DYNAMICS OF ARSENIC MOBILIZATION IN FLUVIAL SYSTEM OF THE GANGA ALLUVIAL PLAIN, NORTHERN INDIA: INFERENCE TO HUMAN ACTIVITY

In the northern part of Indian , the Gomati River (a tributary of the Ganga River) was selected for the dynamics of Arsenic mobilization in the fluvial system of the warm humid sub-tropical climate classified in monsoon, post-monsoon, winter , summer seasons. River water samples were collected in two phases: 36 samples during winter season (January-February 2006) and 36 samples during a year-long survey (June 2009 - May 2010) for the evaluation of longitudinal and seasonal variability, respectively. All river water samples were filtered by using 0.45 µm membrane filters and analyzed by ICP-MS for their dissolved Arsenic (dAs) concentrations. Result shows the dAs concentration in the Gomati River was lower than World Health Organization limit (10 µg/l) and varies longitudinally and seasonally by factor of 6 and 10, respectively. In winter season, the dAs concentration increases downstream from 1.49 to 9.62 µg/l and shows positive significant correlation with dissolved phosphorous and sedimentary organic carbon content. It also vary from 0.53 to 5.67 µg/l, with distinct seasonal variations characterized by the decreasing positive peaks during monsoon to post-monsoon seasons; the low and stable during winter season and consistently increasing trend in summer season. From winter to summer season, 10 times increase in temperature is closely related to 4-fold increase of dAs concentration in the river water. Nearly 70 % of river’s annual dAs flux (8.99 × 10³kg) passes in the Ganga River duriing the year.