Preprints
https://doi.org/10.5194/amt-2021-186
https://doi.org/10.5194/amt-2021-186

  23 Jul 2021

23 Jul 2021

Review status: this preprint is currently under review for the journal AMT.

Fragment ion-functional group relationships in organic aerosols using aerosol mass spectrometry and mid-infrared spectroscopy

Amir Yazdani1, Nikunj Dudani1, Satoshi Takahama1, Amelie Bertrand2, André S. H. Prévôt2, Imad El Haddad2, and Ann M. Dillner3 Amir Yazdani et al.
  • 1ENAC/IIE Swiss Federal Institute of Technology Lausanne (EPFL), 1015 Lausanne, Switzerland
  • 2Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
  • 3Air Quality Research Center, University of California Davis, Davis, California, USA

Abstract. Aerosol mass spectrometry (AMS) and mid-infrared spectroscopy (MIR) are two analytical methods for characterizing the chemical composition of OM. While AMS provides high-temporal-resolution bulk measurements, the extensive fragmentation during the electron impact (EI) ionization makes the characterization of OM components limited. The analysis of aerosols collected on PTFE filters using MIR, on the other hand, provides functional group (FG) information with reduced sample alteration but results in a relatively low temporal resolution. In this work, we compared and combined MIR and AMS measurements for several environmental chamber experiments to achieve a better understanding of the AMS spectra and the OM chemical evolution by aging. Fresh emissions of wood and coal burning were injected into an environmental simulation chamber and aged with hydroxyl and nitrate radicals. A high-resolution time-of-flight (HR-TOF) AMS measured the bulk chemical composition of fine PM. Fine aerosols were also sampled on PTFE filters before and after aging for the offline MIR analysis. After comparing AMS and MIR bulk measurements, we used multivariate statistics to identify the influential functional groups contributing to AMS OM mass for different aerosol sources and aging processes. We also identified the key mass fragments resulting from each functional group for the complex OM generated from biomass and fossil fuel combustion. Finally, we developed a statistical model that enables estimation of the high-time-resolution functional group composition of OM using collocated AMS and MIR measurements. Using this approach, AMS spectra can be used to interpolate the functional group measurements by MIR, allowing us to better understand the evolution of OM during the aging process.

Amir Yazdani et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-186', Anonymous Referee #1, 10 Aug 2021
  • RC2: 'Comment on amt-2021-186', Anonymous Referee #2, 19 Sep 2021

Amir Yazdani et al.

Amir Yazdani et al.

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Short summary
While the Aerosol Mass Spectrometer provides high time resolution characterization of the overall extent of oxidation, the extensive fragmentation of molecules and specificity of the technique has posed challenges toward deeper understanding of molecular structures in aerosols. This work demonstrates how functional group information can be extracted from a suite of commonly-measured mass fragments using collocated infrared spectroscopy measurements.