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As the Arctic’s permafrost thaws in a warming climate, an enormous amount of toxic mercury is being released into the environment, which would have serious health implications for the flora and fauna spread across the globe, a recent study has warned.
According to the study published in the journal Environment Resesarch Letters, researchers conducted experiments in Alaska’s Yukon river basin to determine how quickly the trapped mercury is being released from the Arctic’s permafrost and how soon a ‘mercury bomb’ could possibly explode.
A significant amount of total mercury (THg) is liberated from permafrost during glacial erosion, while a variable but generally lesser portion is subsequently redeposited by migrating rivers, stated the study led by American researcher Magdalene Isabel Smith.
The mercury content was generally higher in sediment, with finer rather than coarser grains. This suggested specific soil types could pose greater risks.
Abrupt thawing events can rapidly mobilise metres-thick deposits of sediment, potentially releasing large mercury stores.
The study gave an instance of how thaw slumps (a type of landslide that occurs in the terrestrial Arctic’s permafrost region) adjacent to a tributary of the Mackenzie river in Canada were shown to elevate suspended particulate mercury contents downstream.
The study revealed the integrated effects of erosion and sedimentation along multiple eroding bends of the Yukon and Koyukuk rivers. The nearly balanced mercury stocks between cutbanks and point bars suggest that most mercury eroded from the banks during river migration is redeposited with sediments in aggrading bars.
The results highlighted the importance of accurately capturing the dynamics of erosion and deposition for understanding mercury transport in Arctic rivers and how they will evolve in a changing climate.
A Joshua West, co-author of the study was quoted as saying: “We think of it as this potential mercury bomb. There’s so much mercury that as that permafrost thaws in a changing climate, it could release an enormous amount that could have potentially serious human health implications, locally, regionally, but even globally”.
To better understand the effects of erosion in the Yukon river basin, floodplain sediments were collected between June and September, 2022 at two locations underlain by discontinuous permafrost within the Yukon river basin: Beaver and Huslia, Alaska.
Mercury is a global environmental contaminant with both natural sources and sources associated with human activities. Much of the mercury contaminating the Arctic is a result of transport by air and ocean pathways from sources outside of the Arctic.
A study published in Nature Reviews Earth & Environment, March 2022 said that over 98 per cent of atmospheric mercury is emitted outside the region and is transported to the Arctic via long-range air and ocean transport.
People living in the Arctic remain among some of the most exposed human populations globally to mercury, and some Arctic wildlife face high and critical levels of exposure.
Many indigenous communities, including Alaskan communities, rely on subsistence fishing and have disproportionately elevated blood mercury levels linked to dietary exposure. Altering mercury inputs to Arctic waterways has an immediate and direct impact on mercury exposure in these communities, as well as affecting the mercury delivered to ecosystems and the Arctic Ocean.