Enhanced bioremediation of petroleum hydrocarbon-contaminated soils under natural seasonal freeze-thaw conditions: the rate and extent of hydrocarbon biodegradation and microbial community response during on-site soil phase changes

This study is a bioremediation field study for field-aged, petroleum-contaminated, unsaturated fine-grained soils at a cold-climate site. Treated and untreated (control) pilot-scale biopiles (3,200 kg each) were installed before a long winter in October 2015, on the ground at an outdoor soil treatment facility in Saskatoon, Saskatchewan, Canada (52º08´N 106º41´W). Starting in November, the biopile experiments were conducted over 260 days, during which the biopiles underwent seasonal soil thermal phase changes from unfrozen to freezing, deep-frozen, thawing and completely thawed. This study uniquely provides the rates and extents of hydrocarbon biodegradation and seasonal shifts in microbial community compositions in the treated and untreated biopiles under the seasonal soil temperature regimes of the cold site, mainly during the unconventional soil treatment period for cold climates.