SPATIAL MAPPING OF BACKGROUND IONIZING RADIATION AND HEAVY METAL CONTAMINATION: AN INTEGRATED RADIOLOGICAL AND TOXICOLOGICAL RISK ASSESSMENT OF SOIL SAMPLES AROUND THE ARIARIA WASTE DUMPSITE, NIGERIA

Uncontrolled waste dumpsites in rapidly urbanizing regions are complex
environmental systems where chemical and radiological hazards coexist but are
often assessed separately, limiting understanding of cumulative exposure and
long-term health risks. This study presents an integrated spatial assessment of
background ionizing radiation (BIR) and heavy metal contamination in soils around
the Ariaria waste dumpsite, Nigeria, with the aim of developing a unified
radiological–toxicological risk framework. In situ gamma radiation measurements
were conducted using a calibrated Geiger–Müller survey meter, while soil samples
were analysed for elemental composition using X-ray fluorescence spectrometry.
Radiological indices, including absorbed dose rate, annual effective dose
equivalent (AEDE), and excess lifetime cancer risk (ELCR), were calculated using
standard models. Heavy metal concentrations were evaluated against
international guideline limits, and spatial patterns were analysed to identify
contamination variability. Results show that the mean absorbed dose (≈193.3 nGy
h⁻¹) exceeds the global average of 89 nGy h⁻¹, indicating enhanced radiation from
radionuclide-bearing wastes. Although AEDE (≈0.30 mSv y⁻¹) remains within
recommended public exposure limits, ELCR (≈1.03 × 10⁻³) exceeds global reference
values, suggesting elevated long-term cancer risk. Geochemical analysis reveals
that chromium, uranium, thorium, nickel, and cobalt exceed regulatory thresholds,
while cadmium, lead, zinc, and arsenic remain within permissible limits. Spatial
patterns indicate heterogeneous contamination driven by waste composition and
subsurface processes. Overall, the co-occurrence of radiological and chemical
contaminants highlights a chronic, multi-pathway exposure scenario with potential
long-term health implications. These findings emphasize the need for integrated
monitoring, improved waste management, and targeted remediation strategies.