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.