Paper No. 281-8
Presentation Time: 3:40 PM
FURTHER INVESTIGATION OF THE RELATIONSHIP BETWEEN POPULATION DENSITY, UNSEWERED WASTE INPUTS AND AS IN BANGLADESH GROUNDWATER
SAN PEDRO, Reisa Joy G.1, WHALEY-MARTIN, Kelly J.2, BOSTICK, Benjamin C.3, MAILLOUX, Brian J.4, VAN GEEN, Alexander5, MOZUMDER, M. Rajib Hassan3, ELLIS, Tyler6 and SLATER, Greg F.2, (1)School of Geography and Earth Science, McMaster University, 1280 Main St. West, Hamilton, ON L8S4L8, Canada, (2)School of Geography and Earth Sciences, McMaster University, 1280 Main St. West, Hamilton, ON L8S 4K1, Canada, (3)Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9w, Palisades, NY 10964, (4)Dept. of Environmental Science, Barnard College, New York, NY 10027, (5)Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, PO Box 1000, Palisades, NY 10964, (6)Columbia University, Lamont-Doherty Earth Observatory, 61 Route 9W, PO Box 1000, Palisades, NY 10964-8000
Over 40 million Bangladeshi rely on groundwater with arsenic (As) concentrations often exceeding the Bangladesh water quality guideline. This geogenic As is thought to be released into groundwater by dissimilatory iron-reducing microbes oxidizing surrounding organic carbon. Previous research at two high-population sites in Araihazar, Bangladesh, site B (Baylakandi) and site F (Lashkardi), suggests human/animal waste is an important source of young organic carbon supporting microbial communities in As-bearing aquifers. This study adds to previous research by investigating two other sites selected to assess whether population density can be an indicator of unsewered waste input into groundwater and how this may effect changes in the geochemical conditions of the aquifer environment.
To achieve this, aquifer matrix cores were collected at Desert Island (DI) and Dopar Tek (DT). DI has light grey, reduced Holocene sediments with low sedimentary arsenic content (1.9 – 4.2 mg/kg) that are generally associated with relatively higher dissolved As content. In contrast, DT has oxidized reddish orange clay-rich Pleistocene sediment with higher sedimentary arsenic content (2.6 – 10.4 mg/kg) generally associated with low dissolved As. DI, located in a low population area, was hypothesized to receive low sewage inputs whereas DT, located close to high populations, was hypothesized to receive higher sewage inputs. Phospholipid fatty acid (PLFA) concentrations and estimated cell abundances at DI (3 x 106 – 1 x 108 cells/g) were generally higher than those observed at DT (8 x 106 - 3 x 107 cells/g). Cell abundances at DT were similar to those previously observed at Site B and F suggesting comparable microbial activity in the oxidized DT sediments and elevated microbial activity at DI. Preliminary analysis of the abundance of coprostanol, a faecal biomarker from the mammalian gut, suggests inputs of unsewered waste are occurring at both DI and DT and may be independent of the variation in local population density. This study aims to expand our understanding of the relationships between population density, local sewage input, and the activities of aquifer microbial communities to ascertain their potential influence on arsenic release.
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