行道树冠形对街谷内流场及 PM10 浓度场的影响.

Urban street greening is usually used as the main measure to mitigate vehicle emissions and improve air quality. However, recent studies have shown that the planting of trees in street canyons may easily lead to the obstruction of internal air flow and the accumulation of pollutants. In order to further reveal the influence of tree crown characteristics on the distribution of the particulate pollutants in street canyon, the urban microclimate numerical simulation software ENVI-met was used to simulate and analyze the influence of the four tree crown profiles on the flow field and PM 10 concentration distribution in street canyon under three wind directions of parallel, oblique and vertical inlet winds downward. The results showed that there was a blocking effect on the air flow in the street canyon of four street tree crowns regardless of the inlet wind downward. The leaf area density(LAD) distribution of tree canopy was an important factor influencing the blocking effect of tree crown. In general, the canopy height with the highest LAD had the most significant decrease on wind speed. There was a certain difference in the influence of tree crown on the PM 10 dispersion of pedestrian height on both sides under different inlet winds. The order of PM 10 accumulation under parallel and oblique wind direction was: conical crown, spherical crown, oval crown, obovate crown, while under vertical wind direction was: obovate crown, spherical crown, oval crown, conical crown. In the future, in the process of tree planting and management in street canyons, it should be combined with the wind direction to select appropriate trees or prune tree crowns to reduce the risk of pollution exposure for pedestrians. The results of the study provide a reference for the planting and management of street trees. [ABSTRACT FROM AUTHOR]