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São Bento do Una, nestled in the interior of Pernambuco, Brazil, occupies a unique geographic position within the semi-arid Sertão region. Located at -8.5228, -36.4439, the city sits at an elevation of approximately 228 meters, contributing to a relatively stable atmospheric layer. The surrounding landscape is characterised by *caatinga* vegetation – a thorny scrubland adapted to prolonged drought – and rolling hills. The Una River, a crucial water source for the region, flows nearby, influencing local microclimates and potentially trapping pollutants during periods of low flow. While not heavily industrialised, São Bento do Una is surrounded by agricultural zones, primarily focused on subsistence farming and livestock raising. These activities contribute to particulate matter through land clearing, animal husbandry, and the use of agricultural machinery. The urban-rural gradient is pronounced; the city centre represents a concentrated source of emissions from vehicle traffic and domestic fuel burning, while the surrounding rural areas contribute through agricultural practices and biomass burning. The city’s location within a valley can exacerbate pollution events, limiting air dispersion. Dust from the dry landscape is a persistent factor, impacting baseline air quality. Understanding this interplay of terrain, land use, and climate is crucial for addressing air quality challenges.

São Bento do Una experiences a distinct wet and dry season, heavily influencing air quality. The dry season, typically from August to December, is characterised by minimal rainfall, increased dust resuspension from the *caatinga* landscape, and a higher frequency of biomass burning for land preparation. This period sees a peak in particulate matter (PM10 and PM2.5) concentrations, impacting respiratory health. January to April brings the wet season, offering a temporary reprieve as rainfall washes away pollutants and suppresses dust. However, increased humidity can also promote the formation of mould and allergens. May and July represent transitional periods with moderate air quality. Temperature inversions, common during the cooler, drier months (June-August), trap pollutants near the ground, worsening conditions. Sensitive groups – children, the elderly, and those with pre-existing respiratory conditions – should limit outdoor activity during the peak of the dry season. Fog, occasionally forming during the cooler months, can also exacerbate particulate matter concentrations. Monitoring wind patterns is vital; winds from the west often carry dust and smoke from agricultural areas, while easterly winds can bring cleaner air. Avoiding strenuous outdoor activity during dry, windy days is advisable.