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| Titel |
Total OH reactivity measurements using a new fast Gas Chromatographic Photo-Ionization Detector (GC-PID) |
| VerfasserIn |
A. C. Nölscher, V. Sinha, S. Bockisch, T. Klüpfel, J. Williams |
| 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 ; 5, no. 12 ; Nr. 5, no. 12 (2012-12-04), S.2981-2992 |
| Datensatznummer |
250003206
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| Publikation (Nr.) |
 copernicus.org/amt-5-2981-2012.pdf |
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| Zusammenfassung |
The primary and most important oxidant in the atmosphere is
the hydroxyl radical (OH). Currently OH sinks, particularly
gas phase reactions, are poorly constrained. One way to
characterize the overall sink of OH is to measure directly the
ambient loss rate of OH, the total OH reactivity. To date,
direct measurements of total OH reactivity have been either
performed using a Laser-Induced Fluorescence (LIF) system
("pump-and-probe" or "flow reactor") or the Comparative
Reactivity Method (CRM) with a Proton-Transfer-Reaction Mass
Spectrometer (PTR-MS). Both techniques require large, complex
and expensive detection systems. This study presents
a feasibility assessment for CRM total OH reactivity
measurements using a new detector, a Gas Chromatographic
Photoionization Detector (GC-PID). Such a system is smaller,
more portable, less power consuming and less expensive than
other total OH reactivity measurement techniques.
Total OH reactivity is measured by the CRM using a competitive
reaction between a reagent (here pyrrole) with OH alone and in
the presence of atmospheric reactive molecules. The new CRM
method for total OH reactivity has been tested with parallel
measurements of the GC-PID and the previously validated PTR-MS
as detector for the reagent pyrrole during laboratory
experiments, plant chamber and boreal field studies. Excellent
agreement of both detectors was found when the GC-PID was
operated under optimum conditions. Time resolution
(60–70 s), sensitivity (LOD 3–6 s−1) and
overall uncertainty (25% in optimum conditions) for total
OH reactivity were similar to PTR-MS based total OH
reactivity measurements. One drawback of the GC-PID system was
the steady loss of sensitivity and accuracy during intensive
measurements lasting several weeks, and a possible toluene
interference. Generally, the GC-PID system has been shown to
produce closely comparable results to the PTR-MS and thus in
suitable environments (e.g. forests) it presents a viably
economical alternative for groups interested in total OH
reactivity observations. |
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