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EXAMINATION OF CHANGES IN AS SPECIATION IN SULFIDIC SOLUTIONS
Citation:
BEAK, D. G., R. T. WILKIN, R. FORD, AND S. KELLY. EXAMINATION OF CHANGES IN AS SPECIATION IN SULFIDIC SOLUTIONS. Presented at SETAC Meeting, Montreal, ON, CANADA, November 05 - 09, 2006.
Impact/Purpose:
To inform the public.
Description:
The fate of arsenic (As) in the environment, its bioavailability and toxicity is fundamentally linked to its speciation. As in aerobic environments is predominantly arsenate (As(V)), however under reducing conditions arsenite (As(III)) species dominate. In sulfidic environments thioarsenite ((As(OH)x(SH)yz-)species along with As(III) are known to play key roles in As speciation. Although (As(OH)x(SH)yz-) species are know to be important in sulfidic environments, little is know about their formation, structure, chemistry, and their stability in the environment. In order to address these questions extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge spectroscopy (XANES) were employed to solutions that contained As(III) and As(V) in the presences of bisulfide. Solutions were analyzed both at presumed equilibrium and in non-equilibrium conditions. A series of solutions containing As(V) in the presence of bisulfide (non-equilibrium) were analyzed at variable pH using EXAFS and XANES analysis. With these techniques it was possible to obtain kinetic information about the reductive precipitation of As and changes in speciation of As(V) to As(III) and/ or (As(OH)x(SH)yz-) with time. The results of these experiments will be presented.