The Behavior of Trace Metals in Water During Natural Acid Sulfate Weathering in an Alpine Watershed
W.R. Miller, R.L. Bassett, J.B. McHugh, W.H. Ficklin, 1997. "The Behavior of Trace Metals in Water During Natural Acid Sulfate Weathering in an Alpine Watershed", 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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Pyrite oxidation in the upper part of Geneva Creek basin has impacted approximately 8 miles of upper Geneva Creek by natural acid drainage (NAD). The maximum concentrations of metals in stream waters for Fe, Mn, and Al are no more than 10 mg/l; Cu, Ni, and Zn are all less than 1 mg/l, and other metals are less than 0.01 mg/l. There are low-volume seeps and flows that exceed these concentrations, but their impact on stream-water chemistry of Geneva Creek is insignificant.
The study area is located in the Colorado Mineral Belt and is underlain by Proterozoic metamorphic and igneous rocks, and intruded by Tertiary felsic stocks with associated pyritic alteration. The naturally acidic waters draining the pyritic altered areas are similar in composition to some of the more familiar acid mine drainage (AMD) waters.
Oxygen-charged waters from snow and rain aggressively oxidize and dissolve pyrite, releasing H+, Fe2+, SO42-, and trace metals to the waters of the study area. Fe2+ is later oxidized forming hydrous iron oxides. The dominant source for trace metals in waters is disseminated pyrite in the pyritic-altered areas, particularly for Cu, Pb, Zn, Bi, Ag, and As.
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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