The amounts of heavy metals discharged from various domestic sources (tap water, gray waters and feces etc.) were quantified at Yokosuka, Hachinohe and Hakodate cities using 4 or 5 monitors at each city.
The values of the heavy metals were Cd 72-192, Ni 405-1, 661, Cr 230-775μg·day^-1·person^-1 and Pb 0.51-6.75, Mn 6.5-8.2, Cu 3.1-55.8, Zn 21.5-44.3, Fe 24.3-111.1 mg·day^-1·person^-1.
The amounts of heavy metals derived from domestic sources were also determined from the budget of them in the sewage treatment plants which accepts only domestic sewage. They were Cd 54-252, Ni 450-1, 876, Cr 396-1, 430μg·day^-1·person^-1 and Pb 0.71-5.04, Mn 7.8-22.0, Cu 2.8-17.9, Zn 19.0-62.7, Fe 96-459mg·day^-1·person^-1.

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Oxygen supply by the photosynthesis of phytoplankton in oxidation ponds was investigated by using outdoor ponds (4m (1) ×8m (w) ×.92m (d)) fed with synthetic wastewater. Hydraulic residence time were 4.4, 8.9, 13.4 and 18.0 days. The numerical model assuming steady state was developed and the following results were obtained by this model.
1) The rate of oxygen supply by phytoplankton per unit area was not so affected by mean residence time nor pond depth, and dependent on the rate of nutrient supply per unit area.
2) The maximum rate of the oxygen supply per unit area ranged from 10 to 15 [g/ (m²day)].
3) The oxidation pond with the depth of im and the appropriate mean residence time of 10 days seemed to be effective for the treatment of gray water.

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To examine the optimum determination method for phosphorus in river sediments, combinations of several digestion and three spectrophotometric methods were tested. The recommened procedure was as follows : a 1g of dried sample is digested with mixture of sulfuric acid (3ml) and nitric acid, or with that of perchloric acid (10ml) and nitric acid, on hot plate untill all visible organics are destroyed and the solution becomes clear. After filtration, the sample solution is subjected to spectrophotometric by Ascorbic acid reduction method.
Analytical results of Pond Sediment (NIES Certified Reference Material) determined by Ascorbic acid reduction method were in good agreement with reference value. In the case of by Vanadomolybdophosphoric acid spectrophotometric method, interference from silicate ion in the solutions digested with HF/HClO₄/HNO₃, HF/HCl was observed seriously. The measuring wavelength is prefered to 420 nm, because of less interference of silicate ion. Stannous chloride reduction spectrophotometric method was not suitable for river sediment.
Further tests were performed to examine the detailed comparison among the three spectrophotometric methods and effects of addition of hydrofluoric acid to 38 samples of river sediments. The analytical values determined by Vanadomolybdophosphoric acid method were 8% higher, and those of Stannous chloride reduction method were 18% lower than those of Ascorbic acid reduction method. When hydrofluoric acid was not used, 255% lower values were obtained. This decrease is considered to suggest the existence of phosphorus in silicate compounds.

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[in Japanese]

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