The effect of chloride ion on the acidic COD determination with potassium permanganate was studied using semi-micro method which is adopted as the official method in the Environmental Quality Standards in Japan and is applied to water samples containing a large quantity of chloride ion such as sea water and estuarine water.
The blank tests were carried out by making produce the same amounts of silver chloride as in water samples in order to maintain the same condition as in the COD determination for water samples. The amounts of potassium permanganate consumed were kept constant at various concentrations of chloride ion by addition of the amount of silver sulphate equivalent to chloride ion in the solution.
In the presence of organic matter and chloride ion, the consumed amounts of potassium permanganate for all given samples increased linearly with the increment of the concentration of chloride ion at various levels of organic matter concentration in spite of addition of silver sulphate equivalent to chloride ion contained.
The degree of increment of the COD value varied with the kinds of organic matters contained in water samples. Furthermore, the effect of chloride ion in artificial sea water on the COD determination was higher than sodium chloride.

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A laboratory experiment was conducted to evaluate the role of sedimentary organic matter on the removal of alkylbenzenesulfonates (ABS) from water to sediment. Kerogen-like materials (an organic fraction which is soluble neither in any organic nor inorganic solvents) were isolated from river (The Tamagawa river) and lake (Lake Haruna) sediments. The kerogen was mixed with ABS with C₁₀ to C₁₃ alkyl chains in aqueous solutions. Obtained results were as follows.
(1) The incorporation of ABS into kerogens followed Freundlich adsorption isotherm equation.
(2) The amount of incorporation of ABS into kerogens increased with the increased of pH. When pH of the solution was 7 and the concentration of ABS and kerogen were 1 mg and 20 mg in 5 ml respectively. The ABS incorporated into kerogen amounted to 42-47 μg/mg-kerogen.
(3) ABS having longer alkyl chains were more likely to incorporated into kerogens than those with shorter chains. This result suggests that the incorporation of ABS is due to hydrophobic-bonding.
(4) When ABS which had been incorporated into kerogens was extracted with methanol, approximately 100% of ABS was recovered from Lake Haruna kerogen, whereas only 30-50% was recovered from the Tamagawa river kerogens.
(5) In the light of the present study, the amount and the relative abundance of ABS with C₁₀ to C₁₃ which were observed for the Tamagawa river sediment can be explained by the mechanism where major sedimentary organic mater plays the important role in the incorporation of ABS from water to the sediment.

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Historical variation and present state of water quality as well as flow rate of the Nogawa River, one of the tributaries of the Tama River, which flows in the southwest of Tokyo are examined The population of the river basin has grown 4.0 times in these 35 years and urbanization change of situations around the river has made the Nogawa River a typical urbane polluted river.
Close show observation of the mechanism of the pollution in the Nogawa River, therefore, may give general keys to show how to restore the water environment in populated area. Two main problems could be referred as concluding remarks :
(1) Though the water quality has been slowly recovered by gradual accomplishment of the river basin sewerage system, such a system has reduced the Nogawa's flow rate seriously.
(2) The Nogawa River has bigger BOD flux at the connection with the Tama River in summer season than in winter time. This is caused by the growth and decomposition of benthic algae (about 3 ton BOD/day is produced in the Nogawa River at summer season). To keep off the growth of benthic algae is one of the important subjects to be considered for the restoration of water quality.

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BOD in sea water was studied in order to investigate the biodegradability of various organic compounds and self-purification in sea water. The BOD₅ values of the 7 | organic compounds which commonly exist in environment or produced in large quantities for commercial use were measured by the sea water dilution method (S.W.D.M) and the standard dilution method (S.D.M), and compared with each other. In addition to the BOD₅ value, BOD₁₀, BOD₁₅ and BOD₂₀ values of several organic compounds were measured and also compared each other.
The BOD of 1 : 1 mixture of glucose and L-glutamic acid was continuously measured by the S.W.D. M and the S.D.M for 10-20 days in order to investigate the temperature effect in sea water compared with the fresh water. Time lag (t₀), kinetic constant (k) and the ultimate BOD value (L) were calculated by the Thomas's slope method. The difference of BOD reaction of the sea water and the fresh water was considered by these results. The BOD in sea water was slightly lower than that obtained in fresh water. The data of BOD, COD _Mn and Adenosine triphosphate (ATP) determined by ATP Photometer in Osaka Bay were compared.

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An application of multivariate analysis (principal component analysis, pattern analysis and cluster analysis) to water pollution research of Tamagawa river, and experimental data based on 36 samples of Tamagawa river in 1978, analyzed for eight elements, were used to demonstrate the ability of those method. The relationships among six elements to indicate water pollution were examined using principal component analysis and cluster analysis. The similarity between two water quality patterns was examined using pattern similarity.

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The mutagenic activities of 17 reagents used in water test were tested using Salmonella typhimurium TA 100 and TA 98. According to the results, five compounds of 17 tested reagents, such as Sodium azide, α-Naphythylamine, p-Dimethylaminobenzylidenerhodanine, o-Tolidine and 8-Hydroxyquinoline were found to be mutagenic on S. typhimurium TA 100, TA 98 or both. Therefore, we must be careful with use of these five reagents and, as soon as possible, make a new method of water test not using these mutagenic compounds.

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Mercury (II) Oxide suspended in sodium chloride solution is in equilibrium between the solid Mercury (II) oxide and dissolved mercury (II) chloride. When the suspension was irradiated using a blacklight lamp, the mercury (II) oxide dissolved rapidly with sodium chloride concentration increase and a trace of mercury (I) chloride was produced.

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