Bioaccumulation of heavy metals in water and mollusks in the Karnafully estuary: Potential human health risk and environmental contamination

This study investigates the bioaccumulation of heavy metals lead (Pb), cadmium (Cd), copper (Cu), and chromium (Cr) in water and mollusks across the Karnafully River estuaryof Bangladesh. Samples were collected from six different sites encompassing diverse ecological conditions over three seasons: monsoon, post-monsoon, and winter. Six mollusk species were analyzed using atomic absorption spectrophotometry to quantify metal concentrations in both tissues and shells. These species are Neritina violocea, Neritina sulculosa, Telescopium telescopium, Cerithida ecingulata, Corbicula fluminea, and Bellamya bengalesis. . The Chaktai canal site had the highest concentration of Cu (13.99+0.92 +0.92 mg/kg) from the mussel species B. Bengalesis during monsoon season, which was higher than the tolerable limit for human. The the lowest concentration of Cu (1.13+0.76 +0.76 mg/kg) from the composite mussel species N. sulculosa were fround from the 15 No. Jetty site in winter.. . The highest concentration of Cr was found at the Marine Academy site (0.54+0.24 +0.24 mg/kg) during the post-monsoon period from the mussel species N. violocea, , while the lowest concentration was found near the Karnafully Bridge (0.05+0.02 +0.02 mg/ kg) during the monsoon from the mussel species Cerithidea cingulata. . The highest concentration of Cd was observed in the Chaktai canal site (0.77+0.04 +0.04 mg/kg) during the winter from the B. bengalesis, and the lowest concentration was recorded in the Karnafully Bridge (0.33+0.06 +0.06 mg/kg) site during the winter season from the Cerithidae cingulata species. The highest amount of Pb was found in Chaktai canal site (0.32+0.06 +0.06 mg/kg) during the monsoon season in B. . bengalesis fuana. The lowest amount was found in Karnafully Bridge (0.09+0.02 +0.02 mg/ kg) in the Cerithidae cingulate species at the same time. The results suggested that the possibility of the occurrence of acute toxicities of Cu, Cr, Cd and Pb was unlikely except for the mussel of T. telescopium in the Marine Academy that indicates heavy metals presence at the Marine Academy site. The study revealed that the average concentrations of the heavy metals were in the order of Cu>Cd>Cr>Pb in the monsoon, postmonsoon, and winter seasons. The principal Component Analysis (PCA) highlighted distinct seasonal patterns in metal accumulation, underscoring the need for seasonal-specific monitoring and management strategies in estuarine ecosystems.