Natural alpha emitting radionuclides in bottled drinking water, mineral ...
Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water Benedik, Ljudmila; Jeran, Zvonka Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, SLOVENIA
Abstract Quantitative information about the activity concentrations of critical alphaemitting radionuclides in food and drink is important in the study of cumulative radiation effects on human health. In most countries there is an increasing tendency to replace tap water by consumption of commercial bottled natural and mineral water. Furthermore, various beverages as well as dietary supplements are also prepared from mineral water, not ordinary tap water. In this work tap water and bottled drinking and mineral water were collected in Slovenia and analysed in order to assess the radiation doses from 238U, 234U, 226Ra and 210Po. On the basis of radionuclide activity concentrations the internal radiation doses to individuals were assessed and are discussed together with the contribution of each particular radionuclide to the dose. Introduction In most European countries, there is an increasing tendency in population to replace tap water of satisfactory quality for human consumption with commercial bottled natural and mineral water. Moreover, various beverages are also prepared from mineral water, not ordinary tap water. Systematic studies on radiological characterisation of drinking water started after 1993, when the recommendations of the Guidelines for drinking water quality, issued by the World Health Organisation were published (WHO, 1993). These guidelines state that drinking water is safe from the radiological point of view if within the range of normal consumption (2 L per day), the annual dose rate originating from the presence of radioactive nuclides does not exceed 0.1 mSv. UNSCEAR reports (UNSCEAR, 1998, 2000) estimated that exposure to natural sources contributes more than 98 % of the radiation dose to the population (medical treatment is not taken into account). The main contribution to dose is largely due to the presence of naturally occurring radionuclides of both the uranium and thorium decay series. Due to their high radiotoxicity, the contributions of 210Po and 228Ra to the dose are more pronounced. The dose contributions of the radionuclides are in the order: 210Po > 228Ra > 210Pb > 226 Ra > 234U > 238U > 224Ra > 235U. Increased concerns concerning the radiological quality of drinking water has led to an increased demand for real data assessment. The old drinking water regulation 980/778/EEC from 1980 (EC, 1980) in which neither radioactivity nor uranium were mentioned, were replaced by the European Directive
Proceedings of Third European IRPA Congress 2010 June 14−16, Helsinki, Finland
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Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
98/83/EC in 1998 (EC,1998). In this Directive, the reference dose level of committed annual effective dose due to drinking water consumption is 0.1 mSv. The Directive points out that the total indicative dose must be evaluated excluding tritium, 40K, 14C, radon and its decay products, but including all other radionuclides of the natural decay chains. The maximum values for radon and long-lived radon decay products such as 210 Pb and 210Po are proposed in the European Commission Recommendation 2001/928/Euratom (EC, 2001). Uranium is covered by the Directive, although its contribution to the dose is minor due its small dose conversion factor. However, uranium is a toxic heavy metal and therefore has to be regulated and controlled. The WHO set the most stringent limitation of 2 µg/L in its 1998 report (WHO, 1998), but later (WHO, 2004) changed this limit to 15 µg/L; the USA (EPA, 2000) set the limit to 20 µg/L. Recently, Germany set the uranium limit of 2 µg/L for mineral water considered suitable for infants (Bundesgesetzblatt, 2006). Considering the importance of water for human consumption, its quality has to be assured and regularly controlled. The assessment of the radiological quality of natural or bottled drinking and mineral waters is also important in view of assessment and reduction of the radiation exposure of the population. For practical purposes, the recommended screening levels for drinking water below which no further actions are required are 0.1 Bq/L for gross alpha activity and 1 Bq/L for gross beta activity. If these values are exceeded, determination of particular radionuclides dissolved in drinking water needs to be performed. In 2004, the WHO published the third edition of its guidelines for drinking water (WHO, 2004) in which the recommended screening level for gross alpha activity was increased from 0.1 to 0.5 Bq/L. Due to the increasing tendency in the consumption behaviour of the population to replace surface tap water of sufficient quality for human consumption with commercial bottled drinking natural and mineral water, several studies to assess the radioactivity levels in bottled drinking and mineral water were performed around Europe. The report of Weknow (Weknow, 2005) gave a good overview of radioactivity levels found in drinking water across Europe, while data on drinking water quality in Slovenia are very scarce. The experimental design of our study was to determine the activity concentrations of the alpha emitters 238U, 234U, 226Ra and 210Po in Slovenian bottled drinking and mineral water, as well as in tap water. The studied samples included bottled drinking and mineral water purchased in the period from October 2009 to March 2010, on the market in Ljubljana. All water samples originated from Slovenia. There are many companies in Slovenia producing natural drinking and mineral water from bedrock aquifers of different depths. Tap water was collected from chosen cities in Slovenia.
Materials and methods For this study we analysed three of the most frequently sold mineral waters and eight bottled drinking waters “from the shelf”. We also analysed six tap waters (Fig.1). All reagents used in the analysis were of analytical grade. The tracer solutions (232U, 209Po, 133 Ba) used in the study were prepared from calibrated solutions purchased from Analytics, Inc. (Atlanta, GA, USA). The producer maintains traceability to NIST standards. An alpha spectrometer (EG&G ORTEC) with a passivated implanted planar silicon (PIPS) semiconductor detector with an active area of 450 mm2 and 28% efficiency for a 25 mm diameter disc was used for alpha-particle spectrometric
Proceedings of Third European IRPA Congress 2010 June 14−16, Helsinki, Finland
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Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
Fig. 1. Locations of tap water and bottling facilities of selected natural and mineral waters from Slovenia.
measurements. The calibration of the detector was made with a standard radionuclide source, containing 238U, 234U, 239Pu and 241Am (code: 67978-121), obtained from Analytics, Inc. A coaxial HP Ge detector was used for measurements of the gamma emitting nuclide 133Ba. For determination of uranium radioisotopes a known amount of 232U tracer (~ 0.5 Bq) was added to the water sample which was acidified with concentrated HNO3 (3mL of acid per 1L of sample). Uranium was preconcentrated from the water samples by coprecipitation with iron(III) hydroxide at pH 9-10 using an ammonia solution. The precipitate was separated by centrifugation, washed with distilled water and dissolved in concentrated nitric acid. The solution was adjusted with distilled water to 3M HNO3 and loaded onto a UTEVA column (Eichrom Industries Inc.) (Horwitz et al., 1993) preconditioned with 5 mL 3M HNO3. The column was then washed with 3M HNO3. Thorium radioisotopes were stripped from the column with 9M and 5M HCl. Uranium radioisotopes were eluted with 15 mL 1M HCl. The microcoprecipitation method with neodymium fluoride was used for thin source preparation in the alpha spectrometric determination (Hindman, 1983, Sill and Williams, 1981). The neodymium fluoride suspension was filtered through a 25 mm diameter 0.1 μm polypropylene filter. The dry filter was mounted on a stainless steel disc. The analytical scheme for determination of 226Ra was adapted from Lozano et al. (Lozano et al., 1997). The procedure is based on coprecipitation of Pb(Ra)(Ba)SO4. The water sample was transferred to a glass beaker and acidified with concentrated H2SO4 (10 mL of sulphuric acid per 1L of sample). After addition of 133Ba tracer together with Ba-carrier, the sample was stirred for approximately 30 min. With
Proceedings of Third European IRPA Congress 2010 June 14−16, Helsinki, Finland
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Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
stirring, 30 mg Pb2+ was added in portions to allow good coprecipitation of radium and barium. After settling, the suspension was centrifuged and washed with distilled water. The PbSO4 precipitate containing radium and barium was dissolved in 4 mL 0.1M EDTA, prepared in 0.5M NaOH. For 226Ra determination 250 μg of 0.3 mg/mL Ba2+ solution was added together with 4 mL of saturated Na2SO4 solution. With stirring, 1:1 acetic acid solution was added until pH 4-5 was reached, thus precipitating BaSO4, while Pb2+ ions remained in solution. Immediately after, 0.2 mL of a 0.125 mg/mL BaSO4 suspension was added, acting as a seeding precipitate to obtain small particles. The suspension was allowed to settle for 30 min and filtered through a 25 mm 0.1μm polypropylene filter. The filter with BaSO4 deposit was dried and mounted on a stainless steel disc and measured by γ−ray spectrometry for 133Ba yield determination and by α−particle spectrometry for determination of 226Ra. For determination of 210Po in water, 209Po (~ 0.3 Bq) tracer was added to 9 L of water. After sample acidification with concentrated HCl (2 mL of acid per 1 L of sample), the radionuclides were coprecipitated with MnO2. Precipitation of MnO2 was achieved by adding KMnO4 and MnCl2 and adjusting the pH to 9 with ammonia solution. The precipitate was then dissolved with a mixture of HCl and H2O2, and adjusted with distilled water to pH 1. To prevent co-plating of other potentially interfering ions (Fe3+, Mn6+), 0.5 g of ascorbic acid was added. The spontaneous deposition of polonium on a 19 mm diameter silver disc was carried out at 90 °C for 4 hours. The Ag disc, covered on one side, was fixed in a holder and immersed in the solution (Benedik and Vreček, 2001). Polonium radioisotopes were then measured by alpha spectrometry. Based on the results of activity concentrations of the four alpha emittors in drinking water presented in Table 1, the internal doses (committed effective dose) for an adult were estimated using an annual consumption rate of 730 L/year accoording to the WHO Guidelines for Drinking Water Quality (2004) and the dose coefficients of the relevant radionuclides from the “International Basic Safety Standards for Protection against Ionizing Radiation and for Safety of Radiation Sources” (IAEA, 1996).
Results and discussion In Table 1 the results of the activity levels of 238U, 234U, 226Ra and 210Po in three different groups of drinking water, natural and mineral bottled water and tap water, are given. As seen the activity concentrations of uranium in the water samples analysed ranged from 1.1 – 57 mBq/L and 2.8 - 173 mBq/L for 238U and 234U, respectively. These values, except for the mineral water BM2 (57 and 173 mBq/L for 238U and 234U, respectively) were relatively low, comparable with some literature data from Italy (Jia and Torri, 2007) and well below the limit values (98/83/EC, 2004, WHO,2004). The lowest absolute values were found in tap waters; however, somewhat elevated levels were measured in three bottled natural waters originating from the east (BN1, BN2) and south (BN3) of the country. 226 Ra (Table 1) was in the range between 0.14 -31.7 mBq/L and like uranium, can be regarded as low and comparable with data reported for Europe (Weknow, 2005). The highest absolute level of 32 mBq/L was found in a bottled natural water (BN1) which also had an elevated uranium level. Elevated activity concentrations higher than 10 mBq/L were found in two mineral (BM2, BM3) and two bottled natural Proceedings of Third European IRPA Congress 2010 June 14−16, Helsinki, Finland
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Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
Table 1. Radionuclide activity concentrations (mBq/L) in natural and mineral bottled water and tap water collected in Slovenia. Sample
Type of sample
U-238
U-234
Ra-226
Po-210
BN1
Natural water
28 ± 3
71± 8
32 ± 4
1,1 ± 0,4
BN2
18 ± 1
57 ± 6
11 ± 1
2,1 ± 0,3
BN3
13 ± 2
15 ± 2
1,7 ± 0,2
0,9 ± 0,2
BN4
2,2 ± 0,5
3,5 ± 0,7
2,3 ± 0,3
0,43 ± 0,12
BN5
8,3 ± 1,1
12 ± 1
0,14 ± 0,05
2,0 ± 0,4
BN6
2,9 ± 0,5
13 ± 2
6,8 ± 0,8
1,2 ±0,3
BN7
5,1 ± 0,6
14 ± 2
16 ± 2
0,24 ± 0,07
BN8
4,2 ± 0,6
8,7 ± 1,2
15 ± 2
0,6 ± 0,2
1,1 ± 0,2
2,8 ± 0,5
2,4 ± 0,3
0,39 ± 0,11
BM2
57 ± 9
173 ± 28
12 ± 2
1,0 ± 0,3
BM3
5,2 ± 1,8
12 ± 2
17 ± 2
0,6 ± 0,1
7,2 ± 0,7
8,5 ± 0,8
1,0 ± 0,2
0,25 ± 0,06
T2
4,8 ± 0,9
6,9 ± 1,1
0,47 ± 0,10
1,0 ± 0,2
T3
6,7 ± 1,1
11 ± 2
1,3 ± 0,1
0,77 ± 0,16
T4
8,2 ± 2,8
8,8 ± 2,9
15 ± 2
1,1 ± 0,2
T5
7,0 ± 0,9
11 ± 1
1,4 ± 0,1
1,8 ± 0,4
T6
1,1 ± 0,3
3,0 ± 0,5
0,30 ± 0,03
0,67 ± 0,19
BM1
T1
Mineral water
Tap water
waters (BN7, BN8) coming from the same region in the eastern part of the country (Fig.1), known for its thermal and mineral springs and spas. With the exception of one sample (T4), tap water had low levels of 226Ra in a narrow range between 0.3-and 1.4 mBq/L. Among the alpha emitters analysed 210Po has the lowest activity concentrations in the range between 0.24-2.1 mBq/L in all three groups of drinking water. In Fig.2 the results of the calculated total effective doses (µSv/a) for adults drinking different types of water are presented. It is seen that doses are on average very low, in the range of 1-11 (µSv/a) and only by drinking for a whole year one mineral (BM2) or one natural bottled water (BN1) would the person obtain a dose higher than Proceedings of Third European IRPA Congress 2010 June 14−16, Helsinki, Finland
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Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
10 µSv/a, which still represents only one tenth of the recommended reference dose level (RDL) of 0.1 mSv from 1 year´s consumption of drinking water (EC 1998).
Fig.2: Total internal dose ( µSv/a) to adult member of the public due to drinking different types of water.
The contribution of each analysed radionuclide to the annual total internal dose varies among different types of water samples, but on average in natural bottled waters the contributions were in the order 226Ra (mean: 46 ± 28%) > 210Po (27 ± 22%) > 234U (19 ±8%) >238U (8 ± 6%) (Fig.3). In mineral water the order was similar (Fig.3). Only in the mineral water BM2 did 234U contribute more than 54%, followed by 226Ra (22 %), 238U (16%) and 210Po (8%). In tap water 210Po (mean: 48 ± 23%) was the main radionuclide contributing to total dose due to its high dose conversion factor. bottled natural water
Po-210 27%
Po-210 18%
U-238 8% U-234 19%
Ra-226 46%
Tap water
bottled mineral water
U-238 8%
U-238 12% U-234 25%
Ra-226 49%
Po-210 48%
U-234 18%
Ra-226 22%
Fig.3 The average contribution (%) of alpha radionuclides to internal commited effective doses to adult members of the public drinking different types of water.
Proceedings of Third European IRPA Congress 2010 June 14−16, Helsinki, Finland
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Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
Conclusions The present study was a pilot study where only four selected alpha emitters were analysed in different drinking waters from Slovenia. From the survey it is evident that the activity concentrations, with the exception of one mineral and two natural drinking waters, were very low also leading to low calculated internal doses which constitute only a few percent of the recommended reference dose level (RDL) of 0.1 mSv. However, beside the analysed radionuclides there are also some other radio isotopes, namely the long- lived radon decay products 210Pb and 228Ra, which both have high dose conversion factors and should be determined and included in dose estimations in the future. References Benedik, L., Vreček, P. Determination of 210Pb and Acta Chimica Slovenica,2001, 48, p. 199-213.
210
Po in environmental samples.
Bundesgesetzblatt Nr. 56. Seite 2762 (2006) Deutche Mineral und Tafelwasserverordnung, 2006. Environmental Protection Agency (EPA) December 7, 2000. Proposed drinking water Standards. US EPA 65 FR 76707, 2000.
European Commission (EC), Council Directive of 15 July 1980 relating to the quality of water intended for human consumption. Official Journal of the European Communities L. 229, 30.8.1980, p. 11-29, 1980. European Commission (EC), Council Directive 98/83/EC of 3 November. The quality of water intended for human consumption. Official Journal of the European Communities L. 330, 5.12.1998, p. 32-54, 1998. European Commission (EC), Commission Recommendation of 20 December on the protection of the public against exposure to radon in drinking water supplies, 2001/928/EURATOM. L.344, 28.12.2001, p. 85-88, 2001. Hindman, F.D. Neodymium Fluoride Mounting for Alpha Spectrometric Determination of Uranium, Plutonium and Americium, Anal. Chem., 1983, 55, 2460-2461 Horwitz, E.P., Chiarizia, R., Dietz, M.L., Diamond, H. Separation and preconcentration of actinides from acidic media by extraction chromatography. Anal. Chim. Acta, 1993, 281, p. 361-372. International Atomic Energy Agency (IAEA). International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources. Safety Report Series, No. 115, Vienna, 1996. Jia, G., Torri, G. Estimation of radiation doses to members of the public in Italy from intakes of some important naturally occurring radionuclides (238U, 234U, 235U, 226 Ra, 238Ra, 224Ra and 210Po) in drinking water. Applied Radiation and Isotopes 65 (2007) 849-857. Sill, C.W., Williams, R.L. Preparation of Actinides for Alpha Spectrometry without Electrodeposition, Anal. Chem., 1981, 53, p. 421-415. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), Sources and Effects of Ionising Radiation, United Nations, New York; 1998. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), Sources and Effects of Ionising Radiation, United Nations, New York; 2000. Proceedings of Third European IRPA Congress 2010 June 14−16, Helsinki, Finland
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Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
WEKNOW/ENDWARE, (Weknow, 2005), Radioactivity in European Drinking Water and Sources Designated for the Production of Drinking water, Available from: http://www.weknow-waternetwork.com/uploads/booklets/04 radioactivity_eu_drw_ver juni2005.pdf, 2005.
World Health Organization (WHO), Guidelines for Drinking Water Quality, Recommendation, second edition, vol. 1. WHO, Geneva; 1993. World Health Organisation (WHO), Health Criteria and Other Supporting Information. In: Guidelines for Drinking-Water Quality, second ed., Addendum to vol. 2, WHO, Geneve, 1998. World Health Organisation (WHO), Guidelines for Drinking Water Quality. WHO, Geneve, Available from: http://www.who.int/water_sanitation_health/, 2004.
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Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water Benedik, Ljudmila; Jeran, Zvonka Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, SLOVENIA
Abstract Quantitative information about the activity concentrations of critical alphaemitting radionuclides in food and drink is important in the study of cumulative radiation effects on human health. In most countries there is an increasing tendency to replace tap water by consumption of commercial bottled natural and mineral water. Furthermore, various beverages as well as dietary supplements are also prepared from mineral water, not ordinary tap water. In this work tap water and bottled drinking and mineral water were collected in Slovenia and analysed in order to assess the radiation doses from 238U, 234U, 226Ra and 210Po. On the basis of radionuclide activity concentrations the internal radiation doses to individuals were assessed and are discussed together with the contribution of each particular radionuclide to the dose. Introduction In most European countries, there is an increasing tendency in population to replace tap water of satisfactory quality for human consumption with commercial bottled natural and mineral water. Moreover, various beverages are also prepared from mineral water, not ordinary tap water. Systematic studies on radiological characterisation of drinking water started after 1993, when the recommendations of the Guidelines for drinking water quality, issued by the World Health Organisation were published (WHO, 1993). These guidelines state that drinking water is safe from the radiological point of view if within the range of normal consumption (2 L per day), the annual dose rate originating from the presence of radioactive nuclides does not exceed 0.1 mSv. UNSCEAR reports (UNSCEAR, 1998, 2000) estimated that exposure to natural sources contributes more than 98 % of the radiation dose to the population (medical treatment is not taken into account). The main contribution to dose is largely due to the presence of naturally occurring radionuclides of both the uranium and thorium decay series. Due to their high radiotoxicity, the contributions of 210Po and 228Ra to the dose are more pronounced. The dose contributions of the radionuclides are in the order: 210Po > 228Ra > 210Pb > 226 Ra > 234U > 238U > 224Ra > 235U. Increased concerns concerning the radiological quality of drinking water has led to an increased demand for real data assessment. The old drinking water regulation 980/778/EEC from 1980 (EC, 1980) in which neither radioactivity nor uranium were mentioned, were replaced by the European Directive
Proceedings of Third European IRPA Congress 2010 June 14−16, Helsinki, Finland
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Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
98/83/EC in 1998 (EC,1998). In this Directive, the reference dose level of committed annual effective dose due to drinking water consumption is 0.1 mSv. The Directive points out that the total indicative dose must be evaluated excluding tritium, 40K, 14C, radon and its decay products, but including all other radionuclides of the natural decay chains. The maximum values for radon and long-lived radon decay products such as 210 Pb and 210Po are proposed in the European Commission Recommendation 2001/928/Euratom (EC, 2001). Uranium is covered by the Directive, although its contribution to the dose is minor due its small dose conversion factor. However, uranium is a toxic heavy metal and therefore has to be regulated and controlled. The WHO set the most stringent limitation of 2 µg/L in its 1998 report (WHO, 1998), but later (WHO, 2004) changed this limit to 15 µg/L; the USA (EPA, 2000) set the limit to 20 µg/L. Recently, Germany set the uranium limit of 2 µg/L for mineral water considered suitable for infants (Bundesgesetzblatt, 2006). Considering the importance of water for human consumption, its quality has to be assured and regularly controlled. The assessment of the radiological quality of natural or bottled drinking and mineral waters is also important in view of assessment and reduction of the radiation exposure of the population. For practical purposes, the recommended screening levels for drinking water below which no further actions are required are 0.1 Bq/L for gross alpha activity and 1 Bq/L for gross beta activity. If these values are exceeded, determination of particular radionuclides dissolved in drinking water needs to be performed. In 2004, the WHO published the third edition of its guidelines for drinking water (WHO, 2004) in which the recommended screening level for gross alpha activity was increased from 0.1 to 0.5 Bq/L. Due to the increasing tendency in the consumption behaviour of the population to replace surface tap water of sufficient quality for human consumption with commercial bottled drinking natural and mineral water, several studies to assess the radioactivity levels in bottled drinking and mineral water were performed around Europe. The report of Weknow (Weknow, 2005) gave a good overview of radioactivity levels found in drinking water across Europe, while data on drinking water quality in Slovenia are very scarce. The experimental design of our study was to determine the activity concentrations of the alpha emitters 238U, 234U, 226Ra and 210Po in Slovenian bottled drinking and mineral water, as well as in tap water. The studied samples included bottled drinking and mineral water purchased in the period from October 2009 to March 2010, on the market in Ljubljana. All water samples originated from Slovenia. There are many companies in Slovenia producing natural drinking and mineral water from bedrock aquifers of different depths. Tap water was collected from chosen cities in Slovenia.
Materials and methods For this study we analysed three of the most frequently sold mineral waters and eight bottled drinking waters “from the shelf”. We also analysed six tap waters (Fig.1). All reagents used in the analysis were of analytical grade. The tracer solutions (232U, 209Po, 133 Ba) used in the study were prepared from calibrated solutions purchased from Analytics, Inc. (Atlanta, GA, USA). The producer maintains traceability to NIST standards. An alpha spectrometer (EG&G ORTEC) with a passivated implanted planar silicon (PIPS) semiconductor detector with an active area of 450 mm2 and 28% efficiency for a 25 mm diameter disc was used for alpha-particle spectrometric
Proceedings of Third European IRPA Congress 2010 June 14−16, Helsinki, Finland
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Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
Fig. 1. Locations of tap water and bottling facilities of selected natural and mineral waters from Slovenia.
measurements. The calibration of the detector was made with a standard radionuclide source, containing 238U, 234U, 239Pu and 241Am (code: 67978-121), obtained from Analytics, Inc. A coaxial HP Ge detector was used for measurements of the gamma emitting nuclide 133Ba. For determination of uranium radioisotopes a known amount of 232U tracer (~ 0.5 Bq) was added to the water sample which was acidified with concentrated HNO3 (3mL of acid per 1L of sample). Uranium was preconcentrated from the water samples by coprecipitation with iron(III) hydroxide at pH 9-10 using an ammonia solution. The precipitate was separated by centrifugation, washed with distilled water and dissolved in concentrated nitric acid. The solution was adjusted with distilled water to 3M HNO3 and loaded onto a UTEVA column (Eichrom Industries Inc.) (Horwitz et al., 1993) preconditioned with 5 mL 3M HNO3. The column was then washed with 3M HNO3. Thorium radioisotopes were stripped from the column with 9M and 5M HCl. Uranium radioisotopes were eluted with 15 mL 1M HCl. The microcoprecipitation method with neodymium fluoride was used for thin source preparation in the alpha spectrometric determination (Hindman, 1983, Sill and Williams, 1981). The neodymium fluoride suspension was filtered through a 25 mm diameter 0.1 μm polypropylene filter. The dry filter was mounted on a stainless steel disc. The analytical scheme for determination of 226Ra was adapted from Lozano et al. (Lozano et al., 1997). The procedure is based on coprecipitation of Pb(Ra)(Ba)SO4. The water sample was transferred to a glass beaker and acidified with concentrated H2SO4 (10 mL of sulphuric acid per 1L of sample). After addition of 133Ba tracer together with Ba-carrier, the sample was stirred for approximately 30 min. With
Proceedings of Third European IRPA Congress 2010 June 14−16, Helsinki, Finland
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Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
stirring, 30 mg Pb2+ was added in portions to allow good coprecipitation of radium and barium. After settling, the suspension was centrifuged and washed with distilled water. The PbSO4 precipitate containing radium and barium was dissolved in 4 mL 0.1M EDTA, prepared in 0.5M NaOH. For 226Ra determination 250 μg of 0.3 mg/mL Ba2+ solution was added together with 4 mL of saturated Na2SO4 solution. With stirring, 1:1 acetic acid solution was added until pH 4-5 was reached, thus precipitating BaSO4, while Pb2+ ions remained in solution. Immediately after, 0.2 mL of a 0.125 mg/mL BaSO4 suspension was added, acting as a seeding precipitate to obtain small particles. The suspension was allowed to settle for 30 min and filtered through a 25 mm 0.1μm polypropylene filter. The filter with BaSO4 deposit was dried and mounted on a stainless steel disc and measured by γ−ray spectrometry for 133Ba yield determination and by α−particle spectrometry for determination of 226Ra. For determination of 210Po in water, 209Po (~ 0.3 Bq) tracer was added to 9 L of water. After sample acidification with concentrated HCl (2 mL of acid per 1 L of sample), the radionuclides were coprecipitated with MnO2. Precipitation of MnO2 was achieved by adding KMnO4 and MnCl2 and adjusting the pH to 9 with ammonia solution. The precipitate was then dissolved with a mixture of HCl and H2O2, and adjusted with distilled water to pH 1. To prevent co-plating of other potentially interfering ions (Fe3+, Mn6+), 0.5 g of ascorbic acid was added. The spontaneous deposition of polonium on a 19 mm diameter silver disc was carried out at 90 °C for 4 hours. The Ag disc, covered on one side, was fixed in a holder and immersed in the solution (Benedik and Vreček, 2001). Polonium radioisotopes were then measured by alpha spectrometry. Based on the results of activity concentrations of the four alpha emittors in drinking water presented in Table 1, the internal doses (committed effective dose) for an adult were estimated using an annual consumption rate of 730 L/year accoording to the WHO Guidelines for Drinking Water Quality (2004) and the dose coefficients of the relevant radionuclides from the “International Basic Safety Standards for Protection against Ionizing Radiation and for Safety of Radiation Sources” (IAEA, 1996).
Results and discussion In Table 1 the results of the activity levels of 238U, 234U, 226Ra and 210Po in three different groups of drinking water, natural and mineral bottled water and tap water, are given. As seen the activity concentrations of uranium in the water samples analysed ranged from 1.1 – 57 mBq/L and 2.8 - 173 mBq/L for 238U and 234U, respectively. These values, except for the mineral water BM2 (57 and 173 mBq/L for 238U and 234U, respectively) were relatively low, comparable with some literature data from Italy (Jia and Torri, 2007) and well below the limit values (98/83/EC, 2004, WHO,2004). The lowest absolute values were found in tap waters; however, somewhat elevated levels were measured in three bottled natural waters originating from the east (BN1, BN2) and south (BN3) of the country. 226 Ra (Table 1) was in the range between 0.14 -31.7 mBq/L and like uranium, can be regarded as low and comparable with data reported for Europe (Weknow, 2005). The highest absolute level of 32 mBq/L was found in a bottled natural water (BN1) which also had an elevated uranium level. Elevated activity concentrations higher than 10 mBq/L were found in two mineral (BM2, BM3) and two bottled natural Proceedings of Third European IRPA Congress 2010 June 14−16, Helsinki, Finland
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Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
Table 1. Radionuclide activity concentrations (mBq/L) in natural and mineral bottled water and tap water collected in Slovenia. Sample
Type of sample
U-238
U-234
Ra-226
Po-210
BN1
Natural water
28 ± 3
71± 8
32 ± 4
1,1 ± 0,4
BN2
18 ± 1
57 ± 6
11 ± 1
2,1 ± 0,3
BN3
13 ± 2
15 ± 2
1,7 ± 0,2
0,9 ± 0,2
BN4
2,2 ± 0,5
3,5 ± 0,7
2,3 ± 0,3
0,43 ± 0,12
BN5
8,3 ± 1,1
12 ± 1
0,14 ± 0,05
2,0 ± 0,4
BN6
2,9 ± 0,5
13 ± 2
6,8 ± 0,8
1,2 ±0,3
BN7
5,1 ± 0,6
14 ± 2
16 ± 2
0,24 ± 0,07
BN8
4,2 ± 0,6
8,7 ± 1,2
15 ± 2
0,6 ± 0,2
1,1 ± 0,2
2,8 ± 0,5
2,4 ± 0,3
0,39 ± 0,11
BM2
57 ± 9
173 ± 28
12 ± 2
1,0 ± 0,3
BM3
5,2 ± 1,8
12 ± 2
17 ± 2
0,6 ± 0,1
7,2 ± 0,7
8,5 ± 0,8
1,0 ± 0,2
0,25 ± 0,06
T2
4,8 ± 0,9
6,9 ± 1,1
0,47 ± 0,10
1,0 ± 0,2
T3
6,7 ± 1,1
11 ± 2
1,3 ± 0,1
0,77 ± 0,16
T4
8,2 ± 2,8
8,8 ± 2,9
15 ± 2
1,1 ± 0,2
T5
7,0 ± 0,9
11 ± 1
1,4 ± 0,1
1,8 ± 0,4
T6
1,1 ± 0,3
3,0 ± 0,5
0,30 ± 0,03
0,67 ± 0,19
BM1
T1
Mineral water
Tap water
waters (BN7, BN8) coming from the same region in the eastern part of the country (Fig.1), known for its thermal and mineral springs and spas. With the exception of one sample (T4), tap water had low levels of 226Ra in a narrow range between 0.3-and 1.4 mBq/L. Among the alpha emitters analysed 210Po has the lowest activity concentrations in the range between 0.24-2.1 mBq/L in all three groups of drinking water. In Fig.2 the results of the calculated total effective doses (µSv/a) for adults drinking different types of water are presented. It is seen that doses are on average very low, in the range of 1-11 (µSv/a) and only by drinking for a whole year one mineral (BM2) or one natural bottled water (BN1) would the person obtain a dose higher than Proceedings of Third European IRPA Congress 2010 June 14−16, Helsinki, Finland
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Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
10 µSv/a, which still represents only one tenth of the recommended reference dose level (RDL) of 0.1 mSv from 1 year´s consumption of drinking water (EC 1998).
Fig.2: Total internal dose ( µSv/a) to adult member of the public due to drinking different types of water.
The contribution of each analysed radionuclide to the annual total internal dose varies among different types of water samples, but on average in natural bottled waters the contributions were in the order 226Ra (mean: 46 ± 28%) > 210Po (27 ± 22%) > 234U (19 ±8%) >238U (8 ± 6%) (Fig.3). In mineral water the order was similar (Fig.3). Only in the mineral water BM2 did 234U contribute more than 54%, followed by 226Ra (22 %), 238U (16%) and 210Po (8%). In tap water 210Po (mean: 48 ± 23%) was the main radionuclide contributing to total dose due to its high dose conversion factor. bottled natural water
Po-210 27%
Po-210 18%
U-238 8% U-234 19%
Ra-226 46%
Tap water
bottled mineral water
U-238 8%
U-238 12% U-234 25%
Ra-226 49%
Po-210 48%
U-234 18%
Ra-226 22%
Fig.3 The average contribution (%) of alpha radionuclides to internal commited effective doses to adult members of the public drinking different types of water.
Proceedings of Third European IRPA Congress 2010 June 14−16, Helsinki, Finland
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Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
Conclusions The present study was a pilot study where only four selected alpha emitters were analysed in different drinking waters from Slovenia. From the survey it is evident that the activity concentrations, with the exception of one mineral and two natural drinking waters, were very low also leading to low calculated internal doses which constitute only a few percent of the recommended reference dose level (RDL) of 0.1 mSv. However, beside the analysed radionuclides there are also some other radio isotopes, namely the long- lived radon decay products 210Pb and 228Ra, which both have high dose conversion factors and should be determined and included in dose estimations in the future. References Benedik, L., Vreček, P. Determination of 210Pb and Acta Chimica Slovenica,2001, 48, p. 199-213.
210
Po in environmental samples.
Bundesgesetzblatt Nr. 56. Seite 2762 (2006) Deutche Mineral und Tafelwasserverordnung, 2006. Environmental Protection Agency (EPA) December 7, 2000. Proposed drinking water Standards. US EPA 65 FR 76707, 2000.
European Commission (EC), Council Directive of 15 July 1980 relating to the quality of water intended for human consumption. Official Journal of the European Communities L. 229, 30.8.1980, p. 11-29, 1980. European Commission (EC), Council Directive 98/83/EC of 3 November. The quality of water intended for human consumption. Official Journal of the European Communities L. 330, 5.12.1998, p. 32-54, 1998. European Commission (EC), Commission Recommendation of 20 December on the protection of the public against exposure to radon in drinking water supplies, 2001/928/EURATOM. L.344, 28.12.2001, p. 85-88, 2001. Hindman, F.D. Neodymium Fluoride Mounting for Alpha Spectrometric Determination of Uranium, Plutonium and Americium, Anal. Chem., 1983, 55, 2460-2461 Horwitz, E.P., Chiarizia, R., Dietz, M.L., Diamond, H. Separation and preconcentration of actinides from acidic media by extraction chromatography. Anal. Chim. Acta, 1993, 281, p. 361-372. International Atomic Energy Agency (IAEA). International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources. Safety Report Series, No. 115, Vienna, 1996. Jia, G., Torri, G. Estimation of radiation doses to members of the public in Italy from intakes of some important naturally occurring radionuclides (238U, 234U, 235U, 226 Ra, 238Ra, 224Ra and 210Po) in drinking water. Applied Radiation and Isotopes 65 (2007) 849-857. Sill, C.W., Williams, R.L. Preparation of Actinides for Alpha Spectrometry without Electrodeposition, Anal. Chem., 1981, 53, p. 421-415. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), Sources and Effects of Ionising Radiation, United Nations, New York; 1998. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), Sources and Effects of Ionising Radiation, United Nations, New York; 2000. Proceedings of Third European IRPA Congress 2010 June 14−16, Helsinki, Finland
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Radionuclide analytics −Poster presentation Ljudmila Benedik and Zvonka Jeran Natural alpha emitting radionuclides in bottled drinking water, mineral water and tap water
WEKNOW/ENDWARE, (Weknow, 2005), Radioactivity in European Drinking Water and Sources Designated for the Production of Drinking water, Available from: http://www.weknow-waternetwork.com/uploads/booklets/04 radioactivity_eu_drw_ver juni2005.pdf, 2005.
World Health Organization (WHO), Guidelines for Drinking Water Quality, Recommendation, second edition, vol. 1. WHO, Geneva; 1993. World Health Organisation (WHO), Health Criteria and Other Supporting Information. In: Guidelines for Drinking-Water Quality, second ed., Addendum to vol. 2, WHO, Geneve, 1998. World Health Organisation (WHO), Guidelines for Drinking Water Quality. WHO, Geneve, Available from: http://www.who.int/water_sanitation_health/, 2004.
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