Phytoextraction-based process of metal absorption from soil in mining areas (tailing dams) by Medicago sativa L. (Alfalfa) (Case study: Sarcheshmeh porphyry copper mine, SE of Iran)

The present work was planned to evaluate the phytoextraction of metal mine tailings, Sarcheshmeh copper mine, SE of Iran, by the endemic plant species Medicago sativa L. (Alfalfa). In this pot experiment, we investigated the effects of seven amendments on the growth of alfalfa and uptaking metals from the mine tailings and stream sediment of tailing dam surface. The mean metal concentrations in both the tailing and stream sediment increased in the order of Hg Te Ag Re Ge In Ga Zr Cu. The results of this work showed that the concentration of these elements in the whole alfalfa plant increased in the order of Hg Ag Ge Re Zr Ga In Te Cu. The bioconcentration factor (BCF) for the metals, except for Cu, was calculated to be higher than one. The translocation factor (TF) was calculated to be greater than one for Re in all treatments (ranging from 858 to 3294), while this factor was mostly lower than one for other metals and metalloids. Leaching the tailings and sediment samples with water to significantly remove water-soluble salts has given rise to an increase in the translocation of metals from roots to shoots in alfalfa. Also adding silica sand improved substrate drainage to transfer metals to rhizosphere. It was found that all of the alfalfa grew well and produced a suitable biomass, showing a high tolerance to heavy metals and metalloids. Our experimental results implied that alfalfa showed a high phytoextraction potential for soils contaminated by heavy metals, while displayed a high uptake of Re. The results of this work should be further developed in order to confirm the potential of this species on the phytomining programs.