Shen Jiaowen, Cui Pengyi, Huang Yuandong, Wu Yiping, Luo Yang, Sin Chung Hyok, Guan Jie
School of Environment and Architecture, University of Shanghai for Science and Technology, No. 516, Jungong Road, Yangpu District, Shanghai, 200093, China.
School of Resources and Environmental Engineering, Shanghai Polytechnic University, Shanghai, 201209, China.
Environ Sci Pollut Res Int. 2023 May;30(22):63148-63174. doi: 10.1007/s11356-023-26370-1. Epub 2023 Mar 24.
Mixed-vegetation planting patterns are commonly seen in urban areas for specific reasons like aesthetic, cooling, and particle deposition effects of the vegetation. However, they may have a negative impact on human health by worsening the air quality inside the street canyon due to the decreased air exchange rate. From the view of precise control of pollutant concentration in the sensitive areas of people's concern in the existed street canyons, thirty-four cases with different vegetation planting patterns and pressure loss coefficients (λ) are studied numerically to investigate the effects of vegetation on airflow and pollutant dispersion inside the canyon. The cases of treeless and 2 rows of tree planting patterns in wind-tunnel measurements were selected for the model validation. The results demonstrate that compared to the treeless case, the greenbelts can greatly change the airflow features and reduce the pollutant concentration at the leeward side, while the only-tree planting patterns have little impact on the flow and deteriorate dispersion within the street canyon. Moreover, rows of greenbelts planted under the corresponding trees can reduce the average pollutant concentrations on the leeward wall and the footpath of the street canyon by up to 22.6% and 33.2%, respectively. Besides, the pattern of 1 row of trees with 1 row of greenbelts planted in the street canyon center should be suggested as the optimal mixed vegetation configuration in this study. That is because compared to the treeless case the pollutant concentration on leeward wall, windward wall, leeward footpath, and windward footpath can be reduced by 14.2%, 10.0%, 24.6%, and 37%, respectively. It is helpful to the city planners to consider whether the disadvantages of planting vegetation inside the street canyon would overwhelm the advantages.
出于美观、降温以及植被的颗粒物沉降效应等特定原因，混合植被种植模式在城市地区很常见。然而，由于空气交换率降低，它们可能会使街道峡谷内的空气质量恶化，从而对人类健康产生负面影响。从精确控制现有街道峡谷中人们关注的敏感区域内的污染物浓度的角度出发，对34个具有不同植被种植模式和压力损失系数（λ）的案例进行了数值研究，以探讨植被对峡谷内气流和污染物扩散的影响。在风洞测量中选择无树和两排树木种植模式的案例进行模型验证。结果表明，与无树情况相比，绿化带可极大地改变气流特征并降低背风侧的污染物浓度，而单棵树的种植模式对气流影响不大，且会使街道峡谷内的扩散情况恶化。此外，在相应树木下方种植的一排排绿化带可分别使街道峡谷背风墙和人行道上的平均污染物浓度降低多达22.6%和33.2%。此外，在本研究中，建议将在街道峡谷中心种植一排树和一排绿化带的模式作为最佳混合植被配置。这是因为与无树情况相比，背风墙、迎风墙、背风人行道和迎风人行道上的污染物浓度可分别降低14.2%、10.0%、24.6%和37%。这有助于城市规划者考虑在街道峡谷内种植植被的弊端是否会超过其优势。
