Pollution Characteristics And Potential Sources Of PM_2.5 And O₃ In Beijing-Tianjin-Hebei Region

Since the implementation of the Action Plan for the Prevention and Control of Air Pollution and the Three-year Action Plan for Winning the Blue Sky Battle,fine particulate matter(PM_2.5)has been well controlled in China,but there is still a big gap between the control targets,and ozone（O₃）has been on a steady rise.Combined air pollution characterized by the two is a major air pollution problem at present,especially in the Beijing-Tianjin-Hebei region.Based on the environmental monitoring data from 2015 to2021,this paper studied the spatial and temporal distribution and interaction of PM_2.5 and O₃ in 13 cities in Beijing,Tianjin and Hebei.The potential sources of PM_2.5 and O₃ in six typical cities of Beijing-Tianjin-Hebei were analyzed based on air flow track data.Meanwhile,the potential sources of O₃ in four important cities of Hebei Province were tracked using the combined data of monitoring data and air quality model simulation data in2017.The main conclusions are as follows:（1）In the Beijing-Tianjin-Hebei region,PM_2.5 concentration is the highest in winter,while O₃ concentration is the highest in summer.According to the spatial distribution of PM_2.5,the most polluted area is in the southwest of Hebei Province.From the spatial distribution of O₃-8h,the most polluted area in 2015 and 2016 was in the northern part of Hebei Province,and the polluted area shifted to the southwest of Hebei Province during2017-2021.This is related to the prevailing development of local steel,coal,manufacturing,petrochemical,thermal power,cement and glass industries.（2）With the increase of O₃ concentration,PM_2.5 concentration increases.O₃ can affect the increase of secondary components of PM_2.5 by affecting atmospheric oxidation.When the concentration of PM_2.5 is high,the concentration of O₃ is low,and the attenuation of photochemical reaction leads to the decrease of O₃ concentration.（3）According to the integrated potential sources of PM_2.5and O₃ in spring,summer,autumn and winter of Handan,Xingtai,Baoding,Shijiazhuang,Beijing and Tianjin from2015 to 2021,the potential source area is wider than the potential source area in the heavy pollution season analyzed year by year.The potential source areas of PM_2.5 and O₃ analyzed year by year in each city during the heavy pollution season are similar,mainly from the inner cities of Hebei Province and several surrounding cities（Shanxi Province,Henan Province,Shandong Province,Anhui Province and Jiangsu Province）.The PM_2.5 and O₃pollution in Handan,Xingtai,Baoding and Shijiazhuang are mutually affected.The potential source areas of PM2.5 and O₃ pollution in Beijing and Tianjin are distributed in Hebei Province,Bohai Sea area,Shandong Province and between the two cities.（4）The accuracy of the fusion data in 2017 is higher than that of the monitoring station data and simulated data.Handan,Xingtai,Baoding and Shijiazhuang have the widest and most concentrated pollution source areas in spring,and the ranking is spring > autumn > summer > winter.The potential source areas of O₃ pollution in the four cities in spring are similar,mainly from the southern cities in Hebei Province.