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Mont-de-Marsan, the préfecture of the Landes department in Nouvelle-Aquitaine, France, occupies a geographically significant position within the southwestern European landscape. Situated at approximately 43.89°N, -0.50°W, the city rests on a gently undulating plateau, part of the Aquitaine Basin, characterized by a relatively low elevation averaging around 60 meters above sea level. This plateau is bordered by the Adour River to the north and the Landes Forest, one of Europe’s largest continuous pine forests, to the south. The surrounding landscape is predominantly rural, a mosaic of agricultural fields (primarily maize and potatoes) and extensive pine plantations, creating a distinct urban–rural gradient. The Landes Forest acts as a significant carbon sink and influences local humidity, but also contributes to particulate matter from controlled burns during certain times of the year. Mont-de-Marsan’s location within the broader Aquitaine Basin means it’s somewhat sheltered from strong Atlantic winds, though prevailing westerly breezes still play a role in air circulation. Historically, the city served as a crossroads, and while industrial activity is not as pronounced as in larger French cities, there are agricultural processing facilities and some light industry contributing to localized emissions. The relatively flat terrain and limited topographical barriers can, under certain meteorological conditions, lead to the stagnation of pollutants, particularly during periods of temperature inversion. The proximity to both agricultural land and the extensive forest creates a complex interplay of potential pollution sources and natural air purification mechanisms.

Mont-de-Marsan’s air quality exhibits a distinct seasonal pattern largely dictated by meteorological conditions. Spring (March-May) often sees a gradual improvement as temperatures rise and winds increase, dispersing accumulated winter pollutants. However, agricultural activities, including fertilizer application and pesticide spraying, can contribute to localized spikes in ammonia and volatile organic compounds. Summer (June-August) typically brings drier conditions and higher temperatures, which can exacerbate ozone formation, particularly during heatwaves. Stagnant air masses are not uncommon, potentially trapping pollutants near ground level. Autumn (September-November) is arguably the most challenging period. Controlled burns in the Landes Forest, a traditional practice for forest management, release significant quantities of particulate matter, impacting air quality considerably. Temperature inversions, common during this season, trap these particles close to the ground. Winter (December-February) often brings cooler temperatures and increased humidity, which can lead to fog formation. While this fog can help to trap pollutants, it also facilitates their removal through wet deposition (rain and snow). Sensitive individuals, such as those with respiratory conditions or young children, should exercise caution during autumn and summer, particularly during periods of forest burning or heatwaves. Limiting strenuous outdoor activity during these times and monitoring local air quality reports are advisable. The generally mild climate means that prolonged periods of severe pollution are less frequent than in more industrialized regions, but awareness of seasonal variations remains crucial for public health.