HR: 15:25h
AN: H33H-08    [Abstracts]
TI: Arsenic Mobility Under Sulfate Reducing Conditions
AU: * Keimowitz, A R
EM: ark@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964 United States
AU: * Keimowitz, A R
EM: ark@ldeo.columbia.edu
AF: Department of Earth and Environmental Sciences, Columbia University, New York, NY 10027 United States
AU: Mailloux, B J
EM: bjm2103@columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964 United States
AU: Cole, P
EM: pc2018@barnard.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964 United States
AU: Simpson, H J
EM: simpsonj@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964 United States
AU: Simpson, H J
EM: simpsonj@ldeo.columbia.edu
AF: Department of Earth and Environmental Sciences, Columbia University, New York, NY 10027 United States
AU: Stute, M
EM: martins@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964 United States
AU: Stute, M
EM: martins@ldeo.columbia.edu
AF: Department of Environmental Science, Barnard College, New York, NY 10027 United States
AU: Chillrud, S N
EM: chilli@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964 United States
AU: Kujawinski, E B
EM: kujawinski@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543 United States
AU: Zheng, Y
EM: yzheng@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964 United States
AU: Zheng, Y
EM: yzheng@ldeo.columbia.edu
AF: School of Earth and Environmental Sciences, Queens College, The City University of New York, Flushing, NY 11367 United States
AB: At a former landfill site in southern Maine approximately 300 ppb arsenic has been observed in groundwater over the last two decades. Laboratory and field measurements support the hypothesis that this arsenic originates within the underlying glaciofluvial sediments containing natural arsenic at concentrations of approximately 6 ppm. Arsenic is mobilized under the landfill by reducing conditions induced by decomposition of organic-rich landfill leachate. The feasibility of arsenic removal by in situ oxidation was investigated with laboratory and pilot field experiments. The high redox buffering capacity of the aquifer solids makes this remediation strategy very difficult to accomplish. A more promising remediation strategy may involve the sequestration of arsenic through the formation of solid phase sulfides under sulfate-reducing conditions. To test this hypothesis, laboratory microcosm experiments were conducted with sediment from beneath the landfill. Acetate was added to the sediments to stimulate sulfate reducing conditions. Microcosms were monitored for changes to the solid and aqueous phase chemistry along with changes to the microbial community. The addition of acetate enabled the native microbial community to establish sulfate reducing conditions. The production of sulfide coincided with a decrease in the observed iron and arsenic concentrations. Over ten days, roughly 70 to 80% of the dissolved arsenic and $>$99% of the dissolved iron was removed from solution. Arsenic was subsequently partially remobilized, possibly due to continued sulfate reduction and an increase in pH. Results indicated that laboratory manipulations of the microbial community and subsurface redox state were able to lower the dissolved arsenic concentrations.
DE: 4802 Anoxic environments
DE: 1803 Anthropogenic effects
DE: 1831 Groundwater quality
DE: 1045 Low-temperature geochemistry
DE: 0400 Biogeosciences
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting