Urban ventilation corridors exacerbate air pollution in central urban areas: Evidence from a Chinese city

Urban ventilation corridors are effective in improving urban air quality and alleviating heat island problems, and are widely used in cities around the world. This paper studies typical smog-polluted cities in China to examine whether urban ventilation corridors will worsen air pollution in cities and then proposes countermeasures. First, this paper identifies compensation spaces outside the central urban area of Xi'an and then analyses the prevailing wind direction in these compensation spaces. Based on these findings, this paper identifies potential cold air passages and assesses the air cleanliness in these compensation spaces according to the spatial distributions of PM2.5 and PM10. The study finds that four compensation spaces are found outside the central urban area of Xi'an and seven potential cold air passages, including six expressways and one railway, and the PM10 and PM2.5 concentrations in three of the four compensation spaces are higher than those in the central urban area. From the beginning (located in the compensation space) to the end (located in the action space) of the cold air passages P1 and P2, PM2.5 decreased by 11.88% and 11.82%, and PM10 decreased by 9.40% and 9.76%. This study discovers that if the urban compensation spaces are located in areas with high concentrations of pollutants, the polluted cold air will be introduced to the central urban area along the cold air passages due to the prevailing wind. Unlike previous studies which concluded that urban ventilation corridors improve air quality in central urban areas, this study demonstrates that urban ventilation corridors are at risk of exacerbating air pollution in central urban areas. Therefore, when planning urban ventilation corridors, a city should make an assessment of the air cleanliness of the compensation spaces mandatory to avoid worsening air pollution in the central urban area and creating an unsustainable climate environment due to the planning of urban ventilation corridors, which may further lead to economic losses and threats to public health.