Genotoxic activities have been detected in the river water. The umu test, which can detect DNA damage, was carried out with blue rayon extracts of various water samples from the river systems and treatment plants. HPLC fractionations followed by MS or UV analysis were applied to the extracts to identify the genotoxic substances. Trp-P-2 (3-amino-1-methyl-5H-pyrido[4,3-b]indole), which is one of mutagenic and carcinogenic heterocyclic amines, was detected in concentration from 1 μg·l^-1 to 1 ng·l^-1. These results show that carcinogenic substances related to humans' daily diet remain after usual biological treatment. To evaluate the level of Trp-P-2, the added risks were calculated by use of the doseresponse relationships obtained in a carcinogenic animal experiment with mice. The values at assumed exposures of 2l per day of samples from the night soil treatment plant over an average life span of 70 years for 70kg person were in excess of 10^-6. Because of the possibility of the reuse of wastewater, the need for the investigation on the safety of the secondary effluent from the treatment plants was suggested.

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To evaluate the toxicity other than mutagenicity or carcinogenicity present in the water environment, in vitro cytotoxicity tests using cultured mammalian cells were utilized. Cytotoxicity was estimated based on the changes in viable cell numbers of primary rat cerebellar cells, rat pheochromocytoma cell PC12h, and normal rat kidney epithelial cell NRK-52E. Evaluation of these in vitro systems was performed by testing reference chemicals proposed by MEIC (Multicenter Evaluation of In Vitro Cytotoxicity), an international program for the validation of in vitro cytotoxicity tests.
When cells in culture were exposed to landfill leachate for 48 hours, viable cell numbers decreased dose dependently. However, fractions prepared by condensation and extraction from the leachates showed much less effects on the viable cell numbers. Their individual cytotoxicity did not account for that of unfractionated leachate, suggesting that component(s) with higher cytotoxicity may not be successfully recovered during the condensation and extraction process.
Among the silica-gel column fractions of acetone-extracts of sediment samples, fractions eluted with acetone showed the highest cytotoxicity.
These results indicate that the cytotoxicity of water samples like landfill leachates or of their extracts can be detected with the present assay system but toxic components may not be recovered quantitatively during the condensation and extraction process.

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Monochloramine (NH₂Cl) which is a highly toxic pollutant is usually contained in chlorinated sewage effluents. Effects of NH₂Cl and chlorinated sewage effluent on freshwater ecosystem were investigated by an algal growth test using a green alga Selenastrum capricornutum.
Toxicity of NH₂Cl for the alga was stronger than that of free chlorine, and NH₂Cl was extremely stable in freshwater. Lowest-observed-effect concentration (LOEC) of NH₂Cl after 96 hours exposure was 0.01 mg-Cl₂l^-1. Comparison of chlorinated effluents with non-chlorinated effluents, the algal growth was inhibited significantly in chlorinated effluents. The final chlorinated effluents collected from the sewage treatment plant also affected the growth of alga, and about 80% of total residual oxidants in the effluents was detected as NH₂Cl. On the contrary, the algal growth was not inhibited in dechlorinated effuents with Na₂SO₃ because of disappearance of the residual oxidant. Judging from these results, it was clear that NH₂Cl was the most important pollutant in chlorinated wastewater effluents for aquatic organisms.

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According to the appointment of Ashby et al., 60% of the environmental carcinogens are negative in Ames test. About non-mutagenic carcinogens, it is reported that there is the relationship between carcinogenicity and the ability to produce active oxygen.
We choosed organochlorine compounds which are non-mutagenic carcinogens and nitroarenes as test chemicals.
As a means to evaluate the ability of chemicals to produce O₂^-, new strain which can detect soxS induced by O₂^- is used. And for positive compounds, umu test is tried. And whether the test with the new strain can become a way of screeing of non-mutagenic carcinogens is discussed.
As a result of these tests, it is cleared that there are compounds which produce O₂^- and H₂O₂ induced by the O₂^- causes DNA damage. This result suggests that new strain can become a means to screen non-mutagenic carcinogens. Intensity of mutagenic activity of organochlorine compounds in umu test decreased when S9mix was added. When 1-naphthol and quinoline are nitrated, they become to produce O₂^-. Aromatic compounds existing in tar can get ability to produce O₂^- after nitrated and can cause DNA damage. Therefore the evaluation of toxic effects of active oxygen should be added to established tests.

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Biodegradability of bisphenol (BPA) in aquatic environments was evaluated by a river die-away method using a variety of river water microcosms. Among 44 microcosms examined, 40 microcosms (ca. 90% of the total) exhibited BPA-degrading capability to a certain degree in an artificial river water. It suggested ubiquitous presence of BPA-degraders. However, among them only 6 samples showed complete degradation or mineralization of BPA shown as complete removal of TOC, and the other 34 microcosms accumulated common metabolites, which were detected as two peaks according to high-pressure liquid chromatography assay. As a result, more than 10% of the initial TOC remained in test microcosms. Eight BPA-degrading bacteria were isolated from river waters and all the isolates accumulated the same metabolites as those accumulated by river water microcosms during BPA degradation. These results suggest that recalcitrant metabolites are produced even if partial degradation of BPA can proceed easily. In some aquatic environments the metabolite(s)-degraders coexist together with the BPA-degraders and they seems essential for the complete degradation or mineralization of BPA.

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Trihalomethane formation potential (THMFP) from chlorination of three species blue-green algae and one species green alga, which often proliferate in eutrophic Lake Kasumigaura, was examined in batch culture experiment. And removal effect of THM-precursor by biological activated carbon fluidized bed reactor (BACFR) was compared with that by biological oxidation reactor packed with honey comb tube (BORHT) under continuous flow conditions. THMFP of green alga Scenedesmus sp. was extremely higher than any other blue-green algae, Microcystis aeruginosa, Oscillatoria mougeotii and Phormidium tenue. DOC concentration and E₂₆₀ as THMFP parameters were efficiently removed by BACFR. The removal of the two parameters by BACFR was 60%, while those of them by BORHT were 20% and 10%, respectively. It was found that BACFR was much more efficient than BORHT to the removal of THM precursor from algae appearing in an eutrophic lake.

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Continuous fluidized bed bioreactor packed with activated carbon and cellulose as a carrier was used to evaluate the removal efficiency of blue-green alga, Phormidium tenue and its metabolite, 2-methylisoborneol (2-MIB).
The removals of P. tenue and total 2-MIB (including intracellular and dissolved 2-MIB) by fluidized bed biological activated carbon (FBA) were 89.1% and 68% at 20°C for 7 days, while those of them by fluidized bed biological cellulose (FBC) were 85.3% and 57% under the same condition. FBA showed relatively higher removal than FBC.
Protozoan, Monas sp. on biofilm was closely correlated with the ingestion of viable cells of P. tenue, and its dissolved 2-MIB was found to be efficiently assimilated by the aggregated bacteria on the biofilm. It was indicated that the removal difference of 2-MIB by continuous fluidized bed bioreactor was dependent on the kind of carriers.

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The value of the parameters in environmental fate model of chemicals has not been well examined. This paper discusses about that. The purpose of this paper is to evaluate the parameter uncertainty using Bayes theorem with the example of agricultural chemicals runoff in the test watershed. Bayeisian Monte Carlo technique is used to quantify errors in chemical fate model caused by uncertain parameters. Often there are a few site-specific data that describes the model parameters. The only information typically available for many parameters is a range of values obtained from related published studies. This technique combines Monte Carlo analysis with Bayesian inference specifying model input parameter distirbutions. The statistical likelihood function is employed to evaluate the ability of any given set of model parameters to describe the observed data on model state variables. Preliminary information on parameter distribution is combined with measurement of state variables to provide improved estimates of parameter distribution. This method was applied to a model developed to evaluate the pesticide runoff process on the Shibuta river, Kanagawa prefecture. The model used is one dimensional and purely advective and one state variable. Six parameters (partition coefficient, degradation rate constant in water, degradation rate constant in soil, soil density) were evaluated.

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The early phase rain fall current of the time appearance characteristic of benzo (a) pyrene contained in combined sewerage overflow, separate sewerage rain-water drainage, and road runoff was investigated. Analytical conditioning method of benzo (a) pyrene was also examined. Benzo (a) pyrene is one of polynuclear aromatic hydrocarbons which are carcinogenic agents contained in auto exhaust, and it is carried in rivers and sea by initial rain fall. As for benzo (a) pyrene accumulated with bottommud, that influence to ecosystem is pointed out.
Benzo (a) pyrene didn't exist in the filtrate of rain water samples, but absorbed with the suspended solid almost. Benzo (a) pyrene was detected with high concentration in road runoff and combined sewerage overflow. It was suggested that sediment in the sewerage pipe and road sediment coexisted in the combined sewerage overflow, and that the road sediment contaminated with benzo (a) pyrene was still drained after the sediment in the pipe which was easy to be transferred.

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We researched the chemical character and its formation mechanism of the ground water of mires as a basic study to conserve of natural mires. The researched area was Sarobetsu mire (23,000ha), in the north of Hokkaido, where its vegetation and other aspects of its nature has been gradually changing, such as the partial development of the mire into agricultural fields. This research shows that ground water of high moor bog region where Sphagnum spp. are dominant is increased only by rain water and in the ground water of the high moor bog, the decomposition of organic matter by bacteria activity is suppressed. And it was found that in the region where the conservation of mires is necessary because of invasion of Sasa palmata in the original bog vegetation, concentrations of general inorganic components and nutrients were extremely high because of their elution from clay mingled into the peat soil, inflow of water rich with nutrients from other water systems and the decomposition of the peat soil by development in the area.

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The release of landfill leachate containing toxic substances such as heavy metals and organochlorines may cause adverse environmental effects on aquatic environment. Therefore, it is important to clarify the effects of landfill leachate on aquatic environment based on risk analysis. Chemical analysis of landfill leachate is very difficult to evaluate its potential effects accurately because landfill leachate contains a lot of unidentified substances. It is expected that bioassay procedure can compensate the deficits of chemical analysis for samples like landfill leachate. In order to evaluate treatment performance and biological effects of landfill leachate, we conducted bioassay procedure for the raw landfill leachate collected from a real landfill disposal site and the effluent treated by the biological activated carbon fluidized bed (BACFB) process and ozone treatment using Photobacterium phosphoreum, i.e., Microtox test. Microtox test showed that EC₅₀ for raw landfill leachate was 6.7%, which means the raw landfill leachate to be severe toxic. On the other hand, the effluent treated by BACFB showed little toxicity. In addition, bioassay for the effluent sample concentrated through Sep pak column was also carried out to evaluate the effect of ozone treatment. It was found that ozone treatment of the effluent of BACFB increased toxicity. But, when the effluent of ozone treatment was treated again by BACFB, the toxicity decreased significantly compared to that of the effluent treated by ozone or by BACFB only. This result suggests that the hybrid treatment system with the combination of BACFB and ozone treatment process is efficient to remove toxic substances from landfill leachate.

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Ozone oxidize bromide ions (Br^-) to form bromate ions (BrO₃^-). With coexisting organic compounds which have 260nm ultraviolet absorbance, ozone oxidize organic compounds and yield aldehydes as organic ozonation by-products prior to forming bromate ions. In laboratory-scale ozonation experiments of natural river water, bromate formation was inhibited by coexisting organic matters in original water, while total organic halides (TOX) and aldehydes were increased. Phosphate also worked as a scavenger to inhibit bromate formation in ozonation. In the constant initial pH conditions, bromate concentration was gradually increased in accordance with low ozone dose per TOC (O₃/TOC), but severely increased at a certain high O₃/ TOC. When pH was as high as 8, bromate formation was accelerated even at lower O₃/TOC. Bromate formation should be prevented by the optimized minimum ozone dose just enough to oxidize target substances.

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Populations of phenol-degrading bacteria in soil and their trichloroethylene (TCE)-degrading capabilities were evaluated to find effective and reasonable in situ bioremediation methods. In eight soil samples, it is observed that bacteria able to grow on inorganic medium including 125 mg·l^-1 of phenol accounted for 6 to 20 % of total aerobic heterotrophic bacteria. Further, TCE-degrading capabilities of fourteen phenol-degrading strains including six isolates from the soil samples described above were compared. Under phenol-induced conditions, the majority of the bacteria could reduce 1mg·l^-1 of TCE to an undetectable limit, while the rests could not completely remove TCE or at all. However, all the strains with only one exception showed TCE-degrading activity to a certain extent (ultimate TCE removal was 20 to 100%), and their specific degradation rates for TCE corresponded to those for phenol. These results suggest the possibility of TCE removal by in situ biostimulation in the presence of effective native phenol-degrading bacteria.

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