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| Titel |
Secondary organic aerosol formation from hydroxyl radical oxidation and ozonolysis of monoterpenes |
| VerfasserIn |
D. F. Zhao, M. Kaminski, P. Schlag, H. Fuchs, I.-H. Acir, B. Bohn, R. Häseler, A. Kiendler-Scharr, F. Rohrer, R. Tillmann, M. J. Wang, R. Wegener, J. Wildt, A. Wahner, Th. F. Mentel |
| 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. 2 ; Nr. 15, no. 2 (2015-01-28), S.991-1012 |
| Datensatznummer |
250119351
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| Publikation (Nr.) |
 copernicus.org/acp-15-991-2015.pdf |
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| Zusammenfassung |
| Oxidation by hydroxyl radical (OH) and ozonolysis are the two major pathways
of daytime biogenic volatile organic compound (BVOC) oxidation and
secondary organic aerosol (SOA) formation. In this study, we investigated
the particle formation of several common monoterpenes (α-pinene,
β-pinene and limonene) by OH-dominated oxidation, which has seldom
been investigated. OH oxidation experiments were carried out in the SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction)
chamber in Jülich, Germany, at low NOx (0.01 ~ 1 ppbV)
and low ozone (O3) concentration (< 20 ppbV). OH concentration
and total OH reactivity (kOH) were measured directly, and through this
the overall reaction rate of total organics with OH in each reaction system
was quantified. Multi-generation reaction process, particle growth, new
particle formation (NPF), particle yield and chemical composition were analyzed
and compared with that of monoterpene ozonolysis. Multi-generation products
were found to be important in OH-dominated SOA formation. The relative role
of functionalization and fragmentation in the reaction process of OH
oxidation was analyzed by examining the particle mass and the particle size
as a function of OH dose. We developed a novel method which quantitatively
links particle growth to the reaction rate of OH with total organics in a
reaction system. This method was also used to analyze the evolution of
functionalization and fragmentation of organics in the particle formation by
OH oxidation. It shows that functionalization of organics was dominant in
the beginning of the reaction (within two lifetimes of the monoterpene) and
fragmentation started to play an important role after that. We compared
particle formation from OH oxidation with that from pure ozonolysis. In
individual experiments, growth rates of the particle size did not
necessarily correlate with the reaction rate of monoterpene with OH and
O3. Comparing the size growth rates at the similar reaction rates of
monoterpene with OH or O3 indicates that, generally, OH oxidation and
ozonolysis had similar efficiency in particle growth. The SOA yield of
α-pinene and limonene by ozonolysis was higher than that of OH
oxidation. Aerosol mass spectrometry (AMS) shows SOA elemental composition
from OH oxidation follows a slope shallower than −1 in the O / C vs. H / C
diagram, also known as Van Krevelen diagram, indicating that oxidation proceeds without significant loss of
hydrogen. SOA from OH oxidation had higher H / C ratios than SOA from
ozonolysis. In ozonolysis, a process with significant hydrogen loss seemed
to play an important role in SOA formation. |
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