**5. Conclusions**

In this study, 14 groundwater samples were collected from the unconfined aquifers of Western Yongqing County to assess the hydrochemical characteristics of groundwater using descriptive, multivariate statistics, and water chemistry analysis methods. The following main conclusions were drawn from this study:

(1) The unconfined aquifers in the western part of Yongqing County revealed weakly alkaline groundwater. In addition, the results suggested fresh and brackish groundwater in the study area. The abundance of cations and anions followed the orders of Na<sup>+</sup> > Ca2+ > Mg2+ > K<sup>+</sup> > Fe2+ and HCO<sup>3</sup> − > SO<sup>4</sup> <sup>2</sup><sup>−</sup> > Cl<sup>−</sup> > NO<sup>3</sup> − > F− > NO<sup>2</sup> −, respectively.

(2) The relative content of anions and cations in groundwater and Piper's trilinear diagram demonstrated complex hydrochemical facies types of groundwater in the study area. The groundwater facies types were HCO<sup>3</sup> <sup>−</sup>−Mg·Ca, HCO<sup>3</sup> <sup>−</sup>−Na, HCO<sup>3</sup> <sup>−</sup>−Na·Ca, and HCO<sup>3</sup> <sup>−</sup>−Na·Mg.

(3) The main factors influencing the hydrochemical characteristics of groundwater were determined to use the principal component analysis, Gibbs diagrams, and ionic ratios. The results revealed that mineral dissolution, as well as some anthropogenic factors, are the main factors influencing the groundwater chemistry in the study area. In addition, Gibbs diagrams and ionic ratios revealed that silicates and carbonates were the main minerals influencing the hydrochemical characteristics of unconfined aquifers in the study area, followed by the alternating cation adsorption.

(4) Simulation of water-rock interactions in the unconfined aquifers was performed using the PHREEQC software. The simulation results are consistent with those obtained using the principal component analysis, Gibbs diagram, and ionic ratios. According to the obtained results, the dissolution of carbonate minerals (calcite and dolomite) and silicate minerals (sodium feldspar and potassium feldspar) were the main factors influencing the hydrochemical characteristics of the unconfined aquifers in the study area.

In conclusion, although there are anthropogenic activities in some areas of Yongqing County, the groundwater quality of the unconfined aquifers in the western part of Yongqing County is relatively good. Therefore, relevant departments need to strengthen the monitoring and management of groundwater quality to ensure scientific management and sustainable utilization of groundwater in Yongqing County.

**Author Contributions:** Conceptualization, X.B.; methodology, Y.L.; software, J.L.; validation, Y.Z.; formal analysis, X.T.; investigation, X.W.; resources, X.B.; data curation, X.T.; writing—original draft preparation, Y.Z.; writing—review and editing, J.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research is funded by Open project of Hebei key laboratory of geological resources and environmental monitoring and protection (JCYKT202101); Natural Science Foundation of Hebei Province of China (D2022403016); Hebei University Science and technology research project (ZD2022119); Science and technology innovation team project of Hebei GEO University (KJCXTD-2021-14); Introduction of foreign intelligence project in Hebei province in 2021 (2021ZLYJ-1); Hebei water conservancy science and technology plan project (2021-45).

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data are all monitored by the Hebei Geological Environment Monitoring Institute, which are true and reliable.

**Acknowledgments:** The authors acknowledge the support provided by Hebei GEO University; Hebei Key Laboratory of Environment Monitoring and Protection of Geological Resources, Hebei Geological Environment Monitoring Institute, Shijiazhuang; Hebei Institute of hydrogeology and engineering geology.

**Conflicts of Interest:** The authors declare no conflict of interest.
