Prevalence and Ecotoxicological significance of heavy metals in sediments of lower stretches of the Hooghly estuary, India

The concentration and distribution of selected eight heavy metals in five stations from lower stretches of the Hooghly estuary were studied to ascertain the level of anthropogenic contaminant loading resulting from the development of the region. Atomic absorption spectroscopy showed that the mean concentration of Fe, Zn, Cu, Ni, Pb, Cr, Cd and As (mg kg-1, dry weight,) ranged from 29950.70 – 39567.94, 61.45 – 98.83, 40.65 – 54.46, 25.44 – 42.78, 36.93 – 48.56, 29.07 – 46.35, BDL – 3.48 and 1.18 – 6.44 respectively. Pollution load index (PLI) and Index of geoaccumulation (Igeo) revealed overall low values but the enrichment factors (EFs) for Cd was typically high for three of the stations. Calculations based on Effect Range Low (ERL) and Threshold Effect Level (TEL) showed that the mean concentration of Cu, Ni and Cd and to some extent Pb exceeded these levels, indicating that there is chance of ecotoxicological effects on benthic organisms dwelling in this region. Inter-elemental relationship and cluster analysis revealed identical behavior of the elements during transport and distribution. The study will help to further the cause of environmental protection of this sensitive biorealm in conjunction with the need for development of the region.