上海市城市林荫道空间结构对NOx和SO2空间分布特征的影响

为减少城市林荫道中交通污染对道路行人的危害，并为行道树选择和养护管理提供技术参数和理论依据，研究了不同树种、不同绿荫覆盖率下的林荫道中ρ（NO_x）和ρ（SO₂）垂直空间分布及其四季变化特征，找出城市林荫道结构与环境效应相关关系.研究表明:①香樟（Cinnamomum camphora）和悬铃木（Platanus acerifolia）林荫道中ρ（NO_x）范围为0.08~0.18 mg/m3，空气质量为轻微污染；ρ（SO₂）范围为0.02~0.04 mg/m3，空气质量为优.②悬铃木行道树对NO_x的消减效果较香樟好，香樟对SO₂的消减效果较悬铃木好.香樟林荫道的绿荫覆盖率> 90%时对NO_x的消减效果最好，在50%~70%时对SO₂的消减效果最好；悬铃木林荫道的绿荫覆盖率在50%~70%时对NO_x的消减效果最好，在>70%~90%时对SO₂的消减效果最好.③香樟和悬铃木林荫道在春、夏两季空气质量优于秋、冬两季.④香樟林荫道中ρ（NO_x）随高度增加有增大趋势，而悬铃木林荫道中ρ（NO_x）随高度增加有减小趋势；在绿荫覆盖率>70%的香樟林荫道中ρ（SO₂）随高度增加有增大趋势，而在悬铃木和香樟绿荫覆盖率 < 70%的林荫道中ρ（SO₂）在4 m处较小.⑤行道树的树高、枝下高、冠幅、叶面积指数和郁闭度是影响城市林荫道环境效应发挥的重要结构参数.研究显示，林荫道的空间结构对气态污染物NO_x和SO₂的空间分布有明显影响，合理选择树种和修剪模式均有利于提升城市空气环境质量. 

Influence of Boulevard Spatial Structures on Distribution Characteristics of NOx and SO2 in Urban Shanghai City

To reduce the harm of air pollution resulted from traffic in urban boulevards to pedestrians, as well as to provide technical parameters and theoretical basis for the selection of road trees and maintenance management, the vertical distribution and seasonal changes of NO_x and SO₂ in boulevards with different tree species and canopy coverage in Shanghai City were studied, and the correlation between the structure of urban boulevards and environmental effect was identified. The research shows that:(1) ρ(NO_x) in boulevards of Cinnamomum camphora and Platanus acerifolia ranges from 0.08-0.18 mg/m3, leading to a lightly-polluted air. ρ(SO₂) ranges from 0.02-0.04 mg/m3, leading to a Class Ⅰ air quality grade. (2) The effect of Platanus acerifolia on NO_x reduction is better than that of Cinnamomum camphora, but Cinnamomum camphora has a better effect in reducing SO₂. When the canopy coverage of boulevards of Cinnamomum camphora is higher than 90%, the optimal effect of NO_x reduction can be achieved. When it ranges from 50%-70%, its effect on SO₂ reduction is optimal. As to boulevards of Platanus acerifolia, its reduction on NO_x and SO₂ are largest when canopy coverage is 50%-70% and 70%-90%, respectively. (3) The air qualities of both boulevards of Cinnamomum camphora and Platanus acerifolia in the spring and summer are better than that in autumn and winter. (4) ρ(NO_x) in boulevards of Cinnamomum camphora increases with heights above ground, whereas ρ(SO₂) in boulevards of Platanus acerifolia decreases with the tree height; ρ(SO₂) increases with heights in boulevards of Cinnamomum camphora with more than 70% canopy coverage, while ρ(SO₂) in boulevards of Platanus acerifolia and Cinnamomum camphora with less than 70% canopy coverage is relatively low at the height of 4 m. (5) Tree height, branching height, crown width, leaf area index and canopy density are significant structural parameters affecting performance of the urban boulevards. This research shows that spatial structures of boulevards exert an obvious effect on spatial distribution of gaseous pollutants (NO_x and SO₂), and proper tree selection and trimming modes could further improve air quality.