Toxic mercury from the Gold Rush is heading toward America’s food basket.
How miners used mercury to get their gold
When gold was discovered in California in 1849, the miners were confronted with a problem: there were huge amounts of the precious metal in the foothills of the Sierra and the only way to get it out was to blast it out of the soil with high-pressure hoses.
The resulting mud containing the gold was run through sluices and mixed with mercury so the gold would settle to the bottom.
The miners used high pressure hoses, called monitors, to blast the hillsides, washing the gold-bearing mud into sluices.
Gold Rush miners are long gone, but they left toxic mercury behind.
Gold Rush miners are long gone, but they left toxic mercury behind.
Much of the mercury remained in the sediment. The sediment washed downstream actually forming new river valleys and terraces, the fan.
The process dramatically altered the landscape; massive mudslides filled whole valleys.
Miners' mercury is making its way to the farms
The remains of the 19th-century practice are still visible in the area, and the poisonous mercury is now slowly making its way toward the fruit and nut orchards, and the rice fields of California’s lush Central Valley, America’s food basket, according to new research by a team of British and American scientists.
The study concentrated on California's Yuba Fan
The Yuba Fan, built up around the Yuba River that runs out of the Sierra Nevada Mountains north of Sacramento, is not far from California’s verdant wine country.
The Yuba fan is totally artificial, created by humans. The fan contains more than a billion cubic meters of sediment reaching down to the Golden Gate.
Floods transport mercury to farmland, contaminating food
Every time there is a big flood the mercury in the sediment moves farther down into the valley.
Mercury has already been found in the food supply
Mercury has already been found in the food supply
Mercury taint from the Gold Rush has been found in the food supply in the San Francisco area, but the contamination in the Yuba fan is hundreds of times greater.
Scientists believe trees do not absorb mercury so fruits and nuts may be safe, although that has not been tested. There is evidence, however, that rice may be vulnerable.
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http://emedicine.medscape.com/article/1175560-overview
http://www.medicinenet.com/mercury_poisoning/article.htm
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