Heavy Metal Contamination in Environmental Compartments of Buriganga River in Dhaka City

Numerous textiles-/tanneries-/pharmaceutical-based industrial processes along with anthropogenic sources, discharge hazardous waste/wastewater into nearby water bodies. These untreated or poorly treated waste streams contain heavy metals that come into contact with sediment/aquatic systems and become part of the food chain. Heavy metals, many of which are persistent, bioaccumulative, and toxic, have a significant impact on environment and ecosystem. Buriganga has been accumulating alarming levels of heavy metals, and currently, it is one of the most polluted rivers in Bangladesh. This study evaluated the levels of selected heavy metals in different environmental compartments of the Buriganga river. Accordingly, three significant locations along the river stretch were selected. The plant (Enhydra fluctuans) and phytoplankton (Lemnoideae) samples and four different species of fish such as Heteropneustes fossilis, Channa striata, Corica soborna, and Wallago attu were collected from the river. Laboratory analysis of cadmium (Cd), chromium (Cr), lead (Pb), nickel (Ni), and zinc (Zn) was performed in all the sediment/plant/river water/fish samples. Contamination factor and plant concentration factors were determined. Concentrations of Cd, Zn, and Ni in the river water were obtained within acceptable ranges, whereas Cr and Pb exceeded the toxicity reference values for surface water standards for aquatic life. Notable concentration levels of heavy metals were measured in the sediments and plants. Specifically, Cr was obtained at an alarming level of 103 mg/kg in soil and 163 mg/kg in the plants near Hazaribagh area, where tannery waste mixes with the river water. Bioaccumulation of the analyzed metals was evidenced in the biological samples.