2004 Denver Annual Meeting (November 7–10, 2004)
Paper No. 139-2
Presentation Time: 8:25 AM-8:40 AM


DATTA, Rupali and SARKAR, Dibyendu, Department of Earth and Environmental Science, Univ of Texas at San Antonio, 6900 N Loop 1604 W, San Antonio, TX 78249, rdatta@utsa.edu

Rapid intrusion of suburban development on former agricultural lands has greatly increased the potential for human exposure to arsenic (As), a group A carcinogen used extensively as pesticides prior to the 1990s. Recent studies have focused on the health risk posed by long-term human exposure to low-level As-contaminated systems, particularly due to soil ingestion from incidental hand-to-mouth activity by children playing in the backyards. In the absence of a “soil model” on As bioavailability, many baseline risk assessments of As-enriched sites assume that all (100%) As present in the soil is bioavailable. This assumption seriously overestimates the actual risk (thereby increasing site clean-up expenses), since various geochemical forms of As are stable and/or insoluble in human digestive juices and are not likely to be bioavailable. A laboratory incubation study was conducted to identify the relationship between geochemical speciation and “in-vitro” bioavailability of As in soils as a function of soil properties. Five different soil types were chosen based on their potential differences with respect to As reactivity: an acid sand with minimal As retention capacity, a sandy loam with relatively high concentration of Fe/Al-oxides (hence, higher As retention capacity), a low-pH clay soil, an organic (muck) soil, and a high pH calcareous soil. The soils were amended with sodium arsenite at three rates: normal (45 mg/kg), above normal (225 mg/kg) and excessive (450 mg/kg). A sequential extraction scheme was developed to identify the various geochemical forms of As in pesticide-applied soils (soluble, exchangeable, organic, Fe/Al-bound, Ca/Mg-bound, residual). Concentrations of these operationally defined soil As forms were correlated with the “in-vitro” bioavailable fractions of As to identify the As species that are most likely to be bioavailable under a variety of soil/pesticide scenarios. Data obtained from arsenic bioavailability studies at 0-time (immediately after spiking the soils with pesticides), 4-month and 1-year incubation period was used to calculate the reduction in potential cancer risk using soil-specific bioavailability data as opposed to total As data. Results demonstrate that As speciation in soils result in significant lowering of As bioavailability, and hence, cancer risk.

2004 Denver Annual Meeting (November 7–10, 2004)
General Information for this Meeting
Session No. 139
Current Perspectives in Environmental Biogeochemistry I
Colorado Convention Center: 107/109
8:00 AM-12:00 PM, Tuesday, 9 November 2004

Geological Society of America Abstracts with Programs, Vol. 36, No. 5, p. 332

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