Preprints
https://doi.org/10.5194/amt-2022-100
https://doi.org/10.5194/amt-2022-100
 
22 Apr 2022
22 Apr 2022
Status: a revised version of this preprint is currently under review for the journal AMT.

The Effect of the Averaging Period for PMF Analysis of Aerosol Mass Spectrometer Measurements during Off-Line Applications

Christina Vasilakopoulou1,2, Iasonas Stavroulas3,4, Nikolaos Mihalopoulos3,4, and Spyros Pandis1,2 Christina Vasilakopoulou et al.
  • 1Department of Chemical Engineering, University of Patras, Patras, Greece
  • 2Institute of Chemical Engineering Sciences, ICE-HT, Patras, Greece
  • 3Department of Chemistry, University of Crete, Heraklion Crete, Greece
  • 4Institute for Environmental Research and Sustainable Development, National Observatory of Athens, Athens, Greece

Abstract. Off-line Aerosol Mass Spectrometer (AMS) measurements can provide valuable information about the ambient organic aerosol in areas and periods in which online AMS measurements are not available. However, these offline measurements have low temporal resolution as they are based on filter samples collected usually over 24 hours. In this study we examine whether and how this low time resolution affects source apportionment results. We used a five-month period (November 2016–March 2017) of online measurements in Athens and performed Positive Matrix Factorization (PMF) analysis to both the original dataset, which consists of 30 min measurements, and to time averages from 1 up to 24 h. The 30 min results indicated that five factors were able to represent the ambient organic aerosol (OA): a biomass burning organic aerosol factor (BBOA) contributing 16 % of the total OA, hydrocarbon-like OA (HOA) (29 %), cooking OA (COA) (20 %), more oxygenated OA (MO-OOA) (18 %), and less oxygenated OA (LO-OOA) (17 %). Use of the daily averages resulted in estimated average contributions that were within 8 % of the total OA compared with the high resolution analysis for the five-month period. The most important difference was for the BBOA contribution which was overestimated (25 % for low resolution versus 17 % for high resolution) when daily averages were used. The estimated secondary OA varied from 35 to 28 % when the averaging interval varied between 30 min and 24 h. The error for the low resolution analysis was much higher for individual days and its results especially for high concentration days are quite uncertain. The low resolution analysis introduces errors in the determined AMS profiles for the BBOA and LO-OOA factors but determines the rest relatively accurately (theta angle around 10 degrees or less).

Christina Vasilakopoulou 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-2022-100', Anonymous Referee #1, 24 Jul 2022
    • AC1: 'Response to the Comments of Referee 1', Spyros Pandis, 13 Sep 2022
  • RC2: 'Comment on amt-2022-100', Anonymous Referee #2, 14 Aug 2022
    • AC2: 'Response to the Comments of Referee 2', Spyros Pandis, 13 Sep 2022

Christina Vasilakopoulou et al.

Christina Vasilakopoulou et al.

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Short summary
Off-line Aerosol Mass Spectrometer (AMS) measurements can provide valuable information about the ambient organic aerosol when online AMS measurements are not available. In this study we examine whether and how the low time resolution (usually 24 h) of the offline technique affects source apportionment results. We concluded that use of the daily averages resulted in estimated average contributions that were within 8 % of the total OA compared with the high resolution analysis.