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| Titel |
Eddy covariance flux measurements of ammonia by high temperature chemical ionisation mass spectrometry |
| VerfasserIn |
J. Sintermann, C. Spirig, A. Jordan, U. Kuhn, C. Ammann, A. Neftel |
| 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. 3 ; Nr. 4, no. 3 (2011-03-24), S.599-616 |
| Datensatznummer |
250001806
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| Publikation (Nr.) |
 copernicus.org/amt-4-599-2011.pdf |
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| Zusammenfassung |
| A system for fast ammonia (NH3) measurements with chemical ionisation mass
spectrometry (CIMS) based on a commercial
Proton Transfer Reaction-Mass Spectrometer (PTR-MS) is presented. It uses electron
transfer reaction as ionisation pathway and features a drift tube of
polyetheretherketone (PEEK) and silica-coated steel. Heating the
instrumental inlet and the drift tube to 180 °C enabled an effective time
resolution of ~1 s and made it possible to apply the instrument for eddy
covariance (EC) measurements. EC fluxes of NH3 were measured over two
agricultural fields in Oensingen, Switzerland, following fertilisations with
cattle slurry. Air was aspirated close to a sonic anemometer at a flow of
100 STP L min−1 and was directed through a 23 m long
1/2" PFA tube heated to 150 °C to an air-conditioned trailer where
the gas was sub-sampled from the large
bypass stream. This setup minimised damping of fast NH3 concentration
changes between the sampling point and the actual measurement.
High-frequency attenuation loss of the NH3 fluxes of 20 to 40% was
quantified and corrected for using an empirical ogive method. The
instrumental NH3 background signal showed a minor interference with
H2O which was characterised in the laboratory. The resulting correction
of the NH3 flux after slurry spreading was less than 1‰. The flux
detection limit of the EC system was about 5 ng m−2 s−1 while the
accuracy of individual flux measurements was estimated 16% for the
high-flux regime during these experiments. The NH3 emissions after
broad spreading of the slurry showed an initial maximum of
150 μg m−2 s−1 with a fast decline in the following hours. |
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