Restoration of copper tailings under covering soil by perennial ryegrass

Lawn grass with strong tolerance plays a significant role in disposing of heavy metal pollution and repairing copper tailings by phytoremediation. Therefore, perennial ryegrass (Lolium perenne) was used to remediate different proportions of copper tailings and soil using pot experiment. The growth status of perennial ryegrass, physicochemical properties of soil, soil enzymatic activities, content of total Cu and available Cu in soil, and content and distribution in ryegrass were investigated and analyzed. The results showed that perennial ryegrass was capable of growing well in copper tailings without any serious damage. Both the nutritional ingredients and the soil enzymatic activities from the copper tailings were distinctly improved. Compared with the blank group without cultivated plants, the organic matter, total N, total P, and total K of the trial group with ryegrass plantings were increased by 55.5%, 44.1%, 30.0%, and 24.9%, respectively. The activities of invertase, urease, phosphatase, and catalase were increased by 24.8%, 20.5%, 11.4%, and 14.2%, respectively. Differences between the two groups existed(P < 0.01). Additionally, the growth and uptake by the perennial ryegrass accelerated the activation of Cu, which reduced the content of Cu in soil by 12.2% to promote the restoration process of the Cu-contaminated soil. The experimental results illustrated that it is not only possible to restore the field copper tailings by utilizing the perennial ryegrass, but it also offered a reference to recover the heavy metal contaminated tailings by using phytoremediation.