A good soil

Diesel-polluted soil from now defunct military outposts in Greenland can be remediated using naturally occurring soil bacteria, according to the evidence of a recently-completed experiment in Mestersvig in the east of the country. The University of Copenhagen contributed.
Envirotec Sept/Oct 21
Landfarming works by distributing contaminated soil in a thin layer, which is then ploughed, fertilized and oxygenated every year to optimize conditions for bacteria to degrade hydrocarbons.

Mothballed military outposts and stacks of rusting oil drums aren’t an unusual sight in Greenland. Indeed, there are about 30 abandoned military installations in the country, where diesel, once used to keep generators and other machinery running, may have seeped into the ground.

This is the case with Station 9117 Mestersvig, an abandoned military airfield on the coast of East Greenland. Forty tons of diesel fuel contaminated the soil at Mestersvig. As a result, Danish Defence and NIRAS, an engineering company, initiated an experiment to optimize the conditions for naturally occurring soil bacteria to break down soil contaminants.

Researchers from the University of Copenhagen‘s Department of Plant and Environmental Sciences began by continuously monitoring bacterial populations and the biodegradation of diesel compounds, with help from the Geological Survey of Denmark and Greenland (GEUS). After five years, the researchers found that the bacteria had bioremediated as much as 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,” explained Professor Jan H. Christensen, who has been responsible for analyzing the chemical fingerprints in the diesel-contaminated soil.


Cold climate first

The method deployed is known as “land farming”, and it proceeds by distributing contaminated soil in a thin layer, which is then ploughed, fertilized and oxygenated every year to optimize conditions for bacteria to degrade hydrocarbons.

The approach is a more familiar fixture in warmer climates and this project marked the first known attempt to test it on a large scale under Arctic conditions. Nor had the method ever been as thoroughly studied and documented as in this experiment, said the group.

According to Anders Risbjerg Johnsen, a microbiologist at GEUS, the landfarming work resulted in regular explosions of soil bacteria, which he was able to keep track of from Denmark using samples of soil.

“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,” said Johnsen.


Clean-up capability

Warmer “summer” temperatures of between 0 and 10ºC only last about three months in Mestersvig. For the rest of the year, the soil is frozen. It was uncertain whether the Greenlandic soil bacteria could break down the leaked diesel as effectively as bacteria in warmer conditions.

Fortunately, the study demonstrated that it could. The researchers hope that naturally occurring bacteria can be used to remediate contamination in the Greenlandic environment at roughly 30 other deserted installations. The lack of infrastructure has made it extremely expensive and resource-intensive to move soil around compared to a similar undertaking in a country like Denmark.

“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,” said Christensen. “It is likely that the approach used in our experiments can be used at many of these sites.”
The researchers are returning to Greenland this year to continue the experiment, and they hope to find that the bacteria have successfully degraded all remaining diesel contamination.