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ARSENIC UPTAKE PROCESSES IN REDUCING ENVIRONMENTS: IMPLICATIONS FOR ACTIVE REMEDIATION AND NATURAL ATTENUATION
Citation:
Wilkin*, R T. ARSENIC UPTAKE PROCESSES IN REDUCING ENVIRONMENTS: IMPLICATIONS FOR ACTIVE REMEDIATION AND NATURAL ATTENUATION. Presented at 226th National Meeting of the American Chemical Society, New York, NY, September 07 - 11, 2003.
Impact/Purpose:
To inform the public.
Description:
Reductive dissolution of iron oxyhydr(oxides) and release of adsorbed or coprecipitated arsenic is often implicated as a key process that controls the mobility and bioavailability of arsenic in anoxic environments. Yet a complete assessment of arsenic transport and fate requires an understanding of uptake processes in iron-reducing and sulfate-reducing redox regimes, conditions often encountered in wetland systems that receive discharge of contaminated groundwater and in iron-based reactive media used for groundwater remediation. Under these redox conditions, arsenic is typically present in solution as an uncharged oxyanion or as a mixture of charged thioarsenic complexes with S/As ratios that range from 1:1 to 4:1. Depending on the aqueous speciation of arsenic, which is largely a function of pH and dissolved sulfide concentration, chemical uptake pathways include sorption to and/or coprecipitation with iron sulfides (mackinawite and pyrite), mixed iron-valence precipitates (green rust), and/or organic matter.