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| Titel |
Characterisation of an inlet pre-injector laser-induced fluorescence instrument for the measurement of atmospheric hydroxyl radicals |
| VerfasserIn |
A. Novelli, K. Hens, C. Tatum Ernest, D. Kubistin, E. Regelin, T. Elste, C. Plass-Dülmer, M. Martinez, J. Lelieveld  , H. Harder |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 7, no. 10 ; Nr. 7, no. 10 (2014-10-08), S.3413-3430 |
| Datensatznummer |
250115927
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| Publikation (Nr.) |
 copernicus.org/amt-7-3413-2014.pdf |
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| Zusammenfassung |
Atmospheric measurements of hydroxyl radicals (OH) are challenging due to a
high reactivity and consequently low concentration. The importance of OH as
an atmospheric oxidant has motivated a sustained effort leading to the
development of a number of highly sensitive analytical techniques. Recent
work has indicated that the laser-induced fluorescence of the OH molecules
method based on the fluorescence assay by gas expansion technique (LIF-FAGE)
for the measurement of atmospheric OH in some environments may be influenced
by artificial OH generated within the instrument, and a chemical method to
remove this interference was implemented in a LIF-FAGE system by Mao et al. (2012). While it
is not clear whether other LIF-FAGE instruments suffer from the same
interference, we have applied this method to our LIF-FAGE HORUS (Hydroxyl
Radical Measurement Unit based on fluorescence Spectroscopy) system, and
developed and deployed an inlet pre-injector (IPI) to determine the chemical
zero level in the instrument via scavenging the ambient OH radical.
We describe and characterise this technique in addition to its application
at field sites in forested locations in Finland, Spain and Germany. Ambient
measurements show that OH generated within the HORUS instrument is a
non-negligible fraction of the total OH signal, which can comprise 30 to
80% during daytime and 60 to 100% during the night. The
contribution of the background OH varied greatly between measurement sites
and was likely related to the type and concentration of volatile organic
compounds (VOCs) present at each particular location. Two inter-comparisons
in contrasting environments between the HORUS instrument and two different
chemical ionisation mass spectrometers (CIMS) are described to demonstrate
the efficacy of IPI and the necessity of the chemical zeroing method for our
LIF-FAGE instrument in such environments. |
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