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| Titel |
Investigating the influences of SO2 and NH3 levels on isoprene-derived secondary organic aerosol formation using conditional sampling approaches |
| VerfasserIn |
Y.-H. Lin, E. M. Knipping, E. S. Edgerton, S. L. Shaw, J. D. Surratt |
| 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 ; 13, no. 16 ; Nr. 13, no. 16 (2013-08-27), S.8457-8470 |
| Datensatznummer |
250085652
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| Publikation (Nr.) |
 copernicus.org/acp-13-8457-2013.pdf |
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| Zusammenfassung |
| Filter-based PM2.5 samples were chemically analyzed to investigate
secondary organic aerosol (SOA) formation from isoprene in a rural
atmosphere of the southeastern US influenced by both anthropogenic sulfur
dioxide (SO2) and ammonia (NH3) emissions. Daytime
PM2.5 samples were collected during summer 2010 using conditional
sampling approaches based on pre-defined high and low SO2 or NH3
thresholds. Known molecular-level tracers for isoprene SOA formation,
including 2-methylglyceric acid, 3-methyltetrahydrofuran-3,4-diols,
2-methyltetrols, C5-alkene triols, dimers, and organosulfate
derivatives, were identified and quantified by gas chromatography coupled to
electron ionization mass spectrometry (GC/EI-MS) and ultra performance
liquid chromatography coupled to electrospray ionization high-resolution
quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS). Mass
concentrations of six isoprene low-NOx SOA tracers contributed to
12–19% of total organic matter (OM) in PM2.5 samples collected
during the sampling period, indicating the importance of the hydroxyl
radical (OH)-initiated oxidation (so-called photooxidation) of isoprene
under low-NOx conditions that lead to SOA formation through reactive
uptake of gaseous isoprene epoxydiols (IEPOX) in this region. The
contribution of the IEPOX-derived SOA tracers to total organic matter was
enhanced by 1.4% (p = 0.012) under high-SO2 sampling scenarios,
although only weak associations between aerosol acidity and mass of IEPOX
SOA tracers were observed. This suggests that IEPOX-derived SOA formation
might be modulated by other factors simultaneously, rather than only aerosol acidity. No
clear associations between isoprene SOA formation and high or low NH3
conditional samples were found. Positive correlations between sulfate
aerosol loadings and IEPOX-derived SOA tracers for samples collected under
all conditions indicates that sulfate aerosol could be a surrogate for
surface accommodation in the uptake of IEPOX onto preexisting aerosols. |
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