10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Understanding the Fate of Highly Oxygenated Molecules in the Particle Phase Using an Extractive Electrospray Ionization Time-of-Flight Mass Spectrometer (EESI-TOF)
VERONIKA POSPISILOVA, Felipe Lopez-Hilfiker, Claudia Mohr, Wei Huang, David Bell, Liine Heikkinen, Josef Dommen, Urs Baltensperger, Andre S.H. Prévôt, Jay G. Slowik, Paul Scherrer Institute
Abstract Number: 463 Working Group: Aerosol Chemistry
Abstract Atmospheric aerosols have significant impacts on human health and Earth´s climate. The highly oxygenated molecules (HOMs) yielded by the oxidation of biogenic and/or anthropogenic precursors contribute to the formation and growth of new particles in the atmosphere due to their low saturation vapor pressures. The molecular identification of these oxidized species in the gas phase is possible via chemical ionization mass spectrometry (CIMS) techniques. However, their identification and behavior in the particle phase remains an open question as currently no instrumentation allows online aerosol measurement on molecular level without thermal decomposition and/or ionization- induced fragmentation.
We present real-time measurements of individual organic aerosol species formed in alpha-pinene oxidation experiments in an atmospheric simulation chamber, as well as their direct observations in a boreal forest in southern Finland using a novel extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) developed at PSI. We demonstrate that the EESI-TOF enables real time analysis of highly oxygenated molecules in the particle phase, without fragmentation, at atmospherically relevant mass loadings. We will present the separation of different generations of aerosol components and compare the results with measurements conducted by a FIGAERO-CIMS (Filter Inlet for Gases and AEROsols coupled to a CIMS), a well-established semi-continuous technique for aerosol composition measurement.
The analysis from these techniques makes it possible to investigate the evolution of these molecules in the particle phase and assess the degree of decomposition and/or accretion reactions occurring during the particle aging. Particle phase fragmentations reactions could be an important process that might reduce the overall efficiency at which low volatility gas phase organics contribute to the aerosol mass. It is also speculated that accretion reactions can lead to oligomerization in the particle phase, which could lead to a less volatile and, therefore, a more persistent form of secondary organic aerosol. Here, we will present evidence for particle-phase decomposition reactions.