Study On Spatio-temporal Distribution Of Traffic-Related Air Pollution Concentration In Urban Area

With the increasing number of vehicles, especially private cars, traffic-related air pollution has become the main contributor of urban air pollution. Because the height of traffic air pollution is close to breathing zone, traffic air pollution has been threatening the health of the urban residents. So it is necessary to study spatio-temporal distribution of traffic-related air pollution under multifactor impact in urban area, which will lay a foundation for urban transportation planning, environmental protection and environmental policy formulation.Usually, study on spatio-temporal distribution of traffic-related air pollution includes emission study and diffusion study of traffic-related air pollution. After reviewing related literature about urban traffic air pollution and comparing the advantages and shortages of previous methodology, the method of spatio-temporal distribution of traffic air pollution concentration based on real-time traffic and meteorological information was proposed.First, with the consideration of real-time traffic information, on the basis of vehicle emission factor model, mesoscale vehicle emission model was established according to average speed, volume and proportion of vehicle type of road link.Then, based on the Gaussian dispersion theory, the dispersion model was developed in the condition of windless and strong wind, which can evaluate the distribution of traffic-related air pollution concentration in a dynamical and continuous way. The handling method was proposed to divide the link sources into the line sources and point sources in different wind conditions. Based on effect region of link sources, the dynamical method to acquire the collection of link sources impacting the receptor was proposed. Different from related study which use statical traffic information and metrological data to evaluate the concentration in independent hour or long term mean concentration, residual traffic pollution and mass conservation are considered in the dispersion model.Finally, taking Beijing as an example, quantitative and qualitative analysis were performed for spatio-temporal distribution of emission intensity and concentration of traffic air pollution between weekday and weekend. The main factors which results concentration variation were discussed and the accuracy of the model was examined.