Abstract View
Simulation of Monoterpene SOA Formation via Multiphase Reactions of Lumping Species Generated from Explicit Gas Mechanisms
ZECHEN YU, Myoseon Jang, Tianyu Zhang, Azad Madhu, Sanghee Han, University of Florida
Abstract Number: 529
Working Group: Aerosol Chemistry
Abstract
Monoterpene Secondary Organic Aerosol (SOA) is simulated using the Unified Partitioning Aerosol Phase Reaction (UNIPAR) model coupled with the near-explicit gas kinetics including MCM V3.3.1 and the proxy radical autoxidation mechanisms under varying aerosol acidity, NOx levels, temperature, and relative humidity. The UNIPAR model predicts SOA formation via multiphase partitioning (gas phase, organic phase, and inorganic phase) and in-particle chemistry of the lumping species, which are classified based on volatility and aerosol phase reactivity. The model streamlines three SOA formation pathways including partitioning of gaseous oxidized products onto both the organic phase and inorganic aqueous phase; oligomerization in organic phase; and aqueous phase reactions (i.e., acid-catalyzed oligomerization and organosulfate formation). The simulation is demonstrated for three different monoterpene SOA data (α-pinene, β-pinene and d-limonene) under various experimental conditions using a large outdoor photochemical smog chamber (UF-APHOR). Terpene SOA growth is significantly accelerated in aqueous phase anchored in acidic seed but much weak with neutral seed because terpene products are hydrophobic and weakly soluble in aqueous phase. The model underestimates the production of polar functional groups, such as -OH, -COOH, and -ONO2, compared to the compositions measured using Fourier Transform Infrared spectral data. Under the current emission trends in which SO2 and NOx have been decreasing, our simulation results suggests that the reduction of sulfate could be a more efficient way to reduce SOA mass than the reduction of NOx in the urban environments.