Journal cover Journal topic
Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union

Journal metrics

  • IF value: 2.989 IF 2.989
  • IF 5-year<br/> value: 3.489 IF 5-year
    3.489
  • CiteScore<br/> value: 3.37 CiteScore
    3.37
  • SNIP value: 1.273 SNIP 1.273
  • SJR value: 2.026 SJR 2.026
  • IPP value: 3.082 IPP 3.082
  • h5-index value: 45 h5-index 45
doi:10.5194/amt-2016-398
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
20 Dec 2016
Review status
A revision of this discussion paper was accepted for the journal Atmospheric Measurement Techniques (AMT) and is expected to appear here in due course.
Evaluation of the accuracy of thermal dissociation CRDS and LIF techniques for atmospheric measurement of reactive nitrogen species
Caroline C. Womack1, J. Andrew Neuman1,2, Patrick R. Veres1,2, Scott J. Eilerman1,2, Charles A. Brock1, Zachary C. J. Decker3, Kyle J. Zarzana1,2, William P. Dube1,2, Robert J. Wild1,2, Paul J. Wooldridge4, Ronald C. Cohen4,5, and Steven S. Brown1,3 1Chemical Sciences Division, Earth Science Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305 USA
2Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309 USA
3Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309 USA
4Department of Chemistry, University of California, Berkeley, CA 94720 USA
5Department of Earth and Planetary Science, University of California, Berkeley, CA 94720 USA
Abstract. The sum of all reactive nitrogen species (NOy) includes NOx (NO2 + NO) and all of its oxidized forms, and the accurate detection of NOy is critical to understanding atmospheric nitrogen chemistry. Thermal dissociation (TD) inlets, which convert NOy to NO2 followed by NO2 detection, are frequently used in conjunction with techniques such as laser induced fluorescence (LIF) and cavity ringdown spectroscopy (CRDS) to measure total NOy when set at > 600 °C, or speciated NOy when set at intermediate temperatures. We report the conversion efficiency of known amounts of several representative NOy species to NO2 in our TD-CRDS instrument, under a variety of experimental conditions. We find that the conversion efficiency of HNO3 is highly sensitive to the flow rate and the residence time through the TD inlet, as well as the presence of other species that may be present during ambient sampling, such as ozone (O3). Conversion of HNO3 at 400 °C, nominally the set point used to selectively convert organic nitrates, can range from 2–6 % and may represent an interference in measurement of organic nitrates under some conditions. The conversion efficiency is strongly dependent on the operating characteristics of individual quartz ovens, and should be well calibrated prior to use in field sampling. We demonstrate quantitative conversion of both gas phase N2O5 and particulate ammonium nitrate in the TD inlet at 650 °C, the temperature normally used for conversion of HNO3. N2O5 has two thermal dissociation steps, one at low temperature representing dissociation to NO2 and NO3, and one at high temperature representing dissociation of NO3, which produces exclusively NO2 and not NO. We also find a significant interference from partial conversion (5–10 %) of NH3 to NO at 650 °C in the presence of representative (50 ppbv) levels of O3 in dry zero air. Although this interference appears to be suppressed when sampling ambient air, we nevertheless recommend regular characterization of this interference using standard additions of NH3 to TD instruments that convert reactive nitrogen to NO or NO2.

Citation: Womack, C. C., Neuman, J. A., Veres, P. R., Eilerman, S. J., Brock, C. A., Decker, Z. C. J., Zarzana, K. J., Dube, W. P., Wild, R. J., Wooldridge, P. J., Cohen, R. C., and Brown, S. S.: Evaluation of the accuracy of thermal dissociation CRDS and LIF techniques for atmospheric measurement of reactive nitrogen species, Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-398, in review, 2016.
Caroline C. Womack et al.
Caroline C. Womack et al.

Viewed

Total article views: 341 (including HTML, PDF, and XML)

HTML PDF XML Total Supplement BibTeX EndNote
226 83 32 341 42 16 32

Views and downloads (calculated since 20 Dec 2016)

Cumulative views and downloads (calculated since 20 Dec 2016)

Viewed (geographical distribution)

Total article views: 341 (including HTML, PDF, and XML)

Thereof 340 with geography defined and 1 with unknown origin.

Country # Views %
  • 1

Saved

Discussed

Latest update: 25 May 2017
Publications Copernicus
Download
Short summary
The accurate detection of reactive nitrogen species (NOy) is key to understanding tropospheric ozone production. Typically, NOy is detected by thermal conversion to NO2, followed by NO2 detection. Here, we assess the conversion efficiency of several NOy species to NO2 in a thermal dissociation cavity ringdown spectrometer, and discuss how this conversion efficiency is affected by certain experimental conditions, such as oven residence time, and interferences from non-NOy species.
The accurate detection of reactive nitrogen species (NOy) is key to understanding tropospheric...
Share