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Pendências, nestled in the coastal plains of Rio Grande do Norte, Brazil, occupies a geographically significant position within the easternmost state of the nation. Located at approximately -5.2600 latitude and -36.7219 longitude, the city’s terrain is predominantly low-lying, characteristic of the broader coastal region. The surrounding landscape is a mosaic of *caatinga* scrubland, a semi-arid biome adapted to seasonal drought, interspersed with patches of coastal forests and agricultural fields. The proximity to the Atlantic Ocean, roughly 15 kilometers to the east, exerts a considerable influence on local climate and, consequently, air quality. Pendências sits within a gradual urban–rural gradient; while it functions as a regional service center for the surrounding agricultural communities, it lacks large-scale industrial zones. The primary economic activities revolve around agriculture (particularly cassava and beans), livestock raising, and small-scale commerce. This limits the direct contribution of heavy industry to air pollution. However, agricultural practices, including the use of fertilizers and occasional controlled burns for land clearing (though increasingly regulated), can contribute to localized particulate matter. The relatively flat topography can also exacerbate the effects of temperature inversions, trapping pollutants closer to the ground, particularly during periods of calm weather. The city’s elevation, averaging around 20 meters above sea level, further contributes to this phenomenon, limiting vertical dispersion of pollutants. The prevailing winds, generally from the northeast, play a crucial role in dispersing or concentrating air pollutants, depending on their strength and direction relative to potential sources.

Pendências experiences a tropical climate with distinct wet and dry seasons, significantly impacting its air quality profile. The dry season, typically spanning from August to December, is characterized by reduced rainfall and increased temperatures. This period often sees a rise in particulate matter concentrations, primarily due to agricultural activities like harvesting and the potential for controlled burns, although these are increasingly restricted. The lack of rainfall means less natural cleansing of the atmosphere, and the drier air can exacerbate dust emissions from unpaved roads and agricultural lands. During the wet season (January to July), increased rainfall effectively ‘washes’ pollutants from the air, leading to a noticeable improvement in air quality. However, periods of intense rainfall can also lead to localized flooding, which can temporarily release pollutants from saturated soils. Fog, though infrequent, can occur during the cooler months (July-September), trapping pollutants near the ground and creating localized episodes of reduced visibility and potentially elevated particulate matter. Temperature inversions, more common during the dry season, occur when a layer of warm air sits above cooler air, preventing vertical mixing and trapping pollutants. Sensitive groups, such as children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly on days with calm winds or when agricultural burning is occurring. Outdoor activities are generally more favorable during the wet season, although heavy rainfall can still impact visibility and air quality. The transition months (June and November) often present a mixed picture, with fluctuating conditions and unpredictable air quality.