In Situ Biodegradation Potential in Petroleum Hydrocarbon-Contaminated Soils Exposed to Seasonal Freeze-Thaw Conditions.

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Petroleum hydrocarbons are non-aqueous phase liquids (NAPLs) that include carcinogenic and toxic organic compounds, and are a cause for concern in soil environments impacted by oil extraction and transportation, accidental oil spills, and the disposal of oil sands wastes. According to the Federal Contaminated Sites Inventory, the most frequently identified contaminants in Canada are petroleum hydrocarbons, and many contaminated sites in Canada are influenced by cold-climate seasonality. Stimulating indigenous cold-adapted bacteria to degrade hydrocarbons has been considered a feasible, less destructive, and low-cost remedial option for hydrocarbon-contaminated soils at summer temperatures in cold climates. However, soils in cold regions remain partially frozen and frozen for 6 to 9 months each year, which greatly shortens the active remediation period, and current remediation practices in cold climates have only been considered effective during short summers (2-4 months), mainly due to colder temperatures and limited site accessibility during non-summer months. Dr. Won Jae Chang's recent study, however, indicated a significant potential for microbial enhancement in hydrocarbon-contaminated soils under seasonal freeze-thaw conditions during pre- and post-summers in cold climates. This new finding provides the rationale for this proposed pilot-scale biopile field study entitled In Situ Biodegradation Potential in Petroleum Hydrocarbon-Contaminated Soils Exposed to Seasonal Freeze-Thaw Conditions. There is a lack of field data about the extent of hydrocarbon biodegradation and microbial response in contaminated soils subjected to natural seasonal freeze-thaw temperatures. Changes in soil temperatures and unfrozen soil water during seasonal freeze-thaw periods are much slower than the rates used in many previous laboratory freeze-thaw studies, and provide the real conditions needed for native hydrocarbon-degrading bacteria to survive and/or adapt to environmental stresses in cold soils. The proposed study will generate field data by monitoring microbial activity under natural temperature cycles and will therefore provide new insight for bioremediation in environmentally challenging conditions.