Sources and Processes Influencing Local Arctic Wintertime Air Pollution

International audience; Wintertime Arctic air pollution is influenced by long-range transport of remote sources and local within-Arctic sources contributing to the build up of Arctic haze. Local emissions and resulting ground-level pollutant abundances are enhanced during cold winters especially during cold stable episodes with strong surface temperature inversions and light winds that limit pollutant dispersion, and lead to air quality exceedances. Fairbanks in Interior Alaska is a city with episodes of severe wintertime pollution. However, there are many uncertainties in our understanding about pollution sources and secondary aerosol formation under cold, dark winter conditions, when photochemistry is limited. The role of meteorological processes in the Arctic boundary layer is also poorly understood and often difficult to model. These issues were comprehensively examined through the collection of datasets on atmospheric composition and meteorology during the international ALPACA (Alaskan Layered Pollution and Chemical Analysis) field campaign in January and February 2022 in Fairbanks. One goal is to understand how meteorological processes influence surface, and vertical distributions, of aerosols and trace gases. Here, we analyze a combination of measurements collected at sites experiencing different pollution levels, including surface aerosol composition, trace gas profiles collected on a tethered balloon (EPFL helikite), wind lidar and other meteorological measurements. An overview of the different measurements will be presented as a function of meteorological conditions, in particular atmospheric stability. Particular episodes will be highlighted showing evidence for vertical exchange (turbulence) or possible influence from elevated power plant stack emissions. Particle dispersion modelling is used to examine emission sources contributing to surface pollution episodes and elevated plumes. The regional extent of pollution from the Fairbanks area will also be considered and compared to pollutant levels in background Arctic Haze air masses. This study contributes to air Pollution in the Arctic: Climate, Environment and Societies (PACES)-ALPACA. The French contribution is part of the CASPA (Climate-relevant Aerosol Sources and Processes in the Arctic)/IPEV project.