| Abstract
| - The risk posed from incidental ingestion to humans ofarsenic-contaminated soil may depend on sorption of arsenate(As(V)) to oxide surfaces in soil. Arsenate sorbed toferrihydrite, a model soil mineral, was used to simulatepossible effects on ingestion of soil contaminated with As(V) sorbed to Fe oxide surfaces. Arsenate sorbed toferrihydrite was placed in a simulated gastrointestinaltract (in vitro) to ascertain the bioaccessibility of As(V) andchanges in As(V) surface speciation caused by thegastrointestinal system. The speciation of As was determinedusing extended X-ray absorption fine structure (EXAFS)analysis and X-ray absorption near-edge spectroscopy(XANES). The As(V) adsorption maximum was found to be93 mmol kg-1. The bioaccessible As(V) ranged from 0 to5%, and surface speciation was determined to be binuclearbidentate with no changes in speciation observed postin vitro. Arsenate concentration in the intestine was notconstant and varied from 0.001 to 0.53 mM for the 177 mmolkg-1 As(V) treated sample. These results suggest thatthe bioaccessibility of As(V) is related to the As(V)concentration, the As(V) adsorption maximum, and thatmultiple measurements of dissolved As(V) in the intestinalphase may be needed to calculate the bioaccessibilityof As(V) adsorbed to ferrihydrite.
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