Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 1999 Mar 30;96(7):3455-62.
doi: 10.1073/pnas.96.7.3455.

Negative pH, efflorescent mineralogy, and consequences for environmental restoration at the Iron Mountain Superfund site, California

D K Nordstrom  1 , C N Alpers
Affiliations

Negative pH, efflorescent mineralogy, and consequences for environmental restoration at the Iron Mountain Superfund site, California

D K Nordstrom et al. Proc Natl Acad Sci U S A. .

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.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Location of Iron Mountain Mine, California (adapted from ref. 15).
Figure 2
Figure 2
Cross-section of Iron Mountain (adapted from ref. 15).
Figure 3
Figure 3
Variations in rainfall, discharge, and copper and zinc concentrations for the Richmond portal effluent, 1986–1987 (adapted from ref. 19).
Figure 4
Figure 4
Growth of cuprian melanterite in a manway of the Richmond Mine with stalactite dripping pH = −0.7 water into plastic beaker. (Photo by D.K.N. and C.N.A.)
Figure 5
Figure 5
Stalagmite of rhomboclase (white) and coquimbite (purple) in the Richmond Mine. (Photo by C.N.A. and D.K.N.)
Figure 6
Figure 6
Cluster of coquimbite, voltaite, and copiapite from the Richmond Mine. (Photo by G. Robinson, Canadian Museum of Nature, Ottawa.)
Figure 7
Figure 7
phreeqe simulation of water composition for mine pool after plugging the Richmond Mine.
See this image and copyright information in PMC

References

    1. USEPA (U.S. Environmental Protection Agency) (1985) Wastes from Extraction and Beneficiation of Metallic Ores, Phosphate Rock, Asbestos, Overburden from Uranium Mining, and Oil Shale: Report to Congress EPA/530-SW-85–033.
    1. Nordstrom D K, Alpers C N Reviews in Economic Geology, editors. In: Environmental Geochemistry of Mineral Deposits. Plumlee G S, Logsdon M J, editors. Littleton, CO: Soc. Econ. Geol.; 1999. , in press.
    1. Choprapawon, C. (1998) Abstracts of International Conference on Arsenic Pollution of Ground Water in Bangladesh: Causes, Effects, and Remedies; Dhaka, Feb. 8–12, 1998, pp. 77–78.
    1. Church T, Arimoto R, Barrie L A, Dehairs F, Dulac F, Jickells T D, Mart L, Sturges W T, Zollar W H. In: The Long-Range Atmospheric Transport of Natural and Contaminant Substances. Knap A H, editor. Dordrecht, the Netherlands: Kluwer; 1990. pp. 37–58.
    1. Buat-Ménard P. In: Global Atmospheric Chemical Change. Hewitt C N, Sturges W T, editors. Amsterdam: Elsevier Science; 1993. pp. 271–311.