Characterization, formation mechanism, and human health risk assessment of fluoride in shallow groundwater of Suzhou city, East China

ABSTRACT Groundwater is a vital water source for human consumption and irrigation. Understanding its fluoride content and health implications is crucial for water resource management. This study investigated the quaternary aquifer in Suzhou, China, collecting and analyzing 49 groundwater samples. Thermodynamic simulation, multivariate statistical analysis, and health risk assessment models were employed to determine fluoride concentration characteristics, hydrochemical controlling mechanisms, and noncarcinogenic risks. Results revealed an average fluoride concentration of 0.89 mg/L, with 26.5% of samples exceeding the Grade III groundwater quality standard. High-fluoride groundwater (>1 mg/L) exhibited spatial heterogeneity and was predominantly of the Na-Mg-HCO3 hydrochemical type. Multivariate analysis and thermodynamics simulations indicated that water–rock interactions (e.g., silicate mineral weathering and fluorite dissolution) governed groundwater hydrochemistry. Fluoride primarily originated from fluoride-bearing mineral dissolution, while negative cation exchange and precipitation of calcite and dolomite enhanced fluoride enrichment. pH had minimal impact on fluoride concentrations under weakly alkaline conditions. Health risk assessment suggested that fluoride in shallow groundwater posed a higher noncarcinogenic risk to children than adults via ingestion. These findings provide valuable insights for regional groundwater resource management.