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Réo, situated in the Centre-Ouest region of Burkina Faso at coordinates 12.3167° N, -2.4667° W, presents a compelling case study in urban geography and its influence on air quality. The city’s location, approximately 15 kilometers northeast of Ouagadougou, the national capital, places it within a transitional zone between the Sudanese savanna and the northern fringes of the Guinean woodlands. This dictates a predominantly flat terrain, averaging around 300 meters above sea level, which, while minimizing topographic barriers to air circulation, can also contribute to pollutant accumulation under certain meteorological conditions. Réo’s immediate surroundings are characterized by a mosaic of agricultural land – primarily millet, sorghum, and maize cultivation – interspersed with acacia savanna. This agricultural activity, particularly during harvesting and burning seasons, represents a significant potential source of particulate matter. The urban–rural gradient is relatively sharp, with the city transitioning quickly into agricultural fields and sparse vegetation. While Réo lacks direct proximity to major rivers or lakes, its reliance on groundwater for water supply highlights the interconnectedness of environmental factors. The city’s position relative to Ouagadougou means it is susceptible to the spillover of industrial and vehicular emissions from the capital, especially during periods of high traffic volume. The prevailing winds, generally from the south-southwest, can transport pollutants from Ouagadougou towards Réo, exacerbating local air quality challenges. The relatively open landscape, however, also allows for some degree of dispersion, mitigating the impact to a degree.

Réo’s tropical savanna climate dictates a distinct wet and dry season cycle, profoundly impacting its air quality. The dry season, typically spanning from November to May, is characterized by lower rainfall and higher temperatures, often accompanied by periods of intense heat. This season frequently witnesses a significant increase in particulate matter concentrations. The lack of rainfall allows dust and smoke from agricultural burning to persist in the atmosphere, with controlled burns for land clearing and crop residue disposal being a major contributor. Temperature inversions, common during the cooler nights of the dry season, trap pollutants near the ground, further worsening air quality. The Harmattan wind, a dry, dusty trade wind blowing from the Sahara, can also transport large quantities of dust and sand into the region, significantly degrading air quality. Conversely, the wet season (June to October) brings relief through frequent rainfall, which naturally washes pollutants from the atmosphere. Higher humidity and cloud cover can also reduce solar radiation, impacting photochemical reactions that contribute to ozone formation. While the wet season generally offers improved air quality, periods of heavy rainfall can lead to flooding and the release of pollutants from stagnant water sources. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly during agricultural burning periods (typically December-February). Limiting outdoor exertion and wearing masks can help mitigate exposure. During the wet season, while overall air quality is better, vigilance regarding waterborne diseases is crucial.