Seasonal variations in heavy metals concentration in water and sediment and associated ecological and human health risk assessment in Chembarambakkam lake, Tamil Nadu, India.

Climate-induced hydrological variability and enhanced anthropogenic pressures are increasingly imposed on fresh water ecosystems, and the transport and bio availability of heavy metals are strongly affected via these pressures. It is therefore essential to know the changes of the metal concentrations seasonally so that this ecosystem integrity can be maintained and the risk to anthropological health can be reduced. The current study aimed to evaluate the seasonal variations of major heavy metals As, Pb, Cd, Cr, Ni, Cu, Zn, Fe, and Al in the water and sediments of Chembarambakkam Lake, which is an important freshwater reservoir of Tamil Nadu, India. The metals selected were those that are both toxicologically relevant and persistent in the environment and have the potential for bioaccumulation and are significant indicators of aquatic pollution and public health risk. The results indicated that there is significant seasonal variation with Cr, Ni, Pb, and Fe having much higher absorption in the post-monsoon season, which indicates higher runoff on catchment, inflow into the catchment, and higher sediment resuspension. Sediment contamination indices (Igeo, Cf, Cdeg, and PERI) identified Fe and Cd as the most significant contaminants in causing ecological risk and pre-monsoon sediment Cdeg values highlighted severe contamination at multiple sampling locations. Water quality indices (HPI and HEI) showed that many of the sampling stations in post-monsoon were classified as moderate to highly contaminated. The results of human health risk assessment revealed that the exposure to Cr, Ni, and As resulted in high non-carcinogenic risks (HI > 1) and carcinogenic risks (TR > 1 × 10-4), with children being the most sensitive population group. More importantly, the carcinogenic risk values exceeded the thresholds and underscored the significance of these metals in public health issues in the freshwater systems under the influence of monsoons.