Bell David M, Pospisilova Veronika, Lopez-Hilfiker Felipe, Bertrand Amelie, Xiao Mao, Zhou Xueqin, Huang Wei, Wang Dongyu S, Lee Chuan Ping, Dommen Josef, Baltensperger Urs, Prevot Andre S H, El Haddad Imad, Slowik Jay G
Laboratory of Atmospheric Chemistry, Paul Scherrer Institute 5232 Villigen Switzerland
Tofwerk 3600 Thun Switzerland.
Environ Sci Atmos. 2022 Nov 4;3(1):115-123. doi: 10.1039/d2ea00105e. eCollection 2023 Jan 19.
OH scavengers are extensively used in studies of secondary organic aerosol (SOA) because they create an idealized environment where only a single oxidation pathway is occurring. Here, we present a detailed molecular characterization of SOA produced from α-pinene + O with a variety of OH scavengers using the extractive electrospray time-of-flight mass spectrometer in our atmospheric simulation chamber, which is complemented by characterizing the gas phase composition in flow reactor experiments. Under our experimental conditions, radical chemistry largely controls the composition of SOA. Besides playing their desired role in suppressing the reaction of α-pinene with OH, OH scavengers alter the reaction pathways of radicals produced from α-pinene + O. This involves changing the HO : RO ratio, the identity of the RO radicals present, and the RO major sinks. As a result, the use of the OH scavengers has significant effects on the composition of SOA, including inclusions of scavenger molecules in SOA, the promotion of fragmentation reactions, and depletion of dimers formed α-pinene RO-RO reactions. To date fragmentation reactions and inclusion of OH scavenger products into secondary organic aerosol have not been reported in atmospheric simulation chamber studies. Therefore, care should be considered if and when to use an OH scavenger during experiments.
羟基（OH）清除剂在二次有机气溶胶（SOA）研究中被广泛使用，因为它们能营造出一种理想化环境，在此环境中仅发生单一氧化途径。在此，我们使用大气模拟舱中的萃取电喷雾飞行时间质谱仪，对使用多种OH清除剂时由α-蒎烯 + O生成的SOA进行了详细的分子表征，并通过流动反应器实验中气相成分的表征进行补充。在我们的实验条件下，自由基化学在很大程度上控制着SOA的组成。除了在抑制α-蒎烯与OH的反应中发挥预期作用外，OH清除剂还改变了由α-蒎烯 + O产生的自由基的反应途径。这涉及改变HO : RO比例、存在的RO自由基的种类以及RO的主要汇。结果，OH清除剂的使用对SOA的组成有显著影响，包括SOA中清除剂分子的包含、碎片化反应的促进以及α-蒎烯RO-RO反应形成的二聚体的消耗。迄今为止，大气模拟舱研究中尚未报道碎片化反应以及OH清除剂产物纳入二次有机气溶胶的情况。因此，在实验中是否以及何时使用OH清除剂时应谨慎考虑。
