La Source, nestled in the Sud department of Haiti (coordinates 18.0714, -73.9006), occupies a geographically significant position along the southern coast. The town’s urban character is distinctly rural, reflecting its relatively small population of 29,180 and its reliance on agriculture and fishing. Situated near the Massif de la Hotte, a rugged mountain range, La Source benefits from a varied terrain. The elevation gently rises from the coastal plain, influencing local wind patterns and potentially trapping pollutants under certain atmospheric conditions. The town is close to the Caribbean Sea, providing a moderating influence on temperature but also introducing the risk of saltwater intrusion and coastal aerosols. Surrounding La Source is a predominantly agricultural landscape, characterized by small-scale farming of crops like coffee, mangoes, and sugarcane. This agricultural activity, while vital to the local economy, can contribute to air pollution through the burning of agricultural waste and the use of fertilizers. The urban–rural gradient is gradual, with small settlements and agricultural fields extending outwards from the town center. The proximity to the Massif de la Hotte creates a rain shadow effect, potentially impacting rainfall patterns and influencing the dispersion of airborne particles. The coastal location also means La Source is susceptible to dust events originating from the Sahara Desert, which can significantly degrade air quality, particularly during the dry season. The lack of major industrial zones within immediate proximity mitigates some pollution risks, but the reliance on traditional cooking methods using wood or charcoal remains a factor.

La Source’s tropical climate dictates a wet and dry season pattern, profoundly influencing its air quality. The dry season, typically spanning from December to April, presents the most significant air quality challenges. Reduced rainfall leads to lower atmospheric moisture, hindering the natural cleansing effect of precipitation. Furthermore, the prevailing winds during this period often exhibit a weaker, more variable nature, increasing the likelihood of stagnant air masses and the build-up of pollutants. Agricultural burning, a common practice for land clearing and waste disposal, intensifies during the dry season, releasing particulate matter and other harmful emissions. Dust events from the Sahara Desert are also more frequent, further degrading air quality. The wet season, from May to November, brings increased rainfall, which helps to wash pollutants from the atmosphere, leading to improved air quality. However, heavy rainfall can also lead to increased humidity and fog, which can trap pollutants near the ground, particularly in low-lying areas. Temperature inversions, where cooler air is trapped beneath warmer air, are less common but can occur, exacerbating pollution episodes. Months like February and March often experience the poorest air quality due to a combination of agricultural burning and dust events. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should limit outdoor activity during these periods. During the wet season, while overall air quality is generally better, periods of heavy fog or persistent drizzle can still pose a risk, and caution is advised.