Limiting factors for hydrocarbon biodegradation at low temperature in Arctic soils

Abstract

Hydrocarbon fuel spills are common in the Arctic. But, little is known about hydrocarbon-degrading microflora in Arctic tundra soils or the potential for bioremediation of these soils. We examined mineralization of radiolabeled hydrocarbons in microcosms containing soils collected from sites across the Canadian Arctic. The soils all contained psychrotolerant microorganisms which mineralized dodecane and substantially removed total petroleum hydrocarbons (TPH) at 7°C. Dodecane mineralization was severely limited by both N and P. Dodecane mineralization kinetics varied greatly among different soils. Multiple regression analysis showed that soil N and TPH concentrations together accounted for 73% of the variability of the lag time preceding dodecane mineralization. Soil characteristics were less effective as predictors of mineralization kinetic parameters other than lag time. High total C concentrations were associated with high mineralization rate constants, and high sand contents were associated with long times for half-maximal dodecane mineralization. Very high concentrations of TPH (100 mg g −1 of dry soil) and heavy metals (e.g., 1.4 mg Pb g −1 of dry soil) did not prevent dodecane mineralization. Inoculation of soils with indigenous or non-indigenous hydrocarbon-degrading microorganisms stimulated dodecane mineralization. Bioremediation of hydrocarbon-contaminated Arctic tundra soils appears to be feasible, and various engineering strategies, such as heating or inoculating the soil, can accelerate hydrocarbon biodegradation.