Spatio-Temporal Characteristics Of PM_2.5 And Influence Factors In Main Cities Of China

In recent years,the deterioration of China's atmospheric environmental quality has become more and more obvious.The frequent occurrence of extreme atmospheric pollution events has caused great harm to people's production,life and health,such as smog and so on.The smog pollution in the urban economic belts such as the Yangtze River Delta,the Pearl River Delta and the Beijing-Tianjin-Hebei Economic Circle is particularly prominent.As the main component of smog,PM2.5 has been attracted widely by government and scholars.The increase of PM2.5 concentration in the air will directly lead to smog pollution,which will greatly increase the toxic and harmful substances in the air.Local governments have proclaimed their own anti-pollution and treatment programs since 2013.However,these schemes didn't combine the distribution regulation and influencing factors of PM2.5 concentration in the air.The"standardized" characteristics of schemes have emerged,which means that the importance is mainly focusing on the atmospheric pollution control in the region but ignoring the regional joint governance.The anti-fouling and treatment schemes in different cities are similar.Proper plan hasn't been drafted until now.After summarizing and combing existed research and related theoretical knowledge,this paper uses the related data of cities in China to explore the temporal distribution and spatial deduction regulations of PM2.5 concentration.And 74 cities which were monitored firstly have been contained.In view of the availability of atmospheric composition data and climate data,38 typical cities are selected to constructed panel data space model to analyze the factors.Firstly,the spatial weight matrix was improved by the law of universal gravitation in order to test the spatial autocorrelation of PM2.5 concentration in the air.The spatial autocorrelation of PM2.5 concentration in the air was confirmed by this way.Secondly,the change of Moran's I in different threshold distance was used to explore maximum radius of the"Coordinated Joint Control".Lastly,the PM2.5 concentration of each city was regarded as dependent variables.At the same time,the climate and atmospheric component variables were regarded as Independent variables.SDM,SEM and SLM were constructed.Then an optimal model was selected through the results of related statistical tests and statistical indicators,such as LM test,robust LM test,the significance of coefficient and so on.Finally,the SDM was selected to explore the factors affecting PM2.5 concentration in the air.It is found that the PM2.5 concentration in the air of each city appears periodic fluctuations of cyclic fluctuations.The pollution of PM2.5 in autumn and winter is often more serious than that in spring and summer.The PM2.5 concentration in the air has obviously regional and spatial differentiation characteristics.Hu line is the boundary between east and west of PM2.5 concentration.There is significant spatial autocorrelation in the distribution of PM2.5 concentration in the air.The PM2.5 concentration in the air in geographically adjacent cities has a certain spatial spillover effect,which means that each 10%increase in PM2.5 concentration in neighboring cities will result in the 6.12 percentage point increase in PM2.5 concentration in the region.With the increase of distance,the spatial autocorrelation of PM2.5 concentration in air will decrease gradually.About 300 km is the maximum threshold distance of PM2.5 'joint prevention and control'.The strength and effect of"joint defense joint control" will gradually become weaker and weaker as the growth in distance.When the threshold distance is above 500 km,the spatial autocorrelation of PM2.5 concentration is not significant.In atmospheric composition variables,CO is a key factor affecting the concentration of PM2.5 in the air.SO2 and O3 are secondary factors affecting the concentration of PM2.5 in the air.In climate variables,temperature and wind speed have a certain negative effect on PM2.5 concentration in the air.But relative humidity has a positive effect on PM2.5 concentration.Finally,in order to further promote the effective implementation of anti-pollution and haze and improve air quality,itis put forward that relevant policy recommendations based on empirical analysis and current situation of China's atmospheric environment and the actual situation.The innovation of this article mainly includes the following three aspects:(1)In terms of data type selection,in order to make up the lack of existed research,this paper uses panel data to study the temporal and spatial distribution of PM2.5 concentration in 74 cities in China.And 38 typical cities were selected for quantitative analysis;(2)In terms of variable selection,the atmospheric component variables and climate variables are brought into the econometric model at the same time.And the factors affecting the concentration of PM2.5 in the air are analyzed comprehensively.(3)In terms of model building,based on the law of universal gravitation,the commonly used spatial weight matrix is improved.Thus,the spatial weight matrix based on the law of universal gravitation can not only represent the geographical distance between the sample cities,but also represent the "distance" of PM2.5 concentration in the air of the sample cities,making the model more objective and realistic.Above all,each city should change the "selfish" approach.The advantage of"joint prevention and control" should be used effectively.The schemes such as restricting motor vehicles,stopping Industrial production periodically and so on are not fit to all cities.With the sustainable development of economics,each city should focus on different perspectives to explore haze treatment plans,such as adjusting industrial structure,optimizing the energy structure and so on.This will transform the mode of economic growth from 'extensive form' to 'intensive mode' in the future.