A063-0013
Physicochemical properties of secondary organic aerosol from biogenic and anthropogenic mixtures
Wednesday, 9 December 2020
Poster
Yu Wang1, Aristeidis Voliotis2, Yunqi Shao2, Dawei Hu2, Taomou Zong3, Xiangxinyue Meng3, Ying Chen4, Mao Du2, Zhijun Wu5, M. Rami Rami Alfarra6,7 and Gordon McFiggans2, (1)University of Manchester, Manchester, M13, United Kingdom, (2)University of Manchester, Manchester, United Kingdom, (3)Peking University, Beijing, China, (4)Lancaster University, Lancaster, United Kingdom, (5)Peking University, State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Beijing, China, (6)Department of Earth and Environmental Sciences, The University of Manchester, Manchester, UK, Manchester, United Kingdom, (7)National Centre for Atmospheric Science, The University of Manchester, Manchester, UK, Manchester, United Kingdom
Abstract:
Globally, Organic Aerosol contributes between 20 and 90% of the fine aerosol mass, impacting aerosol chemical, physical and optical properties, further on the cloud activation and air quality. However, our understanding on its physicochemical properties is still lagging behind, especially the secondary organic aerosol (SOA) formation evolution involved of inorganic compounds along with increased complexity of biogenic/anthropogenic precursors. In this study, we designed a series of chamber experiments to explore physicochemical properties of the multi-component aerosol particles from various single/iso-reactive mixed biogenic (α-pinene, isoprene) and anthropogenic (o-cresol) volatile organic compound (VOC) photochemistry on ammonium sulphate seed. These experiments were performed under VOC/NO
x ratio of 3~9 in an 18-m
3 atmospheric-relevant Manchester Aerosol Chamber (MAC). State-of-art instruments were deployed to derive physicochemical properties, such as H-TDMA, CCN counter, HR-ToF-AMS, Impactor apparatus for aerosol hygroscopicity, CCN activity, chemical composition and phase state, respectively.
Our results demonstrate that the organic-inorganic ratio is the main factor determining the physical properties in all investigated single and mixed biogenic/anthropogenic VOC systems, whereas the OA composition is less important. Besides, relative humidity is also a key factor influencing phase state apart from organic-inorganic ratio. Using simplified κ-Köhler theory and ZSR mixing rule, a good agreement between the observed hygroscopicity and predicted value from size-resolved chemical composition among all investigated VOC systems. This successful closure indicates the predictability of aerosol hygroscopicity of increased complexity in OA composition with a simplified theoretical model. Furthermore, the comparison with the closure between CCN activity and chemical composition gives us a sense of instrumentation and OA composition differences. These findings have important implications on atmospheric processes in the real atmosphere, such as the diurnal variation of ambient RH, various biogenic and anthropogenic sources in different environments.
