| Composite tailings (CT) are produced as a measure to reduce the volume of oil sand tailings by accelerating self-weight consolidation. Water released in the process is known as CT water, which is saline, making the reclamation of CT for revegetation difficult. A growth chamber study was conducted to monitor the effect of saline CT water on the growth of dogwood (Cronus stolonifera, Michx.), and highlander grass (Elymus trachycaulus subsp. Trachycaulus), and to determine the suitable thickness of an unsaturated tailings sand cap separating CT water and the surface reclamation material. Eighteen columns were constructed, each of 56 cm in diameter and 100 cm in height. Each column was filled with tailings sand to a depth of 65 cm and then capped with 30 cm of reclamation material consisting of soil and peat mix. Constant CT water levels at 0, 30, and 60 cm from the soil/sand interface were maintained throughout the experiment. Dogwood and highlander grass were grown in these columns for one year. Tap water was applied at 3 mm (low) and 6 min (high) every alternate day to dogwood, and every third day to highlander grass to simulate the dry and the wet conditions respectively. Treatments receiving low irrigation showed significant increase in the salt content in the sand cap in one year. During the drought period, access to the saline CT water kept the plants alive for 66 days in the growth chamber condition. CT water level at 60 cm below the soil/sand interface prevented the accumulation of salt in the rooting zone. Based on the shoot dry weight data, highlander grass was found to be more salt tolerant than dogwood. |
