Persistence and bioaccumulation of potentially toxic elements in the Gromo-Gandellino ancient mine site (Seriana valley, northern Italy)

In this study, earth materials and plants (Calluna vulgaris and Dryopteris filix-mas) growing on three main dumps located in the Gromo-Gandellino ancient mine site (Seriana Valley, Northern Italy) were collected, in order to assess Potentially Toxic Elements (PTE) contents. Ag, As, Cd, Co, Cu, Ni, Pb and Zn concentrations in earth material and plant tissues were analyzed by ICP-AES. Bioaccumulation (BF) and Translocation Factor (TF) were calculated for plants and a multivariate statistical analysis (PCA) was applied. Results showed that in the waste rocks PTE concentration is one order of magnitude higher than in the natural soils: considering the average concentrations Zn and Pb exceed respectively 3,500 and 3,000 mg•kg-1, while As reaches 860 mg•kg-1. Calluna vulgaris shows several BF values > 1, displaying an evident predisposition to accumulate metals, especially in the roots and to tolerate high As concentrations in soil. In Dryopteris filix-mas metal concentrations are close to baseline values. These species are not hyperaccumulators, however, they are interesting for soil stabilization and could be used to re-establish a vegetative cover in those sites where natural vegetation is rare, due to high metal concentrations. In particular, Calluna vulgaris could be used in contaminated land for phytostabilization.