*4.1. Descriptive Statistical Analysis*

*3.2. Data Analysis Methods* In addition to, descriptive statistics, the principal component analysis test was performed in this study using the SPSS software to determine the main influencing factors affecting the hydrochemical characteristics of groundwater in Yongqing County [14,15]. In order to determine the hydrochemical characteristics of groundwater, the SPSS statistical analysis software was used to perform descriptive statistical analysis (minimum, median, maximum, mean, and standard deviation) on the results data of 18 hydrochemical parameters of groundwater samples (Table 1).

In addition, ionic ratios were used to analyze the alternate adsorption of cations and investigate the main sources of hydrochemical elements in groundwater. On the other hand, the PHREEQC software was used for hydrogeochemical inversion simulations. According to the results obtained, pH values ranged from 7.5 to 8.3, with a mean value of 7.8, which indicates that the pH of groundwater in the western part of Yongqing County is slightly alkaline. In addition, the mineralization ranged from 345.5 to 1800.9 mg/L, with a mean value of 896.8 mg/L. In fact, some groundwater samples showed high mineralization values (above 1 g/L), indicating fresh-brackish groundwater. The TDS concentration

range was 243.7–1333.6 mg/L, with a mean value of 638.4 mg/L, showing significant spatial variation in the TDS concentrations in the study area with the presence of higher concentrations than that of the National Standard for Drinking Water (GB 5749-2006). On the other hand, Na<sup>+</sup> was the most abundant cation in groundwater, with a mean concentration value of 116.764 mg/L, followed, respectively, by Ca2+, Mg2+, K<sup>+</sup> , and Fe2+ . Whereas HCO<sup>3</sup> − was the highest anion in groundwater, with a mean concentration value of 516.77 mg/L, followed, respectively, by SO<sup>4</sup> <sup>2</sup>−, Cl−, NO<sup>3</sup> −, F−, and NO<sup>2</sup> −.


**Table 1.** Descriptive statistics of chemical parameters of groundwater.

By comparing the average concentration values of the hydrochemical parameters of groundwater with the Drinking Water Standards' (GB 5749-2006), it was found some ions exceeded the drinking limit values, which suggests a deterioration of the groundwater quality in the study area [16,17]. The main manifestations were SO<sup>4</sup> <sup>2</sup>−, NO<sup>3</sup> <sup>−</sup>, Mn, F−, Na<sup>+</sup> , and two combined indicators TH and TDS.
