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| Titel |
Winter and summer time size distributions and densities of traffic-related aerosol particles at a busy highway in Helsinki |
| VerfasserIn |
A. Virtanen, T. Rönkkö, J. Kannosto, J. Ristimäki, J. M. Mäkelä, J. Keskinen, T. Pakkanen, R. Hillamo, L. Pirjola, K. Hämeri |
| 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 ; 6, no. 9 ; Nr. 6, no. 9 (2006-06-29), S.2411-2421 |
| Datensatznummer |
250003968
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| Publikation (Nr.) |
 copernicus.org/acp-6-2411-2006.pdf |
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| Zusammenfassung |
| Number concentrations and size distributions of traffic related aerosol
particles were measured at a roadside in Helsinki during two winter
campaigns (10–26 February 2003, 28 January–12 February 2004) and two summer
campaigns (12–27 August 2003, 6–20 August 2004). The measurements were
performed simultaneously at distances of 9 m and 65 m from the highway.
Total number concentrations were measured by a condensation particle counter
(CPC) and particle size distributions by a scanning mobility particle sizer
(SMPS) and an electrical low pressure impactor (ELPI). This study
concentrates on data that were measured when the wind direction was from the
road to the measurement site. The total concentrations in the wintertime
were 2–3 times higher than in the summertime and the concentrations were
dominated by nucleation mode particles. The particles smaller than 63 nm
(aerodynamic diameter) constituted ~90% of all particles in the
wintertime and ~80% of particles in the summer time. The particle
total concentration increased with increasing traffic rate. The effect of
traffic rate on particles smaller than 63 nm was stronger than on the larger
particles. The particle distributions at the roadside consisted of two
distinguishable modes. The geometric mean diameter (GMD) of nucleation mode
(Mode 1) was 20.3 nm in summer and 18.9 nm in winter. The GMD of the larger
mode consisting mostly of traffic related soot particles (Mode 2) was 72.0 nm
in summer and 75.1 nm in winter. The GMD values of the modes did not
depend on the traffic rate. The average particle density for each mode was
determined by a parallel density fitting method based on the size
distribution measurement made by ELPI and SMPS. The average density value
for Mode 1 particles was 1.0±0.13 g/cm3 and 1.0±0.07 g/cm3
both in summer and winter respectively, while the average density
value for Mode 2 was 1.5±0.1 g/cm3 and 1.8±0.3 g/cm3
for summer and winter, respectively. |
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