Influence of inheritance and pedogenesis on heavy metal distribution in soils of Sicily, Italy

The recognition of the potential health hazards associated with heavy metals has focused attention on the levels and behaviours of these elements both in natural and contaminated environments. Various soil types developed from different parent materials in Sicily, Italy, have been analysed in order to compare heavy metal distribution under different geopedological conditions. Total metal concentrations, metal partitioning and distribution profiles are discussed in relation to the inheritance factor and pedogenic processes. Parent material composition largely influences the contents of heavy metals in most of the analysed soils, mainly differentiating pedons for their metal concentration on the basis of sedimentary and volcanic parent materials. However, an exception is represented by the carbonate-free Alfisols and Mollisols, which are markedly enriched in heavy metals with respect to the underlying limestones and calcarenites. On the basis of chemical and mineralogical results, supported by data from sequential extraction (SEP), heavy metal enrichment in these soils is associated with the formation of common to abundant Fe–Mn oxides and clay accumulation. For Mollisols there is evidence for a major role of organic matter in heavy metal retention in surface horizons. In the other pedons, pedogenic processes appear to mainly influence the redistribution of heavy metals throughout the soil horizons rather than affecting the total content. Argillopedoturbation seems to be responsible for a uniform distribution of heavy metals in Vertisol profiles on marly clays. Accumulation of heavy metals in the topsoil of Inceptisols on clays with gypsum and Entisols on gypsarenites and diatomites is caused partially by adsorption on organic matter and mainly by dissolution of primary gypsum and opal-A. A pedogenic influence is less evident in young Andisols whose heavy metal composition greatly reflects that of hawaiitic pyroclastic deposits interbedded within the profiles. However, a certain redistribution of Cu accumulated as metal–organic matter complexes is evidenced in the surface horizon by SEP.