Fractionation of Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn has been performed in bottom sediment samples collected along a 75 km section of the middle Odra River by a modified method of 5-step sequential extraction according to Tessier. The results have shown the presence of Cu, Ni, Zn and Mn already in exchange fraction (I); the mean percent content of metals in mobile phases (exchange and carbonate) reached 35% (Cu), while the maximum values reached 59% (Ni). From among the metals studied, Zn, Mn, Fe, Cr and Ni were dominant in the species bound to hydrated iron and manganese oxides, so the metals contained in the bottom sediments were not permanently immobilized.
Good correlation was found between the concentrations of Zn, Mn and Cd in the mobile phases (I+II) and their total concentrations. Similarly, the concentrations of all metals determined in the reducible fraction and in the fraction bound to organic matter (except for Cd and Cr) were well correlated to their total content.