Organic-inorganic composite modifiers enhance restoration potential of Nerium oleander L. to lead-zinc tailing: application of phytoremediation.

Lead-zinc tailings are complex heavy metal solid wastes produced in the mining process. In this study, two kinds of organic-inorganic mixed improvers mushroom residue + calcium carbonate (M + C) and peat soil + calcium carbonate (N + C) were selected. Then, the effect of two improvers and a woody plant, Nerium oleander L., on the combined remediation of lead-zinc tailings was compared, respectively. The results showed that two combined improvers can slightly improve the pH of tailing, significantly increase the activity of phosphatase and catalase, effectively reduce the contents of DTPA-extractable Pb and Zn, and significantly improve the structure of tailing. However, the improvement effect of M + C was better than that of N + C on tailings' physical and chemical properties. Two improvers can reduce the enrichment and the stress degree of Pb and Zn on the N. oleander and increase the accumulation of Pb and Zn while promoting the growth of the N. oleander. The content of Pb and Zn showed the trend of root > stem > leaf under the two improvers, and the content of Zn was basically higher than that of Pb. To sum up, the combination of two modifiers and N. oleander has a good effect on the remediation of lead-zinc tailings, and the remediation effect of M + C was better than N + C.