- Email: [email protected]
129I Variability in precipitation over Europe
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 259 (2007) 508–512 www.elsevier.com/locate/nimb
129
I Variability in precipitation over Europe
S. Persson
a,*
, A. Aldahan b, G. Possnert a, V. Alfimov c, X. Hou
d
a
Tandem Laboratory, Uppsala University, Box 529, SE-751 21 Uppsala, Sweden Department of Earth Sciences, Uppsala University, SE-752 36 Uppsala, Sweden c Institute of Particle Physics, ETH Ho¨nggerberg, CH-8093 Zu¨rich, Switzerland Radiation Research Department, Risø National Laboratory, DK-4000 Roskilde, Denmark b
d
Available online 1 February 2007
Abstract We present results and an overview of studies on 129I in precipitation over Europe during the last decade, covering latitudes 37–70N. The data show about three orders of magnitude variability in concentrations but without specific correlation to latitude when all Europe is considered. The total amount of 129I provided annually by precipitation over Europe composes only a tiny portion of the annual marine discharge but a significant portion of the gaseous discharges from the nuclear reprocessing facilities. Contribution of gaseous releases seems to be significant, although difficult to estimate. As shown by this study, a unified sampling procedure and systematic measurements of 129I in precipitation throughout Europe are needed to achieve a coherent picture about the loading and sources of 129I in precipitation and the atmosphere. 2007 Elsevier B.V. All rights reserved. PACS: 92.60.Jq; 89.60. k; 93.30.Ge; 92.60.Sz Keywords: Iodine-129; Precipitation; AMS; Atmosphere; Europe
1. Introduction Although precipitation is the main pathway of iodine to the earth’s surface continental reservoirs, little is known about the distribution of the element in the atmosphere. As seas represent the main reservoir of iodine, precipitation along coastal regions is expected to be more enriched with iodine than inland areas. The complex chemical forms, relatively rapid transformation of iodine compounds and short residence time in the atmosphere contribute to the difficulty of understanding the atmospheric distribution. A similar situation is encountered with the distribution of the long-lived radioactive isotope 129I. The main sources of this isotope are nuclear fuel reprocessing facilities in
*
Corresponding author. Tel.: +46 18 4713613; fax: +46 18 555736. E-mail address: [email protected] (S. Persson).
0168-583X/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.01.193
Europe, releasing 129I both into running waters (marine and rivers) and into the atmosphere. Gaseous releases of 129 I contribute to <10% of the total known releases from the Sellafield and La Hague facilities [1]. During the years 1988–1997, total gaseous 129I releases from the Marcoule facility, 68.5 kg [2], were in the same order of magnitude as those from Sellafield and La Hague, 65.5 kg (Fig. 1). In spite of the relatively large amounts of gaseous releases, quantifying their contribution to 129I in precipitation is difficult, since the knowledge about the pathways of 129I in the atmosphere is still vague. Many questions concerning transfer from the sea to the atmosphere, the influence of weather conditions, wind patterns and chemical parameters remain to be answered. With the aim of elucidating the problem, we have an ongoing project on 129I in precipitation from three stations in Sweden and we here present first results of this project. These results are compared with published data on the distribution and inventory of 129I over Europe. The overview
S. Persson et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 508–512
509
Table 1 129 I Concentrations in precipitation from stations 1–5
Fig. 1. Yearly gaseous releases from Sellafield, La Hague and Marcoule. No data are published for Marcoule before 1988. Values for Sellafield 1952–1975 and Marcoule 1958–1987 are estimates [1,2,13].
covers latitudes 37N to 70N (southern Spain to northern Sweden) and includes both rain and snow. 2. Materials and analytical technique 2.1. New data from this study Precipitation from three stations in Sweden was collected during the years 2000–2002. In addition, one sample from northern Italy and two from Norway were collected (Table 1, Fig. 2). Most of the samples represent a single rain or snow event, but in some cases the sample acquisition was done during a couple of days. The samples were collected in a funnel covered with a 20 lm mesh net and stored in polyethylene bottles in a cold dark room. The colorimetric method used for iodine extraction is the same as described in [3], but with some minor modifications. After filtering the sample through a 0.45 lm membrane filter, Woodward iodine was added as a carrier. The solution was then reduced with NaHSO3 to convert iodate to iodide and acidified to pH = 2. Then the iodine was extracted into CHCl3, back extracted into water, and precipitated as AgI, which was finally washed twice with distilled water. The AgI was mixed with niobium powder and pressed into cupper holders for the AMS measurement, which was done at the Uppsala Tandem Accelerator. Standards prepared from the 129I reference material NIST SRM 4949C were used for normalization of the measured 129I/127I ratio. Chemical blanks prepared with the same procedure as the samples were regularly processed and used for background correction. Generally the total error was less than 10% of measurement including counting statistics and blank correction. For a few samples, we also analyzed the stable iodine concentration in order to calculate the isotopic ratio. This was done with HR-ICP-MS at the Radiation Research Department, Risø National Laboratory in Denmark. An internal standard 20 ppb of Sb was used, and the blank counts were about 3–8% of the sample counts with a detection limit of 0.030 ppb.
Station
Sampling date
129
Abisko 1 2 3 4 5 6 7 8 9
25-dec-00a 06-apr-01 30-jul-01 13-aug-01 18-aug-01 18-okt-01 30-okt-01 05-nov-01a 13-nov-01a
2.9 ± 0.2 18.4 ± 1.0 6.3 ± 0.4 5.7 ± 0.4 7.3 ± 0.5 10.6 ± 0.7 10.6 ± 0.5 5.9 ± 0.3 7.5 ± 0.4
Uppsala 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
28-dec-99a 20-jan-00a 03-feb-00a 03-mar-00a 05-apr-00a 24-maj-00 28-maj-00 24-apr-01 18-jul-01 20-aug-01 11-okt-01 31-okt-01 21-dec-01a 31-jan-02a 04-maj-02 30-jun-02
2.5 ± 0.1 1.7 ± 0.1 28.2 ± 3.4 19 ± 2.4 2.1 ± 0.2 10.4 ± 0.7 15.1 ± 1.0 3.6 ± 0.2 18.4 ± 1.1 23.9 ± 1.2 3.9 ± 0.4 2.7 ± 0.2 6.2 ± 0.3 6.7 ± 0.4 3.5 ± 0.2 8.0 ± 0.5
Kvidinge 26 27 28 29 30 31 32 33 34
30-jun-01 20-aug-01 12-okt-01 29-okt-01 21-dec-01 02-feb-02a 27-maj-02 17-jun-02 24-jun-02
12.4 ± 0.7 25.2 ± 1.3 21.3 ± 1.0 18.5 ± 1.1 22.1 ± 1.1 38.7 ± 2.6 10.4 ± 0.6 16.9 ± 0.8 62.3 ± 3.9
Bergen 35 36
12-jan-03 2-apr-03
15.8 ± 0.7 41 ± 1.9
N. Italy 37
23-aug-02
6.6 ± 0.4
a
I (108 atoms l 1)
Snow.
2.2. Published data We have collected data on 129I in precipitation over Europe from several published reports during the last decade (Table 2, Fig. 2). These studies have used different methods and sampling techniques (Table 3), which make a direct comparison of the published results rather problematic. The temporal resolution of the data varies between daily (single event) and three months (multiple events sample). In some cases, the sampling was done continuously and in others, several periodic samples were mixed into one sample. In the case of continuous sampling, dry deposition
510
S. Persson et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 508–512
Fig. 2. Map showing the locations of stations used and the nuclear reprocessing facilities Sellafield (S), La Hague (H) and Marcoule (M, closed in 1997). The arrow points in the direction of the Mayak complex in Russia.
Table 2 Results and information about the sampling stations Latitude N
Number of samples
Average 129I concentration 108 atoms l 1
Std. dev. 108 atoms l
1 Abisko 2 Uppsala
68 60
3 Kvidinge 4 Bergen 5 Northern Italy
56 60 45
9 33 16 9 2 4 1 27 29 57 13 19 26 14 13
8.3 11.1 9.7 25.3 28.4 3.0 6.6 36.1 56.3 15.8 16.3 84.1b 60.7b 74.8b 88.8b
5 11 9 16 18 4
Station
6 Lower Saxony 7 Zu¨rich/Du¨bendorf 8 Seville 9 Upper Bavaria 10 Waldhof 11 Deuselbach 12 Brotjacklriegl 13 Schauinsland a b c
52 47 37 48 53 50 48.5 48
17 100 79 12
1
Range 108 atoms l 2.9–18.4 0.4–41.2 1.7–28.2 10.3–57 15.8–41 0.3–9.4 6.6 11–70 2.16–445 0.22–600 4.8–50 23–300c 14–130c 9–270c 18–420
1
Year of sampling
References
2000–2001 1998–1999 2000–2002 2001–2002 2003 1998 2001 1997–1999 1994–1997 1996–1999 2003–2004 1994–1995 1994–1995 1994–1995 1995
This study [4] This study This study This study [4] This study [7,9]a [10] [5,11] [6,12] [8]a [8]a [8]a [8]a
Only inland stations were taken into account, i.e. the results from the Norderney [8,10] and Westerland [9] islands were not included. Average for 1995 only, as published in [8]. Estimates from the figures in [8].
S. Persson et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 508–512
511
Table 3 Sampling and preparation procedures for the different studies Location on map
Sampling period
Chemical treatment before storage
Filtering
Extraction method
Schnabel et al. [10]
7
1 month
2,5
Lo´pez-Gutie´rrez et al. [5,11] Szidat et al. [7,9]
8
Single event, in some cases a couple of days 1 month or 25 liters
Not specified 0.45 lm
CHCl3
Buraglio et al. [4]
NaOH until pH = 14 to destroy organic compounds None
14 daysa
Krupp and Aumann [8] Reithmeier et al. [6,12] This study
10–13
Varying, no details given.
Not specified
Not specified Not specified Nob
CHCl3
6
NaOH to separate iodine from organic molecules NaOH to preserve the samples
9
Integrated into samples representing 1–2 months. Single event, in some cases a couple of days
Not specified
0.2 lm
Anion exchange column Anion exchange column CCl4
None
0.45 lm
CHCl3
1–5
CCl4
a
Samples from 3 months were integrated into one sample; periods with little precipitation are underrepresented. Half of each sample was filtered in order to determine particulate-bound 129I. The results discussed in this paper are total 129I concentrations, including this part. b
is included in the results, whereas the dry deposition portion is negligible in single event sampling. In addition, methods differ in whether the water is filtered before extraction of iodine and whether NaOH is added before storage (Table 3). 3. Results and discussion The results of samples measured in this study show average concentrations of 8.3 · 108 atoms l 1 (Abisko), 9.7 · 108 atoms l 1 (Uppsala) and 2.5 · 109 atoms l 1 (Kvidinge), with a large scatter for all three stations (Tables 1 and 2). These stations show latitude dependence with the lowest average value in the north and the highest average value in the south. Kvidinge is located near the coast (20 km), which may also explain the observed higher concentrations. The Uppsala average is about the same as in the previous study by Buraglio et al. [4]. For northern Italy, one sample from 2001 was measured and it gives 6.6 · 108 atoms l 1, which lies within the range of earlier measurements. Two samples from Bergen, located at the Norwegian Atlantic coast were measured. Concentrations for these samples were 10.3 · 108 and 5.7 · 109 atoms l 1 resulting in an average slightly above that in Kvidinge. Data from this study together with published data from other parts of Europe show a general concentration range of 108–1010 atoms l 1 with a few samples above and below this range (Table 2). Average concentration for the sampling stations vary at (3–89) · 108 atoms l 1. The large spread of the concentrations, combined with the temporal spread between the stations, does not permit a conclusive picture about latitude dependence as shown by the Swedish stations alone (Fig. 3). However, sites close to the Atlantic coast (3, 4 and 6) exhibit relatively higher average concentrations than the inland ones. The station in northern Italy has the overall lowest average value (3 · 108 atoms l 1), but the number of samples is too small to confirm this observation.
Fig. 3. Average 129I concentrations for the 13 stations and the latitudes of the major 129I emitters in Europe (vertical lines). The numbers within parentheses show the sampling years for each station. For simplicity, we show just the average values in spite of the large spread. Details of the stations in Table 1.
A decreasing trend in concentrations can be observed during the years 1995–2004; especially stations measured before 1997 (stations 7, 10–13) show higher concentrations than the latter ones. These stations are also mainly situated far from the Atlantic Ocean. A comparison between stations 9 and 12, that are situated very close to each other (Fig. 1) confirms the decreasing trend in 129I concentration; the average concentration in 2003–2004 is less than 1/4 of that in 1995. A possible explanation for this observation can be the shutdown of the Marcoule facility (Fig. 1) during the late 1990s (September 1997). The gaseous releases from La Hague also happened to decrease during the same period, but the magnitude was smaller than that of the Marcoule facility (Fig. 1). Evaluation of the pre-1997 129I load in Europe from the Marcoule facility needs further
512
S. Persson et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 508–512
(3.61–6.57) · 10 7 for station 6 [7] and (6.0–9.7) · 10 7 for station 10–13 [8]. To roughly estimate the annual amount of 129I fallout by precipitation over Europe, we have used the average values of the data sets (without the few extreme values of Zu¨rich and Seville) and an average annual precipitation rate of 600 mm. The calculation reveals a fallout rate of about 2.5 kg 129I, which represents represent <1% of the total annual releases or about 1/3 of the annual gaseous releases. A more detailed calculation should obviously include normalization to the precipitation amount as well as some geographical weighting of the stations. 4. Conclusions Fig. 4. Temporal variation of
129
I of three sampling stations in Europe.
investigation in future studies. Unfortunately, absence of Scandinavian data before 1997 hinders estimating the effect of the gaseous emissions reduction to this region. Some details of the temporal variability in 129I concentration are illustrated by the relatively long records from Uppsala, Zu¨rich and Seville (Fig. 4). In all the three data sets, there are strong non-periodic fluctuations, which may have different environmental explanations, e.g. seasonal variations, weather conditions and washout effects. An even more significant source to the fluctuations is probably the daily emission of gaseous releases from the reprocessing facilities. Information concerning the daily releases are unfortunately lacking, but the monthly data from [5] confirm the non-periodic fluctuations in Fig. 4 that may relate to stochastic emission patterns. Although both Seville and Zu¨rich exhibit higher temporal fluctuations than Uppsala, the Seville 129I range as well as the spread seems to be lower after 1997 compared to the period before. This observation could again be explained by the dominant gaseous releases from the Marcoule facility (Fig. 1) prior to 1997. It is important to remember that there might exist additional, unknown sources of 129I, especially in Eastern Europe, that may have contributed to atmospheric input. One candidate is the Mayak complex in the southern Ural Mountains of Russia, for which presently no data are published. Although this study mainly focuses on the concentration of 129I, the 129I/127I ratio, as pointed out by several investigations, represents an additional parameter in understanding the pathways from the sources to the atmosphere. In our study, we have analyzed the stable iodine content of a few samples from the three Swedish sample stations. The average stable iodine concentrations for the stations were 2.1, 1.6 and 2.9 lg/l, respectively. Applying these values to our data, we get the estimated average isotopic ratios 8.3 · 10 8, 1.3 · 10 7 and 1.8 · 10 7. Published measured values on the isotopic ratio in precipitation from other stations used in this overview are 1.5 · 10 7 for station 9 [6],
The results of this investigation indicate large variation in temporal and spatial distribution of 129I in precipitation over Europe without constrained latitudinal dependence. Different sample collection procedures and variable temporal coverage of the records did not permit establishment of exact source or controlling factors that affect the distributions trends observed. Accordingly, unified sample collection procedures and long periods of time series data are needed in order to capture details of variability in 129I atmospheric loading over Europe. Acknowledgement We would like to thank Christer Jonasson and his team for collecting precipitation samples in Abisko and the Swedish Radiation Protection Institute for their financial support. References [1] J.M. Lopez-Gutierrez, M. Garcia-Leon, C. Schnabel, M. Suter, H.-A. Synal, S. Szidat, R. Garcia-Tenorio, Sci. Total Environ. 323 (2004) 195. [2] Cogema Marcoule Rapport Environnement, 1997. [3] N. Buraglio, A. Aldahan, G. Possnert, Nucl. Instr. and Meth. B 172 (2000) 518. [4] N. Buraglio, A. Aldahan, G. Possnert, I. Vintersved, Environ. Sci. Technol. 35 (2001) 1579. [5] J.M. Lopez-Gutierrez, F.J. Santos, M. Garcia-Leon, C. Schnabel, H.-A. Synal, T. Ernst, S. Szidat, Nucl. Instr. and Meth. B 223–224 (2004) 495. [6] H. Reithmeier, Ph.D. thesis, Fakulta¨t der Physik, Technische Universita¨t Mu¨nchen, 2005. [7] S. Szidat, A. Schmidt, J. Handl, D. Jakob, W. Botsch, R. Michel, H.-A. Synal, C. Schnabel, M. Suter, J.M. Lopez-Gutierrez, W. Stade, Nucl. Instr. and Meth. B 172 (2000) 699. [8] G. Krupp, D.C. Aumann, J. Environ. Radioact. 46 (1999) 287. [9] S. Szidat, Ph.D., Fachbereich Chemie, Universita¨t Hannover, 2000. [10] C. Schnabel, J.M. Lopez-Gutierrez, S. Szidat, M. Springer, H. Wernli, J. Beer, H.-A. Synal, Radiochim. Acta 89 (2001) 815. [11] J.M. Lopez-Gutierrez, M. Garcia-Leon, C. Schnabel, M. Suter, H.-A. Synal, S. Szidat, J. Environ. Radioact. 55 (2001) 269. [12] H. Reithmeier, V. Lazarev, F. Kubo, W. Ruhm, E. Nolte, Nucl. Instr. and Meth. B 239 (2005) 273. [13] H. Reithmeier, V. Lazarev, W. Ru¨hm, M. Schwikowski, H.W. Ga¨ggeler, E. Nolte, Environ. Sci. Technol. 40 (2006) 5891.
Nuclear Instruments and Methods in Physics Research B 259 (2007) 508–512 www.elsevier.com/locate/nimb
129
I Variability in precipitation over Europe
S. Persson
a,*
, A. Aldahan b, G. Possnert a, V. Alfimov c, X. Hou
d
a
Tandem Laboratory, Uppsala University, Box 529, SE-751 21 Uppsala, Sweden Department of Earth Sciences, Uppsala University, SE-752 36 Uppsala, Sweden c Institute of Particle Physics, ETH Ho¨nggerberg, CH-8093 Zu¨rich, Switzerland Radiation Research Department, Risø National Laboratory, DK-4000 Roskilde, Denmark b
d
Available online 1 February 2007
Abstract We present results and an overview of studies on 129I in precipitation over Europe during the last decade, covering latitudes 37–70N. The data show about three orders of magnitude variability in concentrations but without specific correlation to latitude when all Europe is considered. The total amount of 129I provided annually by precipitation over Europe composes only a tiny portion of the annual marine discharge but a significant portion of the gaseous discharges from the nuclear reprocessing facilities. Contribution of gaseous releases seems to be significant, although difficult to estimate. As shown by this study, a unified sampling procedure and systematic measurements of 129I in precipitation throughout Europe are needed to achieve a coherent picture about the loading and sources of 129I in precipitation and the atmosphere. 2007 Elsevier B.V. All rights reserved. PACS: 92.60.Jq; 89.60. k; 93.30.Ge; 92.60.Sz Keywords: Iodine-129; Precipitation; AMS; Atmosphere; Europe
1. Introduction Although precipitation is the main pathway of iodine to the earth’s surface continental reservoirs, little is known about the distribution of the element in the atmosphere. As seas represent the main reservoir of iodine, precipitation along coastal regions is expected to be more enriched with iodine than inland areas. The complex chemical forms, relatively rapid transformation of iodine compounds and short residence time in the atmosphere contribute to the difficulty of understanding the atmospheric distribution. A similar situation is encountered with the distribution of the long-lived radioactive isotope 129I. The main sources of this isotope are nuclear fuel reprocessing facilities in
*
Corresponding author. Tel.: +46 18 4713613; fax: +46 18 555736. E-mail address: [email protected] (S. Persson).
0168-583X/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.01.193
Europe, releasing 129I both into running waters (marine and rivers) and into the atmosphere. Gaseous releases of 129 I contribute to <10% of the total known releases from the Sellafield and La Hague facilities [1]. During the years 1988–1997, total gaseous 129I releases from the Marcoule facility, 68.5 kg [2], were in the same order of magnitude as those from Sellafield and La Hague, 65.5 kg (Fig. 1). In spite of the relatively large amounts of gaseous releases, quantifying their contribution to 129I in precipitation is difficult, since the knowledge about the pathways of 129I in the atmosphere is still vague. Many questions concerning transfer from the sea to the atmosphere, the influence of weather conditions, wind patterns and chemical parameters remain to be answered. With the aim of elucidating the problem, we have an ongoing project on 129I in precipitation from three stations in Sweden and we here present first results of this project. These results are compared with published data on the distribution and inventory of 129I over Europe. The overview
S. Persson et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 508–512
509
Table 1 129 I Concentrations in precipitation from stations 1–5
Fig. 1. Yearly gaseous releases from Sellafield, La Hague and Marcoule. No data are published for Marcoule before 1988. Values for Sellafield 1952–1975 and Marcoule 1958–1987 are estimates [1,2,13].
covers latitudes 37N to 70N (southern Spain to northern Sweden) and includes both rain and snow. 2. Materials and analytical technique 2.1. New data from this study Precipitation from three stations in Sweden was collected during the years 2000–2002. In addition, one sample from northern Italy and two from Norway were collected (Table 1, Fig. 2). Most of the samples represent a single rain or snow event, but in some cases the sample acquisition was done during a couple of days. The samples were collected in a funnel covered with a 20 lm mesh net and stored in polyethylene bottles in a cold dark room. The colorimetric method used for iodine extraction is the same as described in [3], but with some minor modifications. After filtering the sample through a 0.45 lm membrane filter, Woodward iodine was added as a carrier. The solution was then reduced with NaHSO3 to convert iodate to iodide and acidified to pH = 2. Then the iodine was extracted into CHCl3, back extracted into water, and precipitated as AgI, which was finally washed twice with distilled water. The AgI was mixed with niobium powder and pressed into cupper holders for the AMS measurement, which was done at the Uppsala Tandem Accelerator. Standards prepared from the 129I reference material NIST SRM 4949C were used for normalization of the measured 129I/127I ratio. Chemical blanks prepared with the same procedure as the samples were regularly processed and used for background correction. Generally the total error was less than 10% of measurement including counting statistics and blank correction. For a few samples, we also analyzed the stable iodine concentration in order to calculate the isotopic ratio. This was done with HR-ICP-MS at the Radiation Research Department, Risø National Laboratory in Denmark. An internal standard 20 ppb of Sb was used, and the blank counts were about 3–8% of the sample counts with a detection limit of 0.030 ppb.
Station
Sampling date
129
Abisko 1 2 3 4 5 6 7 8 9
25-dec-00a 06-apr-01 30-jul-01 13-aug-01 18-aug-01 18-okt-01 30-okt-01 05-nov-01a 13-nov-01a
2.9 ± 0.2 18.4 ± 1.0 6.3 ± 0.4 5.7 ± 0.4 7.3 ± 0.5 10.6 ± 0.7 10.6 ± 0.5 5.9 ± 0.3 7.5 ± 0.4
Uppsala 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
28-dec-99a 20-jan-00a 03-feb-00a 03-mar-00a 05-apr-00a 24-maj-00 28-maj-00 24-apr-01 18-jul-01 20-aug-01 11-okt-01 31-okt-01 21-dec-01a 31-jan-02a 04-maj-02 30-jun-02
2.5 ± 0.1 1.7 ± 0.1 28.2 ± 3.4 19 ± 2.4 2.1 ± 0.2 10.4 ± 0.7 15.1 ± 1.0 3.6 ± 0.2 18.4 ± 1.1 23.9 ± 1.2 3.9 ± 0.4 2.7 ± 0.2 6.2 ± 0.3 6.7 ± 0.4 3.5 ± 0.2 8.0 ± 0.5
Kvidinge 26 27 28 29 30 31 32 33 34
30-jun-01 20-aug-01 12-okt-01 29-okt-01 21-dec-01 02-feb-02a 27-maj-02 17-jun-02 24-jun-02
12.4 ± 0.7 25.2 ± 1.3 21.3 ± 1.0 18.5 ± 1.1 22.1 ± 1.1 38.7 ± 2.6 10.4 ± 0.6 16.9 ± 0.8 62.3 ± 3.9
Bergen 35 36
12-jan-03 2-apr-03
15.8 ± 0.7 41 ± 1.9
N. Italy 37
23-aug-02
6.6 ± 0.4
a
I (108 atoms l 1)
Snow.
2.2. Published data We have collected data on 129I in precipitation over Europe from several published reports during the last decade (Table 2, Fig. 2). These studies have used different methods and sampling techniques (Table 3), which make a direct comparison of the published results rather problematic. The temporal resolution of the data varies between daily (single event) and three months (multiple events sample). In some cases, the sampling was done continuously and in others, several periodic samples were mixed into one sample. In the case of continuous sampling, dry deposition
510
S. Persson et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 508–512
Fig. 2. Map showing the locations of stations used and the nuclear reprocessing facilities Sellafield (S), La Hague (H) and Marcoule (M, closed in 1997). The arrow points in the direction of the Mayak complex in Russia.
Table 2 Results and information about the sampling stations Latitude N
Number of samples
Average 129I concentration 108 atoms l 1
Std. dev. 108 atoms l
1 Abisko 2 Uppsala
68 60
3 Kvidinge 4 Bergen 5 Northern Italy
56 60 45
9 33 16 9 2 4 1 27 29 57 13 19 26 14 13
8.3 11.1 9.7 25.3 28.4 3.0 6.6 36.1 56.3 15.8 16.3 84.1b 60.7b 74.8b 88.8b
5 11 9 16 18 4
Station
6 Lower Saxony 7 Zu¨rich/Du¨bendorf 8 Seville 9 Upper Bavaria 10 Waldhof 11 Deuselbach 12 Brotjacklriegl 13 Schauinsland a b c
52 47 37 48 53 50 48.5 48
17 100 79 12
1
Range 108 atoms l 2.9–18.4 0.4–41.2 1.7–28.2 10.3–57 15.8–41 0.3–9.4 6.6 11–70 2.16–445 0.22–600 4.8–50 23–300c 14–130c 9–270c 18–420
1
Year of sampling
References
2000–2001 1998–1999 2000–2002 2001–2002 2003 1998 2001 1997–1999 1994–1997 1996–1999 2003–2004 1994–1995 1994–1995 1994–1995 1995
This study [4] This study This study This study [4] This study [7,9]a [10] [5,11] [6,12] [8]a [8]a [8]a [8]a
Only inland stations were taken into account, i.e. the results from the Norderney [8,10] and Westerland [9] islands were not included. Average for 1995 only, as published in [8]. Estimates from the figures in [8].
S. Persson et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 508–512
511
Table 3 Sampling and preparation procedures for the different studies Location on map
Sampling period
Chemical treatment before storage
Filtering
Extraction method
Schnabel et al. [10]
7
1 month
2,5
Lo´pez-Gutie´rrez et al. [5,11] Szidat et al. [7,9]
8
Single event, in some cases a couple of days 1 month or 25 liters
Not specified 0.45 lm
CHCl3
Buraglio et al. [4]
NaOH until pH = 14 to destroy organic compounds None
14 daysa
Krupp and Aumann [8] Reithmeier et al. [6,12] This study
10–13
Varying, no details given.
Not specified
Not specified Not specified Nob
CHCl3
6
NaOH to separate iodine from organic molecules NaOH to preserve the samples
9
Integrated into samples representing 1–2 months. Single event, in some cases a couple of days
Not specified
0.2 lm
Anion exchange column Anion exchange column CCl4
None
0.45 lm
CHCl3
1–5
CCl4
a
Samples from 3 months were integrated into one sample; periods with little precipitation are underrepresented. Half of each sample was filtered in order to determine particulate-bound 129I. The results discussed in this paper are total 129I concentrations, including this part. b
is included in the results, whereas the dry deposition portion is negligible in single event sampling. In addition, methods differ in whether the water is filtered before extraction of iodine and whether NaOH is added before storage (Table 3). 3. Results and discussion The results of samples measured in this study show average concentrations of 8.3 · 108 atoms l 1 (Abisko), 9.7 · 108 atoms l 1 (Uppsala) and 2.5 · 109 atoms l 1 (Kvidinge), with a large scatter for all three stations (Tables 1 and 2). These stations show latitude dependence with the lowest average value in the north and the highest average value in the south. Kvidinge is located near the coast (20 km), which may also explain the observed higher concentrations. The Uppsala average is about the same as in the previous study by Buraglio et al. [4]. For northern Italy, one sample from 2001 was measured and it gives 6.6 · 108 atoms l 1, which lies within the range of earlier measurements. Two samples from Bergen, located at the Norwegian Atlantic coast were measured. Concentrations for these samples were 10.3 · 108 and 5.7 · 109 atoms l 1 resulting in an average slightly above that in Kvidinge. Data from this study together with published data from other parts of Europe show a general concentration range of 108–1010 atoms l 1 with a few samples above and below this range (Table 2). Average concentration for the sampling stations vary at (3–89) · 108 atoms l 1. The large spread of the concentrations, combined with the temporal spread between the stations, does not permit a conclusive picture about latitude dependence as shown by the Swedish stations alone (Fig. 3). However, sites close to the Atlantic coast (3, 4 and 6) exhibit relatively higher average concentrations than the inland ones. The station in northern Italy has the overall lowest average value (3 · 108 atoms l 1), but the number of samples is too small to confirm this observation.
Fig. 3. Average 129I concentrations for the 13 stations and the latitudes of the major 129I emitters in Europe (vertical lines). The numbers within parentheses show the sampling years for each station. For simplicity, we show just the average values in spite of the large spread. Details of the stations in Table 1.
A decreasing trend in concentrations can be observed during the years 1995–2004; especially stations measured before 1997 (stations 7, 10–13) show higher concentrations than the latter ones. These stations are also mainly situated far from the Atlantic Ocean. A comparison between stations 9 and 12, that are situated very close to each other (Fig. 1) confirms the decreasing trend in 129I concentration; the average concentration in 2003–2004 is less than 1/4 of that in 1995. A possible explanation for this observation can be the shutdown of the Marcoule facility (Fig. 1) during the late 1990s (September 1997). The gaseous releases from La Hague also happened to decrease during the same period, but the magnitude was smaller than that of the Marcoule facility (Fig. 1). Evaluation of the pre-1997 129I load in Europe from the Marcoule facility needs further
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(3.61–6.57) · 10 7 for station 6 [7] and (6.0–9.7) · 10 7 for station 10–13 [8]. To roughly estimate the annual amount of 129I fallout by precipitation over Europe, we have used the average values of the data sets (without the few extreme values of Zu¨rich and Seville) and an average annual precipitation rate of 600 mm. The calculation reveals a fallout rate of about 2.5 kg 129I, which represents represent <1% of the total annual releases or about 1/3 of the annual gaseous releases. A more detailed calculation should obviously include normalization to the precipitation amount as well as some geographical weighting of the stations. 4. Conclusions Fig. 4. Temporal variation of
129
I of three sampling stations in Europe.
investigation in future studies. Unfortunately, absence of Scandinavian data before 1997 hinders estimating the effect of the gaseous emissions reduction to this region. Some details of the temporal variability in 129I concentration are illustrated by the relatively long records from Uppsala, Zu¨rich and Seville (Fig. 4). In all the three data sets, there are strong non-periodic fluctuations, which may have different environmental explanations, e.g. seasonal variations, weather conditions and washout effects. An even more significant source to the fluctuations is probably the daily emission of gaseous releases from the reprocessing facilities. Information concerning the daily releases are unfortunately lacking, but the monthly data from [5] confirm the non-periodic fluctuations in Fig. 4 that may relate to stochastic emission patterns. Although both Seville and Zu¨rich exhibit higher temporal fluctuations than Uppsala, the Seville 129I range as well as the spread seems to be lower after 1997 compared to the period before. This observation could again be explained by the dominant gaseous releases from the Marcoule facility (Fig. 1) prior to 1997. It is important to remember that there might exist additional, unknown sources of 129I, especially in Eastern Europe, that may have contributed to atmospheric input. One candidate is the Mayak complex in the southern Ural Mountains of Russia, for which presently no data are published. Although this study mainly focuses on the concentration of 129I, the 129I/127I ratio, as pointed out by several investigations, represents an additional parameter in understanding the pathways from the sources to the atmosphere. In our study, we have analyzed the stable iodine content of a few samples from the three Swedish sample stations. The average stable iodine concentrations for the stations were 2.1, 1.6 and 2.9 lg/l, respectively. Applying these values to our data, we get the estimated average isotopic ratios 8.3 · 10 8, 1.3 · 10 7 and 1.8 · 10 7. Published measured values on the isotopic ratio in precipitation from other stations used in this overview are 1.5 · 10 7 for station 9 [6],
The results of this investigation indicate large variation in temporal and spatial distribution of 129I in precipitation over Europe without constrained latitudinal dependence. Different sample collection procedures and variable temporal coverage of the records did not permit establishment of exact source or controlling factors that affect the distributions trends observed. Accordingly, unified sample collection procedures and long periods of time series data are needed in order to capture details of variability in 129I atmospheric loading over Europe. Acknowledgement We would like to thank Christer Jonasson and his team for collecting precipitation samples in Abisko and the Swedish Radiation Protection Institute for their financial support. References [1] J.M. Lopez-Gutierrez, M. Garcia-Leon, C. Schnabel, M. Suter, H.-A. Synal, S. Szidat, R. Garcia-Tenorio, Sci. Total Environ. 323 (2004) 195. [2] Cogema Marcoule Rapport Environnement, 1997. [3] N. Buraglio, A. Aldahan, G. Possnert, Nucl. Instr. and Meth. B 172 (2000) 518. [4] N. Buraglio, A. Aldahan, G. Possnert, I. Vintersved, Environ. Sci. Technol. 35 (2001) 1579. [5] J.M. Lopez-Gutierrez, F.J. Santos, M. Garcia-Leon, C. Schnabel, H.-A. Synal, T. Ernst, S. Szidat, Nucl. Instr. and Meth. B 223–224 (2004) 495. [6] H. Reithmeier, Ph.D. thesis, Fakulta¨t der Physik, Technische Universita¨t Mu¨nchen, 2005. [7] S. Szidat, A. Schmidt, J. Handl, D. Jakob, W. Botsch, R. Michel, H.-A. Synal, C. Schnabel, M. Suter, J.M. Lopez-Gutierrez, W. Stade, Nucl. Instr. and Meth. B 172 (2000) 699. [8] G. Krupp, D.C. Aumann, J. Environ. Radioact. 46 (1999) 287. [9] S. Szidat, Ph.D., Fachbereich Chemie, Universita¨t Hannover, 2000. [10] C. Schnabel, J.M. Lopez-Gutierrez, S. Szidat, M. Springer, H. Wernli, J. Beer, H.-A. Synal, Radiochim. Acta 89 (2001) 815. [11] J.M. Lopez-Gutierrez, M. Garcia-Leon, C. Schnabel, M. Suter, H.-A. Synal, S. Szidat, J. Environ. Radioact. 55 (2001) 269. [12] H. Reithmeier, V. Lazarev, F. Kubo, W. Ruhm, E. Nolte, Nucl. Instr. and Meth. B 239 (2005) 273. [13] H. Reithmeier, V. Lazarev, W. Ru¨hm, M. Schwikowski, H.W. Ga¨ggeler, E. Nolte, Environ. Sci. Technol. 40 (2006) 5891.