## 3 Results and Discussion
### Seasonal Variability of Gaseous Pollutants under Urban and Rural Conditions  
Table 1 presents the statistical processing data on gaseous pollutants (SO\({}_{2}\), NO\({}_{2}\), and NO), which we used for the comparative analysis of their concentration in the air at the Irkutsk and Listvyanka stations. As shown in the table, the highest concentrations of sulfur and nitrogen oxides were recorded in the air of the Southern Baikal region during the heating season, from October to April. Analysis of Figures 4-7 revealed that the concentrations of sulfur and nitrogen oxides were correlated between each other (the Pearson correlation coefficient was 0.97). Taking into account that most sulfur dioxide  
Figure 3: Frequency distribution graphs of 20-minute averaged concentrations of SO\({}_{2}\), NO, and NO\({}_{2}\) at the Irkutsk and Listvyanka monitoring stations during the heating (blue) and non-heating (red) seasons. The ordinate axis shows the recurrence of the concentrations within a certain range. The abscissa axis shows the pollutant concentration ranges. The data are averaged for 2020–2023. emissions in the region result from the combustion of solid organic fuel (Hakutsk and Listvyanka, 2018), it is logical to assume that the thermal power industry is the main source of sulfur dioxide and nitrogen oxides in the air above the Listvyanka station. The winter maximum is most likely associated with the operational intensity of the thermal power plant, depending on the ambient temperature. A strong negative linear correlation between the average monthly air temperatures near large sources of air pollution (Irkutsk) and the concentrations of sulfur and nitrogen oxides in the air confirms this. The Pearson correlation coefficient was \(-0.93\) for SO\({}_{2}\) and air temperature and \(-0.97\) for NO\({}_{2}\) and air temperature. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \(\mu\)g m\({}^{3}\) & \multicolumn{3}{c}{**\({}^{\prime\prime}\)Irkutsk\({}^{\prime\prime}\) Station (Urban)**} & \multicolumn{3}{c}{**\({}^{\prime\prime}\)Listvyanka\({}^{\prime\prime}\) Station (Rural)**} \\ \hline \hline
**Avg. Time = 20 min** & **SO\({}_{2}\)** & **NO** & **NO\({}_{2}\)** & **SO\({}_{2}\)** & **NO** & **NO\({}_{2}\)** \\ \hline Average & 7.0–19.8 & 7.8–19.3 & 14.9–28.3 & 7.2–22.1 & 1  
Figure 5: Intra-annual variability of nitrogen dioxide (NO\({}_{2}\)) concentrations at the Irkutsk and Listvyanka stations from 2020 to 2023, without atypical values (outliers). The ordinate axis shows the concentrations (\(\upg/\text{m}^{3}\)); the abscissa axis shows the month. The diagram shows the median (bold line), the first quartile (lower boundary of the box), and the third quartile (upper boundary of the box). Figure 6: Intra-annual variability of nitrogen oxide (NO) concentrations at the Irkutsk and Listvyanka stations from 2020 to 2023, without atypical values (outliers). The ordinate axis shows the concentrations (\(\upg/\text{m}^{3}\)); the abscissa axis shows the month. The diagram shows the median (bold line), the first quartile (lower boundary of the box), and the third quartile (upper boundary of the box). Figure 7: Weekly and daily variations in the concentrations of nitrogen and sulfur oxides in the heating (October to April, blue) and non-heating (May to September, red) seasons. Shading shows the 95% confidence intervals of the mean value. Analysis of Table 1 indicated that the concentrations of gaseous pollutants both at the Irkutsk station and the Listvyanka station were widely scattered. If the distribution median is used as an average, the absolute value decreases. This means that there are many atypical values, the so-called outliers, which distort the overall pattern towards the overestimation of gas concentrations, especially at the rural station.