Study On The Air Pollution Characteristics Of Changchun Based On CALPUFF Model

With the rapid development of Changchun industry and economy and the continuous improvement of people's living standards in recent years,the types and concentrations of pollutants discharged into the environment are obviously changing,and the problem of air pollution presents a more regional and complex characteristic.In order to evaluate the emission sources of air pollution in Changchun,explore the characteristics of air pollution in Changchun,and provide effective reference in the establishment of air pollution prevention and control programs,in this paper,the basic information of pollution emissions in Changchun was collected,and an atmospheric pollution source emission database was estimated and compiled to analyze the contribution characteristics of Changchun air pollution emission sources.Then the CALPUFF air quality model system was used to simulate the concentration distribution results of three kinds of atmospheric pollutants of SO₂,NO_X and PM_2.5.5 during each month,each season and the heavy pollution weather of Changchun in 2015 respectively,and the cause analysis in combination with meteorological factors was carried out in order to explore the distribution characteristics of air pollution in Changchun.The following conclusions were reached:?1?The emission database results showed that:the total emission of atmospheric pollutants fine particulate matter(PM_2.5)of Changchun in 2015 is 72857.55 tons,the total emission of sulfur dioxide is 90961.61 tons,the total emission of nitrogen oxides is127206.26 tons.The industry is the primary contribution source of air pollution in PM_2.5and SO₂,and the contribution rate is 43.08%and 44.74%respectively,the biomass combustion source is the largest contribution source of NO_X,and the contribution rate reaches 41.21%.According to the pollution effect,the primary contribution source of PM_2.5.5 and SO₂ is point sources,the contribution rate is 50.2%and 47.81%respectively,the primary contribution source of nitrogen oxides is area source,and the contribution ratio is 37.41%.?2?The correlation coefficients between the monthly average concentration of monitoring values and the model simulation values of three kinds of pollutants are 0.98,0.81 and 0.96,respectively.The results of the simulation concentration of SO₂,NO_X and PM_2.5.5 in each season showed that the concentration level is highest in winter?01-01 to04-22,10-22 to 12-31?,followed by autumn?08-24 to 10-21?,and the relatively weak pollution exists in spring?04-23 to 06-22?and summer?06-23 to 08-23?,which may be related to heating coal combustion in winter and the climatic characteristics of windy spring.There is no obvious characteristic showed in the spatial distribution,but the pollution peak area of each season includes one place in the center of the municipal district.That may be related to motor vehicle exhaust in the urban area.?3?The results of various seasonal meteorological factors in Changchun in 2015showed that the average wind speed in spring is 3.4m/s,the average wind speed in summer is 2.34m/s,and the average wind speed in autumn and winter is 2.19m/s and2.67m/s respectively.The dominant wind direction in spring and summer is southwest westerly wind and wind direction is concentrated in the same time,the dominant wind direction in autumn and winter is southwest and the wind direction is relatively dispersed.The height level of atmospheric mixing layer decreases gradually with the change of season,which is not conducive to the diffusion of pollutants,and there is no significant correlation between temperature level and pollution concentration distribution.The relative humidity reaches and is maintained at a high level after summer.?4?The simulation results of pollutant concentration during heavily polluted weather showed that the concentration level is shown by the trend of rapid increase and then getting stable after reduction of the second day,and there are two concentration peak area in south surrounding area which center on Yitong County,and north surrounding area which center on the intersection of Dehui and Jiutai City.Corresponding characteristics of meteorological factors show that the level of mixing layer height decreased significantly during this period and the temperature difference change in second day is negative which in third to fourth day is positive,then the relative humidity is increased to more than 60%after 14:00 on second day and has been stable at a high level.The average wind speed is 2.7m/s,and the wind speed during the first two days is higher than the two days later.The wind direction in the first and the second day is dispersed whose main components are northeast and north wind respectively,and the wind direction in the latter two days is relatively dispersed whose dominant components are northwestern west and east wind respectively.