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| Titel |
Advances in understanding, models and parameterizations of biosphere-atmosphere ammonia exchange |
| VerfasserIn |
C. R. Flechard, R.-S. Massad, B. Loubet, E. Personne, D. Simpson, J. O. Bash, E. J. Cooter, E. Nemitz, M. A. Sutton |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 7 ; Nr. 10, no. 7 (2013-07-30), S.5183-5225 |
| Datensatznummer |
250018370
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| Publikation (Nr.) |
 copernicus.org/bg-10-5183-2013.pdf |
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| Zusammenfassung |
| Atmospheric ammonia (NH3) dominates global emissions of total reactive
nitrogen (Nr), while emissions from agricultural production
systems contribute about two-thirds of global NH3 emissions; the
remaining third emanates from oceans, natural vegetation, humans, wild
animals and biomass burning. On land, NH3 emitted from the various
sources eventually returns to the biosphere by dry deposition to sink areas,
predominantly semi-natural vegetation, and by wet and dry deposition as
ammonium (NH4+) to all surfaces. However, the land/atmosphere
exchange of gaseous NH3 is in fact bi-directional over unfertilized as
well as fertilized ecosystems, with periods and areas of emission and
deposition alternating in time (diurnal, seasonal) and space (patchwork
landscapes). The exchange is controlled by a range of environmental factors,
including meteorology, surface layer turbulence, thermodynamics, air and
surface heterogeneous-phase chemistry, canopy geometry, plant development
stage, leaf age, organic matter decomposition, soil microbial turnover, and,
in agricultural systems, by fertilizer application rate, fertilizer type,
soil type, crop type, and agricultural management practices. We review the
range of processes controlling NH3 emission and uptake in the different
parts of the soil-canopy-atmosphere continuum, with NH3 emission
potentials defined at the substrate and leaf levels by different
[NH4+] / [H+] ratios (Γ).
Surface/atmosphere exchange models for NH3 are necessary to compute the
temporal and spatial patterns of emissions and deposition at the soil, plant,
field, landscape, regional and global scales, in order to assess the multiple
environmental impacts of airborne and deposited NH3 and NH4+.
Models of soil/vegetation/atmosphere NH3 exchange are reviewed from the
substrate and leaf scales to the global scale. They range from simple
steady-state, "big leaf" canopy resistance models, to dynamic, multi-layer,
multi-process, multi-chemical species schemes. Their level of complexity
depends on their purpose, the spatial scale at which they are applied, the
current level of parameterization, and the availability of the input data
they require. State-of-the-art solutions for determining the emission/sink
Γ potentials through the soil/canopy system include coupled,
interactive chemical transport models (CTM) and soil/ecosystem modelling at
the regional scale. However, it remains a matter for debate to what extent
realistic options for future regional and global models should be based on
process-based mechanistic versus empirical and regression-type models.
Further discussion is needed on the extent and timescale by which new
approaches can be used, such as integration with ecosystem models and
satellite observations. |
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