Trace metal contamination is a major problem globally, especially in developing countries. In this study, the levels of trace metals (Cr, Ni, Cu, As, Cd, and Pb) in water and sediment of some peripheral rivers of Dhaka City, Bangladesh, were investigated. Huge amount of municipal wastes, industrial effluents and agricultural runoff from the periphery of Dhaka City notably are dumped to these rivers. Most of the effluents channeled into these rivers are not treated. Sediment and water samples were collected from selected stations along the various rivers in winter and summer seasons and analyzed for the trace metals of concern. Considering the sampling sites, the decreasing order of total metal concentration in water samples were Cr > Cu > As > Ni > Pb > Cd and in sediment were Cr > Pb > Ni > Cu > As > Cd. Total concentrations of Cr, As and Pb in the water samples were higher than WHO guidelines for drinking water quality for some sites. Geoaccumulation index (I geo ) revealed high values of Cd for all the stations. The extent of metal pollution in the rivers around Dhaka City implied that the condition is much frightening and probably severely affecting the aquatic ecology of the rivers.

No abstract

No abstract

The spatial distribution of metal bioavailability (Ni, Cu, Zn, and Pb) was first evaluated within the waters of Daliao River watershed, using the diffusive gradient in thin films (DGT) and chemical equilibrium models. To assess potential risks associated with metal bioavailability, site-specific 95% protection levels (HC5), risk characterizations ratios (RCR) and ratios of DGT-labile/HC5 were derived, using species sensitivity distribution (SSD). The highest bioavailability values for metals were recorded in the main channel of the Daliao River, followed by the Taizi River. Dynamic concentrations predicted by WHAM 7.0 and NICA-Donnan for Cu and Zn agreed well with DGT results. The estuary of the Daliao River was found to have the highest risks related to Ni, Cu, and Zn. The number of sites at risk increased when considering the total toxicity of Ni, Cu, and Zn.

No abstract