Coke As An Amendment To Mature Fine Tailings

Mature fine tailings (MFT) and coke are waste products of the oil sands industry which can potentially be used in reclamation after oil sands mining, but they have chemical and physical properties that make them inhospitable for plant growth and development, such as high concentrations of sodium, sulphate, chloride and total extractable hydrocarbons. A greenhouse study was conducted to determine whether substrates of various mixtures of MFT, tailings sand, peat mineral mix, coke and fertilizer would support germination, emergence and growth of three grass species commonly used for oil sands reclamation. These grass species were Agrostis scabra (ticklegrass), Elymus trachycaulus (slender wheat grass) and Festuca saximontana (rocky mountain fescue). Various soil and vegetation parameters were monitored for a period of 112 days in the greenhouse. Chemical and physical properties were determined in all mix substrates before and after the greenhouse study.

Plant growth was most inhibited in treatments with high proportions of MFT and coke. A. scabra and F. saximontana were most affected by MFT and coke, while E. trachycaulus was least affected. Plant performance varied with substrate, amendment and capping treatments. Amended and capped MFT plants performed better than others growing in unamended and uncapped MFT. Treatments with high MFT had exchangeable ions and hydrocarbons that could be detrimental to plant growth. Plants survived in coke; however, a reduction in biomass, plant density, cover and health was observed. This may be due to its coarse texture and may increase the potential for water stress in plant species. Suggested future research: (1) look at effects of site modification, including chemical bioavailability and soil nutrient conditions; (2) evaluate different capping materials and depths that could increase and ensure plant growth in the long term; (3) identify substrate mixes to prevent soil water loss and improve the soil nutrient content for a more hospitable plant growing environment; (4) characterize fungi and bacteria present in mature fine tailings and coke and their interactions – mycorrhizae infection in key plant species may increase reclamation success.