Abstract
The object of this study is to predict the distribution of dioxins deposited on the bottom of Tokyo Bay using a 3-dimensional flow model (a Hybrid Box Model) linked with a diffusion model.
On the basis of the load fluxes from rivers, the distribution of dissolved and particulate (small and large fractions) in seawater and the mass of dioxins accumulated in 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 dioxins concentration in the sediment showed good agreement with the observed data.
From the analyses, it was estimated that 50.83% of the dioxins inflow into the bay was deposited onto the bottom, and that 48.10% flowed out of the bay. Dioxins sedimentation was greater in the inner and middle parts of the bay, and decreased toward the bay entrance.
