Assessment of Heavy Metal Contamination in Soils around Major Junctions along Lugbe Airport Road, Abuja, Nigeria

Abstract

Heavy metal contamination of roadside soils poses significant environmental and public health concerns in rapidly urbanizing cities. This study assessed the concentrations, distribution, contamination levels, and health risks of six heavy metals (Pb, Cd, Cu, Zn, Cr, Ni) in soils around two major junctions along Lugbe Airport Road, Abuja, Nigeria: Police Sign Board Junction (PSJ) and Federal Housing Junction (FHJ). A total of 80 soil samples were collected from surface (0-10 cm) and subsurface (10-20 cm) depths during wet and dry seasons. Heavy metal analysis was performed using Atomic Absorption Spectrophotometry (AAS). Results revealed elevated lead (Pb) concentrations at PSJ (range: 68.2–98.7 mg/kg; mean: 85.9 mg/kg), with selected sampling points exceeding the Nigerian permissible limit of 85 mg/kg. Cadmium (Cd) levels (2.30–2.65 mg/kg) approached regulatory limits, while Zn (175.5–192.0 mg/kg), Cu (16.7–19.3 mg/kg), Cr (30.0–34.2 mg/kg), and Ni (13.5–15.6 mg/kg) remained below standards. Cadmium (Cd) levels (2.30-2.65 mg/kg) approached regulatory limits, while Zn (175.5-192.0 mg/kg), Cu (16.7-19.3 mg/kg), Cr (30.0-34.2 mg/kg), and Ni (13.5-15.6 mg/kg) remained below standards. Metal concentrations followed the order: Zn > Pb > Cr > Cu > Ni > Cd. Contamination assessment using geo-accumulation index (Igeo) classified Pb and Cd as "heavily contaminated" (Class 4), Zn as "moderately to heavily contaminated" (Class 3), while Cu, Cr, and Ni showed low to moderate contamination. Pollution load index (PLI) values > 1 confirmed soil quality deterioration at both locations. Health risk assessment revealed that children face potential non-carcinogenic risks (Hazard Index > 1), primarily from Pb exposure, while adults showed no significant risk. Carcinogenic risks for Cr and Ni remained within acceptable limits (10⁻⁶-10⁻⁴). Seasonal variations showed significantly higher dry season concentrations (p < 0.05), and surface soils exhibited greater contamination than subsurface. The study concludes that vehicular emissions are the primary source of heavy metal contamination, with Pb posing the greatest concern. Continuous monitoring, remediation interventions, and public health awareness are urgently recommended.