China’s air pollution has been effectively controlled in recent years. However, in some major city clusters with fast growing economies and large population density, air quality is still far below the world recommended health standards. Chongqing is the largest municipality located in southwestern China. The well-developed industrial economy and the highly dense population here result in a large number of anthropogenic emissions of air pollutants, combined with its complex geography and stable meteorological conditions, continuously causing server air pollution. While research has been done focusing on air pollution in other major city clusters, relatively less research has been done on air pollution in Chongqing. Not to mention further study the effects of urban morphology on local pol...[ Read more ]

China’s air pollution has been effectively controlled in recent years. However, in some major city clusters with fast growing economies and large population density, air quality is still far below the world recommended health standards. Chongqing is the largest municipality located in southwestern China. The well-developed industrial economy and the highly dense population here result in a large number of anthropogenic emissions of air pollutants, combined with its complex geography and stable meteorological conditions, continuously causing server air pollution. While research has been done focusing on air pollution in other major city clusters, relatively less research has been done on air pollution in Chongqing. Not to mention further study the effects of urban morphology on local pollutant dispersion using fine-scale air quality models. In such a case, this study first establishes a coupled air quality model called WRF-CMAQ-ADMS, then uses the model to study Chongqing’s air pollutant distribution pattern in January and April 2022. It is found that at the morning traffic peak and at night, the central city of Chongqing has high spots of NO₂ and particulate matter, along with other high concentration spots near the airport, power plant, and industries area. Over half a month of days with PM_2.5 concentration exceeded air quality standards, which should draw more government and public attention. This study also conducted a sensitive experiment on how urban buildings affect pollutant concentrations and found that the street canyon effect can increase NO₂ and PM_2.5 by up to 8 μg/m³and 7 μg/m³, respectively, and up to 8% and 12% after doubling the building height for NO₂ and PM_2.5. In the vertical direction, there is a change in the NO₂ concentration layer every 40 meters on average. As the height increases, the pollutant concentration decreases, while PM_2.5 has less change in the concentration layer at the same height. However, people living in tall buildings on roadsides are more likely affected by high ozone concentrations than ground-level people. Road intersections and roads where buildings are close to the street are more significantly affected by the street canyon effect.