Photochemistry in Organic Aerosols

二次有机气溶胶直接和间接地对气候造成辐射强迫，并影响城市空气质量。该奖项的主要目标是：(1)研究在SOA中发生的直接和间接光解过程的机制和意义，以及(2)研究云处理过程中涉及水溶性SOA的水溶液光化学。模型SOA将在烟雾室中产生，并暴露在各种状态的模拟太阳辐射下：低相对湿度(RH)下的干燥SOA、高相对湿度下的水合SOA、与云和雾相关的浓度的水中溶解的SOA以及冷冻水萃取物中的SOA。利用高分辨质谱仪等分析手段对模拟太阳辐射前后的半导体光电子能团的分子组成进行表征。在一组平行的实验中，将使用PI实验室开发的独特的光谱和质谱学工具来测量SOA的光解作用光谱。我们将确定几种嵌入在类SOA材料中的具有代表性的羰基化合物的绝对光解量子产率和详细的光解机理。这些信息将被用来估计在大气中的SOA颗粒和含有溶解的SOA的云滴中发生的光化学反应的速率。这个项目将提供对SOA中的光化学反应和在SOA材料的水溶液中的光化学反应的分子水平的理解。研究结果还将有助于相关学科研究(1)空气中陈年有机物对健康的影响，以及(2)涉及太阳辐射与其他介质中复杂有机混合物之间相互作用的过程(例如，有机聚合物和涂料的光降解、土壤有机物的光化学、溶解有机物的光降解和水的净化)。该项目将支持两名研究生，并将通过在主要会议上的发言和同行评议的出版物广泛传播调查结果。首席研究员和学生还将通过正在进行的教育和外展活动向公众宣传基础研究的重要性和兴奋感，包括为期两周的暑期研讨会，为高中科学教师提供动手实验室培训，并为普通公众提供演示、实验室参观和教育研讨会。

Secondary Organic Aerosols (SOA) contribute to radiative forcing on climate both directly and indirectly and also affect urban air quality. The main goals of this award are: (1) To investigate the mechanism and significance of direct and indirect photolysis processes occurring in SOA and (2) to investigate aqueous photochemistry involving water-soluble SOA during cloud-processing. Model SOA will be generated in a smog chamber and exposed to simulated solar radiation in various states: Dry SOA at low relative humidity (RH), hydrated SOA at high RH, SOA dissolved in water at concentrations relevant to clouds and fogs, and SOA in frozen aqueous extracts. The molecular composition of SOA will characterized by high-resolution mass spectrometry and other analytical methods before and after exposure to the simulated solar radiation. In a parallel set of experiments, photodissociation action spectra of SOA will be measured using unique spectroscopic and mass-spectrometric tools developed in the PI's laboratory. The absolute photodissociation quantum yields and detailed mechanisms of photolysis will be determined for several representative carbonyl compounds embedded in SOA-like materials. This information will be used to estimate rates of photochemical reactions occurring inside atmospheric SOA particles and inside cloud droplets containing dissolved SOA.This project will provide molecular-level understanding of photochemical reactions in SOA and in aqueous solutions of SOA material. Results will also contribute to related disciplines investigating (1) health effects of aged organic matter in air and (2) processes involving interactions between solar radiation and complex organic mixtures in other media (e.g., photodegradation of organic polymers and coatings, photochemistry of soil organics, photodegradation of dissolved organic matter, and water purification). The project will support two graduate students and findings will be widely disseminated through presentations at major conferences and peer-reviewed publications. The principal investigator and student will also communicating the importance and excitement of fundamental research to the general public through ongoing educational and outreach activities including a two-week long summer workshop that provides hands-on laboratory training for high school science teachers and presentations, lab tours, and educational seminars for the general public.