Unveiling single-particle composition, size, shape, and mixing state of freshly emitted Icelandic dust via electron microscopy analysis

Abstract. Iceland is a major high-latitude dust source area. Airborne Icelandic dust influences the climate system via interacting with radiation, clouds, and biogeochemical systems, impacts the snow/ice albedo, and air quality. These impacts are sensitive to its mineralogical, chemical, and physical composition. However, comprehensive particle measurement and analysis of Icelandic dust is still limited. This study examines dust samples collected during a field campaign in the Dyngjusandur desert (August–September 2021) using active and passive aerosol sampling. Over 190,000 individual particles, ranging from 0.1 to 120 µm, were analyzed for their chemical and physical properties using scanning electron microscopy/energy dispersive X-ray spectroscopy (ccSEM/EDX). Results show heterogeneity in particle size, shape, and composition. The most abundant particle type was Medium-Al mixed particles, likely glass-like, comprising 35–93 % of the aerosol volume. Sulfate particles, suggesting volcanic contributions, were detected in some samples. Iron (Fe) and titanium (Ti)-rich particles made up 3.5 % and 1.8 % of the aerosol volume, respectively, mainly in the fine fraction. The median aspect ratio ranged from 1.37 to 1.53, increasing with particle size. Our findings highlight key differences in Icelandic dust compared to Moroccan dust, including higher iron and titanium content and a lack of potassium in Icelandic dust. Additionally, Icelandic dust shows a size-dependent increase in aspect ratio, unlike Moroccan dust, which remains constant. These observations can improve model simulations of high-latitude dust’s role in the Earth system.