Comment on egusphere-2023-1102

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> During the past decades, the source apportionment of organic aerosol (OA) in the ambient air has been improving substantially. The database of source retrieval model resolved mass spectral profiles for different sources has been built with the aerosol mass spectrometer (AMS). However, distinguishing similar sources (such as wildfires and residential wood burning) remains challenging, as the hard ionization of AMS mostly fragments compounds and therefore cannot capture the detailed molecular information. Recent mass spectrometer technologies of soft ionization and high mass resolution have allowed for aerosol characterization at the molecular formula level. In this study, we systematically estimated the emission factors and characterized the primary OA (POA) chemical composition with the AMS and the extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) for the first time from a variety of solid fuels, including beech logs, spruce and pine logs, spruce and pine branches and needles, straw, cow dung, and plastic bags. The emission factors of organic matter and hydrocarbon gases are 16.2 &plusmn; 10.8 g kg^-1 higher than that of wood (beech, spruce, and pine), straw, and plastic bags burning (in the range from 1.3 to 6.2 g kg^-1 and 30.3 &plusmn; 8.5 g kg^-1 for cow dung burning, which is generally 0.003 to 0.04 based on fuel types and combustion efficiency for wood (beech, spruce, and pine) and cow dung and 2.8 to 9.4 g kg^-1). The POA measured by the AMS shows that the <em>f</em>₆₀ (mass fraction of <em>m</em>/<em>z</em> 60) varies from burning. The contribution of some polycyclic aromatic hydrocarbons is linked to burning fuels. On molecular level, the dominant compound of POA from wood, straw, and cow dung is C₆H₁₀O₅ (mainly levoglucosan), contributing ~7 % to ~30 % of the total intensity, followed by C₈H₁₂O₆ with fractions of ~2 % to ~9 %. However, as they are prevalent in all burns of biomass material, they cannot act as tracers for the specific sources. By using the Mann-Whitney U test among the studied fuels, we find specific potential new markers for these fuels from the measurement of the AMS and EESI-TOF. Markers from spruce and pine burning could be resin and conifer needle-related. The product from pyrolysis of hardwood lignins is found especially in beech logs burning. Nitrogen-containing species are selected markers primarily for cow dung open burning. These markers provide important support for the source apportionment.