 |
| Titel |
Are sesquiterpenes a good source of secondary organic cloud condensation nuclei (CCN)? Revisiting β-caryophyllene CCN |
| VerfasserIn |
X. Tang, D. R. Cocker, A. Asa-Awuku |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 18 ; Nr. 12, no. 18 (2012-09-18), S.8377-8388 |
| Datensatznummer |
250011452
|
| Publikation (Nr.) |
 copernicus.org/acp-12-8377-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| Secondary organic aerosol (SOA) was formed in an environmental reaction
chamber from the ozonolysis of β-caryophyllene (β-C) at low
concentrations (5 ppb or 20 ppb). Experimental parameters were varied to
characterize the effects of hydroxyl radicals, light and the presence of
lower molecular weight terpene precursor (isoprene) for β-C SOA
formation and cloud condensation nuclei (CCN) characteristics. Changes in
β-C SOA chemicophysical properties (e.g., density, volatility,
oxidation state) were explored with online techniques to improve our
predictive understanding of β-C CCN activity. In the absence of OH
scavenger, light intensity had negligible impacts on SOA oxidation state and
CCN activity. In contrast, when OH reaction was effectively suppressed
(> 11 ppm scavenger), SOA showed a much lower CCN activity and slightly
less oxygenated state consistent with previously reported values. Though
there is significant oxidized material present (O / C > 0.25), no
linear correlation existed between the mass ratio ion fragment 44 in the bulk
organic mass (f44) and O / C for the β-C-O3 system. No
direct correlations were observed with other aerosol bulk ion fragment
fraction (fx) and κ as well. A mixture of β-C and lower
molecular weight terpenes (isoprene) consumed more ozone and formed SOA with
distinct characteristics dependent on isoprene amounts. The addition of
isoprene also improved the CCN predictive capabilities with bulk aerosol
chemical information. The β-C SOA CCN activity reported here is much
higher than previous studies (κ < 0.1) that use higher precursor
concentration in smaller environmental chambers; similar results were only
achieved with significant use of OH scavenger. Results show that aerosol
formed from a mixture of low and high molecular weight terpene ozonolysis can
be hygroscopic and can contribute to the global biogenic SOA CCN budget. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|