Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York 14853, United States.
Environ Sci Technol. 2012 Jan 3;46(1):312-9. doi: 10.1021/es201938v. Epub 2011 Nov 30.
Highway-building environments are prevalent in metropolitan areas. This paper presents our findings in investigating pollutant transport in a highway-building environment by combing field measurement and numerical simulations. We employ and improve the Comprehensive Turbulent Aerosol Dynamics and Gas Chemistry (CTAG) model to simulate the spatial variations of black carbon (BC) concentrations near highway I-87 and an urban school in the South Bronx, New York. The results of CTAG simulations are evaluated against and agree adequately with the measurements of wind speed, wind directions, and BC concentrations. Our analysis suggests that the BC concentration at the measurement point of the urban school could decrease by 43-54% if roadside buildings were absent. Furthermore, we characterize two generalized conditions in a highway-building environment, i.e., highway-building canyon and highway viaduct-building. The former refers to the canyon between solid highway embankment and roadside buildings, where the spatial profiles of BC depend on the equivalent canyon aspect ratio and flow recirculation. The latter refers to the area between a highway viaduct (i.e., elevated highway with open space underneath) and roadside buildings, where strong flow recirculation is absent and the spatial profiles of BC are determined by the relative heights of the highway and buildings. The two configurations may occur at different locations or in the same location with different wind directions when highway geometry is complex. Our study demonstrates the importance of incorporating highway-building interaction into the assessment of human exposure to near-road air pollution. It also calls for active roles of building and highway designs in mitigating near-road exposure of urban population.
公路建设环境在大都市中很常见。本文通过结合现场测量和数值模拟，介绍了我们在调查公路建设环境中污染物传输方面的研究结果。我们采用并改进了综合紊流气溶胶动力学和气体化学（CTAG）模型，以模拟纽约南布朗克斯区 I-87 公路和一所城市学校附近的黑碳（BC）浓度的空间变化。CTAG 模拟的结果与风速、风向和 BC 浓度的测量值进行了对比，并得到了充分的验证。我们的分析表明，如果路边建筑物不存在，城市学校测量点的 BC 浓度可降低 43-54%。此外，我们还在公路建设环境中描述了两种广义条件，即公路建设峡谷和公路高架桥建设。前者是指固体公路路堤和路边建筑物之间的峡谷，BC 的空间分布取决于等效峡谷纵横比和流循环。后者是指公路高架桥（即下方有空地的高架公路）和路边建筑物之间的区域，此处不存在强烈的流循环，BC 的空间分布取决于公路和建筑物的相对高度。这两种配置可能在不同位置出现，也可能在具有不同风向的同一位置出现，具体取决于公路几何形状的复杂性。我们的研究表明，将公路建设的相互作用纳入到对人类暴露于道路附近空气污染的评估中非常重要。它还呼吁在建筑和公路设计中发挥积极作用，以减轻城市人口的道路附近暴露程度。
