Potential for passive mitigation of coal-derived acid mine drainage in abandoned stream channels

Passive treatment of coal mining-derived acid mine drainage (AMD) utilizes natural processes to neutralize the acidity and remove dissolved metal contaminants. In some cases, microbial communities develop, with no human intervention, that can induce the removal of harmful components of AMD (e.g. acidity, dissolved Fe, Al, and Mn). To better understand how these beneficial processes might develop, we studied the Huff Run system in eastern Ohio, where a portion of the stream was artificially diverted to prevent direct entry of AMD into the stream. There are now two abandoned channels of the stream that now receive raw AMD, and we hypothesized that the increased residence time of the AMD in these abandoned channels could result in diminished AMD impact on Huff Run. We tracked seasonal changes in the aqueous chemistry and microbiology through two abandoned channels, referred to as Farr and Lyons. The Fe, Al, and Mn were removed from solution as AMD moved through the Farr channel, with net alkaline water, and abundant Bacillus and Paenibacillus phylotypes. Dissolved Fe was removed from AMD over the course of the Lyons channel, but neither Al nor Mn were, and the sediments contained abundant phylotypes attributable to Alicyclobacillus sp., which are capable of oxidative precipitation of Fe(II) under acidic conditions. Our results indicate that the enhanced AMD retention in the abandoned channels can lead to removal of metals from AMD. This appears to occur due to abiotic and microbiological processes, which are controlled by AMD chemistry.

煤矿开采产生的酸性矿井排水（Acid Mine Drainage，AMD）的被动治理技术，通过自然过程中和酸性物质并去除溶解态金属污染物。在部分场景中，无需人工干预即可形成微生物群落，这类群落可介导酸性矿井排水中有害组分（如酸度、溶解态Fe、Al、Mn）的去除。为深入解析这类有益过程的形成机制，我们对俄亥俄州东部的哈夫伦（Huff Run）流域开展研究：该流域内部分溪流被人工改道，以避免酸性矿井排水直接汇入干流。当前该溪流存在两条废弃河道，均接纳未经处理的酸性矿井排水；我们提出假说：酸性矿井排水在废弃河道中停留时间的延长，可削弱其对哈夫伦溪流的环境影响。我们针对这两条分别命名为法尔（Farr）和莱昂斯（Lyons）的废弃河道，追踪了水体化学与微生物学特征的季节变化。当酸性矿井排水流经法尔河道时，水体中的Fe、Al、Mn均被去除，此时水体呈净碱性，且检测到大量芽孢杆菌属（Bacillus）与类芽孢杆菌属（Paenibacillus）的系统发育型序列。而酸性矿井排水流经莱昂斯河道时，仅溶解态Fe被去除，Al与Mn并未被移除；该河道沉积物中存在大量可归为环酸杆菌属（Alicyclobacillus sp.）的系统发育型序列，这类菌群可在酸性条件下介导Fe(II)的氧化沉淀。研究结果表明，废弃河道对酸性矿井排水停留时间的延长，可实现排水中金属污染物的去除。该过程的实现似乎依赖于非生物与微生物介导的反应，而这些反应的调控受酸性矿井排水的化学特征影响。