RADON CONCENTRATION MEASUREMENTS IN WATERS IN GREECE AND CYPRUS

Transcription

1 RADON CONCENTRATION MEASUREMENTS IN WATERS IN GREECE AND CYPRUS A.Louizi 1, D.Nikolopoulos 1 A.Tzortzi 1, E.Vogiannis 2, V.Koukouliou 3, D.Thanassas 1, A.Serefoglou 1 and E.Georgiou 1 1 Medical Physics Department, Athens University, Medical School, Athens, GREECE 2 Waste Management Laboratory, Department of Environmental Studies, University of the Aegean, Mytilene, GREECE 3 Greek Atomic Energy Commission, Department of Environmental Radioactivity, Athens, GREECE INTRODUCTION Radon ( 222 Rn) is a colorless, odorless and chemically inert gas. It is generated through the disintegration of the 238 U series. Its parent nucleus is 226 Ra present in soil, rocks and waters. Radon generated from radium present in waters is dissolved, and if does not escape, it is concentrated in the liquid. The concentration of radon in waters is a parameter which is related to the radon potential of an area (1,2). Radon in water is recognized as an agent of radiation burden due to drinking of potable water. The mechanisms through which drinking of water additionally burdens human health are not yet well understood. Nevertheless, it is considered that the main part of the dose due to radon, when consuming water, is delivered in the stomach region (3). On the other hand, radon present in water may escape liquid phase and enter in the indoor atmosphere mainly due to domestic uses. Since radon present in the indoor environment is the main source of human exposure to radiation, this additional escape may also contribute to this exposure. The indoor radon concentration increase due to the water s domestic uses is about 1 per 10 4 Bqm -3 i.e. for every 10 4 Bqm -3 of radon present in domestically used water, a resulting indoor radon concentration increase by 1 Bqm -3 will occur (4,5). In addition to this, it is recognised that radon presence in water is the agent that may cause, by far, the most deaths due to water drinking (5). For Greece there have been reported measurements on indoor radon concentrations by various investigators (6-17). The concentrations found were low (<40 Bqm -3 ). To our knowledge for Cyprus a limited work has been published referring only to indoor radon concentrations (18). In this consensus, preliminary results of radon measurements performed in water samples collected from Greece and Cyprus are presented. MATERIALS AND METHODS The radon content of drinking water samples was determined with Alpha Guard Pro (Genitron Ltd.) equipped with an appropriate unit (Aqua Kit). The samples were collected from various cities in Greece and Cyprus. In addition, surface water samples from rivers, lakes and seas as well as underground water samples from Greece and Cyprus were also collected and measured. Radon in water was measured by setting Alpha Guard in a special mode (flow) using the Aqua Kit unit. This unit consisted of a vessel used for forced degassing of radon diluted in water samples and a security vessel coupled at the outlet side of the degassing vessel which is used for

2 water drop deposition. The vessels, Alpha Guard and Alpha Pump were connected via plastic tube pieces, which prevented escape of radon gas. Forced degassing of radon gas was performed by circulating the air in the set up with the use Alpha Pump. For water sampling and transporting, adequate glass storage vessels of 200 to 1000 ml, with adjustment glass stoppers with standard NS 29/32 grounding, as well as sealing rings and security clamps for taper grounding, were used. Concerning water sampling and since radon is a very mobile gas which can easily escape from water during sampling and transportation, strict collection protocols were followed. For water sampling from water taps, these were opened for 10 minutes before drawing the sample. The storage vessels were completely filled and immediately closed under water in order to avoid the formation of air bubbles. For sampling of surface and thermal waters the glass vessels were sunk into the water and completely filled under water in order to avoid the formation of air bubbles. After drawing the sample the vessels were immediately closed with the glass stoppers. Laboratory measurements were performed at least one hour after drawing the sample in order to assure the full decay of any thoron content and to the minimum achievable time interval, so as the radon content to be the highest possible in order to allow higher precision. For the measurement the glass stopper was removed and immediately exchanged with the degassing cap. Afterwards, water quantity was reduced to about half and measured, according to the protocol proposed by the manufacturer. Before measurement, radon in the measurement setup was minimized by circulating the enclosed air at a rate of 1L/min via Alpha Pump for about 10 minutes, through a special unit containing active charcoal. The precise evaluation of the radon concentration within the setup was performed with repeated measurements. The charcoal filtering was continued until the radon concentration measured was below (5+/2) Bqm -3. The concentration of radon in water was calculated according to equation (1): V System V 3 Sample C = 10 C + AlphaGuard + k C0 (1) VSample In this equation C Alpha Guard is the radon concentration of a sample of volume V Sample as measured by Alpha Guard Pro, C 0 is the background concentration within the measuring setup of V System total volume and k is the diffusion coefficient for radon in water. This was estimated from equation (2) T k = e (2) where T is the average absolute temperature of the sample during measurement. The overall uncertainty in the estimation of C in equation (1) was calculated taking into account the measurement uncertainties in C 0, C Alpha Guard, V Sample, V System, and T as well as the calibration uncertainty (3%) of Alpha Guard Pro. RESULTS AND DISCUSSION A total of 35 measurements in Greece and 15 in Cyprus were performed. The primary data sorted according to the nature of water (potable, underground, medicinal or surface) are presented in Tables 1,2 and 3. Namely, Table 1 summarises the results obtained in Greece and Table 2 the reciprocal from Cyprus. Table 3 presents the overall measured concentration ranges.

3 As can be seen from these Tables, radon concentrations in drinking water samples in Greece ranged between (1.1±0.5) Bq/L and (410±50) Bq/L. The corresponding concentrations in underground potable waters in Cyprus ranged between (0.4±0.3) Bq/L and (15±4) Bq/L. Three samples collected from the city of Arnea Chalkidekis (Northern Greece) presented high concentrations of (120±20) Bq/L, (320±40) Bq/L and (410±50) Bq/L. One water sample located in Lesvos Island (North-East part of Greece) presented radon concentration (140±20) Bq/L. Six more samples presented high concentrations in potable hot spring water samples characterized as medicinal drinking water. These samples were collected from the city of Loutraki (Attica prefecture) and ranged between (220±10) Bq/L and (340±20) Bq/L. For potable and non-potable underground water samples in Greece and Cyprus the radon concentrations ranged between (0.4±0.3) Bq/L and (15±4) Bq/L, while for surface water samples they ranged between (2.7±0.8) Bq/L and (24±6) Bq/L. According to US-EPA (United States Environmental Protection Agency) the upper limit for the radon content in water is 11 Bq/L (19) while according to the European Commission Recommendation of 20 December 2001 (20) on the protection of the public against exposure to radon in drinking water supplies, no remedial action should be required if the concentration is less than 100 Bq/l. If the radon concentration exceeds 1000 Bq/L, remedial could be considered justifiable from the radiation protection point of view. According to the latter recommendation, the measured radon concentrations in potable water samples collected from Greece and Cyprus are low with the exception of the 3 water samples from Arnea Chalkidekis and the one from Lesvos Island. Arnea Chalkidekis is identified as an area of high radon potential (10,14). Similar results to those of potable waters of Arnea Chalkidekis are reported in near areas by other investigators (22). However, all the elevated concentrations are higher than the usually reported values for potable waters for Greece (23-26) and other countries (27-29). However, all the reported measurement results from Arnea Chalkidekis and Lesvos Island are above 100 Bq/L but bellow 1000 Bq/L and thus, lie in the intermediate range. Our results show that further measurements in different types of water are warranted before final conclusions can be drawn. REFERENCES 1. Nazaroff WW, Potable water as a source of airborne 222 Rn in U.S. dwellings: A review and assessment. Health Phys, 1987, 52: United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), Sources and effects of Ionizing Radiation. United Nations (ed), New York, British Research Establishment (BRE), Radon in drinking water, Issue 27, U.S. Environmental Protection Agency (EPA), Final Draft for the drinking water criteria document on radon. Report No TR U.S.EPA. Washington D.C., Erladson B, Jacobsson B, Jonsson G, Studies of the radon concentration in drinking water from the horst Soderasen in southern Sweden J. Env.Radioac. 53: , Krtidis P, Angelou P: Concentrations of 222 Rn in well and tap waters of North-Eastern Attiki. Demo 84/5 (Greek Atomic Energy Commission, NCRP Democritus Athens, Georgiou E, Ntalles K, Molfetas A, Athanassiadis A, Proukakis C, Radon measurements in Greece. In: Radiation Protection Practice. IRPA 7, Volume I, New York, Pergammon Press, pp , Proukakis C, Molfetas M, Ntalles K, Georgiou E, Serefoglou A, Indoor radon measurements in Athens, Greece. In: British Nuclear Energy Society Conference on Health Effects of low dose ionizing radiation-recent advances and their implications, London: BNSE, pp , Papastefanou C, Stoulos S, Manolopoulou M, Ioannidou A, Charalambous S, Indoor radon concentrations in Greek apartment dwellings, Health Phys., 66(3): , 1994

4 10. Louizi A, Koukouliou V, Nikolopoulos D, Ntalles K, Vecios P, Proukakis C, Exposure of the Arnea Chalkidikis inhabitants to radon-risk assessment. Phys.Med., XV(3):221, Ioannides KG, Stamoulis KC, Papachristodoulou CA, A survey of 222 Rn concentrations in dwellings of the town of Metsovo in North-Western Greece. Health Phys., 79(6): , Geranios A, Kakoulidou M, Mavroidi P, Moschou M, Fischer S, Burian I., Radon survey in Kalamata (Greece). Rad Prot Dosim, 93(1):75-79, Nikolopoulos D, Louizi A, Koukouliou, V, Serefoglou, A Georgiou, E, Ntalles, K, Proukakis C, Radon Survey in Greece-risk assessment. J.Environ.Radioact. 63(2), (2002) 14. Louizi A, Nikolopoulos D, Koukouliou V, Kehagia K, Study of a Greek area with enhanced radon concentrations, Rad. Prot.Dosim. 106(3), (2003) 15. Papaefthimiou H, Mavroudis A, Kritidis P, Indoor radon levels and influencing factors in houses of Patras, Greece, J.Environ.Radioact. 66, (2003) 16. Clouvas A, Xanthos S, Antonopoulos-Domis M, Long term measurements of radon equilibrium factor in Greek dwellings, Rad. Prot. Dosim. 103(3), (2003) 17. Clouvas A, Xanthos S, Antonopoulos-Domis M A, combination study of indoor radon and in situ gamma srectrometry measurements in Greek dwellings, Rad. Prot. Dosim. 103(3), (2003) 18. Christofides S, Christodoulides G, Airborne 222 Rn concentration in Cypriot houses. Health Phys. 64(4): , U.S. Environmental Protection Agency (EPA): National Primary Drinking Water Regulations; Radionuclides. Proposed Rule 40 CFR Parts 141 and 142, Federal Register, Vol 56, No 138, 1991: /143/EURATOM: Commission Recommendation of 21 February 1990 on the Protection of the public against indoor exposure to radon L 080, 27/3/1990, Savidou A, Sideris G, Zouridakis N, Radon in public water supplies in Migdonia Basin, Central Macedonia, Northern Greece, Health Phys. 80(2) (2001) 22. Zouridakis N, Ochsenkuen K M, Savidou A, Determination of Uranium and radon in potable water samples, J.Environ.Radioact (2002) 23. Kritidis P, Angelou P, Concentrations of 222 Rn in well and tap waters of north-eastern Attiki, DEMO 84/5 (Athens:Democritus Research Center) (in Greek) (1984). 24.Kritidis P, Angelou P, Concentrations of 222 Rn and its short-lived decay products at a number of Greek radon spas, Nucl. Instr. Method. B (1986) 25.Danali-Cotsaki S, Margomenou-Leonidopoulou G, 222 Rn in Greek spa waters:correlation with rainfall and seismic activities, Health Phys. 64(6) (1993) 26.Trabidou G., Florou H, Angelopoulos A, Sakelliou L, Environmental study of the radioactivity of the spas in the island of Ikaria, Rad. Prot. Dosim. 63(1) (1996). 27.Zalewski M., Kaprinska M, Mnich Z, Kapala J, Zalewski P, Study of 222 Rn concentrations in drinking water in the north-eastern hydroregions of Poland, J.Environ.Radioact (2001) 28.Erladson B, Jakobson B, Jonson G, Studies of the radon concentration in drinking water from the horst Soderasen in Southern Sweden, J. Environ. Radioact (2001) 29.Horvarth A, Bohus L O, Urbani F, Marx G, Piroth A, Greaves E D, Radon concentrations in hot spring waters in northern Venezouela, J. Environ. Radioact (2000)

5 Table 1. Overall measurement results for waters in Greece i/i Area W ater Type Date C (Bq/L) σ (C ) (B q /L) 1 Goudi (Attika) Potable 10/07/ Loutraki (Attika) Potable 10/07/ Loutraki (Attika) Potable 10/07/ Loutraki (Attika) Potable 10/07/ Nikea (Attika) Potable 11/06/ Kallithea (Attika) Potable 10/28/ Koridallos (Attika) Potable 11/07/ Koridallos (Attika) Potable 11/07/ Kallithea (Attika) Potable 11/12/ V rillisia (A ttika) P otable 07/04/ V rillisia (A ttika) P otable 10/04/ Am aliada (Ilia) Potable 08/30/ Pirgos (Ilias) Potable 08/30/ Pirgos (Ilias) Potable 08/30/ Arnea (Chalkideki) Potable 07/07/ Arnea (Chalkideki) Potable 07/07/ Arnea (Chalkideki) Potable 07/07/ Vam os (Chanion) Potable 07/25/ Vrisses (Chanion) Potable 07/24/ Kasteli (Chanion) Potable 07/25/ Charakas (Iraklion) Potable 08/04/ Parakila (Lesvos) Potable 07/25/ Larissa (Thessalia) Potable 07/06/ Larissa (Thessalia) Potable 07/06/ Larissa (Thessalia) Potable 07/06/ Charakas (Iraklion) Underground 07/28/ Paranim fi (Irakion) Underground 07/30/ Filothei (Attika) Underground 10/17/ Eftalou (Lesvos) Medicinal 07/25/ Polichnitos (Lesvos) Medicinal 07/25/ Gera (Lesvos) Medicinal 07/25/ Eftalou (Lesvos) Medicinal 07/25/ Loutraki (Attika) Medicinal 06/30/ Loutraki (Attika) Medicinal 06/30/ Loutraki (Attika) Medicinal 10/29/ Loutraki (Attika) Medicinal 10/29/ Loutraki (Attika) Medicinal 10/29/ Pinios river (Ilia) Surface 08/29/ Pinios river (Thessalia) Surface 07/06/ Iraklion (Iraklio) Surface 07/31/

6 Table 2. Overall measurement results for waters in Cyprus i/i Area W ater Type D ate C (B q/l) σ (C ) (B q/l) 1 Vrissoules Underground Potable 30/12/ Derinia Underground Potable 01/01/ Derinia Underground Potable 01/01/ Derinia Underground Potable 01/01/ Derinia Underground Potable 01/01/ Kakopetria Underground Potable 01/03/ Lefkosia Underground Potable 30/12/ Lefkosia Underground Potable 30/12/ Lefkosia Underground Potable 30/12/ Lefkosia Underground Potable 30/12/ Liopetri Underground Potable 25/12/ Liopetri Underground Potable 25/12/ Monacos Underground Potable 28/12/ Paralim ni Underground Potable 26/12/ Paralim ni Underground Potable 26/12/ Paralim ni Underground Potable 26/12/ Paralim ni Underground Potable 26/12/ Strovili Underground Potable 28/12/ Strovili Underground Potable 28/12/ Frennaros Underground Potable 01/04/02 9 3

7 Table 3. Overall measurement ranges per water type measured i/i Water Type Range (Bq/L) 1 Potable (1.1±0.5) (1.5±0.4) 2 Potable (Arnea Chalkidikis) (120±20) (320±40) 3 Underground (1.2±0.7) (15±4) 4 Surface (2.7±0.8) (24±6) 5 Medicinal (220±10) (230±10)