Receptor Components Reconstruction Analysis Of Fine Particulate Matter In The Atmosphere Of Changchun City

In recent years,China's air pollution incidents have occurred frequently,and pollution with PM_2.5 as the primary pollutant has been the most prominent,causing widespread concern in society.With the in-depth understanding of the hazards of atmospheric particles,many countries have carried out relevant research in order to better understand and master the pollution patterns of atmospheric particles.The extent of the impact of PM_2.5 on the environment is related to its compositional characteristics.Understanding the composition and main chemical composition of PM_2.5 is a prerequisite for the study of PM_2.5 sources and hazards.This research was conducted from April 2013 to February 2015 on 9 of the Jun Zilan Park,Bus Factory,Garden Service,Labor Park,Institute of Posts and Telecommunications,Economic Development Zone Environmental Protection Department,High-tech Zone Management Committee,Jingyue Park and Daishan Park.The point-in-place PM_2.5 sampling and chemical analysis of the components were performed to obtain the chemical composition of PM_2.5 receptors in Changchun City.The main conclusions of this study are as follows:In terms of compositional proportion,the proportion of organic components in the main receptor components in 2013 and 2014 was the largest and became the most important part of the pollution process.The concentration of organic matter in autumn and winter seasons was significantly higher than that in spring and summer,mainly because Changchun City entered the heating period in October.The large area of centralized heating caused a sharp increase in the amount of coal burned,which led to an increase in the concentration of organic matter.The concentration of SNA in autumn and winter was significantly higher,indicating that the urban air has more obvious secondary pollution.In 2013 and 2014,NO₃^-concentration was higher than other seasons,which were 6 times and 7 times of summer NO₃^-concentration,respectively.Because the particulate NO₃^-is dominated by volatile components,it is susceptible to temperature.When the temperature is high in the summer,particulate nitrates easily convert to gaseous state.In the fall,low temperatures favor the presence of nitrates in particulate form.SO₄^2-has typical regional pollution characteristics.The concentrations in autumn and winter of 2013 and 2014 were higher than those in spring and summer.In autumn and winter,coal-fired heating produces precursors with more pollutants,and adverse weather conditions cause the pollutants to aggregate and undergo a secondary conversion process,resulting in a higher concentration of pollutants.In 2013 and 2014,the concentration of NH₄⁺was significantly higher in autumn and winter than in spring and summer.Spring was higher than summer,and NH₄⁺was the lowest in summer.the increase of gaseous precursors'emissions leads to an increase in the concentration of NH₄⁺.As NH₄⁺is related to agricultural activities?fertilizer use,straw burning,etc.?,the concentration in spring is higher than in summer.The NH₄⁺component of the atmospheric particulates is mainly in the form of a combination with SO₄^2-and NO₃^-.The nitrates in PM_2.5 are mainly in the form of ammonium nitrate.The summer temperatures are high,and ammonium nitrate is not easily retained in particulates.Therefore,the concentration of nitrate in the particulate matter in summer is lower.EC is mainly contributed by local pollution sources,and has the highest concentration in autumn and winter in 2013 and 2014.The concentrations in spring and summer have little difference.The seasonal variation of Cl^-concentration is most obvious.In the winter of 2013,the Cl^-concentration was 2 times of the annual average and 20 times of summer.In the autumn of 2014,the concentration of Cl^-was twice the annual average and 11 times that of summer.The concentration of Cl^-in autumn and winter is obviously higher than that in summer.On the one hand,it may be because NaCl and KCl in the particles react with atmospheric acid gases?such as HNO₃?to generate gaseous HCl,resulting in the loss of chlorine salt in the particles;On the other hand,NH₄Cl in the particles is volatile in the high-temperature atmosphere,resulting in the reduction of chlorine salts.In addition,coal combustion is also one of the main sources of Cl^-,autumn and winter seasons are heating periods,and the increase in coal consumption leads to an increase in Cl^-concentration,indicating that Cl^-is greatly affected by local coal combustion.In terms of spatial distribution,spot pollution levels in the northern and southeastern parts of Changchun City in 2013 and 2014 were higher.The prevailing wind direction in Changchun City is the southwesterly wind.These points are in the direction of the downwind,and they are more susceptible to upwind pollutants,so their total mass concentration is relatively large.The two highest concentrations are the food factory and the bus factory.These two locations both represent the industrial area of Changchun City.The Changchun City No.1 Thermal Power Plant is located around the Jun Zilan Park,and Changchun Railway Vehicle Co.,Ltd.is located around the bus plant.The site with the lowest concentration of Jingyuetan is located in Jingyuetan Park in Changchun City.It represents the tourist area of Changchun City,and its air pollution is lighter.In terms of seasonal distribution,the concentration of PM_2.5 in Changchun City in 2013 was high in autumn and winter and low in spring and summer.In 2014,the PM_2.5 concentration was high in autumn and winter and low in spring and summer.Among them,the concentrations of OM in 2013 showed a general pattern of C _winter>C _autumn>C _spring>C _summer.;The remodeling of SNA in PM_2.5 changed to C _autumn>C _winter>C _spring>C _summer;The overall concentration of Cl^-is expressed as C _winter>C _autumn>C _spring>C _summer;EC concentration presents overall C _winter>C _autumn>C _spring>C _summer.The concentration of OM in autumn 2014 presented C _autumn>C _winter>C _summer>C _spring;the seasonal change of SNA reconstruction in PM_2.5 was C _autumn>C _winter>C _spring>C _summer;the concentration of Cl^-appeared C _autumn>C _Winter>C _Chun>C Summer;EC concentration showed C autumn>C winter>C spring>C summer.