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4树种叶片表面颗粒物洗脱特征与其微观形态的关系
房瑶瑶1, 王 兵1, 牛 香1
中国林业科学研究院 森林生态环境与保护研究所,国家林业局森林生态环境重点实验室
摘要:
【目的】深入了解不同树种叶片的颗粒物(Particulate Matter,PM)滞纳能力在降水事件中的恢复特征。【方法】对颗粒物滞纳量达到饱和状态的核桃、刺槐、加拿大杨和银杏4个树种的叶片进行模拟降雨处理,降雨量设置为0,0.66,1.32,1.98和2.64 mm,测定并计算单位面积叶片粒径2.0~8.0 μm的颗粒物(PM2.0~8.0)和粒径小于2.0 μm的颗粒物(PM2.0)的洗脱率,并观察叶片的微观结构,分析其对颗粒物洗脱作用的影响。【结果】单位面积叶片颗粒物饱和滞纳量最大的是核桃,其对PM2.0~8.0、PM2.0的饱和滞纳量分别为(37.05±2.54)和(5.30±0.74) μg/cm2,其次为刺槐(对PM2.0~8.0和PM2.0的饱和滞纳量分别为(8.17±1.15)和(2.47±0.14) μg/cm2);加拿大杨和银杏叶片的饱和滞纳量较低。洗脱率测算结果显示,银杏叶片表面2个粒径范围的颗粒物均最易洗脱,在降雨量为2.64 mm时,PM2.0~8.0、PM2.0的洗脱率分别为99.36%和99.44%;刺槐叶片表面PM2.0~8.0比PM2.0更易洗脱,在降雨量为2.64 mm时,PM2.0~8.0、PM2.0的洗脱率分别为78.79%和52.02%;核桃叶片表面PM2.0比PM2.0~8.0更易洗脱,在降雨量为2.64 mm时,PM2.0~8.0、PM2.0的洗脱率分别为83.13%和95.84%;加拿大杨叶片表面2个粒径范围颗粒物的洗脱率相近,在降雨量为2.64 mm时,PM2.0~8.0、PM2.0的洗脱率分别为87.36%和80.29%。扫描电镜图显示:核桃叶片表面呈现不规则平滑褶皱,气孔较小,数量较多,蜡质呈无定形态;刺槐叶片表皮毛分布丰富,表皮细胞呈顶部平缓的凸起状,且表面分布形态规律的蜡质晶体,气孔十分稀疏;加拿大杨叶片表皮细胞无明显凸起,蜡质层平滑,气孔较大,数量与核桃相比较少;银杏叶表皮细胞具有明显的穹状凸起,整个叶片覆盖厚且形态规律的蜡质晶体,气孔大而稀疏。【结论】具有规则形态结构的蜡质层(加拿大杨、银杏)和穹状凸起表皮细胞及不具有表皮毛(银杏)的叶片颗粒物饱和滞纳量较低,而洗脱率较高;反之,叶片(核桃,刺槐)的颗粒物饱和滞纳量较高,洗脱率较低。
关键词:  叶片  颗粒物滞纳量  人工降雨  颗粒物洗脱率  叶片表面微观形态
DOI:
分类号:
基金项目:林业公益性行业科研专项(20130430101;2012040101)
Relationship between leaf micro-morphology and particulate matter wash-off characteristics of four tree species
FANG Yaoyao,WANG Bing,NIU Xiang
Abstract:
【Objective】This study aimed to understand the restore characteristics of leaf surface in capturing particulate matter (PM) in rainfall process.【Method】This study selected foliage samples of 4 species with saturation PM capturing capacity to study its response to simulated precipitations (0,0.66,1.32,1.98,and 2.64 mm).Wash-off rates of PM2.0-8.0 (diameter of particulate matter 2.0-8.0 μm) and PM2.0 (diameter of particulate matter less than 2.0 μm) for leaves were calculated and the effects of leaf-surface micro-morphology structure on wash-off of PM2.0-8.0 and PM2.0 were also analyzed.【Result】The saturated amounts of particles captured by per unit leaf area of the four species were different with a decreasing order of Juglans regia ((37.05±2.54) μg/cm2 for PM2.0-8.0 and (5.30±0.74) μg/cm2 for PM2.0)>Robinia pseudoacacia ((8.17±1.15) μg/cm2 for PM2.0-8.0 and (2.47±0.14) μg/cm2 for PM2.0)>Populus canadensis>Ginkgo biloba.With the precipitation of 2.64 mm,wash-off rates of PM2.0-8.0 (99.36%) and PM2.0 (99.44%) of G.biloba were high.Wash-off rate of PM2.0-8.0 (78.79%) was much higher than PM2.0 (52.02%) for R.pseudoacacia,while wash-off rate of PM2.0-8.0 (83.13%) was much lower than PM2.0 (95.84%) for J.regia.For P.canadensis,wash-off rates of PM2.0-8.0(87.36%) and PM2.0 (80.29%) had no significant difference.The Scanning Electron Microscope (SEM) pictures showed that the surface of J.regia foliage had smooth wrinkles irregularly,stomas were small but large in number,and the wax layer was amorphous.R.pseudoacacia foliage surface was richly endowed with trichomes,epidermis cells had flat top covered with organized crystal wax layer,and stomas were in sparse levels.On the foliage surface of P.Canadensis,epidermis cells and wax were smooth,stomas were large in size but smaller in number compared with J.regia.For the G.biloba,epidermis cells were convex and densely covered by wax crystals,and stomas were thin and in large size.【Conclusion】Leaves with convex epidermal cells and without trichome (G.biloba & P.canadensis),covered by regular wax crystals (G.biloba) had low particle capturing capability and high PM wash-off rate.Conversely,the particle capturing capability of foliage (J.regia & R.pseudoacacia) was high,and the wash-off rate was low.
Key words:  foliage  particles captured  simulated precipitation  wash-off rate  micro-morphology structure