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Dolisie, the second-largest city in the Republic of the Congo, occupies a crucial position within the Niari region, approximately 70km inland from the Atlantic coastline. Situated at coordinates -4.2006, 12.6792, the city rests on a relatively flat, gently undulating plateau, part of the coastal plain. The surrounding landscape is characterised by dense tropical rainforest, interspersed with savannas as one moves further inland. The Loeme River flows nearby, influencing local humidity and potentially contributing to localised temperature inversions. Dolisie’s growth is linked to its role as a transport hub, connecting the coastal areas with the interior, and a centre for timber and agricultural processing. This industrial and agricultural activity, while economically vital, introduces potential sources of particulate matter and gaseous pollutants. The urban-rural gradient is relatively sharp; the city centre is densely populated, transitioning quickly to agricultural land and forested areas. This proximity to both natural and anthropogenic sources significantly impacts air quality. Dust from unpaved roads, particularly during the drier months, is a common issue. The city’s location, shielded somewhat by the coastal range, can also trap pollutants, exacerbating air quality concerns. The terrain doesn’t offer significant natural ventilation.

Dolisie experiences a tropical climate, defined by distinct wet and dry seasons rather than traditional four seasons. Air quality generally deteriorates during the dry season (June to September) as reduced rainfall leads to increased dust resuspension from unpaved roads and agricultural lands. Lower humidity also means pollutants are less likely to be washed out of the atmosphere. This period sees increased concentrations of particulate matter, impacting respiratory health. The wet season (October to May) typically brings improved air quality, as rainfall effectively cleanses the air. However, even during the wet season, localised pollution from vehicle emissions and small-scale industrial activities persists. November and December often experience high humidity and potential for stagnant air, trapping pollutants near the ground. Temperature inversions, common in the early mornings, can worsen air quality regardless of the season. Sensitive groups – children, the elderly, and those with pre-existing respiratory conditions – should limit strenuous outdoor activity during the dry season, particularly in the late afternoon. Monitoring wind patterns is crucial; winds from agricultural areas can carry dust and smoke into the city. Avoiding peak traffic hours can also reduce exposure to vehicle emissions.