Arsenic distribution in waters and its geochemical behavior in sediment of Mahanadi estuary in India.

Distribution of arsenic in the marine environment is associated with its biogeochemical behavior. Indeed, very few studies have been conducted along the seasonal cycle to show its non-conservative behavior in the tropical estuary. The Mahanadi River, one of the major tropical rivers in the peninsular India, drains densely populated and industrialized region of Paradeep port. Over this 1-year study, the variations of inorganic arsenic were examined along the salinity gradient of the Mahanadi estuary, with the aim to provide some insights into the mechanisms that control arsenic concentrations and behavior under estuarine mixing. Arsenic in the estuary was derived from both natural and anthropogenic sources, and it displayed partial removal from the water in the mixing zone. Results of geo-accumulation index indicated that sediments were uncontaminated and they acted as a sink for arsenic. The diffusive fluxes from water to sediment were estimated to be 9.05 μg m(-2) day(-1) at Chaumohona, 9.83 μg m(-2) day(-1) at Kaudia, and 11.85 μg m(-2) day(-1) at Neherubunglow. The findings of the study suggest that both the removal of arsenic by biogeochemical processes and its diffusive transport from water to sediment are of major importance for both the non-conservative behavior of arsenic in the estuary and its export to the coastal water.