Linking soil-freezing characteristics to bioremediation for contaminated cold-climate soil: Review of recent progress

ABSTRACT: Soil is a complex material in which physical, chemical, and biological processes are occurring. Linking physical and chemical soil data to biological data can reveal the underlying interactive mechanisms that drive soil microbial responses. Seasonal soil freezing is an excellent example of such soil processes interacting closely. This study reviews the accumulated outcomes of recent bioremediation research into how soil-freezing characteristic curves (SFCCs) are related to soil biological data in hydrocarbon-contaminated soils in cold climates. Soil biostimulation treatments change the SFCCs of petroleum hydrocarbon-contaminated site soils and the conventional physical soil parameters of the SFCC (θ = αTβ) can be effectively related to the feasibility of cold-tolerant bioremediation and its optimization. This finding enabled us to optimize unfrozen water retention in favour of cold-tolerant passive bioremediation extended to seasonal freezing conditions, beyond the short active treatment season, resulting in significant hydrocarbon biodegradation in freezing and frozen soil. Furthermore, linking soil-freezing data and microbial data led to the development of an integrated soil respiration and thermal modelling tool that is useful for optimizing soil treatments for cold-tolerant bioremediation in remote cold regions, prior to site remediation.