In this study, we investigated the impact of fluctuating water levels on the distribution of lead (Pb) and zinc (Zn) in soil and sediments at a historical Pb-Zn smelting site along the Xiangjiang River. Despite the high pH levels (7 to 11) in the study area, which generally inhibits heavy metal solubility, we found that regular changes in water levels still affect Pb-Zn movement. Soil analysis revealed distinct redox zones within the unconfined aquifer, as shown by the variable Fe/Mn and Ce/Ce* ratios. Advanced techniques such as Mn K-edge XAFS, Mössbauer spectroscopy, and TOF-SIMS indicated persistent Fe-Mn redox cycling and highlighted the presence of Pb and Zn-rich manganese oxides near sulfur-bearing minerals. These findings suggest that acidic microzones produced by the oxidation of sulfur-bearing minerals become "refuges" for microbial and heavy metal activity. Considering that sulfur-containing minerals are widespread waste types in nonferrous metal smelting sites, these findings are instructive for a better understanding of the transformation mechanisms of heavy metal ions in nonferrous metal smelting-polluted environments and for guiding pollution remediation strategies.

中文翻译：

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硫化物与铁锰矿物的耦合促进高pH洪泛区土壤氧化还原循环中铅和锌的迁移


在这项研究中，我们调查了水位波动对湘江沿岸历史铅锌冶炼场土壤和沉积物中铅 (Pb) 和锌 (Zn) 分布的影响。尽管研究区域的 pH 值较高（7 至 11），通常会抑制重金属的溶解度，但我们发现水位的定期变化仍然会影响 Pb-Zn 的运动。土壤分析揭示了无承压含水层内明显的氧化还原区，如可变的 Fe/Mn 和 Ce/Ce* 比率所示。 Mn K 边缘 XAFS、穆斯堡尔光谱和 TOF-SIMS 等先进技术表明存在持续的 Fe-Mn 氧化还原循环，并强调了含硫矿物附近存在 Pb 和富锌锰氧化物。这些发现表明，含硫矿物氧化产生的酸性微区成为微生物和重金属活动的“避难所”。鉴于含硫矿物是有色金属冶炼场所普遍存在的废物类型，这些研究结果对于更好地了解有色金属冶炼污染环境中重金属离子的转化机制以及指导污染修复策略具有指导意义。