Research On Correlation Between The Morphological Characteristics Of Neighborhoods And PM_2.5 In Central Urban Area Of Beijing

Air pollution caused by rapid urbanization has seriously affected the life of urban residents,and air quality could be improved by formulating reasonable urban planning strategies.Based on the impact path of urban form on air quality and took neighborhoods,PM_2.5 and wind environment as the research elements,the study used the quantitative analysis of urban morphological characteristics and the methods of PM_2.5 and meteorological parameter measurement,computational fluid dynamics simulation,statistical analysis and urban planning and design theory to explore the impact mechanism of urban form at the neighborhoods level on human settlements and the optimization strategy of urban form about improving air quality,which provided corresponding reference and policy basis for future urban planning and urban design.The sutdy was divided into five chapters.First of all,the study reviewed the existing researches on the correlation between urban form and air quality form the theoretical study of urban morphology,quantification of urban morphological characteristics,urban morphology and atmospheric pollutant diffusion,and summarized the characteristics that the existing research was disconnected from the actual environment and lacked common characteristics and so on.Secondly,according to the impact path of urban form on air quality and the selection of actual neighborhoods,the study constructed the framework of the interaction mechanism between urban form and air quality and selected ten neighborhoods morphological parameters.At the same time,the study used the Computational Fluid Dynamics simulation technology to obtain the distribution and concentration of PM_2.5and wind environment data on typical dates.Thirdly,the study analyzed the influence of the morphological characteristics of different neighborhoods on PM_2.5 diffusion based on the numerical simulation results and filtrated the morphological parameters with high correlation between PM_2.5 and wind speed through Pearson correlation analysis:Building density（BD）,Average building envelope（ABE）,Average building volume（ABV）,Average building floors（ABF）,Standard deviation of building height（SDH）,Greenbelt coverage rate（GCR）.Based on this,the study analyzed the interaction mechanism between the above six morphological parameters and the distribution and diffusion of PM_2.5and wind environment.Among them,in single factor curve Estimation analysis,it is showed a positive/cosine curve trend of BD/ABE with PM_2.5;GCR was significant to dust retention along with canopy vertical height;When ABV=40000m³ and ABF=20F,the lowest PM_2.5 concentration was observed;Increased SDH could promote airflow and enhance the capacity of PM_2.5 diffusion;Multiple linear regression was used to determine the influence degree of each factor on PM_2.5 and wind speed:In the influence on PM_2.5 concentration and diffusion,the order of contribution was ABF>SDH>GCR>ABV.In the influence on wind speed,the order of contribution was ABE>BD>GCR>SDH>ABF.After that,based on the research conclusions,the local areas with serious pollution within the research scope were selected to conduct simulation verification of pollutant diffusion optimization.Then,the study verified the existing general conclusions and confirmed the rationality with the comparison of the analysis of the XY horizontal and the YZ vertical cross of different schemes.Finally,the study proposed four optimization strategies of urban form for air quality improvement in neighborhoods from the perspectives"density form optimization","structural form optimization","building form optimization"and"functional form optimization"based on the verified conclusions.