Time-series monitoring and ecological risk assessment of heavy metal pollution in Mahanadi estuary, east coast of India

Mahanadi estuary is situated in the eastern part of India with several industries along its bank, which makes the system highly vulnerable to different types of pollutants. To assess the coastal pollution due to possible heavy metal contamination in the surface sediment of the estuary, seasonal observations (pre-monsoon, post-monsoon, and winter) were made from a time-series monitoring station near the estuary mouth. The study showed that the average concentrations of nine heavy metals were in the order of Fe> Pb> Cr >Zn >Co> Cu> Ni> Cd> Hg in both pre-monsoon and post-monsoon, whereas in winter their order was Fe >Pb >Cr> Zn> Ni> Cu> Co> Cd> Hg. The one-way ANOVA of metal concentrations shows significant seasonal variations (p<0.01) except for Hg, Cu, Zn, and Fe. The high concentration of metals in post-monsoon and winter indicated seasonal influences of potential sources in the upstream. The concentrations of Cd, Pb, Co, Ni, Zn, and Hg showed prominent tidal variation, and Cd concentration was high only in ebb tide in both pre-monsoon and post-monsoon. The pollution indices - Enrichment Factor (EF), Geo-accumulation Index (I-geo), and Pollution Load Index (PLI) along with Potential Ecological Risk Assessment (PERI) were used for the environmental assessment of Mahanadi estuary sediment collected during pre-monsoon, post-monsoon, and winter season. The high EF of Pb and Cd shows contamination of sediments by these metals from external sources such as industrial and other anthropogenic activities. Pollution indices showed that the sediment of the Mahanadi estuary is not contaminated with respect to metals except Cd. Numerical Sediment Quality Guidelines, applied to assess adverse biological effects of these metals, suggested possibilities of occasional biological effect due to Cd. (C) 2021 Elsevier B.V. All rights reserved.