Groundwater arsenic contamination in the Brahmaputra and the Barak flood plains of Assam

3^rd International Conference on Hydrology & Meteorology

September 15-16, 2014 Hyderabad International Convention Centre, India

K P Sarma

Accepted Abstracts: Hydrol Current Res

Abstract :

Occurrence of groundwater Arsenic (As) in excess of the permissible limit in the fluvial plain of the Brahmaputra and the Barak is known to have affected 7 lakhs of population in 21 of the 27 districts of Assam. The As affected areas in the state are mostly located in the alluvial plains of the rivers Brahmaputra and Barak. In Assam, the Brahmaputra Flood Plains (BFP) and the Barak Valley Plains (BVP) are the two most important river systems which have given rise to extensive alluvial plains on which majority of the population of the state is dependent. Both BFP and the BVP have conditions conducive for the release of As in groundwater. In Assam, the source of As is considered to be geogenic where arsenic is released into the groundwater by reductive dissolution of ferric oxyhydroxides, to which arsenic was adsorbed during fluvial transport. In most of the high groundwater As areas, the level of groundwater Fe is high and a positive relation exists between As and Fe, moreover it was found that DOC (from representative samples) also had positive relation with the groundwater As. The reducing condition of the aquifers is manifested by high Fe, high DOC, low NO3- and low ORP. It is believed that the process responsible for release of As in the groundwater of these two river plains is reductive dissolution of iron hydr(oxides). Both the Brahmaputra as well as the Barak are perennial mountainous rivers with high sediment loads, the mountainous weathered sediments appear to be the ultimate source of the As bearing minerals. It has been established that the ultimate source of As in BFP could be the Himalayan Mountains while the Barail hill range could be the source of As in the BVP.