Susumu Nozoe

Development of a dynamic transfer model of 14C from the atmosphere to rice plants

A dynamic compartment model was investigated to describe (14)C accumulation in rice plants exposed to atmospheric (14)C with temporally changing concentrations. In the model, rice plants were regarded to consist of three compartments: the ear and the mobile and immobile carbon pools of the shoot. Photosynthetically fixed carbon moves into the ear and the mobile carbon pool, and these two compartments release a part of this carbon into the atmosphere by respiration. Carbon accumulated in the mobile carbon pool is redistributed to the ear, while carbon transferred into the immobile carbon pool from the mobile one is accumulated there until harvest. The model was examined by cultivation experiments using the stable isotope, (13)C, in which the ratios of carbon photosynthetically fixed at nine times during plant growth to the total carbon at the time of harvest were determined. The model estimates of the ratios were in relatively good agreement with the experimental observations, which implies that the newly developed compartment model is applicable to estimate properly the radiation dose to the neighboring population due to an accidental release of (14)C from nuclear facilities.

Workplace Concentrations and Exposure Assessment of Monoterpenes in Rosemary- and Lavender-growing Greenhouses

Workplace Concentrations and Exposure Assessment of Monoterpenes in Rosemary‐ and Lavender‐growing Greenhouses: Akira TANI, et al. Institute for Environmental Sciences, University of Shizuoka—

A dynamic transfer model for the estimation of 14C radioactivity in Japanese radish (Daikon) plants.

Abstract A dynamic compartment model was developed to describe 14C accumulation in the Japanese radish plant, which is an important crop in the area around Japan’s first commercial nuclear fuel reprocessing plant in Rokkasho, Aomori, Japan. Photosynthetically fixed carbon is distributed into the leaf and the root compartments, and a part of the carbon accumulated in the leaf compartment is redistributed to the root compartment. The model parameters were estimated by using data obtained from exposure of the plant to 13CO2. The model estimates were in good agreement with the experimental observations, showing that the newly developed compartment model is applicable to assessment of the accumulation of 14C in Japanese radish plants around the nuclear facility. In this study, respiration rate was set to be proportional to the carbon mass of the compartment, though the respiration rate has been assumed generally to be proportional to the growth rate of the compartment. While the estimates using both respiration rates differed only slightly from each other, the ratio of the respiratory rate of the root to that of the leaf was too high in the case of the respiratory rate proportional to the growth rate.