Division of Environmental Science and Ecological Engineering, Korea University, Seoul, Republic of Korea.
Chemosphere. 2010 Nov;81(9):1124-30. doi: 10.1016/j.chemosphere.2010.08.060.
The chemical attenuation of As by soils from abandoned mine sites was evaluated. Several soil samples, including As contaminated soil from the mine impacted areas, as well as As-free soils down-gradient from the mine sites, were collected across abandoned mine sites. Leaching and adsorption experiments were conducted under batch and 1-D water flow conditions. The cumulative As mass from 10 step sequential leaching experiments with six As contaminated soils, using 10 mM CaCl₂ solution, was less than 1% of the total As present in soils, indicating that As in contaminated soils is strongly adsorbed onto soil particles, which can serve as a long term potential As source. As adsorption by As-free soils was clearly nonlinear, with Freundlich N values (sorption nonlinearity) ranging from 0.56 to 0.87. Both the total As content in mine soils and the concentration-specific adsorption coefficient for arsine-free soils were best described by coupling the pH with various forms of Fe/Al oxides. In the breakthrough curves (BTCs) for As contaminated soils, an initial high concentration of As (called first-flush) was observed, and this flush export leveled off after the displacement of a few pore volumes. In the BTCs from layered soils, where clean down-gradient soils were overloaded above the mine soil, the appearance of measurable As was retarded, showing that the As attenuation by soils was effective in a flow water system. Also, the observed perturbation in the concentration of As during flow interruption supports that leaching/attenuation of As via flowing water occurs under nonequilibrium conditions. The results from both batch leaching/adsorption and column displacement experiments strongly suggested that the leaching of As from mine soils was rate limited and the risk of As leaching from soils can be mitigated by attenuation mechanisms, such as adsorption, provided by down-gradient clean soils.
评估了土壤对废弃矿区砷的化学衰减作用。采集了来自废弃矿区的土壤样本，包括受矿区影响的砷污染土壤以及矿区下游无砷土壤。在批处理和一维水流条件下进行了淋滤和吸附实验。用 10 mM CaCl₂溶液进行的 6 种砷污染土壤的 10 步连续淋滤实验，累积砷浸出量不到土壤中总砷含量的 1%，表明污染土壤中的砷强烈吸附在土壤颗粒上，这可以作为长期潜在的砷源。无砷土壤的砷吸附明显是非线性的，Freundlich N 值（吸附非线性）范围为 0.56 至 0.87。矿区土壤中的总砷含量和无砷土壤的浓度特定吸附系数都与 pH 值与各种形式的铁/铝氧化物的耦合关系最好。在砷污染土壤的穿透曲线（BTC）中，观察到初始高浓度的砷（称为第一次冲洗），并且在几个孔隙体积置换后，冲洗出口水平稳定。在分层土壤的 BTC 中，干净的下游土壤在矿区土壤之上被过度加载，可测量的砷出现被延迟，表明土壤对砷的衰减在流动水系统中是有效的。此外，在流动中断期间观察到砷浓度的扰动表明，在非平衡条件下通过流动水进行的砷浸出/衰减。批处理淋滤/吸附和柱置换实验的结果都强烈表明，从矿区土壤中浸出砷是受速率限制的，并且通过下游清洁土壤提供的吸附等衰减机制可以减轻土壤中砷浸出的风险。
