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| Titel |
Evaluation and modelling of the size fractionated aerosol particle number concentration measurements nearby a major road in Helsinki – Part I: Modelling results within the LIPIKA project |
| VerfasserIn |
M. A. Pohjola, L. Pirjola, A. Karppinen, J. Härkönen, H. Korhonen, T. Hussein, M. Ketzel, J. Kukkonen |
| 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 ; 7, no. 15 ; Nr. 7, no. 15 (2007-08-03), S.4065-4080 |
| Datensatznummer |
250005152
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| Publikation (Nr.) |
 copernicus.org/acp-7-4065-2007.pdf |
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| Zusammenfassung |
| A field measurement campaign was conducted near a major road
"Itäväylä" in an urban area in Helsinki in 17–20 February
2003. Aerosol measurements were conducted using a mobile laboratory
"Sniffer" at various distances from the road, and at an urban background
location. Measurements included particle size distribution in the size range
of 7 nm–10 μm (aerodynamic diameter) by the Electrical Low Pressure
Impactor (ELPI) and in the size range of 3–50 nm (mobility diameter) by
Scanning Mobility Particle Sizer (SMPS), total number concentration of
particles larger than 3 nm detected by an ultrafine condensation particle
counter (UCPC), temperature, relative humidity, wind speed and direction,
driving route of the mobile laboratory, and traffic density on the studied
road. In this study, we have compared measured concentration data with the
predictions of the road network dispersion model CAR-FMI used in combination
with an aerosol process model MONO32. For model comparison purposes, one of
the cases was additionally computed using the aerosol process model UHMA,
combined with the CAR-FMI model. The vehicular exhaust emissions, and
atmospheric dispersion and transformation of fine and ultrafine particles
was evaluated within the distance scale of 200 m (corresponding to a time
scale of a couple of minutes). We computed the temporal evolution of the
number concentrations, size distributions and chemical compositions of
various particle size classes. The atmospheric dilution rate of particles is
obtained from the roadside dispersion model CAR-FMI. Considering the
evolution of total number concentration, dilution was shown to be the most
important process. The influence of coagulation and condensation on the
number concentrations of particle size modes was found to be negligible on
this distance scale. Condensation was found to affect the evolution of
particle diameter in the two smallest particle modes. The assumed value of
the concentration of condensable organic vapour of 1012 molecules cm−3
was shown to be in a disagreement with the measured particle size
evolution, while the modelling runs with the concentration of condensable
organic vapour of 109–1010 molecules cm−3 resulted in
particle sizes that were closest to the measured values. |
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