A Study On The Relationship Between Urban Composite Form And Air Quality In China

Air pollution is an important environmental factor that restricts the development of cities and regions,which will bring direct and indirect negative effects on human health,social economy and ecological environment.With the rapid development of China in recent years,the urban air quality of China is facing unprecedented challenges.It is considered to be an important change that improving air quality from the source treatment based on environmental chemistry to the comprehensive treatment based on urbanform.However,limited by the availability of data and the immaturity of theoretical methods,the research on urban form and air quality has been limited for a long time.This study,which is based on city actual boundary of 334 local administrative regions(extracting urban land use data from land use/land cover data),air quality indexes(concentration of PM2.5,PM10,O3,NO2 and SO2)and a urban social-natural-economic form measurement index system(including the urban physical structure,social economy,human activity intensity and support management),gives us great insight to the relationship betweenurban social-natural-economic form andthe air quality.First of all,with analysis methods of spatial statistical,global andlocal Moran’s I indexes and Getis-Ord G,the daily meteorological and ground air quality monitoring data from January 1,2015 to December 31,2015 were used to research the spatial distribution pattern and quality evaluation of all air quality indexes under stable meteorological condition(wind speed less than 4 m/s,no special weather conditions such as fog,rain and snow).In order to further understand the regional air quality characteristics,we also studied regional characteristics and quality evaluation of each air quality index in the seven geographical regions(north,east,central,south,southwest,northwest and northeast China)and seven urban agglomerations(Yangtze River Delta,Beijing-Tianj in-Hebei,Pearl River Delta,Chengdu-Chongqing,Guanzhong plain,Liaodong Peninsula,Changsha-Zhuzhou-Xiangtan).Secondly,for representing the urban form comprehensively,in this paper,using the land use/land cover,population spatial,social economy and Point of Interest(POI)data,based on the previous urban form which mainly include physical structure and socio-economic factors,the elements of human activities intensity and support management are superimposed to construct a multi-level urban social-natural-economic form measurement index system.And then,this paper established 150 regression equations between the air qualityindexes and each index of the urban social-natural-economic form,focusing on the relationship between the two.Regional air quality improvement approach between air quality and urban social-natural-economic form has been discussed above each typical regions.At last,the relationship of air pollution and urban social-natural-economic form has been studied comprehensively by establishing the structural equation model(SEM)of them.This study provides a scientific case study for systematic understanding of urban social-natural-economic form and ecological environment,and can give us a new perspective for understandingthe complex relationship of man-earth system in details in the future.The main research results are as follows:(1)In 2015,air pollution in China was relatively serious,among which the average annual concentration of PM2.5,PM10 and SO2 exceeded the WHO Air Quality Guidelines(AQGs).PM2.5 and PM10 exceeded the AQGs in all cities of China,with 60%of cities exceeding the AQGs in NO2 and 20%exceeding the AQGsin SO2.All air quality indexes(PM2.5,PM10,O3,NO2 and SO2)have significant spatial autocorrelation and agglomeration,as the Moran’s I index(0.692,0.568,0.157,0.469 and 0.523,respectively)are all greater than 0 and reach the significant level of 0.01.The areas with serious air pollutionare mainly concentrated in the north China plain(dominated by PM10 and PM2.5),southwest xinjiang province(dominated by O3)and northeast China(dominated by SO2),while the areas withlow air pollution are mainly located in southwest and south China.(2)According to the 150 regression equations established by pairwise between urban social-natural-economic form and air quality indexes,the urban social-natural-economic form plays an important role in urban air quality.With the increase of urban population size,urban land area,road area,green space area,total retail sales of consumer goods,total electricity consumption and total gas supply,air pollution will increase.The greater the shape complexity of the urban structure,the smaller the concentration,and the better the air quality.The higher level of urbanphysical structure and social economy are conducive to the alleviation of air pollution.The influence of human activity intensity and air quality is significant.In addition,many cities need more investment because of the imbalance between supporting management investment and air quality demand.(3)The SEM betweenurban social-natural-economic form and air quality is considered to be fitted,both CFI and NFI(0.934 and 0.946,respectively)are greater than 0.9.Results showed that the path coefficients of the physical structure(W),social economy(E),human activity intensity(R)and supportmanagement(Z)on air quality are 0.21,0.26,0.54 and-0.81,respectively,which means that he impact of human activity intensity on air quality is stronger thanphysical structure and social economy,and more investment in support management will significantly reduce air pollution.(4)Among the seven geographical regions,the air quality in south China is better and more coordinated with the urban social-natural-economic form,and the air quality in east China is improved under the influence of urban form.The air pollution in north China should be related to the large amount of energy consumption,while the serious air pollution in central China should be related to the extensive use of land and the unreasonable industrial structure.Human activity intensity and the level of support management in northwest,northeast and southwest China is low and the regional air quality varies greatly.Among the seve urban agglomerations,the air pollution in beijing-tianjin-hebei and changzhou-zhuzhou-xiangtan urban agglomerations is relatively serious,while the develpoment model of Pearl River Delta urban agglomeration is more scientific.The urban agglomerations in guanzhong plain,chengdu-chongqing and liaodong peninsula need to improve the air quality by enhancing the urban vitality.In the future air pollution control work,the pollution characteristics of different regions should be combined for targeted and comprehensive treatment.