Urban form and air pollution disperse: Key indexes and mitigation strategies

Modern cities are experiencing increasingly severe air pollution issues due to massive emissions from industrial waste and vehicles. Additionally, urban spatial patterns and architectural layouts make near-surface urban air pollutants difficult to disperse. Thus, they accumulate at human height level, affecting people's health. This study performs a three-dimensional simulation of features of spatial forms such as the site coverage, average height, plot ratio or floor area ratio, degree of enclosure, and height difference. The study makes use of a typical high-density built-up area as an example for empirical analysis. The research results show that the factors of three-dimensional forms of urban space, and the urban near-surface wind environment affected by it, have apparent effects on the flow of near-surface urban air pollutants. In particular, site coverage, average height, and degree of enclosure are the key indexes affecting the flow of near-surface air pollutants, while average height shows the most significant impact. Based on these findings, the study proposes mitigation strategies to optimize main urban form indexes from the above three aspects, in order to promote near-surface urban air pollutant dispersion and reduce the impact of air pollution on human health.