ワカサギ中の放射性セシウム濃度の体重依存性と経年変化 [in Japanese] Body-size Effect and Dynamics of Radiocesium for Wakasagi <i>Hypomesus nipponensis</i> [in Japanese]
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The accident of the Fukushima Dai-ichi Nuclear Power Plant in March, 2011, released large amounts of radiocesium into the atmosphere, and contaminated the environment of Gunma Prefecture in eastern Japan. In particular, 640 Bq kg<sup>–1</sup>-wet of radiocesium concentration was found in wakasagi (<i>Hypomesus nipponensis</i>) in Lake Onuma on Mt. Akagi in August, 2011. Thus, to elucidate the body-size effect in weight-dependent and dynamics of radiocesium in the ecosystem of Lake Onuma, we determined the age of wakasagi, the body-weight class of the radiocesium concentration in wakasagi and the effective ecological half-life (<i>T</i><sub>eff</sub>) of radiocesium in wakasagi 0+ from 2012 to 2016. The body-size effect was found for the <sup>137</sup>Cs concentration of wakasagi fished from 2012 to 2015, <i>i.e.</i>, the concentration of <sup>137</sup>Cs increased with the increase in its body weight. On the other hand, no body size effect was found in 2016. This result may be caused by the following two factors: the <sup>137</sup>Cs concentration of the lake water reached a steady state after May 2014; wakasagi is a small plankton-feeding fish, while it is known that larger piscivorous fishes show the strong body size effect. <i>T</i><sub>eff</sub> of the <sup>137</sup>Cs concentration in wakasagi 0+ consists of two components, fast- and slow-term ones, and the decay rate of the <sup>137</sup>Cs concentration in wakasagi 0+ was greatly reduced. As stated above, the radiocesium contamination in Lake Onuma has still been lasting; we are thus continuing our monitoring studies.
- BUNSEKI KAGAKU
BUNSEKI KAGAKU 66(3), 195-200, 2017
The Japan Society for Analytical Chemistry