Methane (CH4) ebullition is a natural process that can occur in lakes and other water bodies. It is mainly a result of CH4 being produced through the decomposition of organic matter by anaerobic bacteria and archaea in sediments. The produced CH4 can accumulate within the sediments, forming large bubbles which can achieve a strong enough buoyancy to breach the sediment-water interface and then rise through the water column until reaching the surface. The concern of CH4 ebullition is that it significantly contributes to atmospheric greenhouse gas concentrations and can adversely affect water quality.
This process has been studied at Base Mine Lake, the first full-scale pit lake in the Athabasca oil sands region, by former students David Hurley, Kai Zhao and Lauren Ing. Understanding the CH4 dynamics in Base Mine Lake can help assess whether pit lakes are a viable land remediation strategy in the oil sands industry. Kai’s work was focused on assessing how CH4 ebullition at Base Mine Lake is affected by factors such as atmospheric pressure variations during ice cover. Using an echo sounder mounted below the ice, Kai showed how ebullition events corresponded to atmospheric pressure drops below a minimum threshold that was approximately equal to the long-term average pressure. Kai’s study also observed that these increased ebullition events were responsible for temporary increases in turbidity. Kai also studied the rise of bubbles in the laboratory (photo below).
Lauren Ing, who recently graduated, focused on quantifying the ebullitive fluxes at Base Mine Lake through the deployment of bubble traps at multiple locations over a two-year period. Lauren also collected ice cores which were able to show how CH4 bubbles can transport oil from the bottom of the lake to the surface waters.
Talia Houston will be studying the spatial patterns of CH4 ebullition in Base Mine Lake. Talia’s passion for understanding methane bubbling at Base Mine Lake began with her very first visit. The photo below, taken during her field visit in August 2024, captures the hydrocarbon sheen on the lake’s surface.
This project is supervised by Dr. Greg Lawrence and Dr. Ted Tedford.
