Particle-retaining characteristics of six tree species and their relations with micro-configurations of leaf epidermis

To help reduce the particulate pollution, we measured the amounts of dust retention of six common tree species in Beijing Forestry University, and studied the characteristics of particles on leaf surface.We also studied the relationship between dust retention ability and microstructure of leaf surface. In this way, it is helpful for the selection of tree species for reducing particulate pollution and optimization of urban greening and beautification. Quantitative determination characteristics of particles retained by foliage of six common greening tree species in Beijing was measured by Mastersizer 2000 laser particle size analyzer. And the results showed that particulate retention capability of foliage was in the order of Pinus tabuliformis>Lonicera maackii>Buxus megistophylla>Syringa reticulate>Fraxinus pennsylvanica>Acer truncatum; However, the particulates retained by Pinus tabuliformis was 44 times of Acer truncatum. It was showed that the size of foliar particulates mainly concentrated in 10-50μm. And the order of average particle size (D50)retention ability of plant species was as follows:Acer truncatum < Syringa reticulata < Buxus megistophylla < Fraxinus pennsylvanica < Lonicera maackii < Pinus tabuliformis. Besides, the order of specific surface area of six tree species was Acer truncatum>Syringa reticulate>Buxus megistophylla>Fraxinus pennsylvanica>Pinus tabuliformis>Lonicera maackii. The relationship between dust retention and leaf surface structure was examined using scanning electron microscope (SEM) by analyzing surface microconfigurations of leaves, and the structure and density of leaf stomata. Results showed that the particleretaining capacity increased with the increase of stomatal size; however, no relationship was observed between the number of stomatal and the opening of stomatal. The effects of microconfigurations of leaf epidermis on the particleretaining capacities were showed in the order of secretion>trench>groove>wrinkle>strip raise. It is concluded that the dust retention ability of tree species in residential areas should be taken into consideration for selecting tree species in order to minimize particulate matter pollution and optimize the ecological service of residential areas.