Throughout the Arctic, there are numerous weather, research, and radio stations, as well as military outposts. A large number of these stations date from the World War II and Cold War periods and are no longer in operation today. After the stations and military outposts were decommissioned, no effort was usually made to dismantle facilities or remove remnants of fuel. And so countless barrels rust away in the Arctic, from which oil, diesel and other fuels leak and seep into the ground. The pollution ranges from a few liters to several tons. In Greenland alone, there are about 30 abandoned military installations like this, where diesel was once used for generators and other machinery and which may have seeped into the ground. The Danish Ministry of Defense and the engineering company NIRAS, with the contribution of the University of Copenhagen, therefore launched an experiment that showed how naturally occurring bacteria remediate the contaminated soil.
A former military airfield on the coast of East Greenland was chosen to conduct the experiment, Station 9117 near Mestersvig north of Scoresby Sound, where 40 tons of diesel fuel contaminated the soil. Over five years, scientists from the University of Copenhagen’s Department of Plant and Environmental Sciences and the Geological Survey of Denmark and Greenland (GEUS) monitored bacterial populations and the biodegradation of diesel compounds in the soil. Their experiment was successful – they found that the bacteria had bioremediated 82 percent of the 5,000 tons of contaminated soil.
“The bacteria have proven extremely effective at breaking down the vast majority of the diesel compounds. As such, this natural method can be applied elsewhere in the Arctic, where it would otherwise be incredibly resource-intensive to remove contaminated soil by way of aircraft or ship,” as Jan H. Christensen, co-author of the study and professor at the Department of Plant and Environmental Sciences at the University of Copenhagen, explains.
“Landfarming” as a remediation method
In warmer climates, so-called “landfarming” has been used for years, with soil bacteria helping to break down drill cuttings, oily sludge and other waste from oil refineries. Before the experiment, however, this method had neither been so thoroughly studied and documented nor tested on a large scale in the Arctic.
Landfarming is a method of spreading contaminated soil in a thin layer, which is then plowed, fertilized and oxygenated each year to optimize conditions for the bacteria to break down hydrocarbons. During the project, explosive growth in soil bacteria occurred regularly, according to Anders Risbjerg Johnsen, lead author of the study and principal investigator at GEUS. “Having a wide variety of hydrocarbon-degrading bacteria is essential as the 10,000 various diesel compounds contaminating the soil require different degradation pathways to be broken down,” he explains.
Also practicable in the Arctic
At the beginning of the experiment, the researchers did not necessarily expect that the Greenlandic bacteria would be able to break down the seeping diesel as well as bacteria in warmer regions. Temperatures in the three warmest summer months in Mestersvig are just between 0 and 10°C, and during the rest of the year the ground is frozen. The scientists were therefore all the more pleased that the naturally occurring bacteria, unaffected by the freezing temperatures, degraded the diesel just as effectively.
“Some degree of diesel pollution can be found at nearly every Arctic site where there was once a weather station, research station or military installation. It is likely that the approach used in our experiments can be used at many of these sites.”
Jan H. Christensen, Professor in the Department of Plant and Environmental Sciences at the University of Copenhagen &
Anders Risbjerg Johnsen, lead author and senior researcher at GEUS
Within one year, the bacteria degraded 64 percent of the diesel, namely the main components (n-alkanes, alkylbenzenes, and alkylnaphthalenes), in the soil of Mestersvig. In contrast, for other compounds such as cyclo-alkanes, hydroxy-PAHs (polycyclic aromatic hydrocarbons) and heterocyclic sulphur compounds, there appear to be no degrading bacteria in Greenlandic soil. These can probably only be degraded very slowly by accompanying processes or not at all. After five years of active landfarming, the recalcitrant fraction (18 per cent) remained in the soil.
The scientists now hope that the microorganisms can also be used at the other decommissioned stations in Greenland to decontaminate the soil, even though the clean-up is extremely expensive and resource-intensive due to the lack of infrastructure.
The researchers will conduct further studies this year and hope that the bacteria will have broken down any remaining diesel compounds.
Julia Hager, PolarJournal
