[Identifying Hydrochemical Characteristics, Control Factors, and Pollution Source of Groundwater in the Oasis Area of...

The groundwater of the oasis areas of Toksun County, Xinjiang, including the Toksun and Kumishi oasis areas, is an important source of water for the production and daily life activities of local people. The sustainable development and utilization of groundwater resources, ecological environment protection, and maintenance of human health are crucial factors to determine the quality and pollution sources of groundwater. In July 2023, nine groups of unconfined and 12 groups of confined groundwater samples were collected from the oasis area. The main water chemical characteristic indicators were measured, and the control factors and pollution sources of groundwater in different regions were studied and discussed by the comprehensive use of mathematical statistics analyses, Piper three-plot, Gibbs chart, ion ratio, and principal component analysis. The groundwater quality was evaluated using the water quality index （WQI） method. The potential risk of NO₃^- in groundwater was evaluated by a comprehensive health risk assessment model. The results showed that the groundwater in the study area was alkaline, and the hydrochemical types were complex and diverse. The water chemical type in the Toksun oasis area mainly comprised Cl·SO₄·HCO₃-Na·Ca, whereas that in the Kumishi oasis area comprised Cl·SO₄-Na·Ca. The overall water quality in the Toksun oasis area was good, and mainly involved Class I and II water （91.7%）. The water quality in the oasis area of Kumishi was poor, and mainly involved Class IV and V water （77.8%）. The health risk assessment showed that infants and adolescents faced higher health risk in the Toksun oasis area. Infants, children, adolescents, and adults in the Kumishi oasis area faced higher health risks, with children being more sensitive to the risk of cancer caused by inorganic substances in groundwater. Source analysis results showed that groundwater of different aquifers in the study area had similar sources or evolution processes, and leaching-enrichment （F1, contribution rate of 66.1%）, human activity （F2, contribution rate of 15.8%）, and original geological conditions （F3, contribution rate of 8.0%） were the main factors affecting the evolution of groundwater quality in the study area.