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Nordstrom DK, Alpers CN.. Negative pH, efflorescent mineralogy, and consequences for environmental restoration at the Iron Mountain Superfund site, California. Proc Natl Acad Sci USA 96: 3455-3462

United States Geological Survey, 3215 Marine Street, Boulder, CO 80303-1066, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 04/1999; 96(7):3455-62. DOI: 10.1073/pnas.96.7.3455
Source: PubMed

ABSTRACT The Richmond Mine of the Iron Mountain copper deposit contains some of the most acid mine waters ever reported. Values of pH have been measured as low as -3.6, combined metal concentrations as high as 200 g/liter, and sulfate concentrations as high as 760 g/liter. Copious quantities of soluble metal sulfate salts such as melanterite, chalcanthite, coquimbite, rhomboclase, voltaite, copiapite, and halotrichite have been identified, and some of these are forming from negative-pH mine waters. Geochemical calculations show that, under a mine-plugging remediation scenario, these salts would dissolve and the resultant 600,000-m3 mine pool would have a pH of 1 or less and contain several grams of dissolved metals per liter, much like the current portal effluent water. In the absence of plugging or other at-source control, current weathering rates indicate that the portal effluent will continue for approximately 3, 000 years. Other remedial actions have greatly reduced metal loads into downstream drainages and the Sacramento River, primarily by capturing the major acidic discharges and routing them to a lime neutralization plant. Incorporation of geochemical modeling and mineralogical expertise into the decision-making process for remediation can save time, save money, and reduce the likelihood of deleterious consequences.

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Available from: Darrell Kirk Nordstrom, Sep 02, 2015
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    • "Nordstrom and Alpers [1] describe the reactions involved in the origin of an AMD from pyrite oxidation through three steps: "
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    • "related with both working and abandoned mining operations . Mineral extraction and beneficiation produce crushed, milled waste rock deposited in tailings causing a potential risk to the environment when exposed to weathering (Nordstrom and Alpers 1999; Dold and Fontboté 2001). They act as a major contributor to environmental pollution, providing sources of heavy metals that may lead to the contamination of the surrounding soils, agricultural areas and villages through weathering (wind erosion, water runoff, and leachates) (Conesa et al. 2006; Navarro Flores and Martínez Sola 2010; Navarro et al. 2008; Chaoyang et al. 2009; Vrhovnik et al. 2011; Bes et al. 2014; Mileusnić et al. 2014,, Kříbek et al. 2014). "
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    ABSTRACT: The present and past mining activity left several abandoned tailings and dams in the Panasqueira tin–tungsten mining area. Seasonal water samples and stream sediments were collected during two different periods (rainy and dry seasons) and analyzed for a wide range of major and trace elements, in order to define the present hydrochemical situation. Rain waters interact with the altered sulfides stored in the tailings which generate runoff waters with high metal concentrations. The waste material derived from the exploitation enhanced acidification and metal-releasing processes, due to the increase in the specific surface, which favors the oxidation of sulfide minerals. Acid drainage and high metal(loid)s (Cd, Fe, Mn, Zn, Cu, As) concentrations in solution were observed in waters leaching the Panasqueira tailing deposits. In dry season, generally the acidic waters, enriched in metals, evaporate progressively depositing sulfate efflorescences characteristic of acidic environments. The elements distribution in precipitated minerals helps in the interpretation of aqueous geochemical data. Aqueous concentrations may be attenuated by goethite, gibbsite, and/or ferrihydrite precipitation in the oxidation zone through adsorption processes. The use of these waters for human consumption and for irrigation represents a threat to humans as they have a potential carcinogenic risk, especially due to the As concentrations. The acid water precipitation is present on the stream sediments, with concentrations exceeding the toxicity limits. Stream sediments are good receptors of metals and metalloids transported by waters. The enrichment factor values, of heavy metal(loid)s from Casinhas stream and Zêzere river sediments, are extremely high in Ag, As, Cd, and Cu revealing enrichments for these potential toxic elements. I geo values shows that samples are strongly to very strongly polluted for Ag, As, Bi, Cd, and Cu. According to the consensus-based SQGs, 80 % of the samples were classified at the level of great concern and adverse biological effects are to be expected frequently in this area.
    Water Air and Soil Pollution 02/2015; 226(2). DOI:10.1007/s11270-014-2255-8 · 1.69 Impact Factor
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    • "Under arid climate or during prolonged dry period in humid conditions, thick crust of sulfate salts can be formed by oxidation, dehydration and neutralization processes (Jambor et al. 2000). While dissolution of the highly soluble sulfate salts occured during rainstorm that can have a catastrophic effect on aquatic ecosystems by releasing significant amounts of Fe, SO 4 2− and potentially hazardous elements such as As, Cd, Cu, Ni and Pb as well as acidity into the leachate (Alpers et al., 1994, 2003; Carbone et al., 2013; Hammarstrom et al., 2005; Jamieson et al., 2005; Nordstrom and Alpers, 1999; Romero et al., 2006). Thus, environmental significance of these sulfate minerals in areas of mining has spawned a great interest to understand their geochemical control on mine water chemistry, and the potential impact on water quality following rain events (Atanassova and Kerestedjian, 2009). "
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    ABSTRACT: This paper presents a detailed mineralogy, acid base accounting (ABA), and selective leaching of coal and mine wastes (MW) from the Jaintia Hills coalfield of Meghalaya, India, investigating their potential in controlling AMD. Mineralogical study revealed that pyrite is the major sulfide mineral in coal and MW, being more enriched in sandstone and carbonaceous shale; while, dolomite and calcite are abundant in a few shale and siltstone bearing rocks, and copiapites are enriched in efflorescent salts (ES). Based on the ABA test, all coals and more than 50% of MW samples showed paste pH < 4, implying they are acid generating. Further, the relationships between net neutralization potential (NNP) and acid producing ratio (APR) revealed that blocky pyrite, pyritiferrous sandstone and ES contribute acid more intensively than coal, siltstone and carbonaceous shale. This inference is consistent with net acid generation (NAG) test. Partitioning of metals in MW indicates high proportions of metals are bioavailable in the blocky pyrite relative to other rock samples. The concentration of Mn is highly bioavailable, while major portions of Pb and Zn are resident in the reducible and oxidizable fractions. In ES, > 80% of all metals are available in soluble fraction; thus it can be the highest polluting residue in the mining environment, however, the stability of the efflorescent minerals can play an important role in controlling the chemistry of mine drainage since their precipitation temporarily scavenges dissolved metals from solution in dry periods and re-dissolves under rain events. In case of coal, only a small fraction of Mn, Ni, Zn, Cd, and Pb are released to the environment, however, their high proportions can become bioavailable under oxidizing conditions besides from other bioavailable forms.
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