State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, 388 Lumo Road, Wuhan, 430074, PR China; College of Resource and Environmental Engineering, Guizhou University, Huaxi District, Guiyang, 550025, PR China.
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, 388 Lumo Road, Wuhan, 430074, PR China.
Water Res. 2017 Mar 15;111:118-126. doi: 10.1016/j.watres.2016.12.048. Epub 2016 Dec 29.
Many karst areas are impacted by acid mine drainage (AMD) which is characterized by low pH, high concentrations of dissolved Fe(II) and toxic contaminants. During the flow of AMD in karst areas, the increase in pH facilitates the oxygenation of Fe(II). Whereas, the oxidizing capacity for Fe(II) oxygenation in AMD is poorly understood. In light of the recent finding that hydroxyl radicals (OH) can be produced from Fe(II) oxygenation, this study experimentally measured the cumulative concentrations of OH produced from oxygenation of simulated AMD (8.93 mM Fe, pH 3) in the presence of limestone (CaCO). With the increase in CaCO dosages from 0.67 to 2.78 g/L, Fe(II) oxidation rate increased accordingly, but the maximum concentration of cumulative OH appeared at the CaCO dosage of 1.39 g/L, being 59.3 μM within 24 h. The production of OH was mainly attributed to the rise of AMD pH due to dissolution of limestone, rendering the appearance of adsorbed Fe(II) on the newly formed lepidocrocite and ferrihydrite and complexed Fe by carbonate (i.e., siderite). Oxygenation of these Fe(II) species was accountable for the production of OH. An appropriate pH (i.e., 5-6) was required for the moderate rate of Fe(II) oxidation, corresponding to the maximum production of OH. The OH produced from AMD oxygenation can concurrently oxidize the contaminants of arsenic and p-aminobenzenesulfonamide. Findings from this study suggest that the oxidizing impact of OH on contaminants transformation as well as organic carbon mineralization should be concerned for the oxygenation of AMD in karst areas.
许多喀斯特地区受到酸性矿山排水（AMD）的影响，其特征是 pH 值低、溶解的 Fe(II) 和有毒污染物浓度高。在 AMD 在喀斯特地区的流动过程中，pH 值的增加促进了 Fe(II)的氧化。然而，AMD 中 Fe(II)氧化的氧化能力还不太清楚。鉴于最近发现羟基自由基（OH）可以从 Fe(II)氧化产生，本研究实验测量了在存在石灰石（CaCO）的情况下模拟 AMD（8.93 mM Fe，pH 3）的氧化过程中产生的 OH 的累积浓度。随着 CaCO 剂量从 0.67 增加到 2.78 g/L，Fe(II)氧化速率相应增加，但在 CaCO 剂量为 1.39 g/L 时出现了最大累积 OH 浓度，24 h 内达到 59.3 μM。OH 的产生主要归因于石灰石溶解导致 AMD pH 值升高，使新形成的纤铁矿和水铁矿以及碳酸盐（即菱铁矿）结合的 Fe 上吸附的 Fe(II)出现。这些 Fe(II)物种的氧化是 OH 产生的原因。适度的 Fe(II)氧化速率需要适当的 pH 值（即 5-6），对应于 OH 的最大产生。AMD 氧化产生的 OH 可以同时氧化砷和对氨基苯磺酰胺等污染物。本研究的结果表明，在喀斯特地区 AMD 氧化过程中，应关注 OH 对污染物转化以及有机碳矿化的氧化影响。
