Hydrogeochemical Processes and Sustainability Challenges of Arsenic- and Fluoride-Contaminated Groundwater in Arid Regions: Evidence from the Tarim Basin, China

The anomalous enrichment of arsenic (As) and fluoride (F) in groundwater in the oasis area at the southern margin of the Tarim Basin has become a critical environmental and sustainability challenge. It poses not only potential health risks but also profound socio-economic impacts on local communities, threatening the long-term security of water resources in arid regions. Therefore, an in-depth investigation of the hydrochemical characteristics of groundwater and the co-enrichment mechanism of As and F is essential for advancing sustainable groundwater management. In this study, 110 phreatic water samples and 50 confined water samples were collected, and mathematical and statistical methods were applied to analyze the hydrochemical characteristics, sources, and co-enrichment mechanisms of As and F. The results show that (1) the groundwater chemistry types are mainly Cl·SO4-Na, SO4·Cl-Na·Mg, Cl·SO4-Na·Mg, and Cl-Na, and the chemistry is primarily controlled by evaporation and concentration processes, with additional influence from human activities and cation exchange; (2) As and F mainly originate from soils and minerals, and are released through dissolution; (3) As and F enrichment is positively correlated with pH, Na+, and HCO3−, but negatively correlated with Ca2+, Mg2+, and SO42−, indicating that a weakly alkaline hydrochemical environment with high HCO3− and Na+, and low Ca2+ promotes their enrichment; (4) strong evaporative concentration in retention zones, combined with artificial groundwater extraction, further intensifies As and F accumulation. This study not only provides an innovative theoretical and methodological framework for exploring trace element enrichment mechanisms in groundwater under arid conditions but also delivers critical scientific evidence for developing sustainable water resource management strategies, mitigating water-related health risks, and supporting regional socio-economic resilience under global climate change.