HR: 14:55h
AN: H13L-06    [Abstracts]
TI: Evaluating sources of arsenic to groundwater in the Mekong Delta based on coupled hydrologic and biogeochemical analyses
AU: * Polizzotto, M
EM: mattyp@stanford.edu
AF: Stanford University, Geological and Environmental Sciences Building 320, Room 118, Stanford, CA 94305, United States
AU: Benner, S G
EM: sbenner@boisestate.edu
AF: Boise State University, Department of Geosciences Math/Geosciences RM 255, Boise, ID 83725, United States
AU: Kocar, B D
EM: bdkocar@gmail.com
AF: Stanford University, Geological and Environmental Sciences Building 320, Room 118, Stanford, CA 94305, United States
AU: Sampson, M
EM: mickey@rdic.org
AF: Resource Development International, Royal Brick Rd, Kien Svay, Kandal, Cambodia
AU: Ouch, K
EM: kagnaouch@yahoo.com
AF: Resource Development International, Royal Brick Rd, Kien Svay, Kandal, Cambodia
AU: Ouch, K
EM: kagnaouch@yahoo.com
AF: University of Louisville, Department of Chemistry 2320 South Brook St, Louisville, KY 40292, United States
AU: Phan, K
EM: kongkeacd@gmail.com
AF: Resource Development International, Royal Brick Rd, Kien Svay, Kandal, Cambodia
AU: Fendorf, S
EM: fendorf@stanford.edu
AF: Stanford University, Geological and Environmental Sciences Building 320, Room 118, Stanford, CA 94305, United States
AB: Tens of millions of people living on the large river deltas of Southeast Asia routinely consume groundwater with unsafe arsenic levels. While there is general agreement that arsenic is naturally derived, the particular sources of arsenic, as well as the mechanisms promoting its release from the solid-phase, remain unresolved, thereby limiting our ability to predict arsenic concentrations in space (between wells) and time (future concentrations). This uncertainty is attributed, in part, to a poor understanding of groundwater flow paths due to extensive irrigation pumping in the Ganges-Brahmaputra River system, where most research has focused. In order to elucidate the most important arsenic sources and the processes controlling arsenic contamination in Southeast Asian groundwater, we have established a field area within the minimally disturbed Mekong River Delta in Cambodia. While the Mekong Delta system in Cambodia has similar depositional history, regional hydrology, and biogeochemical conditions to other arsenic-contaminated deltaic aquifers of Asia, land use alteration, inclusive of irrigation, is minimal. Thus, the hydrology of our system remains governed by natural rather than anthropogenic processes, allowing us to formulate a steady-state, coupled hydrologic and biogeochemical model of arsenic release and transport. Using robust principles of mass balance, we show that, while liberation mechanisms within the deeper aquifer sediments may contribute arsenic to the groundwater, the majority of the dissolved arsenic is derived from arsenic release at the near-surface and is transported through the aquifer, a finding that has important implications for management of the arsenic crisis.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0432 Contaminant and organic biogeochemistry (0792)
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
SC: Hydrology [H]
MN: 2007 Fall Meeting