Exploring the Chemical Evolution of Aerosol Particle Composition and Physical Properties using Single Particle Levitation
RAVLEEN KAUR KOHLI, James F. Davies,
University of California, Riverside Abstract Number: 131
Working Group: Aerosol Chemistry
AbstractIn the atmosphere, aerosol particles become transformed by various heterogeneous reactions that alter their physical properties and chemical composition. Consequently, these transformations regulate the dynamics of aerosols and ultimately have a significant impact on the atmospheric role of these particles. A major area of focus in present day atmospheric research is to understand and predict how aerosol particles evolve due to heterogeneous oxidation reactions with ozone (O3) and radicals, such as OH· as the oxidants. This has led to extensive explorations of their physical and chemical properties through the development of various single particle and ensemble measurement techniques.
In this work, I discuss the development of an experimental platform that couples a linear quadrupole electrodynamic balance (LQ-EDB) with electrospray ionization - mass spectrometry (ESI-MS) through an open port sampling interface (OPSI) for exploring single levitated particles undergoing chemical evolution. We have demonstrated the effectiveness of this approach towards the qualitative and quantitative analysis of single particles containing a range of atmospherically relevant compounds (Kaur Kohli et al., Anal. Chem., 2022). Measurements were made on the evaporation dynamics of chemically evolving multi-component organic droplets containing a range of small n-ethylene (n=3, 4 and 6) glycols. The measured compositional evolution was shown to be consistent with the evolving size using a simple multicomponent evaporation model (Kaur Kohli et al., Anal. Chem., 2021).
Here, we apply the combined LQ-EDB-ESI-MS methodology to simulate heterogeneous reactions happening in atmosphere, such as ozonolysis, on single levitated particles and precisely measure their physical and optical properties as a function of their evolving composition during the reaction. The results provide important insights on how oxidative aging of ambient aerosol particles influences their physicochemical characteristics by understanding reaction kinetics based on the phase state, degree of oxidation, and new product formation.