Abstract View
Simulation of the Impact of Particle Phase State on SOA Formation from the Photooxidation of Isoprene and Beta-pinene Cocktail in the Presence of Electrolytic Salts
ZECHEN YU, Myoseon Jang, University of Florida
Abstract Number: 532
Working Group: Aerosol Chemistry
Abstract
In the presence of the inorganic salts, the formation of secondary organic aerosol (SOA) can be influenced by a particle phase state: liquid-liquid phase separation (LLPS) and homogeneous aerosol phase (HAP). The particle phase state is not only dynamic under the ambient environment where humidity are dynamically changing, but it also changes with SOA’s polarity and hygroscopicity of inorganic salts. In this study, the model approach to determine aerosol phase state will be discussed and the impacts of aerosol phase state on SOA production will also be evaluated. For the determination of aerosol phase state, the phase separation relative humidity (SRH) between organic and inorganic phase is predicted using a polynomial equation, which is obtained by fitting SOA physicochemical parameters (i.e., organic to carbon (O:C) ratio, molecular weight, and hydrogen-bonding ability) and inorganic salt compositions to SRH data. Both literature data and the measured data in this study using an optical microscopy are used for the derivation of SRH predictive equation. The SRH prediction is then implemented into the Unified Partitioning Aerosol Phase Reaction (UNIPAR) model to predict SOA via multiphase reactions of hydrocarbons. The UNIPAR model coupled with aerosol phase state prediction is demonstrated by simulating SOA formation from the photooxidation of the blend of isoprene and β-pinene at different ratios under varying seed conditions to yield SOA varying at O:C ratios and salts compositions. Isoprene SOA typically grows in HAP and β-pinene SOA in LLPS. We also demonstrate the difference between the prediction of SOA mass with the true phase state and that with the false phase state based on the hypothesis test theory.