Asian Journal of Environment and Disaster Management (AJEDM)

Volume 3 Number 3 (2011)

Asian Journal of Environment and Disaster Management 2011 3 3

doi: 10.3850/S1793924011000903

Prediction of Distribution of Deposits of Dioxins from Rivers on the Bottom of Tokyo Bay

Satoshi Imanoa, Akira Wadab and Tomoaki Nakamurac
Advanced Research Institute for the Science and Humanities, Nihon University, 12–5, Gobancho, Chiyoda-ku, Tokyo, 102–8251, Japan.


Object of this study was to predict distribution of deposited dioxins in the bottom of Tokyo Bay by means of a 3-dimensional flow model (a Hybrid Box Model) linked with a diffusion model. To improve the accuracy of the analysis of dioxins concentration, the absorption-desorption processes, aggregation-disaggregation processes, sinking of suspended substances and other factors were taken into account.

On the basis of the load fluxes from rivers, the distribution of concentration (separately for dissolved dioxin and small and large particulate dioxins) in seawater and mass of dioxins sedimentation to the bottom of the bay were calculated by the models. Results were compared to the published observation data in order to examine applicability of the used models.

From the analysis, it was estimated that 23.30% of the dioxins inflow into the bay is deposited onto the bottom, and that 69.46% flow out of the bay. Dioxins sedimentation was greater in the inner and middle parts of the bay and decreased in the direction to the bay entrance. Estimated dioxins concentrations in the sediment showed a good agreement with the observed data.

Keywords: Deposited dioxins, Tokyo bay, Hybrid box model, Diffusion analysis.

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