Toshio Kaji

Recent environmental tritium levels in Japan-II Coastal seawater and lake water

Tritium concentrations were analyzed for coastal seawater and lake water collected from various places in Japan. Low tritium concentrations were observed for coastal seawater of small islands and it was attributed to a short residence time of the ground-water in such a small island. Tritium concentrations in lake water showed a significant variation. And it was revealed that the size of the lake and its drainage area were the dominant factors controlling the tritium concentrations in lakes.

Tritium concentrations of the deep sea-water in the Japan Sea and the Pacific Ocean

Tritium concentrations were determined for sea-water samples collected from the Japan Sea and the Pacific Ocean. In the Japan Sea, it was recognized that tritium was distributed around 2000 m in depth. This means that the vertical mixing of water mass is taking place. On the other hand, in the Pacific Ocean, the tritium concentration appears to reach zero at about 1000 m although more than 1 TU concentration are detected for samples collected from deeper water. Hypothetical origins of tritium in the deep water in the Pacific Ocean are discussed.

Tritium concentrations of river water on northern and southern islands of Japan

Tritium concentrations were measured for river waters on two islands in Japan. Significant difference was observed on the distribution of tritium concentrations on both islands, the river water samples from the northern island had higher concentrations and the average was about twice compared to that from the southern island. Higher tritium concentration in precipitation and the larger area of the northern island would be responsible for higher tritium concentrations in river waters.