A Research team led by the Alfred Wegener Institute investigated the environmental risks from drilling mud pits in Canada’s Mackenzie Delta.
Industrial waste, some of it highly toxic, lies dormant in thousands of locations in the Arctic permafrost regions. These sites threaten to endanger ecosystems and the local population if the permafrost soil thaws and becomes increasingly unstable due to the massive warming of the Arctic. In August, researchers from the Alfred Wegener Institute AWI, together with national and international partners, are therefore taking a close look at sludge pits in the Mackenzie Delta, where 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 euro. The goal of the project is to record the risk of the contaminated sites spreading 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 that only thaw on the surface in summer were long regarded not only as a stable foundation for houses or industrial infrastructure, but also as an insurmountable barrier for solid and liquid substances.
In recent decades, industrial waste has been carelessly disposed of in many places in the permafrost regions of the Arctic in pits, on heaps or in closed lakes, from mining waste containing heavy metals to toxic drilling mud and radioactive waste. However, climate change, which is progressing two to four times faster in the far north than on global average, is causing the soil to thaw ever deeper, thereby turning more unstable and more permeable. As a result, contamination could spread into the environment and endanger sensitive ecosystems, which are also the basis of many people’s livelihoods.
At the beginning of August, an expedition team led by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) traveled to the Mackenzie Delta in northwest Canada – an area that has warmed by 0.3 degrees Celsius per decade since 1940. There, the researchers will 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 sludge from drilling for oil and gas,” explains AWI researcher Dr. Moritz Langer from the Permafrost Department, who is leading the project. The 100 to 200-metre mud ponds were then filled with sediment, so that today the tundra is adorned with a number of small hills. However, a toxic mixture lies beneath the mounds: “In addition to sediment and rock, the mud also contains fluids rich in salt or kerosene, which companies have used as antifreeze during drilling. 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 adjacent areas or bodies of water. “This has not been systematically investigated to date,” says Langer. “In addition, the drillings and the antifreeze used are often poorly documented, so nobody knows what exactly is slumbering in the permafrost.”
Over the next four weeks, the researchers will therefore take 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 sludge pits and investigate their stability.
On the one hand, this knowledge is relevant for the indigenous population 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 here in the permafrost include fuels such as diesel and petrol as well as heavy metals, including 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 only exists incomplete or hardly publicly accessible data for many industrial sites and activities in the Arctic, which makes risk assessment difficult. “It is all the more urgent that we get an overview of the type and extent of the contaminated sites and develop concepts for securing and remediating them,” says Langer.
This is also because the renaturation 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.
During the expedition to north-western Canada, the research team will first examine the mud pits in a relatively large area that encompasses various ecosystems. Soil and water samples will be taken in the vicinity of the mud pits in order to analyze them for pollutants. In addition, hydrological and thermal soil measurements will be carried out and the 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 developing strategies together with local partners to minimize the risk of leaking contaminated drilling fluids.
Press release by the Alfred Wegener Institute
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