Distributions of tritium and 137Cs in coastal seawater and biota off Aomori and Iwate prefectures, Japan

Abstract

We investigated the dynamics of tritium (3H) from 2003 to 2012 in the marine environment off Aomori and Iwate prefectures. To better understand this radionuclide’s behavior, we compared 3H and 137Cs in collected samples. In the comparison, for the activity concentrations of 3H, these data excluded the period from 2006 to 2008 during intermittent test operation of the Rokkasho Nuclear Fuel Reprocessing Plant; for the activity concentrations of 137Cs, the data excluded the period from 2011 to 2012 after the Fukushima Daiichi Nuclear Power Station accident. The mean concentration ratio (CR) of tissue-free water tritium (TFWT) was close to 1.0, indicating that the concentration of this nuclide in marine biota was almost equal to that in seawater, and it therefore was not accumulated to high levels in marine biota. The lowest CR of 137Cs was higher than 30, suggesting that this nuclide was accumulated to relatively high levels in marine biota. Furthermore, the lack of correlations by Spearman’s test (R < 0.4, P > 0.05) between the CR of TFWT and that of 137Cs for three different species (Gadus macrocephalus, Lophius litulon, and Oncorhynchus keta) provides convincing evidence that the dynamics of TFWT and 137Cs in marine ecology are decoupled.