【目的】研究不同绿化树种在单位叶面积、单叶、单株和单位绿地面积4级层次上对空气中PM2.5等颗粒物的滞留量，为优化城市绿化植物配置、降低空气中 PM2.5等颗粒物污染危害提供科学依据。【方法】以北京市23种常见绿化植物为研究对象，经水洗、不同孔径滤膜过滤后用万分之一天平称量不同孔径滤膜上滞留的颗粒物质量，用扫描仪测出叶单面面积，计算出单位叶面积 PM2.5等颗粒物(总颗粒物 PM 及其 PM2.5、PM ＞2.5的粒径组成)滞留量。用单叶面积、叶面积指数计算单叶、单株和单位绿化面积上叶片 PM2.5等颗粒物滞留量。采用多重比较分析不同植物 PM2.5等颗粒物滞留量的差异。【结果】单位叶面积的 PM，PM2.5，PM ＞2.5滞留量在植物种间差异显著，最大差别分别可达8.6，9.8，10.5倍。各植物种的单叶、单株和单位绿地面积的 PM，PM2.5，PM ＞2.5滞留量亦表现出显著差异。在单叶层次，对 PM，PM2.5，PM ＞2.5的滞留量差别可分别达到239，198，285倍；在单株层次，可达3600，4100，3600倍；在单位绿地面积层次，可达18.3，20.5，18.1倍。不同生活型植物的单位叶面积、单叶、单株和单位绿地面积的 PM，PM2.5和 PM ＞2.5滞留量总体趋势表现为乔木＞藤本＞灌木。对不同叶习性而言，单位叶面积的 PM，PM2.5和 PM ＞2.5滞留量为常绿植物＞落叶植物，而在单叶、单株和单位绿地面积层次上则为落叶植物＞常绿植物。在单位绿地面积层次上，对 PM2.5等颗粒物的滞留量较高的树种有二球悬铃木、垂柳、元宝枫、榆树等，中等的有油松、雪松、大叶黄杨等，较弱的有日本小檗、黄杨、小叶女贞等。【结论】不同植物 PM2.5等颗粒物滞留量在单位叶面积、单叶、单株和单位绿地面积4级层次上均表现出显著差异。由于植物滞留 PM2.5等颗粒物的数量取决于单位叶面积 PM2.5等颗粒物滞留量及其叶面积指数，因此在选择高滞留 PM2.5等颗粒物的树种时需同时考虑这2个因素，尤其是将不同生活型和具不同叶习性的植物合理混交配置，从而提高叶面积指数和滞留 PM2.5等颗粒物能力，这是增强城市森林降低空气中 PM2.5等颗粒物污染的有效途径。%[Objective]Selection of plant species with strong ability to retain pollutants of particulate matters ( PM) and its size fractions and suitable for local conditions should be chosen to ensure greening policy be designed to reduce PM pollution. In this study,the amounts of PM and its size fractions ( PM2. 5 ,PM >2. 5 ) captured by leaves of twenty-three plant species on the basis of per unit leaf area,per leaf,per plant and per unit green area in the region of Beijing were investigated to find out the appropriate species. [Methods]The amounts of PM ( PM2. 5 ,PM >2. 5 ) captured by leaves of twenty-three plant species were examined in this study. The collected leaf samples were washed using a brush with ultrapure water ( ELGA,Buckinghamshire,UK) and then filtered through two types of membranes ( w1 ) with pore sizes of 2. 5 and 0. 1 μm,respectively. Then the membrane with PM (w2) was weighed using balance with an accuracy of 0. 1 mg (SI-114,Denver Instrument,USA) after dried at 40 ℃ for 24 h. The total hemi-surface leaf area (S) was measured using Image J software (Version 1. 46; National Institutes of Health,Bethesda,MD,USA) after scanning (HP Scanjet 3570c,Japan). The PM (PM2.5 and PM >2.5) retention amounts were calculated as (w2 -w1)/S. The PM (PM2.5 and PM >2. 5 ) retention amounts per leaf,per tree and per unit green area were calculated based on the PM ( PM2. 5 and PM >2. 5 ) retention amount per unit leaf area,single leaf area,and leaf area index ( LAI) . Data were subjected to ANOVA with multiple comparisons by using SPSS 19 (IBM,USA),with a level of significance at P < 0. 05.[Results]Leaf PM, PM2.5 and PM >2.5 per unit leaf area differed among species,by 8. 6,9. 8,and 10. 5 folds,respectively. Leaf PM,PM2.5 and PM >2. 5 on the basis of per leaf,per plant and per unit green area also showed significant differences among species. The maximum difference reached up to 239,198,and 285 (per leaf);3 600,4 100 and 3 600 (per plant);18. 3,20. 5 and 18. 1 (per unit green area) folds. In general,the PM,PM2.5 and PM >2.5retention amounts of different life form was in the order of tree > liana > shrub. For the species with different leaf habit,the evergreen species had a higher PM,PM2.5 and PM >2.5 retention amount per unit leaf area than that of deciduous species. However,the PM,PM2.5 and PM >2.5 retention amounts on the basis of per leaf,per plant and per unit green area were on the contrary. Platanus acerifolia, Salix babylonica,Acer truncatum,and Ulmus pumila were efficient species in capturing PM and its size fractions. Pinus tabulaeformis ,Cedrus deodara and Buxus megistophylla had a medium ability to accumulate PM and its size fractions. Less efficient species were Berberis thunbergii,Buxus sinica,Ligustrum quihoui.[Conclusions]The amounts of PM and its size fractions captured by leaves on the basis of per unit leaf area,per leaf,per plant and per unit green area all showed significant differences among species. The ranking presented in terms of capturing PM and its size fractions can be used to select species for atmospheric PM pollution removal in the region of Beijing. Since the quantity of PM and its size fractions captured by leaves depends on the PM and its size fractions retention amount per unit leaf area and leaf area index, efficient plant species and plant configuration designs considering different life form and leaf habit can be used to decrease human exposure to the pollutants.
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