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Negative pH, efflorescent mineralogy, and consequences for environmental restoration at the iron mountain superfund site, California

By:
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DOI: 10.1073/pnas.96.7.3455

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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.

Additional Publication Details

Publication type:
Conference Paper
Publication Subtype:
Conference Paper
Title:
Negative pH, efflorescent mineralogy, and consequences for environmental restoration at the iron mountain superfund site, California
DOI:
10.1073/pnas.96.7.3455
Volume
96
Issue:
7
Year Published:
1999
Language:
English
Larger Work Title:
Proceedings of the National Academy of Sciences of the United States of America
First page:
3455
Last page:
3462
Number of Pages:
8