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Ségou, a city of approximately 16,000 inhabitants in the Atlantique Department of Benin, occupies a crucial position within the country’s agricultural heartland. Located at coordinates 6.6167° N, 2.2167° E, the city sits on the inner Niger Delta floodplains, a relatively flat terrain characterized by fertile alluvial soils. This low elevation, coupled with its proximity to the Niger River, significantly influences local climate and air quality. The surrounding landscape is dominated by savannah grasslands and seasonally flooded areas, transitioning to more densely vegetated zones further from the river. Ségou isn’t a major industrial centre, but serves as a vital market town for agricultural produce, meaning significant dust from handling and transport of crops is a consistent factor. The urban-rural gradient is quite sharp; the city core quickly gives way to agricultural fields and smaller villages. This proximity to agricultural activity introduces potential for particulate matter from burning agricultural waste and the use of fertilizers. The prevailing winds, influenced by the Harmattan from the Sahara and the moist air masses from the Atlantic, play a key role in dispersing or concentrating pollutants. The flat topography limits natural ventilation, potentially exacerbating pollution episodes during calm periods.

Ségou experiences a distinct wet and dry season, heavily influencing its air quality. The dry season, roughly November to April, is characterized by the Harmattan wind, bringing Saharan dust southward. This leads to elevated particulate matter (PM10 and PM2.5) levels, peaking between December and February. Reduced rainfall during this period also means less atmospheric cleansing. January and February are generally the least favourable months for outdoor activity, particularly for those with respiratory conditions. The transition period, April-May, sees increasing humidity and sporadic rainfall, offering temporary relief. The wet season, June to October, brings significant rainfall and higher humidity, effectively washing away much of the accumulated dust and pollutants. Air quality generally improves dramatically during these months, with September and October being the most favourable for outdoor activities. However, increased humidity can also promote mold growth, potentially triggering allergic reactions. Temperature inversions, common during the cooler, drier nights, can trap pollutants near ground level, even during the wet season. Sensitive groups – children, the elderly, and those with pre-existing respiratory illnesses – should take extra precautions during the dry season and periods of calm weather.