## 3 Results
### Response of Karsi Groundwater Quality Indicators to Changes in Porosity  
#### 3.3.1 Changes in pH of Groundwater at Various Depths under Different Porosity Conditions  
Indoor experiments under different porosity conditions of undisturbed soil tested the pH values of groundwater at various depths, as indicated in Table 9 and Figure 10.  
(i) As shown in the results, in the soil surface karst zone under various porosity conditions, the pH value range of groundwater exhibited fluctuations between 5.91 and 6.29, typically acidic, with a fluctuation range of 0.38, indicating relatively minor fluctuations. (ii) Within the soil layer of the surface karst zone, with smaller porosity, karst groundwater pH values tend to increase, exhibiting greater fluctuations and more instability. (iii) As demonstrated in Figure 10, throughout the entire soil surface karst zone, the general trend of groundwater pH values showed a tendency to decrease with increasing soil depth. The change was approximately linear in the 0.1\(-\)0.3 m depth range, reaching extreme values at a depth of 0.3 m under varying porosity rates. This was followed by a slight upward fluctuation trend with increasing soil depth, although the magnitude of this rise was quite minimal. Figure 9: The TEC curve for different depths of groundwater under different temperature conditions. \begin{table}
\begin{tabular}{c c c c} \hline \multirow{2}{*}{**Depth/(m)**} & \multicolumn{3}{c}{**Temperature**} \\ \cline{2-4}  & **10**\({}^{\circ}\)**C** & **20**\({}^{\circ}\)**C** & **30**\({}^{\circ}\)**C** \\ \hline
0.1 & 222 & 470 & 1600 (_max_) \\
0.2 & 186 & 467 & 1178 \\
0.3 & 196 & 432 & 1068 \\
0.4 & 200 & 457 & 1137 \\
0.5 & 60 (_min_) & 139 & 1158 \\ Average value E & 173 & 393 & 1228 \\ Range R & 162 & 331 & 532 \\ \hline \end{tabular}
\end{table} 
Table 8: The TEC of different depths of groundwater under different temperature conditions. 3.2 Changes in ORP (Oxidation-Reduction Potential) of Groundwater at Various Depths under Different Porosity Conditions  
Indoor experiments under different soil porosity conditions tested the oxidation-reduction potential (ORP) values of groundwater at various depths, as indicated in Table 10 and Figure 11.  
(i) As shown from the results, in the soil surface karst zone with varying porosity rates, the oxidation-reduction potential (ORP) values of groundwater fluctuated between 22.50 and 49.72, indicative of overall low potential and strong oxidizing conditions. The variation range of 27.22 suggests substantial and unstable fluctuations. (ii) Within the soil layer of the soil surface karst zone, the smaller the porosity results in minimized groundwater ORP values and secondary stability, exhibiting greater fluctuations and more instability. (iii) As demonstrated in Figure 11, across the entire soil surface karst zone, the general trend is for groundwater ORP values to increase with increasing soil depth, although the rate of change gradually diminishes. An extreme value is observed at a depth of 0.4 m, followed by a minor downward fluctuation trend between 0.4 and 0.5 m depth; however, the extent of this downward fluctuation is minimal. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Depth/(m)**} & \multicolumn{3}{c}{**Porosity**} \\ \cline{2-4}  & **0.60** & **0.55** & **0.50** \\ \hline
0.1 & 35.89 & 24.72 & 22.50 (_min_) \\
0.2 & 42.17 & 36.83 & 30.67 \\
0.3 & 48.67 & 38.50 & 34.67 \\
0.4 & 49.72 (_max_) & 46.17 & 43.28 \\
0.5 & 45.62 & 37.78 & 35.89 \\ Average value E & 44.41 & 36.80 & 33.40 \\ Range R & 13.83 & 21.44 & 20.78 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: The ORP values of different depths of groundwater under different porosity conditions. Figure 10: The PH curve for different depths of groundwater under different porosity conditions.