A Comparison of Ambient and Chamber Organic AMS Spectra Under Varying RO2 Regimes

Elinor Caballero, Nadia Tahsini, Matthew Goss, Lesly Franco Deloya, Erik Helstrom, Jesse Kroll, HANNAH KENAGY, University of Minnesota

     Abstract Number: 604
     Working Group: Aerosol Chemistry

Abstract
The fate of organic peroxy radicals (RO₂) is a key control on product distributions, and hence the amount and properties of secondary organic aerosol (SOA) produced, from volatile organic compound (VOC) oxidation. Historically, environmental chamber experiments of SOA formation were designed to access “limiting conditions” in which the fate of RO₂ was dominated entirely by reaction with a single co-reactant, namely either NO or HO₂. A new model-informed approach to chamber experiment design now allows us to run experiments that more closely match the atmospheric distribution of RO₂ fates, including mixtures of RO₂+NO, RO₂+HO₂, RO₂+RO₂, and RO₂ isomerization reactions. Here, we compare organic aerosol spectra measured by an aerosol mass spectrometer (AMS) during ambient measurements and during chamber experiments with a variety of RO₂ fate distributions. We use the cosine similarity score to quantify the level of similarity between ambient spectra and experimental spectra, testing our hypothesis that spectra from chamber experiments that better mimic atmospheric RO₂ fate distributions are more similar to ambient spectra than those collected during “limiting condition” experiments. In addition, we look for spectral markers of RO₂ fate from experiments and examine their patterns of spatiotemporal variability in ambient AMS data.