Deeper groundwater chemistry and geochemical modeling of the arsenic affected western Bengal basin, West Bengal, India

Abhijit Mukherjee, Alan E. Fryar

Research output: Contribution to journalArticlepeer-review

232 Scopus citations

Abstract

A regional scale hydrogeochemical study of a ∼21,000-km2 area in the western Bengal basin shows the presence of hydrochemically distinct water bodies in the main semiconfined aquifer and deeper isolated aquifers. Spatial trends of solutes and geochemical modeling indicate that carbonate dissolution, silicate weathering, and cation exchange control the major-ion chemistry of groundwater and river water. The main aquifer water has also evolved by mixing with seawater from the Bay of Bengal and connate water. The isolated aquifers contain diagenetically altered water of probable marine origin. The postoxic main aquifer water exhibits overlapping redox zones (metal-reducing, sulfidic and methanogenic), indicative of partial redox equilibrium, with the possibility of oxidation in micro-scale environments. The redox processes are depth-dependent and hydrostratigraphically variable. Elevated dissolved As in the groundwater is possibly related to Fe(III) reduction, but is strongly influenced by coupled Fe-S-C redox cycles. Arsenic does not show good correlations with most solutes, suggesting involvement of multiple processes in As mobilization. The main river in the area, the Bhagirathi-Hoogly, is chemically distinctive from other streams in the vicinity and probably has little or no influence on deep groundwater chemistry. Arsenic in water of smaller streams (Jalangi and Ichamati) is probably introduced by groundwater discharge during the dry season.

Original languageEnglish
Pages (from-to)863-894
Number of pages32
JournalApplied Geochemistry
Volume23
Issue number4
DOIs
StatePublished - Apr 2008

Bibliographical note

Funding Information:
This project has been executed with the cooperation of the Public Health Engineering Directorate (PHED), Government of West Bengal. However, the ideas presented in this paper are those of the authors and have not been officially endorsed by the Government of West Bengal or any other person or organization. Special thanks to P.K. De, A. Banerjee, A. Bhattacharya, and G. RoyChowdhury (PHED) for helping with selection of sampling sites; T. Datta and B. Hazra (PHED), Barindra Lal Mukherjee and Murali Singh for sampling; Trish Coakley, Bob King and John May (UK ERTL), Millie Hamilton (UK Forestry), Elisa D’Angelo (UK Plant and Soil Science), Jason Backus (Kentucky Geological Survey) and Chris Eastoe (University of Arizona) for sample analyses; Helena Truszczynska (UK SSTARS) for statistical analyses; Kevin Henke (UK CAER), Roger Lee, and Rich Wanty for reviews. The project was financially supported by the University of Kentucky, the Kentucky NSF-EPSCoR program, and the Geological Society of America (Grant No. 7751-04).

ASJC Scopus subject areas

  • Environmental Chemistry
  • Pollution
  • Geochemistry and Petrology

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