Mechanism of arsenic release to groundwater,Bangladesh and West Bengal |
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| Institution: | 1. Geological Sciences, University College London, Gower St., London, WC1E 6BT, UK;2. Mott MacDonald International Ltd., 122 Gulshan Avenue, Dhaka -1212, Bangladesh;3. Department of Geology, University of Dhaka, Dhaka -1000, Bangladesh.;1. Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen, Denmark;2. Research Centre for Environmental Technology and Sustainable Development (CETASD), Hanoi University of Science (VNU), Hanoi, Viet Nam;3. Dept. of Hydrogeology, Hanoi University of Mining and Geology (HUMG), Hanoi, Viet Nam;1. School of Environmental Studies (SOES), Jadavpur University, Kolkata 700 032, India;2. Global Centre for Environmental Remediation (GCER), University of Newcastle, Faculty of Science and Information Technology, Callaghan Campus, Callaghan, New South Wales, NSW 2308, Australia;3. Department of Dermatology, Institute of Post Graduate Medical Education and Research, SSKM Hospital, Kolkata, India;4. Kolkata National Medical College and Hospital, Kolkata, India;5. Department of Neurology, Medical College, Kolkata, India;1. Earth Process Modeling Group, CSIR-National Geophysical Research Institute, Hyderabad, India;2. Academy of Scientific & Innovative Research (AcSIR), Ghaziabad, 201 002, India;3. Electrical Geophysics Group, CSIR-National Geophysical Research Institute, Hyderabad, India;1. School of Environmental Studies & State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, 430074 Wuhan, China;2. Ecohydrology Research Group, Department of Earth and Environmental Sciences and Water Institute, University of Waterloo, Waterloo, Canada;3. Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen, Denmark |
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| Abstract: | In some areas of Bangladesh and West Bengal, concentrations of As in groundwater exceed guide concentrations, set internationally and nationally at 10 to 50 μg l−1 and may reach levels in the mg l−1 range. The As derives from reductive dissolution of Fe oxyhydroxide and release of its sorbed As. The Fe oxyhydroxide exists in the aquifer as dispersed phases, such as coatings on sedimentary grains. Recalculated to pure FeOOH, As concentrations in this phase reach 517 ppm. Reduction of the Fe is driven by microbial metabolism of sedimentary organic matter, which is present in concentrations as high as 6% C. Arsenic released by oxidation of pyrite, as water levels are drawn down and air enters the aquifer, contributes negligibly to the problem of As pollution. Identification of the mechanism of As release to groundwater helps to provide a framework to guide the placement of new water wells so that they will have acceptable concentrations of As. |
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