The exchange of atmospheric ammonia with vegetated surfaces. I: Unfertilized vegetation
Article first published online: 15 DEC 2006
Copyright © 1993 Royal Meteorological Society
Quarterly Journal of the Royal Meteorological Society
Volume 119, Issue 513, pages 1023–1045, July 1993 Part B
How to Cite
Sutton, M. A., Flower, D. and Moncriefe, J. B. (1993), The exchange of atmospheric ammonia with vegetated surfaces. I: Unfertilized vegetation. Q.J.R. Meteorol. Soc., 119: 1023–1045. doi: 10.1002/qj.49711951309
- Issue published online: 15 DEC 2006
- Article first published online: 15 DEC 2006
- Manuscript Revised: 21 DEC 1992
- Manuscript Received: 19 NOV 1991
- UK Natural Environment Research Council (Special Topic in Atmospheric Chemistry) and by the research program of the UK Department of the Environment
Micrometeorological techinques have been used to measure the surface/atmosphere exchange of gaseous ammonia (NH3) over semi-natural and unfertilized plant communities. A range of temperate ecosystems have been examined, including moorland, cut meadows and coniferous forest. Apart from a recently harrowed calcareous grassland, where deposition velocities, Vd (1 m), were in the range 1–11 mm s−1, ammonia was found to deposit rapidly (Vd typically 15–20 mm s−1 for short vegetation) with surface resistances, Rc, not significantly different from zero. Limited measurements over forest were consistent with a larger Vd (mean 66 mm s-1) as a consequence of increased turbulence over the aerodynamically rough surface.
These observations show that, except for the harrowed calcareous site, ammonia is efficiently deposited to leaf surfaces, and that the mean air concentration at the surfaces approaches zero. The results are used as a basis for estimating annual dry deposition of ammonia to semi-natural and unfertilized vegetation. For example sites in the British Isles, subject to typical background air concentrations, the estimated annual dry deposition of ammonia is in range 2-41 kg fixed nitrogen per hectare, showing that this is a major source of fixed atmospheric nitrogen.