Dry Mature Fine Tailings As An Oil Sands Reclamation Substrate

The objective of this research was to investigate the potential for native plant species to establish in Suncor’s mature fine tailings (MFT) and capped MFT as part of the solid landscape approach to reclamation of the materials. It was hypothesized that the chemical properties of the MFT would limit, if not prevent, plant germination and growth, and that capping with other waste materials could ameliorate these limitations. Two greenhouse experiments were conducted in 2006 to address the research objectives. In the first experiment, desiccated evaporative MFT was amended with peat-mineral mix and tailings sand and nine native grasses, nine native forbs and five native shrubs were assessed. In the second experiment, fresh evaporative and freeze thaw MFT were investigated without amendment under drained and undrained conditions; four native grasses, four native forbs and two native shrubs were assessed.

Plant growth was inhibited in MFT treatments compared to commercial potting soil. Native grasses were more tolerant of MFT than native forbs or shrubs. Freeze thaw and evaporative MFT had electrical conductivity, sodium adsorption ratio, total extractable hydrocarbons, benzene, toluene, ethylbenzene, xylene(s) and polycyclic aromatic hydrocarbons values that are detrimental to plant growth. Freeze thaw MFT contained higher concentrations of hydrocarbons than fresh or desiccated evaporative MFT but this did not result in poorer establishment. This suggests elevated hydrocarbon concentrations, not salinity or nutrient issues, are mainly responsible for these results. Evaporative MFT capped or mixed with tailings sand and a layer of peat mineral mix were most effective covers. The native grass A. trachycaulum, was most tolerant of MFT and performed better in undrained MFT than drained. Salinity was greater in treatments without drainage, but drainage conditions only negatively affected performance of C. canadensis, K. macrantha and S. spathula. MFT chemical properties reduced plant establishment but did not prevent it. Assessment of the effects capping treatments and depths have on plant response in fresh MFT is recommended.