A comprehensive framework for determining efficient bioremediation strategies for petroleum hydrocarbon-contaminated soils in cold regions**

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There are a significant number of petroleum hydrocarbon-contaminated sites in Canadian northern territories and bioremediation, where soil microbes transform hazardous petroleum hydrocarbon compounds to less hazardous or non-hazardous products, is considered a cost-effective technology for clean up of those sites. However, low temperatures in cold regions may limit microbial degradation activity, and thus soil heating or optimizing bioremediation for different temperature regimes is required for improving bioremediation performance. Biostimulation by addition of nutrients, moisture, and oxygen to the contaminated soils can enhance microbial activity in northern sites. However, it is unclear if biostimulation can be tailored to the hydrocarbon-degrading microbial community only, rather than other soils microbes that may not be involved in hydrocarbon biodegradation. This study will systematically assess how temperature regimes and biostimulation affect the microbial community composition and activity, and if the timing of nutrient addition could lead to more efficient bioremediation operations adapted to low temperatures. The assessment of new biostimulation approaches will be based on data collected from microcosms and as well as pilot-scale bioreactors operated using various site soils and at different temperature regimes relevant to the sites. Residual, un-degraded fractions of contamination that are above regulatory clean-up levels is a common challenge. As part of this study, we will assess if the soil aggregate micro-structure and in particular, the fraction of pores inside soil aggregates which are not accessible to soil microorganisms, is a determining factor for bioremediation endpoints. The studies will be conducted in close collaboration with the industrial partner, Hydro-Quebec, who is interested in the sustainable development of the north and its communities. Undergraduate, PhD and postdoctoral students will be trained in this project on new approaches for effective bioremediation in northern sites.**