Heavy metals in contaminated soils of the Rio Sitzerri floodplain (Sardinia, Italy): characterization and impact on pedodiversity

VACCA, ANDREA;BIANCO MR;MUROLO M;VIOLANTE P.

2012-01-01

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Abstract

Four representative soils located in areas of the Rio Sitzerri floodplain (Sardinia, Italy), which were flooded and covered by materials coming from the metalliferous mine of Montevecchio, were studied to define the total content and the geochemical forms of heavy metals and to discuss their impact on pedodiversity. The significance of heavy metal concentrations in the contaminated soils was assessed by the comparison with data coming from three selected reference soils representative for non-contaminated areas. Most soils are deep or very deep and consist of a sequence resulting from different sedimentary cycles. The soils located in areas that were flooded and covered by materials coming from the Mine are characterised by the presence of buried horizons and are mainly contaminated by Zn, Ni, Pb, and Cd and, to some extent, by Cr and Cu. The sequential extractions indicated the presence of reactive forms in all the soils and for all contaminating metals, whose mobility risk is increased by the generally very strongly acid to slightly acid soil reaction values. As regards pedodiversity, the heavy metal contamination clearly influenced quantity, quality and function of the soils. The morphological diversity of pedons, the taxonomic and functional pedodiversity and the soilscape pattern were all strongly affected, causing irreparable damage to the local economy and to the environment. This study highlights the need for the planning of remediation actions focused on the correct disposal and management of the mining residues at Montevecchio and can contribute in a significant way to set future environmental regulations.