Phytoremediation of abandoned mine sites: a focus on recent research activities carried out at DICAAR

The cessation of mining activities without proper rehabilitation measures has left significant negative legacy on the surrounding environments. The unreclaimed tailings disposal sites represent worldwide one of the main contamination sources of heavy metal, since water erosion and wind dispersion result in a considerable heavy metal migration, affecting soil and water resources even at large distances from the mine tailing deposits. Soil remediation based on conventional physical and chemical stabilization technologies often entails high costs due to the wide areas involved, whereas phytoremediation, based on the use of plants and associated soil microbes to reduce the concentrations or toxic effects of contaminants in the environment, is widely accepted as a cost-effective environmental restoration technology. The long term success of phytoremediation depends on the possibility of identifying both plants able to tolerate high concentrations of heavy metals and amendments able to mitigate the toxicity of tailings and improve the soil agronomic properties. Ideal candidates for phytoremediation should be metal-tolerant or metallophytic native plants, since they possess biological mechanisms for resistance to metals and they are seemingly suited to the local climate. Within this framework, the research activity carried out at the Department of Civil-Environmental Engineering and Architecture (DICAAR) of the University of Cagliari has been focusing on the application of phytoremediation in reclamation projects for the abandoned mine sites in the area of Sulcis-Iglesiente-Guspinese (south-western Sardinia, Italy). This paper provides a short background of the topic and describes the main research projects carried out in this field, together with a summary of some of the scientific results achieved at DICAAR