Assessment of heavy metal contamination and ecological risk due to remobilization in water, bank sediments, and adjacent soils of the Buriganga River, Bangladesh

The distribution of heavy metals in water, bank sediment and soil near the bank by remobilization was assessed throughout this study. Six water (n = 6) and six sediment samples (n = 6) were collected from three locations of the river Buriganga. The order of mean concentrations detected in water samples is Zn>Fe>Ni>Pb>Cu>Cr>Cd and for sediment samples is Fe>Zn>Ni>Cr>Cu>Pb>Cd. In physicochemical analysis, the ranges of temperature, pH, COD and total solids were found to be 22–26°C, 7.08–7.27, 1.6–32.8 mg/L and 27–3305 mg/L, respectively. Additionally, moisture content in the bank sediment samples sustained a greater amount (Average 24.651%) compared to field sediments (Average 0.64%). The mean concentrations of Ni, Cr and Pb in river water was excessively high compared to the threshold values set by WHO. The maximum degree of contamination factor (203.561) and pollution load index (14.01) were observed at the Sowarighat field sediment area, indicating a higher level of pollution. Besides, based on geoaccumulation (I geo ) values, samples are enriched by heavy metals in the order: Cr>Ni>Fe>Pb>Cu>Cd>Zn. Moreover, the heavy metal contamination was significantly higher in the field sediment samples compare to bank sediment, indicating the accumulation of the hazardous metals from river water towards floodplains via mobilization because of seasonal floods and flows.