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| Titel |
In-cloud processes of methacrolein under simulated conditions – Part 3: Hygroscopic and volatility properties of the formed secondary organic aerosol |
| VerfasserIn |
V. Michaud, I. Haddad, Yao Liu, K. Sellegri, P. Laj, P. Villani, D. Picard, N. Marchand, A. Monod |
| 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 ; 9, no. 14 ; Nr. 9, no. 14 (2009-07-28), S.5119-5130 |
| Datensatznummer |
250007536
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| Publikation (Nr.) |
 copernicus.org/acp-9-5119-2009.pdf |
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| Zusammenfassung |
| The hygroscopic and volatility properties of secondary organic
aerosol (SOA) produced from the nebulization of solutions after
aqueous phase photooxidation of methacrolein was experimentally
studied in a laboratory, using a Volatility-Hygroscopicity Tandem
DMA (VHTDMA). The obtained SOA were 80% 100°C-volatile
after 5 h of reaction and only 20% 100°C-volatile after
22 h of reaction. The Hygroscopic Growth Factor (HGF) of the SOA
produced from the nebulization of solutions after aqueous-phase
photooxidation of methacrolein is 1.34–1.43, which is significantly
higher than the HGF of SOA formed by gas-phase photooxidation of
terpenes, usually found almost hydrophobic. These hygroscopic
properties were confirmed for SOA formed by the nebulization of the
same solutions where NaCl was added. The hygroscopic properties of
the cloud droplet residuals decrease with the reaction time, in
parallel with the formation of more refractory compounds. This
decrease was mainly attributed to the 250°C-refractive
fraction (presumably representative of the highest molecular weight
compounds), which evolved from moderately hygroscopic (HGF of 1.52)
to less hygroscopic (HGF of 1.36). Oligomerization is suggested as a
process responsible for the decrease of both volatility and
hygroscopicity with time. The NaCl seeded experiments enabled us to
show that 19±4 mg L−1 of SOA was produced after 9.5 h
of reaction and 41±9 mg L−1 after 22 h of in-cloud
reaction. Because more and more SOA is formed as the reaction time
increases, our results show that the reaction products formed during
the aqueous-phase OH-oxidation of methacrolein may play a major role
in the properties of residual particles upon the droplet's
evaporation. Therefore, the specific physical properties of SOA
produced during cloud processes should be taken into account for a
global estimation of SOA and their atmospheric impacts. |
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