Análisis temporal del NO2 en Sabadell y evaluación del uso de sensores low-cost como herramienta complementaria en la monitorización de calidad del aire

Abstract

Urban air pollution is one of the main environmental problems affecting cities, due to its negative impacts on human health and quality of life. Among the various air pollutants, nitrogen dioxide (NO₂) stands out because of its close relationship with combustion processes—particularly those associated with road traffic—and its relevance in densely populated urban environments. This study analyses the behaviour of NO₂ in the municipality of Sabadell (province of Barcelona), considering its temporal evolution and placing it within the broader supramunicipal context of the Vallès Occidental area. To this end, data from official monitoring stations of the Xarxa de Vigilància i Previsió de la Contaminació Atmosfèrica (XVPCA) for the period 2019–2024 are used, together with measurements obtained from low-cost sensors during 2023 and 2024. The analysis focuses on the spatial and temporal characterisation of the pollutant, with particular attention to seasonal and hourly variability, as well as comparisons with regulatory limit values and health-based guidelines. The results show a similar temporal pattern across the analysed municipalities, with higher concentrations in 2019, a marked decrease in 2020, and a more stable evolution in subsequent years. In the case of Sabadell, a clear seasonal pattern is observed, with higher concentrations during winter and hourly peaks associated with traffic rush hours on working days. Although annual mean concentrations comply with the current legal limit values, frequent exceedances of the guideline values recommended by the World Health Organization are recorded. The comparison between low-cost sensors and the official reference station indicates that, despite differences in absolute concentration levels depending on location, several sensors are able to reproduce the temporal evolution of NO₂ in a consistent manner. These findings highlight the potential of low-cost sensors as a complementary tool to expand the spatial coverage of air quality monitoring, support citizen science initiatives, and improve the understanding of air pollution at the local scale.