| In recent years,the Guanzhong Plain has been perplexed by deteriorating air pollution.As a result,it has been enlisted as one of the National Air Pollution Prevention and Control Areas in China.The contribution of vehicular emission to air pollution is noticeable in the Guanzhong metropolitan area that encompasses Xian,Baoji,Tongchuan,Xianyang,and Weinan.The air pollution is posing detrimental impacts to the sustainable development of economy and the physical and mental health of local residents.On the other hand,unregulated pollutants emitted by motor vehicles,such as ammonia,volatile organic compounds,formaldehyde,acrolein and benzene are important precursors of photochemical smog pollution and secondary aerosols,which are also harmful to human beings but still haven't received much attention.However,studies on high-resolution inventory of particulate matter and unregulated pollutants that are emitted by vehicles are scarce.The knowledge gap leads to lack of technical support for enacting emission reduction strategy and accuracy of relevant model simulation.Therefore,we studied the high-resolution emission inventory of highway mobile sources,and evaluated several emission reduction and control strategies based on the derived high-resolution spatial and temporal emission inventory.The research results are as follows:?1?The MOVES model were used to study the emission factors of regular vehicular gas pollutants,unregulated pollutants,emitted particulates and the brake and tire wear particles.All parameters were revised to simulate the situation of Guanzhong Plain.The AP-42 model was used to study the emission factors of resuspended road dust in Guanzhong area.We established a motor vehicle pollutant emission inventory for the Guanzhong metropolitan area in 2012.The results showed that a.the emission of regular gas pollutants from mobile sources were 81.9,454,1 and 4.2 k tons of for NOx,CO,NH3 and SO2,respectively;b.the emission of organic pollutants were 41,43,1.2,41.676,0.573,0.273,0.043,0.118 and 0.958 k tons for VOCs,TOG,CH4,NMHC,formaldehyde,acetaldehyde,propylene aldehyde,1,3-butadiene and benzene;c.the fuel emission were 7.16 k tons PM;d.the brake wear emission were 1.99 k tons PM;e.the tire wear emission were 0.42 k tons PM;f.the emission of resuspended road dust was 54.4 and 224.8 k tons for PM2.5 and PM10,respectively.It is found that the emission of PM from resuspended road dust is noticeably larger than that from mobile sources.The shares of major pollutants emission in the Guanzhong metropolitan area,from highest to lowest,were Xian?50%?> Weinan?23%?> Xianyang?include Yanglin??12%?> Baoji?10%?> Tongchuan?5%?.The share of different types of vehicle varied largely: heavy trucks contributed most PM2.5?33.1%?,PM10?33.61%?,NOx?33.85%?;small-size buses and heavy trucks contributed most brake and tire wear PM,32.52%,43.33% and 32.05%,20.08%,respectively;heavy trucks contributed most sulfur dioxide?31.31%?,aldehydes?30%?;and small-size buses and motorcycles contributed most CO,VOCs,1,3-butadiene,benzene and methane,32.86%,17.58%,26.64%,26.45%,38.85% and 32.64%,55.67%,43.29%,49.04%,30.97%,respectively Small-size buses and heavy trucks contributed most NH3 emission,49.5% and 31.31%,respectively.?2?The spatial and temporal distribution methods and GIS techniques were used to characterize the spatial and temporal variation of mobile source emission for highway,non-highway,expressway,and non-expressway in Xi'an.The results showed that: a.the mobile emission is closely associated with the vehicle flow?i.e.the emission of most sources at 12:00 pm was found to be significantly higher than that at 1:00am?,except for urban highways and north-south expressways;b.the emission on weekdays was noticeably higher than that on weekends;c.the emission in urban area is lower than that in suburban area,and the distribution pattern of high emission mobile sources is well consistent with that of the actual traffic pollution features.?3?The spatial and temporal allocation were characterized using the equivalent surface source network length weight factor method.Specifically,the spatial allocation of 3×3km resolution of NOx,VOCs,NH3,formaldehyde and other aerosol and photochemical smog precursors were obtained.Given serious traffic pollution in Xian city,we obtained the spatial variation of 1×1km high resolution.The results showed that the vehicle emissions of grid presented a clear strip-plane distribution.A high vehicle emission area were formed with Xi'an,Xiangyang?Yanglin included?,and Weinan city as the center.The area has high emission rate of NOx and VOCs,which have high potential of photochemical smog pollution formation.the emission rate gradually reduced from the core to outreached area.The emission on weekdays was higher than that on weekends.The higher the resolution of plane source grid is,the more vehicle emissions match with the road network.?4?Different pollution control strategies were evaluated using the localized parameter MOVES model in this study.These strategies include oil quality improvement,yellow label cars elimination,alternative fuel use,and traffic restriction.The result showed that emission factors of SO2,PM2.5 and the SO42- particulate in PM10 would be significantly reduced?>60%?if oil quality improvement were applied.Yellow label cars elimination would significantly reduce the emission factors of fuel gas particulates and VOCs,but increase the CH4 emission factors related with middle and heavy trucks.Using nature gas as alternative fuel would lead to zero emission of NH3,SO2,VOCs and formaldehyde from large gasoline buses,zero organic pollution emission from small cars,a 95% reduction of PM2.5 from large diesel buses,and an increase in THC and CO emission.Traffic restriction would have significant reduction on PM2.5 and PM10 emission factors from fuel gas,and 7.5% reduction of organic pollutants emission.The NOx,CO and VOCs emission reduction from trucks were 73%,39%,and 53% respectively.Reasonable combination of these strategies could improve the overall emission reduction effect in Guanzhong metropolitan area. |
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