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Masatoshi Yamada - One of the best experts on this subject based on the ideXlab platform.

  • Temporal variation of iodine-129 concentRations in kelps (Saccharina) from coastal waters off northern Japan.
    Marine pollution bulletin, 2020
    Co-Authors: Takahito Ikenoue, Masatoshi Yamada, Shinji Oikawa, Masashi Kusakabe, Jun Misonoo
    Abstract:

    Abstract ConcentRations of 129I and 127I in kelps (Saccharina) collected from coastal waters off northern Japan were monitored from 2007 to 2019. During the 2007–2008 test opeRation of the Rokkasho nuclear fuel reprocessing plant, 129I discharge from the plant increased, and the 129I concentRation and 129I/127I Atom Ratio in the kelps reached maxima of 42 μBq/g-dry and 264 × 10−11, respectively. By 2009, both had decreased by one order of magnitude. After the Fukushima Dai-ichi Nuclear Power Plant accident in 2011, the 129I concentRation and 129I/127I Atom Ratio in the kelps increased to 2.24 μBq/g-dry and 11.6 × 10−11, respectively. After 2012, the Ratio in kelps decreased to (2.1–8.9) × 10−11, which is almost the same as the seawater value off Aomori Prefecture before the test opeRation. The 129I/127I Atom Ratio in kelps thus represents the ambient seawater Ratio during the growth period of the kelps.

  • improved approach for routine monitoring of 129i activity and 129i 127i Atom Ratio in environmental samples using tmah extraction and icp ms ms
    Analytica Chimica Acta, 2018
    Co-Authors: Hirofumi Tazoe, Guosheng Yang, Masatoshi Yamada
    Abstract:

    Abstract To reconstruct 131I deposition and identify the source of radioiodine due to the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, 129I activity and 129I/127I Atom Ratio should be obtained by preparing and analyzing large numbers of samples economically. In this study, great efforts were made to realize mild TMAH (tetramethyl ammonium hydroxide) extraction of environmental samples at 90 °C to obtain solutions suitable for the following triple-quadrupole inductively coupled plasma-mass spectrometry (ICP-QQQ) MS/MS mode analysis. After releasing iodine from organic matter in the TMAH extraction solution via K2S2O8 oxidation, organic matter was removed effectively by solvent extraction and back-extraction to avoid a serious matrix effect during ICP-QQQ analysis. At the same time, interfering elements, especially, Mo, Cd, and In were also removed effectively, to avoid their undesirable interferences during mass spectrometric analysis. In addition, 0.01% (NH4)2SO3 was selected to introduce I− into ICP-QQQ to ensure there was no memory effect and a stable signal was gotten. Subsequently, ICP-QQQ MS/MS mode was applied to further eliminate polyAtomic interferences (127I(H2 and D)+, 97MoO2+, 113InO+, and 113CdO+) and isobaric interference from 129Xe+. Finally, the developed method was successfully applied to measure 129I/127I Atom Ratios ((2.61–27.0) × 10−7) and 129I activities (3.51–11.4 mBq kg−1) in soil samples. The developed method allows a greater number of ordinary laboratories to participate in the field of radioiodine analysis.

  • Improved approach for routine monitoring of 129I activity and 129I/127I Atom Ratio in environmental samples using TMAH extraction and ICP-MS/MS.
    Analytica chimica acta, 2018
    Co-Authors: Guosheng Yang, Hirofumi Tazoe, Masatoshi Yamada
    Abstract:

    Abstract To reconstruct 131I deposition and identify the source of radioiodine due to the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, 129I activity and 129I/127I Atom Ratio should be obtained by preparing and analyzing large numbers of samples economically. In this study, great efforts were made to realize mild TMAH (tetramethyl ammonium hydroxide) extraction of environmental samples at 90 °C to obtain solutions suitable for the following triple-quadrupole inductively coupled plasma-mass spectrometry (ICP-QQQ) MS/MS mode analysis. After releasing iodine from organic matter in the TMAH extraction solution via K2S2O8 oxidation, organic matter was removed effectively by solvent extraction and back-extraction to avoid a serious matrix effect during ICP-QQQ analysis. At the same time, interfering elements, especially, Mo, Cd, and In were also removed effectively, to avoid their undesirable interferences during mass spectrometric analysis. In addition, 0.01% (NH4)2SO3 was selected to introduce I− into ICP-QQQ to ensure there was no memory effect and a stable signal was gotten. Subsequently, ICP-QQQ MS/MS mode was applied to further eliminate polyAtomic interferences (127I(H2 and D)+, 97MoO2+, 113InO+, and 113CdO+) and isobaric interference from 129Xe+. Finally, the developed method was successfully applied to measure 129I/127I Atom Ratios ((2.61–27.0) × 10−7) and 129I activities (3.51–11.4 mBq kg−1) in soil samples. The developed method allows a greater number of ordinary laboratories to participate in the field of radioiodine analysis.

  • 135Cs activity and 135Cs/137Cs Atom Ratio in environmental samples before and after the Fukushima Daiichi Nuclear Power Plant accident.
    Scientific reports, 2016
    Co-Authors: Guosheng Yang, Hirofumi Tazoe, Masatoshi Yamada
    Abstract:

    (135)Cs/(137)Cs is a potential tracer for radiocesium source identification. However, due to the challenge to measure (135)Cs, there were no (135)Cs data available for Japanese environmental samples before the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. It was only 3 years after the accident that limited (135)Cs values could be measured in heavily contaminated environmental samples. In the present study, activities of (134)Cs, (135)Cs, and (137)Cs, along with their Ratios in 67 soil and plant samples heavily and lightly contaminated by the FDNPP accident were measured by combining γ spectrometry with ICP-MS/MS. The arithmetic means of the (134)Cs/(137)Cs activity Ratio (1.033 ± 0.006) and (135)Cs/(137)Cs Atom Ratio (0.334 ± 0.005) (decay corrected to March 11, 2011), from old leaves of plants collected immediately after the FDNPP accident, were confirmed to represent the FDNPP derived radiocesium signature. Subsequently, for the first time, trace (135)Cs amounts before the FDNPP accident were deduced according to the contribution of global and FDNPP accident-derived fallout. Apart from two soil samples with a tiny global fallout contribution, contributions of global fallout radiocesium in other soil samples were observed to be 0.338%-52.6%. The obtained (135)Cs/(137)Cs database will be useful for its application as a geochemical tracer in the future.

  • 135cs activity and 135cs 137cs Atom Ratio in environmental samples before and after the fukushima daiichi nuclear power plant accident
    Scientific Reports, 2016
    Co-Authors: Hirofumi Tazoe, Guosheng Yang, Masatoshi Yamada
    Abstract:

    (135)Cs/(137)Cs is a potential tracer for radiocesium source identification. However, due to the challenge to measure (135)Cs, there were no (135)Cs data available for Japanese environmental samples before the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. It was only 3 years after the accident that limited (135)Cs values could be measured in heavily contaminated environmental samples. In the present study, activities of (134)Cs, (135)Cs, and (137)Cs, along with their Ratios in 67 soil and plant samples heavily and lightly contaminated by the FDNPP accident were measured by combining γ spectrometry with ICP-MS/MS. The arithmetic means of the (134)Cs/(137)Cs activity Ratio (1.033 ± 0.006) and (135)Cs/(137)Cs Atom Ratio (0.334 ± 0.005) (decay corrected to March 11, 2011), from old leaves of plants collected immediately after the FDNPP accident, were confirmed to represent the FDNPP derived radiocesium signature. Subsequently, for the first time, trace (135)Cs amounts before the FDNPP accident were deduced according to the contribution of global and FDNPP accident-derived fallout. Apart from two soil samples with a tiny global fallout contribution, contributions of global fallout radiocesium in other soil samples were observed to be 0.338%-52.6%. The obtained (135)Cs/(137)Cs database will be useful for its application as a geochemical tracer in the future.

Suresh K. Aggarwal - One of the best experts on this subject based on the ideXlab platform.

Jian Zheng - One of the best experts on this subject based on the ideXlab platform.

  • determination of 240pu 239pu Atom Ratio in seawaters from the east china sea
    Radiation Protection Dosimetry, 2011
    Co-Authors: Masatoshi Yamada, Jian Zheng
    Abstract:

    The (240)Pu/(239)Pu Atom Ratios in seawater samples on the East China Sea continental shelf were measured. These Ratios for surface and bottom waters had no significant difference. They were significantly higher than the average global fallout Ratio of 0.18. It was proposed that the oceanic currents are accounted for delivery of close-in Pu from the Pacific Proving Grounds (PPG) to the studied areas. The contribution of the PPG close-in fallout was calculated to be 40 % on average. The (240)Pu/(239)Pu Atom Ratios should provide useful background data before the expected expansion of nuclear power capacity in East and South Asian countries and for distinguishing future sources of Pu.

  • Determination of 240Pu/239Pu Atom Ratio in seawaters from the East China Sea.
    Radiation protection dosimetry, 2011
    Co-Authors: Masatoshi Yamada, Jian Zheng
    Abstract:

    The (240)Pu/(239)Pu Atom Ratios in seawater samples on the East China Sea continental shelf were measured. These Ratios for surface and bottom waters had no significant difference. They were significantly higher than the average global fallout Ratio of 0.18. It was proposed that the oceanic currents are accounted for delivery of close-in Pu from the Pacific Proving Grounds (PPG) to the studied areas. The contribution of the PPG close-in fallout was calculated to be 40 % on average. The (240)Pu/(239)Pu Atom Ratios should provide useful background data before the expected expansion of nuclear power capacity in East and South Asian countries and for distinguishing future sources of Pu.

  • temporal variation of 240pu 239pu Atom Ratio and 239 240pu inventory in water columns of the japan sea
    Science of The Total Environment, 2010
    Co-Authors: Masatoshi Yamada, Jian Zheng
    Abstract:

    The (239+240)Pu concentRations and (240)Pu/(239)Pu Atom Ratios were determined by alpha spectrometry and double-focusing SF-ICP-MS for seawater samples obtained in 1984 and 1993 from the Yamato and Tsushima Basins of the Japan Sea in the western North Pacific margin. The total (239+240)Pu inventories in the whole water columns were approximately doubled during the period from 1984 to 1993 in the two basins. The increasing rates were estimated to be 5.1 Bq m(-2)yr(-1) in the Yamato Basin and 4.2 Bq m(-2)yr(-1) in the Tsushima Basin and they corresponded to ~0.02% of the annual (239+240)Pu inflow rate into the Japan Sea through the Tsushima Strait. The mean (240)Pu/(239)Pu Atom Ratios were ~0.240 and significantly higher than the mean global fallout Ratio of 0.18. Furthermore, there were no temporal or spatial variations of (240)Pu/(239)Pu Atom Ratios during this period in the Japan Sea. The total (239+240)Pu inventories originating from the close-in fallout increased from 17.6 Bq m(-2) to 34.6 Bq m(-2) in the Yamato Basin and from 20.1 Bq m(-2) to 34.6 Bq m(-2) in the Tsushima Basin; however, the relative percentage of ~40% from the close-in fallout was unchanged during this period. A likely mechanism for the increasing Pu inventory would be the continuous inflow of the Tsushima Current from the western North Pacific, and the removal of Pu from surface waters by scavenging onto the settling particles, followed by regeneRation of Pu from the settling particles during the downward transport.

  • Temporal variation of 240Pu/239Pu Atom Ratio and 239+240Pu inventory in water columns of the Japan Sea.
    The Science of the total environment, 2010
    Co-Authors: Masatoshi Yamada, Jian Zheng
    Abstract:

    The (239+240)Pu concentRations and (240)Pu/(239)Pu Atom Ratios were determined by alpha spectrometry and double-focusing SF-ICP-MS for seawater samples obtained in 1984 and 1993 from the Yamato and Tsushima Basins of the Japan Sea in the western North Pacific margin. The total (239+240)Pu inventories in the whole water columns were approximately doubled during the period from 1984 to 1993 in the two basins. The increasing rates were estimated to be 5.1 Bq m(-2)yr(-1) in the Yamato Basin and 4.2 Bq m(-2)yr(-1) in the Tsushima Basin and they corresponded to ~0.02% of the annual (239+240)Pu inflow rate into the Japan Sea through the Tsushima Strait. The mean (240)Pu/(239)Pu Atom Ratios were ~0.240 and significantly higher than the mean global fallout Ratio of 0.18. Furthermore, there were no temporal or spatial variations of (240)Pu/(239)Pu Atom Ratios during this period in the Japan Sea. The total (239+240)Pu inventories originating from the close-in fallout increased from 17.6 Bq m(-2) to 34.6 Bq m(-2) in the Yamato Basin and from 20.1 Bq m(-2) to 34.6 Bq m(-2) in the Tsushima Basin; however, the relative percentage of ~40% from the close-in fallout was unchanged during this period. A likely mechanism for the increasing Pu inventory would be the continuous inflow of the Tsushima Current from the western North Pacific, and the removal of Pu from surface waters by scavenging onto the settling particles, followed by regeneRation of Pu from the settling particles during the downward transport.

  • Vertical Distributions of Plutonium and 137Cs in Lacustrine Sediments in Northwestern China: Quantifying Sediment Accumulation Rates and Source Identifications
    Environmental science & technology, 2010
    Co-Authors: Jian Zheng, Haiqing Liao, Masatoshi Yamada
    Abstract:

    We investigated the vertical distributions of 239+240Pu and 137Cs activities and 240Pu/239Pu Atom Ratios in two lakes in northwestern China. The 240Pu/239Pu Atom Ratio from the Chinese nuclear test (CNT) site at Lop Nor is too complicated to identify the regional fallout source. However, radionuclides from the test site may be resolved mainly by the vertical distribution of radionuclides because there is no overlap between the global fallout peak and the local fallout peak. We analyzed Pu isotopes and 137Cs in sediments from two lakes (Sugan and Shuangta) located in northwestern China, near the CNT, and Lake Sihailongwan located in northeastern China to date recent lacustrine sediments and resolve global/local fallout sources. The apparently low 240Pu/239Pu Atom Ratio of 0.103 ± 0.010 at Lake Sugan was likely representative of the fallout from the Lop Nor site. Our results also demonstrated that the 239+240Pu activity was more useful for recent chronology of lacustrine sediments, compared to 137Cs. Sedime...

Toshiharu Kayama - One of the best experts on this subject based on the ideXlab platform.

  • concentRations of 137cs 90sr 108mag 239 240pu and Atom Ratio of 240pu 239pu in tanner crabs chionoecetes japonicus and chionoecetes opilio collected around japan
    Marine Pollution Bulletin, 2010
    Co-Authors: Takami Morita, Yoshihito Ohtsuka, Ken Fujimoto, Yoko Minamisako, Rika Iida, Masae Nakamura, Toshiharu Kayama
    Abstract:

    The anthropogenic radionuclides, (137)Cs, (90)Sr, (108m)Ag, (239+240)Pu, were measured in two Chionoecetes species, red queen crab (Chionoecetes japonicus) and snow crab (Chionoecetes opilio) collected around Japan during 1996-2007. There was no increase in the concentRations of these radionuclides and no large variation of the Atom Ratio of (240)Pu/(239)Pu during this research period. These results indicated that the source of the radionuclides was not the radioactive wastes dumped by the former USSR and Russia and originated from past nuclear weapon tests. The higher Atom Ratio in the crab species than that from global fallout would be contributed by the Pacific Proving Grounds close-in fallout. The variability of the concentRation of radionuclides in the crab species would result from the variability of the composition and quantity in the diet. However, the decrease in the concentRation of radionuclides with sampling depth would depend on the concentRation in the seawater and diet.

  • ConcentRations of 137Cs, 90Sr, 108mAg, 239+240Pu and Atom Ratio of 240Pu/239Pu in tanner crabs, Chionoecetes japonicus and Chionoecetes opilio collected around Japan
    Marine pollution bulletin, 2010
    Co-Authors: Takami Morita, Yoshihito Ohtsuka, Ken Fujimoto, Yoko Minamisako, Rika Iida, Masae Nakamura, Toshiharu Kayama
    Abstract:

    The anthropogenic radionuclides, (137)Cs, (90)Sr, (108m)Ag, (239+240)Pu, were measured in two Chionoecetes species, red queen crab (Chionoecetes japonicus) and snow crab (Chionoecetes opilio) collected around Japan during 1996-2007. There was no increase in the concentRations of these radionuclides and no large variation of the Atom Ratio of (240)Pu/(239)Pu during this research period. These results indicated that the source of the radionuclides was not the radioactive wastes dumped by the former USSR and Russia and originated from past nuclear weapon tests. The higher Atom Ratio in the crab species than that from global fallout would be contributed by the Pacific Proving Grounds close-in fallout. The variability of the concentRation of radionuclides in the crab species would result from the variability of the composition and quantity in the diet. However, the decrease in the concentRation of radionuclides with sampling depth would depend on the concentRation in the seawater and diet.

D. Alamelu - One of the best experts on this subject based on the ideXlab platform.