Gold Rush's Poisonous Legacy: Mercury Will Linger for 10,000 Years

It was previously thought that most of the mercury from this mining, much of which took place more than 150 years ago, had already exited the river system, Singer said. But a study by Singer and colleagues published this week in the journal Proceedings of the National Academy of Sciences showed this isn't the case. Instead, the study found that there is enough mercury-contaminated sediment to significantly add to levels of the heavy metal downriver and in the San Francisco Bay for the next 10,000 years. The sediment is washed away by large floods but also by the meandering of the river, which curves back and forth within its valley and exposes long-buried, polluted dirt, he added.
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