基于城市微气候模拟软件的城市道路绿化带对PM2.5消减作用的研究

随着经济的快速发展及机动车保有量的持续增长,车辆造成的道路污染问题日益严重。广州作为中国重要的经济发展城市,交通源排放问题高度集中,机动车排放是城市PM2.5的主要来源之一,开展减缓城市道路污染危害的研究具有重要意义。本研究为调查绿化带对广州城市道路PM2.5的影响,运用实测与城市微气候模拟软件（ENVI-met）模拟结合的研究方法,实测并分析城市道路空间PM2.5的浓度分布及其影响因素,使用实测数据对模拟软件进行验证分析,模拟研究理想道路模型下不同高宽比、风向等因素及绿化带植配类型对PM2.5的消减作用。研究表明：（1）城市道路空间PM2.5浓度分布受污染源、街道高宽比、风速风向、绿化带等综合影响,自然消减情况下,其主要受风速风向和高宽比双因素影响;（2）通常街道高宽比越大,越有利于道路空间PM2.5的扩散;（3）城市道路空间PM2.5自然沉降最小距离为12 m,0-12 m范围内应保持无障碍物的开敞环境,PM2.5消减的关键范围是12-24 m,此范围内可以利用生态手段沉降颗粒物;（4） PM2.5消减率受绿化带和风向的双控制,应根据主导风向选择绿化带植配方式。在主导风平行面和垂直迎风面绿化带对PM2.5有正消减效应,建议植配类型为"乔-乔+灌+草";在主导风垂直背风面绿化带对PM2.5呈负消减效应,植配类型为"乔-灌"绿化带消减率接近于自然消减率,而植配类型为"乔-灌+草"和"乔-乔+灌+草"的绿化带加重了颗粒物在该区域的积聚。

Effect of urban road green belts on PM2.5 reduction based on ENVI-met

With the rapid development of the economy and the continued growth of vehicle ownership, the road pollution problem caused by vehicles is becoming increasingly serious, however, vehicle pollution is one of the main sources of PM2.5 in cities. Guangzhou, as an important economic development city in China, with a high concentration of pollution problems caused by emissions from traffic sources. Study on mitigating the hazards of urban road pollution is of great significance. The objective of this study is to investigate the contribution of green belts to the reduction of road PM2.5 in Guangzhou, which varies according to the intensity of motor vehicle emissions, road orientation, street aspect ratio and green belt planting type. Based on the research object of Guangzhou city roads, using the method of measurement and ENVI-met simulation. Firstly, the PM2.5 concentration distribution in urban road space and its influencing factors are measured and analyzed, secondly, validated the simulation software using measured data, finally simulated the PM2.5 reduction effect of different factors under the ideal road model, as well as simulated the PM2.5 reduction effect of different planting types of green belts. Results showed that:1) the distribution of PM2.5 concentration in urban road space was influenced by pollution sources, street aspect ratio, wind speed and wind direction, and green belt etc. Under natural abatement, it is mainly influenced by the double factors of wind speed and wind direction and height and aspect ratio. 2) Generally, it benefits for spread of PM2.5 in the road space with gradually increasing the street aspect ratio, as the rate of PM2.5 dispersion is increased. 3) The minimum distance of PM2.5 natural settlement in the space of main urban roads in Guangzhou was 12 m, an open and ventilated environment should be maintained within 0-12 m, with few ground obstacles. The key range of PM2.5 reduction was 12-24 m; within which ecological methods can be better used to settle particulate matter. 4) The reduction rate of PM2.5 was controlled by the green belt and the wind direction. Different green belt planting methods should be selected according to the dominant wind direction. The green belt on the parallel side and vertical windward side had positive PM2.5 effect, the recommended planting type was tree+tree irrigation grass, while on the vertical leeward side the green belt had negative effect, and the richer the planting type is, the more serious the PM2.5 gathering phenomenon becomes, the recommended planting type was tree+irrigation.