Development of resistance models to describe measurements of bi-directional ammonia surface-atmosphere exchange

Sutton, M. A.; Burkhardt, J. K.; Guerin, D.; Nemitz, E.; Fowler, D.. 1998 Development of resistance models to describe measurements of bi-directional ammonia surface-atmosphere exchange. Atmospheric Environment, 32 (3). 473-480.

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Ammonia fluxes over vegetated land are bi-directional, with differences between emission and deposition occurring in relation to environmental conditions (temperature and wetness), plant community (e.g. arable land, unfertilized ecosystems), as well as other factors such as plant phenology. In the present paper, measurements of net NH3 fluxes over arable cropland are reported in the range −50 to 40 ng m−2s−1. These are used as examples to highlight the factors affecting the exchange process. Net fluxes are expected to depend on the competition between deposition to leaf surfaces and bi-directional exchange with a “stomatal compensation point” for leaf tissues (χs). Current models describe this effect poorly, and two new resistance models are described here. These estimate a “canopy compensation point” (χc), as the net potential for NH3 emission from the canopy. In the simpler of the two models, leaf surface uptake is parametrized using a resistance (Rw). This model is able to reproduce bi-directional fluxes, though there is also evidence that both cuticular NH3 adsorption and desorption may occur, dependent on previous fluxes. A more complex dynamic approach is therefore developed, treating cuticular uptake as a capacitance (Cd). The dynamic model is able to reproduce the pattern of desorption, but further development of both models is required to provide descriptions valid over longer periods and for a range of ecosystem types.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Programmes pre-2009 publications > Biogeochemistry
UKCEH and CEH Sections/Science Areas: _ Atmospheric Sciences
ISSN: 1352-2310
Additional Keywords: Wheat, fluxes, emission, resistance analogy, Air pollution, Atmospheric chemistry, Atmospheric composition, Ammonia, Crops, Meteorology, Mathematical models, Desorption, Ecosystems, Dry deposition, Micrometeorology, Canopy compensation point
NORA Subject Terms: Ecology and Environment
Atmospheric Sciences
Date made live: 03 Sep 2008 13:46 +0 (UTC)

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