D. Kirk Nordstrom, 1997. "Some Fundamentals of Aqueous 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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Aqueous geochemistry is the application of chemistry to reactions between rock and natural water. Analytical chemistry, inorganic and organic chemistry, and physical chemistry are used to understand and interpret the dominant processes that effect a redistribution of the elements in man's environment. Examples of these processes are the dissolution and precipitation of minerals, adsorption and desorption of ions, oxidation-reduction or redox reactions, gas uptake or production, transformations involving organic matter, complexation and chelation, evaporation, ion exchange, and anthropogenic changes. In the field of aqueous geochemistry these processes are known to occur in a variety of environments including rain, fog, snow, soils, bedrock weathering, streams, rivers, lakes, estuaries, ground waters, subsurface brines, diagenetic environments, the formation and weathering of mineral deposits, and the global movement of elements and compounds. Aqueous geochemistry is synonymous with low-temperature geochemistry, where the approximate temperature and pressure limits of 0-100°C and 1-500 bars commonly apply. The term environmental geochemistry is often used to emphasize the environmental aspects of geochemistry. Another common term, hydrogeochemistry, is usually applied to the aqueous geochemistry of ground waters. These four terms all refer to the same basic subject matter.
In physics and chemistry, great advances are made through theoretical research, experimental research, or optimally through a blend of both. In aqueous geochemistry, a third aspect plays an essential role: field observations. By applying the best that theoretical chemistry and physics can offer to the interpretation of field observations aided by reliable experimental and analytical determinations, the aqueous geochemist is at the crossroads of theory, experiment and the natural environment. Geological phenomena are of a much greater complexity than the carefully controlled systems investigated in physics and chemistry, so that the geochemist has had to expand his knowledge creatively beyond the traditional boundaries of the physical sciences. The challenge of this type of scientific research is not generally appreciated (Alvarez, 1990). There are far more unknown and uncontrolled variables in natural systems than in the typical physicochemical investigation carried out in the laboratory. The hydrological, microbiological, macrobi- ological, and meteorological sciences are all necessary in addition to geology and chemistry.
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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