GEO-SPATIAL ANALYSIS OF GROUNDWATER QUALITY AND HEAVY METAL CONTAMINATION IN PERI-URBAN COMMUNITIES OF LAGOS AND OGUN STATES

Abstract

Groundwater remains the primary source of drinking water for many peri-urban communities in Nigeria, yet its quality is increasingly threatened by anthropogenic contamination. This study investigates the spatial distribution and health implications of heavy metal contamination in groundwater across selected peri-urban communities in Lagos and Ogun States. A cross-sectional analytical design was adopted, integrating field sampling, laboratory analysis, and geospatial techniques. Groundwater samples (n = 120) were collected from wells and boreholes across twelve communities and analyzed for physicochemical parameters and heavy metals (Pb, Cd, Cr, As, Hg) using Atomic Absorption Spectrophotometry (AAS) and ICP-MS. Spatial mapping was conducted using ArcGIS, while statistical analyses, including correlation and regression, were performed using SPSS. Results indicate that mean concentrations of Pb (0.021 mg/L), Cd (0.008 mg/L), and As (0.015 mg/L) exceeded WHO permissible limits in several locations. GIS mapping revealed distinct contamination hotspots near industrial clusters and waste disposal sites. Health risk assessment showed Hazard Quotient (HQ) values above 1 for Pb and Cd in 58% of sampled locations, indicating significant non-carcinogenic risks. The study concludes that groundwater in peri-urban Lagos and Ogun is compromised and poses serious public health threats. Policy interventions, including stricter environmental regulation and community-based water treatment strategies, are recommended.