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Speciation And Distribution Of Arsenic In Fresh Water Pond Sediments Impacted By Contaminated Ground-Water Discharge (Presentation)
Citation:
LUXTON, T. P., K. G. SCHECKEL, P. J. CLARK, AND R. G. FORD. Speciation And Distribution Of Arsenic In Fresh Water Pond Sediments Impacted By Contaminated Ground-Water Discharge (Presentation). Presented at International Conference On The Bioavailability Of Trace Elements, Florence, ITALY, July 07, 2011.
Impact/Purpose:
To evaluate changes in the speciation of sediment bound arsenic as a function of sediment chemical composition and proximity to arsenic enriched groundwater water seeps.
Description:
The speciation and mineralogy of sediments contaminated with arsenic due to arsenic enriched groundwater discharging into the pond at the Ft. Devens Super Fund Site in Ft. Devens, MA were determined using X-ray absorption fine structure and X-ray diffraction spectroscopy. Speciation and mineralogical results indicate arsenic is predominantly present in the reduced form of arsenite adsorbed or co-precipitated with ferrihydrite. Spatial patterns in the distribution and concentration of arsenic combined with major element ground water chemistry indicate changes in the speciation of arsenic based on sediment locations of known ground water seeps into the pond. Adsorption of arsenic onto ferrihydrite, derived from the oxidation and precipitation of ferrous iron from groundwater, is the primary mechanism by which arsenic is initially sequestered. Changes in the local sediment composition and areas of ground water discharge play a role in the final speciation of deposited arsenic-bound-ferrhydrite precipitates. Changes in the immediate surface water or sediment chemistry (pH, dissolved oxygen, oxidative-reduction potential) due to sediment or water column disturbance may result in potential instability of arsenic phases over extended time periods.