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Montanhas, nestled in the state of Rio Grande do Norte, Brazil, occupies a unique position within the Seridó region, a transition zone between the coastal plains and the interior highlands. Located at approximately -6.4858° latitude and -35.2878° longitude, the city’s elevation, though modest, contributes to localized microclimates. The surrounding landscape is characterized by a mix of *caatinga* vegetation, a semi-arid biome adapted to drought conditions, and gently rolling hills. This *caatinga* environment, while naturally resilient, can exacerbate air quality issues during the dry season due to increased dust and particulate matter. Montanhas sits relatively far from major coastal industrial belts, minimizing direct impacts from large-scale industrial emissions. However, its proximity to agricultural zones, particularly those employing conventional farming practices, introduces potential sources of ammonia and pesticide drift. The urban–rural gradient around Montanhas is gradual, with small agricultural holdings and scattered rural communities blending into the urban fabric. The city’s location inland, away from the immediate influence of the Atlantic Ocean, means it experiences less frequent coastal breezes that could naturally disperse pollutants. The terrain, with its subtle undulations, can also trap air, particularly during periods of low wind speed, leading to localized air quality challenges. The limited water bodies in the immediate vicinity further restrict natural air purification processes, making the city’s air quality highly dependent on local emissions and meteorological conditions.

Montanhas experiences a distinctly tropical climate with a pronounced wet and dry season, significantly influencing its air quality profile. The dry season, typically spanning from August to November, presents the most challenging period. Reduced rainfall combined with high temperatures and frequent periods of calm wind conditions create an environment prone to dust storms and particulate matter accumulation. The *caatinga* vegetation, naturally shedding leaves and releasing dust, contributes to this issue. Temperature inversions, where cooler air becomes trapped beneath a layer of warmer air, are also more common during these months, preventing pollutants from dispersing vertically. Conversely, the wet season (December to July) brings relief. Frequent rainfall effectively ‘washes’ pollutants from the atmosphere, significantly improving air quality. The increased humidity also reduces dust generation. However, periods of intense rainfall can lead to localized flooding, potentially releasing contaminants from soil and runoff. During the transitional months (May-June and August-September), air quality is generally moderate, influenced by fluctuating wind patterns and rainfall. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, limiting outdoor activities during peak dust events. Maintaining indoor air quality through proper ventilation and air filtration is also advisable. The prevalence of agricultural activities throughout the year, though more intense during planting and harvesting seasons, contributes to background levels of ammonia and other agricultural pollutants, impacting air quality regardless of the season.