Chemical Methods to Estimate Bioavailable Arsenic in Contaminated Soils and Solid Media. R. R. Rodriguez, N. T. Basta, S. W. Casteel, and L. W. Pace, Sverdrup Environmental, Inc., 13723 Riverport Dr., Maryland Heights, MO 63043; Oklahoma State University, Dept. of Plant and Soil Sciences, Stillwater, OK 74074; and University of Missouri, Veterinary Medicine Diagnostic Lab., Columbia, MO 65201
The ability of chemical methods to estimate bioavailable arsenic in contaminated soil and solid media was evaluated. Chemical methods include an in-vitro method (IVG), that simulates the human gastro-intestinal environment, as well as soil chemical fractionation methods that extract different pools of soil arsenic. Fifteen contaminated soils and solid media, ranging in arsenic concentration from 233 to 17,456 mg kg-1, were analyzed by IVG and fractionation methods. Arsenic measured by IVG and fractionation methods were then compared with in-vivo bioavailable arsenic determined from feeding trials using the immature swine model. Arsenic extracted by the IVG stomach phase and intestinal phase were linearly correlated (r2 = 0.69 and 0.67, respectively) with in-vivo bioavailable arsenic (P < 0.01). Analysis of variance showed the IVG stomach phase and intestinal phase were not statistically different from the in-vivo method. Five chemical extractants, ranging from deionized water to very aggressive reagents that dissolve occluded arsenic, were used to fractionate soil arsenic. Results suggest the fraction of bioavailable arsenic in contaminated soils includes desorbable non-occluded forms and some arsenic associated with iron, manganese, and aluminum oxides. Chemical methods may be useful tools to evaluate the bioavailable fraction of arsenic in contaminated materials to lower uncertainty and develop more reasonable estimates of risk.
Work supported by U.S. EPA Research Grant No. R825410-01-0.
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