The Concentration Of Atmospheric Suspended Particulate Matter In Green Space With Different Vegetation Structure In Urban Forest Park

With the acceleration of China's urbanization process,the problem of atmospheric suspended particulate matter pollution has become increasingly serious.The sources of this problem are numerous and complex.It is difficult to control from the source,and it has not been significantly improved.The green space constructed by urban forest is the only space system with self-purification function in the urban ecosystem.Through reasonable planning and construction,the urban ecological environment can be effectively adjusted and improved.Therefore,in the planning and construction of urban forest,in order to maximize the ecological service function of urban forest to improve air quality,this study took the Olympic Forest Park in Beijing as an example with an area of 680ha.A classification model of urban forest structure based on three types of vegetation structural factors,horizontal structure,species composition,and vertical structure was developed through the method of combining satellite image interpretation and field investigation.Screening open lawn green space,semi-open lawn green space,semi-closed single-layered broadleaved forest,closed single-layered broadleaved forest,closed single-layered mixed forest and hard control group as research types according to the filed condition.Based on the coordinated consideration of meteorological factors such as wind speed,temperature,relative humidity,month and time changes,and the characteristics of the green space itself such as vegetation structure,green area,plant species diversity,the study on the relationship between urban forest and atmospheric suspended particulate matter such as TSP,PM₁₀,PM_2.5and PM_1.0concentrations was carried out.The general linear model and linear regression model were established by Minitab17 statistical software for multivariate analysis,and the significance and difference of research factors on the reduction effect of atmospheric suspended particulate matter concentration were tested.The main results were as follows:1. Meteorological factors all had a very significant effect on the concentration of atmospheric suspended particulate matter with four particle sizes.The concentration was negatively related to wind speed and temperature,and positively related to relative humidity.2. The change of the month had a very significant effect on the concentration of atmospheric suspended particulate matter with four particle sizes.The concentration was higher in winter and the highest value appeared in January.Spring and Autumn followed,and there were some ups and downs.The concentration was the lowest and stable in summer.For the four kinds of particles with different particle diameters,the concentration trend was similar with the change of the month.3. The change of the time period had a very significant effect on the concentration of atmospheric suspended particulate matter with four particle sizes.The concentrations of TSP and PM₁₀with larger particle sizes showed a nearly straight upward trend,with the lowest in the morning,the middle at noon,and the highest in the afternoon.The smaller particles PM_2.5and PM_1.0showed the lowest concentration in the morning,and the concentrations were higher and similar at noon and afternoon.4. The type of vegetation structure of urban forest had a very significant effect on the concentration of atmospheric suspended particulate matter with four particle sizes.Overall,the concentration in the hard control group was the highest,followed by the higher concentration of open lawn green space.The reduction effect of semi-open lawn green space,semi-closed single-layered broadleaved forest and closed single-layered broadleaved forest was centered.Closed single-layered mixed forest had the best reduction effect.5. Under the two area gradients?2.7-3.0ha,0.4-0.5ha?set up in this study,it was found that the change of area had a very significant effect on the concentration of atmospheric suspended particulate matter with four particle sizes,but it had different effects on urban forest with different vegetation structures.For the three types of vegetation structure,open lawn green space,semi-open lawn green space and semi-closed single-layered broadleaved forest,the concentration in larger green area was higher,and the performance of open lawn green space was the most obvious among them.However,for closed single-layered broadleaved forest and closed single-layered mixed forest,the concentration was relatively low in large green area,and closed single-layered mixed forest of different areas had similar and strong reduction capabilities.6. The Shannon-Wiener diversity index and Simpson diversity index in urban forest with different vegetation structures had very significant differences.They were the highest among semi-closed single-layered broadleaved forest and closed single-layered mixed forest,followed by semi-open lawn green space,open lawn green space,and the lowest was closed single-layered broadleaved forest.The Shannon-Wiener diversity index had a very significant effect on TSP and PM₁₀concentrations,and a significant effect on PM_2.5and PM_1.0concentrations.The Simpson diversity index only had a very significant effect on TSP and PM₁₀concentrations.With the increase of the plant species diversity index,the concentration of atmospheric suspended particulate matter showed a downward trend.