4.3.3. Inter-Ion Distance Diagram Analysis

According to the results of factor analysis and Gibbs diagram, it is evident that rock dominance and mineral dissolution were the main factors controlling the hydrochemical characteristics of groundwater. Therefore, to further investigate the mineral species derived from rock weathering and dissolution and to verify the results obtained using the principal component analysis, the HCO<sup>3</sup> <sup>−</sup>/Na<sup>+</sup> , Ca2+/Na<sup>+</sup> , Mg2+/Na<sup>+</sup> , and Ca2+/Na<sup>+</sup> ratios were used to distinguish between the influences of different rock and mineral weathering on groundwater components.

The results showed that most of the water sampling points were plotted between silicate weathering and carbonate dissolution zones, which suggests significant influences of the weathering of silicate and carbonate minerals on the hydrochemical characteristics of groundwater (Figures 7 and 8).

**Figure 7.** Relationship betweenCa2+/Na<sup>+</sup> and HCO<sup>3</sup> − /Na<sup>+</sup> of the phreatic aquifer in Yongqing **Figure 7.** Relationship between Ca2+/Na<sup>+</sup> and HCO<sup>3</sup> <sup>−</sup>/Na<sup>+</sup> of the phreatic aquifer in Yongqing County.

It can be seen from Figure 6 that all water sampling points fall in the rock dominance control zone, which indicates that that rock dominance was the main influencing factor controlling the hydrochemical characteristics of groundwater in the study area. As shown in Figure 6a, Na+ has a wide distribution and exhibit high proportions in some samples, indicating that sodium ions may be generated by a variety of sources. However,

produced from the similar source or through the same geochemical process (Figure 6b). It should be noted that the Gibbs diagrams revealed only the natural factors influencing the groundwater chemical characteristics, while the human factors were not considered.

According to the results of factor analysis and Gibbs diagram, it is evident that rock dominance and mineral dissolution were the main factors controlling the hydrochemical characteristics of groundwater. Therefore, to further investigate the mineral species derived from rock weathering and dissolution and to verify the results obtained using the

> − /Na<sup>+</sup>

were used to distinguish between the influences of different rock and mineral weathering

The results showed that most of the water sampling points were plotted between silicate weathering and carbonate dissolution zones, which suggests significant influences of the weathering of silicate and carbonate minerals on the hydrochemical charac-

is small and the distribution is concentrated, indicating that all Cl–

, Ca2+/Na<sup>+</sup>

, Mg2+/Na<sup>+</sup>

, and Ca2+/Na

is

<sup>+</sup>ratios

the proportion of Cl–

4.3.3. Inter-Ion Distance Diagram Analysis

principal component analysis, the HCO<sup>3</sup>

teristics of groundwater (Figures 7 and 8).

on groundwater components.

County.

**Figure 8.** Relationship between Ca2+/Na<sup>+</sup> and Mg2+/Na<sup>+</sup> of phreatic aquifer in Yongqing County. **Figure 8.** Relationship between Ca2+/Na<sup>+</sup> and Mg2+/Na<sup>+</sup> of phreatic aquifer in Yongqing County.

In order to further check whether the ion exchange process occurred in groundwater, the relationship diagram between Ca2+ + Mg2+-HCO<sup>3</sup> − -SO<sup>4</sup> <sup>2</sup><sup>−</sup> and Na++K+−Cl−were used for discrimination [30]. Water sampling points in the first quadrant of graphs (positive X and Y-coordinate values) suggest that rock salt dissolution is not the source of Na<sup>+</sup> and K<sup>+</sup> , while the dissolution of peritectic minerals is not the source of Ca2+ and Mg2+ in groundwater, which is explained by the presence of a higher amount of Na++K<sup>+</sup> than Cl<sup>−</sup> and lower amount of Ca2++Mg2+than HCO<sup>3</sup> − -SO<sup>4</sup> 2− (Figure 9). In addition, equal ions concentrations suggest that a cation exchange process occurred in groundwater. In order to further check whether the ion exchange process occurred in groundwater, the relationship diagram between Ca2++Mg2+-HCO<sup>3</sup> −-SO<sup>4</sup> <sup>2</sup><sup>−</sup> and Na++K+−Cl<sup>−</sup> were used for discrimination [30]. Water sampling points in the first quadrant of graphs (positive X and Y-coordinate values) suggest that rock salt dissolution is not the source of Na<sup>+</sup> and K + , while the dissolution of peritectic minerals is not the source of Ca2+ and Mg2+ in groundwater, which is explained by the presence of a higher amount of Na++K<sup>+</sup> than Cl− and lower amount of Ca2++Mg2+ than HCO<sup>3</sup> <sup>−</sup>-SO<sup>4</sup> <sup>2</sup><sup>−</sup> (Figure 9). In addition, equal ions concentrations suggest that a cation exchange process occurred in groundwater.

> 2+-HCO<sup>3</sup> − -SO<sup>4</sup>

2- and Na<sup>+</sup> + K<sup>+</sup>


ions of phreatic aquifer in

**Figure 9.** Relationship between Ca2++Mg

Yongqing County.

K<sup>+</sup>

**Figure 8.** Relationship between Ca2+/Na<sup>+</sup> and Mg2+/Na<sup>+</sup> of phreatic aquifer in Yongqing County.

ter, the relationship diagram between Ca2+ + Mg2+-HCO<sup>3</sup>

and lower amount of Ca2++Mg2+than HCO<sup>3</sup>

In order to further check whether the ion exchange process occurred in groundwa-

for discrimination [30]. Water sampling points in the first quadrant of graphs (positive X and Y-coordinate values) suggest that rock salt dissolution is not the source of Na<sup>+</sup> and

> − -SO<sup>4</sup> 2−

groundwater, which is explained by the presence of a higher amount of Na++K<sup>+</sup>

centrations suggest that a cation exchange process occurred in groundwater.

, while the dissolution of peritectic minerals is not the source of Ca2+ and Mg2+ in

− -SO<sup>4</sup>

<sup>2</sup><sup>−</sup> and Na++K+−Cl−were used

(Figure 9). In addition, equal ions con-

than Cl<sup>−</sup>

**Figure 9.** Relationship between Ca2++Mg 2+-HCO<sup>3</sup> − -SO<sup>4</sup> 2- and Na<sup>+</sup> + K<sup>+</sup> -Cl<sup>−</sup> ions of phreatic aquifer in Yongqing County. **Figure 9.** Relationship between Ca2++Mg2+-HCO<sup>3</sup> −-SO<sup>4</sup> 2- and Na++K<sup>+</sup> -Cl− ions of phreatic aquifer in Yongqing County.

According to the results obtained, all the water sampling points were plotted on the 1:1 line, indicating that the cation exchange process occurred in the unconfined aquifers of the study area.
