煤矸石对铜尾矿中重金属(Zn,Pb,Cd,Cr和Cu)形态及生物有效性的影响

摘要

铜尾砂堆积在地表会随着淋溶和风化作用溶出重金属元素,对环境产生一定危害,其生态修复的关键是进行基质改良,进行植物修复.通过黑麦草盆栽实验,将淮南煤矸石添加入铜尾砂,探讨矸石对铜尾砂中重金属行为的影响.结果表明:矸石添加能显著提高铜尾砂pH、有机质和养分水平(总氮、总磷和总钾),缓解尾矿砂贫瘠环境.矸石添加后,铜尾砂中Zn,Pb,Cd和Cu的交换态和碳酸盐结合态重金属逐步向铁锰结合态、有机结合态和残渣态转化(除个别处理Pb和Cu残渣态),铜尾砂中有效态Zn,Pb,Cd和Cu浓度不断降低,从而降低了黑麦草中相应重金属浓度,总体表现为铜尾砂-黑麦草系统内Zn,Pb,Cd和Cu生物活性降低效应.然而,由于矸石中Cr浓度相对铜尾砂偏高,其添加会引起尾矿砂中有效态Cr浓度及Cr迁移性增加而增大黑麦草对Cr的吸收.因此,煤矸石可对尾矿砂中Zn,Pb,Cd和Cu产生一定稳定化作用,而虽然矸石内源性Cr会释放到铜尾砂,其也可被黑麦草富集,由此,煤矸石可视为一种潜在的废弃物改良剂,对铜尾砂具有一定生态改良潜力.%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 amendment.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.