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[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, 208 Pb/206 Pb 2.014-2.130), the Pb in the A horizon soils has lower 206 Pb/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.