2007 Fiscal Year Final Research Report Summary
Tidal flat development trial utilizing dredged sludge and aquatic weeds in an eutrophic closed water system.
| Project/Area Number |
16380161
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Irrigation, drainage and rural engineering/Rural planning
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| Research Institution | OKAYAMA UNIVERSITY |
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Principal Investigator |
OKI Yoko OKAYAMA UNIVERSITY, Graduate School of Environmental Science, Professor (30127550)
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| Co-Investigator(Kenkyū-buntansha) |
ADACHI Tadashi Okayama University, Graduate School of Environmental Science, Professor (20012007)
WATANABE Masaji Okayama University, Graduate School of Environmental Science, Professor (30243546)
NAKASHIMA Yoshitaka Okayama University, Graduate School of Environmental Science, Assistant Professar (50304340)
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| Project Period (FY) |
2004 – 2007
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| Keywords | Eutrophic lake / Artificial tidal flat development / Aquatic weed community / Water quality / Biotope / Polluted load / Planting technology / Environment conservation activities |
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| Research Abstract |
This study attempts creation of a biotope and reduction in water pollution by developing aquatic weed community in an artificial tidal flat using dredged sludge in Lake Kojima located in southern Okayama Prefecture, where nutrient enrichment has advanced. Changes in physical and chemical factors affecting the tidal flat are grasped to predict the material balance between living things in the tidal flat, water systems, and bottom sludge. We propose continued operation and maintenance of the biotope. Results obtained are described below.
1. Basic study related to creation and development of ecosystem in tidal flat developed land : Results of surveys of community development of planting species in a natural state revealed that Zizania latifolia, Schoenoplectus validus, and Typha angustifolia developed the community and formed a vegetation revetment. Furthermore, the larger the plant community, the more shellfish reside there. Submerged plants were planted in porous ceramics to develop a pl
… More
anting method.
2. Grasping of formation processes of physical and chemical factors of tidal flat developed land : Measurements of EC and pH of the soil at the fresh water side from the waterfront line were higher than those at the continental area, both at the surface layer and 5cm below ground. Although sediment and local scour are generated according to the presence or absence of typhoons, development of the underground parts of plant communities made a great contribution.
3. Survey of the pollution load from farmland flowing into Lake Kojima : Although the farmland has nitrogen reduction action, loading of phosphorus to the outside tends to increase concomitantly with increased amounts of applied fertilizer and precipitation.
4. Survey of distribution of aquatic weeds and water pollution in Lake Kojima : Although mass generation of Trapa japonica occurred annually, no indication of regrowth of submerged plants was recognized. Regarding water quality, no tendency of phosphorus reduction was noticed.
5. Model analysis of tidal flat developed land by data processing : Flows generated around an artificial tidal flat in Lake Kojima were analyzed quantitatively.
As described above, establishment of an ecosystem according to its food chain, accumulation of organic substances, and purification of water quality were confirmed by planting of large aquatic weeds in the artificial tidal flat. However, based on these results, proposal of a method of operation and maintenance of the biotope is premature. Less
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