Braunschweig researchers investigate highly toxic legacy in permafrost Expedition to drilling mud sumps in subarctic Canada

The thawing of permafrost soils in the Arctic is revealing a disturbing legacy of past industrialisation: drilling mud sumps containing potentially toxic waste are threatening the region’s fragile ecosystems. In Canada’s Mackenzie Delta, an area with an exceptionally high density of freshwater habitats, these contaminated sites could release contaminated substances into the environment – with potentially devastating consequences for ecosystems and the local population. Professor Antje Schwalb and PhD student Emma Cameron from the Institute of Geosystems and Bioindication at Technische Universität Braunschweig undertook an expedition to the Northwest Territories in Canada as part of the ThinIce project (funded by the funded by the Federal Ministry of Education and Research) to investigate lakes and ponds there.

Drilling mud sump near Tuktoyaktuk, Northwest Territories, Canada, with evidence of collapse leading to the formation of a pond on the sump cap. Picture credits: Moritz Langer/ Vrije Universiteit Amsterdam

Between the 1970s and 1990s, the Mackenzie Delta was intensively developed for oil and gas production. More than 230 drilling mud sumps – specially excavated pits for the disposal of drilling waste – were created at that time. These sumps, which were originally stably embedded in the permafrost, could become unstable due to the progressive thawing of the permafrost and release pollutants. The toxic substances could easily find their way into neighbouring bodies of water and cause lasting damage to water quality and biodiversity in the region. In addition, indigenous communities whose livelihoods and health are closely linked to intact ecosystems in the Arctic are directly exposed to these risks.

Ecological risks of drilling mud sumps 

Professor Antje Schwalb and PhD student Emma Cameron therefore analysed lakes and ponds near drilling mud sumps, which were filled with drilling fluids containing salt and oil by oil and gas companies and then covered with the excavated material. The aim of the ThinIce project, led by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), is to gain fundamental insights into the ecological risks of drilling mud pits in the Mackenzie Delta under changing climate conditions. The research team is also working closely with Canadian scientists, regional authorities and the national administration of the Inuvialuit communities.

Professor Antje Schwalb and Emma Cameron spent a total of four weeks in Canada’s Northwest Territories, travelling by foot with the ThinIce team to sites between Inuvik and Tuktoyaktuk, supported by the Inuvialuit Land Administration and the Northwest Territories Geological Survey. In total, four sumps were visited in August, and samples were collected from 15 waterbodies, including five sediment cores, to reconstruct changes in the aquatic environments since the establishment of the sumps. “These sediment cores will help address major knowledge gaps in the region, allowing us to trace how sump contents have impacted the surrounding environment, given the lack of long-term monitoring in the region”, says Emma Cameron. The samples are now being analyzed for bioindicators and contaminant biomarkers to gain insights into the ecological and chemical conditions of the waterbodies, both in the present day and through a reconstruction of past conditions.

Prof. Dr. Antje Schwalb and Emma Cameron collecting sediment and water samples from a small lake near a drilling mud sump. Picture credits: Moritz Langer/ Vrije Universiteit Amsterdam

Some members of the ThinIce team at their first study site in early August. Picture credits: Rachele Lodi/ Università Ca' Foscari Venezia

Emma Cameron stabilizing three short sediment cores collected from a large lake close to Tuktoyaktuk. Picture credits: Antje Schwalb/ TU Braunschweig

Aurora borealis over the rowhouse accommodations in Inuvik, Northwest Territories, Canada. Picture credits: Mehriban Aliyeva/ Alfred Wegener Institute

The journey across the Subarctic tundra to reach a drilling mud sump site. Picture credits: Emma Cameron/ TU Braunschweig

Emma Cameron pulling the boat she used for sampling with the help of a local environmental monitor. Picture credits: Antje Schwalb/ TU Braunschweig

The early morning drive along the Inuvik Tuktoyaktuk Highway. Picture credits: Moritz Langer/ Vrije Universiteit Amsterdam

Prof. Dr. Antje Schwalb and Emma Cameron examining a surface sediment sample from a pond on the perimeter of a drilling mud sump. Picture credits: Moritz Langer/ Vrije Universiteit Amsterdam

Emma Cameron helping the geophysics team dig a trench to bury an Electrical Resistivity Tomography (ERT) monitoring cable. Picture credits: Neri Fromm/ RWTH Aachen University

Emma Cameron collecting sediment and water samples from a small pond that has formed on the sump cap. Picture credits: Antje Schwalb/ TU Braunschweig

Subarctic conditions 

“The study region has been hit particularly hard by climate change, and record temperatures, eroding coastlines, and wildfires are becoming the norm”, says Emma Cameron. Upon arrival in Inuvik, temperatures were in the mid-thirties, fluctuating throughout the stay, with some days dropping to around 5 degrees Celsius accompanied by high winds and rain.” Arctic weather is always unpredictable, but the entire team adapted remarkably well, even though it was the first Arctic experience for many”. Additionally, the tundra is challenging to traverse due to its instability, requiring the team to haul heavy gear on their backs while pulling sleds behind them.

This was the ThinIce team’s inaugural field season, and they will return in March 2025 to work in winter conditions, enabling Emma Cameron to collect samples from the ice surface through drilled holes. Later in the year, they will return for another summer expedition in August, 2025. These expeditions will involve visits to additional mud sumps to enhance the understanding of the legacies left by the intensive oil and gas operations that were highly active around 50 years ago.