Human Activity and Hydrogeochemical Processes Relating to Groundwater Quality Degradation in the Yuncheng Basin, Northern China

Groundwater quality degradation has raised widespread concerns about water supplies and ecological crises in China. In this study, hydrogeochemistry, environmental stable isotopes (δ18O, δD), and principal component analysis were conducted together to reveal the mechanism’s response to the hydrogeochemical and quality degradation of groundwater in Yuncheng Basin, Northern China, so that reasonable water resource management strategies can be developed. The study reveals that groundwater faces a tremendous risk of quality decrease during the past decade: (1) the hydrochemical facies of groundwater shows that the bicarbonate and chloride type water was replaced with sulfate type water and the occupying area of SO4·Cl-Na, SO4·HCO3-Na type water expanded dramatically in shallow and intermediate-deep aquifers. (2) Major ion chemistry and hydrogen and oxygen isotope compositions indicate that the major hydrogeochemical processes responsible for groundwater quality deterioration include the dissolution of evaporates (i.e., halite, gypsum, and mirabilite), ion exchange, and evaporation process. Additionally, (3) anthropogenic activities (overutilization of fertilizer) have resulted in nitrate contamination, and have thereby led to groundwater quality degradation.

Hydrogeochemistry of high-fluoride saline groundwater in the Yuncheng Basin, northern China

The presence of saline groundwater has become one of the most acute problems for water resource management worldwide, since it causes deterioration in water quality and endangers future exploitation of groundwater resources. In addition, high levels of groundwater salinity are often associated with an increase in the concentrations of fluoride (F). Diverse mechanisms govern salts and fluoride enrichment in groundwater. In this case, saline groundwater with elevated fluoride (up to 14.1 mg/L) in the Yuncheng Basin (YB) was investigated. The research shows: (i) large-scale contamination of F in groundwater is closely associated with groundwater salinization processes in the area; (ii) groundwater with high F concentrations has distinctive major ion chemistry: Na-rich and Ca-poor with a high pH and HCO3- content. The major ion chemistry and pH are controlled by mineral dissolution, cation exchange, and evaporation in the aquifer systems which are also important for F mobilization.