Three Times More Mercury is in the Upper Ocean Since the Industrial Revolution

First Posted: Aug 07, 2014 07:06 AM EDT

Mercury is still causing problems in our environment and now, scientists have found that it may be far more prevalent in our oceans than we first thought. Researchers have now measured the amount of mercury at various depths in order to find out exactly how much contamination we're dealing with.

Mercury can be naturally occurring, but it also leaches into the environment from manmade causes. For example, coal burning plants and creating cement can produce mercury. Yet exactly how much of this metal can be found in the environment has long remained a mystery.

"It would seem that if we want to regulate the mercury emissions into the environment and in the food we eat, then we should first know how much there is and how much human activity is adding every year," said Carl Lamborg, the lead scientist, in a news release. "At the moment, however, there is no way to at least separate the bulk contributions of natural and human sources over time."

The researchers first looked at data sets that offered details about oceanic levels of phosphate, which behaves in a similar way to mercury in the oceans. By determining the ratio of phosphate to mercury in water deeper than 3,300 feet, the scientists were able to estimate mercury in the ocean that originated from natural sources.

So what did they find? The most obvious signs of mercury from pollution were in the North Atlantic. The Tropical and Northeast Pacific, though, seemed relatively unaffected. Yet overall, they found the ocean contains about 60,000 to 80,000 tons of mercury pollution. In addition, ocean waters shallower than 300 feet have tripled in mercury concentration since the Industrial Revolution, and the ocean as a whole has shown an increase of roughly 10 percent.

"With the increases we've seen in the recent past, the next 50 years could very well add the same amount we've seen in the past 150," said Lamborg. "The trouble is, we don't know what it all means for fish and marine mammals. It likely means some fish also contain at least three times more mercury than 150 years ago, but it could be more. The key is now we have some solid numbers on which to base continued work."

The findings are published in the journal Nature.

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