Uncertainty Analysis for Kinetic Simulation of Alpha-Pinene Ozonolysis SOA Formation based on Explored Chemical Processes

Chuanyang Shen, HAOFEI ZHANG, University of California, Riverside

     Abstract Number: 145
     Working Group: Aerosol Chemistry

Abstract
As one of the most abundant monoterpenes in the atmosphere, α-pinene ozonolysis is a critical pathway in the atmospheric chemistry of volatile organic compounds (VOCs), significantly influencing air quality and climate. Its oxidation products contribute substantially to aerosol mass, especially in forested areas. In this study, we present a comprehensive analysis of α-pinene secondary organic aerosol (SOA) formation via ozonolysis, using a 0-D kinetic modeling framework to simulate gas-phase reactions and subsequent SOA formation based on near-explicit chemical mechanisms which have been explored in prior work. We compare our simulation results with both existing chamber experiments and field measurements. This study aims to evaluate how different chemical mechanisms and treatments of specific processes affect the prediction of SOA yields and compositions. Moreover, we explore the effects of RO2 unimolecular autoxidation rates, alkoxy radicals' fates, particle-phase reactions, and volatility saturation concentration (C*) estimation on aerosol formations and found that these factors can bring great uncertainty to the SOA prediction. Specifically, a reduction in all autoxidation rates by a factor of 10 from the default values based on prior computational calculations can lead to an approximately 40% reduction in SOA formation. Employing two C* estimation methods, SIMPOL and EPI, we found that that SIMPOL predicts significantly lower volatilities than EPI. These results underscore the substantial uncertainty associated with detailed chemical mechanisms and C* estimations in SOA modeling.