Study On The Regulation Of Common Tree Species And Plant Communities On Atmospheric Particle In Urban Areas Of Chongqing

In this study,the common tree species and plant communities were studied in urban area of Chongqing.Through the sampling of plant leaves and the monitoring of the concentration of atmospheric particles inside and outside the common plant community,the quantitative measurement of atmospheric particles was carried out by using aerosol re-generator and Dustmate dust(respirable particulate matter)detector.The effects of common tree species on the subduction of atmospheric particles and the subtracting effect of common plant communities on atmospheric particles were studied in urban area of Chongqing.The main findings are as follows:(1)Through the collection of 82 species of tree leaves in urban area of Chongqing,it was found that the particulate matter adsorbed on the leaves of the tree species was mainly composed of particulate matter with particle size greater than 10?m,the proportion of PM10 to TSP adsorbed on various tree species was generally lower than 30%,and the proportion of PM2.5 is much lower than that of PM10 and TSP,accounting for less than 5%.The capacity of TSP adsorbed on unit area of different tree species is consistent with the capacity of adsorbed PM10,that of PM2.5 is inconsistent.The ability of absorbing TSP and PM10 of Platanus acerifolia and Viburnum dilatatum was the strongest among 61 tree species sampled in city park,while Bauhinia purpurea weakest.Unit leaf area adsorption capacity of PM10 and TSP of Mallotus barbatus and Lindera glauca are relatively strong among 21 tree species,adsorption capacity of TSP and PM10 of Bischofia polycarpa and Michelia alba is weak.(2)The adsorption capacity of TSP and PM10 in the leaves of trees with four growth forms(evergreen shrubs,deciduous trees and deciduous shrubs)was different.The relationship sorted for deciduous shrubs> deciduous trees and evergreen shrubs> evergreen trees,the average adsorption of PM10 in the four growth forms species in summer is between 20% and 30%,while the average adsorption of PM2.5 accounts for less than 5% of TSP;The adsorption capacity of TSP,PM10 and PM2.5 of coniferous tree species was significantly higher than that of broad-leaved species per unit leaf area.(3)The adsorption capacity of atmospheric particles in the trees with different leaf surface structure was different.The adsorption capacity of TSP,PM10 and PM2.5 species in the broad-leaved tree species with more villi or more trenches were higher than those of the tree species with different leaf surface structure.The adsorption capacity of atmospheric particles of Pinus massoniana,Cedrus deodara and other coniferous tree species with pine-needle leaves is relatively strong which was significantly higher in PM2.5 than other tree species.(4)Through the study of six tree species in three seasons,it was finded out that the adsorption capacity of tree species in different seasons was different: The adsorption capacity of TSP was the highest in winter,and there was no significant difference between spring and summer.The adsorpsion of PM10 and PM2.5 in tree leaves are the highest in winter,followed by spring,the lowest in summer.In addition,the proportion of PM10 adsorbed on the leaves of the tree species was significantly different in different seasons,and the proportion of PM10 was the lowest in summer.(5)Through the study of six tree species in three different habitats,it was finded that there were significant differences in the adsorption of atmospheric particulate between tree species in different habitats: the retaining amount of TSP and PM10 in the unit leaf area of the tree species were positively correlated with the degree of ambient air pollution,and the retaining amount of TSP and PM10 in the leaves per unit area was Road greenbelt> urban park> country park,but there was no significant regularity of the same kind of tree species in the adsorption of PM2.5 in different habitats.In addition,there was a significant difference in the proportion of PM10 in the leaves of different species in different habitats.(6)There were some differences in the ability of different plant communities to control atmospheric particle: the rate of reduction of TSP,PM10 and PM2.5 was higher in natural plant communities than that of artificial plant communities,and the reduction rate of TSP was higher than that of PM10 and PM2.5.The reduction rate of TSP,PM10 and PM2.5 in pollen forest and coniferous and broad-leaved mixed forest was higher than that other plant communities,and the rate of reduction of atmospheric particle in sparse grassland and grassland or lawn was the lowes.The size of canopy closure is closely related to the ability of plant communities to regulate atmospheric particle,the plant communities with the canopy density of more than 0.6 had higher abundance of atmospheric particle than the plant communities with canopy density of 0.4 to 0.6 and canopy density less than 0.2.