Assessment of metal pollution in Ulhas estuary, Mumbai, India

Abstract

In order to understand historical trend of pollution level by heavy metals in Mumbai – a commercial and industrial centre, a sediment core from the intertidal region of Ulhas estuary was analyzed for various chemical parameters such as organic matter, sediment components and selected metals. Analysis of these data through Pearson's correlation coefficient displayed inter-elemental associations. Factor and cluster analyses showed that finer sediment components and organic matter along with Fe-Mn oxides played a significant role in accumulation and distribution of metals. Various pollution indices such as Enrichment Factor (EF), Pollution Load Index (PLI) and Geo-accumulation index (Igeo) were computed which showed that the concentrations of Fe and Ni in the sediments were slightly higher than or equal to their background values. On the other hand, the concentrations of Mn, Cu, Pb, Co, Cr and Zn in the sediments were found to be significantly higher than their background values. PLI showed increasing trend of metal pollution over the years. Based on Igeo values, all the elements were grouped in the unpolluted class except for Cu and Pb which were found to be moderately polluted, especially in the upper portion of the core. Elevated levels of Cu and Pb may be attributed to the increasing use of anti-fouling paints and vehicle exhausts, respectively.