Contrasting Influence of Nitrogen Oxides on the Cloud Condensation Nuclei Activity of Monoterpene‐Derived Secondary Organic Aerosol in Daytime and Nighttime Oxidation
Chengqi Zhang, Yindong Guo, Hongru Shen, Hao Luo, Iida Pullinen, Sebastian H. Schmitt, Mingjin Wang, Hendrik Fuchs, Astrid Kiendler‐Scharr, Andreas Wahner, Thomas F. Mentel, Defeng Zhao
Abstract
Abstract Anthropogenic nitrogen oxides may influence the cloud condensation nuclei (CCN) activity of biogenic secondary organic aerosols (SOA) in both daytime photooxidation and nighttime NO 3 oxidation, which has significant implications for the climatic impact of SOA. We investigated the influence of NO x on the CCN activity of monoterpene‐derived SOA in OH oxidation and in NO 3 oxidation. In OH oxidation, NO x had little influence on the hygroscopic parameter κ of organic aerosol ( κ Org ), which was attributed to the minor fraction of organic nitrates (ON) in SOA (<24%), resulted from the low branching ratio of RO 2 + NO to form ON. In contrast, in NO 3 oxidation κ Org was much reduced compared to OH/O 3 oxidation due to a dominant fraction of ON. We report κ of MT‐derived ON formed in photo‐oxidation and NO 3 oxidation (0.029–0.052) for the first time to our knowledge, which may be used to improve model simulations of CCN concentrations.