The dependence of oxygenation kinetics of Fe(II)to Fe(III) on pH and DO was examined in relation to the mechanism of phosphate release from sediments.
In determination of the oxygenation kinetics of Fe(II), the observed redox potential was used for estimation of the Fe(II) concentrations in solutions. The oxygenation rate of Fe(II) increased with pH and DO. In the region DO≥1mg·l^-1, the oxygenation rate(r) was independent to oxygen concentration and varied remarkably with pH as r =k₂·[Fe(II)]·P0₂·[OH^-]² for 5.6≤pH≤7.0, r=k_1/2·[Fe(II)]·P0₂·[OH^-]^1/2for 7.0<pH≤8.0, and r=k₀·[Fe(II)]·P0₂ for 8.0<pH≤9.0. Whereas in the region of DO<1mg·l^-1, the rate was found to depend on DO. That is r=k₂·[Fe(II)]·[OH^-]²·[DO]/2.5(1+[DO]) for 5.6≤pH≤7.0, r=k_1/2·[Fe(II)]·[OH^-]^1/2·[DO]/(1+3.2[DO]) for 7.0<pH≤8.0.
The dependence of the oxygenation rate of Fe(II) on DO and pH found in the present study showed a quantitative agreement with the dependence of the phosphate release rate from sediments on DO, which has been reported in numerous literature. It suggests that the mechasism of phosphate release is essentially explained by the oxygenaion kinetics of Fe (II).

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A simple numerical model was constructed and the oxygen supply rate into the trench soil water treatment system was estimated as the function of the wastewater feed rate. The effects of the width of the site, the depth of the infiltration surface and the depth of the groundwater level were investigated. Three soils were examined and the soil of high hydraulic conductivity appeared to be preferable, loam soils should be avoided. By multiplying the number of trenches per unit length of width, and by making the depth of the trench shallow, the wastewater feed rate per unit area of the site is able to be improved. For andosol and silty caly loam soil, about the feed rates of 0.2m·d^-1and 0.1m·d^-1were estimated to be treated respectively.

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A screening method for 34 kinds of organic pollutants such as pesticides and harmful chemicals in water by GC/MS-SIM was developed for investigation of the cause of fish mortality accident.
One liter of water sample was extracted with dichloromethane and measured by GC/MS-SIM without future separation.
The detection limit of alomst pollutants were decided to 0.01μg·ml^-1 according as the toxicity for the fish.
The recovery was 67117% and 5197% with dichloromethane and hexane, respectively.
This method was applied to river water from a golf links, as a result CAT, TPN, Flutoluanil and Isoprothiolane were found at ng·ml^-1 level.

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[in Japanese]

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