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Acid Mine Drainage |
Pollution of the environment by acid, metal-rich solutions is a major environmental problem at sites around the world. Acid solutions form when rocks rich in sulfide minerals are oxidized on exposure to air and water (acid rock drainage). Mining activities associated with extraction of metals, coal, and U increase the permeability and porosity of rocks and greatly accelerate rates of formation of acid solutions. The acid solutions that form in association with mining activities are referred to as acid mine drainage (AMD).
AMD is particularly severe if the concentration of sulfide minerals in the rocks in high, the ability of the surrounding rocks to buffer the pH is low, and the deposit is open to the air. These conditions can lead to generation of formation of large volumes of very acidic solution (similar to battery acid) that is rich in iron and toxic metals.
Perhaps one of the most intriguing aspects of the problem is that the majority of AMD formed is the direct result of microbial activity. Thus, we are studying the linkages between the geochemistry of AMD systems and their microbial communities. Much of this work is directed toward understanding the physiology of organisms adapted to live in extreme environments (extreme acidophiles) and the microbial ecology of AMD systems.