## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Agglomeration** & **2018** & **2019** & **2020** & **2021** & **2022** \\ \hline Tricity & 9.49 (0.37–42.90) & 5.17 (0.31–26.05) & 5.59 (0.34–25.62) & 7.50 (0.38–42.40) & 4.47 (0.35–26.39) \\ Upper Silesia & 25.59 (1.27–89.95) & 21.96 (0.96–74.67) & 19.78 (1.43–69.09) & 21.75 (1.18–83.61) & 14.18 (1.38–45.62) \\ Cracow & 21.15 (1.20–101.58) & 16.96 (0.70–77.63) & 16.36(0.72–80.06) & 16.27 (0.88–72.37) & 9.90 (0.66–40.55) \\ Lublin & 9.35 (0.10–47.53) & 6.30 (0.08–21.60) & 8.56 (0.31–31.42) & 10.64 (0.24–40.35) & 7.27 (0.35–30.61) \\ Lodz & 16.47 (0.26–64.08) & 12.83 (0.36–49.02) & 11.60 (0.47–41.27) & 12.47 (0.32–41.32) & 10.83 (0.44–38.72) \\ Szczecin & 18.50 (0.77–68.97) & 6.85 (0.47–40.55) & 5.21 (0.54–27.26) & 5.61 (0.25–21.54) & 6.11 (0.45–30.12) \\ Warsaw & 10.23 (0.29–39.24) & 8.17 (0.38–31.77) & 6.56 (0.18–25.74) & 8.05 (0.35–47.85) & 5.46 (0.35–16.83) \\ Wroclaw & 14.04 (0.41–87.93) & 9.34 (0.35–50.72) & 12.14 (0.35–55.92) & 10.97 (0.35–45.99) & 5.55 (0.43–36.88) \\ \hline \end{tabular}
\end{table} 
Table 1: Annual average (min–max) concentrations of PM-bound the sum of PAHs in the period 2018–2022 in Polish Agglomerations, ng\(\cdot\)m\({}^{-3}\). may be the result of local episodes of low emissions, increased road traffic, and specific meteorological conditions favouring the accumulation of pollutants. The studies by [PERSON] and [PERSON] (2018), as well as [PERSON] et al. (2019), showed a strong link between high Pb levels and weather conditions like temperature and rainfall. They also highlighted how seasonal air inversions and stagnant air are important. [PERSON] et al. (2019) noted that road transport is a significant source of heavy metals, including Pb, in PM\({}_{10}\) in cities that don't have heavy industry, particularly in places with poor air circulation. They also emphasised the importance of seasonal air inversion and stagnation. Furthermore, the highest annual mean As concentrations, ranging from 1.71 to 2.66 ng\(\cdot\)m\({}^{-3}\), were recorded in Wroclaw each year. Such high As concentrations can be linked to local emission sources, primarily the individual heating of buildings and emissions from road transport, especially during the heating season. Additionally, the meteorological conditions typical of Wroclaw--frequent temperature inversions and episodes of poor air ventilation--favour the accumulation of As near the ground surface, thereby increasing its concentration in the air ([PERSON] and [PERSON], 2018). In Lublin, abnormally high annual mean nickel values (up to 3.79 ng\(\cdot\)m\({}^{-3}\)) were observed between 2018 and 2020. Such high values may be due to local emissions, including the combustion of fuel oil and low-quality fuels in the municipal sector, as well as the activities of small workshops and metalworking businesses. The presence of Ni was also confirmed in Lublin street dust, indicating the role of road transport and dust resuspension ([PERSON] and [PERSON], 2018). Unfavourable dispersion conditions during the heating season, such as temperature inversion, may have further favoured Ni accumulation at ground level (Lublin, 2018). However, in Szczecin, researchers observed an unusually high annual mean nickel concentration of 2.01 ng\(\cdot\)m\({}^{-3}\) in 2022, despite generally lower concentrations of other metals being present. This variation may be partly attributed to the limited availability of measurement data in earlier years (approximately 50% of days monitored), as well as to specific local emission sources. Contributors are likely to include emissions from port operations, waterborne transport, and transshipment terminals, all of which are characteristic of this coastal region. Furthermore, frequent shifts in wind direction and high air humidity, which are common meteorological features in Szczecin, may influence the dispersion and deposition patterns of pollutants (Lublin, 2018).