Depositional environment and elemental distribution with time in mudflats of dharamtar creek, west coast of India

Two sediment cores collected from intertidal mudflats of Dharamtar creek, one near the mouth and the other from the middle region of Amba River were analyzed for sediment components, organic carbon and selected metals (Al, Fe, Mn, Ni, Co, Cr, Zn and Pb). The sediments are mainly composed of silt and clay contributing greater than 90% in both the cores, indicating calm environment prevailed during deposition of sediments However, between the two cores, sediments in the middle estuarine region were deposited in relatively violent hydrodynamic environment compared to that near the mouth of the creek. Organic carbon concentration was found to be slightly higher near the mouth. The distribution of metals is largely controlled by sediment components, organic carbon and Fe-Mn oxyhydroxides at both the locations. When the average values are considered, Mn and Co shows higher concentration in the middle estuarine region whereas, Fe along with Al shows higher concentrations near the mouth. Enrichment factor calculated indicates minor enrichment of Mn, Fe and Zn and moderately to moderately severe enrichment with respect to Ni, Co, Cr and Pb in the creek. Index of geo-accumulation (Igeo) computed indicated that Dharamtar creek is moderately polluted with respect to Pb and Co, unpolluted to moderately polluted with Ni, Cr and Fe and practically unpolluted with Zn and Mn.