## 3 Results and Discussion
### Spatial Distribution of Atmospheric Impurities in the Snow Cover of the Baikal Basin  
In order to understand the overall picture of soluble pollutants in the snow water of the Baikal Basin, the distribution of electrical conductivity was mapped (Figure 4). The map allowed estimating the acreage and pathways of transfer of emissions from industrial enterprises, as well as zoning the region according to the degree of soluble pollutants in water (aerosol load). As a result, increased levels of snow cover pollution were identified in cities as sources of pollution (Figure 4). The city of Angarsk, being the most prone to anthropogenic pollution, had an industrial zone with a length of more than 30 km and a total atmospheric emission of more than 110 thousand tons per year [78]. The atmospheric emissions from the Irkutsk agglomeration and the cities of Buryatia extended for tens of kilometers along the prevailing transfer pathway as well as along the main traffic flows and were locally determined near small settlements located on the coast. The plumes from industrial enterprises of the Irkutsk agglomeration were found on the ice of South Baikal in the area of Cape Kadilny (marked with an asterisk in Figure 4). The impact of emissions from the cities of Selenginsk and Kamensk, which are the sources of pollution in Buryatia, was visualized in the delta of the Selenga River (Figure 4). For determining the level of pollution by acidic components of the snow cover, a schematic map of the distribution of the pH value of the snow waters of the Baikal Basin was constructed (Figure 5). It is known that the pH value of atmospheric precipitation is mainly due to the presence of nitrogen, carbon, and sulfur oxides in the atmosphere. The pH value of atmospheric precipitation in the background regions of the world is 5.1-5.5 [79]. In the cities of the region, where alkaline aerosol particles (ash) from coal-fired thermal power plants are emitted into the atmosphere, the pH value varied from 6.25 to 7.75. High pH values varying from 11.05 to 11.07 units were determined in snow water near cement production enterprises (Angarsk, Kamensk). Acid atmospheric fallout (pH-4-5) was identified in the snow water of Southern Baikal and in the area of the Baikal State Biosphere Reserve (4.7). The lowest values (4.44) were recorded on the ice of Southern Baikal (Kadilny-Mishikha cape), which could be associated with the transfer of sulfur and nitrogen oxides from large thermal power plants located in the valley of the Angara River. The rest of Baikal (districts 12-14) had pH values varying from 5.25 to 6.5 (Figure 5). Figure 4: Schematic map of the spatial distribution of electrical conductivity in the snow water of Lake Baikal. Figure 5: Schematic map of the spatial distribution of pH in the snow water of the Baikal basin. After analyzing Table 1 and Figure 3, the main tracer substances for each group of sources were selected. The visual distribution of tracers in the snow cover of the Baikal basin allowed constructing fallout fields and determining the areas of pollutant distribution. After a detailed examination of the Irkutsk agglomeration, which included three large industrial centers (Figure 1, districts 1-3) and the Irkutsk-rural region connecting them, it was found that high levels of tracer accumulation were visualized near the sources of pollution (Figures 6-8). A more detailed analysis of the spatial distribution of sulfates (Figure 6) allowed drawing a number of conclusions. The maximum accumulations of sulfates were located near heat sources, which was considered to be typical for both urban centers and rural ones (Figure 6). The highest level of sulfate accumulation was determined in the city of Angarsk and was localized near a large thermal power plant (from 1250 to 1440 mg/m\({}^{2}\)).