 |
| Titel |
Gas-particle interactions above a Dutch heathland: III. Modelling the influence of the NH3-HNO3-NH4NO3 equilibrium on size-segregated particle fluxes |
| VerfasserIn |
E. Nemitz, M. A. Sutton |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 4, no. 4 ; Nr. 4, no. 4 (2004-07-02), S.1025-1045 |
| Datensatznummer |
250001836
|
| Publikation (Nr.) |
 copernicus.org/acp-4-1025-2004.pdf |
|
|
|
|
|
| Zusammenfassung |
| Micrometeorological measurements of size-segregated particle number fluxes
above Dutch heathlands and forests have repeatedly shown simultaneous
apparent emission of particles with a diameter (Dp)<0.18 µm and
deposition of larger particles when measured with optical particle counters.
In order to assess whether this observation may be explained by the
equilibrium reaction of ammonia (NH3), nitric acid (HNO3) and
ammonium (NH4+), a new numerical model is developed to predict the
vertical concentration and flux profiles of the different species as
modified by the interaction of equilibration and surface/atmosphere
exchange processes. In addition to former studies, the new approach
explicitly models the height-dependence of the NH4+ and total
aerosol size-distribution. Using this model, it is demonstrated that both
gas-to-particle conversion (gtpc) and aerosol evaporation can significantly
alter the apparent surface exchange fluxes, and evoke the observed
bi-directional particle fluxes under certain conditions. Thus, in general,
the NH3-HNO3-NH4NO3 equilibrium needs to be considered
when interpreting eddy-covariance particle fluxes. Applied to an extensive
dataset of simultaneous flux measurements of particles and gases at Elspeet,
NL, the model reproduces the diurnal pattern of the bi-directional exchange
well. In agreement with the observation of fast NH4+ deposition,
slow nitric acid deposition (both as measured by the aerodynamic gradient
method) and small concentration products of NH3×HNO3 at
this site, this study suggests that NH4+ evaporation at this site
significantly alters surface exchange fluxes. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|