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article image26m lbs of toxic mercury from Gold Rush era poisons CA heartland

By Nancy Houser     Oct 30, 2013 in Environment
Fresno - Contamination of toxic mercury used in California's early Gold Rush days will soon seep into the San Francisco waterways. The contaminated soil will drastically impact the state's agricultural heartland for close to 10,000 years.
According to ABC News, "During the 19th century gold rush, miners used mercury to process gold throughout the West. An estimated 26 million pounds of mercury was used for gold recovery in the Sierra Nevada and Klamath-Trinity Mountains."
Scientists have long been aware of mercury contamination from historical mining practices, but recently a study by a group of U.K. and U.S. scientific researchers studied the soil from a Sierra Nevada mining deposits that points downstream. It was found that the mercury levels were up to hundreds of times higher than background levels.
Further studies showed that toxic mercury used in the historic gold mining was released in the Sacramento-San Joaquin River Delta and San Francisco Bay from episodic floods, periods when long dry periods alternated with flooding that would evaporate or soak into the ground every 10 years or so.
Another study, according to Science News, stated that "researchers led by Michael Bliss Singer of the University of St. Andrews in Scotland measured mercury levels in sediments at 105 locations upstream of the bay."
In an October 28, 2013, report by the research team in the Proceedings of the National Academy of Sciences, it was stated that mining sediments would continue to release mercury over the next 10,000 years. And as climate change continued to intensify the rainstorms, the mercury discharges will increase.
More about toxic mercury, gold rush era, California, sierra nevada, KlamathTrinity Mountains
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