PM_2.5 Pollution Characteristics And Source Apportionment Of Transmission Channels Along Taihang Mountain

During 2017 heating period,the Beijing-Tianj in-Hebei region implemented a series of powerful measures.This paper selected the transmission channels along the Taihang Mountains during the heating seasons of 2016 and 2017 to study the PM2.5 pollution characteristics and source changes.We analyzed regional and urban air quality,gaseous pollutants,PM2.5 and its main components,employed principal component analysis methods to apportion sources of PM2.5,and used the backward trajectory and potential source contribution analysis to explore the potential pollution sources in the cities.The main conclusions of the paper are as follows:(1)The overall regional PM2.5 concentrations during the heating seasons during 2016 and 2017 were 136.34?g/m3 and 98.03 ?g/m3,respectively.Compared with 2016 heating season,SO2,NO2,and CO concentrations decreased by 44.69%,18.87%,and 31.28%during 2017 heating season,respectively.Simultaneously the concentrations of PM2.5 and SO42-,NO3-,and OC in PM2.5 all decreased slightly varying degrees,but the EC concentration increased significantly.(2)During the two-year heating season,the cities in the northern part of the Taihang Mountains have more polluted days than the cities in the south.The air quality of the cities in the heating season in 2017 has improved significantly,PM2.5 in the central of the Taihang Mountains were higher than that in the sides during 2016,while it was converse during the 2017 heating season.(3)During the 2017 heating season,the concentration of SNA ions(SO42-,NO3-,NH4+,collectively referred to as SNA)in all cities showed a downward trend,the concentrations and proportions of Mg2+and Ca2+ ions both increased significantly,indicating that the impact of dust sources in the cities has increased.The proportion of SNA ions and the SOR and NOR values of gaseous pollutant conversion in the southern cities were higher than those in the north cities.The difference in primary sulfate concentration between the north and south cities was small,and the high SO42-in the southern city was mainly due the SO42-formed by the second conversion was higher,corresponding to the high SOR and NOR values in the south.(4)In the 2017 heating season,the OC concentration and proportion of all cities decreased,and the POC concentration decreased,while the EC concentration and proportion increased significantly,indicating that the city's coal-fired emissions control has achieved success,but the impact of vehicle sources has increased.The concentration of SO2,NO2 and CO decreased.During the two-year heating season,OC,EC concentration and proportion,and POC concentration in the north cities were higher than those in the south cities,which was consistent with the changing trend of gaseous pollutants such as SO2,NO2,and CO.It shows that the cities in the northern part of Taihang Mountain have serious emissions from coal-burning and motor vehicles.(5)The principal component analysis results show that the main sources of pollution in the northern and southern cities of Taihang Mountain in the two-year heating seasons were secondary sources,dust sources,coal-fired sources,and motor vehicle sources.The comparison of the two-year source analysis results shows that the areas was greatly affected by dust sources in 2017 along the Taihang Mountain,which corresponds to the component results.(6)The analysis results of backward trajectory and potential source contribution show that the cities along the Taihang Mountain in the 2016 heating season were most affected by the cities in the south.The cities in the north of the Taihang Mountain were affected by Shanxi Province,and the cities in the south were more affected by Shandong Province.The cities in the south and northeast have more serious impact on the areas during the 2017 heating season.