| Lanzhou is an industrial city in the northwest of China.Air pollution in the city is in the forefront of the world.The type of air pollution changed from coal-burning pollution into soot-Hybrid vehicle exhaust pollution.Serious air pollution caused serious impact of population and the ecologi-cal on the surrounding,clean atmosphere is significant for human existence.TO control of air pollution and to improve air quality,Lanzhou began to implement the "123" plan in the beginning of 2005(Complete to change oil into gas of buses in one year and change oil into gas of taxis in two years,Complete to change the urban coal-fired boiler into gas works in three years ) In the background of "oil to gas",it have great importance to research the causes and types of air pollution and to control of air pollution and improve the atmospheric environment.They are helpful to protect the health of people and to promote economic and social sustained and coordinated development of various undertakings.This article was based on the online monitoring data and remote sensing data and field research.It used Lanzhou city atmospheric environmental monitoring data.It researched the characteristics of Lanzhou city level of air pollutant emissions and vehicle exhaust emission systematically.The artical analyzed characteristics of the spatial and temporal distribution of air pollutants of Lanzhou City in recent years with using of GIS combined with remote sensing data.In the mean of site data collection,it researched the methods of calculating memission source strength.Taking nitrogen dioxide as an example,using CALINE4 vehicle emission dispersion model simulated the spread of pollutants can calculate the the rate of motor vehicle exhaust sharing in two ways:the regional emissions and the path of regional pollutant concentrations.The main findings are as follows:(1)The main spatial and temporal distribution of air pollutantsIn recent years,the major pollutants in Lanzhou are inhalable particles,nitrogen dioxide, sulfur dioxide,etc.sulfur dioxide and inhalable particles has decreased.Nitrogen dioxide showed a slight decline in the trend of shock.The Change of major pollutants showed a U-trend during the years.The higher concentration of pollutants concentrated in the winter and the spring.The trend of major pollutants change is similar to W-type during the day,two peak periods in the 12:00-13:00 and 16:00-18:00.The overall downward trend of main air pollutants in Lanzhou City,is moving in the direction of enhancing the environmental quality of development.The high sulfur dioxide concentration of the region are mainly distributed in western of Lanzhou during the non-heating period,that is,the Honggu District and the western part of Xigu District.The high concentration region,which is densely populated east,moved to the eastern region during the heating period,that is,Chengguan district,Anning district,Qilihe district,and the eastern part of Xigu district.The high nitrogen dioxide concentration of the region are mainly distributed in the eastern part of Xigu district,Anning District,as well as the little part of Chengguan district during the non-heating period,which are mainly distributed in the Chengguan District The heating period,as well as the adjacent districts Strip.The industrial pollution in Xigu district and the high-density motor vehicle in Chengguan district are the main sources of nitrogen oxides.Anning districtis in the area of junction of Chengguan and Xigu,subject to cross-impact of causing air pollution.(2) The laws of motor vehicle exhaust proliferation in LanzhouThe article gave a research to the laws of vehicle exhaust pollutants proliferation,making nitrogen dioxide as an example.The law of nitrogen dioxide concentration changes:the closer the distance of the road Center,the higher.The curve showed a trend of echelon decline:the concentration got down from 1.23mg/m~3 to 1.027mg/m~3 in 0-30 meters,and that remained at 1.027mg/m~3 from 30 to 40meters.The concentration began to decline after 0.975mg/m~3,when the distance got into 50-190 meters,it remain at 0.924mg /m~3 around,and then dropped to 0.873mg/m~3 in the distances of 200 meters.Nitrogen oxides concentration in road center is more than 10-15 times of the urban air standards.(3)The vehicle exhaust emissions in LanzhouThe list of motor vehicle emissions of Lanzhou city in the year of 2006 as follows:Carbon monoxide got 14.28 million tons,nitrogen oxides got 1.58 million tons,hydrocarbon compounds got 1.57 million tons.The major pollutants of bus and taxi emissions:carbon monoxide 12373tons, nitrogen oxides 4528tons,hydrocarbon compounds 5246tons.Three kinds of main pollutants emissions of buses and taxi accounted for the total emissions of motor vehicles 69.29%,34.81% and 55.96%in the year of 2000,this proportion decreased significantly,respectively,accounted for: 8.67%,33.41%,28.67%in the year of 2006.Regional pollutant emissions from motor vehicles to share the total rate of carbon monoxide was more than 80%,nitrogen dioxides total contribution rate of was around 30%.Nitrogen dioxides in road center concentration domain sharing contribution rate was 95%.Different models to share the rate of pollutants,nitrogen oxides:cars accounted for 49%of emissions,medium cars accounted for 24 percent,large cars accounted for 27%.Carbon monoxide:cars accounted for 78%, medium cars accounted for 19%,large cars accounted for only 3%.Hydrocarbon compounds:cars accounted for 64%,medium medium cars accounted for 33%,large cars accounted for 4%,cars is the main model in the emissions of pollutants in Lanzhou city(nitrogen oxides,carbon monoxide, hydrocarbon compounds).In recent years,air pollution in vehicle exhaust contribution have increased,carbon monoxide and nitrogen oxides-sharing rate had continuously rising trend.From the emissions reduction of the total public transport system,we can see,the "123" project in Lanzhou is effective for the reduction of pollutants of urban transport system,but the the exhaust emissions from motor vehicles on air pollution in Lanzhou city has a increased trend,mainly due to the growth rates of motor vehicles.
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