounter in an aquatic or a marine incident. This judgment was based on the assumption that the lighter “ends,” as the fractions are called, are more soluble in water and thus water-borne organisms are more inclined to be exposed. Certainly, a multitude of comparative studies supported the notion that the solubility of different oils and petroleum distillates in water was correlated with toxicity (primarily in the form of acute lethality) to target organisms. Tagatz, for example, was representative of toxicological results that clearly supported this conceptual framework.16 Using acute lethality as an endpoint, he tested the toxicity of gasoline, diesel, and heavy (bunker) fuel oil to American shad (Alosa sapidissima) and found that gasoline was most toxic, diesel less but similarly so, and Bunker C much less toxic. With these kinds of results in hand, spill responders distilled them into general rules of thumb related to oil fate and effects: Light or refined products: short environmental residence time due to volatilization; high acute toxicity due to high-water solubility and ability to penetrate cellular membranes. Heavy or residual products: long environmental residence time and high tendency to physically foul feathers, fur, and orifices due to high viscosity; but low acute toxicity due to low-water solubility. Crude oils: somewhere in between light and heavy products, depending on the chemistry of the specific crudes. We still mostly adhere to these generalizations today, especially with respect to acute (lethal) toxicity: we expect mortalities of water column or benthic organisms if a light product spills and is subjected to mixing energy; while heavy fuel oils are ugly and persistent, we usually don’t worry much about direct toxicity except that resulting from physical fouling of wildlife. This sounds simple enough; but complications begin to arise when the spilled product does not fit neatly into one of our predesigned categories. For example, many of the heavy fuel products that are used as bunker or boilers fuels are “cut” with a lighter distillate to facilitate pumping and transfer. And, today many of the most commonly transported oils are intermediate fuel oils that fall somewhere between light and heavy. Things get even messier as we stray beyond consideration of acute lethality only and also consider chronic and sublethal endpoints. And a sense of confused exasperation or resignation settles in if we look beyond impacts to only organisms, and consider populations and ecosystemsdor focus in the other direction and examine suborganismal effects: physiological, developmental, molecular. Once we commit to moving beyond the unrealistically simplistic, our quest to understand the effects of oil may begin to look hopelessly incomprehensible: it is not. There are, however, many pieces to be sorted through and assembled in order to build a perspective on oil toxicity and effect that takes into account its many complex components.

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Oil effects research has had its shares of peaks and valleys. Like most other science, the research is driven by the availability of funding. In the case of oil, the funding tends to be correlated with leasing activities or the occurrence of major disasters. The leadup to major oil development on the continental shelf of Alaska included a major new multidisciplinary scientific effort and provided support for new research. Oil spills in various parts of the world spiked interest and support for effects and monitoring studies. The idea that oil toxicity is more complicated than its water solubility had its origins, as is the case with many other shifts in beliefs and practices related to oil spills, in the wake of the Exxon Valdez. This 1989 oil spill in Prince William Sound, Alaska (which remains the largest U.S. spill in history) provided the impetus for more oil spill effects studies than for any other spill in history, many of them funded by the Exxon Valdez Oil Spill Trustee Council (the research and restoration oversight body formed with settlement monies paid by Exxon). After the spill occurred but prior to the creation of the Exxon Valdez Oil Spill Trustee Council, federal agencies undertook their own efforts to characterize early damages from the spill. Fisheries biologists and pathologists from the Montlake Laboratory of National Oceanic and Atmospheric Administration’s (NOAA’s) National Marine Fisheries Service in Seattle sampled fish throughout the spill-affected regions and used two different methods (analysis of biliary fluorescent aromatic compounds and measurement of hepatic cytochrome P4501A) to quantify exposures to Exxon Valdez oil.17 High values for both markers were encountered in fish during the first year of the spill (1989), especially in Dolly Varden char which frequent shallow waters close to the shoreline (where large quantities of oil stranded). Values declined substantially in 1990, indicating lower exposure. Results for bottomfish were lower, but still indicated an elevated degree of exposure above background levels. The positive results for these biochemical markers importantly suggested that organisms not in the immediate vicinity of oil can still be exposeddand thus, at risk. While confirming exposure and quantifying what that exposure is, we are still faced with the formidable task of answering the so-called so what? question: what is the significance of a given degree of exposure to oil? For the spill in Prince William Sound, the Auke Bay Laboratory of NOAA Fisheries in Juneau, Alaska, became a focal point for U.S. federally sponsored Exxon Valdez oil spill studies, and one of the areas of interest was the effect of very low levels of weathered crude oil on important fisheries species in Alaska, pink salmon (Onchorhynchus gorbuscha) and Pacific herring (Clupea pallasi). Carls et al. found that exposure of Pacific herring eggs to total PAH (polyaromatic hydrocarbons) levels rarely contemplated in a toxicological settingd <1 part per billion (ppb)dresulted in a profound suite of impacts to larval fish: at 0.7e7.6 ppb, malformations, genetic damage, decreased size, inhibited swimming, and mortality; at 0.4 ppb total PAH, yolk sac edema and immaturity consistent with premature hatching.18 Interestingly, fresher oil was less toxic

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(i.e., higher effects concentrations of 9e34 ppb) than the weathered product. This was attributed to a relatively higher proportion of higher-molecula-weight PAHs in the weathered product. Heintz et al. came to similar conclusions in examining the effects of weathered North Slope crude oil on pink salmon.19 Their toxicity endpoint of embryo mortality was found to be significantly higher at 1.0 ppb total PAH derived from very weathered oil and was similar to that determined by Carls et al.18 Heintz et al. simulated exposures of pink salmon to Exxon Valdez oil by incubating eggs in water that had been percolated through gravel coated with artificially weathered Alaska North Slope crude (i.e., same source oil from the Exxon Valdez spill).20 The “preweathering” skewed the PAH composition toward alkyl-substituted naphthalenes and larger hydrocarbons. The salmon smolts that survived the initial exposure were tagged (coded wire tags) and released, to return two years later. Salmon that had been exposed to total PAH concentrations of 5.4 ppb experienced 15% reduced survival compared to unexposed salmon. This concept of delayed mortality due to early exposure was a new concept; the idea that sublethal exposure resulted in compromise of fitness later had not been previously considered. Heintz et al. concluded that evaluation of oil toxicity by short-term effects alonedfor example, in early exposures in salmon streamsd underestimated long-term effect. The take-home lesson was well-articulated by the authors: “Reliance on toxicity tests that fail to realistically simulate exposure conditions is likely to misguide water-quality managers.” The fact that a number of earlier oil-related toxicity studies took place in the same Auke Bay Lab with very different conclusions (e.g., effects levels at much higher concentrations, in the range of 1000e1400 ppb; relative resistance of salmonid eggs to oil exposure versus juveniles) was recognized by Carls et al.18 They noted that the water-soluble fraction of the test oil for the earlier study, a Cook Inlet crude oil, was comprised of mono- and di-aromatic hydrocarbons; in contrast, the test oil for the more recent study, the North Slope crude that had been carried by the Exxon Valdez, had higher proportions of multi-ring and alkylsubstituted PAHs. The take-home message for us is that composition of the spilled oils, and their weathering state, are key determinants of toxicity. The other take-home messages are that the more recent literature on oil toxicity reflects a much lower threshold for effects than we had previously accepted and that oil exposures to early life stages may have delayed consequences long afterward. The other key fishery in Prince William Sound at the time of the Exxon Valdez oil spill was that for Pacific herring (Clupea pallasi), or more accurately Pacific herring roe. A series of herring-related studies took place after the spill with support from the Exxon Valdez Oil Spill Trustee Council to determine and characterize oil-related injuries; these included McGurk and Brown; Hose et al.; Kocan et al.; and Norcross et al. The coordinated investigations involved both field and laboratory efforts.21-26

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The reader is referred to the source papers for details of each of the studies, but a summary of results from the five investigations includes the following. l

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Mean eggelarval mortality (defined as the ratio of larval density at hatch to mean egg density divided by the number of elapsed days between the two estimates) was twice as great in oiled areas compared to unoiled areas, supporting the hypothesis of oil injury to herring embryos and larvae. Between 1989 and 1991, herring egg masses were collected from oiled and unoiled beaches and incubated to hatch. Larvae were assessed for morphological deformities, cytogenetic abnormalities, and histopathological lesions. In 1989, oiled areas had significantly more morphological deformities and cytogenetic abnormalities than did the unoiled reference. In 1990 and 1991, there were no significant differences between oiled and unoiled. Herring embryos were exposed to oilewater dispersions of Prudhoe Bay crude oil in seawater. Genetic damage was the most sensitive biomarker for exposure, followed by physical deformities, reduced mitotic activity, lower hatch weight, and premature hatching. Embryos placed at oiled sites in Prince William Sound three years after the spill yielded a greater proportion of abnormal and lower weight larvae than did unoiled sites. Herring larvae collected throughout Prince William Sound two to four months after the spill occurred. Many exhibited morphological malformations, genetic damage, and small size consistent with oil exposure damage observed in laboratory experiments. Collections in 1995 showed much different, normal parameters. Adult herring collected three years after the spill at a site oiled by the Exxon Valdez showed lower percent hatch and fewer morphologically normal larvae than fish from an unoiled site.

The sum of these studies indicate that early (i.e., 1989) exposure to Exxon Valdez oil resulted in a number of toxicological endpoints, from genetic damage to abnormal development. The impacts appeared to be transient, with some fading by the following year. However, in-situ deployments of embryos indicated potential lingering effects from oiled beaches up to three years after the spill. Although several different endpoints were used to assess damage to the herring, the mechanisms of toxicity were not investigated. From an operational perspective, research results of this type force us to reconsider cleanup endpoints and the relationships between response options and the amounts of oil left in the environment once endpoints are met. Subparts-per-billion effects levels are orders of magnitude beyond what we have tacitly accepted in the past, and discussion of their implications for the future will likely occur.

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27.5. ROUTE OF EXPOSURE: THE ANTHRAX EXAMPLE Anthrax, of course, has absolutely nothing to do with the effects of oil. It does, however, provide some interesting, and hopefully relevant, insights into routes of exposure and the differences in toxicity effect that can result. We will use these observations to consider the implications for oil. Shortly after the horrific events of September 11, 2001, heightened levels of alert, paranoia, and sophisticated criminal pathology intersected in a series of seemingly random incidents involving anthrax. Anthrax is a serious infectious disease caused by exposure to the bacteria Bacillus anthracis. Anthrax commonly affects hoofed animals such as sheep and goats, but humans who come into contact with infected animals can be infected as well. In the past, the people at greatest risk for anthrax were farm workers, veterinarians, and tannery and wool workers. However, the virulence and lethality of anthrax bacteria inevitably brought it under scrutiny as a potentially effective biological agent of aggressiondthereby introducing us all to the startling adjective “weaponized,” and the bizarre concept of “weapons-grade” anthrax to describe highly refined cultures maximized for human lethality by secret biological warfare labs around the world. In the weeks and months following the 9/11 terrorist attacks in the United States, a series of what appeared to be random incidents occurred around the country, mostly on the East Coast. These involved intentional exposures to anthrax spores, usually packaged in ordinary letters mailed to media outlets and politicians. At least 22 infections and exposures were confirmed, and five people died, including two employees of a U.S. Postal Service processing facility in Washington, D.C. The 2001 anthrax attacks, of course, have nothing to do with oil toxicity. They are, however, instructive and representative for showing how route of exposure to a toxin can make a significant, and sometimes life-or-death, difference in effect of that exposure. In the case of anthrax, we learned that cutaneous (skin) exposure to the bacteria was obviously a concern, but considerably less deadly than inhalation. For example, an infant who was cutaneously infected at ABC News in New York (unknown source) survived; in Washington D.C., several postal workers were exposed to inhalation anthrax, and two died. The Centers for Disease Control (CDC) issued guidance and fact sheets about exposures to anthrax.26 This brings us to the relevant point about route of exposuredthat it makes a difference. (For anthrax, italicized emphasis is added.)26 l

Cutaneous: most (about 95%) anthrax infections occur when the bacterium enters a cut or an abrasion on the skin, such as when handling contaminated wool, hides, leather, or hair products (especially goat hair) of infected animals. Skin infection begins as a raised itchy bump that resembles an

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insect bite but within 1e2 days develops into a vesicle and then a painless ulcer, usually 1e3 cm in diameter, with a characteristic black necrotic (dying) area in the center. Lymph glands in the adjacent area may swell. About 20% of untreated cases of cutaneous anthrax will result in death. Deaths are rare with appropriate antimicrobial therapy. Inhalation: initial symptoms may resemble a common colddsore throat, mild fever, muscle aches, and malaise. After several days, the symptoms may progress to severe breathing problems and shock. Inhalation anthrax is usually fatal. Gastrointestinal: the intestinal disease form of anthrax may follow the consumption of contaminated meat and is characterized by an acute inflammation of the intestinal tract. Initial signs of nausea, loss of appetite, vomiting, and fever are followed by abdominal pain, vomiting of blood, and severe diarrhea. Intestinal anthrax results in death in 25 to 60% of cases.

27.6. ROUTE OF EXPOSURE: OIL As was the case with the preceding anthrax example, route of exposure also makes a difference for oil. However, the results of those different exposures are not nearly as consistent or predictable for oil as for anthrax. We can nonetheless use the same template for exposure to examine the distinct differences in resultant effect. l

Cutaneous, fur, feathers: this is the most familiar route of exposure during an oil spill, almost exclusively because it is the most visible. As a result, it is highly “mediagenic,” and both print and video news coverage rely on images of oil-fouled birds, mammals, and other animals to link a spill to biological impacts. The nature of those impacts can range from cutaneous irritation to serious impairment of fur and feather function. Many, if not most, petroleum oils irritate unprotected skin, human or otherwise. This was confirmed for wildlife by Frost, who examined large numbers of dead, oiled harbor seals after the Exxon Valdez spill.27 She observed that some of these animals had severely irritated skin and inflamed eyes, which would be expected with direct contact of those tissues with fresh oil. In a raredpossibly the onlyddirect study of the effects of oil on sea turtles, Lutcavage et al. investigated the consequences of oil exposure to sea turtles.28 Contact of sea turtle skin with oil, particularly the soft pliable areas of the neck and flippers, caused skin to slough off in layers. However, it is through the fouling of fur and feathers that we see the direct and nearly immediate consequences of oil exposure. For all birds and many mammals, the physical structure of fur and feathers permits avian flight and

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most importantly, thermal insulation: disruption of the physical integrity of feather and fur by oil contamination substantially decreases or eliminates altogether the animal’s ability to retain its warmth. As a result, wildlife exposed to oil in this way can suffer from hypothermia and ultimately may perish. Wildlife rehabilitation efforts in the wake of an oil spill (another favorite media image) focus not only on removal of the oil contamination, but also on restoring the structure and integrity of fouled fur or feathers so that the affected animals can effectively thermoregulate. Inhalation/respiratory: most of the petroleum products spilled in the environment have a volatile component, which is apparent to anyone who has worked in the vicinity of spilled oil, pumped gas, or filled a kerosene lamp: it has a distinct odor. Oil vapors can be harmful both to response personnel and to exposed organisms. The Material Safety Data Sheet (MSDS) for Alaska North Slope crude oil summarizes the occupational inhalation hazard from that particular product: “May cause respiratory tract irritation.29 Initially, high concentrations will cause central nervous system depression and symptom such as headache, drowsiness, dizziness, nausea, lack of coordination. If exposure continues, convulsions, coma, and death may result. Inhalation of high concentrations of a mist may lead to a pneumonia.” It is reasonable to predict that oil vapor concentrations just above a floating oil slick, at the airewater interface, would be high, particularly in conditions of low winds and elevated temperatures. For those organisms frequenting this portion of the open-water habitatdbirds, marine mammals, sea turtlesd inhalation exposure may well represent a significant risk factor. Confirmation of that risk and exposure, however, is difficult to quantify. The linkage between oil vapor exposure and actual damage or impairment has been largely indirect or circumstantial, but some of these links are compelling. Frost observed external signs of irritation and behavioral abnormalities in oiled harbor seals (Phoca vitulina richardsi) following the 1989 Exxon Valdez oil spill.27 She also found mild to severe neurological lesions in oiled seals, consistent with hydrocarbon toxicity, and suggested that these may have played a role in the disoriented and lethargic behavior observed in the animals immediately after the spill. Stronger indirect evidence linking the Exxon Valdez spill to population-level impacts in another marine mammal in Prince William Sound, the killer whale Orcinus orca, was provided by Matkin et al.30 Prior to that incident, many marine mammal experts felt that spill impacts to large cetaceans would likely be minimal. For example, Geraci wrote that, “On the whole, it is quite improbable that a species or population of cetaceans will be disabled by a spill at sea, whatever the likelihood that one or a few animals might be affected or even killed.” However, long-term studies in the aftermath of the Exxon Valdez suggest exactly this.31

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Matkin et al. not only documented nearly immediate and substantial postspill declines in two long-studied orca pods in Prince William Sound (33% and 41%), but also followed population recovery for the next 16 years.30 Their results showed that the resident AB pod had still not attained pre-spill numbers, and the transient AT1 pod continued to decline. The population trajectory and structure (e.g., loss of reproductive age females) for the latter was such that the authors predicted eventual extinction for the transient group. The links to putative Exxon Valdez oil vapor exposure for the orcas are photographic, but undeniable: several photographs show groups of whales adjacent to or cutting through oil slicks, and one by Los Angeles Times photographer Rosemary Kaul shows members of AT1 at the stern of the stricken tanker (this photo is incorporated into Matkin et al.30). Gastrointestinal: observations of surface-oiled birds and mammals show that contaminated animals will preen feathers and fur in an effort to remove the source of fouling, and thus, considerable quantities of oil can potentially be ingested. Hartung and Hunt examined the effects of this kind of gastrointestinal exposure in ducks for a range of different oils and found that all induced gastrointestinal irritation, pneumonia, fatty livers, and adrenal cortical hyperplasia.32 Lutcavage et al. found sea turtles incidentally ingested oil, and as a result, oil was observed clinging to the nares, eyes, and upper esophagus, and was found in the feces.28 Oiled turtles had up to a fourfold increase in white blood cell counts, a 50% reduction in red blood cell counts, and red blood cell polychromasia. Most serum blood chemistries (e.g., BUN, protein) were within normal ranges, although glucose returned more slowly to baseline values than in the controls. Gross and histologic changes were present in the skin and mucosal surfaces of oiled turtles, including acute inflammatory cell infiltrates, dysplasia of epidermal epithelium, and a loss of cellular architectural organization of the skin layers. The cellular changes in the epidermis are of particular concern because they may increase susceptibility to infection. Although many of the observed physiological insults resolved within a 21-day recovery period, the long-term biological effects of oil on sea turtles remain completely unknown.

This discussion of routes of exposure has, for reasons of simplicity, used birds and mammals as illustrative examples. The same concepts are applicable to water column or benthic inhabitants in the marine environment, but are complicated by the aqueous medium and the distinct differences in both oil physical behavior and the resultant exposure scenarios we can anticipate to occur. Most of our remaining discussion about oil toxicity will focus on fish and other aquatic and marine organisms. In order to lay the foundation for our discussion on these points, it is necessary to rewind the tape somewhat to take another look at the physical chemistry of oil in water.

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27.7. OIL CHEMISTRY, PHYSICAL BEHAVIOR, AND OIL EFFECTS Having discussed routes of exposure for oils, and determined that (a) they do make a difference and (b) adverse effects of those exposures are apparent, we can begin to delve more deeply into the subject of oil effects to learn about the components of oil that are harmful and the mechanisms by which they confer that harm. This brings us to oil chemistry, and what it is we focus on in contemplating oil effects. It is not our intent here to repeat the preceding material on basic oil chemistry. However, oil chemistry is unavoidably relevant to understanding exposure in the water and issues of comparative and relative toxicity, and we would be remiss if we failed to discuss it at some rudimentary level in the context of oil effect. As discussed in the chemistry segment of the book (Chapter 5) and as alluded to earlier in this chapter, the chemical composition of different oils varies considerablydwhich by itself translates into a variable range of potential impacts to exposed organisms and communities. The mixtures we generically consider as “oil” are comprised of several classes of compounds, as well as thousands of individual hydrocarbon and nonhydrocarbon chemicals. In this discussion related to toxicity, we will focus on hydrocarbons and one class of hydrocarbons; but we also need to recognize that oils contain many classes of compounds that are not hydrocarbons; we will reserve a discussion of the toxicity of those compounds for some future volume. The most commonly found hydrocarbon molecules in petroleum are alkanes (linear or branched), cycloalkanes, aromatic hydrocarbons, or larger, more complex chemicals such as asphaltenes. As we have emphasized, each oil we will encounter during a spill event has a unique mix of compounds that contributes to or even defines its physical and chemical properties, like color and viscosity, as well as its toxic impact to exposed organisms. The highly variable chemistry of petroleum products means that the range of products in the complex mixture spilled at the outset of an incident can be great. Adding to this chemical complexity is the fact that the composition is not static, that the compositional characteristics of the oil begin changing immediately in response to its surroundings. The sum of the changes brought about by contact with the environment, called weathering, is discussed in detail in Chapter 5. A number of processes are included under the umbrella of weathering: evaporation, emulsification, dissolution, and physical and biological oxidation. All of these processes begin transforming the original source product into a mixture with different physical and chemical characteristics, and, it would follow, different toxicity. Neff et al., for example, found that artificially weathering different oils changed their chemical composition and their relative toxicities.33 The study identified the mononuclear aromatic hydrocarbons as the most acutely toxic fraction of the oils tested, but with weathering, the

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proportion of monoaromatic hydrocarbons decreased and the contribution of PAHs to oil toxicity increased. Oil toxicity is, then, a moving target. The idea that different chemicals have different toxicities or modes of action would seem to be intuitively obvious. Defining how this works, and how we might apply it, is (to substantially understate the magnitude of the challenge) difficult. A well-known, and generally well-accepted, approach to modeling how the structure of a chemical affects its biological activity, including toxicity, is called structure activity relationships (SARs)dalso called quantitative structure activity relationships (QSARs). QSAR is defined as the process by which chemical structure is quantitatively correlated with a biological activity or chemical reactivity. Frequently used surrogates for chemical structure are certain physical behaviors, such as lipophilicity. A standard measure of lipophilicity is the octanolewater partitioning coefficient, or Kow. Octanol (straight-chain fatty alcohol with eight carbon atoms and the molecular formula CH3(CH2)7OH) and water do not mix. The distribution of a compound between water and octanol is used to calculate the equilibrium partition coefficient ‘P’ of that molecule (often expressed as its logarithm to the base 10, log P). Water/octanol partitioning is thought to be a relatively good approximation of the partitioning between the cytosol and lipid membranes of living systems. Di Toro et al. use Kow as the basis for a model to estimate the toxicity of weathered and unweathered crude oils.34,35 They defined toxicity of oil mixtures as the toxicity of each individual component of the oil at the water solubility of that component and termed the approach the target lipid model. Di Toro et al. demonstrated that components with lower log Kow have greater toxic potential than those with higher log Kow. Weathering removes the lower log Kow chemicals with calculated greater toxic potential, leaving the higher log Kow chemicals with lower calculated toxic potential. The replacement of more toxically potent compounds with less toxically potent compounds lowers the toxicity of the aqueous phase in equilibrium with the oil, which is consistent with many studies concluding that weathering lowers the toxicity of oil. The authors asserted that the contrary ideadthat weathering increases toxicityd was based on the erroneous use of the total petroleum hydrocarbons or the total PAHs concentration as if either were a single chemical that could be used to gauge the toxicity of a mixture, regardless of its makeup. This, as we shall see, continues to be debated. The importance of compositional chemistry in determining physical behavior and fate, together with toxic effects, is not a new concept: Anderson et al. published a remarkably complex and robust examination of differential oil behaviors, organism toxic thresholds, and the challenges of appropriately documenting the relationships between the two, and we review the results in the next few paragraphs.14 They chemically characterized four oils (South Louisiana crude, Kuwaiti crude, No. 2 fuel oil, and No. 6 fuel oil) and determined how each oil mixed into water. Differences between calculated and

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measured concentrations of the soluble fractions in water were shown (a key piece of exposure-relevant information that is only infrequently provided in laboratory experiments 35 years later). Finally, the toxicities of the wateraccommodated fractions of each oil were derived for six test species. The test species were grass shrimp (Palaemonetes pugio); sheepshead minnow (Cyprinodon variegatus); mysid (Mysidopsis almyra); brown shrimp (Penaeus aztecus); and silverside (Menidia beryllina). The basic solubility characteristics of the four oils used by Anderson et al. immediately show differences. They measured (by infrared spectrometry) the concentrations of total petroleum hydrocarbons in 10% water-soluble fraction mixtures and found quite a range: from a high of 19.8 parts per million (ppm) for South Louisiana crude to a low of 6.3 ppm for the No. 6 heavy fuel oil. Realizing that relative toxicities also depend not only on total hydrocarbon concentration but also on the composition within that total hydrocarbon mix, Anderson et al. also determined constituent chemical mix by gas chromatography.14 Differences exist among the different oils, but particularly between the crude oils and the refined products. Specifically, the water-soluble fractions of the crudes were enriched in light aliphatic compounds and light aromatic hydrocarbons, while those for the refined oils contained higher concentrations of naphthalenes. The refined products also contained much higher concentrations of the three-ringed aromatics, fluorenes, and phenanthrenes. Solubility and compositional differences likely played roles in the substantial species toxicity differences that the authors observed. Some results are as follows: l l l l

The three crustaceans were more sensitive to No. 2 fuel oil than the fish. No. 6 oil was about equally toxic to fish and crustaceans. Both crude oils were about equally toxic to fish and crustaceans. Ranked species sensitivity, from least to most sensitive, was as follows: C. variegatus M. beryllina F. similus P. aztecus P. pugio M. almyra

Anderson et al. noted that the highest toxicity water-soluble fractions were prepared from the two refined oils, No. 2 and No. 6, despite their lower overall total petroleum hydrocarbon concentrations. The investigators attributed the higher toxicity of the refined oils relative to the crudes to their much higher concentrations of two- and three-ringed aromatic hydrocarbons. The oil constituent category most often associated with toxic effectsdby many, if not most oil effects researchersdis that for the aromatic hydrocarbons, which includes single- and multiple-benzene-ring hydrocarbons. The mononuclear (or monocyclic) aromatic hydrocarbons (MAHs) include the so-called

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BTEX compounds: benzene, toluene, ethyl benzene, and xylenes. The BTEX compounds are highly volatile and are major constituents of light oils and refined fuels. BTEX are relatively water-soluble, providing an enhanced route of exposure to organisms living and respiring in the water. BTEX are considered to be acutely toxic to exposed organisms, acting as neurotoxins.6 Benzene is a known human carcinogen, and ethyl benzene and xylenes are suspected. PAHs consist of multiple benzene rings. Though generally ubiquitous in the environment, PAHs are major constituents of petroleum and are also associated with incomplete combustion of carbon-based materials. The connection of some PAHs to human toxicology is well known, particularly as carcinogens; Sir Ernest Kennaway isolated PAHs from coal tar in the 1920s and demonstrated their carcinogenicity in the 1930s.36 Researchers such as Anderson et al. began to provide the basic information about PAH drivers of oil toxicity, and more recent work has detailed and refined our understanding of the mechanisms of PAH toxicity.14 As a starting point, Barron et al. evaluated four models of chronic PAH toxicity in fish.37 Those four models (and some additional background) were: Narcosis A reversible anesthetic effect caused by hydrophobic chemicals partitioning into cell membranes and nervous tissue, resulting in central nervous system dysfunction. Aryl hydrocarbon receptor (AhR) agonism A cytosolic transcription factor (a protein that binds to specific DNA sequences and thereby controls the transfer of genetic information from DNA to mRNA). AhR is normally inactive, bound to several cochaperones (proteins that assist in protein folding and other functions). High affinity binding of PAHs to fish AhR leads to gene transcription and causes early life-stage toxicity resembling blue sac disease (distinguished by abnormal accumulation of liquid or edema in between the membranes surrounding the yolk sac). Alkyl phenanthrene toxicity Early life-stage toxicity (hemorrhages, yolk sac edema, skeletal deformities, mortality) in fish embryos caused by exposure to alkyl phenanthrenes substituted with two to four carbons. Combined toxicity Inputs contributions from each of the other three toxicity mechanisms/ models and assumes toxicity is additive. Barron et al. compared model results to known lethal and sublethal effects of PAH mixtures to pink salmon and Pacific herring.37 The alkyl phenanthrene model did a very good job (80%) of predicting early life-stage toxicity. The narcosis model was about 50% accurate, while the AhR agonism model underpredicted toxicity. The combined model performed about as well as the alkyl phenanthrene model.

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Incardona et al. reiterated the general notion that for aquatic species, PAHs are generally accepted as exerting their toxic effect through either of two modes of action: first, the “dioxin-like” toxicity mediated by activation of the aryl hydrocarbon receptor (AhR), which controls a battery of genes involved in PAH metabolism, such as cytochrome P4501A; and second, “nonpolar narcosis,” in which tissue uptake is dependent on hydrophobicity and toxicity is mediated through nonspecific partitioning into lipid layers (the latter is consistent with the “classical” observations of oil impact, particularly in fish, in which exposed organisms appear to be stunned, or narcotized).38,39 Incardona et al. studied and determined the effects of PAHs on the development of zebrafish (Danio rerio), a small freshwater tropical fish that provides a good model for vertebrate toxicological impacts.38 They found that three-ring PAHs most abundant in weathered crude oil (e.g., phenanthrene) induced a suite of malformations in zebrafish embryos essentially identical to those described for herring and salmon embryos exposed to weathered crude oil under post-spill conditions (see Carls et al.18 and Heintz et al.19). The primary mechanism underlying the toxicity of three-ring PAHs appeared to be inhibition of cardiac conduction. The subsequent loss of circulation and accumulation of edema produced secondary effects on craniofacial structures and the body axis. Because cardiac morphogenesis is intimately linked to cardiac function, and in fish continues well into the juvenile period, the cardiac arrhythmias produced by three-ring PAHs resulted in altered heart structure. The authors suggested that these irreversible effects on cardiac structure associated with cardiac dysfunction during development could contribute to sublethal effects occurring at later life stages. Incardona and his colleagues focused on the parent phenanthrene compound, not the alkyl-substituted derivatives that formed the basis of the alkyl phenanthrene model of PAH toxicity described by Barron et al. However, the latter group noted that others had determined that alkylated phenanthrenes were more than 100 times more toxic that the parent compound. The recent laboratory research, like that of Incardona et al., indicates that more “classical” models of PAH toxicity based on interference of hydrophobic chemicals like PAHs with nerve transmission, resulting in narcosis (such as that of Di Toro et al.), may not reflect the underlying toxicological mechanism. While many toxicological models are based on physical measurements or estimates of hydrophobicity, the ongoing research into toxicological mechanisms indicates that current models of PAH toxicity in fish may be oversimplified because individual PAHs are pharmacologically active compounds with distinct and specific cellular targets. Ironically, after evaluating the merits of the four mechanistic models of PAH toxicity, Barron et al. noted the relatively good correlation of adverse effects observed in herring and salmon with total PAH concentration. They recommended that in the absence of a fully developed mechanistic model of PAH toxicity, total PAH concentration could be used as a simple metric of

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exposure and predicted effect in fish. This, however, is the approach faulted by Di Toro et al., indicating that there are gaps in the understanding and application of oil toxicology that remain to be addressed.35

27.8. FRESHWATER/SALTWATER DIFFERENCES A survey of the literature on oil toxicity shows, after only a cursory examination of the results, much more information for the saline versus freshwater environments. This apparent disparity becomes even more obvious (and occasionally life-threatening) if one attends freshwater oil spill conferences and attempts to discuss only marine results or case studies. Vandermeulen synthesized the available information on freshwater oil effects and confirmed that “research on effects of petroleum hydrocarbons on freshwater biota is surprisingly limited . restricted generally to only a few animal and plant genera.”40 But he also came to some of the same conclusions for freshwater organisms that we have emphasized to this point: that the toxicity of petroleum varies with the type of product its state of weathering, its chemical composition, and degree of impact vary with the age and life-cycle stage of the organism affected. Hall and Anderson approached the question of the role of salinity in influencing toxicity in a more systematic way, analyzing its influence for a number of classes of compounds and a range of organisms.41 Although they found no consistent trend for aromatic hydrocarbons, they did note the importance of other factors, such as life history stages. Rice et al. synthesized the results of over 10 years of oil-related research at the NOAA Fisheries Auke Bay Laboratory.42 For the question of the role of salinity, they directly compared toxicities for organisms that inhabit both fresh and salt water. They stated that for salmonids (Dolly Varden trout, Salvelinus malma; sockeye salmon, Oncorhynchus nerka; and pink salmon fry, Oncorhynchus gorbuscha), salinity consistently increased the toxicity of hydrocarbons. Juvenile salmonids were about twice as sensitive in seawater as in fresh water. In coho salmon (Oncorhynchus kisutch), toxicity as expressed in LC50 increased linearly with salinity. Moles et al. examined the sensitivity of both freshwater and anadromous Alaskan fishes.43 Among other observations, they found that salmonids in seawater were twice as sensitive to oil exposure as they were in fresh water, and they suggested that the increased sensitivity resulted from additional stress of entering seawater and the physiological changes associated with the transition. However, Stickle et al. examined serum osmolality in coho salmon and concluded that the increase in sensitivity of the salmon smolts in seawater was not a consequence of ion-regulation failure, but rather, the loss of ionregulation capability reflected toxic interactions elsewhere.44 In other words, the exposure did not directly cause the osmotic chaos, but was responsible for other physiological disruptions that did.

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Benville and Korn suggested the role of physical fate considerations in different salinities in driving the toxicity of oil.45 That is, they noted that increasing salinity decreased the amount of an aromatic hydrocarbon (they focused on monoaromatics) that would dissolve into waterdsuggesting that all other things being equal, hydrocarbons are more toxic in fresh water versus salt water. The authors suggested that as aromatic hydrocarbons become more structurally complex, solubility is less influenced by salinity, and the freshwateresaltwater toxicity playing field (to introduce the inevitable sports metaphor) is somewhat leveled. Although we risk insurrection among the inland ranks by making this statement, the available literature on oil effects in fresh water is, for the most part, similar to that for seawater in that a variable range of impact is conveyed, making generalizations difficult. Differences between the two broad habitat types could be distilled to differences in oil behavior attributable to physical processes and to the presence of endemic classes of organisms, such as amphibians. The physical processes affecting spilled oil in a freshwater environment might be expected to be simpler than an equivalent spill in the marine environment, due to the absence of tidal and current influences, and a generally reduced nearshore wave regime. A riverine spill would involve continuous downstream transport and the potential interactions of oil with sediment loading. From a biological effects perspective, these physical influences are most likely to affect considerations of exposure: mixing into the water column, pulsed exposure, potential for sediment-associated water column, or benthic oil exposures. The general considerations of effect, however, are essentially the same as those for the marine environment, and such discussions in freshwater references sound identical to those in the marine equivalents. Despite the somewhat simpler physical processes driving the behavior of oil in freshwater habitats, the assessment of effects may, in fact, be more difficult because less is known about oil fate and effects there. A 1999 American Petroleum Institute review of the subject concluded that greater study is required for several freshwater subject areas, including benthic community structure, nutrient dynamics, and food chain processes.46 Similarly, a lack of information was identified for sensitivity of freshwater plants to both oil and response approaches like vegetation cutting, and the toxicological and physical effects of oil exposure to endemic animals like reptiles, amphibians, and mammals. Another volume focused on the freshwater environment summarized the state of knowledge with respect to oil fate and effects in fresh water. The summary and conclusions by Trett et al. stated an implicit or explicit theme common to nearly all syntheses of oil effects:47 “It would be pleasing to be able to summarize work on oils and their behaviour and effects in freshwater systems with a series of succinct, welldefined conclusions. However, many of these areas of study are still in their formative stages. Consequently, we are not in a position to make broad

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generalisations with any confidence. It is hoped that future work will overcome many of the fundamental flaws and gaps in our understanding.” For biological and ecological effects in fresh water, Trett et al. noted that while numerous studies exist, effort has not been evenly focused across taxonomic groups.47 Further, that while links between number of aromatic rings and degree of alkylation to increasing toxicity were documented, actual results of toxicity tests varied widely even among closely related species. Finally, they commented that in contrast to toxicity studies, relatively little work on mutagenicity and carcinogenicity in freshwater species had taken place. In other words, the interpretive framework for oil effects in the freshwater environment is just as frustrating as it is for the marine environment. Amphibians do present an interesting case, unique to fresh water, in that their life cycles are so intimately associated with and dependent on the aquatic habitat. Widely publicized declines of amphibian populations worldwide have prompted investigations into potential causes. Beyond the obvious potential impacts of environmental degradation and contamination, investigators have also assessed synergistic interactions. Little et al. studied photoenhanced toxicity (more detailed discussion follows below) of water-soluble fractions of weathered petroleum.48 They found that solar radiation substantially increased toxicity of the weathered oil fraction. Beyond the synergistic potential of light and oil to increase toxicity to amphibians, the fundamental reliance of this class of animals on clean water would present a concern during spills in freshwater habitats. It has long been known (Jorgensen49 cites a study by Spallanzani in 1803) that amphibians satisfy a significant portion of their respiratory requirements cutaneously, that is, by breathing through their skin. Any interference with this ability, as could be expected in oil contact by either/both physical fouling and PAH inhibition of proper cell function, would impair the fitness of the exposed animal. As there is little that could be done for extensively oiled animals in a spill situation, minimization of exposure would be a priority for resource protection.

27.9. TROPICAL ENVIRONMENTS For our brief foray into oil toxicity, it is necessary to reduce distinctly complex habitats into simpler distinguishing characteristics and then refer interested readers to the ample literature on environments of concern. It is a necessary concession; otherwise, this single chapter would overwhelm the rest of the book and diminish the lucrative payments that the other authors expect to receive for their contributions (which we believe will be calculated by the editor as a percentage of total book weight basis). Tropical habitats, for example, can be thought of as having distinct features, such as warm temperatures, exceptional water clarity, and potentially highenergy light regimes. In our narrowed focus on the effects of oil in tropical environs, we will incorporate considerations specific to the habitat into what we

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already purport to know about general oil effects. In this way, we not only are efficient; we also distinguish a few of the unique considerations we may face when oil spills in such places. The elevated temperature regime likely to be encountered in tropical spills imposes a number of confounding factors on assessment of real and projected oil effects. Warmer temperatures will accelerate the processes of weathering; thus, responders will need to be mindful of the dynamic setting in which they are examining toxicity. Volatile fractions of the spilled oil will disappear rapidly, leaving behind a potentially very different toxicological mix. Physical characteristics will change considerably from night to day and from shade to direct sun. What is a liquid pool at noon may solidify in place by dusk. Potential for vertical movement down into beaches and sediments may be a factor if the spilled products shift from one state to the other. Under these conditions, all of our basic toxicological and effects rules and guidelines articulated above still apply. Temperature, however, will be a primary determinant of exposure and chemical composition. One physical characteristic of tropical environments that has the potential to substantially alter the spill toxicology of a given incident is the role of light in changing the chemistry and pathology of spilled products. The interplay of ultraviolet (UV) radiation with the toxicity of oil components like PAHs has been known for many years. Mottram, Doniach, and Doniach (in 1938 and 1939) documented light-mediated PAH toxicity with the single-celled organism, Paramecium caudatum.50,51 The clarity of water in many tropical regimes, combined with the intensity of sunlight (especially in summer months and closer to the equator), may result in conditions that can drastically alter the toxicity of oil to exposed organisms. Specifically, intense sunlight may provide high enough energy to alter the chemical structure of compounds in the oil and serve to dramatically increase toxicity. The mechanism for this toxicity has been summarized by Pelletier et al.52 Phototoxicity occurs when UV radiation is absorbed by the conjugated bonds of PAH molecules, exciting them to a higher energy state. The absorbed energy is transferred from the excited PAHs to ground-state dissolved oxygen, forming singlet-oxygen intermediaries. The resulting singlet oxygen and other oxygen free radicals are highly oxidizing and can destroy biomolecules in tissues. The half-life of singlet oxygen is extremely short in seawater (~2 s) but is much greater in lipophilic tissues where hydrophobic PAHs accumulate, resulting in the greater potential for tissue destruction. Ironically, several of the photoxicity studies we reference below involve light conditions not for the intense exposures expected in tropical waters, but in much more moderate conditions: midlatitude freshwater lakes, or subarctic marine waters. For example, Landrum et al. studied the apparent changes in toxicity of anthracene and benzo(a)pyrene in freshwater fish and water fleas.53 These authors determined that the observed increases in toxicity (sometimes hundreds

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of times greater than previously reported concentrations) resulted from photomodification of bioaccumulated PAHs rather than from photodegradation products. Similarly, Barron and Ka’aihue noted that ultraviolet light increased the apparent toxicity of oil products, weathered oil, and PAHs as much as 2e1000 times.54 They also supported the mechanism of phototoxicity described above by Pelletier et al. in which the mechanism of toxicity appeared to occur through a process of photosensitizationdin which the bioaccumulated chemical transfers light energy to other molecules causing toxicity through tissue damagedversus photomodificationdactual chemical transformation of a chemical by light energy. According to Barron and Ka’aihue, the available evidence indicates that the phototoxic components of oil are individual three- to five-5 ring PAHs and heterocycles. Determinants of photoenhanced toxicity include the extent of oil bioaccumulation in aquatic organisms and the spectra and intensity of UV exposure. The potential hazard of photoenhanced toxicity may be greatest for embryo and larval stages of aquatic organisms that are relatively translucent to UV and inhabit the photic zone of the water column and intertidal areas. What does this mean for oil spill response? It suggests that light-induced changes to oil-related compounds bioaccumulated into the transparent and translucent earlier life stages of marine organisms are more apt to be found in the upper photic zones of the water column and could amplify the anticipated effects of a spill. We could conjure a very bad scenario in which a spill of oil occurred coincident with the mass spawning event of, say, corals. Not only would a large toll be inflicted by the oil alone, but potentially significant additional impacts could be expected from photoenergized PAHs incorporated into the lipid-rich tissues of planktonic life stages. One cautionary note about phototoxicity: McDonald and Chapman suggested that while processes and mechanisms of phototoxicity are well demonstrated and well described, their relevance to environmental management is less clear.55 They argue that phototoxic effects are in fact ameliorated by physical, chemical, and biotic factors (such as the presence of dissolved organic carbon, humic materials, or particulate matter; artificiality of laboratory exposure environments; physiological or behavioral adaptations of exposed organisms; and sensitive life-stage habitat preferences). The authors noted that at the time of their article, no studies existed that “clearly and directly implicate PAH phototoxicity with adverse ecological effects in field populations.” They quote Swartz et al.56 who state that the results of PAH phototoxicity studies to date ‘‘may be toxicologically correct, but ecologically irrelevant.’’ They recommended that management decisions not be based solely on a single line of evidence, such as phototoxic potential, until more compelling links to real-world impacts are made.

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27.10. ARCTIC ENVIRONMENTS Arctic or Antarctic habitats are known (or have been known, until recently) for cold temperatures and unique physical features provided by ice and seasonally restricted or unrestricted access to light. As was the case for tropical habitats, when we think about the impacts of oil in these environments, a logical approach is to consider how their unique characteristics might or might not alter the general statements about oil effects we have made to this point. Rice et al. included a discussion of the effect of temperature on apparent toxicity of oil mixtures.42 With their focus on Alaskan conditions, they obviously emphasized lower temperatures. They identified two primary effects of low temperatures on the toxicity of aromatic hydrocarbons that were difficult to separate: increased toxicity due to increased persistence of aromatic hydrocarbons in water; and increased toxicity due to physiological modification of exposed organisms. The flip side of the effects-of-temperature coin we discussed above might be expected for cold water environments: physical characteristics of spilled oil will be driven toward more viscous, perhaps solid states, and slower weathering. The implications for oil effects assessment would include a potentially longer environmental residence in the absence of directed cleanup efforts and a more stable/consistent chemical composition for the spilled product. Rice et al.’s comparison of similar fish and invertebrate species from cold and warmer waters suggested that cold-water organisms were more sensitive, but differences were not great and were attributed to temperature-driven considerations of oil persistence.42 However, a broader examination of the effect of water temperature on oil toxicity revealed an inconsistent and variable relationship between the two, and this finding suggests that temperature alone may not be a significant influence for differences in oil toxicology. It is possible (and, it should be noted, speculative on our part) that unique physiological adaptations to life in cold-water environments (see Portner57and Abele and Puntarulo58) may represent risk factors for inhabitants of polar waters. Some examples include the following: Sidell studied the physiology of high-lipid content in Antarctic fish.59 We might ask, how would the presence of lipophilic petroleum derivatives affect the function of this adaptation? Sidell and O’Brien discussed a unique feature of Antarctic icefishes (Family Channichthyidae): their lack of hemoglobin.60 How might oil interfere with the alternative physiological mechanism for transporting oxygen in these fish? The authors also noted that the constantly cold Antarctic waters are nearly completely oxygen-saturated. Will this affect how oil behaves and the kinds of effects it will have on exposed organisms? We cannot answer these questions now, but perhaps with the renewed interest in oil leasing in arctic waters, opportunities will arise to pursue research questions of this type for indigenous resources.

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A topic that likely has more relevance to spill remediation than assessment of spill effects is oil biodegradation, which is an important mechanism for reducing hydrocarbon levels in the environment. It occurs as a natural process and as the key piece of a directed human cleanup strategy called bioremediation. As the term suggests, biodegradation is driven by organismsdin this case, microorganisms such as bacteria and fungidthat utilize hydrocarbons as a food source and thereby break oil down into less complex and ultimately less toxic compounds. While few biodegradation studies have specifically focused on high-latitude regions, related microbiological investigations have shown that temperature is a critical parameter for rates of degradation. That is, biodegradation has been reported to occur more rapidly in warm temperatures (>10 C), suggesting that biodegradation and bioremediation would not be advisable in arctic or Antarctic spill situations. However, Pelletier et al. evaluated biodegradation in sub-Antarctic intertidal sediments and found that in fact low seawater temperatures (3e4 C) had no effect on oil-degrading communities and rates.61 This suggests that at least in some cases, low temperatures may not out-of-hand preclude the use of some traditional or typical approaches for reducing both exposure and toxicity, such as bioremediation.

27.11. ECOLOGICAL EFFECTS OF OIL SPILLS Having labored through the process of trying to describe the narrowly focused effects of oildon organisms, on their physiology, and on cellular functionsdit should be apparent that the task of describing, in general terms, the broader ecosystem or ecological effects is many times more complex and difficult. This, however, does not mean that summaries and syntheses have not been attempted, as the need has been recognized for decades. Templeton reviewed a number of oil effects and oil spill studies current to that date, but did not synthesize the information into more general observations of effects at higher levels of biological organization, such as habitats.62 A conference held in 1978 (American Institute of Biological Sciences63) attempted to do both, review and synthesize. The proceedings brought together a wealth of information, but while the final day of the workshop was devoted to identifying future directions and research needs, the synthesis of the information was generally left to the reader. Teal and Howarth reviewed seven oil spills that occurred after 1975 (the publication date of the benchmark National Academy of Sciences report on Petroleum in the Environment).64 They noted that: Oil spills have produced measurable effects on ecosystems that have not been readily predictable from laboratory studies on isolated organisms. However, ecosystem-level interactions are poorly understood even without the complications resulting from effects of pollution.

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Teal and Howarth defined eight questions on which to concentrate in their review:64 1. 2. 3. 4. 5. 6. 7. 8.

How long does spilled oil persist in marine systems? Does spilled oil sink, and by what mechanisms? What are the effects of oil on benthic and littoral systems? What are the effects of oil on plankton, and what is their importance? What are the effects on fish and fisheries? What are the effects of crude oil versus refined products? Can experimental studies be used to infer effects from actual spills? Can ecosystem effects be inferred from effects on individual species?

They used the questions as a framework for deriving some general lessons from the seven spills.64 These yielded five empirical generalizations: 1. 2. 3. 4. 5.

Oil regularly reaches sediments after a spill. Oil is persistent in anoxic sediment conditions. Oil contaminates zooplankton and benthic invertebrates. Fish are contaminated to a lesser extent. Oil decreases abundance and diversity of benthic communities.

Clark et al. reported on the effects of a chronic leak of a U.S. Navy special fuel oil from an unmanned troopship that grounded on the rocky intertidal shoreline of northern Washington State.65 They documented continued exposure to the oil over a five-year period. During the first year, dead and abnormal sea urchins and deformed seaweeds were observed near the wreck itself. Despite the short-term shifts in intertidal communities, long-term community balance was not apparently affected. Similarly, Coats et al. monitored long-term impacts to the intertidal communities affected by the Exxon Valdez oil spill in Prince William Sound, AK.66 Although substantial inherent environmental variability presented challenges to the tracking of both effects and recovery, the authors determined that short-term impacts from both oil and cleanup (high-pressure hot water washing) faded after around three to four years. The apparent recovery of intertidal communities was contrasted to longer-term impacts reported in other communities studied after the Exxon Valdez. Harwell and Gentile reviewed over 300 papers related to the Exxon Valdez spill from both government and Exxon Mobil sources.67 They applied a risk assessment paradigm to evaluate a range of organisms from invertebrates to seabirds and marine mammals, and concluded that those resources not in decline at the time of the spill recovered within six years, with others approaching recovery by 15 years post-spill. Notable exceptions were those ecosystem attributes related to orca pods. This was a very different outcome from that found in a similar analysis by Peterson et al., who concluded that persistent low-level exposures to residual oil from the Exxon Valdez oil spill continued to cause impacts to wildlife

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through indirect effects and cascades within the ecosystem.68 It might be worth mentioning that the two sets of authors were funded by opposing interests in the debate over ongoing effects from this spill: Harwell and Gentile by ExxonMobil, and Peterson et al. by the state and federal trustees. Landis analyzed this very situation, asking why such stark differences existed between the results of the authors.69 He concluded that at least part of the difference could be explained by the infusion of different social values or policy goals into the science, what he termed “normative science.” This is beyond the purview of our discussion here, but the reader is referred to the original papers for further insights into this related but sidebar topic. The interpretive difficulties imposed by natural environmental variability was acknowledged by researchers monitoring impact and recovery from other large oil spills. Newey and Seed described rocky intertidal conditions following the Braer spill off the coast of Shetland (Scotland) in 1993 and spoke of the controversies that sometimes arose stemming from the problem of determining when naturally variable systems subject to a variety of stochastic events have returned to pre-spill states.70 Newey and Seed described the rocky intertidal as a mosaic of patches of biological communities in different successional stages depending on the timing of the event responsible for creating the patch. They noted, as had previous spill researchers (e.g., Southward71,72), that oils spills imposed a relatively uniform pattern of development on the shore, with a reduced degree of community diversity. They estimated that recovery on such shorelines could take as long as 10 or more years. Jackson et al. were researchers working at the Smithsonian Tropical Research Institute in Panama, when more than 8 million liters of medium weight crude oil spilled from a storage tank on the Caribbean coast.73 It was the largest spill into sheltered coastal habitat in the tropical Americas. As such, these researchers were uniquely positioned and qualified to document the shortand long-term effects of the release across a range of coastal tropical resources, including mangroves, sea grasses, intertidal reef flats, and subtidal reefs. Importantly, the large group of authors interpreted their observations within areas of specialization, and in a larger context of patterns and significance. They noted where documentation of damage matched that for previous spills assessments, as in a higher degree of disruption and disturbance to sheltered communities vis-a`-vis those along open coasts. However, they also noted areas where their results diverged from those of other oil impact studies, as in the record of extensive mortalities of subtidal corals and sea grass infauna. Jackson et al. also recorded a range of sublethal impacts and inferred longer-term effects to the tropical system communities than was evident from initial mortalities.73 The latter assertionsdthat sublethal effects to key components of a given ecosystemdwould be echoed by researchers of another large spill, the Exxon Valdez spill in Prince William Sound. We have already discussed the actual and projected long-term impacts of that event to orca whales (Matkin et al.30) and to pink salmon (Heintz et al.19). Heintz addressed this question directly, by

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modeling a pink salmon population over a 70-year period and overlaying PAH effects determined from previous studies and randomly varying density dependence on the simulated salmon run.74 Heintz determined that conditions of 100% exposure to a hypothetical spill resulting in an aqueous PAH concentration of 18 nL/L (nanoliters per liter) would cause an 80% decrease in population productivity and 11 percent probability of extinction after 35 generations (i.e., 70 years). The overall population growth rate, however, declined by only 5%. The modeling showed that for low-exposure levels, density dependence compensated for reduced population size and appeared to buffer or mediate against population extinction. However, if the equilibrium size is sufficiently reduced, the buffering capacity is overwhelmed by random environmental variation and the risk of extinction increases. The Exxon Valdez Oil Spill Trustee Council has tracked trends in recovery of many individual impacted resources and has worked to interpret the results in the context of the overall health of Prince William Sound as an integrated whole. The reader is referred to the many publications and references generated from this ambitious and long-term effort.75 In marsh habitatsda critical environment that we have not discussed in any detail to this pointdeffects studies have shown that oil spills can have long-term impacts. Marshes are frequently defined by limited water circulation and exposure conditions, which contribute to persistence of spilled oil. Culbertson et al. reported on continued adverse impacts to Spartina marsh grass 37 years after a barge spill of No. 2 fuel oil in Buzzards Bay (MA), which resulted in sediment instability, topographic changes, and habitat loss.76 The 1974 Metula supertanker spill in the Strait of Magellan, Chile, provided a stark contrast for large oil spills occurring in high latitudes because there was virtually no cleanup of the spilled light Arabian crude oil. Particularly impacted shorelines included sheltered gravel beaches and marshes. Follow-up visits to assess the extent of recovery (e.g., Owens et al.; Shigenaka et al.; Gundlach; Baker et al.77-80) revealed a slow pace of recovery, particularly in the marsh. This spill, in a remote portion of Patagonia, represented one end of the spectrum of oil spill impact and confirmed that, unabated, large quantities of oil released into the environment result in substantial, profound, and long-term consequences. The common conclusions drawn from larger perspective analyses of oil effects in very different spill settings may be that less apparent, sublethal effects have the potential to significantly affect the fundamental structure of regional ecosystems and the long-term viability of key members of those systems; and that overwhelming amounts of oil released into the environment do result in visible, measurable, long-term impacts.

27.12. THE FUTURE OF OIL EFFECTS SCIENCE It should be apparent that we have learned a great deal about oil effects. It should also be apparent that there remains much that we do not know.

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Throughout this chapter, we have identified specific knowledge gaps, which might be used as the basis for ongoing research. Almost from the beginning, we have consistently focused on aromatic hydrocarbons as the petroleum constituents of concern in considering the toxicity of oil. We do not know the significance, if any, of most of the many other chemical constituents of oil. Even for PAHs, we do not understand very much about mechanisms of toxicity. Our abilities to model oil spill impacts are rudimentary, largely because of the lack of information.81 Application of what we know about effectsdthe surprising impact of very low concentrations of weathered oil, for exampledremains unclear. That is, how do we manage environmental exposures at the limits of what we are able to reliably measure and comprehend? New techniques offer some promise in being able to provide a more detailed but holistic picture of oil effects to individual organisms. Examples include molecular diagnostic technologies (e.g., Downs et al.) that can trace back to physiological impairment to specific enzyme functions and cellular processes.82 This technique has been used to evaluate exposure and mechanisms after the Exxon Valdez oil spill, but further refinement and validation would greatly improve its utility as a tool for understanding the past and current effects of oil in an environment of interest. Anderson and Lee reviewed numerous molecular, cellular, and physiological biomarkers and concluded that there were differences in organism responses to two- and three-ring PAHs (associated with petroleum) versus four- and five-ring PAHs (associated with combustion).83 When mixtures of PAHs exist at spill locations, interpretation of biomarker results can be rendered difficult. They concluded that at the present time, the links between biomarkers and higher order biological endpoints (e.g., toxicity, reproductive failure) was not well established. This represents an area of potentially high return for research activities. As we discussed in the preceding section, specific issues related to oil spill effects in high-latitude regions are not well articulated and have not been revisited in North America (it should be noted that Norwegian researchers have focused on at least some of these, for reasons that should be apparent) since the initial push to develop offshore continental shelf regions of Alaska in the 1970s. Warming of arctic waters in particular has spurred much renewed interest in new leases and thus represents both risk (of spills in challenging conditions) and opportunity (to better determine what the risks are). After some promising attempts to institutionalize and fund oil spill research in the United States, it appears that we have reverted to external drivers (e.g., leasing and large spills) as determinants of research support availability. We can be hopeful, but the current global economic climate suggests that there will be significant competition for research dollars (euros, yuan, rupees) well into the foreseeable future.

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27.13. SUMMARY AND CONCLUSIONS We began this conversation by referring to the empirical science and the predictive art involved in toxicology and estimation of oil effects. We have endeavored to guide the reader through a number of different conceptual frameworks for interpreting what we know and how we apply it to the specifics of a given spill incident to define risk. The 2003 update of Oil in the Sea (National Research Council, 2003) noted the progress made toward understanding the toxic effects of petroleum in a variety of organisms and environments. We continue to make progress, particularly with respect to better defining mechanisms of how oil can be harmful at the organism, physiological, and cellular levels. We also have a better idea of how those impacts translate and extrapolate to population and community levels, and we have identified examples in real spills that appear to show this. However, the needs articulated in 2003 (e.g., understanding of natural variability, assessment of higher level effects of spill events, influence of longterm climatic and global-scale shifts on impact and recovery assessments, etc.) remain, and other questions stemming from new scientific insights have arisen. The recent determination of how specific aromatic hydrocarbons exert their toxicity on fish is a promising development toward the goal of forecasting the effects of hydrocarbon mixtures on organisms of concern. The ability to understand the long-term consequences of sublethal exposures is the basis for projecting future effects on populations and ecosystems. Although the known reserves of petroleum are declining and production activities have peaked, oil will continue to be a significant part of the world’s energy portfolio for years to come. As a result, we will continue to move oil; and we will continue to spill oil. The effects of oil on the environment will, therefore, continue to be part of the collective consciousness for the foreseeable future.

ACKNOWLEDGMENTS The author gratefully acknowledges the unselfish support and encouragement of Dr. Alan Mearns, Senior Scientist with the NOAA Emergency Response Division in Seattle. As usual, Dr. Mearns plumbed the depths of his personal library and personal recollection to provide relevant, and occasionally irrelevant, source material to include in this discussion.

Disclaimer The findings and conclusions in this chapter are those of the author and do not necessarily represent the views of the National Oceanic and Atmospheric Administration (NOAA).

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REFERENCES 1. Doull J, Bruce MC. In: Klaassen CD, Amdur MO, Doull J, editors. Origin and Scope of Toxicology, Casarett and Doull’s Toxicology, The Basic Science of Poisons. 3rd ed., vol. 3. New York: Macmillan Publishing Company; 1986. 2. Boyd JN, Scholz D, Hayward Walker A. Effects of Oil and Chemically Dispersed Oil in the Environment. IOSC 2001;1213. 3. Mielke JE. Oil in the Ocean: The Short- and Long-term Impacts of a Spill. Congressional Research Service Report for Congress; 1990. Report 90e356 SPR. 4. Ganning B, Reish DJ, Straughan D. Recovery and Restoration of Rocky Shores, Sandy Beaches, Tidal Flats, and Shallow Subtidal Bottoms Impacted by Oil Spills, Chapter 1. In: Cairns J, Buikema AL, editors. Restoration of Habitats Impacted by Oil Spills. vol. 7. Boston: Butterworth Publishers; 1984. 5. International Tanker Owners Pollution Federation, Effects of Oil Spills, http://www.itopf.com/ marine-spills/effects, accessed July 2010. 6. National Research Council. Oil in the Sea III: Inputs, Fates, and Effects. Washington, DC: National Academies Press; 2003. 7. Hoefler C. Chapter 2: When Oil Spills, http://www.ec.gc.ca/ee-ue/default.asp?lang¼En&n¼ 88F67B04, 2006. 8. Farwell C, Reddy CM, Peacock E, Nelson RK, Washburn L, Valentine DL. Weathering and the Fallout Plume of Heavy Oil from Strong Petroleum Seeps Near Coal Oil Point, CA. Environ Sci Technol 2009;3542. 9. Clarke KC, Hemphill JJ. The Santa Barbara Oil Spill, A Retrospective. In: Danta D, editor. Yearbook of the Association of Pacific Coast Geographers. vol. 64. Honolulu: University of Hawai’i Press; 2002. 10. Helix ME. Biological Communities Near Natural Oil and Gas Seeps, http://www.mms.gov/ omm/Pacific/enviro/seeps2.htm, 1992. 11. Spies RB. The Biological Effects of Petroleum Hydrocarbons in the Sea: Assessments From the Field and Microcosms. In: Boesch DF, Rabalais NN, editors. Long-Term Environmental Effects of Offshore Oil and Gas Development. vol. 411. London: Elsevier Applied Science; 1987. 12. Spies RB, Stegeman JJ, Hinton DE, Woodin B, Smolowitz R, Okihiro M, et al. Biomarkers of Hydrocarbon Exposure and Sublethal Effects in Embiotocid Fishes From a Natural Petroleum Seep in the Santa Barbara Channel. Aquat Toxicol 1996;195. 13. Overton EB, Sharp WD, Roberts PO. Chapter 5: Toxicity of Petroleum. In: Cockerham LG, Shane BS, editors. Basic Environmental Toxicology. vol. 133. New York: John Wiley; 1994. 14. Anderson JW, Neff JM, Cox BA, Tatem HE, Hightower GM. Characteristics of Dispersions and Water-Soluble Extracts of Crude and Refined Oils and Their Toxicity to Estuarine Crustaceans and Fish. Mar Bio 1974;75. 15. USEPA Emergency Response Program, Types of Crude Oil, http://www.rivermedia.com/ consulting/er/oilspill/crude.htm, accessed 2009. 16. Tagatz ME. Reduced Oxygen Tolerance and Toxicity of Petroleum Products to Juvenile American Shad. Chesapeake Science 1961;65. 17. Collier TK, Krahn MM, Krone CA, Johnson LL, Myers MS, Chan S-L, et al. Survey of Oil Exposure and Effects in Subtidal Fish Following the Exxon Valdez Oil Spill: 1989e1991. In: Exxon Valdez Oil Spill Symposium, February 2e5, 1993. Anchorage, AK: Program and Abstracts; 1993.

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18. Carls MG, Rice SD, Hose JE. Sensitivity of Fish Embryos to Weathered Crude Oil: Part I. Low-Level Exposure During Incubation Causes Malformations, Genetic Damage, and Mortality in Larval Pacific herring (Clupea pallasi). Environ Toxicol Chem 1999;481. 19. Heintz RA, Short JW, Rice SD. Sensitivity of Fish Embryos to Weathered Crude Oil: Part II, Increased Mortality of Pink Salmon (Oncorhynchus gorbuscha) Embryos Incubating DownStream from Weathered Exxon Valdez Crude Oil. Environ Toxicol Chem 1999;494. 20. Heintz RA, Rice SD, Wertheimer AC, Bradshaw RF, Thrower FP, Joyce JE, et al. Delayed Effects on Growth and Marine Survival of Pink Salmon Oncorhynchus gorbuscha After Exposure to Crude Oil During Embryonic Development. Marine Ecology Progress Series 2000;205. 21. McGurk MD, Brown ED. Egg-Larval Mortality of Pacific Herring in Prince William Sound, Alaska, After the Exxon Valdez Oil Spill. Can J Aquat Sci 1996;2343. 22. Hose JE, McGurk MD, Marty GD, Hinton DE, Brown ED, Baker TT. Sublethal Effects of the Exxon Valdez Oil Spill on Herring Embryos and Larvae: Morphological, Cytogenetic, and Histopathological Assessments, 1989e1991. Can J Fish, Aquat Sci 1996;53:2355. 23. Kocan RM, Hose JE, Brown ED, Baker TT. Pacific Herring (Clupea pallasi) Embryo Sensitivity to Prudhoe Bay Petroleum Hydrocarbons: Laboratory Evaluation and In-Situ Exposure at Oiled and Unoiled Sites in Prince William Sound. Can J Aquat Sci 1996;2366. 24. Norcross BL, Hose JE, Frandsen M, Brown ED. Distribution, Abundance, Morphological Condition, and Cytogenetic Abnormalities of Larval Herring in Prince William Sound, Alaska, Following the Exxon Valdez Oil Spill. Can J Aquat Sci 1996;2376. 25. Kocan RM, Marty GD, Okihiro MS, Brown ED, Baker TT. Reproductive Success and Histopathology of Individual Prince William Sound Pacific Herring 3 Years After the Exxon Valdez Oil Spill. Can J Aquat Sci 1996;53:2388. 26. CDC, Centers for Disease Control (U.S.), Questions and Answers About Anthrax, http://www. bt.cdc.gov/agent/anthrax/faq, July 2010. 27. Frost KJ. Harbor seal, Phoca vitulina richardsi, Restoration Notebook, Exxon Valdez. Ancorage, Alaska: Oil Spill Trustee Council; 1997. 28. Lutcavage ME, Lutz PL, Bossart GD, Hudson DM. Physiologic and Clinicopathologic Effects of Crude Oil on Loggerhead Sea Turtles. Arch Environ Contam Toxicol 1995;417. 29. Alyeska Pipeline Service Company, Material Safety Data Sheet (MSDS) for Crude Oild Alaska North Slope Crude Oil, Material Safety data Sheet #4686, dated 8-9-93. http://www. valdezlink.com/inipol/msds_crude_oil.htm, accessed 1993. 30. Matkin CO, Saulitis EL, Ellis GM, Olesiuk P, Rice SD. Ongoing Population-Level Impacts on Killer Whales Orcinus orca Following the ‘Exxon Valdez’ Oil Spill in Prince William Sound, Alaska. Marine Ecology Progress Series 2008;269. 31. Geraci JR. Physiologic and Toxic Effects on Cetaceans, Chapter 6 in Sea Mammals and Oil: Confronting the Risks. vol. 167. Cambridge, UK: Academic Press; 1990. 32. Hartung R, Hunt GS. Toxicity of Some Oils to Waterfowl. J Wildlife Manage 1966;564. 33. Neff JM, Ostazeski S, Gardiner W, Stejskal I. Effects of Weathering on the Toxicity of Three Offshore Australian Crude Oils and a Diesel Fuel to Marine Animals. Environ Tox Chem; 2000:1809. 34. Di Toro DM, McGrath JA, Hansen DJ. Technical Basis for Narcotic Chemicals and Polycyclic Aromatic Hydrocarbon criteria, I: Water and Tissue. Environ Toxicol Chem; 2000:1951. 35. Di Toro DM, McGrath JA, Stubblefield WA. Predicting the Toxicity of Neat and Weathered Crude Oil: Toxic Potential and the Toxicity of Saturated Mixtures. Environ Toxicol Chem 2007;24. 36. Waller RE. 60 Years of Chemical Carcinogens: Sir Ernest Kennaway in Retirement. J Roy Soc Med 1994;96.

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37. Barron MG, Carls MG, Heintz R, Rice SD. Evaluation of Fish Early Life-Stage Toxicity Models of Chronic Embryonic Exposures to Complex Polycyclic Aromatic Hydrocarbon Mixtures. Toxicol Sci 2004;60. 38. Incardona JP, Collier TK, Scholz NL. Defects in Cardiac Function Precede Morphological Abnormalities in Fish Embryos Exposed to Polycyclic Aromatic Hydrocarbons. Toxicol Appl Pharmacol 2004;191. 39. Incardona JP, Day HL, Collier TK, Scholz NL. Developmental Toxicity of 4-Ring Polycyclic Aromatic Hydrocarbons in Zebrafish is Differentially Dependent on AH Receptor Isoforms and Hepatic Cytochrome P4501A Metabolism. Toxicol Appl Pharmacol 2006;308. 40. Vandermeulen JH. Toxicity and Sublethal Effects of Petroleum Hydrocarbons in Freshwater Biota. In: Vandermeulen JH, Hrudey SE, editors. Oil in Freshwater: Chemistry, Biology, Countermeasure Technology. vol. 267. Oxford, UK: Pergamon Press; 1987. 41. Hall LW, Anderson RD. The Influence of Salinity on the Toxicity of Various Classes of Chemicals to Aquatic Biota. Crit Rev Tox 1995;281. 42. Rice SD, Adam Moles D, Karinen JF, Korn S, Carls MG, Brodersen CC, et al. Effects of Petroleum Hydrocarbons on Alaskan Aquatic Organisms: A Comprehensive Review of All Oileffects Research on Alaskan Fish and Invertebrates Conducted by the Auke Bay Laboratory, 1970-81. Seattle, WA: NOAA Technical Memorandum NMFS F/NWC-67; 1984. 43. Moles A, Rice SD, Korn S. Sensitivity of Alaskan Freshwater and Anadromous Fishes to Prudhoe Bay Crude Oil and Benzene. Trans Amer Fish Soc 1979;408. 44. Stickle WB, Sabourin TD, Rice SD. Sensitivity and Osmoregulation of Coho Salmon, Oncorhynchus kisutch, Exposed to Toluene and Naphthalene at Different Salinities. In: Vernberg WB, Calabrese A, Thurberg FP, Vernberg JF, editors. Physiological Mechanisms of Marine Pollutant Toxicity. vol. 331. New York, NY: Academic Press; 1982. 45. Benville Jr PE, Korn S. The Acute Toxicity of Six Monocyclic Aromatic Crude Oil Components to Striped Bass (Morone saxatilis) and Bay Shrimp (Crago franciscorum). Calif Fish Game 1977;204. 46. American Petroleum Institute. API Publication Number 4675. In: Stalfort D, editor. Fate and Environmental Effects of Oil Spills in Freshwater Environments. Washington, DC: American Petroleum Institute; 1999. 47. Trett MW, Hutchinson JD, Mason CF, Frankland B, Khan DH, Shales S. Chapter 9: Summary and Conclusions. In: Green J, Trett MW, editors. The Fate and Effects of Oil in Freshwater. vol. 259. Amsterdam, NL: Elsevier Applied Science; 1989. 48. Little EE, Calfee R, Cleveland L, Skinker R, Zaga-Parkhurst A, Barron MG. Photo-Enhanced Toxicity in Amphibians: Synergistic Interactions of Solar Ultraviolet Radiation and Aquatic Contaminants. J Iowa Acad Sci 2000;67. 49. Jorgensen CB. Amphibian Respiration and Olfaction and Their Relationships: From Robert Townson (1794) to the Present. Biol Rev Cambridge Philosophical Society 2000;297. 50. Mottram JC, Doniach I. The Photodynamic Action of Carcinogenic Agents. Lancet 1938;1156. 51. Doniach I. A Comparison of the Photodynamic Activity of Some Carcinogenic with Noncarcinogenic Compounds. J Exp Pathol 1939;227. 52. Pelletier MC, Burgess RM, Ho KT, Kuhn A, McKinney RA, Ryba SA. Phototoxicity of Individual Polycyclic Aromatic Hydrocarbons and Petroleum to Marine Invertebrate Larvae and Juveniles. Environ Tox Chem 1997;2190. 53. Landrum PF, Giesy JP, Oris JT, Allred PM. Photoinduced Toxicity of Polycyclic Aromatic Hydrocarbons to Aquatic Organisms. In: Vandermeulen JH, Hrudy S, editors. Oil in Fresh Water: Chemistry, Biology, Technology. vol. 324. Oxford, UK: Pergamon Press; 1986.

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54. Barron MG, Ka’aihue L. Potential for Photoenhanced Toxicity of Spilled Oil in Prince William Sound and Gulf of Alaska Waters. Mar Pollut Bull 2001;86. 55. McDonald BG, Chapman PM. PAH PhototoxicitydAn Ecologically Irrelevant Phenomenon? Mar Pollut Bull 2002;1321. 56. Swartz RC, Ferraro SP, Lamberson JO, Cole FA, Ozretich RJ, Boese BL, et al. Photoactivation and Toxicity of Mixtures of Polycyclic Aromatic Hydrocarbon Compounds in Marine Sediment. Environ Toxicol Chem 1997;2151. 57. Portner HO. Physiological Basis of Temperature-Dependent Biogeography: Trade-Offs in Muscle Design and Performance in Polar Ectotherms. J Exper Biol 2002;2217. 58. Abele D, Puntarulo S. Formation of Reactive Species and Induction of Antioxidant Defense Systems in Polar and Temperate Marine Invertebrates and Fish. Comp Biochem Phys A 2004;405. 59. Sidell BD. Physiological Roles of High Lipid Content in Tissues of Antarctic Fish Species. In: DiPrisco G, Maresca B, Tota B, editors. Biology of Antarctic Fish. Berlin: Springer-Verlag; 1991. 60. Sidell BD, O’Brien KM. When Bad Things Happen to Good Fish: The Loss of Hemoglobin and Myoglobin Expression in Antarctic Icefishes. J Exper Biol 2006;1791. 61. Pelletier E, Delille D, Delille B. Crude Oil Biodegradation in Sub-Antarctic Intertidal Sediments: Chemistry and Toxicity of Oiled Residues. Mar Environ Res 2004;311. 62. Templeton WL. Ecological Effects of Oil Pollution. J Water Pollut Con Fed 1972;1128. 63. American Institute of Biological Sciences. The Proceedings of the Conference on Assessment of Ecological Impacts of Oil Spills. American Institute of Biological Sciences; 1978. 64. Teal JM, Howarth RW. Oil Spill Studies: A Review of Ecological Effects. Environ Manag 1984;27. 65. Clark RC, Patten BG, DeNike EE. Observations of a Cold-Water Intertidal Community After 5 Years of a Low-Level, Persistent Oil Spill from the General M.C. Meigs. J Fish Res Board Can 1978;754. 66. Coats DA, Fukuyama AK, Skalski JR, Kimura S, Shigenaka G, Hoff RZ. Monitoring of Biological Recovery of Prince William Sound Intertidal Sites Impacted by the Exxon Valdez Oil Spilld1997 Biological Monitoring Survey. Seattle, WA: NOAA Technical Memorandum NOS OR&R1. NOAA; 1999. 67. Harwell MA, Gentile JH. Ecological Significance of Residual Exposures and Effects from Exxon Valdez Oil Spill. Integr Environ Assess Manag 2006;204. 68. Peterson CH, Rice SD, Short JW, Esler D, Bodkin JL, Ballachey BE, et al. Long-Term Ecosystem Response to the Exxon Valdez Oil Spill. Science 2003;2082. 69. Landis WG. The Exxon Valdez Oil Spill Revisited and the Dangers of Normative Science. Integ Environ Assess Manag 2007;439. 70. Newey S, Seed R. The Effects of the Braer Oil Spill on Rocky Intertidal Communities in South Shetland, Scotland. Mar Pollut Bull 1995;274. 71. Southward AJ. Cyclic Fluctuations in Population Density During 11 Years Recolonisation of Rocky Shores in West Cornwall Following the Torrey Canyon Oil Spill in 1967. In: Naylor E, Hartnoll RG, editors. Cyclic Phenomena in Marine Plants and Animals. New York, NY: Pergamon Press; 1979. 72. Southward AJ. An Ecologist’s View of the Implications of the Observed Physiological and Biochemical Effects of Petroleum Compounds on Marine Organisms and Ecosystems. Phil Trans R Soc Lond B 1982;241. 73. Jackson JBC, Cubit JD, Keller BD, Batista V, Burns K, Caffey HM, et al. Ecological Effects of a Major Oil Spill on Panamanian Coastal Marine Communities. Science 1989;37.

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74. Heintz RA. Chronic Exposure to Polynuclear Aromatic Hydrocarbons in Natural Habitats Leads to Decreased Equilibrium Size, Growth, and Stability of Pink Salmon Populations. Integr Environ Assess Manag 2007;351. 75. Exxon Valdez Oil Spill Trustee Council. Legacy of an Oil Spill, 20 Years after Exxon Valdez: Exxon Valdez Oil Spill Trustee Council, 2009 status report. Anchorage, AK: Exxon Valdez Oil Spill Trustee Council; 2009. 76. Culbertson JB, Valiela I, Pickart M, Peacock EE, Reddy CM. Long-Term Consequences of Residual Petroleum on Salt Marsh Grass. J Appl Ecol 2008;1284. 77. Owens EH, Sienkiewicz AM, Sergy GA. Evaluation of Shoreline Cleaning versus Natural Recovery: The Metula Spill and the Komi Operations. IOSC 1999;503. 78. Shigenaka G, Henry Jr CB, Roberts PO. Pavement in Patagonia, Asphalt in Alaska: Case Studies in Oil Spill Pavement Formation, Fate, and Effects. vol. 135. Seattle, Washington: NOAA Technical Memorandum NOS ORCA. NOAA; 1998. 79. Gundlach ER. Comparative Photographs of the Metula Spill Site, 21 Years Later. IOSC 1997;1042. 80. Baker JM, Guzman LM, Bartlett PD, Little DI, Wilson CM. Long-Term Fate and Effects of Untreated Thick Oil Deposits on Salt Marshes. IOSC 1993;395. 81. Barron MG, Podrabskya T, Ogleb S, Ricker RW. Are Aromatic Hydrocarbons the Primary Determinant of Petroleum Toxicity to Aquatic Organisms? Aquat Tox 1999;253. 82. Downs CA, Shigenaka G, Fauth JE, Robinson CE, Huang A. Cellular Physiological Assessment of Bivalves After Chronic Exposure to Spilled Exxon Valdez Crude Oil Using a Novel Molecular Diagnostic Biotechnology. Environ Sci Techn 2002;2987. 83. Anderson JW, Lee RF. Use of Biomarkers in Oil Spill Risk Assessment in the Marine Environment. Hum Ecol Risk Assess 2006;1192.

Part XI

Contingency Planning and Command

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Chapter 28

Introduction to Oil Spill Contingency Planning and Response Initiation Merv Fingas

Chapter Outline 28.1. An Overview of 1027 Response to Oil Spills 28.2. Activation of 1028 Contingency Plans 28.3. Training 1029

28.4. Structure of Response 1030 Organizations 28.5. Oil Spill Cooperatives 1030 28.6. Private and Government 1031 Response Organizations

28.1. AN OVERVIEW OF RESPONSE TO OIL SPILLS Oil spills will continue to occur as long as society depends on petroleum and its products. This is due to the inherent potential for human error and equipment failure in producing, transporting, and storing petroleum. Although it is important to focus on ways to prevent oil spills, methods for controlling them and cleaning them up must also be developed. An integrated system of contingency plans and response options can speed up and improve the response to an oil spill and significantly reduce the environmental impact and severity of the spill. The purpose of contingency plans is to coordinate all aspects of the response to an oil spill, including stopping the flow of oil, containing the oil, and cleaning it up. The scope covered by contingency plans could range from a single bulk oil terminal to an entire section of coastline. Oil spills, like forest fires and other environmental emergencies, are not predictable and can occur anytime and during any weather. Therefore, the key to effective response to an oil spill is to be prepared for the unexpected and to plan spill countermeasures that can be applied under even the worst possible conditions. Oil spills vary in size and impact and require different levels of response. Contingency plans can be developed for a particular facility, such as a bulk Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10028-0 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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storage terminal, which would include organizations and resources from the immediate area, with escalating plans for spills of greater impact. Contingency plans for provinces, states, or even an entire country usually focus more on roles and responsibilities and provide the basis for cooperation between the appropriate response organizations rather than on specific response actions. Most contingency plans usually include the following: l l

l l

l l l

l l

l

A list of persons and agencies to be notified immediately after a spill occurs An organization chart of response personnel and a list of their responsibilities, as well as a list of actions to be taken by them in the first few hours after the incident Area-specific action plans A communications network to ensure response efforts are coordinated among the response team Protection priorities for the affected areas Operational procedures for controlling and cleaning up the spill Reference material such as databases, GIS systems, sensitivity maps, and other technical data about the area Procedures for informing the public and keeping records An inventory or database of the type and location of available equipment, supplies, and other resources Scenarios for typical spills and decision trees for certain types of response actions such as using chemical treating agents or in-situ burning

To remain effective, response options detailed in contingency plans must be tested frequently. This testing is conducted by responding to a practice spill as though it were real. This varies from tabletop exercises to large-scale field exercises in which equipment is deployed and oil is theoretically “spilled” and recovered. Such exercises not only maintain and increase the skills of the response personnel, but also lead to improvements and fine tuning of the plan as weaknesses and gaps are identified.

28.2. ACTIVATION OF CONTINGENCY PLANS The response actions defined in contingency plans, whether for spills at a single industrial facility or in an entire region, are separated into the following phases: alerting and reporting, evaluation and mobilization, containment and recovery, disposal, and remediation or restoration. In practice, these phases often overlap, rather than follow each other consecutively. Most contingency plans also allow for a ‘tiered response’, which means that response steps and plans escalate as the incident becomes more serious. As the seriousness of an incident is often not known in the initial phases, one of the first priorities is to determine the magnitude of the spill and its potential impact. Alerting the first response personnel and the responsible government agency is the first step in activating an oil spill contingency plan. Reporting a spill to the

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designated agency, regardless of the size or seriousness of the spill, is a legal requirement in most jurisdictions. The first response personnel assess the situation and initiate actions to control, contain, or minimize the environmental damage as soon as possible. Until the full command structure is in place and operating, employees carry out their responsibilities according to the contingency plan and their training. This emphasizes the need for a detailed contingency plan for this phase of the operation and the importance of a high level of training in first response. Stopping the flow of oil is a priority in the first phase of the operation, although response may need to be immediate and be undertaken in parallel with stopping the flow. In the case of a marine accident such as a ship grounding, stopping the flow of oil may not be possible. However, the spillage may be minimized by pumping oil in the ruptured tanks into other tanks or by pumping oil from leaking tankers into other tankers or barges. These operations may take up to a week to complete and are often delayed by bad weather. During this time, emphasis has still been on containing the oil or diverting it from sensitive areas. As oil spills pose many dangers, safety is a major concern during the early phases of the response action. First, the physical conditions at the site may not be well known. Second, some petroleum products are flammable or contain volatile and flammable compounds, creating a serious explosion and fire hazard in the early phases of the spill. Third, spills may occur during bad weather or darkness, which increases the danger to personnel. As more of the individuals called appear on the scene and begin to take up their duties, the response plan falls into place. Response strategies vary from incident to incident and in different circumstances and take varying amounts of time to carry out. Response to a small spill may be fully operational within hours, whereas for a larger spill, response elements such as shoreline assessment after cleanup may not take place until weeks after the incident.

28.3. TRAINING A high-caliber training program is vital for a good oil spill response program. Response personnel at all levels require training in specific operations and on using equipment for containing and cleaning up spills. To minimize injury during response, general safety training is also crucial. In some countries, response personnel are required to have 40 hours of safety training before they can perform fieldwork. Ongoing training and refresher courses are also essential in order to maintain and upgrade skills. Training techniques for spill response include tools such as audiovisuals and computer simulation programs that make the training more realistic and effective.

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28.4. STRUCTURE OF RESPONSE ORGANIZATIONS Most contingency plans define the structure of the response organization so that roles and command sequences are fully understood before any incident occurs. The On-Scene Commander (OSC) is the head of the response effort and should be experienced in oil spill response operations. The OSC is responsible for coordinating all major decisions on actions taken. This person ensures that the various aspects of the operation are coordinated and sequenced and that a good communications system is in place. The OSC is supported by a fully trained staff or response team whose duties are clearly defined in the contingency plans. One or more individuals are often designated as Deputy OSCs to ensure that there is backup for the OSC and that multiple shifts can be run. A popular command structure today is a system called the Incident Command System, or ICS. This involves common elements to ensure uniformity across organizations and to make it easier for federal responders to deal with contingency plans in areas other than their own familiar territories. The Unified Command System, or UCS, is similar to ICS, but involves the joining of the company, state or province, and federal response structures. The idea is to join forces to maximize the resources available to deal with the spill and to avoid duplication. The care and effort taken in developing the plan are also important to its success. In addition, the response team and the plan itself must be flexible enough to accommodate different sizes of spills and different circumstances. And finally, sufficient resources must be available to prepare and implement the plan, and to carry out frequent testing of the plan.

28.5. OIL SPILL COOPERATIVES As most oil companies or firms that handle oil do not have staff dedicated to cleaning up oil spills, several companies in the same area often join forces to form cooperatives. By pooling resources and expertise, these oil spill cooperatives can then develop effective and financially viable response programs. The cooperative purchases and maintains containment, cleanup, and disposal equipment and provides the training for its use. A core of trained people is available for spill response, and other response personnel can quickly be hired on a casual basis for a large spill. Neighboring cooperatives also join forces to share equipment, personnel, and expertise. Oil spill cooperatives vary in size, but are usually made up of about 10 full-time employees and several million dollars worth of equipment and cover an area of several thousand square kilometers. In recent years, very large cooperative response organizations have been formed that cover entire countries. In Canada, the Eastern Canada Response Corporation (ECRC) has developed response depots across marine waters and

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through the St. Lawrence Seaway. Burrard Clean has similarly set up cleanup depots in British Columbia, and another cooperative has been organized for the Prairie Provinces. In the United States, the Marine Spill Response Corporation (MSRC) and the National Response Corporation (NRC) have similar capabilities spanning the entire country. These organizations involve as many as 300 full-time employees and over 100 million dollars worth of equipment. Such large response organizations have also been formed in Southampton, England and in Singapore.

28.6. PRIVATE AND GOVERNMENT RESPONSE ORGANIZATIONS In many countries, private firms also provide oil spill containment and cleanup services. These firms are often also engaged in activities such as towing, marine salvage, or waste oil disposal and sometimes operate remote cleanup operations or maintain equipment depots. Many of these firms have contracts with the cooperatives to provide services. Private firms can often recruit large numbers of cleanup personnel on short notice and are valuable allies to industry and government organizations dealing with spills. Their resources are often included in local and regional contingency plans. Government response organizations, such as the Coast Guard or Navy, often have large stockpiles of equipment and trained personnel. They often respond to a spill when there are no responsible parties or before full response capabilities have been organized. The Coast Guard often provides rapid response for lightering (unloading) stricken tankers and dealing with sunken vessels, which the private sector sometimes cannot do. Government organizations are often responsible for monitoring cleanup operations to ensure that measures taken are adequate and that environmental damage is minimal. For example, Environment Canada has set up Regional Environmental Emergencies Teams (REETs), and the U.S. Environmental Protection Agency (U.S. EPA) has established Regional Response Teams (RRTs) to coordinate the environmental aspects of spill response. These teams are made up of members from various federal and provincial/state organizations. Government agencies have significant resources that can be incorporated into response efforts. These include scientific expertise, on-site and laboratory services, as well as monitoring instruments to measure parameters related to health and safety issues. In some spill situations, especially large spills, volunteers are an important part of the response effort. Volunteers are usually trained and given accommodation, and their efforts are coordinated with the main spill cleanup.

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Chapter 29

The Role of the International Tanker Owners Pollution Federation Limited Karen Purnell

Established in 1968, the International Tanker Owners Pollution Federation Limited’s (ITOPF’s) technical team of marine biologists, chemists, engineers, and economists have responded to over 650 ship-source spills in 99 countriesdincluding such landmark cases as Amoco Cadiz, Exxon Valdez, Braer, Erika, and Prestigedgiving the organization unparalleled first-hand experience of the realities of combating major marine spills. ITOPF is at constant readiness to respond to spills anywhere in the world and is often on the spot within hours of an incident to provide practical advice and assistance on cleanup operations and pollution damage assessment. ITOPF is financed through subscriptions from its shipowner members and associates paid through their Protection & Indemnity insurers (P&I Clubs). ITOPF’s membership currently comprises over 6,100 tanker owners and bareboat charterers, who between them own or operate about 10,800 tankers, barges, and combination carriers with a total gross tonnage (GT) of over 320 million GT. This represents virtually all of the world’s bulk oil, chemical, and gas carrier tonnage. Associates comprise the owners and bareboat charterers of all other types of ship, currently totaling some 521 million GT. ITOPF’s activities are overseen by an international Board of Directors representing the organization’s independent and oil company tanker owner Members, its Associates, and P&I insurers. While spills from tankers and other shipping provide the majority of its work, ITOPF is also called upon to respond, on a consultancy basis, to spills from other sources, such as pipelines, offshore oil installations, and onshore tank farms. For shipping, ITOPF’s advice is given in relation to spills of oil (carried as cargo or bunkers), chemicals and other substances, materials or items carried onboard. Advice is also occasionally given in relation to physical damage to coral reefs resulting from ship groundings. ITOPF has Observer status at both the International Maritime Organization (IMO) and the Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10029-2 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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International Oil Pollution Compensation Funds (IOPC Funds) and regularly contributes to discussions on matters relating to ship-source pollution. ITOPF’s first task on being advised of a new spill is to evaluate the probable behavior, fate, and impact of the oil or chemical and the local capability to organize an effective cleanup response. Our role on site varies according to the circumstances, but it usually includes advising and assisting all parties on the most appropriate cleanup operation, with the aim of mitigating any damage; helping to secure equipment and to organize the cleanup where there is a need to supplement the local response capability; monitoring the cleanup (in order to provide subsequent reports of events and of the technical merit of actions in relation to claims for compensation); and investigating any damage to the environment and to coastal resources such as fisheries, mariculture, industry, and recreational areas. In every case, ITOPF’s staff work closely with all the parties involved in a spill, with the aim of reaching mutual agreement on measures that are reasonable and best suited to the particular circumstances. ITOPF is frequently asked to assess the technical merits of claims for compensation arising from spills. On many occasions, this is a natural extension of our on-site involvement at the time of the incident. It usually involves assessing the reasonableness of cleanup costs and the merits of claims for damage to economic resources. The assessment of damage to fisheriesd especially mariculture facilitiesdis a particular area of specialization that often requires detailed analysis of complex claims, frequently in conjunction with other specialists who have in-depth knowledge of the affected area and the economics of its particular fisheries. ITOPF’s advice is also regularly sought on environmental damage claims. ITOPF’s role in claims analysis is geared toward providing advice on the technical merit of claims. The final decision on settling any claim rests with those who will pay the actual compensation (usually the P&I Clubs and the IOPC Funds). In view of its long involvement with oil spills, ITOPF is frequently asked by governments, industry, international agencies, and other organizations to assist with the preparation of contingency plans and also to undertake other advisory assignments. ITOPF organizes and participates in numerous training courses and seminars around the world and regularly assist with oil spill exercises designed to test contingency plans and response arrangements. Considerable effort is devoted to the provision of practical information on oil spill response techniques and related topics. ITOPF has published a series of Technical Information Papers (TIPs) that are gradually being revised and added to, in addition to other occasional publications and an extensive website. Since 1974, ITOPF has maintained a database of oil spills from tankers, combined carriers, and barges. This is one of the most comprehensive of its kind and allows long-term trends to be analyzed, which has proved useful for assessing the risk of oil spills for contingency planning purposes and for evaluating the possible consequences of changes in tanker design and

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operation. By using the Geographic Information System (GIS), which is freely available on ITOPF’s website, spills can be displayed on maps and analyzed alongside other data sets, such as tanker traffic and cargo volume routing data, as well as the status of international conventions. ITOPF’s statistics provide compelling evidence for the downward trend in the frequency of oil spills from tankers. The average number of large spills per year during the 2000s was less than half of that witnessed during the 1990s, and an eighth of the average for the 1970s. This dramatic reduction has been due to the combined efforts of the tanker industry and governments (largely through the International Maritime Organization (IMO)) to improve safety and pollution prevention. Despite the downturn in tanker spills, spills from nontankers continue to occur, and even small incidents can often cause significant environmental damage and economic loss. The demand for ITOPF’s technical services continues unabated, and it remains committed to promoting effective response to spills of oil, chemicals, and other hazardous substances in the marine environment.

ADDITIONAL INFORMATION www.itopf.com

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Chapter 30

Safety Issues at Spills Quek Qiuhui

Chapter Outline 30.1. Introduction 1037 30.2. Organization Structure 1037 30.3. Health and Safety 1038 Risk Analysis/Risk Assessment 30.4. Air Monitoring 1038 30.5. Site Safety and Health 1043 Plan

30.6. Different Types of Hazards on Site 30.7. Recommended Safety Procedures 30.8. Emergency Procedures During a Response 30.9. Other Issues 30.10. Conclusion

1048 1049 1054 1059 1062

30.1. INTRODUCTION Protection of human safety and health is a fundamental objective of any organization. Safe work practices help to minimize safety and health risks to responders and the surrounding community. The types of hazards that could occur during a spill and the safety precautions required to minimize injury will be described in this chapter. Such precautions include the proper use of personal protective equipment (PPE), safe handling of response equipment/chemical dispersants, and following standard operating procedures. The chapter will also identify the appropriate emergency procedures during a response covering fire and explosion, hazardous atmosphere, and medical emergencies. The safety precautions associated with using volunteers, as well as the additional hazards and training issues that they face, will be identified.

30.2. ORGANIZATION STRUCTURE There is a need to establish a structured chain of command at the onset of an incident. Roles and responsibilities must be clearly defined such that everyone knows their individual roles. Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10030-9 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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Correct reporting procedures should be laid out so that everything is standardized and in the correct format that will aid planning for future operations. The chain of command is a two-way process; thus, communication issues may arise from the workforce upward as well as from the management downward. This is important to safety because all personnel will thus have an identified leader where they can consult for any queries or issues regarding safety concerns. However, it is also important to point out that health and safety is the responsibility not only of the supervisors but also all personnel on site.

30.3. HEALTH AND SAFETY RISK ANALYSIS/RISK ASSESSMENT Prior to any task or cleanup operation, a risk assessment for each specific task assigned to that work site will need to be done to decide what safety measures to employ. Not all tasks at the site will be the same, and all will require varying degrees of control. For example, the type of oil contaminant will be different in various incidents. The type of safety measures to be taken depends on what the product is, how weathered it is, and what is mixed in it (i.e., dead animals). In another example, concentrations of oil may differ among incidents toodhence considerations such as whether oil is concentrated in one area (e.g., high-energy cove) or whether it is spread out along a highly aerated beach. An example of a generic risk assessment form is presented in Table 30.1.

30.4. AIR MONITORING After the completion of the risk assessment and before entry into the site for any oil spill response, air monitoring at the spill site and surrounding areas will be required to ensure site, responder, and local community safety. A Site Entry Protocol has been developed that includes monitoring of the following substances by a site characterization team donning full face masks and protective suits (i.e., Tyvek suits) to ensure that air quality is satisfactory before any response can take place: l l l l l

Oxygen Carbon monoxide Hydrogen sulphide Volatile organic compounds Benzene

These tests need to be completed by trained competent personnel, and the instruments have to be calibrated prior to use. All monitoring results need to be documented in a proper manner with the frequency of sampling clearly stated on the documentation forms. A sample of an air monitoring form with the acceptable levels of air quality can be found in Table 30.2. Please note that these levels are to be used as a guideline only inasmuch as the acceptable levels of air quality differ between countries. Finally, the results of the monitoring

Chapter | 30 Safety Issues at Spills

TABLE 30.1 Generic Risk Assessment Form

Work Activity

Conducted by: (Name, Designation)

Review conducted by: (Name, Designation)

Location

Approved by: (Name, Designation)

Review approved by: (Name, Designation) Risk Control

Assets

Reputation

Person Assigned

Environment

Residual Risk Matrix

People

Reputation

Assets

Description Hazard Consequence of Process/ Description Sequence

People

No

Environment

Risk Matrix

Post Work Activity Review Review e.g. Additional Risk Control Person (Implementation Assigned date, where applicable)

1st Release

Last Review

Revision

Next Review

Date

(Continued )

1039

1040

TABLE 30.1 Generic Risk Assessment Formdcont’d Inherent Risks

Increasing Likelihood (of consequences) Reputation

Assets

Environment

People

Severity

Consequences

A

B

C

D

Remote

Probable

Highly Frequent probable

Minor

1A

1B

1C

1D

2

Moderate

2A

2B

2C

2D

3

Major

3A

3B

3C

3D

4

Critical

4A

4B

4C

4D

Residual Risks

Reputation

Assets

Environment

People

Severity

Residual Likelihood (of consequences) A B C D Remote

Probable

Highly Frequent probable

1A

1B

1C

1D

2 3

Minor Moderate Major

2A 3A

2B 3B

2C 3C

2D 3D

4

Critical

4A

4B

4C

4D

1

Implement control measures for each identified hazard to ensure that risk level does not increase, and to reduce the Medium risk to as low as reasonably practicable. Risk control action plan may be developed in an attempt to reduce risk rating. Develop risk control action plan immediately to eliminate or mitigate and reduce the risk as low as reasonably practicable. Intermediate control measures shall be High implemented to reduce risk if jobs are to be continued. Existence of such risk must be communicated to management.

Low Medium High

No significant risks. Monitor for continual change. Residual risk acceptable. Implement additional risk control measures if necessary. Residual risk is NOT acceptable. Review control measures and action plan. Substitute/ amend process where possible and necessary.

Contingency Planning and Command

Consequences

Manage for continual improvement.

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1

Low

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Chapter | 30 Safety Issues at Spills

TABLE 30.2 Sample Site Entry Instructions Site Characterization (SC) and Main Body to arrive near spill site (200 m away) at a time when benzene reaches 0.5 ppm as predicted by software used.

SC Team to set mixed gas detector limits as follows: Alarm

1 (TWA)

2 (STEL)

O2

19.5 %

23.5 %

H2S

10 ppm

10 ppm

STEL not available

CO

25 ppm

240 ppm

STEL not available, thus use 20% of IDLH

VOC (use Isobutylene)

50 ppm

150 ppm

STEL is set based on 50% of TWA of Gasoline.

l l

Remark

SC team to don benzene protection (full face mask). SC team to use gas detector for benzene detection and quantification (benzene level to not exceed TWA of 0.5 ppm).

Moving toward spill site (main body to stay 200 m away from spill site) l Gas meters should be held at chest level. l At every 50-m interval, use gas detector to check benzene concentration in air. At this point, manually record (hardcopy) the gas readings as well. l In event any alarm is sounded or when the concentration is greater than the TWA, the SC team will start moving backwards. Backtrack till the alarm stops. l Three scenarios before reentering: 1. If the alarm levels show readings between the STEL and TWA: l Wait for at least 15 minutes before reentering the site. 2. If the alarm levels show readings higher the STEL levels and IDLH: l Wait for at least 2 hours before reentering the site. 3. If the alarm levels show readings higher than IDLH levels: l Wait for at least 4 hours before reentering the site. l Upon reaching spill site without any alarm sounding, SC team to move around to more oil-concentrated sites. l If all concerned spill areas are covered by SC team without any alarms sounding, communicate with Main Body to move in. SC team is now safe to remove their full face masks. l Main Body can now move in without donning any respiratory aid with continuous gas monitoring. During Spill Cleanup l Air concentration (both benzene and mixed gas) to be checked every 4 hours. Stop when air concentration is clear of toxic gases (i.e., benzene ~ 0; VOC ~ 0; H2S ~ 0). l Both SC team and Main Body would carry the same set of detectors and do their own monitoring. l Personnel working in these sites must have a l Personal gas meter attached at chest level of their bodies l Escape mask l In event any alarm is sounded or when the benzene concentration is more than 0.5 ppm, don escape mask and leave spill site immediately. (Continued )

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TABLE 30.2 Sample Site Entry Instructionsdcont’d TWA ¼ Time-Weighted Average (the concentration of the substance in air that can be breathed for 5 consecutive 8-hour workdays, 40-hour work week, by most people without adverse effect), STEL ¼ Short-term exposure limit (the concentration of the substance in air that can be breathed for 15 minutes per workday by most people without adverse effect), Ceiling ¼ this concentration should not be exceeded at all time. SITE CHARACTERIZATION Site Name Location/Map Reference

Initial Test (200 m away from spill source) Gas Test

Limits

% O2

>19.5%< 23.5%

% LEL

<10%

H2S

Alarm 1: 10 ppm Alarm 2: 10 ppm TWA ¼ 10 ppm Ceiling ¼ 15 ppm

VOC

Alarm 1: 50 ppm Alarm 2: 150 ppm

Benzene

Alarm: 0.5 ppm TWA ¼ 0.5 ppm STEL ¼ 2.5 ppm

Results

Date/ Time

Follow-Up Tests (subsequent every 50 m)

Results

Date/ Time

O2 ¼ Oxygen, CO ¼ Carbon Monoxide, LEL ¼ Lower Explosive Limit, H2S ¼ Hydrogen Sulphide, TWA ¼ Time-Weighted Average, STEL ¼ Short-term exposure limit, Ceiling ¼ this limit should not be exceeded at all time, CMS ¼ Chip Measurement System, ppm ¼ Parts per million SITE GAS MONITORING Site Name Location/Map Reference

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Chapter | 30 Safety Issues at Spills

TABLE 30.2 Sample Site Entry Instructionsdcont’d Follow-Up Tests (every 4 hours) Gas Test

Limits

% O2

>19.5%< 23.5%

% LEL

<10%

H2S

Alarm 1: 10 ppm Alarm 2: 10 ppm TWA ¼ 10 ppm Ceiling ¼ 15 ppm

VOC

Alarm 1: 50 ppm Alarm 2: 150 ppm

Benzene

Alarm: 0.5 ppm TWA ¼ 0.5 ppm STEL ¼ 2.5 ppm

Results

Date/Time

Tests completed by Initial Test 1st Follow up 2nd Follow up 3rd Follow up Name Signature Note: Gas limits mentioned are meant as a guide only. Please check the appropriate gas limits that are applicable during a response with the relevant authorities or organization.

should be made available to all personnel accessing the spill site. This would be so that these personnel are made aware that they are not to enter a spill site until it is deemed safe to do so. Air monitoring will need to be done on the initial site entry at every 50- m advancement to the site from a radius of 200 m, after which air quality readings are to be taken continuously in the work area throughout the response.

30.5. SITE SAFETY AND HEALTH PLAN After completion of the risk assessment and air monitoring, a comprehensive survey to identify all possible hazards will need to be completed. This is usually done by the shoreline supervisor using a standard form (Table 30.3). This process identifies all potential risks on site to personnel tasked with the cleanup operations. Some examples of risks associated with cleanup operations are terrain, product being handled, tidal ranges, and possible buried utilities, such as electrical cables.

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TABLE 30.3 Sample Site Safety and Health Plan SITE SAFETY & HEALTH PLAN Applies to site Date

Time MSDS on site?

Product(s) Site characterization Area

Tick all relevant boxes Ocean Bay

Inland

Pipeline

Mountainous

Docks

Shoreline

Sandy

Yes

No

River

Salt marsh

Mudflats

Refinery

Tank Farm

Bunded Area

Rocky

Cliffs

Other (specify)

Farming

Public

Notes (Note High and Low water times if applicable)

Recreational Notes

Weather Wind chill

Commercial Other

Ice/frost Fog/mist

Industrial

Snow Sun

Rain Other (specify)

Wind Speed ……….. knots Cloud High Cover Low

Government

Wind N Direction W Temp………….. ºC

Notes

Site Type

% Site Access

Load Bearing

Cliffs

Metalled road

Firm

will support any vehicle

Bedrock

Track

Good

4-wheel drive

Boulders (>10 cm)

Pathway

Pebbles (1-10 cm)

Steps

Gravel (2mm - 1cm)

Slipway

Sandy

Car park

Mud

Boat

Man-made

Other

Soft tracked vehicles Very will not support vehicles soft Access/site information.

Marsh/mangrove Other: Bird handling Boat safety Chemical hazards Cold stress Electrical hazards Fatigue Inclement weather

Site Specific Hazards Fire, explosion, in-situ burn Heat stress Helicopter operations Motor vehicles Overhead/buried utilities Work near water Dangerous animals

Slips, trips, and falls Steam and hot water Tides Trenches, excavations UV radiation Visibility Other (specify)

4 SITE SAFETY AND HEALTH PLAN

Use

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Chapter | 30 Safety Issues at Spills

TABLE 30.3 Sample Site Safety and Health Plandcont’d Notes

Personal Protective Equipment (PPE) Foot protection Coveralls Head protection Cold weather clothing Survival suit

Impervious suits Personal air monitors Other (specify)

Ear protection Eye protection SCBA

Hand protection Personal flotation Respirators

Notes

Site Facilities Required Sanitation Security Notes

First Aid Shelter

4 SITE SAFETY AND HEALTH PLAN

WHERE THERE IS A RISK OF HARM TO PERSONNEL PROTECTIVE EQUIPMENT SHOULD BE ISSUED AND USED CORRECTLY BY ALL PERSONNEL ON SITE WITH NO EXCEPTION

Decontamination Other (specify)

Site alerting/Alarm system CAR HORN OR SOMETHING RECOGNISABLE

Evacuation Plan MUSTER POINTS, ROLES AND RESPONSIBILITIES, ETC

Local Emergency Medical Facilities : NAME/NUMBER/RADIO CHANNNEL/CALIFICATION AND DATE First Aid: Doctor : Hospital : Ambulance :

NAME AND NUMBER NAMES ADDRESS NUMBER 112 (International) 999 (UK)

Other Authorities

HARBOUR MASTER

Other Authorities

COAST GAURD

(Continued )

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Contingency Planning and Command

TABLE 30.3 Sample Site Safety and Health Plandcont’d Always seek to use mechanical aids first, and remember the guidelines of 25 kg for men and 15 kg for women Who will be involved with manual handling? OSRL staff Contractors (Trained) Volunteers (Trained) Volunteers (Untrained) Manual handling

NOT APPLICABLE

Contractor (untrained) Other (specify)

NOTE - Shaded areas require manual handling training, use guideline document to record the basic field training.

Noise Assessment If you have to raise your voice to communicate then you are NOT APPLICABLE exceeding the 80 db limit Diesel Driven Power Air Inflation Pump/Water Small Skimmer Pack Pump Pressure Washer Large Diesel Pump Product Uplift Skimmers If you tick any of the above, hearing protection is required, Other (Specify) consider if single or double protection is necessary Notes PPE required?

Working at Height Platforms Scaffolding Notes

NOT APPLICABLE Ladders Cliffs/ledges

Lifting Operations Ensure that any lifting gear used is within its inspection date and in good condition.

Tanker walkways Others (specify)

NOT APPLICABLE

Other (specify) Notes (if the lift is considered ‘complicated’ please prepare a lifting plan prior to work commencing) Check weights and capabilities before lifting. Confined Space As a guideline, a confined space is an area without a separate NOT APPLICABLE access and egress point. If you are unable to step out of the working area, then that is a confined space. Storage Tanks Silos Enclosed Drains Sewers Open Topped Chambers Vats Unventilated or poorly Beaches restricted by Ductwork headland and tide ventilated rooms Bunds Excavations Other (specify) If any of the shaded areas are ticked, please contact your Line Manager for advice. Gantry cranes

Mobile cranes

Tower cranes

Forklifts

4 SITE SAFETY AND HEALTH PLAN

Notes (Record the manual handling hazards identified and remedial action)

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Chapter | 30 Safety Issues at Spills

TABLE 30.3 Sample Site Safety and Health Plandcont’d Notes (ensure that entry and exit points are clearly defined on the sketch or picture of the site) Use caution! Hot Work

NOT APPLICABLE

Open flame work Notes

Welding

Other (specify)

SECTION 5 Sketch of Site SKETCH MAP OF AREA (Plan view and shore profile/s)

5 SITE SURVEY AND CONTAMINATION REPORT

Scale

A, B, C, etc. oiling zones Boom anchor points Likely disposal sites Backshore features Access restrictions Position H/L tide Photo locations Oil distribution Site:

POINTS TO REMEMBER

KEY

Key landmarks Access points North arrow % Cover Slope Scale Pits Date:

Initials:

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PART | XI

Contingency Planning and Command

30.6. DIFFERENT TYPES OF HAZARDS ON SITE Different safety issues will be presented during a response. Listed below are the common hazards/safety issues faced by responders: a. Hazards (Health) i. Ingestion of hydrocarbons and other associated chemicals (e.g., dispersants, surface-washing agents, shoreline cleaners) ii. Inhalation of toxic components iii. Skin contact with oil and other chemicalsdresulting in a possible degreasing effect on skin tissue and inflammation of skin.4 Prolonged or repeated skin contact may result in dermatitis, as well as increased body uptake of some crude oil components. Increased sensitivity to oils can also occur as a result of repeated exposures. iv. StressdBoth physical and mental stress as a result of the cleanup operations. b. Hazards (Safety) i. Fire/Explosion ii. Natural Hazards l Wild animals (crocodiles in mangrove areas, bears, oiled birds, etc.) l Certain types of shorelines pose more dangers than others. For instance, inaccessible sites like exposed rocky headlands and wave-cut platforms, boulders, and steep slopes are more likely to cause accidents as compared to an easily accessible site. l Working in/near water increases the danger of drowning. l Weather and other calamities have to be considered as the yardstick of when to halt cleanup operations, and evacuation remains an important matter to be addressed. The most common hazards from nature will be lightning and thunder followed by rain, ultraviolet radiation, and wind. The presence of lightning protectors or conductors at the site could be considered. l Climate conditions pose additional risks to cleanup responders. All responders should be trained to recognize and guard against the symptoms of heat or cold stress and provide the appropriate first aid. Heat stress is caused by the inability of the body to dissipate excess heat generated from physical exertion, temperature and humidity, or wearing of protective clothing and equipment. Cold stress is caused by a rapid loss of heat from the body that can cause localized minor-to-severe injuries, as well as system dysfunction. The most prevalent cold stress injuries involve the extremities: typically, the hands, ears, nose, and/or feet. l Noncompliance to standard operating procedures/operating work instructions.

Chapter | 30 Safety Issues at Spills

1049

iii. Excessive noise is one of the most common hazards that responders may be exposed to during a response. If there is a need for shouting within a radius of 0.6 to 1 m, the sound pressure levels (noise) are assumed to be above the threshold for wearing hearing protection (85 decibels). iv. Commonly used electronic equipment like mobile phones have not been certified intrinsically safe to operate in hazardous atmospheres, unlike hand-held transceivers and oil spill response equipment. Hence, it may be prudent to consider banning the use of mobile phones in the “hot” zone (the dirtied zone where all the cleanup work is being carried out). c. Equipment Handling i. Moving parts within the machine (e.g., belting within the power-packs) and high-pressure hydraulic hoses used in hydraulic driven pumps and skimmers. ii. Equipment failure (e.g., underrated hydraulic hoses applied to excess working pressure). iii. Lifting hazard during handling of heavy oil spill response equipment like skimmers, booms, pumps, and power-packs and transporting these during lifting operations. iv. Human error in handling equipment

30.7. RECOMMENDED SAFETY PROCEDURES Once the safety issues or hazards have been identified, the next step is to control them.8 The following sections cover specific hazard controls that are applicable during an oil spill response.

30.7.1. Site Evaluation Process Working in an oil spill environment is a hazardous operation. Hence, in an effort to reduce risks, a comprehensive assessment has to be completed. Safe working practices have to be ensured, with ongoing supervision and continuous training of the responders working on site. From the initial information given by the spiller, a preliminary evaluation can be done by the main command center and a first draft plan can be produced. Site entry monitoring is then carried out by a shoreline supervisor, and the information from the survey is put into the initial draft plan. The area is then continually monitored, and the plan may be adjusted as the situation changes. Please refer to Figure 30.1 for components of a site evaluation process. Employers must ensure that responders at any site of operation comply with local health and safety regulations and conduct their work in a proper and safe manner. This applies to all oil spill cleanup sites even though they may be far removed from the normal place of work.

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PART | XI

Preliminary Evaluation (off site)

Contingency Planning and Command

Initial Site Entry

Initial Draft of SSHP

Continual Monitoring and Feedback

SSHP Revision

FIGURE 30.1 Components of a site evaluation process using the Site Safety and Health Plan Concept (SSHP).

30.7.2. Site Control Measures Employees’ exposure to varying levels of contaminants must be controlled, and correct PPE must be worn at all times during cleanup operations. These measures have to be modified as the operation develops, meaning that the PPE level may vary as the task progresses due to the weathering process and task reallocation, and either increasing or decreasing concentrations of light ends are being released.9 Personnel involved in any oil spill cleanup operation can get very dirty. It is important to keep oily gear and dirty personnel out of living quarters in order to maintain satisfactory conditions. Setting up a decontamination zone is one way of achieving sanitary conditions. Within this zone should be washing stations and lockers for responders to change into clean clothes, as well as facilities for cleaning and storing soiled PPE, such as rain gear and rubber boots. To prevent secondary contamination, there must be a designated entrance from the hot zone and a designated exit into the cold zone, as shown in Figure 30.2. Site control program should include: 1. Site Map: A site map is required with access/evacuation routes and decontamination zone identification for personnel and equipment routing and control. Figure 30.3 shows a generic site map with zones marked.

Dirty Side – Remove Dirty Gear

Shower – Clean and Rinse

Clean Side

Single Entrance From Hot Zone

Single Exit Into Cold Zone FIGURE 30.2 Proposed decontamination zone layout.

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Chapter | 30 Safety Issues at Spills

Site Command and Control

Legend

Source

Shelter

6

Area

Shelter Area

5

Spill material

4 2

Hot zone Escape routes

Site Air Monitor Staging

Lay

Area

Down

boundary

Area

Decon Zone

Decon Zone

Equipment

3

Oily Waste Storage

1 Controlled Access Point

Toilet Refreshment Area / Shelter

Command Hot Zone

Post

Warm Zone Cold Zone

First Aid

Site Entrance

Evacuation Area

Controlled Access Point

1

Tasks 1: Site Security 2. Site Air Monitoring 3. Decontamination 4. Search & Rescue 5. Firefighting 6. Containment & Recovery of spilt material

FIGURE 30.3 Generic site layout map.

2. Work Zone Designation: Work zones need to be in place so personnel know the parameters of the operation areas (i.e., hot, warm, and cold zones). Please refer to Figure 30.4 for an explanation of the different operating zones. 3. Nearest medical assistance facility in case of injuries. 4. Buddy system for operations so that personnel can monitor each other’s safety and well-being during the response.

Contaminated

Clean “Cold” or Support Zone Shower / Changing Area Toilets Rest Area Support Equipment Food and Drink

“Warm” or Decontamination Zone Wash, rinse, and remove outer and inner garments Wash boots

“Hot” or Exclusive Zone Work Zone Tool / Equipment drop Rubbish drop

FIGURE 30.4 Operating zone segregation.

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Contingency Planning and Command

30.7.3. Personal Protective Equipment The decision on the levels of PPE will be determined during the Site Safety and Health Survey and while risk assessments are being conducted. The tasks to be carried out and the product to be handled will be taken into account. Some operational requirements need to be considered: 1. Duration of acceptable exposure in the “hot” zone for trained personnel levels of PPE will be set and adhered to, but the duration in time may vary depending on the task being carried out and the climate. Refer to Table 30.4 for the minimum levels of PPE required for different operations. 2. Climate In the event that the weather is warm, the duration of one donning bulky PPE has to be limited to prevent heat stroke and exhaustion. 3. Maintenance/Storage PPE needs to be stored in a dry clean environment, that is secure and controlled. Some of the PPE may require maintenance (e.g., the Self-Contained Breathing Apparatus (SCBA)).10 4. Decontamination Adequate decontamination areas need to be in place. 5. Training Personnel will require training on the correct way to don the PPE and to check for expiration dates.

30.7.4. Excessive Noise Excessive noise is one of the most common hazards that responders may be exposed to during a response. If there is a need for shouting within a radius of 0.6 to 1 m, the sound pressure levels (noise) are assumed to be above the threshold for wearing hearing protection (85 decibels). Hearing protection must be worn when there is a continuous exposure to noise levels above 85 decibels. Figure 30.5 relates the different sound pressure levels and routine activities. This will help us in estimating the noise levels when working in a spill site.

30.7.5. Heat Stress Responding to spill emergencies increases the risk for heat stress. The use of protective equipment (especially in tropical areas) compounds the problem by increasing the heat load, preventing adequate heat dissipation, and decreasing evaporative cooling. It is important to prevent heat-induced illnesses and injuries and to recognize early symptoms of heat stress. The four “stages” of heat stress and their relevant first aid recommendations are presented in Table 30.5.

e Benzen

mpler

H2S

Gas Sa

Noise

Heat

Cold

Water

w Boat cre

Lifting

ne Cold zo rm hot/ wa Visitor zone econ.

shing

d Visitor

L.P. wa

leaner

ashing H.P. w h al brus Chemic y al spra

Chemic

lc Manua

isor

river Plant d

Superv

Dayglo vest Coveralls Oil skin suit Safety boots Safety wellingtons Chest wader Rigger gloves PVC gloves Tape seals Ear defenders Safety glasses Goggles Bump hat Safety helmet Personal floatation device Tyvek ® suit Thermal suit Immersion suit Air monitor patch Respirator1 TECPS2

Chapter | 30 Safety Issues at Spills

TABLE 30.4 Typical Minimum PPE Requirements4

Note: 1 Chemical cartridge respirator with full facepiece & organic vapour cartridge filter with an assigned protection factor (APF) of 50 2 Totally encapsulating chemical protective suit

1053

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PART | XI

Fridge

20

Circular Saw Hammer Drill Machine Tool House-hold Appliances Conversation Office Background

50

Contingency Planning and Command

Chain Saw Ambulance Siren Cry of Child Fire Alarm

100 Units in dbA

85dbA: Compulsory protection for 8 hours of exposure

Rock Concert Plane Taking Off Jack Hammer Thunder Bulldozer

120

120dbA: Any exposure may lead to irreversible auditory damage

140

160

140dbA: Maximum admitted exposure, even, with ear protection

FIGURE 30.5 Different sound pressure levels.

30.7.6. Cold Stress All responders in cold climates must be trained to recognize and guard against the symptoms of cold stress and provide proper first aid. The “stages” of cold stress and their relevant first aid recommendations are outlined in Table 30.6.

30.7.7. Monitoring Program Responders will need to be monitored throughout the operational day, which is everyone’s responsibility. Certain employee-specific symptoms of fatigue, stress, exposure, and any medical conditions need to be addressed.

30.8. EMERGENCY PROCEDURES DURING A RESPONSE During a spill response, the potential emergencies that can occur include: l l l

Fire and explosion Hazardous atmosphere/hazardous chemicals Medical emergencies

30.8.1. Fire and Explosion A major safety risk during crude oil or refined product spill response is from fire or explosions. This risk is site and substance specific and must be evaluated before response personnel enter a spill area or damaged vessel/equipment. (Refer to Sections 30.7.1 and 30.4 for site evaluation process and air monitoring, respectively). Explosions present a physical risk from:

Heat Stress Stage

Symptoms

Heat Rash (prickly heat)

l

Rash on the skin

5

Typical Causes l

Humid environment or wearing protective equipment that holds moisture next to the skin

First Aid Recommendation l l l

Heat Cramps

l l l

Heat Exhaustion

l l l

Heat Stroke

l l l

Muscle spasms in hands, feet, abdomen May also be accompanied by nausea/vomiting Person becomes quiet/stops work

l

Pale, clammy, moist skin Nausea/ headache, dullness of response/work pace Person may become quiet, sit down, or faint

l

Skin may be dry, reddish, and hot Person may faint or become disorientated Convulsions may occur with vomiting and rapid pulse rates

l

l

l

Large electrolyte loss due to sweating, which disrupts the electrolyte balance in the body

l

Excessive water loss, inadequate replacement Responder may not be acclimatized to work, equipment, and/or climate

l

Temperature regulatory control has failed Body can no longer rid itself of excess heat

l

l

l l l

l l l l

Provide place for responder to thoroughly wash skin Offer rest periods in cool location Apply medicated powder Offer fluids with proper balance of electrolytes, such as commercially available sports drinks Offer rest periods for routine fluid intake

Chapter | 30 Safety Issues at Spills

TABLE 30.5 Heat Stress Stages and Appropriate First Aid

Relocate responder to cool place (shade) Remove protective equipment (if appropriate) Offer plenty of liquids with electrolytes Seek medical care/advice

Seek immediate medical care Remove protective clothing Wet with cold water, cold beverage bottles If person is conscious, provide small but continuous amount of cool water/electrolytes Do not leave person unattended

1055

1056

TABLE 30.6 Cold Stress Stages and Appropriate First Aid5 Cold Stress Stage

Symptoms

Frost Nip

l

l

l

l

Skin has “waxy” or white appearance Skin is not flexible on the surface Beneath the surface, tissue is still flexible Painful

l

Bodily tissue is cold, pale, and solid

l

l

l l l

Deep Frostbite

l

l l

l

l l l l l

Shivering Personality change Slow movement Person may become gradually quiet over several minutes Shivering may stop and person may be conscious but not coherent

l l l

l l l

Hypothermia Due to Immersion (rapid loss of core temperature)

l l l

Even a short immersion unprotected in cold water can cause rapid hypothermia Death could occur in less than 30 minutes Above symptoms occur rapidly

Warm responder’s affected body part slowly Provide warm shelter and offer warm fluids Seek medical follow-up

Seek immediate medical care Cover responder but do not try to bend or flex body part prior to medical care Seek immediate medical care Perform CPR if necessary Gently remove wet clothing, cover with blankets or a sleeping bag (get in with victim to provide extra warmth) If conscious, give “sips” of warm water or milk Do not give alcohol Never leave victim alone

Contingency Planning and Command

Hypothermia in Air (gradual loss of core temperature)

Warm responder’s affected body part slowly Keep responder warm until color and sensation of touch return to normal

PART | XI

Sudden whitening of the skin Skin is still flexible but firmer than normal Pain is typically experienced

l

Superficial Frostbite

First Aid Recommendations

Chapter | 30 Safety Issues at Spills

l l l

1057

Injuries/fatality Flying debris Atmospheric overpressure

Burning hydrocarbons result in a variety of combustion products. Therefore, only experienced personnel with proper safety, respiratory protection, and hazard detection equipment should approach a burning vessel or spilled material. Personnel should always: l l

Approach from upwind, upstream, or uphill side, if possible Retreat if heat intensity is severe or if material is spreading When preparing to work in a potentially hazardous area, personnel should:

l l l l

l

l

l l

Assess the need to enter the area Determine the fire hazard potential of the material or mixture spilled Be alert to possible oxygen deficiency Obtain a combustible gas/oxygen meter that is calibrated and in good working order Understand how the instrument will respond to the materials being measured Test the atmosphere when approaching the spill (especially if in vessel, tank, manway, or low-lying area) Use equipment and tools that are intrinsically safe/explosion proof Observe confined space procedures if entering a confined space area

In potentially flammable atmospheres, restrict use of instruments that are not intrinsically safe. These include: l l l l l

Open lights Flames Internal combustion engines Nonapproved radio transmission devices Cellular phones

All hydrocarbons have a concentration range in which they are combustible. When either too little or too much hydrocarbon is present in the air, the mixture will not burn. Also, in confined areas, the oxygen level must be 10% or higher for combustion to occur. When evaluating the risk of fire or explosion, the key measurement is the lower explosive limit (LEL). The LEL is the lowest concentration of a vapor for a given material that will support combustion. Below this concentration, the mixture is too lean (dilute) and cannot support combustion. Detectors are used to determine whether or not a mixture is combustible (see Table 30.7). However, most combustible gas detectors (LEL meters) will not work properly in an area that has an oxygen level below 14e16%. Therefore, to test confined spaces or inert containers for hydrocarbon level, the oxygen content must be measured first by properly protected personnel.

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TABLE 30.7 Proposed Work instructions for Different LEL Readings5 If LEL meter reading is:

Then:

0% to less than 10% of LEL

Hot work (i.e., with potential ignition sources) is allowed

Greater than 10% and less than 25% of LEL

Proceed with care, especially where there is poor air movement or circulation

Greater than 25% of LEL

Leave the area quickly and carefully

Note: LEL readings do not detect toxic hazards. A reading of just one-tenth of a low LEL of 1% could still be toxic (1000 ppm of hydrocarbons can be dangerous to life and death). Although flammability testing should be one of the first levels of assessment, the decision to enter or work in an area should not be based solely on flammability.

30.8.2. Hazardous Atmosphere/Hazardous Chemicals Crude oil contains substances that can cause acute as well as chronic health effects. Acute effects are more immediately evident and typically result from relatively short duration, high-exposure conditions. Most of the acutely toxic substances are highly volatile and are present in their highest concentrations soon after the spill. Chronic effects may develop some time after the initial exposure and are often associated with longer duration, lower concentration exposures.11 Should there be an accidental release of fresh crude during a response, responders have to evacuate the hot zone and follow the site entry protocol to reenter the spill site to continue cleanup operations. The primary health risks associated with fresh crude are related to the inhalation of: l l l

l

Hydrogen sulphide Volatile organic compounds Benzene In the event the gas monitor alarm triggers off for the hazardous gases above and those mentioned in Section 30.4, crafts/personnel are to don the escape mask and evacuate/escape from the site immediately by moving directly across the wind. A proposed evacuation area and escape routes in a cleanup site are shown in Figure 30.6. Do not escape upwind or downwind.

30.8.3. Medical Emergencies During a spill response, responders are exposed to demanding physical activities under possibly adverse climate and site conditions. In the event of a medical emergency, the casualty will be brought into the First Aid area shown in Figure 30.6, and qualified first aiders will render the appropriate treatment. If

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Chapter | 30 Safety Issues at Spills

Escaping From the Site Escape

Up Wind

Source of Leak

Across Wind

Down Wind

Wind

Escape

Figure 30.6

Evacuation plan when gas monitor alarm is activated.

further treatment is required, the casualty has to be shifted to a medical facility as soon as possible. The incident will be reported to the Incident Management Team who will notify the next of kin of the casualty. The organization that has overall responsibility for the cleanup operations will have to consider medical evacuation if the cleanup site is remote and has limited medical facilities available.

30.9. OTHER ISSUES 30.9.1. Personnel Training Trained contractors in some oil spill response organizations have been tested in real time exercises and were incorporated successfully in actual spill responses. During spill response, contractors historically have safely participated in the response and cleanup activities. It has been demonstrated that contractors who have undergone training have a higher level of safety awareness as compared to those who have not undergone training. Properly trained contractors are an invaluable asset during a spill response where they are effectively integrated into the overall response structure. A training program should be implemented to ensure that support personnel are adequately prepared. An example of the content might include:2 l l l l

Safety during oil spill response Inshore equipment deployment Offshore equipment deployment Dispersant application operations

Training time will vary depending on spill scenario and the requirements of the responders.

30.9.2. Volunteers Volunteers in a spill response usually come from a myriad of backgrounds and skills. It may be a daunting task for an incident commander to decide which

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Contingency Planning and Command

areas volunteers should be allocated to as there may simply be too many of them with different specialties. In addition, it may be a difficult task to provide professional supervision and to ensure their safety. Hence it is recommended in many instances that volunteers be used in areas where they will not come in direct contact with oil (e.g., in wildlife rehabilitation and cleanup).1 Table 30.8 presents a full list of tasks that might be allocated to volunteers.

30.9.2.1. Additional Hazards Faced by Volunteers on Site Untrained personnel, like volunteers, have an uphill task in combating safety issues during an oil spill. Most of them are made to sign indemnity forms only and may not know what exactly is required of them. Additional hazards faced by volunteers above those discussed in Section 30.3 are as follows. l

l

Insufficient training and unfamiliarity with oil spill response equipment. In these cases, the volunteers should handle machines only under direct supervision or after they have received sufficient training. The employer should provide training and written certification upon completion of training to all personnel according to most standards.6,7 There are currently no international training standards on the type of training that untrained personnel must undergo before allowing to work. There are no specific requirements to certify an instructor. There are only guidelines given in the number of training hours required and the type of topics that have to be covered in the training. The standard of training usually depends on the employer itself, and different companies have different training programs and standards. Volunteers may not be used to putting on PPE. They may be unsure of how to don the PPE correctly or even be aware of the importance of evaluating and applying the correct PPE to the type of product spill as well as the physical and environmental conditions that may vary from site to site.

30.9.2.2. Volunteer Training Issues In the case of personnel such as volunteers who are not trained in oil spill response during peacetime, there are no international standards for the training that they must undergo before they are permitted to work in the spill site. The question of the level of training those volunteers are supposed to have so that they will be comfortable in helping out in the response remains to be answered. The less trained and prepared the volunteers are, the higher the risk they face during an oil spill response, even though they are not directly doing oil recovery. The level of training that untrained personnel currently undergo depends solely on their employer. Only the United States has an official standard called the Occupational Safety and Health Administration (OSHA) implemented under the U.S. Department of Labor. The standard states that responder companies have to provide a qualified trainer and train personnel designated

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TABLE 30.8 Non-Oil Recovery Work Areas for Volunteers3 1. Logistics. a. Inventory control b. Procurement c. Distribution of PPE d. Cleaning of PPE* e. Construction of temporary support structures

2. Personnel Services a. Lodging attendants b. Laundry service c. Message centre d. Direct diverted traffic e. Site security

3. Transportation a. Carpools b. Trucking c. Vehicle cleaning* d. Scheduling e. Dispatching f. Road building

4. Boat Operation (Boat owners who volunteer their services.) a. Area security, directing other vessels away from contaminated areas, allowing work vessels in and directing to familiar locations b. Observation of floating oil* c. Transporting assessment teams or cleanup crews*

5. Food Preparation and Distribution (Often a Red Cross Service) a. Cooking b. Serving c. Cleaning up d. Stocking

6. Wildlife Rehabilitation (This requires specific training provided by wildlife experts) a. Beach patrol/wildlife notification b. Oiled wildlife retrieval and transport* c. Bird cleaning* d. Phone answering, dispatching, messaging

7. Medical a. First Aid attendants* b. Dispatching c. Transporting sick or injured personnel

8. Shoreline Clean-up Support a. Cleanup of nonoiled debris and trash in areas prior to oil impact b. Guides for shoreline cleanup assessment teams (SCAT)* c. Crowd control, onlooker security*

9. Public Relations and Community Liaison a. Guide visitors and media b. Open homes for lodging of responders c. Volunteer coordination *Indicates that the person may be exposed to some oil. Specific hazard training required.5

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as initial responders in OSHA-required Hazardous Waste and Emergency Response Operations (HAZWOPER) classes. However, OSHA does not have any specific requirements to certify an instructor; it simply states that the qualification of trainer may be shown by academic degrees, completed training courses, and/or work experience.7 This raises another concern regarding the quality of training that the volunteer could receive and hence the amount of risk that he or she is facing due to lack of knowledge.

30.10. CONCLUSION Both trained spill response specialists and volunteers will play a part in a large oil spill response. The cleanup of spilled oil is important, but not as important as ensuring the safety of those who are involved or may be affected by the spill. The health and safety of responders is a critical aspect of a successful operation. There are four key points surrounding responder safety, and these are intended to provide guidance regarding the options available for carrying out safe cleanup operations. l l

l

l

Use of volunteers in nonoil recovery area (if at all possible). Safety issues and the importance of the site evaluation process. The process is a useful guideline for response managers and supervisors to determine relevant hazards and put in place control measures. Safety procedures to be carried out during a response. These guidelines are useful for identifying and mitigating risks. The practicability of training responders during peacetime. Responders who have undergone training have a higher level of safety awareness.

ACKNOWLEDGMENTS I would like to express my sincere thanks to all my colleagues in Oil Spill Response who have rendered their full support and guidance in particular, Ho Yew Weng, David Salt, Mark Chan, Lee Barber, and Matt Clements.

REFERENCES 1. Gass MR, Przelomski HR. Volunteers: Benefit or Distraction? An International Protocol for Managing Volunteers During an Oil Spill Response. IOSC 2005, 19th Triennial International Oil Spill Conference. Miami Beach, FL: 2005. 2. Azeri, Chirag, Gunashli. Contractor Control Plan Oil Spill Response Azeri, Chirag, & Gunashli Full Field Development Phase 1 Project Construction Programme . Website: http:// www.bp.com/liveassets/bp_internet/bp_caspian/bp_caspian_en/STAGING/local_assets/ downloads_pdfs/t/ACG_English_ESAP_Contractor_Control_Plans_Oil_Spill_Response__ Construction__Content_ACG_Phase_1_Oil-esponse_CCP.pdf. Azerbaijani; 2003. 3. Industry Technical Advisory Committee (ITAC) for Oil Spill Response. Technical Paper: Management of Volunteers in Spill Response. Southampton, UK; 2006.

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4. International Petroleum Industry Environmental Conservation Association (IPIECA). IPIECA Report Series. Volume 11: Oil Spill Responder Safety Guide. London, United Kingdom; 2002. 5. Exxon Mobil Research and Engineering Company. Oil Spill Response Field Manual. Fairfax, VA: Exxon Mobil Research and Engineering Company; 2005. 6. Brown K. Safety First in Marine Spill Response. IOSC 2005, 19th Triennial International Oil Spill Conference. Miami Beach, FL; 2005. 7. United States Department of Labor, Occupational Safety & Health Administration: Training and Certification Procedures of Hazwoper, website: http://www.osha.gov/html/faq-hazwoper. html, Washington, DC; 1991. 8. United Steelworkers Training Guides to Industry, Resource Handout: Controlling Hazards, website: http://www.uswsafetyguide.org/Controlling%20Hazards.php, USA; 2009. 9. British Columbia, British Columbia Inland Oil Spill Response Plan, website: http://www.env. gov.bc.ca/eemp/resources/response/pdf/marine_oil_response_plan.pdf, British Columbia; 2007. 10. British Columbia, British Columbia Marine Oil Spill Response Plan, website: http://www. env.gov.bc.ca/eemp/resources/response/pdf/inland_oil_response_plan.pdf, British Columbia; 2007. 11. Department of Trade and Industry Energy Development Unit (DTI), Oil Spill Response Guidelines for the UK Offshore Oil Industry, website: http://www.og.dti.gov.uk/regulation/ guidance/environment/OPRCTrainingGuidance.pdf, United Kingdom; 2007.

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Part XII

Postassessment and Restoration

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Chapter 31

Natural Resource Damage Assessment Gary S. Mauseth and Heather Parker

Chapter Outline 31.1. 31.2. 31.3. 31.4.

Introduction Regulatory Regimes Objectives Making the Public Whole 31.5. Alternative Sites

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31.6. Use of Models 31.7. The Nrda Process in the United States Acronyms

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31.1. INTRODUCTION In a number of countries around the world, regulations are in place requiring that assessments of environmental injuries and appropriate restoration measures be carried out. It is important to note that the regulatory schemes discussed here are compensatory and not punitive in nature and objective. In most countries, legislation exists providing for criminal or punitive penalties to dissuade and punish the discharge of oil to global waters. Further, flag states and international organizations have developed regulations designed to minimize oil pollution. The oil and shipping industries have also implemented a range of measures to achieve the same goal. This chapter addresses the assessment of environmental injury and the determination of appropriate actions to restore the environment. Expeditious and equitable restoration benefits not only the responsible parties and governmental authorities, but most importantly, the impacted resources.

31.2. REGULATORY REGIMES The current regulatory programs in the United States are derived from the Comprehensive Environmental Responses, Compensation, and Liability Act of Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10031-0 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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1980 (CERCLA), and the Oil Pollution Act of 1990 (OPA). These laws and their associated regulations were enacted by Congress in an attempt to restore the environment to its original condition and to right the wrongs wrought by accidental events and the carelessness of those handling hydrocarbons on society’s behalf. Although potentially adversarial and litigious, the U.S. approach to Natural Resource Damage Assessment (NRDA) has become highly sophisticated in recent years and has moved away from monetary compensation toward focusing instead on restoration measures. The European Union has recently developed the Environmental Liability Directive (ELD), which has many commonalities with the OPA and CERCLA schemes, including the provision for recovery of diminished ecological services during the recovery process, known as interim lost use.1 The Directive affords preexisting treaties and agreements precedence while in force. The collective application of Fund Convention (FC) of 1992, the 1969 and 1992 Civil Liability Convention (CLC), and the 2001 Bunkers Convention will limit application of the ELD with respect to shipping casualties. The extent to which the Directive will be applied in the short term is, therefore, likely to be limited to discharges from shore-based facilities and terrestrial incidents. However, the waiver applied to the maritime conventions above is to be reviewed by the European Commission before the end of April 2014 on the basis of the experience of member states. The majority of the countries in the world are signatories to the international regime (Figure 31.1).* The international compensation regimedthat is, CLC, FC, and the 2003 Protocol to the FC, known as the Supplementary Fund (SF)d also provides compensation for the costs of measures intended to repair damage to the marine environment. While the “polluter pays” doctrine is embraced by the international regime and the owner of the spilling tanker is held strictly liable, the issue of who is at fault is deferred to an arena outside of the incident response. A number of fundamental differences between the U.S. regime under OPA and the approach incorporated within the international regime can be identified. The CLC/FC regime addresses compensation of victims and covers the reimbursement of costs incurred under the broad headings of preventive measures (incident response), property damage, economic loss, and environmental damage. The ship owner is strictly liable for the first tranche of compensation, up to the ship’s limit of liability, followed by the ‘92 Fund and subsequently the Supplementary Fund up to their limits of 203 million and 750 million International Monetary Fund (IMF) Special Drawing Rights (SDR), respectively.** The main compensatory differences between the international and the U.S. * Several countries have passed national legislation regarding oil spill restoration and compensation. Examples include Canada’s Ship-Source Oil Pollution Fund and the Republic of Korea’s Prevention of Marine Pollution Act. These countries also participate in the IOPC Fund agreements. **

Equivalent to US$306.7million and US$1,133 million, respectively, as of February 24, 2010.

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FIGURE 31.1 Geographical coverage of the international regime.

regimes can be encapsulated under the following headings: (1) objectives, (2) making the public whole, (3) differing interpretations of what is meant by restoration or reinstatement of damaged environments, (4) restoration of alternative sites, and (5) use of models.

31.3. OBJECTIVES OPA ‘90 is a legislative statute that (in part) requires the Responsible Party (RP) to remediate the spilled oil and compensate those economically injured for identifiable losses, and it further requires that “trustees”*** for natural resources ensure that injuries to natural resources are identified and damages compensated. Specifically, Section 1066 D.1 of the OPA states: Measure of DamagesdIn GeneraldThe measure of natural resource damages is a) The cost of restoring, rehabilitating, replacing, or acquiring the equivalent of, the damaged natural resources; b) The diminution in value of those natural resources pending restoration (known as interim lost use); plus c) The reasonable cost of assessing those damages.

By way of contrast, while OPA ’90 requires the RP to clean up the spill and compensate for ecological service losses, the international regime provides reimbursement to victims of oil pollution and for the costs of cleanup through ***

In the Unites States, trustees are federal, state, and local government agencies, as well as Native American tribes that are allocated the responsibility for managing specific natural resources on behalf of the public.

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a system of tiered international treaties. The first layer, CLC, is provided by the ship owner, while the second and third layers, FC and SF, are provided by receivers of oil cargoes (usually oil companies).

31.4. MAKING THE PUBLIC WHOLE A significant difference between the United States and international regimes is that one of the objectives of OPA ‘90 is to make “the environment and the public whole” such that the emphasis is on compensating the public for the loss of goods and services provided by the damaged environment. The international regime, on the other hand, follows the traditional insurance concept of placing claimants in the same economic position as they would have been had the incident not occurred. In the latter case, compensation for impairment of (injury to) the environment is limited to loss of profit from such impairment and costs of reasonable measures of reinstatement actually undertaken or to be undertaken. In the United States, following the publication of National Oceanic and Atmospheric Administration (NOAA’s) 1996 OPA regulations (61 Federal Register (FR) 500; January 5, 1996; 15 Code of Federal Regulations (CFR) Part 990), the emphasis has been very much on restoration. While for some time settlements were tied to monetary value, more recently settlements have been achieved where restoration measures agreed to by the trustees and RP are undertaken. In some cases, restoration measures may be implemented by vessel interests, or the RP, and the trustees may not necessarily know the costs of those measures. If the trustees and the RP cannot reach agreement on injuries or compensation, the trustees have the option to request funds from the Oil Spill Liability Trust Fund (OSTLF).2 The OSTLF was created by OPA and managed by the U.S. Coast Guard. The OSLTF may choose to seek compensation from the RP and/or file a legal claim for the compensation. Under the CLC/FC/SF regime the emphasis is also on restoration or reinstatement of the injured environment. With publication of the Fund’s Claims Manual 2005**** the interpretation of the international regime was elaborated to encourage governments to undertake studies to determine whether reinstatement measures would be appropriate. To date, however, there have not been any claims for reinstatement measures under the international regime, although such were mooted in the case of damaged mangroves following the 2006 SOLAR 1 incident in the Philippines. In an important debate within the ’92 Fund Assembly in October 2006, where all member states are represented, two significant principles were elucidated. The debate, while focused on criteria for the settlement of claims for the removal of oil from sunken wrecks, clarified that rather than being solely restricted to economic considerations, the Conventions were intended to cover measures taken for the protection of the marine environment. It was stated that ****

Subsequently updated by the 2008 edition; see http://www.iopcfund.org/publications.htm.

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where there was “a significant risk of causing substantial damage to the marine environment, even very high costs of a removal operation would normally not be considered disproportionate in relation to the potential environmental consequences.” On the other hand, the debate reinforced the regime’s determination “that the costs of operations undertaken for social or political reasons should not be recoverable under the Conventions.”3 In contrast to the international regime, one of the features of the U.S. regulations concerned with public restitution is the concept of compensation for being deprived of the use of goods and services provided by noneconomic resources. A specific example is lost recreational use due to beaches or recreational fisheries being closed. As noted above, in the international regime the closest that might be considered an admissible claim of this nature, for example, would be a claim for lost income from a national park as a result of reduced entrance fees, or car parking charges, whereas, the U.S. regulations include these losses as well as addressing the public’s loss of opportunity to enjoy a natural resource.

31.4.1. Injury Assessment The purpose of the Compensation Conventions and other regimes may be relatively straightforward, but the path through determination of what is injured may be long and tortuous. In a large or complex case, specifically targeted scientific studies are necessary to quantify environmental impact. The collection of data to evaluate lost resource “services” may be problematic due to the ephemeral nature of some evidence such as bird corpses and water chemistry as well as inaccessibility and adverse weather. The lack of background data robust enough to define prior conditions against which post-spill conditions can be compared is common. Even events in areas of large anthropogenic or other exogenous influences may have data sets that lack adequate site-specific baselines and can confound interpretation. In countries such as China, the will to conduct good science in the wake of pollution incidents is not matched by available resources or effective procedures, while in Europe and North America there is no such shortage.4 During the Exxon Valdez case, numerous large studies were conducted by both the trustees and the spiller. Many of these studies were redundant and resulted in controversial outcomes that supported a trend toward using science to support adversarial positions. This approach has been damaging and has hindered the development of amicable governmenteindustry partnerships.4 In the United States, the theme in the new millennium has become cooperation between the RP and the federal, state, and local government agencies designated as trustees for the natural resources injured by the incident. Federal regulations and guidelines were modified to require the trustees to invite the RP to cooperate in the assessment of injuries and the development of a plan to restore the resources.

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The foundation of the cooperative approach is collaborative development and conduct of the technical studies to quantify injury. The ultimate objective is to mutually develop data that expedite agreement on injury and implementation of restoration. An advantage to the RP is that redundant assessment studies for the RP and trustees are avoided as OPA requires the RP to reimburse the cost of the government’s studies, as well as its own. An additional advantage is that the RP has direct knowledge of trustee concerns and may have the opportunity to participate in focusing injury studies to address the research questions and in developing cost-effective restoration. While the trustees are required to invite the RP into a cooperative process, the best results generally arise from collaborative scientific endeavors. Participation of all parties in the process of study design, data interpretation, evaluation of additional data needs, and program modifications leads to better science and less divergence of opinion as to injury and restoration. The RP is invited to participate both technically and financially. If the RP wishes to participate, the terms of participation may, but will not always, be memorialized by a Memorandum of Understanding (MOU). The NOAA has posted examples of these documents on the Internet.5

31.4.2. Interpretation of Restoration or Reinstatement Restoration and reinstatement might be thought to be synonymous and are, in fact, often used interchangeably in the context of remediation of environmental damage. However, in the context of the U.S. and the international regimes, the interpretation of each is quite different. Guidance provided by the ‘92 Fund’s Claims Manual indicates that the reinstatement measures should have a realistic chance of significantly accelerating natural recovery without adverse consequences for other natural or economic resources and should be proportional to the extent and duration of the damage and the benefits likely to be achieved. The U.S. regulations also recognize natural recovery as a key mechanism for restoration, but introduce the concept of primary and compensatory restoration. Compensatory restoration is intended to compensate for “lost” or forgone environmental services during the period that the environment is undergoing recovery, whereas primary restoration refers to actions taken to restore or accelerate recovery and is equivalent to reinstatement under the international regime. Figure 31.2 represents the hypothetical case of a marsh that provides a variety of ecological services such as habitat for fish rearing, avian cover, prey production, and shoreline protection. The effects of primary restoration efforts taken to accelerate recovery such as oil removal, replanting or other measures to reduce the duration and magnitude of the lost services are indicated by the dotted curve. These lost services are represented by the hashed Area A, which are expressed in terms of lost acre-years of marsh. As

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Incident

HABITAT

(e.g. hectares of marsh)

100%

A

Recovery

Decrease in A due to accelerated restoration

TIME

(Years)

FIGURE 31.2 Primary restoration.

mentioned above, the U.S. law requires compensation for diminution of ecological services pending recovery or “interim lost use.” Therefore, Area A must be compensated in some manner. In this simplified illustration, the hypothetical creation of marsh services where none previously existed is considered in Figure 31.3. In this case, compensatory marsh is created prior to recovery of the impacted marsh, and the services generated take some time to reach maximum output. The extra element of restoration incorporated within the U.S. regulations, while easily understood conceptually, can lead to controversial outcomes in application. Once the scale of the restoration project is determined and the new habitat is established, it is logically expected to provide environmental services over some considerable time, stretching far into the future. This contrasts with the conceptual diagram in Figure 31.3, where the two areas A and B are equally balanced by creating the hectares of marsh necessary to provide the equivalent hectare-years. The restored services are “discounted” to account for the fact that the services provided by restoration are in the future, and because consumption in the present is deemed more valuable by society than in the future. Discounting, typically at 3% per annum, also allows services provided at different times to be normalized so that comparisons can be made like with like. If the new habitat is appropriately constructed, it should substantially outlive the assumed 3% time

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Incident

Federal Discount Rate

B HABITAT (e.g. hectares of marsh)

100%

A

Recovery

Compensatory Restoration Complete

Decreased in B by Federal Discount Rate

TIME

(Years)

FIGURE 31.3 Habitat Equivalency Analysis compensatory restoration beyond the pre-spill baseline.

horizon; thus, it is likely to more than replace the lost services, and hence the potential controversy over the approach. The mechanism widely used to assess the amount of restoration required is termed Habitat Equivalency Analysis (HEA).6 The nuances of the HEA model will be discussed below. For instance, the restoration measures may not be effective. In the example above, the new marsh plants may not grow successfully or may be destroyed before reaching their full potential by some natural event, such as a storm. In order to protect against such eventualities, trustees will usually require provisions for (1) monitoring the effectiveness of the restoration measures and (2) reopening restoration efforts should the initial measures fail either through unsuccessful growth or damage due to natural phenomena. As mentioned above, the international regime has no experience of reinstatement measures (as of this writing), but in due course such claims are anticipated since they are provided for under the Conventions. When such claims are presented, they will most probably include costs for monitoring, although concerns over the need for reopening could well lead to further legal debate under the international regime. Claims for the potential costs of further reinstatement measures should the project fail might be considered speculative future costs. Subsequent claims for additional reinstatement measures in the event of such a failure might perhaps also be restricted by time constraints incorporated within the Conventions; that is, claims need court protection within three years of the incident and are extinguished if claims are not brought within six years.

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31.5. ALTERNATIVE SITES Under the U.S. regulations, the use of alternative sites is an essential consequence of the concept of compensatory restoration. Often the most appropriate mechanism for primary restoration is deemed to be natural recovery, but then restoration of another site may be required to provide compensatory restoration while the damaged site recovers. According to the ‘92 Fund’s Claims Manual, “reinstatement measures taken at some distance from, but still within the general vicinity of, the damaged area may be acceptable under the international regime, so long as it can be demonstrated that they would actually enhance the recovery of the damaged components of the environment.”3 This guidance would seem to exclude some approaches accepted in the United States where different habitats can be held equivalent to the damaged habitat. They may not have any bearing on the recovery of the damaged resource itself, but rather replace the services that the damaged habitat would have provided. Often, it is not possible to restore some injured resources in place. For example, seabirds may be suffering mortalities while oil is floating in their foraging areas offshore. Once oil has been removed from the sea surface, U.S. law requires efforts to restore impacted populations to pre-spill levels. A typical approach to restoring these populations is to alter factors that limit the preexisting population, such as breeding habitat or nesting area predators. One illustration of this principle is provided by the extermination of rats from Langara Island in an effort to restore seabird populations following a spill off Vancouver Island, British Columbia.7 Rats were responsible for a significant decline in the population of ground-nesting seabirds. The restoration measure resulted in some collateral damage in the mortality of other bird species as a result of them either eating poisoned bait or scavenging dead rats. Although Canada was a signatory to the CLC and FC at the time, this restoration was not undertaken under the international regime but as a result of litigation in the United States from where the spill originated. An approach that has been followed in several U.S. projects is the intent to restore migratory bird losses by the purchase of land some distance from the spill site (perhaps even in a different country), to protect the birds’ breeding grounds. By managing the land, trustees anticipate that development of the land and disturbance of the birds can be prevented, thereby improving breeding success. It is open to question whether such a claim presented under the international regime would be found admissible. According to the Claims Manual guidance, it is questionable whether the purchase of distant lands would be considered as meeting the provision “within the general vicinity of the damaged area,” although such an approach may well have a reasonable chance of success in “actually enhancing the recovery of the damaged components of the environment.” An entirely different approach has been accepted in one incident within the U.S. jurisdiction involving damage to coral rather than oil pollution, in which

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the restoration measures accepted were the placement of buoys to better mark the reef and so avoid future groundings. If similar measures were to be proposed under the international regime for pollution damage by oil, admissibility would certainly be queried but might not be discounted.

31.6. USE OF MODELS Simple models to calculate monetary recompense for environmental damage have been adopted by a number of countries, including some members of the CLC/FC regime. Although the calculations follow a number of variations on a general theme, the main input parameter is the quantity of oil spilled leading to a monetary valuation per unit volume, for example, US$/liter. Other factors that are sometimes included in the calculation include the type of oil spilled and the sensitivity of the affected habitat. Arbitrary values are assigned to these characteristics and applied as multipliers, This approach has the advantage of reaching quick settlements and minimizing transaction costs, such as prolonged biological studies to determine the extent of damage, but bears no relation to any environmental damage suffered. It does, however, overcome the difficulty of translating the outcome of such studies into monetary value. While this and similar approaches might provide a practical solution for small spills, in the case of substantial incidents, the quantum of the claims produced quickly becomes disproportionate to both the damage suffered and transaction costs. In both the Russian Federation and some of the ex-Soviet States, notably Ukraine, versions of the Soviet-era “Metodika” are retained in national legislation. The Ukrainian regulations may provide the simplest expression of the approachdwhere compensation for environmental damage and losses flowing from that damage are calculated as US$329/kg of oil spilled into the sea. It was the application of the Metodika in one of the earliest cases to be dealt with under the ’71 Fund Convention (the forerunner to ’92 FC) that prompted the rejection of models in the international regime. One of the very first resolutions adopted by the International Oil Pollution Compensation (IOPC) Fund Assembly in October 1980 stated that “the assessment of compensation to be paid by the IOPC Fund is not to be made on the basis of an abstract quantification of damage calculated in accordance with theoretical models.” More complex computer models have been developed over the years to determine environmental injury resulting from oil spills. OPA ’90 allows the use of such models if they are reliable and “state of the art.” However, demonstrating reliability is difficult, as little data have been obtained that allow the models to be verified against actual outcomes. Such models would not meet the admissibility criteria of the international regime. The difficulties that such models face in reflecting the true effects of oil pollution damage can be illustrated by considering the enormous range of factors that influence modeled estimates of injury. First are the physical and chemical characteristics of the spilled substance and the physical

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characteristics of the receiving environment. These are important in terms of oil weathering, based on meteorological conditions at the time of the spill. Second, identification and quantification of biological species that are actually exposed to the pollutant are additional factors to be considered. Finally, the toxicity of the material to those identified species has to be modeled taking into account the differing tolerances of the affected species to the various components of oil and their dilution within the marine environment. Given these difficulties, it might be anticipated that the preferred strategy would be to measure the actual impact of an incident through environmental field studies. However, these models tend to be used when actual data on the effects of the spill are unavailabledfor example, when ephemeral data immediately following an incident has not been collected or when such studies are deemed unlikely to capture the full range of injuries flowing from the incident. Under the U.S. regulations, trustees routinely use models to scale adequate and proportional restoration measures. The technique most frequently used to calculate the amount of habitat necessary to compensate for interim lost use is HEA. The implicit assumption of HEA is that the public is willing to accept a trade-off between a unit of lost services from a damaged resource in exchange for an equivalent unit of services provided by the restored habitat. A key feature of the technique is the selection of a common metric that applies to both the damaged and restored resource, recalling that these are likely to be different. For example, compensatory restoration for bird loss might be achieved under the U.S. regulations by restoration of marsh habitat if that were likely to promote recovery of the particular bird population through the provision of enhanced foraging opportunities. For this, a metricda parameter common to both the lost birds and the restored marshdneeds to be selected in order to determine the scale of the restoration project. In the example above, the metric might be the typical foraging area for the particular bird species. However, it is important to note that since the technique relies on this metric, a single common parameter linking the damaged and restored resources, the outcome can be very sensitive to the metric chosen. An alternative metric for the example above might be the area required for breeding pairs. It is highly likely that the outcome of the analysis using these two metrics would be quite different. In the absence of experience under the international regime, it is less clear whether use of HEA or some similar approach would be admissible. Although the HEA method has been developed to a very sophisticated level, the International Maritime Organization (IMO) and United Nationals Environmental Program (UNEP) have determined that the underlying concepts are unacceptable under the international regime.8

31.7. THE NRDA PROCESS IN THE UNITED STATES The current Department of the Interior (DOI) NRDA process used for hazardous waste sites (and prior to the implementation of OPA NRDA regulations in 1996

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for oil spill natural resource damage claims) is defined in regulations (43 CFR Part 11) developed by the DOI to meet the statutory requirements of CERCLA. In January 1996, NOAA published final regulations for use on oil spill natural resource damage claims, thus implementing the requirements of OPA (61 Federal Register (FR) 500; January 5, 1996; 15 CFR Part 990). NOAA also produced a series of OPA guidance documents explaining how to interpret these regulations.9 The NOAA damage assessment regulations replaced the DOI regulations only for those incidents involving oil spills to navigable waters.

31.7.1. DOI CERCLA NRDA Regulations The DOI regulations (Rule; 43 CFR Part 11) include several fundamental concepts that dictate the requirements and procedures to be followed in conducting an NRDA. These concepts are listed here because they are important to understanding the NRDA process: l l l

l l

l

l

Damages are for injuries residual to response or remedial actions. Damages are compensatory, not punitive. The public and responsible parties are involved in the process through notice, review, and comment. Recovered damages must be used for restoration. The rebuttable presumption (the plaintiff is considered correct unless sufficient data are provided to refute the plaintiff’s data) is an important element of decision making. Use of the regulations is optional; trustees do not have to follow the regulations or implement an NRDA. Emergency restoration is a temporary action designed to avoid or minimize injury.

Both the DOI and NOAA NRDA regulations involve a step-by-step process beginning with notification of the incident and culminating with the implementation of restoration actions (Table 31.1). The order in which the process is implemented is not rigid and is influenced partially by the nature of the particular release and circumstances. The process consists of three phases as briefly discussed in the following: I. Preassessment PhasedIn the Preassessment Phase, the trustee(s) receive formal notification from the Environmental Protection Agency or the U.S. Coast Guard of a release of hazardous substances or discharge of oil. The trustee(s) gather relevant information on the discharge or release and determine whether there have been actual injuries to trust resources or whether there is a potential for injuries to occur. A determination is also made on the probability of a successful damage claim. II. Assessment Plan PhasedIn this phase, under the DOI NRDA regulations, the assessment procedure to be used, Type A or Type B, is determined and an assessment plan is developed for coordination and communication

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requirements. The plan must provide for confirmation that at least one trust resource has been exposed to the oil or toxic substance. The economic methodology for damage determination is also identified. Type A assessments involve the use of the Natural Resource Damage Assessment Model for Coastal and Marine Environments (NRDAM/ CME). This computer model consists of three submodels: the physical fate, biological effect, and economic damages. The model (1) determines injury, as determined through the interaction of physical fates and biological effects submodels; (2) quantifies injury through the biological effects submodel; and (3) calculates damages through the economic damages submodel. Minimal empirical scientific studies may be conducted to document or supplement model input and findings. The DOI has also proposed a Type A model for Great Lakes Environments (NRDAM/GLE). Type B assessments involve the implementation of specific scientific studies to document and quantify injury. A pathway link must be established to document that the resource injury was caused by the release or discharge of concern. The injury and associated baseline services must be quantified and the resulting damages calculated. III. Postassessment PhasedA “Report of Assessment” is produced in this phase, which describes and presents all decisions and scientific and economic methods and information used in the assessment. A demand for damages is prepared and presented to the RP. A restoration plan is prepared, and a restoration financial account is established. Several important provisions of CERCLA govern the damage assessment and restoration process. Again, these provisions strongly influence the flexibilities and limitations of the DOI Rule: l

l

l

l

l

Trustees can recover the cost of assessment in addition to natural resource damages. Recovered damages must be used by trustees for the restoration, rehabilitation, replacement, or acquisition of the injured natural resource. Regulations specify that injury is for a measurable adverse change in the chemical, physical quality, or viability of a natural resource. Assessments conducted in conformance with the regulations are afforded the effect of a rebuttable presumption in an administrative or judicial proceeding. Regulations allow for negotiated settlements and require trustee notification since a covenant not to sue must include a written agreement by the trustees.

31.7.2. NOAA NRDA Regulations The damage assessment regulations issued by NOAA in January 1996 (61 FR 500; January 5, 1996; 15 CFR Part 990) to implement OPA are similar to

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the DOI regulations for CERCLA (Table 31.1). However, there are a few important differences that merit brief discussion. General differences include the promotion of pre-spill planning, the determination of the assessment approach in the Preassessment Phase, and the use of additional assessment methods by the trustee. There are also some specific and critical procedural and technical differences. Injury under the NOAA Rule is defined as “any adverse change in a natural resource, or any impairment of a human or ecological service provided by a resource.” This is a much more liberal definition than the DOI definition, which requires that a “measurable” adverse change be identified. The effect is that liability is more easily established under OPA as long as compensation can be quantified and is adequate to account for the injury.

TABLE 31.1 Comparison between CERCLA and OPA NRDA Processes (43 CFR Part 11; 15 CFR Part 990). CERCLA

OPA I. Pre-spill A. Pre-spill Planning B. Trustee Coordination

I. A. B. C.

Preassessment Phase Preassessment Screen Data Collection & Sampling Preassessment Screen Determination

II. Preassessment Phase A. Determination of Jurisdiction B. Determination to Conduct Restoration Planning C. Data Collection D. Notice of Intent D. Administrative Record

II. Assessment Phase A. Coordination B. Notification C. Planning D. Decision on Type of Assessment 1. Type A or Type B E. Assessment 1. Injury Determination 2. Injury Quantification 3. Damage Determination

III. Restoration Planning Phase A. Injury Assessment 1. Determination 2. Quantification B. Restoration Selection 1. Developing Alternatives 2. Evaluations of Alternatives 3. Developing Restoration Plans 4. Restoration Selection

III. A. B. C. D.

IV. A. B. C. D. E.

Post-Assessment Phase Report of Assessment v Demand Restoration Account Restoration Plan

Restoration Implementation Phase Administrative Record Presenting a Demand Discounting and Compounding Unsatisfied Demands Opening an Account for Recovered Damages F. Additional Considerations

Chapter | 31 Natural Resource Damage Assessment

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Additional assessment methods, not available under CERCLA, which are identified in the NOAA Rule, are the Compensation Formula and Expedited Damage Assessment approaches. The NOAA Rule requires the development of an administrative record for all NRDAs, which will serve as the primary mechanism for public review and comment. A Damage Assessment and Restoration Plan (DARP) must be prepared, become part of the record, and be made available to the public and RP for review and comment. Some of the procedural differences between hazardous waste site and oil spill NRDAs can significantly influence the quality of science conducted and nature of damage claims. The most significant factor is the amount of time in which interested parties have to conduct their respective roles in the incident investigation and damage assessment. While the restricted amount of time can compromise the process and quality of the NRDA outcome for oil spills, a more liberal amount of time for hazardous waste site NRDAs presents a better opportunity to conduct science with fewer constraints and reach more reliable and relevant conclusions.

ACRONYMS CERCLA: CLC: DARP: ELD: FC: HEA: IOPC Funds: MOU: NOAA: NPFC: NRDA: NRDAM/CME: NRDAM/GLE: OPA: OSLTF: RP: SF:

Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (US) Civil Liability Convention (International) Damage Assessment and Restoration Plan Environmental Liability Directive (EU) 1992 Fund Convention (International) Habitat Equivalency Analysis International Oil Pollution Compensation Funds (International) Memorandum of Understanding National Oceanic and Atmospheric Administration (US) Pollution Fund Center (US) Natural Resource Damage Assessment (US) Natural Resource Damage Assessment Model for Coastal and Marine Environments Natural Resource Damage Assessment Model for Great Lakes Environments Oil Pollution Act of 1990 (US) Oil Spill Liability Trust Fund (US) Responsible Party (US) 2003 Protocol to the FC, known as the Supplementary Fund (International)

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REFERENCES 1. Official Journal of the European Union. Directive 2004/35/CE of the European Parliament and of the Council of 21 April 2004 on Environmental Liability with Regard to the Prevention and Remedying of Environmental Damage. OJ L 2004;143(56). 2. National Pollution Funds Center (NPFC), United States Coast Guard (USCG) Internet site at http://www.uscg.mil/npfc; July 2010. 3. International Oil Pollution Compensation (IOPC) Funds, Obtained at Internet site at http:// www.iopcfund.org; July 2010. 4. Moller, T. Integration of Scientific Perspectives into the Application of Maritime Law. The 31st Pacem In Maribus Conference, Australia: Townsville; 2005. 5. NOAA Damage Assessment, Remediation, and Restoration Program (DARRP), Examples of Co-Trustee and Trustee-RP Agreements, Obtained at Internet site at http://www.darrp.noaa.gov/ library/pdf/PPD_AP-D.PDF. 6. NOAA. Habitat Equivalency Analysis: An Overview, NOAA DARRP, Obtained at internet site at http://www.darrp.noaa.gov/economics; July 2010. 7. Kaiser GW, Taylor RH, Buck PD, Elliott JE, Howald GR, Drever MC. The Langara Island Seabird Habitat Recovery Project: Eradication of Norway Ratsd1993e1997. Technical Report Series No. 304. Canadian Wildlife Service, Pacific and Yukon Region, British Columbia. Delta: BC; 1997. 8. IMO/UNEP. Guidance Manual on the Assessment and Restoration of Environmental Damage Following Marine Oil Spills. London, UK: IMO; 2009. 9. NOAA Damage Assessment, Remediation, and Restoration Program (DARRP). OPA guidance. NOAA DARRP. Obtained at Internet site at http://www.darrp.noaa.gov/library/1_d.html; 2010.

Chapter 32

Seafood Safety and Oil Spills Greg Challenger and Gary Mauseth

Chapter Outline 32.1. Introduction 1083 32.2. Seafood Exposure 1085 to Oil 32.3. Spill Response and 1087 Seafood Safety Management 32.4. Seafood Safety 1090 Assessment: Reopening a Closed Fishery

32.5. Chemical Analytical Evaluation 32.6. Seafood Sensory Evaluation 32.7. Trends in Lifting Fishery Bans 32.8. Long-Term Implications of Oil Spills on Seafood

1090 1092 1096 1098

32.1. INTRODUCTION The viability of marine fisheries is of economic, human health, and ecological importance to a wide sector of the world’s population. Oil spills can result in real and perceived effects to commercial, subsistence, and recreational fisheries. Concerns are often centered primarily on health risk to consumers and, secondarily on the tainting of marketable seafood products with a foreign odor or flavor. Economic impacts associated with product marketability and consumer confidence may occur even in the absence of health risk or taint. Commercial fish and shellfish stocks are under increasing management scrutiny for seafood safety and environmental health, partly due to increasing public awareness of environmental health issues. Figures 32.1 and 32.2 illustrate typical seafood images. Managers need to be certain that there are no demonstrable health risks prior to reopening harvest. This priority is shared by those responsible as it might relate to long-term liability. Responsible individuals also share the desire to ensure that there is no loss in market confidence so that fishers and mariculture operations can resume work as soon as possible. This chapter presents oil spill and seafood exposure scenarios, response options, and fishery advisory/closure considerations. Human health and Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10032-2 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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FIGURE 32.1 Typical crab traps.

FIGURE 32.2 A fishing fleet in harbor.

Chapter | 32 Seafood Safety and Oil Spills

1085

product marketability assessment techniques are also presented, with recent case studies as examples.

32.2. SEAFOOD EXPOSURE TO OIL A substantial portion of the world’s fishing industry shares its home ports with numerous other industries; hence, fishery or mariculture infrastructure is often in the path of accidental oil spills. The potential for direct effects of oil on shellfish, finfish, and fishery gear exists in most significant oil spills. The magnitude and extent of effect of an oil spill on fisheries depends on the nature of the oil, oceanographic conditions, interactions with biota and their habitat preferences, feeding behavior, and differing uptake and physiological responses of the numerous groups of seafood organisms. The nature of oil spilled and the physical and chemical properties that change over time, collectively called weathering, will also affect the exposure and impact of an oil spill. Weathering processes have been addressed thoroughly in other chapters of this handbook. The main initial processes that dictate the potential for seafood exposure include evaporation, dispersion into the water column, and, to a lesser degree, sedimentation.1 Crude oils and refined products may contain hundreds or thousands of different carbon-based molecules that also contain hydrogen, nitrogen, oxygen, sulphur, and trace metals. The prevalence of various hydrocarbon compounds contributes to oil properties in the environment. Three main groups of hydrocarbon compounds in oil are saturates, aromatics, and polar compounds. The aromatics include monocyclic compounds (BTEX) and polycyclic aromatic hydrocarbons (PAHs) and typically have higher evaporation rates, water solubility, and toxicity than other compounds in oil. Monocyclic aromatics in particular have higher evaporation rates, solubility, and toxicity than other aromatics. In general, the higher-molecular-weight PAHs have lower solubility and less acute toxicity, but have higher chronic toxicity. Saturates (alkanes and waxes) have low solubility and low toxicity by comparison. Saturates are also more rapidly degraded by biological activity and are not believed to contribute to seafood tainting.2 The polar compounds (resins and asphaltenes) are large molecules with low water solubility and lower acute toxicity. The general groups of oils that have similar characteristic composition of hydrocarbon compounds are: l

Gasoline, diesel-like products, and light crude oilsdThese oils have a low specific gravity, high rate of spreading, and a high percentage of aromatics that can evaporate with little or no residue remaining. They present a substantial risk of seafood contamination due to high rates of natural dispersion and water solubility. The main seafood exposure is uptake of water-soluble components via gills and ingestion or absorption of bioavailable dispersed droplets.

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l

l

l

PART | XII

Postassessment and Restoration

Medium crude and fuel oilsdMedium crude oils still have a significant aromatic hydrocarbon component and can persist longer than lighter oils. They present a moderate to high risk of seafood contamination due to both dispersion and persistence. Heavy crude and fuel oilsdThese oils have high specific gravity and very little product loss due to evaporation. They present a low risk to finfish and subtidal organisms because they typically float and have low water solubility. They present a fouling and toxicity risk to intertidal shellfish. Nonfloating oilsdThese oils have a very high molecular weight and will sink in fresh water. They present a low risk of finfish contamination but can become a chronic source of exposure for benthic organisms.

Seafood may be exposed to oil as dissolved hydrocarbons (wateraccommodated fraction), dispersed oil droplets in the water column, whole oil in the intertidal zone, or subtidal sediments. Exposure to the water-accommodated fraction in an oil spill is typically short-lived due to water and biota movement. Uptake is rapid as is elimination or depuration, although there is considerable variation by species. Exposure to particulate oil or dispersed oil droplets in the water column also results in short exposure times, but exposure concentrations may be higher than if the dissolved fraction alone was present. Elimination times may also be longer due to the presence of whole oil PAHs with higher molecular weights. Exposure to contaminated sediments or suspended sediments in the water column may occur to filter feeders. Elimination will be slowed by ongoing pollution and by multiple re-suspension events of oiled sediment with high-molecular-weight PAHs. Oiled intertidal and subtidal sediments also present possible pathways of ingestion to deposit feeders (bivalves) and sediment and detrital grazers (shrimp, gastropods, and crustaceans). Pore water in the intertidal zone may also contain dissolved PAHs. Finfish, free-swimming squid and shrimp, and other organisms in the open ocean do not typically become exposed to sufficient oil to result in tainting or health concerns.1,3-5 Oil concentrations and duration of exposure in open water are typically very limited. Exceptions may include very large releases of products with high aromatic content and/or high dispersion into the water column (e.g., the North Cape and Braer oil spills). Finfish in offshore or nearshore pens may be more susceptible to oil exposure since it is dictated by the oil in water alone. The greatest impact to fisheries is frequently in the intertidal zone and very shallow nearshore where biota may be physically coated or smothered in oil and are more likely to ingest whole oil. The intertidal zone supports fisheries for numerous crustacea; bivalves such as oysters, clams, and mussels; echinoderms; and edible seaweeds. In addition to direct exposure to whole oil and ingestion, oil may inhibit physiological and reproductive function for juveniles of a broad array of species, including offshore species that utilize the intertidal zone during early stages of their life cycle. Other ecological factors influence uptake and elimination or depuration of hydrocarbons in

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1087

seafood. Rate of water filtering in gills plays an important role in biocentration, or accumulation as a result of direct uptake of dissolved oil in water. Dissolved oil signatures are distinct from whole oil, and both have been observed in seafood. Whole oil signatures of diesel fuel have been observed in salmon in a freshwater river with high turbulence and dispersion.6 Some fish and bivalves filter large volumes of water and are often used as indicators of pollution due to their ability to bioconcentrate the oil by a factor of up to 100,000 times or more for some PAHs.7 While finfish can uptake PAHs rapidly due to high ventilatory rates in gills, they typically do not bioaccumulate as much as bivalves and eliminate PAHs faster due to their increased metabolic capacity.8 Metabolic capacity differences in organisms result in some finfish reported to depurate in one month or less, with crustaceans slightly slower, ranging from a few weeks to a few months and bivalves typically depurating the slowest, ranging from several weeks to up to a year in severe cases such as the Exxon Valdez.5 Water temperature can also affect uptake and elimination of PAH with a varying range of optimal values for different organisms. In general, colder water slows metabolic activity and uptake and depuration of PAH. Reproductive and seasonal changes in body lipids, carbohydrates, and protein levels can also affect uptake and elimination of PAH. Organisms with higher lipid content tend to accumulate more tissue PAH due to the oleophilic nature of lipids.2,9 Oysters and clams may uptake two to three times more PAH when at the high point of lipid reserves during spawning cycles.10

32.3. SPILL RESPONSE AND SEAFOOD SAFETY MANAGEMENT The differences in exposure potential under differing oil behavior, biological receptor physiology, and fishery operations dictate the importance of local knowledge of fisheries as part of regional spill response plans. Since most seafood impacts occur in intertidal zones, on-water recovery of oil can reduce seafood exposure dramatically. However, on-water recovery rarely prevents shoreline impacts, and areas of high seafood density may be at risk. In many regions, mariculture operations have historically not been included in habitat sensitivity mapping as they are not considered a natural resource by the regulatory authorities. Responders need to be aware of potential mariculture areas that may not be included in regional response plans and weigh the priorities of protection accordingly. Oil booms, physical barriers, and sorbent material can contain, deflect, or absorb oil, but it is rarely possible to prevent some exposure. Dispersants may increase exposure and tainting and should not be used if there is a risk of seafood contact with water column and dispersed oil droplets.1 In cases where circulated seawater is drawn in from the environment for either shoreside mariculture facilities or vessel circulation systems, shortterm halting of circulation may prevent exposure. Time limits to these activities are dependent on the tolerance of the species being protected from buildup of

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wastes or anoxic conditions. Sorbent filters may also be placed in filter systems to continue operations, as was done aboard fishing vessels during the 2004 Selendang Ayu spill in Alaska and in mariculture facilities during the 2002 Prestige oil spill off the coast of Spain and 1999 Erika oil spill off northern France. Shoreline cleanup and remediation techniques should be considered carefully in intertidal seafood and mariculture areas. Most cleanup methods cause damage themselves, and the benefits of removing the oil should be weighed against the costs of the effects. High activity of personnel or equipment in soft intertidal sediments where many bivalve and seaweed culture operations exist have been found to result in significantly greater oil persistence than if left to recover naturally.11 Techniques should be selected for their ability to remove oil without disturbance to fine sediments. During the response, managers must also act quickly to make determinations regarding the necessity of public health announcements or communication of risk. Yender et al. provide a guide for fishery managers, public health officials, and regulators following oil spills (Figure 32.3).5 The communication of risk lies with the local or regional public health authorities, although those responsible share concerns based on their potential short-term and long-term liability. There are numerous ways to communicate risks, including advisories, guidance to the fishing industry, and fishery closures. Fishery closures can be imposed to prevent the oiling of fishery gear or as a precautionary measure intended to protect public health. However, a fishery closure by regulatory authorities often occurs immediately following a spill, with minimal information available as opposed to after an evaluation as suggested by Yender et al. (Figure 32.3).5 In several past incidents involving formal closures, the regional regulatory authorities defined closure areas based on anecdotal visual observations of oil exposure or the predicted exposure pathways rather than actual verified exposure. Once a fishery is closed, it can be difficult to evaluate the seafood safety in order to lift bans on harvest. Most regions do not offer guidance for evaluating seafood safety following oil spills. The time needed to prepare an evaluation and develop criteria in regions with no PAH assessment standards can lead to substantial market losses. If no fishery ban is imposed until an assessment is conducted, it may require several weeks or months to conduct proper analytical chemical analyses and sensory testing of potentially exposed seafood when harvesting may be occurring in the interim. Other options to protect seafood may include voluntary harvest restrictions pending analyses or oil spill operational closures to fishing and recreational vessels during an active response. Operational closures can be instituted by the local regional authority, such as the Navy or Coast Guard, overseeing the oil spill. The risk communication decision must consider the balance between an unnecessary closure that can have market impacts and foregoing restrictions that could result in tainted product on the market or human health risks. Prudent decisions to close and

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FIGURE 32.3 Decision process for managing seafood safety after an oil spill.5

reopen fisheries should be based on the best available information regarding the fate and effects of spilled oil, resource vulnerability and sensitivity, sensory testing methods, and the experience base gleaned from prior incidents. Management strategies often reflect cultural differences. In Asia there were few reported instances of formal closures, seafood tainting, or contamination before the 2007 Hebrei Spirit oil spill in Korea.1 Asian nations had in the past favored voluntary bans on fishing activity until gross oil removal was complete.1 In North America and Europe, advisories and closures in conjunction with

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chemical analytical and sensory analyses are more common and are likely to become the normal process for other regions.

32.4. SEAFOOD SAFETY ASSESSMENT: REOPENING A CLOSED FISHERY Closing a fishery may be a reasonable precautionary measure in an oil spill, but when confronted with the task of reopening a closed fishery, multiple protocols may be required. These protocols could be operational, sensory evaluation, chemical evaluation, or a combination of all three. Operational protocols typically include the removal of the oil source from the closure area or the absence of oil on the water or shorelines in the closure area. Sensory evaluation may require the specific seafood involved in the closure to pass certain olfactory testing criteria. Chemical evaluation may require PAH concentrations in water or sediment, and/or Benzo[a]pyrene (BaP) equivalents in tissue samples to fall below a certain criteria, or a return to pre-spill or spatial control baseline levels of PAH.

32.5. CHEMICAL ANALYTICAL EVALUATION Several types of chemical analytical analyses may guide health authorities and fisheries managers: sampling the environment during the oil spill in fishery areas, direct analysis of seafood tissues potentially exposed, or a combination of both. Risk-based PAH criteria are available in some regions for water, sediment, and tissues, although risk-based tissue criteria are often spill specific owing to differences in consumption rates or background PAH levels. In some instances, including recent spills in Canada and Europe, baseline levels were used as a guide to evaluate fisheries. Figures 32.4 and 32.5 show seafood being analyzed. Risk-based evaluation of the seafood tissue body burden of certain PAHs has been used most extensively in the United States. Potential carcinogens in oil include numerous PAH compounds with varying potency (Table 32.1). Carcinogenic risks of multiple PAHs are evaluated by weighting the relative potency of each chemical to that of a known carcinogen, benzo[a]pyrene (BaP). Concentrations of known carcinogens are expressed collectively as BaP equivalents. BaP equivalents are quantified in a sample by measuring tissue PAH using gas chromatography/mass spectrometry (GC/MS) methods and applying the relative weighting or potency factors for each suspected carcinogen and summing the results. Tolerable contaminant levels are developed using the cancer potency of BaP, body weight, and life span of consuming individuals, exposure duration, consumption rate, and an “acceptable risk” or probability of obtaining cancer. Body weight and life span of 70 kg and 70 years have been regularly used in past cases.3 A risk of cancer of 1 in one million (10-6) is often used; however, a risk of 1 in 100,000 was applied in

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FIGURE 32.4 A Steelhead sampled for subsequent analysis.

areas with background contamination in the T/B North Cape spill and in San Francisco Bay after the Cosco Busan oil spill in 2007, among others (Table 32.2).12 The risk factor is selected as acceptable for the public by the relevant health authorities and does not imply an actual relationship between the concentrations of BaP and cancer. The number of PAH compounds considered in calculating BaP equivalents, as well as the relative potency or weighting of some compounds, often differs on a case-by-case basis (Table 32.2). Other factors used in risk analyses have also differed in cases resulting in inconsistent determination and communication of human health risks in the United States. Analysis of oils for exotic compounds that do not occur in oil or are not found in meaningful quantities, such as herbicides, pesticides, Polychlorinated Biphenols (PCBs), heavy metals, and unusual PAHs not found in spilled oil, have occurred in past cases and as a result have delayed decisions.13 Selection of species to sample should be based on possible exposure pathways and on the likelihood of the species being harvested for consumption. Reference sample collection should preferably be collected before oil arrives in a location, but nearby locations or spatial reference samples usually have to suffice. Differing background conditions of reference and impact areas are often confounding when analyzing the specific sources of hydrocarbons in seafood. There are many combustion and natural sources of PAH in the environment. Since many fisheries share ports with industry, background PAH

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FIGURE 32.5 Inspection of crustacean feeding parts for oil.

contamination should be considered when developing risk criteria. Sampling tissue seafood in the presence of oil is not recommended and may affect the result. Sometimes it is unavoidable in intertidal communities. In these cases it is important to consider sampling techniques to avoid collecting oil and seafood, as well as instructions to the laboratory regarding careful washing and extraction of tissues without contacting potential oil on the shell or other outer surfaces. Marketability can also be affected by oil on the shell alone even if it is not found in tissues.

32.6. SEAFOOD SENSORY EVALUATION Since the specific petroleum constituents that can cause petroleum taint are relatively unknown, chemical analyses are not accurate indicators of the

Weighting Factors e Relative Potency Analyte

North Cape

Provence

Julie N

Kure

New Carissa

Selendang Ayu

Cosco Busan

Benzo[a]pyrene

1

1

1

1

1

1

1

Benzo[a]anthracene

0.014

0.014

0.1

0.1

0.014

0.1

0.1

Benzo[b]fluoranthene

0.1

0.1

0.11

0.1

0.1

Benzo[k]fluoranthene

0.01

0.1

0.07

0.1

0.1

0.01

0.01

0.013

0.01

0.01

Dibenzo[a,h]anthracene

1

0.36

1.05

1.0

0.36

Indeno[1,2,3-cd]pyrene

0.1

0.1

0.25

0.1

0.1

2.41

1.77

Chrysene

0.013

0.013

pyrene

0.13

0.13

0.13

fluoranthene

0.02

0.02

0.02

Benzo[g,h]perylene SUM

Chapter | 32 Seafood Safety and Oil Spills

TABLE 32.1 Comparison of Relative Weighting Factors for BAP Equivalent Calculations

0.03 1.177

1.177

2.32

1.77

2.687

1093

1094

TABLE 32.2 Comparison of Cancer Risk Variables in U.S. Oil Spills with Chemical Tissue Criteria Total Relative Potency of BAP Considered

Low BAP Safe Level (ppb)

T/B NORTH CAPE 1996

5

NA**

10-5

5

30

1.177

20

M/T PROVENCE 1996

5

NA**

10-6

5

30

1.177

20

M/V KURE 1997

7

9.5

10-6

2

50

1.77

5

M/T JULIE N 1999

5

NA**

10-6

NA**

NA**

2.32

16

M/V NEW CARISSA 1999

10

7.3

10-6

2

32.5

2.687

10

M/V SELENDANG AYU 2005

7

7.3

10-6

3

11.9

2.31/2.41 (2005/2006)

18.8

M/V COSCO BUSAN 2007

7

11.5

10-4

30

32.5

1.77

43.7

Spill

**Details on the risk criteria development are not available from the state.

Postassessment and Restoration

Exposure Upper Cancer Duration Consumption Risk (years) Rate (g/day)

PART | XII

Number of PAHs Cancer Considered for Potency of BAP BAP Analyses (mg/kg/day)

Chapter | 32 Seafood Safety and Oil Spills

1095

presence of taint, and sensory evaluation is the only effective way to determine whether seafood is tainted (Figure 32.6). Oil-tainted food has been found to be unpalatable at very low levels of tissue concentration. The International Maritime Organization (IMO) guidance suggests as a general rule, that if seafood is taint-free, it is safe to eat.1 This has been found to be true in every case we have encountered. Tainting of seafood due to oil spills has been evaluated in the United States, Scotland, England, Canada, Japan, South Korea, and other countries and can be among the most efficient methods for evaluating seafood safety. Tainting of seafood due to oiling has been subject to considerable research.14-23 Seafood tainting from petroleum is temporary, and the duration of taint depends on uptake and depuration rates of organisms, type of oil, exposure duration, and temperature.24 While a strong correlation between taint and PAH levels has been reported from specific spills, oil concentration is no guarantee that taint will be detected.3 Numerous oil spills have identified exposure in the absence of taint.5 Sensory guidelines have been written by The National Oceanic and Atmospheric Administration’s (NOAA’S) National Marine Fisheries Service in the United States and by Canada’s Food Inspection Agency that document methodology to objectively assess seafood for tainting (also termed adulteration).25 Collection, preservation, transport, quality control, and assessment methods are documented. The International

FIGURE 32.6 Examples of sensory evaluation of seafood.

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Organization for Standardization (IOS) also provides information on the training of sensory panels.26 Sensory testing consists of a blind assessment of a statistically valid subset of samples from the potentially affected fisheries conducted by a panel of trained experts. The tester is asked to record the presence or absence of petroleum-derived taint in raw and cooked seafood samples of unknown origin. Panel members have been shown to be two to three times more sensitive than the general public.27 The advantages of sensory testing include reduced time and effort to conduct tests and the apparent increased sensitivity to human olfaction to detect petroleum taint at levels below human health risk chemical criteria. Uncertainties include experience and sensitivity of panel members, ratio of taint positives among panel members that should constitute an unmarketable product for the general public, and source of taint failures. Several sensory tests at spills have resulted in taint failures among panel members for reasons other than the spill. In the North Cape, sensory testers were asked to reject a sample based on their evaluation of the presence of a No. 2 oil odor.28 In some cases, other factors such as mud, putrification, and fecal odor reduced the assessor’s ability to discriminate petroleum taint. While spillrelated tainting results in the continued closure of the fishery, background tainting may not (Table 32.3).

32.7. TRENDS IN LIFTING FISHERY BANS Past trends of increasing stringency of both chemical and sensory criteria have been observed in several cases, although several recent oil spills have avoided lengthy evaluation, suggesting lessons from previous spills and that increased guidance documentation for managers may have been effective. As a result of more sensitive chemical criteria, samples often fail for reasons other than an oil spill, rendering the seafood theoretically unharvestable. There is no evidence tht oil-induced cancers occur following spills or that human exposure to carcinogenic hydrocarbons is significantly increased even when tissue PAHs can temporarily increase 100-fold or more following oil spills.23 Chemical or sensory failures for reasons other than the oil spill, however, sometimes do not result in the continued closure of a fishery. The justification for opening the fishery and the delicate task of informing citizens that seafood has historically been safe rests with the government health departments. For this reason, sensory testing and comparison with spatial reference samples may become increasingly useful in assessing seafood safety. The stringent scrutiny applied to oil spills is seldom, if ever, applied to fisheries by authorities on a routine or systematic basis to evaluate the quality and safety of fisheries in the absence of a spill. Many of the areas where spills occur have been subject to anthropogenic contamination for decades. Legally harvestable species in the North Cape, Julie N, Kure, and New Carissa were found to approach or exceed rejection criteria in either chemical or sensory

Spill

Panel Size

Site Failure Criteria

Total Tests

Number of Individual Failures

Number of Site Failures

Background Failures Without Closures

Corresponding Chemical Criteria Failures

T/B NORTH CAPE

10

3 of 10

15,610

unknown

10

2

0*

M/T PROVENCE

2

1 of 2

30

0

0

0

0

M/T JULIE N

3

2 of 3

1,400

57

0

0

0

M/V KURE

5

unknown

1,725

1

1

1

0

M/V NEW CARISSA

5

1 of 3

<100

0

0

0

1**

SELENDANG AYU

unknown

unknown

10

0

0

0

0

COSCO BUSAN

3

unknown

18

0

0

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Chapter | 32 Seafood Safety and Oil Spills

TABLE 32.3 Comparison of Sensory Evaluation Following Spills

* Failure threshold raised for pre-existing contamination. **Chemical criteria failure unrelated to oil from the NEW CARISSA.

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criteria due to background contamination from pre-spill sources. Perceptions relating to the source of the contamination may have a greater influence on the viability of a fishery than the physical, chemical, and biological characteristics of the harvest. The development and implementation of criteria for closing and subsequently reopening a fishery would have many benefits. Authorities working to develop criteria should consider the extensive database from heavily scrutinized cases, as well as the strategies applied in recent oil spills, whereby lengthy closures and extensive sampling have been avoided. Closing a fishery may be a reasonable precautionary measure in an oil spill. However, when confronted with the task of reopening a closed fishery, careful review of spill response observations, the fate and effects of the spilled oil, existing literature, and past case studies is warranted to avoid potentially costly, contentious, and ultimately unnecessary restrictions. However, in the absence of recognized standards for oil spill seafood safety, the following concerns remain: 1. Increasing stringency of chemical criteria and source allocation of oil in environmental media and seafood tissues compared to background contamination. 2. Lack of standardization, which has led to a desire or need for states to develop independent criteria and to avoid unnecessary closures and delays in reopening fisheries. 3. Analysis of oils for exotic compounds that do not occur in oil, such as herbicides, pesticides, PCB, heavy metals, and 5-methylchrysene, has also delayed decisions. None of these compounds were identified in the source oil in any of these cases. 4. Expanded scope of sampling programs due to a desire to observe temporal comparisons with baseline samples even after all previous samples have passed criteria and the fishery is reopened.

32.8. LONG-TERM IMPLICATIONS OF OIL SPILLS ON SEAFOOD Seafood management after oil spills may include concerns of potential population effects due to the loss of adult marine organisms and/or effects to early developmental life stages. PAHs have been shown to result in biomarker activity that is indicative of exposure in many organisms, but population or habitat effects from biomarker activity among individuals have not been demonstrated. Also observed are sublethal developmental effects on individuals from PAH exposure; however, population effects on adults in the fishery have not been clearly demonstrated. The lack of reliable population data, variable fishing effort and catch data, and natural variation of seafood populations make it difficult to determine any long-term population effect. Population effects from the fishery closure itself can occur. Halting intensive

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fishing operations has effects on the distribution and abundance of seafood organisms as well as their predators and prey. Some fishery closures have been reported to result in benefits to exploited fish stocks due to reduced predation by man.1 Many regions require restoration for losses caused by oil spills, including commercially important species. Interactions between restoration actions and potential harvest losses should be considered under compensation regimes to fishermen for business interruption.

REFERENCES 1. International Maritime Organization. IMO/FAO Guidance on Managing Seafood Safety During and After Oil Spills. London: IMO Publication 1590E; 2002. 2. Heras H, Ackman RG, MacPherson EJ. Tainting of Atlantic Salmon (Salmo solar) by Petroleum Hydrocarbons Using Short Term Exposure. Mar Pollut Bull 1992;310. 3. Law RJ, Hellou J. Contamination of Fish and Shellfish Following Oil Spill Incidents. Environ Geosci 1999;90. 4. Mauseth GS, Challenger GE. Trends in Rescinding Seafood Harvest Closures Following Oil Spills. IOSC; 2001. 5. Yender R, Michel J, Lord C. Managing Seafood Safety After an Oil Spill, Seattle: Hazardous Materials Response Division, Office of Response and Restoration, National Oceanic and Atmospheric Administration. http://response.restoration.noaa.gov; 2002. 6. Challenger GE. Uptake and Depuration of Polycyclic Aromatic Hydrocarbons in Steelhead Trout (Oncorhychus mykiss), Chinook Salmon (Oncorhychus tshawytshca), Mountain Whitefish (Prosopium williamsoni), and Sucker (Catostomus sp.) in the Clearwater River Idaho Following a Diesel No. 2 Fuel Spill. AMOP 2004:167. 7. Neff JM. Bioaccumulation in Marine Organisms: Effects of Contaminants From Oil Well Produced Water. Oxford, UK: Elsevier; 2002. 8. Meador JP, Stein JE, Reichert WL, Varanasi U. Bioaccumulation of Polycyclic Aromatic Hydrocarbons by Marine Organisms. Rev Environ Contam Toxic 1995;79. 9. National Research Council. Polycyclic Aromatic Hydrocarbons in the Aquatic Environment: Formation Sources, Fate, and Effects on Aquatic Biota, NRCC 18981. National Academy Press; 1983. 10. Bender ME, DeFur PO, Huggett RJ. Polynuclear Aromatic Hydrocarbon Monitoring in Estuaries Utilizing Oysters, Brackish Water Clams, and Sediments. In: Oceans 1986 Conference Proceedings, Monitoring Strategies Symposium, vol. 3. Marine Technology Society; 1986;791. 11. Challenger GE, Sergy G, Graham A. Vegetation Response and Sediment Polycyclic Aromatic Hydrocarbon Attenuation in a Carex Marsh in Howe Sound, British Columbia, Canada Following a Spill of Bunker C Fuel Oil. IOSC 2008:847. 12. Mauseth GS, Martin CA, Whittle K. Closing and Reopening Fisheries Following Oil Spills; Three Different Case Studies with Similar Problems. AMOP 1997;1283. 13. Brown JS, Boehm PD, Hardenstine JH, Douglas GS. The North Cape Oil Spill Assessment: PAHs Not Equal to Oil. AMOP 1997:1409. 14. ASTM Special Technical Publication No. 433. Basic Principles of Sensory Evaluation. American Society for Testing and Materials; 1968;105.

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15. ASTM Special Technical Publication No. 434. Manual on Sensory Testing Methods. American Society for Testing and Materials; 1968;77. 16. ASTM Special Technical Publication 758. Guidelines for the Selection and Training of Sensory Panel Members. American Society for Testing and Materials; 1981;35. 17. Williams UP, Kiceniuk JW, Fancey LL, Botta JR. Tainting and Depuration of Taint by Lobsters (Homarus americanus) Exposed to Water Contaminated with a No. 2 Fuel Oil: Relationship with Aromatic Hydrocarbon Content in Tissue. J Food Sci 1989;54. 18. Williams UP, Kiceniuk JW, Botta JR. Polycyclic Aromatic Hydrocarbon Accumulation and Sensory Evaluation of Lobster (Homarus americanus) Exposed to Diesel Oil at Arnold’s Cove, Newfoundland. Can Tech Rep Fish Aquat Sci 1985:493. 19. McLeese DW. The Potential for Exposure of Lobsters to Creosote During Commercial Storage in the Maritime Provinces of Canada. Can Tech Rep Fish Aquat Sci 1983:207. 20. Uthe JF, McLeese DW, Sirota GR, Burridge LE. Accumulation of Polycyclic Aromatic Hydrocarbons by Lobsters (Homarus americanus) Held in a Tidal Pound. Can Tech Rep Fish Aquat Sci 1984:319. 21. Botta JR. Freshness Quality of Seafoods: A Review. In: Shahidi F, Botta JR, editors. Seafoods: Chemistry, Processing Technology, and Quality, vol. 140. Elsevier Applied Science Publishers; 1994. 22. Davis HK, Geelhoed EN, MacRae AW, Howgate P. Sensory Analysis of Trout Tainted by Diesel Fuel in Ambient Water. Water Sci Tech 1992;11. 23. Howgate P. Measurement of Tainting in Seafoods, Int Symp On Seafood Quality Determination, Anchorage, AK; 1987:127. 24. Moller TH, Dicks B, Whittle KJ, Girin M. Fishing and Harvesting Bans in Oil Spill Response. IOSC 1999:339. 25. Reilly TI, York RK. Guidance on Sensory Testing and Monitoring of Seafood for Presence of Petroleum Taint Following an Oil Spill. NOAA Technical Memorandum NOS OR&R 9, http:// response.restoration.noaa.gov; 2001. 26. International Organization for Standardization (IOS). Sensory Analysis; Methodologyd Vocabulary. Geneva: International Organization for Standardization, ISO 5492; 1992. 27. Moffat CF, Whittle KJ. Polycyclic Aromatic Hydrocarbons, Petroleum, and Other Hydrocarbon Contaminants. Moffat C, Whittle KJ, editors. Persp. Environmental Contaminants in Food, Chap.10, vol. 364, 1999. 28. Mauseth GS, Challenger GE. Closing and Opening of Fisheries Following Oil Spills. A Case Study in Humboldt Bay, CA. AMOP 1998;167.

Part XIII

Specific Case Studies

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Chapter 33

The Torrey Canyon Oil Spill, 1967 Robin J. Law

Chapter Outline 33.1. Case Study

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33.1. CASE STUDY Around 9 on the morning of Saturday March 18, 1967, the tanker Torrey Canyon, bound for Milford Haven from the Persian Gulf, ran aground on the Seven Stones reef 15 miles west of Land’s End.1 Its cargo was 119,000 tons of Kuwaiti crude oil. Oil immediately began to leak from the ruptured tanks, forming a slick to the east of the Isles of Scilly. By Monday evening, it was estimated that 30,500 tons of oil had been released to the sea, and a slick ca. 20 miles long was moving first south then east, threatening the coasts of the southwest UK and northern France. At-sea activities to treat the oil began on the evening of March 18, undertaken by the Royal Navy, which took overall control of the response. Recently, the navy had been using mixtures of solvents and detergents for cleaning up after small oil spills in ports and harbors.1 The navy therefore applied the same mixtures to the oil released from the Torrey Canyon using hoses, in an attempt to disperse the oil before it beached and caused heavy coastal pollution or to remobilize from beaches and harbors. Following advice from the UK Ministry of Agriculture, Fisheries, and Food, no detergents were used within estuaries with commercially important shellfish beds so as to avoid contaminating them and damaging the fisheries.1 The more cautious use of detergents by the French authorities reflected the greater economic importance and the more offshore location of their shellfish industry. On the French coast, some 2300 tons of detergents were used in beach cleaning.1 Trials of steam cleaning techniques were also conducted on rocky beaches. This method was effective, and, as the treated area was at high-water Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10033-4 British Crown Copyright Ó 2011.

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mark with few animals, no deleterious effects were noted. At sea, 3000 tons of powdered chalk were used to sink perhaps 20,000e30,000 tons of weathered oil and to prevent it from coming ashore. This method appeared to be effective in this instance, but such techniques could have a downside, which needs to be considered before use on a site-specific basis. Sinking oil with chalk could cause problems with blanketing of life on the seabed, tainting of commercial fish and shellfish, and the development of anoxia within enclosed sea areas as bacterial action begins to degrade the oil. However, these effects were not studied during this incident. Also, of course, the oil may subsequently be washed ashore during storms. Nevertheless, large quantities of oil began to come ashore near St. Just on the west coast of Cornwall on the morning of March 25 and, on the following days, around St. Ives on the north coast and Mount’s Bay on the south coast. Just over one week after the grounding, it was estimated that 49,000 tons of oil had been released from the vessel. On the evening of March 26, the Torrey Canyon broke its back and a further 40,000e50,000 tons of oil were released into the sea. It was bombed by the Royal Air Force during March 28e30; oil both in the ship and on the sea was set alight, but the fires could not be sustained in spite of the addition of aviation fuel as an accelerant. By the end of April, when it sank, all of the oil aboard the ship had probably been lost. In addition to oil beaching on the Cornish coasts, from April 11 heavy oiling occurred on the coasts of the Island of Guernsey and Brittany in France. Approximately 10,200 tons of detergents were used to treat about 14,250 tons of oil on the beaches of Cornwall (a treatment rate of 1:1.4, huge by modern standardsdcurrent treatment rates are generally between 1:10 and 1:30) and approximately 3160 tons of detergents were applied to oil at sea. Concerns were expressed regarding the likely consequences of both the oil spill itself and the response actions on commercial fisheries and marine life more broadly. Recent experience of three oil spills in Milford Haven, Wales, just prior to the Torrey Canyon spill had shown that the detergents used to treat oil had killed crabs, barnacles, winkles, inshore fish, and other animals in large numbers.1 As a consequence, the Marine Biological Association of the UK, based in Plymouth, undertook ecological studies. At the time, little information was available regarding the toxicity of the detergents used. Earlier studies undertaken at the Ministry of Agriculture, Fisheries, and Food Laboratory at Burnham-on-Crouch with exposures of 1e24 hours had shown that solvent/ detergent mixtures (similar to, though not identical with, those used during the incident itself) were lethal to a range of commercially important shellfish at concentrations from 3 to 250 ppm.1 No information was available regarding sublethal effects at that time. The detergents used during the incident contained a high proportion of aromatic hydrocarbons (up to 62% of the product 1) and so would be expected to be of high acute toxicity. Twelve proprietary detergents were reported as having been used during the response, including products from BP, Esso, and Petrofina.1

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The ecological studies initially focused on discovering whether the detergent spraying of oil at sea had adversely affected fish, crustaceans, mollusks, and other animals living on the seabed and plants and animals in the areas where the oil had passed or stranded. Surveys of the effects of oil and detergents on intertidal plants and animals were also undertaken.1,4 Pollution by the oil from the Torrey Canyon was found to have little biological effect other than the death of more than 30,000 seabirds.2 In a sample of 1223 dead birds of eight different species collected on UK coasts, almost 98% were guillemots and razorbills. These species are particularly vulnerable to spilled oil, as was also seen during the recent UK incident involving the container ship MSC Napoli.3 The main bird mortality caused by the Torrey Canyon involved local British populations, especially the larger auks, including disproportionately high numbers of young birds that are more migratory.2 Some subadult shags (birds of the cormorant family) seeking nesting sites were also killed. The effects of the oil and detergent on intertidal marine life were studied at two sites on the Cornish coast and were found to be more marked than for the oil alone in both intertidal and subtidal areas.4 After dispersant spraying on beached oil, heavy mortalities were observed among fish and invertebrates on the rocky shores (e.g., in rock pools). It was clear from this study that the mixture of emulsified oil and detergent was much more toxic than the oil itself. The authors concluded that where littoral marine life was concerned, the use of detergents to clean up oil on the shore constituted a “cure” worse than the “disease” itself.4 The effects on littoral and sublittoral ecosystems dominated by attached macrophytes were also studied at eight locations, including two that were unpolluted by the incident. Pollution effects were most marked within the littoral zone, falling off below the low water mark.5 The main changes seen were that the balance of ecosystems was altered by the destruction of grazing organisms at detergent-treated sites. This effect was most marked in littoral ecosystems in which the herbivores play an important role in curbing the primary producers, algae, and most drastic when detergents were applied directly to the shore at low water. No long-term damage was observed to the algae due to either the oil or the detergents, and on shores left untreated there was evidence of removal of oil by natural agencies. The decision to treat or not treat shorelines is now made on an individual basis, weighing the benefits and costs of intervention.

REFERENCES 1. Smith JE, editor. “Torrey Canyon” Pollution and Marine Life. Cambridge: Cambridge University Press; 1968. 2. Bourne WRP, Parrack JD, Potts GR. Birds Killed in the Torrey Canyon Disaster. Nature 1967;1123.

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3. Law RJ. compiler. Environmental Monitoring Conducted in Lyme Bay Following the Grounding of MSC Napoli in January 2007, with an Assessment of Impact, Science Series. Cefas, Lowestoft: Aquatic Environment Monitoring Report 2008;61. 4. O’Sullivan AJ, Richardson AJ. The Torrey Canyon Disaster and Intertidal Marine Life. Nature 1967;448. 5. Bellamy DJ, Clarke PH, John DM, Jones D, Whittick A, et al. Effects of Pollution From the Torrey Canyon on Littoral and Sublittoral Ecosystems. Nature 1967;1170.

Chapter 34

The Ekofisk Bravo Blowout, 1977 Robin J. Law

Chapter Outline 34.1. Case Study

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34.1. CASE STUDY On April 22, 1977, a blowout occurred during maintenance operations on the Bravo platform of the Ekofisk oil field in the North Sea and oil began to escape at a rate of 2000e3000 tons per day.1 The release rate was estimated using the flow rate from the well and the elapsed time. As the oil was released high into the air, about 30% had evaporated by the time it reached the sea surface. From April 24 to May 1, Norwegian and UK scientists undertook a coordinated program of research, collecting samples from four research vessels. During this period, samples of subsurface seawater, surface sediments, and fish and shellfish were collected on a grid system around the Ekofisk platform location. Subsurface seawater samples were collected using 2.7 l glass Winchester bottles mounted in a weighted stainless steel frame deployed by means of a nylon rope.2 The bottle is sealed using a Polytetrafluroethylene (PTFE) stopper that can be opened at the sampling depth using a second nylon rope. This avoids contamination from the sea-surface microlayer that would result if the bottle were lowered open. Surface sediments were collected using a 0.1 m2 modified Day grab, previously solvent-cleaned. Fish and shellfish were collected using a Granton trawl. The same analytical methods were used in both national laboratories, which had earlier aligned their procedures.1 This was one of the first incidents in which capillary (high-resolution) gas chromatography-mass spectrometry was deployed in an oil spill investigation, allowing individual alkanes and polycyclic aromatic hydrocarbons (PAH) compounds to be identified and quantified. No sizable quantities of floating oil were encountered by the UK vessel during the survey, but thin sheens of oil Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10034-6 British Crown Copyright Ó 2011.

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were seen at some locations to the east of the platform and about 10e20 miles away.1 Concentrations were low in all the water samples, with maximums of only 3.9 and 8.1 mg/l for the summed aliphatic and aromatic hydrocarbons determined, respectively. Such concentrations are less than 10 times normal background concentrations in the offshore North Sea and of no toxicological significance. Samples of fish and sediments showed only low concentrations of both aliphatic and aromatic hydrocarbons, and the pattern of aliphatics found was predominantly natural in origin. Subsequent studies (May 3e5) undertaken by Scottish scientists using sediment traps suggested that, at that time, particulate oil was probably present in suspension in the water column as a result of natural dispersion. The highest concentrations were observed in the traps closest to the surface. About 9000 to 13,000 tons of oil remained at sea when the well was capped on April 30,3 but none reached land as it dispersed naturally at sea during the next few weeks. There was no evidence that the oil released from the platform contributed significantly to the burden in fish or sediments as a result, and there was only low-level contamination in seawater samples in the area.

REFERENCES 1. Law RJ. Determination of Petroleum Hydrocarbons in Water, Fish, and Sediments Following the Ekofisk Blow-Out. Mar Poll Bull 1978;321. 2. Kelly C, Law RJ, Emerson HS. Methods of Analysing Hydrocarbons and Polycyclic Aromatic Hydrocarbons (PAH) in Marine Samples, Science Series, vol. 12. Cefas, Lowestoft: Aquatic Environment Protection: Analytical Methods; 2000. 3. Berge G. The Ekofisk Bravo Blow Out Part 1. Introduction and Preliminary Findings. ICES C.M. 1977/E:55 1977.

Chapter 35

The Sea Empress Oil Spill, 1996 Robin J. Law

Chapter Outline 35.1. Introduction 35.2. Mechanical Recovery at Sea 35.3. Dispersant Spraying at Sea 35.4. Shoreline Cleanup 35.5. Dispersant Use on Beaches 35.6. Impacts on Seabirds 35.7. Mortalities of Fish and Shellfish

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35.8. Effects on Fish and Shellfish Stocks and Plankton 35.9. Contamination of Fish and Shellfish 35.10. Removal of Fishery Restrictions 35.11. Conclusion

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35.1. INTRODUCTION The tanker Sea Empress grounded on rocks at the entrance to Milford Haven, West Wales, while entering port on February 15, 1996. During the next week, 72,000 tons of its cargo of 131,000 tons of Forties blend crude oil and 480 tons of heavy fuel oil IFO-380 were spilled.1 Forties blend crude oil is a light, low sulphur crude oil from the North Sea, with an American Petroleum Institute (API) gravity of 40.3 . The spilled volumes were determined by difference once the vessel was taken into port and unloaded. The coastline in this area has great environmental importance, and its waters support a diverse fishery with extensive estuarine shellfish beds vulnerable to oil contamination.2-4 Following the spill, local fishermen agreed to a voluntary fishery closure, which was later formalized by regulation as a precautionary measure to protect human consumers. The fishery closure area covered about 810 square miles (2,100 km2) of coastal waters5 (see Figure 35.1). In support of this, a monitoring program for fish and shellfish in the area was initiated, with samples being collected by Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10035-8 British Crown Copyright Ó 2011.

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FIGURE 35.1 The coast of southwest Wales affected by oil spilled from the Sea Empress. The line marks the outer boundary of the fishery closure area, and the star symbol marks the Sea Empress grounding site.

local fishermen hired for the task, from research vessels and by shoreline collection. Within this program, concentrations of hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) were determined in fish and shellfish tissues, as well as in edible seaweeds that are eaten locally. Further details of the sampling program are given elsewhere.6 Hydrocarbon concentrations were also determined in seawater and surface sediments in order to assess the movement and distribution of the spilled oil. Seawater concentrations were determined both in discrete water samples using liquideliquid extraction followed by ultraviolet (UV) fluorescence spectrometry and continuously using an Aquatracka fluorimeter towed behind a research vessel in different studies. Sediment concentrations were determined in samples collected using a stainless steel spoon (on beaches) or a 0.1 m2 modified Day grab (subtidally) and stored at e20 C in glass jars. Sediments were subjected to alkaline digestion followed by solvent extraction and UV fluorescence spectrometry. In all cases, the excitation and emission wavelengths used were 310 nm and 360 nm, respectively.

35.2. MECHANICAL RECOVERY AT SEA For most of the period during which spilled oil was on the sea, wind speeds above 30 knots (force 7 or greater) prevented recovery operations from taking

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place. In all, approximately 4000 tons (about 3% of the oil spilled) of water-inoil emulsion were recovered by this means.7

35.3. DISPERSANT SPRAYING AT SEA Spilled oil at sea was treated using 446 tons of chemical dispersants sprayed from aircraft, mostly on the ebbtides as the oil was carried away from the entrance to Milford Haven and into deeper water5 (see Figure 35.2). Remotesensing aircraft equipped with IR and UV sensors were used to direct the spraying operation from above, which meant that few other remote-sensing data were gathered. Some radar satellite images were available, but interpretation of these images close to land proved problematic due to wind shadow from cliffs also flattening the sea surface.1 Tidal flows in the area are strong, and typical tidal excursions to the west of Milford Haven are about 20 km during spring tides. During the spill, approximately 11,000 to 16,000 tons of emulsified oil came ashore, contaminating 200 km of coastline.1 The successful treatment of mainly fresh oil using dispersants is believed to have prevented a further 57,000 to 110,000 tons of emulsion from coming ashore. Chemically dispersed oil forms very small droplets, which are transported in the upper part of the water column and which are very amenable to bacterial degradation. Concentrations of oil below dispersed slicks were found to be within the range 1 to 10 mg/l, rapidly diluting to <1 mg/l.8 Fine sediment

FIGURE 35.2 The coast of southwest Wales affected by oil spilled from the Sea Empress. The dotted line marks the outer limit of bulk oil contamination. The figure also shows the main area of dispersant spraying from aircraft, beaches on which dispersants were used, and the main areas of at-sea recovery.

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areas throughout the western Bristol Channel and off the coast of West Wales were sampled using a 0.1 m2 modified Day grab and analyzed for hydrocarbons as above, in case naturally dispersed oil was being transported to sediment sinks as was the case in the Braer oil spill.9 Only low hydrocarbon concentrations were observed, confirming that this process was not a factor in the Sea Empress incident.

35.4. SHORELINE CLEANUP The initial priorities were to remove bulk oil from accessible sites (except for a number that were left to clean naturally for comparison purposes) and to cleaning Tenby and Saundersfoot beaches in time for the Easter holidays. A number of techniques were used, including the use of suction equipment, excavators, absorbent material, flushing with water at low pressure, and the manual use of shovels and scrapers. JCB vehicles were used to dig trenches to trap oil on amenity beaches, but in order to minimize environmental damage on more sensitive shorelines, the use of heavy machinery and intrusive cleanup techniques was avoided wherever possible.1 Most of the bulk oil was removed by mid-March 1996. The operation then turned to removing bulk oil from the inaccessible locations and removing residual oil from the beaches cleaned initially. Again, several techniques were used, according to the shoreline material, the type and extent of oil contamination, the degree of exposure to wave action. and other environmental considerations. These included manual digging and scraping, the use of absorbent material, the removal of oiled sand and other beach material (taking care to remove the minimum of beach material along with the oil), low- and high-pressure water washing, surf washing, and the washing of cobbles and shingle in pits or cement mixers.1 Within the UK National Contingency Plan, the central government is responsible for holding stockpiles of equipment and dispersants and for mounting the response at sea, while local authorities have accepted a voluntary responsibility to clean shorelines. As part of the Milford Haven port oil spill plan, each of the local oil companies also agreed to take responsibility for shoreline cleanup necessitated by a spill from a tanker carrying oil to its refinery.1 A Joint Response Centre (JRC) was established to coordinate and integrate these activities. Difficulties were encountered as, on April 1, 1996, all of the district and county councils in the area were reorganized to form the two unitary authorities of Carmarthenshire and Pembrokeshire. This did not seriously impact the practical cleanup activities, but the distraction of council staff with this competing priority did reduce resources, particularly for administrative support. The maintenance of records and documentation was hampered, leading to delays in cost recovery from the compensation fund. The Environment Team in the JRC played an important role in devising the cleanup strategy, advising on priorities and the selection of techniques to be used in specific locations and circumstances.1

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35.5. DISPERSANT USE ON BEACHES All of the beaches marked in Figure 35.2 were treated with chemical dispersants or cleaning agents, generally using backpack sprayers. Most of the 12 tons used was applied to amenity beaches around Tenby and Saundersfoot, and at Skrinkle Haven. The major amenity beaches in the area were sufficiently clean to open in time for the Easter holidays, nine weeks after the spill.5

35.6. IMPACTS ON SEABIRDS The waters of the Welsh coast around the impacted area are of outstanding international importance for their breeding seabirds, wintering sea-duck, and waterfowl.1 Oiled birds, both live and dead, were collected along the whole coastline affected. By June 1996, 7000 birds of 36 species had been collected, 85% of which came ashore between February 24 and March 4, 1996, when most bulk oil was on the sea. The species most affected was the common scoter, which comprised two-thirds of the birds recorded (4600). Most of the remainder were auks, mainly guillemots (1600) and razorbills (340). The wintering population of common scoter was badly affected, with 10,000 fewer birds in 1997 than in 1996.

35.7. MORTALITIES OF FISH AND SHELLFISH There were no reported mortalities of commercial fish or crustacean species as a result of the spill. Large numbers of dead or moribund shellfish (mostly bivalve mollusks) were, however, washed ashore during the weeks following the spill.1 None of these involved the major, commercially exploited stocks (mostly cockles and mussels) in estuarine areas (particularly the Three Rivers area and the Burry Inlet; see Figure 35.1 for locations). These incidents involved a number of species (including cockles, clams, and razorshells10) and occurred within the area of bulk oil contamination (Figure 35.2). Studies of the seabed benthic communities showed little impact from the spill except for marked reductions in the number of amphipods in areas to the north of the grounding site, within Milford Haven.5,11 The amphipods, which are particularly vulnerable to oil, were likely affected by naturally dispersed oil being carried into Milford Haven on flooding tides rather than chemically dispersed oil, as oil was chemically treated some miles from shore as the tide ebbed. The entrance to Milford Haven is extremely turbulent, and so oil released into the flooding tides would disperse very effectively. Recovery of the amphipod fauna was evident in a survey undertaken in 1998 and continuing in a later survey in 2000.12 Overall, the range of species affected was very similar to those documented previously in the same general geographic area and similar environmental conditions, those involving the Torrey Canyon and the Amoco Cadiz.13

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35.8. EFFECTS ON FISH AND SHELLFISH STOCKS AND PLANKTON Although there was no evidence of damage to commercial stocks, the Sea Empress Environmental Evaluation Committee suggested that further assessment might be necessary to establish whether breeding and recruitment of some species (e.g., bass, edible crabs, lobsters, and whelks) had been successful in 1996.1 Bass spawned in 1996 were found to be more abundant on the south side of the Bristol Channel (unaffected) than on the north side (affected) and were particularly scarce within Milford Haven itself. This was because young (0egroup) bass at sites along the South Wales coast to the west of Swansea Bay (Figure 35.1) were less likely to have attained the 60 mm overall length critical for survival through the first winter than those from nursery areas in Devon and Cornwall.5 In 1997, however, there was no indication that young bass were less abundant in South Wales nurseries than on the south side of the Bristol Channel.14 The late recruitment of young bass in 1996 was attributed to lower water temperatures in February and March than in 1997 and 1998, and occurred in other areas as well.15 Herring in Milford Haven represent a discrete stock and so were of particular interest in the context of the Sea Empress oil spill. It was not possible to study spawning success in 1996, but the presence of adult fish in spawning condition in 1997 indicated there was no long-term impact.1 There was a possibility that chemically dispersed oil in the upper water column may have adversely impacted phytoplankton and zooplankton communities. As this spill involved the most intensive use of dispersants to date, data from the routine surveys undertaken in the Bristol Channel and adjacent areas using the continuous plankton recorder (CPR) were studied. The CPR is a plankton sampling instrument designed to be towed behind merchant ships on their normal sailings; it had been deployed on a number of ferries and cargo vessels crossing the area of interest. All common taxa showed normal abundance levels, and vulnerable taxa showed no marked changes.16 Also, there were no striking changes in the plankton communities overall. This indicated that oil spilled from the Sea Empress had no dramatic effects on the plankton of the southern Irish Sea during the period FebruaryeOctober 1996.

35.9. CONTAMINATION OF FISH AND SHELLFISH 35.9.1. Finfish Hydrocarbon and PAH concentrations in all species of finfish, including migratory salmon and sea trout, remained low throughout the incident. Summed PAH concentrations in salmon flesh were up to 186 mg/kg wet weight, much lower than those observed following the Braer spill in 1993.9 In the Braer incident, concentrations up to 14,000 mg/kg wet weight were observed in caged salmon 10 days after the grounding.17 In all cases, finfish accumulated two-ring

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PAH compounds (naphthalenes) across the gills from the dissolved phase.9 These compounds carry the potential for the tainting of fish flesh, but tests by a trained panel did not detect taint in any fish samples taken during the incidents.

35.9.2. Crustacea Other than within Milford Haven itself, concentrations in crustacean species also remained low, and two-ring PAH predominated.5 Again, no taint was detected in crab or lobster samples tested as above.

35.9.3. Whelks At the time of the Sea Empress spill, there was a sizable fishery around Carmarthen Bay from which whelks were being exported to the Far East. After oil reached Carmarthen Bay on February 25, sampled whelks showed clear signs of contamination with sum PAH concentrations up to 3800 mg/kg wet weight. Contamination was localized, however.5 As for finfish and crustaceans, tworing PAH predominated and no taint was evident.

35.9.4. Bivalve Mollusks All commercial species from the area (cockles, mussels, scallops, and native and Pacific oysters) were collected and analyzed as above. Contamination in mussels and other bivalves mirrored the spread of bulk oil contamination and affected animals taken between St. David’s in the north to the Three Rivers area in the east (Figure 35.2). The highest levels of contamination were mostly in stocks that are not exploited commercially, particularly those within Milford Haven. At many of the sites within the closure area, sum PAH concentrations were >1000 mg/kg wet weight. The highest concentrations were seen in mussels from Milford Haven, >100,000 mg/kg within 10 days of the grounding. This was a result of the ingestion while filter-feeding of naturally dispersed oil droplets from the water column shortly after release of oil from the vessel on flooding tides.18 As concentrations of oil-derived PAH fell, a seasonal cycle in the concentrations of combustion-derived PAH was observed, particularly within Milford Haven (Figure 35.3). In both 1996 and 1997, concentrations of benzo[a]pyrene peaked in March and fell to close to zero in midsummer. This was not related to the spilled oil, as Forties crude oil contains only low concentrations of benzo[a]pyrene. Its main sources in Milford Haven are industrial and domestic combustion sources in the local area.

35.10. REMOVAL OF FISHERY RESTRICTIONS Fisheries were reopened in stages as the monitoring data showed that concentrations posed no further risk to consumers and absence of taint.

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FIGURE 35.3 The concentrations of benzo[a]pyrene in mussels from Angle and Dale, inside Milford Haven, over the 500 days following the grounding of the Sea Empress.

Controls relating to fish and crustaceans were removed relatively rapidly, after 3 and 8 months, respectively. The major cockle beds in the Burry Inlet and the Three Rivers area were also lightly contaminated and were reopened after 4½ and 7 months, respectively. Restrictions covering intertidal mussels in the southeast portion of the closure area and oysters within Milford Haven were the last to be lifted, 19 months after the spill.

35.11. CONCLUSION Given the large volume of oil spilled, the effects of the Sea Empress oil spill were much less severe than could have been expected. There were no mortalities of fish or crustaceans reported, and the mass strandings of mollusks that occurred on a number of occasions did not impact commercial species. There is little doubt that the intensive aerial application of chemical dispersants to the spilled oil reduced the impact of the oil spill by significantly reducing the amount of oil that reached the shoreline and intertidal areas. A wide range of further studies were conducted with the aim of assessing the overall impact of the spill, addressing both marine and terrestrial species. None showed major or long-term impacts as a result of the spill.1

REFERENCES 1. SEEEC. The Environmental Impact of the Sea Empress Oil Spill. Final Report of the Sea Empress Environmental Evaluation Committee. London: The Stationery Office; 1998. ISBN 0 11 702156 3.

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2. Gray MJ. The Coastal Fisheries of England and Wales, Part III: A Review of Their Status 1992-1994, Fisheries Research Technical Report. Lowestoft: MAFF Directorate of Fisheries Research 1995;100. 3. Pawson MG, Pickett GD, Walker P. The Coastal Fisheries of England and Wales, Part IV: A Review of Their Status 1999e2001. Cefas, Lowestoft: Science Series Technical Report 2002;116. 4. Walmsley SA, Pawson MG. The Coastal Fisheries of England and Wales, Part V: A Review of Their Status 2005e2006. Cefas, Lowestoft: Science Series Technical Report 2007;140. 5. Law RJ, Kelly C. The Impact of the “Sea Empress” Oil Spill. Aquat Living Resour 2004;389. 6. Kelly CA, Law RJ. Monitoring of PAH in fish and shellfish following the Sea Empress incident. In: Edwards R, Sime H, editors. The Sea Empress Oil Spill: Proceedings of the International Conference Held in Cardiff, February 11e13, 1998, vol. 467. London: Chartered Institute of Water and Environmental Management; 1998. 7. Marine Pollution Control Unit. The Sea Empress incident: A Report by the Marine Pollution Control Unit. Southampton: The Coastguard Agency; 1996. ISBN 1 901518 00 0. 8. Lunel T, Swannell R, Rusin J, Wood P, Bailey N, et al. Monitoring the Effectiveness of Response Operations During the Sea Empress Incident: A Key Component of the Successful Counter-Pollution Response. Spill Sci Tech Bul 1995;99. 9. Law RJ. Braer Spill, in Oil Spill Science and Technology; 2010:1119. 10. Rutt GP, Levell D, Hobbs G, Rostron DM, Bullimore B, et al. The Effect on the Marine Benthos. In: Edwards R, Sime H, editors. The Sea Empress Oil Spill: Proceedings of the International Conference Held in Cardiff, February 11-13, 1998, vol. 189. London: Chartered Institute of Water and Environmental Management; 1998. 11. Levell D, editor. The Milford Haven Waterway Macrobenthic Survey, October 1996, OPRU/ CORDAH, Neyland, Pembrokeshire, Report No. OPRU/22/97;1997. 12. Nikitik CCS, Robinson AW. Patterns in Benthic Populations in the Milford Haven Waterway Following the Sea Empress Oil Spill with Special Reference to Amphipods. Mar Poll Bull 2003;1125. 13. Law RJ. Torrey Canyon Spill, in Oil Spill Science and Technology; 2010:1103. 14. Lancaster JE, Pawson MG, Pickett GD, Jennings S. The Impact of the Sea Empress Oil Spill on Seabass Recruitment. Mar Poll Bull 1998;677. 15. Reynolds WJ, Lancaster JE, Pawson MG. Patterns of Spawning and Recruitment of Sea Bass to Bristol Channel Nurseries in Relation to the 1996 Sea Empress Oil Spill. J Mar Biol Assoc UK 2003;1163. 16. Batten SD, Allen RJS, Wotton COM. The Effects of the Sea Empress Oil Spill on the Plankton of the Southern Irish Sea. Mar Poll Bull 1998;764. 17. Whittle KJ, Anderson DA, Mackie PR, Moffat CF, Shepherd NJ, McVicar AH. The impact of the Braer Oil on Caged Salmon. In: Davies JM, Topping G, editors. The Impact of an Oil Spill in Turbulent Waters: The Braer. London: The Stationery Office Ltd.; 1997. 18. Law RJ, Kelly CA, Nicholson MD. Polycyclic Aromatic Hydrocarbons (PAH) in Shellfish Affected by the Sea Empress Oil Spill in Wales in 1996. Polycyc Arom Hydrocarb 1999;229.

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Chapter 36

The Braer Oil Spill, 1993 Robin J. Law and Colin F. Moffat

Chapter Outline 36.1. Introduction 1119 36.2. At-Sea and Shoreline 1119 Response 36.3. Fate of the Braer Oil 1121

36.4. Impacts of the Braer Oil 1121 36.5. Conclusion 1125

36.1. INTRODUCTION On the January 5, 1993, the tanker Braer was en route from Norway to Canada with a cargo of 84,700 tons of Gullfaks crude oil.1 In storm conditions and following a loss of engine power, it ran aground on Garth Ness in the south of the Shetland Islands (Figure 36.1). Over the next 12 days, the entire cargo and about 1500 tons of heavy fuel oil carried as bunkers was lost in the sea. During this period, the average wind speed was Force 8 or greater with gusts up to Force 12. Sea conditions were equally violent, and this caused the rapid dispersion and dissolution of the oil throughout the water column. Some oil (possibly <1% of the total1) was also carried into the air and driven inshore by wind and spray. In order to coordinate the monitoring and impact assessment studies, which began soon after the grounding, the UK government established the Ecological Steering Group on the Oil Spill in Shetland (ESGOSS) as overseer.1

36.2. AT-SEA AND SHORELINE RESPONSE A Joint Response Centre was established in Shetland to ensure an integrated response to the incident, and remote-sensing surveillance and dispersant spraying aircraft were deployed to the islands.1 Burning the oil at sea had been ruled out because of the risk to life and property if the whole cargo was to catch fire, but Gullfaks crude oil (a medium crude oil with an American Petroleum Industry (API) gravity of 29.31) should be amenable to treatment using chemical dispersants, and so this was the preferred option. Preparations were Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10036-X British Crown Copyright Ó 2011.

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FIGURE 36.1 Map of the Shetland Isles showing the site of the grounding of the MV Braer on the southern tip of Shetland. An Exclusion Zone was established on January 8, 1993, by order under the Food and Environment Protection Act 1985 (FEPA). The order prohibited the harvesting of farmed or wild fish or shellfish within the zone to prevent contaminated product from reaching the marketplace and posing a threat to consumers. The initial zone was extended 5 miles westward to that shown on the map, on January 27, 1993. Restrictions were lifted first for wild fish on April 23, 1993, farmed salmon on December 8, 1993, crustaceans other than Nephrops on September 30, 1994, and mollusks other than mussels on February 9, 1995. Finally, in May 2000, the remaining restrictions for mussels and Nephrops were removed.

also made for spraying from vessels and oil recovery should the weather moderate sufficiently. Options for salvage were also considered, but the severity of the weather precluded examination of the vessel. Approximately 100 tons of dispersants were sprayed from the air onto thick oil identified by aerial surveillance during the day after the grounding, but the bad weather subsequently prevented the aircraft from flying. The Braer broke up on January 12, and cargo salvage efforts were abandoned. All other salvage considerations were likewise abandoned following a diver survey of the wreck on January 24. Less than 1% of the oil carried by the Braer came ashore on beaches, and 14% is likely to have evaporated,1 so it was concluded that about 85% went into the water column. The evaporation estimate was low because the properties of the oil include a relatively slow rate of evaporative loss1; also, the oil spent little time on the sea surface before it was dispersed into the water column by the severe weather. Booms and barriers were deployed to protect sensitive areas, and absorbent booms were deployed to protect salmon farms in the island inlets. Little shoreline cleanup was required, and oil (possibly a few tens of tons) was

Chapter | 36 The Braer Oil Spill, 1993

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removed by mechanical and manual means. The reasons were twofold. First, very little of the oil emulsified, but instead was rapidly dispersed. Second, the impermeable rock and rain-saturated beaches of sand, shingle, and cobbles allowed the brown, oily water to rush up and down with little or no penetration nor lodgement, except in a few small patches. No oil recovery at sea was attempted due to the severe weather that prevailed during the incident.

36.3. FATE OF THE BRAER OIL High concentrations of oil were detected, using ultraviolet (UV) fluorescence spectrometry, in the inshore waters off south Shetland (up to 50,000 mg/l immediately following the spill)1 and in sediments on the southwest side of the island (mean 2000 mg/kg dry weight) (Figure 36.2). This involved both collection and analysis of discrete samples and continuous monitoring using an Aquatracka-towed fluorimeter. Initial screening of sediments for hydrocarbon content was achieved using UV fluorescence spectrometry with subsequent characterization of the hydrocarbons by gas chromatography-mass spectroscopy. It is estimated that approximately 30,000 tons of the spilled oil (36%) was deposited in sediment.1 This includes oil that was carried, presumably in dispersed form, for almost 100 km to the southeast of Shetland, to be deposited in a sedimentary sink 50 km south-east of Fair Isle (Figure 36.2). This oil is in deep water and unlikely to be remobilized by wave action, even during storms.

36.4. IMPACTS OF THE BRAER OIL 36.4.1. On Land Short-term impacts (up to a few months) on natural vegetation were observed onshore close to the wreck site.1 Contamination of grass, vegetation, and root crops in a large area of South Shetland led to their being excluded from grazing or sale for a period, and sheep that had fed there were excluded from the human food chain for 6 months.1 Effects across the 60 km2 of farming land1 affected were therefore limited to the short term.

36.4.2. On Seabirds Five species of seabirds comprised 89% of the 1768 birds found oiled as a result of the incident: shags, black guillemots, kittiwakes, long-tailed ducks, and eider ducks.1 In the subsequent year, reduced breeding numbers were apparent for shag and black guillemot, but increased numbers were seen in affected colonies during 1994e1995. No effects on foraging behavior were seen in four species of seabirds (kittiwakes, Arctic terns, shags, and guillemots) despite feeding in oiled areas.1 The oil spill did not have a major impact on the abundance of young sandeels, food for the chicks of Arctic terns and kittiwakes.

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FIGURE 36.2 Distribution of oil in sediments (parts per million). Accumulations of oil occurred in two locations, on the southwest side of Shetland and toward Fair Isle. Gray-shaded areas correspond to areas of muddy sediment.

36.4.3. On Otters and Seals In the month following the incident, six otters were found dead in Shetland.1 None of these deaths could be attributed with confidence to the impact of oil. Cub production was very low throughout Shetland in 1993, probably due to the reduced numbers of inshore benthic fish (such as five-bearded rockling, butterfish, and eel pout) on which they may feed. Some seals suffered from eye and nasal discharges as a result of exposure to oil, but these effects were shortlived. Twenty-two seals were found dead in the two weeks after the spill, but most were decomposed and probably died earlier. In general, seal and otter populations were affected only slightly or not at all by the oil spill.

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36.4.4. On Commercial Fish and Shellfish Following the grounding of the Braer, a fisheries Exclusion Zone was established to prevent contaminated fish and shellfish from entering the human food chain. In support of this effort, and because of the high value and vulnerability of fish and shellfish to contamination by oil and polycyclic aromatic hydrocarbons (PAHs) as a result of the large quantity of oil (ca. 72,000 tons) dispersed into the water column, a major monitoring program was undertaken.1 Fish and shellfish were collected both from fish markets (for reference samples collected outside the Exclusion Zone) and from research vessels and hired fishing vessels (within the Exclusion Zone). The first samples were collected around January 13e17, 1993. In these samples both hydrocarbon (aliphatic hydrocarbons and PAHs) composition and concentration and the level of petroleum-associated taint in edible flesh were assessed, the latter using a trained sensory assessment panel. Full details of the procedures used are given elsewhere.1,2 Sensory assessment is a relatively cheap and rapid method of analyzing a large number of samples; several thousand samples were analyzed in the first few months following the Braer spill. A highly trained sensory panel can produce consistent data that can be readily used to select samples for more detailed, instrumental analysis. All species sampled during January 1993 were found, by gas chromatography-mass spectroscopy (GC-MS), to contain elevated concentrations of PAHs. GC-MS is the instrumental method of choice because it permits quantitative analysis of both parent and alkylated PAHs. In wild fish, concentrations fell rapidly from a maximum of 2650 mg/kg wet weight to reference concentrations (less than 40 mg/kg wet weight) when there was also an absence of taint. The fishery was reopened during April 1993. Concluding on appropriate reference or background concentrations for PAH in fish is fundamental, for this provides clear criteria for removing harvesting restrictions. In the case of the Braer, the absence of any petrogenic taint was also a condition for lifting restrictions. Low levels of contamination of free-living finfish by PAH was also a feature of the Sea Empress spill,3 primarily as a result of the accumulation of two- and three-ring PAH (naphthalenes and phenanthrenes) from the dissolved phase via the gills. Such contamination is rapidly lost as the dissolved concentrations fall. Crabs and lobsters retained significant levels of contamination for a longer period, on the basis of both sensory and instrumental analysis. Restrictions on the collection and sale of crustaceans other than Nephrops norvegicus (Norway lobsters) were removed in September 1994, 20 months after the spill.1 As for fish, an absence of petrogenic taint was a prerequisite of removal of a harvesting ban, and PAH concentrations were required to be within the established reference concentration range. Bivalve mollusks (mussels and scallops) accumulated high concentrations (greater than 20,000 mg/kg wet weight) of two- to six-ring PAHs, including those that are of carcinogenic potential and of concern in the human food chain.4 Lower concentrations were seen in whelks, probably

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because they are carnivores rather than filter-feeders, as filter-feeders can ingest dispersed oil droplets directly.3 Restrictions were removed for all mollusks except mussels in February 1995, two years after the spill.1 After this, controls were in place for only mussels and Norway lobsters, in which PAH concentrations remained higher than the reference levels as a result of oil having become entrained in the inner sounds and voes of Shetland.3 Long-term monitoring of PAH contamination in mussels, using both sensory assessment and GC-MS, was continued as a result,5 but in 1996 concentrations were still higher than the reference concentrations, although no taint could be detected. Parallel studies in sediments in which PAH profiling was undertaken using GC-MS indicated that the primary source of PAH in the majority of Shetland Island sediments sampled was pyrogenic rather than petrogenic (i.e., from combustion sources rather than oil), and that concentrations within the Exclusion Zone were not significantly higher than those in sediments from outside the zone.6 Considerable additional investigation was required into why concentrations in mussels were so variable. When the primary source of contamination (the oil spill) is no longer a significant source of PAHs, and PAH concentrations are close to reference values, potential local, minor sources of PAHs should be investigated, as should the impact of seasonality. In this context, there is a need to establish winter and summer reference concentrations for mussels. The final fishery restrictions, for mussels and Norway lobster, were lifted seven years after the spill. Fisheries are an important part of Shetland’s economy, and the value of the commercial fish and shellfisheries affected by the spill was around £22 million in 1993.

36.4.5. On Farmed Salmon Farmed salmon production in Shetland from over 100 farms in inshore waters was valued at around £33 million in 1993, around 20% of which production was within the affected zone.1 Monitoring was established as for commercial fish and shellfish, with assessment of hydrocarbon composition and concentration as well as taint. From January 1993 to May 1994, 125 batches of salmon from sites both within and outside the Exclusion Zone were assessed. This represented 12,800 individual samples, a huge effort. Inside the zone, summed PAH concentrations reached a maximum of 14,000 mg/kg wet weight after about 10 days, compared to a mean of 30 mg/kg outside the zone. The dominant components for the within-zone salmon were the substituted naphthalenes, which are oil-derived components. Rapid, exponential-like loss to about 1000 mg/kg wet weight occurred over the next 25 days. This was followed by a lower reduction in concentrations over the ensuing 150 days. The large number of data available allowed some statistical investigation of the relationship between concentrations of individual PAH compounds and the presence of taint, which suggested some similarity in behavior between taint and the concentrations of substituted naphthalenes (two-ring PAH derived from oil).

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Fish of the 1991 year class, which would have been marketed from early spring 1993 onward, were destroyed in February 1993 due to elevated PAH concentrations and the presence of taint. The 1992 year class fish were destroyed later, as individual fish were still tainted. Restrictions for farmed salmon were lifted in December 1993.

36.4.6. On Benthic Communities Twelve intertidal sites were studied, both those sites affected by the oil and those selected as reference sites.1 Effects on rocky shores close to the wreck site were more evident than in the sediments. Limpet populations were absent from the mid-lower shores, leading to a consequent bloom of algae that persisted for some months. No effects were observed in subtidal rocky areas exposed at low water. Two offshore locations were also studied, at which deposition of oil had taken place. Only minor impacts on community diversity were observed, although amphipods were absent from the most heavily contaminated sites in 1993. From studies conducted after the Sea Empress spill, amphipods seem to be particularly vulnerable to dispersed oil in the water column.3 Recovery of the amphipod fauna was evident in that instance after two years, as confirmed by a subsequent survey two years later.7 In the case of the Braer, recovery was underway but incomplete in 1994.1 No gross impacts were observed.

36.4.7. On the Human Population The fact that crude oil was carried in the atmosphere onto land gave rise to a strong smell of oil, resulting in reports of irritation to nose and eyes among the local population.1 Also, there was fear of a possible explosion, but the site was checked instrumentally and the vapor was found to be well outside explosion limits. Because of the high winds, some of the chemical dispersants being sprayed onto the oil on the sea close to shore drifted over the land, affecting people and houses upwind. Monitoring of organic vapors and hydrocarbons in the air was put in place as soon as possible in order to reassure the public that there were no real risks and that evacuation was unnecessary. A health study was begun on January 13, open to the population within a 3-mile radius of the Braer wreck site. This confirmed anecdotal reports of headache, throat, and skin irritation, and itchy eyes within the first days of the incident. Studies of biological markers and toxicological screening profiles failed to show any exposures likely to affect human health. In the event, there were no casualties, and no long-term health implications have been found.

36.5. CONCLUSION The Braer oil spill is one of the largest spills, in terms of quantity of oil released into the environment, to have occurred anywhere in the world (the 14th largest

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as of early 2009 according to International Tanker Owners Pollution Federation (ITOPF)). Overall, the oil spill had a minimal impact on the environment and ecology of South Shetland. Adverse impacts did occur, but were both localized and limited. The very light nature of the oil minimized overt shoreline impacts. However, those same properties enabled its widespread availability, which resulted in its incorporation into areas of fine sediments and the biota living in their vicinity. The combination of sensory assessment (as a screen) and GC-MS proved extremely effective for the analysis of biota, while a combination of UV fluorescence spectrometry (as a screening technique) and GC-MS was successful for sediment and water. The need for reference data was essential, as appropriate criteria should be established for removing any harvesting restrictions. When setting such criteria, however, there is a need to consider the impact of seasonality and the potential for local sources of PAHs to increase concentrations in biota, especially mussels. There remains today oil from the tanker associated with sedimentary deposits, specifically in the Burra Haaf and the southeast Fair Isle sedimentary basins, but these deposits are now covered with uncontaminated, more recent, deposits. The resilience of ecosystems and species populations was clearly demonstrated, and provides confidence and reassurance for the future.

REFERENCES 1. Davies JM, Topping G, editors. The Impact of an Oil Spill in Turbulent Waters: The Braer. London: The Stationery Office Ltd.; 1997. 2. Davis HK, Moffat CF, Shepherd NJ. Experimental Tainting of Marine Fish by Three Chemically Dispersed Petroleum Products, with Comparisons to the Braer Oil Spill. Spill Sci Technol Bull 2002;257. 3. Law RJ, Kelly C. The impact of the “Sea Empress” oil spill. Aquat Living Res 2004;389. 4. Law RJ, Kelly C, Baker K, Jones J, McIntosh AD, Moffat CF. Toxic Equivalency Factors for PAH and Their Applicability in Shellfish Pollution Monitoring Studies. J Environ Mon 2002;383. 5. Webster L, Angus L, Topping G, Dalgarno EJ, Moffat CF. Long-Term Monitoring of Polycyclic Aromatic Hydrocarbons in Mussels (Mytilus edulis) Following the Braer Oil Spill. Analyst 1997;1491. 6. Webster L, McIntosh AD, Moffat CF, Dalgarno EJ, Brown NA, Fryer RJ. Analysis of Sediments from Shetland Island Voes for Polycyclic Aromatic Hydrocarbons, Steranes, and Triterpanes. J Environ Mon 2000;29. 7. Nikitik CCS, Robinson AW. Patterns in Benthic Populations in the Milford Haven Waterway Following the Sea Empress Oil Spill with Special Reference to Amphipods. Mar Pollut Bull 2003;1125.

Chapter 37

1991 Gulf War Oil Spill Jacqueline Michel

Chapter Outline 37.1. Review of the Spill

1127

37.1. REVIEW OF THE SPILL The intentional release of 11 million barrels of crude oil into the Arabian Gulf during the 1991 Gulf War resulted in the largest oil spill in history. The spill sources were eight tankers, a refinery, a tank field, and two terminals. Most of the oil was transported south along the shoreline, with the bulk of the floating oil trapped behind Abu Ali Island, north of Jubail, Saudi Arabia. An estimated 1,163,000 barrels of oil were recovered from the water surface.1 Gundlach et al. summarized land-based shoreline surveys that showed 706 km in Saudi Arabia had been oiled, with 366 km classified as heavy, 220 km as moderate, 34 km as light, and 86 km as very light.2 Shoreline cleanup was conducted in a few small areas, including important offshore turtle nesting beaches and a mangrove forest on Gurmah Island. An estimated 50e100% of the intertidal biota were killed; in heavily oiled marshes, less than 1% of the plants survived.3,4 Estimated costs for cleanup in 1991 ranged from $210e540 million. The Saudi government submitted a claim in 2003 to the United Nations Compensation Commission for environmental damages resulting from the spill. In 2006, they were awarded $465 million for coastal restoration projects, which were begun in 2008. Studies conducted in 1992 and 1993 to monitor the fate of the oil stranded in Saudi Arabia reported severe impacts to intertidal habitats, particularly the halophyte marsh/algal mat complexes and mud flats at the heads of sheltered bays.5,6 One year after the spill, all of the halophytes were dead, and there was no sign of living epibiota in the upper intertidal zone. The oil had penetrated up to 40 cm in the heavily burrowed sand and mud flats. Two years after the spill, there had been little improvement; in some areas, the subsurface oil migrated Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10037-1 Copyright Ó 2011 Elsevier Inc. All rights reserved.

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deeper, up to twice the depths in 1992. On sand flats, the heavy surface oil layers acted as barriers to subsurface oil flushing and weathering. One year after the spill, Michel et al. conducted an assessment of the contamination of subtidal habitats.7 They conducted 197 bottom-observation dives and collected 170 bottom sediment and sediment trap samples. The results showed no evidence of large-scale sinking of the oil. The sediments were lightly contaminated, with up to 900 mg/g total hydrocarbons and the highest concentration in sheltered, muddy basins. Total polynuclear aromatic hydrocarbons (PAHs) were in the range of 1e7 mg/g, which is considered to be below levels of toxic concerns. One year later, studies showed no significant long-term impacts to seagrass beds, coral reefs, and unvegetated sandy and silty substrates.8,9 Shrimp stocks in the Gulf were severely impacted, with 1992 spawning biomass reduced to 1% and total biomass at 27% of pre-spill levels.10An estimated 30,000 seabirds were killed, and breeding success in 1992 and 1993 severely declined; however, seabird colonies appeared to recover by 1995.11,12 In 2002, the Kingdom of Saudi Arabia conducted shoreline assessments to determine the impacts of the 1991 oil spill as the basis for environmental damage claims.7 The Oiled Shoreline Survey consisted of transects at 250-m spacing along 800 km of coastline in Saudi Arabia. The field teams completed 3107 transects; dug, described, and photographed 19,515 trenches; and collected 26,158 samples for total petroleum hydrocarbon (TPH) analysis, 2660 samples for detailed chemical characterization and fingerprinting, and 134 bivalve tissue samples. Intertidal ecologists used a Rapid Environmental Assessment to assess the ecological condition of the shoreline along each transect, recording all the macroepibiota observed by habitat and intertidal zone adjacent to each transect. One indicator of the ecological condition of intertidal habitats is the extent and degree of oiled sediments. By this measure, the impact of the Gulf War oil spill 12 years later was massive. Twelve years later, there were 8,000,000 m3 of oiled sediments in the intertidal zone (Table 37.1). Of this volume, 31% was described as “heavy” oiling; 41% was “moderate,” and 25% was “light.” Less than 1% occurred as asphalt pavements. Most of the oil (67%) occurred as oiled burrows, a consequence of the very high, pre-spill densities of intertidal crabs. The mean TPH content in heavily oiled sandy sediments was 41,200 milligrams per kilogram (mg/kg); in heavily oiled burrows, the mean TPH was 13,800 mg/kg. Pre-spill data on the ecological condition of intertidal habitats in Saudi Arabia were not sufficient to support pre- and post-spill comparisons; thus, the approach taken was to compare oiled and unoiled sites. The species richness values (total number of macroepifaunal species) for each habitat and zone at comparison transects were analyzed to calculate the mean and 95% confidence limits. The lower 95% confidence limit (rounded up to the nearest whole number) became the species richness threshold for that habitat and zone

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TABLE 37.1 Sediment Volumes and PAH Data for Each Type of Oil Residue for the Sediment Samples Collected in 2002/2003. (The percent of samples that exceed the ER-L and ER-M are shown.) Visual Oil Descriptor

Volume (m3) and % of Total Oiled Sediments

No Visible Oil

No. Mean TPH Samples (mg/kg)

Mean TPAH (ng/g)

435

343

379

Lightly Oiled Burrows (LOB)

1,359,000 (17%)

150

3210

3580

Lightly Oiled Residues (LOR)

630,000 (8%)

143

5520

6240

Moderately Oiled Burrows (MOB)

2,156,000 (27%)

296

8200

20,620

Moderately Oiled Residue (MOR)

1,172,000 (14%)

902

20,200

25,850

Heavily Oiled Burrows (HOB)

1,846,000 (23%)

166

13,800

79,900

Heavily Oiled Residues (HOR)

669,000 (8%)

467

41,200

126,890

Other Oil Residues

260,000 (3%)

Totals

8,092,000

2286

combination. If an oiled transect had a species richness value lower than the threshold, it was considered to be “nonrecovering,” based on the assumption that the return of species is the first stage of recovery. If an oiled transect has a species richness value equal to or greater than the threshold, it was considered to be “recovering.” Species richness is very limited as a measure of ecological health, although it is widely used. Species richness cannot differentiate between the presence of a single individual of a species and the normal abundance of that species. Further analysis of the data at the “recovering” transects showed that the species assemblages were different from the comparison transects, indicating a disturbed community structure. The characteristic species for that habitat and zone had lower occurrences, whereas there were many noncharacteristic but opportunistic species present. Table 37.2 is a summary of the species richness data on the recovery status of 10 different habitats and two intertidal zones along the Saudi Arabian shoreline. As one might expect, the sheltered habitats show the least recovery, whereas the more exposed habitats show the most recovery after 12 years.

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TABLE 37.2 Ecological Recovery Expressed as Percentage of Transects Recovering to a Comparison Threshold Value, by Habitat and Zone in the Oil-impacted Areas. (Note that there can be multiple habitats per zone in a transect, so the totals for each zone exceed the number of transects.) ZONE Supralittoral

Upper Shore

Recovering/ Disturbed* (%)

NonRecovering (%)

No. of OilImpacted Transects

Recovering/ Disturbed* (%)

NonRecovering (%)

Exposed outer sand beaches

536

62.1

37.9

181

71.8

28.2

Moderately exposed sand beaches

1,532

35.9

64.1

65

76.9

23.1

Exposed rocky shores

123

81.3

18.7

204

69.1

30.9

Moderately exposed rocky shore

228

68.9

31.1

428

32.2

67.8

Sheltered rocky shores

105

85.7

14.3

158

42.4

57.6

Exposed and moderately exposed sandy tidal flats

e

e

e

1,362

59.0

41.0

Sheltered muddy tidal flats

e

e

e

566

28.8

71.2

Salt marsh on sand

264

30.7

69.3

98

40.8

59.2

Salt marsh on mud

444

10.8

89.2

337

12.8

87.2

Mangroves

23

56.5

43.5

47

10.6

89.4

PART | XIII Specific Case Studies

HABITAT

No. of OilImpacted Transects

Chapter | 37 1991 Gulf War Oil Spill

1131

The factors limiting recovery include the following. l l l

l l

The chemical toxicity of the oil residues. The physical toxicity of heavy and hardened oil residues. Other physical barriers, such as extensive and thick algal mats, that affect seedling success, settlement of larvae, and the viability of burrowing animals. Barth stated that these extensive algal mats completely seal the surface, preventing microbial oil degradation as well as any resettlement by macrofauna.13 Limited sources for recruitment of biota. Hydrologic functioning of tidal channels.

REFERENCES 1. Tawfiq NI, Olsen DA. Saudi Arabia’s Response to the 1991 Gulf Oil Spill. Mar Pollut Bull 1993;333. 2. Gundlach ER, McCain JC, Fadlallah YH. Distribution of Oil Along the Saudi Arabian Coastline (May/June 1991) as a Result of the Gulf War Oil Spills. Mar Pollut Bull 1993;93. 3. Jones DAI, Watt J, Plaza TD, Woodhouse TD, Al-Sanei M. Natural Recovery of the Intertidal Biota Within the Jubail Marine Wildlife Sanctuary after the 1991 Gulf War Oil Spill. In: Krupp F, Abuzinada AH, Nader IA, editors. A Marine Wildlife Sanctuary for the Arabian Gulf, vol. 137. Frankfurt, Germany: National Commission for Wildlife Conservation and Development, Riyadh, Saudi Arabia and Senckenbbergische Naturforschende Gesellschaft; 1996. 4. Boer B, Warnken J. Flora of the Jubail Marine Wildlife Sanctuary, Saudi Arabia. In: Krupp F, Abuzinada AH, Nader IA, editors. A Marine Wildlife Sanctuary for the Arabian Gulf, vol. 290. Frankfurt, Germany: National Commission for Wildlife Conservation and Development, Riyadh, Saudi Arabia and Senckenbbergische Naturforschende Gesellschaft; 1996. 5. Hayes MO, Michel J, Montello TM, Aurand DV, Al-Mansi AM, Al-Momen AH, et al. Distribution and Weathering of Shoreline Oil One Year After the Gulf War Oil Spill. Mar Pollut Bull 1993;135. 6. Hayes MO, Michel J, Montello TM, Aurand DV, Sauer TC, Al-Mansi A, et al. Distribution and Weathering of Oil from the Iraq-Kuwait Conflict Oil Spill Within Intertidal HabitatsdTwo Years Later. IOSC 1995;443. 7. Michel J, Hayes MO, Getter CD, Cotsapas L. The Gulf War Oil Spill Twelve Years Later: Consequences of Eco-Terrorism. IOSC 2005:1e6. 8. Kenworthy WJ, Durako MJ, Fatemy SMR, Valavi H, Thayer GW. Ecology of Seagrasses in Northeastern Saudi Arabia One Year After the Gulf War Oil Spill. Mar Pollut Bull 1993;213. 9. Richmond MD. Status of Subtidal Biotopes of the Jubail Marine Wildlife Sanctuary with Special References to Soft-Substrata Communities. In: Krupp F, Abuzinada AH, Nader IA, editors. A Marine Wildlife Sanctuary for the Arabian Gulf, vol. 159. Frankfurt, Germany: National Commission for Wildlife Conservation and Development, Riyadh, Saudi Arabia and Senckenbbergische Naturforschende Gesellschaft; 1996. 10. Matthews CP, Kedidi S, Fita NI, Al-Yahya A, Al-Rasheed K. Preliminary Assessment of the Effects of the 1991 Gulf War on Saudi Arabian Prawn Stocks. Mar Pollut Bull 1993;251. 11. Symens P, Alsuhaibany AH. Status of the Breeding Population of Terns (Sternidae) Along the Eastern Coast of Saudi Arabia Following the 1991 Gulf War. In: Krupp F, Abuzinada AH, Nader IA, editors. A Marine Wildlife Sanctuary for the Arabian Gulf, Environmental Research

1132

PART | XIII Specific Case Studies

and Conservation Following the 1991 Gulf War Oil Spill, vol. 404. Frankfurt, Germany: National Commission for Wildlife Conservation and Development, Riyadh, Kingdom of Saudi Arabia and Senchenberg Research Institute; 1996. 12. Symens P, Werner M. Status of the Socotra Cormorant in the Arabian Gulf after the 1991 Gulf War Oil Spill, with an Outline of a Standardized Census Technique. In: Krupp F, Abuzinada AH, Nader IA, editors. A Marine Wildlife Sanctuary for the Arabian Gulf, Environmental Research and Conservation Following the 1991 Gulf War Oil Spill, vol. 390. Frankfurt, Germany: National Commission for Wildlife Conservation and Development, Riyadh, Kingdom of Saudi Arabia and Senchenberg Research Institute; 1996. 13. Barth H. The Influence of Cyanobacteria on Oil Polluted Intertidal Soils at the Saudi Arabian Gulf Shores. Mar Pollut Bull 2003;1245.

Chapter 38

Tanker SOLAR 1 Oil Spill, Guimaras, Philippines: Impacts and Response Challenges Ruth Yender and Katharina Stanzel

Chapter Outline 38.1. 38.2. 38.3. 38.4.

Incident Summary Impact Summary Shoreline Cleanup Mangrove Cleanup and Recovery

1133 1134 1139 1143

38.5. Fisheries Impacts and Health Concerns 38.6. Summary Disclaimer

1144 1145 1146

38.1. INCIDENT SUMMARY The tanker SOLAR 1 (998 GT) sank on August 11, 2006 in the Guimaras Strait, approximately 18 km southwest of Guimaras Island in the Western Visayas region of the central Philippines (Figure 38.1). The Philippines registered vessel was on its way from Bataan in the northern Philippines to Mindanao in the south when it sank in rough seas. A substantial but unknown amount of the tanker’s cargo of about 2100 tons of IFO 217, an intermediate fuel oil, was spilled upon sinking. The vessel continued to release oil for several weeks at a decreasing rate from its location on the seafloor at a depth of approximately 630 m. Salvage efforts conducted 7 months after the incident to remove any oil remaining in the wreck revealed that nearly all of the oil onboard the SOLAR 1 had already been released. The Philippine Coast Guard, which at the time was the lead government agency for oil spill response in the Philippines, managed the SOLAR 1 response with limited resources and under intense political pressure and press attention. Because the Philippines has a regionalized governmental structure, much of the response planning and interagency exchange took place both in Iloilo City (Panay Province) at a regional level and in Manila at the national level, while Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10038-3 Copyright Ó 2011 Elsevier Inc. All rights reserved.

1133

1134

PART | XIII Specific Case Studies

FIGURE 38.1 Map of SOLAR 1 approximate sinking site and heavily oiled shorelines (Map courtesy of the International Tanker Owners Pollution Federation Limited).

the island and islets of Guimaras actually represent an independent province of the Philippines. Government environmental and public health agencies and the national and regional disaster coordinating committees were involved at strategic levels, while the national oil company Petron Corporation, the cargo owner, assisted with operational and logistical support. Political demands and press attention frequently made directing response operations more difficult for response managers, giving rise to a number of peripheral activities focused mainly on public opinion. On-water response was limited primarily to chemical dispersant application from vessels and light aircraft. Although some visual observations indicated that dispersants were effective when applied appropriately to floating oil, the scale of dispersant operations was limited, as the bulk of the oil had stranded on shorelines within a few days after the sinking and initial release. Low volumes of oil continued to seep from the sunken wreck and naturally dissipate within 4 km from the sinking site. These chronic small releases of oil therefore posed no threat to nearshore resources and would in any event have been too minor to treat effectively. No skimming or other on-water oil recovery was conducted.

38.2. IMPACT SUMMARY Much of the oil released from the SOLAR 1 eventually stranded on island shorelines and in coastal mangroves, harming sensitive tropical habitats,

Chapter | 38 Tanker SOLAR 1 Oil Spill, Guimaras, Philippines

1135

disrupting fishing and subsistence activities, and affecting coastal communities. The southern shores of Guimaras Island (the largest of the islands in the Guimaras Strait), as well as several smaller islands to the south and east, were heavily impacted by spilled oil (Figure 38.1). The shoreline impact was patchy, and the most significant contamination was found in areas with predominantly southwestern exposure to wind and waves. This included stretches from Lusaran Point eastward to Lugmayan Point on Guimaras, and the southern shores of smaller islands, including Panobolon and Guiwanon. The Taklong Island National Marine Reserve (TINMAR) in the southwest of Guimaras Island, which includes extensive stands of mangroves, and the associated Marine Biological Station operated by the University of the Philippines Visayas (UPV) were also impacted by oil. The coastline of Guimaras is very complex and comprises hundreds of small bays, peninsulas, and islets. Associated with the more sheltered areas are extensive mangrove stands as well as seagrass beds. Coral reefs also fringe much of the coast. These ecosystems support numerous small fishing villages. In addition to trap, net, and line fishing from small outrigger canoes (Figure 38.2), the area is extensively fished with fixed filter nets and corrals, set up in shallow subtidal areas and harvested at regular intervals. Oil stranded along several shoreline types, including sand, pebble, cobble, coral rubble, and boulder beaches (Figure 38.3). Oil on some of these beaches seeped into the sediment or was buried under clean sediment deposited by wave action. Areas of limestone bluffs and cliffs were also coated by oil. Philippine natural resource agencies estimated approximately 650 ha of mangrove forest were affected by the spill, with seedlings, roots and trunks coated in bands between 10 and 130 cm high (Figure 38.4).1 Spill impacts to mangroves are of particular concern because of the mangroves’ extreme ecological importance and their known sensitivity to the effects of oil and cleanup.2 Naturally established stands in the affected area are very diverse, with

FIGURE 38.2 Oiled fishing outrigger canoes along Southern Guimaras Island coast.

1136

PART | XIII Specific Case Studies

FIGURE 38.3 Cobble Beach showing band of stranded oil from SOLAR 1 spill.

more than 30 different mangrove species.3 Tolerant of high-salt concentrations and oxygen-poor soils, mangroves are adapted to thrive in intertidal marine environments. Mangrove ecosystems, with their complex, tidally inundated root structures, provide critical habitat for juvenile fish and invertebrates,

FIGURE 38.4 Oiled mangroves in Taklong Island National Marine Reserve.

Chapter | 38 Tanker SOLAR 1 Oil Spill, Guimaras, Philippines

1137

stabilize shorelines, regulate flooding, recycle nutrients, and provide a protective buffer zone from tsunamis and storm events such as tropical cyclones. Prop roots and pneumatophores, the root structures of some mangrove trees, have specialized structures known as lenticels, which are large pores for gas exchange. If roots and lenticels are coated with oil, inhibition of gas exchange can lead to stress and ultimately suffocation of the trees. Within weeks of the SOLAR 1 oil spill, however, visual inspection of oiled mangroves revealed that most oiled roots had apparently increased the growth rates of cells from these pores, shedding oiled layers and freeing the lenticels up for gas exchange, while the surrounding root surface remained oiled (Figure 38.5). Direct contact with oil or contamination of sediments may also cause toxic effects to mangroves, although this is a greater concern with lighter, more toxic oils. Following the SOLAR 1 oil spill, mangroves in more heavily oiled areas without good tidal flushing displayed signs of stress. Yellowing of leaves (chlorosis), partial defoliation, and, in some cases, proliferation of roots and trunk sprouts and other symptoms known to be associated with oil exposure were observed.4 Adult tree mortality, however, was confined to a few small areas (totaling less than 1 ha), where oil remained trapped in sediments several weeks or months after the spill, causing chronic contamination and leaching. Heavily oiled mangrove seedlings and young trees

FIGURE 38.5 Oil-free lenticels on oiled mangrove prop root.

1138

PART | XIII Specific Case Studies

FIGURE 38.6 Surviving oiled mangrove seedling with new leaves.

tended either to die rapidly with the necrosis of the apical buds, or to survive and quickly produce new leaves to compensate for leaves coated with oil (Figure 38.6). The trees most affected belonged to three species of Rhizopora and Avicennia marina. Regarding other biological impacts, no significant bird or other wildlife mortalities were observed during the response or reported by local residents, specialist scientists, or resource managers.5 The apparent absence of observed major impacts to wildlife may be due in part to the depleted status of many wild populations in the affected area, resulting from decades of overfishing, destructive fishing practices, and replacement of natural habitats by fish ponds. Because of the patchy nature of oil contamination along the shorelines, no large-scale ecological impacts were anticipated or indeed observed after the incident.5 Anecdotal evidence indicated limited intertidal crustacean and shellfish narcosis, and mortality occurred in some heavily oiled areas immediately after the spill. Follow-up surveys, however, did not find any longer-term effects.5 There were also initial reports of physical oiling and increased mucus production in a nearshore coral reef that had been affected during spring low tides. However, dive surveys several weeks after the sinking of the SOLAR 1

Chapter | 38 Tanker SOLAR 1 Oil Spill, Guimaras, Philippines

1139

found no remaining oil and no bleaching of the reef areas in question.5 No longterm impacts to corals in the spill area have been reported.

38.3. SHORELINE CLEANUP An estimated 124 km of shoreline were oiled to varying degrees.5 In attempts to protect shorelines from oiling, local residents improvised and deployed “artisan” boom and sorbents made from materials such as bamboo, banana leaves, coconut husks, and rice straw (Figures 38.7 and 38.9). This boom, though impressively resourceful, was not effective. Commercial exclusion and containment booms, which would have been much more effective, were not readily available. Village residents, many of whom live in the immediate vicinity of impacted shorelines, began to manually clean beaches and oiled structures as soon as the oil came ashore. In the weeks following the spill, the Philippine Coast Guard oversaw cleanup operations, assisted by the cargo owner, Petron Corporation, and contractors hired by the shipowner. The remoteness and rugged terrain of the affected area made shoreside access for cleanup difficult and oversight of cleanup operations challenging. Manual removal was the primary technique used to clean shorelines, conducted predominantly by local fishermen and residents employed through a “cash-for-work” program run by the Petron Corporation. Cleanup of sandy

FIGURE 38.7

“Artisan” boom made by village residents from local natural materials.

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PART | XIII Specific Case Studies

FIGURE 38.8 “Artisan” boom made by village residents from local natural materials.

shorelines was accomplished relatively rapidly and efficiently, so that no significant volumes of mobile oil remained 3 weeks after the vessel sank. Cleanup of gravel beaches, considered here to include pebble, cobble, coral rubble, and boulder beaches, proved more difficult. Some heavily oiled gravel was manually removed and bagged for disposal. Generally, removal of substrate from gravel beaches is best kept to a minimum in order to reduce the effects of altering the beach profile, prevent erosion, and reduce waste generation. Oiled gravel left in place was manually wiped using sorbent pads (Figure 38.10). Early in the response, some misguided cleanup techniques, such as washing individual oiled cobbles in barrels of kerosene, were briefly attempted on shorelines in some locations. This practice was of concern because kerosene exposure by contact and inhalation can pose health risks to cleanup workers and could cause additional environmental damage through toxic effects of the solvent. Cleanup operations continued on gravel beaches for approximately 12 weeks after the spill. Though oil remained in the gravel at that point, the practical limits of oil removal, without causing more environmental harm than benefit from further cleaning, had been reached. Residual oil that could not be effectively removed remained to degrade naturally over time.

Chapter | 38 Tanker SOLAR 1 Oil Spill, Guimaras, Philippines

1141

FIGURE 38.9 Village resident making snare or “Pom Pom” boom.

Storage, removal, and disposal of collected oily waste presented a number of challenges. Temporary waste storage sites were established near waste collection areas, often near human habitations (Figure 38.11). In the rush to remove bulk oil from the shores, few provisions were initially made to segregate these storage sites, to protect them from rain and strong sunlight, or to prevent leaching. Plastic bags used for storage were susceptible to accelerated degradation through ultraviolet (UV) light exposure; generally they were not durable enough, and many soon began to leak (Figure 38.12). Because local disposal of oily waste was deemed politically unacceptable, bagged waste was instead moved to a wharf in the southwest of Guimaras Island. From there, it was transported by barge to a cement plant in Northern Mindanao where it was used as an alternative fuel and raw material in the production of cement. Because road access was difficult or nonexistent, waste had to be collected from many temporary storage sites by outrigger canoes powered by small engines. In total, an estimated 282,000 bags (about 2100 tons) of oily material were shipped for disposal, transported in barges making nine separate journeys.

1142

PART | XIII Specific Case Studies

FIGURE 38.10 Cleanup worker manually removing oil from gravel with sorbent pads.

FIGURE 38.11 Bags of oiled sediment and debris accumulating in village.

Chapter | 38 Tanker SOLAR 1 Oil Spill, Guimaras, Philippines

1143

FIGURE 38.12 Oil seeping out of improperly stored oily waste.

38.4. MANGROVE CLEANUP AND RECOVERY Mangrove habitats are known to be highly sensitive to oil pollution and subsequent cleanup, since their root structures are easily damaged by trampling. The trampling can also push oil further into the usually very fine sediments, where it persists in low-oxygen conditions and can become a source of chronic pollution. Given this sensitivity and the extent and nature of the oiling following the SOLAR 1 incident, experts with the Philippine Department of Environment and Natural Resources (DENR), UPV, and an international advisory team concurred that natural recovery and monitoring were the best response strategy for most areas of oiled mangroves, followed by restoration, if needed. The emphasis was put on the fact that mangrove plants that might otherwise survive oiling could easily be damaged further by inappropriate cleanup. Mangrove experts also recommended that bioremediation agents, dispersants, or chemical shoreline cleaners not be applied directly onto mangrove plants or surrounding sediment. These efforts would pose a significant risk of trampling and damaging mangroves, without appreciably accelerating rates of oil degradation. Also, the chemicals themselves, depending on formulation, could have toxic effects on mangroves and associated fauna and present further

1144

PART | XIII Specific Case Studies

risk of chronic pollution, were they to seep into surrounding sediments. In contrast to chemical shoreline cleaners and bioremediation products, dispersant formulations are designed for application to oil on open water and are neither intended nor appropriate for application on shorelines or vegetation. As recommended by mangrove experts, little cleanup was conducted in oiled mangroves. In a few areas, however, partly because of the decentralized nature of the response management, cleanup workers failed to adhere to this advice and some cutting of roots, removal of oiled seedlings, and application of dispersants and other chemical products to trees occurred. Anecdotal evidence subsequently suggested that mangrove trees displaying leaf chlorosis and other signs of severe stress within a few weeks after the spill were observed primarily in areas where roots had been cut or chemical products had been applied. Monitoring observations made for nearly two years after the spill indicated that the oiled mangroves largely survived and suffered much less mortality and stress than initially feared. Only a few small patches with a total area of under 1 ha of dead mangroves were observed, primarily in some protected areas at the heads of small bays and inlets. Most of these areas are characterized by lower rates of tidal flushing and were impacted by significant volumes of fresh oil after the vessel sank. In some locations where mangroves were observed to die, oil had been retained in fine sediments and paludal depressions for months after the spill, creating a chronic source of exposure. Studies by the UPV and the DENR found that less than 1.5% of impacted mangrove trees (i.e., about 510 individual trees) died. Overall, the impacted mangroves suffered only minor mortality and appeared to be recovering naturally. Several factors likely contributed to the high survival rate of oiled trees following this spill. First, as previously mentioned, lenticels on oiled roots were observed to shed cells at an elevated rate, reducing potential suffocation. Second, tidal flushing in most affected areas was sufficient to help abrade oil off coated tree surfaces. Third, the relatively lower toxicity of this heavy oil compared with more toxic lighter oils or fuels (e.g., jet fuel, gasoline or diesel) likely accounted for lower mortality rates than have been observed after spills elsewhere and involving lighter products.

38.5. FISHERIES IMPACTS AND HEALTH CONCERNS Subsistence and small-scale commercial fishing activities in the Guimaras area were disrupted by the spill. Many fishermen reported that their nets were oiled and that they had no alternative means of fishing until those nets could be replaced. In addition, the traditional practice of collecting intertidal crustaceans and mollusks such as mangrove clams (Anodontia edentula, “Imbao”) at low tide was affected not only by oil in the early days after the spill, but later also by fears of invisible contamination. The Philippine Bureau of Fisheries and Aquatic Resources (BFAR) did not ban fishing or institute seafood advisories, basing this decision largely on U.S. seafood guidance documents and sensory

Chapter | 38 Tanker SOLAR 1 Oil Spill, Guimaras, Philippines

1145

evaluation techniques.6-8 Experience from past oil spills around the world indicates that seafood is rarely contaminated by oil spills to levels that would represent risk to human health. Finfish are able to metabolize and eliminate petroleum compounds very rapidly and efficiently. Due to public perceptions that fish from the entire area might be contaminated, however, local fishermen and fish pond owners were reluctant to catch or harvest fish, and market rates were affected throughout Guimaras Province and neighboring Iloilo City on Panay. Thus, perceptions that seafood might be contaminated affected fisheries much longer than warranted and far beyond the areas actually contaminated by oil. Several village residents and cleanup workers complained of health effects from the spilled oil. The Philippine Department of Health (DOH) reported measuring high hydrogen sulfide levels near oiled shorelines in some locations. These measurements conflicted with much lower results obtained from monitoring in the spill area conducted by other Philippine government departments, causing confusion and doubt. Nevertheless, as a precautionary measure, the DOH evacuated some nearshore villages for several weeks, creating additional hardship for residents. Significantly elevated hydrogen sulfide levels as reported by the DOH have never been reported from stranded oil at other oil spills elsewhere in the world. Hydrogen sulfide gas can be produced during the decomposition of organic matter and is therefore commonly found near mangrove swamps in low concentrations. Low levels of hydrogen sulfide also could be generated from waste bags containing decomposing seaweed and other organic materials as well as oily sediment. Levels generated, however, would not be expected to reach concentrations representing a human health risk.

38.6. SUMMARY The sinking of the tanker SOLAR 1 in the Guimaras Strait resulted in the Philippines’ largest known oil spill in recent history, affecting extensive areas of mangroves and beaches along the southern coast of Guimaras Island and smaller islands in the Strait. The spill disrupted fisheries and affected subsistence villages along the impacted coastline. Limited resources and difficulties accessing this relatively remote area posed substantial challenges for the spill response and cleanup, which was managed by the Philippine Coast Guard with operational support from the owners of the vessel and its cargo. If more onwater response resources had been readily available and deployed, the extent of shoreline impacted by the oil likely would have been reduced, though not completely prevented. Boom improvised from natural materials by Village residents were quickly deployed but not effective. Village residents hired for the response manually cleaned oiled shorelines. Sandy shorelines were cleaned relatively rapidly and effectively, but cleanup continued for about 3 months on gravel beaches, where oil had seeped into the coarse sediment. Removal of

1146

PART | XIII Specific Case Studies

heavily oiled gravel and manual cleaning of gravel in-situ were conducted to the limits of practical effectiveness. Oil that could not be removed without causing more environmental harm was left to degrade naturally. This is the same approach, with the same limits in effectiveness, applied at most cleanups of oiled gravel beaches elsewhere in the world. Impacted mangroves, left largely uncleaned as recommended by experts, suffered only minor patches of mortality after the spill and continue to recover naturally. This result supports the advisability of employing low-impact cleanup methods or natural recovery for oiled habitats that are highly sensitive to potential adverse impacts from cleanup.

DISCLAIMER The findings and conclusions in this chapter are those of the authors and do not necessarily represent the views of the U.S. National Oceanic and Atmospheric Administration (NOAA) or the International Oil Pollution Compensation Funds.

REFERENCES 1. Department of Environment and Natural ResourcesdRegion VI, Republic of the Philippines, ed. Assessment of Oil Spill-Affected Mangrove Stands in Guimaras, Monitoring Report; 2007. 2. Yender, Ruth. Response, in Oil Spills in Mangroves, Planning and Response Considerations. R. Hoff, ed. Department of Commerce, National Oceanic and Atmospheric Administration, NOAA Ocean Service, Office of Response and Restoration; 2007:36e47. 3. Primavera JH, Sabada RS, Lebata MJHL, Altamirano JP. Handbook of Mangroves in the PhilippinesdPanay. Iloilo, Philippines: SEAFDEC Aquaculture Department; 2004. 4. Snedaker SC, Biber PD, Aravajo RJ. Oil Spills and Mangroves: An Overview, Managing Oil Spills in Mangrove Ecosystems, OCS Study MMS 97e0003, U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico OCA Region; 1996. 5. Task Force SOLAR 1, editor. Discussion Papers for the Scientific Conference on Guimaras: Integrating Rapid Assessments and Developing Rehabilitation Protocols for SOLAR 1 Oil Spill, National Disaster Coordinating Council, Republic of the Philippines; 2006. 6. Reilly TI, York RK. Guidance on Testing and Monitoring of Seafood for Presence of Petroleum Taint Following an Oil Spill, Technical Memorandum NOS ORR 9, U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Ocean Service, Office of Response and Restoration; 2001. 7. Yender R. Improving Seafood Safety Management After an Oil Spill. Proc. of 2003 International Oil Spill Conference, 2003. 8. Yender R, Michel J, Lord C. Managing Seafood After an Oil Spill. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Ocean Service, Office of Response and Restoration; 2002.

Conversions

To Convert From

Into

Multiply By

acres acres atmosphere (pressure) atmosphere (pressure)

hectares square metres (m2) N m 2 (Pascals) pounds per square inch (psi) m3/day cubic feet cubic metres (m3) Imperial gallons U.S. gallons Litres tonnes " " " Pa s mPa s cubic metres (m3) barrels cubic feet millilitres (mL) Imperial gallon inches metres Litres Litres acres centimetres pounds miles miles (nautical) knots metres per second (m/s) kilometres per hour (km/hr) barrel/day feet kilometres kilometres grams kPa square metres (m2) square feet pounds

0.405 4047 1.01 105 14.7

barrel/day barrels barrels barrels barrels barrels barrels (oil) " " " centipoise (viscosity) centipoise (viscosity) cubic feet cubic metres (m3) cubic metres (m3) cubic metres (m3) cubic metres (m3) feet feet gallon (Imperial) gallon (U.S.) hectares inch kilograms kilometres kilometres kilometres per hour (km/hr) knots knots m3/day metres miles miles (nautical) pounds psi (pressure) square feet (ft2) square metres (m2) ton - long

Oil Spill Science and Technology. DOI: 10.1016/B978-1-85617-943-0.10001-2 Copyright Ó 2011 Elsevier Inc. All rights reserved.

0.159 5.615 0.159 35 42 159 0.159 density 0.136 (crude oil) 0.116 (gasoline) 0.150 (Bunker C) 0.001 1 0.0283 6.29 35.3 1,000,000 220 12 0.305 4.55 3.79 2.47 2.54 2.2 0.62 0.54 0.54 0.52 1.85 6.29 3.28 1.61 1.85 453.6 6.89 0.093 10.76 2240

1147

1148

Conversions

To Convert From

Into

Multiply By

ton - short ton - short tonne tonne

pounds tonnes kilograms ton - short

2000 0.907 1000 1.1

Index

Acoustic sensor systems, 139 Adhesion, 72e73 Aircraft spills, 37e38 American Petroleum Institute gravity, 57, 74, 66e67 Analysis, see Chemical analysis API gravity, see American Petroleum Institute gravity Aromatics, 73 Athos I, 965e967 Asphaltenes, 53e55, 73 Barges, 26e29 Beach cleaners, see Surface washing agents Beach cleanup, see Shoreline countermeasures Beatty, D., 275, see D. Simecek-Beatty Benzene toluene ethyl-benzene xylenes, 53 Biodegradation, 193e194, 535e539 Biodegradation agents, 432e433 Canadian approval of, 659e661 U.S. approval of, 674e681 Biomarkers, 99e107 Blowouts, 22 Booms, 303e313 Ancillary equipment, 313 Boom configurations, 308e309 Boom failures, 309e313 Bubble barriers, 315 Deflection angles, 307 Effects of weather, 345e353, 383 Sorbent booms, 314e315 Braer, 1119e1126 Brown, C., 111, 171, 643

BTEX, see Benzene toluene ethyl-benzene xylenes Bubble barriers, 315 Bulk properties, 63e77 Bunker C, 54e56 Bunker fuel, 54e56 Canadian testing/approval treating agents, 662 Approval, 662 Biodegradation agents, 659e661 Demulsifiers, 657e658 Dispersants, 645e647 Herding agents, 658 Recovery agents, 658 Sinking agents, 661 Solidifiers, 658e659 Surface washing agents, 653e657 Swirling flask, 647e649 Toxicity, 645 Endocrine disrupting, 664 Genotoxicity, 664e665 Sub-lethal effects, 665e666 Case studies, 1103e1146 Challenger, G., 1083 Chemical analysis, 87e107 Chromatography, see Gas chromatography Communicating uncertainty, 291e292 Composition of oil, 51e54 Computer models, 198e199 Containment, 303e315 Contingency planning, 1027e1031 Conversions, 1147e1148 Cooperatives, see Oil spill cooperatives 1149

1150

Crude oil, 54e56 Current uncertainty, 284e287 De Nouy ring, 68e69 Density, 55e77, 66e67, 81 DBL-152, 967e974 Diamondoids, 105e106 Diesel fuel, 54e56 Dispersant effectiveness, 71e72 Dispersants, 429, 435e582 Accelerated weathering, 561e562 Application systems, 560e561, 592e594, 596e599 Application, 551e552, 560e561, 583e610 Monitoring, 596e602 Nomograms, 594e610 Spray aircraft, 593e594 Spray equipment, 592e594, 596e599 Assessment of use, 553e555, 584e591 Biodegradation, 535e539 Biodiesel, 559e560 Canadian approval of, 645e647, 662 Composition effects, 506e511 Dispersant ratio, 511e512 Droplet size, 518e519 Effectiveness, 451e481 Effects of weather on, 372e378, 398e403, 557e558 Energy effects, 499e506 Formulations, 437e440 Testing formulation differences, 629e642 Interaction with sediment, 555e556 Laboratory effectiveness, 464e467 Modeling dispersion, 556e557 Monitoring effectiveness, 481e499

Index

Net Environmental Benefit Analysis, 587e591 Photoenhanced toxicity, 533e534 Salinity effects, 512e518 SERVS protocol, 483e486 SMART protocol, 482e485 Spill of opportunity research, 555 Stability, 441e451 Stokes’ rise, 447 Tank tests, 467e481 Temperature and salinity effects, 558e559 Temperature effects, 572 Toxicity testing, 534e535, 613e615, 629e642, 645e646 Toxicity, 519e533 U.K. approval of, 611e625 U.S. approval of, 674e681 Use, 539e551 Disposal, 335e337 Dissolution, 192 Distillation fractions, 56e58 Dynamic viscosity, 67 Ecological effects, see Effects of oil Effects of weather, 339e429 Effects of oil, 985e1023 Arctic environments, 1012e1014 Ecological effects, 1014e1017 Freshwater/saltwater, 1007e1010 Future of effects science, 1017e1018 Oil chemistry and behaviour, 1002e1007 Routes of exposure, 998e1002 Toxicity impact, 991e997 Tropical environments, 1010e1012 Ekofisk Bravo blowout, 1107e1108 Emulsification, 190e191, 71, 243e273 Emulsion breakers, 430e431 Emulsion stability, 71, 243e273

Index

Emulsions, 243e273 Entrained, 243e273 Kinetics estimator, 260 Meso-stable, 243e269 Modeling of, 249e269 Stability, 243e273 Ensemble forecasting, 289e299 Environmental Protection Agency, see U.S. Environmental Protection Agency Etkin, 7, see D. Schmidt-Etkin Evaporation, 188e190, 201e242 Air boundary regulation, 201e203 Diffusion regulation, 2002e3, 211e216 Equations for prediction, 218e226 Skinning, 231e232 Theoretical concepts, 205e212 Thickness effects, 228e231 Use in spill modeling, 233e239 Evaporated oils, 79e82 Exxon Valdez, 12 Facilities spills, 34 FID, see Flame ionization detector Field analysis, 107 Fieldhouse, B., 643, 683, 713 Fingas, M., 3, 51, 87, 111, 187, 201, 243, 303, 339, 429, 435, 583, 683, 713, 737, 1027 Flame ionization detector, 90 Flash point, 55e57, 66, 60e70 Forecast uncertainty, 275e299 Gas Chromatography, 89e107 Gasoline, 54e56 Gulf War spill -1991, 1127e1132 Hollebone, B., 63 Hydrocarbon groups, 73e77 Ice conditions, 382e383 IFO, see Intermediate fuel oil

1151

Integrated airborne sensor systems, 139 Intermediate fuel oil, 54e56 Interfacial tension, 56e58, 64e66, 67e69, 83 Imports of oil, 4 Infrared sensors, 120e123 In-situ burning, 737e903 Advantages/disadvantages, 756e759 Air quality, 767e794 Aircraft safety, 887 Assessment, 756e759, 859 Boom configurations, 824e834, 872e878 Burn rate, 738, 877e878 Burning inside ships, 886 Containment, 813e836 Effects of weather on, 373e381, 403e404, 800e802 Emissions, 767e794 Environmental and health concerns, 766e794 Equipment, 813e849 Fire resistant booms, 815e822 Health and safety, 878e886 Helitorch, 836e844 How conducted, 752e756 Ice, 810e812 Ignition, 835e849 Land, 807e810 Marshes, 802e807 Monitoring and sampling, 853e857, 871e887, 889e894 Oil properties, 794e800 Public health, 887e894 Residue recovery, 857e859 Safety zones, 887e889 Science of, 737e404 Support vessels, 852e853 Tests, 744e752 Treating agents, 850e852

1152

In-situ burning (Continued ) Uncontained burning, 849, 859e861 ITOPF, see International Tanker Owner’s Pollution Federation International Tanker Owner’s Pollution Federation, 1033e1035 Kirby, M., 611, 629 Lake Wabamun spill, 973e974 Lamarche, A., 923 Largest oil spills, 13e15 Laser fluorosensors, 124e125, 171e184 Aircraft requirements, 180e182 Cost estimates, 182 Excitation sources, 172e173 Oil classification, 175 Outputs, 176e180 Principles of operation, 171e175 Range-gating, 173 Law, R., 1103, 1107, 1109, 1119 Manual recovery, 329e330 Marine oil spills, 17 Mauseth, G., 1067, 1083 Michel, J., 959, 1127 Microwave scatterometers, 134e135 Modeling, 197e199, 275e299 Evaporation, see Evaporation Model uncertainty, 275e299 Mouse, see Emulsions Movement of oil, 196e197 Natural dispersion, 191e192 Natural oil seepage, see seeps Natural resource damage assessment, 1067e1082 Habitat equivalency analysis (HEA), 1074e1078 Injury assessment, 1071e1072

Index

Interpretation of restoration, 1072 Natural Resource Damage Assessment Model (NRDAM), 1079 NOAA regulations, 1079e1081 Regulatory regimes, 1067e1069 U.S. process, 1077 Use of models, 1076e1077 Neall, P., 629 NEBA, see Net Environmental Benefit Analysis Net Environmental Benefit Analysis, 587e591, 911 Nichols, W., 673 Non-tank vessels, 32e33 NRDA, see Natural resource damage assessment Oil composition, see Composition of oil Oil exploration, 17e20 Oil platforms, 19e20 Oil properties, 63e85 Measurement, 63e85 Oil refining, 28 Oil spill cooperatives, 1030e1031 Oil-fines interation, 192e193 Olefins, 53 Optical sensors, 114e120 Over-washing, 194e195 Owens, E., 907 Parker, H., 1067 Pendant interfacial tension, 69 Philippine oil spill, 1133e1146 Photo-oxidation, 192 Physical countermeasures, 303e337 Booms, 303e315 Disposal, 335e337 Manual recovery, 329e330 Pumps, 332e334 Separation, 334e335 Skimmers, 315e315 Sorbents, 325e329

Index

Temporary storage, 330e332 Phytane, 90e91 Pipelines, 24e28 Polar compounds, 53 Pour point, 56e58, 66, 70 Pristane, 90e91 Produced water, 22 Production spills, 17e20 Puerto Rican, 275 Pumps, 332e334 Centrifugal pumps, 332e333 Positive displacement pumps, 333e334 Vacuum systems, 333 Purnell, K., 1033 Qiuhui, Q., 1037 Radar sensors, 125e134 interferometric radar, 135 SLAR -Side-looking Airborne Radar, 125e130 SAR - Synthetic Aperture Radar, 125e134 ship-borne radar, 131 surface-wave radars, 135 radar processing, 132e135 Radarsat, 143e144 Railroads, 26 Real-time displays and printers, 150 Recovery, see Physical countermeasures Recovery enhancers, 431 Regional Response Team (U.S.), 680e681 RRT, see regional response team Remote-controlled aircraft, 149 Remote sensing, 111e169 Acoustic systems, 139 Infrared sensors, 120e123 Laser fluorosensors, 123e124, 171e184 Microwave sensors, 124e135 radars, 124e135

1153

Oil-under-ice detection, 144e145 Optical sensors, 114e122 Radars, 124e135 Real-time information, 150 Recommendations, 154e158 Outine surveillance, 150 Satellite remote sensing, 140e144 Slick thickness, 135 Ultraviolet sensors, 123 Underwater detection, 145e149 Visible indications, 112e114 Resins, 53e55, 73 Refinery effluents, 30e31 Response, see Spill response Response organizations, 1030 Rooke, J., 629 Routine surveillance, 150e153 Runoff, see Urban runoff Safety, 1037e1063 Air monitoring, 1038e1043 Hazardous chemicals, 1058e1059 Medical emergencies, 1058e1059 Personal protective equipment, 1052 Recommended procedures, 1049e1054 Response emergencies, 1054e1058 Risk analysis/assessment, 1028e1043 Site control measures, 1050 Site safety plan, 1043e1047 Type of hazard, 1048e1049 Volunteers, 1059e1062 SARA, see Saturates, Aromatics, Resins and Asphaltenes Saturates, Aromatics, Resins Asphaltenes, 73e77 Aromatics, 73e77 Asphaltenes, 73e75 Measurement, 73e77 Resins, 73e75 Saturates, 73e77

1154

Satellite remote sensing, 140e144 SCAT, see Shoreline cleanup assessment technique Schmidt-Etkin, D., 7 Sea Empress, 1109e1117 Seafood safety, 1083e1100 Chemical analytical assessment, 1090e1092 Long-term implications, 1098e1099 Re-opening a fishery, 1090, 1096e1098 Seafood oil exposure, 1085e1087 Seafood safety management, 1087e1090 Sensory evaluation, 1092e1096 Sedimentation, 192e193 Seeps, 8e11 Separation, 334e335 Shigenaka, G., 985 Shoreline cleanup assessment technique, 910e912, 924e928, 933e937 Shoreline automated assessment, 923e953 Data management, 923e953 Geographic information systems (GIS), 942e943 Oiling observation issues, 951e952 Shoreline cleanup assessment technique, SCAT, 924e928, 933e937 Shoreline oiling summary (SOS), 930 Treatment recommendations, 934 Shoreline countermeasures, 907e920 As low as reasonably possible (ALARP), 911 Automated assessment, 923e953 In-situ treatment, 915e920

Index

Natural recovery, 912e913 Net environmental benefit (NEB), 911 Physical removal, 913e915 Sediment relocation, 919e920 Shoreline cleanup assessment technique (SCAT), 910e912 Shoreline protection, 909 Shoreline treatment, 909e919 Treatment decision process, 910 Waste generation, 919e920 Shoreline oiling summary (SOS), 930 Simecek-Beatty, D., 275 Sinking agents, 431e432 Sinking, 194e195 Skimmers, 315e325 Effects of weather, 353e372, 383e398 Elevating skimmers, 322e323 Oleophilic skimmers, 316e320 Skimmer performance, 323e325 Suction skimmers, 321e322 Weir skimmers, 320e321 Slick thickness sensors, 135e139 SMART protocol, 447e485 Solar I, 1133e1146 Solidifiers, 713e733 Solidifier testing, 732e733 U.S. approval of, 674e681 Sorbent booms, 314 Sorbents, 325e329 Specific gravity, 57, 74 Spill Modeling, 187e199, 198 Spill occurrences, see Spill statistics Spill rates, see Spill statistics Spill response, 1027e1031 Spreading of oil, 196 Statistics, see Spill statistics Stokes’ rising, 447 Submerged oil, 959e981 Athos I, 965e967 DBL-152, 967e974

1155

Index

Lake Wabamun spill, 973e974 Vessel submerged oil recovery system, V-SORS, 966e977 Bottom oil detection, 976e979 Bottom oil recovery, 978e981 Sulphur content, 70 Sunken shipwrecks, 39e41 Surface tension, see Interfacial tension Surface washing agents, 430, 653e657, 683e705 Application, 697e700 Assessment, 700e704 Canadian approval of, 653e657, 662 Effectiveness, 686e697 Toxicity, 697 U.S. approval of, 674e681 Stability of emulsions, see Emulsion stability Standard methods, 100e103 Stanzel, K., 1133 Sesquiterpanes, 105e106 Spill statistics, 2e5, 7e45 Solubility, 55e57 Sampling, 87e88 Tainting of seafood, see Seafood safety Tank vessels, see Tankers Tanker barges, see Barges Tanker trucks, 26e29 Tankers, 23e26 Tarball formation, 195 Temporary storage, 330e332 Thin-layer chromatography, 74e75 Torrey Canyon, 11, 1103e1106 Toxicity of oil, see Effects of oil Toxicity of dispersants, see dispersants Toxicity of dispersed oil, see dispersants Trajectory models, 198e199, 292e294

Trajectory verification, 292e294 Treating agents, 429e433 Biodegradation agents, 432e432, 659e661 Canadian approval of, 634e668 Dispersants, see dispersants in main listing Emulsion breakers, 430e431, 657e658 Recovery enhancers, 431, 658 Sinking agents, 431e432, 661 Solidifiers, 431, 658e659 Surface-washing agents, 430, 653e657 U.S. approval of, 673e682 Training, 1029 Turbulent diffusion, 287e288 Two-stroke engines, 33 Underwater detection, 145e149 U.S. oil spills, 43e45 U.K. approval of treating agents, 611e625 Effect of ingredients, 629e642 U.S. EPA approval of treating agents, 673e682 Product schedule, 674e681 Surface washing agents, 676e677 Surface collecting agents, 676e677 Bioremediation agents, 677 Sorbents, 678e679 RRT, 680e681 Ultraviolet sensors, 123 UCM, see Unresolved complex mixture Unit conversions, 1147e1148 Unresolved complex mixture, 90 Urban runoff, 38e39 Vacuum systems, 333 Vapor pressure, 58

1156

Vessel submerged oil recovery system, V-SORS, 966e977 Viscosity, 54e56, 64, 67, 83 Visible detection, 112e120 Volunteers, 1059e1062 V-SORS, see Vessel submerged oil recovery system Water content, 70 Water-in-Oil emulsions, see Emulsions Weather, effects of on countermeasures, 339e426 A priori guides, 343e345

Index

Booms, 345e353, 383 Components, 341e342 Dispersants, 372e378, 398e403 Ice conditions, 382, 383 Models, 383 Others, 381, 404 Skimmers, 353e372, 383e384 Spreading, 340e341 Weathering, 197e194, 288e289 Weathered oils, 79e82 World War II, 11 Yardley, H., 629 Yender, R., 1133