Geomorphic controls on shallow groundwater arsenic contamination in Bengal basin, India

The study was conducted to explore the influence of geomorphic features scattered throughout the area on the occurrence and distribution of arsenic in shallow groundwater. GIS techniques were frequently used to identify the geomorphic features and to correlate with arsenic distribution patterns. The study shows that the occurrence of geomorphic features and their distribution have a vital role in the heterogeneous distribution pattern of arsenic in shallow groundwater. The frequency distribution of geomorphic features is found similar to the arsenic distribution pattern. The moderate to highly contaminated zones are mostly consolidated to the central and southeastern part of the study area. Arsenic contamination levels are varying in different fluvial plains of the study area following the trend of Older Deltaic Plain (ODP) > Older Flood Plain (OFP) > Active Flood Plain (AFP). It has also been observed that arsenic contamination along the different geomorphic features follows the trend of abandoned channels > back swamps > other water bodies > swamps > cut-off meanders > meander scars > ponds > oxbow lakes > channel bar > point bars >channel islands. The present study indicates that the geomorphic features play a significant role in the mobilization of arsenic in shallow groundwater by supplying accumulated organic matter.