Particle-Phase Formation of OOMs in Biogenic New Particles: New Insights from LC-ESI Orbitrap and FIGAERO-CIMS Mass Spectrometer Analysis
VIGNESH VASUDEVAN GEETHA, Lee Tiszenkel, Robin Russo, Daniel J. Bryant, Shanhu Lee, The University of Alabama in Huntsville
Abstract Number: 56
Working Group: Aerosol Chemistry
Abstract
Formation of low-volatility oxygenated organic molecules (OOMs) from volatile organic compounds (VOCs) such as monoterpenes is a major topic of interest in atmospheric chemistry. OOMs are key ingredients for the formation and growth of new particles and the formation of secondary organic aerosol (SOA) particles. It is generally believed that OOMs form in the gas phase via autoxidation reactions and then undergo gas-to-particle conversion; for example, this is the mainstream mechanism of new particle formation (NPF) currently. Recent studies have also shown possible pathways for OOMs formation within SOA particles; however, it is not clear how particle-phase reactions contribute to the formation of OOMs in newly formed particles. We conducted laboratory experiments of NPF using alpha-pinene ozonolysis reactions in a fast flow reactor, and analyzed the chemical composition of OOMs in the gas phase as well as in the nearly formed particles (up to approximately 50 nm) using the filter inlet for gas and aerosol attached to chemical ionization mass spectrometer (FIGAERO-CIMS) and the offline liquid chromatography (LC)-Orbitrap mass spectrometers. The combination of these two independent high-resolution mass spectrometer techniques enables us to gain new insights into the particle-phase OOMs compositions at different time scales based on the detailed isomer-resolved molecular structures and volatility analysis. The LC-Orbitrap MS/MS mass spectrometer analysis shows the presence of isomeric compounds with distinctively different structural moieties, which can be attributed to different formation pathways, such as gas-to-particle conversion, particle-phase, and heterogeneous reactions. This presentation will discuss particle-phase formation of OOMs – a previously unidentified yet potentially significant process – in newly formed particles