Concentration of heavy metal (trace chalcophile elements) in the bottom sediment of the Watarase River, which has been notorious for the pollution problem caused by the copper mine, was determined and the behaviour of these elements in the riverbed was also examined. The results were as follows ;
1. Heavy metal concentrations in the bottom sediment were extreamly high as compared with those of other typical rivers in Japan.
2. The heavy metals originated from the mine drainage might flow down together with the suspended substances at the time of flooding.
3. The ratios of each metal concentration in the bottom sediment depends upon the concentration of each metal in suspended substances at the time of flooding.
4. The rapid decrease in the slope of riverbed around mid-stream accelerate the precipitation of suspended substances and affects metal concentration ratios in the bottom sediment.

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Fluctuation of water quality in newly constructed Hayade Reservoir in Niigata Prefecture was observed from 1978 to 1982. Sampling was carried out at surface, middle and bottom layer respectively. Water quality data of each sample were determined for several items and 7 items (100/ DO%, COD, IC, TN, TP, EC, WT) were analyzed by the Principal Component Analysis (PCA) method. More than 75% of total variance of the original data were contributed to the first component by the PCA method.
Therefore, Water Quality Index (WQI) derived from the first component could be used to evaluate the pollution levels caused by natural factors in this reservoir. The pollution levels were related negatively to WQI. From the analysis of fluctuating changes in WQI, pollution level was remarkably progressed in the summer of the first year at bottom layer. Contribution for eutrophication at the initial stage of reservation to pollution level of reservoir was also obvious.

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The effects of synthetic detergents and soap on algal growth and physiological activities were studied using a freshwater alga, C. pyrenoidosa and a marine alga, T. pseudonana. The tested synthetic detergents inhibited completely the growth of both algae at concentrations above 10 mg/l (as surface-active agent). The tested soap inhibited the growth of T. pseudonana at a concentration of 100 mg/l. The growth of C. pyrenoidosa was not influenced by the soap. The synthetic detergents decreased the photosynthetic activity, ATP content and chlorophyll a content of both algae, especially those of T. pseudonana at concentrations above 10 mg/l. The soap increased the activity and contents of C. pyrenoidosa, but it gave inhibitory effects on those of T. pseudonana at a concentration of 100 mg/l. The mechanism of this inhibition seemed to be different from that of inhibition by the synthetic detergents. The characteristic differences between the algae were consequently suggested. The phosphate-containing and phosphate-free synthetic detergents showed the same inhibitory effects as LAS.

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A survey on inhibitory effects of household laundry detergents and their builders on the growth of three species of freshwater algae Selenastrum capricornutum, Nitzschia fonticola and Microcystis aeruginosa was conducted.
The EC 50 values of 15 commercial detergents tested ranged from 0.5 to 100% of the recommended usage level (in the basin of washing machine) of the detergents. The EC 50 of values of sodium triphosphate and zeolite were ca. 50% of their concentrations estimated from usage levels. Other builders such as sodium carbonate, sodium silicate, sodium sulfate, fluorescent and detergent enzyme had little inhibitory effects within the range of usage levels.
It was estimated from the comparison of EC 50 values between the detergents themselves and each surfactant in the detergents that the major contributor for the inhibitory effects of the detergents were not builders but surfactants in the detergents.

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