Metal pollution in surface sediments of the Vembanad wetland: Seasonal variation, source apportionment, and human health risk assessment.

This study examines the origins, distribution, and health impact of potentially toxic elements (PTEs) found in the surface sediments of Vembanad Wetland, a Ramsar site on India's southwest coast. Sediment from 14 sampling locations was seasonally analysed for Fe, Mn, Cu, Ni, Co, Zn, Cr, Pb and Cd. The average concentration of PTEs (mg/kg) follows the order: Fe (35,668.07 ± 20,082.98) > Mn (307.5 ± 36.71) > Zn (155.96 ± 99.45) > Cr (119.94 ± 79) > Ni (92.66 ± 32.69) > Cu (42.29 ± 17.26) > Pb (21.67 ± 11.65) > Co (20.64 ± 14.32) > Cd (2.21 ± 0.78). Higher average contamination factor (CF), enrichment factor (EF) and geoaccumulation index were observed for Cd (CF = 4.17, EF = 7.73, Igeo = 2.18) and Zn (CF = 4.85, EF = 2.44, Igeo = 0.38), indicating substantial anthropogenic enrichment. The average values of pollution indices such as PLI (1.49), TRI (11.69), mCd (15.1), and RI (251.69) indicate moderate to significant pollution. Average modified hazard quotient (mHQ) values revealed that Ni (3.19), Cr (2.76), Cd (1.99), and Zn (1.64) posed notable ecological risks. A potential health concern from prolonged exposure was indicated by the increased average total carcinogenic risk (TCR) values for Ni (9.24E-2), Cr (6.57E-2), and Cd (3.62E-2) in children. Multivariate analyses (PCA, PCC, HCA) suggested common contamination sources, with PCA-MLR confirming industrial discharge and agricultural runoff as dominant contributors. This study uniquely integrates seasonal variability, advanced pollution indices, and health risk evaluation, highlighting the urgent need for targeted management strategies in these sensitive aquatic systems.