The effect of bottom sediments on the content of heavy metals in meadow soils

Abstract

The objects of the study were grasslands situated along the watercourse that collect matter directly from surface runoff from the surrounding fields and ditches. Therefore, the chemical composition of the bottom sediments can be varied. The aim of the study was to determine the content of anthropogenic fractions of selected heavy metals in meadow soils where the material from the watercourse maintenance was stored. Soil samples were collected along the banks of the Witonia »A« Channel (soil with sediment), and 30 meters from the watercourse (soil without sediment). The pH of soils without sediment was in the range 6.2–6.6, whereas the soil with sediment had a pH $\geq$ 7.0. The content of organic matter was 5.7–31.5%. The concentration of anthropogenic fractions of elements was determined by atomic absorption spectrometry after extraction with a (1 + 4) HCl solution. The anthropogenic enrichment coefficients (AEC) calculated in relation to the geochemical background level, were within the range: 0.9–2.8 for Zn, 1.2–3.5 for Cu, 0.7–3.1 for Pb, 1.0–2.8 for Ni and 0.3–0.9 for Cd. The AEC values for lead, copper, cadmium and nickel were usually higher in samples without sediment. A significant correlation between the metal and organic content ($R^{2}$ = 0.7–0.9) was found. On two sites, the level of heavy metals under investigation shows a significant local influence from anthropogenic pressure.