Research On The Evolution Of Spatial Structure In City Regions And Its Influence On Environmental Pollution

The speeding up of urbanization has made the conflict between society and environment in cities increasingly prominent,and the adjustment of spatial structure has become one of the important measures to control urban environmental pollution.On the one hand,excessively concentrated population distribution can cause problems such as traffic congestion,ecological space reduction,and concentrated emissions of pollutants.On the other hand,disorderly and dispersed population distribution may also cause cities to face problems such as resource waste caused by inadequate environmental regulation and low utilization of public infrastructure.Therefore,it is necessary to explore the impact mechanism of urban spatial structure on urban environmental pollution,and analyze the path mechanism of the monocentric urban structure with high population density concentration and the polycentric structure with decentralized population for alleviating environmental pollution,which is the core and focus of this study.For this purpose,this paper sorts out and discusses the relevant concepts of urban spatial structure and the impact mechanism and action path of urban spatial structure on environmental pollution firstly;Secondly,taking the prefecture-level cities in the Yellow River basin as an example,based on DMSP/OLS and NPP/VIIRS night light remote sensing data,the urban primacy index and Herfindahl index are constructed simultaneously to measure and characterize the urban spatial structure of the city in the Yellow River basin,and their spatiotemporal evolution characteristics are analyzed in depth;Then,taking the grid data of PM_2.5annual average concentration as the indicator of environmental pollution,the static distribution characteristics and dynamic evolution trend of environmental pollution in prefecture level cities in the Yellow River basin are analyzed;Finally,based on the STIRPAT model as the basic framework,this paper explores the impact of urban spatial structure on environmental pollution and the threshold effect and spatial effect in the urban scale of the Yellow River basin by constructing the ordinary panel econometric model,panel threshold econometric model and spatial panel econometric model.The research findings are as follows:（1）It is feasible to control environmental pollution based on urban spatial structure,but there is no fixed spatial structure that can help any city reduce environmental pollution.For cities with small populations,monocentricity structure can effectively inhibit environmental pollution,while for cities with large populations,polycentricity structure is more suitable for urban development as a spatial support;（2）The centrality of urban spatial structure in the Yellow River basin presents a spatial pattern of"high-low-high-low"staggered distribution from east to west,and most cities present a monocentric spatial structure;From the perspective of dynamic evolution trend,the overall spatial structure of the region is relatively stable,showing a weak trend of evolution towards a polycentric structure;（3）The PM_2.5concentration in the Yellow River basin basically presents a stepwise spatial distribution pattern of decreasing from east to west,and the overall pollution situation has improved,but the PM_2.5pollution situation in Henan and the central and western areas of Shandong,which are located in the lower reaches of the Yellow River,is still serious;In addition,the regional PM_2.5pollution has obvious gradient effect,and the phenomenon of polarization starts to appear with the passage of time,and the trend of evolution is further strengthened;（4）The impact of the spatial structure of prefecture level cities in the Yellow River basin on environmental pollution has a threshold effect.When the city size is small,monocentricity structure can effectively curb environmental pollution.When the city size crosses the threshold,the inhibition of monocentricity structure on environmental pollution no longer exists,and may even aggravate environmental pollution in the reverse direction;（5）The impact of urban spatial structure on environmental pollution has a spatial effect,that is,the urban spatial structure of a single center layout in this region can inhibit the local environmental pollution,but will strengthen the environmental pollution in the adjacent areas.This paper enriches the existing research on the impact of urban spatial structure on environmental pollution.The research conclusions can not only provide a new direction and path for environmental pollution control in the Yellow River Basin,but also provide reference for environmental pollution governance in other regions of China.