## 1 Introduction  
Sulfur dioxide (SO\({}_{2}\)) and nitrogen oxides (NOx) are among the most widespread gaseous pollutants in the air and have a significant impact on the regional and global air quality, human health, environmental conditions, and climate change [1, 2, 3, 4, 5]. The high-temperature combustion of organic fuels (coal and oil) and biomass [6, 7, 8], as well as thunderstorm activity [9] and the microbial N-cycle [10, 11], are the main sources of NOx (NOx = NO + NO2). NO\({}_{2}\) is involved in the nitrogen cycle in the \"air-water-soils\" system [12], which affects the intensity of oxidation processes in the air [13] and, in the presence of volatile organic compounds in the air, leads to the formation of ground-level ozone [14, 15]. The main SO\({}_{2}\) sources are volcanic activity, the combustion of organic fuels, and the purification of sulfide ones [16, 17]. Volcanic SO\({}_{2}\) is emitted into the air at high altitudes above the atmospheric boundary layer (ABL). Anthropogenic SO\({}_{2}\) emissions from thermal power and industrial facilities enter mainly within the ABL. Nitrogen and sulfur oxides in the ground level of the atmosphere participate in many physicochemical reactions. During the oxidation, nitrogen dioxide reacts with ammonia, leading to the formation of ammonium nitrate aerosol. Sulfur dioxide is oxidized in the reactions with the hydroxyl radical, ozone, or hydrogen peroxide, producing sulfate aerosols. This contributes to air pollution by particulate matter with an aerodynamic diameter <2.5 \(\upmu\)m (PM\({}_{2.5}\)) [18; 19; 20; 21], possessing a serious risk to human health [22; 23; 24], reducing the meteorological visibility [25; 26], and affecting the weather and climate through direct radiative forcing and indirect changes in cloud formation and optical properties [27; 28]. Elevated concentrations of SO\({}_{2}\) and NO\({}_{\mathrm{x}}\) in the air increase the risks of respiratory and oncological diseases and negatively affect the reproductive systems of organisms [29; 30; 31; 32; 33]. Nitrogen and sulfur oxides are generally recognized as acid gases that contribute to the occurrence of acid rain, leading to the acidification of water bodies and soils, which possesses a serious threat to biodiversity, especially for plants [34]. High concentrations of nitrogen oxides have a negative impact on agricultural crops because they reduce the efficiency of plant growth, resulting in a decrease in yields. The atmospheric air in the Southern Baikal region is subject to constant pollution by various impurities due to the large concentrations of industrial enterprises in the cities of the region that are located close to each other. Enterprises of the fuel and energy complex, chemistry and petrochemistry, metallurgy, woodworking, and pulp and paper production play a leading role in the industrial structure. In 2022, the emissions of air pollutants from anthropogenic sources in the Irkutsk Region amounted to 739,000 tons per year. Of them, 40% entered the atmosphere from the enterprises situated in a relatively small area in the Angara River valley (Irkutsk-Cheremkhovo industrial hub). This is 3 times higher than the emissions from the anthropogenic sources in the Republic of Buryatia (107,000 tons per year) and 12 times higher than the emissions from the anthropogenic sources located in the Central Ecological Zone of Lake Baikal [35; 36; 37] (Figure 1). Overall, the pollutants entering the air in the Southern Baikal region account for about 100 items, among which fuel combustion products (nitrogen and sulfur dioxides and carbon oxide) predominate in the amount of the annual influx to the atmospheric air. Emission plumes from large regional coal-fired thermal plants can reach the water area and the watershed basin of Lake Baikal, the world's deepest lake, with a large volume of fresh water. Previous studies indicated the impact of technology-related emissions from the industrial complexes of the Southern Baikal region on air pollution in the southern basin of Lake Baikal.