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| Titel |
Nighttime HOx chemistry in the Pearl River Delta and Beijing in summer 2006: intense oxidation without sunlight |
| VerfasserIn |
K. D. Lu, F. Rohrer, A. Hofzumahaus, F. Holland, H. Fuchs, T. Brauers, R. Dlugi, X. Li, S. R. Lou, M. Shao, T. Zhu, A. Wahner, Y. H. Zhang |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250062059
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| Zusammenfassung |
| Due to the absence of sunlight, unexpected high nighttime OH concentrations reported in
previous field studies are of high interest for in-depth understanding of trace gas removal and
reaction kinetics. In summer 2006, within the framework of PRIDE-PRD2006 and
CAREBEIJING2006, we performed intensive in-situ measurements for HOx radicals
and ancillary parameters at two non-urban sites in Pearl River Delta and Beijing,
respectively. During nighttime, quite similar features for both campaigns were observed.
Measured nighttime OH and HO2 concentrations were about 0.5Â –Â 3Ã106cm-3
and 0.2Â –Â 5Ã108cm-3, respectively. A box model with the established chemical
mechanism (RACM-MIM-GK) underestimated these observed OH concentrations by an
order of magnitude while reproduced the observed HO2 taking into account the
known interference from ambient RO2 radicals (Fuchs et al. 2011). By testing the
recently proposed recycling mechanisms applied for daytime chemistry, we found
both a small primary source and a secondary source of OH radicals, the last one
comparable to daytime observations (Lu et al., 2011, Hofzumahaus et al., 2009).
Interestingly, the widely applied LIM0 and MIM2+ showed marginal impacts on the
modeled nighttime OH concentrations under high isoprene concentrations. With the
help of a simple 1Â d simulation, we found that direct input of ROx radicals by
vertical transport was negligible while the input of PAN and MPAN could be of
significance. Averaged nighttime pollutant turnover rates by OH were as high as 8 ppb/h
and 4 ppb/h for PRD and Beijing, respectively, dominating nighttime oxidation
processes.
Fuchs, H., et al. Detection of HO2 by laser-induced fluorescence: calibration and
interferences from RO2 radicals, Atmos. Meas. Tech., 4, 1209-1225, 2011.
Hofzumahaus, A. et al. Amplified Trace Gas Removal in the Troposphere, Science, 324,
1702-1704, 2009.
Lu, K. D. et al. Observation and modelling of OH and HO2 concentrations in the Pearl River
Delta 2006: a missing OH source in a VOC rich atmosphere, Atmos. Chem. Phys. Discuss.,
11, 11311-11378, 2011. |
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