Grantee Research Project Results
2006 Progress Report: Biogeochemistry of Arsenic in Contaminated Soils of Superfund Sites
EPA Grant Number: R830842Title: Biogeochemistry of Arsenic in Contaminated Soils of Superfund Sites
Investigators: Sarkar, Dibyendu , Datta, Rupali
Institution: The University of Texas at San Antonio
EPA Project Officer: Hahn, Intaek
Project Period: August 1, 2003 through July 31, 2005 (Extended to July 31, 2007)
Project Period Covered by this Report: August 1, 2005 through July 31, 2006
Project Amount: $391,473
RFA: Superfund Minority Institutions Program: Hazardous Substance Research (2002) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Safer Chemicals , Land and Waste Management
Objective:
Accurate human health risk assessment due to exposure to Arsenic (As) and appropriate in-situ remedial alternative is a factor of soil physicochemical properties, which strongly influence As biogeochemistry. We are evaluating this hypothesis by pursuing the following specific aims: (1) Examine the relationship between geochemical speciation of As and bioavailable As as a function of soil properties. (2) Evaluate the use of Water Treatment Residuals (WTR) as soil amendments in reducing soil As bioavailability. (3) Identify the molecular biological mechanisms behind detoxification of As in plant systems. Development of an universal model from prediction of As fate and bioavailability together with As remediation across soils types in pesticide-contaminated systems is a step towards attaining our long range goal to reduce human bioavailability of As from ingested soils in an interactive (and realistic) plant-soil-water system.
Progress Summary:
In Phase I of the greenhouse study, column experiments were initiated and were completed in June 2005. Two types of soils were selected based on the physico-chemical properties, which are most likely to influence As retention. Pesticides (sodium arsenate and DMA) were used at two different rates (675 and 1500 mg kg-1) representing superfund conditions. Rice (used as the test crop) was grown for a period of 6 months. Rice was harvested twice, after 3 and 6 months. Soils were collected at different time periods: immediately after spiking (time-0), after 6 months (time-final) and after 1 and 3 years.
The second set of column experiments was started in late June 2004. It involved two soils (Immokalee and Orelia), and two pesticides (Sodium arsenate and DMA) added at a rate of 1500 mg kg-1 of soil. Both soils were amended with Al-WTR and Fe-WTR at two rates (5% and 10%) expected to be effective in reducing soluble As. Rice was used as the test crop.
To better understand the effect of soil-aging on As bioaccessibility and speciation, columns from both of the experimental set ups were retained (without the cultivar) and were sampled once in a year. The columns are being maintained at optimum soil moisture conditions (“pot-holding capacity”). Soil sampling has been done in June 2007 (Year 3 of the study) and the study is currently in progress. This will further evaluate the impact of soil ageing on the geochemical speciation, thereby affecting As bioaccessibility. Aqueous speciation study of As has also been conducted to see whether there are changes in the oxidation state of As.
Soil samples collected at different time periods were extracted for soil-As forms by a sequential extraction technique and for bioavailable As by in-vitro gastrointestinal method as described by Datta and Sarkar (2004). In all the three soils except for Pahokee Muck, most of the total extractable As was in the soluble form. Soluble form decreased significantly after 1 year of soil-pesticide equilibration. Arsenic bioaccessibility also decreased with time in all the four soils, indicating the affect of ageing as well as soil properties on bioaccessibility. Selected in-vivo study using As-contaminated soils were conducted on male/female BALB/c mice. In-vivo bioavailability was calculated from the blood collected by cardiac puncture at different time periods.
Results obtained so far with WTRs suggests that significantly higher levels of the added As was transformed into bound forms, thus decreasing its bioaccessibility in Fe-WTR and Al-WTR amended soils. Arsenic bioaccessibility decreased immediately after spiking for both the WTRs, with more reduction at higher application rate (10%). Geochemical speciation after 1 year of soil-WTR-pesticide equilibration showed that As in the WTR amended soils was mostly in Fe-and Al-bound form, therefore less available, thereby decreasing As bioaccessibility.
In the third year of the study in-vitro results were compared with the relative bioavailability determined from dosing trails using BALB/c mice. Arsenic extracted from the in-vitro stomach and intestinal phases were linearly correlated. Additionally, direct stomach samples were collected from mice and were digested and analyzed according to the U.S. Environmental Protection Agency (EPA) (600/R-94/111 -200.2) method. Arsenic extracted from these stomach samples was also linearly correlated with in-vitro stomach phase arsenic.
In Year 3, the effect of gastric solution properties (solid:solution ratio [SSR]; pH; and residence time [hour]) on As bioaccessibility and speciation in the human stomach was investigated to elucidate those gastric solution properties that maximize As bioaccessibility. In-vitro experiments were conducted using liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICPMS) of soluble As species As(III), As(V), MMA, DMA, crystalline and amorphous As mineral phases, and As amended Fe/Al-WTRs). Results showed that except for Fe/Al-WTR and Arsenopyrite, all the other experimental samples retained their initial As oxidation state. Maximum bioaccessibility for all the As sorbents was observed for the following combination of gastric solution properties: 1 hour, pH = 1, and SSR = 1200.
Future Activities:
We plan to study changes in solid-phase As speciation and bioaccessibility of soluble and solid As phases in the human stomach in the presence of a common gastric bacterium. We hypothesize that stomach bacteria mediate transformations of the soil As particles in the gastric solution such as As(V) reduction to the more toxic As(III), affecting As fate and stability. Test samples will include crystalline and amorphous As mineral phases as well as aged As contaminated soils. Results will be examined in light of changes in As concentration and oxidation state in the gastric phase using high performance LC-ICPMS. In addition, the molecular biological studies on rice and fern will be completed.
References:
Rodriguez RR, Basta NT, Casteel SW, Pace LW. An in-vitro gastrointestinal method estimate bioavailable arsenic in contaminated soil and solid media. Environmental Science & Technology 1999;33:642-649.
Sarkar D, Datta R. A modified in-vitro method to assess bioaccessible arsenic in pesticide-applied soils. Environmental Pollution 2003;126:363-366.
U.S. EPA. Sample preparation procedure for spectrochemical determination of total recoverable elements in biological tissues. 1991.
Journal Articles on this Report : 9 Displayed | Download in RIS Format
| Other project views: | All 47 publications | 11 publications in selected types | All 9 journal articles |
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Datta R, Sarkar D. Consideration of soil properties in assessment of human health risk from exposure to arsenic-enriched soils. Integrated Environmental Assessment and Management 2005;1(1):55-59. |
R830842 (2004) R830842 (2005) R830842 (2006) |
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Datta R, Sarkar D, Sharma S, Sand K. Arsenic biogeochemistry and human health risk assessment in organo-arsenical pesticide-applied acidic and alkaline soils: an incubation study. Science of the Total Environment 2006;372(1):39-48. |
R830842 (2006) |
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Makris KC, Sarkar D, Datta R. Aluminum-based drinking-water treatment residuals: a novel sorbent for perchlorate removal. Environmental Pollution 2006;140(1):9-12. |
R830842 (2006) |
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Makris KC, Sarkar D, Datta R. Evaluating a drinking-water waste by-product as a novel sorbent for arsenic. Chemosphere 2006;64(5):730-741. |
R830842 (2005) R830842 (2006) |
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Sarkar D, Parra-Noonan M, Datta R. Distribution of arsenic in chemically variant dipping vat site soils. Bulletin of Environmental Contamination and Toxicology 2004;73(5):838-845. |
R830842 (2004) R830842 (2005) R830842 (2006) |
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Sarkar D, Datta R. Human health risks from arsenic in soils: does one model fit all? Archives of Environmental & Occupational Health: An International Journal 2004;59(7):337-341. |
R830842 (2005) R830842 (2006) |
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Sarkar D, Datta R, Sharma S. Fate and bioavailability of arsenic in organo-arsenical pesticide-applied soils. Part-I: incubation study. Chemosphere 2005;60(2):188-195. |
R830842 (2004) R830842 (2005) R830842 (2006) |
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Sarkar D, Makris KC, Datta R, Khairom A. Effects of remedial treatment on phosphorus availability in an arsenical pesticide contaminated soil. Bulletin of Environmental Contamination and Toxicology 2006;77(2):297-304. |
R830842 (2006) |
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Sarkar D, Makris KC, Vandanapu V, Datta R. Arsenic immobilization in soils amended with drinking-water treatment residuals. Environmental Pollution 2007;146(2):414-419. |
R830842 (2006) |
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Supplemental Keywords:
arsenic, soil, pesticides, in-vitro bioaccessibility, in-vivo bioavailability, microbes, speciation, risk assessment, water treatment residuals, chemical remediation,, Health, RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Waste, Water, POLLUTANTS/TOXICS, Hazardous, Risk Assessments, Contaminated Sediments, Hazardous Waste, Geochemistry, Arsenic, Environmental Monitoring, Water Pollutants, arsenic mobility, contaminant transport, assessment methods, contaminated sediment, sediment quality survey, water quality, biogeochemistry, contaminated soil, bioaccumulation, sediment transport, water treatment, ecology assessment models, superfund site, reservoir sediments, risk management, arsenic exposureProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.