327-7 14C Analysis of Microbial DNA from Bangladesh Groundwater: Implications for Deep Aquifer Sustainability

See more from this Division: Topical Sessions
See more from this Session: Groundwater Arsenic: A Global Environmental Health Problem and Sustainable Mitigation II

Wednesday, 8 October 2008: 3:05 PM
George R. Brown Convention Center, 342BE

Elizabeth Trembath-Reichert, Department of Environmental Sciences, Barnard College, New York, NY, Brian Mailloux, Barnard College, Columbia University, New York, NY, Martin Stute, Environmental Science, Barnard College, New York, NY, A. van Geen, Lamont-Doherty Earth Observatory of Columbia Univ, Palisades, NY, Greg Freyer, Environmental Health Science, Columbia University, New York, NY, Yan Zheng, Queens College, CUNY, Flushing, NY 11367, Palisades, NY, Greg O'Mullan, Biology and Paleo Environment, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, Rachel Foster, Ocean Sciences, UCSC, Santa Cruz, CA, James Thomas, Division of Hydrologic Sciences, Desert Research Institute, Reno, NV and Bruce Buccholz, Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA
Abstract:

Over 50 million people in Bangladesh are exposed to arsenic contaminated groundwater. Arsenic is mobilized from Bangladesh sediments into groundwater via microbial heterotrophic respiration. During respiration, microbes incorporate proximal organic carbon (OC) into cellular structures such as DNA. The source of this OC is debated and could be derived from the sediment or recharge waters. Previous studies have used indirect methods to determine the OC source by collecting methane, dissolved OC, and dissolved inorganic carbon samples from aquifers. To directly determine the source of the OC used by microbes inducing arsenic release, we developed a method for 14C analysis of microbial DNA from the arsenic contaminated aquifers. Microbes were collected by filtering over 2000L of groundwater through 0.2µm filters at Site F in the Lashkardi Village, Araihazar, using sampling wells from the shallow and deep aquifers. Microbial DNA was extracted and purified, and three DNA samples were submitted for radiocarbon analysis. Radiocarbon results from the two shallow aquifer samples were inconclusive due to carbon contamination from gel electrophoresis DNA extraction materials. Gel extraction is not a viable method of DNA extraction for radiocarbon analysis, and we are currently developing purification procedures that do not introduce carbon. An alternate purification method was used for the deeper low-arsenic Pleistocene Dupa Tilla aquifer sample, which yielded a robust 14C signature. The deep aquifer 14C analysis indicates the presence of a young OC source. These results suggest the need for further study of the effects of young OC intrusion into the deep aquifer in Bangladesh.

See more from this Division: Topical Sessions
See more from this Session: Groundwater Arsenic: A Global Environmental Health Problem and Sustainable Mitigation II

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