VARIABILITY OF HEAVY-METALS CONTENT IN BOTTOM SEDIMENTS OF THE WILGA RIVER, A TRIBUTARY OF THE VISTULA RIVER (KRAKOW AREA, POLAND)

The concentration of heavy metals in the sediments of the Wilga River has been studied. Comparison of a sample from the city border with tha t from the river outlet reveals increasing metal concentrations by fac tors of ca. 27 for Cr, 8 for Cu, 5 for Zn and Ni and 3 for Pb. Since 1 989, for most metals, a decreasing trend in concentrations, at compare d sampling sites, has been noted. Nevertheless, the amount of heavy me tals is still rather high and ranges (in mg/kg) as follows: 185-715 Zn , 38-196 Pb, 27-195 Cu, 3-52 Cr, 3-98 Ni and 1-8 Cd. A strong variabil ity of metal concentration along the river course has been found. Thei r elevated concentration results from some sources of pollution situat ed in the river valley, including: industrial plants, their settling p onds and busy roads. It is very probable that morphological features o f the river, like river bends, cause the increase of metal contents. I t has been found that the amount of heavy metals contributed by grain fractions <20 mu m is most frequently comparable with or higher than t he proportions of that fraction in the fine fraction of sediment (< 63 mu m). Copyright (C) 1996 Elsevier Science Ltd