Estimates of IEPOX Based SOA Formation in CMAQ 5.3.2 Using Updated Kinetics and Thermodynamics

JAIME GREEN, Yuzhi Chen, Jason Surratt, William Vizuete, University of North Carolina at Chapel Hill

     Abstract Number: 430
     Working Group: Aerosol Chemistry

Abstract
Field and laboratory measurement data have shown the importance of an aerosol’s physiochemical properties in determining its interactions with gas-phase oxidation products derived from biogenic volatile organic compound (BVOC) emissions and on the formation and evolution of secondary organic aerosols (SOA), with implications on climate and air quality. Recent flow tube and smog chamber experiments systematically generated SOA and were subsequently collected by a particle-into-liquid sampler (PILS) for time-resolved chemical measurements. PILS samples were then analyzed for SOA constituents by either reverse-phase liquid chromatography (RPLC) or hydrophilic liquid interaction chromatography (HILIC) coupled to electrospray ionization-high resolution-quadrupole-time-of-flight mass spectrometry (ESI-HR-Q-TOFMS) and inorganic aerosol constituents by ion chromatography (IC). These experimental systems have produced new insights on how acidity, organic water, and phase state alters the formation of isoprene epoxydiols (IEPOX)- derived SOA. IEPOX-derived SOA formation processes are not well represented in the current Community Multiscale Air Quality Model (CMAQ) model and could result in a significant under-prediction of the production of organic sulfur, affecting multiphase reactivity, phase state, aerosol growth, and reactive uptake of other chemical species. This work describes the use of the F0AM-CMAQ box model which utilized experimental data to evaluate and develop modifications to the existing CMAQ model, leading to CMAQ model simulations for the model year of 2013, for the domain covering the Southeastern US. The F0AM-CMAQ model is based on the Framework for 0-D Atmospheric Modeling (F0AM) model, CMAQ 5.3.2, integrating the inorganic aerosol thermodynamic equilibrium model (ISORROPIA) and the Aerosol Inorganic-Organic Mixtures Functional Groups Activity Coefficients model (AIOMFAC) with the purpose of determining the acid-base activity of the components of the aerosols at varying percentages of relative humidity. Based on the 0D box model comparison results, a new set of implicit parameters for IEPOX SOA formation will be developed for CMAQ and compared with current implementation of SOA formation, testing differences between predicted particle size, glass transition temperature for the southeastern US model domain. The parameter set will also utilize the application of the AIOMFAC thermodynamic model to determine the chemical and physical properties of aerosols in CMAQ based on the aerosol chemical components. These model runs will guide future updates to the CMAQ model related to isoprene derived SOA.