Effects of Capping Strategy and Water Balance on Salt Movement in Oil Sands Reclamation Soils

The success of oil sands reclamation can be impacted by soil salinity depending on the materials used for soil reconstruction and the capping strategies applied. Using both a greenhouse-based column experiment and numerical modeling, we examined the potential pathways of salt migration from saline groundwater into the rooting zone under different capping strategies (the type and the thickness of the barrier layer) and water balance scenarios. The experimental results showed that there would be salinity issues in the cover soil within several growing seasons if there was a shallow saline groundwater table and if the soil was not properly reconstructed. The thickness of the barrier layer was the most significant factor affecting the upward movement of saline groundwater and salt accumulation in the cover soil. The suitable thickness of the barrier layer for preventing the upward movement of saline groundwater and salt accumulation in the cover soil for each material varied. A numerical simulation for a 15-year period further indicates that, when the cover soil was 50 cm of peat-mineral soil mix and when wet, dry, or normal climatic conditions were considered, the minimum barrier thickness to restrain salt intrusion into the cover soil in the long term was about 75 or 200 cm for coarse tailings sand or overburden barrier material, respectively. In view of the above, to minimize salt migration into the rooting zone and ensure normal plant growth, oil sands reclamation should consider salt migration when designing soil capping strategies.

Characterizing Uncertainty in the Hydraulic Parameters of Oil Sands Mine Reclamation Covers and its Influence on Water Balance Predictions

One technique to evaluate the performance of oil sands reclamation covers is through the simulation of long-term water balance using calibrated soil–vegetation–atmosphere–transfer models. Conventional practice has been to derive a single set of optimized hydraulic parameters through inverse modelling (IM) based on short-term (

Hydraulic Redistribution in Slender Wheatgrass (Elymus trachycaulus Link Malte) and Yellow Sweet Clover (Melilotus officinalis L.): Potential Benefits for Land Reclamation

Hydraulic redistribution (HR) by plant roots can increase moisture content in the dry, mostly upper, parts of the soil. HR helps maintain the viability of fine roots, root hydraulic conductivity, microbial activity and facilitate nutrient uptake. Plants can supply water to other surrounding plants by HR under drought conditions. In oil sands reclamation areas in Northeastern Alberta, Canada, reconstructed soils commonly suffer from the problems of drought, high pH, salinity, and compaction, which often impact revegetation success. In this study, we investigated the HR potential of two herbaceous plants that are frequently present in oil sands reclamation sites: slender wheatgrass (Elymus trachycaulus Link Malte) and yellow sweet clover (Melilotus officinalis L.), using a vertically split-root growth setup and treatments with deuterium-enriched water. Our objective was to test the potential benefits of HR on drought responses of seedlings of the commonly used plant species for oil sand reclamation, balsam poplar (Populus balsamifera L.), when these plants were grown together under controlled environment conditions. We found that both wheatgrass and yellow sweet clover could redistribute water in the upward and downward directions. However, the amount of water released by the roots was not sufficient to alleviate the effects of drought stress on the associated balsam poplar seedlings. Longer-term field studies should be carried out in order to examine, under different environmental conditions, the potential benefits of HR in these herbaceous plants to the establishment and growth of other plant species that are used for land reclamation.

Microbial communities associated with barley growing in an oil sands reclamation area in Alberta, Canada

Microbial communities that colonize the plant rhizosphere and the root interior can ameliorate plant stress and promote growth. These plant–microbe associations are being investigated to assist in reclamation soils in northern Alberta. This study assessed the diversity of bacterial species associated with barley plants growing at different cover managements and slope positions in an oil sands reclamation area. Phospholipid fatty acid analysis of the microbial communities indicated that both cover type and slope, in addition to soil total and organic carbon, NH4+, and organic matter, were significant determinants of microbial community composition. However, analysis of denaturing gel gradient electrophoresis (DGGE) banding patterns revealed that while most bulk and rhizosphere soils differentiated by cover management, no clustering was observed in endophytes. In addition, techniques to assess culture-dependent endophytic bacteria revealed a dominance of the class Gammaproteobacteria, in which Enterobacteriaceae (44%), Xanthomonaceae (30%), and Pseudomonaceae (26%) were the most abundant families in this class. Several endophytic isolates also matched those from DGGE profiles. The results of this study suggest that plants growing on oil sands reclamation covers host a wide range of bacterial endophytes, which should be assessed as to their potential to assist plant establishment and growth at such sites.