Journal Article

PreJuSER-14711

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Eddy covariance flux measurements of ammonia by high temperature chemical ionisation mass spectrometry

Sintermann, J. ; Spirig, C. ; Jordan, A. ; Kuhn, U.FZJ* ; Ammann, C. ; Neftel, A.

2011
Copernicus Katlenburg-Lindau

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Please use a persistent id in citations: http://hdl.handle.net/2128/20775  doi:10.5194/amt-4-599-2011

Abstract: 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 degrees C enabled an effective time resolution of similar to 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 degrees 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 mu g m(-2) s-1 with a fast decline in the following hours.

Keyword(s): J

Note: We thank the Swiss National Science Foundation for funding this project (TERMS, 200021-117686/1). In addition, the research leading to these results has received funding from the (EU) Seventh Framework Programme - (FP7/2007-2013) under grant agreement no (PIEF-GA-2008-220842) - as well as from the EU project NitroEurope (Contract 017841) that is funded under the EC 6th Framework Programme for Research and Technological Development. We are very grateful to Kerstin Zeyer and Lukas Emmenegger from the Swiss Federal Laboratories for Materials Science and Technology (EMPA) who provided the in-field calibration device. Finally, we thank Markus Jocher from our group for his constant support.

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Contributing Institute(s):

1. Troposphäre (IEK-8)

Research Program(s):

1. Atmosphäre und Klima (P23)

Appears in the scientific report 2011

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