title: Trace metal mobilization from oil sands froth treatment thickened tailings exhibiting acid rock drainage.
abstract: Froth treatment thickened tailings (TT) are a waste product of bitumen extraction from surface-mined oil sands ores. When incubated in a laboratory under simulated moist oxic environmental conditions for ~450d, two different types of TT (TT1 and TT2) exhibited the potential to generate acid rock drainage (ARD) by producing acid leachate after 250 and 50d, respectively. We report here the release of toxic metals from TT via ARD, which could pose an environmental threat if oil sands TT deposits are not properly managed. Trace metal concentrations in leachate samples collected periodically revealed that Mn and Sr were released immediately even before the onset of ARD. Spikes in Co and Ni concentrations were observed both pre-ARD and during active ARD, particularly in TT1. For most elements measured (Fe, Cr, V, As, Cu, Pb, Zn, Cd, and Se), leaching was associated with ARD production. Though equivalent acidification (pH2) was achieved in leachate from both TT types, greater metal release was observed from TT2 where concentrations reached 10,000ppb for Ni, 5000ppb for Co, 3000ppb for As, 2000ppb for V, and 1000ppb for Cr. Generally, metal concentrations decreased in leachate with time during ARD and became negligible by the end of incubation (~450d) despite appreciable metals remaining in the leached TT. These results suggest that using TT for land reclamation purposes or surface deposition for volume reduction may unfavorably impact the environment, and warrants application of appropriate strategies for management of pyrite-enriched oil sands tailings streams.
authors.affiliation: Department of Renewable Resources, University of Alberta, Edmonton, AB, T6G 2E3, Canada.
authors.forename: Alsu
authors.initials: A
authors.lastname: Kuznetsova
authors.affiliation: Department of Renewable Resources, University of Alberta, Edmonton, AB, T6G 2E3, Canada.
authors.forename: Petr
authors.initials: P
authors.lastname: Kuznetsov
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada.
authors.forename: Julia M
authors.initials: JM
authors.lastname: Foght
authors.affiliation: Department of Renewable Resources, University of Alberta, Edmonton, AB, T6G 2E3, Canada. Electronic address: tariq.siddique@ualberta.ca.
authors.forename: Tariq
authors.initials: T
authors.lastname: Siddique
mesh_terms: D003890:Desiccation; D004784:Environmental Monitoring; D007220:Industrial Waste / Q000032:analysis; D008670:Metals / Q000032:analysis / Q000737:chemistry*; D008906:Mining; D061329:Oil and Gas Fields; D012037:Refuse Disposal / Q000379:methods*; D014131:Trace Elements / Q000032:analysis / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D007220:Industrial Waste; D008670:Metals; D014131:Trace Elements; D014874:Water Pollutants, Chemical
keywords: Acid rock drainage; Oil sands; Pyrite oxidation; Thickened tailings; Trace metals in leachate