Influence Of Urban Spatial Structure On PM2.5 Concentration Distribution

China’s urban process has entered a new stage of high-quality development,but the ecological and environmental problems bring about by rapid development have seriously hindered the construction of ecological civilization and sustainable economic and social development in China.Among them,the problem of haze pollution consisting of fine particulate matter PM2.5 has increasingly become the focus of attention of the majority of scholars.This paper selects the central urban area of Jinan City,which has a high incidence of haze pollution and is densely populated with buildings,as the study area,and uses the urban road network to divide blocks as the study unit.The spatial and temporal distribution patterns of PM2.5 concentrations in Jinan from 2019 to 2020 are firstly investigated;then,building-based urban spatial structure indicators are constructed based on the characteristics of building height arrangement,plan layout and three-dimensional distribution.Finally,the correlation and spatial correlation between urban spatial structure indicators and PM2.5 concentration and the spatial heterogeneity of their effects are quantitatively analyze.The results of the study show that:（1）PM2.5 concentrations in the central urban area of Jinan City have decreased from 2019 to 2020,but still fail to reach the national ambient air quality secondary standard.The spatial and temporal differences in PM2.5 concentrations in the central urban area of Jinan are obvious,with a "U-shaped" trend of decreasing from winter to summer and increasing from summer to winter in time,and a general trend of PM2.5concentration distribution from scattered to concentrated to scattered.The overall trend of PM2.5 concentrations in winter months is different from that in spring,summer and autumn months.（2）PM2.5 concentrations are significantly negatively correlated with indicators such as mean elevation,standard deviation of elevation and mean absolute building height,and are significantly correlated with indicators such as mean building height,mean building volume,volume ratio,outdoor activity area,building density,total building volume and occupancy ratio,both in the whole area and in different height ranges.The mean elevation,standard deviation of elevation,mean absolute building height,maximum absolute building height,mean building height,mean building proximity,and mean building volume of adjacent areas were negatively correlated with PM2.5 concentrations in most months.The standard deviation of building height,mean building footprint,total building footprint,standard deviation of building footprint,outdoor activity area,building density,total building volume of adjacent areas The standard deviation of building height,average building base area,total building base area,standard deviation of building base area,outdoor activity area,building density,total building volume,standard deviation of building volume,occupancy ratio and volume ratio are mostly positively correlated with PM2.5 concentration.（3）In general,urban spatial structure indicators alone have a more significant effect on PM2.5 concentrations than multiple factors acting together.Mean absolute building height and standard deviation of absolute building height,mean absolute building height and maximum absolute building height,outdoor activity area and mean building proximity,mean building proximity and floor area ratio,total building footprint and outdoor activity area,mean building footprint and mean absolute building height,total building footprint,standard deviation of building footprint and outdoor activity area,total building footprint,outdoor activity area and The interaction of the combination of indicators such as total building footprint,outdoor activity area and average building proximity had a significant effect on PM2.5concentrations.（4）Both the discrete degree of PM2.5 concentration and the average concentration affect the strength of the correlation between urban spatial structure indicators and PM2.5 concentration.The correlation between the spatial structure indicators and PM2.5concentrations generally increased in May based on the global perspective and different height ranges;the correlation between the spatial structure indicators and PM2.5 concentrations generally decreased in October and December;the spatial structure indicators of adjacent regions in months with higher PM2.5 concentrations had a more significant impact on PM2.5concentrations.（5）There is spatial heterogeneity in the influence of urban spatial structure indicators on PM2.5 concentrations.The spatial distribution of the influence of spatial structure indicators on PM2.5 concentrations varies,with a gradual change from the central of densely built-up areas to the surrounding areas and in the east-west direction.The results of this study can provide a reference for the study of solving the haze pollution problem based on the perspective of urban spatial layout,and provide spatial development ideas for the prevention and control of air pollution and sustainable improvement of the ecological environment,which are of reference significance for promoting sustainable urban development and advancing the modern and intelligent governance of cities.