Impact Of The Coal Banning Zone On Atmospheric Fine Particles And Visibility In The Beijing-Tianjin-Hebei Region

The Beijing-Tianjin-Hebei?BTH?region,which has the most severe air pollution in China,built a 10,000 km² coal banning zone for pollution control in 2017.In this study,to evaluate the impact of banning coal zone on visibility?VIS?,a chemical composition analysis,a chemical mass closure and the revised IMPROVE algorithm were applied to estimate the chemical components and lighting extinction coefficients(b_ext)of the fine particulate matter(PM_2.5)collected at three urban sites?Beijing?BJ?,Tianjin?TJ?and Shijiazhuang?SJZ??and a regional background site?Xinglong?XL??during autumn and winter of 2016-2017.Compared to measurements from 2016,the average PM_2.5.5 from 2017 decreased by 44?g m^-3?BJ?,37?g m^-3?TJ?,69?g m^-3?SJZ?and 10?g m^-3?XL?,respectively,accompanied by an improved VIS?3.2-4.6 km?.The degradation of VIS caused by atmospheric aerosol is due to the light extinction.The b_ext clearly decreased by 58%,51%,56%and 54%at BJ,TJ,SJZ and XL,respectively.However,the reductions/improvements were more significant in winter than those in autumn,especially at BJ and TJ located in the coal banning zone.The decline?improvement?in PM_2.5?VIS?was 16%-37%?15%-27%?in autumn but 29%-60%?21%-83%?in winter.The reductions in SO₄^2-?Cl^-?in winter were 2.8?3.2?and 7.4?16.4?times larger than those in autumn at BJ and TJ,respectively.Reductions in ammonium sulfate,one of the main species of PM_2.5.5 caused by coal burning,were particularly pronounced at three urban sites in winter?59%-68%?.In addition,the reductions in b_ext in winter were 2.3?BJ?,339.4?TJ?,1.9?SJZ?and 0.4?XL?times larger than those in autumn.From 2016 to 2017,the contribution of annual coal sources to PM_2.5 in Beijing and Tianjin decreased significantly,and the decrease was even more significant in winter.The contribution of coal sources to PM_2.5 in Shijiazhuang increased slightly.The results reveal that banning coal zone has a marked effect on controlling pollution in the BTH,especially in winter?scattering aerosol sulfate?.