Assessment of spatial distribution and potential ecological risk of the heavy metals in relation to granulometric contents of Veeranam lake sediments, India.

The contents and spatial distributions of heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) have been studied in surface sediments of Veeranam lake, Tamilnadu, India. Heavy metal contents are higher in open water area (limnetic zone) (OWA) than other two regions such as inflow river mouth (littoral zone) (IFR) and outflow river mouth region (OFR). Present metal contents are compared with both background and toxicological reference values. The comparative results suggest that the present metals except Cd and Pb create an adverse effect on the aquatic ecosystems associated with this lake. The Pollution Load Index (PLI) and Potential Ecological Risk (PER) are calculated and calculated PLI values (range: 1.18-4.09 with an average of 2.03) show that the present sediments are polluted significantly and these values are higher in OWA region. From the PER values, each single element has low potential ecological risk. However, Cd shows higher ecological risk. The comprehensive PER index of the sediments shows moderate degree. The magnetic susceptibility is higher in OWA region. Granulometric analysis confirms that the silt is major content. Multivariate Statistical analyses (Pearson Correlation, Cluster and Factor analysis) were carried out and obtained results suggested that the heavy metals in present lake have complicated contamination sources or controlling factors and the heavy metals such as Cr, Cu, Ni and Zn may be incorporated in magnetic minerals which are presented in silt grains. Also it shows that the role of silt is incorporating the cations on their surface and raising the level of magnetic susceptibility and heavy metal contents. The present study recommends that the heavy metal levels are unlikely to cause additional adverse health risks to the aquatic ecosystem associated with this lake.