17:15 〜 18:45
[AAS09-P17] Phase state and Viscosity of Secondary Organic Aerosols and Their effects on IEPOX-SOA particle formation simulated over China
キーワード：Multiphase chemistry, Chemical transport models, Glass transition, Reactive uptake
Secondary organic aerosols (SOA) can exist in liquid, semi-solid or amorphous solid states, which are rarely accounted for in current chemical transport models (CTMs). Missing the information of SOA phase state and viscosities in CTMs impedes accurate representations of SOA formation and evolution, thus affecting the predictions of aerosol effects on air quality and climate. We have previously developed a method to estimate the glass transition temperature (Tg) of an organic compound based on volatility. In this study, we apply this method to predict the phase state and viscosities of SOA particles over China in summer of 2018 using the Weather Research and Forecasting model coupled to Chemistry (WRF-Chem). This is the first time that spatial distributions of the SOA phase state over China are investigated by a regional CTM. Simulations show that Tg values of dry SOA range from ~290 K to 320 K, with higher values in the northwestern China where SOA particles have low volatilities. Considering the water uptake by SOA particles, the SOA viscosity also shows a prominent geospatial gradient that highly viscous or solid SOA particles are mainly found in the northwestern China. Isoprene epoxydiol secondary organic aerosols (IEPOX-SOA) are key components of sub-micrometer biogenic SOA particles. Based on the predicted viscosity of SOA particles which is a function of chemical composition, ambient temperature and relative humidity, we further simulate the effects of particle phase state on the reactive uptake of IEPOX, which has implications in properly representing the particle phase state involved multiphase chemistry in CTMs.