Journal of Nuclear and Radiochemical Sciences, Vol. 8, No. 2, pp. 137-142, 2007

Soil-to-crop Transfer Factors of Radium in Japanese Agricultural Fields
S. Uchida* and K. Tagami
Office of Biospheric Assessment for Waste Disposal, National Institute of Radiological Science, Anagawa 4-9-1,
Inage-ku, Chiba-shi 263-8555, Japan
Received: October 24, 2006; In Final Form: February 20, 2007
The concentrations of 226Ra in upland field crops (e.g., cabbage, leek, onion, potato, and so on) and associated soils
collected from 45 locations throughout Japan were determined in order to obtain soil-to-crop transfer factors(TFs). Concentrations of 226Ra in the soils collected in southwestern Japan were higher than those in northeasternJapan; however, no correlations between 226Ra concentrations in crops and soils were observed. The TFs ranged
from <1.1 × 10 –3 to 5.8 × 10 –2 with a geometric mean of 6.4 × 10 –3. These data were within the 95% confidential
range of TF-Ra for several crops as reported in the IAEA Technical Reports Series No. 364. Among the alkaline
earth metals, TF-Ba was similar to TF-Ra.

1. Introduction

2. Experimental

Radium-226 ( Ra), an α emitter with a half-life of about
1600 y, is a natural decay product of 238U. Radium-226 is of
special interest because it is an important radionuclide for theassessment of radioactive waste disposal. This radionuclide
can reach humans through several transfer paths in the environment. Once Ra is taken into the human body by ingestionof food and water or inhalation, it can distribute into bonewhere it has a long biological half-life; exposure to Ra cancause cancers and other body disorders. Therefore, its longterm management is required and understanding of Ra behavior in the environment is important.
In mathematical models that are used for long-term radiological assessment, environmental transfer parameters areneeded. Among them, the soil-to-crop transfer factor (TF) is a
key parameter that directly affects the internal radiation dose
assessment for the ingestion pathway. TF is defined as the ratioof radioactivity concentration in plant to radioactivity concentration in soil. Although 226Ra is present in the environment,
due to its low concentration in crops, TFs that have beenobtained from agricultural fields are limited.1–5 In many cases,
therefore, TFs used in such models were from the Technical
Report Series 364 (TRS-364) compiled by IAEA.3 These data
were obtained in temperate zones mainly from Europe andNorth America, and thus, the numbers of TFs for rice and crops
native to Japan were limited. Yunoki et al.2 measured TF-Ra
for spinach and Chinese cabbage, but they collected their samples from only two fields. Recently, Sasaki et al.4 tried to measure crop TF-Ra, however, most sample concentrations were
under the detection limit, and only two hulled rice sample data
were available from their study. Thus, it is necessary to collectTFs of Ra nationwide.
In this study, we determined the concentrations of 226Ra in
upland field crops (leafy vegetables, onion, potato, and so on)
and associated soils collected from 45 locations throughout
Japan in order to obtain TFs. We also measured alkaline earth
metal concentrations to compare their behavior with Ra, whichis the last member of this group and whose lighter members,
Mg and Ca, are plant nutrients.
226*Corresponding author. E-mail: s_uchida@nirs.go.jp.
Fax: +81-43-206-3267.

2.1. Samples. Upland field soils (plowed soil layer: up to ca.
20 cm depth) were collected nationwide from 45 fields in
2002–2004 (Figure 1). From each sampled field, 5 sub-samples, approximately 1 kg on fresh weight basis each, were collected in the harvesting season and these sub-samples weremixed well. About 15 kg amounts (on a fresh weight basis) of
the edible part of crops were also collected for 13 green vegetable samples (cabbage, Chinese cabbage, etc.), 9 tuber samples(potato, sweet potato, and taro), 7 allium species samples (leeksand onion), 2 legume samples (bean and peanut), 7 fruit vegetable samples (cucumber, tomato, sweet pepper, and egg plant),
4 root vegetable samples (carrot and Japanese radish), and 5
cereal samples (wheat and barley).
Three kg of the soil sub-samples were air-dried and passed
through a 2-mm mesh sieve. For crop samples, edible parts
were washed with deionized water at least 3 times until theremoval of dust and soil particles was completed. The washed

Figure 1. Sampling sites in Japan.

© 2007 The Japan Society of Nuclear and Radiochemical Sciences
Published on Web 10/19/2007

138 J. Nucl. Radiochem. Sci., Vol. 8, No. 2, 2007

3. Results and Discussion
3.1. 226Ra concentrations in soils and crops. The concentrations of 226Ra in the soil and the crop samples are listed inTable 1. The concentrations of 226 Ra in upland soil samples
ranged from 13.9 to 60.3 Bq kg–1-dry. Since the main island ofJapan is geologically classified into two parts at the ItoigawaShizuoka Tectonic Line, the 226 Ra concentrations in samples
collected in the northeastern and southwestern parts of Japan
were compared and their probability distributions are plottedin Figure 2. T-test (p < 0.01) showed that the concentrations
were higher in the southwestern part (geometric mean: 36.5 Bqkg–1) than in the northeastern part (geometric mean: 25.7 Bqkg–1), possibly due to geological differences between theseareas.
Since potato, sweet potato, carrot, and Japanese radish samples were not peeled, 226Ra contamination from soil particles
that remained on the crop surface was suspected. In order tocheck for remaining soil particle amounts in these crop sam-ples, Ti concentrations were checked. The results showed that
Ti concentrations in tuber and root vegetable samples werelower than in green vegetable samples which were not in contact with soil. Thus we assumed that 226Ra contamination due
to soil particles was negligible.
Radium-226 is a progeny nuclide of 238U and the half-life of226
Ra is shorter than that of 238U, thus, after a long time, theirradioactivities reach an equilibrium in soil. Thus, radioactivities between 226Ra and U are compared as shown in Figure 3.
We also compared Th radioactivities with 226Ra ones because
U and Th behave similarly geologically. In northeasternJapanese soil samples, correlations between 226Ra and both U
and Th were high (t-test, p < 0.001); in particular, U and 226Ra
had a 1:1 radioactivity ratio which means that they reachedequilibrium. Southwestern soil samples had lower correlations
for U and Th compared to northeastern soil samples, though U
and 226Ra in the southwestern soil samples had a 1:1 radioactivity ratio as well. The results implied that 226Ra and U reached
an equilibrium in these soil samples; however, we must consider the effect of excess U which could come from phosphatic
fertilizers. Previously, we estimated that about 50% of total
238
U in upland field soils came from these fertilizers.8 It is
known that 226Ra is included in the fertilizers9,10 and their use
in agricultural fields must have a small contribution as externalradiation to the population. Thus, using the previously reported
approach,8 we estimated 226Ra from the fertilizers (Raess) as follows:
Raess = Ratotal – [Thobs] × U/ThN × A ,where Ratotal is the total 226Ra radioactivity concentration in asoil sample, [Thobs] is Th concentration in the soil, U/ThN is theaverage value of naturally observed [U]/[Th] concentration
ratio (0.23), and A is a conversion factor from U concentration
to 226Ra radioactivity since 1 mg kg–1 U is equal to 12.3 Bq kg–1
of 226Ra when U and 226Ra reach equilibrium.
The Raess values were 2.9–31.6 Bq kg–1 in the southwesternpart (geometric mean: 15.5 Bq kg–1) and 1.7–26.4 Bq kg–1 inthe northeastern part (geometric mean: 14.3 Bq kg–1). No
regional difference was observed by t-test. Concerning thecontributing percentages of Raess to total 226Ra in soil samples,

99.99
Northeast
Southwest

99.9
99
Cummulative percent

parts were paper-towel dried, chopped and freeze-dried except
for taro which was also peeled before chopping. For leek samples, green and white parts were separated. Leaves of Japaneseradish are also edible parts so that roots and leaves were separated and elemental compositions of both of them were measured. Finally, 45 soil samples and 51 crop part samples wereobtained.
2.2. Measurements. For the soil samples, about 60 g ofeach pretreated soil sample were charged and sealed into aplastic vessel. These samples were kept at room temperature
for more than 30 days to reach an equilibrium condition withprogeny nuclides of 226Ra, that is, 222Rn, 218Po, 214Pb, and 214Bi.
Then, the concentration of 214Pb was measured with a Ge detector system (Seiko EG&G Ortec) from which 226 Ra could be
calculated. To check the accuracy of the method, we used two
reference materials, IAEA-315 (marine sediment) and IAEA368 (Pacific Ocean sediment).
In order to measure 226Ra, a chemical separation was carriedout using about 15 g of each incinerated crop sample (450 °C,
24 h). Use of 5 g of incinerated crop has been recommended
for the standard method used in Japan.6 However, to obtain alower level for the detection limit (DL), we tripled the sample
amount in the present study. The radiochemical separation
steps were the same as used in the standard method.6 Since
there is no stable Ra isotope, the chemical yield of Ra was
obtained using barium (Ba), which is just above Ra in the periodic table. This selection was based on their similar chemical
behaviors. In brief, the separation method was as follows: 30
mL of HNO3 (1 + 1) were added to the incinerated sample andthis was evaporated to dryness. The dried material was dissolved in HCl (1 + 1), and the residue was removed by filtration. After addition of Ba, Ra was coprecipitated with BaSO4
and Ba recovery was measured by a gravimetric method. The
sample was then dissolved in EDTA-4Na solution and 10 mLof organic solvent (Scintisol AL-1) were added. The mixture
was kept for two weeks to reach radioactivity equilibrium with222
Rn. Then, the organic layer that includes only 222Rn was collected and the radioactivity of 222Rn was measured with a liquid
scintillation counter (Aloka, LB-2 or LB-5). From the counts,
226
Ra was calculated. No reference materials were used forplant samples, but, in order to obtain counting efficiency, weused a standard 226Ra solution and 222Rn was extracted.
For comparison, we measured concentrations of four alkaline earth metals, Mg, Ca, Sr, and Ba, and also U and Th by
inductively coupled plasma mass spectrometry (ICP-MS) using
a part of each soil and crop sample. The ICP-MS samples were
thoroughly ground into fine powder and stored at room temperature. Before measurements, the samples were oven driedat 80 °C. We have reported method details elsewhere.7

Uchida
7

95
90
80
70
50
30
20
10
5
1
.1
.01

10

100
226

-1

Ra concentration / Bq kg dry

Figure 2. Probability distributions of 226Ra concentrations in agricultural soils collected from northeastern and southwestern parts ofJapan.

J. Nucl. Radiochem. Sci., Vol. 8, No. 2, 2007 139

Soil-to-crop Transfer Factors of Radium in Japanese Agricultural Fields

TABLE 1: Concentrations of 226Ra in soil and crop samples on dry weight basis and transfer factors
226

Ra concentration / Bq kg–1
Soil
Crop

TF ( × 10 –3)

Crop name

Latin nameCabbage

Brassica oleracea var. capitata

20.5 ± 0.9

0.105 ± 0.015

5.1 ± 0.8

Cabbage

Brassica oleracea var. capitata

26.1 ± 1.0

0.594 ± 0.019

22.8 ± 1.1

Cabbage

Brassica oleracea var. capitata

39.0 ± 1.0

0.409 ± 0.014

10.5 ± 0.5

Cabbage

Brassica oleracea var. capitata

22.5 ± 0.9

0.242 ± 0.022

10.8 ± 1.1

Cabbage

Brassica oleracea var. capitata

23.8 ± 0.8

0.118 ± 0.015

5.0 ± 0.7

Chinese cabbage

Brassica rapa L.

13.9 ± 1.1

0.594 ± 0.029

42.7 ± 3.9

Chinese cabbage

Brassica rapa L.

36.5 ± 0.9

0.466 ± 0.025

12.8 ± 0.7

SpinachSpinacia oleracea L.

28.8 ± 0.9

0.226 ± 0.038

7.8 ± 1.3

Lettuce

Lactuca sativa L.

41.7 ± 1.1

0.323 ± 0.031

7.7 ± 0.8

Lettuce

Lactuca sativa L.

30.9 ± 0.9< 0.128

Carrot (leaves)

Daucus carota L.

42.8 ± 0.9

1.147 ± 0.046

26.8 ± 1.2

Japanese radish (leaves)

Raphanus sativus L.

60.3 ± 1.2

0.463 ± 0.023

7.7 ± 0.4

Nozawana

Brassica rapa var. hakabura

17.6 ± 0.8

0.522 ± 0.046

29.7 ± 2.9

Leek (green)

Allium fistulosum

20.1 ± 1.0

0.125 ± 0.021

6.2 ± 1.1

Leek (green)

Allium fistulosum

16.5 ± 0.8

0.313 ± 0.015

19.0 ± 1.3

Leek (green)

Allium fistulosum

25.4 ± 0.9

0.416 ± 0.018

16.4 ± 0.9

Leek (green)

Allium fistulosum

29.9 ± 0.9

1.723 ± 0.047

57.6 ± 2.4

Leek (white)

Allium fistulosum

20.1 ± 1.0

0.116 ± 0.014

5.8 ± 0.8

Leek (white)

Allium fistulosum

16.5 ± 0.8

Leek (white)

Allium fistulosum

29.9 ± 0.9

0.835 ± 0.035

27.9 ± 1.5

Leek (white)

Allium fistulosum

25.4 ± 0.9

0.414 ± 0.105

16.3 ± 4.2

Onion

Allium cepa L.

36.5 ± 0.9

0.074 ± 0.007

2.0 ± 0.2

Onion

Allium cepa L.

26.1 ± 0.9< 0.331< 0.029

Onion

Allium cepa L.

43.9 ± 1.0

0.152 ± 0.010

3.5 ± 0.2

CarrotDaucus carota L.

42.8 ± 0.9

1.431 ± 0.048

33.4 ± 1.3

Japanese radish

Raphanus sativus L.

60.3 ± 1.2

0.219 ± 0.030

3.6 ± 0.5

Japanese radish

Raphanus sativus L.

33.7 ± 1.1

0.519 ± 0.031

15.4 ± 1.0

Japanese radish

Raphanus sativus L.

38.0 ± 1.1

0.406 ± 0.026

10.7 ± 0.8

PotatoSolanum tuberosum L.

22.7 ± 1.0

0.039 ± 0.007

1.7 ± 0.3

PotatoSolanum tuberosum L.

35.7 ± 0.9

0.040 ± 0.004

1.1 ± 0.1

PotatoSolanum tuberosum L.

48.9 ± 1.0

0.122 ± 0.009

2.5 ± 0.2

PotatoSolanum tuberosum L.

31.7 ± 0.9

0.083 ± 0.008

2.6 ± 0.3

PotatoSolanum tuberosum L.

33.9 ± 1.0

0.066 ± 0.010

1.9 ± 0.3

Sweet potato

Ipomoea batatas L.

28.5 ± 0.9

0.047 ± 0.006

1.7 ± 0.2

Sweet potato

Ipomoea batatas L.

16.0 ± 0.6

0.040 ± 0.005

2.5 ± 0.3

Taro

Colocasia esculenta

45.5 ± 1.0

0.113 ± 0.013

2.5 ± 0.3

Taro

Colocasia esculenta

39.3 ± 1.0

Cucumber

Cucumis sativus L.

29.1 ± 0.9

0.212 ± 0.033

7.3 ± 1.1

Sweet pepper

Capsicum annuum L.

33.3 ± 1.0

0.111 ± 0.015

3.3 ± 0.5

Sweet pepper

Capsicum annuum L.

30.8 ± 1.0< 0.073

TomatoSolanum lycopersicum L.

43.5 ± 0.9< 0.047< 0.051

TomatoSolanum lycopersicum L.

41.9 ± 1.0< 0.063

Egg plant

Solanum melongena L.

19.6 ± 1.0< 0.070

Egg plant

Solanum melongena L.

41.8 ± 1.0

0.085 ± 0.018

2.0 ± 0.4

SoybeanGlycine max

30.0 ± 0.9

0.101 ± 0.010

3.4 ± 0.3

PeanutArachis hypogaea L.

17.5 ± 0.8

0.120 ± 0.006

6.9 ± 0.4

Wheat

Triticum aestivum L.

35.5 ± 1.1

0.171 ± 0.005

4.8 ± 0.2

Wheat

Triticum aestivum L.

24.9 ± 1.0

0.123 ± 0.006

4.9 ± 0.3

Wheat

Triticum aestivum L.

41.5 ± 0.9

0.059 ± 0.004

1.4 ± 0.1

BarleyHordeum vulgare L.

34.3 ± 0.9

BarleyHordeum vulgare L.

31.9 ± 0.9< 0.0150.049 ± 0.005

1.5 ± 0.2

140 J. Nucl. Radiochem. Sci., Vol. 8, No. 2, 2007

Uchida

70

50
40

-1

Th232-NE
U238-NETh and U concentrations / Bq kg

Th and U concentrations / Bq kg-1

60

U: r =0.91 (p<0.001)

30
20
10
0

Th: r = 0.79 (p<0.001)

0

10
226

20

30

40

50

Ra concentration / Bq kg

Figure 3. Correlations between concentration of(right) parts of Japan.

226

50
U: r =0.67 (p<0.01)

40
30
20
10
0

60

Th232-SW
U238-SW60

Th: r =0.48 (p<0.05)

0

10

-1

20
226

Ra and those of232

Th and30

40

50

Ra concentration / Bq kg

60

70

-1

238

U in soil samples collected in northeastern (left) and southwestern

TABLE 2: TF-Ra data in green vegetables
Crop
Cabbage
SpinachChinese cabbage

Number of
data
4

–1 c

(4.0 ± 2.7) × 10

18

(3.8 ± 1.1) × 10–1 c

1

AMa

GMb

95% confidence range

Reference7–3 c

9.6 × 102

6

1.3 × 10–2 c

2

9

–2

2

8

1.4 × 10–2

2.0 × 102

9

4.9 × 10–2

Spinach4–2< 2.1 × 10

4

Cabbage8< 2.2 × 10–2

4

Mixed green vegetables

2.5 × 10–3–9.8 × 10–1

–2

Vegetables

96

Leafy vegetables

13

1.6 × 10–2

1.2 × 10–2

3.0 × 10–3–5.2 × 10–2

This study

Cabbage5

1.1 × 10–2

9.2 × 10–3

2.6 × 10–3–3.2 × 10–2

This study

2–2Chinese cabbage

2 × 103

5

2.8 × 10

This studyaArithmetic mean. bGeometric mean. c Recalculated value from fresh weight basis TF to dry weight basis.

we obtained 10–76% in the southwestern part (geometricmean: 42%) and 11–77% in the northeastern part (geometricmean: 52%). The results implied that half of the total 226Ra in
agricultural soils was from phosphatic fertilizers.
In the radiochemistry procedures for 226Ra measurements inthe crops, Ba was used as a yield tracer of 226Ra, and the recovery throughout the separation procedure was more than 97%
for all the samples. The DL was lowered since a 15-g ash sample was used; that is, the DL obtained was about 0.7 Bq kg–1ash. If 5-g ash samples were used as recommended in thest a nd a rd met ho d , 6 t he DL wou ld b e 2 Bq kg – 1 -a sh.
Unfortunately, even though we lowered the DL, 226Ra concentrations for 9 crop samples could not be measured in the present study. For measurable crop samples, the values ranged
from 0.039 to 1.72 Bq kg–1-dry (geometric mean: 0.19 Bq kg–1dry) as listed in Table 1; the values were much lower than thosein the soils. Although Bettencourt et al.1 reported that 226 Ra
uptake depends on its concentration in the soil, we observed nocorrelation between 226Ra concentrations in soil and crops inthis study, possibly due to inclusion of many crop types.

Concerning leek samples, we compared 226Ra concentrations ingreen and white parts but t-test results showed no difference
between them.
3.2. Soil-to-crop transfer factor of 226Ra. Using the obtained
data for 226Ra in the 42 crops and the data for associated soil
samples, we calculated the TFs. The TF can be quantified as
TF =Element concentration in the edible parts at harvest (Bq kg–1-dry or mg kg–1-dry)Element concentration in the soil (Bq kg–1-dry or mg kg–1-dry).

The results ranged from 1.1 × 10 –3 to 5.8 × 10 –2 with a geometric mean of 6.4 × 10 –3 (Table 1). These data were within
the 95% confidential range of TF-Ra for several crops asreported in the TRS-364.3 The TFs of leafy vegetables (cabbage, lettuce, etc.) had the highest values (geometric mean: 1.2
× 10 –2) compared to other crop types, i.e., root vegetables, fruit
vegetables, legumes, cereals, and allium species. Then the values for leafy vegetables were compared with reported values;
these are summarized in Table 2. Except for the results
reported by Bettencourt et al.,1 the reported values2–5 were

J. Nucl. Radiochem. Sci., Vol. 8, No. 2, 2007 141

Soil-to-crop Transfer Factors of Radium in Japanese Agricultural Fields
10

TF-Ca

1
0.1
0.01
0.001
0.1
1
TF-Mg

10

10

10

1

1
TF-Sr

0.1

0.001
0 . 01

0.01

0.1
1
TF-Mg

0.001
0.0001

10

1

0.1
TF-Ba

TF-Ba

0.01
TF-Ca

1
1

1

0.1
0.01
0.001
0.00010.01

0.1

r=0.71(p<0.001)

0.1

0.01
0.001

0.1
1
TF-Mg

0.1

0.01
0.001

0.00010.0001

10

0.01
TF-Ca

0.0001
0.001

1

0.1

0.1
1
TF-Mg

10

0.1
TF-Sr

1

10

0.01

0.001
0.0001

0.01
TF-Ca

0.1
r=0.83(p<0.001)

TF-Ra

TF-Ra

TF-Ra

0.001
0.01

0.01

0.1
r=0.75(p<0.001)

0.01

r=0.81(p<0.001)

1

TF-Ra

0.01

r=0.92(p<0.001)

TF-Ba

TF-Sr

0.0001
0.01

0.01

0.001
0.001

0.01

0.1
TF-Sr

1

10

0.01

r=0.85(p<0.001)

0.001
0.0001 0.001 0.01
TF-Ba

0.1

1

Figure 4. Correlations between TFs of alkaline earth metals for upland field crops.

almost the same as those in this study, i.e., on the order of 10 –2.
Since reported TFs of Ra are limited, we also measured TFs
of Mg, Ca, Sr, and Ba which are in the same alkaline earth
metal group. Comparison allowed us to clarify similarities in
distribution of the TF values for Ra and these elements.
Correlations between TFs of each element are plotted in Figure
4. Among the TFs of alkaline earth metals, t-test results
showed no correlation for TF-Mg with other alkaline earth elements, while TF-Ca and TF-Sr showed the highest correlation(r = 0.92, p < 0.001). It is well known that Mg and Ca areessential elements for plants but their roles are different, sosome difference in TF correlation was reasonable.
Relatively high correlations with TF-Ra (p < 0.001) were
found in the following order: TF-Ba (r = 0.85) > TF-Sr (r =0.83) > TF-Ca (r = 0.75). Except for Mg, TFs of elements next
to each other in the periodic table, i.e., Ca-Sr, Sr-Ba, and BaRa, showed higher correlations, possibly because their chemical properties are closer with respect to ionic radius, crystalline
structure, and solubility. For instance, the ionic radius of Ra is
1.43 Å while that of Ba is 1.35 Å, so they are very close to eachother; Since Ca is an essential element, Sr, Ba, and Ra mightalternatively be absorbed by plants. Vandenhove et al.11
reported that Ba is considered a better tracer for Ra than Sr,given the significant linear correlation found between the TFBa and TF-Ra in tracer studies although the regression curve
does not have 1:1 slope as we observed in this study. Under
agricultural environment conditions, TF-Ba would also be agood analogue of TF-Ra. However it should be noted that therange of TF-Ba was wider than that of TF-Ra.
In the present study, we measured TFs of Ra in various crop
samples; however, it is difficult to compare area differences inJapan because each crop type did not have a large enough sample size. Further studies are needed for upland crops.
Acknowledgement. This work has been supported by the
Agency for Natural Resources and Energy, the Ministry of
Economy, Trade and Industry (METI), Japan.
References(1) A. O. Bettencourt, M. M. G. R. Teixeira, M. D. T. Elias,
and M. C. Faisca, J. Environ. Radioactivity 6, 49 (1988).
(2) E. Yunoki, T. Kataoka, K. Michiro, H. Sugiyama, M.
Shimizu, and T. Mori, J. Radioanal. Nucl. Chem. 174, 223(1993).
(3) International Atomic Energy Agency, Handbook of
Parameter Values for the Prediction of Radionuclide
Transfer in Temperate Environments, Technical Report
Series 364, IAEA, Vienna (1994).
(4) T. Sasaki, Y. Tashiro, H. Fujinaga, T. Ishii, and Y. Gunji,
Japanese J. Health Phys. 37, 208 (2002) (in Japanese withEnglish abstract).
(5) S. C. Sheppard, M. I. Sheppard, J. C. Tait, and B. L.
Sanipelli, J. Environ. Radioactivity 89, 115 (2006).

142 J. Nucl. Radiochem. Sci., Vol. 8, No. 2, 2007
(6) Ministry of Education, Culture, Sports, Science andTechnology, Japan, Analytical Methods for theDetermination of Radium. Standard Radioactivity Analysis
and Measurement Methods Manuals Series No. 19 (1990)(in Japanese).
(7) S. Uchida, K. Tagami, and I. Hirai, J. Nucl. Sci. Technol.
44, 628 (2007).
(8) K. Tagami and S. Uchida, Radioisotopes 55, 71 (2006) (inUchidaJapanese).
(9) M. M. Makweba and E. Holm, Sci. Total Environ. 133, 99(1993).
(10) H. Hamamo, S. Landsberger, G. Harbottle, and S. Panno, J.
Radioanal. Nucl. Chem. 194, 331 (1995).
(11) H. Vandenhove, T. Eyckmans, and M. Van Hees, J. Environ.
Radioactivity 81, 255 (2005).