Distribution of some selected major and trace elements in four Italian soils developed from the deposits of the Gauro and Vico volcanoes

The vertical distribution of 21 elements (K, Ca, Ti, Fe, Mn, Cr, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Y, Zr, Pb, Th, U, Hg) in four Italian soils derived from volcanic materials has been investigated. Most of the elements, and in particular lithogenic ones, show little enrichment/depletion indicating a low degree of weathering and a great similarity to the parent material. In relative terms, the degree of soil evolution (horizon expression and weathering) and the depletion of the more mobile elements (K, Ca and Sr) seem to increase with increasing rainfall and soil age. Discontinuities in the soil profile due to the accretion of new volcanic material are detectable from the geochemical composition of the horizons. Some metallic elements such as Hg, Pb, Cu, Mn and Zn show enrichment in the organic-rich horizons (O and A), but the intensity of enrichment suggests that, besides biocycling and weathering processes, human activity (soil management, fertilizing and atmospheric pollution) may be significant sources of trace elements.