Photochemistry of Secondary Organic Aerosol

本项目的重点是提供对二次有机气溶胶(SOA)颗粒内发生的光化学反应的分子水平的理解。SOA对气候的直接和间接辐射强迫都有贡献，并影响城市和偏远地区的空气质量。这项研究的主要目的是了解异戊二烯和部分单萜被臭氧或硝酸根(NO3)氧化而产生的光化学过程。为了实现这一目标，将制备模型SOA，并利用气溶胶光解离光谱方法研究得到的SOA材料的吸收光谱和光解离光谱。同时，将利用超高分辨率质谱仪对模拟太阳辐射前后的模型萜类SOA的组成进行详细的分析。此外，还将测量嵌入在类SOA材料中的几种模型羰基的光解的绝对量子产率。太阳辐射与有机物质之间的相互作用直接关系到几个研究领域，包括有机聚合物和涂料的光降解、土壤有机物和溶解有机物的光化学、有机光化学和水净化。这项研究还将为预测老化的有机颗粒物对健康的影响提供有用的信息。两名研究生将通过该奖项获得资助。

The focus of this project is on providing a molecular level understanding of photochemical reactions occurring inside secondary organic aerosol (SOA) particles. SOA contributes to both direct and indirect radiative forcing of climate, and affects air quality in the urban and remote atmosphere. The primary goal of this research is to understand the photochemical processing of SOA derived from the oxidation of isoprene and selected monoterpenes by ozone or the nitrate radical (NO3). To achieve this goal, model SOA will be prepared and the absorption spectra and photodissociation spectra of the resulting SOA material will be investigated using the method of aerosol photodissociation spectroscopy. In parallel, the composition of model terpene SOA will be analyzed in detail using ultrahigh-resolution mass spectrometry before and after the SOA is exposed to simulated solar radiation. In addition, absolute quantum yields for photolysis of several model carbonyls embedded in SOA-like materials will be measured. This information will be used to estimate rates of photochemical reactions occurring inside atmospheric SOA particles.The interaction between solar radiation and organic materials is directly relevant to several areas of research, including the photodegradation of organic polymers and coatings, photochemistry of soil organics and dissolved organic matter, organic photochemistry, and water purification. This research will also provide information useful for predicting the health effects of aged organic particulate matter. Two graduate students will be supported through this award.