Keywords: urban street canyons, traffic pollution, carbon monoxide concentration, traffic-produced turbulence, pollutant dispersion, urban air quality, dispersion modelling, air pollution, vehicle emissions, road transport emissions
Evaluation of turbulence from traffic using experimental data obtained in a street canyon
The present study analyses the influence of traffic-produced turbulence (TPT) on CO concentration using full-scale measurements obtained in Gottinger Strasse (Hannover, Germany). Cases with airflow within ±11.25° from the direction perpendicular to the street axis were used. The values C = Ci–Cb (Ci is concentration measured inside the street canyon and Cb is the background concentration) were plotted against ambient wind speed (U) for different traffic volumes. For windward conditions, the data verified the form C ∝ U-m and for leeward situations, C ∝ (aU²+bV²)-1/2 (a is a function of street geometry, b depends on the characteristics of the vehicles and traffic density, V is the average vehicle speed). We obtained empirical expressions for b, for C/C0 (C0 is the concentration 'without' the influence of the TPT) and for a critical wind speed (UC) (which does aUC² = bV²). The ratio C/C0 is 0.71 when U=UC, not depending on the traffic flow.