Division of Environmental Science and Ecological Engineering, Korea University, Seoul 136-713, Republic of Korea.
Division of Environmental Science and Ecological Engineering, Korea University, Seoul 136-713, Republic of Korea.
Chemosphere. 2015 Sep;134:150-8. doi: 10.1016/j.chemosphere.2015.04.018. Epub 2015 May 15.
Leaching of metallic elements (Cu, Zn, As, Cd, and Pb) from two mine-impacted soils (DY and BS) was evaluated by batch decant-refill and seepage flow experiments. During eight consecutive leaching steps, aqueous As concentrations remained relatively constant (approx. 1.6 and 0.1 mg L(-)(1) for DY and BS, respectively), while Cu (0.01-3.2 mg L(-1)), Zn (0.2-42 mg L(-1)), and Cd (0.004-0.3 mg L(-1)) were quickly reduced. The reduction of Pb concentration (0.007-0.02 mg L(-1) and 0.2-0.9 mg L(-1) for DY and BS, respectively) was much lesser. This pattern was well-explained by the biphasic leaching model by allocating a large fast leaching fraction (ffast>0.2) for Cu, Zn, and Cd while a negligible ffast for As and Pb (<0.001). For all elements in column effluents, mass export through first-flush and steady-state concentration were elevated under slow seepage, with the greatest impact observed for As. Element export was enhanced after flow interruption, especially under fast seepage. A transient drop in As export in slow seepage was likely due to sorption back to soil phase during the quiescent period. The ratio of Fe(2+)/Fe(3+) and SO4(2-) concentration, related to the dissolution of sulfide minerals, were also seepage rate-dependent. The results of batch and column studies imply that the leachate concentration will be enhanced by initial seepage and will be perturbed after quiescent wetting period. The conversion from kinetically leachable pool to readily leachable pool is likely responsible for nonequilibrium metal leaching from the long-term abandoned mine soils.
采用批式淋滤-渗滤实验，评估了两种矿山污染土壤（DY 和 BS）中金属元素（Cu、Zn、As、Cd 和 Pb）的浸出情况。在连续 8 个淋滤步骤中，水样中的 As 浓度基本保持稳定（分别约为 1.6 和 0.1 mg L(-)(1)），而 Cu（0.01-3.2 mg L(-1)）、Zn（0.2-42 mg L(-1)）和 Cd（0.004-0.3 mg L(-1)）则迅速降低。Pb 浓度的降低幅度较小（分别约为 0.007-0.02 mg L(-1)和 0.2-0.9 mg L(-1)）。这一模式很好地通过双相淋滤模型得到解释，该模型为 Cu、Zn 和 Cd 分配了较大的快速淋滤分数（ffast>0.2），而 As 和 Pb 的 ffast 可忽略不计（<0.001）。对于柱流出液中的所有元素，在缓慢渗流条件下，首次冲洗和稳定态浓度下的质量输出较高，而 As 的影响最大。中断水流后，元素的输出会增强，特别是在快速渗流条件下。缓慢渗流中 As 输出的短暂下降可能是由于在静止期内被重新吸附到土壤相中。与硫化物矿物溶解有关的 Fe(2+)/Fe(3+)和 SO4(2-)浓度的比值也依赖于渗流速率。批式和柱实验的结果表明，初始渗流会提高淋出液浓度，而在静止润湿期后，淋出液浓度会发生波动。从动力学上可提取的金属池向易提取的金属池的转化可能是长期废弃矿山土壤中金属非平衡浸出的原因。
