Distribution Of Dissolved Trace-Metals In Western Bay Of Bengal

Abstract

Concentrations of Ni, Zn, Cd, Cu, Mn, Pb and Fe have been determined in 93 water samples (17 inshore and 7 offshore stations), collected at different depths, from the western Bay of Bengal (between visakhapatnam and Madras) during March 1988. Surface distributions reveal that relatively high concentrations of trace metals and nutrients are associated with low salinities in inshore and vice versa in the offshore waters. The depth profiles of Ni, Zn and Cd with surface depletion and bottom enrichment resemble those of nutrients indicating their involvement in the biogeochemical cycles. While the profiles of Cu are indicative of its involvement in the scavenging process at intermediate depth, those of Mn and Pb with surface enrichment and bottom depletion, appear to be controlled by river inputs and anthropogenic atmospheric flux. However, surface enrichment and bottom depletion observed in the case of Fe profiles, contrary to its normal oceanic distribution, are attributed to the precipitation and/or adsorption on suspended particles leading to its transport to the sediments. The atomic ratios of Ni, Zn and Cd with nutrients are evaluated through their regression equations and compared with those reported earlier for Pacific, Atlantic and Indian Oceans.