<p>This study is a preliminary investigation evaluating the seasonal accumulation of atmospheric Potentially Toxic Elements (PTEs) at four urban sampling stations in the city centre of Çanakkale using the moss bag technique. Samples of the species <i>Alleniella complanata</i>, used for the first time as a bioindicator, were exposed for 45&#xa0;days at four stations at seasonal intervals. Following exposure, PTEs accumulated in the moss bags were analyzed using an ICP-OES instrument, and the accumulation levels were evaluated using the pollution indices Contamination Factor (CF), Pollution Load Index (PLI), and Relative Accumulation Factor (RAF). Seasonal differences were examined using the Friedman test, relationships between metals were analyzed using Spearman correlation analysis, and common variance structures and potential source patterns were investigated using Principal Component Analysis (PCA). The results revealed that PTE concentrations after exposure exceeded the initial levels and varied depending on seasonal periods. Friedman test results showed that Cr, Zn, Pb, and As exhibited statistically significant differences between seasons, whereas no significant seasonal variation was observed for Cu. RAF &gt; 1 values indicated element enrichment and pointed to the bioindicator potential of <i>A. complanata</i> under the current experimental conditions. CF values were generally found within the “moderate contamination (1 ≤ CF &lt; 3)” range, while PLI &gt; 1 values indicated a cumulative metal load persisting throughout the year. Spearman correlation analysis identified significant positive relationships between the Cr–As and Pb–Cu pairs. The two-component PCA model explained 83.9% of the total variance, and the obtained patterns showed high positive loadings of As and Cr in PC1, and Zn and Cu in PC2. The results generated exploratory hypotheses suggesting that the pollution load may be associated with common potential sources.</p>