## 3 Results and Discussion
### Analysis of Residents' Complaints  
Figures 5 and 6 present the spatial distribution of complaints reported to the City Hall in each time. Figure 5 contains the spatial distribution of the number of complaints in the study area in the years 2012-2021, and Figure 6 contains the spatial distribution of complaints in individual years. The analysis of Figure 6 shows that the largest number of complaints was recorded in the western (Scarpa housing estate) and northwestern (Lukasiewicz housing estate) parts of the city (south of the refinery). In the case of Figure 7, it can be observed that the highest number of complaints was reported in 2018, and the lowest number was reported in 2012. Considering the situation in 2018 and 2020, between October and November, the refinery carried out works during which one of the chimneys was shut down and a reserve emitter was activated. Any malfunctions and repairs (modernisation) may cause a stronger odour effect than under normal operating conditions [63]. Figure 5: Spatial distribution of the number of complaints in the surveyed area in the years 2012–2021. Figure 6: Spatial distribution of complaints in the surveyed area in individual years. Figure 7 shows the histograms of the cumulative number of complaints per year. The lines in the bar graph correspond to the streets/locations where the complaints were found each year. Figure 8 shows morning-moustache graphs--number of complaints per year. Figures 7 and 8 show that the highest number of complaints was recorded in 2016 (160) and 2018 (228). Figure 11 shows a polar chart showing the intensity and nuisance of the odour effect as a function of the wind direction. Table 2 contains descriptive statistics of odour annoyance and odour intensity splinted by wind direction. Figure 11: The intensity and nuisance of the odour impact depending on the wind direction. Explanation: Intensity scale: 0—I don’t notice the smell; 1—very weak; 2—weak; 3—clear; 4—strong; 5—very strong; 6—extremely strong. Scale of nuisance: 0—no nuisance; 1—little nuisance; 2—nuisance; 3—great nuisance; 4—extreme nuisance. Figure 10: Distribution plot of odour intensity values. Explanation: 0—no odour; 1—very weak; 2—weak, 3—clearly; 4—strong; 5—very strong; 6—extremely strong. Figure 9: Distribution plot of odour annoyance values. Explanation: 0—no odour; 1—no nuisance; 2—small nuisance; 3—nuisance; 4—large nuisance; 5—extreme nuisance. Figure 12 provides a summary of the answers to the question \"How often do you experience odour nuisance?\" according to the mean values of odour annoyance and odour intensity, broken down by wind direction. Table 3 provides a summary of the answers to the question about frequency of odour nuisance. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c c c} \hline \hline  & & & & \multicolumn{4}{c}{**Odour Annoyance**} & & & & \multicolumn{4}{c}{**Odour Intensity**} \\  & **E** & **N** & **NE** & **NW** & **S** & **SE** & **SW** & **W** & **E** & **N** & **NE** & **NW** & **S** & **SE** & **SW** & **W** \\ \hline Valid & 39 &  
The analysis of Figure 10 shows that most respondents indicated a north wind, N (32%), a northwest wind, NW (26%), and northeast wind, NE (22%), for both odour annoyance and odour intensity. The analysis of Figure 13 shows that the odour nuisance felt by the inhabitants of the agglomeration is related to the occurrence of winds mainly from the N, NW, and NE directions. Those who reported high odour nuisance and significant intensity pointed to the refinery as the source of the nuisance or described the odour as \"chemical,\" \"suffocating\", \"oil\", or \"like a gas station\". The direction of the wind indicated that the refinery may have been the source of these complaints. On the other hand, with the wind blowing from the direction of the wastewater treatment plant, respondents spoke of a \"sew-age\", \"sludge\", and \"rotten\" odour. These characteristics, described in question 7, \"Can you determine what is causing your odour nuisance?\", make it possible to distinguish between these sources.