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Our field survey showed that thequality of shallow groundwater around the KatsuraRiver in the Kyoto Basin was strongly affected by theinfiltration of river water. Furthermore, that thedeterioration of the groundwater in the southern areato the west of the Katsura River may be related to theincrease in groundwater extraction. To clarify themechanism of groundwater deterioration, we havedeveloped a stochastic method to simulate groundwaterflow. The results showed that there was a largereduction in the groundwater level where groundwaterextraction was intense and recharge flowed from theKatsura River to the high extraction areas in thesouthern region. Another simulation showed that if thegroundwater extraction was 10% of the present removalrate, there would be little recharge from the KatsuraRiver into the groundwater and the quality of thegroundwater would be improved. Thus, we conclude thatthe cause of groundwater deterioration is probably dueto the induced recharge of deteriorated river waterfrom the Katsura River.

137Cs released from atmospheric nuclear detonation tests has been transported worldwide in the environment and finally taken up by humans through various pathways. In particular, ingestion pathways are important for evaluating the human health risks caused by the chronic global low-level radioactive contamination. In this research, the mathematical model for the evaluation of the dietary intake of 137 Cs and the related risks to Japanese are proposed by coupling the previously published global 137 Cs distribution model with the regional models such as various food ingestion models and the model of the domestic and international supply. Predictions from the proposed model were compared with the monitoring data of 137 Cs in Japanese total diet as an attempt at validation. The major findings obtained in this research include that the proposed model is promising for evaluating tbe risk to Japanese health caused by the dietary intake of global radioactive fallout 137 Cs, the 137 Cs is taken up by Japanese mostly through farm products, the ingestion of 137 Cs through imported foods is increasing, the risk to the Japanese health of inducing cancer by 137 Cs internal exposure reached a maximum in 1963, gradually decreasing to the lowest present level, and the risk to infants is the highest.

長崎大水害を対象にして, 廃棄物処理システムが直接的・間接的に被害を被る場合に, 災害ごみを含めて廃棄物流動がどのように変化するかを評価するための数学モデルを構築した。水害後に実際に採用された廃棄物対策がそれぞれ講じられない場合を想定し, 廃棄物流動をシミュレーションにより推定し, 講じられた対策の効果を評価した。本研究により得られた主要な結論を要約すると以下のようになる。(1) 構築した数学モデルは, 廃棄物処理システムを構成するプロセスが一時的に機能を喪失する条件下での, 廃棄物流動を説明するモデルとして利用することができる。(2) 水害後に採用された廃棄物対策の内では, 発生源での廃棄物滞留を早期に解消する面からは, 輸送能力の増強や一時保管場の設置等の効果が著しく, 仮焼却 (野焼き) の効果は大きくなかったといえる。(3) 廃棄物処理システムを構成する各プロセスの処理能力や輸送能力等の増強は, システム内での廃棄物流動が過不足なくバランスするように調整された場合に, その効果が最大になる。

わが国における紙資源のライフサイクルを評価するために構築した数学モデルを用いて, 紙資源のリサイクルの推進によって, 物質としての紙資源の流動がどのように変化するかを解析した。紙資源ライフサイクルの要素プロセスにおけるエネルギー原単位, 費用原単位を推定し, ライフサイクル全体の資源消費, エネルギー収支関係や費用収支関係が, 古紙リサイクルの推進によって現状からどのように変化するかを定量的に検討した。古紙の資源としての回収とエネルギーとしての回収との間にはトレードオフが成立する可能性があるが, 熱エネルギーの回収レベルが低い現状では現実的な意味を持たないこと, 製紙部門による古紙の買い入れ価格と古紙回収費用の組み合わせによって, 製紙部門および廃棄物処理部門の費用負担パターンが異なること, 費用負担が減少する部門から増加する部門へ, 費用負担の減少分の一部を移す施策を導入することにより, 古紙回収が経済的に促進される可能性があること等を明らかにした。

The activated charcoal passive collector method can be applied to measure the concentration of 222 Rn in river water. The 222 Rn collector is composed of dry activated charcoal sealed in a polyethylene bag. However, we found it very difficult to keep activated charcoal in a collector dry during the period the collector was left in a river. The degree of dampness and the time lapsed when activated charcoal became wet were thought to affect the quantity of 222 Rn collected. First, we studied the effect of some parameters in the activated charcoal passive collector method qualitatively in three experiments. We found that the quantity of 222 Rn collected in a collector was not so sensitive to the quantity of activated charcoal in the collector or the thickness of polyethylene film under the condition of wet activated charcoal, and that wet activated charcoal accumulated less 222 Rn than dry activated charcoal. We present some equations which could explain how much 222 Rn was collected in a collector when activated charcoal was submerged directly in water and when activated charcoal was packed in a polyethylene bag but completely wet. These equations were proved effective by being compared with the results of the other experiments. Finally, we recommended some conditions which proved useful when measuring at an actual river.

廃棄物処分場跡地と対照地区から土壌とクローバーを採取し, 放射化分析法により希少元素濃度を測定した。土壌中濃度は, 26元素中14元素で廃棄物処分場跡地の方が有意に高かったが, 人為的な汚染があるとは断定できなかった。希土類元素のクローバー中濃度は非常に低く, 植物に吸収されにくい形態で環境中に存在することが示唆された。比較的高いクローバー中濃度を示した希少元素は, 第4周期以降の必須元素と同族の元素であった。

A new method to measure 222 Rn concentration in water is described. This method is an application of the activated charcoal passive collector method, which is sometimes used for measurement of 222 Rn concentration in air. The model and the equation which express the quantity of 222 Rn adsorbed in activated charcoal in the collector were constructed, inspected experimentally, and proved to work well enough for the measurement of relative concentration of 222 Rn in water. We used this method to measure the 222 Rn concentration in water at ∼ 20 points in an actual river. Based on the fact that the concentration of 222 Rn in ground water is generally much higher than that of surface water, we found several possible groundwater seepage points along the river. For the absolute measurement of 222 Rn concentration in water by this method, it would also be necessary to investigate the effect of temperature on the quantity of 222 Rn collected in a collector.

Fallout {sup 137}Cs from atmospheric nuclear detonation test have been monitored worldwide since the late 1950`s. The deviation and the correlation among these monitoring data were analyzed, and their surface deposition characteristics were estimated by the compartment model developed in this research. In the analysis, the scale of space (i.e., size of each compartment) and the degree of detail (i.e., number of compartments) were statistically determined using the global distribution data of {sup 137}Cs. The mathematical model was evaluated by comparing the numerically simulated results with the fallout monitoring data including the {sup 137}Cs concentration in sea water. The major findings obtained in this research include that the deposition pattern of {sup 137}Cs is dependent on the latitude zone but not on the longitude, the mathematical model is promising for evaluating the dynamic performance of {sup 137}Cs in global atmospheric environment and its surface deposition, {sup 137}Cs is accumulated more in both the surface and deep ocean water of the North Pacific Ocean and the North Atlantic ocean than that of other oceans, the {sup 137}Cs inventory is decreasing after the peak time in 1965, and the {sup 137}Cs inventory in the deep ocean water is decreasing more slowly thanmore » that in the surface ocean water. 26 refs., 10 figs., 3 tabs.« less

The flow rate and sediment concentration of inflow into settling basins usually vary with respect to time; thus the sediment concentration of effluent also varies following these variations. This sediment concentration variation of settling basin effluents was analyzed theoretically by a lumped-parameter model. The resuspension of deposits from the bottom of the basin by scouring was taken into account in the computation of effluent concentration. Some numerical calculations are carried out and the results prove that the flow rate of settling basins should be carefully controlled because if the volume of water in the basin decreases greatly the sediment concentration in effluent increases sharply.

In order to estimate and evaluate the radioactivity concentration in an aquatic ecosystem, the transfer of radioactivity through a food web should be considered. In this paper, systems analysis on the above problem was performed and a quantity of radioactivity in organisms concentrated through their diet was presented. It was found from numerical evaluation that whether the transfer of radioactivity through a diet is significant or not depended on such ecological factors as ration rates, assimilation rates, uptake rates and turnover rates, etc. The degree of the importance of these parameters on the concentration process of radioactivity was quantitatively evaluated by the mathematical technique of sensitivity analysis.

A dynamic parameter estimation method for the settling basin model is brought out on the assumption that a continuous-valued time-varying parameter can be approximated with a sequence of discrete-valued time-invariant parameters by dividing a time interval into short subintervals in which the parameter is allowed to be time-invariant. Employing test data, the model parameter and the effluent concentration are calculated to confirm the applicability of the method. The method is also applied to the primary settling basins in a municipal wastewater treatment facility to determine its practicability. The calculated results with both the test and plant scale data show that this method is a useful tool for the dynamic prediction of the effluent sediment concentration of settling basins.

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.

The main objectives of this study are to construct a dynamic eutrophication model of Lake Biwa which is the largest one in Japan and to obtain an quantitative relationship between the amount of nutrients and biomass of various species of planktons. This will provide basic information for the future management of water quality to prevent the further deterioration toward a dangerous direction of eutrophication. The lake is devided into two parts geographically and the larger one consists of two layers taking into account the thermal stratification during summer season. The major elements involved in the model are three types of phytoplanktons, zooplankton and nutrients (nitrogen and phosphorus) in both organic and inorganic forms. The particular feature of the study is that lots of experimental and field works have been done for identification of the model structure and parameters under the sponsorship of the Japan Society of Civil Engineers and the Ministry of Construction (Lake Biwa Office).