Heavy metal contamination assessment of the Taloka and Wurno aquifers, Sokoto Basin, northwestern Nigeria

A comprehensive heavy metal pollution assessment of the Taloka and Wurno aquifers within the Sokoto Basin, northwestern Nigeria, was carried out. Field mapping, borehole logging and water quality analysis were integrated to describe the distribution of heavy metals in groundwater. Heavy metal evaluation points to variations between the Taloka and Wurno aquifers. A plausible hypothesis is that the dissolution of iron-rich lithologies in the Taloka aquifer contributes to the elevated iron (Fe) concentrations observed in the Taloka Formation. In contrast, redox reactions involving organic-rich shales and limestones of the overlying Dange Formation may contribute to the relatively higher concentrations of potentially toxic metals, particularly lead (Pb) and arsenic (As), observed in the Wurno Formation. The Wurno aquifer is also more vulnerable to surface contamination due to its shallower stratigraphic position. The concentrations of As and Pb in a substantial number of groundwater samples from both aquifers exceed the World Health Organization (WHO) safe limits for heavy metals in drinking water. The findings indicate a possible combined geogenic and anthropogenic influence on groundwater quality in both aquifers and highlight the need for continuous groundwater monitoring, targeted water treatment interventions and sustainable aquifer management strategies.