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

The recognition of the potential health hazards associated with heavy metal s has focused attention on the levels and behaviours of these elements both in natural and contaminated environments. Various soil types developed fro m different parent materials in Sicily, Italy, have been analysed in order to compare heavy metal distribution under different geopedological conditio ns. Total metal concentrations, metal partitioning and distribution profile s are discussed in relation to the inheritance factor and pedogenic process es. Parent material composition largely influences the contents of heavy me tals in most of the analysed soils, mainly differentiating pedons for their metal concentration on the basis of sedimentary and volcanic parent materi als. However, an exception is represented by the carbonate-free Alfisols an d Mollisols, which are markedly enriched in heavy metals with respect to th e underlying limestones and calcarenites, On the basis of chemical and mine ralogical results, supported by data from sequential extraction (SEP), heav y metal enrichment in these soils is associated with the formation of commo n to abundant Fe-Mn oxides and clay accumulation. For Mollisols there is ev idence for a major role of organic matter in heavy metal retention in surfa ce horizons. In the other pedons, pedogenic processes appear to mainly infl uence the redistribution of heavy metals throughout the soil horizons rathe r than affecting the total content. Argillopedoturbation seems to be respon sible for a uniform distribution of heavy metals in Vertisol profiles on ma rry clays. Accumulation of heavy metals in the topsoil of Inceptisols on cl ays with gypsum and Entisols on gypsarenites and diatomites is caused parti ally by adsorption on organic matter and mainly by dissolution of primary g ypsum and opal-A. A pedogenic influence is less evident in young Andisols w hose heavy metal composition greatly reflects that of hawaiitic pyroclastic deposits interbedded within the profiles. However, a certain redistributio n of Cu accumulated as metal-organic matter complexes is evidenced in the s urface horizon by SEP. (C) 2000 Elsevier Science B.V. All rights reserved.