The Retention Capability Of PM_2.5 And Its Explanation By Leaf Surface Micro-structure And Configuration Of Urban Green Plant

Plant leaves plays significant role for improving the quality of urban environment by acting as biological filters to capture atmospheric particulate matter. In this paper, the captured amount of TSP(total suspended particles) and PM2.5(particles with diameter ≤ 2.5 μm)per unit leaf area for 20 plants commonly used for urban greening in Beijing were measured by water washing methods, and the micro-structure of leaf surface of these plants were investigated by scanning electron microscopy so we can fine the differences between leaves with different dust retention amount. Urban green land plays an important role in controlling particulate matter(PM) pollution, thus improving urban air quality. However, choice the suitable plant species and structure is the basis for controlling PM pollution through plants. In this paper, we measured the captured amount of TSP and PM2.5 per unit leaf area for common plants in 16 sampling plots which with different plant structures. The total PM retention amount of the sampling plots and the PM retention of per unit green land area were calculated as well. The main conclusion is as following:1) There is significant difference in the captured amount of TSP and PM2.5 per unit leaf area among the plant species, with the variation ranges of 0.40~3.44 g/m2(TSP)and 0.04~0.39 g/m2(PM2.5), respectively. The captured amounts of TSP and PM2.5 by shrub and vine plants are higher than those of trees.2) The difference in groove width on leaf surface may be the main reason for explaining the difference of TSP and PM2.5 retention among plant species. The leaves with groove width of about 5 μm have a larger captured amount of PM2.5, too broad and too narrow grooves are not beneficial to trap particulate matter. The captured amount of PM2.5 on leaf surface increases with increasing groove depth. The leaves with more stoma have larger particle retention.3) Sampling plots with main plants as trees like Pinus tabulaeformis, Paulownia Sieb, and Sabina chinensis have higher TSP and PM2.5 retention amounts than those with shrubs like Euonymus japonicus, Ligustrum quihoui,and Hibiscus syriacus. The TSP and PM2.5 retention ability is related to not only dust retention amount per unit leaf area but also total leaf area.