title: Arsenic in Groundwater: The Deep Late Pleistocene Aquifers of the Western Bengal Basin.
abstract: in groundwaters from 145 wells across central West Bengal, India, those from Pleistocene aquifers at depths >70 m beneath paleo-interfluves contain <10 μg/L As. Pleistocene aquifers beneath deep paleo-channels typically host groundwaters containing 10-100 μg/L As at depths between 120 and 180 m. The depth profiles of As and SO4 and the conservative tracers Cl/Br, δ(18)O, and δ(2)H show that the As in Pleistocene groundwater beneath deep paleo-channels is relict and does not arise from migration downward of As-polluted groundwater in overlying aquifers. We postulate that the As was liberated in situ by reduction of minimal iron oxyhydroxides in the gray Pleistocene sands by organic matter infiltrating from riverbeds during late Pleistocene or earliest Holocene times. Mitigation of the widespread As-pollution in shallow aquifers through exploitation of deep Pleistocene aquifers would improve if guided by an understanding of the distribution of buried paleo-channels and paleo-interfluves and the knowledge that As may be present naturally in groundwater at depths >150 m beneath deep paleo-channels.
authors.affiliation: Department of Earth Sciences, University College London , Gower Street, London WC1E 6BT, U.K.
authors.forename: J M
authors.initials: JM
authors.lastname: McArthur
authors.affiliation: Department of Environment Management, Indian Institute of Social Welfare and Business Management , College Square (West), Kolkata-700073, India.
authors.forename: U
authors.initials: U
authors.lastname: Ghosal
authors.affiliation: Department of Environment Management, Indian Institute of Social Welfare and Business Management , College Square (West), Kolkata-700073, India.
authors.forename: P K
authors.initials: PK
authors.lastname: Sikdar
authors.affiliation: School of Environmental Science, University of Liverpool , Brownlow Street, Liverpool L69 3GP, U.K.
authors.forename: J D
authors.initials: JD
authors.lastname: Ball
mesh_terms: D001151:Arsenic / Q000032:analysis*; D001965:Bromides / Q000032:analysis; D002712:Chlorides / Q000032:analysis; D005843:Geography; D060587:Groundwater / Q000737:chemistry*; D007194:India; D007553:Isotope Labeling; D010084:Oxidation-Reduction; D013431:Sulfates / Q000032:analysis; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000032:analysis*; D060986:Water Wells
chemical_list: D001965:Bromides; D002712:Chlorides; D013431:Sulfates; D014874:Water Pollutants, Chemical; D001151:Arsenic