Characterizing the Physical and Chemical Mass Transport of Dissolved Salts in Layered Oil Sands Waste Undergoing Reclamation
This research aims to characterize the physical and chemical transport processes driving the distribution of dissolved salts in experimental reclamation scenarios that layer centrifuged fine tailings, petroleum coke, and reclamation material. Six field lysimeters were constructed at an oil sands mine near Fort McMurray, Alberta to assess various layering scenarios under both saturated and unsaturated conditions. Physical characteristics (temperature, water content), pore water geochemistry, and bulk mineralogy were characterized through collection of samples via multi- level monitoring wells, cores, and data loggers. Complimentary laboratory column experiments were set up to monitor the migration of dissolved ions over time, and conservative transport models developed as a means of assessing the major mass transport processes controlling salt distribution. Logger data and pore water chemistry revealed that self-weight consolidation and seasonal freeze- thaw cycles facilitate a volume change in the CFT that translates to an advective release of pore water toward the surface. Depth profiles of major ions and electrical conductivity consistently demonstrate that dissolved salt concentrations become elevated at the surface of saturated systems without a reclamation cover due to evaporation. Data suggests evaporative solute concentration has a larger influence on pore water chemistry in saturated systems. Measurable analyte concentrations were not observed near the surface of unsaturated systems with petroleum coke, due to a lack of available pore water to act as a vehicle for salt movement. Column experiments support the field data, suggesting that the saturated arrangements are at greater risk of surface salt accumulation than unsaturated complements. Both field and column experiments demonstrate that petroleum coke cannot host exchange reactions that mitigate dissolved salt migration. Modeling results support the idea that advection - hydrodynamic dispersion is the primary transport regime in early time due to initially rapid settlement of CFT. In the long-term, transport transitions to primarily diffusion dominated.
Salts, Transport, Oil Sands, Reclamation, Geochemistry, Contaminant Transport, Hydrogeology
Master of Science (M.Sc.)