Seasonal variation of trace elements in water and sediment of the Turag and Balu Rivers, Bangladesh

Abstract

The Turag and Balu Rivers are heavily polluted due to the large quantities of untreated municipal sewage and industrial wastewater received from Dhaka City, the capital of Bangladesh. Thus, this study aimed to assess the pollution in trace metal levels in water and sediment over time and space. Trace elements were found in the following descending order: Fe>Ca>Mn>Mg>Zn>Pb>Cu>Cd in Turag River water. Trace elements were found in the following descending order: Fe>Mn>Ca>Mg>Zn> Pb>Cu>Cd in Balu River water. In the Turag River and the Balu River, trace metals were measured in the following descending order in the sediment:Fe>Mn>Pb>Zn>Cu>Ca>Cd>Mg and Fe>Mn>Cu>Zn>Ca> Pb> Mg> Cd, respectively. Metals exhibited no significant differences (p>0.05), except for Ca (p<0.05) in both the Turag and Balu Rivers. The correlation matrix (CM) demonstrated a sizeable anthropogenic metal influx in the water and sediment of the rivers. Ca, Mg, Cu, and Cd showed significant seasonal fluctuations (P<0.05) in Turag River water, whereas Fe, Mn, Zn, Pb, and Cd showed noteworthy differences (P<0.05) in the Balu River water. Ca vs Mg (r=0.963) revealed a very high linear solid relationship in Turag River water. A solid linear relationship was determined for Ca vs Fe (r=0.981) in Balu River water and for Cd vs Pb (r=0.977). A solid linear relationship was observed between Cd and Pb (r=0.870) in Turag River sediment. The water and sediment quality of the rivers have deteriorated due to anthropogenic sources of industrial, household and irrigation discharges. The present research can be beneficially used for the management and protection plan of the river for environmental monitoring and assessment.