## 3 Results
### Temperature Variations and Karsi Groundwater Quality Indicator Responses  
#### 3.2.1 Changes in pH of Groundwater at Various Depths under Different Temperature Conditions  
Indoor experiments at different temperatures measured the pH values of groundwater at various depths, as shown in Table 4 and Figure 5.  
(i) As shown in the results, under varying temperature conditions, the pH value of groundwater in the soil surface karst zone exhibited fluctuations within the range of 5.88-6.32, typically demonstrating acidic characteristics. The variation range was relatively narrow at 0.44, indicating modest fluctuation levels. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Depth/(m)**} & \multicolumn{3}{c}{**Temperature**} \\ \cline{2-4}  & **10 \({}^{\circ}\)C** & **20 \({}^{\circ}\)C** & **30 \({}^{\circ}\)C** \\ \hline
0.1 & 6.18 & 6.30 & 6.32 (_max_) \\
0.2 & 5.99 & 6.12 & 6.25 \\
0.3 & 5.94 & 6.05 & 6.10 \\
0.4 & 5.88 (_min_) & 5.98 & 6.03 \\
0.5 & 5.92 & 6.02 & 6.08 \\ Average value E & 5.98 & 6.09 & 6.16 \\ Range R & 0.3 & 0.32 & 0.29 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The pH values of groundwater under different temperature and depth conditions. Figure 5: The pH curve of different depth of groundwater under different temperature conditions. (ii) As demonstrated in Figure 5, across the entire soil surface karst zone, the overall trend shows that the groundwater pH tends to decrease with increasing soil depth. However, this rate of change gradually diminishes, reaching an extreme value at a depth of 0.4 m. This is followed by a slight upward fluctuation between 0.4 m and 0.5 m, although the extent of this increase is minimal. (iii) The pH value of karst groundwater tends to increase with higher temperatures, exhibiting smaller fluctuations and a tendency towards stability. Conversely, in winter, with the lowest temperatures, groundwater pH reaches its minimum value. 2.2 Changes in GRP (Oxidation-Reduction Potential) of Groundwater at Various Depths under Different Temperature Conditions  
In the experiments conducted under varying temperature conditions, the oxidation-reduction potential (ORP) values of groundwater were measured at different depths. The results of these measurements are detailed in Table 5 and Figure 6.  
(i) As shown in the results, under varying temperature conditions, the ORP (oxidation-reduction potential) values in the groundwater of the soil surface karst zone exhibited a range of fluctuation between 15.67 and 56.00. This range suggests an overall low potential and strong reduction characteristic, with a variation extent of 40.33, indicating considerable and unstable fluctuations. (ii) As demonstrated in Figure 6, the general trend in the ORP values of groundwater across the entire soil surface karst zone is an increase with greater soil depth, signifying a decrease in reduction and an increase in oxidation. Nevertheless, this rate of change gradually decreases, peaking at a depth of 0.4 m. Beyond this point, a minor decreasing fluctuation trend is observed between 0.4 and 0.5 m depth, though the extent of this decline is minimal. (iii) Under different temperature conditions, lower temperatures correlate with higher karst groundwater ORP, displaying minimal fluctuations and a tendency towards stability. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Depth/(m)**} & \multicolumn{3}{c}{**Temperature**} \\ \cline{2-4}  & **10**\({}^{\circ}\)**C** & **20**\({}^{\circ}\)**C** & **30**\({}^{\circ}\)**C** \\ \hline
0.1 & 43.11 & 15.67 (_min_) & 24.33 \\
0.2 & 49.00 & 26.33 & 34.33 \\
0.3 & 47.33 & 33.67 & 40.83 \\
0.4 & 56.00 (_max_) & 37.33 & 45.83 \\
0.5 & 47.23 & 31.28 & 39.66 \\ Average value E & 48.53 & 28.86 & 37.00 \\ Range R & 12.89 & 21.67 & 22.67 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The ORP values of different depths of groundwater under different temperature conditions. Figure 6: The ORP curve for different depths of groundwater under different temperature conditions.