# Pilot Study of Microplastics in Snow from the Zhetysu Region (Kazakhstan)
## 3 Results and Discussion
28-7 particles/m\({}^{2}\)), concentrations also remain significant, which confirms the dominance of the diffuse and background nature of the pollution. This is especially relevant for regions with open relief and pronounced wind activity, such as the foothills of Zhongar Alatau and flat areas, where microplastics can migrate tens of kilometers from the emission sources. Figure 4: Spatial distribution of microplastics (particles/m\({}^{2}\)) in the snow cover of the Zhetysu region, presented in four different angles for a more detailed visualization of the plastic particle concentration in the study area. The role of atmospheric transport is particularly evident in the dominance of small particles (less than 0.5 mm), which, due to their aerodynamic characteristics, are able to stay in the air medium for a long time and travel considerable distances [58]. Such particles have been detected even in the most remote and inaccessible mountainous areas, which is consistent with the data from the scientific literature on the global distribution of aerosol pollutants of anthropogenic origin [59]. The results indicate a significant contribution of atmospheric transport of microplastics. The observed presence of plastic microparticles even in high-mountainous, poorly affected areas indicates that microplastics have become a global atmospheric pollutant. The smallest particles (<0.5 mm) can be transported by air currents for tens and hundreds of kilometers, and they can fall with snow [2]. According to other studies, the daily deposition of microplastics in remote mountainous areas reaches up to hundreds of particles per m\({}^{2}\)[60]. Our observations in the Zhetysu region are consistent with this order of magnitude of microplastic presence, even far from direct sources. It is likely that the main sources of microplastics deposited with precipitation in our study area are distant cities, agricultural land (e.g., microfibers from agro-film degradation), and dust storms carrying plastic particles from far-located polluted areas. Additionally, it is necessary to consider the migration of plastic after snowfall, as the migration capacity of microplastics directly depends on their size and density. Small particles (up to 1 mm) are highly mobile and can travel both in the air and with water flows, spreading over long distances. In the Zhetysu region, this is particularly important as most of the territory is covered with snow cover, which serves as an accumulator for microplastic particles, which then get into water bodies and soils after snow melting. Based on literature sources [1,2] and our own data, it can be noted that the level of microplastic pollution in snow depends on several factors. First, there is the proximity to microplastic sources: areas located near cities, industrial facilities, and motorways usually display higher concentrations, whereas remote, sparsely populated places show lower MP levels. For example, a study of snow in northern Japan [13] demonstrated that concentrations reached \(\sim\)4 \(\times\) 10\({}^{3}\) particles L\({}^{-1}\) near highways and urban areas, while they fell to \(\sim\)10\({}^{2}\) particles L\({}^{-1}\) in distant protected zones. This confirms that local sources (tire wear, urban dust, illegal littering, etc.) strongly influence the microplastic content. Second, atmospheric transport plays an important role: small plastic particles can be carried by wind over long distances, so even in comparatively clean regions, microplastics transported by air masses from elsewhere may be present. Wind can also redistribute snow, including microplastics, over short distances. Third, climatic and geographical features add to the variability: the precipitation regime (snowfall intensity), local relief, and prevailing wind directions determine how many microparticles are deposited with atmospheric precipitation. Finally, the temporal factor (seasonality) is also important: snow accumulates pollutants throughout the entire deposition period, so winter sampling reflects several months of deposition.