In activated sludge process, most of the virus amount in wastewater was transferred to the activated sludge phase. For the quantitative discussion of this transferred virus amount, an efficient eluate is necessitated. The objectives of this research are to find out an efficient eluate and to clarify the optimal conditions for the elution. Beef extract and chaotrophic salts were studied for the components of eluates and the individual effects of these two components on virus elution were examined. Then an eluate consisting of beef extract and chaothropic salts was examined, and its effect on virus elution was also experimented at different pHs. Poliovirus type I (strain LSc, 2ab) was used as a model for enteric virus. It was found out that the both beef extrct and the salts greatly influence virus elution. Among the salts used, NaNO₃ showed the largest elution effect. Under neutral condition, i.e. pH7.0, a mixture of 1M NaNO₃ and 3% beef extract gave the largest elution rate of 78%.

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The line width (half width) of ¹⁷O magnetic resonance and spin-lattice relaxation time, T₁, of ¹⁷O nucleus were measured for the electrolyte aqueous solution at 298 K by NMR spectroscopy. The values of T₁ were independent of pH, but the line width broadened depending on pH as did that of pure water. These half width including the broadening were well estimated from T₁ which reflects the rotational mobility of water molecule and the exchange rates of protons depended on pH. The half widths of tap water passed through the commercial purifiers and reformers with the functions such as magnetic field, far infrared radiation by the ceramics, electrolysis, etc. were also calculated from T₁ and the exchange rate constants of protons in pure water. Therefore, the half width of water in ¹⁷O-NMR suggested by Matsushita can not apply as the factor for a size of water clusters.

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The rainfall-weighted means of Zn and Cu in precipitations collected from Sakata city of Yamagata-ken, and Mizushima industrial area and environs and Okayama city of Okayama-ken were distributed in the range of 70-73 μg·l^-1 and 1.9-3.0 μg·l^-1, respectively, and 39-51 μg·l^-1 and 1.0-1.2 μg·l^-1, respectively, in the sparsely populated area above the Takahashi River Basin. Almost precipitations showed the pH acidified lower than 5.6, and positive correlations were observed between the concentrations of hydrogen ion and those of Zn and Cu in precipitations collected from Sakata city.
Owing to the high concentrations of Zn in precipitations, the Cu/Zn ratios were distributed in the range of 0.024-0.042 and agreed approximately with those for plant and animal materials.
The concentrations of Zn and Cu in precipitations from Sakata city were found to be slightly high in the winter season from November to March, but these seasonal variations were not found for Okayama city and Takahashi River Basin. On the other hand, positive correlations were observed among 6 sampling sites for Zn and Cu in precipitations collected from Okayama city and Takahashi River Basin.

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