Hydrogeochemical comparison and effects of overlapping redox zones on groundwater arsenic near the Western (Bhagirathi sub-basin, India) and Eastern (Meghna sub-basin, Bangladesh) margins of the Bengal Basin

Abhijit Mukherjee, Mattias von Brömssen, Bridget R. Scanlon, Prosun Bhattacharya, Alan E. Fryar, Md Aziz Hasan, Kazi Matin Ahmed, Debashis Chatterjee, Gunnar Jacks, Ondra Sracek

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141 Scopus citations

Abstract

Although arsenic (As) contamination of groundwater in the Bengal Basin has received wide attention over the past decade, comparative studies of hydrogeochemistry in geologically different sub-basins within the basin have been lacking. Groundwater samples were collected from sub-basins in the western margin (River Bhagirathi sub-basin, Nadia, India; 90 samples) and eastern margin (River Meghna sub-basin; Brahmanbaria, Bangladesh; 35 samples) of the Bengal Basin. Groundwater in the western site (Nadia) has mostly Ca-HCO3 water while that in the eastern site (Brahmanbaria) is much more variable consisting of at least six different facies. The two sites show differences in major and minor solute trends indicating varying pathways of hydrogeochemical evolution However, both sites have similar reducing, postoxic environments (pe: + 5 to - 2) with high concentrations of dissolved organic carbon, indicating dominantly metal-reducing processes and similarity in As mobilization mechanism. The trends of various redox-sensitive solutes (e.g. As, CH4, Fe, Mn, NO3-, NH4+, SO42-) indicate overlapping redox zones, leading to partial redox equilibrium conditions where As, once liberated from source minerals, would tend to remain in solution because of the complex interplay among the electron acceptors.

Original languageEnglish
Pages (from-to)31-48
Number of pages18
JournalJournal of Contaminant Hydrology
Volume99
Issue number1-4
DOIs
StatePublished - Jul 29 2008

Bibliographical note

Funding Information:
The authors acknowledge the Swedish International Development Agency (Sida-SAREC), Swedish Research Council (VR-Sida), Strategic Environmental Research Foundation (MISTRA), Geological Society of America and University of Kentucky for research grants for fieldwork in Bangladesh and India. We thank Ann Fylkner and Monica Löwen (Department of Land and Water Resources Engineering, Royal Institute of Technology, Stockholm), Carl-Magnus Mörth (Department of Geology and Geochemistry, Stockholm University), and Trish Coakley and John May (Environmental Research and Teaching Laboratory, University of Kentucky) for the sample analyses. We also appreciate the support rendered by the officials of the Directorate of Public Health Engineering, Government of West Bengal, and Bangladesh Water Development Board, Government of Bangladesh, the Public Health Engineering Directorate, Government of West Bengal, and Sudipta Rakshit, University of California at Berkeley.

Keywords

  • Arsenic
  • Bengal Basin
  • Groundwater
  • Hydrogeochemistry
  • Redox

ASJC Scopus subject areas

  • Environmental Chemistry
  • Water Science and Technology

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