API Groundwater Arsenic Manual Attenuation of Naturally-Occurring Arsenic at Petroleum Impacted Sites PUBLICATION 4761 FEBRUARY 2011 API Groundwater Arsenic Manual Attenuation of Naturally-Occurring Arsenic at Petroleum Impacted Sites PUBLICATION 4761 FEBRUARY 2011 ERM’s Austin Office 206 E. 9th St., Suite 1700 Austin, Texas 78701 T: 512-459-4700 F: 512-459-4711 www.erm.com Contributing Authors Richard A. Brown, Ph.D. Roger Lee, Ph.D. Katrina Patterson, P.G. Mitch Zimmerman, P.G. Franz Hiebert, Ph.D., P.G. Delivering sustainable solutions in a more competitive world SPECIAL NOTES API publications necessarily address problems of a general nature. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed. 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Suggested revisions are invited and should be submitted to the Director of Regulatory and Scientific Affairs, API, 1220 L Street, NW, Washington, DC 20005. iii TABLE OF CONTENTS EXECUTIVE SUMMARY IX GLOSSARY XIV 1.0 INTRODUCTION 1 1.1 PURPOSE OF MANUAL 1 1.2 SOURCES OF ARSENIC – OCCURRENCE AND DISTRIBUTION 2 1.2.1 Natural Sources of Arsenic 2 1.2.2 Anthropogenic Sources Of Arsenic 3 1.3 FACTORS CONTROLLING ARSENIC FATE AND TRANSPORT 4 1.4 IMPACT OF PETROLEUM HYDROCARBON RELEASES ON ARSENIC MOBILITY 6 1.5 GOVERNING PRINCIPLES 8 1.6 ORGANIZATION OF MANUAL 10 2.0 FUNDAMENTALS OF ARSENIC GEOCHEMISTRY AND NATURAL ATTENUATION AS APPLIED TO PETROLEUM IMPACTED SITES 12 2.1 FUNDAMENTALS OF ARSENIC GEOCHEMISTRY 12 2.1.1 Redox Chemistry of Arsenic 12 2.1.2 pH 14 2.2 MECHANISMS OF ARSENIC MOBILIZATION/SOLUBILIZATION AT PETROLEUM IMPACTED SITES 16 2.2.1 Microbiology of Petroleum Hydrocarbon Spills 16 2.2.2 Effect of Petroleum Biodegradation on Arsenic Mobility 18 2.3 NATURAL ATTENUATION MECHANISMS FOR ARSENIC 21 2.3.1 Arsenic Oxidation 23 2.3.2 Arsenic Immobilization Through Sorption 24 2.3.3 Mineral Phase Formation 25 2.3.4 Precipitation 26 2.3.5 Stability and Reversibility 26 2.4 CONCEPTUAL MODELS FOR ARSENIC NATURAL ATTENUATION27 2.4.1 Release and Plume Expansion 28 2.4.2 Steady-State Plume 30 2.4.3 Retreating Plume Conditions 30 3.0 ASSESSMENT AND SITE CHARACTERIZATION TO EVALUATE ARSENIC NATURAL ATTENUATION 34 3.1 DEVELOPMENT OF A SITE-SPECIFIC CONCEPTUAL MODEL 36 3.1.1 Defining Ambient Arsenic 36 3.1.2 Defining Overall Site Conditions 38 3.1.3 Defining Petroleum Hydrocarbons and Redox Processes 40 v 3.1.4 Defining Attenuation Processes 43 3.1.5 Defining Risk 44 3.2 USES OF THE SSCM 47 4.0 REMEDIATION TECHNOLOGIES FOR ARSENIC IN GROUNDWATER IMPACTED BY PETROLEUM HYDROCARBONS 48 4.1 HYDROCARBON REMEDIATION TECHNOLOGIES 49 4.2 ARSENIC TREATMENT TECHNOLOGIES 49 4.2.1 Phytoremediation 50 4.2.2 Precipitation/Coprecipitation 50 4.2.3 Adsorption 51 4.2.4 Permeable Reactive Barriers 51 5.0 CASE STUDIES FOR ARSENIC MOBILIZATION AND ATTENUATION AT PETROLEUM IMPACTED SITES 53 5.1 AN OPERATING OKLAHOMA REFINERY 53 5.1.1 Site Description 53 5.1.2 Ambient Conditions 53 5.1.3 Hydrocarbon Impacts 55 5.1.4 Arsenic Mobilization 55 5.2 WEST TEXAS REFINERY 57 5.2.1 Site Description 57 5.2.2 Ambient Conditions 58 5.2.3 Hydrocarbon Impacts 58 5.2.4 Arsenic Mobilization 60 5.3 FORMER RESERVE PIT 63 5.3.1 Site Description and Geology 63 5.3.2 Ambient Conditions 64 5.3.3 Hydrocarbon Impacts 64 5.3.4 Arsenic Mobilization 65 5.3.5 Remediation Actions and Arsenic Stabilization 65 5.4 FORMER FUEL STORAGE FACILITY 65 5.4.1 Site Description 66 5.4.2 Arsenic Mobilization 67 5.4.3 Hydrocarbon Impacts 67 6.0. CONCLUSIONS 70 7.0. REFERENCES 72 7.1 CITED REFERENCES 72 7.2 ADDITIONAL READING 77 vi TABLE OF CONTENTS (CONT’D) List of Tables Table 1-1 Industrial and Agricultural Uses of Arsenic (Historic and Current) Table 1-2 Summary of Arsenic Concentration in 26 Crude Oils Table 2-1 Relative Solubilities of Arsenite and Arsenate Table 2-2 Effect of Microbial Metabolic Pathways on pH Table 2-3 Solubility of Metal Arsenates Table 2-4 Factors Affecting Arsenic Mobilization for Plume Expansion Stage Table 2-5 Factors Affecting Arsenic Mobilization for the Steady State Stage Table 2-6 Factors Affecting Arsenic Mobilization for Retreating Plume Stage Table 3-1 Key Groundwater Geochemical Parameters for Assessment of Natural Attenuation of Arsenic at Petroleum Hydrocarbon Sites Table 3-2 Key Microbiological Parameters for Assessment of Natural Attenuation of Arsenic at Petroleum Hydrocarbon Sites Table 3-3 Molecular Hydrogen Concentrations Characteristic of Reducing Zones in Groundwater Table 3-4 Examples of Ecological Benchmark Screening Concentrations for Arsenic in Various Media Table 4-1 Hydrocarbon Remediation Technologies List of Figures Figure 1-1 Arsenic Concentrations in Groundwater Across the U.S. Figure 1-2 Arsenic Speciation in Groundwater Regimes Figure 1-3 Conceptual Model of Biodegradation of a Petroleum Hydrocarbon Plume Figure 1-4 Attenuation of Petroleum Sites Figure 1-5 Conceptual Model of Arsenic Mobility and Attenuation at a Petroleum Hydrocarbon Plume Figure 2-1 Standard Electrode Potential for Arsenic Figure 2-2 Eh-pH Diagram for As-Fe-S Figure 2-3 Adsorption of Arsenic Oxyanions to Oxyhydroxide Coating on Mineral Grain in an Aquifer Figure 2-4 Plan View of Metabolic Zones in Hydrocarbon Plume Figure 2-5 Arsenic Reduction in Relation to Biological Processes Figure 2-6 Adsorption of Arsenate and Arsenite on Hydrous Ferric Oxide (HFO) as a Function of pH Figure 2-7 Change in Hydrocarbons, Arsenic and Redox in Reactive Zones Expanding Plume Figure 2-8 Change in Hydrocarbons, Arsenic and Redox in Reactive Zones – Steady State Plume Figure 2-9 Change in Hydrocarbons, Arsenic and Redox in Reactive Zones – Retreating Plume Figure 3-1 Site-Specific Conceptual Model (SSCM) Development Path Figure 3-2 Exposure Pathway Flow Diagram vii Figure 5-1 Current (2007) Extents of Hydrocarbons in the Shallow Aquifer at the Oklahoma Refinery Figure 5-2 Arsenic Concentration in Groundwater from Background Wells Figure 5-3 Soil Arsenic Concentration vs. Soil Iron Concentration Figure 5-4 Dissolved Arsenic vs. Dissolved Iron in Terrace Aquifer Water, Second Half of 2004 Figure 5-5 Average Total Arsenic Concentration in RCRA Monitoring Wells (2003 – 2007) Figure 5-6 Aerial Photo of Subject Refinery in West Texas When It Was Operating in the 1950’s Figure 5-7 Cross-section of Upper Trujillo Sandstone (UTS) and Lower Trujillo Sandstone (LTS) Figure 5-8 Potentiometric Surface Map of Groundwater in the UTS Figure 5-9 Concentration of Benzene in Groundwater of the UTS Figure 5-10 Concentration of Arsenic in Groundwater of the UTS Figure 5-11 Sandstone Core From Outside of Petroleum-Impacted Zone Showing Orange to Red Coloring, Which Indicates High Iron Content and Oxidizing Groundwater Conditions Figure 5-12 Graph of Arsenic vs. Total Organic Concentrations in Groundwater at the West Texas Site Figure 5-13 Aerial View of Reserve Pit with Surrounding Sample Locations Figure 5-14 Plot of Arsenic Concentration versus Iron Concentration in Water Samples from 2006 Figure 5-15 Plot of Dissolved Iron versus pH in Water Samples from 2006 Figure 5-16 Eh versus Dissolved Arsenic Concentrations at the Former Fuel Storage Site Figure 5-17 TPH Concentrations versus Arsenic Concentrations at the Former Fuel Storage Site Figure 5-18 TPH Concentrations versus Eh at the Former Fuel Storage Site viii