Un exemple contredisant votre hypothèse :
Finally, it has been observed that aquatic plants possessed high levels of the natural radionuclide polonium-210, which seems to be originated mainly from soil rather than from atmospheric supply.  

Kelecom et al., A multidisciplinary approach to the study of the fluminense vegetation, 1 : An Acad Bras Cienc. 2002 Mar ;74(1):171-81.