Mercury Pollution Increased Drastically Over the 20th Century

First Posted: Jun 30, 2015 10:33 AM EDT

Mercury pollution has increased drastically over the 20th century. Scientists have studied a 600-year-old ice core and have found that global mercury levels have increased in the atmosphere quickly in the modern era.

The toxic metal, mercury, is emitted due to coal burning, mining, volcanoes, weathering and other human and natural sources. This mercury can then contaminate ecosystems around the world. In addition, past mercury emissions persist in the environment for decades, and this "legacy" mercury can continue to pollute ecosystems even after emissions decrease.

Past mercury emissions are estimated from historical records of metal production and industrial/commercial activity or from the natural archives of atmospheric mercury deposition. In order to get a better sense of the history of mercury, the researchers examined an ice core.

So what did they find? Analysis revealed that the first major mercury pollution peaked occurred during the North American Gold Rush of the late 19th century, when mercury was used to extract gold and silver from ores and sediments. Following the end of the Gold Rush, mercury levels quickly returned to near natural levels. Then, starting in the middle of the 20th century, mercury pollution began an unprecedented increase to maximum levels in the early 1970s. After, though, the pollution decreased as mercury was removed from many commercial products and emissions regulations were enacted.

With that said, the core also showed a renewed increase in mercury since the early 1990s until the record ends in 1998. This is likely due to the rise of coal burning in Asia and small-scale gold mining in developing countries.

"The ice core record shows clearly how efforts to reduce mercury emissions have decreased pollution in the past," said Sam Beal, lead author of the new study, in a news release. "But the recent rise in mercury pollution from coal burning and small-scale gold mining show that there is more work to be done."

The findings are published in the journal Environmental Science & Technology.

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