210Pb based trace element fluxes in the nearshore and estuarine sediments off Bombay, India

Seven sediment cores from the Thana creek-Bombay harbour complex (THC) have been studied for excess 210Pb (210Pbexc, that portion of 210Pb not supported by decay of 226Ra in sediment), Corg, Mn, Fe, Co, Ni, Cu, Zn and Al. The sediment accumulation rates based on 210Pb depth profiles decrease from 1.9 cm/yr, in the northern segment of the THC, to 0.4 cm/yr, in the southern segment. The calculated inventories of 210Pbexc increase from 16 dpm/cm2, for the core from the southern area, to 187 dpm/cm2, for the northernmost core, which was much higher compared to the atmospheric fallout inventory of 40–50 dpm/cm2. The inner creek acted as a sink for 210Pb while active winnowing prevailed in the southern segment. Trace elements depth profiles in sediments did not exhibit signatures of significant environmental pollution. Variations in metal concentrations, metal/Al ratios and low excess metal inventories, suggested that the majority of the anthropogenic metals were either exported beyond the creek and nearshore region thus making the THC a passive link between the land and the sea for trace metals or largely removed prior to their entering the THC proper.