水口山某废石场重金属垂向分布特征及浸出毒性

多金属矿区因采冶活动遗留的废石存量大，其重金属污染问题已备受关注.目前对废石场中重金属的分布特征和浸出毒性研究较少.本研究以湖南省水口山矿区某废石场为对象，垂直钻孔并取样分析7种重（类）金属，包括Pb、Zn、As、Cd、Cu、Ni和Cr的垂向分布特征和浸出毒性，并结合主量元素（Fe、Mn、Al和Mg）浸出行为、物相表征和统计学分析等方法，研究了重金属垂向迁移特征及其影响因素.结果表明，所有废石样品的7种重（类）金属含量均显著高于湖南省土壤背景值，污染累积指数从高到低依次为Cd、Pb、As、Cu、Zn、Cr和Ni.聚类分析将重金属分为3类，第1类是As、Fe和Pb，主要与方铅矿、黄铁矿有关，第2类是Cd、Zn和Cu，主要与闪锌矿有关，第3类是Cr和Ni，与自然风化有关.浸出毒性进一步发现，Cd、Zn、As、Cu和Ni的浸出浓度随深度增加而逐渐降低.其中，Cd和Zn表现出高浸出风险，且浸出行为显著相关，与闪锌矿转化为硫酸锌有关.Pb和Cu显示出0~0.5 m范围内的局部高浸出风险，而As和Cr属于低浸出风险.Pb和As浸出行为的差异性与As受Fe吸附有关.废石中的黄铁矿氧化降低pH促进重金属的释放迁移，而生成的次生铁（氢）氧化物能通过吸附稳定重金属；废石中的方解石有利于升高pH而降低重金属迁移风险.研究结果可为开发针对废石堆场的重金属污染防控技术和生态修复技术提供数据支撑和理论依据.

The vertical distribution characteristics and leaching toxicity of heavy metals in the mine waste dump of Shuikou Mountain

The pollution of heavy metals in mine waste dumps has attracted much attention due to the large amount of mine waste left by mining and metallurgical activities in polymetallic mining areas. Nowadays, there are few studies on the vertical distribution characteristics and leaching toxicity of heavy metals in mine waste dumps. In this study, a series of vertical drilling samples from a mine waste dump of Shuikou Mountain, Hunan province were analyzed, focusing on the vertical distribution and leaching toxicity of heavy metals (Pb, Zn, As, Cd, Cu, Ni and Cr). Moreover, the vertical migration of heavy metals and corresponding influence factors were studied on the base of leaching behaviors of main metals (Fe, Mn, Al and Mg), phase distribution and statistical analysis. The results showed that the contents of heavy metals in all the mine waste dump samples were significantly higher than the background value in Hunan Province, and the pollution accumulation index in descending order was Cd, Pb, As, Cu, Zn, Cr and Ni. Cluster analysis divided heavy metals into three categories. The first classes were As, Fe and Pb which were mainly related to galena and pyrite. The second classes were Cd, Zn and Cu, mainly related to zinc blende. The third classes were Cr and Ni which were associated with natural weathering. The leaching toxicity results was further found that the leaching concentration of Cd, Zn, As, Cu and Ni gradually decreased with the increasing depth. Among them, Cd and Zn performed high leaching risks, and the leaching behaviors were significantly related to the conversion of sphalerite to zinc sulfate. Pb and Cu exhibited high local leaching risks in the range of 0~0.5 m, while As and Cr showed to low leaching risks. The difference of leaching behaviors between Pb and As were related to the adsorption of As by Fe, because the oxidation of pyrite in the mine waste dump reduced the pH and promoted the release and migration of heavy metals, and the generated secondary iron (hydr)oxides could further stabilize heavy metals through adsorption. The calcite in the mine waste dump was beneficial to increase the pH and reduce the risks of heavy metal migration. The research results could provide data support and theoretical basis for the development of heavy metal pollution control technology and ecological restoration technology for mine waste dumps.