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RADIOCHEMICAL INVESTIGATIONS ON NATURAL MINERAL
WATERS FROM BUCOVINA REGION, ROMANIA
MARIAN ROMEO CALIN1, ILEANA RADULESCU1, ALINA CATRINEL ION2,
FLORINELA SIRBU3
1Horia Hulubei National Institute for Physics and Nuclear Engineering-IFIN HH, Department of Life and
Environmental Physics, 30 Reactorului Str., P.O. Box MG-6, 077125, Bucharest–Magurele, Romania 2 University Politehnica of Bucharest, Department of Analytical Chemistry and Environmental
Engineering, 6 Polizu, Str. No. 1–7, 011061, Bucharest, Romania 3Ilie Murgulescu Institute of Physical Chemistry of the Romanian Academy, 202 Splaiul
Independentei Str., 060021, Bucharest, Romania
Received September 24, 2015
The access to a safe drinking water is essential to human health. In this respect,
the major ion composition, electrical conductivity and pH of nine natural mineral
drinking waters were studied. The waters originate from a volcanic aquifer containing
carbonate rocks, situated in northern part of Romania. It was found that the low
permeability of the aquifer allows a reduced infiltration of the rain water, seasonal
influence showing good chemical stability, oscillating around less than 10%.
Correlations were found between Ca2+, Mg2+ and HCO3– for both carbonated and non-
carbonated natural mineral water sources. In addition, an assessment of dose and risk
resulting from consuming these waters has been also performed. Gross alpha, gross
beta and radionuclides of natural decay chains 238U, 232Th, 226Ra and 40K activity
concentrations were measured, and the associate effective doses for these
radionuclides were determined. The results for the effective doses calculated for an
adult member of the public in Romania derived from the intake of naturally occurring
radionuclides in these waters vary between: 0.32–1.87 (µSv/yr) for 40K; 0.82–1.56 for 238U; 1.10–12.25 (µSv/yr) for 232Th and 4.49–32.70 (µSv/yr) for 226Ra. Based on this,
these waters can be recommended for regular consumption by infants and children,
too. This assessment on natural mineral water springs from the Bucovina region
updates data on the activity concentrations and effective doses due to intake of natural
radionuclides from drinking water in Romania.
Key words: ground water, major ion composition, activity concentration,
radionuclides, gross-α and gross-β, effective dose.
1. INTRODUCTION
The access to a safe drinking water is essential to human health [1]. The
European Union (EU) recognizes about 1000 brands [2] of natural mineral water and
its directives emphasize that bottled natural mineral water must be groundwater,
providing information about regional geology, characterized by its mineral content,
trace elements or other constituents and, where appropriate, by certain effects and be
clearly distinguishable from other ordinary drinking water [3–5].
Rom. Journ. Phys., Vol. 61, Nos. 5–6, P. 1051–1066, Bucharest, 2016
1052 Marian Romeo Calin et al. 2
The EU has already regulations for action levels for trace elements in bottled
water [6–8]. According to EU Directive 80/777/EEC, natural mineral waters are
defined as uncontaminated waters from underground aquifers [9], its chemical
composition resulting from chemical processes under natural conditions and
reflecting the mineralogical composition of the rocks. In this respect, the major ion
composition, electrical conductivity and pH of nine natural mineral drinking waters
are presented in this paper, on samples collected on long period of time (2.5–3
years) to study the chemical stability of these waters. For example, the higher
dissolved uranium concentration is associated with carbonate and bicarbonate
content, due to complexation [10]. In these conditions, radium behaves differently,
by precipitating with carbonates.
The paper presents data for the activity concentrations of 238
U, 232
Th, 226
Ra
and also for 40
K in nine carbonated and non-carbonated mineral waters. The study
evaluated the levels of natural radionuclides and chemical components, their
determination in ground water being useful as a direct input to environmental and
public health studies. Considering the high radiotoxicity of 226
Ra, its presence in
water and the associated health risk requires particular attention. An assessment of
the annual effective doses received from mentioned radionuclides is made, the
gross α and β activities in waters being measured for screening purposes.
According to WHO guidelines, the recommended screening levels for drinking
water below which no further action is required, are 0.5 Bq/L for gross alpha
activity and 1 Bq/L for gross beta activity [11].
This study further showed that radionuclides activity concentrations and thus
estimated annual effective ingestion doses assessed from natural bottled mineral
water consumption, whose locations are in different areas of Bucovina, vary
considerably. Since considerable amounts of natural mineral water are used in
Romania for drinking purposes, an extension of this survey to analysis of natural
mineral waters is needed to provide additional information and to get an overall
picture of the combined annual effective ingestion doses due to natural mineral
water consumption.
2. MATERIALS AND METHODS
2.1. CHEMICAL INSTRUMENTATION
The data set on the major ion composition of carbonated natural mineral
waters consists of samples from nine carbonated and non-carbonated natural
mineral waters, collected from the northern part of Romania called Bucovina
region. pH and electrical conductivity were firstly measured in 50 mL beakers,
filled with mineral water. The waters were monthly monitored and analyzed in 24
hours after sampling. Samples were filtered on 0.45 μm cellulose membrane filters,
the mineral components being analyzed by ion chromatography standardized
3 Radiochemical investigations on natural mineral waters from Bucovina region 1053
methods of analysis. Fluoride was measured using ion-selective electrodes, based
on a method previously developed in our group [12, 13]. Specific electric
conductivity (EN 27888:1993-11) and pH (DIN 38404-5:1984-01, C5) were
immediately analyzed after opening the bottles. Analytical method: IC standardized
method SR EN ISO 10304-1: 2009 IC standardized method SR EN ISO
14911:1999.
Stock standard ion solutions: 1000 mg/L are purchased as certified solutions,
or prepared from ACS 70 reagent grade, potassium or sodium, or other carbonate
salts.
All bottles were soaked in Milli-Q water, placed in an ultrasonic bath and
rinsed three times with Milli-Q water before use. An aliquot (20 mL) of the
samples was transferred into propylene vials and degassed for 30 minutes before
analysis. The instrument was calibrated weekly using external standards. A
regression fit value of over 0.995 was obtained for each element. Preparation and
analysis of samples, standards and blanks were carried out in triplicate. The method
detection limit (MDL) for the anions was calculated three times the standard
deviation of the signal of the blank sample analyzed 10 times [14]. Mineral water
samples are differently treated before analysis [15], depending on their
characteristics.
2.2. INSTRUMENTS FOR RADIOMETRIC MEASUREMENTS
Gross alpha–beta measurements were performed using the low background
system PROTEAN ORTEC MPC-2000-DP, with the following configuration:
scintillation radiation detector ZnS dual detector phosphor (zinc sulphide and
plastic), high power voltage; electronic modules for signal processing:
preamplifier, amplifier, counter; display module; operation and display control-
board equipped with LCD display; mechanical sample feeder; PC interface,
specialized software used for transferring acquired data and processing–PIC
Communicator–Protean Instrument Corporation. The system was calibrated
regarding its efficiency using sets of standard radioactive sources manufactured by
Radionuclide Metrology Laboratory (LMR IFIN-HH). One 241
Am–alpha source
(T1/2 = 432.6 ± 0.60 years) and of 90
(Sr-Y) – beta source (T1/2 = 28.80 ± 0.07 years)
were used. The working geometry used was fixed in metallic trays, inside the lead
castle system, directly facing the probe-detector for the measurement geometry UP
ALPHA + BETA manual count – the metallic tray being at 3 mm below the probe-
detector.
The calculated efficiencies of the detection were subsequently introduced in
the system for two working geometries: measuring geometry – gross alpha-beta =
= 31,37 ± 0.25 (%) – the alpha efficiency and = 44.94 ± 0.69 (%) – the beta
efficiency, where the spillover factor is = 25.59 ± 0.50 (%) and measuring
geometry up alpha – beta = 36.23 ± 0.29 (%) – the alpha efficiency and = 48.53 ±
1054 Marian Romeo Calin et al. 4
± 0.74 (%) – the beta efficiency, where the spillover factor is = 31.08 ± 0.60 (%)
[16].
The samples were measured in 10 intervals of 100 min., the total acquisition
time being 16.6 h. In addition, a measurement with empty metallic tray for this
geometry was performed to establish the background count rate.
A low background coaxial p-type HPGe detector (model GEM 25P4) with a
relative efficiency of 35% and energy resolution of 1.73 keV at 1332.5 keV for 60
Co is used for determining the activity concentrations of the 40
K, 238
U, 232
Th and
their progenies. The detector, used for environmental radiation measurements, has
a Germanium crystal with a diameter of 59.1 mm and a length of 54.1 mm,
corresponding to a volume and mass of active Germanium of 148 cm3 and 0.8 kg,
respectively. The detector is linked to a DigiDART, Ortec data acquisition system
and to a Gamma Vision spectrum analysing software tool.
The calibration of the detector for energy, peak shape and efficiency was
carried out using certified volume sources for 60
Co, 134
Cs, 137
Cs, 152
Eu and 241
Am,
supplied by the institute’s radiation metrology laboratory. These radioisotopes
cover a relatively wide energy range (from 59.54 keV for 241
Am to 1408.00 keV for 152
Eu) and allow the construction of an empirical efficiency curve versus the energy
of interest (from 46.54 keV for 210
Pb to 2614.53 keV for 208
Tl) [17]. A 10 cm
thickness lead shielding and 2 mm of copper lining is built around the detector to
diminish the contribution of environmental radioactivity to its background.
3. RESULTS AND DISCUSSION
3.1. CHEMICAL ANALYSIS RESULTS
For the water samples, the concentration of main ions (Ca2+
, Mg2+
, Na+, K
+,
HCO3–, SO4
2–, Cl, F
– and NO3
–), electrical conductivity and pH are determined
being very important as a compositional fingerprint characteristic to the local
geology and to the position of the aquifer. The original geological description of
these of these mineral waters consists of dolomite and calcite containing traces of
quartz, muscovite, biotite, goethite and limonite [18]. In the aquifer, the principal
chemical reactions mainly involve the ions: Ca2+
, Mg2+
and HCO3–:
CaMg(CO3)2 + H2O- Ca2+
+ Mg2+
+ 2HCO3–
(1)
CaCO3 + H20- Ca2+
+ HCO3–+ HO
– (2)
The natural mineral waters presented in this study (Fig. 1) have
mineralization as shown by the electrical conductivity measurements which range
from 290 to 1883 μS/cm (for non-carbonated and carbonated, respectively). Major
ion components including statistical measures are presented in Table 1.
5 Radiochemical investigations on natural mineral waters from Bucovina region 1055
ROMANIA NORTH
Hungary
Bulgaria
Serbia
Ukraine
Moldova
BlackSea
Fig. 1 – Investigated test area on Romania’s map.
The chemical analyses of the nine investigated waters indicate that elemental
concentrations of Sb, Ni and Cu, expressed in micrograms per liter (µg/L) are in
the range 0.1–0.5 µg/L, 0.1–20, 1–80, respectively. The Mn values are 1–2 µg/L
for non-carbonated waters and > 0.5 mg/L before Mn removal for the carbonated
one.
Table 1
Mineral waters chemical data: mean values of pH, electrical conductivity and major ion composition,
analyzed each month (in triplicate), for three years
Source pH C.e.µ
(S/cm)
Cl
(mg/L) 2
4SO (mg/L)
3HCO
(mg/L)
2Ca
(mg/L)
2Mg
(mg/L)
Na
(mg/L)
K
(mg/L) 2O
Diss. 2CO
free
NO3-
(mg/L)
Dry rez.,
(mg/L)
MW1 6.13 1672 3.54 21.03 1220.2 267.25 67.0 5.02 2.48 2.43 1320 <0.1 1018.0
MW2 7.91 351.0 0.71 7.82 225.7 50.75 16.0 0.54 1.19 10.53 3.96 0.67 185.0
MW3 7.97 352 1.06 11.60 213.5 49.60 16.40 0.78 0.69 10.20 3.30 6.44 186
MW4 7.88 334.0 0.71 11.11 204.4 47.40 14.60 0.82 1.25 9.88 3.52 3.49 171.0
MW5 7.85 313.0 0.71 10.74 195.2 42.90 15.80 0.55 0.45 10.37 3.30 1.86 164.0
MW6 7.83 325,0 1.06 10.0 198.3 48.12 12.70 0.90 0.74 9.56 3,30 3.92 168.0
MW7 7.83 291.0 0.71 10.28 173.8 41.95 11.10 1.04 0.71 10.04 3.52 1.84 150.0
MW8 7.83 314 1.06 11.93 195.2 49.40 12.50 0.95 0.43 10.37 4.4 3.95 191.0
MW9 7.74 305 1.06 10.24 195.2 43.50 15.60 0.54 0.57 10.29 4.4 2.17 187.0
From the data it can be observed that the pH varies in the range 6.13–7.91, in
correlation with the CO2 from the aquifer, which contributes to the slightly acidic
character of the spring. The dissolution of primary minerals is limited and the
carbonation of water may lower the pH by 1–2 units transforming the CO2 in
HCO3–. The groundwater composition is dominated by HCO3
–, as well as by Ca
2+
1056 Marian Romeo Calin et al. 6
and Mg2+
, as reflected by the values of the electrical conductivity. The studied
natural carbonated and non-carbonated mineral waters are Ca-Mg-HCO3–
ones, the
correlation between the HCO3– (mg/L) versus conductivity for the dataset depict
the contribution of HCO3– to groundwater chemistry. The conductivity values are
related to total dissolved solid of this natural mineral water (Fig. 2).
Fig. 2 – Conductivity values versus total dissolved solid of natural mineral water.
SO42–
present in the samples shows that the composition is influenced by a
volcanic contribution explained by the SO42–
enrichment by oxidation of reduced S
species from volatile releases. The main source of the sulphate ions present in the
chemical composition of the studied water is the rain, the aquifer itself containing
no sulphates in its geochemical composition. The important spread of SO42–
concentrations could shows a possible connection with the seasonal temperatures.
The alkali metals present are randomly correlated with HCO3–, the data
depicting a large excess of HCO3– in relation with Na
+ and K
+. The data suggests
mineralization processes specific to carbonate rocks, but also it indicates that a part
of the HCO3– is derived from the CO2 in the soil. The enrichment in alkalis may be
attributed to silicate weathering, which also contributes to increased HCO3–
content. It was observed a correlation between the K+
concentration and the beta
activity, because 40
K significantly contributes to the gross beta activity.
In contact with the carbonate rocks, the water will partially dissolve them,
high concentrations of Ca2+
, Mg2+
and HCO3– being specific to their chemical
compositions. The relation between alkali-earth and HCO3– shows a dependence
suggesting a basic rock aquifer reach in Ca2+
, Mg2+
and HCO3– species and a
stronger correlation between their concentrations. All the samples display Mg2+
contents above 10% of the cations, but the dominant one remains Ca2+
, the ratio
between these two cations being always constant. The greater release rate of Ca2+
7 Radiochemical investigations on natural mineral waters from Bucovina region 1057
compared to Mg2+
is a function of the calcite component of the carbonates which
would preferentially dissolve over dolomite [19]. The greater length of the Ca-O
bond in comparison with the Mg-O one makes the release of Ca2+
energetically
favorable [20], this being more common in natural systems. The higher dissolved
uranium concentration in underground waters is associated with HCO3–
content,
uranium presenting a higher solubility based on complex formation with
carbonates. The correlation between the gross alpha activity and the HCO3–
concentration gave no significant results, future investigation being necessary.
The presence of alkali and alkali-earth metals does not correlate between
each other, consistent with the high water mineralization. The water of the spring
has short residence time, involving a high water-rock ratio, with almost no effect of
silicate hydrolysis. In comparison with Ca2+
and Mg2+
concentrations, the
concentrations of Na+ and K
+ are less important, K
+ content being less than 2 % in
all samples, due to the weathering of silicate and to the high content of CO2 of the
water infiltrating into the aquifer for carbonated sources [21–23]. Zn2+
present in
the studied mineral waters in a range of concentrations 0.02–0.05 mg/L alters the
dissolution rate as well as the ratio of release of Ca2+
to Mg2+
and the application of
rate constants to natural systems in comparison with the synthetic ones with a
simplified aqueous chemistry [24, 25].
3.2. RADIOMETRIC ANALYSIS RESULTS
The activity concentrations for gross alpha, gross beta, annual effective
doses and radionuclides are presented in Tables 2–5. These ranges between 0.40
mBq/L and 45.40 mBq/L for gross-alpha, 1.51 mBq/L and 47.45 mBq/L for gross-
beta activities. The results obtained for gross alpha-beta measurements provide
basic information for consumers and competent authorities concerning the internal
exposure risk due to drinking water intake. It also represents a basis for comparison
when the dose contribution from artificial radionuclides released to the
environment as a result of any human practices and accidents in the studied area
are evaluated. It was observed that it is a poor correlation between the total
dissolved solids and the dissolved alpha activity, even if the samples belong to the
same aquifer.
The results obtained for total effective doses, taking into account the measured
radionuclides in all the analysed natural mineral waters are in the range of: 17.58–
33.95 µSv/yr with a mean value of 23.02 µSv/yr in 2012; 2.37–47.37 µSv/yr with a
mean value of 20.20 in 2013; 3.68–15.45 µSv/yr with a mean value of 8.36 in 2014
(Table 2). All values are well below the reference level of the committed effective
1058 Marian Romeo Calin et al. 8
dose (100 µSv/yr) recommended by the WHO [11]. For more accurate dose
evaluation, the doses from some other important alpha and beta emitters, such as
radon should also be included.
Table 2
The activity concentration for gross alpha, gross beta and annual
effective dose for natural mineral water samples
nd: not determined.
Figures 3–5 show comparative results obtained in the case of the above
mentioned radionuclides [26–42]. The range of activity concentrations starts from
few mBq/L or detection limit up to a bit more than 1 Bq/L in case of 40
K (Fig. 3)
and 226
Ra (Fig. 5), while for 238
U this has very low values of a few mBq/L or
detection limit up to few hundreds of mBq/L (Fig. 4). Other reported values of 226
Ra activity concentrations in drinking water samples were up to 1.37 Bq/L in
[33], since for 238
U values up to 0.103 Bq/L were measured in [27]. In the case of 232
Th, there aren’t many reference values reported in the scientific literature, so
comparative data are not presented. However, the reported values for 232
Th in for
drinking water are comparable to the values reported in [28].
Sample
code
Residue
[g/L]
Gross Alpha
[mBq/L]
Gross Beta
[mBq/L]
Annual Effective Dose
DEFF[µSv/year]
Year 2012-2014 2012 2013 2014
MW1 1.0007 30.93 ± 2.41 1.84 ± 0.08 33.95 47.37 15.45
MW2 0.1963 2.10 ± 0.76 7.45 ± 1.40 17.97 13.86 5.44
MW3 0.1871 0.40 ± 0.20 4.80 ± 1.40 nd nd 8.98
MW4 0.1872 4.05 ± 1.70 47.45 ± 18 22.53 6.45 6.54
MW5 0.1821 2.35 ± 1.05 16 ± 2.18 nd 12.01 9.05
MW6 0.1428 5.30± 2.60 4.80 ± 1.40 nd nd 9.35
MW7 0.1515 1.55 ± 0.41 12.9 ± 3.14 nd 19.22 3.68
MW8 1.5370 45.40 ± 5.50 5.28 ± 0.34 nd 40.06 nd
MW9 0.2886 17.10 ± 7.80 1.51 ± 0.70 nd 2.37 nd
Mean
± 1σ 0.3866 12.13 ± 5.49 11.34 ± 4.08 23.02 20.20 8.36
Range 0.1428 –
1.0007 MDA – 45.40 MDA – 47.45
17.58–
33.95
2.37–
47.37
3.68–
15.45
9 Radiochemical investigations on natural mineral waters from Bucovina region 1059
Austria [36] Italy [27] Poland [29] Romania [32] Spain [30] Turkey [33]
0
500
1000
1500
2000
2500
40
K
Acti
vit
y c
on
cen
trati
on
(m
Bq
/L)
Fig. 3 – 40K activity concentrations range in natural mineral water.
Aust
ria
[36]
Aust
ria
[31]
Cro
atia
[39
]
Fin
land [40
]
Ger
man
y [3
5]
Gre
cee
[38]
Hungar
y [3
7]
Ital
y [2
6]
Ital
y [2
6]
Pola
nd [29
]
Rom
ania
[32
]
Slo
venia
[34
]
Turk
ey [41
]
0
50
100
150
200
250
300 238
U
Acti
vit
y c
on
cen
trati
on
(m
Bq
/L)
Fig. 4 – 238U activity concentrations range in natural mineral water.
1060 Marian Romeo Calin et al. 10
Aus
tria [3
6]
Aus
tria [3
1]
Cro
atia [3
9]
Finl
and
[40]
Ger
man
y [3
5]
Gre
cee [3
8]
Hun
gary
[37]
Italy [2
7]
Italy [2
6]
Polan
d [2
9]
Rom
ania [3
2]
Slove
nia [3
4]
Spain
[30]
Turk
ey [4
1]
0
200
400
600
800
1000
1200
1400
1600
226
Ra
Acti
vit
y c
on
cen
trati
on
(m
Bq
/L)
Fig. 5 – 226Ra activity concentrations range in natural mineral water.
For the total annual effective dose calculation, (DEFF) equation 3 was used:
DEFF = (3)
where: DEFF is the annual effective ingestion dose due to relevant radionuclide in
μSv/yr, Ci is radionuclide activity concentration in the water sample in Bq/L, K is
the annual consumption rate of 150 L/yr for infants, 350 L/yr for children and 500
L/yr for adults, respectively, according to the ICRP, IAEA, WHO and UNSCEAR
[11, 44–45], Fi is the dose coefficient (conversion factors: 2.8×10–7
, 2.3×10–7
,
4.5×10–8
and 6.2×10–9
Sv/Bq for 226
Ra, 232
Th, 238
U and 40
K of the relevant
radionuclide for each age group given in the International Basic Safety Standards
for Protection against Ionizing Radiation and for Safety of Radiation Sources). In
the calculation of the total effective doses, per member of the public in Romania,
resulting from intake of naturally occurring alpha or beta radionuclides in drinking
water has been considered an average consumption of 1 litre per day × 365 days,
and the Fi coefficients.
Table 2 presents the amount of residue remaining after evaporation (slow
evaporation) of 5 L of water, too. The amount of residue after evaporation is higher
11 Radiochemical investigations on natural mineral waters from Bucovina region 1061
for MW1 sample than for other mineral natural water samples, this first sample
being mineral natural carbonated water.
Table 3 presents the activity concentrations of 40
K, 238
U, 232
Th and 226
Ra in
the residue of the water samples for the time interval 2012–2014. It can be
observed the activity concentration values for 40
K is in the range of 0.14–0.87
Bq/L, for 238
U of 0.050–0.17 Bq/L, for 232
Th of MDA-0.047 Bq/L and for 226
Ra of
MDA-0.32 Bq/L (Table 4).
Regarding the variation of activity concentrations (Tables 2 and 3) of water
samples analysed, this is fairly constant for the three years. However, it can be
noticed in the results of gross alpha, gross beta, and gamma spectrometry analyses
a slight decrease with time. As can be observed from Table 3, the measured activity
concentrations of 232
Th on water samples are in many cases extremely low, below
the minimum detectable activity (MDA) of the system used in the laboratory. The
same can be observed in Table 4 for the average of total effective doses of adult
member of the public.
Table 3
The activity concentrations of 40K, 238U, 232Th and 226Ra
in the residue of the water samples
Sample
code 40K [Bq/L] 238U [Bq/L] 232Th [Bq/L]
226Ra
[Bq/L]
Year 2012–2014
MW1 0.77 ± 0.09 0.086 ± 0.010 0.020 ± 0.003 0.28 ± 0.03
MW2 0.60 ± 0.06 0.095 ± 0.011 0.008 ± 0.001 0.09 ± 0.02
MW3 0.14 ± 0.03 0.070 ± 0.008 0.036 ± 0.004 0.044 ± 0.005
MW4 0.57 ± 0.06 0.081 ± 0.007 0.013 ± 0.002 0.09 ± 0.02
MW5 0.35 ± 0.04 0.064 ± 0.007 <0.37 (MDA) 0.09 ± 0.04
MW6 0.27 ± 0.03 0.09 ± 0.01 <0.03 (MDA) 0.07 ± 0.01
MW7 0.27 ± 0.03 0.050 ± 0.006 <0.37 (MDA) 0.11 ± 0.01
MW8 0.87 ± 0.08 0.088 ± 0.010 0.047 ± 0.005 0.32 ± 0.03
MW9 0.61 ± 0.06 0.060 ± 0.005 <0.28 (MDA) <0.20 (MDA)
Range 0.14–0.87 0.050–0.095 MDA –0.047 MDA –0.32
Mean ± 1σ 0.51 ± 0.10 0.085 ± 0.02 0.025 ± 0.005 0.14 ± 0.04
Table 4 shows the total effective doses per each years for an adult member
of the public in Romania resulting from intake of naturally occurring alpha or beta
radionuclides (40
K, 238
U, 232
Th and 226
Ra) in drinking water. The mean effective
doses (Table 3) are: 0.32–1.87 (µSv/yr) for 40
K; 0.82–1.56 for 238
U; 1.10–12.25
(µSv/yr) for 232
Th and 4.49–32.70 (µSv/yr) for 226
Ra.
1062 Marian Romeo Calin et al. 12
Table 4
Total effective doses for an adult member of the public in Bucovina-Romania resulting from intake of
naturally occurring alpha or beta radionuclides in natural mineral water
Table 5 presents the analysis of the dose contribution fractions from
potassium, uranium, thorium and radium. The dose contribution fractions of the
analysed water samples are in the following order: 12.11 % from potassium, 13.01
% from uranium, 19.07 % from thorium and 72.32 % from radium.
The higher contribution ratios of 226
Ra are connected to the higher water
solubility of radium than its thorium and uranium precursors [46–47]. 226
Ra is a
radiotoxic radionuclide which can be adsorbed in soft tissues and bones. For 226
Ra
the measured values are not higher than in other European countries, such as
Hungary, Poland and Spain, as it can be observed from Fig. 5.
Table 5
Analysis of the dose contribution fraction from: potassium, uranium, thorium and radium
Sample
code
Dose fraction
from40K (%)
Dose fraction
From 238U (%)
Dose fraction
from232Th (%)
Dose fraction
from226Ra (%)
MW1 3.79 3.23 27.87 65.12
MW2 9.85 11.38 14.08 64.70
MW3 3.49 12.55 34.93 49.01
MW4 10.18 11.75 8.61 69.46
MW5 7.50 9.96 nd 82.54
MW6 6.52 15.82 nd 77.64
MW7 5.01 6.74 nd 88.25
MW8 4.68 3.63 9.88 81.81
MW9 57.98 42.02 nd Nd
Mean 12.11 13.01 19.07 72.32
nd: not determined
Sample
code
Mean 40K
[µSv/yr]
Mean 238U
[µSv/yr]
Mean 232Th
[µSv/yr]
Mean 226Ra
[µSv/yr]
Year 2012–2015
MW1 1.66 1.42 12.25 28.62
MW2 1.35 1.56 1.93 8.87
MW3 0.32 1.15 3.20 4.49
MW4 1.30 1.50 1.10 8.87
MW5 0.79 1.05 nd 8.70
MW6 0.61 1.48 nd 7.26
MW7 0.61 0.82 nd 10.74
MW8 1.87 1.45 3.95 32.70
MW9 1.38 1.00 nd Nd
Range 0.32–1.87 0.82–1.56 1.10–12.25 4.49–32.70
13 Radiochemical investigations on natural mineral waters from Bucovina region 1063
Table 6
Dose coefficients Fi of the relevant radionuclides in (nSv/Bq) for three age groups
Age group 238U 232Th 226Ra 40K
1–2 years 120 450 960 42
2–7 years 80 350 620 21
7–12 years 68 290 800 13
12–17 years 67 250 150 7.6
>17 years 45 230 280 6.2
In the calculation of the total effective doses, per member of the public in
Romania, resulting from intake of naturally occurring alpha or beta radionuclides
in drinking water has been considered an average consumption of 1 litre per day ×
365 days, and the Fi coefficients given in Table 6.
4. CONCLUSIONS
Chemical and radiochemical characterization of nine natural mineral
carbonated and non-carbonated waters was performed. Samples were collected
during three years in order to identify the trends of the chemical and radiochemical
evolution. The evaluation with time over the chemical composition of the studied
mineral water shows good chemical stability oscillating around less than 10%. It
was also observed that the low permeability of the aquifer allows a reduced
infiltration of the rain water. In the aquifers containing carbonate rocks, the waters
present higher concentrations of alkali-earth metals in correlation with HCO3–,
which is less correlated with the reduced amounts of Na+ and K
+ from these rocks,
but well-correlated with uranium and radium solubility in radiometric analysis.
The content of natural radionuclides such as 40
K, 238
U, 232
Th and 226
Ra in
these natural mineral waters has also been investigated, showing that natural
radioactivity levels vary in a broad range. The 226
Ra radionuclide content varies
from 0.07 Bq/L to about 0.32 Bq/L. The 226
Ra radionuclide, with a half-life of 1630
years, can supply important scientific information concerning mechanisms and
rates of water–rock interaction and transport of this element in aquifers. The 232
Th
isotopes content varies from 0.008 Bq/L to about 0.047 Bq/L, 40
K between
0.14–0.87 Bq/L and 238
U of 0.050–0.095 Bq/L. The results obtained are very well
in agreement with those reported in many European countries, as was shown in
Figs. 2–4. The results obtained for the total effective doses for an adult member of
the public in Romania resulting from intake of naturally occurring alpha or beta
radionuclides in natural water, are: 0.32–1.87 (µSv/yr) for 40
K,0.82–1.56 for 238
U,
1.10–12.25 (µSv/yr) for 232
Th and 4.49–32.70 (µSv/yr) for 226
Ra. Taking into
account the measured radionuclides listed above, the mean annual effective doses
for all the analysed drinking water samples are in the range of 2.37–47.37 µSv/yr
1064 Marian Romeo Calin et al. 14
(Table 3), all being well below the reference level of the committed effective dose
(100 µSv/yr) recommended by the WHO.
Relatively small variations of the concentrations of 226
Ra, 232
Th and 40
K from
one spring to another for these natural mineral carbonated and non-carbonated
water samples at the Bucovina area indicate that the origins of these waters are the
same, but that they could come from different depths and may pass through slightly
different geological layers. The application of radiometric spectrometry methods
for determination of both radionuclide activity give valuable information
concerning mutual transportation between surface, subsurface and deeply situated
natural mineral water layers.
The surveillance of the natural mineral waters has to be done continuously to
get consistent data with international rules. Analyses done on samples of natural
waters are in good agreement with the Directive 2009/54/EC of the European
Parliament. The obtained data can provide basic information for consumers and
competent authorities to be aware of the actual problem of radiation. Records on
the activity concentrations and effective doses due to intake of natural
radionuclides from natural mineral water must be updated as some of the data are
older than 20 years. In all these last 20 years many suppliers of natural mineral
water have appeared on the market and more important new springs are in used.
Acknowledgments. This study was supported by the PNCDI II Program, Project No. PN 09 37
03 01/2014 and 2015, by the Romanian Ministry for Education and Research.
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