Characterization of Groundwater Hydrochemistry and Comprehensive Water Quality Assessment in the Zi River Basin,...

Identifying and analyzing the hydrochemical groundwater characteristics and their spatiotemporal variations of pollution origins are crucial for safeguarding the regional groundwater environment. The present work adopts in total 100 typical water samples gathered from the Zi River Basin (ZRB) between 2019 and 2021. Using statistical computation and integrated hydrogeochemical methods, the study investigated the hydrochemical characteristics of groundwater in the ZRB, as well as the sources and formation mechanisms of pollutants. Moreover, the present work examined whether groundwater meets irrigation and drinking water standards, and evaluated the potential risks posed by NO₃ ^- to human health. The analysis results indicate that the groundwater in the study area falls within the freshwater category, exhibits weak alkalinity, and has a total dissolved solids (TDS) content ranging from 58.68 to 3237.59 mg/L; the primary hydrochemical type is HCO₃·Ca. Carbonate rock weathering is the paramount factor constraining the composition of groundwater in the study area, followed by the influence of human activities and cation exchange processes. The evaluation of suitability for human drinking consumption showed that the groundwater quality in the study area is excellent, with 84% applicable to direct consumption and 16% suitable for consumption after treatment. The evaluation of suitability for irrigation demonstrated that most of the collected groundwater samples satisfy the requirements of direct irrigation, and no risk of soil salinization was observed. Three principal components can be extracted from the data., with a cumulative contribution rate of 90.57%. According to the Positive Matrix Factorization (PMF), variations in nitrate ion concentrations in groundwater are primarily associated with human-induced activities such as industrial production and agricultural cultivation production. On the basis of the nitrate health risk exposure assessment, more than one-third of groundwater within the research area is unfit for direct consumption, and children face a more severe risk of cancer from nitrate exposure than adults. The findings can serve as a reference for regions facing similar challenges.