Abstract Air pollution is a critical public health issue worldwide, South America faces unique challenges due to rapid urban growth, industrial expansion, and recurrent biomass burning. Existing studies have largely focused on regional or national scales, overlooking detailed spatio-temporal dynamics in cities. This study provides a comprehensive assessment of air pollution spatio-temporal trends from 2013 to 2023 in six major South American cities: Bogotá, Buenos Aires, Montevideo, Quito, Santiago de Chile, and São Paulo. We evaluated four key pollutants, NO 2 , O 3 , PM 10 , and PM 2.5 , using in situ monitoring networks complemented with reanalysis (boundary layer and pollution dynamics), and fire detections datasets (biomass burning). A key innovation is the use of a Lagrangian Tracker, which identifies persistent hotspots and transport pathways of pollutants, offering new insights into transboundary pollution. Results show that nearly all cities experienced reductions in particulate matter concentrations, while three of the six cities exhibited rising O 3 levels, reflecting complex interactions between emissions, meteorology, and atmospheric chemistry. Santiago de Chile recorded the highest levels of NO 2 and PM, strongly influenced by topography and biomass burning in JJA. Bogotá and Quito were notably impacted by regional fire emissions, whereas coastal cities such as Buenos Aires and Montevideo benefited from greater pollutant dispersion but still exceeded the World Health Organization guidelines. By integrating ground-based, satellite, and reanalysis data with advanced trajectory modeling, this research provides detailed spatio-temporal evaluations of air pollution in South America and highlights the urgent need for coordinated regional strategies to reduce health and economic burdens. Graphical Abstract The panel on the left illustrates the countries of interest along with the cities included in the analysis. The right section presents the mean concentrations of PM 10 and PM 2.5 . The upper middle panel illustrates the degree of compliance with local air quality standards, while the lower middle panel shows the spatial distribution of fire hotspots across South America.
González et al. (Tue,) studied this question.