Distribution of Cu, Ni, Pb, Zn in natural brown forest soil profiles from the Cserhát Mts., NE Hungary

Distributions of total and bioavailable amounts of heavy metals (Cu, Ni, Pb, Zn) were studied in four brown forest soil profiles developed on different types of bedrock. In the study area (Cserhát Mts., NE Hungary) facilities are provided to recognize the role of bedrock and pedogenic processes in the distribution of heavy metals in soils characterized by natural background level of heavy metals. Distribution of total and soluble metal concentrations are generally similar in the studied profiles, differences were observed only in case of zinc. Among the studied metals the following bioavailability sequence was observed: Pb (25% of total Pb) > Cu (20% of total Cu) > Ni (10% of total Ni) > Zn (2.5% of total Zn). The obvious effect of organic matter on trace metal distribution is supported by its influence on the distributions of Pb and Zn. Distributions of Cu and Zn is determined by the presence of amorphous A1 and Fe oxides. The stronger retention of trace metals by clay minerals is suggested by the good negative correlation of clay mineral and available Pb, Ni, and Zn contents of soils. Clay minerals and organic matter have contrary effect on heavy metal retention in soils. There are factors dependent (e.g. clay minerals) on and independent (e.g. organic matter) of bedrock, of which common effect forms the actual distribution of heavy metals in soils