| With the rapid development of urbanization in the Yangtze River Delta,automobile exhaust has become the main source of urban fine particulate matter（PM）pollution.Traffic green belt has been proved to be able to reduce atmospheric particulate matter concentration.It is particularly important to study the optimal urban green space allocation mode for the purpose of blocking effect of atmospheric particles.In order to analyze the horizontal and vertical distribution characteristics of PM2.5concentration and its seasonal variation,this paper carried out continuous monitoring of atmospheric particulate matter concentration in typical green belt structure.At the same time,combined with meteorological data,the impact of meteorological factors on the effect of atmospheric particulate matter retention in green space was further analyzed,in order to provide theoretical and data support for optimizing plant configuration of urban green space and improving the living environment oriented urban and rural green space planning and design,and the results were as follows:（1）The diurnal variation of PM2.5 concentration inside and outside the forest belt showed a"three peak"type,namely 4:00-10:00,16:00-22:00,22:00-4:00.The overall trend of horizontal gradient and vertical gradient was the same,with the increase of the width and height of the forest belt,the emergence time of the peak and valley concentration slightly deviated,but the difference was not significant.The concentration of PM2.5 was higher in night than in day,and higher in autumn and winter than in spring and summer.（2）When the width reached 20m,the effect of reducing the concentration of PM2.5 in the air was the best,with a reduction rate of 35%-45%.In autumn,the particle reduction effect of the green belt starts to show up at 10m.he reduction rate in winter has the best reduction effect on the PM2.5concentration at the width of 10m.The particulate matter in the air was reduced by about 20%.As the width increases,the reduction effect was not much different,and the reduction rate remained at 20%.Therefore,in view of ecological requirements and maximization of land use,the minimum reasonable width of the road green belt for the main traffic arteries in the city should be no less than 10m,and the20m green belt width has the best effect on reducing particulate pollution.（3）In terms of height,the PM2.5 concentration from high to low was 4.5m in the middle of canopy,0m near the ground,1.5m in trunk and 3M in trunk.The PM2.5 concentration in the air at 0m was reduced by about 12%to 17%,and the PM2.5 concentration at 1.5m was reduced by about 30%,and the PM2.5 concentration at 3m was reduced by about 35%to 40%.（4）Study the correlation between PM2.5concentration and meteorological factors and found that PM2.5 concentration was negatively correlated with temperature and positively correlated with relative humidity. |
