by A new study warns of significant stocks of mercury that could be released into the environment as permafrost thaws.
The mercury is stored in sediments along the banks of the Yukon River, and if the permafrost that holds that sediment in place thaws, thousands of years of mercury are at risk of being released into one of the North’s largest waterways.
Isabel Smith is a doctoral student at the University of Southern California and one of the co-authors of the study, which was published in August in the journal Environmental Research Letters.
“One of the things permafrost does is stabilize some of these banks,” she explained. “And when we lose that permafrost, it creates large deposits of sediment that end up in the river.”
According to Smith, a significant amount of mercury enters the Arctic due to the element’s chemical properties and air circulation.
“The mercury stored specifically in permafrost comes from the atmosphere and plants breathe it in and then store it,” Smith said.
“Then when these plants die, instead of rotting as they would normally in warmer climates, they are frozen and preserved.”
Isabel Smith is a doctoral student at the University of Southern California and one of the study’s co-authors. (Caitrin Pilkington/CBC)
“So over time, these reserves of mercury-rich soils that have formed over thousands of years build up.”
The study involved employees from MIT, the California Institute of Technology, Delft University and the Yukon River Inter-Tribal Watershed Council. This included monitoring river erosion using satellite imagery and collecting and analyzing sediment samples at several locations in the Yukon River basin in Alaska.
Previous research has found that the Northern Hemisphere’s permafrost contains the world’s largest reservoir of mercury. Now researchers are trying to better understand the extent of the risk.
Edda Mutter is scientific director at the Yukon River Inter-Tribal Watershed Council, an Indigenous non-profit organization with members from the Yukon and Alaska.
“We knew there was significant mercury in the core and permafrost,” she said. “But what we don’t fully understand is how much of this mercury is potentially mobile.”
The new research states: “A significant amount [mercury] released from permafrost during bank erosion” and that river migration rates influence the extent of mercury transport through the waterway.
Mutter says future work will likely focus on understanding how much of that mercury is methylmercury, which is created when microbes react with naturally occurring mercury.
“This is really the type of mercury of concern that poses a threat,” she said. “It’s highly toxic.”
A permafrost collapse near Whitehorse in 2023, with the Takhini River below. The Takhini flows into the Yukon River. (Cheryl Kawaja/CBC)
Methylmercury is more easily absorbed into the bloodstream and bioaccumulates, meaning consumption of larger animals and fish can pose a real danger to humans.
Although it may take decades for the effects to become apparent, the paper says mercury releases could pose a significant threat to human health.
“On the Alaska side, many communities still get their drinking water directly from the river,” Mutter said. “It also poses a threat to subsistence living.”
Mutter said the research raises new questions for communities near the Yukon River that are already struggling with the effects of increasing erosion on infrastructure.
“How can we be proactive and look at improving water treatment systems and drinking water treatment systems, but also how we address the larger issue… [of] Climate change?”
