Abstract
Object of this study is to predict distribution of dioxin deposited on the bottom of Tokyo Bay by means of a 3-dimensional flow model linked with a diffusion model. On the basis of the load fluxes from rivers, the distribution of concentration (separately for dissolved dioxin and small and large particulate dioxin) in seawater and mass of dioxin sedimentation to the bottom of the bay were calculated by the models.
We have divided the bottom sediment layers into 3 layers: the boundary layer (between sea water layer and the particle layer), the bioturbated layer, and the diffusion layer; and constructed an analysis model that treats the coupling of matter between sea water and the bottom sediment layer.
Results were compared to the published observation data in order to examine applicability of the used models.
Estimated dioxin concentrations in the sediment show good agreement with the observed data.
From the analysis, it was estimated that 80% of the dioxin inflow into the bay is deposited onto the bottom, and that 16% flow out of the bay. Dioxin sedimentation is greater in the inner and middle parts of the bay, and decreases in the direction toward the bay entrance.
