Preprints
https://doi.org/10.5194/amt-2022-248
https://doi.org/10.5194/amt-2022-248
 
12 Sep 2022
12 Sep 2022
Status: this preprint is currently under review for the journal AMT.

Characterization of offline analysis of particulate matter with FIGAERO-CIMS

Jing Cai1,2,, Kaspar Daellenbach1,2,3,, Cheng Wu4,5, Yan Zheng6, Feixue Zheng1, Wei Du1,2, Sophie Haslett4, Qi Chen6, Markku Kulmala1,2, and Claudia Mohr4 Jing Cai et al.
  • 1Aerosol and Haze Laboratory, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
  • 2Institute for Atmospheric and Earth System Research, Faculty of Science, University of Helsinki, Helsinki 00014, Finland
  • 3Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen, Switzerland
  • 4Department of Environmental Science, Stockholm University, Stockholm, 11418, Sweden
  • 5Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, Gothenburg, SE-412 96, Sweden
  • 6State Key Joint Laboratory of Environmental Simulation and Pollution Control, Beijing Innovation Center for Engineering Science and Advanced Technology, College of Environmental Science and Engineering, Peking University, Beijing, 100871, China
  • These authors contributed equally to this work.

Abstract. Measurements of the molecular composition of organic aerosol (OA) constituents improve our understanding of sources, formation processes, and physicochemical properties of OA. One instrument providing such data at a time resolution of minutes to hours is the Chemical Ionization time-of-flight Mass Spectrometer with Filter Inlet for Gases and AEROsols (FIGAERO-CIMS). The technique collects particles on a filter, which are subsequently desorbed, and the evaporated molecules are ionized and analyzed in the mass spectrometer. However, long-term measurements using this technique and/or field deployments at several sites simultaneously, require substantial human and financial resources. The analysis of filter samples collected outside the instrument (offline) may provide a more cost-efficient alternative and makes this technology available for the large number of particle filter samples collected routinely at many different sites globally. Filter-based offline use of the FIGAERO-CIMS limits this method albeit to particle-phase analyses, likely at reduced time resolution compared to online deployments. Here we present the application and assessment of offline FIGAERO-CIMS, using Teflon and Quartz fiber filter samples that were collected in autumn 2018 in urban Beijing. We demonstrate the feasibility of the offline application with “sandwich” sample preparation for the identified over 900 organic compounds with (1) high signal-to-noise ratios, (2) high repeatability, and (3) linear signal response to the filter loadings. Comparable overall signals were observed between the Quartz fiber and Teflon filters for 12-h and 24-h samples, but with larger signals for semi-volatile compounds for the Quartz fiber filters, likely due to adsorption artifacts. We also compare desorption profile (thermogram) shapes for the two filter materials. Thermograms are used to derive volatility qualitatively based on the desorption temperature at which the maximum signal intensity of a compound is observed (Tmax). While we find that Tmax can be determined with high repeatability for one filter type, we observe considerable differences in Tmax between the Quartz and Teflon filters, warranting further investigation into the thermal desorption characteristics of different filter types. Overall, this study provides a basis for expanding OA molecular characterization by FIGAERO-CIMS to situations where and when deployment of the instrument itself is not possible.

Jing Cai et al.

Status: open (until 26 Oct 2022)

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Jing Cai et al.

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Short summary
In this manuscript, we introduce the offline application of FIGAERO-CIMS by analyzing Teflon and Quartz filter samples that were collected at a typical urban site in Beijing with the deposition time varying from 30 min to 24 h. This method described provides a feasible, simple, and quantitative way to investigate the molecular composition and volatility of OA compounds by using FIGAERO-CIMS to analyze offline samples.