中文摘要：

选择北京典型城市带状绿地——西四环旁侧4种不同垂直结构及5种不同郁闭度的带状绿地为研究对象,采用小尺度定量测定的方法,研究城市带状绿地结构类型与空气负离子浓度、空气含菌量间的关系。每天8：00—18：00,每2 h分别对带状绿地和对照处的空气负离子、空气含菌量进行同步测定,连续测定7 d。结果表明：（1）当绿地垂直结构为乔-草、乔-灌-草时,绿地的空气负离子效应显著;当绿地垂直结构为乔-草时,绿地的抑菌作用显著（绿地宽度42 m,p〈0.05）。（2）当郁闭度超过0.44时,绿地的空气负离子效应显著（p〈0.05）,绿地的抑菌作用明显;当郁闭度超过0.67时,抑菌作用明显且趋于稳定（绿地宽度42 m）。

英文摘要：

Taking four green belts with different internal constitution and five green belts with different canopy density along the west fourth ring road of Beijing as test objects,and using small-scale quantitative measurement method,this paper studied the effects of the different structure of urban green belts on the air quality in Beijing to provide scientific basis for the construction of urban green belts.The air anion concentration and bacteria rate were measured every two hours from 8： 00 to 18： 00 every day for continuous seven days.The results showed：（1） The green belts with internal constitution of tree-shrub-herbage and tree-herbage had a significant effect on the increase of air anion concentration and had a significant effect on the decrease of bacteria rate with internal constitution of tree-herbage（width 42 m,p0.05）.（2）When the canopy density reached 0.44,green belts had a significant effect on the increase of air anion concentration and an obvious effect on the decrease of bacteria rate（p0.05）,and when the canopy density exceeded 0.67,the effect was obvious and stable（width 42 m）.