scholarly journals Fukushima-derived radiocesium in western North Pacific sediment traps

2013 ◽  
Vol 10 (2) ◽  
pp. 2455-2477 ◽  
Author(s):  
M. C. Honda ◽  
H. Kawakami ◽  
S. Watanabe ◽  
T. Saino
Keyword(s):  
North Pacific ◽  
Nuclear Power ◽  
Western North Pacific ◽  
Specific Activity ◽  
Removal Rate ◽  
Mixed Layer Depth ◽  
Dry Weight ◽  
Sediment Traps ◽  
137Cs Activity ◽  
Sinking Particles

Abstract. At two stations in the western North Pacific, K2 in the subarctic gyre and S1 in the subtropical gyre, time-series sediment traps were collecting sinking particles when the Fukushima Daiichi Nuclear Power Plant (FNPP1) accident occurred on 11 March 2011. Radiocesium (134Cs and 137Cs) derived from FNPP1 accident was detected in sinking particles collected at 500 m by late March 2011 and at 4810 m by early April 2011 at both stations. The sinking velocity of 134Cs and 137Cs was estimated to be 8 to 36 m day−1 between the surface and 500 m and > 180 m day−1 between 500 m and 4810 m. 137Cs specific activity varied from 0.14 to 0.25 Bq g−1 dry weight. These values are higher than those of surface seawater, suspended particles, and zooplankton collected in April 2011. Although the radiocesium may have been adsorbed onto or incorporated into clay minerals, correlations between 134Cs and lithogenic material were not always significant; therefore, the form of the cesium associated with the sinking particles is still an open question. The total 137Cs flux by late June at K2 and by late July at S1 was 0.5 to 1.7 Bq m−2 at both depths. Compared with 137Cs input to both stations by April 2011, estimated from the surface 137Cs activity and mixed layer depth and by assuming that the observed 137Cs flux was constant throughout the year, the estimated removal rate of 137Cs from the upper layer (residence time in the upper layer) was 0.3 to 1.5% (68 to 312 yr). The estimated removal rates and residence times are comparable to previously reported values.

scholarly journals Concentration and vertical flux of Fukushima-derived radiocesium in sinking particles from two sites in the Northwestern Pacific Ocean

2013 ◽  
Vol 10 (6) ◽  
pp. 3525-3534 ◽  
Author(s):  
M. C. Honda ◽  
H. Kawakami ◽  
S. Watanabe ◽  
T. Saino
Keyword(s):  
Residence Time ◽  
Nuclear Power ◽  
Removal Rate ◽  
Mixed Layer Depth ◽  
Dry Weight ◽  
Sediment Traps ◽  
Northwestern Pacific ◽  
137Cs Inventory ◽  
Sinking Particles ◽  
Open Question

Abstract. At two stations in the western North Pacific, K2 in the subarctic gyre and S1 in the subtropical gyre, time-series sediment traps were collecting sinking particles when the Fukushima Daiichi Nuclear Power Plant (FNPP1) accident occurred on 11 March 2011. Radiocesium (134Cs and 137Cs) derived from the FNPP1 accident was detected in sinking particles collected at 500 m in late March 2011 and at 4810 m in early April 2011 at both stations. The sinking velocity of 134Cs and 137Cs was estimated to be 22 to 71 m day−1 between the surface and 500 m and >180 m day−1 between 500 m and 4810 m. 137Cs concentrations varied from 0.14 to 0.25 Bq g−1 dry weight. These values are higher than those of surface seawater, suspended particles, and zooplankton collected in April 2011. Although the radiocesium may have been adsorbed onto or incorporated into clay minerals, correlations between 134Cs and lithogenic material were not always significant; therefore, the form of the cesium associated with the sinking particles is still an open question. The total 137Cs inventory by late June at K2 and by late July at S1 was 0.5 to 1.7 Bq m−2 at both depths. Compared with 137Cs input from both stations by April 2011, estimated from the surface 137Cs concentration and mixed-layer depth and by assuming that the observed 137Cs flux was constant throughout the year, the estimated removal rate of 137Cs from the upper layer (residence time in the upper layer) was 0.3 to 1.5% yr−1 (68 to 312 yr). The estimated removal rates and residence times are comparable to previously reported values after the Chernobyl accident (removal rate: 0.2–1%, residence time: 130–390 yr).

scholarly journals Ecosystem model-based approach for modeling the dynamics of <sup>137</sup>Cs transfer to marine plankton populations: application to the western North Pacific Ocean after the Fukushima nuclear power plant accident

2016 ◽  
Vol 13 (2) ◽  
pp. 499-516 ◽  
Author(s):  
M. Belharet ◽  
C. Estournel ◽  
S. Charmasson
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Pacific Ocean ◽  
Dose Rate ◽  
North Pacific ◽  
Nuclear Power ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
Ecosystem Model ◽  
Western North Pacific Ocean

Abstract. Huge amounts of radionuclides, especially 137Cs, were released into the western North Pacific Ocean after the Fukushima nuclear power plant (FNPP) accident that occurred on 11 March 2011, resulting in contamination of the marine biota. In this study we developed a radioecological model to estimate 137Cs concentrations in phytoplankton and zooplankton populations representing the lower levels of the pelagic trophic chain. We coupled this model to a lower trophic level ecosystem model and an ocean circulation model to take into account the site-specific environmental conditions in the area. The different radioecological parameters of the model were estimated by calibration, and a sensitivity analysis to parameter uncertainties was carried out, showing a high sensitivity of the model results, especially to the 137Cs concentration in seawater, to the rates of accumulation from water and to the radionuclide assimilation efficiency for zooplankton. The results of the 137Cs concentrations in planktonic populations simulated in this study were then validated through comparison with the data available in the region after the accident. The model results have shown that the maximum concentrations in plankton after the accident were about 2 to 4 orders of magnitude higher than those observed before the accident, depending on the distance from FNPP. Finally, the maximum 137Cs absorbed dose rate for phyto- and zooplankton populations was estimated to be about 5  ×  10−2 µGy h−1, and was, therefore, lower than the predicted no-effect dose rate (PNEDR) value of 10 µGy h−1 defined in the ERICA assessment approach.

scholarly journals RADIATION SAFETY ASSESSMENT OF CARROT AND BEET PRODUCTS CULTIVATED IN THE BLACK EARTH ZONE OF RUSSIA IN THE OREOL OF THE EASTERN CHERNOBYL TRACE

2022 ◽  
pp. 15-20
Author(s):  
T. A. Paramonova ◽  
O. L. Komissarova ◽  
N. V. Kuzmenkova ◽  
L. A. Turykin ◽  
O. E. Denisova
Keyword(s):  
Nuclear Power ◽  
Radiation Safety ◽  
Specific Activity ◽  
Dry Weight ◽  
Total Biomass ◽  
Permissible Level ◽  
Root Crops ◽  
Contamination Of Soils ◽  
Good Agreement ◽  
Accumulation Coefficients

On the territory of the Plavsky radioactive hotspot of the Tula region of Russia, formed as a result of the accident at the Chernobyl nuclear power plant in 1986, an assessment of the radiation safety of growing carrots and beets was carried out in 2019. It has been established that at present the content of 137Cs in arable leached chernozems of the surveyed lands is 90–170 kBq/m2 , which is 2.5–4.5 times higher than the permissible level of density of surface radioactive contamination of soils. However, the specific activity of the radionuclide in carrot and beetroot crops does not exceed 5 Bq/kg, which is significantly less than the maximum permissible level of 137Cs accumulation in vegetables (600 Bq/kg for absolutely dry weight). The accumulation coefficients of 137Cs in the total biomass of carrots and beets are 2.0·10−2 and 7.5·10−2, and in eaten root crops – 1.1·10−2 and 2.0·10−2, respectively, which is in good agreement with the IAEA estimate for the intensity of the transition 137Cs in the production of vegetable roots from loamy and clayey soils.

scholarly journals Glycerol dialkyl glycerol tetraethers and TEX86 index in sinking particles in the western North Pacific

2012 ◽  
Vol 53 ◽  
pp. 52-62 ◽  
Author(s):  
Masanobu Yamamoto ◽  
Akifumi Shimamoto ◽  
Tatsuo Fukuhara ◽  
Yuichiro Tanaka ◽  
Joji Ishizaka
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Sinking Particles ◽  
Glycerol Dialkyl Glycerol Tetraethers

scholarly journals Inverse estimation of source parameters of oceanic radioactivity dispersion models associated with the Fukushima accident

2013 ◽  
Vol 10 (4) ◽  
pp. 2349-2363 ◽  
Author(s):  
Y. Miyazawa ◽  
Y. Masumoto ◽  
S. M. Varlamov ◽  
T. Miyama ◽  
M. Takigawa ◽  
...  
Keyword(s):  
Atmospheric Deposition ◽  
North Pacific ◽  
Nuclear Power ◽  
Western North Pacific ◽  
Source Parameters ◽  
Simulation Models ◽  
Observation Data ◽  
Fukushima Accident ◽  
Field Observation Data ◽  
Two Parameters

Abstract. With combined use of the ocean–atmosphere simulation models and field observation data, we evaluate the parameters associated with the total caesium-137 amounts of the direct release into the ocean and atmospheric deposition over the western North Pacific caused by the accident of Fukushima Daiichi nuclear power plant (FNPP) that occurred in March 2011. The Green's function approach is adopted for the estimation of two parameters determining the total emission amounts for the period from 12 March to 6 May 2011. It is confirmed that the validity of the estimation depends on the simulation skill near FNPP. The total amount of the direct release is estimated as 5.5–5.9 × 1015 Bq, while that of the atmospheric deposition is estimated as 5.5–9.7 × 1015 Bq, which indicates broader range of the estimate than that of the direct release owing to uncertainty of the dispersion widely spread over the western North Pacific.

scholarly journals Community structure and seasonal changes in population structure of pelagic polychaetes collected by sediment traps moored in the subarctic and subtropical western North Pacific Ocean

Zoosymposia ◽  
2020 ◽  
Vol 19 (1) ◽  
pp. 41-50
Author(s):  
KANAKO AMEI ◽  
NAOTO JIMI ◽  
MINORU KITAMURA ◽  
NAOYA YOKOI ◽  
ATSUSHI YAMAGUCHI
Keyword(s):  
Population Structure ◽  
Community Structure ◽  
North Pacific ◽  
Seasonal Changes ◽  
Western North Pacific ◽  
Dominant Species ◽  
North Pacific Ocean ◽  
Sediment Traps ◽  
Subarctic Region ◽  
Pelagic Polychaetes

Community structure and seasonal changes in the population structure of pelagic polychaetes were studied based on zooplankton samples collected by sediment traps moored at 200 m depth in the subarctic and subtropical western North Pacific throughout the year. Eight species belonging to seven genera and seven families occurred at the subarctic station, while twelve species belonging to ten genera and seven families were identified at the subtropical station. Polychaete abundance was 5.37 ± 0.44 ind. m-2 day-1 (annual mean ± standard error) at the subarctic station, and 1.36 ± 0.15 ind. m-2 day-1 at the subtropical station. Polychaete abundance at the subarctic station was high from May to August, but no seasonal patterns were observed at the subtropical station. The dominant species in the subarctic was Tomopteris septentrionalis, which accounted for 62.9% of annual mean abundance; at the subtropical station, the dominant species was Pelagobia sp. (22.8%). In the subarctic, small specimens of T. septentrionalis (<3 mm in body length) occurred only in winter (December-March). No clear seasonal changes in population structure of the subtropical Pelagobia sp. were detected. The latitudinal patterns we observed in the polychaete communities of the western North Pacific were similar to those previously observed in the eastern North Pacific. Changes in the population structure of T. septentrionalis suggest that the life cycle of this species is seasonal in the subarctic region.

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