Supplementary material to "Measurement report: Role of Organic Coating and Chemical Composition on Ice Nucleation Potential of Atmospheric Particles in European Arctic"

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Individual particles were classified based on their elemental composition (as atomic %) obtained from SEM-EDX measurements (Figure S2).Particles containing both phosphorus and potassium ≥ 0.4 at.% were identified as biogenic.The remaining non-biogenic particles were categorized into dust-laden, Na-laden, non-dust, and other groups.Dust-laden particles were defined by elevated mineral content ([Al, Si, Fe, Ca] ≥ 4 at.% and > [Na]) and were subdivided into dust ([C, N, O] < 85 at.%) and aged dust ([C, N, O] ≥ 85 at.%), the latter further classified as carbonaceous-coated dust ([S] < 1 at.%) or sulfate-rich dust ([S] ≥ 1 at.%).Na-laden particles were defined by [Na] > 1 at.% and [Na] ≥ [Al, Si, Fe, Ca], and were classified as Na-rich when [Na] ≥ [S] or as Na-rich sulfates when [Na] < [S]. Among non-dust particles ([Al, Si, Fe, Ca] < 4 at.%),those dominated by [C, N, O, S] (> 99 at.%) with [S] ≥ 0.5 at.% were classified as sulfates, while those dominated by [C, N, O] (> 99 at.%) were classified as carbonaceous.Particles that did not meet any of the above criteria were grouped as other. S2. Surface Type Influence and Free-Tropospheric Residence from FLEXPART Back-TrajectoriesWe used FLEXPART back-trajectory analysis to estimate the surface type influence and free-tropospheric (FT) residence time for ground-level aerosol samples (SA1-SA5) over a 168-hour period.The calculated percentages represent the time air masses spent over closed ice, open ice, open water, and land, as well as the duration spent in the FT, based on ERA5 reanalysis data and back-trajectory altitudes relative to the boundary layer (Table S3).Additionally, black carbon contributions were inferred from source apportionment using ERA5 sea ice edge data combined with back-trajectory analysis (Figure S3 and Table S4).These metrics provide critical context for understanding the origin, transport pathways, and potential ageing processes of sampled aerosols, which are important for interpreting their observed ice-nucleating properties.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.