BIOACCUMULATION OF ZINC UNDER THE INFLUENCE OF SEWAGE SLUDGE AND LIMING AND ITS SPECIATION IN SOIL

This study evaluated the impact of sewage sludge at doses of 10%, 20% and 30% of fresh soil (37, 74 and 110 Mg . ha(-1) DM) weight in a pot and of liming on the content of zinc in the tested plants: Italian ryegrass (in the first and fourth year of the experiment), sunflower and maize (in the second and third year), and in the soil after each harvest. Fertilization with sewage sludge significantly diversified the content of zinc in the cultivated plants. The concentration of this metal in soil also increased: the highest dose (110 Mg . ha(-1)DM) of sewage sludge) resulted in a two-to three-fold increase of zinc content in comparison with the control objects. In general, liming significantly diversified the content of zinc in the tested plants and in the soil. After the first, second and third years, the complexes of zinc with the organic fraction (F4) were predominant in the soil, in the fourth year with the organic fraction (F4) and residual fraction (F7) Liming resulted in an increase in the zinc content in the residual fraction in comparison with the non-limed soil. The content of Zn in the tested plants increased together with the amount of Zn in the soil which was bound to organic matter (F4) and to manganese oxides (F3), which was confirmed by the highest positive correlation coefficient. The species of the tested plant significantly impacted the bioaccumulation of zinc. The highest zinc bioaccumulation factor was recorded for the biomass of Italian ryegrass in the first year of the experiment with lower values determined for the biomass of sunflower and maize.