The AGU reports that geoscientists have discovered permafrost in the northern hemisphere that stores massive amounts of natural mercury, a finding with significant implications for human health and ecosystems worldwide. In a new study, geoscientists measured mercury concentrations in permafrost cores from Alaska and estimated how much mercury has been trapped in permafrost north of the equator since the last Ice Age. The study reveals northern permafrost soils are the largest reservoir of mercury on the planet, storing nearly twice as much mercury as all other soils, the ocean and the atmosphere combined. The new study was published today in Geophysical Research Letters, a journal of the American Geophysical Union.
"This discovery is a game-changer," said Paul Schuster, a hydrologist at the U.S. Geological Survey in Boulder, Colorado and lead author of the new study. "We've quantified a pool of mercury that had not been done previously, and the results have profound implications for better understanding the global mercury cycle." Warmer air temperatures due to climate change could thaw much of the existing permafrost layer in the northern hemisphere. This thawing permafrost could release a large amount of mercury that could potentially affect ecosystems around the world. Mercury accumulates in aquatic and terrestrial food chains, and has harmful neurological and reproductive effects on animals.
"There would be no environmental problem if everything remained frozen, but we know the Earth is getting warmer," Schuster said. "Although measurement of the rate of permafrost thaw was not part of this study, the thawing permafrost provides a potential for mercury to be released—that's just geochemistry." The new findings have major implications for understanding how Earth stores mercury and for human and environmental health, according to James Shanley, a research hydrologist at the U.S. Geological Survey in Montpelier, Vermont, who was not involved with the new research.
"This study is very novel and makes a big discovery in an area that was previously somewhat ignored," Shanley said. "It shows permafrost represents a huge source of mercury, and if it thaws due to climate change the mercury could be released and could significantly add to the global mercury burden."
Schuster believes his team's research gives policymakers and scientists new numbers to work with and calibrate their models as they begin to study this new phenomenon in more detail. He intends to release another study modeling the release of mercury from permafrost due to climate change, and said this work changes scientists' perspective of the global mercury cycle. "Some 24 percent of all the soil above the equator is permafrost, and it has this huge amount of locked-up mercury in the frozen soil at and near the surface," he said. "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."
For details, see: Paul F. Schuster et al, 2018, "Permafrost Stores a Globally Significant Amount of Mercury", Geophysical Research Letters (2018). DOI: 10.1002/2017GL075571
Original URL: https://phys.org/news/2018-02-scientists-massive-reserves-mercury-hidden.html#jCp
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