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Bacteria used to clean up diesel contaminated soil

According to the results of an extensive five-year experiment, the diesel-contaminated soil in Greenland has been cleaned using naturally occurring soil bacteria.

The country has about 30 abandoned military installations where diesel fuel, once used to run generators and other machinery, may have seeped into the ground.

At the abandoned military airfield Station 9117 Mestersvig, 40 tons of diesel fuel was found contaminating the soil. To clean it up, the Danish Defense and ONDRAF/NIRAS, an engineering firm, started an experiment to optimize conditions for naturally occurring soil bacteria to break down soil contaminants.

Bacterial populations and the biodegradation of diesel compounds were continuously monitored by scientists from the University of Copenhagen. 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 been shown to be extremely effective in breaking down the vast majority of diesel compounds. As such, this natural method can be applied elsewhere in the Arctic where it would otherwise be incredibly labor intensive to remove contaminated soil by plane or ship,” said Professor Jan H Christensen from the University of Copenhagen.

The method, known as landfarming, is usually associated with warmer climates around the world. Prior to this project, landfarming had never been widely tested under Arctic conditions. Nor had the method ever been studied and documented as thoroughly as in this experiment.

Landfarming works by thinly dividing contaminated soil, which is then plowed, fertilized and oxygenated each year to optimize conditions for bacteria to break down hydrocarbons.

According to microbiologist Anders Risbjerg Johnsen, the land farming work resulted in regular explosions of soil bacteria, which he was able to monitor from Denmark using advanced samples of soil bacteria.

“Having a wide variety of hydrocarbon-degrading bacteria is essential, as the 10,000 different diesel compounds that pollute the soil require different degradation pathways to break down,” he said. Warmer ‘summer’ temperatures of 0 to 10 degrees only last about three months in Mestersvig.

The rest of the year the ground is frozen. For example, it was uncertain whether Greenlandic soil bacteria could break down the leaked diesel as well as bacteria in warmer conditions.

But the study showed that the bacteria could easily break down diesel contaminants in the soil, despite the frigid temperatures. In the future, the researchers hope that naturally occurring bacteria could be used to remediate contamination in the Greenland environment at about 30 other abandoned installations.

The lack of infrastructure has made it extremely expensive and labor intensive to move land, as could be done in Denmark for example.

“Some degree of diesel pollution can be found in almost every Arctic location that once housed a weather station, research station or military installation. It is likely that the approach used in our experiments could be used in many of these locations,” the researchers said.

They will return to Greenland this year to conduct new studies on the experiment. They hope to find that the bacteria have successfully broken down any remaining diesel contamination.