Urban Morphology and Traffic-Related Carbon Monoxide in Historic Urban Areas: A Multiscale Analysis in Cuenca, Ecuador

Understanding how historic urban morphology and atmospheric conditions shape the spatial and vertical distribution of traffic-related carbon monoxide (CO) remains challenging in intermediate cities of the Global South. This study examined CO distribution across three spatial scales in the Historic Center of Cuenca, Ecuador, a UNESCO World Heritage Site, integrating urban functional analysis, morphology, traffic-flow assessment, sensor monitoring (2025), and dispersion modeling (May 2025). The historic center concentrated 30% of non-residential land uses and 20% of traffic congestion; CO at a high-traffic station (9 m) was 2.4 times that at a lower-traffic station (20 m). Mean modeled CO at 1.5 m peaked at 0.52 mg/m3 during 07:00–08:00 h; for similar flows, it was five times higher than at 08:00–09:00 h. Modeled concentrations decreased by up to 66.7% between 1.5 and 9 m, with the largest decreases under stable morning and evening conditions; the model met urban acceptance criteria against multi-height measurements. These results suggest that traffic intensity alone does not explain CO concentrations in historic urban canyons: morphology and atmospheric stability are likely to jointly regulate pollutant accumulation and dispersion, underscoring the need to incorporate vertical air-pollution gradients into mobility planning and sensor siting in historic centers.