Biomediated Geomechanical Processes for Dust Mitigation and Monitoring at Mine Tailings Impoundments

采矿作业每年产生大量的废物。这些材料中有很大一部分是以泥浆形式排放的尾矿，并包含在被称为尾矿库的土结构中。这些大型的土制建筑受到了严格的监管和公众的关注，因为它们所包含的材料存在危险。特别是，与这些蓄水池中的尾矿相关的主要物理危害之一是扬尘造成的空气污染。控制与粉尘排放相关的危害的传统方法有几个局限性，并对人类健康和环境产生潜在的负面副作用。此外，对尾矿粉尘排放敏感性的监测是有限的，并对采矿业造成长期成本。最近利用生物改良技术进行地基加固的研究表明，利用微生物来改善粒状土的工程性质是有效的。然而，在铁矿尾矿等材料上使用生物工程带来了许多重大挑战，如处理微米和亚微米颗粒，以及应用、分配和潜在的长期水质问题的技术。因此，这个项目的总体目标是双重的。首先，将开发和测试用于稳定尾矿以减少粉尘排放的新的、可持续的、低影响的生物地质工程实践。这将需要对生物中和胶结过程(例如，碳酸钙或铁的沉淀)和/或人工隐晶(生物结壳)的形成进行工程刺激。由此产生的结皮将提高尾矿库的表面强度，减少逃逸粉尘排放的可能性，从而减轻对人类和环境健康的相关危害。其次，这些努力将与监测尾矿对粉尘排放敏感性的创新遥感技术相结合。具体地说，根据遥感热像计算的热惯量将用于监测尾矿的生物改造效果，并分析尾矿对粉尘排放的敏感性。这些目标将通过一系列实验室规模的盒子模型评估来实现。这种生物替代地质力学过程的应用，以及监测这种近地表过程的遥感技术的发展，将使社会在几个方面受益。世界各地都可以观察到来自活跃、不活跃和废弃矿山的尾矿场。这些尾矿在几十年到几百年里都没有植被，是颗粒物排放的重要来源。新建立的矿场对颗粒物排放进行了监测，但较老的矿场仍未进行监测。大型地表尾矿库中的尾矿及其相关金属污染物在温暖和寒冷的天气气候下都容易发生重大粉尘事件。一些更戏剧性的除尘事件发生在寒冷的气候中，因为冻结的孔隙水升华，也被称为干冻，在冻结的尾矿上留下一层干燥的(干燥的)尾矿，很容易使尾矿进入空气中，并成为逃逸粉尘的一大来源。由于粉尘对人类生活条件的影响，粉尘控制一直是一个重要而敏感的问题。粉尘导致人类呼吸道健康问题(如哮喘、支气管炎、肺气肿等)并可能因能见度和路况不佳而导致车辆事故。相应地，需要有效和经济的降尘技术，以及监测尾矿库和预测何时可能发生粉尘事件的方法。

Massive volumes of waste materials are produced annually by mining operations. A significant fraction of these materials is in the form of tailings that are discharged as a slurry and contained in earthen structures known as tailings disposal impoundments. These large earthen structures are subject to intense regulatory and public attention because of the hazards associated with the materials they contain. In particular, one of the key physical hazards associated with tailings in these impoundments is the air pollution from blowing dust. Conventional approaches for controlling the hazard associated with dust emissions have several limitations and potential negative side effects on human health and the environment. In addition, monitoring of mine tailings for susceptibility to dust emissions is limited and poses a long-term cost to the mining industry. Recent research using biomediated techniques for ground improvement have shown the effectiveness of using microorganism to improve the engineering properties of granular soils. However, the use of bioengineering on materials such as iron-mine tailings, presents many significant challenges such as dealing with micron and submicron particles, as well as techniques for application, distribution, and potential long-term water quality issues. Therefore, the overall goals of this project are two-fold. First, novel and sustainable, low-impact biogeoengineering practices for stabilization of mine tailings to mitigate dust emissions will be developed and tested. This will entail the engineered stimulation of biomediated cementation processes (e.g., calcium carbonate or iron precipitation) and/or artificial cryptogam (biological crust) formation. The resulting crust will improve the surface strength of mine tailings impoundments, reducing the potential for fugitive dust emissions, and thereby mitigating the associated hazards to human and environmental health. Second, these efforts will be coupled with innovative remote sensing techniques for monitoring the susceptibility of tailings to dust emissions. Specifically, thermal inertia computed from remotely sensed thermal images will be used for monitoring the effect of biomodification of mine tailings and to analyze the susceptibility of the tailings to dust emissions. These goals will be achieved via a series of bench-scale laboratory box model evaluations. Society will benefit in several ways from this application of biomediated geomechanical processes, and the development of remote sensing techniques for monitoring such near-surface processes. Mine tailings sites from active, inactive, and abandoned mine are observed throughout the world. These mine tailings remain un-vegetated for tens to hundreds of years, and are a significant source for emission of particulate matter. The particulate matter emissions are monitored in newly established mines, but the older sites remain unmonitored. Mine tailings and their associated metal contaminants, which are contained in large surface tailings impoundments, are prone to significant dust events, both in warm and cold weather climates. Some of the more dramatic dusting events occur in cold climates due to the sublimation of the frozen pore waters, also known as dry freezing, leaving a layer of desiccated (dry) tailings on frozen tailings, easily allowing the tailings to become airborne and a large source of fugitive dust. Dust control has been a significant and sensitive issue because of the effects of dusts on human living conditions. Dust causes human respiratory health problems (e.g., asthma, bronchitis, emphysema, etc.) and can lead to vehicle accidents due to poor visibility and road conditions. Correspondingly, there is need for effective, and economical dust mitigation techniques, as well as methods for monitoring tailings impoundments and predicting when dust events might occur.