Research On The Impact Of Park Green Space Pattern On The PM_2.5 In Chongqing’s Main City Based On LUR Model

With the acceleration of urbanization and industrialization,PM_2.5 has now become an important factor affecting environmental quality.The green space as a"scenery landscape"can greatly weaken the concentration of PM_2.5.The spatial layout and aggregation degree of park green space will affect the diffusion of PM_2.5 by affecting the air flow,so targeted research The impact of the related pattern indicators of park green space on PM_2.5,and how to optimize the form of park green space to assist PM_2.5pollution prevention measures can provide a further regulation for the urban planning and park design stage on the basis of the original park planning principles The idea of PM_2.5 is to make better use of the ecological benefits of the park’s green space.The main research contents of this paper are as follows:First,the changes of PM_2.5 mass concentration in the main city of Chongqing from 2013 to 2018,and the seasonal and spatial distribution characteristics are analyzed;the park green space pattern of the main city of Chongqing from 1996 to 2018 A brief analysis of the development,change and distribution of the country.Secondly,by using the Gole Earth map with a resolution of 1.2m,the high-resolution information of the park green space in the main urban area of Chongqing is extracted to pave the way for subsequent research;the use of bivariate correlation analysis and multiple stepwise linear regression analysis at the data level Obtain the correlation between the park green space pattern and PM_2.5;and through the PCA principal component analysis between the park green space pattern index,screen for the large correlation with PM_2.5 and no redundancy,while fully characterizing the park The index of green space pattern is used to further analyze the influence relationship between the two;and the screened park green space pattern index and PM_2.5 are multi-scale coupling analysis to study the scale of the relationship between the park green space pattern and PM_2.5 Impact;Then,based on the conventional independent variables of the LUR model,innovatively add park green space pattern indicators,compare the results of two models before and after adding new variables to simulate PM_2.5,and further analyze the impact of park green space pattern on PM_2.5.Finally,the mechanism of the park green space pattern affecting PM_2.5 is briefly analyzed,and a pattern optimization strategy based on mitigating PM_2.5 concentration is proposed.The main research conclusions are as follows:1.The status of the park green space pattern in the main urban area of Chongqing has a greater correlation with the PM_2.5 concentration,that is,the PM_2.5 concentration value is generally lower in areas with larger park green areas and more concentrated areas.The PM_2.5 concentration in the main urban area of Chongqing has the characteristics of high concentration and low coefficient of variation in autumn and winter,low concentration and high coefficient of variation in spring and summer,and the average PM_2.5 concentration in summer,autumn and annual is low-high near Tangjiatuo in Jiangbei District The phenomenon of cohesion;in autumn,there is a low-low cohesion near the natural occurrence in Beibei District;the average PM_2.5concentration and mass in autumn,winter,and year all exist near Yuxin Street in Banan District.This is quite different from the park green space pattern in the main urban area,which leads to a large gap in the benefits of mitigating PM_2.5 concentration in the green parks of the regional parks in the two seasons of vigorous plant growth in spring and summer.2.This study shows that the green-red reduction index（EXG-EXR）can be used as a vegetation separation index for extracting high-resolution green space information in the main urban area of Chongqing.Through the more open-source and economical high-resolution Goole Earth map,the color threshold of landmarks is used to separate the green and non-green areas in the main urban area of Chongqing,so that high-resolution green space information can be extracted.3.The correlation between park green space pattern and PM_2.5 changes with the change of scale.Among them,the shape index（SHAPE-MN）,landscape separation（DIVISION）,maximum patch ratio（LPI）and patch fragmentation（PD）are generally manifested in the buffer zone with a radius of 1km to 3km,with the increase of scale,Correlation with PM_2.5 is enhanced accordingly.The absolute value of the slope of the best fit of SHAPE-MN increased from the range of 0.346 to 3.492 to the range of8.518 to 15.48;the range of DIVISION increased from 4.519 to 22.264 to the range of175.4 to 848.6;the LPI increased from the range of 0.011 to 0.062 As large as the range of 0.198 to 1.036;PD increased from the range of 0.109 to 0.226 to the range of0.7223 to 1.734.4.After adding the independent variable of"Park Green Space Pattern",the fitting degree of the LUR model to simulate PM_2.5 has been significantly improved.The adjusted R-square of the spring,summer,autumn,winter and annual average models have increased by 0.1946,0.3499,and 0.1314,respectively.,0.1538 and 0.1671.This shows that the landscape pattern of the park’s green space actually affects the PM_2.5concentration value.And by analyzing the regression coefficients of the independent variables in the model,it can be concluded that the coefficients of SHAPE-MN in the model are distributed between-1.369 and-3.136,the coefficients of LPI are mainly distributed between-0.413 and-1.455,and the coefficient of DIVISION The main distribution is between 0.793 and 2.315,and the coefficient of PD is mainly distributed between 0.105 and 1.621.Specifically,the more complex the green space shape in the park green space pattern,the higher the proportion of the largest park green space patches,and the lower the green space separation and fragmentation,the more conducive to mitigating the PM_2.5 concentration value.5.The park green space planning and design can be carried out through idle plots beside street corners,unused land,etc.,to further expand the total park green space area,increase the aggregation between park green spaces,improve the connectivity between park green spaces,The patches of greenery in small parks extend into a large area of greenery in the park,increasing the length of contact between the greenery of the park and the external environment,which can give full play to the ecological benefits of parkland in mitigating PM_2.5.