Tropospheric ozone(O3)pollution is increasing in the Beijing-Tianjin-Hebei(BTH)region de-spite a significant decline in atmospheric fine aerosol particles(PM2.5)in recent years.How-ever,the intrinsic reason for the elevation of the regional O3 is still unclear.In this study,we analyzed the spatio-temporal variations of tropospheric O3 and relevant pollutants(PM2.5,NO2,and CO)in the BTH region based on monitoring data from the China Ministry of Ecology and Environment during the period of 2014-2019.The results showed that summertime O3 concentrations were constant in Beijing(BJ,0.06μg/(m3·year))but increased significantly in Tianjin(TJ,9.09 μg/(m3·year))and Hebei(HB,6.06μg/(m3·year)).Distinct O3 trends between Beijing and other cities in BTH could not be attributed to the significant decrease in PM2.5(from-5.08 to-6.32 μg/(m3·year))and CO(from-0.053 to-0.090 mg/(m3·year))because their decreasing rates were approximately the same in all the cities.The relatively stable O3 con-centrations during the investigating period in BJ may be attributed to a faster decreasing rate of NO2(BJ:-2.55μg/(m3·year);TJ:-1.16 μg/(m3·year);HB:-1.34 μg/(m3·year)),indicating that the continued reduction of Nox will be an effective mitigation strategy for reducing regional O3 pollution.Significant positive correlations were found between daily maximum 8 hr average(MDA8)O3 concentrations and vehicle population and highway freight trans-portation in HB.Therefore,we speculate that the increase in rural Nox emissions due to the increase in vehicle emissions in the vast rural areas around HB greatly accelerates regional O3 formation,accounting for the significant increasing trends of O3 in HB.

Yifei Song;Yuanyuan Zhang;Junfeng Liu;Chenglong Zhang;Chengtang Liu;Pengfei Liu;Yujing Mu

Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences,Beijing 100085,China;University of Chinese Academy of Sciences,Beijing 100049,China;Center for Excellence in Urban Atmospheric Environment,Institute of Urban Environment,Chinese Academy of Sciences,Xiamen 361021,China

环境科学学报（英文版）

[1]Yifei Song;Yuanyuan Zhang;Junfeng Liu;Chenglong Zhang;Chengtang Liu;Pengfei Liu;Yujing Mu-.Rural vehicle emission as an important driver for the variations of summertime tropospheric ozone in the Beijing-Tianjin-Hebei region during 2014-2019)[J].环境科学学报（英文版）,2022(04):126-135

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