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| Titel |
Formation of hydroxyl radicals from photolysis of secondary organic aerosol material |
| VerfasserIn |
K. M. Badali, S. Zhou, D. Aljawhary, M. Antiñolo, W. J. Chen, A. Lok, E. Mungall, J. P. S. Wong, R. Zhao, J. P. D. Abbatt |
| 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. 14 ; Nr. 15, no. 14 (2015-07-16), S.7831-7840 |
| Datensatznummer |
250119904
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| Publikation (Nr.) |
 copernicus.org/acp-15-7831-2015.pdf |
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| Zusammenfassung |
| This paper demonstrates that OH radicals are formed by photolysis of
secondary organic aerosol (SOA) material formed by terpene ozonolysis. The
SOA is collected on filters, dissolved in water containing a radical trap
(benzoic acid), and then exposed to ultraviolet light in a photochemical
reactor. The OH formation rates, which are similar for both α-pinene
and limonene SOA, are measured from the formation rate of p-hydroxybenzoic
acid as measured using offline HPLC analysis. To evaluate whether the OH is
formed by photolysis of H2O2 or organic hydroperoxides (ROOH), the
peroxide content of the SOA was measured using the horseradish
peroxidase-dichlorofluorescein (HRP-DCF) assay, which was calibrated using
H2O2. The OH formation rates from SOA are 5 times faster than
from the photolysis of H2O2 solutions whose concentrations
correspond to the peroxide content of the SOA solutions, assuming that the
HRP-DCF signal arises from H2O2 alone. The higher rates of OH
formation from SOA are likely due to ROOH photolysis, but we cannot rule out
a contribution from secondary processes as well. This result is
substantiated by photolysis experiments conducted with t-butyl hydroperoxide
and cumene hydroperoxide which produce over 3 times more OH than
photolysis of equivalent concentrations of H2O2. Relative to the
peroxide level in the SOA and assuming that the peroxides drive most of the
ultraviolet absorption, the quantum yield for OH generation from α-pinene SOA is 0.8 ± 0.4. This is the first demonstration of an
efficient photolytic source of OH in SOA, one that may affect both
cloud water and aerosol chemistry. |
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