Measurements, Risk Assessment, and Source Apportionment of Radioactivity Levels in Soil of Okaba and Okobo Coalfields and Environs, Ankpa, Kogi State, Nigeria

Coal mining can elevate natural radioactivity in surrounding environments, posing radiological risks. This study assessed the activity concentrations of 238U, 232Th, and 40K in 40 composite soil samples collected from active and abandoned mines, waste dumps, farmlands, and residential areas in the Okaba and Okobo coalfields, Kogi State, Nigeria, using high-purity germanium gamma spectrometry. Radiological hazards were evaluated (radium equivalent activity, absorbed dose rates, annual effective doses, hazard indices, annual gonadal equivalent dose, excess lifetime cancer risk), and source apportionment was performed using radionuclide ratios, Pearson correlation, and principal component analysis (PCA).Mean activities (238U: 77.1 Bq·kg−1; 232Th: 81.9 Bq·kg−1; and 40K: 1193 Bq·kg−1) were significantly higher than global averages (p < .001). Ten locations (25%) exceeded the 370 Bq·kg−1 radium equivalent safety limit. The mean absorbed dose rate (570 nGy·h−1) was approximately 10× the global average, and the excess lifetime cancer risk (6.36 × 10−3) exceeded the global reference value (0.29 × 10−3, United Nations Scientific Committee on The Effects of Atomic Radiation report from 2000) by a factor of 20.Source apportionment using PCA with Kaiser criterion (eigenvalues > 1) revealed two dominant sources: geological (66.4% of variance, 232Th and 40K) and anthropogenic mining (31.1%, 238U). The elevated radiological parameters indicate potential long-term health risks, with uranium enrichment linked to artisanal mining activities. Urgent regulatory enforcement is required, aligned with the Sustainable Development Goals 3 (health), 12 (responsible consumption), and 15 (life on land).