In September 1984, a large amount of foam was observed in Lake Chuzenji. One of the purposes of this study is to find out causes of the foam. Because carbohydrate concentration in lake water was relatively high (2.25mg·l^-1 in filtered water) and carbohydrate (mainly arabinose and galactose) occupied about 1/3 of freeze dried material from lake water of foaming, it was supposed that carbohydrate was one of the main causes of the foam.
To clarify the carbohydrate origin, aquatic macrophytes and fallen leaves were steeped in distilled water. Carbohydrate concentration released from aquatic macrophytes into distilled water elevated about 100mg·l^-1 after 100 days. Carbohydrate concentration released from fallen leaves rapidly elevated 66mg·l^-1 after 5 days. The carbohydrate constituents of foam were similar to these of aquatic macrophytes and fallen leaves.
According to the results, one of the main causes of the foam seems to be carbohydrate released from aquatic macrophytes in September, autumn and winter and from fallen leaves in autumn and winter.

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Filtered water from a water treatment plant and aqueous solutions of model compounds for humic substance were chlorinated. Trihalomethans (THM), chloral hydrate (CH), dichloroacetic acid (DCA), and trichloroacetic acid (TCA), which were produced in the chlorination reaction, were determined in each case. THM were determined by ECD-GC. A method using GC/MS or ECD-GC was developed for determining CH, DCA, and TCA.
When the filtered water from Ushikubi water treatment plant was chorinated at pH7 and at 20°C, the total of CH, DCA, and TCA was compared to the total amount of THM. The quantity of these chlorinated products increased with time and the ratio to the total organic halide reached to 38% (as chlorine equivalent) after 6 days.
In the chlorination using 1, 3-dihydroxybenzene, 1, 3-dihydroxynaphthalene, or their derivatives as the model compound, the main product was always chloroform. On the other hand, TCA was often produced as the main species when other monohydroxy or dihydroxy aromatic compounds were chlorinated.

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The behaviour of suspended sediments in an estuary was investigated by use of an annular flume with the condition of cyclically changed shear stress and field data on suspended solids and velocities obtained at the River Chikugo.
Conclusions derived in this study were as follows :
(1) The behaviour of suspended solids in the case of mulls differed from that in the case of sands.
(2) In the case of muds, the changes of suspended solids were explained by introducing four critical shear stresses, namely, τ_ce1, τ_ce2, τ_cd1 and τ_cd2.
(3) In an estuary, the high SS waters moved up- and down-stream undertaking the erosion and deposition.
(4) Erosional and depositional fluxes in a tidal cycle at the River Chikugo were estimated based on the field data. The variation of these fluxes with bed shear stress showed the same tendency as those obtained in the experiments.

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[in Japanese]

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