Abstract View
Simulations of Kinetically-Limited IEPOX-SOA Reactive Uptake with Glass Transition Temperatures Predicted by Volatility and Chemical Composition Implemented in CMAQv5.3
SARA FARRELL, Quazi Rasool, Havala Pye, Yue Zhang, Ying Li, Yuzhi Chen, Chitsan Wang, Haofei Zhang, Ryan Schmedding, Manabu Shiraiwa, Jason Surratt, William Vizuete, University of North Carolina at Chapel Hill
Abstract Number: 116
Working Group: Aerosol Chemistry
Abstract
A major assumption in air quality models is that organic and inorganic constituents found in fine aerosols are homogeneously mixed. In recent years studies have shown that these aerosols can in fact form organic coatings with an aqueous inorganic core. This core-shell morphology has implications for cloud condensation nuclei activation, human health, and secondary organic aerosol formation via reactive uptake. Schmedding and Rasool et al., 2020 used the Community Multi-Scale Air Quality Model (CMAQ), version 5.2, to implement a phase separation algorithm dependent on glass transition temperature (Tg) and the average oxygen to carbon ratios (O:C) of the whole aerosol. When conditions were favorable for phase separation, the Tg, calculated based off of Shiraiwa et al 2017, of the organic shell was used to predict the viscosity and thus diffusivity of the isoprene epoxydiol (IEPOX) into the particle. A key assumption in this study was that 10% of aerosol liquid water (ALW) would reside in the organic layer.
This current investigation aims to implement the aforementioned phase separation algorithm and Tg equation into the latest version of CMAQ, version 5.3 (CMAQv5.3), through which organic ALW is parameterized based on hygroscopicity parameters. Furthermore, this research also analyses various Tg equations in CMAQv5.3 from recently published studies that are based on O:C ratios, saturation vapor concentrations, and elemental composition. Taking advantage of these new equations, and new ALW estimates in CMAQv5.3, this study evaluates various Tg parameterization's effect on phase state and multi-phase chemistry reactions leading to IEPOX-derived SOA. Model output for each parameterization will be cross-compared and validated by observational data. The findings of this work support future model development of CMAQ and will inform future experimental work further investigating how oxygenated organic coatings can impact multiphase chemistry.