EAGER -- Field tests of low-impact treatment for acid mine drainage

这个探索性项目将研究通过刺激自然微生物过程来扭转酸矿排水条件的现场技术。当开采过程中开采出的硫化物矿物暴露在地球表面氧化和水解时，就会产生酸矿水。然而，在这些矿区的土壤和河流沉积物中有一个微生物群落，主要是硫酸盐还原和铁还原细菌，它们有能力扭转受影响水域典型的低pH值和高重金属含量的状况。将在马萨诸塞州西部一个长期废弃的黄铁矿Davis矿的出水口建立一个实地研究地点，以监测在出水口引入反应性填充物所造成的地球化学变化。这种反应性填充物将由石灰石和有机堆肥的混合物组成，它将提供酸性水的初始中和和碳源，以刺激微生物种群。将在实验地点的上游和下游定期收集水样，以监测由于引入混合物而导致的化学变化。如果注意到持续的积极变化，则将对引入活性填料前后的溪流沉积物中的微生物群落进行分析。调查结果将为原位铁和硫酸盐还原细菌的成功生长和发育所需的条件提供重要数据，这些条件可以帮助长期逆转酸的产生和金属的运输。酸性矿井排水是一个全球性的问题，通常与广泛的煤炭开采有关，但它经常发生在偏远地区废弃的贱金属矿周围。清理这些垃圾场往往需要精心设计工程，不仅成本高昂，而且会破坏环境。然而，如果可以改变受影响矿区地表水的条件，使硫酸盐和铁还原细菌的自然群落能够生长和繁荣，这些微生物可以建立一种自我维持的方法来中和过量的酸度并去除金属。该项目将研究可以优化这种有益结果的条件的过程。

This exploratory project will investigate field techniques by which natural microbial processes can be stimulated to reverse the conditions of acid-mine drainage. Acid-mine drainage is produced when sulfide minerals excavated during mining operations are exposed to oxidation and hydrolysis at the Earth's surface. However, within the soils and stream deposits of these mine sites there is a community of microorganisms, largely sulfate-reducing and iron-reducing bacteria, that have the capability of reversing the conditions of low pH and elevated heavy metal content typical of affected waters. A field study site will be established at the outflow of Davis Mine, a long-abandoned pyrite mine in western Massachusetts, to monitor the changes in geochemistry that result from the introduction of a reactive fill into the outflow. This reactive fill will consist of a mix of limestone and organic compost that will provide an initial neutralization of the acidic water and a carbon source to stimulate the microbial population. Water samples will be collected at regular intervals upstream and downstream of the experiment site to monitor changes in chemistry resulting from the introduction of the mixture. If persistent positive changes are noted, the microbial communities within the stream sediments both before and after introduction of the reactive fill will be assayed. The results of the investigation will provide important data on the conditions required for successful growth and development of the in situ iron- and sulfate-reducing bacteria that can help in a long-term reversal of acid generation and metal transport. Acid-mine drainage (AMD) is a global problem that is often associated with extensive coal mining, but it occurs frequently around abandoned base-metal mines in remote areas. Cleaning up these sites often involves elaborate engineering efforts that are both costly and environmentally disruptive. However, if the conditions within the surface waters of an affected mine site can be modified so that the natural community of sulfate- and iron-reducing bacteria can grow and prosper, these microorganisms could establish a self-sustaining method for neutralizing the excess acidity and removing the metals. This project will examine the processes that can optimize the conditions for such a beneficial outcome.