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Montivilliers, nestled in the heart of Normandy, France, presents a fascinating case study in how geography shapes urban air quality. Situated approximately 15 kilometers northeast of Rouen, the regional capital, it occupies a relatively low-lying position within the Pays de Caux, a gently undulating coastal plain. The coordinates 49.5469° N, 0.1889° E place it close to the Seine Estuary, influencing local weather patterns and potential pollutant transport. The surrounding landscape is predominantly agricultural, characterized by fertile fields and pastures, a typical feature of the Norman countryside. This proximity to agricultural zones introduces potential sources of ammonia and particulate matter from farming activities, particularly during planting and harvesting seasons. The urban–rural gradient is gradual; Montivilliers itself is a small, primarily residential town, but its nearness to Rouen means it’s impacted by the larger city’s industrial and transportation emissions. The town’s elevation is minimal, generally below 50 meters, which can exacerbate the trapping of pollutants, especially during periods of temperature inversion. The presence of the Seine River, while providing a scenic backdrop, can also contribute to localized humidity and fog formation, impacting pollutant dispersion. The regional industrial belt, concentrated around Rouen, contributes to background levels of nitrogen oxides and sulfur dioxide, which are then subject to local meteorological conditions and topography. The relatively flat terrain limits natural ventilation, potentially leading to pollutant accumulation under certain weather scenarios.

Montivilliers’ air quality experiences a distinct seasonal cycle heavily influenced by regional weather patterns. Winter months (December-February) often see the poorest air quality, primarily due to temperature inversions. Cold, stable air becomes trapped near the ground, preventing vertical mixing and concentrating pollutants released from Rouen’s industrial activity and local heating systems. Fog, common during these months, further restricts dispersion. Spring (March-May) brings a gradual improvement as temperatures rise and wind speeds increase, dispersing pollutants more effectively. Agricultural activities, however, can introduce ammonia emissions during this period. Summer (June-August) generally offers the best air quality, with frequent sunshine, higher temperatures, and prevailing winds that efficiently flush out pollutants. However, occasional heatwaves can lead to stagnant air conditions and ozone formation. Autumn (September-November) presents a transitional period. As temperatures cool, the risk of temperature inversions returns, though typically less severe than in winter. Rainfall is more frequent, which can help to wash pollutants from the atmosphere. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should be particularly cautious during winter and early spring, limiting outdoor exertion on days with visible fog or stagnant air. During the warmer months, while generally favorable, monitoring for ozone alerts is advisable, especially during heatwaves. The agricultural cycle dictates periods of heightened ammonia levels, impacting air quality, particularly in the spring and autumn. Overall, understanding these seasonal variations is crucial for managing potential health risks associated with air pollution in Montivilliers.