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Ntoum, nestled within the Estuaire Province of Gabon, occupies a geographically significant position at the confluence of the Komo River and the Atlantic Ocean. Its coordinates (0.3905, 9.7610) place it within a low-lying coastal plain, characterized by a gently undulating terrain rarely exceeding 30 meters above sea level. The city’s urban fabric is interwoven with the riverine landscape, with the Komo providing vital transportation routes and influencing local microclimates. Surrounding Ntoum is a mosaic of dense tropical rainforest and mangrove forests, typical of the Gabonese coastal ecosystem. This proximity to extensive vegetation generally acts as a natural air filter, absorbing pollutants and releasing oxygen, though deforestation in surrounding areas can disrupt this balance. The Estuaire Province is a key agricultural region, with palm oil plantations and small-scale farming prevalent in the areas surrounding Ntoum. This agricultural activity, while economically important, can contribute to localized air pollution through the burning of vegetation and the use of fertilizers. Further inland, the landscape gradually transitions to higher ground and denser forest. Ntoum’s location on the coast also exposes it to maritime influences, including sea breezes and occasional salt spray, which can impact air quality. The urban–rural gradient is relatively sharp, with the city’s built environment quickly giving way to the natural landscape, though increasing population density is slowly encroaching on previously rural areas, potentially altering the natural air purification processes. The city’s position within a humid tropical climate also influences atmospheric stability and pollutant dispersion.

Ntoum experiences a distinct wet and dry season, profoundly impacting its air quality profile. The dry season, typically spanning from June to September, often sees a slight increase in particulate matter. This is largely attributable to reduced rainfall, which limits the natural cleansing effect of precipitation, and increased dust lifted by drier winds. Agricultural burning, a common practice during this period for land preparation, also contributes significantly to localized pollution events. The relative lack of cloud cover during the dry season can also lead to higher surface temperatures, promoting photochemical reactions that form ground-level ozone, although this is less pronounced than in more temperate climates. Conversely, the wet season (October to May) brings frequent rainfall, effectively scrubbing the atmosphere and reducing overall pollution levels. High humidity during this period can, however, trap pollutants closer to the ground, creating localized pockets of poor air quality, particularly in areas with limited ventilation. Fog, a relatively infrequent occurrence, can exacerbate this effect by further restricting pollutant dispersion. The prevailing winds, generally from the south-west, play a crucial role in transporting pollutants, often bringing maritime air inland. During the transition months (May and September), wind patterns can be more variable, leading to unpredictable air quality fluctuations. Sensitive groups, such as children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly during periods of agricultural burning, and be mindful of localized fog events during the wet season. Outdoor activities are generally more favourable during the wet season, although vigilance regarding localized pollution pockets remains important.