TY - JOUR
T1 - Redox control of arsenic mobilization in Bangladesh groundwater
AU - Zheng, Y.
AU - Stute, M.
AU - Van Geen, A.
AU - Gavrieli, I.
AU - Dhar, R.
AU - Simpson, H. J.
AU - Schlosser, P.
AU - Ahmed, K. M.
N1 - Funding Information:
We thank Dr. I. Hussain of the National Institute of Preventive Medicine of Bangladesh for logistic assistance during our January and March 2000 field trips. We thank our field assistants Mohammed Shahnewaz, Mujibur Rahman, and Shahinur Islam for the long but enjoyable hours spent in the field. Queens College students, Jennifer Rommel, Bettina Ben-Elizer, Timothy Brutus and Ohinka Singh helped with sample analyses and preparation. Funding was provided by the US NIEHS/Superfund Basic Research Program P42ES10349. The Columbia University Earth Institute provided funding for initial fieldwork and other aspects of our research. Ratan Dhar is also supported by a CUNY graduate center science fellowship. This is Lamont-Doherty contribution 6372.
PY - 2004/2
Y1 - 2004/2
N2 - Detailed hydrochemical measurements, δ34SSO4 and 3H analyses were performed on 37 groundwater samples collected during February 1999, January and March 2000 from 6 locations in eastern and southeastern Bangladesh to examine redox processes that lead to As mobilization in groundwater. The study sites were chosen based on available nation-wide As surveys to span the entire spectrum of As concentrations in Bangladesh groundwater, and to represent 3 of 5 major geological units of the Ganges-Brahmaputra Delta: uplifted Pleistocene terrace, fluvial flood plain and delta plain. Arsenic was found to be mobilized under Fe-reducing conditions in shallow aquifers (<35 m depth), presumably of Holocene age. It remained mobile under SO4-reducing conditions, suggesting that authigenic sulfide precipitation does not constitute a significant sink for As in these groundwaters. The redox state of the water was characterized by a variety of parameters including dissolved O2, NO3-, Mn2+, Fe2+ concentrations, and SO4 2-/Cl- ratios. High dissolved [As] (> 50 μg/l; or > 0.7 μM ) were always accompanied by high dissolved [HCO3 -] (> 4 mM), and were close to saturation with respect to calcite. Groundwater enriched in As (200-800 μg/l; or 2.7-10.7 μM) and phosphate (30-100 μM) but relatively low in dissolved Fe (5-40 μM) probably resulted from re-oxidation of reducing, As and Fe enriched water. This history was deduced from isotopic signatures of δ34SSO4 and 3H2O (3H) to delineate the nature of redox changes for some of the reducing groundwaters. In contrast, As is not mobilized in presumed Pleistocene aquifers, both shallow (30-60 m) and deep (150-270 m), because conditions were not reducing enough due to lack of sufficient O 2 demand.
AB - Detailed hydrochemical measurements, δ34SSO4 and 3H analyses were performed on 37 groundwater samples collected during February 1999, January and March 2000 from 6 locations in eastern and southeastern Bangladesh to examine redox processes that lead to As mobilization in groundwater. The study sites were chosen based on available nation-wide As surveys to span the entire spectrum of As concentrations in Bangladesh groundwater, and to represent 3 of 5 major geological units of the Ganges-Brahmaputra Delta: uplifted Pleistocene terrace, fluvial flood plain and delta plain. Arsenic was found to be mobilized under Fe-reducing conditions in shallow aquifers (<35 m depth), presumably of Holocene age. It remained mobile under SO4-reducing conditions, suggesting that authigenic sulfide precipitation does not constitute a significant sink for As in these groundwaters. The redox state of the water was characterized by a variety of parameters including dissolved O2, NO3-, Mn2+, Fe2+ concentrations, and SO4 2-/Cl- ratios. High dissolved [As] (> 50 μg/l; or > 0.7 μM ) were always accompanied by high dissolved [HCO3 -] (> 4 mM), and were close to saturation with respect to calcite. Groundwater enriched in As (200-800 μg/l; or 2.7-10.7 μM) and phosphate (30-100 μM) but relatively low in dissolved Fe (5-40 μM) probably resulted from re-oxidation of reducing, As and Fe enriched water. This history was deduced from isotopic signatures of δ34SSO4 and 3H2O (3H) to delineate the nature of redox changes for some of the reducing groundwaters. In contrast, As is not mobilized in presumed Pleistocene aquifers, both shallow (30-60 m) and deep (150-270 m), because conditions were not reducing enough due to lack of sufficient O 2 demand.
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U2 - 10.1016/j.apgeochem.2003.09.007
DO - 10.1016/j.apgeochem.2003.09.007
M3 - Article
AN - SCOPUS:0842289081
SN - 0883-2927
VL - 19
SP - 201
EP - 214
JO - Applied Geochemistry
JF - Applied Geochemistry
IS - 2
ER -