Guangdong Provincial Key Laboratory of Petrochemcial Pollution Processes and Control, School of Environmental Science and Engineering, Guangdong University of Petrochemical Technology, Maoming, 525000, China; The Ministry of Education Key Laboratory of Pollution Control and Ecosystem Restoration in Industry Clusters, School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China.
The Ministry of Education Key Laboratory of Pollution Control and Ecosystem Restoration in Industry Clusters, School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China.
Environ Res. 2020 Jul;186:109490. doi: 10.1016/j.envres.2020.109490. Epub 2020 Apr 9.
In acid mine drainage (AMD) polluted rivers, considerable fraction of potential toxic elements are temporarily sequestered by sediments. There are two main potential environmental hazards associated with the sediments, acidity liberation and re-mobilization of metallic elements, during environmental conditions change. The effects of AMD standstill and water dilution on metallic elements migration were assessed in an AMD standstill test and a dialysis experiment. Maintaining AMD standstill, often occurring in AMD damming process, could induce the occurrence of iron secondary minerals precipitation along with attenuation of dissolved elements and a decrease in water pH value. Both field sediments and lab precipitates were confirmed as being dominant with schwertmannite which was the most important source and sink for acidity and metallic elements. The mechanism of cation heavy metals scavenging implied by FTIR results mostly depended on the exchanging of H from surface hydroxyl groups (-OH) in schwertmannite-rich sediments. For arsenic oxyanion, its adsorption included surface complexation with iron hydroxyl groups at the mineral surface, as well as anion exchange of SO present in the structure. The quantities of acidity release differed significantly from 20 to 3714 mol H/t depending on the iron hydroxyl minerals type and their contents in the corresponding sediments in 35 d dialysis, with the release rate well fitted by the second order model. Slight degree of phase transformation in schwertmannite dominant sediment had resulted in a high risk of metallic element release during the 35 d dilution duration. The significant risk of metallic elements release was ranked in the order of Cd > Mn > Zn > Pb, and with more than 89% of Cd released from FS6 and 82% from LPS1. Relatively, Cu and As in sediments were much more stable. Overall, damming was an effective and low cost pretreatment strategy for AMD pollution control. Knowledge of the characteristics of iron secondary minerals in river sediments is essential premise for both comprehensive assessment of site contamination status and effective remediation strategy decision.
在酸性矿山排水 (AMD) 污染河流中，相当一部分潜在有毒元素被沉积物暂时固定。在环境条件变化时，与沉积物相关的主要潜在环境危害有两个，即酸度释放和金属元素的再迁移。在 AMD 静止试验和透析试验中评估了 AMD 静止和水稀释对金属元素迁移的影响。AMD 静止，通常发生在 AMD 筑坝过程中，会导致铁次生矿物沉淀的发生，同时溶解元素减少，水的 pH 值降低。现场沉积物和实验室沉淀均被确认为主要含有水铁矿，水铁矿是酸度和金属元素的最重要的源和汇。FTIR 结果表明的阳离子重金属捕集机制主要取决于水铁矿丰富沉积物表面羟基 (-OH) 中 H 的交换。对于砷阴离子，其吸附包括矿物表面铁羟基的表面络合，以及结构中存在的 SO 的阴离子交换。根据 35 天透析实验，不同类型的铁羟基矿物及其在相应沉积物中的含量决定了酸度释放量在 20 至 3714 mol H/t 之间有显著差异，释放率很好地符合二级模型。在水铁矿占主导地位的沉积物中，轻微的相变程度导致在 35 天稀释过程中金属元素释放的风险很高。金属元素释放的风险程度排序为 Cd > Mn > Zn > Pb，其中 89%以上的 Cd 从 FS6 释放，82%从 LPS1 释放。相比之下，沉积物中的 Cu 和 As 更稳定。总的来说，筑坝是 AMD 污染控制的一种有效且低成本的预处理策略。了解河流沉积物中铁次生矿物的特征是全面评估场地污染状况和有效修复策略决策的必要前提。
