Study On Plant Configuration Design Of Ring Expressway Based On PM_2.5 Reduction Effect Of Plant

It is urgent to improve the air quality of the environment,due to the more and more times of fog and haze by the acceleration of industrial development and urban construction process.PM_2.5 is one of the main components of the fog and haze,which is the culprit of weather of fog and haze.In 2018,Xi’an ranked the ninth from the last among 168 major cities in China.In2019,it quitted from the last 20 in China,with measures such as limiting traffic and increasing green area,so as to deal with the PM_2.5pollution.Although the air quality is improving,the primary pollutant is still the particulate matter.The dust retention rate of the road green belt is significantly higher than that of other urban green areas.The green belt of Xi’an ring expressway is 40-60 meters wide,which is also a nearly 100 km ring green corridor.Xi’an ring expressway plays an important role in sharing transit traffic and alleviating the urban traffic.Therefore,it can fully use the wide and strong extensibility of the green belt around the city to alleviate traffic pollution and improve air quality,which is of great significance.This paper chooses four typical plant configuration plots and one control plot,taking the tidal green belt as the research object,through the collection of the speed change data of cars on the Xi’an ring expressway.This paper uses the Excel and SPSS25 to analyze the change rule of PM_2.5 concentration in four seasons of each plot as well as the effects of meteorological factors and plant community structure characteristics on PM_2.5concentration by monitoring the real-time data of PM_2.5 and meteorological factors.It optimizes the plant configuration program of green belt around the city based on the effects of green belt on PM_2.5reduction.Next is to use ENVI-met to simulate the optimized program and the current program in order to verify the PM_2.5reduction effect of the optimized program as well as summarize and practice the main design points of green belt plant configuration of Xi’an ring expressway.The main research results are as follows:（1）The change rule of PM_2.5 concentration.In the morning,the concentration of PM_2.5is higher than that in the afternoon.The peak value of a day is in the rush hour,while the valley value is in the afternoon.The change of PM_2.5 concentration of a day in spring,autumn and winter forms an"L"shape with many groups of peaks and valleys values of PM_2.5 concentration in summer.The concentration of PM_2.5 in winter is significantly higher than that in the other three seasons.（2）The relationship between meteorological factors and PM_2.5concentration.The PM_2.5concentration is negatively correlated with wind speed and temperature,while is positively correlated with relative humidity in the season of Spring,Autumn and Winter.There is not so much relationship between summer and meteorological factors.（3）Plant consfiguration design.The analysis of field measurement and simulation show that in order to improve the ability of introducing,retaining and reducing PM_2.5in the green belt around the city,how to increase the proportion of evergreen tree species,select tree species with good PM_2.5 retention ability as well as pay attention to the construction plant spatial level are the key methods.This paper summarizes the design principles and key points of green belt around Xi’an ring expressway with practice.This paper can guide the configuration design of the green belt plant around Xi’an ring expressway,which is of practical significance to improve the air quality of the green belt based on the effect of plants on the PM_2.5 reduction.