Asian Journal of Environment and Disaster Management (AJEDM)

Volume 2 Number 2 (2010)

Asian Journal of Environment and Disaster Management 2010 2 2

doi: 10.3850/S179392402010000256

Effect of Reducing Effluent Loads in Tokyo Bay on the Improvement of Water Quality

Akira Wada1 and Kazuyuki Hasegawa2
1Advanced Research Institute for the Sciences and Humanities, Nihon University, 12-5 Goban-cho, Chiyoda-ku, Tokyo 102-8251, Japan.
2Marine Ecology Research Institute, 300 Iwawada, Onjuku, Isumi, Chiba, 299-5105, Japan.


Water pollution in semi-enclosed sea areas influences not only the natural environment itself of the waters but also the social environment of surrounding area as well.

Causes and mechanisms of water pollution are intertwining each other in specific conditions of the sea areas. To cope with problems of the marine environmental problems, areaspecific managements are necessary.

In this research, an attempt is made to predict the quality of water in Tokyo Bay on the basis of the flow field determined using the box model. Comparison was made between calculation reproducing the present conditions of the water quality and measured values. As a result, we consider it basically possible to reproduce many items and to examine the effect of water quality in a diversifiedmanner. Possibility is discussed to improve the water quality of Tokyo Bay by reduction of nitrogen and phosphorus load in the bay.

When inflowloads fromriverswere reduced, the decrease of phytoplankton corresponding to the ratio of reduction was recognized in summer time. However, its effect was not reflected in dissolved oxygen in the bottom layer and consequently no improvement was made in the oligo-oxygen status. Also, in winter time, no effect on phytoplankton was recognized and no remarkable change was observed in dissolved oxygen as well.

Keywords: Box model, Ecological model, Tokyo bay, Water quality.

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