HR: 0830h
AN: B41D-0917    [PDF]
TI: Effects of Bacterial Respiratory Reduction Processes on the Transformation and Transport of Ferric Hydroxide Complexed Arsenic
AU: * Herbel, M J
EM: mherbel@stanford.edu
AF: Stanford University, Department of Geological & Environmental Sciences, Stanford, CA 94305 United States
AU: Fendorf, S
EM: fendorf@stanford.edu
AF: Stanford University, Department of Geological & Environmental Sciences, Stanford, CA 94305 United States
AU: Neiss, J
EM: jneiss@pangea.stanford.edu
AF: Stanford University, Department of Geological & Environmental Sciences, Stanford, CA 94305 United States
AB: The mobility of arsenic in contaminated aquifers is primarily controlled by the presence of iron (hydr)oxides and sulfides. Under reducing conditions bacteria that can alter or produce these compounds will have a strong effect on the chemistry and hence the mobility of arsenic. Here we investigate how arsenic complexed with ferrihydrite is mobilized under dynamic flow conditions in the presence of anaerobic bacteria that can reduce As(V) and/or Fe(III) through dissimilatory processes. Ferrihydrite-coated sands were loaded with 200-300 mg Kg$^{-1}$ As(V) or As(III) and inoculated with {\it Sulfurosprillum barnesii} strain SES-3 or {\it Bacillus benzoevorans} strain HT-1. The sands were packed into columns through which minimal ground water media was passed. In columns containing arsenite loaded ferrihydrite and SES-3, As(III) release was most intense initially when microbial activity was high and decreased thereafter. Similar results were observed with arsenate loaded ferrihydrite and SES-3, yet arsenate reduction to arsenite occurred prior to the onset of high Fe(II) in solution. These results suggest that arsenic release into the aqueous phase is stimulated by iron reduction and is not wholly dependent on arsenic redox transformations.
DE: 0400 Biogeosciences
DE: 1045 Low-temperature geochemistry
DE: 1065 Trace elements (3670)
DE: 1806 Chemistry of fresh water
DE: 1831 Groundwater quality
SC: Biogeosciences [B]
MN: 2003 Fall Meeting