Influence of coal gangue aided phytostabilization on metal availability and mobility in copper mine tailings

Copper mine tailings without proper remediation deposited permanently in tailings ponds would pose adverse impacts to the environment. Coal gangue, with high nutrients, used in infertile soil, is investigated in microcosm trials to explore the possibility of immobilize metals within the copper mine tailing in this research. Therefore, a pot trial was conducted using coal gangue and Vetiveria zizanioides for phytostabilization of the metals in copper mine tailing. Results indicated that applying coal gangue not only increased the pH, organic matter content and nutrient contents of the amended tailings, but also decreased the DTPA-extractable concentrations of Zn, Pb, Cd, and Cu in the amended tailings. The application of coal gangue converted the exchangeable and carbonate fractions of Zn, Pb, Cd, and Cu into unavailable forms of Fe-Mn oxide and/or organic matter fractions, thus reducing those metal contents in mobile fractions of the amended tailings. This study shows that treatments with coal gangue inhibited Zn, Pb, Cd, and Cu translocation from tailings to Vetiveria zizanioides. In contrast, the accumulation of Cr in the plant was increased by the addition of coal gangue. Collectively, these results support the hypothesis that coal gangue is a potential waste-derived amendment with the ability to reduce the mobility of most of the studied metals in copper mine tailings. This study also proposed a new approach to dispose the waste of coal gangue as an amendment for phytostabilization of copper mine tailings.