Use of native plants for the remediation of abandoned mine sites in Mediterranean semiarid environments.

Abandoned tailing dumps from mining industry represent important sources of metal contamination in the surrounding environments. This study evaluates the potential of two Mediterranean native plants, Pistacia lentiscus and Phragmites australis, for phytoremediation of two Sardinian contaminated mine sites. A 6 months study has been conducted at greenhouse-controlled conditions with the aim of investigating the plant capability to tolerate high metal concentrations and to extract or immobilize them within the roots. The possibility to mitigate stress on the plants and improve treatment efficiency by adding compost as amendment was also evaluated. Both species were able to restrict accumulation of Cd, Pb and Zn to the root tissues exhibiting a metal concentration ratio of plant roots to soil bioavailable fraction higher than two (four in the case of Zn). However, the two species showed different adaptation responses, being the survival of P. australis after 6 months in contaminated soil lower (25 %-58 %) than that observed for P. lentiscus (77 %-100 %). Compost addition resulted in a lower metal uptake in tissues of both plants and a higher survival of P. australis, whilst almost no effect was observed as regard the growth of both species. The two tested species appear to be promising candidates for phytostabilization, P. lentiscus exhibiting a greater adaptability to heavy metal contaminated matrices than P. australis.