Journal of Japan Society on Water Environment
Online ISSN : 1881-3690
Print ISSN : 0916-8958
ISSN-L : 0916-8958
Volume 25, Issue 3
Displaying 1-4 of 4 articles from this issue
Original Papers
  • in the Coastal Area of the Hiroshima Prefecture
    Hitoshi TAMAKI, Wataru NISHIJIMA, Harue TOMINAGA, Toshinobu TERAWAKI, ...
    2002 Volume 25 Issue 3 Pages 151-156
    Published: March 10, 2002
    Released on J-STAGE: March 15, 2007
    JOURNAL FREE ACCESS
    The objective of this study is to evaluate the effect of transparency on the change in eelgrass (Zostera marina L.) bed area in eutrophic coastal zone of the Hiroshima Prefecture between 1976-77 and 1999.
    Eelgrass in the coastal areas where high deposition on leaves and steep slope (>5/100) were observed tended to colonize shallower zone than other coastal areas (29 sites: Denmark, Netherlands, USA and Japan) under the same lighting condition. In addition to transparency, deposition on leaves and steep slope seemed to limit the eelgrass distributions there.
    Losses of some eelgrass habitats occurred even though transparency was same or increased, and at a few sites eelgrass bed increased without change in transparency. Thus, the transparency is not always responsible for the change in eelgrass bed. Although there were sites where the bed area changed in proportion to the change in transparency, the maximum depth limit was shallower than that estimated from transparency, or eelgrass habitat in shallow area disappeared significantly by other factors such as slope, deposition on leaves and burial.
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  • Kentaro YUTANI, Takashi ASAEDA, Shiromi KARUNARATNE
    2002 Volume 25 Issue 3 Pages 157-162
    Published: March 10, 2002
    Released on J-STAGE: March 15, 2007
    JOURNAL FREE ACCESS
    Growth performance of a wetland species, Phragmites australis in a swampy section was investigated focusing on the effects of summer harvesting. Communities harvested in June, the time of rapid growth and minimum rhizome reserves, were compared with non-harvesting communities and those harvested in July, when shoot was growing slowly and rhizomes already recovered.
    Harvesting markedly decreased shoots and buds diameters, the spatial leaf density, and increased total production, if harvested in July particularly, and buds density. Rhizome biomass and rhizome bulk density decreased after harvesting. However, with July cut communities, rhizome biomass and rhizome bulk density were recharged at November. In June cut communities, on the other hand, only rhizome bulk density was recovered because of their high mortality rate.
    These results were particularly useful in the management of reed swamp such as harvesting in June causes the suppression of reeds and, in late July to early August, removes nutrients from the ground.
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  • Yoshihiro SUZUKI, Toshiroh MARUYAMA
    2002 Volume 25 Issue 3 Pages 163-169
    Published: March 10, 2002
    Released on J-STAGE: March 15, 2007
    JOURNAL FREE ACCESS
    In coagulation and foam separation method using protein (casein or gelatin), the effect of saline on removal of suspended matters was examined. When casein was used as collector and frother, the extremely high treatability for kaolin suspension contained NaCl (10,000mg·l-1) was observed. The turbidity removal efficiency was over 99% by using cassein. In comparison with NaCl free kaolin suspension, the optimum dosage of casein decreased in about 1/3. In contrast, the treatment remarkably lowered using gelatin with NaCl. Adsorptions of casein on suspended particles such as kaolin, Fe2O3, and graphite, were increased under NaCl coexistence, however, gelatin adsorption remarkably decreased. It was proven that the adsorption of protein on the suspended particle was the important factor that controls the treatment of this method. Coagulation and foam separation using casein showed the high applicability for not only general sewage but also high saline wastewater. In the condition of ferric coagulant 20mg-Fe·l-1, casein 2-3 mg·l-1, pH 5.6-5.7, 98-99% removal rates were obtained. Furthermore, this method was very effective for removal of suspended solids from estuarine saline water.
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