Effects of coal gangue addition on the chemical fraction and bioavailability of heavy metals (Zn,Pb,Cd,Cr and Cu) in copper mine tailings

By leaching and weathering,the heavy metals in the copper mine tailings would release and pose potential danger to the environment. The key problem of ecological remediation for the copper mine tailings is substrate amend-ment. Through pot experiment and vegetated with Lolium perenne L. ,the coal gangue sampled from a coal waste rock pile in Huainan coal field was added into the copper mine tailings and the behavior of heavy metals in the amended copper mine tailings were investiaged. Results indicated that the pH,organic matter and nutrient elements (total N,P and K) were markly improved by coal gangue application. Applying coal gangue could shift the Zn,Pb,Cd and Cu bound with exchangeable and carbonate fraction to those bound with Fe-Mn oxide,organic matter and residual fraction (except Pb and Cu associated with residual fraction in some treatments),and thus decreased DTPA-extractable Zn, Pb,Cd and Cu concentrations in copper mine tailings,resulting those metals decreased in the Lolium perenne L. as well. Generally,applying coal gangue reduced the bioavailability of heavy metals (Zn,Pb,Cd and Cu) in copper mine tailings-Lolium perenne L. system. However,the addition of coal gangue increased the Cr concentration in the amended tailings and increased the mobility of Cr,which also promoted the uptake of Cr by the Lolium perenne L. . As a result, applying the coal gangue to the copper mine tailings immobilized the Zn,Pb,Cd and Cu in the tailings and brought in the Cr which could be effectively been absorbed in the Lolium perenne L. . The coal gangue could be recognized as a potential waste-derived amendment for the ecological remediation of copper mine tailings.