典型Pb/Zn矿区土壤重金属污染特征与Pb同位素源解析

以我国典型的铅锌矿区——湖南水口山铅锌矿区及其周围地区为研究对象，分析自然土壤(A层和C层)样品中不同重金属(Pb、Zn、Cr、Cu、Cd、Hg)的污染特征和Pb同位素组成.结果表明，受铅锌选矿和冶炼活动的影响，研究区域A层土壤明显受到重金属的污染，尤其是在中心区域(水口山矿区)，土壤中Pb、Zn、Cr、Cu、Cd、Hg含量最高达3966.88、 2086.25、 135.31、 185.63、 56.15、 16.434 mg/kg；受原生地质环境的影响，C层土壤重金属含量虽然变化很大，但基本反映土壤背景值.土壤中不同重金属的潜在生态危害大小顺序为Cd>Hg>Pb>Cu>Zn=Cr.中心区域多重金属综合潜在生态危害明显高于周围区域，其34%、 33%、 11%、 22%的采样点分别属于轻微、中等、强和很强生态危害，而周围区域属于轻微、中等、强和很强生态危害的采样点比例分别为68%、 16%、 10%、 6%.与C层Pb同位素相比(²⁰⁶Pb/²⁰⁷Pb为1.168～1.246，²⁰⁸Pb/²⁰⁶Pb为2.014～2.130)，由于人为Pb源的污染A层土壤中²⁰⁶Pb/²⁰⁷Pb值(1.166～1.226)低而²⁰⁸Pb/²⁰⁶Pb值(2.043～2.135)高.与铅锌选矿、冶炼废水和烟尘中Pb同位素比值对比表明，A层土壤铅污染主要来自于冶炼厂烟气粉尘的沉降.

Heavy Metal Contamination and Pb Isotopic Composition in Natural Soils Around a Pb/Zn Mining and Smelting Area

The heavy metal (Pb, Zn, Cr, Cu, Cd, and Hg) concentrations in the A horizon and C horizon soils, collected around the Pb/Zn mining and smelting area of Shuikoushan in Hunan, China, were investigated, and the Pb isotopic compositions were also determined to identify the potential origin of Pb in the A horizon soil. Compared with C horizon soils, the A horizon soils exhibit elevated heavy metal concentrations, especially in the vicinity of the mining and smelting area. This reveals that the surface soil was contaminated to some degree. The contents of Pb, Zn, Cr, Cu, Cd, and Hg in soils are up to 3966.88, 2086.25, 135.31, 185.63, 56.15, and 16.434 mg/kg, respectively. The potential risks caused by different metals are in the order of Cd > Hg > Pb > Cu > Zn=Cr. Much higher potential ecological risk was observed for the central area (Shuikoushan Pb/Zn mining and smelting area) than for the surrounding area. About 34%, 33%, 11%, and 22% of the sampling sites demonstrate low, moderate, considerable, and very high potential ecological risk in the central area, while about 68%, 16%, 10%, and 6% of the sampling sites show low, moderate, considerable, and very high potential ecological risk in the surrounding area, respectively. Compared with the Pb isotopic compositions in the C horizon soils (²⁰⁶Pb/²⁰⁷Pb 1.168-1.246,²⁰⁸Pb/²⁰⁶Pb 2.014-2.130), the Pb in the A horizon soils has lower ²⁰⁶Pb/²⁰⁷Pb ratios (1.166-1.226) and higher ²⁰⁸Pb/²⁰⁶Pb ratios (2.043-2.135). The Pb in the A horizon soils predominantly derives from two-component mixing resources. One is the parent materials of C horizon, and the other is the atmospheric deposition of the smelting flue gas dust.