Study On The Correlation With Urban Green Space Landscape Pattern And PM_2.5 Concentration Distribution

Recent years,due to the severe PM_2.5 air pollution facing by China,the control of PM_2.5 pollution has become urgent and imperative.In controlling the pollution of PM_2.5,the landscape pattern of urban green space plays a vital part.Therefore,it is of considerable significance to study the relations between the landscape pattern of urban green space and PM_2.5 mitigation.In this thesis,Xi'an City is chosen as the research object.Based on the PM_2.5 monitoring data from 11 air pollution monitoring stations in Xi'an City and the data of the surrounding green spaces,this thesis has adopted a series of statistical methods,such as the Pearson correlation coefficient and Land use regression model,to analyze the influence of Xi'an's urban green space pattern on PM_2.5 concentration.The findings are as follows:?1?From the perspective of time distribution,Xi'an witnesses a lower PM_2.5 concentration in spring and summer while a higher one in autumn and winter,with the highest point being detected in January and the lowest in July.From the spatial distribution,a higher concentration of PM_2.5 is detected in the northwest part of Xi'an while the lower concentration part is in the southeast.The highest point is detected in the High-Voltage Switch Gear Factory and the lowest one in the Xingqing Residential Community.The analysis results show that the time and spatial distribution of PM_2.5 in Xi'an is related to the temperature,precipitation and the urban green space patterns.?2?From the spatial distribution of urban green space in Xi'an,districts with better vegetation cover are the ones on the outskirts of the city,such as Chang'an District,Weiyang District,Yanta District and Baqiao District.While for the districts inside the city which have been developed for years,such as Lianhu,Beilin and Xincheng districts,the vegetation cover rates are lower.Though the vegetation cover in Xi'an has been rising in recent years,the green spaces in the peripheral districts,influenced by the concentric zone model of urbanization in Xi'an,have been severely damaged.?3?The results of the Pearson correlation analysis and Land use regression model can be summarized as follows: the increase of the urban green space can help to reduce PM_2.5 pollution;the shape of urban green space might have a relatively complex influence on the PM_2.5 concentration.Generally speaking,the complexity of the shape of urban green space at small and medium-sized scales tends to reduce PM_2.5 concentration.In contrast,on a larger scale,the complexity tends to increase PM_2.5 pollution.When the green spaces have the same total size,moderately dispersion of the green space can mitigate PM_2.5 pollution more effectively.Even,dispersed and diverse distribution of green space at various types or the city land use with different vegetation coverage can help to alleviate PM_2.5 pollution.?4?Based on the analysis,this thesis suggests that to improve the ability of the urban green space to alleviate PM_2.5 pollution,measures should be taken into consideration in the future concerning planning and design of the green space in Xi'an,including increasing the number of the city green lands,controlling the canopy density and vegetation coverage of urban green space,optimizing the boundaries of urban green space,moderately dispersing the distribution of the urban green space,diversifying the types of green space and adjusting the shape of urban green space based on different scales.