Examination of Traffic Pollution Distribution in a Street Canyon Using the Nantes'99 Experimental Data and Comparison with Model Results

During the Nantes'99 experiment, pollution concentrations, temperature, flow and turbulence conditions were measured at several locations in Rue de Strasbourg, Nantes, France. Traffic was measured by vehicle counters at different places within the street. Traffic speed was monitored as well. The measuring campaign was conducted in the period June–July 1999 but only data from a selected intensive observation period are used in this study. This period was selected to suit conditions required for study of the traffic produced turbulence and the thermal effects and is characterised by quite low wind speeds. The data are used here for examination of concentration distributions in the street. Measurements are compared to model results calculated by a simple parameterised model, the Operational Street Pollution Model (OSPM) and a 3-D CFD model MISKAM. Both models reproduce reasonably well the observed distribution of pollutants in the street. Due to predominantly low wind speed conditions, such effects as the traffic produced turbulence play a quite significant role. The model results provided by MISKAM are scaled using a velocity scale depending on the traffic produced turbulence. Application of a scaling velocity depending on wind speed only, provides unrealistic results.