The objective of this study is to clarify principal factors causing a deterioration of eelgrass meadows (Zostera marina L.) by the coast of Iwakuni Japan, after the typhoon attack on 24 September 1999. We investigated effects of fine sediment deposition on the deterioration of eelgrass meadows.
Aerial photographs showed significant losses to the vegetative cover of eelgrass meadows near the estuary after the typhoon. Large amounts of sediments settled over the bottom after the typhoon. Sites near the estuary had higher deposits of suspended sediments on the eelgrass leaves. The deposition resulted in a 50% decrease in light intensity. The shading reduced the daily periods of irradiance-saturated photosynthesis required for eelgrass growth to less than 1/2. Comparison of diatom communities in the sediments indicated that the sediments originated from terrestrial sources, i. e. flooding rivers.
These results suggest shading by fine sediments, supplied from flooding rivers, caused the deterioration of eelgrass meadows.

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To clarify the treatability of kaolin suspension by coagulation and foam separation method using poly aluminum chloride (PAC) and milk casein (casein), the characteristics of pH, dosage of PAC and casein, operating conditions such as foam separation time and air flow rate, and effects of alkalinity were examined. The results obtained by this study can be summarized as follows.
(1) The conditions to treat the sample of 200mg·l^-1 kaolin suspension containing 50mg·l^-1 of NaHCO₃ to under 2 turbidity units were obtained to be pH8.5-10, PAC 10mg-Al·l^-1, casein 15mg·l^-1, foam separation time of 5min, air flow rate of 0.2l·min^-1.
(2) The sample of 50-1,000mg·l^-1 kaolin suspension can be treated to under 2 turbidity units by controlling the dosages of PAC and casein.
(3) The requirement amount of casein was considered to be the sum of a portion of adsorbing onto the flocs as a collector and another portion of residual as a frother to remove flocs by coagulation and foam separation.
(4) Optimum pH range expanded to neutral side with NaHCO₃ dosage increased. Optimum pH range for 200mg·l^-1 kaolin suspension changed from 8.5-10 at 50mg-NaHCO₃·l^-1 to 7-10 at 150mg-NaHCO₃·l^-1.
(5) Optimum pH range was 6.5-9 for 200mg·l^-1 kaolin suspension of tap-water.
From these results, it was clarified that the coagulation and foam separation using PAC and casein was very effective to remove suspended matters such as kaokin particles.

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The level of pollution of the Yodo River system was examined with environmental water qualities, mutagenicity and trihalomethanes formed by chlorination of river waters and sewage effluent along the river. Mutagenic formation potential (MFP) of the extracts from chlorinated waters was measured by Ames test using S. typhimurium TA100 strain without metabolic activation. The trihalomethanes (THM) such as chloroform, bromodichloromethane, dibromochloromethane and bromoform were also analyzed for THM formation potentials (THMFP) in the same water samples. In the Yodo River system, MFP and THMFP increased at the downstream of the Uji and Katsura Rivers, while around the upper stream of the Kizu River. As to the contributions of the pollution loads in MFP and THMFP from the Kizu, Uji and Katsura Rivers to the Yodo River, the rates of the MFP were 8.6%, 59.1% and 32.3%, and the THMFP were 19.5%, 54.5% and 26.0%, respectively. The contributions of the sewage effluent to the Katsura River were 38% in MFP and 36% in THMFP. These results indicated that river waters along the Yodo River were contaminated with high levels organic compounds, as precursors of genotoxicity and carcinogenicity formed by chlorination.

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To evaluate the diversity of microorganisms in soil as an environmental index, the analysis of DNA directly extracted from soil is very useful. In this study, We compared different methods employed for the direct extraction of DNA from the soil. The following method was most effective in DNA yield: that is, lysis with a high-salt extraction buffer (1.5 M NaCl) containing 1% hexadecyltrimethylammonium bromide (CTAB), and proteinase K at extended heating (2h) in 1% SDS solution. Also a method proposed by TOYOTA Co., Ltd. was effective; it needed little time (1hr) to complete the extraction process while the other methods needed more than two hours. For DNA purification, combination of PVPP (Polyvinylpolypyrrolidone) columns and Sepharose 4B columns was most effective.

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