Pollution Characteristics And Source Apportionment Of Atmospheric Fine Particulate Matter(PM_2.5)in Taiyuan

In recent years,frequent occurrence of haze phenomenon has caused widespread concern of the society.The essence of haze phenomenon is fine particulate matter(PM2.5)pollution.In this research,representative sampling sites in Taiyuan urban area were selected to online observe the main chemical components of PM2.5 in different seasons in 2017,including water-soluble ions,carbonaceous components and inorganic elements.Combined with the air automatic monitor data and meteorological data,the annual air quality of taiyuan urban area and the chemical composition characteristics of PM2.5 were analyzed.Then,the characteristics of air mass transmission in different seasons were analyzed by combining the backward trajectory model.Finally,the source apportionment of PM2.5 was conducted by using positive matrix factorization(PMF)in winter.The main conclusions of this research were as followed:(1)The annual mass concentrations of PM10 and PM2.5 were 127.44 and 69.75 ?g/m3 in taiyuan urban area,respectively,and the seasonal variation trend was higher in winter and lower in summer.Correlation analysis shows that PM10 and PM2.5 were well correlated with SO2.NO2 and CO,and CO has a good correlation with SO2 and NO2.According to meteorological parameters,the annual average values of temperature(T)and relative humidity(RH)are 13.50? and 49.80%,respectively.The wind speed range is 0.2?5.8m/s,and its annual average value is 0.62 m/s.(2)SO42-NO3-and NH4+ are the main chemical components of water-soluble ions,and the sum of mass concentrations in winter was significantly higher than that in other seasons.According to ion balance and correlation analysis,the ratio of anion and cation equivalent concentration(AE/CE)was less than 1.and secondary aerosols are mainly in the form of(NH4)2SO4 and NH4NO3 in all four seasons.The mass concentration of carbon components were 30.24,13.27,8.80 and 14.21?g/m3,SOC/OC ratios were 43.75%,42.28%.71.33%,and 49.27%in winter,spring,summer and autumn,respectively.The correlation between OC and EC was 0.22 in summer,indicated that the OC and EC homology was poor in summer,and the source of carbonaceous components was more complicated.K.Ca,Fe,Zn and Pb were the main chemical components of inorganic elements.The sum of main elements mass concentrations accounted for 92.43%,94.09%and 93.53%of the total mass concentrations of inorganic element in winter,spring and summer,respectively.The average EF of Cr,Ni,Cu,Zn and Ba are greater than 10 in different seasons,indicated that the above elements were greatly affected by human activities,the average EF of K,Ca.Mn and Pb were in the range of 1 to 10,indicated that the above elements were affected by both human and natural sources.(3)The study of regional transmission characteristics shows that the PM2.5 concentration in the winter cluster trajectory was significantly higher than other seasons.The concentration of PM2.5 in the airflow from Mongolia,Inner Mongolia and other regions was relatively lower than from Henan,Shanxi.Hebei and Shaanxi.There were significant differences in the chemical components of the clustering trajectories from different directions in different seasons.The results of the PMF source apportionment showed that the main sources of PM2.5 pollution are secondary sources,coal burning sources,motor vehicle sources,process process sources and dust sources in winter.The contributions of secondary sources,coal combustion and vehicle emissions were higher in polluted days than clean days.Thus,air pollution control strategies should pay more attention to control secondary sources precursors on the basis of controlling the primary emission sources in polluted days.