New paper presents model for representing the effects of freeze-thaw cycles on methanogenic hydrocarbon degradation

Monday, March 20, 2023

Cold regions are warming much faster than the global average, resulting in more frequent and intense freeze thaw cycles (FTCs) in soils. A new paper published in the journal Chemosphere investigated the effects of FTCs on toluene biodegradation using a combined experimental and model approach. The paper is authored by Mehdi Ramezanzadeh, a recent Masters graduate and current research assistant in the Ecohydrology Research Group. Co-authors from Ecohydrology Research Group include Stephanie Slowinski, Fereidoun Rezanezhad, Kathleen Murr, Christina Lam, Christina Smeaton, Clement Alibert, Marianne Vandergriendt, and Philippe Van Cappellen. The experiment and the numerical simulation show that methanogenic degradation is the primary toluene attenuation mechanism under the electron acceptor-limited conditions experienced by the soil samples, representing 74% of the attenuation, with sorption contributing to 11%, and evaporation contributing to 15%. Also, the model predicted contribution of acetate-based methanogenesis to total produced CH4 agrees with that derived from the 13C isotope data. Freezing-induced soil matrix organic carbon release was shown to be an important process causing DOC increase following each freezing period according to the calculations of carbon balance and SUVA index. The simulation results of a no FTC scenario indicate that, in the absence of FTCs, CO2 and CH4 generation would decrease by 29% and 26%, respectively, and that toluene would be biodegraded 23% faster than in the FTC scenario. The model presented in this paper, which was validated with the experimental data, advances our ability to represent FTC processes in soils and their impacts on the degradation of toluene and other PHCs. The paper can be accessed HERE.