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Poço Branco, nestled in the heart of Rio Grande do Norte, Brazil, occupies a geographically significant position within the Agreste region, a transitional zone between the semi-arid hinterland and the coastal plains. Located at approximately -5.6228° latitude and -35.6628° longitude, the city’s terrain is characterized by undulating hills and valleys, typical of the region's weathered sandstone bedrock. The elevation averages around 450 meters above sea level, contributing to localized microclimates and influencing air circulation patterns. Poço Branco is surrounded by a landscape dominated by caatinga vegetation, a unique thorny scrubland adapted to arid conditions. This vegetation, while resilient, can contribute to particulate matter during the dry season through natural processes like leaf shedding and wind erosion. The city’s proximity to the Rio Piranhas, though not directly adjacent, influences regional humidity and can impact atmospheric stability. The urban–rural gradient around Poço Branco is relatively sharp; the city transitions quickly into agricultural lands primarily used for subsistence farming and livestock grazing, with some commercial cultivation of fruits and vegetables. While Poço Branco itself lacks major industrial zones, it serves as a regional hub for agricultural processing, which can introduce localized emissions. The prevailing winds, generally from the northeast, carry air masses across the caatinga, potentially transporting dust and pollutants from surrounding areas, impacting air quality within the city limits. The relatively open landscape allows for some dispersion, but topographic features can also trap pollutants under certain meteorological conditions.

Poço Branco experiences a distinctly tropical climate with a pronounced wet and dry season, significantly impacting its air quality profile. The dry season, typically spanning from August to November, is characterized by intense solar radiation, high temperatures, and minimal rainfall. This period often sees a rise in particulate matter concentrations due to increased wind erosion from the surrounding caatinga and agricultural lands. The lack of rainfall prevents the natural cleansing effect of precipitation, allowing dust and other pollutants to accumulate. Temperature inversions, common during the cooler nights of the dry season, can trap pollutants near the ground, exacerbating the situation. Conversely, the wet season (December to July) brings frequent rainfall and higher humidity, which naturally washes away particulate matter and reduces dust levels, leading to improved air quality. However, heavy rainfall events can occasionally lead to localized flooding and the release of pollutants from inundated areas. The months of February and March, coinciding with the transition between seasons, can be particularly challenging, with periods of intense heat and dust storms. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, limiting outdoor activities during peak sunlight hours and avoiding areas with high dust levels. During the wet season, while generally cleaner, vigilance is still advised during periods of heavy rainfall and potential flooding.