Radiological impact of natural radionuclides from soils of Salamanca, Mexico.

Salamanca is the centre of a large industrial complex associated with the production and refining of oil-derived products in the state of Guanajuato, Mexico. The city also hosts a large chemical industry, and in past years a major fertilizer industry. All of them followed NORM (naturally occurring radioactive materials) industrial activities, where either raw materials or residues enriched in natural radionuclides are handled or generated, which can have an environmental radiological impact on their environmental compartments (e.g. soils and aquatic systems). In this study, activity concentrations of radionuclides from the U and Th natural series present in superficial urban soils surrounding an industrial complex in Salamanca, México, have been determined to analyse the possible environmental radiological impact of some of the industrial activities. The alpha-particle and gamma-ray spectrometry is used for the radiometric characterization. The results revealed the presence of 10-42, 11-51 and 178-811Bq/kg of U, Th and K, respectively, without any clear anthropogenic increment in relation to the values normally found in unaffected soils. Thus, the radioactive impact of the industrial activities on the surrounding soils can be evaluated as very low, representing no radiological risk for the health of the population.