Huawei Li | Chemical and Environmental Engineering PhD Candidate

Time: 1:00 PM

Date: Wednesday, June 3

Location: Hybrid; CE-CERT RM 105 and Zoom (ID: 96829675418 Passcode: 752860)

Title: Secondary Organic Aerosol Formation from Biogenic and Non-Traditional Urban Organic Emission Sources

Abstract:  Secondary organic aerosol (SOA) formation from both biogenic and emerging urban emission sources remains highly uncertain due to incomplete understanding of oxidation chemistry and realistic emission behavior. This dissertation investigates SOA formation from α-pinene, volatile chemical products (VCPs), and compacted hot mix asphalt (HMA) emissions using environmental chamber experiments, oxidation flow reactor (OFR) studies, and atmospheric modeling. Results demonstrate that α-pinene SOA formation is strongly influenced by evolving organic peroxy radical (RO₂•) chemistry, NOx conditions, and HO₂•/RO₂• ratios, indicating that commonly used branching ratio parameters alone cannot fully describe SOA behavior. Updated volatility basis set parameters incorporated into GEOS-Chem simulations increased predicted SOA concentrations in terpene-rich regions. Experiments involving selected VCP compounds and commercial formulations showed substantial variability in aerosol formation depending on molecular structure and product composition. Complete commercial formulations frequently generated greater SOA than the summed contribution of individually tested ingredients, highlighting important formulation-level interactions. Laboratory and outdoor studies of compacted HMA pavement demonstrated that measured VOC/IVOC emissions and SOA formation potentials were substantially lower than several previously reported estimates under realistic environmental conditions. Overall, this work improves understanding of SOA formation from diverse emission sources and provides improved constraints for atmospheric models and urban emission inventories.