## 4 Results
### Pollution Source Identification of Elements in Stream Sediment  
To determine the link between two variables, the bivariate approach of correlation analysis is commonly used. Environmental studies have frequently employed correlation analyses [58; 59; 60]. Several element pairs exhibit strong positive correlations, illustrating common sources or similar geochemical behaviour (Table 2). For example, Cu-Zn (r = 0.97) and Ni-Cu (r = 0.77) indicate a strong geochemical affinity, likely derived from sulfide mineralisation or anthropogenic inputs such as industrial or mining activities. Th-U (r = 0.95) and Pb-U (r = 0.87) also exhibit high correlations, implying a shared lithogenic origin, possibly from phosphate-bearing rocks or mineral assemblages. Tl-U (r = 0.91) and Tl-Th (r = 0.79) suggest that Tl may exhibit similar environmental mobility or origin to those of U and Th. Conversely, significant negative correlations are observed between specific element \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Element** & **Min** & **Max** & **Mean** & **Std (\(\sigma\))** & **Median** & **LOD** \\ \hline V & 118.00 & 330.33 & 184.69 & 63.44 & 118.00 & 0.05 \\ Cr & 106.22 & 1153.27 & 212.24 & 263.58 & 1153.00 & 0.01 \\ Co & 11.67 & 35.74 & 23.13 & 6.36 & 11.70 & 0.01 \\ Ni & 35.41 & 61.49 & 43.30 & 6.85 & 35.40 & 0.05 \\ Cu & 25.47 & 216.22 & 88.61 & 61.48 & 25.50 & 0.05 \\ Zn & 42.79 & 439.27 & 187.71 & 142.91 & 96.90 & 0.05 \\ Tl & 0.03 & 0.11 & 0.06 & 0.03 & 0.10 & 0.01 \\ Pb & 2.90 & 8.67 & 5.72 & 1.69 & 7.83 & 0.05 \\ Th & 0.77 & 1.81 & 1.40 & 0.30 & 1.67 & 0.01 \\ U & 0.25 & 0.91 & 0.57 & 0.21 & 0.87 & 0.01 \\ \hline \end{tabular}
\end{table} 
Table 1: Basic statistical parameters for (n = 15) for average elemental concentrations (mg/kg) in urban stream sediments (Std = Standard Deviation (1\(\sigma\)); LOD = Limit of Detection). Moderate correlations: Co-V (r = 0.71) suggests that similar lithological units or redox conditions may control both elements. Pb-Th (r = 0.86) and Pb-Tl (r = 0.75) imply that lead could be transported or deposited alongside Th and Tl, likely reflecting similar geochemical pathways. Strong positive correlations suggest element pairs with common origins or co-mobilisation, whereas negative correlations reflect divergent behaviour, possibly due to different mineral hosts or environmental processes. The results of the hierarchical cluster analysis (HCA) reveal three distinct clusters of sediment samples based on their metal concentration patterns. Cluster 1 (K8, K11-K15) contained moderate levels of Cr and Zn, lower Cu content, and relatively higher Th-U ratios. Cluster 2 (K1-K3) exhibited higher levels of V and Co, while other metals were relatively lower. Cluster 3 (K4-K7, K9-K10) showed the highest levels of Cu and Zn, along with moderate to high levels of Ni and Cr. This cluster likely represented regions with significant pollution and corresponded to most contaminated areas, especially in terms of Cu and Zn. Cluster 2 was closer to the natural background levels, despite elevated V and Co concentrations. Cluster 1 showed moderate levels of Cr and some radioactive elements (Th-U) (Table 3, Figure 4). Upper Continental Crust (UCC) [61] values were used as a reference for comparison (Table 3). The observed clustering could have been caused by a combination of anthropogenic and environmental variables. The highest concentrations of Cu, Zn, Ni, and Cr were found in Cluster 3, which was probably associated with regions more impacted by urban or industrial activities. These sites were located near residential areas, road networks, or untreated wastewater discharge points. Cluster 2 samples, on the other hand, which had higher V and Co levels, but generally lower metal levels, might have come from upstream regions that were comparatively little affected, perhaps representing natural geogenic sources with little anthropogenic interference.