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| Titel |
An automated dynamic chamber system for surface exchange measurement of non-reactive and reactive trace gases of grassland ecosystems |
| VerfasserIn |
L. Pape, C. Ammann, A. Nyfeler-Brunner, C. Spirig, K. Hens, F. X. Meixner |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 6, no. 3 ; Nr. 6, no. 3 (2009-03-18), S.405-429 |
| Datensatznummer |
250003534
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| Publikation (Nr.) |
 copernicus.org/bg-6-405-2009.pdf |
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| Zusammenfassung |
We present an automated dynamic chamber system which is optimised for
continuous unattended flux measurements of multiple non-reactive and
reactive trace gases on grassland ecosystems. Main design features of our
system are (a) highly transparent chamber walls consisting of chemically
inert material, (b) individual purging flow units for each chamber, and (c)
a movable lid for automated opening and closing of the chamber. The purging
flow rate was chosen high enough to keep the mean residence time of the
chamber air below one minute. This guarantees a proven efficient mixing of
the chamber volume and a fast equilibration after lid closing. The dynamic
chamber system is able to measure emission as well as deposition fluxes of
trace gases. For the latter case, the modification of the turbulent
transport by the chamber (compared to undisturbed ambient conditions) is
quantitatively described by a bulk resistance concept.
Beside a detailed description of the design and functioning of the system,
results of field applications at two grassland sites are presented. In the
first experiment, fluxes of five trace gases (CO2, H2O, NO,
NO2, O3) were measured simultaneously on small grassland plots. It
showed that the dynamic chamber system is able to detect the characteristic
diurnal cycles with a sufficient temporal resolution. The results also
demonstrated the importance of considering the chemical source/sink in the
chamber due to gas phase reactions for the reactive compounds of the
NO-NO2-O3 triad. In a second field experiment, chamber flux
measurements of CO2 and methanol were compared to simultaneous
independent eddy covariance flux measurements on the field scale. The fluxes
obtained with the two methods showed a very good agreement indicating a
minimal disturbance of the chambers on the physiological activity of the
enclosed vegetation. |
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