Plant Configuration And Dust Retention Effect Of Road Green Space In Nanchang City

Atmospheric particulate matter is the main cause of many problems,such as climate,environment,health and etc.Its large presence has seriously affected the ecological environment and human health.With the rapid development of urban motor vehicle,particulate matter pollution such as motor vehicle exhaust and road dust in the road space have become the primary factors for the deterioration of urban atmospheric environment.Road green space,as an important part of the urban green space system,it not only has the function of beautifying the urban environment and enriching the urban landscape,but also self-purification ability,which is really important in reducing particulate air pollutants and improving the environmental quality of urban roads.Based on the field survey about road green space in Nanchang City,this paper analyzes the plant configuration characteristics of three types of greenbelts,sidewalk greenbelt,vehicle greenbelt and Roadside green space;By measuring the grain size composition of dust retention and folia dust from the common road greening trees and different plant configuration communities,analyzing inter-species differences and dynamic changes of particulate matter retained by plants,and differences in adsorption capacity of particulate matter;combined with Spearman rank correlation coefficient analysis and scanning electron microscopy Observing method,and analyzing the influencing factors of vegetation dust retention ability,the main conclusions are as follows:（1）A total of 164 green roads in the first ring line of Nanchang City were selected for investigation.It was found that the road greening sections are mainly one-plate two-belt,two-plate three-belt,three-plate four-belt and four-plate five-belt.Road greening plants have the highest frequency of application of Cinnamomum camphora（L.）Presl.,and the application frequency of Osmanthus sp.,Koelreuteria paniculata,Platanus acerifolia Willd.,Ginkgo biloba L.,Rhododendron simsii Planch.,Pittosporum tobira,Photinia×fraseri Dress,Loropetalum chinense var.rubrum,Camellia japonica L.,and Lagerstroemia indica L.are quite high.In the road green space,the form of sidewalk greenbelt is simplex,most are single-row formed trees;the vehicle greenbelt and the roadside green space are various in forms,paying attention to the matching of the shrubs,the circulation and combined planting of the viewing,foliage and ornamental plants make the road with a different visual aesthetic,and it is rewarded all year round.（2）By measuring the dust retention of commonly used green plants Rhododendron simsii Planch.,Photinia×fraseri Dress,Loropetalum chinense var.rubrum,Camellia japonica L.,Osmanthus sp.,Magnolia grandiflora L.,Cinnamomum camphora（L.）Presl.,and Elaeocarpus decipiens Hemsl.,it is found that the different plants have different ability to retain atmospheric particulate matter,and the amount of dust per unit leaf area is basically Rhododendron simsii Planch.>Photinia×fraseri Dress>Loropetalum chinense var.rubrum>Camellia japonica L.>Osmanthus sp.>Magnolia grandiflora L.>Cinnamomum camphora（L.）Presl.>Elaeocarpus decipiens Hemsl..The amount of dust in the leaf area is affected by the structure of the gully,bulge,stomata,villi and viscous material,the higher the roughness,the more favorable for the retention of particulate matter.The waxy layer structure,growth morphological characteristics,planting form and intensity of the leaves are also important factors in the dust retention.（3）Among the green spaces with different greening configurations,the community structure,the number of species,the planting methods and the quantity will affect the dust retention capacity.Through the measurement of the total dust retention of arbor-type,shrub type and Arbor and shrub types,the dust retention capacity of the tree was basically as follows:Arbor and shrub-types>shrub-type>arbor-type.The application of Arbor and shrub types on the road can improve the adsorption capacity of the particles;also facilitate the timely diffusion of pollutants.The arbor-type community affects the spread of pollutants due to the high canopy,and the total amount of dust retention is low.Species diversity has a positive effect on the dust-retaining of plant communities.When the number of species is large and the community mix and planting space are reasonable,the green space can provide greater dust-saving benefits.（4）Among the commonly used green plants in Nanchang,the cumulative frequency distribution of leaf dust particles of Elaeocarpus decipiens Hemsl.,Photinia×fraseri Dress,Loropetalum chinense var.rubrum,and Camellia japonica L.shows a single peak.Rhododendron simsii Planch.,Osmanthus sp.and Cinnamomum camphora（L.） Presl,are double-peak.Magnolia grandiflora L,are multi-peak.The particle size of plant leaf surface dust and road dust is mainly 10～100μm,followed by 2.5～10μm and 100～2000μm,and 0.02～2.5μm minimum.The ability of different plant leaves to retain particle size is quite different.Cinnamomum camphora（L.） Presl.,Osmanthus sp.,Elaeocarpus decipiens Hemsl.and Loropetalum chinense var.rubrum are the strongest in retaining PM₁₀ and PM_2.5.Photinia×fraseri Dress,Camellia japonica L,and Rhododendron simsii Planch have the strongest ability to retain TSP.The content of 10～100μm and 100～2000μm in road dust is 90.87%,while the particle size of leaf surface dust is smaller,containing more PM_2.5 and PM₁₀,indicating the purification effect of plants on the atmospheric environment.