More pollutants could possibly build up in the atmosphere and the food web with the thawing of the permafrost because of climate change. With the land becoming warmer, it may release large quantities of mercury back into the environment.
The massive natural reserves of mercury bound up in Arctic permafrost could be 10 times more than the all the mercury that people have released into the environment from burning coal and other sources of pollution the last three decades. The mercury in the Arctic permafrost is the biggest pool of mercury on Earth, The National Geographic reported.
Wrong assumption
It turns out that before the start of the study, published in the Geophysical Research Letters journal on Monday, people thought there is no or little mercury in the permafrost, Kevin Schaefer of the National Snow and Ice Data Center at the University of Colorado, said. Because it is a natural source, some of it will be released because of what humans are doing with climate change, Paul Schuster, a hydrologist at the US Geological Survey, said.
But it remains unclear how much mercury will be released or in what form it will be to become toxic to humans. It could be released by volcanic eruptions, the weathering of rock, and forest fires. However, the primary way that mercury is released by humans is through burning coal, medical waste or some types of mining.
Mercury returns to the Earth once airborne. It ends up in land or water where it is picked up by fish and animals and accumulates in higher amounts as it works its way up the food web.
Neurotoxins
As a powerful neurotoxin, mercury in some forms can harm brain development, affect cognition, memory, language, and even visual and motor skills of children. If in excessive amounts, it can hamper vision, speech, and muscle movements even in adults. Mercury can also compromise the immune and reproductive systems and cause cardiovascular problems.
It is the reason why authorities have made fish advisories for mercury near polluted streams and rivers. Children and pregnant women have been advised to avoid eating tuna and other long-lived fish such as the swordfish.
Other than in fish, mercury is also known to build up in birds, seals, walruses, polar bears, and whales even in areas that are away from pollution sources by thousands of kilometers. This has resulted in the highest levels of mercury in the blood of indigenous people across the Arctic who rely on subsistence hunting for food.
How much mercury is under the permafrost?
The study estimated more than 58 million liters of mercury buried in the Arctic permafrost. It is two times the amount of mercury which can be found in the rest of the planet's soils, ocean, and atmosphere combined, Live Science reported.
The permafrost accounts for about 22.79 million square kilometers of land, or about 24 percent of the exposed Earth, the National Snow and Ice Data Center said. For the study, the researchers drilled 13 permafrost soil cores from different sites in Alaska between 2004 and 2012. They measured the total amounts of mercury and carbon in every sample. It proved to be consistent with thousands of other soil cores taken from other sites around the world.
Based on the mercury contents of the 13 cores, the total amount of mercury sealed below the North American permafrost is about 793 gigagrams, the researchers estimated. The Northern Hemisphere is estimated to lose anywhere between 30 percent and 99 percent of its permafrost by 2100, a 2013 study warned. It is based on the assumption that the current human greenhouse gas emissions will continue unabated.
Edda Mutter, the science director for the Yukon River Inter-Tribal Watershed Council, warned that the trapped mercury could seep into nearby waterways and transform into methylmercury. It is a toxin that can cause birth defects and motor impairments in animals. The contamination could go up to the food chain from microorganisms to people, Mutter said.
While initially, the mercury releases would place the Arctic people and wildlife at higher risks, what happens in the Arctic does not stay in the Arctic, Schuster said. It will eventually be dispersed throughout the planet and will move around.
Mercury contamination in Senegal
Meanwhile, in Senegal, a new study by Duke University researchers said that they found high levels of mercury and methylmercury in soils, sediments, and rivers near artisanal gold mines. Almost every sample collected from four mining villages had mercury at levels at least 10 times higher than the benchmarks set by the US Environmental Protection Agency and the World Health Organization.
In some cases, it was 100 times higher, Jacqueline Gerson, a PhD student in ecology at Duke University, said, Science Daily reported. It makes the level of contamination some of the highest ever reported at artisanal and small-scale gold mining sites worldwide.
[researchpaper 리서치페이퍼=Vittorio Hernandez 기자]