10/10/2020
The 2nd Japan Radiation Safety Management Association
Japan Health Physics Society Joint Conference
Content
土壌から米への放射性セシウム吸収に及ぼす
隣接する田の性質の違いとその経年変化
Difference in properties among neighboring fields affecting
absorption of radiocesium from soil to rice
and their secular change
I. Purpose
• To investigate the depth dependence of 137Cs
I. Purpose
concentration for the soil
II. Sampling and Method
• To investigate the oxidative/reductive atmosphere
III. Results and Discussion
in the paddy field
• To investigate the soil size distribution and
IV. Conclusion
radioactivity
Hai Thanh NGUYEN1,2), Masaya TSUJIMOTO1,2), Sunao MIYASHITA2), Satoru NAKASHIMA1,2,3)
• To investigate the year dependence of
1) Radioactivity Environmental Protection Course, Phoenix Leader Education Program, Hiroshima University
2) Graduate School of Science, Hiroshima University
3) Natural Science Center for Basic Research and Development, Hiroshima University
radiocesium in soil
2
Dec 5, 2019
II. Sampling and Method
Fig.1.
D
II. Sampling and Method
II. Sampling and Method
• Soil samples were collected Apr. 2014, and Mar. 2018
• Sampling by depth: 0-5 cm, 5-10 cm, 10-15 cm, 15-20 cm, 20-25 cm
and >25 cm
• We categorized the soil samples in accordance with the method of
classification of geomaterials for engineering purposes by The
Japanese Geotechnical Society (JGS0051).
• The surface soil samples (0-5 cm) were grouped into five by sieving
• X < 75 µm,
• 75 µm < X < 250 µm,
• 250 µm < X < 850 µm,
• 850 µm < X < 2 mm,
• and 2 mm < X
Sample site: Fukushima City, Fukushima Prefecture
C
B
A
Pond
~60 km
3
•
•
•
•
•
57Fe
Mӧssbauer spectroscopic measurement was performed at
room temperature with a 57Co (Rh) radiation source moving in a
constant acceleration mode on Wissel MB-500.
The Mӧssbauer parameters were obtained by least-squares fitting
to Lorentzian peaks.
The spectra were calibrated by the six lines of α-Fe, the center of
which was taken as zero isomer shift.
The radioactivity of Cs-134, Cs-137, and K-40 was measured by
using a p-type High-purity Germanium detector (GEM30-70,
ORTEC) with a 30% relative efficiency.
Relative gamma-ray counting efficiency curve using a certified
mixed-radionuclide gamma-ray reference source (MX033U8PP,
Japan Radiation Association) containing Cd-109 (88 keV), Co-57 (122
and 136 keV), Ce-139 (166 keV), Cr-51 (320 keV), Sr-85 (514 keV),
Cs-137 (662 keV), Mn-54 (835 keV), Y-88 (898 and 1836 keV), and
Co-60 (1173 and 1332 keV).
• The activity concentration of Cs-134, Cs-137 and K-40 were
Source: Google maps
4
5
determined from the -ray energies of 796, 662 and 1460 keV,
respectively.
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10/10/2020
III. Results and Discussion
Field B
600
Field C
400
Field D
200
Field A
800
Field B
600
Field C
400
Field D
200
0
0
0-5 cm 5-10 cm 10-15 cm15-20 cm20-25 cm >25 cm
0-5 cm 5-10 cm 10-15 cm15-20 cm20-25 cm >25 cm
3000
2500
Field A
2000
Field B
1500
Field C
1000
Field D
500
Field D
15
10
K-40 in 2018
500
450
450
250
Field B
200
Field C
150
Field D
100
50
Field B
Field C
150
A-1
0-5 cm 5-10 cm 10-15 cm 15-20 cm 20-25 cm >25 cm
A-2
A-3
B-1
B-4
C-4
C-5
D-1
D-2
-10
-5
0
5
10
Velocity/ (mm/s)
black: < 75 m
blue: 75 m - 250 m
green: 250 m - 850 m
red: > 850 m
140426 C-3S 0-5 cm
RT
0.980
0.975
0.99
black: < 75 m
blue: 75 m - 250 m
green: 250 m - 850 m
red: > 850 m
140426 D-3S 0-5 cm
RT
0.98
0.97
-5
0
Velocity/ (mm/s)
5
-10
10
-5
0
5
10
Velocity/ (mm/s)
57Fe Mӧssbauer
The radioactive cesium is
adsorbed strongly to the clay
0.975
0.99
The change in minimum relative transmission depending on soil size of
samples taken in Mar 2018
1.00
black: < 75 m
blue: 75 m - 250 m
green: 250 m - 850 m
red: > 850 m
180314 A-3S 0-5 cm
RT
0.98
0.97
0.990
0.99
180314 B-3S 0-5 cm
RT
black: < 75 m
blue: 75 m - 250 m
green: 250 m - 850 m
red: > 850 m
0.98
0.97
-10
-5
0
5
-10
10
-5
Velocity/ (mm/s)
0
Velocity/ (mm/s)
5
10
0.970
The amount of iron may affect
desorption of radioactive
cesium from large sized soil
Grain size
Fig. 6. The change in the least relative transmission depending on soil size (2014).
0.99
black: < 75 m
blue: 75 m - 250 m
green: 250 m - 850 m
red: > 850 m
140426 C-3S 0-5 cm
RT
0.98
0.97
iron works as catalyst to
dissolve radioactive cesium
from soil
0.985
0.980
●：Field A
〇：Field B
▲：Field C
△：Field D
0.975
0.970
0.965
0.995
Relative Transmission
> 850 m
1.000
1.00
Relative Transmission
0.965
9
III. Results and Discussion
spectroscopy
1.00
Relative Transmission
●：Field A
〇：Field B
▲：Field C
△：Field D
8
b. Iron amount depending on soil size of samples taken in Mar 2018
The small sized soil
includes clay much
0.990
250 m - 850 m
10
Fig. 5. Change of 57Fe Mӧssbauer absorption depending on the soil size.
III. Results and Discussion
The change in minimum relative transmission depending on soil size of
samples taken in April 2014
75 m - 250 m
0.985
D-3
7
III. Results and Discussion
< 75 m
0.975
Fig. 4. Ratio of Fe(II) to the sum of divalent and
trivalent iron. A-1 to D-3 show the sampling point.
Field D
0
0-5 cm 5-10 cm 10-15 cm 15-20 cm 20-25 cm >25 cm
black: < 75 m
blue: 75 m - 250 m
green: 250 m - 850 m
red: > 850 m
140426 B-3S 0-5 cm
RT
0.980
100
50
0
0.990
0
Field A
250
200
0.985
1.00
-10
300
5
0.995
Relative Transmittance
Field A
300
0.990
0.970
5
400
350
Relative Transmission
400
350
0
1.000
20
0-5 cm 5-10 cm 10-15 cm15-20 cm20-25 cm >25 cm
500
0.995
Velocity/ (mm/s)
Ratio of Fe(II)/ %
Field C
1000
-5
10
0
Radioactivity (Bq/Kg)
Radioactivity (Bq/Kg)
5
Field B
1500
0.98
0.970
0
Fig. 3. Typical 57Fe Mӧssbauer spectrum at room temperature.
Field A
1.000
black: < 75 m
blue: 75 m - 250 m
green: 250 m - 850 m
red: > 850 m
140426 A-3S 0-5 cm
RT
-10
-5
Velocity/ (mm/s)
2000
spectroscopy
0.97
-10
K-40 in 2014
Relative Transmittance
0.980
0.99
0.970
2500
0-5 cm 5-10 cm 10-15 cm15-20 cm20-25 cm >25 cm
0.980
0.985
500
0
0.985
0.990
0.975
Cs-137 in 2018
3500
3000
Radioactivity (Bq/Kg)
Radioactivity (Bq/Kg)
Cs-137 in 2014
3500
57Fe Mӧssbauer
1.00
The spectrum consists of
divalent iron (Fe2+),
trivalent iron (Fe3+), and
hematite (a-Fe2O3)
0.995
Relative Transmittance
Field A
800
1000
Relative Transmission
1200
1000
1.000
Relative Transmission
1200
a. Iron amount depending on soil size of samples taken in April 2014
2. Investigating the oxidative/reductive atmosphere in the paddy field
Cs-134 in 2018
1400
Radioactivity (Bq/Kg)
Radioactivity (Bq/Kg)
Cs-134 in 2014
1400
Relative Transmission
1. The soil size distribution vs radioactivity (Fig.2.)
III. Results and Discussion
Relative Transmission
III. Results and Discussion
0.990
0.985
black: < 75 m
blue: 75 m - 250 m
green: 250 m - 850 m
red: > 850 m
180314 D-3S 0-5 cm
RT
0.980
< 75 m
75 m - 250 m
250 m - 850 m
> 850 m
Grain size
Fig. 8. The change in the least relative transmission depending on soil size (2018).
0.975
0.970
-10
-5
0
Velocity/ (mm/s)
5
10
-10
-5
0
5
10
Velocity/ (mm/s)
Fig. 7. Change of 57Fe Mӧssbauer absorption depending on the soil size.
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IV. Conclusion
•
Reference
137Cs
penetrated more in fallowed fields compared
with the cultivated fields.
Thank you for your kind attention!
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Radioactive Caesium in Rice in Fukushima Prefecture after the 2011 Nuclear Accident, Radioisotopes, 68, 1–6（2019）(Note)
2) Lepage, H., Evrard, O., Onda, Y., Lefèvre, I., Laceby, J. P., and Ayrault, S.: Depth distribution of radiocesium in Fukushima paddy fields and implications for ongoing decontamination works, SOIL
Discuss., 1, 401-428, https://doi.org/10.5194/soild-1-401-2014, 2014.
• The oxidative atmosphere affects the features of
the field and induces the uptake of radioactive
cesium by rice plants.
3) Nakao, Atsushi & Takeda, Akira & Ogasawara, Sho & Yanai, Junta & Sano, Oki & Ito, Toyoaki. (2015). Relationships between Paddy Soil Radiocesium Interception Potentials and Physicochemical
Properties in Fukushima, Japan. Journal of Environment Quality. 44. 780. 10.2134/jeq2014.10.0423.
4) Tsujimoto, M., Miyashita, S., Nguyen, H. T. and Nakashima, S., A correlation between the transfer factor of radioactive caesium from soil into rice plants and the grain size distribution of paddy
soil in Fukushima, Radiation Safety Management, 15, 1–8 (2016)
2) White, P. J. and Broadley, M. R., Mechanisms of caesium uptake by plants, Sci. Ed., 113, 241–256 (2000)
5) Endo, S., Kajimoto, T. and Shizuma, K., Paddy-field contamination with 134Cs and 137Cs due to Fukushima Daiichi Nuclear Power Plant accident and soil-to-rice transfer coefficients, J. Environ.
• The amount of iron embedded in larger soil
particles may also affect the transfer of radioactive
cesium from soil to the rice body.
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6) Nakanishi, M. T., Kobayashi, I. K. and Tanoi, K., Radioactive caesium deposition on rice, wheat, peach tree and soil after nuclear accident in Fukushima, J. Radioanal. Nucl. Chem., 296, 985–989
(2013)
7) Ohmori, Y., Inui, Y., Kajikawa, M., Nakata, A., et al., Difference in caesium accumulation among rice cultivars grown in the paddy field in Fukushima Prefecture in 2011 and 2012, J. Plant Res.,
127, 57–66 (2014)
8) Nihei, N., Tanoi, K. and Nakanishi, M. T., Inspections of radiocaesium concentration levels in rice from Fukushima Prefecture after the Fukushima Daiichi Nuclear Power Plant accident, Sci. Rep.,
5, 8653 (2015)
• There is a possibility that the iron works as catalyst
to dissolve radioactive cesium from soil.
9) Saito, T., Ohkoshi, S., Fujimura, S., Iwabuchi, K., et al., Effect of potassium application on root uptake of radiocaesium in rice, Proceedings of Int. Symp Environmental Monitoring and Dose
Estimation of Residents after Accident of TEPCO’s Fukushima Daiichi Nuclear Power Stations. Part 3–5, Kyoto Univ. Res. Reactor Inst., (2012)
10) Fan, Q. H., Tanaka, M., Tanaka, K., Sakaguchi, A., et al., An EXAFS study on the effects of natural organic matter and the expandability of clay minerals on caesium adsorption and mobility,
Geochim. Cosmochim. Acta, 135, 49–65 (2014)
• The fallowing effect was observed in the amount
of iron of soils larger than 850 micrometer.
11) Matsuda, N. and Nakashima, S., Radioactive Cesium in Water and Soil and Its Absorption by Rice Plant, Japanese J. Rad. Safety Manage., 13, 89–91 (2014), in Japanese
12) Komori, M., Shozugawa, K., Nogawa, N. and Matsui, M., Evaluation of Radioactive Contamination Caused by Each Plant of Fukushima Daiichi Nuclear Power Station Using 134Cs/137Cs Activity
Ratio as Index, Bunseki Kagaku, 62, 475–483 (2013)
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