Spatiotemporal distribution, trophic transfer, and research uncertainty of heavy metals in a subtropical highly polluted Buriganga River: A critical review

The Buriganga River is an urban river heavily impacted by many pollutants from multiple sources, such as the direct and indirect discharge of land-based pollutants and sewage from the Asian megacity of Dhaka, Bangladesh. Previous research reports have documented the severe ecotoxicological impacts on the surrounding environment of urban river through heavy metal contamination. This review critically assessed the spatiotemporal distribution of heavy metals, like iron (Fe), copper (Cu), lead (Pb), cadmium (Cd), nickel (Ni), chromium (Cr), zinc (Zn), manganese (Mn) and mercury (Hg) in water and sediment of the Buriganga River and their consequences on the inhabiting fish species. For this purpose, archive of earlier published peer-reviewed papers between 1993 and 2021 was meticulously analyzed. All published studies have indicated that lead (Pb), cadmium (Cd), and mercury (Hg) heavily pollute the Buriganga River. The analyzed samples have suggested the presence of different heavy metals in the various fish species, which may pose a potential health risk for humans through food web toxicity. In addition, the trophic transfer and several research uncertainties of the published research have been conclusively summarised. As a result, we highlighted the urgent need to implement policy framework, considering people living around the river as the primary stakeholders in a pioneering attempt to protect the degradation of river water quality and aquatic organisms. National and local awareness to change people's behavior towards managing their waste is the first step towards rehabilitating and restoring the Buriganga River in Bangladesh. Besides, establishing laws regulating the waste released from industries is highly recommended, especially for toxic elements exhibiting higher concentrations than the recommended level.