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Moju, Pará, Brazil, occupies a strategically important position within the Amazon biome, approximately 110 kilometers northeast of Belém, the state capital. Situated at -1.8839° latitude and -48.7689° longitude, the city’s geography is dominated by the Amazon River basin’s low-lying terrain, with elevations rarely exceeding 30 meters above sea level. This flat topography, characteristic of the Amazon floodplain, significantly influences local air circulation patterns. Moju lies within a transitional zone, exhibiting a gradual urban–rural gradient as it expands outwards from the city center. To the west, the landscape transitions into dense rainforest, while to the east, agricultural lands, particularly soybean and cattle farms, become increasingly prevalent. The proximity to the Curuçá River, a major tributary of the Amazon, introduces a humid, tropical climate and influences local weather systems. The region’s economy is driven by agriculture, mining (particularly bauxite), and port activities related to Belém’s port. Industrial activity, though not as extensive as in larger Amazonian cities, is present, primarily involving processing of agricultural products and supporting the mining sector. This combination of agricultural practices, resource extraction, and burgeoning urban development contributes to a complex interplay of factors impacting air quality. The surrounding landscape, a mosaic of forest, farmland, and waterways, dictates the dispersal of pollutants and the potential for transboundary air pollution events, particularly during periods of drought or altered wind patterns. The relatively flat terrain limits vertical mixing, potentially trapping pollutants closer to the ground.

Moju’s tropical climate dictates a wet and dry season cycle, profoundly impacting its air quality. The dry season, typically spanning from July to November, presents the most significant air quality challenges. Reduced rainfall leads to lower atmospheric moisture, hindering the natural cleansing effect of precipitation. Furthermore, the dry conditions exacerbate the risk of agricultural burning, a common practice for land clearing and crop residue removal. These fires release substantial quantities of particulate matter and gaseous pollutants, significantly degrading air quality. Temperature inversions, more frequent during the dry season, trap pollutants near the surface, intensifying their impact. The prevailing winds during this period often originate from the south, potentially carrying pollutants from agricultural regions further north. Conversely, the wet season (December to June) brings increased rainfall, which effectively washes pollutants from the atmosphere. Higher humidity also promotes the deposition of particulate matter. While the wet season generally offers improved air quality, periods of prolonged fog, particularly in the early morning, can temporarily reduce visibility and trap pollutants. During the transition months (May/June and November/December), fluctuating weather patterns can lead to unpredictable air quality episodes. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, limiting outdoor activities during peak burning periods and periods of stagnant air. Maintaining indoor air quality through proper ventilation and air filtration is also advisable.