Trace Metals in the Bed Sediment of Small Urban Streams

Trace metals (TMs) are still a serious problem in urban streams because of their toxicity and continuing significant levels in the aquatic environment, especially in bed sediments. Concentrations of Cd, Cr, Cu, Ni, Pb and Zn were monitored in the sediments of several small streams in the Prague area. These streams differ in the main source of pollution (combined sewer overflow CSO, storm water drain – SWD, or waste water treatment plant WWTP). The potential TMs hazard was assessed by several indexes, and the dependence of TMs concentrations on various sediment material characteristics was evaluated. The bioavailability of TMs was also assessed by comparing the binding strength of metals in the sediment and their concentrations in aquatic organisms in these creeks. Of the metals studied, Cd is the most available from sediments, but the other metals were also easily released from the sediment to the liquid phase. There were also differences in TMs bioavailability from sediments of creeks with different main pollution source, and was higher in creeks impacted by WWTP and SWD.