The study examines seasonal variation, pollution status, and potential health risks associated with heavy metals in the lower Thamirabarani River basin in Southern India. Twenty river water samples collected during pre- and post-monsoon seasons were analyzed for cadmium (Cd), lead (Pb), arsenic (As), chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), and iron (Fe). The concentrations during the pre-monsoon followed the order Zn (0.126 mg/L) > Cu (0.031 mg/L) > Cr (0.0186 mg/L) > Ni (0.009 mg/L) > Fe (0.0083 mg/L) > Pb (0.006 mg/L) > As (0.005 mg/L) > Cd (0.0005 mg/L). During the post-monsoon season, the concentrations slightly decreased due to dilution and flushing, following the order Zn (0.113 mg/L) > Cu (0.027 mg/L) > Cr (0.015 mg/L) > Ni (0.009 mg/L) > Fe (0.007 mg/L) > Pb (0.005 mg/L) ≈ As (0.005 mg/L) > Cd (0.0004 mg/L). The Heavy Metal Pollution Index (HPI: 21.07–47.55) and Heavy Metal Evaluation Index (HEI: 1.35–2.78) indicated low contamination levels in both seasons. The health risk assessment identified ingestion as the dominant exposure route, with dermal contact negligible. The Hazard Index (HI) values for adults were below the acceptable limit (HI < 1). At the same time, children had HI values exceeding the threshold (1.818 pre-monsoon and 1.552 post-monsoon), suggesting a potential non-carcinogenic health risk. Correlation and cluster analyses revealed familiar anthropogenic sources and strong seasonal control on metal distribution. This study integrates pollution indices, multivariate statistics, and health risk assessment to examine the dynamics of metals in a tropical monsoon river system. The findings emphasize the influence of monsoonal hydrology and land-use practices on metal mobility in the lower Thamirabarani Basin. The findings emphasize the influence of monsoonal hydrology and land-use practices on metal mobility in the lower Thamirabarani Basin and provide useful insights for improving regional water-quality management.
Abishek et al. (Fri,) studied this question.