A.L. Mills, 1997. "The Role of Bacteria in Environmental Geochemistry", The Environmental Geochemistry of Mineral Deposits: Part A: Processes, Techniques, and Health Issues Part B: Case Studies and Research Topics, G.S. Plumlee, M.J. Logsdon, L.F. Filipek
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Many of the geochemical processes occurring at earth-surface temperature and pressure are influenced by microorganisms, particularly the bacteria. Like any other living entity, the bacteria as an aggregate have a single goal, to reproduce and perpetuate their life-form. To accomplish this goal the bacteria must utilize energy and materials that can only be obtained from their surrounding environment. As the process of growth and reproduction occurs, a variety of changes occur in the environment in which the microbe lives. The chemical makeup of waters inhabited by bacteria is altered, and any equilibrium reactions taking place in that water or between that water and associated solid phases may cause a shift in the chemical composition of aqueous- or solid-phase materials. Some materials, such as oxygen, may simply be consumed by the microbes. The resultant anoxic conditions may induce concomitant changes in some redox-sensitive species of elements such as sulfur. Bacterial utilization or production of oxidized or reduced chemical species may cause further large shifts in the redox status of the local environment. Production of acidogenic or proton-consumptive species can cause radical shifts in pH in either direction, depending on the organism, the starting material, and the products formed. Indeed, the current state of the earth's surface conditions is due in large part to the action of microorganisms on the chemicals found in the environment. Photosynthetic organisms (including the cyanobacteria, which are often referred to as blue-green algae) created the oxidizing atmosphere. Many important geochemical reactions occur against thermodynamic predictions, while others occur at rates that would be considered impossible if only the abiotic reactions operated.
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The Environmental Geochemistry of Mineral Deposits: Part A: Processes, Techniques, and Health Issues Part B: Case Studies and Research Topics
Environmental issues have become important, if not critical, factors in the success of proposed mining projects worldwide. In an ongoing and intense public debate about mining and its perceived environmental impacts, the mining industry points out that there are many examples of environmentally responsible mining currently being carried out (e.g., Todd and Struhsacker, 1997). The industry also emphasizes that the majority of mining-environmental problems facing society today are legacies from the past when environmental consequences of mining were poorly understood, not regulated, or viewed as secondary in importance to societal needs for the resources being extracted. On the other hand, environmental organizations (e.g., Mineral Policy Center, 1999) point to recent environmental problems, such as those stemming from open-pit gold mining at Summitville, Colorado, in the late 1980s (see Summitville summaries in Posey et al., 1995; Danielson and Alms, 1995; Williams, 1995; Plumlee, 1999), or those associated with a 1998 tailings dam collapse in Spain (van Geen and Chase, 1998), as an indication that environmental problems (whether accidental or resulting from inappropriate practices) can still occur in modern mining. Recent legislation imposing a moratorium on new mining in Wisconsin, and banning new mining in Montana using cyanide heap-leach extraction methods further underscore the seriousness of the debate and its implications for mineral resource extraction.
In this debate, one certainty exists: there will always be a need for mineral resources in developed and developing societies. Although recycling and substitution will help meet some of the worlds resource needs, mining will always be relied upon to meet the remaining needs. The challenge will be to continue to improve the ways in which mining is done so as to minimize its environmental effects.
The earth, engineering, and life sciences (which we group here under the term “earth-system sciences,” or ESS for short) provide an ample toolkit that can be drawn upon in the quest for environmentally friendly mineral resource development. The papers in this two-part volume provide many details on tools in the scientific toolkit, and how these tools can be used to better understand, anticipate, prevent, mitigate, and remediate the environmental effects of mining and mineral processing.
As with any toolkit, it is the professional’s responsibility to choose the tool(s) best suited to a specific job. By describing the tools now available, we do not mean to imply that all of these tools need even be considered at any given site, nor that