## 3 Results
### TEM/EDX Analysis  
The deposition method resulted in a surface density of approximately \(10^{4}\) nanoparticles per square millimeter. The particle size distribution at the nanoscale is illustrated in Figure 2: no significant variation was observed across the collected samples. Particles of different origins were observed: based on their composition and morphology, the particles were classified as biological, mineral dust, S-rich, sea salt, carbonaceous, and metal oxide nanoparticles, with mineral dust being the most abundant class, followed by carbonaceous nanoparticles. Table 1 summarizes the types of particles, including their structural/morphological properties, size, and sampling locations. Representative TEM images of these categories are illustrated in Figure 3.  
Diatoms and marine salts were predominantly identified in the samples collected near the coast (sample D), indicating a significant influence of marine aerosols on the composition of the snow. Additionally, S-rich particles were abundant in the sample closest to the coast, and their origin could be attributed to marine phytoplankton, as reported in a previous study [28]. As represented by the HAADF image and EDX maps (Figure 4), numerous mineral dust particles and aggregates, characterized by irregular shapes and sharp edges, were identified in all samples. These particles were mainly constituted by O, Na, Si, Al, Ca, P, K, Mg, and Fe, and their origins were attributed to natural geological processes, meaning they originated from the Earth's crustal surface and were further dispersed through LRAT [6; 7]. Figure 2: The size distribution of the nanoparticles in the snow samples. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Particle Types** & **Major Elements** & **Structure and Morphology** & **Size** & **Samples** \\ \hline Biological & O, SI, Al & Amorphous, mainly diatoms & \textgreater{}500 nm & D \\ Mineral dust & O, Na, Si, Al, Ca, P, K, & Crystalline and amorphous, irregular & \textgreater{}10 nm & All samples \\ Mg, Fe & shapes with sharp edges & & \\ S-rich & Mainly S, minor Cl, Si & Amorphous, sponge-like morphology & 50–150 nm & All samples, abundant in D \\ Sea salt & Na, Cl, S, Mg & Crystalline, mainly cubic & \textgreater{}200 nm & D \\  & Mainly C and O and & Chain-like aggregates of nearly spherical & \\  & traces of S, Ca, K, Pb, Zn & carbon nanoparticles; onion-like & 10–100 nm & A, B \\  & Mainly C, Si, Al, and Fe & nanostructure of graphitic layers & \\ Fly ash & Mainly C, Si, Al, and Fe & Amorphous, spherical shape & 50–300 nm & A, B, C, E \\  & P, Mg, Ca, and K & Crystalline and amorphous, aggregates of & \\ Mixing state of & C, O, Na, Si, Al, Ca, P, K, & fly ash, soot, and mineral dust. Core-shell & \textgreater{}100 nm & A, B, C, E \\ individual particles & Mg, Fe & and complex morphology & \\ Ti/Fe oxide & Ti, Fe, O & Crystalline, isolated or aggregated & 5–100 nm & A, B, C, E \\ nanoparticles & Cd oxide & Cd, O & Crystalline, isolated & 50–100 nm & A, B \\ nanoparticles & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Type and morphology of particles detected in each sample. Figure 3: TEM images showing the typical and more abundant particles in the snow samples. (**a**) A: TEM image of a diatom; (**b**) a HAADF-STEM image of a S-rich particle; (**c**) a HAADF-STEM image of a mineral fragment; (**d**) TEM and HAADF-STEM images of different mixed carbonaceous nanoparticles; (**e**) a HAADF-STEM image of metal oxide nanoparticles. The presence of soot and fly ash particles in the Antarctic snow can be attributed to both local sources and LTRA. Locally, contributions arise from the research stations and anthropogenic activities involving the combustion of fossil fuels for transportation (ships, vehicles, aircraft) and power generation, as well as for heating. On the other hand, long-distance sources encompass natural events such as wildfires, volcanic eruptions, and specific natural processes characterized by the incomplete combustion of organic matter.