建筑和绿化对街谷空气污染物扩散的影响

Influence of Buildings and Tree Planting on Air Pollutants Diffusion in Street Canyon

在静风条件下,对上海松江区典型的对称和不对称街谷内CO2和CO的浓度和PM1.0进行了连续实测.引入街谷约束物(建筑或绿化)高度与约束物距机动车道中心距离之比,即高远比(H/D),表征该约束物对街谷空气污染物扩散的阻碍作用.研究结果表明:背景风速低于0.5m/s时,绿化和建筑对污染物扩散稀释的影响同样重要;污染物浓度的扩散衰减特性与街谷高远比和污染物种类有关;高远比越大,越不利于空气污染物扩散;自街谷机动车道中心到人行道,PM1.0衰减程度大于气态污染物.

CO2 and CO concentrations and PM1.0 are continuously monitored in typical symmetry and asymmetry street canyons in Songjiang, Shanghai under static ambient conditions, respectively. Ratio of the height of street canyon restrictive objects （buildings or tree planting） to the distance of them apart from the center of motor vehicles driveways, H/D, is introduced to denote the block effect on air pollutants diffusion. The research result indicates that when the ambient wind speed is less than 0.5 m/s, tree planting is as important as buildings on the effect of blocking air pollutants diffusion. And diffusion and reduction characteristics of the concentrations depend on the ratios of street canyon and pollutant species. The higher the H/D, the stronger the disadvantage of diffusion is. The gradient for PM1. 0reduction is greater than the cases of gaseous pollutants from the center of motor vehicles driveways to side pavement.