Contamination levels and ecological risk of heavy metals in sediments from the tidal river Halda, Bangladesh

Abstract

The study assessed the contamination level of seven heavy metals (Pb, Cd, Cr, Ni, Zn, As, and Cu) along with their potential ecological risks in sediments from the Halda river which is the largest natural carp breeding ground in South Asia. The concentration levels (mg/kg) of seven heavy metals from ten sampling sites were organized in the following descending order: Zn (71.89) > Cr (31.86) > Cu (31.85) > Ni (26.67) > Pb (20.46) > As (2.69) > Cd (0.05). Among the metals, Zn, Cr, Ni, and Cu exceeded some standard limits. Sediment quality guidelines (SQGs) suggested that the concentration of Pb, Cu, and Ni could occasionally cause an adverse effect on the ecosystem. However, the geo-accumulation index (Igeo), contamination factor (CF), and pollution load index (PLI) for heavy metals suggested that the contamination level was low. Moreover, the risk index (RI) and potential ecological risk index ( $$ {E}_r^i $$ ) confirmed the low ecological risk (as RI < 100 and $$ {E}_r^i $$ < 30) from heavy metals for the river ecosystem except for the Pb and Cu. High CF and $$ {E}_r^i $$ values for Pb in one site (S4) are deemed as combining elements of multiple metallic portions used in industrialization. The univariate and multivariate statistical analyses such as correlation matrix, principal component analysis, and cluster analysis of the metals for different sites signified that the metals were originated from similar anthropogenic activities like untreated industrial effluents and wastage disposal to the river system.