Accumulation of Heavy Metals in Four Plants Grown on Mine Waste Rock Dump and Ecological Risk

A field experiment was conducted to compare the growth and heavy metal accumulation of Neyraudia reynaudian, Vetiveria zizanioide, Paspalum notatum and alfalfa on the copper mine waste rock dump, soil reconstructed by 10cm soil covering on 20cm limestone amendment layer, on 20cm coal fly ash amendment layer, on 20cm red mud amendment layer and on waste rock directly without any amendment layer. The results indicated that biomass of soil reconstructed with alkaline substances layer was about 3 times higher than that without any amendment layer. Neyraudia reynaudian was a typical heavy metal excluder, the concentrations in shoots of the plants were the lowest among the four plants tested. The most of metal accumulated in Neyraudia reynaudian distributed in its root, and transportation of metal in this plant from root to shoot was restricted. Neyraudia reynaudian, accumulated a relatively low level of heavy metals in their shoots and roots, was more suitable for phytostabilization of toxic mined lands than the other plants tested. Therefore, Neyraudia reynaudian was regarded as lower ecological risk species used for phytoremediation (for both phytostabilization and phytoextraction) of copper mine acid waste rock dump.