Estimation and evaluation of radioactive contamination through a food web in an aquatic ecosystem. 1. An application of the compartment model to transfer of radioactive substances through a food chain.

Abstract

A transfer of radioactive substance through a food chain in an aquatic ecosystem was analyzed through application of modified three compartment model of Aten's. The modification of the original model is an introduction of two processes, an excretion of radioactivity from Fish-1 (preys) to sea water and an direct uptake of radioactivity by Fish-2 (predator) from sea water. In the model, a following ration rate coefficient (k12) was defined as a mass transfer coefficient of a radioactive nuclide from preys to a predator: k12 = θ(M1 ÷ M2) where θ is an assimilation rate of a radioactive nuclide, M1 is a daily average ration taken by a predator, and M2 is a weight of the predator. In the experimental system, pike cichlids and minows were used as predators and preys. And 137Cs was used as a radionuclide in the system. The accumulation of a 137Cs in pike was explained by application of the above modified three compartment model and various parameters in the model were determined. This shows that the transfer of a radionuclide through a food chain can be estimated by knowing the uptake rate and the turnover rate of Fish-2 (predator). They in ecological term are a daily average ration and an assimilation rate respectively.