Food grown in parts of California is being threatened by mercury left over from mining practices used during the gold rush in the 1800s, according to research in the Proceedings of the National Academy of Sciences. Researchers studied an area known as the Yuba Fan with the aid of historical information and NASA imagery. The tainted sediment moves when the land floods, they found. "The Yuba Fan is totally artificial, created by humans," said Michael Singer of the University of St. Andrews in Scotland.
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