Groundwater Hydrogeochemistry, Uranium Mobility and Human Health Risk in the Mikir Hills, Assam, India: An Integrated Multivariate, Machine-Learning and Risk-Assessment Framework

Publication Details

Publication Date

10/11/2026

Volume / Issue

Vol 1, Issue 6 (2026)

Article No.

015

Journal

British Journal of Contemporary Research

DOI

https://doi.org/10.67693/BJCR-6UTHFG7U

Received

10 Oct 2026

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22

Downloads

10

Abstract

Groundwater in the Mikir Hills of Assam, India, occurs within a complexly layered lithostratigraphic framework spanning Archaean basement gneisses to Quaternary alluvium. To characterise the hydrogeochemical controls on major ions, trace metals, and uranium (U) behaviour, a dataset of 143 groundwater samples across 16 core parameters (U, Na, K, Ca, Mg, Cl, SO₄²⁻, HCO₃⁻ , pH, electrical conductivity, TDS, Cu, Pb, Zn, Ni, and Fe) was evaluated using an integrated multivariate, geochemical, and machine-learning framework. Hydrochemical facies analysis demonstrates that groundwaters are predominantly of Ca–Mg–HCO₃⁻ (52%) and mixed Ca–Na–HCO₃⁻ (30%) types, with Gibbs formulations confirming rock-weathering dominance alongside negative chloro-alkaline indices denoting reverse ion exchange. Speciation modeling indicates widespread supersaturation with respect to calcite (SI=+0.42) and dolomite (SI=+0.77), confirming that carbonate buffering establishes circumneutral-to-alkaline conditions. Nonparametric correlation and principal component analysis (PCA; four components explaining 67.2% of total variance) show that U is decoupled from bulk mineralisation (loading −0.04 on PC1) and instead loads on PC3 (0.64) and PC4 (0.35) alongside Cu, Fe, and Zn. Random Forest (RF) regression reveals negative cross-validated performance (R2=−0.077), whereas RF classification effectively discriminates upper-quartile U concentrations (>0.50 μg/L) with a ROC-AUC of 0.794. The Entropy-Weighted Water Quality Index (EWQI) identifies 38% of samples within poor-to-very-poor categories, driven predominantly by Fe and localized trace elements. Chemical health-risk assessment establishesnon-carcinogenic hazard quotients (HQ) exceeding 1.0 in 19% of adult and 31% of child cohorts, with cumulative hazard indices (HI>1.0) reaching 47% and 58%, respectively. These findings demonstrate that U migration is governed by redox-mediated Fe–Mn cycling, carbonate ligand complexation, and structural fracture conduits rather than bulk salinity. Identification of overlapping anomalies in high-strain corridors and fault zones—specifically at the Akashiganga–Udganga Convergence—host a significant alignment of peak gaseous Radon (>1100 counts/50 s) alongside Aqueous Radium (Ra) and Aqueous Uranium (U) anomalies, designating this convergence zone as the prime vector target for concealed mineralization.

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