| The Beijing-Tianjin-Hebei region is a major national strategic area that includes Beijing,Tianjin and Hebei province.The coordinated development of The Beijing-Tianjin-Hebei region is one of China’s three current strategies.The first initiative of coordinated development is to give priority to ecology and build green buildings.First of all,this study analyzed the PM2.5concentration data from 2018 to2021 in the Beijing-Tianjin-Hebei region.Temporal and spatial evolution of pollution.Then,in order to further investigate the regional differences,sources and distribution dynamics of PM2.5 pollution,the Dagum Gini coefficient and Kernel density estimation method were used to analyze the panel data of PM2.5concentration in Beijing-Tianjin-Hebei region from 2000 to 2018.Finally,the convergence trend of PM2.5in Beijing-Tianjin-Hebei region was analyzed byβconvergence test.It is of great significance to investigate the spatial and temporal distribution characteristics,spatial difference and evolution trend of PM2.5concentration pollution in The Beijing-Tianjin-Hebei region,and to provide scientific basis for the formulation of feasible control policies,and to promote the improvement of atmospheric environment quality in the Beijing-Tianjin-Hebei region.The main research results include the following:（1）From 2018 to 2021,PM2.5pollution in The Beijing-Tianjin-Hebei region was significantly reduced,with an average annual decrease of 10.18%,but the overall PM2.5concentration still exceeded the second-level national standard limit（35μg/m3）.By 2021,only three cities--Zhangjiakou,Chengde and Beijing--will have second-level LEVELS of PM2.5.（2）From 2018 to 2021,the spatial difference of PM2.5concentration in Beijing-Tianjin-Hebei region was significant,and gradually increased from north to south.The seasonal variation of PM2.5concentration was the highest in winter and the lowest in summer.The monthly variation is u-shaped,and the diurnal variation trend is dominated by double peak phenomenon.The change of PM2.5concentration showed a double peak type hourly change,with the first peak at 9 o’clock,the second peak at 23 o’clock,and the trough at 15 o’clock.It continued to rise from 0 to 11hours,gradually decreased from 11 to 17 hours,and gradually increased from 17 to 23hours.（3）The relative difference of PM2.5concentration in Beijing-Tianjin-Hebei region showed a decreasing trend as a whole,and the main source of the overall difference was the regional difference.The regional difference of PM2.5pollution in the northwest ecological conservation area was the largest,while the regional difference of PM2.5pollution in the southern functional expansion area was the smallest.The difference between the ecological conservation area in the northwest and the functional expansion area in the south was the largest,except for the eastern coastal development area and the functional expansion area in the south,the difference between the other areas was decreasing.（4）The location,morphology and ductility of PM2.5concentration distribution curves in Beijing-Tianjin-Hebei region from 2000 to 2018 were significantly different.The absolute difference of PM2.5concentration in The Beijing-Tianjin-Hebei region as a whole showed a slight increase,but the absolute difference showed a significant trend of decline from 2013 to 2018.The absolute difference of PM2.5pollution in the four regions of Beijing,Tianjin and Hebei has also shown a narrowing trend in recent years,and PM2.5pollution has been improved to varying degrees.（5）The Beijing-Tianjin-Hebei region has a significant positive spatial correlation.Based on the analysis of absoluteβconvergence test,the PM2.5pollution in The Beijing-Tianjin-Hebei region as a whole has absoluteβconvergence,and the PM2.5concentration gap is gradually narrowing to a common level.The overall PM2.5pollution in Beijing-Tianjin-Hebei region also has conditionalβconvergence.The proportion of tertiary industry and the increase of green space will significantly reduce the PM2.5concentration pollution in this region. |
