Industrial waste lurks in thousands of sites in the Arctic permafrost regions – some of it is highly toxic. If the permafrost thaws increasingly deeper due to the massive warming of the Arctic deeper and becomes unstable, ecosystems and the local communities can be endangered by the waste. In August, researchers from the Alfred Wegener Institute, together with national and international partners, therefore, keep a close eye on drilling mud pits in the Mackenzie Delta in which residues from oil and gas exploration are stored. The expedition is part of the joint project "ThinIce" (Thawing industrial legacies in the Arctic - a threat to permafrost ecosystems), which is funded by the German Federal Ministry of Education and Research with 1.9 million euros. The aim of the project is to record the risk of the contaminated sites expanding and possible environmental consequences, as well as to develop strategies to minimize the risk.
Permanently frozen and several hundred meters thick in places: permafrost soils, which only thaw superficially in summer, was long believed to be not only a stable foundation for houses or industrial infrastructure, but also as an invincible barrier for solid and liquid substances. In recent decades, industrial waste from mining waste containing heavy metals to toxic drilling mud and radioactive waste has been carelessly disposed of in pits, on heaps or in closed lakes in many places in the permafrost regions of the Arctic. However, climate change, which is progressing two to four times faster in the far north than the global average, is causing the ground to thaw deeper: It is becoming unstable and more permeable. As a result, contaminated sites could spread into the environment and contaminate sensitive ecosystems, which are also the basis of many people's lives.
At the beginning of August, an expedition team led by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) will be travelling to the Mackenzie Delta in north-western Canada – an area that has warmed by 0.3 degrees Celsius per decade since 1940. There, the researchers want to investigate the danger posed by more than 200 drilling mud pits. TU Braunschweig, Leibniz Universität Hannover and RWTH Aachen University are also involved in the ThinIce research project. The research team is working closely with Canadian scientists, regional authorities and the provincial administration of the Inuvialuit communities.
"Between the 1970s and 1990s, around 230 pits were dug in the Mackenzie Delta to dispose of mud that was produced during drilling for oil and gas," explains AWI researcher Dr Moritz Langer from the Permafrost Department, who is leading the project. The 100 to 200 meters mud pools were then filled with sediment, so that today the tundra is traversed by a number of small mounds. However, a toxic mixture lies beneath them: "In addition to sediment and rock, the mud also contains fluids rich in salt or paraffin, which companies have used as anti-freezing compounds in the drilling process. The latter in particular are environmentally critical because they are poorly degraded by microorganisms in the soil," says Langer.
It is unclear what risk the drilling fluids pose to neighboring areas or bodies of water. "This has not yet been systematically investigated," says Langer. "In addition, the drillings and the anti-freezing compounds used are often poorly documented, so nobody knows what exactly is lurking in the permafrost." Over the next four weeks, the researchers will therefore be taking soil and water samples from some of the mounds and their surroundings. To identify possible leaks and assess the spread of toxic substances and their ecological consequences. They will also use geoelectric measurements to look inside the mud pits and analyze their stability.
On the one hand, this knowledge is relevant for the indigenous communities in the Mackenzie Delta, as many of the contaminated sites are located near settlements or in hunting and fishing areas. On the other hand, findings on the release of toxic substances from contaminated permafrost soils could also help in the search for solutions to the problem of contaminated sites in other regions of the Arctic.
"There are a total of around 4,500 industrial sites and up to 20,000 contaminated areas in the Arctic permafrost regions," says Moritz Langer. These figures are based on a study that he published together with other researchers in the journal Nature Communications in 2023. The majority of industrial sites are located in Alaska, Canada and Russia. The most common environmental toxins stored in the permafrost here include fuels such as diesel and petrol as well as heavy metals, such as lead and mercury. And as the soil continues to warm and ground ice is lost, the risk of environmental toxins being released increases.
Similar to the Mackenzie Delta, there is only incomplete or hardly any publicly accessible data for many industrial sites and activities in the Arctic, which makes risk assessment difficult. "This makes it all the more urgent that we get an overview of the nature and extent of the contaminated sites and develop concepts for securing and remediating them," says Langer. This is also because the renaturalization of contaminated areas becomes increasingly expensive the deeper the permafrost thaws, or even impossible if heavy machinery can no longer be used on the unstable soils.
On the upcoming expedition in north-west Canada, the research team will initially investigate the drilling mud pits in a relatively large area that encompasses various ecosystems. Soil and water samples will be taken in the vicinity of the drilling mud pits in order to analyze them for pollutants. In addition, hydrological and thermal soil measurements will be carried out and the drilling mud pits will be surveyed in detail using drones. In 2025, further expeditions will then take targeted samples at selected locations. The results from the project will serve as a basis for working with local partners to develop strategies to minimize the risk of leaking contaminated drilling fluids.
The team posts regular updates and photos of the field research online on the ThinIce website.
