Hydrogeochemistry, Petrography, and Groundwater Quality in the Waru–Apo Area (Abuja FCT, Nigeria)

Abstract

Groundwater is the primary source of domestic water supply in many parts of Abuja, Nigeria, particularly within crystalline basement terrains where surface water is limited. However, increasing urbanization and anthropogenic activities, especially abattoir operations and unregulated waste disposal, pose significant risks to groundwater quality. This study integrates geological mapping, petrographic analysis, soil geochemistry, and hydrogeochemical evaluation to assess groundwater quality and its linkage to soil contamination in the Waru–Apo area of Abuja FCT. Field investigations identified migmatite, granite gneiss, biotite gneiss, and anatectic granite as dominant lithologies, with fractures and quartz veins enhancing aquifer vulnerability. Twenty-two groundwater and ten soil samples were analyzed using Atomic Absorption Spectroscopy (AAS) to determine major ions and trace metals. Hydrochemical facies are predominantly Na–SO₄ and Na–Mg–SO₄ types, indicating ion exchange, sulphate dissolution, and rock–water interaction. Elevated concentrations of chromium, cadmium, and lead exceeded WHO and NSDWQ permissible limits in several locations. Strong correlations between soil and groundwater metals (Cr r = 0.82; Cd r = 0.74; Pb r = 0.65) confirm contaminant migration from surface soils impacted by abattoir and domestic wastes. Pollution indices reveal generally low-to-moderate contamination with localized hotspots. The study recommends systematic groundwater monitoring, improved waste management practices, provision of alternative potable water sources, and public awareness programs to mitigate health risks. These findings provide critical insights for sustainable groundwater management in rapidly urbanizing basement complex regions.