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Mahatsinjo, nestled within the Mahajanga Province of Madagascar, occupies a geographically unique position on the Mozambique Channel coastline. Located at approximately -17.7487° latitude and 47.0172° longitude, the city’s terrain is characterized by a gently sloping coastal plain, transitioning inland to low hills and savannas. This relatively flat topography, combined with its proximity to the Mozambique Channel, significantly influences local air quality patterns. The surrounding landscape is dominated by extensive mangrove forests along the coast, providing a natural buffer but also a potential source of biomass burning during dry periods. Inland, agricultural zones, primarily focused on vanilla, rice, and cashew cultivation, contribute to localized emissions, particularly from fertilizer use and field burning practices. Mahatsinjo’s urban footprint is small, reflecting its limited population of around 14,675, creating a gradual urban-rural gradient. The city’s position within a broader agricultural region means that agricultural activities, rather than large-scale industrial belts, are the primary drivers of regional air pollution. The prevailing trade winds, generally blowing from the east, transport pollutants both onshore and offshore, impacting air quality depending on the season and intensity of these winds. Elevation is minimal, rarely exceeding 30 meters above sea level, which limits dispersion of pollutants and can exacerbate ground-level concentrations. The coastal location also means the city is susceptible to sea breezes, which can temporarily improve air quality by flushing out pollutants, but also introduce salt aerosols.

Mahatsinjo’s tropical climate dictates a distinct wet and dry season cycle, profoundly impacting its air quality. The dry season, typically spanning from May to October, presents the greatest air quality challenges. Reduced rainfall leads to increased dust levels from exposed soil, particularly from agricultural fields and unpaved roads. Agricultural burning, a common practice for land clearing and residue disposal, intensifies during this period, releasing significant quantities of particulate matter and volatile organic compounds. The lack of consistent rainfall also limits the natural cleansing effect of precipitation. Conversely, the wet season (November to April) generally brings improved air quality. Frequent rainfall effectively washes pollutants from the atmosphere, and higher humidity can suppress dust generation. However, periods of prolonged fog, particularly in the transitional months, can trap pollutants near the ground, leading to localized episodes of reduced visibility and potentially elevated concentrations of certain pollutants. Wind patterns also play a crucial role; stronger easterly trade winds during the dry season can disperse pollutants, while calmer conditions can lead to stagnation. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly during periods of agricultural burning. Limiting outdoor exertion and wearing masks can help mitigate exposure. The transitional months, with their potential for fog, require vigilance, as localized air quality can deteriorate rapidly.