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Modelling microbial processes of soil organic matter mineralization and methane production

  • Author / Creator
    Venegas Garcia, Pablo
  • Increased anthropogenic greenhouse gas emissions have gained attention from researchers and world leaders due to the potential for global warming. Part of the primary greenhouse gas emitters come from the agriculture and oil and gas industrial sectors. The sources of two prioritized greenhouse gases, carbon dioxide and methane, are now the subject of extensive research because of the adverse effects of such gases on a global scale. Particularly, microbial biodegradation of organic compounds is under consideration due to microbial capacity to produce different greenhouse gases at high rates or scales, including carbon dioxide and methane, depending on environmental or soil features. For example, rapid soil organic matter (SOM) mineralization derived from increased microbial degradation activities due to labile substrate availability in soils can elevate atmospheric carbon dioxide in short periods. Also, under anaerobic conditions, specific microbial communities can slowly degrade hydrocarbons found in oil sand tailing ponds, increasing atmospheric methane concentrations over a long time.

    In this thesis, we formulated data-validated mathematical models to estimate carbon dioxide and methane emissions from microbial organic matter biodegradation processes in soils. Under aerobic conditions, a base model captures the biodegradation kinetics of labile compounds and soil organic matter under carbon and nitrogen stoichiometric constraints. The model quantifies the necessary labile carbon-to-nitrogen to increase microbial SOM mineralization and time to achieve a maximum degradation rate for different nutrient-rich soils. An extended version of this model allows us to include soil health indicators to understand the dynamic interaction between plant microbes and soils. Our theoretical results for this specific approach reveal a threshold for which the input of fertilizers would be needed for plant growth, providing insightful information that might benefit the agricultural sector for agricultural soil management. Considering anaerobic conditions, a mechanistic mathematical model allowed us to quantify hydrocarbon degradation kinetics and methane emissions from oil sands tailings. We collected experimental data to evaluate hydrocarbon degradation rates subject to different temperatures to capture a broad spectrum of degradation kinetics, which are required to incorporate the temperature variations in oil sands tailing ponds and end pit lakes into the model. Our results quantify the differences between the model's predictions and governmental reports, showing a significant discrepancy. Furthermore, the model predicts that hydrocarbon concentration in oil sands tailing ponds would reach a steady state when a constant input of tailings and diluents into ponds is assumed, implying a constant methane biogenesis rate.

  • Subjects / Keywords
  • Graduation date
    Fall 2024
  • Type of Item
    Thesis
  • Degree
    Doctor of Philosophy
  • DOI
    https://doi.org/10.7939/r3-bsb1-x272
  • License
    This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.