Effects of snowmelt infiltration on sulfate redistribution in a reclamation cover

Abstract

Oil sands mining in Alberta involves the removal of large amounts of overburden to access the oil sands. Reclamation of these overburden systems remains a challenge for the industry. Currently, there is a lack of understanding of how overburden cover systems in Alberta oil sands will function with respect to the water balance and long-term build-up and release of solutes. In this research, a conceptual model was developed, informed by interpretations of field observations. A one-dimensional heat, flow, and solute transport model was built to simulate the long-term evolution of sulfate under varying assumptions of snowmelt infiltration and sulfate production. The findings show that snowmelt infiltration is a critical control on the distribution and export of sulfates within the system. Simple infiltration models over-predict runoff and under-predict infiltration. Enhanced snowmelt infiltration scenarios are more consistent with field observations and therefore more representative of the system. The model suggested that larger snowmelt infiltration volumes result in increased soil salinization in the shallow subsurface horizon of the profile, likely due in part to evapoconcentration. Increased infiltration also resulted in increased net percolation, which results in more solute leaching to the deeper groundwater system in the short term. In the long term, it is suspected enhanced net percolation and increased infiltration might lead to a reduction in the salinity of the reclamation cover, reversing the soil salinization.