Geostatistical and multivariate analysis of phosphate evolution and its relationship with heavy metals in shallow groundwater in a Semi-Arid Basin

Understanding phosphate distribution and its interactions with heavy metals using multivariate and geostatistical analyses is essential for sustainable water resources management in semi-arid basins. This study aims to investigate the potential sources of phosphate and its relationship with heavy metals in shallow groundwater over sixty-three (63) sampling locations during wet, dry, and intermediate seasons (Physical parameters TDS, EC, DO, pH, and Turbidity) were analysed in situ using hand-held meters, while phosphates and heavy metals were analysed in the laboratory. Results were further analysed using Several Samples Anova (i.e., Kruskal-Wallis Test), Ordinary Kriging (OK), Correlation (Pearson's (r)) and Principal Component Analysis (PCA). Results revealed a significant difference in pH level and dissolved oxygen (DO) concentration (p = <= 0.001). However, based on seasonal analysis, there is no significant difference in phosphate, EC, TDS, and turbidity (p = >= 0.001); DO and phosphate concentrations are above WHO and Nigeria's drinking water quality guidelines. Pearson's Correlation (r) revealed a positive relationship between phosphate, vanadium, nickel, and cobalt. In contrast, phosphate correlates weakly and negatively with heavy metals (Zn, Cd, Ti, Ba, Cu, Ni, As, Co, Pb, Mn, Cr, and Al). The weak negative correlation between phosphate and Cr, Cd, and Zn suggests phosphate can increase metal immobilisation via precipitation as insoluble metal-phosphate compounds. The positive correlation between phosphate and heavy metals (Co and Ni) suggests competing geochemical processes. The PCA revealed that most of the variability in phosphate concentration is explained by the seasonality, which accounts for 88.196% of the variance. Shallow groundwater classification using ordinary kriging (OK) revealed poor-quality water. Phosphate concentrations exceed the WHO reference guideline (<= 1.00 mg/l) value. Theoretically, this study has increased our understanding of how high phosphate concentrations correlate with heavy metals in shallow groundwater aquifers. This study's results lay the foundation for future studies over broader geographical and temporal scopes, increasing coverage of water quality and sustainable drinking water quality management in semi-arid environments. Thus, a sustainable water quality management framework has been proposed to guide future assessment and effectively implement remediation strategies concerning water quality pollution remediation in semi-arid regions.