In the investigation of the herbicide's fate of the river flowing into Lake Teganuma, CNP and Benthiocarb were found, and Benthiocarb was found in higher concentration than CNP. This different behavior between the two herbicides in the same environment is usually explained by their solubility and adsorption ability. Such physicochemical properties are related to molecular structures. Hydrocarbons and chlorinated biphenyls in aqueous solution show a linear relationship between the logarithm of solubilities and the total surface areas (TSA) or the total molecular volumes (TMV). On the other hand polar compounds which have heteroatoms and polar groups are very soluble. The adsorption equilibrium of the organic compounds has been found to be related to the molecule's contact surface area with the adsorbent surface. The adsorption rate is influenced by molecular shape along with contact probability. Therefore it can be considered that solubility of CNP is lower than that of Benthiocarb and that CNP is likely to adsorb more than Benthiocarb. They occur in accordance with the environmental behavior of the herbicides in a natural environment.

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Effects of environmental conditions, i.e., amount of riverbed biofilm, flow velocity, dissolved oxygen, and water temperature, on the purification rate of pollutants in a small channel discharging gray water were investigated. In order to investigate the effects, artificial substrata (unglazed tile, 4.6mm×4.6mm) were set on the riverbed. The substrata were taken from the channel once a week, and purification rate, i.e., removal rates of dissolved organic carbon (DOC), dissolved nitrogen (D-N), ammonium nitrogen (NH₄-N), nitrate nitrogen (NO₃-N), and dissolved phosphorus (D-P), was measured. Removal rates of DOC, D-N and D-P were increased with the increase in the amount of riverbed biofilm under high DO condition although the rate were decreased under low DO condition. Increase in flow velocity improved the removal rates by accelerating the diffusion of DO and substrates from liquid phase to inner parts of riverbed. High water temperature caused the decrease in DO with enhanced oxygen consumption in wastewater and riverbed biofilm, resulting in the decrease in the removal rates. On the other hand, high removal rate of NO₃-N was observed under low DO condition.

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The aeration of trichloroethylene in water to gas phase was tested with different aeration velocities. It was confirmed that the trichloroethylene was transferred from the water to the air in a fairly short time. The trichloroethylene transferred to the air was illuminated by the low pressure mercury lamp (253.7nm) in a quartz tube reactor. 96% of the trichloroethylene in the air was decomposed within 5 minutes by the photochemical reaction. The reaction products in the air and in the water was analyzed by means of GC/MS. Dichloroacetic acid and trichloroacetic acid were detected in the water as the decomposition products.

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The concentration of total phosphorus in sandy and muddy bottom sediment were studied by using two kinds of procedures, the H₂SO₄-HNO₃ digestion and the HF-HNO₃ digestion. The recovery ratio of the H₂SO₄-HNO₃ digestion procedure to the HF-HNO₃ digestion procedure was between 90% and 101% and the mean value was 97%. The analitic accuracy of the H₂SO₄-HNO₃ digestion procedure based up on the coefficient of variation was between 0.3% and 1.4%.
There were no recongnizable differences of values between ground and unground samples in the H₂SO₄-HNO₃ digestion procedure. It was necessary to use a watch glass to prevent a loss of phosphorus during the evaporation of sulfric acid due to heating.
These procedures were also used for other kinds of rock samples such as basalt, andesite, rhyo-dacite welded tuff, sandstone etc. The recovery ratio of the H₂SO₄-HNO₃ digestion procedure to the HF-HNO₃ digestion procedure was between 79% and 104% (mean : 94%). These results suggested that the H₂SO₄-HNO₃ digestion procedure was useful as an extraction procedure for measuring total phosphorus of bottom sediment and was applicable to rock samples.

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