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Propriá occupies a strategic position within the interior of Sergipe, fundamentally defined by its intimate relationship with the São Francisco River. This riverine setting creates a distinct urban character where the built environment clings to the fertile banks, contrasting sharply with the surrounding semi-arid hinterland of the Caatinga biome. Geographically, the city sits within a low-lying depression, where the terrain is predominantly flat, facilitating the movement of moisture-laden breezes from the river that often mitigate extreme heat. However, this same topography can trap particulate matter during periods of atmospheric stability. The regional position of Propriá makes it a hub for agricultural activity, particularly fruit cultivation and livestock, which establishes a permeable urban-rural gradient. This proximity to agricultural zones is a primary driver of local air quality fluctuations, as the clearing of land and the management of crop residues often involve biomass burning. The surrounding landscape is characterized by xeric shrublands and deciduous forests, which contribute significant amounts of mineral dust to the air during the windier periods. Consequently, the air quality is a tug-of-war between the purifying effects of the river’s humidity and the pollutants generated by seasonal agricultural practices. The lack of heavy industrial belts means that chemical smog is rare, but the organic aerosols from the surrounding countryside define the city's atmospheric profile, making the river the primary lung and vital atmospheric filter for this interior Sergipe community.

In Propriá, the air quality narrative is dictated by the binary rhythm of the tropical semi-arid climate, oscillating between the rainy season and the prolonged dry period. During the wet months, typically from April to August, frequent precipitation serves as a natural scrubbing mechanism, washing particulate matter from the atmosphere and suppressing the dust common to the Caatinga. This period offers the cleanest air, making it ideal for outdoor activities and respiratory relief. Conversely, the dry season, peaking between October and January, presents significant atmospheric challenges. As humidity drops and the landscape parches, the region becomes prone to biomass burning and agricultural fires, which release dense plumes of smoke and fine particulate matter. These pollutants often linger due to temperature inversions that trap stagnant air near the river valley, preventing vertical dispersion. During these peak dry months, sensitive groups, including children and the elderly, should limit prolonged outdoor exertion, particularly during the mid-afternoon when heat-induced turbulence can kick up mineral dust. The prevailing winds from the east often bring relief, but during periods of calm, the smoke from nearby fields can settle over the urban center. To maintain respiratory health, residents are encouraged to favor early morning activities when the air is cooler and slightly more humid. Understanding this seasonal cycle is crucial for navigating the environmental health risks inherent to the interior of Sergipe's unique and fragile riverine ecosystem.