## 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
Conversely, with the highest temperatures, groundwater GRP shows the most significant fluctuations and is least stable. 2.3 Changes in COD (Chemical Oxygen Demand) of Groundwater at Various Depths under Different Temperature Conditions  
Indoor experiments at different temperatures measured the chemical oxygen demand (COD) values of groundwater at various depths, as shown in Table 6 and Figure 7.  
(i) As shown in the results, under various temperature conditions, the chemical oxygen demand (COD) values of groundwater in the soil surface karst zone demonstrated fluctuations between 7.74 and 25.15, with a range of 17.41. This significant fluctuation indicates that the groundwater in this karst surface zone generally exhibits high chemical oxygen demand and is substantially polluted. (ii) As demonstrated in Figure 7, the overall trend of COD values throughout the soil surface karst zone tends to increase with increasing soil depth, displaying a generally linear positive correlation. (iii) At consistent temperature conditions, with a temperature rise, the COD values in karst groundwater increase, exhibiting more significant fluctuations and instability. When temperatures reach their lowest, groundwater COD values are at their minimum, with the smallest fluctuations, indicating greater stability. 2.4 Changes in TBC (Oxidation-Reduction Potential) of Groundwater at Various Depths under Different Temperature Conditions  
Indoor experiments under different temperature conditions measured the total bacterial count (TBC) values of groundwater at various depths, as shown in the Table 7 and Figure 8. \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 & 7.87 & 10.64 & 14.05 \\
0.2 & 7.74 (_min_) & 9.84 & 16.47 \\
0.3 & 10.21 & 12.20 & 17.21 \\
0.4 & 12.34 & 14.58 & 21.32 \\
0.5 & 14.39 & 19.86 & 25.15 (_max_) \\ Average value E & 10.51 & 13.42 & 18.84 \\ Range R & 6.65 & 10.02 & 11.10 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The COD values of different depths of groundwater under different temperature conditions. Figure 7: The COD curve for different depths of groundwater under different temperature conditions. (i) As shown in the results, under varying temperature conditions, the total bacterial count (TBC) value range of groundwater in the soil surface karst zone was observed to fluctuate between 26,900 and 386,667, with a substantial range of 359,767, indicating significant fluctuations. This suggests that the groundwater in this karst surface zone is subject to severe TBC exceedance, indicative of serious microbial pollution. (ii) As demonstrated in Figure 9, across the entire soil surface karst zone soil layer, at lower temperatures, there is a general trend of decreasing groundwater TBC values with increasing soil depth, although the range of this change is quite minimal. Conversely, at higher temperatures, the overall trend is for groundwater TBC values to disperse more with increasing soil depth. (iii) Under different temperature scenarios, with the summer temperature rise, karst groundwater TBC values increase, displaying larger fluctuations and more instability. When temperatures are at their lowest, groundwater TBC values reach their minimum and exhibit the smallest fluctuations, indicating greater stability. 2.5 Changes in TEC (Total _Escherichia coli_) of Groundwater at Various Depths under Different Temperature Conditions  
Indoor experiments under different temperature conditions measured the total Escherichia coli (TEC) values of groundwater at various depths, as indicated in Table 8 and Figure 9.  
(i) As shown from the results, under diverse temperature conditions, the total _E. coli_ count (TEC) values in the groundwater of the soil surface karst zone exhibited fluctuations between 60 and 1600, with a range of 1540.