Study On The Scale And Morphology Of Urban Green Space With PM2.5 Reduction

Both developed and developing countries have been plagued by serious particulate air pollution problems during the rapid development of urbanization.According to the 2018 global PM2.5 pollution data released by the World Health Organization,there are 58 Chinese cities with the highest concentration of 100 cities.China’s high-density urban form,industrialization and the popularity of small cars have led to particularly serious air pollution problems.In recent years,with the monitoring of particulate matter carried out in many cities across the country,research results have gradually increased,and the rise of urban green infrastructure has become one of the effective ways to reduce airborne particulate matter.Microscopically,green plants in urban green infrastructure are natural and excellent "vacuum cleaners";macroscopically,the network construction of urban green infrastructure is a low-input and high-reward strategy to reduce particulate matter.Previous studies have lacked the research results of the influence of different morphological characteristics of urban green space on the concentration of particulate matter.Therefore,this paper mainly selects the heavily polluted Wuhan urban area as the research area to study the reduction effect of urban green space on PM2.5.By analyzing the PM2.5 data inside and outside the 10 urban green spaces obtained by the actual measurement,the following two aspects of the green area reduction PM2.5 were studied.On the one hand,it demonstrates the correlation between the scale of green space and the internal PM2.5 reduction.Firstly,the remote sensing image of urban green space is obtained by Google Earth software,the shape information of green space is obtained by Arcgis software,and Patch area、Patch perimeter、Shape index、Fractal dimension index、Related circumscribing circle are calculated by Fragstatsstat software.The landscape pattern indicator data obtained data for quantifying the shape of 10 urban green spaces.Secondly,PM2.5 data of 10 green areas inside and outside is obtained by collecting self-set fixed monitoring points inside the green space and external self-designed reference monitoring points,and the internal PM2.5reduction data of each green space is obtained by comparative analysis.Finally,the morphological data and PM2.5 subtraction data were integrated,and the correlation analysis was carried out by SPSS software.The morphological indicators with significant correlation were screened out,and the regression analysis was performed on the indicators with significant correlation,and the regression equation corresponding to the morphological indicators was obtained.On the other hand,the effect of green space on the surrounding PM2.5is demonstrated.Firstly,the remote sensing images of urban green space and surrounding areas are obtained through Google Earth software.Combined with the investigation of the inside and outside of the green space,a suitable mobile monitoring circuit running through the green space is selected.Then,the GPS navigator records the position information and the motion camera records the environmental information,and monitors the green field and the surrounding PM2.5 concentration by the mobile route monitoring method.Finally,the distribution characteristics of PM2.5 in urban green space and surrounding areas were analyzed,and the correlation between distance and PM2.5 was analyzed by Spss statistical software.Through the actual survey of PM2.5 concentration inside and outside the urban green space and comprehensive data statistics and analysis,the following results were obtained:1.There is a significant correlation between the scale of green space and the PM2.5 concentration reduction.（1）The concentration of PM2.5 in the green space is generally lower than that outside the green space,and the larger the green area is,the larger the difference of the concentration of PM2.5 inside and outside the green area is,the average PM2.5 concentration difference can reach 8.82ug/m3;（2）The plaque area,plaque circumference and landscape shape index of the green space are significantly positively correlated with the PM2.5concentration of the particulate matter.The larger the area,perimeter and shape index,the more obvious the effect of greenfield reduction of PM2.5;The regression equations are y=0.107x+4.182（R2=0.333）;y=0.001x+3.059（R2=0.373）;y=7.074x-3.888（R2=0.178）;（3）There is a significant negative correlation between the green area and the PM2.5 concentration per hectare.The green area is larger,the green concentration is reduced by PM2.5,and the regression equation is obtained:y（28）.2075x^-.0627_{（R2=0.632）.}2,the greater the size of the green space,the greater the impact on the surrounding PM2.5（1）The PM2.5 concentration inside the green space is generally lower than the surrounding concentration.The PM2.5 concentration is generally high at both ends,and the middle is low concave.The green space has the effect of purifying the internal PM2.5 concentration.（2）Small green space（0.5-1.7ha）has no obvious influence on the surrounding PM2.5;medium-sized green space（7.5-12.2ha）has obvious influence on the surrounding PM2.5,and can affect 180 meters at the farthest.The concentration of PM2.5 in the surrounding 6-8ug/m3 is reduced;the large green space（21-64.4ha）has a significant influence on the surrounding PM2.5,which can affect 180 meters at the farthest,and can reduce the PM2 of7-14ug/m3 at the maximum..5 concentration;（3）The larger the green space is,the farther it will affect the surrounding PM2.5,and the greater the impact.The green space（0.5-64.4ha）has a significant effect on the surrounding PM2.5,which can affect 144 meters at the farthest,and can reduce the PM2.5 concentration of 5-8ug/m3 at the periphery.