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| Titel |
Aerosol fluxes and particle growth above managed grassland |
| VerfasserIn |
E. Nemitz, J. R. Dorsey, M. J. Flynn, M. W. Gallagher, A. Hensen, J.-W. Erisman, S. M. Owen, U. Dämmgen, 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 ; 6, no. 8 ; Nr. 6, no. 8 (2009-08-12), S.1627-1645 |
| Datensatznummer |
250003952
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| Publikation (Nr.) |
 copernicus.org/bg-6-1627-2009.pdf |
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| Zusammenfassung |
| Particle deposition velocities (11–3000 nm diameter)
measured above grassland by eddy covariance during the EU GRAMINAE
experiment in June 2000 averaged 0.24 and 0.03 mm s−1 to long (0.75 m)
and short (0.07 m) grass, respectively. After fertilisation with 108 kg N ha−1
as calcium ammonium nitrate, sustained apparent upward fluxes of
particles were observed. Analysis of concentrations and fluxes of potential
precursor gases, including NH3, HNO3, HCl and selected VOCs, shows
that condensation of HNO3 and NH3 on the surface of existing
particles is responsible for this effect. A novel approach is developed to
derive particle growth rates at the field scale, from a combination of
measurements of vertical fluxes and particle size-distributions. For the
first 9 days after fertilization, growth rates of 11 nm particles of
7.04 nm hr−1 and 1.68 nm hr−1 were derived for day and night-time
conditions, respectively. This implies total NH4NO3 production
rates of 1.11 and 0.44 μg m−3 h−1, respectively. The
effect translates into a small error in measured ammonia fluxes (0.06%
day, 0.56% night) and a large error in NH4+ and NO3−
aerosol fluxes of 3.6% and 10%, respectively. By converting rapidly
exchanged NH3 and HNO3 into slowly depositing NH4NO3,
the reaction modifies the total N budget, though this effect is small
(<1% for the 10 days following fertilization), as NH3 emission
dominates the net flux. It is estimated that 3.8% of the fertilizer N was
volatilised as NH3, of which 0.05% re-condensed to form
NH4NO3 particles within the lowest 2 m of the surface layer. This
surface induced process would at least scale up to a global NH4NO3
formation of ca. 0.21 kt N yr−1 from NH4NO3 fertilisers and
potentially 45 kt N yr−1 from NH3 emissions in general. |
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