Major ion hydrogeochemistry and health risk of groundwater nitrate in selected rural areas of the Guanzhong Basin, China

Abstract

In this study, the hydrochemical characteristics of groundwater were assessed based on 64 shallow groundwater samples collected in the Guanzhong Basin, China, and the health risk of nitrate (NO₃^-) in drinking water was assessed. In addition, the spatial distributions of major water quality indicators were investigated, while bivariate plots, saturation index, and stable isotopes were used to reveal the processes controlling groundwater hydrogeochemistry. The results showed that groundwater in the study area was mostly fresh water. However, the maximum and average NO₃^– concentrations were 397.0 and 92.9 mg/L, respectively, indicating serious groundwater NO₃^– pollution. The percolation of contaminated river water exhibited considerable impacts on groundwater quality. Carbonate dissolution was the major process controlling the hydrochemical characteristics of groundwater, while human activities were responsible for the high concentrations of groundwater pollutants, especially NO₃^–. Evaporation fraction of groundwater in the study area revealed by stable hydrogen and oxygen isotopes ranged from 4 to 13% and 4 to 11%, respectively. High non-carcinogenic health risks of NO₃^– to adults and children were observed in about 46.88 and 75% of the collected groundwater samples, respectively. The risk value ranges were 0-6.00 and 0-14.06, with average values of 1.36 and 3.19, for adults and children, respectively.

Keywords:

• Groundwater quality
• hydrochemical characteristics
• nitrate pollution
• geochemical modeling
• solute geochemistry

Acknowledgments

The journal editors and reviewers who gave valuable comments that are helpful for us to further improve the quality of the manuscript are sincerely acknowledged. The external experts who gave valuable instructive comments on the implementation of the research project are also acknowledged. In addition, we are grateful for the help in field investigation and sampling rendered by team members including Rui Duan, Yanan Guo, Yanlin Li, Yongqiang Yang, Qixiao Zhang. Last, but not the least, we are grateful for the help from Lingxi Li, Fei Xu and Song He in drawing the spatial distribution maps, calculating the evaporation fractions and health risks, and discussing the methods.

Conflict of  interest

The authors declared that they have no conflict of interest.

Authors contributions

Duoxun Xu led the research project, conceptualized the core idea of the research and participated in the discussion. Peiyue Li wrote the early drafts of the paper, refined the idea, analyzed the data, supervised the research and finalized this paper. Xin Chen, Shengfei Yang, Pei Zhang and Fa Guo participated in the water sampling, water analysis, reading the manuscript.

Data availability

The raw data of this research may be provided upon reasonable request.

Additional information

Funding

This research was financially supported by the National Natural Science Foundation of China (42072286 and 41761144059), China Geological Survey Project (DD20211574), the Qinchuangyuan "Scientist + Engineer" Team Development Program of the Shaanxi Provincial Department of Science and Technology (2022KXJ-005), the Fok Ying Tong Education Foundation (161098), and the National Ten Thousand Talent Program (W03070125).