Hourly Measurements of Organic Molecular Markers in Urban Shanghai, China: Primary Organic Aerosol Source Identification and Observation of Cooking Aerosol Aging

Qiongqiong Wang, Xiao He, Min Zhou, Dan Dan Huang, Liping Qiao, Shuhui Zhu, Ying Ge Ma, Hong Li Wang, Li Li, Cheng Huang, X. H.Hilda Huang, Wen Xu, Douglas Worsnop, Allen H. Goldstein, Hai Guo, Jian Zhen Yu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

8 Citations (Scopus)

Abstract

Molecular markers in ambient organic aerosol (OA) provide highly specific source information. Their traditional quantification is based on offline analysis of filter samples, and the coarse time resolution and labor-intensive nature hugely limit the utility of the tracer data. In this study, hourly organic molecular markers in fine particulate matter were measured using a recently commercialized thermal desorption aerosol gas chromatography-mass spectrometry (TAG) technique at an urban location in Shanghai, China during a three-week campaign from 9 November to 3 December, 2018. Selected primary OA molecular markers, including anhydrosugars, fatty acids, aromatic acids, and polycyclic aromatic hydrocarbons (PAHs), were examined in detail. Their diurnal variations showed characteristic features representing the corresponding emission source activities. For example, stearic acid showed a clear peak around 7 pm, in accordance with the enhanced cooking activities during mealtime. Diagnostic ratios of related makers of different reactivities provided unique information in uncovering the source information and tracking evolution of the OA in the atmosphere, for example, ratios of levoglucosan to its isomers and K+ identified crop residue burning as the major form of biomass burning (BB). Ratios of unsaturated and saturated fatty acids gave unambiguous indication of atmospheric degradation of unsaturated fatty acids after emissions. Oleic acid to stearic acid ratios in ambient data (0.83 ± 0.54) were lower than those in the source profiles (1.2-6.5). Furthermore, the oleic acid to stearic acid ratio was found to be highly correlated with O/C ratios (Rp: -0.66), suggesting the possible utility of oleic acid as a model compound to examine the heterogeneous reaction of cooking-related OA. PAH ratio-ratio plots helped identify varying influences of major combustion sources associated with air masses of different origins, revealing that BB and coal combustion were dominant under the influence of long-range transport air mass, while vehicle emissions were dominant under local/median-range air mass influence. This study demonstrated the utility of high time-resolution organic markers in capturing the dynamic change of source emissions and atmospheric aging, providing observational evidence to support their use in source apportionment.

Original languageEnglish
Pages (from-to)1670-1685
Number of pages16
JournalACS Earth and Space Chemistry
Volume4
Issue number9
DOIs
Publication statusPublished - 17 Sep 2020

Keywords

  • atmospheric aging
  • biomass burning
  • cooking aerosol
  • organic molecular markers
  • primary organic aerosols
  • source identification
  • thermal desorption aerosol gas chromatography-mass spectrometry

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Atmospheric Science
  • Space and Planetary Science

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