Linearity assumption in soil-to-plant transfer factors of natural uranium and radium in Helianthus annuus L.

The linearity assumption of the validation of soil-to-plant transfer factors of natural uranium and 226Ra was tested using Helianthus annuus L. (sunflower) grown in a hydroponic medium. Transfer of natural uranium and 226Ra was tested in both the aerial fraction of plants and in the overall seedlings (roots and shoots). The results show that the linearity assumption can be considered valid in the hydroponic growth of sunflowers for the radionuclides studied. The ability of sunflowers to translocate uranium and 226Ra was also investigated, as well as the feasibility of using sunflower plants to remove uranium and radium from contaminated water, and by extension, their potential for phytoextraction. In this sense, the removal percentages obtained for natural uranium and 226Ra were 24% and 42%, respectively. Practically all the uranium is accumulated in the roots. However, 86% of the 226Ra activity concentration in roots was translocated to the aerial part.