Yukio Sugimura

Chemical forms of minor metallic elements in the ocean

In order to clarify the chemical forms of minor metallic elements occurring in the ocean, a new method of separation of organic compounds of metals in sea water by using XAD-2 resin was contrived. By applying the new method of determination, it is found that, (1) More than 80 % of V, Fe, Cd and Cu dissolved in sea water are present in organic forms regardless of the depth; (2) A most part of Co and Pb are present in organic forms near the surface, but they change into inorganic forms in the deep layer up to 50 to 60%; (3) Of the total amounts of dissolved Al, Ni, Zn, Ag, Mo, and U, less than 30 % are present in organic forms in sea water anywhere in the ocean; (4) Up to 45% of Se is in organic forms.

The dissolved organic iron in seawater

Abstract Using a new method of separation and determination of dissolved organic iron in seawater using Amberlite XAD-2 resin, concentrations of dissolved organic iron were determined in coastal waters of Japan and pelagic seawaters in the western North Pacific. The contents of the total iron (particulate + dissolved) and the dissolved inorganic iron were also obtained. In coastal water the total amount of iron decreases rapidly with distance from the shore. In the open sea in the coastal region, the dissolved iron varies from 2.2 to 3.8 μg1 −1 ; of this 80 to 90% is organic. In pelagic areas, except for small maxima near the thermocline and at 4000 m, the dissolved iron content in seawater is almost constant. The mean value is 2.9 μg1 −1 , of which 80 to 90% is organic. It is concluded that in contrast to the general view up to now, most of the dissolved iron in seawater is in organic forms.

The content of selenium and its chemical form in sea water

By using the new fluorometric method of determination of the total selenium (Σ Se), Se (IV) and Se (VI), the content of selenium in sea weter was determined in the western North Pacific. Results showed that the content ofΣ Se in surface water ranged from 0.06 to 0.12μg l−1, while in deeper layers, the content increased to 0.20μg l−1. It was found that Se (IV) showed rather uniform distribution with depth, while Se (VI) increased with depth to about three times that in the surface. The ratio of Se (IV) to theΣ Se ranged from 0.5 to 0.8 in the surface and 0.4 to 0.6 in the deep. The coexistence of the hexa- and tetravalent ions of selenium was confirmed both in surface and deep layers. Some results of observations on the content of selenium in the coastal areas of Japan were also reported.

A New Fluorometric Method of Analysis of Selenium in Sea Water

A new method of determination of selenium and separation of Se(IV) and Se(VI) in sea water is described. The selenium is determined by fluorometric method using Se-DAN complex in cyclohexane media. Prior to the fluorometric determination, Se(IV) is separated from sea water by means of Se(IV)-DDTC complex which is adsorbed on the macroreticular resin. As to the separation of the total selenium from sea water sample, the reduction and coprecipitation method is used. Se(VI) is determined with the same method as used for the total selenium after the separation of Se(IV). The average recoveries are 92.5±1.3% for Se(IV) and 97.4±0.9% for ∑Se. The standard deviation of analytical results is below 10%.

The uranium content and the activity ratio234U/238U in marine organisms and sea water in the western North Pacific

The uranium content and activity ratio A234U/A238U were determined in open ocean water, marine plankton, marine algae and sea water in the environment in which plankton and algae live. The average uranium content of 3.34±0.28×10−6 g/l and the average activity ratio of 1.13±0.04 were obtained in open ocean water. The uranium contents in plankton and algae were respectively from 1.7 to 7.8×10−7 g/g and 0.4 to 23.5×10−7 g/g on dry basis with the respective concentration factors of 48 to 260 and 10 to 733. The activity ratio in plankton and algae ranged from 1.07 to 1.18 which coincided well with those in the environmental sea water.

Thorium concentration and the activity ratios230Th/232Th and228Th/232Th in sea water in the western North Pacific

The concentration of thorium isotopes and the activity ratios of230Th/232Th and228Th/232Th in sea water collected in the Kuroshio region, the mixing area of Oyashio and Kuroshio, the Japan Sea and the East China Sea in the western North Pacific were determined. Thorium isotopes were analyzed by α-ray spectrometry after separating them with an anion exchange resin. The average content of thorium (232Th) of 2.2×10−9 g/l was obtained in the open Pacific waters. The ratio of230Th/232Th is in accord with that of the top layer of the sediment in the same area. The high values of228Th/232Th ratio up to 36 were observed in sea water. The excess228Th in sea water may be due to the migration of228Ra through the water-sediment interface. Thorium content in suspended matter was 10 to 20% of the total thorium content in the Pacific water.