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| Titel |
Intercomparison of ammonia measurement techniques at an intensively managed grassland site (Oensingen, Switzerland) |
| VerfasserIn |
M. Norman, C. Spirig, V. Wolff, I. Trebs, C. Flechard, A. Wisthaler, R. Schnitzhofer, A. Hansel, A. Neftel |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 9, no. 8 ; Nr. 9, no. 8 (2009-04-16), S.2635-2645 |
| Datensatznummer |
250007203
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| Publikation (Nr.) |
 copernicus.org/acp-9-2635-2009.pdf |
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| Zusammenfassung |
| As part of a field campaign in the framework of the NitroEurope project,
three different instruments for atmospheric ammonia (NH3) measurements
were operated side-by-side on a managed grassland site in Switzerland: a
modified Proton Transfer Reaction Mass Spectrometer (PTR-MS), a GRadient of
AErosol and Gases Online Registrator (GRAEGOR), and an Automated Ammonia
Analyzer (AiRRmonia). The modified PTR-MS approach is based on chemical
ionization of NH3 using O2+ instead of H3O+ as
ionizing agent, GRAEGOR and AiRRmonia measure NH4+ in liquids
after absorption of gaseous NH3 in a rotating wet-annular denuder and
through a gas permeable membrane, respectively. Bivariate regression slopes
using uncorrected data from all three instruments ranged from 0.78 to 0.97
while measuring ambient NH3 levels between 2 and 25 ppbv during a 5
days intercomparison period. Correlation coefficients r2 were in the
range of 0.79 to 0.94 for hourly average mixing ratios. Observed
discrepancies could be partly attributed to temperature effects on the
GRAEGOR calibration. Bivariate regression slopes using corrected data were
>0.92 with offsets ranging from 0.22 to 0.58 ppbv. The intercomparison
demonstrated the potential of PTR-MS to resolve short-time NH3
fluctuations which could not be measured by the two other slow-response
instruments. During conditions favoring condensation in inlet lines, the
PTR-MS underestimated NH3 mixing ratios, underlining the importance of
careful inlet designs as an essential component for any inlet-based
instrument. |
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