Sulfur biogeochemistry of syncrude untreated composite tailings and those undergoing restoration

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Syncrude, ranked as the world's largest producer of synthetic crude from oil sands and the biggest single source in Canada, faces a number of significant challenges associated with management of its tailings ponds. Air emissions monitors in the area around the Fort McMurray oil sands have identified a steady increase in sulphur-based pollutants, including hydrogen sulfide (H2S). These emissions occur from tailings areas currently under reclamation. Recently, a dewatering well was shutdown on Syncrude's Mildred Lake property due to safety risks associated with H2S releases. Other, potentially larger scale H2S releases are possible in the future. The goal of the proposed research is to provide the necessary science-based understanding of sulphur dynamics for Syncrude to manage its composite tailings (CT) waste more effectively. The objectives of the proposed three-year field and laboratory collaborative research project in partnership with Syncrude are to: (1) identify if microbial activity occurring within composite tailings (CT) is linked to the generation of hydrogen sulphide gas, (H2Sg), and (2) assess CT sulphur biogeochemical evolution associated with Syncrude's first fen restoration project, providing an understanding of any potential positive or negative geochemical implications for tailings restoration. The proposed research will be carried out over a three-year time frame to assess CT sulphur biogeochemistry over sufficient spatial and temporal scales to (1) establish CT deposit heterogeneity and (2) identify CT evolution under fen creation. The results of the proposed research will provide Syncrude with new understanding of their tailings that will enable the company to develop strategies to manage its tailings more effectively with respect to sulphur in accordance with Directive 74. It will benefit Canada through improved environmental management of oil sands tailings, increased sustainability of oil sands activities and the training of 16 HQP in leading edge environmental science research. These HQP will develop the critical skills and experience in tailings exploration and biogeochemical management that will be needed for the future of the oil sands in Canada.