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Dorval, Quebec, a vibrant city nestled on Montreal Island, occupies a strategically important position just west of Montreal’s Trudeau International Airport, significantly influencing its urban character and air quality. The city’s geography is relatively flat, a characteristic of the St. Lawrence Lowlands, with elevations rarely exceeding 100 meters above sea level. This gentle terrain, combined with its proximity to Lake Saint-Louis, a widening of the St. Lawrence River, creates a unique microclimate susceptible to temperature inversions, particularly during colder months. The surrounding landscape is a blend of urban development and pockets of green space, including residential areas, commercial zones, and the expansive Dorval Park. To the east lies the sprawling metropolis of Montreal, a major industrial and transportation hub, while westward stretches a gradual urban-rural gradient transitioning into agricultural lands and smaller settlements. The airport itself represents a significant localized source of emissions, with aircraft movements contributing to both ground-level and upper-atmosphere pollution. The St. Lawrence River acts as a natural corridor for air movement, potentially dispersing pollutants but also capable of concentrating them under specific meteorological conditions. The city’s location within the broader Montreal urban agglomeration means it shares in the regional air quality challenges, influenced by industrial activity further upriver and the overall density of the metropolitan area. The relatively low elevation and flat topography limit vertical mixing, further exacerbating the potential for pollutant accumulation.

Dorval’s air quality experiences a distinct seasonal cycle heavily influenced by Quebec’s continental climate. Winter, spanning December to February, often presents the most challenging conditions. Cold temperatures and frequent high-pressure systems lead to temperature inversions, trapping pollutants near the ground. Reduced solar radiation and shorter daylight hours limit photochemical reactions that would otherwise break down pollutants. Fog, common during these months, further restricts dispersion. Spring (March-May) brings a gradual improvement as temperatures rise and wind patterns become more variable, aiding in pollutant dispersal. However, early spring can still experience lingering inversions. Summer (June-August) generally offers the best air quality, with warmer temperatures promoting atmospheric mixing and increased photochemical degradation of pollutants. Occasional heatwaves can, however, contribute to ozone formation. Autumn (September-November) sees a transition period, with decreasing temperatures and increasing humidity. Leaf litter decomposition releases volatile organic compounds (VOCs), contributing to localized air quality issues. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during winter months, limiting outdoor exposure on days with stagnant air. During summer, monitor for ozone alerts and reduce strenuous outdoor activity during peak ozone hours. The airport's operations are consistent year-round, but the impact is more noticeable during periods of reduced wind and temperature inversions, requiring careful monitoring and mitigation strategies.