Correlation between traffic density and particle size distribution in a street canyon and the dependence on wind direction J. Voigtländer1, T. Tuch1,2, W. Birmili1, and A. Wiedensohler1 1Leibniz Institute for Tropospheric Research, Leipzig, Germany 2UFZ Center for Environmental Research, Department of Human Exposure Research and Epidemiology, Leipzig, Germany
Abstract. Combustion of fossil fuel in gasoline and diesel powered vehicles is
a major source of aerosol particles in a city. In a street canyon,
the number concentration of particles smaller than 300 nm in
diameter, which can be inhaled and cause serious health effects, is
dominated by particles originating from this source.
In this study we measured both, particle number size distribution
and traffic density continuously in a characteristic street canyon
in Germany for a time period of 6 months. The street canyon with
multistory buildings and 4 traffic lanes is very typical for larger
cities. Thus, the measurements also are representative for many
other street canyons in Europe. In contrast to previous studies, we
measured and analyzed the particle number size distribution with
high size resolution using a Twin Differential Mobility Analyzer
(TDMPS). The measured size range was from 3 to 800 nm, separated
into 40 size channels.
Correlation coefficients between particle number concentration for
integrated size ranges and traffic counts of 0.5 were determined.
Correlations were also calculated for each of the 40 size channels
of the DMPS system, respectively. We found a maximum of the
correlation coefficients for nucleation mode particles in the size
range between 10 and 20 nm in diameter.
Furthermore, correlations between traffic and particles in
dependence of meteorological data were calculated. Relevant
parameters were identified by a multiple regression method. In our
experiment only wind parameters have influenced the particle number
concentration significantly. High correlation coefficients (up to
0.8) could be observed in the lee side of the street canyon for
particles in the range between 10 and 100 nm in diameter. These
values are significantly higher than correlation coefficients for
other wind directions and other particle sizes. A minimum was found
in the luff side of the street. These findings are in good agreement
with theory of fluid dynamics in street canyons.
Citation: Voigtländer, J., Tuch, T., Birmili, W., and Wiedensohler, A.: Correlation between traffic density and particle size distribution in a street canyon and the dependence on wind direction, Atmos. Chem. Phys., 6, 4275-4286, doi:10.5194/acp-6-4275-2006, 2006.