Conceptualizing a Stress-Tolerant Bioremediation Strategy for Petroleum Hydrocarbon-Contaminated Soils in Cold Climates: A Preliminary Review

The stress-tolerance of sub-zero microbial activity in seasonally freezing and thawing petroleum hydrocarbon (PHC)-contaminated cold-climate soils, as well as associated soil physical and chemical factors for creating unfrozen microsites in cryosoils, have not yet been extensively understood. As soils freeze at in situ seasonal rates, soil microenvironments are subjected to multiple stresses—sub-zero temperatures, osmotic stress, and water scarcity. Microbial survivors in frozen soils are likely adapted to those multiple stresses. The dual tolerance to high salinity and low temperatures of hydrocarbon degraders has been reported in non-saline PHC-impacted soils from polar sites. Understanding how indigenous hydrocarbon-degrading bacteria abundant in freezing PHC-contaminated soils is vital for developing bioremediation strategies for cold-climate sites. We revealed that sub-zero biodegradation activity deviates from the current understanding of biological activity that is based on the bioavailability of hydrocarbons and soil bioremediation conditions, suggesting a new stress-tolerant bioremediation concept for seasonally freezing and thawing PHC-contaminated soils. This study reviews the recent advances in bioremediation knowledge and practices for PHC-contaminated soils in cold climates with a focus on seasonal freeze/thaw stresses. This study extracts information about fundamental underlying soil drivers in the purpose of conceptualizing a new stress-tolerant bioremediation strategy for PHC-contaminated soils in cold climates.