Methane Ebullition Regulated by Hydrostatic Pressure Variations during Open-water Season in a Pit Lake

Abstract:

Methane ebullition has been monitored using echosounders in Base Mine Lake. This lake was formed by backfilling tailings in a mined-out pit, which was capped with 10 m of water. Residual hydrocarbons in the tailings produce methane bubbles that rise through the lake at various locations. High frequency (1 min – 30 min intervals) ebullition data was collected through the entire open-water season. Water level, bottom water temperature, wind speed, atmospheric pressure, and lakebed images were also collected to analyze the variations of ebullition. The results show that ebullition is primarily controlled by variations in total hydrostatic pressure. However, as the echosounder is floating beneath the water surface, the results could be impacted by the spatial heterogeneity of methane ebullition.