The quality of leachate collected from waste landfills which received industrial and municipal waste in Hanoi was analyzed in order to obtain information on the current situation of pollutants in these sites. The leachate collected from Tay Mo landfill and Nam Son landfill showed the high concentration of iron and mercury. It was also recognized that the high strength of COD and color of leachate are the primary problems to be resolved at both sites. The application of several advanced oxidation processes (AOPs) to Tay Mo landfill leachate revealed that Fenton reaction and photo-Fenton reaction under pH adjustment effectively removed COD and color from the leachate and degraded the humic substance in it. Mutagenicity of the leachate was increased by UV-TiO₂-H₂O₂, Fenton (pH 3) and UV-Fenton (pH 3) treatments. This indicates that degradation of organic matters in the leachate resulted in the generation of toxic intermediates. Further investigation of the operating conditions of AOPs is necessary to minimize the environmental impact of waste landfill leachate.

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Various countermeasures have been taken against eutrophication in lake. However, such countermeasure may increase CO₂ emission even if lake water quality is improved. An integrated evaluation of such trade-off is necessary in terms of comprehensive environmental improvement. The objectives of this study are to develop and apply an integrated assessment method of the improvement of water environment by multiple countermeasures and the impact of global warming by additional CO₂ emission. The method comprised the quantification of reduced water pollutants and additional CO₂, estimation of environmental improvement and impact, economic evaluation and the comparison of them. Along with the method, multiple countermeasures against point source and non-point source for environmental improvement of Lake Suwa in Nagano Prefecture were evaluated. Environmental improvement in Lake Suwa was simulated by applying an ecosystem model and its economic value was estimated by applying the Contingent Valuation Method. On the other hand, CO₂ emission was calculated by applying an inventory analysis of Life Cycle Assessment, and the economic value of global warming was estimated by using marginal social costs. It is inferred that the completion of sewerage systems and the change of fertilization practices are effective within environmental aspects of eutrophication and global warming.

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Recently, wetlands are gradually shrinking in Japan and many other countries due to human activities. Especially, the bog-mire system is valuable, because it was formed over a span of thousand years and a unique ecosystem is maintained there. However, the bog-mire ecosystem is delicate to external impact. We investigated the quality of ground water and the chemical properties of accumulated peat in lakes and wetlands at different succession stages at Wakasakanai costal dune located in northern Hokkaido, Japan, and studied the change of water quality and water cultivation system in the succession process. The results are summarized as follows. We proved chemically in situ that the surface ground water of wetland changes from minerotrophic to ombrotrophic, with peat accumulation. This change was caused by the inversion of ground water flow. These tendencies were clarified by Principal Component Analysis of water quality. Carbon content was about 50% in peat soil. This percentage composition did not differ much at different depths. Nitrogen content was 3-4% in lake mud, and humic soil, but in peat soil the content became lower, being about 1% in sphagnum peat soil. On the surface of sphagnum peat soil, it became slightly high because living plants seem to take in nitrogen. From the point of view of soil composition, the nutrient content must be low to form sphagnum peat. To conserve the bog-mire system or the sphagnum area, surface ground water must be kept ombrotrophic. To this end, ground water flowing downstream is necessary.

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An impact analysis on waterborne diseases in several types of future world was carried out considering global warming. Diarrhea, which is strongly affected by water supply and sanitation, was selected as an indicator of health impact. In order to estimate diarrheal incidence, water supply coverage, sanitation coverage, annual average temperature, and per capita GDP data were subjected to multiple regression analysis. Water supply coverage and annual average temperature were selected as independent variables. Four SRES scenarios (A1B, A2, B1, and B2) developed by IPCC were used to estimate water supply coverage, annual average temperature, and diarrheal incidence per capita in 2025 and 2055. The estimation results indicate large differences in future diarrheal incidence among regions not only because of the present temperature and water supply coverage but their future changes as well. A comparison of the results for the four scenarios shows the importance of high environmental consciousness as well as rapid economic growth in reducing diarrheal incidence. Moreover, the results indicate that it is necessary to develop more policy initiatives that consider regional social and environmental conditions in order to improve the situation of water supply coverage.

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An example of the chemical evolution of snowpack associated with its thawing phenomenon was presented. The snowpack was accumulated during an isolated event of snowfall. Bulk snow core was sampled for each occasion with a time interval of several hours, and chemically analyzed. Sea-salt originated species, such as Na⁺, Mg²⁺ and Cl^-, showed a rapid reduction in concentration with time compared to other species (H⁺, NO₃^-, SO₄^2-). The result suggests that sea-salt species can be selectively enriched in snow thaw discharge. Such a behavior may be attributed to the structure of each snowflake, consisting of acid-rich crystal and sea-salt-rich rimed cloud droplets.

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Leachates from solid waste disposal sites and road deposits were focused on as sources of heavy metals in water environment. A comparative study of the concentrations of heavy metals was carried out for samples collected in the Philippines and in Japan. Heavy metals were not removed in the oxidation ponds designed for leachate treatment in the Philippines. The chemical compositions of the leachates from a site in the Philippines and that from a site with a low content of incineration residuals in Japan were similar in terms of general water quality parameters. Relatively high concentrations of lead and antimony and very high concentrations of tin were observed in the leachate from the site in the Philippines. The comparison of the concentrations of heavy metals in road deposits showed that the concentrations of heavy metals in unit dry weight of road deposits were in the same range regardless of the countries where the samples were collected. It was suggested that lead might be a suitable indicator of the pollution of sediments in water environment caused by urban deposits. A model calculation showed that the contribution of disposal site leachates to that of the overall heavy metal loads discharged to the water environment in Tokyo was 1/200 of the contribution of road deposits, while the same calculation showed 1/10 for the Philippine case.

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At the center of Lake Kasumigaura, water temperature, DO, pH, and chlorophyll a were measured at 6 different depths at 24-minute intervals for four 1-week periods. Using the models for vertical mixing and air-water exchange, the vertical distribution of biological changes in the lake water was estimated quasi-continuously, although the estimation was difficult when the decay of stratification occurred. Simultaneous measurements of DO and pH demonstrated the accuracy of the estimated biological activities. This system shows potential for field measurements of biological activities, e. g., primary productivity and respiration in the columns of aquatic systems.

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Waters from the Sakawa River and its tributaries were tested by conducting a colony forming assay with Bulb 3T3 A31-1-1 and Vero cells, both of which showed good sensitivities to the test waters and some pesticides. The waters were also subjected to standard water analyses, such as bacterial count, concentrations of nitrate and nitrite, chemical oxigen demand (COD), and electrical conductivity. The river waters were collected 7 times at 13 points from August 1995 to July 1997. Relative cell plating efficiencies at maximum concentrations of the river waters (net river water in the medium was 81%) were used to compare the cytotoxicities of the waters. The ranking of each water in terms of the given parameters was determined with the plating efficiency, or each parameter of chemical analysis, then in cells (total ranking of cytotoxicity), or in the water analysis (total ranking of standard water analysis). On the whole, the results of total ranking of cytotoxicity and those of standard water analysis were strongly correlated, although some waters showed strong cytotoxicity even when judged as ‘clean waters’ by the water analysis. Overall, the data suggest the usefulness of biological testing to detect complex pollutants in environmental waters.

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The aqueous-phase sorption of microorganic pollutants into liposomes and the effects of coexisting humic substances on the sorption were experimentally evaluated. The liposome, used for simulating a living cell membrane, was synthesized in the laboratory, and two PAHs (polycyclic aromatic hydrocarbons, i. e., pyrene and phenanthrene) were used as sorbates in this research. A new methodology for measuring the degree of PAHs sorption into the liposome was developed using the fluorescence enhancement phenomenon observed with the sorption. The batch sorption results indicate that the sorption into the liposome (i. e., liposome/water sorption coefficient (K_lipw)) could be a better parameter for estimating the transport of microorganic pollutants into a living cell than the n-octanol/water partition coefficient (K_ow), and humic substances suppress this transport by binding microorganic pollutants.

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This study aimed to confirm whether or not an ammonia-oxidizing bacterium (Nitrosomonas europaea) could degrade natural estrogens, estrone (E1), 17β-estradiol (E2), and a synthetic estrogen, ethynyl estradiol (EE2). Cultivation of N. europaea in a culture medium containing each estrogen at a concentration of 0.4 mg·l^-1 demonstrated that N. europaea could degrade up to 95% of the estrogens during the first 187 hours of cultivation. The obtained degradation rate constants of the three estrogens did not show significant difference. It should be noted that the degradation of the three estrogens by N. europaea produced unknown compounds, as confirmed by analyzing the culture mediums of N. europaea by reversed-phase high-performance liquid chromatography equipped with an electrochemical detector (HPLC-ECD). Based on the finding that these electrochemically detectable compounds were more easily eluted than their parent compounds, i. e. E1, E2 and EE2, on the HPLC-ECD, it was suggested that N. europaea degraded the three estrogens to produce more polar compounds containing phenolic groups.

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Characteristics of rhizome resource storage of common reed, Phragmites australis, were investigated in terms of rhizome age. Rhizome biomass and nitrogen and phosphorus concentrations, and total standing stock were measured to understand storage dynamics of each rhizome age. The biomass of one-year-old rhizomes did not decrease in the growing season, while a large reduction in biomass was observed in older rhizomes. Phosphorus and nitrogen concentrations of old rhizomes remained constant throughout the year, while those of young rhizomes decreased particularly from April to May and July to November, indicating that changes in phosphorus concentrations mainly occur in young rhizomes. The standing stock, however, decreased from April to May and September onwards, except for that of young rhizomes which was supposed to be transported to form new shoots.

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Polluted soils (S-2, S-3, and S-4) were prepared by additing of chemical compounds containing molybdenum (Mo) and nickel (Ni). Under the various pH, temperatures and extraction times, the amounts of Mo and Ni that dissolved in the soils were examined by inductively coupled plasma atomic emission spectrometry. The amounts of Mo that dissolved in the polluted soils increased as the pH in the extracted solutions increased, while those of Ni increased as the pH in the solutions decreased. The amounts of Mo and Ni dissolved in the prepared polluted soils increased as the temperature of the solutions and the extraction time increased.

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