The palaeosol model of arsenic pollution of groundwater tested along a 32km traverse across West Bengal, India

M. A. Hoque, J. M. McArthur, P. K. Sikdar

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Abstract

The distribution of As-pollution in groundwater of the deltaic aquifers of south-eastern Asia may be controlled by the subsurface distribution of palaeo-channel sediments (As-polluted groundwaters) and palaeo-interfluvial sediments (As-free groundwaters). To test this idea, termed the palaeosol model of As-pollution, we drilled 10 sites, analysed groundwater from 249 shallow wells (screened < 107 mbgl), field-tested another 149 for As, and used colour as a guide to the presence or absence of As-pollution in a further 531 wells. Our work was conducted along a 32-km traverse running W to E across southern West Bengal, India. At seven drill sites we logged a palaeo-interfluvial sequence, which occurs as three distinct units that together occupy 20 km of the traverse. These palaeo-interfluvial sequences yield As-free groundwaters from brown sands at depth < 100 m. The palaeo-interfluvial sequences are separated by two deep palaeo-channels, which were logged at 3 sites. The palaeo-channel deposits host As-polluted groundwater in grey sands. Our findings confirm the predictions of the palaeosol model of As-pollution. We show again that well-colour can be used both to successfully predict the degree of As-pollution in groundwater, and to locate regions of buried palaeo-interfluve that will yield As-free groundwater for the foreseeable future.
Original languageEnglish
Pages (from-to)157-165
Number of pages9
JournalScience of the Total Environment
Volume431
Early online date7 Jun 2012
DOIs
Publication statusPublished - 1 Aug 2012
Externally publishedYes

Keywords

  • groundwater arsenic
  • palaeosol
  • Begal Basin
  • West Bengal
  • well-clour
  • palaeo-interfluve

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