Characteristics And Source Apportionment Of Atmospheric Fine Particulate Matter And VOCs Pollution In Yiyang City

In recent years,the characteristics of air pollution in China have changed from traditional single pollution to compound pollution with interaction of multiple sources,dominated by PM_2.5and O₃.The causes of PM_2.5and O₃are very complex.To accurately analyze their sources,it is necessary to comprehensively analyze their components and precursor characteristics.Therefore,the study on the composition characteristics of PM_2.5and O₃precursor VOCs is of great significance to analyze their sources.In addition,PM_2.5and O₃show great temporal and spatial differences.Therefore,analyzing the concentration level,chemical composition and source of PM_2.5and VOCs in different regions and seasons is very important to continuously improve China’s overall air quality and reduce the concentration of pollutants in urban air.Based on the sampling and detection of PM_2.5and VOCs in different seasons in Yiyang City in 2020,this study systematically analyzes the concentration level,seasonal variation trend and the characteristics of chemical components（water-soluble ions,carbonaceous aerosols and heavy metal elements）of PM_2.5in Yiyang City,analyzes the component characteristics and changes of PM_2.5in the process of heavy pollution,and finally analyzes the source of PM_2.5in the atmosphere according to the local industrial structure.The concentration level and component characteristics of VOCs in Yiyang City were analyzed quantitatively,and the reaction activities of different VOCs components and species were evaluated.Finally,the emission source with the greatest contribution to O₃and PM_2.5in Yiyang City was determined.In addition,the concentration changes of PM_2.5and O₃under the influence of air mass in different seasons are analyzed.The main conclusions of the paper are as follows:1.PM_2.5pollution in Yiyang City is mainly concentrated in autumn and winter,especially in Heshan District.For the chemical components of PM_2.5,it is found that organic matter（OM）in PM_2.5accounts for the largest proportion,and the rapid growth of secondary organic components is the main reason for exceeding the standard of PM_2.5in winter.The mass concentration of NO₃^-in water-soluble ions is the largest,followed by SO₄^2-and NH₄⁺.The order of heavy metal concentration at each site is Heshan>Ziyang>Olympic sports.Among the overall sources of PM_2.5in Yiyang City,secondary generation accounts for the largest proportion,which is 30.0%.Among the primary emission sources,the proportion of main sources is as follows:dust source（20.9%）>biomass/coal combustion source（19.4%）>motor vehicle emission（16.9%）>industrial process emission（12.8%）.2.The average concentration of VOCs is 28.67 ppbv.The concentration of VOCs in autumn is much higher than that in summer.The concentration of VOCs in the morning is higher than that in the afternoon.Among VOCs,alkanes and oxygenated VOCs account for a large proportion,with a total of more than 54%,followed by oxygenated VOCs（25.3%）,halogenated hydrocarbons（16.2%）,aromatic hydrocarbons（10.1%）,alkynes（6.1%）and other VOCs（2%）.The analysis of VOCs activity shows that olefins and aromatic hydrocarbons are the active components to generate secondary aerosols and O₃,and toluene and m/p-xylene are the active species to generate secondary aerosols and O₃.PMF analyzed that there are six sources of atmospheric VOCs in the main urban area of Yiyang City,which are coal and biomass combustion（34%）,transportation（24%）,solvent use（16%）,industrial process（14%）,fuel volatilization（8%）and natural source（4%）.The activity evaluation of emission sources shows that transportation sources have a great impact on the formation of O₃,while solvent sources have a great impact on the formation of PM_2.5.3.Under the guidance of different air masses in Yiyang City,the concentrations of PM_2.5and O₃are different.The maximum concentration of PM_2.5under the guidance of four kinds of air masses in winter is 86.8μg/m3,and the maximum concentration of O3 under the guidance of four kinds of air masses in spring is 80μg/m3.The analysis of potential source contribution shows that the potential source of O₃is mainly distributed in the west of Yiyang City,PM_2.5is mainly from the northeast of Yiyang City,and the potential source contribution of NO₂is concentrated in the north and west of Yiyang City.