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| Titel |
Technical note: Measuring tropospheric OH and HO2 by laser-induced fluorescence at low pressure. A comparison of calibration techniques |
| VerfasserIn |
S. Dusanter, D. Vimal, P. S. Stevens |
| 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. 2 ; Nr. 8, no. 2 (2008-01-25), S.321-340 |
| Datensatznummer |
250005428
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| Publikation (Nr.) |
 copernicus.org/acp-8-321-2008.pdf |
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| Zusammenfassung |
| The hydroxyl radical (OH) is one of the most important oxidants in the
atmosphere, as it is involved in many reactions that affect regional air
quality and global climate change. Because of its high reactivity,
measurements of OH radical concentrations in the atmosphere are difficult,
and often require careful calibrations that rely on the production of a
known concentration of OH at atmospheric pressure. The Indiana University OH
instrument, based on the Fluorescence Assay by Gas Expansion technique
(FAGE), has been calibrated in the laboratory using two different
approaches: the production of OH from the UV-photolysis of water-vapor, and
the steady-state production of OH from the reaction of ozone with alkenes.
The former technique relies on two different actinometric methods to measure the
product of the lamp flux at 184.9 nm and the photolysis time. This quantity
derived from N2O actinometry was found to be 1.5 times higher than that derived from O2
actinometry. The water photolysis and ozone-alkene techniques are shown to agree
within their experimental uncertainties (respectively 17% and 44%),
although the sensitivities derived from the ozone-alkene technique were
systematically lower by 40% than those derived from the water-vapor UV-
photolysis technique using O2 actinometry. The agreement between the two
different methods improves the confidence of the water-vapor photolysis method
as an accurate calibration technique for HOx instruments. Because
several aspects of the mechanism of the gas phase ozonolysis of alkenes are
still uncertain, this technique should be used with caution to calibrate OH
instruments. |
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