Metal pollution in water and sediment of the Buriganga River, Bangladesh: an ecological risk perspective

Both industrial and domestic wastewater are drained into the Buriganga River, Dhaka, Bangladesh. In order to screen metal pollutant levels and to assess ecological risks, this study was conducted on water and sediment samples from the Buriganga River. A total of 13 metals in water and sediment samples were determined by atomic absorption spectroscopy. For sediment samples, the geo-accumulation index (I geo), contamination factor (CF), potential ecological risk index, and pollution load index (PLI) were calculated. The I-geo increased in order of Ag > Pb > Cu > Zn > Hg > Cd > Cr > Co > Ni > As > Se > Sb > Be > Tl in both summer and winter seasons. The CFs identified major contaminating (moderate to very high) metals to be Ag, Pb, Cu, Zn, Hg, and Cd. Hg and Cd posed the highest ecological risk in the study area, and 86% of samples showed moderate (95-190) to considerable (190-380) ecological risk index. PLI attributed similar to 71% of the sampling site are polluted (PLI > 1) in both seasons. For water samples, degree of contamination (C-d), heavy metal evaluation index (HEI), heavy metal pollution index ( HPI), and Nemerow index ( NI) were calculated. C-d showed similar to 86% of the water samples have low to high degree of contamination, while HEI reflects 28% of the samples were highly polluted and HPI indicated 86% of samples were low to highly polluted. In addition, NI revealed that the river water is severely polluted by metals.