Effects of temperature warming during a bioremediation study of natural and nutrient-amended hydrocarbon-contaminated sub-Antarctic soils

Although petroleum contamination is recognized as a significant threat to polar environments, documented research on the environmental consequences of terrestrial spills in cold regions is still scarce. Full-scale in situ remediation of petroleum-contaminated soils has not yet been used in Antarctica, partly because it has long been assumed that air and soil temperatures are too low for an effective biodegradation. To test this assumption, the effects of temperature on the hydrocarbon mineralization rate have been quantified during a field pilot study carried out on artificially contaminated sub-Antarctic soils. The field study was initiated in December 2000 on two selected soils of the Grande Terre (Kerguelen Archipelago, 69degrees42'E-49degrees19'S). The first site supported an abundant vegetal cover, while the second one was a desert soil exempt of plant material. Two series of five experimental plots (0.75 x 0.75 m) were settled firmly into each of the studied soils. Each plot received 500 ml of diesel fuel or Arabian light crude oil, and half of them were covered with a black plastic sheet. All the plots were sampled on a regular basis over a 2-year period. Under natural sub-Antarctic conditions, the field tests revealed that up to 95% of total hydrocarbons were degraded within 1 year, indicating that low temperatures (0-7degreesC) can still allow oil biodegradation by indigenous microorganisms. Soil coverage induced a small but permanent increase of the temperature in the surface soil of 2degreesC (annual mean) and favored the degradation of alkanes over aromatics. The present observations increase the number of possible scenarios involving controlled temperature design and effects in future in situ bioremediation strategies in sub-Antarctic soils. (C) 2004 Elsevier B.V. All rights reserved.