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| Titel |
Atmospheric hydrogen peroxide and organic hydroperoxides during PRIDE-PRD'06, China: their concentration, formation mechanism and contribution to secondary aerosols |
| VerfasserIn |
W. Hua, Z. M. Chen, C. Y. Jie, Y. Kondo, A. Hofzumahaus, N. Takegawa, C. C. Chang, K. D. Lu, Y. Miyazaki, K. Kita, H. L. Wang, Y. H. Zhang, M. Hu |
| 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 ; 8, no. 22 ; Nr. 8, no. 22 (2008-11-24), S.6755-6773 |
| Datensatznummer |
250006463
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| Publikation (Nr.) |
 copernicus.org/acp-8-6755-2008.pdf |
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| Zusammenfassung |
| Atmospheric hydrogen peroxide (H2O2) and
organic hydroperoxides were measured from 18 to 30 July in 2006 during the
PRIDE-PRD'06 campaign at Backgarden, a rural site located 48 km north of
Guangzhou, a mega-city in southern China. A ground-based instrument was used
as a scrubbing coil collector to sample ambient air, followed by on-site
analysis by high-performance liquid chromatography (HPLC) coupled with
post-column derivatization and fluorescence detection. The H2O2
mixing ratio over the 13 days ranged from below the detection limit to a
maximum of 4.6 ppbv, with a mean (and standard deviation) of (1.26±1.24) ppbv
during the daytime (08:00–20:00 LT). Methyl hydroperoxide (MHP),
with a maximum of 0.8 ppbv and a mean (and standard deviation) of (0.28±0.10) ppbv during the daytime, was the dominant organic hydroperoxide.
Other organic peroxides, including bis-hydroxymethyl hydroperoxide (BHMP),
peroxyacetic acid (PAA), hydroxymethyl hydroperoxide (HMHP), 1-hydroxy-ethyl
hydroperoxide (1-HEHP) and ethyl hydroperoxide (EHP), were detected
occasionally. The concentration of H2O2 exhibited a pronounced
diurnal variation on sunny days, with a peak mixing ratio in the afternoon
(12:00–18:00 LT), but lacked an explicit diurnal cycle on cloudy days.
Sometimes a second peak mixing ratio of H2O2 was observed during
the evening, suggesting that H2O2 was produced by the ozonolysis
of alkenes. The diurnal variation profile of MHP was, in general, consistent
with that of H2O2. The estimation indicated that in the morning
the H2O2 detected was formed mostly through local photochemical
activity, with the rest probably attributable to vertical transport. It is
notable that relatively high levels of H2O2 and MHP were found in
polluted air. The unexpectedly high level of HO2 radicals detected in
this region can account for the production of hydroperoxides, while the
moderate level of NOx suppressed the formation of hydroperoxides. High
concentrations of hydroperoxides were detected in samples of rainwater
collected in a heavy shower on 25 July when a typhoon passed through,
indicating that a considerable mixing ratio of hydroperoxides, particularly
MHP, resided above the boundary layer, which might be transported on a
regional scale and further influence the redistribution of HOx and
ROx radicals. It was found that hydroperoxides, in particular
H2O2, play an important role in the formation of secondary sulfate
in the aerosol phase, where the heterogeneous reaction might contribute
substantially. A negative correlation between hydroperoxides and
water-soluble organic compounds (WSOC), a considerable fraction of the
secondary organic aerosol (SOA), was observed, possibly providing field
evidence for the importance of hydroperoxides in the formation of SOA found
in previous laboratory studies. We suggest that hydroperoxides act as an
important link between sulfate and organic aerosols, which needs further
study and should be considered in current atmospheric models. |
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