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Abstract：
Volatile chemical products (VCPs) are increasingly recognized as significant sources of volatile organic compounds (VOCs) in urban atmospheres, potentially serving as key precursors for secondary organic aerosol (SOA) formation. This study investigates the formation and physicochemical transformations of VCP-derived SOA, produced through ozonolysis of VOCs evaporated from a representative room deodorant air freshener, focusing on the effects of aerosol evaporation on its molecular composition, light absorption properties, and reactive oxygen species (ROS) generation. Following aerosol evaporation, solutes become concentrated, accelerating reactions within the aerosol matrix that lead to a 42% reduction in peroxide content and noticeable browning of the SOA. This process occurs most effectively at moderate relative humidity (∼40%), reaching a maximum solute concentration before aerosol solidification. Molecular characterization reveals that evaporating VCP-derived SOA produces highly conjugated nitrogen-containing products from interactions between existing or transformed carbonyl compounds and reduced nitrogen species, likely acting as chromophores responsible for the observed brownish coloration. Additionally, the reactivity of VCP-derived SOA was elucidated through heterogeneous oxidation of sulfur dioxide (SO2), which revealed enhanced photosensitized sulfate production upon drying. Direct measurements of ROS, including singlet oxygen (1O2), superoxide (O2•-), and hydroxyl radicals (•OH), showed higher abundances in dried versus undried SOA samples under light exposure. Our findings underscore that drying significantly alters the physicochemical properties of VCP-derived SOA, impacting their roles in atmospheric chemistry and radiative balance.
摘要：
挥发性化学产品（VCP）越来越被认为是城市大气中挥发性有机化合物（VOCs）的重要来源，可能是二次有机气溶胶(SOA)形成的关键前体。这项研究调查了VCP衍生的SOA的形成和物理化学转化，通过臭氧分解从具有代表性的房间除臭剂空气清新剂中蒸发的挥发性有机化合物产生，关注气溶胶蒸发对其分子组成的影响，光吸收性能，和活性氧（ROS）的产生。气溶胶蒸发后,溶质变得浓缩，加速气溶胶基质内的反应，导致过氧化物含量减少42％，SOA明显褐变。这个过程在中等相对湿度(~40%)下最有效，在气溶胶固化前达到最大溶质浓度。分子表征表明，蒸发VCP衍生的SOA会从现有或转化的羰基化合物与还原的氮物种之间的相互作用中产生高度共轭的含氮产物，可能作为发色团负责观察到的棕色着色。此外,通过二氧化硫（SO2）的非均相氧化阐明了VCP衍生的SOA的反应性，这表明干燥后光敏硫酸盐的产生增强。ROS的直接测量，包括单线态氧（1O2），超氧化物（O2·-），和羟基(·OH)，在光照下，干燥的SOA样品与未干燥的SOA样品的丰度更高。我们的发现强调，干燥会显著改变VCP衍生的SOA的物理化学性质，影响它们在大气化学和辐射平衡中的作用。
