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Aliança, nestled in the Zona da Mata region of Pernambuco, Brazil, occupies a geographically significant position at the foothills of the Chapada de Aliança, a dramatic tableland that heavily influences its microclimate and air quality. Located approximately 25 kilometers from the coastal city of Recife, Aliança’s coordinates (-7.6028, -35.2308) place it within a transitional zone between the humid coastal plains and the drier, more undulating interior. The terrain is characterized by rolling hills and valleys, with elevations ranging from around 300 to 700 meters above sea level, contributing to localized variations in temperature and wind patterns. The surrounding landscape is a mosaic of sugarcane plantations, small-scale agriculture, and remnants of Atlantic Forest, a biodiversity hotspot. This agricultural intensity, particularly the prevalence of sugarcane, is a key factor impacting air quality, with burning practices historically contributing to particulate matter. The urban–rural gradient is relatively sharp; Aliança itself is a modest municipality, transitioning quickly into agricultural lands and the rugged terrain of the Chapada. The proximity to Recife, a major industrial and commercial hub, means Aliança is indirectly affected by regional pollution trends, although the intervening distance and topography offer some buffering. The city’s location within a humid tropical climate zone, with consistent rainfall, generally aids in pollutant dispersal, but periods of drought can exacerbate issues. The Chapada’s influence creates localized rain shadows and can trap pollutants under certain meteorological conditions.

Aliança’s tropical climate dictates a wet and dry season pattern, significantly impacting its air quality profile. The dry season, typically spanning from August to December, presents the greatest air quality challenges. Reduced rainfall leads to lower atmospheric moisture, hindering the natural cleansing effect of precipitation. Furthermore, the dry vegetation increases the risk of wildfires, often intentionally set for land clearing or agricultural purposes, releasing substantial amounts of particulate matter and carbon monoxide. Temperature inversions, common during the cooler, drier nights, trap pollutants near the ground, intensifying their concentration. The months of September and October often experience the poorest air quality due to a combination of these factors. Conversely, the wet season (January to July) brings frequent rainfall and higher humidity, naturally scrubbing the atmosphere and dispersing pollutants. Stronger winds associated with the wet season also aid in ventilation. While the wet season generally offers improved air quality, periods of dense fog, particularly in the mornings, can temporarily reduce visibility and trap pollutants in localized areas. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, limiting outdoor activities during peak pollution periods, typically in the mornings. Agricultural workers should be particularly vigilant regarding smoke exposure. During the wet season, while overall air quality is better, those with allergies should be mindful of pollen counts, which can fluctuate.