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Bignona, nestled within the Ziguinchor Region of Senegal, occupies a geographically significant position at approximately 12.81° N, 16.23° W. The city’s terrain is predominantly low-lying, characteristic of the Casamance River delta, with elevations rarely exceeding 30 meters above sea level. This flatness, coupled with its proximity to the Atlantic Ocean and the Casamance River, significantly influences local air quality. The surrounding landscape is a mosaic of dense mangrove forests, fertile agricultural lands, and small villages, creating a distinct urban-rural gradient. Bignona itself exhibits a relatively compact urban footprint, reflecting its smaller population of around 22,000. The Casamance River acts as a natural barrier to the east, while the Atlantic coastline lies to the west, impacting prevailing wind patterns and potential salt spray deposition. Agriculture is a dominant land use in the immediate vicinity, with rice cultivation and cashew farming being particularly prevalent. These agricultural practices, while vital to the regional economy, can contribute to localized air pollution through the use of fertilizers and the burning of agricultural residues, particularly during harvest seasons. There are no major industrial belts directly adjacent to Bignona; however, Ziguinchor, the regional capital, lies approximately 30 kilometers north, and occasional industrial emissions from that area can be transported southward, impacting Bignona’s air quality. The deltaic environment also means that the soil is often saturated, potentially affecting the dispersion of pollutants and creating stagnant air pockets during certain weather conditions.

Bignona’s tropical climate dictates a distinct wet and dry season cycle, profoundly influencing its air quality profile. The dry season, typically spanning from November to May, is characterized by lower humidity and increased sunshine hours. While this might seem beneficial, the lack of rainfall allows dust and particulate matter to accumulate, leading to periods of reduced visibility and potentially impacting respiratory health. Wind patterns during this period are often variable, sometimes resulting in stagnant air conditions, particularly in the low-lying areas near the river. The harmattan wind, a dry and dusty trade wind originating from the Sahara, can occasionally impact Bignona during January and February, significantly increasing particulate matter concentrations. Conversely, the wet season (June to October) brings frequent rainfall, which naturally washes pollutants from the atmosphere, leading to a general improvement in air quality. However, heavy downpours can temporarily disrupt traffic and increase vehicle emissions. Fog, though infrequent, can form during the transition periods between seasons, trapping pollutants near the ground. Sensitive groups, including children, the elderly, and individuals with pre-existing respiratory conditions, should exercise caution during the dry season, particularly during periods of high dust or stagnant air. Outdoor activities are generally more favourable during the wet season, although vigilance regarding traffic-related pollution remains important. The agricultural burning practices, common during the transition to the dry season, can create localized spikes in air pollution, so awareness of these events is crucial.