Urban viaduct has a prominent traffic pollution problem due to its elevated emission source and complex wind field, which seriously affects surrounding commuters and residents. To alleviate exposure risk at viaduct, it is important and urgent to understand the spatiotemporal variation of traffic pollution. But at present, relative studies, especially on the three-dimensional pollution characteristic, are limited, and the effect of traffic flow or wind field on pollutant distribution is not clear if fully considering roadside building structure. This study intends to investigate the three-dimensional distribution of typical traffic pollutant (i.e., PM2.5) alongside a viaduct in Guangzhou by using a moveable measurement platform. Based on the measured data including PM2.5 mass concentration, essential meteorological factors and traffic volume of four vehicle types, the study explores the statistical relationship between pollutant and influencing factors. Then, a numerical method combining a microscopic traffic flow simulation, an exhaust emission model and a computational fluid dynamics method is developed to model dynamic variation of pollutant distribution. To obtain a robust method, the study well validates the hybrid model using the measured data. The modelling results will reveal the mechanism of dynamic traffic, roadside construction, and micro-meteorology affecting pollution distribution alongside the viaduct. The study also puts forward a series of strategies for reducing roadside pollution at the viaduct. The well-validated hybrid model is then used to determine the optimal strategy of pollution reduction for a specific scenario. The work not only reveals the dynamic distribution law and key influencing factors of traffic pollutant at urban viaduct, but also provides an important practice basis for traffic infrastructure construction and roadside building design to effectively alleviate air pollution of typical traffic emission source.

CICTP