UNVEILING URBAN AIR QUALITY SEASONAL DYNAMICS IN SAN MIGUEL DE TUCUMÁN, ARGENTINA, BY SCANNING ELECTRON MICROSCOPY

Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (EDS) was used to analyze particulate matter (PM) in San Miguel de Tucumán, Argentina, a densely populated urban area influenced by agricultural and industrial pollution. This study investigates PM concentration and composition during sugarcane harvest and non-harvest periods (2019-2020), accidentally coinciding with the COVID-19 lockdowns. SEM-EDS enabled the classification of PM by size (Dust, PM ₁₀ , and PM _2.5 ) and by composition (Terrigenous PM and Carbonaceous PM). Higher PM concentrations were detected during harvest periods, with a notable increase in carbon-rich PM _2.5 (PMC _2.5 ) in 2019 compared to 2020. Unexpectedly, this variation was primarily attributed to reduced population mobility during the 2020 lockdowns, rather than changes in industrial activity. Satellite data on nitrogen oxides (NOx) supported these findings, revealing emission patterns consistent with vehicular activity. Overall, this study demonstrates the effectiveness of SEM-EDS in characterizing air pollutants and highlights the critical influence of population mobility on urban air quality. The findings support the implementation of targeted air pollution control strategies - particularly during harvest seasons- to mitigate both health and environmental impacts.