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Riachão do Dantas, nestled in the state of Sergipe, Brazil, occupies a relatively flat portion of the Agreste region, a transitional zone between the coastal *zona da mata* and the drier *sertão*. Located at approximately -11.0689 latitude and -37.7250 longitude, the city’s terrain is characterised by gently undulating hills and plateaus. The surrounding landscape is predominantly caatinga, a semi-arid scrubland vegetation, interspersed with small agricultural plots. The city’s elevation is modest, contributing to limited natural dispersion of pollutants. While not directly on the coast, Riachão do Dantas is influenced by maritime air masses, though these are often modified by the inland topography. The urban-rural gradient is fairly sharp; the city centre represents a concentrated area of human activity, while the periphery quickly transitions into agricultural land. A key factor influencing air quality is the prevalence of small-scale farming, including potential burning of agricultural residue. The lack of significant industrial belts within the immediate vicinity means that the primary pollution sources are likely to be related to vehicle emissions, domestic fuel burning (wood and charcoal), and dust from unpaved roads, exacerbated by the region’s climate. The city’s position within a broader rain shadow also impacts atmospheric conditions.

Riachão do Dantas experiences a distinct wet and dry season, heavily influencing its air quality. The wet season, typically running from March to August, brings relief from dust and particulate matter as rainfall effectively washes pollutants from the atmosphere. However, increased humidity can also foster mold growth, potentially impacting respiratory health. The driest months, September to February, are when air quality tends to decline. This is due to increased dust resuspension from agricultural activities and unpaved roads, coupled with lower wind speeds that hinder pollutant dispersion. Temperature inversions, common during the cooler, drier nights, trap pollutants near ground level, worsening conditions. February and March often see the highest concentrations of particulate matter due to widespread agricultural burning preparing fields for the next planting season. Sensitive groups – children, the elderly, and those with pre-existing respiratory conditions – should limit strenuous outdoor activity during these peak pollution periods. Monitoring wind patterns is crucial; winds from the west can carry dust from the drier *sertão* regions. Overall, the wet season offers the most favourable conditions for outdoor activity, while the late dry season demands increased vigilance.