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| Titel |
Formation and occurrence of dimer esters of pinene oxidation products in atmospheric aerosols |
| VerfasserIn |
K. Kristensen, K. L. Enggrob, S. M. King, D. R. Worton, S. M. Platt, R. Mortensen, T. Rosenoern, J. D. Surratt, M. Bilde, A. H. Goldstein, M. Glasius |
| 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. 7 ; Nr. 13, no. 7 (2013-04-10), S.3763-3776 |
| Datensatznummer |
250018578
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| Publikation (Nr.) |
 copernicus.org/acp-13-3763-2013.pdf |
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| Zusammenfassung |
The formation of carboxylic acids and dimer esters from α-pinene oxidation
was investigated in a smog chamber and in ambient aerosol samples collected
during the Biosphere Effects on Aerosols and Photochemistry Experiment
(BEARPEX). Chamber experiments of α-pinene ozonolysis in dry air and
at low NOx concentrations demonstrated formation of two dimer
esters, pinyl-diaterpenyl (MW 358) and pinonyl-pinyl dimer ester (MW 368),
under both low- and high-temperature conditions. Concentration levels of the
pinyl-diaterpenyl dimer ester were lower than the assumed first-generation
oxidation products cis-pinic and terpenylic acids, but similar to
the second-generation oxidation products 3-methyl-1,2,3-butane tricarboxylic
acid (MBTCA) and diaterpenylic acid acetate (DTAA). Dimer esters were
observed within the first 30 min, indicating rapid production simultaneous
to their structural precursors. However, the sampling time resolution
precluded conclusive evidence regarding formation from gas- or particle-phase
processes. CCN activities of the particles formed in the smog chamber
displayed a modest variation during the course of experiments, with κ
values in the range 0.06–0.09 (derived at a supersaturation of 0.19%).
The pinyl-diaterpenyl dimer ester was also observed in ambient aerosol
samples collected above a ponderosa pine forest in the Sierra Nevada
Mountains of California during two seasonally distinct field campaigns in
September 2007 and July 2009. The pinonyl-pinyl ester was observed for the
first time in ambient air during the 2009 campaign, and although present at
much lower concentrations, it was correlated with the abundance of the
pinyl-diaterpenyl ester, suggesting similarities in their formation. The
maximum concentration of the pinyl-diaterpenyl ester was almost 10 times
higher during the warmer 2009 campaign relative to 2007, while the
concentration of cis-pinic acid was approximately the same during
both periods, and lack of correlation with levels of cis-pinic
and terpenylic acids for both campaigns indicate that the formation of the
pinyl-diaterpenyl ester was not controlled by their ambient abundance. In
2009 the concentration of the pinyl-diaterpenyl ester was well correlated
with the concentration of DTAA, a supposed precursor of diaterpenylic acid,
suggesting that the formation of pinyl-diaterpenyl dimer was closely related
to DTAA. Generally, the pinyl-diaterpenyl ester was found at higher
concentrations under higher temperature conditions, both in the
smog-chamber study and in ambient air aerosol samples, and exhibited much higher
concentrations at night relative to daytime in line with previous results.
We conclude that analysis of pinyl dimer esters provides valuable information
on pinene oxidation processes and should be included in studies of formation
and photochemical aging of biogenic secondary organic aerosols, especially at
high temperatures. |
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