Distribution of potentially toxic elements in sediments of the municipal river channel (Balu), Dhaka, Bangladesh: Ecological and health risks assessment

Abstract

The concern of potential toxic elements (PTEs) contamination in the river ecosystem is growing due to anthropological activity. The contents of seven PTEs in sediments from the Balu River channel were analyzed using atomic absorption spectroscopy (AAS) and an environmental risk model. Several PTEs were found in the sediment at high levels, including zinc (Zn), copper (Cu), arsenic (As), lead (Pb), cadmium (Cd), nickel (Ni), and mercury (Hg), that might pose a risk to human and ecological health. The highest mean concentration of PTEs in sediment followed in decreasing order Zn (1365.21 mg/kg) > Cu (149.34 mg/kg) > Pb (46.34 mg/kg) > Ni (34.78 mg/kg) > As (6.31 mg/kg) > Cd (2.34 mg/kg) > Hg (1.03 mg/kg). In addition, most of these PTEs were significantly correlated (p < 0.05) among the sites and exceeded the safety guideline value. The geo-accumulation index (Igeo), contamination factor (CF), and pollution load index (PLI) showed high levels of PTEs contamination and moderately polluted to highly polluted levels of these elements. At the BL3, BL4, and BL6 sites within the study site, the ecological risk (PERI) score was extremely high, and the PERI values range found was from 75.39 to 355.72. Every PTE had a slightly greater concentration during the dry season than the wet season. Interestingly, PTE accumulation from sediment indicated non-carcinogenic risk (${\mathrm{HQ}}_{\mathrm{dermal}}$) in human health, whereas most of the sites showed carcinogenic risk (${\mathrm{CR}}_{\mathrm{dermal}}$) to human health (adult and child) due to Cd and Ni accumulation. Multivariate statistical analysis (MVSA) indicated the most likely anthropological sources were the untreated wastes discharged in the river sampling area. People who come into contact with polluted sediments are constantly exposed to Ni and Cd pollution, which increases the risk of cancer and non-cancerous diseases. So, continuous PTE monitoring is advised by this study to assess ecological and human health risks.