Phytoremediation of multi-metal contaminated copper tailings with herbaceous plant and composite amendments

Abstract

After the closure of the large tailing pond of copper sulfide mine, ecological restoration must be carried out. The ecological restoration method of directly using tailing as a vegetation matrix to replace guest soil is a new method. The key to this method lies in improving the substrate environment and carry out phytoremediation. A field test was performed to carry out an enhanced phytoremediation technique for multi-metal contaminated copper tailings by Sudan grass (Sorghum sudanense (Piper) Stapf.), ryegrass (Lolium perenne L.), and Bermuda grass (Cynodon dactylon), using conditioner (TH-LZ01) and straw combination into composite amendments as soil amendments, aimed to obtain the maximum of phytoremediation effect. The 5% conditioner and 0.5% straw (C2S2) were recommended as the optimum chemical proportions for amendment materials. We could find that the chlorophyll, catalase activity, plant length and fresh weight in the 5% conditioner and 0.5% straw (C2S2) applied treatments were notably higher when compared with those of other treatments, indicating that composite amendments could alleviate the toxicity of metals to plants. In addition, adding composite amendments can obviously improve the restoration effect of Sudan grass, ryegrass and Bermuda grass on the pH, water content, electrical conductivity and organic matter of copper tailings. Compared with no treatment, the absorption of metal in leaves of plants treated with composite amendments is lower, but that in roots is enhanced, revealing that the stability of metal in roots is enhanced by composite amendments treatment to a great extent. By applying composite amendments, the metal removal effect of ryegrass appeared to be particularly effective, and by the following order: Cd (48.5%) > Zn (45.8%) > Pb (27.7%) > Cu (21.9%), followed by Sudan grass and Bermuda grass.