Mercury is released when ground frozen for millennia in permafrost thaws, something that climate change is making increasingly common.
The Yukon River, which flows through Alaska to the Bering Sea, erodes permafrost on its banks and carries sediment downstream. As our planet warms, This permafrost erodes more quickly and releases a toxic metal in the environment: mercury.
Although the mercury released by thawing permafrost does not pose a toxic threat today, Your impact will grow over time. It gradually accumulates in the food chain, and fish and wild animals consumed by humans pose a future threat as it accumulates.
A new study published by researchers at the University of Southern California (USC) Dornsife College of Letters, Arts and Sciences looks for more accurate ways to measure the extent of the mercury problem in the Arctic.
Why is there mercury in the Arctic?
The natural atmospheric circulation makes pollutants tend to move to higher latitudes.
This causes mercury accumulates in the Arcticor, where it is absorbed by plants, which die and become part of the soil. It freezes in permafrost – where the ground remains frozen all year round – and, over thousands of years, mercury concentrations have been accumulating in the ground. In this form, it is not especially dangerous.
The toxic metal is released when the ground thaws, something that climate change is becoming more and more frequent. The Arctic is warming four times faster than the global average.
This mercury, which for millennia has remained sequestered by el permafrost in the sediments, it is being eroded and released into the environment.
It could pose a serious environmental and health threat to the 5 million inhabitants of the Arctic and the more than 3 million people who live in areas where Permafrost is expected to disappear completely by 2050.
“There could be a giant mercury bomb in the Arctic about to explode,” says Josh West, co-author of the study and professor of Earth Sciences and Environmental Studies at USC Dornsife.
The risk of consuming mercury through drinking water is minimal and most humans are exposed to some level of mercury in their diet. Additionally, eroded sediments are often redeposited downstream. Understanding the dynamics of this movement is vital to understanding the magnitude of the threat looming over Arctic communities.
Predicting the problem of mercury pollution in the Arctic
The new research studies a more precise method to measure the amount of mercury released of permafrost by the river and estimate the total mercury pending release.
Previous methods of estimating levels of this toxic metal face limitations such as soil sampling depth, meaning results vary greatly. Only the top three meters of permafrost had been sampled..
Instead, the study looked at mercury in sediments from river banks and sandbanks, taking advantage of deeper layers of soil. The levels of this toxic metal were consistent with the highest estimates from previous studieswhich the researchers say means their method is probably accurate.
The team also used satellites to see how the course of the Yukon River could change in the coming years and how that could affect the erosion of mercury-laden riverbanks. They hope this will help predict the movement of this contaminant.
The researchers also found that sediments with finer grains contained more mercury than those with coarse grains. This suggests that different soil types could pose different risks.
“Taking all of these factors into account should give us a more precise estimate of the total mercury that could be released as permafrost continues to melt in the coming decades,” said Isabel Smith, a doctoral candidate at USC Dornsife and corresponding author of the study.
