Politécnica de Madrid

Radiological index for evaluating affected areas due to uranium mining

A female researcher from Universidad Politécnica de Madrid is involved in a project that has developed a radiological index to assess the risk of pollution in uranium mining areas.

Waste from uranium mining areas is a potential source of environmental contamination. Thus, the establishment of a quantitative parameter that can be used to decide whether these contaminated areas should be rehabilitated or decommissioned would be very useful.

In this context, a multidisciplinary team of researchers from Universidad Politécnica de Madrid (UPM), Institute of Natural Resources and Agrobiology of Salamanca (IRNASA-CSIC), Research Centre for Energy, Environment and Technology (CIEMAT) and the Miguel de Cervantes European University (UEMC) have developed the quantitative parameter after analyzing an abandoned uranium mining area in Salamanca.

Credit: piqsels

Numerous uranium mines in Spain were abandoned after using them. The location of these mines does not pose a risk for the general population, but the dispersion and dissolution of minerals can occur due to meteorological agents. This process can trigger the release and transfer of contaminants to the trophic chain.

Chapter 40 of the U.S. Code of Federal Regulations (CFR) is the most specific regulation for rehabilitating areas impacted by uranium mining. This regulation sets the radiological criteria to reduce the activity concentration of radionuclides found in these areas.

Two samples of soils were extracted from an abandoned uranium mining area in Salamanca (Spain): a non-vegetative sample and a rhizosphere sample, which is an area of roots. There are diverse processes that can trigger variations in the natural radioactive series, thus their identification and quantification can help uncover the different biochemical-geological processes.

“our working hypothesis was that the hazards of an area impacted by uranium mining, as well as its rehabilitation needs, can be established using a gamma spectrometry index while still also considering the regulations set out in Chapter 40 of the CFR” María José Suárez, the UPM researcher involved in this study, says.

The technique used to establish the activity concentration of radionuclides needed to propose the index was the gamma spectrometry, a non-destructive method that directly measures all gamma-emitting radionuclides in a sample. The obtained results using this index allowed researchers to assess the dispersion caused by soil erosion due to the prevailing wind directions according to the wind rose.

The researchers also concluded that the presence of reducing conditions and fungi and plants were the main factors that affected the soil radionuclide mobility in the studied areas. “The results from our index indicate that a lot of the pollution hazard at the site we studied in Salamanca (Spain) had dispersed over the study area. We believe that this will facilitate the future use of gamma spectrometry to characterize and study areas contaminated by uranium mining operations” María José Suárez concludes.

According to the researchers, the determination of environmental radioactivity is a scientific field that allows researchers to study many processes in-depth that occur in nature such as erosions, dating and geological, chemical, and biological processes.


Gil-Pacheco E, Suárez-Navarro JA, Sánchez-González SM, Suarez-Navarro MJ, Hernáiz G5, García-Sánchez A1. A radiological index for evaluating the impact of an abandoned uranium mining area in Salamanca, Western Spain (2020). Environmental Pollution 258, 113825. https://doi.org/10.1016/j.envpol.2019.113825