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Aleg, situated in the Brakna region of Mauritania at coordinates 17.0580°N, -13.9090°W, is a small city deeply embedded within the Sahelian zone. The terrain is predominantly flat, characteristic of the Adrar Plateau’s southern fringes, transitioning into the more expansive plains further east. This flatness contributes to limited natural air dispersion. The city’s elevation is relatively low, around 30-50 meters above sea level, further reducing the potential for atmospheric mixing. Aleg lies inland, some distance from the Atlantic coastline, meaning maritime influences on air quality are minimal. The surrounding landscape is primarily savannah grassland and scrubland, interspersed with small-scale agricultural areas focused on millet, sorghum, and livestock rearing. While not a major industrial hub, Aleg serves as a regional market centre, with associated transport activity. The urban-rural gradient is sharp; the city itself is compact, quickly giving way to sparsely populated rural areas. Dust from the Sahara Desert is a significant factor, frequently carried by Harmattan winds, impacting air quality. The lack of substantial vegetation cover exacerbates dust resuspension, and the dry climate limits natural particulate matter removal. The city’s location within a broad river valley, though not immediately adjacent to a major water body, can experience localised humidity variations that affect pollutant behaviour.

Aleg experiences a distinct wet and dry season, heavily influencing air quality. The dry season, roughly from November to June, is characterised by consistently high temperatures and the prevalence of Harmattan winds originating from the Sahara. These winds bring substantial amounts of dust, significantly degrading air quality and causing respiratory irritation. February to May are typically the worst months for dust exposure, with visibility often reduced. The wet season, spanning July to October, offers temporary relief. Rainfall suppresses dust, but increased humidity can promote the growth of moulds and mildews, potentially triggering allergic reactions. While the rain washes particulate matter from the air, it also creates muddy conditions, increasing vehicle emissions as vehicles struggle on unpaved roads. Temperature inversions, common during the cooler nights of the dry season, trap pollutants near the ground, worsening conditions. The transition periods – November and July – are often marked by fluctuating conditions. Sensitive groups, including children, the elderly, and those with pre-existing respiratory conditions, should limit outdoor activity during peak dust periods (February-May) and take precautions during the wet season to avoid mould exposure. Monitoring local weather patterns is crucial for anticipating air quality changes.