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| Titel |
Diode laser-based cavity ring-down instrument for NO3, N2O5, NO, NO2 and O3 from aircraft |
| VerfasserIn |
N. L. Wagner, W. P. Dubé, R. A. Washenfelder, C. J. Young, I. B. Pollack, T. B. Ryerson, S. S. Brown |
| 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 ; 4, no. 6 ; Nr. 4, no. 6 (2011-06-28), S.1227-1240 |
| Datensatznummer |
250002019
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| Publikation (Nr.) |
 copernicus.org/amt-4-1227-2011.pdf |
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| Zusammenfassung |
| This article presents a diode laser-based, cavity ring-down spectrometer for
simultaneous in situ measurements of four nitrogen oxide species, NO3,
N2O5, NO, NO2, as well as O3, designed for
deployment on aircraft. The instrument measures NO3 and NO2 by
optical extinction at 662 nm and 405 nm, respectively; N2O5 is
measured by thermal conversion to NO3, while NO and O3 are
measured by chemical conversion to NO2. The instrument has several
advantages over previous instruments developed by our group for measurement
of NO2, NO3 and N2O5 alone, based on a pulsed Nd:YAG and
dye laser. First, the use of continuous wave diode lasers reduces the
requirements for power and weight and eliminates hazardous materials.
Second, detection of NO2 at 405 nm is more sensitive than our
previously reported 532 nm instrument, and does not have a measurable
interference from O3. Third, the instrument includes chemical
conversion of NO and O3 to NO2 to provide measurements of total
NOx (= NO + NO2) and Ox (= NO2 + O3) on two
separate channels; mixing ratios of NO and O3 are determined by
subtraction of NO2. Finally, all five species are calibrated against a
single standard based on 254 nm O3 absorption to provide high accuracy.
Disadvantages include an increased sensitivity to water vapor on the 662 nm
NO3 and N2O5 channels and a modest reduction in sensitivity
for these species compared to the pulsed laser instrument. The in-flight
detection limit for both NO3 and N2O5 is 3 pptv (2 σ,
1 s) and for NO, NO2 and O3 is 140, 90, and 120 pptv (2 σ,
1 s) respectively. Demonstrated performance of the instrument in a
laboratory/ground based environment is better by approximately a factor of
2–3. The NO and NO2 measurements are less precise than research-grade
chemiluminescence instruments. However, the combination of these five
species in a single instrument, calibrated to a single analytical standard,
provides a complete and accurate picture of nighttime nitrogen oxide
chemistry. The instrument performance is demonstrated using data acquired
during a recent field campaign in California. |
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