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Although fruit development primarily depends on photoassimilation by leaves, immature green fruits can also directly assimilate atmospheric CO2. To elucidate the process of C accumulation due to direct assimilation by fruit, we conducted a 13CO2 exposure experiment in an orchard in late June with immature ‘Fuji’ apples (Malus domestica). Four fruits from three trees were enclosed in transparent plastic bags and exposed to 13CO2 using an in-situ exposure system. Fruits were collected prior to and immediately following exposure in early July, late September and mid-November, and 13C concentrations in the peduncle, skin, flesh and core (including seeds) were measured. The higher assimilated 13C concentrations measured following exposure indicated that the fruits directly assimilated atmospheric 13C. The 13C concentration in fruit skin was higher immediately after exposure and in early July compared with that prior to exposure. In late September and mid-November, 13C concentrations were close to natural levels.

14C released from nuclear facilities is transferred to cattle through their consumption of 14C contaminated grasses. To estimate the concentrations of 14C in their meat, we conducted two sets of experiments. In the first experiment, 230 mg of 13C per day was administered to cattle aged 10 months for 28 days in the form of 13C-labeled grass. The 13C concentration in the semitendinosus muscle decreased exponentially after reaching its peak value. The mean half-life was 76 ± 13 days. In the second experiment, 550 mg of 13C per day was administered to 24-month-old cattle. The change in the semitendinosus muscle was smaller than that recorded in the first experiment, even though the amount of 13C administered per body weight was slightly higher than that in the first experiment. Consequently, the half-life was not determined. Therefore, further studies are required to clarify the metabolism of carbon in 2-year-old cattle.

14C is the most important radionuclide for assessing exposure dose around the Rokkasho nuclear fuel reprocessing plant, Aomori Prefecture, Japan. A simplified model with ample margins has been used so far for the assessment of the dose derived from 14C. Realistic dose estimate of 14C using more realistic model is necessary for safety. Apple production is an important core industry in Aomori Prefecture. To construct the dynamic model for apple, using 13C as a tracer to substitute for 14C, we collected data on 13C abundance in organs including fruit after 13CO2 exposure at various fruit growth stages. We developed 13CO2 exposure systems for three intact fruit-bearing shoots (1), whole mature tree (2) and young potted trees (3). Systems (1) and (2) also can determine net amounts of carbon and 13C photoassimilated. System (3) is capable of precise feedback control of 13CO2 and 12CO2 concentrations based on on-time determination.

In this study, we aimed to investigate the photoassimilation process of 14CO2 into agricultural plants through determining the photoassimilated carbohydrate-13C in each part (leaves, current branch and fruit) of the fruit-bearing apple shoots exposed to 13CO2 in different growth stages (early and late fruit development stages). The carbohydrate content was assessed as soluble (ethanol-extracted fraction) and other (HCl-extracted and residual fractions) components. The total (i.e. sum of the three fractions) bulk carbohydrate concentrations in all parts of the shoots were statistically similar between different growth stages. The changes in the concentration of 13C-labeled soluble carbohydrate (i.e. ethanol-extracted fraction) to the total content between different growth stages were statistically unclear among all parts of the shoot. These results suggest that the distribution ratio of photoassimilated 13C in soluble and other components in the apple shoot was thereabout constantly independent of the growth stages.

Deciduous trees accumulate carbon (C) in woody parts during the growth season which is subsequently used for the initial development and growth of newly formed organs in the following season; however, it is unclear which period during the growth season contributes to C accumulation. Three-year-old potted Malus domestica (apple) trees were grown in controlled growth chambers during the growth season and exposed to 13CO2 in an exposure chamber at seven different periods of the growth season, including vegetative and reproductive growth periods. Approximately half of the trees were harvested in late autumn, and the remaining trees were grown in a field in the following year. The 13C accumulation in the different organs in late autumn, and its concentration in the new aboveground growth during the following growth season, was determined. The concentration of the photoassimilated 13C in woody parts (shoots, trunk, rootstock and coarse roots) in the late autumn was higher in the trees labeled during the period of vigorous vegetative growth than in those labeled during other periods of growth. Furthermore, 13C concentration in the leaves, annual shoots, flower buds and flowers in the following early spring was also high in the trees labeled during this period. The concentration of 13C in the flower buds and flowers was positively correlated with that in the woody parts in the late autumn and old shoots in the following spring. Hence, the seasonal accumulation of photoassimilated C in woody parts in late autumn is related to growth rates during the growth season and its use for the initial development of newly formed organs in the following spring. These results suggest that under non-stressed conditions, C accumulated during the period of vigorous vegetative growth largely contributes to the C reserves that are used for the development of new organs in the following year.

Evaluating the transfer and metabolism of carbon (C) in apple fruit is key to estimating the potential accumulation of atmospheric

Carbon-14 released from nuclear facilities has been assessed to contribute significantly to the radiation dose that people are exposed to through the food chain. However, the current dose coefficient for members of public, which is the ratio of the 50-year committed effective dose to ingested 1 Bq 14C, recommended by the International Commission on Radiological Protection (ICRP) is not based on experimental human metabolic data for 14C in nutrients and diet. Therefore, to validate the coefficient, we administered 13C-labelled nutrients consisting of four amino acids, three fatty acids, and one monosaccharide to volunteers as substitutes for 14C labelled nutrients and measured the 13C concentration in various excreta samples. Although metabolic models were constructed from the excretion data, a significant fraction of administered 13C was not recovered from some nutrients. The dose coefficients of 14C in uniformly labelled Japanese diet, which were estimated under several assumptions about the unrecoverable fraction, varied from (6.2 ± 0.9) × 10–11 to (8.9 ± 4.4) × 10–10 Sv Bq−1 and were approximately comparable to the current value of 5.8 × 10–10 Sv Bq−1 recommended by the ICRP. Further studies are necessary to elucidate the metabolism of 14C in various nutrients in the unrecoverable fraction.

Evaluating the transfer and metabolism of carbon (C) in apple fruit is key to estimating the potential accumulation of atmospheric 14C in fruit near and around nuclear facilities. We developed a dynamic compartment model for apple fruit-bearing shoots, assuming that the shoots are a simple unit of source and sink for photoassimilates. Fruit-bearing shoots of Malus domestica “Fuji” at different fruit growth stages were exposed to 13CO2 in situ, followed by sampling at 72 h after exposure or at harvest. The 13C/(13C+12C) mole ratio in fruits, leaves, and current branch were measured to construct a five-compartment model of 13C (fruit, each fast and slow component of leaves, and current branch). The C inventories in the compartments were presented in accordance with the measured growth curves of C in the organs. The model simulated the 13C dynamics in plant tissues well. Simulation results of photoassimilate distribution using the model indicated that the retention of photoassimilated C at the harvest depended on the growth rate of C in the organs at the exposure.

Iodine-129 with a long half-time of 1.6 × 10

The retention of 13C in the human body after oral administration of 13C-labeled glucose was studied in three healthy volunteer subjects to estimate the 50 year cumulative body burden for 13C as an index of the committed dose of the radioisotope 14C. After administration of 13C-labeled glucose, the volunteers ingested controlled diets with a fixed number of calories for 112 d. Samples of breath and urine were collected up to 112 d after administration. Samples of feces were collected up to 14 d after administration. Hair samples were obtained at 119 d after administration and analyzed as a representative index of the rate of excretion of organic 13C via pathways such as skin cell exfoliation and mucus secretion. All samples were analyzed for 13C/12C atomic ratio to determine the rate of excretion via each pathway. We then constructed a metabolic model with a total of four pathways (breath, urine, feces, and other) comprising seven compartments. We determined the values of the biokinetic parameters in the model by using the obtained excretion data. From 74% to 94% of the 13C administered was excreted in breath, whereas 0.1). In addition, the dataset for one of the three subjects was markedly different from those of the other two. When we estimated the 50 year cumulative body burden for 13C by using our model and we included non-statistically significant parameters, a considerable cumulative body burden was found in the compartments excreting to the other pathway. Although our results on the cumulative body burden of 13C from orally administered carbon as glucose were inconclusive, we found that the compartments excreting to the other pathway had a markedly long residence time and therefore should be studied further to clarify the fate of carbon in the human body. In addition to excreta, data for serum and blood cell samples were also collected from the subjects to examine the metabolism of 13C in human body.

Iodine-129 with a long half-time of 1.6 × 107 y was discharged into the Pacific Ocean during the final safety tests of the first commercial nuclear fuel reprocessing plant in Japan, at Rokkasho, Aomori Prefecture. Olive flounder (Paralichthys olivaceus) is an important fishery along this coast. It is necessary to determine whether 129I accumulates in this species to assess the possible public acceptance. We developed a short-term metabolism model of 125I in the flounder using retention data for 1–6 days after the olive flounder had ingested a freshwater fish species, medaka (Oryzias latipes), that had been labeled with 125I by keeping them in water containing 125I for 7 days. A single compartment model constructed from whole-body retention data for 125I in the olive flounder, excluding the gastrointestinal tract and its contents, revealed a biological half-time of 2.9 days for 125I. When the gill and other tissues were separated to individual compartments, the biological half-time in the gill was three times longer than that in the other tissue, though the half-time in the gill is not statistically significant. The distribution of 125I among various tissues in the flounder 6 days after the ingestion of labeled medaka once a day for 6 days differed from that of stable I, suggesting that the biological half-time is longer in certain tissues. Further study is necessary to elucidate the metabolism of radioiodine in the flounder.

A dynamic compartment model was developed to describe C 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 CO2. 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 C 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.

The retention of

To evaluate annual CO2 exchange rates in a wetland ecosystem, ecosystem respiration rate (Re), net ecosystem productivity (NEP), and gross primary productivity (GPP) were investigated using the Closed Geosphere Experiment Facility (CGEF) located in northeastern Japan. The CGEF is highly airtight and equipped with a Geosphere Module (GM). The GM has a ground area of 5.8 × 8.7 m2 and an average height of 11.9 m, including a soil depth of 3.1 m. A wetland ecosystem dominated by Phragmites australis was introduced into the CGEF. Air temperature and CO2 concentration in the GM were controlled automatically. The hourly nighttime Re increased exponentially with the hourly average air temperature. Both hourly NEP and GPP depended on hourly photosynthetic photon flux density (PPFD). In addition, daily ecosystem CO2 exchange rates (Re, NEP, and GPP) were influenced by above-ground plant biomass. The annual NEP was found to be 64.2 ± 19.2 g C m−2 yr−1 and it resulted from the annual GPP of 555.8 ± 17.0 g C m−2 yr−1 and annual Re of −491.6 ± 15.6 g C m−2 yr−1. Therefore, the wetland ecosystem behaved as a CO2 sink for the entire year. The annual CO2 exchange rates obtained were reasonable values compared to the findings of published studies in P. australis–dominated wild wetlands using the eddy covariance technique and the combined method of internal gas pressures and flow measurements and harvesting.

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.

Human habitation and animal holding experiments in a closed environment, the Closed Ecology Experiment Facilities (CEEF), were carried out. The CEEF were established for collecting experimental data to estimate carbon transfer in the ecosystem around Rokkasho nuclear fuel reprocessing plant. Circulation of O 2 and CO 2 , and supply of food from crops cultivated in the CEEF were conducted for the first time in the habitation experiments. Two humans known as eco-nauts inhabited the CEEF, living and working in the Plant Module (PM) and the Animal and Habitation Module (AHM), for a week three times in 2005. On a fresh weight basis, 82% of their food was supplied from 23 crops including rice and soybean, cultivated and harvested in the PM, in the 2nd and 3rd experiments. For the goats, the animals held in the experiments, all of their feed, consisting of rice straw, soybean plant leaves, and peanut shells and peanut plant leaves, was produced in the PM in the 2nd and 3rd experiments. The O 2 produced in the PM by photosynthesis of the crops was separated by the O 2 separator using molecular sheaves, then accumulated, transferred, and supplied to the AHM atmosphere. The CO 2 produced in the AHM by respiration of the humans and animals was separated by the CO 2 separator using solid amine, then accumulated, transferred, and supplied to the PM atmosphere. The amount of O 2 consumed in the AHM was 46–51% of that produced in the PM, and the amount of CO 2 produced in the AHM was 43–56% of that consumed in the PM. The surplus of O 2 and the shortage of CO 2 was a result of the fact that waste of the goats and the crops and part of the human waste were not processed in these habitation experiments. The estimated amount of carbon ingested by the eco-nauts was 64–92% of that in the harvested edible part of the crops. The estimated amount of carbon ingested by the goats was 36–53% of that in the harvested inedible part of the crops. One week was not enough time for determination of gas exchange especially for humans and animals, because fluctuation of their gas exchange was quite high. The amount of transpired water collected as condensate was 818–938 L d −1 , and it was recycled as replenishing water compensating transpiration loss of nutrient solution. The amount of waste nutrient solution discharged from the PM was 1421–1644 L d −1 . The waste nutrient solutions from rice and other crops were processed through micro filters (MFs) separately. The MF filtrated solutions were processed with reverse osmosis (RO) membrane filter separately and divided into filtrated water and concentrated waste nutrient solution. The concentrated waste nutrient solution from the crops other than rice was processed through an ultra-micro filter (UF) and reused, although that from rice was discharged in 2005. Concentrations of nutritional ions in the UF filtrated solution were determined, the depleted ions were added back, the UF filtrated solution was diluted with the RO membrane filtrated water, and the nutrient solution for the crops other than rice was regenerated. The nutrient solution for rice was newly made each time, using concentrated solution from an external source and the RO membrane filtrated water. Average amounts of water used in the AHM (L d −1 ) were determined as follows: drinking by humans (filtrated water), 1.5; cooking, etc. (filtrated water other than for drinking), 14.3; drinking by goats, 3.8; showering (hot water), 13.2; showering (cold water), 0.1; washing of hand and face and brushing teeth, 4.1; washing of dishes, dish clothes and towels, 36.4; and washing of animal holding tools, 0.3. The waste water was processed by a RO purification system and recycled for toilet flushing and animal pens washing. A circulation experiment for water was started in 2006 and a circulation experiment for waste materials is planned for 2007. In 2006, a single duration of the air circulation experiments was 2 weeks, although the human habitants were changed after 1 week.

The objective of the present study was to examine whether the temperature dependence of respiration at a crop-stand scale could be directly represented by an Arrhenius function that was widely used for representing the temperature dependence of leaf respiration. We determined temperature dependences of bulk respiration of monospecific stands of rice and soybean within a range of the air temperature from 15 to 30°C using large closed chambers. Measured responses of respiration rates of the two stands were well fitted by the Arrhenius function (R2 = 0:99). In the existing model to assess the local radiological impact of the anthropogenic carbon-14, effects of the physical environmental factors on photosynthesis and respiration of crop stands are not taken into account for the calculation of the net amount of carbon per cultivation area in crops at harvest which is the crucial parameter for the estimation of the activity concentration of carbon-14 in crops. Our result indicates that the Arrhenius function is...

Productivities of 29 crops in the Closed Ecology Experiment Facilities (CEEF) were measured. Rice and soybean showed higher productivities than these given by the Advanced Life Support System Modeling and Analysis Project Baseline Values and Assumption Document (BVAD), but productivities of some other crops, such as potato and sweet potato, were lower. The cultivation data were utilized to develop a 1-week cycle menu for Closed Habitation Experiment. The menu met most of the nutritional requirements. Necessary cultivation area per crew was estimated to be 255 m2. Results from this study can be used to help design the future Advanced Life Support System (ALSS) including the CEEF.

In order to predict carbon sequestration of vegetation with the future rise in atmospheric CO2 concentration, [CO2] and temperature, long term effects of high [CO2] and high temperature on responses of both photosynthesis and transpiration of plants as a whole community to environmental parameters need to be elucidated. Especially in the last decade, many studies on photosynthetic acclimation to elevated [CO2] at gene, cell, tissue or leaf level for only vegetative growth phase (i.e. before formation of reproductive organs) have been conducted all over the world. However, CO2 acclimation studies at population or community level for a whole growing season are thus far very rare. Data obtained from repeatable experiments at population or community level for a whole growing season are necessary for modeling carbon sequestration of a plant community. On the other hand, in order to stabilize material circulation in the artificial ecological system of Closed Ecology Experiment Facilities (CEEF), it is necessary to predict material exchange rates in the biological systems. In particular, the material exchange rate in higher plant systems is highly variable during growth periods and there is a strong dependence on environmental conditions. For this reason, dependencies of both CO2 exchange rate and transpiration rate of three rice populations grown from seed under differing conditions of [CO2] and day/night air temperature (350 microL CO2 L-1, 24/17 degrees C (population A); 700 microL CO2 L-1, 24/17 degrees C (population B) and 700 microL CO2 L-1, 26/19 degrees C (population C)) upon PPFD, leaf temperature and [CO2] were investigated every two weeks during whole growing season. Growth of leaf lamina, leaf sheath, panicle and root was also compared. From this experiment, it was elucidated that acclimation of instantaneous photosynthetic response of rice population to [CO2] occurs in vegetative phase through changes in ratio of leaf area to whole plant dry weight, LAR. But, in reproductive growth phase (i.e. after initiation of panicle formation), the difference between photosynthetic response to [CO2] of population A and that of population B decreased. Although LAR of population C was almost always less than that of population A, there was no difference between the photosynthetic response to [CO2] of population A at 24 degrees C and that of population C at 26 degrees C for its whole growth period. These results are useful to make a model to predict carbon sequestration of rice community, which is an important type of vegetation especially in Asia in future global environmental change.

In order to determine a required plant cultivation area which can sustain human life in a closed environment, the material circulating measurement system including a Closed-type Plant Cultivation Equipment (CPCE) in which the metabolic data of plants can be accurately measured has been constructed. According to results from cultivation experiments using rice, the harvest index was 29.9% for 110 days, and the required crop area to supply food, oxygen and water for one person was calculated to be about 111m2, 36m2 and 0.9m2, respectively.

宇宙での運用状況を想定し, その第1段階として, CELSS用水再生循環システム構成の検討および装置の開発・運転試験を行い, 以下の知見を得た.1) CELSS用水再生循環装置を試作し, その運転操作状況などからみて, 設計どおりの運転制御が行われたが, 耐久性の面では装置上改善すべき必要性が認められた.2) 加熱蒸発および運転実験より, 本人工尿では, 60%以上の水の回収は困難であることが明らかになった.3) 用水処理性能低下を招く析出物は, 主としてリン酸とカルシウム, マグネシウムによる化合物であることが判明した.4) RO膜の本供試水での除去率は, 公称除去率と比べ, 20～80%低いことが認められた.とくにアンモニアは除去率が低く, その後のTPVでも処理が難しいので対策が必要と考えられた.

CELSS is to be considered in constructing a closed environment for sustaining life including human beings in space stations and space colonies. The waste management system is a key subsystem of the integrated material recycling system which must be developed to support long-term manned space activity. This paper presents the results of waste processing of rabbit feces using wet oxidation of waste manegement system. It was considered 75% of N in feces were converted to N2 gas, 60% of Ca in feces remained in the furnace and K in feces were smoothly dissolved in the solution. The insoluble residue contained most of P and Fe in feces. The wet oxidized solution contained Ni and Cr which were eluted from the furnace made of SUS. It was found that the nutrient balance of a wet oxidized solution which added P and Fe, removed Ni and Cr, were not so different compared with a hydroponic solution.

In order to control the material circulation in the Closed Ecology Experiment Facilities (CEEF), it is necessary to clarify material flow in the Closed Plant Experiment Facility (CPEF) of CEEF. We tried to grow rice plants and measure the nitrogen contents in rice plant and nutrient solution in plant cultivation bed to trace the material balance in CPEF. The measurements were carried out under the condition of 750 ppm (v/v) CO2 at 26/19 degrees C in the plant cultivation room. The measurements showed the absorbed nitrogen amount in plant was less than the outflow nitrogen amount from nutrient solution. This difference between absorbed and outflow quantity reached to 17%.