Spatial Distribution and Radiological Risk Assessment of Natural Radionuclides in Soils from Zacatecas, Mexico

This study investigated the spatial distribution and radiological risks of naturally occurring radionuclides (226Ra, 232Th, 40K) in 37 soil samples from Zacatecas, located in north-central Mexico, using high-resolution gamma spectrometry. Results revealed 40K concentrations (mean: 736.81 Bq kg−1), nearly double the global average, while 226Ra (29.96 Bq kg−1) and 232Th (29.72 Bq kg−1) aligned with worldwide norms. Geoaccumulation indices identified moderate 40K accumulation at 22 sites, with El Capulín classified as moderately contaminated (Igeo = 1.07). Radiological risk indices showed absorbed dose rates (62.52 nGy h−1) and excess lifetime cancer risk (0.330 × 10−3) exceeding global thresholds by 4% and 14%, respectively. Multivariate analyses demonstrated strong Spearman correlations (ρ = 0.75–1.00) among risk indices, while spatial interpolation identified southern/western regions as high-risk zones. These findings emphasize the necessity of integrating spatial analysis with multivariate statistical techniques in environmental radioprotection frameworks. While most of the study area complies with international safety standards, the identified zones exceeding dose thresholds warrant prioritized management to mitigate potential cumulative health risks.