Abstract Volatility is one of the most important physical properties of organic aerosol (OA), as it determines the partitioning of its components between the vapor and particulate phases. Despite their atmospheric importance, multicomponent OA volatility estimates remain quite uncertain. This study combined thermodenuder (TD) and isothermal dilution measurements to characterize secondary OA (SOA) generated from the ozonolysis of α-pinene and cyclohexene. The SOA from both precursors evaporated similarly in the TD, but behaved quite differently when isothermally diluted by similar amounts. The α-pinene ozonolysis SOA evaporated by only 20% after 2 h of dilution by a factor of around 20, while 65% of the cyclohexene ozonolysis SOA evaporated at the same conditions. The volatility distributions were first estimated by fitting only the evaporation in the TD. This approach resulted in similar volatility distributions for the two systems. Then, the model was used to fit both the evaporation in the TD and the dilution chamber. This technique estimated drastically different volatility distributions with the α-pinene ozonolysis SOA consisting of mostly low-volatility compounds and the cyclohexene ozonolysis SOA consisting of mostly semi-volatile compounds. In the next stage of analysis, the model was updated to account for vapor-phase wall-losses occurring in the dilution chamber. This approach resulted in slightly less volatile SOA and provided some information about the losses of vapors to the walls, but the results were fairly uncertain. These results show the necessity of combining thermal measurements with other techniques to accurately estimate OA volatility. Copyright © 2020 American Association for Aerosol Research

中文翻译：

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使用热蒸发技术确定大气有机气溶胶挥发性分布的挑战

摘要 挥发性是有机气溶胶 (OA) 最重要的物理特性之一，因为它决定了其组分在气相和颗粒相之间的分配。尽管它们在大气中很重要，但多组分 OA 挥发性的估计仍然相当不确定。该研究结合了减热器 (TD) 和等温稀释测量，以表征由 α-蒎烯和环己烯的臭氧分解产生的次级 OA (SOA)。来自两种前驱体的 SOA 在 TD 中的蒸发相似，但在等温稀释相似量时表现完全不同。α-蒎烯臭氧分解 SOA 在稀释 20 倍左右后仅蒸发 20%，而在相同条件下，65% 的环己烯臭氧分解 SOA 蒸发。挥发性分布首先通过仅拟合 TD 中的蒸发来估计。这种方法导致两个系统的波动率分布相似。然后，该模型用于拟合 TD 和稀释室中的蒸发。该技术估计了主要由低挥发性化合物组成的 α-蒎烯臭氧分解 SOA 和主要由半挥发性化合物组成的环己烯臭氧分解 SOA 的显着不同的挥发性分布。在分析的下一阶段，更新模型以说明稀释室中发生的气相壁损失。这种方法导致 SOA 的挥发性稍低，并提供了一些关于蒸汽到壁的损失的信息，但结果相当不确定。这些结果表明将热测量与其他技术相结合以准确估计 OA 挥发性的必要性。版权所有 © 2020 美国气溶胶研究协会