Preprints
https://doi.org/10.5194/egusphere-2022-933
https://doi.org/10.5194/egusphere-2022-933
 
30 Sep 2022
30 Sep 2022
Status: this preprint is open for discussion and under review for Atmospheric Measurement Techniques (AMT).

Online measurement of highly oxygenated compounds from organic aerosol

Ella Häkkinen1, Jian Zhao1, Frans Graeffe1, Nicolas Fauré2, Jordan Krechmer3, Douglas Worsnop3, Hilkka Timonen4, Mikael Ehn1, and Juha Kangasluoma1 Ella Häkkinen et al.
  • 1Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, Helsinki, 00140, Finland
  • 2Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, SE-41296 Gothenburg, Sweden
  • 3Aerodyne Research Inc., Billerica, Massachusetts, 01821, United States
  • 4Atmospheric Composition Research, Finnish Meteorological Institute, 00560 Helsinki, Finland

Abstract. Highly oxygenated compounds are important contributors to the formation and growth of atmospheric organic aerosol, and thus have an impact on Earth’s radiation balance and global climate. However, knowledge of the contribution of highly oxygenated compounds to organic aerosol and their fate after condensing into the particle phase has been limited by the lack of suitable detection techniques. Here, we present a new online method for measuring highly oxygenated compounds from organic aerosol. The method includes thermal evaporation of particles in a new inlet, Vocus inlet for aerosols (VIA), followed by identification of the evaporated highly oxygenated compounds by a nitrate chemical ionization mass spectrometer (NO3-CIMS). The method does not require sample collection, enabling highly time-resolved measurements of particulate compounds. We evaluate the performance of the method by measuring the detection limit and performing background measurements. We estimate a detection limit of below 1 ng m−3 for a single compound and below 1 μg m−3 for SOA with the sampling set-up used here. These detection limits can be improved upon by optimizing the flow setup. Furthermore, we detect hundreds of particulate highly oxygenated compounds from organic aerosol generated from different precursors. Our results are consistent with previous studies showing that the volatility of organic compounds decreases with increasing m/z ratio and higher level of oxygenation, and that organic aerosol consists of monomers and oligomeric compounds. By comparing the gas- and particle-phase compounds, we found indications of potential particle-phase reactions occurring in organic aerosol. Future work will focus both on further improving the sampling design, as well as on better understanding the evaporation dynamics of the system, but already these initial tests show that VIA coupled to the NO3-CIMS is a promising method for investigating the transformations and fate of the compounds after condensing into the particle phase.

Ella Häkkinen et al.

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Ella Häkkinen et al.

Ella Häkkinen et al.

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Short summary
Highly oxygenated compounds contribute to the formation and growth of atmospheric organic aerosol, and thus impact the global climate. Knowledge of their transformations and fate after condensing into the particle phase has been limited by the lack of suitable detection techniques. Here, we present an online method for measuring highly oxygenated compounds from organic aerosol. We evaluate the performance of the method and demonstrate that the method is applicable to different organic species.