Assessment of Trace Metal Pollution in Surface Sediments from Southwestern Part of Bay of Bengal, India

Twenty-nine shelf sediment samples have been collected from the Southwestern part of the Bay of Bengal in 5 transects lying offshore between the coasts of Cuddalore and Nagapattinam district, Tamil Nadu, India. Collected samples were analyzed for sediment texture, organic matter (OM), and trace metals (Fe, Cu, Co, Mn, Pb, Zn, Cr, and Ni). Sandy fractions were found to be abundant in all transects except transect 3, because of the existence of the Pichavaram estuary fed by river Vellar in the north and Coleroon in the south. Among all the trace metals, Fe is the most abundant in the sediment samples. And metals such as Co, Pb, Cr and Ni are higher than the average background values, suggesting adverse effects of human activities in polluting the marine environment. The pollution indices viz. Enrichment Factor (EF), Geoaccumulation Index (Igeo), and Contamination Factor (CF) were calculated to assess trace metal pollution. The results imply that Cu, Co, Mn, Pb, Zn, Cr, and Ni in most of the sampling sites are highly contaminated in terms of Geoaccumulation Index (Igeo). Pb, Zn and Cr are heavily contaminated, while Cu, Mn, Ni, and Co showed moderate contamination, as demonstrated by the CF values. Pearson correlation and principal component analysis (PCA), explain the combination of geogenic and anthropogenic sources contributing trace metals to the marine system.