RADON CONCENTRATIONS IN WATER AND INDOOR AIR IN NORTH - WEST REGIONS OF ROMANIA *

Transcription

1 RADON CONCENTRATIONS IN WATER AND INDOOR AIR IN NORTH - WEST REGIONS OF ROMANIA * D.C. NITA a, M. MOLDOVAN b, T. SFERLE c, V.D. ONA d, B.D. BURGHELE b a Environmental Radioactivity and Nuclear Dating - Research Group, Babes-Bolyai University, Cluj-Napoca, Romania b Faculty of Environmental Science and Engineering, Babes-Bolyai University Cluj-Napoca, Romania. mircea.moldovan@ubbcluj.ro (corresponding author) + c UCECOM Spiru Haret High School, Cluj-Napoca, Romania d Spitalul Clinic Municipal Cluj-Napoca, Romania Received November 15, 2012 Radon is a radioactive noble gas of natural origin that may be found anywhere in soil, air and in different types of water: surface, wells and springs. It is worth carrying out surveys for radon in natural water and indoor air for radiation protection as well for geological considerations. The results presented in this paper are from a survey carried out in Transylvania region, in North West of Romania for radon concentrations in water and indoor air. The measurements were made using a LUK-VR system based on radon gas measurements with Lucas cell for water and with track detectors based on CR-39 for indoor air. The results show that the radon concentrations are within the range of 0.9 to 68.9 BqL -1 with an average value of 11.4 BqL -1 for all types of water covered within this survey. The indoor radon concentrations range from 26 Bqm -3 to 415 Bqm -3 with an average of Bqm -3. Key words: radon in water, indoor radon. 1. INTRODUCTION Radon is produced during the radioactive decay chain of uranium, found naturally in traces in the earth's crust. This noble gas produced by the decay of radium is emitted continuously from the earth's crust and can reach the earth's surface by different processes [1]. Radon gas can dissolve can and accumulate in groundwater. If these radon containing types of water are frequently used in household (for showering, dishwashing and laundry), radon gas is released into the dwellings. When radon accumulates in indoor air may represent an increased health risk, especially lung cancer [2, 3]. * Paper presented at the First East European Radon Symposium FERAS 2012, September 2 5, 2012, Cluj-Napoca, Romania. Rom. Journ. Phys., Vol. 58, Supplement, P. S196 S201, Bucharest, 2013

2 2 Radon concentrations in water and indoor air in N-W Romania S197 However, the risk from radon released from water use is less than the risk due to indoor accumulated radon. If the groundwater is used as drinking water it must be taken into account the water radon content. According to the EPA reports the radon in drinking water caused 168 cancer deaths per year of which 89% lung cancer caused by indoor radon released from water and 11% of stomach cancer caused by drinking water containing radon [4]. Since drinking water is an essential element of life so far has been issued, by the competent institutions, regulations regarding radon concentration in drinking water. The European Commission suggests a concentration reference level of 100 BqL -1 for radon in drinking water and if the activity is over 1000 BqL -1 then remedial measures should be taken [5]. For the same purpose the Environmental Protection Agency proposed a Maximum Contaminant Level (MCL) for radon in drinking water 11.1 BqL -1 [4]. The amount of radon released indoor due to water usage is much lower compared to the radon amount that accumulates indoor from the soil. Radon gas released from water will contribute to the total concentration of indoor air with about 1-2%. The radon in water activity contribution to radon in air activity was estimated as follows: 1000k Bqm -3 of radon in water enriched the indoor air with an average concentration of 100 Bqm -3 [5]. 2. MATERIALS AND METHODS 2.1. STUDY AREA Radon concentrations have been determined in several drinking water samples (wells, spring, tap, river water) as well as in indoor for houses of North Transylvania, Romania. Measurements were carried out in 4 counties (Satu Mare, Maramureş, Sălaj, Bihor). From the geological point of view, North Transylvania mainly corresponds to a post-tectonic depression, surrounded by the Alpine chain of the Carpathians. In the Eastern Carpathians, three main units can be separated: the Flysch zone to the East, the Mesozoic and metamorphic zone in the central part, and the volcanic zone to the west. The western part of the chain (Apuseni Mountains) composed of a mosaic of magmatic, metamorphic and sedimentary rocks [6]. In the present research results of radon measurements in 66 drinking water samples and 15 water samples from rivers are presented. The majority of these water samples are used both as drinking water as well as for other domestic uses by the population in the area. In the same area, a total of 12 measurements of radon in indoor air, with track detectors were made.

3 S198 D.C. Nita et al SAMPLING PROCEDURE a. Radon in water The water samples were collected by means of 500 ml plastic bottles in monthly periods between January and June The bottles were filled completely and tightly closed to prevent the entry of air into the bottle and the escape of radon gas from the bottle. The samples were transported to the laboratory in order to determine the radon concentrations with the minimum delay and were measured at the earliest possible time. The radon in water was measured using a LUK-3A device specially adapted for radon in water measurement. This equipment called LUK-VR consists of a 500 ml scrubber in which a known quantity of water (300 ml) is introduced. Before measuring, the water was tempered to room temperature. The measurements protocol has already been described in previous papers [7]. b. Radon in indoor air The indoor measurements of the present survey were performed with the help of nuclear track detectors provided by Radosys Ltd. Hungary, which uses CR-39 chips for passive monitoring of radon in the indoor air. Each device consists of a cylindrical plastic vial provided with an appropriate lid and a 1 cm 2 CR-39 chip. The radon present indoor enters the vial through the space created between the lid and the vial body. Once inside, the alpha particles emitted during the radon decay hit the CR-39 chip living tracks. After 3 month exposure, all detectors are returned to the lab and etched in a 6.25 M solution of NaOH and analyzed using a Radosys microscope. The track density found is used to calculate the radon exposure and the indoor concentration for each location investigated. The measurements protocol has already been described in previous papers [8] EFFECTIVE DOSES The annual effective doses for ingestion and inhalation were estimated according to parameters introduced by UNSCEAR report [9]. a. The annual effective dose due to intake of radon was calculated on the basis of the mean activity concentration using the relation: D water = F Rn * C w* A w (1) where: F Rn is the committed effective dose per unit intake of radon in water for adults ( 10-8 SvBq -1 ) [9], C w is the water consumption rate (Ly -1 ) taken to be 1 L per day, A w is the activity of radon in water (Bq L -1 ).

4 4 Radon concentrations in water and indoor air in N-W Romania S199 b. The annual effective dose due to inhalation of radon was estimated on the basis of the mean activity concentration as follows: D air = C a (ε r +ε d f)o (2) where: C a represents the mean annual radon activity concentration expressed in Bqm -3 ; ε r and ε d are dose conversion factors for radon gas and its short-lived progeny respectively, ε r = 0.17 nsvh -1 per Bqm -3 and ε d = 9 nsv h -1 per Bqm -3 ; F is the equilibrium factor between radon and its short-lived progeny, assumed as f = 0.4 in our study; O represent the occupational factor for the average European, O =7000 hy -1 [9]. 3. RESULTS AND DISCUSSION a. Radon in water The results presented and discussed in this paper includes 81 water samples, 66 drinking water samples collected from wells, springs and from tap, connected to the municipal or communal systems supply while 15 water samples were taken from surface water (rivers and lakes). The radon results of the 81 water samples collected from different types of waters show relatively low to medium radon concentration levels. Low radon concentration values were associated with surface and tap waters, whereas the highest value of 68.9 BqL -1 was found for a sample collected from spring water. The overall results per types of waters (surface, well, spring and tap) measured in this survey are presented in Table 1. It is worth mentioning that almost all samples measured in this study are in fact drinking waters except for the surface water (18). The results of this study, for each water classifications, are presented in Table 1. Table 1 Descriptive statistics of water samples Water A.M. ± S.D. G.M. ± G.S.D. Median Range Frequency sample (Bq L -1 ) (Bq L -1 ) (Bq L -1 ) (Bq L -1 ) Well waters ± ± Spring waters ± ± Tap water ± ± Surface water ± ±

5 S200 D.C. Nita et al. 5 The summary results of radon content in drinking water from different sources in studied area are: most samples were taken from wells (34.5%) where values were between 5.6 and 35 BqL -1 with an average of 18.5 BqL -1 ; spring waters (24.69%) had values between 10.2 and 68.9 BqL -1 with an average of 22.7 BqL -1, while from tap water samples (22.2%) were obtained values between 1.2 and 4.5 BqL -1 and an average of 2.5 BqL -1. Fifteen water samples (15.1%) were collected from surface waters i.e. lakes, rivers and brooks. The radon concentration levels show a range of values from 0.9 to 4.5 BqL -1. The frequency distribution shows that most radon concentration values are round about 1.3 BqL -1 and very few values exceed this value. However, the radon concentrations in the surface water are low and below the maximum contaminant level of 11 BqL -1 in water [5]. Upon comparing the results with US data it was found with the exception of five sites, that the obtained values fall far below the action contamination level recommended by EPA to be 150 BqL -1 [4], the action level set for radon concentration in drinking water in Slovakia (1000 BqL -1 ) and the advisory level for radon in water in Norway (500 BqL -1 ) [10]. However, the average radon concentration observed in this study is significantly high relative to similar data reported from Ghana (8.1 BqL -1 ) and India (2.1 BqL -1 ) [11, 12]. The average effective doses (ingestion and inhalation due to radon from water) were calculated using committed effective dose of radon in water for adults from UNSCEAR [9]. From the present data, the average effective dose equivalents have been estimated to be 24.2 µsvy -1 in tap water, µsvy -1 in spring water and µsvy -1 in well water, respectively and the last two values have a contribution to the natural dose from Romania of about 8%. b. Radon in indoor air Indoor radon measurements were in number of 10 and scattered on a rather large area. Thus, as expected, the activity concentrations presented large variations from one location to the next with a range starting from 26 Bq m -3 and having a pick at 415 Bq m -3. The annual average radon concentration (AM) and corresponding standard deviation (SD) for the entire investigated region were found to be ± 68 Bq m -3, which is comparable with the mean of 144 Bq m -3 previously obtained in Serbia [13] and 126 Bq m -3 obtained by Cucoş-Dinu et al. [8] in Romania. Depending on investigated locality, the mean seasonal effective doses were found to range between 0.07 msv and 1.2 msv. It is to be mentioned that investigated sites differ, not only by map location but also by the building type, not to mention the great influence the building material and filling can have over the radon activity measured inside. It should be stressed that in the last ICRP publication about radon it was stated a new reference value of 300 Bqm -3 defined in terms of measurable concentration which can be directly related with the risks derived from radon progeny inhalation [14].

6 6 Radon concentrations in water and indoor air in N-W Romania S CONCLUSIONS The radon concentration in 36 water samples were found to be higher than the maximum contamination level recommended for radon in drinking water by EPA (MCL) and no radon concentration was found to exceed the European Commission reference level. The results from this study indicate that the activity concentrations of 222 Rn in water range between 0.9 and 68.9 BqL -1 with an overall average of 11.4 BqL -1 and corresponding annual effective dose in the range of msv with an average of 1.9 msv. These values are within the levels allowed elsewhere or recommended by the WHO [15]. In this case study only three locations exceed the reference value of 300 Bqm -3, (Nuşfalău with 366 Bqm -3, Sacuieni with 415 Bqm -3 and Carei with 326 Bqm -3 ). The mean seasonal effective dose for indoor exposure was about half of the national average value of 2.4 msv as previously reported for the Romanian population [16]. No correlations were observed between radon in water and indoor radon. REFERENCES 1. D.C. Niţă, C. Cosma, P. Botond, M. Moldovan, Studia UBB Phys, 1/2009, , (2009). 2. J. Nikolov, N. Todorovic, S. Forkapic, I. Bikit, D. Mrdja, Wld. Acad. Sci., Eng. Tech., 52, (2011). 3. C. A. Roba, V. Codrea, Ş. Olah, D. Niţă, C. Cosma, Geothermics, 4, (2012). 4. EPA (U. S. Environmental Protection Agency), 64. Federal Register, Washington, (1999). 5. E.C.(European Commission), 2001/982/Euratom, L344/ I. Balintoni, Ghergari L., T. Babut, Studia UBB, Geo., XLVII, 2, (2002). 7. C. Cosma, M. Moldovan, T. Dicu, T. Kovacs, Rad. Meas., 43, (2008). 8. A. Cucoş-Dinu, C. Cosma, T. Dicu, R. Begy, M. Moldovan, B. Papp, D.C. Niţă, B. Burghele, C. Sainz, Sci. Tot. Env., 431, (2012). 9. UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation). Annex E, United Nations, New York (2006). 10. G. Akerblom, Depar. Env. Monit. Dosim., Radon Legislation and National Guidelines, Swedish radiation protection institute. SSI report: 99. ISSN (1999). 11. E.O. Darko, O.K. Adukpo, J.J. Fletcher, A.R. Awudu, F. Otoo, J. Rad. Nucl. Chem., 283(2), (2009). 12. R. Somashekar, P. Ravikumar, J. Rad. Nucl. Chem., 285(2), (2010). 13. G. Dubois, Joint Research Center Report, Luxembourg (2005). 14. ICRP 115 (International Commission on Radiological Protection), ICRP Publication 115Ann. ICRP, 40, (2010). 15. WHO (World Health Organization), Vol. 1, Geneva, Switzerland (2009). 16. C. Cosma, K. Szacsvai, A. Dinu, D. Ciorba, T. Dicu, L. Suciu, Isot. Env. Health S, 45, 1 10 (2009).