**4. Conclusions**

In this study, the hydrochemical characteristics and sources of Sr-rich groundwater in the Tianjiazhai area were analyzed using descriptive analysis, correlation analysis, Piper trilinear diagrams, Gibbs plots and ion ratios. In addition, the formation mechanisms of Sr in groundwater were discussed, taking into account the specific geological and hydrogeological conditions of the study area, as well as the hydrogeochemical theory. The results showed that:


The sandstone of Yanchang Formation is widely distributed in the Shimachuan River basin, and the hydrodynamic and hydrochemical conditions of Shimachuan River basin are conducive to the enrichment of strontium in groundwater, and the strontium in groundwater flowing into Yellow River will be more enriched. Therefore, the development of this study is of typical significance and can provide a scientific basis for the study of strontiumrich groundwater in the whole Shimachuan River basin. However, due to the special geological environment of the study area, soil erosion is more serious, the groundwater quality is poor in the downstream region, and the sediment content in the groundwater injected into the Yellow River is especially large. Therefore, the above changes should be further explored in future research.

This study provides a deeper understanding of the hydrochemical characteristics and sources of Sr-rich groundwater in the Tianjiazhai area. The results obtained can also provide a scientific basis and theoretical guidance for the development, utilization, and protection of Sr-rich groundwater.

**Author Contributions:** Research conceptualization, C.L. and W.W.; data curation, D.W. and A.O.; methodology, C.L.; writing—original draft, C.L.; writing—review and editing, W.W. and X.K., supervision, W.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** All processed data generated or used during the study appear in the submitted article. Raw data may be provided on reasonable request from the corresponding author.

**Acknowledgments:** We acknowledge the Shaanxi Province 139 Coal Geology and Hydrology Co. for the access to original information.

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