## 3 Results and Discussion
### Spatial Distribution of Atmospheric Impurities in the Snow Cover of the Baikal Basin
In Irkutsk, the maximum accumulations of pollutants were identified not only near the largest thermal power plant, located in the southwest of the city (550 mg/m\({}^{2}\)), but also near small communal boiler houses (600 mg/m\({}^{2}\)), which also largely participated in the city's heat supply. Local increases in sulfates were also identified near the village of Khomutovo (440 mg/m\({}^{2}\)) due to a coal-fired boiler house located in it. A similar distribution pattern was observed on the territory of the Republic of Buryatia (Figure 1, district 4). The highest levels of tracer accumulation were noted in Ulan-Ude near large boiler houses located in the southwest (1010 mg/m\({}^{2}\)) and west of the city and a thermal power plant located in the center (425 mg/m\({}^{2}\)). Another high accumulation of sulfate ions (1021 mg/m\({}^{2}\)) was determined at a sufficient distance from the sources of pollution in the delta of the Selengis River (Figure 1, district 8) and was caused by the anthropogenic emissions from the Selenginsky Pulp and Cardboard Mill located at a distance of \(\sim\)45 km to the southeast (Figure 6) from the delta and large settlements Kamensk and Kabansk (30-35 km from the delta). On the territory of the Baikal State Natural Biosphere Reserve, located on the eastern coast of Southern Baikal at a distance of more than 100 km from large anthropogenic sources, an increase in the accumulation of sulfates in the snow cover was also identified  
Figure 8: Schematic map of the spatial accumulation of ammonium ions (NH4\({}^{+}\)) in the snow cover of the Baikal basin. (200 mg/m\({}^{2}\)). At the same time, according to Figure 3, their concentrations in the snow of the reserve were low, which was due to the large amount of moisture content exceeding the moisture content in cities by more than three times (Table 1). Figure 7 demonstrates the spatial distribution of nitrates. The high-temperature combustion of fossil fuels by vehicles and industry is the main anthropogenic source of nitrates. Nitrates, unlike other considered compounds, were more evenly distributed over the studied area (Figure 7). An increased accumulation of nitrates was traced along the main pathway of transfer of air masses from stationary sources and along highways. The maximum accumulation of nitrates was recorded in the snow cover of the Baikal State Natural Biosphere Reserve (360 mg/m\({}^{2}\)), which was due to the large moisture content in this area. Figure 8 shows a schematic map of the accumulation of ammonium in the snow cover. The main sources of atmospheric ammonia were soil, agriculture, and, to a lesser extent, industry [80]. Sulfates and nitrates, as well as ammonium ions, were also tracers of long-range gas-phase transfer of impurities [81; 82]. The distribution of ammonium was quite homogeneous in the central ecological zone of the lake, and local accumulation values were determined in industrial centers (Figure 1, districts 1-5). According to the results of a geostatistical analysis of a large amount of data, the factors of remoteness from industrial enterprises, population density, and snow cover height were the most important factors affecting the amount of tracer accumulation in the snow cover of the Baikal region.