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THE INFLUENCE OF TRAFFIC ON URBAN AIR QUALITY - MODEL PREDICTIONS AND THEIR COMPARISON TO MEASUREMENTS

Abstract:

We estimate here the effect of vehicular emissions on urban air quality by a mathematical model for predicting dispersion of pollution from a network of roads and streets. The model includes an emission model, treatment of the meteorological time series, a dispersion model and a statistical analysis of the computed time series of concentrations. The dispersion model is based on a partly analytic solution of the Gaussian diffusion equation for a finite line source The predicted results show that the highest CO -concentrations occur in the Helsinki downtown area and at the junctions of the main streets and roads. Comparison of the model predictions with the national air quality standards shows that the standard values for the hourly concentrations are exceeded at a few spatially limited areas, mainly in the downtown area. The concentrations in the catalysator scenario were mainly below the current air quality standards. We have compared the model predictions against the air quality measurements at two stations of the YTV in the Helsinki downtown area. The measured monthly averaged concentrations were clearly higher at both stations, compared to the predicted concentrations. However, the annual variation of the measured and predicted concentrations was very similar.