Hydrogeochemical and statistical analysis of arsenic and fluoride in aquifers located along the trans-Mexican volcanic belt: a preliminary comparative approach

This study assesses groundwater quality in five representative aquifers along the Trans-Mexican Volcanic Belt (TMVB): Celaya (CVA), Irapuato (IVA), Zimapán (ZA), Morelia-Querendaro (MQA) and Mexico City Metropolitan Zone (AMZMC), focusing on processes controlling arsenic (As) and fluoride (F−) occurrence and mobility. Main objectives are to compare hydrogeochemical facies, identify release mechanisms (sulfide oxidation, silicate alteration, desorption), and quantify predictive factors via statistical analysis, addressing lithological heterogeneity in a common volcanic context. A multitemporal dataset of 155 well samples (2005–2023) was compiled, analyzing physicochemical parameters (pH, T°, E.C.), major ions (HCO₃⁻, SO₄2⁻, Ca2⁺, Na⁺, etc.), As, F⁻, and stable isotopes (δ1⁸O, δ2H, δ13C) using Piper-D'Amore diagrams, factor analysis (FA), ANOVA, and multiple linear regression in JASP. Findings show 63% of As variability explained by SO₄2⁻ (coef. 6.1 × 10⁻4, p < 0.001), linked to sulfide oxidation (Factor 2: Ca-SO₄-As); F⁻ correlates with low Mg and high pH/T° (R2 = 0.48, Factor 4), favored by felsic alteration (rhyolites, biotite). ZA stands out for As in fractured carbonates; CVA/IVA for thermal F⁻. Conclusions highlight local modulation (lithology > regional volcanism) for health risks, recommending targeted monitoring of sulfides (ZA) and thermal zones (Guanajuato), with future paths for synchronized sampling and redox modeling. This comparative framework unifies prior isolated assessments, supporting sustainable TMVB aquifer management.