| 摘要: |
| 【目的】城市街道中人群活动密集，其空气质量问题值得关注。为解决街道峡谷内颗粒污染物难以扩散的问题，探究垂直绿化净化街道峡谷空气的能力和策略。【方法】以垂直绿化的滞尘效应为研究对象，通过现场调研与实测、正交实验结合计算机软件数值模拟等方法，定量探讨垂直绿化在街道峡谷形态、相对风向、布局方式等多种因素共同作用下的滞尘效应，并比较各因素的影响强弱。【结果】1）街道峡谷宽度、布局方式与水平向布置密度对垂直绿化滞尘效应影响最强。2）垂直绿化更适宜布置在道路较窄的城市支路以及迎风时长较多的建筑立面。【结论】得出滞尘效应最优的因素水平组合，总结出垂直绿化滞尘效应最佳的设计策略与滞尘能力模型，并评估垂直绿化在武汉市的滞尘潜力，为垂直绿化在街道峡谷中的应用提供理论依据。 |
| 关键词: 垂直绿化 街道峡谷 滞尘效应 可吸入颗粒物 ENVI-met |
| DOI：10.12409/j.fjyl.202207010378 |
| 分类号:TU985.12.4 |
| 基金项目:国家自然科学基金“建筑活墙能效评估模型的理论建构与实测验证”（编号 51708232）；湖北省长江生态保护基金会“垂直绿化对城市街道峡谷的空气净化作用研究”（编号 CCF-HZKJ-XMHT- 202009-001） |
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| Dust Retention Effect and Application of Vertical Greening in Street Canyon: A Case Study of Wuhan City |
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CHEN Qiuyu1, LENG Junyan2, LIU Xiaohu1
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1.Huazhong University of Science and Technology;2.Central-South Architectural Design Institute Co., Ltd
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| Abstract: |
| [Objective] In recent years, air pollution problems caused by particulate matter have attracted wide attention. Urban streets are easy to accumulate particulate matter from automobile exhaust. The “canyon” shape formed by the street and buildings on both sides can prevent the diffusion of pollutants. Vertical greening can well retain fine particles and is suitable for dust retention in street canyons, which is expected to be an effective method to improve air quality. This research evaluates, analyzes and compares the influence of relevant factors on the dust retention capacity of vertical greening in urban street canyons. [Methods] This research implements a field investigation and measurement of vertical greening facilities in Wuhan City to find out the influence of environmental factors on pollutant concentration and verify the reliability of numerical simulation results. Based on an innovative combination of a number of simulations, the research explores the overall influence of six different factors: street canyon height, street canyon width, relative wind direction, leaf area density (LAD), horizontal density of vertical greening, and layout form of vertical greening. The research selects the dust retention amount at both the windward and leeward sides of vertical greening as the experimental index, and summarizes the morphological characteristics of street canyons and wind directions. Altogether 18 experimental conditions are determined by the orthogonal experimental design. The research adopts Navier-Stokes equations to solve the wind field of the ENVI-met model adopted, whose resolution ranges from 0.5 m to 10 m. Selecting the data of typical summer meteorological days in Wuhan as research data, the research assumes that the inhalable particulate matters are emitted from continuous linear sources where the emission height of automobile exhaust is 0.3 m, and distributed bidirectionally in the middle of street canyons. Additionally, the research has the PM10 emission factor of small passenger cars assumed as 0.72 and the emission rate thereof as 180 μg/m·s, and figures ou the emission factor of PM2.5 by multiplying that of PM10 by a coefficient of 0.7. Moreover, the research adopts the simple plant module was to set three vertical greening modes with different leaf area densities, with the height and width of vertical greening being respectively set as 6 m and 0.5 m. Street length is set as 60 m to best prolong the retention time of pollutants. [Results] The pollutant concentration results of the filed measurement show a trend of “single peak and single valley”, with the highest and lowest concentrations occurring at 10:30 and 16:30 respectively, and the pollutant concentration on the side near the driveway being slightly lower than that near the vertical greening side. The results of simulation by ENVI-met software show the concentration distribution of PM2.5 and PM10 at a height of 1.5 m at 20:00 in the test site. The concentration of particulate matters is highest near the source of pollution, and they accumulate on the windward side of the street canyon. With the southeast wind blowing to the northwest, the concentration of pollutants at the eastern point is relatively low, which is consistent with the measured situation. The simulated value is consistent with the measured data after the dimensionless operation process, indicating a high reliability of the ENVI-met simulation for the purpose of this research. For both the leeward and the windward sides, the optimal combination of relevant factors for the best dust retention effects of vertical greening is as follows: street ca楮捹慯汮†杷物敤整湨椬渠朱′栠慭猻†杳牴敲慥瑥⁴愠灣灡汮楹捯慮琠楨潥湩灨牴漬猠瀶攠捭琻猠楥湬瑴桩敶爠敷捩潮湤猠瑤物畲捥瑣楴潩湯漬映‴戵爮愰溰挻栠⁌牁潄愬搠猳Ⱞ‰愠湭搲 瑭栳攻†楬浡灹牯潵癴攠浤敥湮瑳潴晹猠瀶愰挥攻†捬潡浹景潵牴琠慯湤摥愠楤物煴畲慩汢極瑴祥椠湬獹瑯牵整攮琠⁉据愠湴票潥渠獯thogonal experiment, the highest dust retention amount is 194,966 μg on the leeward side and 1,627,110 μg on the windward side. The research adopts the range analysis method to evaluate the merits and demerits of each factor in the results of the orthogonal experiment. The analysis results show that the width of street canyon, layout mode and layout density have the strongest influence on the dust retention effect on the leeward side or the windward side. The research also establishes a dust retention capacity model for vertical greening to calculate the dust retention amount of vertical greening for street canyons in Wuhan City. [Conclusion] The research has the implementation strategy of vertical greening for urban street canyons summarized as follows. 1) Vertical greening is suitable for narrow urban branch roads, where the environment of street canyon is more enclosed, and the particle pollutants are more difficult to spread. The layout of vertical greening in these streets make the best of the dust retention capacity of vertical greening to absorb particle pollutants and achieve the best purification effect. 2) Vertical greening is suitable for the layout of building facades with more windward hours. The dust retention amount of vertical greening on the windward side can reach more than 85% of the total retention amount on the both sides. The layout design strategy of vertical greening can be described as follows: To ensure the best layout of vertical greening, such factors as leaf area density, layout density and layout mode should be respectively set as 2.0 m2/m3, 60%, and discontinuous layout on the leeward side of street canyon, and as 1.0 m2/m3, 60% and discontinuous layout on the windward side of street canyon. This research provides a theoretical basis and puts forward a referential design strategy for the application of vertical greening application. Vert |
| Key words: vertical greening street canyon dust retention effect inhalable particulate matter ENVI-met |
