Exploring the Hygroscopic Growth, Phase and Chemistry of Light-Absorbing Aerosol using Single Particle Levitation

JAMES F. DAVIES, Roya Bahreini, Malsha Amugoda, Prakriti Singh, Stephanie Salas, Erin Bowey, University of California, Riverside

     Abstract Number: 27
     Working Group: Aerosol Chemistry

Abstract
Single particle levitation analysis of aerosol allows for samples to be manipulated in a contactless manner and exposed to environmental conditions that mimic the atmosphere over extended timescales. Using a linear quadrupole electrodynamic balance, we can confine and analyze multiple particles in a vertical stack, facilitating direct comparisons between particles of different composition and allowing for time-resolved chemical analysis by sequential sampling into a mass spectrometer.

Here, we report measurements on the hygroscopic growth properties for a range of phenolic and nitrophenolic species, identify how changes in the functional group identity and positioning has a strong influence on interactions with water. Further, we explore how particles containing mixtures of these chromophores with ammonium sulfate vary from the pure state, focusing on phase transitions and changes in the amount of condensed phase water. We extend our measurements to chamber generated BrC SOA to characterize the hygrosopic growth and phase behavior of chemically complex samples. Finally, we describe preliminary work on the photolysis chemistry of individual chromophores held in levitated particles across a range of compositions using single particle levitation coupled with mass spectrometry. Overall, these measurements facilitate a compositionally-resolved investigation into the physical properties and chemistry of BrC aerosol that will improve our understanding of this important class of atmospheric aerosol.