## 3 Results
### Characteristics of the Water Chemical Indicators for Four Typical Water Bodies
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Water Chemical** \\ **Indictors** \\ \end{tabular} } & \multirow{2}{*}{**TN (mg/L)**} & \multicolumn{2}{c}{**TDN**} & \multicolumn{2}{c}{**NH\({}_{4}\)****-N**} & \multicolumn{2}{c}{**NO\({}_{3}\)**-N**} & \multicolumn{2}{c}{**Chl-a**} & \multicolumn{2}{c}{**COD\({}_{\text{Mn}}\)**} \\  & & & **(mg/L)** & **(mg/L)** & **(mg/L)** & **(mg/L)** & **(mg/L)** \\ \hline \multirow{3}{*}{Canal (n = 8)} & Range & 2.21–3.06 & 2.10–2.84 & 0.06–0.12 & 1.31–2.54 & 2.35–11.19 & 2.88–3.96 \\  & Mean & 2.58 & 2.42 & 0.09 & 1.81 & 5.42 & 3.41 \\  & SD & 0.37 & 0.31 & 0.02 & 0.5 & 3.53 & 0.35 \\ \hline \multirow{3}{*}{Lake (n = 8)} & Range & 1.89–2.93 & 1.81–2.76 & 0.06–0.13 & 1.03–2.18 & 1.51–6.23 & 2.67–5.25 \\  & Mean & 2.44 & 2.31 & 0.1 & 1.64 & 4.35 & 3.47 \\  & SD & 0.37 & 0.38 & 0.03 & 0.4 & 1.8 & 0.8 \\ \hline \multirow{3}{*}{Pond (n = 8)} & Range & 2.31–2.75 & 2.18–2.71 & 0.05–0.18 & 1.52–22 & 2.13–5.08 & 2.88–3.58 \\  & Mean & 2.55 & 2.46 & 0.1 & 1.8 & 3.68 & 3.29 \\ \cline{1-1}  & SD & 0.17 & 0.19 & 0.05 & 0.23 & 1.14 & 0.24 \\ \hline \multirow{3}{*}{River (n = 8)} & Range & 1.67–3.35 & 1.60–3.15 & 0.03–0.14 & 0.99–2.51 & 1.10–5.45 & 2.08–4.25 \\ \cline{1-1}  & Mean & 2.46 & 2.28 & 0.07 & 1.76 & 3.37 & 3.09 \\ \cline{1-1}  & SD & 0.6 & 0.55 & 0.04 & 0.57 & 1.79 & 0.76 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristics of water chemical indicators of canals, lakes, ponds, and rivers. C and N Contents and Source Contributions of Sedimentary Organic Matter in Four Typical Water Bodies  
All characteristics of the C and N contents of sedimentary organic matter of canals, lakes, ponds, and rivers are listed in Table 3. In general, the TON contents of sediment organic matter in the four water bodies exhibited minor differences, and the average TON content was 0.23-0.29%. However, the TON contents in lakes and rivers were slightly higher. The order of the average TOC content in the sediments of different types of water bodies was Lake (3.01) > River (2.52) > Pond (2.20) > Canal (2.00). The average TOC content in lake sediments was 1.51 times that in canals. Further analysis of the C/N ratio of the four types of water bodies revealed that the order of this ratio was Pond (8.90) > Lake (8.79) > River (8.30) > Canal (8.27). The maximum C/N ratio (10.90) was found in lakes, while the minimum C/N ratio (6.96) was found in canals. By combining C/N ratios, \(\delta^{13}\)C, and \(\delta^{15}\)N values, the sedimentary organic matter sources in the four types of water bodies in urban areas can be qualitatively analyzed. Figure 2 shows the \(\delta^{13}\)C and \(\delta^{15}\)N results for the four types of water sediments. For \(\delta^{13}\)C values, the ranges for canals, lakes, ponds, and rivers are \(-\)25.15% to \(-\)28.70%, \(-\)25.15% to \(-\)28.70%, \(-\)22.47% to \(-\)27.96%, and \(-\)26.78% to \(-\)28.54%, respectively. For \(\delta^{15}\)N values, the ranges are 1.12-2.74%, 0.68-7.60%, 1.77%\(-\)5.76%, and 0.83-6.83%, respectively. In addition, to further analyze and calculate the carbon and nitrogen sources of sediment organic matter, the C/N ratios, \(\delta^{13}\)C, and \(\delta^{15}\)N values of phytoplankton, terrestrial, and sewage sources were determined. The average C/N ratios, \(\delta^{13}\)C, and \(\delta^{15}\)N values of phytoplankton/terrestrial/sewage sources are 7.01%/10.76%/15.25%, \(-\)27.29%/\(-\)23.33%/\(-\)22.06%, and 9.46%/3.43%/7.05%, respectively. The C/N ratios, \(\delta^{13}\)C, and \(\delta^{15}\)N values of the different end members differ significantly, indicating three typical sources of water pollution, which provides a reliable theoretical basis for the source analysis of sediment organic matter. Using the \(\delta^{13}\)C and \(\delta^{15}\)N values of the end elements in the isotope ternary mixing model, the relative contributions of potential sources of sedimentary organic matter in the four urban water bodies were quantitatively calculated (Figure 3).