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| Titel |
Insights into secondary organic aerosol formed via aqueous-phase reactions of phenolic compounds based on high resolution mass spectrometry |
| VerfasserIn |
Y. L. Sun, Q. Zhang, C. Anastasio, J. Sun |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 10 ; Nr. 10, no. 10 (2010-05-26), S.4809-4822 |
| Datensatznummer |
250008478
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| Publikation (Nr.) |
 copernicus.org/acp-10-4809-2010.pdf |
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| Zusammenfassung |
| Recent work has shown that aqueous-phase reactions of phenolic compounds – phenol (C6H6O), guaiacol (C7H8O2), and syringol
(C8H10O3) – can form secondary organic aerosol (SOA) at high
yields. Here we examine the chemical characteristics of this SOA and its
formation mechanisms using a High-Resolution Time-of-Flight Aerosol Mass
Spectrometer (HR-AMS), an Ion Chromatography system (IC), and a Total
Organic Carbon (TOC) analyzer. The phenolic SOA are highly oxygenated with
oxygen-to-carbon (O/C) ratios in the range of 0.80–1.06 and carbon
oxidation states (=2×O/C-H/C) between −0.14 and +0.47. The
organic mass-to-carbon (OM/OC) ratios determined by the HR-AMS (=2.21–2.55) agree well with values determined based on the SOA mass measured
gravimetrically and the OC mass from the TOC analyzer. Both the O/C and
OM/OC ratios of the phenolic SOA are similar to the values observed for
ambient low-volatility oxygenated/secondary OA (LV-OOA). Oxalate is a minor,
but ubiquitous, component of the SOA formed from all three phenolic
precursors, accounting for 1.4−5.2% of the SOA mass, with generally
higher yields in experiments with H2O2 added as an OH source
compared to without. The AMS spectra show evidence for the formation of
syringol and guaiacol dimers and higher oligomers via C-C and C-O coupling
of phenoxyl radicals, which are formed through oxidation pathways such as
abstraction of the phenolic hydrogen atom or OH addition to the aromatic
ring. This latter pathway leads to hydroxylation of the aromatic ring, which
is one mechanism that increases the degree of oxidation of the SOA products.
Compared to direct photochemical reactions of the phenols, OH-initiated
reactions favor the formation of smaller oxidation products but less dimers
or higher oligomers. Two unique and prominent ions in the syringol and
guaiacol SOA spectra, m/z 306 (C16H18O6+) and m/z 246
(C14H14O4+), respectively, are observed in ambient
aerosols significantly influenced by wood combustion and fog processing. Our
results indicate that cloud and fog processing of phenolic compounds,
especially in areas with active biomass burning, might represent an
important pathway for the formation of low-volatility and highly oxygenated
organic species, which would remain in the particle phase after fog/cloud
evaporation and affect the chemical and optical properties of atmospheric
particles. |
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