## 3 Results and Discussion
### Single Factor Pollution Index Evaluation
#### 3.3.2 Characteristics of the Spatial Distribution of Single-Factor Evaluation Results  
(1) Water quality class evaluation  
The method of single-factor evaluation of water quality grades is to take the worst grade of each point as the final water quality grade of the point. The results of the single factor evaluation of the water quality grade at each point were plotted (Figure 5) for the spatial distribution characteristics of water quality. Among the 24 sites in the Wanquan River, most of them meet the surface water quality standard of V and above (Figure 5), while only three sites near the Tayang River, WQH17, WQH18, and WQH19, are of poor V quality, in addition to the sample sites in the northern section of the Wanquan River, where the water quality reaches IV or above. This indicates \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Sampling Sites** & **NH\({}_{4}\)\({}^{*}\)-N** & **TN** & **TP** & **COD** & **BOD\({}_{\text{S}}\)** & **COD\({}_{\text{Mn}}\)** & **Cr\({}^{\text{\#}}\)** & **As** & **Hg** & **One-Factor** \\  & & & & & & & & & & & & \\  & & & & & & & & & & & & \\ \hline WQH01 & 0.78 & 1.05 & 1.70 & 0.35 & 0.63 & 1.22 & 0.54 & 0.02 & 0.20 & Light pollution \\ WQH02 & 0.33 & 0.67 & 0.65 & 0.35 & 0.35 & 0.72 & 0.04 & 0.01 & 0.20 & Non-polluting \\ WQH03 & 0.35 & 0.64 & 0.50 & 0.35 & 0.60 & 0.62 & 0.04 & 0.01 & 1.50 & Light pollution \\ WQH04 & 0.32 & 0.64 & 0.40 & 0.13 & 0.20 & 1.02 & 0.36 & 0.00 & 0.20 & Light pollution \\ WQH05 & 0.28 & 0.60 & 0.40 & 0.25 & 0.43 & 0.93 & 0.24 & 0.05 & 0.50 & Non-polluting \\ WQH06 & 0.52 & 0.66 & 0.65 & 0.40 & 0.70 & 0.83 & 0.36 & 0.01 & 0.20 & Non-polluting \\ WQH07 & 0.49 & 0.66 & 0.75 & 0.40 & 0.90 & 0.90 & 0.36 & 0.00 & 0.40 & Non-polluting \\ WQH08 & 0.42 & 0.65 & 0.80 & 0.25 & 0.60 & 0.97 & 0.32 & 0.01 & 1.40 & Light pollution \\ WQH09 & 0.29 & 0.59 & 0.45 & 0.30 & 0.55 & 0.72 & 0.32 & 0.03 & 0.20 & Non-polluting \\ WQH10 & 0.25 & 0.60 & 0.50 & 0.25 & 0.28 & 1.00 & 0.22 & 0.00 & 0.70 & Light pollution \\ WQH11 & 0.35 & 0.65 & 0.45 & 0.25 & 0.45 & 0.88 & 0.28 & 0.04 & 1.60 & Light pollution \\ WQH12 & 0.32 & 0.68 & 0.45 & 0.25 & 0.33 & 0.93 & 0.28 & 0.00 & 2.10 & Light pollution \\ WQH13 & 0.26 & 0.64 & 0.40 & 0.25 & 0.35 & 0.92 & 0.42 & 0.00 & 1.50 & Light pollution \\ WQH14 & 0.24 & 0.67 & 0.40 & 0.30 & 0.30 & 1.03 & 0.32 & 0.02 & 0.20 & Light pollution \\ WQH15 & 0.22 & 0.61 & 0.40 & 0.40 & 0.23 & 0.80 & 0.42 & 0.01 & 2.60 & Light pollution \\ WQH16 & 0.23 & 0.66 & 0.45 & 0.40 & 0.18 & 0.82 & 2.72 & 0.06 & 1.60 & Light pollution \\ WQH17 & 2.60 & 2.82 & 1.40 & 0.40 & 0.80 & 0.95 & 0.68 & 0.02 & 2.00 & Light pollution \\ WQH18 & 1.56 & 1.82 & 1.30 & 0.40 & 0.28 & 0.92 & 0.48 & 0.05 & 2.80 & Light pollution \\ WQH19 & 1.92 & 2.55 & 1.35 & 0.40 & 0.90 & 0.97 & 0.36 & 0.01 & 3.40 & Moderate pollution \\ WQH20 & 0.12 & 0.45 & 0.40 & 0.30 & 0.30 & 0.95 & 0.32 & 0.00 & 0.20 & Non-polluting \\ WQH21 & 0.56 & 0.70 & 0.40 & 0.65 & 0.23 & 1.00 & 0.44 & 0.04 & 1.80 & Light pollution \\ WQH22 & 0.28 & 0.47 & 0.30 & 0.80 & 0.23 & 0.97 & 0.22 & 0.01 & 3.20 & Moderate pollution \\ WQH23 & 0.13 & 0.33 & 0.30 & 0.80 & 0.15 & 0.98 & 0.36 & 0.08 & 0.20 & Non-polluting \\ WQH24 & 0.55 & 0.68 & 0.30 & 0.75 & 0.06 & 0.92 & 0.40 & 0.00 & 2.40 & Light pollution \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Evaluation results of the single factor pollution index method for each sampling point in the Wanquan River. Figure 4: Single factor pollution index for each water quality indicator of the Wanquan River. that the overall water quality of the Wanquan River is currently good, but water quality monitoring and management need to be strengthened near the Tayang River.