Abstract:Six greening tree species (Pinus bungeana, Pinus tabulaeformis, Salix babylonica, Acermono, Ginkgo biloba, Populus spp.) from the Western mountains of Beijing were selected as research materials. The PM2.5 adsorption capacity of their leaves was measured in summer and autumn through the use of an aerosol generator. The surface micro-morphological characteristics of the collected leaves were also analyzed by atomic force microscopy (AFM) to determine the leaf surface roughness parameters. The relationship between the PM2.5 adsorption capacity and the micro-morphological characteristics of the collected leaves were investigated. The results showed that the average annual absorption capacity of PM2.5 per unit leaf area of coniferous species (1.70 μg/cm2) was larger than that of broad-leaved trees (0.48 μg/cm2). The order of the average annual absorption capacities of PM2.5 per unit leaf area for these trees was P. bungeana (1.71 μg/cm2), P. tabulaeformis (1.67 μg/cm2), Salix babylonica (0.54 μg/cm2), Acermono (0.51 μg/cm2), Ginkgo biloba (0.47 μg/cm2), and Populus spp. (0.39 μg/cm2). The seasonal adsorption capacities per unit leaf area of PM2.5 for coniferous trees followed the order winter (2.86 μg/cm2), spring (1.39 μg/cm2), autumn (1.13 μg/cm2), and summer (0.96 μg/cm2); and autumn (0.56 μg/cm2), summer (0.55 μg/cm2), and spring (0.015 μg/cm2) for broad-leaved trees. There was a significant positive linear correlation between leaf roughness and PM2.5 adsorption per unit area (P < 0.01), and the adsorption capacities of PM2.5 for coniferous species were significantly affected by leaf surface roughness. The atmospheric environment of Beijing, as an international metropolis, tends to be seriously polluted by PM2.5. According to the seasonal characteristics of PM2.5 adsorption and the relationship between adsorption capacity of PM2.5 and the micro-morphological characteristics for collected leaves from these greening trees, a suitable allocation of coniferous and broad-leaf trees with their different adsorption capacities of PM2.5 could applied to urban green space system and provide basic data for the scientific screening of city greening tree species.
