矿业废弃地重金属形态分布特征与迁移转化影响机制分析

Analysis on the Distribution Characteristics and Influence Mechanism of Migration and Transformation of Heavy Metals in Mining Wasteland

为探究矿业废弃地重金属形态分布特征和迁移转化的影响机制,在广东大宝山矿区矿业废弃地采集土壤和尾砂样品,分析重金属形态特征;采用Pb稳定同位素分析进行矿区污染源解析,并结合矿区典型矿物的X射线衍射分析(XRD)、透射电镜-能谱分析(TEM-EDS)和拉曼分析,以及室内模拟浸出实验,阐明矿区重金属迁移转化的特征和影响因素.结果表明,矿区土壤和沉积物样品中Cd、Pb和As的赋存形态以残渣态为主,占总量的比例范围为85%~95%;其次为铁锰氧化物结合态(1%~15%).矿区土壤和尾砂中的主要矿物类型为黄铁矿(FeS_(2))、黄铜矿(CuFeS_(2))和金属氧化物,同时也存在少量的闪锌矿(ZnS)和方铅矿(PbS).酸性条件(pH=3.0)有利于Cd和Pb从土壤、尾砂和矿物(黄铁矿和黄铜矿)中释放迁移,并从残渣态向非残渣态转化.铅同位素分析显示土壤和尾砂中的重金属(Pb)主要来自采矿区金属矿物的释放,矿区柴油的贡献率在30%以内.多元统计分析表明矿区土壤和尾砂重金属主要来源于3种类型的矿物污染源,即黄铁矿、黄铜矿和闪锌矿+金属氧化物,其中Cd、As和Pb主要由闪锌矿和金属氧化物贡献.矿业废弃地重金属形态变化易受环境因素的影响,开展矿业废弃地重金属污染源头控制应考虑重金属的形态特征和迁移转化影响因素.

In order to explore the distribution characteristics and the influence mechanism of migration and transformation of heavy metals in mining wasteland,soil and tailings samples were collected from the mining wasteland in the Dabaoshan Mining area,Guangdong Province,and the morphological characteristics of heavy metals were analyzed.At the same time,the pollution sources of the mining area were analyzed using Pb stable isotope analysis,and the characteristics and influencing factors of heavy metal migration and transformation in the mining area were expounded by combining X-ray diffraction analysis,transmission electron microscope-energy spectrum analysis(TEM-EDS),and Raman analysis of typical minerals in the mining area,as well as laboratory-simulated leaching experiments.Morphological analysis showed that the forms of Cd,Pb,and As in the soil and tailings samples in the mining area were mainly the residual phase,accounting for 85%-95% of the total,followed by the iron and manganese oxide-bound form(1%-15%).The main mineral types in the soil and tailings in the Dabaoshan Mining area were pyrite(FeS_(2)),chalcopyrite(CuFeS_(2)),and metal oxides,as well as a small amount of sphalerite(ZnS)and galena(PbS).Acidic conditions(pH=3.0)were beneficial to the release and migration of Cd and Pb from soil,tailings,and minerals(pyrite,chalcopyrite)and from the residual phase to the non-residual phase.Lead isotope analysis showed that the lead in the soil and tailings mainly came from the release of metal minerals in the mining area,and the contribution of diesel in the mining area was less than 30%.Multivariate statistical analysis showed that Pyrite,Chalcopyrite,Sphalerite,and Metal oxide were the main sources of heavy metals in the soil and tailings in the mining area,in which Cd,As,and Pb were mainly contributed by sphalerite and metal oxide.The form change in heavy metals in the mining wasteland was easily affected by environmental factors.The form characteristics and migration and transformation factors of heavy metals should be considered in the source control of heavy metal pollution in mining wasteland.