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Edmundston, New Brunswick, sits nestled in a valley along the Saint John River, a defining geographical feature influencing its air quality. The city’s location in northwestern New Brunswick places it within a transitional zone between the Appalachian Mountains and the flatter, more agricultural lands of the Saint John River Valley. Elevation is relatively low, averaging around 160 meters above sea level, contributing to potential temperature inversions, particularly during colder months. Surrounding Edmundston are extensive boreal forests, a significant source of biogenic volatile organic compounds (BVOCs) which, while natural, can contribute to ozone formation in the presence of sunlight and nitrogen oxides. The urban-rural gradient is fairly sharp; the city itself is compact, quickly giving way to forested areas and smaller rural communities. Historically, Edmundston’s economy was heavily reliant on forestry and pulp & paper mills, though diversification is occurring. While large-scale industrial emissions have decreased, legacy effects and ongoing operations still play a role in local air quality. The proximity to the US border (Madawaska, Maine) also means that transboundary air pollution events are possible, influenced by prevailing wind patterns. The river itself doesn’t directly contribute to particulate matter, but its valley can channel air masses, concentrating pollutants during stagnant conditions.

Edmundston experiences a pronounced seasonal air quality pattern dictated by its continental climate. Winter, from December to February, often sees the best air quality, despite wood burning for heating. Cold temperatures promote atmospheric mixing, dispersing pollutants, and reduced biogenic emissions from forests. However, temperature inversions can trap pollutants near the ground during calm, clear nights. Spring (March-May) brings increased pollen counts, impacting those with allergies, and potential for dust from snowmelt and agricultural activity. Summer (June-August) is when ozone formation is most likely, driven by sunlight and warmer temperatures reacting with emissions from vehicles and industry. High humidity can exacerbate these conditions. August often sees peak ozone levels. Fall (September-November) presents a mix; decreasing temperatures improve ozone levels, but wood smoke from heating becomes more prevalent. October and November can experience periods of stagnant air, leading to localized pollution build-up. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit strenuous outdoor activity during summer afternoons and periods of wood smoke advisories. Monitoring wind direction is crucial, as pollutants can drift from nearby sources.