AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Chemical Role of Water on Secondary Organic Aerosol Formation and Ageing
CHRISTOPHER SNYDER, Giuseppe Petrucci, University of Vermont
Abstract Number: 732 Working Group: Aerosol Chemistry
Abstract Secondary organic aerosols (SOA) make up a significant fraction of the aerosol mass burden, yet our fundamental understanding of their roles in atmospheric processes remains limited. Recent laboratory studies suggest that the physical and chemical properties of some SOA may be driven by the presence of water at different stages of the SOA lifecycle (i.e. particle genesis vs. chemical aging). However, recent evidence suggests that bulk chemical metrics, such as O:C ratio, are not always sufficient to accurately predict these SOA properties and that a molecular level understanding is needed to better understand the mechanisms, chemical and physical, by which atmospheric SOA impacts Earth’s atmosphere. We present initial results on the characterization of a dual-chamber system designed to separate particle genesis from aging, permitting each process to be studied independently. Furthermore, soft ionization aerosol mass spectrometry was used to measure chemical composition of SOA under varying conditions of relative humidity during and post particle formation. Herein we describe challenges with the reproducible generation of SOA, as well as the unexpectedly dominant role of mixing within the chamber in impacting particle physical and chemical properties. Finally, as proof-of-principal of this innovative design, results are presented for compositional differences in SOA, as well as SOA yields and particle size distributions, generated from ozonolysis of the green leaf volatiles cis-3-hexenyl acetate (CHA) and cis-3-hexenol (HXL). Preliminary results show SOA yield decreases as humidity increases. For HXL, SOA yield dropped from 5.4% at low humidity to 2.4% at high humidity. The difference in SOA yield was more drastic for CHA going from 2.2% at low humidity to 0.2% at high humidity.