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Title:
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NH3 flux measurements at Schagerbrug and Oostvaardersplassen, the Dutch contribution to the GRAMINAE experiment
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Author(s):
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Published by:
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Publication date:
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ECN
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1-7-2000
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ECN report number:
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Document type:
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ECN-C--00-079
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ECN publication
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Number of pages:
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Full text:
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53
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Download PDF
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Abstract:
This report summarizes the results of the research at ECN on the exchangeof ammonia between the atmosphere and grasslands within the GRAMINAE
framework. The term exchange is used because of the bi-directional nature of
ammonia, that can be taken up (dry deposition) as well as released (emission)
by this type of surface. The main objective was to investigate the net
contribution to atmospheric ammonia provided by the exchange with grasslands
in relation to meteorological parameters and the land use management
(fertilization and/or grass cutting). Besides, a comparison was made between
the ammonia exchange obtained over intensively managed grasslands
(Schagerbrug) and semi-natural grasslands (Oostvaardersplassen). Ammonia
concentration gradients above a grassland in an intensively managed
agricultural region in the North West of the Netherlands (Schagerbrug) were
determined in the period July 1998 to July 2000. Use was made of three
annular denuders (AMANDA). From the vertical concentration gradients the
surface- atmosphere exchange of ammonia was calculated using the aerodynamic
gradient technique. Measurements of the ammonia exchange were also performed
at a grassfield that is part of a major wetland reserve close to the IJssel
lake (IJsselmeer), in the center of the Netherlands (Oostvaardersplassen),
during the period June 1994-September 1995. At Schagerbrug, low net emissions
or small depositions were measured during the winter months, with a net
emission per month up to 5 kg NH3/ha in summer. The net annual emission was
23 kg N/ha, with manure application contributing for about 50% to this level.
At the Oostvaardersplassen mainly deposition occurs, but large emissions were
measured in autumn. these emissions were probably the result of horses and
geese residing in this nature area. A resistance model that take into account
plant physiological data like apoplast NH4" concentrations and pH was
evaluated and applied to the measured exchange fluxes obtained at the site
Schagerbrug. Results show a good agreement between field observations and
model simulations, although some improvements have to be made during
nighttime periods. 12 refs.
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