Study On The Influence Of PM_2.5 From Vehicle In Guanzhong Region On Ambient Air Quality Based On CALPUFF Model

With the increase of vehicle population in Guanzhong Region, the primary pollution source of Guanzhong Region has gradually changed from the single source of coal soot to comprehensive sources of coal soot, dust and tail gas. Estimating the spatial and temporal distribution of PM2.5 in Guanzhong area, as well as researching the contributing regulation of vehicle emissions PM2.5 affecting the surface concentration of pollutant, is crucial to clarify and solve the existing complex pollution problem, and is of great practical signicance for government and administrative organizations to make environment protection policies, and to plan the road network.In this study, Meteorology Modeling system version 5(MM5) and CALPUFF were adopted to calculate the concentrations of PM2.5 emissed from vehicle in spring, summer, autumn and winter of the year of 2012 in the Guanzhong area, and to deeply analyze the effects of terrain features, weather conditions, vehicle emission sources and other factors on the diffusion of vehicle emissions PM2.5. Based on vehicles source and great-emissing industrial sources of Xi’an, the current paper studied the contributing regulation of vehicle emissions PM2.5 affecting the surface concentration. The main conclusions are as follows:(1) Influenced by interdiction of southern Qinling Mountains and northern Loess Plateau, in spring, summer, autumn and winter, the northeast wind is predominant in the wind field of Guanzhong Region, and large scale of whirlwind is easily formed near Xianyang and Xi’an city, which impede the long-distance transport of pollutants. The characteristics of change on the height the mixing layer of Cities in Guanzhong area are shown that the layer in the daytime is higher than that in night, and in summer(about 1640 m at most) is higher than that in winter(about 800 m at most); The levels of atmosphere stability of cities in Guanzhong Region are mainly in the level of moderately unstable(B) and slightly unstable(C) in the daytime, and the level of slightly stable(E) at night.(2) In 2012, the total emission of PM2.5 from vehicle in Guanzhong Region is 4,000 tons, of which 1,900 tons were produced in Xi’an, accounting for 47.5% of the totality for Guanzhong Region. In January 2012, in the research area of Xi’an, the total amount of PM2.5 emissed from vehicles is 108.34 tons, and that from industrial source is 265.541 tons, vehicle emission PM2.5 is accounting for 28.98% of the total emissions from vehicle and industrial source.(3) A regulation is shown that the concentration of vehicle emission PM2.5 declines from the downtown to the suburb area in four seasons in 2012; and vehicle emission PM2.5 impact siginifcantly on air quality near the emission source. And among all the cities in the Guanzhong area, the ambient PM2.5 concentration contributed from vehicle in Xi’an is the highest in Guanzhong Region.(4) In January 2012, at the 17 receiving points in the search area in Xi’an, the ambient PM2.5 concentrations contributed from vehicle are all more than half of concentrations from vehicle and industry. At the receiving point far away from the vehicle source, the ambient PM2.5 concentration contributed from vehicle decreases, while that contributed from industry source increases.