关键词: 洗脱称量粒度分析法(EWPA), 大气颗粒物, PM_2.5, 树木叶片, 叶片结构性滞尘

Abstract: [Objective] The difference between real and plastic leaves in the retention of fine particles (PM_2.5),inhalable particles (PM₁₀),total suspended particulates(TSP) and other atmospheric particulates was studied to distinguish ‘dust-retention related to leaf structures(DRLS)’ and ‘dust-retention unrelated to leaf structures(DULS)’. This study provides a scientific basis to explore the contribution of trees to alleviating the pollution of atmospheric particulates and to optimize the configuration of different tree species.[Method] Six typical afforestation tree species of Beijing were selected for the study. Dynamic foliage absorption was continuously detected for the four quarters of a year, baseline samples and leaf samples with accumulated particles were collected in a ten-day rainless period. Besides, the smooth plastic leaves(made of PTFE, friction coefficient is 0.04)were used as control to simulate the DULS and elution-weighing-particle size-analysis (EWPA) was used to measure the amount of dust adhesion per unit area of each tree species, DULS and the retaining amount of different sizes of particles within the 10 days.[Result] 1) Platycladus orientalis had the strongest dust detention. The total retention amounts per unit leaf area of P. orientalis was (124.76±19.27) μg·cm^-2, 2.24 times of the lowest retention by Acer truncatum with (16.92±2.61) μg·cm^-2. 2) DULS accounted for only 19.65%-42.29% of total dust-retention, while DRLS accounted for 57.71%-80.35%. 3) P. orientalis had the strongest ability of DRLS, comprising 80.35% of the total stagnation. While A. truncatum had the weakest retention ability and its DRLS accounted for 57.71% of the total dust. DRLS of conifer species made up 77.42% of the total dust-retention on average while broadleaf species accounted for 63.96%. 4) Among the different size classes of particles retained by conifer species, PM_2.5 accounted for 13.83%±0.19% of total and PM₁₀ accounted for 56.82%±1.07%. Among various sizes of particles retained by broadleaf species, PM_2.5 accounted for 8.09%±0.94% of total dust and PM₁₀ accounted for 70.29%±3.56%.[Conclusion] Tree leaves play a specific and significant role in retaining atmospheric particulates. The ability of dust adhesion of conifer species tested was significantly higher than that of the broadleaf species. The conifers was strong in retaining small particles in the atmosphere, while the broadleaf trees was better in retaining big particles. The study proved that afforestation species makes great contribution to pollution alleviation of atmospheric particulates and provides a scientific basis for a reasonable choice of tree species to mitigate atmospheric particle pollution.

Key words: elution-weighing-particle size-analysis (EWPA), atmospheric particulate matter, PM_2.5, tree leaves, dust-retention related to leaf structures