Local background concentration of heavy metals in various soil types formed from glacial till of the Inowroclawska Plain

In the present study, local background concentrations of heavy metals were determined in soils which have been minimally influenced by human activities. The ground moraine landscape of the Inowrocławska Plain is dominated by Phaeozems, which occur in numerous associations with Luvisols and Cambisols. Four profiles of Phaeozems, three profiles of Luvisols and two profiles of Cambisols had been researched earlier, especially their morphology, selected physicochemical properties, texture and mineralogical composition. Selected properties were also measured to determine their influence on the content and distribution of trace elements in soil profiles. For determination of the concentration of metals in the soil profiles, the following indices were used: distribution factor (DI), enrichment factor (EF) and transfer factor (TF). The total content of metals in the genetic horizons and the local geochemical background level of metals in soils were determined. With the knowledge of the natural content of elements in the parent material, assumed to be the geochemical background, a degree of contamination of surface soil horizons can be evaluated. The content of Zn, Cu, Ni, Pb, Cr, Mn (mg kg–1) and Fe and Ti (g kg–1), which was defined as the content of the local background, was: 40.6; 12.6; 14.3; 12.9; 5.5; 309.9 and 16.5; 1.4, respectively. The distribution of Ni, Cr, Cu, Mn and Fe in the soil profiles can be explained as the effect of pedogenic factors, although in the case of, a tendency towards accumulation of Zn and Pb in the humus horizons as a result of anthropogenic input was observed. The distribution of pedogenic Ni, Cu, Cr and Mn was influenced by specific adsorption of metals on Fe oxides. The results indicate that the metals were bound more strongly to iron oxides than to organic matter. Based on the results of geochemical studies on selected arable soils from the Iowrocławska Plain, an integrated method was applied to assess the local background using an iterative 2s-technique (mean + 2 standard deviation). The relationships between trace elements and the conservative element such as Fe were used to predict the expected values of trace elements in topsoil. The results substantiate the importance of determining local background concentrations.