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Capela, Sergipe, Brazil, occupies a strategically important position within the Sergipe River Basin, a region characterized by a gently undulating coastal plain. Located at approximately -10.5028° latitude and -37.0528° longitude, the city’s terrain is predominantly low-lying, rarely exceeding 50 meters above sea level. This flatness, typical of the northeastern Brazilian landscape, contributes to a relatively stable atmospheric boundary layer, which can sometimes exacerbate pollution events. The surrounding landscape is a mosaic of small-scale agriculture – primarily sugarcane and cassava cultivation – interspersed with patches of Atlantic Forest remnants. To the east lies the Atlantic Ocean, providing a moderating influence on temperature and humidity, but also a potential pathway for marine-derived aerosols. Capela’s proximity to the Sergipe River itself is significant; the river acts as a drainage corridor and can influence local humidity and wind patterns. While not directly adjacent to major industrial belts, the broader Sergipe state experiences some industrial activity related to sugar processing and port operations in Aracaju, the state capital, approximately 70 kilometers away. This creates a subtle urban–rural gradient, with Capela experiencing a mix of agricultural emissions and potential downwind impacts from regional industrial sources. The city’s relatively small population (31,645) suggests a primarily rural character, but increasing urbanization and vehicle ownership could gradually alter its air quality profile. The flat topography and coastal location mean that pollutants tend to linger, particularly during periods of low wind speed and stable atmospheric conditions.

Capela’s tropical climate dictates a distinct wet and dry season pattern, profoundly influencing its air quality. The dry season, typically from August to January, is characterized by lower rainfall and increased sunshine hours. However, this period often sees a rise in particulate matter concentrations. The lack of rainfall means fewer natural cleansing events, and agricultural burning, a common practice for land preparation, releases significant amounts of smoke and aerosols into the atmosphere. Temperature inversions, where a layer of warm air traps cooler air near the ground, are more frequent during the dry season, further hindering pollutant dispersion. The months of September through November are particularly concerning, as agricultural activity intensifies. Conversely, the wet season (February to July) brings frequent rainfall and higher humidity, which naturally washes pollutants from the air and increases atmospheric mixing. Stronger winds associated with occasional thunderstorms also help to disperse pollutants. Fog, though not a frequent occurrence, can sometimes develop during the transition periods between seasons, trapping pollutants near the surface. Sensitive groups, such as children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly on days with visible smoke or haze. Outdoor activities are generally more favorable during the wet season, although heavy rainfall can still impact visibility and air quality due to increased humidity. The interplay of agricultural practices, meteorological conditions, and the city’s geographic setting creates a dynamic air quality profile throughout the year.