Nickel geochemistry of oil sands fluid petroleum coke deposits, Alberta, Canada
Date
2018-04-30
Authors
Nesbitt, Jake A.
Robertson, Jared M.
Swerhone, Lawrence A.
Lindsay, Matthew
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Canadian Science Publishing
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Article
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Abstract
Nickel (Ni) leaching from oil sands petroleum coke can have toxicological effects on aquatic organisms. However, geochemical controls on Ni release, transport and attenuation within coke deposits remains limited. We examined the geochemistry of fluid coke and associated pore-waters from two deposits at an oil sands mine near Fort McMurray, Alberta, Canada. Synchrotron-based micro-X-ray fluorescence (µXRF) and micro-X-ray absorption near edge structure (µXANES) spectroscopy show that Ni(II)-porphyrin complexes dominate, but inorganic phases including Ni(II)-sulfide and Ni(II)-oxide comprise a minor component of fluid coke. Sequential chemical extractions suggested that sorption-desorption reactions may influence Ni mobility within fluid coke deposits. Although only a small proportion of total Ni (< 4%) is susceptible to leaching under environmentally-relevant concentrations, dissolved Ni concentrations (n = 65) range from 2 to 120 μg/L (median 7.8 μg/L) within the two deposits and generally decrease with depth below the water table. Pore-water Ni concentrations are negatively correlated with pH, but not with dissolved sulfate, bicarbonate, or chloride. Overall, our findings suggest that pore-water pH and sorption-desorption reactions are principal controls on dissolved Ni concentrations within oil sands fluid petroleum coke deposits.
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Keywords
X-ray absorption spectroscopy, geochemistry, nickel, oil sands, petroleum coke
Citation
Nesbitt, J.A., Robertson, J.M., Swerhone, L.A. & Lindsay, M.B.J. (2018). Nickel geochemistry of oil sands fluid petroleum coke deposits, Alberta, Canada. FACETS, 3, 469–486. https://doi.org/10.1139/facets-2017-0115
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Citation
Nesbitt, J.A., Robertson, J.M., Swerhone, L.A. & Lindsay, M.B.J. (2018). Nickel geochemistry of oil sands fluid petroleum coke deposits, Alberta, Canada. FACETS, 3, 469–486. https://doi.org/10.1139/facets-2017-0115