Particulate Matter Exposure of Rural Interior Communities as Observed by the First Tribal Air Quality Network in the Yukon Flat

A tribal-owned network of aerosol monitors and meteorological stations was installed at Ts’aahudaaneekk’onh Denh (Beaver), Gwichyaa Zheh (Fort Yukon), Jalgiitsik (Chalkyitsik), and Danzhit Khànlaii (Circle) in the Yukon Flats, Alaska. Surface inversions occurred under calm wind conditions due to radiative cooling. In May, local emissions governed air quality with worst conditions related to road and river dust. As the warm season progressed, worst air quality was due to transport of pollutants from upwind wildfires. During situations without smoke or when smoke existed at layers above the surface inversion, concentrations of particulate matter of less than 2.5 micrometer in diameter or less (PM2.5) were explainable by the local emissions; 24-h means remained below 25 μg·m-3. Absorption of solar radiation in the smoke layer and upward scattering enhanced stability and fostered the persistence of the surface inversions. During smoke episodes without the presence of a surface inversion, daily mean concentrations exceeded 35 μg·m-3 often for several consecutive days, at all sites. Then concentrations temporally reached levels considered unhealthy.