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Concentration-dependent NH3 deposition processes for mixed moorland semi-natural vegetation

Jones, M. R.; Leith, I. D.; Fowler, D.; Raven, J. A; Sutton, M. A.; Nemitz, E.; Cape, J. N.; Sheppard, L. J.; Smith, R. I.; Theobald, M. R.. 2007 Concentration-dependent NH3 deposition processes for mixed moorland semi-natural vegetation. Atmospheric Environment, 41 (10). 2049-2060. 10.1016/j.atmosenv.2006.11.003

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Abstract/Summary

Dry deposition modelling typically assumes that canopy resistance (R-c) is independent of ammonia (NH3) concentration. An innovative flux chamber system was used to provide accurate continuous measurements of NH3 deposition to a moorland composed of a mixture of Calluna vulgaris (L.) Hull, Eriophorum vaginatum L. and Sphagnum spp. Ammonia was applied at a wide range of concentrations (1-100 mu g m(-3)). The physical and environmental properties and the testing of the chamber are described, as well as results for the moorland vegetation using the 'canopy resistance' and 'canopy compensation point' interpretations of the data. Results for moorland plant species demonstrate that NH3 concentration directly affects the rate of NH3 deposition to the vegetation canopy, with R-c and cuticular resistance (R-w) increasing with increasing NH3 concentrations. Differences in 3 3 R-c were found between night and day: during the night R-c increases from 17 s m(-1) at 10 mu g m(-3) to 95 s m(-1) at 80 mu g m(-3) whereas during the day R-c increases from 17 s m(-1) at 10 mu g m(-3) to 48 s m(-1) at 80 mu g m(-3). The lower resistance during the day is caused by the stomata being open and available as a deposition route to the plant. R-c increased with increasing NH3 concentrations and was not significantly different between day and night (at 80 mu g m(-3) NH3 day R-w = 88 s m(-1) and night R-w = 95 s m(-1)). The results demonstrate that assessments using fixed R-c will over-estimate NH3 deposition at high concentrations (over similar to 15 mu g m(-3)).

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.atmosenv.2006.11.003
Programmes: CEH Programmes pre-2009 publications > Biogeochemistry > BG01 Measuring and modelling trace gas, aerosol and carbon > BG01.1 UK nitrogen and sulphur compounds
CEH Programmes pre-2009 publications > Biogeochemistry > BG02 Recovery from acidification and eutrophication > BG02.2 Critical Loads
CEH Sections: Billett
ISSN: 1352-2310
Additional Keywords: canopy resistance, compensation point, cuticular resistance, flux chamber, dry deposition, ammonia
NORA Subject Terms: Botany
Meteorology and Climatology
Ecology and Environment
Atmospheric Sciences
Date made live: 10 Dec 2007 16:23
URI: http://nora.nerc.ac.uk/id/eprint/1352

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