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dc.contributor.authorDompierre, Kathryn
dc.contributor.authorLindsay, Matthew
dc.contributor.authorCruz-Hernández, Pablo
dc.contributor.authorHalferdahl, Geoffrey
dc.identifier.citationDompierre, K.A., Lindsay, M.B.J., Cruz-Hernández, P. & Halferdahl, G.M. (2016). Initial geochemical characteristics of fluid fine tailings in an oil sands end pit lake. Science of the Total Environment, 556, 196–206.
dc.description.abstractGeochemical characteristics of fluid fine tailings (FFT) were examined in Base Mine Lake (BML), which is the first full-scale demonstration oil sands end pit lake (EPL) in northern Alberta, Canada. Approximately 186 M m3 of FFT was deposited between 1994 and 2012, before BML was established on December 31, 2012. Bulk FFT samples (n = 588) were collected in July and August 2013 at various depths at 15 sampling sites. Temperature, solids content, electrical conductivity (EC), pH, Eh and alkalinity were measured for all samples. Detailed geochemical analyses were performed on a subset of samples (n = 284). Pore-water pH decreased with depth by approximately 0.5 within the upper 10 m of the FFT. Major pore-water constituents included Na (880 ± 96 mg L−1) and Cl (560 ± 95 mg L-1); Ca (19 ± 4.1 mg L-1), Mg (11 ± 2.0 mg L-1), K (16 ± 2.3 mg L-1) and NH3 (9.9 ± 4.7 mg L−1) were consistently observed. Iron and Mn concentrations were low within FFT pore water, whereas SO4 concentrations decreased sharply across the FFT-water interface. Geochemical modeling indicated that FeS(s) precipitation was favoured under SO4-reducing conditions. Pore water was also under-saturated with respect to gypsum [CaSO4·2H2O], and near saturation with respect to calcite [CaCO3], dolomite [CaMg(CO3)2] and siderite [FeCO3]. X-ray diffraction (XRD) suggested that carbonate-mineral dissolution largely depleted calcite and dolomite. X-ray absorption near edge structure (XANES) spectroscopy revealed the presence of FeS(s), pyrite [FeS2], and siderite. Carbonate-mineral dissolution and secondary mineral precipitation have likely contributed to FFT dewatering and settlement. However, the long-term importance of these processes within EPLs remains unknown. These results provide a reference for assessing the long-term geochemical evolution of oil sands EPLs, and offer insight into the chemistry of pore water released from FFT to the overlying water cover.en_US
dc.rightsAttribution-NonCommercial-NoDerivs 2.5 Canada*
dc.subjectoil sandsen_US
dc.subjectend pit lakesen_US
dc.subjectprocess-affected wateren_US
dc.subjectmine closureen_US
dc.titleInitial geochemical characteristics of fluid fine tailings in an oil sands end pit lakeen_US
dc.description.versionPeer Revieweden_US

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