Challis, Jonathan K.Parajas, AngeliqueAnderson, Julie C.Asiedu, EvelynMartin, Jonathan W.Wong, Charles S.Ross, Matthew S.2021-06-212022-05-312022-05-312020Challis et al. (2020). Photodegradation of bitumen-derived organics in oil sands process-affected water. Environmental Science: Processes and Impacts, 22, 1243-1255. https://doi.org/10.1039/D0EM00005Ahttps://hdl.handle.net/20.500.14078/2360The chemical composition of water-soluble organics in oil sands process-affected water (OSPW) is primarily composed of natural constituents of bitumen that are solubilized and concentrated during aqueous extraction of oil sands. OSPW organics are persistent and acutely toxic, and a leading remediation strategy is long-term ageing in end-pit lakes, despite limited data available on its photochemical fate. Here, direct photolysis of whole OSPW, or of its constituent fractions, was examined at environmentally relevant wavelengths (>290 nm) in bench-top studies. Changes in the chemical profiles of whole OSPW, acid- (AEO), and base-extractable organics (BEO) were characterized by liquid chromatography with ultra-high resolution mass spectrometry in negative (−) and positive (+) ionization modes. Following 18 d of irradiation, photolysis reduced the total ion intensity in all samples in both modes. The most photo-labile species included the O2−, O3−, O4−, O2S−, and O4S− chemical classes, which were depleted in whole OSPW by 93–100% after only 5 d. In positive mode, detected species were more recalcitrant than those detected in negative mode, with an average reduction across all heteroatomic classes of 75 ± 11.0% after 18 d. Estimated environmental half-lives for heteroatomic classes ranged from 57 d (O4S−) to 545 d (O3N+), with a greater recalcitrance for classes detected in positive mode compared to negative mode. Under field conditions in end-pit lakes, natural photolysis may be an important mechanism for effective OSPW remediation, and we suggest that future end-pit lakes be shallow to maximize light penetration and natural photolysis in ageing OSPW.2.02MBPDFenAll Rights Reservedhydrocarbonsoil and gas fieldsphotolysiswater pollutantsArticle Post-Print