Dynamic modelling of the radiological impact of the Fukushima accident on marine biota

A model to simulate dynamically the uptake and turnover of radionuclides by marine biota is applied to the Fukushima accident situation. The approach incorporates a two-compartment biokinetic model based on first order linear kinetics, with interchange rates between the organism and its surrounding environment. Model rate constants were derived as a function of known parameters: biological half-lives of elimination, concentration factors and a sample point of the retention curve, allowing for the representation of multicomponent release. The model was tested with activity concentrations of 131I, 134Cs and 137Cs in seawater measured at several coastal locations in the vicinity of Fukushima from 23 March - 30 July 2011 when the marine discharges were close to their peak. The model was then used to predict the activity concentrations of 131I, 134Cs and 137Cs in fish, crustaceans, molluscs and seaweed, and the dose rates to biota arising thereof. It is concluded that a dynamic modelling can assess better the impact to marine biota of radioactivity released by this accident, decreasing by 2 orders the magnitude the dose estimates. On the basis of this reassessment, the populations of marine organisms considered in this study appear not to have been at high risk.