Mobility of trace metals in serpentinite-derived soils of the Pollino Massif (Southern Italy): insights on bioavailability and toxicity

This paper deals with the evaluation of geo- and bioavailability of trace elements, including heavy metals, present in a typical serpentinite-derived soil of the Pollino Massif (Southern Italy). Precisely, the research was aimed to (1) assess processes and factors controlling the mobility of metals in the soil in order to identify the elements "potentially harmful" for the human health, (2) estimate possible metals accumulation in horticultural crops, and (3) evaluate phyto- and genotoxicity of Cr naturally present in soils and water. The studied profile has a homogeneous mineralogical composition consisting of metal-rich phases as prevailing minerals. The three-step sequential extraction was performed on soil samples from which four fractions (exchangeable, reducible, oxidizable, and residual) were obtained and analysed by ICP-MS. The lowest contents of metals are in the exchangeable and oxidizable fractions suggesting a metal contamination is unlikely for the studied soil. Conversely, the residual and reducible fractions are the more metal enriched fractions. Among heavy metals, mainly Pb and Cd and subordinately Ni, Cr, Cu, and Zn are associated with Fe- and Mn-oxi/hydroxides that, under acidic conditions, may release the adsorbed metals in circulating water. The high contents of heavy metals, including Cr and Ni, of analysed vegetables suggest a metal transfer from soil to plant. However, no significant effects onVicia fabaseeds were observed by in vivo phyto- and genotoxicity tests. Conversely in vitro genotoxicity tests, performed on HepG2 human cell line, showed that DNA damage and cytotoxic effect depending on Cr concentration may occur.