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| Titel |
Gas-particle interactions above a Dutch heathland: I. Surface exchange fluxes of NH3, SO2, HNO3 and HCl |
| VerfasserIn |
E. Nemitz, M. A. Sutton, G. P. Wyers, P. A. C. Jongejan |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 4, no. 4 ; Nr. 4, no. 4 (2004-07-02), S.989-1005 |
| Datensatznummer |
250001834
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| Publikation (Nr.) |
 copernicus.org/acp-4-989-2004.pdf |
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| Zusammenfassung |
| A field measurement campaign was carried out over a Dutch heathland to
investigate the effect of gas-to-particle conversion and ammonium aerosol
evaporation on surface/atmosphere fluxes of ammonia and related species.
Continuous micrometeorological measurements of the surface exchange of
NH3, SO2, HNO3 and HCl were made and are analyzed here with
regard to average fluxes, deposition velocities (Vd), canopy resistances
(Rc) and canopy compensation point for NH3. Gradients of SO2,
HNO3 and HCl were measured with a novel wet-denuder system with online
anion chromatography. Measurements of HNO3 and HCl indicate an
Rc of 100 to 200 s m-1 during warm daytime periods, probably at
least partly due to non-zero acid partial pressures above NH4NO3 and NH4Cl on the leaf surfaces. Although it is likely that this
observation is exacerbated by the effect of the evaporation of airborne
NH4+ on the gradient measurements, the findings nevertheless add
to the growing evidence that HNO3 and HCl are not always deposited at
the maximum rate. Ammonia (NH3) fluxes show mainly deposition, with
some periods of significant daytime emission. The net exchange could be
reproduced both with an Rc model (deposition fluxes only) using
resistance parameterizations from former measurements, as well as with the
canopy compensation point model, using parameterizations derived from the
measurements. The apoplastic ratio of ammonium and hydrogen concentration
(Γs=[NH4+]/[H+]) of 1200 estimated from the
measurements is large for semi-natural vegetation, but smaller than
indicated by previous measurements at this site. |
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