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    !, "#$+ % &++' +-  ++  ,+ ()  +.  ,  + ( *Determination of Radium Concentrations in Hot-Spring
Waters with Cation Exchange Resin
Takashi SAITO+, Hiroshi UEDA,, Tomoko OHTA+ and Jun SATO+ +Department of Industrial Chemistry, School of Science and Technology, Meiji University,
Higashi-mita, Tama-ku, Kawasaki, Kanagawa Pref. ,+.ῌ2/1+, Japan+
To whom all correspondences should be addressed.
,
Present address : Hitachi ULSI Systems Co. Ltd., Otemachi, Chiyoda-ku, Tokyo +**ῌ***., Japan+

Abstract
Experimental conditions are discussed for a new analytical method for determining
Ra and ,,2Ra concentrations in hot-spring waters. The method is aimed to be applicableto the ﬁeld works. The acidity of the sample water is adjusted to *.+ M HCl and Ra
isotopes are collected by the cation exchange resin in a successive ion exchange procedures of batch operations : the second ion exchange procedure is applied to the same
sampled water after the removal of the resin in the ﬁrst procedure. The concentration of
Ra isotopes in the sample water can be estimated from the amount of Ra isotopes
recovered in the two operations by calculation. The amounts of ,,0Ra and ,,2Ra on theresin are obtained by a g-ray spectrometry for the -/+ keV g-ray from ,+.Pb and for the 3++
keV g-ray from ,,2Ac, both in radioactive equilibrium with precursors, respectively. The
present estimation method is applicable to / l of hot-spring waters having ,,0Ra concentrations of larger than +* mBq/l, and may be applicable to the ordinary undergroundwaters of less than + mBq/l by using /* l of sample water.
,,0

Key words : radium concentration, hot-spring water, cation exchange resin, ﬁeld work,
gamma-ray spectrometry

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Introduction

Several techniques have been reported in the literature on the determination of theconcentrations of ,,0Ra in thermal spring waters or natural waters, including the coprecipitation with BaSO. or with PbSO. followed by a-ray spectrometry, g-ray spectrometry and liquid
scintillation spectrometry (Sato et al, +31/ ; Honma and Murakami, +311 ; Horiuchi and
Murakami, +312 ; Environment Agency of Japan, +312 ; Horiuchi et al., +313 ; Horiuchi, +32+ ;Moron et al., +320 ; Yamamoto et al., +323 ; Hancock and Martin, +33+ ; Burnett and Tai, +33, ;Yamamoto et al., +33.). “Guide to the analysis of mineral spring waters” appeared in J. Soc.
Eng. Mineral Springs, Jpn, issued in +312 recommends the procedure of the coprecipitation of
Ra with BaSO. followed by the measurement of ,,,Rn in equilibrium with ,,0Ra by a liquid,,0

scintillation spectrometer (Environment Agency of Japan, +312).
However, Ba reagents frequently contain small but signiﬁcant amounts of ,,0Ra of several
fractions of + Bq/g. As the amount of ,,0Ra impurity in BaCl, · ,H, O reagents from - major
makers in Japan was found to be in the range of ,*ῌ+** mBq/g, several tens mBq of ,,0Ra
might be mixed by the coprecipitation with several tens mg of Ba. Yamamoto et al (+323) who
found the amount of ,,0Ra impurity in Ba reagents ranged +**ῌ.** mBq/g proposed theprocedure to eliminate ,,0Ra impurity from Ba compounds by cation exchange separation
using CyDTA (cyclohexanediaminetetraacetic acid) as eluant. An a-ray spectrometry wasapplied for ,,0Ra separated from the coprecipitating Ba compounds thus puriﬁed. Theseobservations show that the separation procedure including coprecipitation of Ra with Ba
compounds is generally not preferable in the determination of a minute amount of ,,0Ra ofless than + mBq/l in the water sample. Forthermore, most of these methods have di$culties
in applying them to the ﬁeld works because of their tedious chemical procedures which need
the transportation of a large amount of sample water to the laboratory for the isolation of
Ra by a series of chemical procedures.

,,0

The experimental conditions of a new easy ﬁeld work method for the isolation andmeasurement of ,,0Ra and ,,2Ra in thermal spring waters or underground waters are studied.
This method consists of two procedures : (+) collection of Ra isotopes by cation exchange
resin for the isolation, and (,) the determination of ,,0Ra and ,,2Ra by g-ray spectrometry.

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5

Experimentals

Most of the present studies on experimental conditions for chemical procedures withcation exchange resin were made by use of Ba instead of Ra, mainly because the amount of
the waste water containing ,,0Ra should be in minimum size. Barium was determined by theatomic absorption spectrometry.
,. +Collection
Collection rate of Ba on resin was investigated with the solution of - and -* ppm

concentrations. The acidity of the solution was adjusted to *.+ M HCl and cation exchange
resin of Dowex /*W-X2, #,*-/*, in H-form, was employed. The amount of water volume was
set to be / l or /* l.
Collection rate was observed with the - methods described below :Method (+) : A -* g of resin was put into a / l of the solution directly and the solution was
stirred for +/ min.
Method (,) : A -* g of resin was put into a /* l of the solution directly and the solution was
stirred for +/ min.
Method (-) : A -* g of resin was placed within a plastic tube. A /* l of the solution was
circulated for +/ min through the tube at a ﬂow rate of 0 l/min with the aid of a
portable pump.
The collection rates vs the operating time is given in Fig. +. Figure + indicates that the
Method (+) is e#ective in case where the amount of the water sample is as small as / l, while
the Method (-) is favorable for the water samples of a larger amount than /* l.
,. ,Estimation of Ra concentration in sample water
The time required for the ion exchange equilibrium between a large volume of sample

water and a small amount of resin will be longer than + hour. However, a short time as
possible is usually required for the operation in the ﬁeld work. Assuming that the temperature and chemical properties of the large volume of sample water may not change

Fig. + Recovery curve of Ba by cation exchange resin.
 : Method (+) ;  : Method (,) ;  : Method (-).

ῐΐῑῒ

6

signiﬁcantly after a shot-time collection operation, the Ra content in the water samples can be
estimated by the amount of Ra recovered by the two successive ion exchange procedures
operated in the ﬁxed time from the same water sample by using the following equations :C+῎C* · a ῌῌῌῌῌῌῌῌῌῌῌῌῌῌῌῌῌῌῌῌ(+)
C,῎(C*῍C+) · a ῌῌῌῌῌῌῌῌῌῌῌῌῌῌῌῌῌ(,)῏ a῎+῍(C,/C+) ῌῌῌῌῌῌῌῌῌῌῌῌῌῌῌῌ(-)῏ C*῎C+/ [+῍(C,/C+)] ῌῌῌῌῌῌῌῌῌῌῌῌῌ(.)
where C* : Total quantity of Ra in the initial water sample, which can be converted into theconcentration by the volume of sampled water.
C+ : Quantity recovered from the initial sample water by the +st operation.
C, : Quantity recovered by the ,nd operation from the remaining water sample after
removal of the resin used in the +st operation.
a : Collection e$ciency in the ﬁxed operation time for the water sample.

The

collection e$ciency is assumed to be the same for the two successive operations.
The operation time was set to the +/ min for the present estimation.
,. -Interference of coexisting ions
Calcium and Fe are one of the major constituents usually existing in the natural waters.

Though some thermal spring waters contain Ca more than /** ppm, most of the concentrations of ,,-/* thermal spring waters from -* localities in Japan are reported to be less than +**ppm (Hirakawa et al., +311). Frequency distribution of concentrations of Ca and Fe are shownin Fig. ,.

Fig. , Frequency distribution of concentration of Ca and Fe ion in Japanese thermal waters. (after Hirakawa et al., +311).

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Fig. -

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Concentration of coexisting ions and ratio of CC to C*.  : Ca ;  : FeInterference of the coexisting ions to the present method was studied with the *.+ M HCl
solutions of -* ppm Ba by mixing a following range of Ca and Fe ions with the solution : theconcentrations of Ca were adjusted to ,/*, /**, 1/*, +,*** and +,,/* ppm, and those of Fe were
adjusted to -**, 0/*, 3/* and +,0** ppm. The calculated concentrations (CC) estimated from C+
and C, by eq. (.) are compared with the known initial concentration C* in Fig. -. As the CC’sfor di#erent Ca and Fe concentrations are approximately equal to the initial C* within theirconcentration range up respectively to +,,/* and 0/* ppm, the interference of coexisting ion to
the present method of estimation can be ignored as far as the samples are the ordinary natural
waters.
,. .

Collection of Ra isotopes
The phosphorite from Florida, U.S.A., was used throughout the following studies. This

phosphorite containing - Bq/g of ,,0Ra was dissolved in 0 M HCl to prepare the stock solutionof ,,0Ra. Initially, the U impurity was eliminated from the stock solution with UTEVA Resin,an extraction chromatograph material supplied by Eichrom Industries, Inc., U.S.A., because
the +20 keV g-ray from ,-/U interferes the +20 keV spectral line from ,,0Ra. An aliquot of the
Ra solution thus reﬁned was poured into a vessel, in which a -* g of cation exchange resin,,0(Dowex /*W-X2, #+**-,**, in H-form) had been placed in advance in order to obtain the initialquantity of ,,0Ra (C*). The acidity of another aliquot was adjusted to *.+ M HCl and the volumeof the solution was adjusted to / l. After the solution and a -* g of cation exchange resin weremixed, the mixture was stirred for +/ min. The resin that collected ,,0Ra was taken out fromthe solution to measure C+ in eq. (+). The second collection procedure was applied to theremaining solution after the removal of the resin in the ﬁrst operation and the resin was takenout to measure C, in eq. (,). Each recovered resin was dried and packed into containers for
g-ray measurement and were stored for one month in order that ,,,Rn attained to be inradioactive equilibrium with ,,0Ra. Radioactivities of ,,0Ra and ,+.Pb in equilibrium with ,,,Rnwere determined by g-ray spectrometry.

῎ῑ῏ῐ

8

Gamma-ray spectrometry,. /Gamma-ray intensities were measured with an HPGe semiconductor detector.

The

counting e$ciency for g-rays in the present detector was estimated by the e$ciency curve
constructed by using the relative counting e$ciencies for the plural g-rays from a single
nuclide such as +/,Eu, 0*Co and +-2La, together with the normalizing point at the +,.0* keV g-ray
from .*K in the chemical reagent of KCl. The logarithmic relationship between the relative
counting e$ciency and the g-ray energy was made to ﬁt to the quadratic function by themethod of least squares and was normalized at +,.0* keV. Radioactivities of ,,0Ra, ,+.Pb, ,+.Biand ,,2Ac were determined respectively by the +20 keV, the -/+ keV, the 0*3 keV and the 3++
keV g-rays.
,. /. +The use of the -/+ keV g-ray from ,+.Pb equilibrated with ,,0Ra

Though the +20 keV g-ray from ,,0Ra itself can be used for the determination of ,,0Ra, thebranching ratio of the +20 keV g-ray is only -.0ῌ. On the other hand, as that of the -/+ keV
g-ray from ,+.Pb is -1.0ῌ, the indirect detection of ,,0Ra by the -/+ keV g-ray from ,+.Pb in
equilibrium with ,,0Ra is more e#ective than the direct use of the +20 keV g-ray from ,,0Ra. If
U coexists in the sample water, the +2/.1 keV g-ray from ,-/U may interfere the determinationof the +20., keV g-ray from ,,0Ra, U should be removed before the ion exchange procedure of
Ra as described before in [,..]. In addition, as the correction factors due to absorption and,,0

self-absorption of the higher energy g-rays are smaller, the use of the -/+ keV from ,+.Pb ispreferable for the spectrometry.
,. /. ,

Escape of ,,,Rn from the sample container

Measurement of ,+.Pb and ,+.Bi for ,,0Ra was made to conﬁrm whether ,,,Rn is completely
in a radioactive equilibrium with ,,0Ra in the container.
Ion exchange resins by which ,,0Ra was collected were packed into containers made of di#erent materials : polypropylene, glass and steel.
The establishment of the equilibrium of ,,,Rn with ,,0Ra in the sample container ischecked by the activity ratio of ,+.Pb to ,,0Ra and ,+.Bi to ,,0Ra. The measured activity ratios
for - di#erent containers are given in Table +.
(+)

Container of polypropylene (0/ mmf, +/ mmH) : The activity ratio has showed to beabout *.1/, indicating that one fourth of the equilibrated ,,,Rn escapes through the material(polypropylene) of the container wall of +.* mm thick.
Table +

Concentrations of ,,0Ra, ,+.Pb and ,+.Bi (in cps), and activity ratios of ,+.Bi and ,+.Pb to ,,0Ra

Container

Ra (+20keV),,0Pb (-/+keV),+.

Bi (0*3keV),+.

Pb/,,0Ra,+.

Bi/,,0Ra,+.

Polypropylene+4,,῍*4-,4+,῍*4--ῌῌ*423῍*4*.
+40-῍*4--ῌῌ*41-῍*4,**411῍*4+,

Glass culture dish+4-3῍*4+,*413῍*4+*ῌῌ*4/,῍*4*,*4*0῍*4*+ῌῌ*4-1῍*4*.
*4*2῍*4*,

Steel(Tin can)*423῍*4-+/4,+῍*4/.
-40*῍*4/*421῍*4,3*432῍*4*//4**῍*4+*-4*-῍*4*2+4**῍*4*/*422῍*4*/.4-2῍*4+*,41,῍*4*3*43-῍*4*/+4+*῍*4-3*430῍*4+**42.῍*4++4+/῍*4-3*433῍*4-/*42.῍*4*3*410῍*4+++4*1῍*4-0 /,  ,**,
(,)

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9Container of glass (1* mmf, +0 mmH) : This container is a pair of glass culture dishhaving the wall of ,.* mm thick and it was sealed with silicone. Di#erent and small activity
ratios are observed. Major part of the ,,,Rn formed from ,,0Ra can easily escape through thepossible cavity between the wall and the sealing material or through the sealing material itself.
(-)

Container of steel (0* mmf, +* mmH) : This container is a tin can having a thin wall of *.,/

mm thick. The activity ratios indicate that ,,,Rn exists in radioactive equilibrium with
Ra. As this type of can is available commercially, the use of tin cans is useful for the,,0routine measurement.

-.
-. +

Results and discussion

Ra concentrations of some hot-spring waters
Eleven hot-spring water samples from Tamagawa, Masutomi, Sarugajo, Arima, Onogawa,Misasa and Hijiori hot-springs were used for the experiment. Radium was separated by
Method (+) in [,.+] for the hot-spring waters of /ῌ+* l and by Method (-) for the well water of/* l. Results are given in Table ,. Concentration of the well water in Table , was deduced
from the 0*3 keV g-ray from ,+.Bi, because the -/+ keV g-ray from ,+.Pb was not determined dueto the larger Compton background than the 0*3 keV from ,+.Bi.

While C+ in eq. (+) was

obtained for all of the sample, C, was not always obtained, because the collection e$ciency is
so large that C, was not detected. In this case, a was assumed to be unity in the estimation of
the concentration.

Di#erent collection e$ciencies (a) were observed for di#erent water

sources which may due to the di#erent properties of respective sample waters. The concentrations of ,,0Ra deduced from the +20 keV spectral line were observed signiﬁcantly larger
than those of ,+.Pb, because the +20 keV spectral line was possibly overlapped with the +20 keV

Table , Concentrations of ,,0Ra and ,,2Ra in several hot-spring waters and one well water (in mBq/l).
Activity ratios of ,,2Ra/,,0Ra are given for some of hot-spring waters
Sample water

Ra ( ,+.Pb),,0

Ra ( ,,2Ac)a,,2

Ra reported,,0Ra/,,0Ra,,2

Tamagawa

0*2++,*++**423*4*0//ῌ,1* (Yokoyama5 +3//)+2-Masutomi +Masutomi ,Masutomi -

3,
.0/
32*2*

/0+*,+.*+-*

*43**4*,*4,1*4*-+0*ῌ-** (Horiuchi and
Murakami5 +312)-1/ (Yamamoto et al45 +33.)
+4,*4,4,*4,

Sarugajo

-2-





Arima +
Arima ,

+20+0-3

0.,0
.0+-

*4/2*4**4.0*4*0

Onogawa +Onogawa ,-,,-,/1+.

.3/0*/--.**4-,*4**4/3*4*-

Misasa

/*,

+*0/



Hijiori

+,,

-*-



,4/*4/

Well water (*)*40.*4+/(*) Well water from Meiji University5 Kawasaki

0ῌ++* (Sato et al45 +31/)-1ῌ11/* (Yokoyama5 +3// ;Ikeda5 +3//)*4-.*4+.
*41-*4,+4/*4,,4+*4,-1ῌ//* (Yokoyama5 +3//),4+*4+῍ῐ῎῏

10
Table -Ra concentrations obtained in di#erent experimental conditions

Volume (l)Resin (mesh)

Masutomi -ῌ+Masutomi -ῌ,

+*
/

,*ῌ/*
+**ῌ,**

Onogawa +ῌ+Onogawa +ῌ,

+*
/

,*ῌ/*
+**ῌ,**Ra ( ,,2Ac)

a ( ,+.Pb)

32*ῌ2*+*,0ῌ,-,.+*ῌ+-*,01-ῌ0-*4,1ῌ*4**43,ῌ*4*+-,,ῌ-,01ῌ2.3/ῌ0*.03ῌ+1*4-,ῌ*4**43+ῌ*4*,

Ra ( ,+.Pb)

,,0

,,2

Table . Ra concentrations obtained in the ﬁeld work and in thelaboratory work
Ra ( ,+.Pb),,0

Ra ( ,,2Ac),,2Ra/,,0Ra,,2

Onogawa , (lab.)
Onogawa , (ﬁeld),/1ῌ+.
,/1ῌ,-/*1ῌ,.
/--ῌ.*,4*ῌ*4+,4+ῌ*4,

Hijiori (lab.)
Hijiori (ﬁeld)

+*ῌ,
+,ῌ,

-,ῌ-*ῌ--4,ῌ*41,4/ῌ*4/g-ray from ,-/U coexisting in the sample waters.
represent those of

Ra and,,0,,2

The concentrations of ,+.Pb and ,,2Ac

Ra, respectively. The concentrations estimated presently are in

the same order of magnitude as the reported values. Di#erent activity ratios of ,,2Ra/,,0Ra
were observed in the variuos water samples from di#erent water source.
Though di#erent collection e$ciency (a) was obtained in di#erent combination of thevolume for sample water and the mesh-size for collecting resin for the sample of Masutomi and Onogawa + as shown in Table -, the two estimated Ra concentrations agreed well witheach other, indicating that the present estimation method is e#ective even when di#erent
collection e$ciency is obtained for any experimental condition of isolation.
-. ,Application to ﬁeld works
The Ra concentrations estimated in an in-situ separation were compared with thosedetermined by the separation method carried out in the labortory for the same water samples
transported.

The Method (-) described in [,.+] was applied to /* l water samples from

Onogawa and Hijiori hot-springs. The good agreement between two data (lab. and ﬁeld)
shown in Table . suggests that the present ﬁeld work analytical method is applicable enough.

Acknowledgements
The authors acknowledge Y. Koike, Meiji University and H. Takahashi, University ofTokyo for their cooperations.
Some parts of this paper were presented at the /-rd (Aug. ,1, ,***) and the /.th (Aug. ,.,,**+) annual meetings of the Balneological Society of Japan, the -2th annual meeting onRadioisotopes and Radiation in the Physical Sciences and Industries (Jul. +-, ,**+) and
APSORC ,**+ meeting (Nov. +, ,**+).

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References
Burnett, W.C. and Tai, W.ῌC. (+33,) : Determination of Radium in Natural Waters by a Liquid
Scintillation. Anal. Chem., 0., +03+ῌ+031.
Environment Agency of Japan (+312) : “Guide to the Analysis of Mineral Spring Waters”., J.
Soc. Eng. Mineral Spring, Jpn., +-, +ῌ1/, (in Japanese).
Hancock, G. J. and Martin, P. (+33+) : Determination of Ra in Environmental Samples by
a-Particle Spectrometry. Appl. Radiat. Isot., .,, 0-ῌ03.
Higuchi, H. (+32+) : The Analytical Methods for Radium in Environmental Samples., Radioisotopes, -*, 0+2ῌ0,1.
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Homma, Y. and Murakami, Y. (+311) : Study on the Applicability of the Integral Counting
Method for the Determination of ,,0Ra in Various Sample Forms Using a Liquid Scintillation Counter. J. Radioanal. Chem., -0, +1-ῌ+2..
Horiuchi, K., Ishii, T. and Murakami, Y. (+313) : Results on the Simultaneous Determination ofRn, ,,*Rn and ,,0Ra Contents in Mineral Springs of Izu Peninsula., J. Balneol. Soc. Jpn., -*,,,,2.ῌ23, (in Japanese with English abstract).
Horiuchi, K. and Murakami, Y. (+312) : Study on the Simultaneous Determination of Radium
and Radon in the Same Water Sample of Mineral Springs. Part +Simultaneously
Determined Contents of Ra and Rn in Water Samples of Misasa, Katsuura, Shirahama,Yugashima, Aziro and MasutomiJ. Balneol. Soc. Jpn., ,3, 02ῌ1/, (in Japanese withEnglish abstract).
Ikeda, N. (+3//) : Chemical Studies on the Hot Spring of Arima III. Investigations on theTenmangu-no-yu Spring, Arima Area. (/). J. Chem. Soc. Jpn., (Nippon Kagaku Zassi), 10,+*13ῌ+*2,, (in Japanese).
Moron, M.C., Garcia-Tenorio, R., Garcia-Montano, E., Garcia-Leon, M. and Madurga, G. (+320) :An Easy Method for Determination of Ra Isotopes and Actinide Alpha Emitters from theSame Water Sample. Appl. Radiat. Isot., -1, -2-ῌ-23.
Sato, J., Yokozawa, O. and Saito, N. (+31/) : Radioactive Nuclides in the Thermal Spring Water
and Its Sinter Deposits from Sarugajo, Tarumizu City, Kagoshima Prefecture. J. Soc. Eng.
Mineral Springs, Jpn., +*, .1ῌ0*, (in Japanese with English abstract).
Yamamoto, M., Komura, K. and Ueno, K. (+323) : Determination of Low-Level ,,0Ra in
Environmental Water Samples by Alpha-Ray Spectrometry. Radiochim. Acta, .0, +-1ῌ+.,.
Yamamoto, M., Toguchi, A., Sashimono, K., Komura, K., Ueno, K. and Sakanoue, M. (+33.) :,+*Pb and ,+*Po in Volcanic Products and Mineral Springs (,) Measurement of ,+*Pb and,+*

Po Contents in Mineral Springs. J. Balneol. Soc. Jpn., .., +2ῌ,1, (in Japanese withEnglish abstract).
Yokoyama, Y. (+3//) : Studies on Radioactive Springs in Japan I-III. J. Chem. Soc. Jpn. (Nippon
Kagaku Zassi), 10, //+ῌ/0,, (in Japanese).