Long Term NH3 Flux Measurements above Grasslands in The Netherlands |
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Authors: | Mosquera J Hensen A van den Bulk W C M Vermeulen A T Erisman J W |
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Institution: | (1) Netherlands Energy Research Foundation, ECN, Petten, The Netherlands |
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Abstract: | Ammonia concentration gradients were measuredabove a grassland in an agricultural region fromJuly 1998 to July 2000 at the locationSchagerbrug in the Netherlands. They were used tocalculate the surface-atmosphere exchange ofammonia by means of the aerodynamic gradienttechnique. Measurements of the ammonia exchangewere also performed at a grass field that is partof a major wetland reserve in the centre of theNetherlands (Oostvaardersplassen), during theperiod June 1994–September 1995. At Schagerbrug,low net emissions or small depositions weremeasured during the winter months, and a netemission up to 5 kg NH3 ha-1 month-1 in summer. The net annual emission was 26 kgN ha-1, with manure application contributingabout 50% of this emission. AtOostvaardersplassen mainly deposition occurred,but large emissions were measured in autumn. Themeasured exchange fluxes are compared to modelevaluations that incorporate plant physiologicaldata, such as apoplastic NH4
+concentrations and pH. Results show a goodagreement between field observations and modelsimulations, although some improvements arenecessary during nighttime periods. Themeasurements are conducted within the GRAMINAEproject, a second tranche project of EC TERI. |
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Keywords: | ammonia fluxes long-termmeasurements resistance modelling |
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