Effect of land-water ecotone on changes in heavy metal content in waters of agricultural area

Concentrations of zinc, cadmium and lead in ionic forms and in forms bound to humic substances isolated from ground and surface waters of drainage catchment were analysed. Higher total concentrations of examined metals were found in ground waters as opposed to surface waters. Particularly clear difference was observed in case of cadmium. Mean concentrations of cadmium in ground waters amounted to 0.92 μg l⁻¹, whereas in surface waters 0.50 μg l⁻¹. Similar tendency of higher heavy metals concentrations in ground waters as compared to surface waters was also observed in case of their ionic forms. Due to strong complexing properties organic matter can bind large amounts of metals and therefore influence bioavailability of the metals for aquatic organisms. Moreover the distribution of metals in aquatic environment depends on the presence of such biogeochemical barrier like belt of meadow, which can modify metals migration.