Study On The Effect Of Parkland Reducing PM2.5 Based On Field Measurement And ENVI-met Simulation

Climate and environmental issues are becoming more and more serious.Air pollution has become a problem faced by most cities.Industrial emissions and automobile exhaust have caused urban PM_2.5 pollution and endangered human health in the city.Urban green space can adsorb particulate matter,which can effectively alleviate air pollution.Parkland is an essential part of the urban green space system.It has a large area and is open to the public.It has both ecological and social services.The use of green space is an effective means to reduce the concentration of PM_2.5 in the atmospheric environment.The reduction effect of parkland on PM_2.5 has reached in related research fields.The design and planning of parkland should consider the reduction of hazards and create healthy activities space.Based on field measurement and simulation technology,this paper quantitatively analyzes the relationship between urban planning indicators of parkland and PM_2.5 concentration,and combines the analysis results to propose a parkland planning strategy based on reducing PM_2.5 pollution,and implements specific spatial design and research.The results have practical significance.This paper reveals the law of the decrease in PM_2.5 in parkland.It explores the relevant optimizable indicators of parkland,which is a theoretical supplement to the current research on the reduction of PM_2.5 in parkland from the perspective of landscape architecture.This paper selects small parkland（<1 hectare）,medium parkland（1-10 hectares）,and ample parkland（>10 hectares）as the research sample objects.In the winter,when the concentration of particulate matter is the most serious in Wuhan,PM_2.5 concentration monitoring is carried out.Through the combination of field measurement and numerical simulation technology,explore the impact of parkland on PM_2.5 inside and around it,as well as the urban planning indicators related to the three types of parkland（quantity characteristics of green spaces,differences in spatial pattern composition,and features of surrounding building environment）.Quantify the relationship.Propose a parkland optimization strategy based on reducing PM_2.5 to improve the efficiency of parkland reduction in PM_2.5.Firstly,through field measurement,the PM_2.5 concentration inside and outside the parkland is calculated.The PM_2.5 concentration distribution inside the parkland and the influence of the parkland on the PM_2.5 concentration distribution in the external environment explained separately.The location data and concentration information recorded by GPS Make connections to explore the quantitative relationship between the distance from the parkland and the PM_2.5 concentration.On this basis,the measured weather conditions divided into light pollution or lower and moderate pollution or higher,and the differences in PM_2.5 concentration distribution under different pollution conditions are analyzed separately.Secondly,the impact of parkland on PM_2.5 quantified by the difference.The reduction effect of parkland is defined,and the correlation analysis and regression analysis of a single factor with the three types of urban planning indicators carried out to obtain the effect of parkland reduction.The main element is to study the reduction laws of parkland on PM_2.5 under multiple factors.The analysis found that:（1）Parkland may not reduce PM_2.5 concentration under better air conditions.The higher the air pollution concentration,the better the reduction effect of parkland.Larger parkland lessen the amount of green area,and the overall trend is large-scale parkland>medium-sized parkland>small parkland.（2）Above the moderate pollution level,increasing the greening rate in the parkland will only not promote the increase of PM_2.5 reduction value.Still,cause the reduction of the reduction value.Boundary effects play a more signicant role in the reduction of PM_2.5 in green spaces in parks.Increasing the intersection of green spaces and non-green spaces in parks will help improve the ability to reduce PM_2.5,and at the same time,increase the gap between green spaces in the park.Connectivity is also beneficial to the reduction of PM_2.5.（3）The removal of PM_2.5concentration by parkland may not be affected by the surrounding environment,and it depends more on the role of parkland itself.（4）The reduction value of parkland to the external environment PM_2.5 and the distance to the parkland show a quadratic function relationship,from 0m to 217m from the parkland.As the distance increases,the reduction value gradually increases.The mitigation effect gradually decreases.When the distance exceeds 217m,the reduction value will gradually decrease as the distance increases.The role of parkland in it will be progressively lower than the external environment.（5）The landscape type will play a huge role in the case of poor air conditions.（6）The urban surface environment will affect the reduction effect of parkland.The rougher the surface,the stronger the impact of parkland on the external environment.Higher buildings hinder the diffusion of PM_2.5 in the environment to a certain extent.Finally,based on the statistically significant indicators derived from the analysis results,combined with ENVI-met simulation,a specific case in Wuhan is selected for optimization design.Comparison and optimization results show that the average PM_2.5 in the parkland after optimization is significantly reduced,0.12-0.18 ug/m3 lower than before optimization,the reduction value is higher after optimization,and the optimized model has a better impact on the surrounding benefits.Combined with the actual measurement and simulation,the optimization strategy of park green space based on the reduction of PM_2.5 is proposed.In high-density urban areas,it is often difficult to increase the size of park green space,so it can be considered to increase three-dimensional green space.It is necessary to provide favorable ventilation conditions to maximize the park connectivity,taking into account the density of vegetation.Increasing the contact area or overall proportion of heterogeneous areas is beneficial to the reduction of PM_2.5.To ensure the integrity of the green space,patches scattered layout.In the surrounding environment of the planning,the building density outside the park should be reduced as far as possible to improve the ventilation condition of the green space.The greater the variation of the building in the vertical space,the more favorable the circulation communication between the atmosphere will be.