School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510006, China.
School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510006, China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, 510275, China; Guangdong Provincial Engineering Research Center for Heavy Metal Contaminated Soil Remediation, Sun Yat-sen University, Guangzhou, 510006, China.
J Environ Manage. 2020 Jun 1;263:110323. doi: 10.1016/j.jenvman.2020.110323. Epub 2020 Mar 13.
Metal tailings are potential sources of strong environmental pollution. In situ remediation involves the installation of a plant cover to stabilize materials and pollutants. Whether metal(loid)s are effectively immobilized in remediated tailing ponds submitted to heavy rainfall remains uncertain. In this study, tailing materials were collected from bare tailings (control), grass-planted (G) and grass-shrub planted (GS) areas on a former Pb/Zn mine site. Batch column experiments were performed with three rainfall intensities of 0.36, 0.48, and 0.50 mL min for 18 d in the lab. The pH, Eh, Cd, Pb, Zn and As concentration in leachate were recorded. Selected leached tailing materials were finally characterized. Results showed that leachates from control were strongly acidic (pH 3.11-4.65), and that Cd, Pb, Zn and As were quickly released at high rate (e.g., 945 mg L Zn). During the experiment up to 4% Cd present in the material was released and almost 1% Zn. With material collected from the G area, leachates were even more acidic (2.16-2.84) with a rainfall intensity of 0.50 mL min and exhibited a high redox potential (588-639 mV). However, concentrations of metals in leachates were much lower than that in the control, except for Zn (e.g., 433 mg L), and they tended to decrease with time. Cumulative leaching rate was still relatively high (e.g., 0.68% Cd; 0.75% Zn) during the first eight days (stage I). However, with the GS treatment, leachate pH gradually raised from acid to alkaline values (3.9-8.2) during stage I, then remained high until the end of the experiment (stage II). Also, amounts of elements released during the 18 d were low in general. The releasing ratios of Cd (R > 0.95), Pb (R > 0.95), As (R > 0.87), and Zn (R > 0.90) fitted well with a two-constant model. In conclusion, under subtropical climate with heavy rainfall, phytostabilization is effective but immobilization of metals is higher with a combination of grass and shrub than with only grass to reduce leaching of As and Zn.
金属尾矿是潜在的强环境污染源。原位修复包括安装植物覆盖物以稳定材料和污染物。在遭受强降雨的情况下，修复后的尾矿中金属（类）是否能有效地被固定仍不确定。在这项研究中，从废弃尾矿（对照）、种草（G）和草灌种植（GS）的矿区采集了尾矿材料。在实验室中进行了三个降雨强度（0.36、0.48 和 0.50 mL min）的 18 天批次柱实验。记录了浸出液的 pH、Eh、Cd、Pb、Zn 和 As 浓度。最后对选定的浸出尾矿材料进行了表征。结果表明，对照尾矿浸出液呈强酸性（pH 3.11-4.65），Cd、Pb、Zn 和 As 以高速率迅速释放（例如，945 mg L Zn）。实验过程中，约有 4%的 Cd 从材料中释放出来，约有 1%的 Zn 释放出来。用来自 G 区的材料进行淋滤时，淋出液的酸度甚至更高（2.16-2.84），在 0.50 mL min 的降雨强度下，表现出较高的氧化还原电位（588-639 mV）。然而，除 Zn 外（例如，433 mg L），淋出液中金属浓度远低于对照尾矿，且随时间呈下降趋势。在第一阶段（I）的前八天，累积浸出率仍然相对较高（例如，0.68% Cd；0.75% Zn）。然而，在 GS 处理下，浸出液的 pH 值在第一阶段从酸性逐渐升高到碱性（3.9-8.2），然后在实验结束前一直保持较高水平（第二阶段）。此外，一般来说，18 天内释放的元素数量较低。Cd（R>0.95）、Pb（R>0.95）、As（R>0.87）和 Zn（R>0.90）的释放比与双常数模型拟合良好。综上所述，在亚热带强降雨气候条件下，植物稳定化是有效的，但草灌结合比单纯种草更能有效固定金属，从而减少 As 和 Zn 的淋溶。
