Allometric methodology for the calculation of biokinetic parameters for marine biota

Biological half-lives of elimination (T(B1/2)) and concentration factors (CF) for different radionuclides and marine organisms were analysed. Tests were carried out in order to investigate the cases in which these parameters can be described by a simple power equation as a function of the volume of the organism, to verify the hypothesis of allometric scaling. Statistically significant trends were found for the CF of plutonium and americium and the T(B1/2) of technetium and radiocaesium across organisms. Some of these trends satisfy the theoretical expectation that allometric relations are a power function of the volume of the organism. For the CF, which relates to retention of a radionuclide, the mean exponent of the power function, -0.29+/-0.02, is close to the theoretical value of -0.25. For the T(B1/2) the mean exponent of the power function is lower at 0.16+/-0.01. The work improves the understanding of the metabolism of radionuclides within organisms for which no direct biokinetic information exists. The allometric relationships derived can be applied to calculate a T(B1/2) for caesium or technetium and a CF for plutonium and americium for any marine species. For the elements N, K, Np and Cm, the same allometric relationships as those derived for their analogues (99)Tc, (137)Cs, (239,240)Pu and (241)Am, respectively, can be applied, when no other data are available.