Dynamic behavior of fallout strontium-90 in rice through production, distribution and consumption in relation to its accumulation in human bone. Preliminary study system dynamics approach

A system dynamics model was proposed for investigating the dynamic behavior of fallout ⁹⁰Sr through production, distribution and consumption of rice, the staple of Japanese food, and the long term accumulation in human bone. The calculated ⁹⁰Sr contents in rice and human bone were compared with the environmental surveillance data to examine the validity of the model. The results obtained in this study under the limited assumptions are as follows: (1) The proposed model is promising for evaluating the long term behavior of fallout ⁹⁰Sr in the environment although identification and determination of some environmental parameters should be improved. (2) The migration of fallout ⁹⁰Sr into the deep soil layers with underground water is most significant among the several transfer pathways considered in the rice-plant field. (3) The influence of rice-crop distribution on the concentration of ⁹⁰Sr in consumer rice is small. Fallout ⁹⁰Sr is transported with rice generally from the coast of the Sea of Japan to those of Pacific Ocean. (4) The concentration of ⁹⁰Sr in rice crops estimated by the proposed model may vary with a factor of 2.5 due to uncertainties in the environmental parameters. (author)