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| Titel |
Secondary organic aerosol formation from the β-pinene+NO3 system: effect of humidity and peroxy radical fate |
| VerfasserIn |
C. M. Boyd, J. Sanchez, L. Xu, A. J. Eugene, T. Nah, W. Y. Tuet, M. I. Guzmán, N. L. Ng |
| 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 ; 15, no. 13 ; Nr. 15, no. 13 (2015-07-10), S.7497-7522 |
| Datensatznummer |
250119884
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| Publikation (Nr.) |
 copernicus.org/acp-15-7497-2015.pdf |
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| Zusammenfassung |
| The formation of secondary organic aerosol (SOA) from the oxidation of
β-pinene via nitrate radicals is investigated in the Georgia Tech Environmental Chamber (GTEC) facility. Aerosol yields are determined for
experiments performed under both dry (relative humidity (RH) < 2 %) and humid (RH = 50 %
and RH = 70 %) conditions. To probe the effects of peroxy radical
(RO2) fate on aerosol formation, "RO2 + NO3 dominant" and
"RO2 + HO2 dominant" experiments are performed. Gas-phase
organic nitrate species (with molecular weights of 215, 229, 231, and 245 amu, which likely correspond to molecular formulas of
C10H17NO4, C10H15NO5,
C10H17NO5, and C10H15NO6, respectively) are
detected by chemical ionization mass spectrometry (CIMS) and their formation
mechanisms are proposed. The NO+ (at m/z 30) and NO2+ (at
m/z 46) ions contribute about 11 % to the combined organics and
nitrate signals in the typical aerosol mass spectrum, with the
NO+ : NO2+ ratio ranging from 4.8 to 10.2 in all experiments
conducted. The SOA yields in the "RO2 + NO3 dominant" and
"RO2 + HO2 dominant" experiments are comparable. For a wide
range of organic mass loadings (5.1–216.1 μg m−3), the aerosol
mass yield is calculated to be 27.0–104.1 %. Although humidity does not
appear to affect SOA yields, there is evidence of particle-phase hydrolysis
of organic nitrates, which are estimated to compose 45–74 % of the organic
aerosol. The extent of organic nitrate hydrolysis is significantly lower
than that observed in previous studies on photooxidation of volatile organic
compounds in the presence of NOx. It is estimated that about 90 and
10 % of the organic nitrates formed from the β-pinene+NO3
reaction are primary organic nitrates and tertiary organic nitrates,
respectively. While the primary organic nitrates do not appear to hydrolyze,
the tertiary organic nitrates undergo hydrolysis with a lifetime of 3–4.5 h. Results from this laboratory chamber study provide the fundamental
data to evaluate the contributions of monoterpene + NO3 reaction to
ambient organic aerosol measured in the southeastern United States,
including the Southern Oxidant and Aerosol Study (SOAS) and the Southeastern Center for Air Pollution and Epidemiology (SCAPE) study. |
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