Impact of parent rock and topography aspect on the distribution of soil trace metals in natural ecosystems

The concentration and dynamic of soil trace metals in natural ecosystems, in particularly, is dependent on the lithology of parent rock as well as topography and geopedological processes. To ascertain more knowledge for this dependency, soils on three parent rocks involving peridotite, pegmatite, and dolerite in two contrasting topography aspects were investigated. The total values of Fe, Mn, Zn, Cu, and Ni were determined and compared for different soil pedons. The concentration of Fe, Mn, and Ni were highest in soils developed from peridotite (127, 1.8 g kg(-1), and 218 mg kg(-1), respectively), intermediate in soils derived from dolerite (81, 1.3 g kg(-1), and 166 mg kg(-1), respectively), and least in soil developed from pegmatite (50, 0.23 g kg(-1), and 20 mg kg(-1), respectively). The values of Zn and Cu, originated from different parent rocks, were in order of dolerite (78 mg kg(-1)) > peridotite (77 mg kg(-1)) > pegmatite (28 mg kg(-1)) and pegmatite (121 mg kg(-1)) > peridotite (111 mg kg(-1)) > dolerite (28 mg kg(-1)), respectively. For most of the studied pedons, profile metals distribution differed among the soils: The values of Fe, Cu, and Ni were enriched in the cambic horizons mainly as result of release, mobilization, and redistribution of the studied metals during geopedological processes, whereas those of Zn and Mn were concentrated in the surface horizons. Probably due to greater weathering rate of trace metal-bearing rocks on north-facing slope, the content of the trace metals along with the geoaccumulation index (I (geo)) and the degree of soil contamination (C (d)) were higher than on south-facing slope. Based on assessment of soil pollution indices, the soils were categorized as unpolluted [I (geo) a parts per thousand currency sign 0 (class 0)], unpolluted to moderately polluted levels [0 < I (geo) < 1 (class 1)], and very low [C (d) < 1.5 (class 0)] to low degree of contamination [1.5 < C (d) < 2 (class 1)].