Delineation of arsenic-contaminated zones in Bengal Delta, India: a geographic information system and fractal approach |
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Authors: | Basab Mukhopadhyay P K Mukherjee Debkumar Bhattacharya S Sengupta |
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Institution: | (1) Geological Survey of India, 27 Jawaharlal Nehru road, 700016 Kolkata, India |
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Abstract: | Groundwater extracted from shallow aquifers in the Bengal Delta is contaminated with arsenic. The fluviodeltaic process that
creates aquifers, ironically, extends its role to also contaminating them with arsenic. The arsenic distribution maps show
a spatial association of arsenic-contaminated wells with palaeo/cut-off/abandoned channels. Weight-on-evidences analysis indicates
that the zones of contamination occur around palaeo-channels within a corridor of 500–700 m that contains most of the contaminated
wells. These corridors are interpreted to be the zone of channel shifting. Contaminated wells represent point fractal geometry
that can be separated into isolated points and clusters. Clusters occur within the zone of channel shifting as obtained by
weight-on-evidences analysis. Isolated points occur within floodplain or back swamp areas. Clusters and isolated point fractals
are interpreted to reflect the process of arsenic release into groundwater. The migration of biomass within the permeable
sandy domain of channel deposits is proposed to be the predominant process in generating clusters. The isolated points represent
restricted biomass spreading in less permeable clay-silt dominated floodplains. |
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Keywords: | Arsenic Palaeochannel Weight-on-evidences analysis Fractal Bengal Delta India |
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