Enrichment and toxicity of trace metals in near-shore bottom sediments of Cuddalore, SE coast of India

In order to identify contaminating trace metals and their sources, studies on trace metals are often included in routine environmental monitoring programs. Twenty-five near-shore bottom sediment samples from the inner shelf region (near Cuddalore) of the Bay of Bengal were analysed for sediment texture, organic matter, carbonate (CaCO₃) concentrations and total trace metal concentrations (TTMs) (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn and Cd) in order to evaluate geochemical processes such as enrichment and their origin. The presence of carbonates (2.5–5.8 %) indicates the dominance of calcareous shells in the region. A relatively high percentage of organic matter (0.2–3.9 %) is attributed to the predominance of finer sediments entering through the minor rivers. High concentrations of TTMs in fine and organic-rich sediments are influenced by municipal and industrial sources, which contention is well supported by correlations of TTMs concentrations with Fe–Mn fractions. Geoaccumulation index (I_geo) calculations indicate that Cr, Cu, Ni, Pb and Cd concentrations are above the values expected from their presence in the discharge of effluents from the industrial zones bordering the shoreline. Comparing the findings of the present study with those from different parts of the World, Cr, Cu, Ni, Pb appear to be enriched in the sediments of the region.