Heavy metals accumulation in willows growing on Spolic Technosols from the abandoned Imperina Valley mine in Italy

Human activities such as metals mining and milling operations provide one of the host important sources of contamination in the environment. Abandoned mines can be an important source of toxic elements. The threat of heavy metal pollution posed by mine soils generally concerns more than one metal. The aim of this study was to assess total concentration of six potentially toxic metals (Cd, Cr, Cu, Pb, Zn and Fe) in the soil and plant samples of three dominant willow species (Salix purpurea L, Salix caprea L. and Salty eleagnos Scop.) collected from abandoned mixed sulphide mine dumps (Imperina Valley, North-east Italy). Results demonstrate that metal concentrations in soils are in general above the Italian average limits and they are also significantly (except Cr), as compared with controls (p <= 0.05), with averages of 2.12 mg Cd kg(-1), 2267 mg Cu kg(-1), 9552 mg Pb kg(-1), 1243 mg Zn kg(-1) and 299,973 mg Fe kg(-1). The phytoremediation ability of selected Salix species for heavy metals was estimated. The results have revealed significant differences among willow species (p <= 0.05) regardless of the species selected. The transfer factor and bioaccumulation coefficient of selected metals varied among plant species and from different sites. Some of the investigated species have potential for soil stabilization and extraction of heavy metals. The results indicate that there is an increasing need for further research projects mainly focused on the mechanisms whereby such willows are able to survive in contaminated soils. (C) 2012 Elsevier B.V. All rights reserved.