Trace element distribution in soils developed on gossan mine wastes and Cistus ladanifer L. tolerance and bioaccumulation

The aim of this study was to evaluate trace element distribution in soils developed on gossan mine wastes and their bioavailability for Cistus ladanifer. The ability of this shrub to accumulate these trace elements and its germination were analysed to confirm the suitability of this species for phytostabilization of mining areas in Mediterranean conditions. Plants and soils were collected in São Domingos mine and Pomarão (non-contaminated site). Concentration of As, Cu, Pb and Zn in soils (total and associated with different soil phases) and roots/leaves/seeds were analysed. Mine soils showed contamination with great total concentrations: As (2643 mg/kg), Cu (226 mg/kg) and Pb (7343 mg/kg). Soil available fractions were small (< 2.8% of total). These elements are mainly associated with residual fraction, and Fe and Mn oxides. The low As and Pb availability in São Domingos soils can be related to the presence of iron(III) lead(II) arsenates in the residual fraction. Arsenic and Zn concentrations in leaves and Cu and Zn in seeds depend on population and soil characteristics but seed viability was not different in both sites. São Domingos leaves reached toxic values for Pb due to high Pb translocation from roots to leaves (0.67–1.46), however no visible phytotoxicity signs were observed. In the São Domingos plant population, As root storage was observed. Plants from both areas were Zn-accumulators while only plants from Pomarão were Pb-accumulators. Cistus ladanifer is suitable for phytostabilization of mine soils with similar characteristics. Seed germination from São Domingos is suitable for revegetation of this mine area.

► São Domingos soils showed great total concentrations of As, Cu and Pb.
► Low As and Pb availability in mine soils is due to Fe(III)Pb(II) arsenates presence.
► Both populations were Zn accumulators and Pomarão plants were Pb accumulators.
► São Domingos plants store As in roots, whereas Cu and Zn are translocated to leaves.
► C. ladanifer is suitable for mine soils phytoremediation in Mediterranean conditions.