Spatiotemporal Dynamics And Influencing Factors Of PM_2.5 Pollution In Cities And Urban Agglomerations

With the rapid development of China's society and economy,environmental problems have begun to emerge.The smog,this invisible "killer" is posing a threat to human life and safety,and it also poses a challenge to the healthy development of our society and economy.Aiming at the phenomenon of PM_2.5 pollution in China,based on the PM_2.5 remote sensing grid data from 2000 to 2015,this paper uses methods such as kernel density estimation model,analysis of spatiotemporal evolution model,spatial autocorrelation analysis,geographic detectors model,and spatial panel models,analyzes the spatio-temporal evolution of PM_2.5 pollution in China,the mapping relationship between PM_2.5 concentration,the level of urban agglomerations,and the size of urban populations,the driving mechanism of changes in PM_2.5 concentrations across the country,and changes in PM_2.5 concentrations in "coastal-inland" regions.Discuss the differences and spillover coupling characteristics.The research content and main conclusions of the paper are as follows:?1?From 2000 to 2015,the change in the annual average concentration of PM_2.5 in China showed an upward trend and then stabilized.The net increase of PM_2.5 nationwide reached 12.9 ?g / m3,a total increase of 61.2%.The PM_2.5 concentration value fluctuates near the national second-level standard value.The area where the national PM_2.5 concentration is lower than the first-level standard decreases year by year.The proportion of highly polluted areas continues to increase,and the air pollution problem is still serious.PM_2.5 pollution in China is mainly accumulated around 2005.The contribution rate of PM_2.5 concentration increase in national-level urban agglomerations is the largest,and regional and urban agglomerations have basically the same increase in PM_2.5 concentration.The changes in the annual average PM_2.5 concentration values of China's various urban agglomerations have an inverted "U" curve.The national average urban agglomerations have the highest annual PM_2.5 concentrations in the past years,followed by regional urban agglomerations and local urban agglomerations.The local urban agglomeration peaked first,followed by national and regional urban agglomerations.The concentration of PM_2.5 pollution in cities in different levels of urban agglomerations is also different.PM_2.5 pollution in national-level urban agglomerations has been aggravated first and then reduced.The urban PM_2.5 pollution in the regional urban agglomerations showed a continuous increasing trend.The concentration values of 35 ?g / m3 and 60 ?g / m3 agglomerated,showing a "double-peak" mode.The peak variation range of PM_2.5 concentrations in local urban agglomerations was small,and PM_2.5 Pollution is mostly distributed between 15 ?g / m3 and 30 ?g / m3.The pollution status of local urban agglomerations is first increased and then reduced.Local cities in non-urban agglomerations have pollution at concentrations of about 67 ?g / m3.Most cities The pollution value is small,about 10?g / m3 to 20?g / m3.?2?Among the eight pollution evolution models of PM_2.5 in China,R-D-D types account for the largest proportion,R-R-R types are the second,and D-D-D types are the least.It is mainly distributed in clusters or bands in space,showing the Fujian-Zhejiang-Guangdong group,Shanxi-Henan-Hubei-Hunan-Jiangxi group,and Gansu-Guizhou group as R-D-D types.The state distribution is of the R-R-D type.In addition,the higher the population size level,the higher the probability that PM_2.5 pollution will exceed.The rate of urban pollution exceeding standards in megacities is 77.78%,the rate of pollution exceeding 60% in megacities,the rate of pollution exceeding 48.21% and 56.58% in large cities and medium cities,and 25% in small cities.?3?There are spatial spillover benefits of PM_2.5 concentration in China,showing high-high?H-H?agglomeration and low-low?L-L?agglomeration.The concentration was the strongest in 2007.The high / high?H-H?agglomeration areas are mainly distributed in Beijing,Tianjin,16 provinces and cities including Shanghai,Anhui,Hebei,Henan,Hubei,Jiangsu,Jiangxi,Jilin,Shandong,Shanxi,Zhejiang,Hunan,Liaoning,Shaanxi,etc.The low / low?L-L?concentration areas are mainly Gansu,Guizhou,Heilongjiang,Inner Mongolia,Ningxia,Qinghai,Sichuan,Tibet Autonomous Region,Xinjiang,Yunnan and other 10 provinces.Risk factors for PM_2.5 pollution at different time sections of different levels.Demographic factors,industrial structure,transportation factors,energy consumption,climate and environment have a greater impact on PM_2.5.PM_2.5 pollution is more inclined to areas with large populations,high total industrial output value,and large coal consumption.The use of public transportation can ease the increase in PM_2.5 concentration.In addition,this paper validates the nested structure of spatial differences and spatial spillovers of PM_2.5 pollution in China's "coastal-inland" regions.