Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 55, Issue 13, Pages 9172-9180Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.0c07502
Keywords
petroleum hydrocarbon; biodegradation; cold climate; contaminated frozen soil; unfrozen water; seasonal freezing; soil-freezing characteristic curve
Categories
Funding
- Natural Sciences and Engineering Research Council of Canada [RGPIN 059022014]
- Canada Foundation for Innovation [33982]
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Manipulating the retention of unfrozen water in freezing contaminated soil to achieve prolonged bioremediation in cold climates has not yet been formulated. This study shows the effects of nutrient and zeolite amendments on unfrozen water retention and hydrocarbon biodegradation in field-aged, petroleum-contaminated soils undergoing seasonal freezing. Nutrients were found to be predominant during early freezing, while increased unfrozen water retention associated with added zeolite surface areas was critical in extending hydrocarbon biodegradation into the frozen phase.
Manipulating the retention of unfrozen water in freezing contaminated soil to achieve prolonged bioremediation in cold climates remains unformulated. This freezing-induced biodegradation experiment shows how nutrient and zeolite amendments affect unfrozen water retention and hydrocarbon biodegradation in field-aged, petroleum-contaminated soils undergoing seasonal freezing. During soil freezing at a site-specific rate (4 to -10 degrees C and -0.2 degrees C/d), the effect of nutrients was predominant during early freezing (4 to -5 degrees C), alleviating the abrupt soil-freezing stress near the freezing-point depressions, elevating alkB1 gene-harboring populations, and enhancing hydrocarbon biodegradation. Subsequently, the effect of increased unfrozen water retention associated with added zeolite surface areas was critical in extending hydrocarbon biodegradation to the frozen phase (-5 to -10 degrees C). A series of soil-freezing characteristic curves with empirical alpha-values (soil-freezing index) were constructed for the tested soils and shown alongside representative curves for clays to sands, indicating correlations between alpha-values and nutrient concentrations (soil electrical conductivity), zeolite addition (surface area), and hydrocarbon biodegradation. Heavier hydrocarbons (F3: C16-C34) notably biodegraded in all treated soils (22-37% removal), as confirmed by biomarker-based analyses (17 alpha(H),21 beta(H)-hopane), whereas lighter hydrocarbons were not biodegraded. Below 0 degrees C, finer-grained soils (high alpha-values) can be biostimulated more readily than coarser-grained soils (low alpha-values).
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