Metal distributions in plants growing on copper mine spoils in Northern Apennines, Italy: the evaluation of seasonal variations

Mine spoil dump material and plants were sampled from the pyrite-chalcopyrite mining area of Vigonzano (Northern Apennines, Italy). Mine spoils have high concentrations of Fe, Mg, Cu, Cr, Co and Ni, and are characterized by moderately to strongly acid environmental conditions. Water leaching tests indicate the following order of extraction: Zn≥Cu>Ni>Fe≥Cr. The plants Silene armeria (Caryophyllaceae) Salix spp. (Salicaceae) and Populus nigra (Salicaceae) were sampled at 4 different growing stages to evaluate seasonal variations in metal concentrations. The results indicate that metal concentrations increase with plant ageing, the highest concentrations being observed in leaves. Low specific diversity in the mine spoil area is the result of severe environmental conditions, but some plants can tolerate high concentrations without sign of stress. Silene armeria is widespread in the Vigonzano mine spoil area and is actually able to tolerate high metal concentrations (up to 504 μg/g Cu, 174 μg/g Zn, 127 μg/g Ni and 138 μg/g Cr), extremely high when compared to those of a S. armeria population from an unpolluted site. The variations of BAC (Biological Accumulation Coefficient) for the plants growing on the Vigonzano mine spoil area indicates that Zn is the element most easily absorbed by plants. An absorption sequence Zn > Co > Cu > Ni > Fe > Cr can be generalized for plants growing on the mine spoil area indicating the importance of soil solution composition in plant absorption.