Determination of natural uranium by various analytical techniques in soils of Zacatecas State (Mexico)

238 U is a radionuclide present in the earth’s crust that provides 65.9% of annual average radiation dose and represents 99.27% of total uranium. 238 U has been determined in samples from undisturbed topsoil in the Zacatecas State, Mexico, using several analytical techniques. ICP-MS and α-spectrometry produced the most reliable results. Uranium concentrations found in topsoil samples (0.4–3.7 mg kg −1 ) were similar to its average crustal abundance (2.8 mg kg −1 ) and indicate high homogeneity without evidence of enrichment. The average concentration of 2.1 mg kg −1 can be established as uranium background level in the topsoil of Zacatecas (Mexico).