Yoriteru Inoue

Optimum allocation of monitoring wells around a solid-waste landfill site using precursor indicators and fuzzy utility functions

Abstract An optimum monitoring well network (number of wells and their locations) is proposed which enables rapid, redundant and economical detection of contaminants in groundwater around a solid-waste landfill site. The procedure also guarantees detection of the contaminants given data on the probability of detection at different points in the saturated zone. The well selection is accomplished using a two-step procedure: 1. (1) A Monte Carlo simulation of contaminant transport in the unconsolidated shallow saturated zone is conducted. In this zone hydrogeological parameters are variable but their stochastic distributions are known. Three governing equations are solved numerically using the finite-difference method to obtain the travel time distribution of each contaminant: the two-dimensional steady-state groundwater flow equation; the two-dimensional transient convective-dispersion equation for sorptive contaminants; and the sorptive-desorptive isotherm equation. 2. (2) The procedure utilizes “fuzzy” theory, comprising of a set of newly developed mathematical techniques to deal with uncertainty in a wide range of man-machine interface issues, to assist in the design of a monitoring well network. The procedure requires a mathematical description of a four-attribute design problem using fuzzy utility functions and fuzzy weights. An optimum monitoring well network is then defined as the network having maximum total utility, which is evaluated as a fuzzy expectation of weighted arithmetic sums of the four utilities. One result of the simulation is the definition of relationships between the contaminant of interest and precursor materials. The precursor material can then serve as an “indicator” for faster detection of contaminant leaked from solid-waste landfill site. The procedures are applied to a hypothetical solid-waste landfill site under appropriate conditions to obtain the optimum monitoring well network for detection of precursor indicators. Sensitivity analysis of the optimum network was conducted by considering changes in components of the mathematical description of the design problem. Components which were changed include total utility evaluation, quality of uncertainty in weight factor and utility evaluation, weigth level determination, delay time requirement, well number limitation and perfect detection constraint.

Experimental study on the concentration process of trace element through a food chain from the viewpoint of nutrition ecology

Abstract This paper describes the importance of a food chain to estimate the concentration of heavy metals from the viewpoint of nutrition ecology. The experiments were performed to investigate the effects of the following experimental conditions on the uptake of heavy metals by a predator, using 137 Cs as a tracer; ration size per day, feeding interval and the change in weight of the predator fish. Top minnows ( Oryzias latipes ) were used as preys and Golden astro ( Astronotus ocellatus ) as predators. The preys were raised without feeding in an aquarium and the predators were fed top minnows. The set of results showed that (1) the concentration of a metal in predator fish increased with the ration size, (2) the feeding interval had no effect on the uptake of the metal by fish under the experimental conditions performed, and (3) the concentration in the growing fish was suppressed increasing in value with the increase of its weight. They suggest the importance of generalization of the experimental food conditions when the study on the concentration process of heavy metals through a food chain is performed. The paper also deals with the compartment model applied to the concentration process of the metal by a fish. The theoretical results depicted well the experimental ones.

Simulation analysis of the concentration process of trace heavy metals by aquatic organisms from the viewpoint of nutrition ecology

Abstract This paper proposed the food condition factor ⌈, which unifies the population density and aggregation index of prey organisms from the viewpoint of the nutrition ecology in the case of modeling the concentration process of heavy metals by aquatic organisms. By using this factor ⌈, we can generalize the food conditions when the experimental researches on the biological concentration process of trace heavy metals through a food chain are performed. Simulation analysis by computer on the concentration process of metals by a fish is made on the basis of the mathematical model described in this paper for the case that the weight of a fish increases with time. The change in weight of a fish is assumed to obey the logistic curve. The simulation results show the biological dilution of the metal concentration in an organism due to increase in the weight of a fish. Under the simulation situation conditions, however, the effect of the growth rate of a fish on the biological dilution was found to be small.

Location of groundwater seepage points into a river by measurement of 222Rn concentration in water using activated charcoal passive collectors

Abstract 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.

Distribution Coefficient kd of Radionuclide between Sample Soil and Water

Distribution coefficients between sample soil and water were determined for 17 soil samples and 9 radionuclides by batch and/or column method. Those experimental data were analyzed on some environmental factors, such as macro ionic component in liquid phase, percolation rate of water through soil column, saturation degree of the soil pore with water, cation exchange capacity of soil and so on, which might have large influence on a variation of kd. Some instructive results were obtained such as: (1) Relative magnitude of kd for 90Sr, 137Cs and 60Co does not depend on the sample soil. kdos is the largest among 3 nuclides and is followed by kdco. kdSr is the smallest. (2) kd for calcium rich soil might be estimated mainly based on Ca+Mg concentration in water phase, and kd for calcium poor soil based on pH in water phase. (3) Positive correlation is observed between kd of 90Sr and cation exchange capacity of soil. (4) kd for unsaturated soil with water are observed to be larger than kd determined for saturated soil with water. (5) 90Y, 110mAg and 59Fe among 9 nuclides used in this work might be stable in non-ionic form in water.

A numerical model for the analysis and evaluation of global 137Cs fallout

Fallout 137Cs from atmospheric nuclear detonation tests has been monitored worldwide since the late 1950s. 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 137Cs. The mathematical model was evaluated by comparing the numerically stimulated results with the fallout monitoring data including the 137Cs concentration in sea water. The major findings obtained in this research include that the deposition pattern of 137Cs is dependent on the latitude zone but not on the longitude, the mathematical model is promising for evaluating the dynamic performance of 137Cs in global atmospheric environment and its surface deposition, 137Cs 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 137Cs inventory is decreasing after the peak time in 1965, and the 137Cs inventory in the deep ocean water is decreasing more slowly than that in the surface ocean water.

MULTI-SPECIES OF PLANKTONS AND NUTRIENTS MODEL OF LAKE EUTROPHICATION - A SIMULATION STUDY IN LAKE BIWA -

ABSTRACT 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).

Evaluation of the radioactive wastes disposal into the deep ocean.

Abstract-This paper presents a hazard assessment for deep sea disposal of low level radioactive solid wastes which originate from nuclear power reactors in Japan. The model takes account of leaching characteristics of radionuclides from wastes solidified with cement, which has not been considered in other papers. Maximum and average concentrations of radionuclides in an upper mixed layer of the sea are estimated and maximum doses for individual and population doses for Japanese people are calculated. In order to evaluate an uncertainty of parameters in the model, a sensitivity analysis was performed. The discussions include: which parameter in an equation of the model affects most the average concentration of radionuclides in upper mixed layer and, to what degree the fluctuation of parameters due to the variation of environmental factors affects the concentration? Generally, the most sensitive parameter is the depth of the sea where the solidified wastes would be deposited. The concentration of radionuclides in the surface water is not sensitively affected by the vertical diffusion coefficient.

Groundwater deterioration caused by induced recharge: Field survey and verification of the deterioration mechanism by stochastic numerical simulation

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.

A Dosimetric Determination of 137Cs Ingestion from Global Fallout and the Related Risks to Japanese

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 137Cs and the related risks to Japanese are proposed by coupling the previously published global 137Cs 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 137Cs 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 the risk to Japanese health caused by the dietary intake of global radioactive fallout 137Cs, the 137Cs is taken up by Japanese mostly through farm products, the ingestion of 137Cs through imported foods is increasing, the risk to the Japanese health of inducing cancer by 137Cs internal exposure reached a maximum in 1963, gradually decreasing to the lowest present level, and the risk to infants is the highest.