Valdez is located in south-central Alaska and is the location where oil tankers are loaded with crude oil piped in from the North Slope of Alaska. The trans-Alaska pipeline has been running since the late 1970s.

Jonathan Bower and colleagues took snow cores from representative sites around Valdez and also sampled cores from the more heavily populated region of Juneau, on Douglas Island, for comparison. This area has a similar climate to that at Valdez but it has no petroleum transport infrastructure.

The researchers analysed the samples for a variety of chemicals, including alkylated aromatics, such as benzene, toluene, ethylbenzene and xylene (a group of compounds known as BTEX). They did this using several methods, including ion chromatography, absorption spectrometry, gas chromatography and mass spectrometry.

The team found significant concentrations of BTEX in the snowpacks around Valdez. "Our result suggests a source of pollutants in Valdez that is not found at Juneau," Bower told environmentalresearchweb. "One possibility is the trans-Alaska pipeline."

While the researchers were not able to determine a specific source for the alkylated organics, they say the most likely source would be the Ballast Water Treatment Facility. At the time of sampling, ballast water offloaded from the holds of tankers was treated at this facility and fumes were vented directly to the atmosphere, explained Bowers. He said that the pollution in this region might be decreased by finding a way to control and recover the fumes rather than venting them straight into the air.

"A good start to this idea has been the implementation of double-hulled tankers for transporting crude oil by the industry," he added. These tankers allow ballast waters to be stored near the ship, away from the areas that contain crude oil. This means that the ballast waters require less treatment.

Bowers says he hopes to see more studies into different types of contaminants in snow. "Scientists have already found snow to be a dynamic and expansive reservoir for many types of chemicals and reactions," he said. "The more we understand what is in the snow, the better prepared we are to understand its role in cycling of pollutants in cold regions."

The team's next step is to look at oxidant formation on snow and ice, and the role that these species play in attenuating pollutants in the environment.

The work was published in Environmental Research Letters as part of a Focus Issue on Connections between Atmospheric Chemistry and Snow and Ice.