AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Investigation of Biogenic Influences and Day/Night Chemistry on Secondary Organic Aerosol by Extractive Electrospray Ionization Time-Of-Flight Mass Spectrometry (EESI-TOF)
GIULIA STEFENELLI, Felipe Lopez-Hilfiker, Veronika Pospisilova, Alexander Lucas Vogel, Christoph Hueglin, Martin Rigler, Urs Baltensperger, Andre S.H. Prévôt, Jay G. Slowik, Paul Scherrer Institute
Abstract Number: 267 Working Group: Aerosol Chemistry
Abstract Anthropogenic and biogenic emissions contain large amounts of volatile organic compounds (VOCs) which may undergo photochemical aging to yield secondary organic aerosol (SOA). The magnitude of SOA production from different sources remains highly uncertain, hindering the estimation of the contribution of these sources to the total ambient organic aerosol. Measurement techniques with high time resolution and chemical specificity are thus urgently needed. PSI has recently developed a novel extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF), which enables real-time chemical analysis of atmospheric particles without thermal decomposition or ionization-induced fragmentation (Lopez-Hilfiker et al., 2017).
We present results from the first field deployment of the EESI-TOF. Measurements were performed during summer 2016 at a well-characterized urban site in Zurich. Positive matrix factorization (PMF) analysis of EESI-TOF data yielded several organic aerosol factors related to primary and secondary emissions. Factors were separated according to different mass spectral fingerprints and aging processes. Some of the retrieved factors correlated strongly with reasonable counterparts from AMS PMF analysis while others provided previously inaccessible insight into sources and ambient processing. Primary factors related to cooking processes, traffic and cigarette smoke emissions were obtained. The retrieved secondary factors were strongly influenced by biogenic emissions, and exhibited significant day/night differences. Factors dominating during daytime showed predominantly ions characteristic of monoterpene and sesquiterpene oxidation while the night-time factor included less oxygenated and more volatile terpene oxidation products, as well as organonitrates which were likely derived from NO3 radical oxidation of monoterpenes. These results contrast with measurements in a Swiss alpine valley during winter 2017, where wood burning emissions were dominant.