To reveal the spatial distribution of dioxins(PCDD/Fs and Co-PCB) in sediment in Tokyo Bay, field observations were conducted. The dioxins concentrations were analyzed at 22 sites in the whole bay region, including Chiba Port and an area near Ichihara anchorage, where high levels dioxins contamination had been observed. The characteristics of the specific congeners and TEQ were determined by combining our field observation results with existing data. The highest levels of TEQ were found near Ichihara anchorage, and levels gradually decreased towards the center of the Bay. The distribution of l,2,3,4,6,7,8-H₇CDD was similar to that of TEQ. The concentration of l,3,6,8-T₄CDD was the highest around an anchorage in Chiba Port, and l,3,6,8-T₄CDD seemed to spread throughout the central region of the Bay. These result suggest that CNP contribution from land was small. The concentration of 2,3,4,7,8-P₅CDF was the highest in the central region. On the other hand, the concentration of Co-PCB was the highest around Tokyo Port. The distributions of isomer ratio ( 1,2,3,4,6,7,8-H₇CDD/1,2,3,4,6,7,9-H₇CDD ) suggests that the source which contaminated sediment in Ichihara anchorage, affected sediment in Tokyo Bay.

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The amounts of Co-PCB emission in Tokyo Bay basin were estimated using a multimedia environmental model, the CoZMo-POP model, which was developed for describing the long-term fate of persistent organic pollutatnts (POPs) in a coastal environment. The Co-PCB concentrations in sediment estimated using the model effectively explained the chronological changes in the concentrations in substances that settled at the bottom of sea water, which were estimated by a sediment mixing model based on the concentrations in sediment core samples. Furthermore, the estimated chronological changes in the amounts of Co-PCB emission in each year were in agreement with the chronological changes in PCB demand in Japan.

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The estimation of changes in human uptake of dioxins in Tokyo Bay basin as a consequence of the reduction of Co-PCB emissions into the environment following the implementation of the Law Concerning Special Measures for Promotion of Proper Treatment of PCB Waste was discussed. Firstly, chronological decreases in Co-PCB concentrations in sediment were estimated, considering the reduction of Co-PCB emission using a multimedia environmental model. Secondly, Co-PCB concentrations in fish in Tokyo Bay were estimated on the basis of the concentrations in sediment and Biota Sediment Accumulation Factors (BSAF). Lastly, the total daily intake (TDI) of Co-PCB, Dibenzo-p-dioxins and Dibenzofurans was chronologically projected considering the daily intakes of these chemicals from fish based on previously estimated concentrations in fish in Tokyo Bay and in other areas. As a result, the TDI in Tokyo Bay Basin in 2016, the target year of the PCB Law, was estimated to be about 1pg-TEQ/(kg-weight · day) .

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This study was designed to investigate the fundamental aspects of a possible system for removing phosphorus ions from wastewater by ion exchange on a zirconium-sulfate-surfactant mesostructured material (ZS). ZS was synthesized by hydrothermal synthesis at 100°C for 48 hr. The highly ordered hexagonal structure of ZS was confirmed by X-ray diffraction (XRD) analysis and transmission electron micrography (TEM). The lattice constant, wall thickness and pore diameter were approximately 47, 17 and 30 Å, respectively. The equilibrium amount of phosphate ions exchanged into ZS at room temperature was as high as 3.4mmol·g^-1-ZS. A fourier-transformation infrared (FT-IR) study and quantitative analyses of introduced P and released S revealed that ion exchange between PO₄^3- and SO₄^2- first occurs during the reaction followed by that between PO₄^3- with OH^-. The structure of ZS was essentially maintained after the ion exchange. It follows that ZS would be a highly efficient ion exchanger for removing phosphate ions.

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We observed populations of phytoplankton species causing red tides in the inner part of the Ariake Sea on July 29th and August 6th of 2002, and August 16th and 23rd of 2004. Hourly vertical profiles of water temperature, salinity, and dissolved oxygen and chlorophyll-a levels have been collected from June 2002 until the present. The diurnal vertical movements of Ceratium furca (Dinophyceae) blooms in 2002 and those of Chattonella antiqua and C. marina (Raphidophyceae) blooms in 2004 were estimated. The average velocities of upward and downward movements of Ceratium were 1.7±0.3 and 0.4-1.0±0.3 m · h^-1, and those of Chattonella were 1.5-2.0±0.3 and 1.7±0.2 m · h^-1, respectively. The Ceratium population moved downward in synchrony with changes in pycnocline layer level , but the Chattonella population moved upward across the pycnocline layer, independently of pycnocline layer level. It is considered that the discrepancy between the movements of the organisms is related to ecological strategies for obtaining nutrients for growth. Moreover, we think that these organisms that cause red tides could bloom rapidly by utilizing nutrients in oxygen deficient layers below the pycnocline layer.

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