The pollution evaluation of the rivers and streams in Aso caldera area was done by principal component analysis and multiple regression analysis out of the methods of multivariate analysis based on the results of field survey on the flow rate, water-quality and bottom fauna of the rivers in December of 1984, April, August and November of 1985.
The first principal components Z₁ (7S, 16I) and Z₁ (7S, 9I) were selected as to show the water-quality characteristics of Aso large volcanic basins.
The products of the difference of the first pricipal component scores and the ratio of the flow rates show some measures of the total amount and the sources of water pollution substances such as iron.
The mutiple regression analysis between bottom fauna and water-quality parameters show that fluoride is the most effective substance for the bottom fauna, and also the correlation between the first principal component Z₁ (10S, 9I) and diversity index of fauna community DI (N) is shown as DI (N) =1.888e^-0.192Z₁
Then it was found that the pollution evaluation of the river environment in Aso caldera area could be done through the methods above and the living of bottom fauna in the rivers are interfered according to progress of the water pollution due to volcanic area characteristics.

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Determinations of Algal Growth Potential (AGP) and limiting nutrients in Lake Kasumigaura were carried out from May 1980 to April 1981 using algal assay procedure.
AGPs of the filtrates and the autoclaved-filtrates (autoclaved at 120°C, 15min.) of Lake Kasumigaura using a blue-green alga, Microcystis flos-aquae were 0.1 to 0.37mgl^-1 and 3.9 to 11.2mgl^-1, respectively. AGPs of the autoclaved-filtrates were approximately ten folds higher than those of the filtrates.
The growth of Microcystis in the filtrates was stimulated by both additions of phosphorus and nitrogen in summer season. While, iron or EDTA was essential for the growth of Microcystis during fall to spring. Therefore, limiting nutrients of the filtrates for Microcystis were both phosphorus and nitrogen in summer season, while iron or EDTA during fall to spring. The limiting nutrient in the autoclaved-filtrate was mostly nitrogen throughout the year.
Selenastrum capricornutum was also used as a test alga. The limiting nutrient for S. capricornutum was phosphorus in the filtrates and the autoclaved-filtrates. No growth stimulation for S. capricornutum was observed by the addition of iron or EDTA.

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Method for eliminating lethal action substances in river sediments was investigated as a part of the study to establish a routine method for monitoring mutagenicity of river sediments. Mutagenicity test was carried out by the pre-incubation method using Salmonella typhimurium TA 98 and TA 100 with and without S9 mix. River sediments were collected at each estuary of four rivers, the Tama river, the Tsurumi river, the Sagami river and the Sakawa river, in Kanagawa prefecture.
All crude extracts from the sediments showed the lethal action on the tester strains. The lethal action was stronger in the extracts from heavily polluted rivers than slightly polluted rivers. Mutagenicity was only observed in the extract from the Sagami river, a slightly polluted river, suggesting the elimination of the lethal action substances is essential for the mutagenicity assay of river sediments.
Treatment of the crude extracts with the activated copper column was effective in reducing the lethal action. However, it was not enough for the complete elimination of the lethal action substances.
Most of the lethal action substances were in the neutral fraction of the crude extract. Then, the neutral fraction was separated by a high performance liquid chromatography (HPLC), and each separated fraction was served for mutagenicity test and survivor test. HPLC was effective for the separation of the lethal action substances and mutagenic substances in the neutral fraction. These results suggest strongly that HPLC is useful for the preparation of test samples for mutagenicity assay of river sediments.

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[in Japanese]

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