The Study On The Potential Source Area And Transmission Characteristics Of PM_2.5 And O₃ Pollution In The Beijing-Tianjin-Hebei And Surrounding Areas

The Beijing-Tianjin-Hebei region is China’s"Capital Economic Circle"and one of the key regions for air pollution prevention and control.The problem of PM_2.5 and O₃compound pollution in the Beijing-Tianjin-Hebei region is becoming increasingly serious,with distinct spatial and temporal distribution characteristics,and is adversely affected by regional transport under pollution emissions from the Beijing-Tianjin-Hebei region and surrounding cities,as well as adverse meteorological conditions.Therefore,it is beneficial to explore the potential transmission contribution of Beijing,Tianjin,Hebei and surrounding areas,as well as the potential transmission pathways for joint prevention and control of air pollution in the Beijing,Tianjin and Hebei region.It is also necessary to explore the potential source area characteristics of PM_2.5 and O₃pollution in the city to reveal the pollution transmission pattern of the city in more detail.The development of pollution prevention and control measures that are more relevant to the prevention and control priorities of the target cities is conducive to a win-win situation for both the region and the city in combating pollution.This paper applies the HYSPLIT model,and the Traj Stat plugin in Meteoinfo software,to simulate the backward trajectories of 13 cities in the Beijing-Tianjin-Hebei region for each season from 2017-2019,and perform PSCF,CWT analysis.The results of the study show that:（1）Cities in southern Hebei Province have a high contribution to the potential transport of PM_2.5 and O₃ pollution,while Beijing,Tianjin and cities in northern Hebei Province have a relatively small contribution to the potential transport.There are also seasonal characteristics to the potential transmission contribution.The area with a high potential contribution to PM_2.5 pollution transmission in spring,autumn and winter extends mainly from the Beijing-Tianjin-Hebei region to the west,and in summer the region extends to the east.（2）The potential transmission direction of PM_2.5 and O₃ pollution in the Beijing-Tianjin-Hebei region has seasonal characteristics,and the potential transmission direction of PM_2.5 and O₃ pollution in spring,summer and autumn is basically from south to north.Winter O₃ pollution is also transported from south to north,while PM_2.5 pollution is transported in a more complex direction.In addition to the transport from south to north,the transport of pollutants from Baoding,Langfang and Tangshan cities to Beijing,Chengde and Tianjin is also more obvious.（3）The potential source cities of PM_2.5 and O₃ pollution in Tianjin are mainly to the southwest of the city.In spring,the southwestern cities of Handan,Heze,Kaifeng,Liaocheng,Puyang and Xinxiang are the main external source areas of PM_2.5and O₃ pollution in Tianjin.In the summer,the southern part of Hebei Province,the northern part of Henan Province and some cities in Shandong Province in this direction are the main external source areas for O₃ pollution in Tianjin in the summer.The situation in autumn is similar to that in spring.In winter,some cities in central and southern Hebei Province,northern Henan Province and western Shandong Province are the main external source areas of PM_2.5 pollution in Tianjin,while Zhangjiakou in northern Tianjin and Tangshan City in eastern Tianjin also have a significant impact on PM_2.5 in Tianjin.（4）Continuing to improve the air quality in the Beijing-Tianjin-Hebei region,the scope of joint prevention and control can be expanded by adding more cities to the south and west on top of the original"2+26"cities.To achieve a win-win situation for both PM_2.5 and O₃,the Beijing-Tianjin-Hebei region and its southern cities need to strengthen joint prevention and control in view of the potential transmission of O₃pollution from Henan Province,Shandong Province and Shanxi Province over a larger and longer distance.