RADIOCHEMICAL INVESTIGATIONS ON NATURAL MINERAL WATERS FROM BUCOVINA REGION, ROMANIA

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1 RADIOCHEMICAL INVESTIGATIONS ON NATURAL MINERAL WATERS FROM BUCOVINA REGION, ROMANIA MARIAN ROMEO CALIN 1, ILEANA RADULESCU 1, ALINA CATRINEL ION 2, FLORINELA SIRBU 3 1 Horia Hulubei National Institute for Physics and Nuclear Engineering-IFIN HH, Department of Life and Environmental Physics, 30 Reactorului Str., P.O. Box MG-6, , Bucharest Magurele, Romania 2 University Politehnica of Bucharest, Department of Analytical Chemistry and Environmental Engineering, 6 Polizu, Str. No. 1 7, , Bucharest, Romania 3 Ilie Murgulescu Institute of Physical Chemistry of the Romanian Academy, 202 Splaiul Independentei Str., , 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 Ca 2+, Mg 2+ and HCO 3 for both carbonated and noncarbonated 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 238 U, 232 Th, 226 Ra and 40 K 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: (µsv/yr) for 40 K; for 238 U; (µsv/yr) for 232 Th and (µsv/yr) for 226 Ra. 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 , Bucharest, 2016

2 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 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: ) and ph (DIN : , C5) were immediately analyzed after opening the bottles. Analytical method: IC standardized method SR EN ISO : 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 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 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 controlboard 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 (T 1/2 = ± 0.60 years) and of 90 (Sr-Y) beta source (T 1/2 = ± 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 probedetector. 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 = ± 0.69 (%) the beta efficiency, where the spillover factor is = ± 0.50 (%) and measuring geometry up alpha beta = ± 0.29 (%) the alpha efficiency and = ±

4 1054 Marian Romeo Calin et al. 4 ± 0.74 (%) the beta efficiency, where the spillover factor is = ± 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 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 cm 3 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 kev for 241 Am to kev for 152 Eu) and allow the construction of an empirical efficiency curve versus the energy of interest (from kev for 210 Pb to 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 (Ca 2+, Mg 2+, Na +, K +, HCO 3, SO 4 2, Cl, F and NO 3 ), 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: Ca 2+, Mg 2+ and HCO 3 : CaMg(CO 3 ) 2 + H 2 O- Ca 2+ + Mg HCO 3 CaCO 3 + H 2 0- Ca 2+ + HCO 3 + 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. (1)

5 5 Radiochemical investigations on natural mineral waters from Bucovina region 1055 Ukraine Hungary Moldova ROMANIA NORTH Serbia Bulgaria Black Sea 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 µg/l, , 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 Cl 2 (S/cm) SO (mg/l) 2 2 HCO 3 Ca Mg Na K CO 2 NO3 - Dry rez., 4 (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) Diss. free (mg/l) (mg/l) MW < MW MW MW MW MW , , MW MW MW O 2 From the data it can be observed that the ph varies in the range , in correlation with the CO 2 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 CO 2 in HCO 3. The groundwater composition is dominated by HCO 3, as well as by Ca 2+

6 1056 Marian Romeo Calin et al. 6 and Mg 2+, as reflected by the values of the electrical conductivity. The studied natural carbonated and non-carbonated mineral waters are Ca-Mg-HCO 3 ones, the correlation between the HCO 3 (mg/l) versus conductivity for the dataset depict the contribution of HCO 3 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. 2 SO 4 present in the samples shows that the composition is influenced by a volcanic contribution explained by the SO 2 4 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 2 no sulphates in its geochemical composition. The important spread of SO 4 concentrations could shows a possible connection with the seasonal temperatures. The alkali metals present are randomly correlated with HCO 3, the data depicting a large excess of HCO 3 in relation with Na + and K +. The data suggests mineralization processes specific to carbonate rocks, but also it indicates that a part of the HCO 3 is derived from the CO 2 in the soil. The enrichment in alkalis may be attributed to silicate weathering, which also contributes to increased HCO 3 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 Ca 2+, Mg 2+ and HCO 3 being specific to their chemical compositions. The relation between alkali-earth and HCO 3 shows a dependence suggesting a basic rock aquifer reach in Ca 2+, Mg 2+ and HCO 3 species and a stronger correlation between their concentrations. All the samples display Mg 2+ contents above 10% of the cations, but the dominant one remains Ca 2+, the ratio between these two cations being always constant. The greater release rate of Ca 2+

7 7 Radiochemical investigations on natural mineral waters from Bucovina region 1057 compared to Mg 2+ 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 Ca 2+ energetically favorable [20], this being more common in natural systems. The higher dissolved uranium concentration in underground waters is associated with HCO 3 content, uranium presenting a higher solubility based on complex formation with carbonates. The correlation between the gross alpha activity and the HCO 3 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 Ca 2+ and Mg 2+ 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 CO 2 of the water infiltrating into the aquifer for carbonated sources [21 23]. Zn 2+ present in the studied mineral waters in a range of concentrations mg/l alters the dissolution rate as well as the ratio of release of Ca 2+ to Mg 2+ and the application of rate constants to natural systems in comparison with the synthetic ones with a simplified aqueous chemistry [24, 25] 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 mbq/l for gross-alpha, 1.51 mbq/l and mbq/l for grossbeta 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: µsv/yr with a mean value of µsv/yr in 2012; µsv/yr with a mean value of in 2013; 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

8 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 Sample code Residue [g/l] Gross Alpha [mbq/l] Gross Beta [mbq/l] Annual Effective Dose D EFF [µsv/year] Year MW ± ± MW ± ± MW ± ± 1.40 nd nd 8.98 MW ± ± MW ± ± 2.18 nd MW ± ± 1.40 nd nd 9.35 MW ± ± 3.14 nd MW ± ± 0.34 nd nd MW ± ± 0.70 nd 2.37 nd Mean ± 1σ Range ± ± MDA MDA 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 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].

9 9 Radiochemical investigations on natural mineral waters from Bucovina region K 2500 Activity concentration (mbq/l) Austria [36] Italy [27] Poland [29] Romania [32] Spain [30] Turkey [33] Fig K activity concentrations range in natural mineral water U Activity concentration (mbq/l) Austria [36] Austria [31] Croatia [39] Finland [40] Germany [35] Grecee [38] Hungary [37] Italy [26] Italy [26] Poland [29] Romania [32] Slovenia [34] Turkey [41] Fig U activity concentrations range in natural mineral water.

10 1060 Marian Romeo Calin et al Ra Activity concentration (mbq/l) Austria [36] Austria [31] Croatia [39] Finland [40] Germany [35] Grecee [38] Hungary [37] Italy [27] Italy [26] Poland [29] Romania [32] Slovenia [34] Spain [30] Turkey [41] Fig Ra activity concentrations range in natural mineral water. For the total annual effective dose calculation, (D EFF ) equation 3 was used: D EFF = (3) where: D EFF is the annual effective ingestion dose due to relevant radionuclide in μsv/yr, C i 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], F i is the dose coefficient (conversion factors: , , and 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 F i 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 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 It can be observed the activity concentration values for 40 K is in the range of Bq/L, for 238 U of Bq/L, for 232 Th of MDA 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 40 K, 238 U, 232 Th and 226 Ra in the residue of the water samples Sample K [Bq/L] U [Bq/L] Ra Th [Bq/L] code [Bq/L] Year MW ± ± ± ± 0.03 MW ± ± ± ± 0.02 MW ± ± ± ± MW ± ± ± ± 0.02 MW ± ± <0.37 (MDA) 0.09 ± 0.04 MW ± ± 0.01 <0.03 (MDA) 0.07 ± 0.01 MW ± ± <0.37 (MDA) 0.11 ± 0.01 MW ± ± ± ± 0.03 MW ± ± <0.28 (MDA) <0.20 (MDA) Range MDA MDA 0.32 Mean ± 1σ 0.51 ± ± ± ± 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: (µsv/yr) for 40 K; for 238 U; (µsv/yr) for 232 Th and (µsv/yr) for 226 Ra.

12 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 Sample code Mean 40 K [µsv/yr] Mean 238 U [µsv/yr] Mean 232 Th [µsv/yr] Mean 226 Ra [µsv/yr] Year MW MW MW MW MW nd 8.70 MW nd 7.26 MW nd MW MW nd Nd Range 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: % from potassium, % from uranium, % from thorium and % 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. Sample code Table 5 Analysis of the dose contribution fraction from: potassium, uranium, thorium and radium Dose fraction from 40 K (%) Dose fraction From 238 U (%) Dose fraction from 232 Th (%) Dose fraction from 226 Ra (%) MW MW MW MW MW nd MW nd MW nd MW MW nd Nd Mean nd: not determined

13 13 Radiochemical investigations on natural mineral waters from Bucovina region 1063 Table 6 Dose coefficients F i of the relevant radionuclides in (nsv/bq) for three age groups 238 U 232 Th 226 Ra 40 K Age group 1 2 years years years years >17 years 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 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 HCO 3, 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 Bq/L to about Bq/L, 40 K between Bq/L and 238 U of Bq/L. The results obtained are very well in agreement with those reported in many European countries, as was shown in Figs 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: (µsv/yr) for 40 K, for 238 U, (µsv/yr) for 232 Th and (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 µsv/yr

14 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 /2014 and 2015, by the Romanian Ministry for Education and Research. REFERENCES 1. S. Grande, S. Risica, Radionuclides in drinking water: the recent legislative requirements of the European Union, J. Radiol. Prot , EUROPEANCOMMISSION: LIST OF NATURAL MINERAL WATERS RECOGNISED BY MEMBER STATES, en.pdf, EU Directive 1996/70/EC of the European Parliament and of the Council of 28 Oct amending Council Directive 80/777/EC on the approximation of the laws of the Member States relating to the exploitation and marketing of natural mineral waters. Off. J. Eur. Communities L299, 26-28, EU Directive 2003/40/EC, 2003 Establishing the list, concentration limits and labeling requirements for the constituents of natural mineral waters and the conditions of using ozoneenriched air for the treatment of natural mineral waters and spring waters. Off. J. Eur. Communities L 126, EU Directive 1998/83EC 1998 Council Directive 98/83/EC on the quality of water intended for human consumption Off. J. Eur. Communities L 330, FAO 1997 Codex standard for natural mineral waters Codex Stan WHO1996 Guidelines for drinking water quality Health criteria and other supporting information World Health Organization, Geneva, 973.

15 15 Radiochemical investigations on natural mineral waters from Bucovina region A.M. Odukoya, Geochemical and quality assessment of groundwater in some Nigerian basement complex, Int. J. Env. Sci. and Tech. DOI: v /s y, Directive 2009/54/EC of the European Parliament and of the Council, On the exploitation and marketing of natural mineral waters, E. Custodio, Groundwater characteristics and problems in volcanic rocks terrains in Isotopic techniques in the study of the hydrogeology of fractures and fissured rocks, IAEA, Vienna, pp World Health Organisation WHO, Guidelines for drinking water quality. 4th edition. Geneva, Switzerland, A.C. Ion, I. Ion, M.M. Antonisse, B.H.M. Snellink-Ruel, D.N. Reinhoudt, Characteristics of fluoride-selective electrode with uranyl salophen receptors in aqueous solutions, J. Russ, General Chem. 71, , I. Ion, D. Bogdan A.C. Ion, Improvement in the determination of traces of nitrate and nitrite in natural mineral waters by ion chromatography, UPB Sci. Bull. series B, 76, , O.W. Lau, S.F. Luk, A survey on the composition of mineral water and identification of natural mineral water, International J. Food Sci. Technol., 37, , V. Jobbagy, A. Dirican, U. Watjen, Radiochemical characterization of mineral waters for a European interlaboratory comparison, Microchim. J., 110, , M.R. Calin, A.E. Druker, I. Radulescu, The calculation of the detection efficiency in the calibration of gross alpha-beta systems, J Radioanal. Nucl. Chem., 295, , M.R. Calin, M.A. Calin, L. Done, A.E. Druker, A.C. Calin, Assessment of calibration parameters for gamma-ray spectrometry systems, J Radioanal. Nucl. Chem., 288, , N. Groselj, G. van der Veer, M. Tusar, M. Vracko, M. Novic, Verification of the geological origin of bottled mineral water using artificial neural networks, Food Chem., 118, , D.N. Lumsden, R.V. Lloyd, Three dolomites, J. Sediment Res., 67, , J. Titiloye, N. De Leeuw, S. Parker, Atomistic simulation of the differences between calcite and dolomite surfaces, Geochim. Cosmochim. Acta, 62, , D. Banks, B. Frengstad, A.K. Midtgard, J.R. Krog, T. Strand, The chemistry of Norwegian groundwaters: II. The chemistry of 72 groundwaters from Quaternary sedimentary aquifers, Sci. Total Environ., 222, , P.M. Dove, The dissolution kinetics of quartz in aqueous mixed cation solutions, Geochimica et Cosmochimca Acta, 63, , P.M. Dove, C.J. Nix, The influence of the alkaline earth cations, magnesium, calcium, and barium on the dissolution kinetics of quartz, Geochimica et Cosmochimica Acta, 61, , M. Gautelier, J. Schott, E.H. Oelkers, An experimental study of dolomite dissolution rates at 80 C as a function of chemical affinity and solution composition, Chem. Geol., 242, , S.M.V. Gifillan, B.S. Lollar, G. Holland, D. Blagburn, S. Stevens, M. Schoell, M. Cassidy, Z. Ding, Z. Zhou, G. Lacrampe-Couloume, Solubility trapping in formation water as dominant CO 2 sink in natural gas fields, Nature, 458, , G. Jia, G. Torri, L Magro, Concentrations of 238 U, 234 U, 235 U, 232 Th, 230 Th, 228 Th, 226 Ra, 228 Ra, 224 Ra, 210 Po, 210 Pb and 212 Pb in drinking water in Italy: reconciling safety standards based on measurements of gross α and β, J Environ. Radioact., 100, , D. Desideri, C. Roselli, L. Feduzi, M.A. Meli, Radiological characterization of drinking waters in Central Italy, Microchem J., 87, 13 19, F.A Khalil, R.M. Amin, M.A.K. El Fayoumi, Natural radioactive nuclides and chemical components in the groundwater of Beni Suef Governate, MiddleEgypt, J. Radiol. Prot., 29, , 2009.

16 1066 Marian Romeo Calin et al N.D. Chau, B. Michalec, Natural radioactivity in bottled natural spring, mineral and therapeutic waters in Poland, J Radioanal. Nucl. Chem., 279, , M. Palomo, A. Penalver, F. Borrull, C. Aguilar, Measurement of radioactivity in bottled drinking water in Spain, Appl. Radiat. Isot., 65, , G. Wallner, T. Jabbar, Natural radionuclides in Austrian bottled mineral waters, J. Radioanal.Nucl. Chem., 286, , M.R. Calin, A.C. Ion, I. Radulescu, Evaluation of quality parameters and of natural radionuclides concentrations in natural mineral water in Romania, J. Radioanal. Nucl. Chem., 303, , P. Yalcin, H. Taskin, E. Kam, M. Terzi, A. Varinlioglu, A. Bozkurt, A. Bastug, B. Tasdelen. Investigation of radioactivity level in soil and drinking water samples collected from the city of Erzincan, Turkey, J. Radioanal. Nucl. Chem., 291, , L. Benedik, Z. Jeran, Radiological of natural and mineral drinking waters in Slovenia, Radiat. Prot. Dosimetry, 151, , M. Beyermann, T. Bünger, K. Schmidt, D. Obrikat, Occurrence of natural radioactivity in public water supplies in Germany: 238 U, 234 U, 235 U, 228 Ra, 226 Ra, 222 Rn, 210 Pb, 210 Po and gross α activity concentrations, Radiat. Prot. Dosimetry, 141, 72 81, V. Gruber, F.J. Maringer, C. Landstetter, Radon and other natural radionuclides in drinking water in Austria: Measurement and assessment, Appl. Radiat. Isot., 67, , V. Jobbágy, N. Kávási, J. Somlai, B. Máté, T. Kovács, Radiochemical characterization of spring waters in Balaton Upland, Hungary, estimation of radiation dose to members of public, Microchem., J, 94, , K. Kehagia, V. Koukouliou, S. Bratakos, S. Seferlis, F. Tzoumerkas, C. Potiriadis, Radioactivity monitoring in drinking water of Attika Greece, Desalination, 213, , M. Rozmaric, M. Rogic, L. Benedik, M. Strok, Natural radionuclides in bottled drinking waters produced in Croatia and their contribution to radiation dose, Sci. Total Environ., 437, 53 60, P. Vesterbacka, I. Makelainen, H. Arvela, Natural radioactivity in drinking water in private wells in Finland, Radiat. Prot. Dosimetry, 113, , P.E. Erden, A. Dirican, M. Seferinoglu, E. Yeltepe, N.K. Sahin, 238 U, 234 U and 226 Ra concentrations in mineral waters and their contribution to the annual committed effective dose in Turkey, J Radioanal. Nucl. Chem., 301, , B. Kucukomeroglu, A. Kurnaz, N. Damla, U. Cevik, N. Celebi, B. Ataksor, H, Taskin, Environmental radioactivity assessment for Bayburt, Turkey, J. Radiol. Prot. 29, , IAEA International Basic Safety Standards for Protection against Ionizing Radiation and for Safety of Radiation Sources, Viena, United Nations Scientific Committee on the Effects of Atomic Radiation UNSCEAR. Report to the General Assembly, with scientific annexes, Vol. 1, Sources and Effects of Ionising Radiation, IAEA Safety Standards, Radiation Protection and Safety of Radiation Sources International Basic Safety Standards, Interim Edition, General Safety Requirements, Vienna, M.E. Kitto, M.S Kim, Naturally occurring radionuclides in community water supplies of New York State, Health Physics, 88, , M.E. Wrenn, P.W. Durbin, B. Howard, J. Lipsztein, J. Rundo, E.T. Still, Metabolism of ingested U and Ra, Health Physics, 48, , 1985.