Geomorphic Controls on Spatial Arsenic Distribution in Aquifers of the Brahmaputra River Floodplains

The present study was conducted to explore the controls of geomorphic features on arsenic (As) mobilization in groundwater aquifers of the Brahmaputra River floodplains. Linear Imaging Self-Scanning Sensor-4 (LISS IV) imagery was used to demarcate different geomorphic units based on spectral signatures and field investigations using ArcGIS 9.3 software. A total of 132 groundwater samples covering four different geomorphic units were tested in the laboratory using Atomic Absorption Spectrophotometer (AAS). Overlay of test results of groundwater samples on classified geomorphic map revealed that out of a total 132 samples 77% sources in younger alluvium and 89% sources tested in older alluvium were found to be affected with As beyond permissible limit of 10 μg/L set by the World Health Organization. As enrichment along the different geomorphic units followed the trend as Younger Alluvium> Older Alluvium> Natural Levees> Floodplain Deep.