Accumulation of technetium in floating aquatic plants

Interfaculty Reactor Institute, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands

Abstract

Technetium (⁹⁹Tc) is of radio-ecological and health-physical interest because of its long half-life and its environmental mobility, given it a potential bioavailability. Plants are able to accumulate substantial amounts of Tc. Three mechanisms are suggested to interfere with the Tc accumulation: (i) changes in the plant physiological status, (ii) competitive effects with nutrient uptake, and (iii) electrostatic cell wall interactions. This study focuses on the question whether these mechanisms apply for aquatic plants grown under natural conditions. Tc accumulation in five aquatic plant species correlated strongly with the calcium concentration in the water. Growth rate or possible competition with Cl^-, NO₃^-, PO₄^3- or SO₄^2- did not significantly affect, if affect at all, the Tc accumulation in submerged aquatic plants. This suggests that water hardness is the dominant factor perturbing the Tc accumulation in submerged aquatic plants, supporting the hypothesis that electrostatic cell wall interactions are associated with it.