Hydrogeochemical dynamics and fluoride-related health risks in groundwater from southwestern Ghana: a multivariate and spatial assessment

Introduction Fluoride enrichment in groundwater is an important hydrogeochemical and public health concern in crystalline basement terrains. This study investigated the hydrogeochemical processes, spatial fluoride distribution, and associated non-malignant health risks in groundwater across the transition zone between Ghana’s Western and Central Regions Methods A total of 48 groundwater samples were analysed for major ions, fluoride, and physicochemical parameters. The dataset was interpreted using descriptive statistics, hydrogeochemical facies analysis, multivariate statistics, PHREEQC-based mineral saturation modelling, GIS-supported spatial analysis, and age-specific hazard quotient assessment. Results Fluoride concentrations ranged from 0.01 to 3.27 mg/L, with 6.25% of samples exceeding the WHO guideline of 1.5 mg/L. Significant correlations with EC, TDS, Na + , SO₄ 2− , and HCO₃ − indicate the influence of silicate weathering, cation exchange, mineral undersaturation, and groundwater residence time. High-fluoride zones were mainly associated with fractured granitoids and areas of prolonged water-rock interaction, especially within parts of Tarkwa-Nsuaem and Twifo Atti Morkwa. Health risk assessment showed clear age-dependent vulnerability, with infants and children recording the highest hazard quotient values. Discussion The findings show that fluoride occurrence in the study area is controlled by the interaction of lithology, groundwater evolution, aquifer residence time, and localized recharge conditions. The study provides an integrated hydrogeochemical and spatial basis for groundwater monitoring, risk communication, and targeted water-quality management in southwestern Ghana.