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| Titel |
Intercomparison of NO3 radical detection instruments in the atmosphere simulation chamber SAPHIR |
| VerfasserIn |
H.-P. Dorn, R. L. Apodaca, S. M. Ball, T. Brauers, S. S. Brown, J. N. Crowley, W. P. Dubé, H. Fuchs, R. Häseler, U. Heitmann, R. L. Jones, A. Kiendler-Scharr, I. Labazan, J. M. Langridge, J. Meinen, T. F. Mentel, U. Platt, D. Pöhler, F. Rohrer, A. A. Ruth, E. Schlosser, G. Schuster, A. J. L. Shillings, W. R. Simpson, J. Thieser, R. Tillmann, R. Varma, D. S. Venables, A. Wahner |
| 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 ; 6, no. 5 ; Nr. 6, no. 5 (2013-05-02), S.1111-1140 |
| Datensatznummer |
250017883
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| Publikation (Nr.) |
 copernicus.org/amt-6-1111-2013.pdf |
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| Zusammenfassung |
| The detection of atmospheric NO3 radicals is still
challenging owing to its low mixing ratios (≈ 1 to
300 pptv) in the troposphere. While long-path differential
optical absorption spectroscopy (DOAS) has been a well-established
NO3 detection approach for over 25 yr, newly sensitive
techniques have been developed in the past decade. This publication
outlines the results of the first comprehensive intercomparison of
seven instruments developed for the spectroscopic detection of
tropospheric NO3. Four instruments were based on cavity
ring-down spectroscopy (CRDS), two utilised open-path cavity-enhanced
absorption spectroscopy (CEAS), and one applied "classical"
long-path DOAS. The intercomparison campaign "NO3Comp" was held at
the atmosphere simulation chamber SAPHIR in Jülich (Germany) in June
2007. Twelve experiments were performed in the well-mixed chamber for
variable concentrations of NO3, N2O5, NO2,
hydrocarbons, and water vapour, in the absence and in the presence of
inorganic or organic aerosol. The overall precision of the cavity
instruments varied between 0.5 and 5 pptv for integration
times of 1 s to 5 min; that of the DOAS instrument was
9 pptv for an acquisition time of 1 min. The
NO3 data of all instruments correlated excellently with the
NOAA-CRDS instrument, which was selected as the common reference
because of its superb sensitivity, high time resolution, and most
comprehensive data coverage. The median of the coefficient of
determination (r2) over all experiments of the campaign
(60 correlations) is r2 = 0.981
(quartile 1 (Q1): 0.949; quartile 3 (Q3): 0.994; min/max: 0.540/0.999). The
linear regression analysis of the campaign data set yielded very small
intercepts (median: 1.1 pptv; Q1/Q3: −1.1/2.6 pptv;
min/max: −14.1/28.0 pptv), and the slopes of the
regression lines were close to unity (median: 1.01; Q1/Q3: 0.92/1.10;
min/max: 0.72/1.36).
The deviation of individual regression slopes from
unity was always within the combined accuracies of each instrument
pair. The very good correspondence between the NO3
measurements by all instruments for aerosol-free experiments indicates
that the losses of NO3 in the inlet of the instruments were
determined reliably by the participants for the corresponding
conditions. In the presence of inorganic or organic aerosol, however,
differences in the measured NO3 mixing ratios were detectable
among the instruments.
In individual experiments the discrepancies
increased with time, pointing to additional NO3 radical
losses by aerosol deposited onto the filters or on the inlet walls of the
instruments. Instruments using DOAS analyses showed no significant
effect of aerosol on the detection of NO3. No hint of a cross
interference of NO2 was found. The effect of non-Lambert–Beer
behaviour of water vapour absorption lines on the accuracy of the
NO3 detection by broadband techniques was small and well
controlled. The NO3Comp campaign demonstrated the high quality,
reliability and robustness of performance of current state-of-the-art
instrumentation for NO3 detection. |
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