Iron Mountain Mine

Iron Mountain Mine, also known as the Richmond Mine at Iron Mountain, is a mine near Redding in Northern California. Geologically classified as a "massive sulfide" ore deposit, the site was mined for iron, silver, gold, copper, zinc, and pyrite intermittently from the 1860s until 1963. The mine is the source of extremely acidic mine drainage which also contains large amounts of zinc, copper and cadmium. One of America's most toxic waste sites, it has been listed as a Federal Superfund site since 1983. [http://www.usdoj.gov/opa/pr/2000/October/619.htm U.S., California Announce Settlement to Clean up one of the Country's Most Toxic Waste Sites] , U.S. Department of Justice press release, 19 October 2000]

History

The site was mined by the Mountain Copper Company, Ltd., both underground using open stope mining techniques and at the surface in the form of open pit and sidehill mining. As a result, the mountain fractured and mineral deposits were exposed to oxygen, water and certain bacteria, resulting in acidic mine drainage.

The mine was designated a Superfund site in 1983 and a water treatment plant was built in 1994. In 2000 the government reached a settlement with Aventis CropScience (now part of Bayer) for the longterm funding of the cleanup efforts.

Location and drainage

The mine is located at coord|40|40|20|N|122|31|40|W|type:landmark|display=inline,title in the Klamath Mountains of Shasta County, about 9 miles northwest of Redding. The mine area is drained by several creeks which ultimately enter the Keswick Reservoir formed by a dam across the Sacramento River. This reservoir is a major source of drinking water for Redding.

The drainage water from the Iron Mountain Mine is the most acidic water naturally found on Earth; some samples collected in 1990 and 1991 have been measured to have a pH value of -3.6. [ [http://www.scienceblog.com/community/older/archives/E/usgs028.html World's Most Acidic Waters Are Found Near Redding, CA] , U.S. Department of the Interior and U.S. Geological Survey news release, 20 March 2000] The drainage water endangers fish, including winter-run Chinook salmon, a federally listed endangered species that spawns in the Sacramento River. Salmon kills have been noted since 1899.

The mine opening contains huge stalactite-stalagmite structures that span from floor to ceiling and are composed of rhomboclase and other iron sulfate minerals.

Bacteria and Archaea

The bacteria and archaea living in the mine are of interest because they can survive in this extreme environment, and because their metabolism contributes to the pollution. They form a pink biofilm several millimeters thick that floats on the surface of the hot water with a pH of 0.8. Since the bacteria cannot be isolated and cultured, scientists have performed community sequencing of the DNA of the five dominant species at once, assembling the genomes afterwards. Four new species were identified in this way in 2004. In 2005 the proteins produced by these bacteria were identified; of the 2033 found proteins 572 were unique to this biofilm. In 2006, Baker identified three novel archaea, the Archaeal Richmond Mine Acidophilic Nanoorganisms. [Baker BJ et al. [http://www.sciencemag.org/cgi/content/abstract/314/5807/1933 Lineages of Acidophilic Archaea Revealed by Community Genomic Analysis] , Science 22 December 2006; 314(5807):1933-1935]

The bacteria obtain carbon from the air's carbon dioxide and nitrogen from the air's N₂ gas. They are aerobes and obtain energy by using oxygen to oxidize ferrous iron dissolved from the iron sulfide rock; in the process they produce sulfuric acid which releases more metals from the rock. [ [http://www.berkeley.edu/news/media/releases/2005/05/05_banfield.shtml Proteomics brings researchers closer to understanding microbes that produce acid mine drainage] , UC Berkely Press Release, 5 May 2005] The bacteria belong to the group of acidophilic ferrous iron oxidizers.

References

External links

* [http://toxics.usgs.gov/topics/rem_act/iron_mountain.html Information and links about Iron Mountain Mine] , from the Toxic Substances Hydrology Program of the USGS