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Somasso, nestled within the Ségou Region of Mali, occupies a geographically significant position at the edge of the Niger River floodplain. Located at approximately 12.87°N, 5.60°W, the city’s terrain is predominantly flat, characteristic of the Sahelian zone, with gentle undulations reflecting the alluvial deposits left by the Niger’s seasonal flooding. The surrounding landscape is a mosaic of savanna grasslands, interspersed with gallery forests along the riverbanks and pockets of cultivated land. Somasso’s proximity to the Niger River, while providing vital water resources and facilitating transportation, also influences local air quality. The river’s presence moderates temperatures slightly, but also contributes to humidity, which can trap pollutants under certain meteorological conditions. The urban fabric of Somasso is a blend of traditional mud-brick architecture and more modern constructions, reflecting its evolving status as a regional market town. Agriculture dominates the surrounding rural areas, with extensive cultivation of millet, sorghum, and maize. This agricultural activity, coupled with the use of traditional cooking methods relying on wood and charcoal, contributes to localized particulate matter emissions. The urban–rural gradient is relatively sharp, with the intensity of human activity and associated pollution increasing noticeably as one approaches the city center. The lack of significant elevation changes means that air pollutants tend to disperse horizontally, rather than vertically, potentially leading to prolonged exposure in areas downwind of emission sources. The region's semi-arid climate and prevailing wind patterns further shape the city's air quality profile.

Somasso’s air quality is inextricably linked to its tropical wet and dry climate. The dry season, typically spanning from November to May, presents the most significant air quality challenges. During these months, reduced rainfall and lower humidity create conditions conducive to the accumulation of particulate matter. Wind speeds are often lower, hindering pollutant dispersion, and temperature inversions can occur, trapping emissions close to the ground. The burning of agricultural residues after harvest, a common practice in the surrounding areas, dramatically increases PM2.5 and PM10 levels. Traditional cooking methods using wood and charcoal, prevalent in both urban and rural households, are also major contributors. The wet season, from June to October, brings relief as increased rainfall washes away particulate matter and higher humidity reduces the concentration of dust. However, periods of intense rainfall can lead to flooding, which can stir up sediment and temporarily degrade air quality. Fog, particularly in the early morning during the transition periods between seasons, can also trap pollutants, creating localized pockets of poor air quality. The months of February and March, coinciding with the end of the harvest and the onset of the dry harmattan winds, are generally the most challenging for air quality. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should limit outdoor activity during these periods and consider using face masks. Maintaining good ventilation indoors and avoiding exposure to smoke from cooking fires are also crucial preventative measures.