Mixing states and composition of fine aerosol particles in the 2023 Canadian wildfire plumes detected in southern Greenland

Abstract. Rapid climate change has driven an increase in extreme wildfire activity. In 2023, huge wildfires occurred in Canada. Smoke generated by the wildfires was exceptionally severe and was transported to Europe and Eurasia across Greenland. Despite their importance for understanding the global climate, studies investigating aerosols, particularly their mixing states and composition, within the wildfire plumes remain limited. Greenland is an ideal location for studying long-range transport of the Canadian wildfire smoke because of the minimal influence of local wildfire and anthropogenic emissions. In this study, atmospheric observations were conducted in southern Greenland during the summer of 2023. Fine-mode aerosol particles were analyzed using transmission electron microscopy to characterize their mixing states and composition at the individual particle level. The influence from the Canadian wildfire smoke, characterized by an increased abundance of carbonaceous and potassium sulfate particles, was observed when the sampled air mass originated from an area affected by wildfires, contrasting from samples from the background period, which was characterized by sea salt and sulfate. In contrast to the observations from fresh wildfires in previous campaigns that detected many spherical organic particles (tarballs), the carbonaceous particles from the Canadian wildfire were predominantly composed of organic materials embedding numerous small soot particles and potassium sulfate. These samples demonstrate mixing states and individual particle composition of aged aerosol particles from large wildfire plumes that had travelled long distance. This information has implications for interpreting their optical properties and aging processes during long-range transport in the Arctic.