This review describes development of sea water resources and comprehensive utilization technology. The effective utilization technology of the material dissolved in seawater, and the high value-added product of seawater origin were reviewed. The configuration of advanced bittern utilization plant and seawater utilization process was investigated. The possibility for development of total seawater utilization systems consisting mainly of salt production and desalination process was discussed.
In order to investigate the behavior of manganese and iron, which may be an index of the movement and circulation of hydrothermal water, seawater and particulate samples were obtained from H3 and H2 in the Myojin knoll caldera, H1 in the Izu-Ogasawara Trench and H4 in the Shikoku basin in April, 2004, and the concentrations of manganese, iron and phosphorus were measured. As a result, the concentrations of dissolved manganese and iron in the maximum layer deeper than 1,000m at the Myojin Knoll Caldera were very high, i.e., 70~100nmol L–1 and 2.6~8.0nmol L–1, respectively. The concentrations of dissolved manganese and iron were higher in H2 than in H3. Its concentration ratio (Fe/Mn) was also higher in H2. It was deduced that there was a difference between the hydrothermal influences in H2 and H3. The concentrations of particulate Mn and Fe were also higher at a level deeper than 1,000m at the Myojin Knoll caldera. The proportion of Fe in oxide fraction to the particulate fraction is higher for H2 than for H3. The data showed that ferrous iron supplied through the hydrothermal actions was changed from hydroxide to oxide, and removed.
This paper describes the vertical profiles of selenite, selenate and organic selenide in the western North Pacific. Selenite and selenate exhibited nutrient like profiles. Organic selenide was detectable throughout water column at all sampling stations. A linear relationship was observed between selenite and selenate and silicate. The correlation coefficient of regression analysis between selenite and silicate was higher than that between selenite and phosphate. The significant correlations were not observed between chlorophyll a and three selenium species. The results of the relationship between selenium and nutrient confirmed that the distribution and behavior of both selenite and selenate in the eastern North Pacific are controlled by silicate. The selenite/silicate ratio exhibited almost constant values throughout the water column at northern two stations, while it shows the higher value from the surface to subsurface at the two southern stations. These results showed that silicate is removed more efficiently from the surface layer than selenite and/or selenite remineralisation is much higher than that of silicate. The range of total selenium concentration and the selenite/selenate ratio below 2,000 m were 1.81&endash;1.95 nmol/l and 0.73&endash;0.93, respectively. These results suggested that the deep water mass age of sampling stations are almost same.