Spatio-temporal distribution profile of heavy metals in Kol wetland ecosystem in southern India

Heavy metals in the agrarian wetlands have substantial implications for the environment, agriculture, and human well-being. This study is a comprehensive examination of heavy metal concentrations and hydrochemical characteristics in the Kol wetland system, a Ramsar site located on the southwest coast of India. It represents the first comprehensive assessment of the distribution of nine heavy metals (Cu, Cd, Zn, Pb, Fe, Ni, Mn, Co, and Cr)to evaluate Kol wetland water suitability for aquatic life and irrigation purposes. To achieve this, surface water samples were collected during two consecutive monsoon periods in September 2018 and 2019. The average concentrations of the heavy metals in the Kol area were: Zn (0.31-618 µg/L), Cu (BDL-212 µg/L), Fe (30.17-4418.5 µg/L), Mn (1.2-506 µg/L), Ni (BDL-61.96 µg/L), Cr (BDL-61.96 µg/L), Cd (BDL-46.19 µg/L), Co (BDL-4.03 µg/L), and Pb (BDL-103 µg/L). While Cd and Zn exceeded recommended limits by the US Environment Protection Agency, all metal concentrations fell within acceptable levels for irrigation set by the Food and Agriculture Organization. The spatial distribution pattern revealed significant disparities among the three zones of the study area, with the central and southern regions exhibiting higher metal concentrations than the northern zone. Pollution indices indicated that Kol water is suitable for irrigation, with medium contamination and threat to aquatic life noted at the S3 station. Principal components analysis highlighted siltation processes and anthropogenic activities as likely sources of heavy metal contamination. This scenario provides valuable data for strengthening the supervision of the Kol wetlands.