Field studies within the SoilCAM project were conducted at two test sites: Trecate in northern Italy and the Norwegian airport at Gardermoen. Both the chosen test sites display organic contaminants and are typical of situations that are difficult to avoid – i.e. the accidental or continuous release of degradable contaminants in permeable soils. The soil systems at these sites are vulnerable to adverse contamination effects, featuring extensive areas of highly permeable subsurfaces where sand and gravel are situated beneath the surface.
The Trecate test site is part of the Po River plain aquifer in Italy’s Piemonte region. In 1994, a large-scale oil well blow-out took place in the region, which was caused by a tank explosion and released approximately 15,000 cubic meters of middleweight crude oil overland, contaminating both soil and groundwater. Since then, the site has been subject to monitoring and remediation programs. The project’s geophysical test site is located on a small part of the contaminated area where three new boreholes with 24 electrodes have been installed to monitor the effects of the contamination. Ever since the oil spill event, non-aqueous-phase-liquids have been detected floating on the water table. This site illustrate the damage of a single large-scale oil spill event with interaction between hydrocarbons, bacteria and various soil compounds that are needed for microbial hydrocarbon degradation in a permeable system. The team monitored seasonal fluctuation of water levels on the movement of contaminants from the near-surface layers to the groundwater, as the groundwater levels in the area are higher at the end of the summer due to recharge from agricultural irrigation.
The second site is situated on the Gardermoen aquifer 40 km north of Oslo. Gardemoen is also the name of Norway’s largest airport at the same location. Gardermoen acts as the main domestic hub and international airport for Norway with more than 21 million passengers travelling through the airport in 2011. The opening of the airport in 1998 was considered to be controversial, as it is situated at the country’s largest rain-fed unconfined aquifer. The area receives approximately 800mm in rainfall each year and is a glacial contact delta. The environmental requirements of the new airport were the strictest in the world at the time. However, there are a number of challenges to be met by the airport. Large amounts of de-icing chemicals are needed to keep the airport functioning in winter, i.e. removal of jet-fuel (propylene glycol on aeroplanes and potassium formate on the runways), which could potentially be an environmental risk. Every winter, 1000-2000 tons of 100% propylene glycol and approximately 200 tons of potassium formate are spread for removal of ice and snow. About 20 % of these chemicals are released into the surrounding areas, where they mix with snow and infiltrate the soil when snowmelt starts in spring. Although these de-icing chemicals used to remove snow and ice in winter are easily degradable, they still constitute the main threat to the groundwater because of the potential of overloading the system.
Liβner H., Wehrer M., Bloem E., and Totsche K.U. 2011. Soil Heterogenity Strongly Affects Fate and Transport of Deicing Chemicals, Geophysical Research Abstracts, Vol. 13, EGU2011-7529-1, 2011.
Article: Getting to the root of contamination problems, published in the magazine Science, Technology and Innovation Projects, 19 digital edition 2. Insight publishers.