School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China.
School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China.
Chemosphere. 2021 Oct;281:130838. doi: 10.1016/j.chemosphere.2021.130838. Epub 2021 May 10.
Atmospheric chromophores have photo-sensitiveness that can participate in photochemical reactions, so they may have the potential to make an important contribution in organic aerosols aging. This study attempts to explain the effects of oxidation reaction and photochemical reaction on atmospheric chromophores. For this study, the summer period (higher sunshine intensity) was selected to observe the mechanisms by the online excitation emission matrix (EEM) fluorescence. The results showed that a lot of secondary organic aerosols were produced in the afternoon, but a large portion of them is non-chromophore. We observed that the secondary chromophores of highly-oxygenated humic-like substances (HULIS) were produced, which suggests a degradation product of less-oxygenated HULIS. The photochemical reaction and oxidation reaction were the important reactions that occur in the afternoon, which drives the oxidation state evolution of the atmospheric chromophores. Atmospheric oxidation processes are the mainly driving reaction for the transformation of atmospheric chromophore. The aged aerosol has a lower fluorescence index and a high degree of humification. It is speculated that the aerosol from night to morning is in the accumulation process dominated by local sources, and then it is mainly in the process of being gradually aged at noon and afternoon. This study will guide to better understand the atmospheric chemical processes of chromophore aerosols and provide guidance for the EEM approach to trace the aerosol aging in the atmosphere.
大气生色团具有光敏感性，能够参与光化学反应，因此它们可能在有机气溶胶老化中具有重要贡献的潜力。本研究试图解释氧化反应和光化学反应对大气生色团的影响。为此，选择夏季（阳光强度较高）进行在线激发发射矩阵（EEM）荧光观测，以研究机制。结果表明，下午会产生大量的二次有机气溶胶，但其中大部分是非生色团。我们观察到高度氧化的类腐殖质物质（HULIS）的二次生色团的产生，这表明其是低氧化态 HULIS 的降解产物。光化学反应和氧化反应是下午发生的重要反应，它们推动了大气生色团的氧化状态演变。大气氧化过程是大气生色团转化的主要驱动反应。老化的气溶胶具有较低的荧光指数和较高的腐殖化程度。据推测，夜间到清晨的气溶胶处于以本地源为主的积累过程中，然后在中午和下午主要处于逐渐老化的过程中。本研究将有助于更好地了解生色团气溶胶的大气化学过程，并为 EEM 方法追踪大气中气溶胶的老化提供指导。
