Sistemi di fitorisanamento di suoli contaminati da metalli pesanti con specie ad elevata produzione di biomassa in ambiente mediterraneo

In Sardinia there are several areas at high metal contamination and, among the most polluted ones, we can find the mining sites. Soil mining remediation is indisputable, but usually very expensive. Among several heavy metal remediation techniques currently available, phytoremediation is considered to be a low-impact technology and less expensive than classical ones. The main objective of this work was investigating about the possibility of using autochthonous species, both bush and leguminous, for heavy metal contaminated soil phytoremediation in a xeric climate. Atriplex halimus shrub was tested in this research work. This plant, which is a perennial, autochthonous saltbush, can produce remarkable aerial biomass amounts, and can grow in very restrictive pedo - climatic conditions. Atriplex halimus growth, survival and metal accumulation in aerial and radical tissues were evaluated through different tests, performed at pot scale, on a soil contaminated by mining activity. Clonal differences were also investigated. Furthermore, amendments were tested to improve the soil characteristics and identify a cheap and effective cultivation system, capable of increasing plant survival and biomass yield. Different methods were evaluated to reduce the times required for plant production before plantation. Plant cultivation by stem cutting were also studied. Medicago polymorpha, a leguminous and Nitrogen fixing species, was tested to reduce amendments during a cultivation crop cycle. Its survival and adaptability in heavy metal contaminated soil was evaluated. This plant grows spontaneously in Mediterranean areas and it was never studied for phytoremediation before the present work. The research work showed that Atriplex halimus can be considered effective for phytoremediation of Sardinian soils contaminated by mining activity. The plants grown in soils contaminated by heavy metals showed in fact a good adaptability, a significant growth and a high metal concentration level in the tissues. Moreover, this work opens up the possibility of using Medicago polymorpha species in phytoremediation activities due to its germination ability and plant survival observed in heavy metal polluted soils.