Increasing global demands for oils are fueling the production of diluted bitumen (DB) from Canada’s oil sands region. More weathered than conventional crude (CC) oils, Alberta bitumen is often diluted with lighter petroleum oils to reduce density and viscosity to meet pipeline specifications for transportation. Being a heavy oil product that is transported in large volumes across Canada and the USA, there has been interest to compare its behavior and toxicity characteristics when spilled to those of CC. To determine the influence of environmental weathering upon DB following a freshwater spill, we conducted separate controlled spills of Cold Lake Blend DB and Mixed Sweet Blend light CC oil in a mesocosm spill-tank system at 24 °C with wave-action for 56 days. DB-contaminated waters remained acutely lethal for a period of 14 days to early life stage fathead minnows () exposed during embryologic development, while CC was lethal for 1 day. However, concentrations of mono- and polycyclic aromatic compounds, often claimed to be principally responsible for the acute and chronic toxicity of crude oils, were consistently higher in CC water compared to DB. Elevated aromatic concentrations in CC water correlated with higher prevalences of developmental malformations, reduced heart and growth rates, and impacts on the aryl hydrocarbon receptor pathway. Organic acids were measured over the course of the studies and O containing naphthenic acids were present at greater relative abundances in DB- compared to CC-contaminated water, with their attenuation correlating with reduced acute and sublethal toxicity. Furthermore, organic acid degradation products accumulated with time and likely contributed to the consistently sublethal toxicity of the weathered oils throughout the experiment. Improved characterization of the fractions including organic acids and those organic compounds found within the unresolved complex mixture of fresh and weathered crude oils is necessary to adequately understand and prepare for the risks that accidental petroleum spills pose to aquatic resources.

中文翻译：

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自然风化作用下淡水中稀释沥青泄漏的水生毒性和化学归宿


全球对石油的需求不断增长，推动了加拿大油砂地区稀释沥青 (DB) 的生产。艾伯塔省沥青比传统原油 (CC) 更易风化，通常用较轻的石油稀释，以降低密度和粘度，以满足管道运输规范。作为一种在加拿大和美国大量运输的重油产品，人们有兴趣将其泄漏时的行为和毒性特征与 CC 进行比较。为了确定淡水泄漏后环境风化对 DB 的影响，我们在中宇宙泄漏罐系统中对 Cold Lake Blend DB 和 Mixed Sweet Blend light CC 油进行单独受控泄漏，温度为 24 °C，波浪作用持续 56 天。对于胚胎发育过程中暴露的生命早期黑头呆鱼来说，受 DB 污染的水域在 14 天内仍具有急性致死性，而 CC 则在 1 天内致死。然而，与 DB 相比，CC 水中的单环和多环芳香族化合物（通常被认为是原油急性和慢性毒性的主要原因）的浓度始终较高。 CC 水中芳香族化合物浓度升高与发育畸形发生率升高、心脏和生长速率降低以及对芳烃受体途径的影响相关。在研究过程中对有机酸进行了测量，与 CC 污染的水中相比，含 O 的环烷酸在 DB 中的相对丰度更高，其衰减与急性和亚致死毒性的降低相关。此外，有机酸降解产物随着时间的推移而积累，并可能导致整个实验过程中风化油的持续亚致死毒性。 为了充分了解和应对意外石油泄漏对水生资源造成的风险，有必要改进对未溶解的新鲜原油和风化原油的复杂混合物中发现的包括有机酸和有机化合物在内的馏分的表征。