Michio Gomyo

ENVIRONMENTAL CONDITION INDEX FOR ESTIMATION ON EUTROPHIC STATE OF ENCLOSED AQUIFER ECOSYSTEM

To evaluate the effect of sediment treatment on aquifer ecosystem, a new ecological index that is composed of water quality, sediment quality and biota quantity was proposed in this study. According to ECI (Environmental Condition Index), DAF treatment (Dissolved Air Flotation) + MgO sprinkling was assessed as the most efficiency method for improvement of eutrophicated ecosystem, that is, this method can make the organic matter quantity in aquatic ecosystem minimum level in comparison with other sediment treatment method. Also, for application of this method to real field remediation such as eutrophicated lake, marsh, reservoir and so on, more detailed analysis for treatment function and optimum condition of sediment treatment was considered to be necessary.

SAND DEPOSITION CHARACTERISTICS OF THIN SAND CAPPING IN SHALLOW WATER

There are terrible problems that the organic sediments on the sea bed destroy the ecosystem all around the closed water. Generally, the two improving methods for the bottom sediments which target such the organic sediments are executed. The one is a dredging method which removes them outside, and the other is a capping sand method which covers the sea bed with the sand. This paper describes the sand deposition characteristics of thin sand capping when the sand was dumped by either a backhoe or a grab bucket into shallow water, because the construction demands the sand piled up as thinly and uniformly as possible. They were clarified through the field research at our construction site. Finally, the average layer thicknesses were almost equal to the planned layer thicknesses in any case of the dumping either the dredged sand or the pit sand. The coefficient of variation of the layer thickness became larger as the planned layer thickness decreased. Thus in the thin sand capping, it found that we have to set more surcharge for the quantity of sands, because the error of layer thickness would grow.

INFLOW OF ULVA SP. OF SPRING SEASON IN YATSU HIGATA

Yatsu Higata is one of the most significant remaining tidal flats in Japan. In recent years, Yatsu Higata has witnessed an extraordinary growth of Ulva sp. algae. This paper explores the possible origins of Ulva sp . in Tokyo Bay and describes field studies intended to explore the relationship between the Ulva sp. found in Yatsu Higata and in Tokyo Bay . As a result, the Ulva sp. flourishes in Yatsu Higata, due to the ready supply of nutrient runoff supplied by the Yatsu River. The movement of Ulva sp. from the flats to beyond may help reduce the pollutant load on Tokyo Bay while simultaneously helping to preserve the Yatsu Higata environment.