AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Online Measurement of Atmospheric Organic Aerosol Using a Novel Extractive Electrospray Ionization Time-of-Flight Mass Spectrometer (EESI-TOF)
Felipe Lopez-Hilfiker, Veronika Pospisilova, Giulia Stefenelli, Yandong Tong, Athanasia Vlachou, Urs Baltensperger, Andre Prévôt, JAY SLOWIK, Paul Scherrer Institute
Abstract Number: 558 Working Group: Urban Aerosols
Abstract Atmospheric organic aerosol (OA) is a complex mixture consisting of thousands of compounds, many of which remain unknown, and is responsible for significant uncertainties in aerosol effects on climate and health. Online measurements have yielded major advances in the elucidation of OA sources and atmospheric transformations, however current techniques rely on thermal desorption and/or electron ionization. This results in substantial molecular decomposition and ion fragmentation, destroying key information for source apportionment and mechanistic studies. We present the first ambient measurements by a novel extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF), which utilizes an ambient temperature, soft ionization technique to provide highly time-resolved (~5 sec) measurements of OA composition without any fragmentation or thermal decomposition. EESI-TOF measurements of OA are linear with mass and, unlike conventional electrospray systems, essentially free of ion suppression or matrix effects.
The EESI-TOF was deployed for several weeks during spring/summer 2016 at the Zurich-Kaserne station of the NABEL monitoring network (Zurich, Switzerland). This deployment coincided with long-term measurements by a quadrupole aerosol chemical speciation monitor (Q-ACSM), which provided complementary information on major OA sources, as well as constraining OA mass and bulk composition. While previous studies at Zurich-Kaserne have identified primary OA from traffic, cooking, and wood burning, quantitative links between secondary organic aerosol (SOA) and specific emission sources remain elusive. Positive matrix factorization (PMF) analysis of the EESI-TOF mass spectral time series was used to assess the potential of this new instrument for SOA source apportionment. The retrieved factors are compared to the time series of marker ions and ancillary measurements, as well as chamber-generated mass spectra, to characterize and constrain ambient SOA sources.