1、 API Groundwater Arsenic Manual Attenuation of Naturally-Occurring Arsenic at Petroleum Impacted Sites PUBLICATION 4761 FEBRUARY 2011 Delivering sustainable solutions in a more competitive world API Groundwater Arsenic Manual Attenuation of Naturally-Occurring Arsenic at Petroleum Impacted Sites PUB
2、LICATION 4761 FEBRUARY 2011 ERMs Austin Office 206 E. 9thSt., Suite 1700 Austin, Texas 78701 T: 512-459-4700 F: 512-459-4711 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. ii SPECIAL NOTES API publications neces
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9、therwise, without prior written permission from the publisher. Contact the Publisher, API Publishing Services, 1220 L Street, N.W., Washington, D.C. 20005. Copyright 2012 American Petroleum Institute iii FOREWORD Nothing contained in any API publication is to be construed as granting any right, by i
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11、ould be submitted to the Director of Regulatory and Scientific Affairs, API, 1220 L Street, NW, Washington, DC 20005. v 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
12、 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
13、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
14、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.
15、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
16、 Conditions 38 3.1.3 Defining Petroleum Hydrocarbons and Redox Processes 40 vi 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
17、 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 Sit
18、e 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 Geo
19、logy 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. REFE
20、RENCES 72 7.1 CITED REFERENCES 72 7.2 ADDITIONAL READING 77 vii TABLE OF CONTENTS (CONTD) 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 T
21、able 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 Re
22、treating 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
23、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 A
24、rsenic 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 f
25、or 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 Ars
26、enate 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 i
27、n Reactive Zones Retreating Plume Figure 3-1 Site-Specific Conceptual Model (SSCM) Development Path Figure 3-2 Exposure Pathway Flow Diagram viii Figure 5-1 Current (2007) Extents of Hydrocarbons in the Shallow Aquifer at the Oklahoma Refinery Figure 5-2 Arsenic Concentration in Groundwater from Bac
28、kground 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 Refiner
29、y in West Texas When It Was Operating in the 1950s 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
30、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 S
31、ite 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 a
32、t 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 SiteAPI PUBLICATION 4761, API GROUNDWATER ARSENIC MANUAL ix EXECUTIVE SUMMARY In January, 2006 the United St
33、ates Environmental Protection Agency (USEPA) lowered the maximum contaminant level (MCL) for dissolved arsenic in groundwater from 0.050 mg/L to 0.010 mg/L due to long term chronic health effects of low concentrations of arsenic in drinking water. This five-fold lowering of the MCL has heightened pu
34、blic and regulatory awareness of dissolved arsenic in groundwater. The World Health Organization (WHO) is considering a similar lowering of groundwater standards for arsenic. Naturally-occurring arsenic may be mobilized into shallow groundwater by inputs of biodegradable organic carbon, including pe
35、troleum hydrocarbons. This manual was developed to explain the mobilization, transport and attenuation mechanisms of naturally-occurring arsenic in groundwater at petroleum impacted sites. This manual: 1) Identifies and categorizes the potential sources of arsenic at petroleum impacted sites, includ
36、ing arsenic contained in native rock and soils and arsenic resulting from anthropogenic sources; 2) Provides information on the arsenic content of petroleum and refined products. Arsenic is not a common or significant trace element in petroleum, and petroleum is not known to be a significant source
37、of mobile arsenic in groundwater. 3) Presents the fundamentals of arsenic biogeochemistry at petroleum impacted sites where the presence of hydrocarbons may result in dissolution of native arsenic due primarily to biodegradation and the resulting electrochemically-reduced conditions; and 4) Provides
38、 validated tools for the assessment of arsenic at petroleum impacted sites and its management through natural attenuation. This manual is not a treatise on arsenic geochemistry but is focused on a very specific issue, the mobilization and attenuation of naturally-occurring arsenic at petroleum impac
39、ted sites. “Naturally-occurring arsenic” refers to arsenic that is present in the solid phase prior to any impacts by degradable organic carbon including petroleum hydrocarbons. Many of the issues and conditions relating to arsenic occurrence and mobility apply for other metals in the subsurface; al
40、though this manual only addresses arsenic specifically, further discussion of other metals can be found in the literature (USEPA, 2007a; USEPA 2007b). Arsenic may be present as a natural trace metal in native rocks and soils or as a result of agricultural, industrial or mining activity. Arsenic may
41、be present as specific minerals, as an amorphous phase, or adsorbed onto iron oxyhydroxides API PUBLICATION 4761, API GROUNDWATER ARSENIC MANUAL x and other soil constituents. Anthropogenic sources of arsenic include pesticide application, wood treating, or mine tailings. Arsenic is not a common or
42、significant trace constituent in petroleum. An important part of understanding the mobility of naturally-occurring arsenic at petroleum impacted sites is having a good characterization of the ambient arsenic geochemistry and of the hydrogeology of the site. An important part of this characterization
43、 is to determine the ambient, background level of dissolved arsenic. The dissolved arsenic level at petroleum impacted sites, even after attenuation, cannot be lower than background. If the background level of arsenic naturally exceeds the new MCL, then the MCL is unachievable as an attenuation or r
44、emediation goal. Ambient dissolved arsenic concentrations exceeding the new (or old) MCL can occur at sites with a high or low natural pH, or at sites that lack iron oxyhydroxides in the soil. Naturally-occurring dissolved arsenic concentrations above the new (and old) MCL are, in fact, common in ma
45、ny parts of the World. The natural solubility of arsenic is controlled by redox conditions (Eh), pH and by the presence of metal oxyhydroxides that can adsorb and bind arsenic. Since the focus of this manual is on arsenic mobilization and attenuation at petroleum impacted sites, the aquifers most co
46、mmonly encountered will, for the most part, be shallow and in contact with the atmosphere. Therefore, the most common background redox condition will be an aerobic environment in which arsenic will be present as the oxidized, less mobile, As+5. The ambient groundwater concentration of the arsenic wi
47、ll be controlled by pH and the soil mineral content (i.e. iron oxyhydroxides). As+5, present as the arsenate anion (AsO4-3), is more soluble at low pH (8). This is in contrast to natural groundwater pH values typically ranging between 4 and 8. Arsenate is also strongly adsorbed to iron oxyhydroxides
48、, which are fairly ubiquitous. When a petroleum release occurs at concentrations sufficient to reach the water table, the hydrocarbons come into contact with the groundwater. The more soluble hydrocarbon fractions dissolve into groundwater, stimulating biological activity. Bacteria degrade the disso
49、lved hydrocarbons and sequentially consume the available terminal electron acceptors (TEAs), progressing from oxygen through nitrate, manganese, iron, sulfate and finally reach methanogenesis, creating progressively more reduced groundwater environments. The redox level attained is a function of the TEA availability and the amount of hydrocarbon released. Once the redox conditions are at or below the Eh for iron reduction, ferric oxides in the soils are reduced to the more soluble ferrous form. Because most soil arsenic is associated with ferric oxides, arsenic w
