Potentially toxic elements source identification and associated health risks in the groundwater of transboundary Komadugu-Yobe basin, Lake Chad region: an integrated approach using chemometric analysis and index-based models

Study region
Transboundary Komadugu-Yobe basin, located in the semi-arid to arid region of Nigeria and Niger Republic, is a vital water resource supporting domestic, agricultural, and industrial activities.
Study focus
This study investigates the pollution levels, potential sources, and human health risks associated with potentially toxic elements (PTEs) in groundwater using an integrated approach combining index-based models and chemometric analysis.
New hydrological insights for the region
The results indicate that Pb, Fe, Mn, and Cd are the key contaminants, with no significant seasonal variations. Pollution indices (Cdeg, HEI, HPI, and mHPI) classify groundwater as less polluted in upgradient areas and highly polluted in downgradient zones. Human health risk assessment (HHRA) reveals significant non-carcinogenic and carcinogenic risks (mean HI > 1 for both adults and children; mean CR > 1.0 × 10⁻³ for adults, and > 1.0 × 10⁻⁴ for children). As, Cd, Mn, and Pb are key the contributors to non-carcinogenic and carcinogenic health risks and potential risks of chronic kidney disease of unknown aetiology (CKDu). Correlation analysis suggests distinct geochemical behaviours of PTEs. Principal Component Analysis/Factor Analysis (PCA/FA) and R-mode Hierarchical Cluster Analysis (HCA) identify mixed sources, including industrial and domestic discharges as well as agricultural activities, as major contributors to groundwater contamination. These findings provide critical insights for policymakers, stakeholders and regulatory institutions to develop effective strategies for sustainable groundwater resource management in the region.