The 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.

中文翻译：

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受油砂处理影响的水中沥青衍生的有机物的光降解。

受油砂加工影响的水（OSPW）中的水溶性有机物的化学成分主要由沥青的天然成分组成，这些成分在油砂的含水萃取过程中被溶解和浓缩。OSPW有机物具有持久性和剧毒性，尽管其光化学命运方面的数据有限，但领先的补救策略是在底坑湖中长期老化。在这里，在台式研究中，在环境相关的波长（> 290 nm）下检查了整个OSPW或其组成部分的直接光解。整个OSPW，酸（AEO）和可碱萃取的有机物（BEO）的化学特性变化通过液相色谱和超高分辨率质谱在负（-）和正（+）电离模式下进行表征。照射18天后，在两种模式下，光解都会降低所有样品中的总离子强度。光不稳定的物种包括O₂ ^-，O- ₃ ^-，O- ₄ ^-，O- ₂小号^- ，和O ₄小号^-化学类别，这是在整个OSPW由93-100％只有5 d后耗尽。在阳性模式下，检测到的物种比在阴性模式下检测到的物种更加顽强，在18天后，所有杂原子类别的平均减少量为75±11.0％。评估的环境半衰期杂原子类从57 d（O介于₄小号^-）545 d（O ₃ Ñ ⁺），与否定模式相比，对在积极模式下检测到的类别的拒服力更大。在底坑湖泊的野外条件下，自然光解可能是有效修复OSPW的重要机制，我们建议未来的底坑湖泊应较浅，以在老化的OSPW中最大化光的渗透和自然光解。