Melting permafrost could release toxic mercury, study reports

Researchers have discovered that rising temperatures could cause large-scale mercury leaks in the Northern Hemisphere.
By Joseph Scalise | Feb 10, 2018
There may be over 15 million gallons of mercury buried beneath the permafrost in the Northern Hemisphere, and global warming could release it all, according to a new study published in the journal Geophysical Research Letters.

Mercury occurs naturally in the Earth, but rarely does it all concentrate in one place. In fact, the mercury detected in the recent research is roughly twice as much as can be found in the rest of Earth's soils, ocean, and atmosphere combined.

Permafrost is any soil that has been frozen for over two years. In the Northern Hemisphere, such soil makes up roughly 8.8 million square miles of land. As time passes, naturally occurring compounds in the atmosphere -- including mercury and carbon dioxide -- can bind with organic material in the soil and become trapped in the frost. It then stays there until the frost thaws.

To see how much mercury is trapped by the permafrost, researchers from the U.S Geological Survey drilled 13 permafrost soil cores from various sites in Alaska between 2004 and 2012. They then measured the total amounts of mercury and carbon in each sample. Using the measurements as a baseline, the team estimated that there is more than 15 million gallons of mercury sealed away below North American permafrost.

"There would be no environmental problem if everything remained frozen, but we know the Earth is getting warmer," said lead author Paul Schuster, a hydrologist at the U.S. Geological Survey, according toLive Science."This discovery is a game-changer."

Past studies have observed climate-change induced permafrost thawing, and if current trends continue more is likely going to occur in the future. In fact, a 2013 study showed that the Northern Hemisphere will lose between 30 and 99 percent of its permafrost by 2100.

While scientists have analyzed several ways melting permafrost could harm the planet, there has been no research done on large-scale mercury leaks. One potential issue is that trapped mercury could seep into waterways and shift into toxic methylmercury. Such contamination could travel swiftly up the food chain and harm a wide range of organisms, from microbes all the way to humans.

To better explore the potential scenarios, the team plans to do a follow up study that will better show the effects of the melting soil.

"24 percent of all the soil above the equator is permafrost, and it has this huge pool of locked-up mercury," added Schuster, in a statement. "What happens if the permafrost thaws? How far will the mercury travel up the food chain? These are big-picture questions that we need to answer."

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