JOPSS - Search Results

Journal Articles

Distribution and settling behavior of americium-241 in the tropical East Pacific

Kinoshita, Norikazu*; Nagaoka, Mika; Nakanishi, Takashi*

Science of the Total Environment, 753, p.142087_1 - 142087_10, 2021/01

https://doi.org/10.1016/j.scitotenv.2020.142087

Times Cited Count：4 Percentile：28.2(Environmental Sciences)

The distribution of the anthropogenic radionuclide americium-241 ( $^{241}$ Am), a decay product of $^{241}$ Pu discharged from atmospheric tests of nuclear weapons, was investigated to resolve its horizontal and vertical migration in the Tropical East Pacific. We analyzed $^{241}$ Am concentrations in seawater samples collected in 2003. On comparing the $^{241}$ Am concentrations with the previously determined concentrations of $^{239+240}$ Pu in the same samples, the vertical profiles of $^{241}$ Am were found to be similar to those of $^{239+240}$ Pu. At some stations, the maximum concentration of $^{241}$ Am occurred 100-200 m deeper than that of $^{239+240}$ Pu. The $^{241}$ Am/ $^{239+240}$ Pu ratios in the North Pacific and South Pacific were comparable to one another, and were typical of the ratio for the Pacific. The $^{241}$ Am distribution was influenced by the water mass at depths below 400 m. The $^{241}$ Am data support the view there is a current flowing at depths of 400-3000 m from the North Pacific through the equator to the South Pacific. In addition, the $^{241}$ Am vertical profile was explained by using a box model that considers the decay of $^{241}$ Pu and adsorption and scavenging by suspended particles. The different depths for the maximum concentrations of $^{241}$ Am and $^{239+240}$ Pu observed at some stations were well explained by the model and by the distribution of CaCO $_{3}$ particles. The residence time of $^{241}$ Am in the Pacific was also estimated by using the model.

Journal Articles

Vertical distributions of Iodine-129 and iodide in the Chukchi Sea and Bering Sea

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

Journal of Nuclear Science and Technology, 57(5), p.537 - 545, 2020/05

https://doi.org/10.1080/00223131.2019.1699189

Times Cited Count：2 Percentile：21.58(Nuclear Science & Technology)

This study investigated the vertical distribution of Iodine-129 ( $^{129}$ I) which is mainly produced by European nuclear reprocessing plants in the Chukchi Sea and Bering Sea. $^{129}$ I was found to be distributed almost uniformly in fallout level, and an increasing in $^{129}$ I concentration levels caused by high $^{129}$ I water inflow from the Atlantic Ocean was not observed. Additionally, we revealed the vertical distribution of iodide, one chemical form of iodine, from the Bering Shelf area to the Chukchi Sea for the first time. The increasing tendency of iodide near sea bottom was observed.

Journal Articles

Radiocaesium activity concentrations in parmelioid lichens within a 60 km radius of the Fukushima Dai-ichi Nuclear Power Plant

Dohi, Terumi; Omura, Yoshihito*; Kashiwadani, Hiroyuki*; Fujiwara, Kenso; Sakamoto, Yoshiaki; Iijima, Kazuki

Journal of Environmental Radioactivity, 146, p.125 - 133, 2015/08

https://doi.org/10.1016/j.jenvrad.2015.04.013

Times Cited Count：20 Percentile：52.45(Environmental Sciences)

Radiocaesium activity concentrations ( $^{134}$ Cs, $^{137}$ Cs) were measured in parmelioid lichens collected within the Fukushima Prefecture approximately 2 y after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. A total of 44 samples consisting of nine species were collected at 16 points within a 60 km radius of the FDNPP. The activity concentration of $^{134}$ Cs ranged from 4.6 to 1000 kBq kg $^{-1}$ and for $^{137}$ Cs ranged from 7.6 to 1740 kBq kg $^{-1}$ . A significant positive correlation was found between the $^{137}$ Cs activity concentration in lichens and the $^{137}$ Cs deposition density on soil, based on the calculated Spearman's rank correlation coefficients as = 0.90 ( 0.01). The two dominant species, Flavoparmelia caperata and Parmotrema clavuliferum, showed strong positive correlations, for which the r values were calculated as 0.92 ( 0.01) and 0.90 ( 0.01) respectively. Therefore, they are suggested as biomonitoring species for levels of radiocaesium fallout within the Fukushima Prefecture.