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Impact of urban drainage on metal distribution in sediments of urban streams.

The concentrations of total and extractable heavy metals (Cu, Zn, Pb, Cd, Cr and Ni) and other sediment properties were determined in sediments of three urban streams in Prague. The mean sediment concentrations (in mg kg(-1) (dry weight)) ranged within 0.2-3.2 (Cd), 20.2-61.7 (Cr), 16.3-135.2 (Cu), 17.8-42.5 (Ni), 20.2-114.8 (Pb) and 79.4-446.3 (Zn). The chemical distribution of metals, determined in four chemical sediment fractions of the sediment, indicates an increase of the distribution of Cu and Zn in more easily available fractions in sediments affected by combined sewer overflows. The highest percentages of Cd and Zn are in the most labile acid-soluble fraction (38-64% and 15-43% respectively), whereas Pb is bound mainly to reducible fraction.