Phytoremediation of multi-metal contaminated mine tailings with Solanum nigrum L. and biochar/attapulgite amendments

A greenhouse experiment was conducted to investigate an enhanced phytoremediation technique for multi-metal contaminated mine tailings by Solanum nigrum L. and using biochar/attapulgite as soil amendments. The 10% attapulgite (MA(2)) and 10% biochar (MB2) were recommended as the optimum chemical proportions for amendment materials. Plant length and fresh weight in the MA(2)/MB2-applied treatments were significantly higher than that in the non-amended treatment, indicating MA(2) and MB2 amendments could alleviate metal phytotoxicity. Metal uptake in plant leaves was lower with MA(2) and MB2 application than that in the non amended treatment. However, metal uptake in plant roots was significantly increased with MA(2) and MB2 application from the fifth month, suggesting that MA(2) and MB2 had significant enhancement on metal stabilization. Temporal variation of metal translocation in soil-to-plant system showed that the function of MA(2) and MB2 reached the plateau nearly in the seventh month. The removal rates of metals were higher after the application of MA(2) than MB2, and by the following order: Cu (39.6%) > Zn (35.0%) > Cd (34.1%) > Hg (32.1%) > Pb (31.8%) > Mn (19.1%). The synergistic effect between S. nigrum L. and MA(2)/MB2 appeared to be particularly effective in terms of metal phytostabilization, and MA(2) was superior to MB2.