Analyzing The Changes Of Pollutant Emission And Source Contributions Over The Beijing-Tianjin-Hebei Region In Winter Based Inversion Emission

In recent years,China has implemented several measures to improve air quality.The Beijing-Tianjin-Hebei（BTH）region is one of the regions that suffered the most serious air pollution in China and has undergone big changes of air quality in the past few years.How to scientifically assess this change process remains the key issue to further improving the air quality over this region in the future.To evaluate the changes of major air pollutant emissions over this region,this paper use the inversion emission dataset base on ensemble Kalman filtering,and through integrating the national ground monitoring pollutant observation data and the Nested Air Quality Prediction Modeling System（NAQPMS）simulation data to inversely estimate the emission rates of SO₂, NO_X,CO and primary PM_2.5over BTH region in February from 2014 to 2019.The results show that SO₂,NO_X,CO,and primary PM_2.5emissions in the BTH region decreased by 83%,37%,41%,and 42%in February from 2014 to 2019,and in Beijing during this period decreased by 86%,67%,59%,and 65%.And the inversion emission inventory can significantly reduce the uncertainty of multi-pollutant simulation in the BTH region,with the root mean square error of the monthly average simulation concentration of SO₂,NO_X,PM_2.5,and CO reduced by 41%,30%,31%,and 22%.Meanwhile,the results of this paper can provide a new reference for assessing the changes of air pollution emissions over the BTH region in recent years and the validation of the bottom-up emission inventory.Then,based on the inversion emission inventory and NAQPMS model,we further explore the pollution characteristics and quantifying the contributions of PM_2.5in Beijing from different source regions.This paper simulates the PM_2.5pollution process in Beijing and its surrounding areas in February from 2014 to 2019.The pollutant source analysis results show that the local contribution rate of monthly average PM_2.5in Beijing in February from 2014 to 2019 is 34%-42%,mainly contributed by surrounding countries,and its contribution rate was 58%-64%.Beijing’s surrounding cities,such as Xingtai,Baoding,Hengshui,and Zhangjiakou,have a large contribution to PM_2.5concentration in Beijing,and the contribution rate is basically more than 5%.The contribution rate of areas around the BTH region is 9%-19%,contribution rate of Inner Mongolia and Shanxi accounts for a relatively large proportion to PM_2.5 concentration in Beijing over the years,and the contribution rate is more than 5%in most cases.