Study On The Dispersion Model Of Vehicle Exhaust Pollutant In Streets Of Wuhan

These years the number of the vehicles of the big cities in China is increasing with the high speed of 17%. It brings prosperity to the economy, but it also contributes much to the air pollution in big cities. According to the results of much research, vehicular exhaust is the main source of the air pollution in big cities and it directly leads to the deterioration of air quality in streets.It's a complicated process for the vehicular exhaust to disperse in street canyon. Many factors may affect this process such as the source intensity, meteorological factors and street geometry and so on. Some typical streets are selected as the objects of this study. Then the characteristics and the current situation of vehicle emission in Wuhan are explored. Emphasis is put on how the meteorological factors and street geometry affect the dispersion process of the vehicular pollutants in streets.CALINE4 and OSPM models are selected to simulate the dispersion process of the vehicular exhausts in the streets according to the characteristics of the meteorological conditions and street geometry in Wuhan. Using CO and NOx concentration data measured by the author on Luoshi and Luoyu roads and the data from Wuhan environmental monitoring station, the modeled values are compared with the measured values. After the input files are created, the models can calculate 1h and 8h average concentration. Because CALINE4 can't be used to calculate the concentration of NOx directly, it is only used to model CO concentration in this research. The results of the calculation shows that CALINE4 can be used for the primary evaluation of the air pollution in streets. OSPM model is modified according to the real condition in Wuhan. The modeled value of the modified OSPM and the measured value show good pertinence. It is concluded that both CALINE4 and the modified OSPM models are capable of simulating the dispersion and forecasting the concentration of vehicle emission in streets of Wuhan,however, OSPM has higher precision than CALINE4.In this paper, the emission sharing rates and the concentration sharing rates are calculated and analyzed. Then the theories and using methods of CALINE4 and OSPM are introduced. Much work has been done to applying the two models that are comparative mature in America and Denmark to Wuhan city. The results of this study have obvious scientific value and practical value to support the decisions of the government with scientific data.