School of Chemistry and Material, Guizhou Normal University, Guiyang, 550025, China.
School of Life Sciences, Guizhou Normal University, Guiyang, 550025, PR China.
Chemosphere. 2022 Mar;291(Pt 1):132792. doi: 10.1016/j.chemosphere.2021.132792. Epub 2021 Nov 5.
The leaching of heavy metals (HMs) from lead-zinc mine tailings caused by natural precipitation and the subsequent migration and transformation characteristics in paddy soil were investigated using simulative experiments. The contents of HMs in the leachate from lead-zinc mine tailings increased with the increasing of liquid-to-solid ratio. Significant differences of contents under the same rainfall were found among different HMs (P < 0.01). The increasing rates of the concentrations for Mn and Zn in leachate were much higher than the other selected HMs. The leaching results of all HMs were well fitted by the DoseResp equation, indicating that the leaching processes are controlled by multiple factors. When the paddy soil was exposed to lead-zinc mine tailings, the HMs could accumulate significantly in the paddy soil, and their contents increased with the simulated time. The average vertical migration rates (mg kg cm d) of HMs in the paddy soil during the four months was ranked in the order of Zn (9.0✕10) > Mn (8.1✕10) > Cu (1.8✕10) > Pb (1.6✕10) > Cd (2.7✕10) > As (2.4✕10). Compared with the other HMs, Mn and Zn can be more easily leached from lead-zinc mine tailings, then migrate into deeper layers in paddy soil. The proportions in five chemical fractions of HMs varied significantly with the impact of lead-zinc mine tailings. The Zn, Cu, and As were mainly presented in residual fraction, while Pb, Mn, and Cd were mainly presented in carbonate-bound, Fe/Mn oxides-bound, and exchangeable fractions, respectively. The risk assessment code results showed that Zn, Mn, Cu, and As posed medium risk, while Pb and Cd posed an extremely high risk to the paddy soil environment. It's found that lead-zinc mine tailings could significantly enhance the ecological risk associated with HMs in the paddy soil.
采用模拟实验研究了自然降水引起的铅锌矿尾矿中重金属（HMs）的淋滤及其在稻田土壤中的迁移转化特征。随着液固比的增加，尾矿浸出液中 HMs 的含量增加。在相同降雨量下，不同 HMs 的含量存在显著差异（P < 0.01）。Mn 和 Zn 浓度在浸出液中的增加率远高于其他选定的 HMs。所有 HMs 的浸出结果均符合 DoseResp 方程，表明浸出过程受多种因素控制。当稻田土壤暴露于铅锌矿尾矿时，HMs 可在稻田土壤中显著积累，其含量随模拟时间的增加而增加。四个月期间 HMs 在稻田土壤中的平均垂直迁移率（mg kg cm d）按 Zn（9.0×10）>Mn（8.1×10）>Cu（1.8×10）>Pb（1.6×10）>Cd（2.7×10）>As（2.4×10）的顺序排列。与其他 HMs 相比，Mn 和 Zn 更容易从铅锌矿尾矿中淋滤出来，然后迁移到稻田土壤的更深层。HMs 五种化学形态的比例随铅锌矿尾矿的影响而发生显著变化。Zn、Cu 和 As 主要以残渣态存在，而 Pb、Mn 和 Cd 主要以碳酸盐结合态、Fe/Mn 氧化物结合态和可交换态存在。风险评估码结果表明，Zn、Mn、Cu 和 As 构成中等风险，而 Pb 和 Cd 对稻田土壤环境构成极高风险。研究发现，铅锌矿尾矿可显著增强稻田土壤中与 HMs 相关的生态风险。
