Some ecological methods of evaluation of water pollution, including biotic indicesand correspondence analysis, which is a kind of multivariate analysis, were comparedusing diatoms and benthic invertebrates as indicator organisms. Though diversityindices have been used for environmental evaluation in some previous works, the present work showed their relatively poor ability of indicating water pollution. The biotic indices or the sample scores of correspondence analysis showed intermediatecorrelation (0.35<r<0.75) with chemical oxygen demand (COD) or electric conductivety (EC). When both COD and EC were taken into a multiple regression model, large multiple correlation coefficients were observed (0.71<R<0.91). As for benthicinvertebrates, the effect of river bed materials was also detectable.

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The adsorption of selenite and selenate by four types of soil in humid regions of Japan was investigated with respect to the effects of pH. Selenite and selenate adsorption by the soils increased as pH of the suspension decreased. Selenate was lessstrongly adsorbed than selenite over the entire pH range. The results suggest the following ability sequense for used soils to adsorb selenium ; the andosol>the acrisol>>athe fluvisol>the cambisol. The selenium adsorption capacities of the four soils were related to increases in the specific surface area, phosphate adsorptioncoefficient, and oxalate extractable Al content of the soils. The sorption of selenitereleased the much amount of Si from the andosol to solutions. Desorption of selenate and selenite was investigated using a sequential extraction. Much of the adsorbed selenite (>60%) was not released by nitrate and sulfate. In contrast, more than 70% of adsorbed selenate was desorbed with nitrate and sulfate extracts, indicating the difference of adsorption mechanism of selenite and selenate. The low pH in soils results in low mobility of Se and selenate has the higher mobility in soils than selenite.

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[in Japanese]

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