## 3 Results and Discussion  
Table 2 presents the minimum, maximum and average values, as well as standard deviations, for different types of NO\({}_{2}\) concentrations obtained in the adopted calculation area for all receptors \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Variant** & **Grid Resolution (m)** & **Number of Receptors in the Grid** & **The Total Computational Time for the Grid 1** \\ \hline V1 & 100 & 67,600 & 453 h 43 min \\ V2 & 250 & 10,816 & 28 h 56 min \\ V3 & 500 & 2704 & 3 h 48 min \\ V4 & 1000 & 676 & 17 min \\ \hline \hline \end{tabular}  
* with regard to a PC with an Intel Core i7-4930 K processor (12 M Cache, up to 3.90 GHz) BOX.  
\end{table} 
Table 1: A general description of the adopted calculation variants of the air pollutant dispersion. present under different examined variants of grids of different resolutions. Table 3 summarizes the differences in minimum, maximum and average values of these concentrations obtained in the examined computational grids between Variant V1 and other variants (Variants V2, V3 and V4). According to the calculations, using grids of lower resolution in the whole calculation area results in a decrease in the highest values (local maxima) among the maximum 1 h and 24 h and average annual concentrations, as compared to a grid with the resolution of 100 m (V1). In the case of grids with the resolutions of 250 m (Variant V2), 500 m (Variant V3) and 1000 m (Variant V4), this reduction amounted to 16%, 20%, and 64%, respectively, in the case of the highest values of maximum 1-h concentrations; 20%, 24%, and 31%, respectively, in the case of maxima of 24-h concentrations; and 4%, 26%, and 38%, respectively, in the case of maxima of average annual concentrations. Therefore, an increase in the computational grid resolution results in an increase in the accuracy of the area surface representation and enables reflecting the extremely high values of concentration that cannot be obtained during calculations performed in grids of lower density. On the other hand, the computational grid with the highest examined resolution (Variant V1) also enabled mapping more points with low concentration values, as the average values of different types of concentrations from the entire examined calculation area are the lowest for this grid. The average area values of the maximum 1-h and 24-h and average annual concentrations for a grid with the resolution of 250 m were higher by, respectively, 4.2%, 6.1%, and 3.2%; for a grid with the resolution of 500 m by, respectively, 12.8%, 23.9%, and 17.5%; and for a grid with the resolution of 1000 m by, respectively, 5.8%, 14.3%, and 4.2% (as compared to the results obtained for a grid with the resolution of 100 m). The maximum overestimated average values (but also the minimal ones), as compared to Variant V1, were therefore obtained for a grid with the resolution of 500 m (Variant V3). In addition, in the case of Variant V3, the greatest spread of the calculation results of the maximum 1-h concentrations occurred, as compared to the average value, while the lowest possible spread was observed in the case of Variant V4 (a grid with the resolution of 1000 m). It should be emphasized that, in the case of grids with the resolution of 100 and 250 m (Variants V1 and V2), the highest values of the maximum 1-h concentrations occurred at the same time, under almost identical weather conditions (wind speed ca. 0.5-0.6 m/s, atmospheric stability class 3, air temperature 259 K, and height of the mixing layer ca. 134-135 m). The grid receptors, for which the aforementioned