Effect of high salinity tailings waters produced from gypsum treatment of oil sands tailings on plants of the boreal forest

Bitumen extraction methods currently in use in the operating oil sands plants produce large volumes of fluid tailings. Ions leached from the ore and added by process chemicals during the extraction process result in tailings waters containing elevated ionic content relative to the non-process-affected waters of the area, in particular the sodium, sulfate, and chloride ions. It is anticipated that the areas requiring reclamation will be affected by this high salinity of the process waters. The objectives of this study were to test the impact of a tailings alternative (consolidated tailings process, based on gypsum treatment of extraction tailings) on the viability of plant species of the northern boreal forest and to determine the relative salt tolerance and suitability of selected plant species for land reclamation. Seedlings were grown for 4 weeks in a greenhouse in solution culture containing mineral nutrients and various dilutions of consolidated tailings water and with Na2SO4 additions (1 g L−1 and 3 g L−1). Of all examined plant species, raspberry and strawberry seedlings were the most susceptible to damage, while the seedlings of white spruce, black spruce and lodgepole pine survived, but showed some effects. In the willow and aspen seedlings, there was a rapid loss of leaves, which were quickly replaced by new, morphologically different leaves. Dogwood and hybrid poplar showed high tolerance to all treatments.