Study On The Impact Of Urban Sprawl On Air Quality In The Yangtze River Delta Region

Since the reform and opening up,China has undergone a rapid urbanization process,with the national urbanization rate continuously increasing from 17.92% in1978 to 60.60% in 2019.The rapid urbanization process makes the space of cities expand rapidly,resulting in the reduction of land use efficiency and the dispersion of Urban morphology.At the same time,excessive attention to the pace of urbanization and the low-quality development model has also led to the phenomenon of urban land expansion faster than the growth rate of the total population in China.This phenomenon frequently occurs in the process of urban development,namely urban sprawl,which causes urban resource shortages,road congestion,air pollution and other urban development problems,especially air pollution control issues,and has become the focus of attention for decision-making departments and scholars.Therefore,it is necessary to have a correct understanding of the relationship between urban sprawl and air quality,in order to provide a reasonable reference for China to implement the scientific development concept of green and sustainable development.In view of this,based on reading and absorbing relevant domestic and foreign research,this article takes cities in the Yangtze River Delta region as the research object,searches for supplementary data,uses an indicator system to construct the urban sprawl index,accurately calculates the urban sprawl index of cities in the Yangtze River Delta region,and conducts spatiotemporal change analysis.Furthermore,from a long-term perspective,analyze the impact of urban sprawl on air quality in the Yangtze River Delta region.Considering the heterogeneity of time,different regions,and different city sizes,construct a dynamic spatial Durbin model to explore the impact of urban sprawl on air quality.The main conclusions of this article are as follows: Firstly,there is significant spatiotemporal heterogeneity in urban sprawl and air quality in the Yangtze River Delta region.Through the spatiotemporal analysis of the urban sprawl index in the Yangtze River Delta region,it can be concluded that overall,the Yangtze River Delta region generally presents a trend of low density and decentralization,with a relatively severe degree of urban sprawl.In addition,urban sprawl has significant regional differences,with the degree of spread ranking from high to low in Anhui Province,Jiangsu Province,Zhejiang Province,and Shanghai City.The degree of spread of cities of different sizes is ranked from high to low in small cities,medium cities,and large cities.For air quality,from the overall trend of time changes,the overall air quality of cities in the Yangtze River Delta region shows a trend of first increasing and then decreasing over time.The changes in air quality in cities of different provinces and scales are basically consistent with the overall trend of urban air quality.From different regions,the order of air quality from good to bad is Zhejiang Province,Shanghai City,Anhui Province,and Jiangsu Province,From different city sizes,the best air quality in the Yangtze River Delta region from 2002 to 2012 was in medium-sized cities,followed by large cities and small cities.From 2012 to 2020,the air quality of small cities was better than that of large cities,but still slightly lower than that of medium-sized cities;Secondly,there is a positive spatial autocorrelation in the annual PM2.5 mean of 41 cities within the study sample,indicating that the air quality of prefecture level cities in the Yangtze River Delta region is affected by the air quality of surrounding cities.In addition,the coefficient of influence of urban sprawl on air quality in prefecture level cities in the Yangtze River Delta region is negative and passes the significance test,indicating that the overall urban sprawl phenomenon in prefecture level cities in the Yangtze River Delta region can improve air quality;From the perspective of provinces and cities,there is a significant negative correlation between urban sprawl in Anhui Province and air quality,while the impact of urban sprawl on air quality in Zhejiang and Jiangsu provinces is not significant;From the perspective of urban scale,urban sprawl in small cities has a significant promoting effect on improving air quality,while urban sprawl in medium-sized cities has a significant deteriorating effect on air quality.The coefficient of impact of urban sprawl in large cities on air quality is negative but has not passed the significance test.