Distribution and source of I-129 in Chukchi Sea and Bering Sea

Miwa, Kazuji ; Obata, Hajime*; Suzuki, Takashi  ; Otosaka, Shigeyoshi  

I-129 in a global environment is originated from the European nuclear fuel reprocessing plants (NFRP), Sellafield in U.K. and La Hague in France, and it is observed a large amount of I-129 inflows from European NFRP into the eastern and central Arctic Ocean. Previous studies on I-129 at surface indicated seawater with high I-129 concentration does not inflow from eastern and central Arctic Ocean to Chukchi Sea, located in western Arctic Ocean. However, there is a possibility of inflow of I-129 because the vertical distribution of I-129 has not observed at the ocean. The purpose of this study is to identify the inflow of seawater with high I-129 concentration from eastern and central Arctic Ocean by observing the vertical distribution of I-129 and water mass structure in Chukchi Sea and Bering Sea. Seawater with high temperature at surface of southern Chukchi Sea (- 66N) and with low temperature at bottom of the northern Chukchi Sea (69N -) were observed. The seawater with low temperature might include high I-129 concentration. However, I-129 concentration in some points was observed ranging from 0.79 to 2.89 (10 atoms/L), which was two orders of magnitude lower than that in the eastern and central Arctic Ocean. And no significant difference of I-129 concentration between seawater at surface and at bottom was shown. Therefore, we could not identify the inflow of seawater with high I-129 concentration from eastern and central Arctic Ocean to Chukchi Sea.