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.
