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| Titel |
Inter-comparison of ammonia fluxes obtained using the Relaxed Eddy Accumulation technique |
| VerfasserIn |
A. Hensen, E. Nemitz, M. J. Flynn, A. Blatter, S. K. Jones, L. L. Sørensen, B. Hensen, S. C. Pryor, B. Jensen, R. P. Otjes, J. Cobussen, B. Loubet, J. W. Erisman, M. W. Gallagher, A. Neftel, M. A. Sutton |
| 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. 11 ; Nr. 6, no. 11 (2009-11-16), S.2575-2588 |
| Datensatznummer |
250004093
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| Publikation (Nr.) |
 copernicus.org/bg-6-2575-2009.pdf |
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| Zusammenfassung |
| The exchange of Ammonia (NH3) between grassland and the atmosphere
was determined using Relaxed Eddy Accumulation (REA) measurements. The use
of REA is of special interest for NH3, since the determination of
fluxes at one height permits multiple systems to be deployed to quantify
vertical flux divergence (either due to effects of chemical production or
advection). During the Braunschweig integrated experiment four different
continuous-sampling REA systems were operated during a period of about 10 days and were compared against a reference provided by independent
application of the Aerodynamic Gradient Method (AGM). The experiment covered
episodes before and after both cutting and fertilizing and provided a wide
range of fluxes −60–3600 ng NH3 m−2 s−1 for testing the
REA systems. The REA systems showed moderate to good correlation with the
AGM estimates, with r2 values for the linear regressions between 0.3
and 0.82. For the period immediately after fertilization, the REA systems
showed average fluxes 20% to 70% lower than the reference. At periods
with low fluxes REA and AGM can agree within a few %. Overall, the
results show that the continuous REA technique can now be used to measure
NH3 surface exchange fluxes. While REA requires greater analytical
precision in NH3 measurement than the AGM, a key advantage of REA is
that reference sampling periods can be introduced to remove bias between
sampling inlets. However, while the data here indicate differences
consistent with advection effects, significant improvements in sampling
precision are essential to allow robust determination of flux divergence in
future studies. Wet chemical techniques will be developed further since they
use the adsorptive and reactive properties of NH3 that impedes
development of cheaper optical systems. |
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