Long-term measurements of the land-atmosphere exchange of ammonia over moorland

Fowler, D.; Flechard, C. R.; Sutton, M. A. ORCID:; Storeton-West, R. L.. 1998 Long-term measurements of the land-atmosphere exchange of ammonia over moorland. Atmospheric Environment, 32 (3). 453-459.

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Measurements of the exchange of ammonia between the atmosphere and moorland vegetation using micrometeorological methods at a site in southern Scotland are reported. The median concentration of continuous measurements over seven months of the log-normally distributed ammonia data at the site is 0.45 μg NH3 m−3 with a geometric standard deviation of 3.4. The measurements made using a continuous wet annular denuder sampling system with a separate denuder at three heights above the surface provided satisfactory fluxes by the aerodynamic flux-gradient method for over 70% of the time between January and August 1995. The site which consists of unimproved moorland vegetation represented an efficient sink for ammonia during the winter months with deposition velocities (Vd) in the range 15 to 30 mm s−1 and canopy resistances (Rc) close to zero. The monthly median Vd declined with time from 25 mm s−1 in February to 5 mm s−1 in August as the result of a steady increase of the canopy resistance in the dry, warmer, summer conditions to typically 100 s m−1 during the daytime. The canopy compensation point increased from zero during winter months to about 0.2 μg m−3 in August and short periods of NH3 emission were observed whenever ambient concentration fell below 0.2 μg m−3 during the summer. The annual input of gaseous NH3 to this moorland surface is approximately 2 kg N ha−1, and is similar to the input of NH+4-N in wet deposition.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Programmes pre-2009 publications > Biogeochemistry
UKCEH and CEH Sections/Science Areas: _ Biogeochemistry & Ecosystem Function
_ Atmospheric Sciences
ISSN: 1352-2310
Additional Keywords: Dry deposition, ammonia, canopy resistance, compensation point, moorland, Atmospheric chemistry, Meteorology, Plants (botany), Atmospheric composition, Climate change, Aerodynamic flux gradient method
NORA Subject Terms: Ecology and Environment
Atmospheric Sciences
Date made live: 08 Sep 2008 11:46 +0 (UTC)

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