 |
| Titel |
Understanding the aqueous phase ozonolysis of isoprene: distinct product distribution and mechanism from the gas phase reaction |
| VerfasserIn |
H. L. Wang, D. Huang, X. Zhang, Y. Zhao, Z. M. Chen |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 15 ; Nr. 12, no. 15 (2012-08-07), S.7187-7198 |
| Datensatznummer |
250011377
|
| Publikation (Nr.) |
 copernicus.org/acp-12-7187-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| The aqueous phase reaction of volatile organic compounds (VOCs) has not been
considered in most analyses of atmospheric chemical processes. However, some
experimental evidence has shown that, compared to the corresponding gas phase
reaction, the aqueous chemical processes of VOCs in the bulk solutions and
surfaces of ambient wet particles (cloud, fog, and wet aerosols) may
potentially contribute to the products and formation of secondary organic
aerosol (SOA). In the present study, we performed a laboratory experiment of
the aqueous ozonolysis of isoprene at different pHs (3–7) and temperatures
(4–25 °C). We detected three important kinds of products, including
carbonyl compounds, peroxide compounds, and organic acids. Our results showed
that the molar yields of these products were nearly independent of the
investigated pHs and temperatures, those were (1) carbonyls:
56.7 ± 3.7 % formaldehyde, 42.8 ± 2.5 % methacrolein (MAC),
and 57.7 ± 3.4 % methyl vinyl ketone (MVK); (2) peroxides:
53.4 ± 4.1 % hydrogen peroxide (H2O2) and
15.1 ± 3.1 % hydroxylmethyl hydroperoxide (HMHP); and (3) organic
acids: undetectable (<1 % estimated by the detection limit). Based on
the amounts of products formed and the isoprene consumed, the total carbon
yield was estimated to be 94.8 ± 4.1 %. This implied that most of the
products in the reaction system were detected. The combined yields of both
MAC + MVK and H2O2 + HMHP in the aqueous isoprene ozonolysis
were much higher than those observed in the corresponding gas phase reaction.
We suggest that these unexpected high yields of carbonyls and peroxides
are related to the greater capability of condensed water, compared to water
vapor, to stabilize energy-rich Criegee radicals. This aqueous ozonolysis of
isoprene (and possibly other biogenic VOCs) could potentially occur on the
surfaces of ambient wet particles and plants. Moreover, the high-yield
carbonyl and peroxide products might provide a considerable source of aqueous
phase oxidants and SOA precursors. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|