The level of air pollution in a street canyon depends on the non-trivial interplay between vehicular exhaust emissions, atmospheric transport, and physico-chemical transformation of pollutants. In this study, we investigate the temporal dynamics of air pollutant concentration in a deep street canyon orthogonal to the wind direction using a two-box model. Simulations provide insights into both steady-state mean concentrations and the magnitude of concentration fluctuations as pollutant nature (inert or reactive), emission signal stochasticity, and the fundamental rates of turbulent transport and chemical transformations vary. Beyond elucidating the role of different parameters on mean pollution levels, the results reveal that extreme air pollutant concentrations are more likely to occur when the characteristic time scale of vehicular exhaust emissions significantly exceeds the ventilation time scale of the street canyon. The innovative modelling approach paves the way for various applications, particularly in the field of optimal traffic management and the study of citizens' exposure to air pollution.

中文翻译：

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理想化城市街道峡谷中排放变异对浓度波动的影响

街道峡谷的空气污染程度取决于车辆尾气排放、大气传输和污染物的物理化学转化之间的重要相互作用。在这项研究中，我们使用两箱模型研究了与风向正交的深街峡谷中空气污染物浓度的时间动态。模拟可以深入了解稳态平均浓度和浓度波动的幅度，因为污染物性质（惰性或反应性）、排放信号随机性以及湍流传输和化学转化的基本速率发生变化。除了阐明不同参数对平均污染水平的作用外，结果还表明，当车辆尾气排放的特征时间尺度显着超过街道峡谷的通风时间尺度时，更有可能出现极端空气污染物浓度。创新的建模方法为各种应用铺平了道路，特别是在最佳交通管理和公民暴露于空气污染的研究领域。