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Clean air in cities: Impact of the layout of buildings in urban areas on pedestrian exposure to ultrafine particles from traffic
Atmospheric Environment ( IF 5 ) Pub Date : 2021-02-14 , DOI: 10.1016/j.atmosenv.2021.118267
Liye Zhu , Dilhara Ranasinghe , Marcelo Chamecki , Michael J. Brown , Suzanne E. Paulson

Traffic-related pollutant concentrations are typically much higher in near-roadway microenvironments, and pedestrian and resident exposures to air pollutants can be substantially increased by the short periods of time spent on and near roadways. The design of the built environment plays a critical role in the dispersion of pollutants at street level; after normalizing for traffic, differences of a factor of ~5 have been observed between urban neighborhoods with different built environment characteristics. We examined the effects of different built environment designs on the concentrations of street-level ultrafine particles (UFP) at the scale of several blocks using the Quick Urban and Industrial Complex (QUIC) numerical modeling system. The model was capable of reasonably reproducing the complex ensemble mean 3D air flow patterns and pollutant concentrations in urban areas at fine spatial scale. We evaluated the effects of several built environment designs, changing building heights and spacing while holding total built environment volumes constant. We found that ground-level open space reduces street-level pollutant concentrations. Holding volume/surface area constant, tall buildings clustered together with larger open spaces between buildings resulted in substantially lower pollutant concentrations than buildings in rows. Buildings arranged on a ‘checkerboard’ grid with smaller contiguous open spaces, a configuration with some open space on one of the sides of the roadway at all locations, resulted in the lowest average concentrations for almost all wind directions. Rows usually prohibit mixing for perpendicular and oblique wind directions, even when there are large spaces between them, and clustered buildings have some areas where buildings border both sides of the roadways, inhibiting mixing. The model results suggest that pollutant concentrations drop off rapidly with height in the first 10 m or so above the roadways. In addition, the simulated vertical concentration profiles show a moderate elevated peak at the roof levels of the shorter buildings within the area. Model limitations and suggestions both for urban design are both discussed.



中文翻译:

城市清洁空气:城市建筑物布局对行人暴露于交通中超细颗粒物的影响

在道路微环境中,与交通有关的污染物浓度通常要高得多,并且由于在道路上和道路附近花费的时间短,行人和居民暴露在空气污染物中的比例可能会大大增加。建筑环境的设计在街道上污染物的扩散中起着至关重要的作用。在对交通进行归一化之后,在具有不同建筑环境特征的城市社区之间观察到约5倍的差异。我们使用快速城市和工业园区(QUIC)数值建模系统,研究了在几个街区尺度上不同建筑环境设计对街道级超细颗粒(UFP)浓度的影响。该模型能够在精细的空间尺度上合理地再现复杂的整体平均3D气流模式和城市地区的污染物浓度。我们评估了几种建筑环境设计的效果,在保持建筑环境总体积不变的情况下,改变了建筑物的高度和间距。我们发现地面开放空间可降低街道污染物浓度。在保持体积/表面积不变的情况下,高层建筑与建筑物之间较大的开放空间聚集在一起导致的污染物浓度大大低于成排的建筑物。建筑物排列在“棋盘式”网格上,具有较小的连续开放空间,该结构在所有位置的巷道一侧均具有一定的开放空间,导致几乎所有风向的平均浓度最低。行之间通常禁止在垂直和倾斜的风向混合,即使它们之间有很大的空间,并且群集的建筑物在某些区域中建筑物与车道的两侧接壤,从而阻止了混合。模型结果表明,污染物浓度随车道上方前10 m左右的高度而迅速下降。此外,模拟的垂直浓度曲线在该区域内较短建筑物的屋顶水平上显示出一个中等的升高峰值。讨论了城市设计的模型局限性和建议。模型结果表明,污染物浓度随车道上方前10 m左右的高度而迅速下降。此外,模拟的垂直浓度曲线在该区域内较短建筑物的屋顶水平上显示出一个中等的升高峰值。讨论了城市设计的模型局限性和建议。模型结果表明,污染物浓度随车道上方前10 m左右的高度而迅速下降。此外,模拟的垂直浓度曲线在该区域内较短建筑物的屋顶水平上显示出一个中等的升高峰值。讨论了城市设计的模型局限性和建议。

更新日期:2021-03-09
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