AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Simulation of Organic Aerosols in China with Two-dimensional Volatility Basis Set
Shuxiao Wang, BIN ZHAO, Neil Donahue, Xiaofeng Huang, Jiming Hao, Tsinghua University
Abstract Number: 168 Working Group: Haze in China: Sources, Formation Mechanisms, and Current Challenges
Abstract Organic aerosols (OA) account for about 20-50% of the PM2.5 concentrations across China, and 20-80% of them are secondary organic aerosol (SOA). However, most widely-used chemical transport models cannot explain either the amount or the degree of oxidation of SOA. In this study, we improved the simulation of OA and SOA in China with a state-of-the-art two-dimensional volatility basis set (2D-VBS). Firstly, we simulated a series of photo-oxidation experiments using the 2D-VBS box model in order to determine the parameterization of 2D-VBS for application in three-dimensional chemical transport models. The simulation results indicate that the first-generation oxidation of traditional SOA precursors should be treated explicitly, and three parallel layers of 2D-VBS with different configurations should be applied to simulate the aging of anthropogenic SOA, the aging of biogenic SOA, and the multi-generation oxidation of primary organic aerosol (POA)/Intermediate Volatility Organic Compounds (IVOC). Based on the configuration above, we developed the CMAQ/2D-VBS chemical transport model, and evaluated its simulation results against field measurements. The evaluation results indicate that CMAQ/2D-VBS significantly improved the simulation results of OA and SOA concentrations, and the simulated O:C, which reflects the oxidation state of OA, agrees well with the observations in most sites. According to CMAQ/2D-VBS, the aging of traditional SOA, the aging of POA, and the oxidation of IVOC together enhance the OA and SOA concentrations in eastern China by about 40% and 10 times, respectively. Anthropogenic non-methane volatile organic compounds (NMVOC), biogenic NMVOC, POA, and IVOC contribute 9%, 5%, 40%, and 46% of the average OA concentrations in eastern China, respectively, and 11%, 7%, 24%, and 58% of the average SOA concentrations, respectively. The results imply that we should pay special attention to the control of IVOC and POA emissions in order to reduce SOA concentrations.