Hydrochemical characteristics analysis and human health assessment in the upper reaches of Zhang Wei River alluvial plain

Abstract

Groundwater is the critical resource for agricultural, industrial, and urban-rural water supplies in arid and semi-arid regions, especially in North China Plain. In this study, 64 groundwater samples were collected to assess the potential for groundwater development and utilization in the upper reaches of the Zhang Wei river. The hydrochemical analysis revealed that the groundwater is primarily composed of HCO3-Ca and HCO3-Na·Ca. The hydrochemical type is influenced by natural water-rock interactions, including evaporite dissolution, silicate weathering, and ion exchange processes. Isotope data for hydrogen and oxygen, characterized by positive deviations from the global meteoric water line, underscore the significant impact of evaporation in the region. An entropy weight index method was employed for water quality evaluation, revealing that over 89% of the samples complied with Class II standards for household use. Furthermore, more than 85% of the area’s groundwater exhibited Total Dissolved Solids (TDS) concentrations below 1,000 mg/L, indicating a predominance of soft water. However, toxic elements such as fluorine (F), iodine (I), and chromium (Cr) were found to exceed drinking water standards, posing a health risk. Particularly, the intake level of fluorine was above the permissible value, potentially causing non-carcinogenic risks to children and infants. In conclusion, while the overall groundwater quality is favorable for the region, the presence of geochemically derived toxic substances necessitates careful consideration of its suitability for drinking purposes.