| The amount of vehicle increased significantly in Xi'an,and the vehicle emission population increased by 10.5 percent per year from 1995 to 2004.The amount of vehicle in the urban area had reached 433,000 in 2006.However,the overall scale of the urban road network was inadequate and the urban road network structure was far from perfect.This resulted in the urban traffic congestion and the severe air pollution.The results obtained on analyzing the distribution of vehicle flow,traffic loading and traveling delay in Xi'an showed that the most congested area located on the 1st Ring Road and the area within the 1st Ring Road.The working condition of vehicle worsened which was indicated through the real time monitoring that the average speed of vehicles on the typical road was 21.2km/h,and the time used for vehicles at a idle speed,accelerating speed, reducing speed and constant speed occupied 12.7%,32.9%,33.3%,21.0%of the total traveling time respectively.The results obtained from the tunnel experiment showed that the average emission factors of CO and NOx exausted by vehicle was 6.89 g/(km·per vehicle) and 0.80 g/(km·per vehicle) respectively,While the total amount of CO,NOx and HC emitted by vehicle was 56700,6500,and 5800 tons respectively in 2005.The influence of vehicle emission on air pollution became more and more serious,and the annual NO2/SO2 average ratio is increased from 2001 to 2005.This result in the air pollution in Xi' an is changing from the coal burning pollution into the vehicle exhaust emissions.It could be found in the monitoring of road pollution caused by vehicle emission that the CO pollution in vehicle tail gas was quite serious,and the area pollution had been formed in the local region.The average value of daily CO average concentrations of background monitoring spots located on the roads,intersection centers and the sidewalks of the roads was 9.501mg/m3,8.001 mg/m3 and 6.894 mg/m3,which was higher than that of the state third grade standard.As for NOx pollution,it was rather better than that of CO,and the average value of daily NOx average concentrations of background monitoring spots located on the roads,intersection centers and the sidewalks of the roads was 0.047 mg/m3, 0.040 mg/m3,0.035mg/m3 which was under that of state second grade standard.Moreover, the average value of O3 concentration was 0.099 mg/m3.The major factors influencing the vehicle emission pollution are including the vehicle emission pollution control,implementation of Inspection/Maintenance system,fuel type, working condition and so on.The most effective air pollution control method could be selected from these factors.For the control of single vehicle emission,the following methods could be used such as source reeducation on new vehicle,strengthening the management of in-use vehicle and phasing out the old cars.Furthermore,strengthening I/M system of in-use vehicle is one of the key points to prevent and control vehicle emission.It could also take some measures to mitigate the traffic congestion and reduce pollution to promote the sustainable mobility in urban city.For example,to improve the quality of vehicle fuel and put more effort to develop the vehicles adopting natural gas,to adjust the layout of city and stress the construction of road network,to optimize the traffic management and develop public traffic,etc.The control and prevention of vehicle emission pollution involves many departments in the government.Therefore,it is the key to establish the managing methods that are managed by the municipal authority and cooperation among different departments to optimize the prevention and management system for vehicle emission pollution control. |
PDF Full Text Request