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Lunsar, nestled in Sierra Leone’s Northern Province, occupies a geographically significant position within the country’s interior. Located at approximately 8.6844° N, -12.5350° W, the town sits on a gently undulating plateau, part of the larger Freetown Peninsula’s hinterland. The surrounding landscape is predominantly characterized by rolling hills covered in a mix of secondary forests, agricultural land, and small-scale mining operations – particularly for bauxite. Lunsar’s elevation, while not exceptionally high, contributes to localized microclimates and influences air circulation patterns. The town is not directly adjacent to any major river or lake, though smaller streams and seasonal waterways crisscross the region, impacting humidity levels. The urban–rural gradient around Lunsar is relatively sharp; the town itself represents a concentrated population center, quickly transitioning to dispersed rural settlements engaged in subsistence farming and artisanal mining. This proximity to agricultural zones means that seasonal burning practices, often used for land clearing, can significantly impact local air quality. Further afield, the region’s bauxite mining activities, while economically important, introduce particulate matter into the atmosphere. The prevailing winds, generally from the southwest during the wet season, can carry pollutants from mining sites and agricultural areas into Lunsar, while the drier season often sees stagnant air conditions, exacerbating localized pollution. The terrain’s topography, combined with these land use patterns, creates a complex interplay affecting air quality dynamics.

Lunsar’s tropical climate dictates a distinct wet and dry season cycle, profoundly influencing its air quality. The wet season, typically spanning from May to October, brings increased rainfall and higher humidity, generally leading to a temporary reduction in particulate matter as precipitation washes pollutants from the atmosphere. However, the wet season also coincides with increased agricultural activity, including burning of vegetation for land preparation, which releases significant amounts of smoke and carbon monoxide. The monsoon-like southwest winds can then transport this smoke across the region, impacting Lunsar’s air quality. The dry season, from November to April, presents a different challenge. Lower rainfall and reduced vegetation cover mean less natural cleansing of the atmosphere. Temperature inversions, common during the cooler nights of the dry season, trap pollutants near the ground, leading to periods of stagnant air and potentially elevated concentrations of particulate matter and other emissions. Fog, occasionally forming in the mornings, further restricts air movement and concentrates pollutants. During the dry season, particularly in January and February, outdoor activities should be approached with caution, especially for children, the elderly, and individuals with respiratory conditions. The increased dust from mining operations during the dry season also contributes to air quality concerns. While the wet season offers some respite, the associated burning practices pose a significant and recurring air quality challenge, demanding sustainable agricultural practices to mitigate its impact.