A baseline toxicity assessment of sediment geochemistry, potentially toxic elements contamination, and ecological risk in sediment profiles of the Bay of Bengal coast, Bangladesh

The marine ecosystems of the Bay of Bengal Coast, Bangladesh have been significantly influenced by anthropogenic activities in recent times. However, the contamination of potentially toxic elements (PTEs) in sediment profiles in the Bay of Bengal, Bangladesh has rarely been stated. A 150-cm-long sediment core was collected to assess the quality of sediments in terms of PTEs contamination and ecological risk. The ranges of PTEs in sediments were 6.05–104.2, 9.31–81.8, 6.57–112.9, 1.98–17.0, 0.48–6.49, 1.85–72.5, 12080–35365, 90.8–810.2, and 11.1–109.5 mg/kg, respectively for Cr, Ni, Cu, As, Cd, Pb, Fe, Mn, and Zn. The overall mean concentrations of Cu, As, Cd, and Pb in sediments were remarkably higher than the standard value, indicating their contamination. Considering the depths of sediment core (0–20, 20–100, and 100–150), potential ecological risk index (RI) were observed as 299.2, 199.5, 151.7 for Cox's Bazar, 420.7, 313.7, and 161.5 for Chittagong, 210.6, 211.5, and 147.8 for Meghna Estuary, and 195.4, 133.6, and 89.1 for the Sundarbans area. The geochemical distribution of PTEs in the exchangeable fraction (F1) of sediments followed in the descending order of Cd > Pb > Ni > Zn > Cu > Mn > As > Fe > Cr, indicate that Cd and Pb had adverse biological toxicity effects. Results of enrichment factor (EF), index of geoaccumulation (I_geo), contamination factor (CF), and sediment quality guidelines (SQGs) suggested that the sediment profiles were considerably degraded by some elements i.e., Cu, As, Pb, and Zn. The multivariate statistical technique indicated that most of the analyzed PTEs were enriched in sediments from anthropogenic activities.