Evaluation of radioactive contamination in aquatic organisms by means of the statistic and the information theory

Concentration of radionuclides in aquatic organisms is affected by various environmental and physiological factors. The concentration factor is, cosequently, widely ranged. In this paper, uncertainty on the concentration process of radionuclides by organisms was evaluated from the viewpoint of the statistic and the information theory. The concept of entropy was introduced as a measure of uncertainty of information and an information source of the stochastic process on the basis that the distribution of the concentration in organisms obeyed the Poisson distribution and that its change with time could be expressed by the stochastic process. Entropy was calculated as a measure of the uncertainty in predicting the most reliable state of concentration step in aquatic organisms out of n states when the frequency distribution of the concentration was obtained. It was found that the entropy of the state vector which expresses the concentration step increases with time and that the entropy of the state 1 and the information source of the Markov Chain decreases inversely. This paper also presents the sample size necessary for obtaining the statistically significant result when aquatic organisms are taken as an indicator of radioactive contamination in environment. (auth.)