DOI: http://dx.doi.org/10.7306/gq.1365
224
Ra and the
224Ra/
228Ra ac tiv ity ra tio in se lected min eral wa ters from the Pol ish Carpathians
Chau NGUYEN DINH1, Lucyna RAJCHEL1, *, Hao DUONG VAN2 and Jakub NOWAK3
1 AGH Uni ver sity of Sci ence and Tech nol ogy, Fac ulty of Ge ol ogy, Geo phys ics and En vi ron men tal Pro tec tion, al. A. Mickiewicza 30, 30-059 Kraków, Po land
2 Ha noi Uni ver sity of Min ing and Ge ol ogy, Fac ulty of Oil and Gas, Viet nam
3 AGH Uni ver sity of Sci ence and Tech nol ogy, Fac ulty of Phys ics and Ap plied Com puter Sci ence, al. A. Mickiewicza 30, 30-059 Kraków, Po land
Nguyen Dinh, Ch., Rajchel, L., Duong Van, H., Nowak, J., 2017. 224Ra and the 224Ra/228Ra ac tiv ity ra tio in se lected min eral wa ters from the Pol ish Carpathians. Geo log i cal Quar terly, 61 (4): 771–778, doi: 10.7306/gq.1365
Min eral and ther a peu tic wa ters widely oc cur ring in the Pol ish Carpathians con tain a vast amount of biogenic el e ments. How - ever, ra dio ac tive el e ments like ra dium iso topes are also found in these wa ters. This pa per pres ents the first re sults of the ac - tiv ity con cen tra tion mea sure ments of 224Ra in se lected min eral wa ters of the Pol ish Carpathians. Ad di tion ally, the con tent of
226Ra and 228Ra, and the ac tiv ity ra tios of 224Ra/228Ra, 224Ra/226Ra and 226Ra/228Ra in the wa ters were de ter mined. The work was based on a method for the si mul ta neous de ter mi na tion of 224Ra, 226Ra and 228Ra in wa ter sam ples us ing the a/b liq uid scin til la tion spec trom e ter. The re sults show that the ac tiv ity con cen tra tions of 224Ra, 226Ra and 228Ra in the min eral wa ters are com pa ra ble and vary from ca. 220 mBq/L to above 1500 mBq/L. The ac tiv ity ra tios of 224Ra/228Ra, 224Ra/226Ra and
226Ra/228Ra are vari able within the ranges of 0.68 to 1.48, 0.65 to 1.48, and 0.78 to 2.05, re spec tively. The com mit ted ef fec - tive dose re sult ing from the in take of 224Ra through the wa ter con sump tion is far lower than that from 226Ra and 228Ra.
Key words: 224Ra, ra dium, min eral wa ters, ef fec tive dose, LSC method.
INTRODUCTION
The de ter mi na tion of ra dium iso topes in wa ter sam ples is very im por tant from the hy dro log i cal and ra dio log i cal point of view. The re la tion be tween the ra dium iso topes’ con cen tra tion in ground wa ter and the li thol ogy of the host aqui fers were re - ported by many sci en tists (e.g., King et al., 1982; Sturchio et al., 1992; Mar tin and Akber, 1999; Lucivjansky, 1999; Ruberu et al., 2005; Grundl and Cape, 2006, Walencik-£ata et al., 2016). The ther mo dy namic prop er ties and ap pli ca tions of the ra dium iso - topes for in ter ac tion be tween ground wa ter and aqui fer rock were stud ied by Davidson and Dick son (1986), Langmuir and Melchior (1985) and Szabo et al. (2012). The con tri bu tion of
226Ra and 228Ra to an nual com mit ted ef fec tive dose re sult ing from the con sump tion of min eral and drink ing wa ters amounts to >70% (Bayés et al., 1996; Manjón et al., 1996; Godoy et al.,
2001; Waller and Steininger, 2007; Waller et al., 2008; Nguyen et al., 2012).
Ac cord ing to the Coun cil Di rec tive (Euratom, 2013), drink - ing wa ter is safe from the ra dio log i cal point of view if with the con sump tion of two litres per day, the an nual com mit ted dose rate orig i nat ing from the pres ence of the ra dio ac tive el e ments in this wa ter is <0.1 mSv. In gen eral, in many coun tries (for ex am - ple in Po land) there are nat u ral ar te sian wa ter in takes serv ing as di rect sources of drink ing wa ter for pop u la tion. In that case, the 224Ra should be taken into ac count in the es ti ma tion of com - mit ted ef fec tive doses.
The Carpathians are the rich est re gion of min eral and ther a - peu tic wa ters in Po land, where nu mer ous spas and bot tling plants are lo cated. A sig nif i cant num ber of min eral wa ters oc - cur ring in this re gion are avail able for con sum ers di rectly from bore holes or springs. The main aim of the work was the de ter - mi na tion of 224Ra con tent in se lected min eral wa ters from the Pol ish Carpathians. For the first time, the re sults of the ac tiv ity con cen tra tion of 224Ra in the Pol ish Carpathian min eral wa ters are pre sented. Ad di tion ally, the con tent of other ra dium iso - topes (226Ra and 228Ra) and the ac tiv ity ra tios of 224Ra/228Ra,
224Ra/226Ra and 226Ra/228Ra were de ter mined. In the pa per, some geo chem i cal and ra dio log i cal as pects of the pres ence of three ra dium iso topes (224Ra, 226Ra and 228Ra) and their ac tiv ity ra tios in stud ied min eral wa ters are also dis cussed.
* Corresponding author, e-mail: lucynar@agh.edu.pl Received: February 14, 2017; accepted: May 28, 2017; first published online: July 3, 2017
SAMPLING AND ANALYSIS METHOD
STUDY REGION AND SAMPLING
The wa ter sam ples were col lected from sev eral min eral wa - ter in takes in the Pol ish Outer Carpathians (Fig. 1). This re gion is com posed chiefly of Cre ta ceous and Mio cene sand stones and mudstone of flysch or i gin, in which car bon ate and si li ceous rocks spo rad i cally oc cur. The for ma tions are strongly folded and di vided onto dif fer ent units. Due to the very com pli cated geo log i cal struc ture, the Carpathians are re garded as a re gion of di verse hydrogeological con di tions (e.g., Rajchel, 2012;
Rajchel and Czop, 2012). This re gion hosts many valu able min - eral wa ter re sources used for balneotherapy and by min eral wa ter plants. The sam ples were col lected from some se lected re sources of ther a peu tic bicarbonated wa ters, wa ters con tain - ing car bon di ox ide, and chlo ride wa ters from the Magura Unit (Zuber-1 and Zuber-2 bore holes, and S³otwinka spring in Krynica-Zdrój; Krakus, Warzelnia and Rabka IG 2 bore holes in Rabka-Zdrój) and the Silesian Unit (Elin 7 and Emma bore holes in Iwonicz-Zdrój; Klimkówka 27 bore hole in Klimkówka;
Lubatówka 12 bore hole in Lubatówka; Ta ble 1). The wa ters are diagenetic and mixed with the in fil tra tion wa ter to dif fer ent de - grees (Rajchel and Czop, 2012).
In the Magura Unit (Inoceramian Bed; Fig. 1) the av er age ura nium and tho rium con cen tra tions are 2.06 and 8.92 ppm, but in the Silesian Unit (Godula, Istebna, Ciê¿kowice and Krosno beds; Oszczypko et. al., 2006) they vary from 1.07 to 1.98 and 4.03 to 10.05, re spec tively (Plewa and Plewa, 1992).
The wa ter sam ples were placed into 2-litre plas tic bot tles.
Be fore sam pling the bot tles were rinsed by HCl 0.1 M and dis - tilled wa ter. To elim i nate the re main ing liq uid, the bot tle was rinsed sev eral times with the wa ter in tended for anal y sis at the
wa ter in take. The sam pling time was re corded and the sam ples were trans ported to the lab o ra tory as soon as pos si ble.
METHODOLOGY
At the lab o ra tory, the wa ter sam ples were weighed and the ra dium iso topes were co-pre cip i tated from the wa ter sam ple to - gether with bar ium as a sul phate com pound. The pre cip i tate was placed into the glass vial of vol ume 22 mL, mixed with 12 mL of the gel scin til la tion cock tail, and mea sured by the Guard ian al pha/beta Wallac Scin til la tion Coun ter (LSC method). For ev ery sam ple, the mea sure ment was per formed daily for two hours. The mea sure ment pro cess lasted un til the ra dio ac tive equi lib rium be tween 226Ra and 222Rn has been es - tab lished. The ap plied chem i cal prep a ra tion and mea sure ment pro ce dures were de scribed in de tail by Nguyen et al. (1997).
Af ter ra dium pre cip i ta tion, only ra dium iso topes (226Ra,
228Ra and 224Ra) oc cur in the ob tained sam ple. 226Ra be longs to the ura nium se ries with 238U as a pri mary el e ment, 228Ra and
224Ra are the mem bers of tho rium se ries with 232Th as a first iso - tope. At the ra dio ac tive equi lib rium oc cur ring in the 226Ra group, there are four al pha de cay iso topes (226Ra, 222Rn, 218Po, 214Po) and two beta de cay iso topes (218Pb, 214Bi). In the 228Ra group, there are only two beta de cay iso topes (228Ra, 228Ac). The 224Ra group emits four al pha and two beta par ti cles. Four al pha par ti - cles are re lated to 224Ra, 220Rn, 216Po (ev ery iso tope emits one a par ti cle per de cay), and 212Bi and 212Po with emis sion of 0.337 a per de cay and 0.663 a per de cay, re spec tively. Two beta par - ti cles are emit ted from 212Pb (one b per de cay), 212Bi (0.663 b per de cay) and 208Tl (0.337 b per de cay; Brown et al. 1986).
Since the half-life (T1/2) of 226Ra is 1620 y, and the lon gest daugh ter in this group is 222Rn with T1/2 equal to 3.825 d, so the sec u lar equi lib rium in the group is es tab lished af ter nearly 500 h Fig. 1. Map of mineral waters sampling sites
from the mo ment of ra dium pre cip i ta tion. In the 228Ra group, the ac tiv ity of 228Ac can reach the 228Ra ac tiv ity in about 20 h af ter the pre cip i ta tion. With ref er ence to the lab time (one month), the
228Th can be re garded as a “sta ble” iso tope due to its T1/2 equal to 1.9 y. The T1/2 of 224Ra is 3.62 d and the lon gest lived prog eny is 212Pb with the T1/2 = 10.6 h, so the tran sient equi lib rium in the group is es tab lished af ter 53 h. Since that mo ment, the to tal al - pha and beta ac tiv i ties of the 224Ra group de crease in ac cor - dance with de cay law. Af ter 500 h, the to tal ac tiv ity of the 224Ra group is be low 2% of the ac tiv ity of this iso tope at the pre cip i ta - tion time. There fore, the con tri bu tion of the 224Ra group to the to tal al pha and beta count rates af ter 500 h elapsed from the ra - dium pre cip i ta tion can be ne glected, and the 226Ra and 228Ra can be es ti mated us ing the al pha and beta count rates mea - sured af ter 500 h from the mo ment of ra dium pre cip i ta tion. For ev ery stud ied sam ple the de pend ence of the net al pha and beta in ten si ties (the in ten si ties of the back ground sam ple were sub - tracted from the ad e quate in ten si ties of the sam ple) on the time elapsed from the pre cip i tat ing mo ment was used to de ter mine the 224Ra, 226Ra and 228Ra con tents.
The 226Ra con cen tra tion in a wa ter sam ple is es ti mated by the for mula:
226 500
500
226 60
Ra = Ra
´ ´ ´
- -
I
F V
a
a ea
[1]
where: I500a – net count rate (cpm) of the sam ple mea sured in the al - pha chan nel af ter 500 h from the mo ment of ra dium pre cip i ta tion;
Fa-Ra500-226 – fac tor cor re spond ing to rel a tive al pha ac tiv ity of the 226Ra group at 500 h elapsed from the sam ple prep a ra tion; this fac tor can be ob tained from the Bate man equa tion or em pir i cally us ing the sam ple pre pared from the 226Ra stan dard so lu tion; ea – the de tec tion ef fi ciency of the liq uid scin til la tion de tec tor for al pha par ti cle and can be es ti mated us ing the sam ple of 226Ra stan dard so lu tion or ar bi - trarily taken to be equal to 100% (Horrocks, 1974); V – wa ter sam ple vol ume; the 60 is the num ber of sec onds in one min ute.
The 228Ra con cen tra tion in the wa ter sam ple is de ter mined us ing the beta count rate. The to tal beta count rate at 500 h elapsed time con sists of both beta count rates from the 228Ra and 226Ra groups. The count rate of the beta par ti cles emit ted from the 226Ra group is cal cu lated by the fol low ing for mula:
IbRa-500-226 =I500a ´Cba [2]
where: C I I
st ba st
b a
= -
- 500 500
; Ib - 500st and Ia- 500st is the count rates for the 226Ra stan dard sam ple af ter 500 h from the mo ment of ra dium pre cip i ta - tion mea sured in the beta and al pha chan nels, re spec tively.
The count rate from the 228Ra group in the sam ple is equal to:
IbRa-500-228 =Ibtotal-500 -IbRa-500-226 [3]
Lo cal ity/type and name of wa ter in take
Depth
[m] Depth of the wa ter in take [m] Wa ter type GPS co or di nates Krynica-Zdrój
Zuberb-1 borehole 810.0 696.2–810.0 HCO3-Na+CO2
591.2 m a.s.l.
49°24’50’’N 20°57’48’’E Krynica-Zdrój
Zuber-2 bore hole 948.5 586.8–670.0 HCO3-Na-Mg+CO2
576.2 m a.s.l.
49°24’53’’N 20°57’44’’E Krynica-Zdrój
S³otwinka spring – – HCO3-Mg-Na-Ca+CO2+Fe
615.0 m a.s.l.
49°25’59’’N 20°57’25’’E Rabka-Zdrój
Warzelnia bore hole 50.2 41.0–45.7 Cl-Na+Fe+I
494.99 m a.s.l.
49°36’36’’N 19°58’02’’E Rabka-Zdrój
Rabka IG 2 bore hole 1215.0 1185–1215 Cl-Na+I+T
563.84 m a.s.l.
49°36’57’’N 19°58’30’’E Rabka-Zdrój
Krakus bore hole 19.0 19.0 Cl-Na+I
495.5 m a.s.l.
49°36’35’’N 19°57’58’’E Klimkówka
Klimkówka 27 bore hole 1255.0 417.0–481.0 HCO3-Cl-Na+CO2+I
462.8 m a.s.l.
49°33’26’’N 21°47’32’’E Iwonicz-Zdrój
Emma bore hole 283.7 102.8–263.0 Cl-HCO3-Na+CO2+I
435.20 m a.s.l.
49°33’38’’N 21°46’58’’E Iwonicz-Zdrój
Elin 7 bore hole 1030.0 85.0–238.0 Cl-HCO3-Na+CO2+I
434.80 m a.s.l.
49°33’39’’ N 21°45’02’’E Lubatówka
Lubatówka 12 bore hole 1151.5 625.0–958.0 Cl-HCO3-Na+CO2+I+T
350.7 m a.s.l.
49°33’59’’N 21°47’32’’E
T a b l e 1 Se lected data on bore holes, springs and me dic i nal wa ters
where: Ib - 500total – the count rate mea sured in the beta chan nel for the sam ple.
The 228Ra con cen tra tion in wa ter sam ple is es ti mated by the for mula:
228 500
228
500
228 60
Ra
Ra
= Ra
´ ´ ´
- -
- -
I
F V
b
b eb
[4]
where: Fb -Ra500-228– the fac tor cor re spond ing to the rel a tive beta ac tiv ity of the 228Ra group af ter 500 h from the mo ment of ra dium pre cip i ta tion, eb – the ef fi ciency of the de tec tion of beta par ti cles emit ted from the
228Ra group. The other sym bols de note the same as in For mula [1].
The count rates mea sured daily in the al pha chan nel con - sist of the count rate orig i nat ing from both the 226Ra and 224Ra groups, so the count rate mea sured at the t-mo ment from the
224Ra con tent in the pre pared wa ter sam ple is de ter mined as fol lows:
IaRa-224( )t =Ibtotal( )t -IaRa-226( )t [5]
where: Iatotal( ), It aRa- 226( ) are the to tal al pha count rate and the al phat count rate orig i nat ing from the 226Ra group, re spec tively; t – the elapsed time from the mo ment of ra dium pre cip i ta tion.
The IaRa - 226( ) can be cal cu lated by the for mula:t
IaRa-226( )t =226Ra´60´V ´FaRa 226- ( )t [6]
where: 226Ra – the ac tiv ity con cen tra tion de ter mined by For mula [1], is the fac tor cor re spond ing to the rel a tive al pha ac tiv ity for the 226Ra group at the time (t) elapsed from the sam ple.
Fa t
Ra - 226
( ) can be cal cu lated us ing the Bate man equa tion or de ter mined em pir i cally us ing the sam ple pre pared from the
226Ra stan dard so lu tion. The a and b spec tra of the pre pared
228Ra stan dard sam ple mea sured at 50 and 265 h elapsed from the ra dium pre cip i ta tion are pre sented in Fig ure 2 and Fig ure 3, re spec tively. The fig ures show that the al pha ac tiv ity de creased in agree ment with the 224Ra de cay and the beta ac tiv ity de - creased clearly more slowly in com par i son with the al pha one.
This fact is re lated to both the con stant beta ac tiv ity of the 228Ra group and the de creas ing beta ac tiv ity of the 224Ra group. The mea sured to tal al pha count rate as a func tion of the elapsed time and its sep a rated com po nents orig i nat ing from the 226Ra and 224Ra groups for the sam ple col lected from the Zuber-2 wa - ter in take is shown in Fig ure 4 as an ex am ple. In or der to es ti - mate the 224Ra con tent, the curve (ac cord ing to the de cay form – ae–bt) pre sent ing the re la tion be tween the com po nent of the al pha count rate of the 224Ra group and time elapsed from the pre cip i tat ing mo ment (af ter 53 h) is fit ted. The con tent of 224Ra is cal cu lated us ing the de cay law of the 224Ra group and Ia -
- 0 Ra 224
which is an or di nate of the in ter sec tion point of the above-men - tioned fit ted curve on the y-co or di nate.
224 0
53
60 53
Ra
Ra 224 Ra 224
Ra 224
= ´
´ ´ ´ ´
-
- - ´
- -
I e -
F V e
a
l
a ea
( )
lRa 224- ´ + Dt 53 =
= ´
´ ´ ´
-
- - ´
- -
I e -
F V
t a
l
a ea
0
60 53 Ra 224
Ra 224 Ra 224 D
[7]
Fig. 2. Al pha and beta spec tra of the 228Ra stan dard so lu tion mea sured by Wallac Winspectral 1414 al pha and beta liq uid scin til la tion coun ter at 50 h elapsed from the ra dium pre cip i ta - tion
Fig. 3. Al pha and beta spec tra of the 228Ra stan dard so lu tion mea sured by Wallac Winspectral 1414 al pha and beta liq uid scin til la tion coun ter at 265 h elapsed from the ra dium pre cip i ta - tion
Fig. 4. To tal al pha count rates and its com po nents of 226Ra and
224Ra groups for the wa ter sam ple col lected from the Zuber-2 in - take (for the fit ting curve value of l = 0.0081 h–1 cor re spond ing to T1/2 equal to 3.57 days)
where: lRa–224 [h-1] – the fit ted value of the 224Ra de cay con stant, and Fa-Ra 22453- the fac tor cor re spond ing to the rel a tive al pha ac tiv ity of the
224Ra group at 53 hours elapsed from the pre cip i tat ing wa ter sam ple, and can be es ti mated us ing the Bate man equa tion for the 224Ra group or de ter mined em pir i cally us ing the sam ple pre pared from the
232Th stan dard so lu tion, where there is ra dio ac tive equi lib rium be - tween 228Ra and 224Ra. Dt [h] – the time elapsed from the wa ter sam - pling mo ment to the pre cip i ta tion point.
In ac cor dance with the def i ni tion de scribed by Cur rie (2008) and prop a ga tion law, the limit of de tec tion was cal cu lated based on the av er age un cer tainty of the count rates in the al pha and beta chan nels for the back ground sam ple, and is equal to 11 mBq/dm3 for 224Ra, 7 mBq/dm3 for 226Ra, and 30 mBq/dm3 for 228Ra.
RESULTS AND DISCUSSION
The ac tiv ity con cen tra tions of 224Ra, 226Ra and 228Ra in the stud ied wa ters vary from 206 to 1116 mBq/L, from 213 to 1545 mBq/L, and from 186 to 752 mBq/L, re spec tively (Ta - ble 2). Fig ures 5, 6 and 7 show the re la tion ships be tween 226Ra and 224Ra, be tween 228Ra and 224Ra, and be tween 228Ra and
226Ra, re spec tively. All points (ex clud ing the wa ter from Lubatówka 12) in the fig ures are scat tered be tween line 1:1.
There are strong lin ear cor re la tions be tween the stud ied ra dium iso topes. The Pearson cor re la tion co ef fi cient for the re la tions be tween 226Ra and 224Ra, be tween 228Ra and 224Ra, and be - tween 228Ra and 226Rais equal to 0.94, 0.88 and 0.85, re spec - tively. The three ana lysed iso topes are vari ants of the same chem i cal el e ment (ra dium); thus, their chem i cal prop er ties and be hav iour in ground wa ter are the same.
The ac tiv ity ra tios of 224Ra/228Ra and 226Ra/228Ra range in the in ter vals of 0.68–1.48 and 0.78–2.05, re spec tively. The av -
er age value of 224Ra/228Ra ac tiv ity ra tio is 1.09, and, if we ex - clude the wa ter from Lubatówka 12, this ra tio de creases to 1.04. The ob served phe nom ena in di cate that the ac tiv ity con - cen tra tion of 224Ra in ground wa ter is gen er ally slightly higher than that of 228Ra, which is re lated to the re coil ef fect. In the tho - rium de cay chain, 224Ra is fol lowed by two al pha de cays, while
228Ra is fol lowed only by one al pha de cay. There fore, 224Ra shows higher prob a bil ity of mi gra tion due to di rect trans fer of the atom across the solid/liq uid phase bound ary or lat tice de - struc tion by re coil ef fect than 228Ra. It is the same pro cess which causes ura nium iso topes dis equi lib rium (the ac tiv ity ra tio of 234U/238U is gen er ally >1) in ground wa ter (Os mond and Cowart, 1976; Nguyen et al., 2011).
In such min eral wa ters, the chem i cal pro cesses dom i nate the re coil ef fect and ra dium iso topes mi grate mainly from host rocks to wa ter due to leach ing pro cesses. The lower con tent of
224Ra than 228Ra can be as so ci ated with the fact that tho rium (228Th is prog eny of 228Ra and par ent of 224Ra) forms low-sol u - ble and highly ad sorbed com pounds in con trast to ra dium (Langmuir, 1997; Nguyen et al., 2011).
The ob served av er age ac tiv ity ra tio val ues (226Ra/228Ra) for all stud ied wa ters are 1.2, be ing typ i cal for highly min er al ised ground wa ter in the Pol ish Carpathians (Nguyen et al., 2016).
Gen er ally, the ac tiv ity con cen tra tions of 226Ra, 228Ra and their ac tiv ity ra tio (226Ra/228Ra) in ground wa ter are re lated to the ad e - quate con tent and ac tiv ity ra tio of their pri mor dial iso topes (238U,
232Th, 238U/232Th) in the host aqui fers (Asikainen and Kahlos, 1979; King et al., 1982; Vesterbacka et al., 2006; Nguyen et al., 2012). For six wa ters from the Magura Unit and three wa ters from the Silesian Unit, the av er age ac tiv ity con cen tra tion ra tios (226Ra/228Ra) are 1.04 and 1.47, re spec tively. The val ues cor re - spond, to a cer tain de gree, to the ra tios of the av er age ura nium and tho rium con cen tra tions in the Magura and Silesian units.
The high est ac tiv ity con cen tra tions of the ra dium iso topes and their ac tiv ity ra tios (226Ra/228Ra and 224Ra/228Ra) were ob served
No. Lo cal ity/
wa ter in take TDS [g/L]
Ac tiv ity con cen tra tion
[mBq/L] Ac tiv ity con cen tra tion ra tio
224Ra 226Ra 228Ra 224Ra/ 228Ra 224Ra/ 226Ra 226Ra/ 228Ra 1 Krynica-Zdrój
Zuber-1 23.2 428 ± 38 568 ± 24 530 ± 38 0.81 0.75 1.07
2 Krynica-Zdrój
Zuber-2 20.5 460 ± 32 447 ± 23 312 ± 34 1.47 1.03 1.43
3 Krynica-Zdrój
S³otwinka 3.52 420 ± 17 284 ± 19 362 ± 30 1.16 1.48 0.78
4 Rabka-Zdrój
Warzelnia 20.6 216 ± 17 314 ± 19 312 ± 25 0.70 0.69 1.01
5 Rabka-Zdrój
Rabka IG 2 23.5 722 ± 45 619 ± 25 598 ± 39 1.21 1.17 1.04
6 Rabka-Zdrój
Krakus 23.8 331 ± 23 442 ± 30 485 ± 41 0.68 0.75 0.91
7 Klimkówka
Klimkówka 27 12.2 218 ± 34 333 ± 15 215 ± 25 1.01 0.65 1.55
8 Iwonicz-Zdrój
Emma 5.92 206 ± 13 213 ± 8 203 ± 18 1.01 0.97 1.05
9 Iwonicz-Zdrój
Elin 7 5.80 245 ± 23 231 ± 17 186 ± 19 1.31 1.06 1.24
10 Lubatówka
Lubatówka 12 20.5 1116 ± 71 1545 ± 88 752 ± 61 1.48 0.72 2.05
T a b l e 2 The ac tiv ity con cen tra tions of 224Ra, 226Ra and 228Ra and their ac tiv ity ra tios
in the stud ied Carpathian min eral wa ters
in the wa ter from Lubatówka 12. This fact can be re lated to the lo cal ge ol ogy and hydrogeological con di tions in this area.
The TDS in the in ves ti gated ground wa ter var ies from 3.5 to 23.8 g/L. The re la tions be tween ac tiv ity con cen tra tions of three ra dium iso topes (224Ra, 226Ra and 228Ra) and TDS are pre - sented in Fig ure 8. There is no clear re la tion be tween the ra - dium con tent in in ves ti gated wa ters and TDS, or it is dif fi cult to no tice be cause of the small amount of data.
Based on the ob tained ac tiv ity con cen tra tions of the ra dium iso topes, the an nual com mit ted ef fec tive doses (E) re sult ing from con sump tion of two litres of the min eral wa ters a day for adults were cal cu lated us ing the fol low ing equa tion:
( )
E V Ai DCFi
i N
= ´ ´
=
å
1
[8]
where: V stands for con sump tion of wa ter (2L per day), Ai – the ac tiv - ity con cen tra tion of the given radionuclide in wa ter ex pressed in
Bq/L, and DCFi stands for the DCFs (Dose Con ver sion Fac tor) for in - ges tion by hu mans be long ing to the given age group (adults in this case). The DCF is equal to the dose in Sv re sult ing from the in ges - tion of 1Bq of the given radionuclide (ICRP, 1995; WHO, 2008).
The cal cu lated com mit ted ef fec tive dose from 226Ra and
228Ra changes in the range from 44 to 316 µSv/year and from 94 to 379 µSv/year, re spec tively. The data show that the dose from the 224Ra var ies from 7.5 to 53 µSv/year and its con tri bu - tion to the to tal an nual com mit ted ef fec tive dose is <8% (Ta - ble 3). Thus, the in take of 224Ra with con sumed wa ter does not pose a sig nif i cant ra dio log i cal risk to hu man health in com par i - son with other two ra dium iso topes (226Ra and 228Ra).
CONCLUSIONS
The ac tiv ity con cen tra tions of 224Ra in the stud ied min eral wa ters are com pa ra ble to that of 226Ra and 228Ra. There is a Fig. 5. 226Ra concentration vs. 224Ra concentration
in the water samples
Fig. 6. 228Ra concentration vs. 224Ra concentration in water samples
Fig.7. 226Ra concentration vs. 228Ra concentration in the water samples
Fig. 8. Activity concentrations of radium isotopes (224Ra, 226Ra and 228Ra) vs. TDS in the water samples
strong lin ear cor re la tion be tween 224Ra and the other two ra - dium iso topes.
The av er age value of the ob served ac tiv ity ra tio (224Ra/228Ra) is slightly above 1 (1.04). This is re lated to the re - coil ef fect; the same pro cess which causes the dis equi lib rium of ura nium iso topes in ground wa ter. The ac tiv ity ra tio of
224Ra/228Ra lower than 1 can be re lated to the fact that tho rium forms low-sol u ble and highly ad sorbed com pounds in an aque - ous en vi ron ment. The ac tiv ity ra tios of 226Ra/228Ra in the Magura and Silesian units are re lated to the av er age con cen tra - tions of ura nium and tho rium in wa ter-bear ing for ma tions oc cur - ring in the units.
The in take of 224Ra with con sumed wa ter does not pose a sig nif i cant ra dio log i cal risk to hu man health in com par i son with
226Ra and 228Ra.
The LSC method is clearly use ful for the si mul ta neous de - ter mi na tion of 224Ra, 226Ra and 228Ra in wa ter sam ples.
Ac knowl edge ments. The au thors would like to ex press their thanks to the anon y mous re view ers for their valu able re - marks. This work was sup ported by the AGH Uni ver sity of Sci - ence and Tech nol ogy pro jects Nos.: 11.11.140.645, 11.11.140.862 and 15.11.220.717.
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1 Krynica-Zdrój
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2 Krynica-Zdrój
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3 Krynica-Zdrój
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4 Rabka-Zdrój
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5 Rabka-Zdrój
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7 Klimkówka
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9 Iwonicz-Zdrój
Elin 7 10 47 94 6.7
10 Lubatówka
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