Enhancing the transfer of ²³⁸U and ²²⁶Ra from soils to Brassica juncea

¹ Natural Radioactivity Group, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain
² Laboratorio de Radiactividad Ambiental, Facultad de Ciencias, Universidad de Salamanca, 37008 Salamanca, Spain

Abstract

In order to test the suitability of using Brassica juncea for the remediation by phytoextraction of soils contaminated with ²³⁸U and ²²⁶Ra, the transfer process to the plant was studied. A soil with high natural uranium mineralization was used for the study. When the soil was not manipulated, the transfer factor (TF) was 0.24 ± 0.02 and 1.5 ± 0.3 for ²³⁸U and ²²⁶Ra, respectively. These low values, especially for ²³⁸U, are due to the radionuclides being associated in the soils with fractions unavailable to the plant. For the possible use of phytoextraction for remediation of contaminated soils it is therefore necessary to enhance the availability of the radionuclides in the soil. In this sense, soil pH is a major factor influencing the availability of these elements in the soil for plant uptake through their speciation. In this work, the effect of pH on the TF of ²³⁸U and ²²⁶Ra was studied. Also, citrate was used to attempt to enhance the bioavailability of the two radionuclides in the soils, and therefore their uptake by Brassica juncea and translocation to the shoots.