Correlation between traffic density and particle size distribution in a street canyon and the dependence on wind direction

[摘要] Combustion of fossil fuel in gasoline and diesel powered vehicles isa major source of aerosol particles in a city. In a street canyon,the number concentration of particles smaller than 300 nm indiameter, which can be inhaled and cause serious health effects, isdominated by particles originating from this source.In this study we measured both, particle number size distributionand traffic density continuously in a characteristic street canyonin Germany for a time period of 6 months. The street canyon withmultistory buildings and 4 traffic lanes is very typical for largercities. Thus, the measurements also are representative for manyother street canyons in Europe. In contrast to previous studies, wemeasured and analyzed the particle number size distribution withhigh size resolution using a Twin Differential Mobility Analyzer(TDMPS). The measured size range was from 3 to 800 nm, separatedinto 40 size channels.Correlation coefficients between particle number concentration forintegrated size ranges and traffic counts of 0.5 were determined.Correlations were also calculated for each of the 40 size channelsof the DMPS system, respectively. We found a maximum of thecorrelation coefficients for nucleation mode particles in the sizerange between 10 and 20 nm in diameter.Furthermore, correlations between traffic and particles independence of meteorological data were calculated. Relevantparameters were identified by a multiple regression method. In ourexperiment only wind parameters have influenced the particle numberconcentration significantly. High correlation coefficients (up to0.8) could be observed in the lee side of the street canyon forparticles in the range between 10 and 100 nm in diameter. Thesevalues are significantly higher than correlation coefficients forother wind directions and other particle sizes. A minimum was foundin the luff side of the street. These findings are in good agreementwith theory of fluid dynamics in street canyons.

[学科分类] 大气科学