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Surubim, nestled in the heart of Pernambuco, Brazil, occupies a strategic position within the Agreste region, a transitional zone between the densely forested Zona da Mata and the arid Sertão. Its coordinates, -7.8331, -35.7547, place it at an elevation of approximately 330 meters above sea level, contributing to a relatively mild climate compared to the lower coastal areas. The surrounding landscape is characterized by undulating hills and valleys, a mosaic of small-scale agriculture, primarily sugarcane and beans, interspersed with patches of caatinga vegetation – a thorny, drought-resistant ecosystem typical of northeastern Brazil. The city itself exhibits a typical Brazilian urban morphology, with a central core radiating outwards, displaying a gradual urban–rural gradient. While not directly adjacent to a major river, Surubim benefits from the presence of smaller streams and seasonal waterways, influencing local humidity and microclimates. The proximity to the industrial belt centered around Petrolina, further north, introduces potential for transported pollutants, although Surubim’s distance mitigates the direct impact. Agricultural practices, including burning of fields after harvest, represent a localized source of particulate matter. The prevailing winds, generally from the northeast, play a crucial role in dispersing or concentrating pollutants, often carrying dust from the Sertão during drier periods. The terrain, with its varied elevations, can create localized areas of stagnant air, particularly during periods of low wind speed, exacerbating air quality challenges. The city’s growth, while moderate, contributes to increased vehicular traffic and associated emissions.

Surubim’s tropical climate dictates a distinct wet and dry season pattern, significantly influencing its air quality. The dry season, typically spanning from August to November, is characterized by reduced rainfall and increased temperatures. This period often witnesses a rise in particulate matter concentrations, primarily due to agricultural burning practices used to clear land for planting and the increased prevalence of windblown dust from the surrounding caatinga and Sertão regions. The lack of rainfall means less atmospheric cleansing, and the drier air allows dust particles to remain suspended for longer. Conversely, the wet season, from December to July, brings frequent rainfall and higher humidity, naturally scrubbing the atmosphere and reducing particulate pollution. During the wettest months (January-March), the increased cloud cover can also reduce solar radiation, impacting photochemical smog formation, though this is less of a concern than particulate matter. Temperature inversions, though not as frequent as in colder climates, can occasionally occur during the dry season, trapping pollutants near the ground, particularly in the valleys surrounding the city. The months of September and October are generally considered the most challenging for air quality due to the combination of agricultural burning and dry, windy conditions. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should limit prolonged outdoor activity during these periods. Increased humidity during the wet season can, however, exacerbate mold allergies for some individuals. Maintaining indoor air quality through proper ventilation and air filtration is advisable throughout the year, but especially during the dry season.