PM_2.5/PM₁₀ ratios in southernmost Brazilian cities and its relation with economic contexts and meteorological factors

The PM_2.5/PM₁₀ ratio is a metric used to distinguish the primary sources of particulate matter (PM) within a given environment. Higher ratios often indicate significant contributions from anthropogenic sources, while smaller ratios suggest a substantial influence from natural origins. However, various contextual factors can influence this ratio. Our study aimed to investigate the PM_2.5/PM₁₀ ratio in four distinct Brazilian cities, each characterized by varying levels of urbanization and primary economic activities. Additionally, we explored meteorological variables that may influence PM behavior across the years and different seasons. Our main finding reveals an association between the spatial distribution of PM and the primary economic activities in the investigated cities, with the highest PM_2.5/PM₁₀ ratio observed in the city engaged in coal activities, even though it did not exhibit the highest levels of PM. Conversely, coastal cities showed the lowest ratios. Furthermore, we observed that meteorological conditions also play a significant role in influencing PM behavior, with wind speed and the UV index emerging as the most influential meteorological parameters affecting this ratio. A subtle increase in PM_2.5/PM₁₀ ratios was noted in the fourth and fifth years of investigation across all cities, suggesting a potential impact from the restriction measures and the subsequent resumption of activities related to the COVID-19 pandemic in the region. However, these ratios stabilized in the post-pandemic years, returning to patterns similar to those observed pre-pandemic. Moreover, winter consistently exhibited the highest PM_2.5/PM₁₀ ratio across all cities, also being the season with the highest levels of both PM₁₀ and PM_2.5. Beyond providing important information about PM behavior in the evaluated scenarios, our findings emphasize the necessity of considering meteorological and economic factors in studies of this nature.