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Diéma, nestled within the Kayes Region of Mali, occupies a strategic position on the Niger River’s floodplain, a landscape profoundly shaping its urban character and air quality. Located at approximately 14.5333° N, 9.2000° W, the city sits at an elevation of roughly 220 meters (720 feet) above sea level, contributing to a relatively flat terrain characteristic of the Sahelian zone. The surrounding landscape is dominated by the expansive floodplains of the Niger River and the transition zone between the Sahel and Sudan savannas, a mosaic of grasslands, scattered acacia trees, and agricultural fields. This proximity to the river provides a vital water source for both the city and the surrounding agricultural communities, supporting a significant rural-urban gradient. Diéma’s location within a semi-arid climate zone means that agricultural practices, particularly the burning of vegetation after harvests, can significantly impact local air quality. While Diéma itself is a relatively small urban center, it serves as a regional market town, attracting agricultural produce from the surrounding areas. The gradual urban-rural transition is evident in the surrounding villages, which are increasingly linked to Diéma’s economy. The prevailing winds, often influenced by the Harmattan during the dry season, can transport dust and pollutants from distant sources, further complicating the city’s air quality profile. The lack of significant industrial belts within immediate proximity mitigates some pollution risks, but the reliance on biomass for cooking and heating remains a key factor.

Diéma’s air quality follows a distinct seasonal pattern dictated by its tropical savanna climate. The dry season, spanning roughly November to May, presents the most challenging conditions. During this period, reduced rainfall and lower humidity contribute to increased dust concentrations, exacerbated by the Harmattan winds which blow from the Sahara, carrying fine particulate matter across vast distances. Temperature inversions, common during the cooler nights of December and January, trap pollutants close to the ground, intensifying localized air quality issues. The burning of agricultural residues after harvests, a traditional practice, releases significant amounts of smoke and particulate matter into the atmosphere, particularly in February and March. Conversely, the wet season (June to October) brings a period of relative improvement. Frequent rainfall effectively washes pollutants from the air, and higher humidity reduces dust levels. However, periods of intense rainfall can lead to flooding, which can release mold spores and other allergens, impacting air quality for sensitive individuals. The monsoon season, while beneficial in terms of overall air quality, can also bring localized issues related to stagnant water and breeding grounds for mosquitoes. Outdoor activities are generally best enjoyed during the wet season, particularly in July and August. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, limiting prolonged outdoor exposure and considering the use of face masks when dust levels are high. The transition months of May and November present a moderate risk, with fluctuating conditions.