4.4.3. Analysis of Simulation Results

The simulation results of the hydrogeochemical processes of groundwater in the study area are shown in Tables 4 and 5.


**Table 4.** Upstream and downstream water saturation indices along the reaction path.

**Table 5.** Results of the inverse simulation along the reaction path.


Note: Positive and negative values indicate dissolution and precipitation, respectively.

The saturation indices of minerals in the upstream and downstream water are reported in Table 4. Positive and negative values indicate oversaturated and unsaturated groundwater samples, respectively. The results showed that calcite, chalcedony, dolomite, hematite, and quartz were all oversaturated. This finding can be explained by the fact that calcite and dolomite are the main minerals of the unconfined aquifers in the study area in the eastern plains in the Taihang Mountain front the remaining minerals revealed negative values, thus indicating unsaturation.

Table 5 shows the molar transfer of possible mineral phases along the reaction path. The results showed precipitation of gypsum, carbon dioxide, K-mica, and fluorite in the unconfined aquifers of the study area. Whereas Calcite, sodium exchange, K-feldspar, manganite, and hematite were in dissolved forms in the unconfined aquifers, with dissolved amounts of 2.20 <sup>×</sup> <sup>10</sup>−<sup>5</sup> , 1.93 <sup>×</sup> <sup>10</sup>−<sup>5</sup> , 3.75 <sup>×</sup> <sup>10</sup>−<sup>6</sup> , and 1.73 <sup>×</sup> <sup>10</sup>−<sup>5</sup> mol/L, respectively. On the other hand, the cation exchange in the unconfined aquifer was characterized by the exchange of Ca2+, Na<sup>+</sup> , and Mg2+, which suggests adsorption of Na<sup>+</sup> and Mg2+ in groundwater, while Ca2+ in the exchange medium was in a dissolved form in groundwater. The amount values of Na<sup>+</sup> , Mg2+, and Ca2+ ion exchange were 6.34 <sup>×</sup> <sup>10</sup>−<sup>3</sup> , 3.19 <sup>×</sup> <sup>10</sup>−<sup>4</sup> , and 3.49 <sup>×</sup> <sup>10</sup>−<sup>3</sup> mol/L, respectively.

The results of the inverse hydrogeochemical simulations performed using the PHREEQC software are consistent with those obtained using the principal components analysis and water chemistry analysis. The main factors influencing the hydrochemical characteristics of groundwater are the dissolution of carbonate minerals (calcite and dolomite) and silicate minerals (sodium feldspar and potassium feldspar).
