Radioecology studies in the vicinity of a closed uranium mine

Jožef Stefan Institute - Jamova cesta 39, SI-1000 Ljubljana Slovenia

^* E-mail: Borut.Smodis@ijs.si
^† E-mail: Marko.Strok@ijs.si
^‡ E-mail: Marko.Cerne@ijs.si

Abstract

Although the influential area of the former uranium mine at Zirovski vrh, Slovenia has been under continuous radiological monitoring, more detailed radioecology studies, focused on assessing mobility and bioavailability of deposited radionuclides, were initiated about five years ago. The mobility of ²³⁸U, ²³⁴U, ²³⁰Th and ²²⁶Ra was studied applying two sequential extraction protocols. The results revealed that both sequential extraction protocols are not comparable as the data obtained are protocol- and radionuclide-dependent. It was found that the most mobile ones were uranium isotopes, followed by ²²⁶Ra and ²³⁰Th. In addition, uptake of particular radionuclides by the wetland plants (Molinia arundinacea, Juncus effusus and Caltha palustris) grown in soils contaminated with seepage waters from the tailings was studied. The plants contained higher levels of ²³⁸U, ²²⁶Ra and ²³⁰Th compared to the plants from the control site. Activity concentration of ²²⁶Ra was the highest for all three plant species. Activity concentration of natural radionuclides in milk collected from the area of Zirovski vrh was comparable to the reference location, except for uranium where the content was higher. The combined annual effective dose for adults consuming milk from the Zirovski vrh area is 13 ± 2 μSv yr⁻¹.