Assessment of heavy metal distribution pattern in the sediments of Tamirabarani river and estuary, east coast of Tamil Nadu, India

The present study aims to investigate the concentration and spatial distribution of trace metals in Tamirabarani river and estuary located in the southeast coast of India. Sediment samples collected from sixteen locations were analysed for Cu, Ni, Cr, Pb, Zn and Cd. The extent of pollution in these sediments was assessed using enrichment factor (EF), contamination factor (CF), geo-accumulation index (I_geo). The EF shows enrichment of Ni in the northern part of the estuary and that of Cu in the south and it is mainly due to the process of weathering. The contamination factor indicates Cd is more highly contaminated than other metals. I_geo index shows that Cd is moderately polluted and its spatial distributions clearly indicate that it is found in estuarine region. The comparison of metal concentration with other estuaries of India indicates that these metals are well below the permissible limit. The metals in the estuary of the study area indicate more of the predominance of natural process than other estuaries in India. It is evident that the samples of river and estuary area are dominantly due to the natural process rather than anthropogenic activity.