Geochemical evidence for heavy metal contamination in the sediment cores of Ennore Southeast Coast of India

Abstract

The sea and more particularly the aquatic systems are the ultimate repository of anthropogenic wastes. However, the capacity for such assimilation is limited thereby leading to pollution. The aquatic systems are under strong anthropogenic pressure (urban, mining, industrial). Sediments are important carriers of heavy metals in the hydrological cycle and because metals are partitioned with the surrounding waters, they reflect the quality of an aquatic system. Industrialization coupled with urbanization has led to stress in Buckingham Canal which runs parallel to Bay of Bengal at a distance of around 1km from the coastline. Ennore Creek lies between Chennai city (40km North) and Pulicat Lagoon lies at Latitude 13º 14 N and Longitude 80º 20 E. Ennore comprises of lagoon, salt marshes and backwaters. Eight sediment cores were collected along Ennore Pulicat stretch to understand the geochemical characteristics of the sediments in the coastal environment and to evaluate the historical level of contamination over time. The cores were sliced at 2.5cm increments and the sediment samples were taken for analysis. The concentrations of heavy metals (Mn, Cr, Ni, Cu, Zn, Cd, Pb, and Hg) and the associated geochemical factors which determine the fate of heavy metals were analyzed. Metal concentrations increase in the southern part of the study area. This could be due to the high concentrations of industrial and urban discharges from Chennai, Manali, Ennore. The concentration of the metals is observed to be high in estuarine region. Increasing heavy metals in these sediments is particularly due to the enhanced OC content, abundance of fine particles with greater surface area. The AF sequence for these metals is: Crgt Nigt Mngt Cugt Zngt Pb. Based on the CF computation, Ennore can be placed under the class of low to moderate degree of contamination. If the present trend of deposition continues Ennore and Pulicat are likely to face serious threat due to metal pollution. newline