Manipulation of unfrozen water retention by nutrient and zeolite amendments extents biodegradation of petroleum hydrocarbons at sub-zero temperatures

This study demonstrated the enhanced biodegradation resilience in seasonally freezing soil from 4 to -10 °C for 150 days since January 2017 in Saskatoon, Saskatchewan, Canada (52° 8' N 106° 41' W). Petroleum hydrocarbon-contaminated unsaturated soil was treated using N-P-K-based nutrient, peat moss and zeolite. The soil freezing characteristic curve (SFCC) shifted in the treated soils compared to the untreated soil. The shift of SFCC was expressed using a, conventional freezing characteristic fitting constant. Soil treatment increased the a values from 0.06 to 0.1 due to lower freezing point, retarded thermal phase transition rate and reduced soil water in large pores by the redistribution of the soil water to small pores. Biomarker-diagnosed F3 (C16-C34) removals were 37% in nutrient and peat moss 4% treated soil, and its 24% occurred between 4 and -5 °C due to high nutrient (249 mg N/kg). F3 removals in nutrient and zeolite treated soil were 34%, and its 22% occurred from -5 to -10 °C due to high surface area by zeolite. F2 (C10-16) was little removed. Analysis of bacterial communities by metagenome sequencing via Illumina Miseq of 16S rRNA V4 amplicons along with the removal of hydrocarbons in freezing soil.