- Email: [email protected]
Level of natural and artificial radioactivity in Algeria
~
Appl. Radiat. lsot. Vol. 49, No. 7, pp. 867-873, 1998
Pergamon
© 1998 Elsevier Science Ltd. All rights reserved
Printed in Great Britain 1350-4487/98 $19.00 + 0.00
PII:S0969-8043(97)10005-7
Level of Natural and Artificial Radioactivity in Algeria B. B A G G O U R A ,
A. NOUREDDINE*
and M. BENKRID
Centre de Radioprotection et de Sfiretr, Laboratoire d'Environnement, 02 Bd. F. Fanon, Bp 399 AlgerGare, Algiers, Algeria
(Received 17 June 1997,"accepted 21 August 1997) A national environmental sampling program was carried out during 1993 to determine natural and artificial radionuclides contents in the (0-15 cm) upper layer of the soil. The main objective was to establish a radioactive reference level in the whole territory, since 131I, 134Csand 137Cs w e r e detected in most of the analysed samples collected right after the Chernobyl accident (May 1986). Soil samples were analysed by direct counting by gamma-ray spectrometry. In addition, terrestrial gamma-ray dose rates in air have been measured out of doors throughout Algeria. In each of the 48 administrative divisions of the country selected sites were chosen to collect soil samples and measure gamma-ray dose rates. The gamma-emitting radionuclides resulting from the radioactive decay of 238U and 232Th, 4°K and 137Cs were detected in most of the analysed samples. Radioactivity concentrations in Bq kg- 1dry mass in soil samples of 226Ra, 214Pb, 214Bi, 2121Pb, 228Ac, 40K and 137Cs range between (5-176), (2-107), (3-65), (297), (3-144), (36-1405) and (0.3-41) respectively. In addition, six selected soil samples were analysed to determine plutonium isotopes contents. Radioactivity concentrations in Bq kg- 1 dry mass of 238Pu and 239 + 240pu vary between (0.012-0.013) and (0.24-0.61) respectively. The dose rates in air measured over the whole country were found to range between 20 and 133 nGy h -1. Presence of 137Cs has been clearly observed. An approach has been made to determine its origin, considering the global fallout, the Chernobyl accident and the French nuclear bomb tests in the 60s as the main potential sources. It is concluded that Algeria has indeed been affected by the Chernobyl accident. © 1998 Elsevier Science Ltd. All rights reserved
Introduction Following the Chernobyl accident on 26 April 1986, a considerable a m o u n t o f radioactive materials was released into the atmosphere contaminating the environment of the whole earth (Olli, 1990). Algeria, with its large coast line (1200 km) facing the European continent was certainly, in north Africa, the country the most exposed to this large scale contamination and might have been affected, to some extent, by the accident. The environmental impact and the change in the man-made radioactivity in the reference level associated to this accident offer an opportunity to launch a number of experimental research works to better identify and understand radioactive anomalies in the country in the future. Consequently two investigations related to the environmental impact of the Chernobyl accident o f 1986 on the Algerian soil have been carried out. The first one was performed in the first semester o f 1986, few weeks after the accident, covering the northern terrestrial strip along the Algerian coast about 1200 km long and 200 km wide. M o s t
of the samples were analysed to identify gammaemitting radionuclides, namely 131I, 134Cs and 137Cs. The second was carried out during 1993 to determine natural and artificial radionuclides contents in the upper layer of the soil throughout the Algerian territory.
ExperimentalMethod Sampling In the first campaign (1986), two mobile laboratories equipped with g a m m a ray detection devices were used. Sampling points, approximately a hundred kilometres apart from each other, were chosen in areas of high population density. Environmental samples, such as milk, rainfall water and grass were then collected manually. All the samples were collected during spring time. On-site g a m m a spectrometry measurements were performed to select samples to undergo detailed radionuclides identification. In the second campaign, in the early 90s, soil sampling was carried out over the whole territory that covers a total area of 2.341.000 km 2. Due to the heterogeneity of the environment, the country
*To whom all correspondence should be addressed. 867
868
B. Baggoura et al. 23
3e
11
Fig. 1. Administrative divisions. has been divided into three main zones: a northern zone, a small strip of land between the Mediterranean Sea and the Atlas mountains, heavily populated in which most agricultural and industrial activities of the country are performed; a central zone, a region located between the Atlas mountains and the Sahara desert, sparsely populated, where the main economic activity is ovine and cattle breeding; and finally a southern zone, a huge desert of approximately 2 million km 2 having a very low population density. The climate, type of vegetation, nature of soil and precipitation contents vary considerably from one zone to the other. Mobile laboratories, four-wheel drive vehicles and aeroplanes were the m a i n means used during the sampling phase. Field sampling was carried out in all the 48 administrative divisions of the country. Samples were picked up at several points at each of the above mentioned sites at different seasons, as shown in Fig. 1. A total number of 219 soil samples of different nature, mainly fine and coarse sands carbonated,
were manually collected in the (0-15)cm undisturbed upper layer using an appropriate shovel. They were dried at 80°C and then put into a 500 cm 3 Marinelli beaker for direct gamma counting after removing stone and grass from the samples and ground to pass a 60 mesh sieve. At the same time, terrestrial gamma-ray dose rates were measured at sampling locations by means of a pressurised argon ionisation chamber, type RSS-112 at 1 m above the top soil. Radioactivity measurement
Some environmental samples (milk, grass, precipitation) collected at several points in Algeria were analysed for qualitative analysis of gammaemitting radionuclides and NaI (Tl)detectors were used. For surface soil samples, a high purity germanium detector with relative efficiency of 23% and energy resolution of 2 keV for the 1332 keV 6°Co peak with a multichannel analyser (4096 channels) were used for gamma spectrometry analysis. Dried samples were placed either in polythene 500 cm 3
Natural and artificial radioactivity in Algeria Marinelli beakers or 250cm 3 plastic bottles of c y l i n d r i c a l f o r m , to be c o u n t e d l o n g e n o u g h to p r o d u c e a c c e p t a b l e c o u n t i n g statistics ( u s u a l l y 24 h). Efficiency c a l i b r a t i o n c u r v e s w e r e o b t a i n e d u s i n g a n I A E A 500 c m 3 M a r i n e l l i b e a k e r c o n t a i n i n g a refere n c e m a t e r i a l o f d e n s i t y 1 g c m -3, c o n t a m i n a t e d b y a s o l u t i o n o f t h e m u l t i - g a m m a e m i t t e r 152Eu. Efficiencies a t t h e e n e r g i e s o f i n t e r e s t w e r e i n t e r p o l a t e d f r o m c a l i b r a t i o n c u r v e s . T h e full e n e r g y peaks taken into account for the qualitative and q u a n t i t a t i v e a n a l y s i s o f 226Ra, 214pb, 214Bi, 212Pb, Z2SAc, 4°K, 134Cs, 137Cs a n d 131I a r e 1 8 6 . 2 k e V , 352.0 k e V , 609.3 k e V , 238.6 keV, 911 k e V , 1460.8 keV, 796 k e V , 661.7 k e V a n d 365.5 k e V respectively. T h e d e t e c t i o n l i m i t f o r t h e 137Cs is less t h a n 1 B q k g -1 d r y m a s s . N o t e t h a t o u r e n v i r o n m e n t a l l a b o r a t o r y h a s p a r t i c i p a t e d in t w o i n t e r n a t i o n a l i n t e r c o m p a r i s o n e x e r c i s e s ( I A E A - 326/327, IAEA-300/315) organised by the IAEA's labora-
869
t o r i e s at S e i b e r s d o r f a n d M o n a c o a n d all o u r results agreed within _10% with reference values. I n a d d i t i o n to t h e s e a n a l y s e s , six soil s a m p l e s were selected to u n d e r g o r a d i o c h e m i c a l s e p a r a t i o n f o r p l u t o n i u m i s o t o p e s d e t e r m i n a t i o n b y a l p h a spectrometry. The detection limit of plutonium isotopes is in t h e r a n g e o f 0 . 0 1 - 0 . 1 B q k g -1 d r y m a s s . T h e e v a l u a t i o n is b a s e d o n a n e s t i m a t i o n o f b a c k g r o u n d o f ( 1 - 9 ) × 10 -5 cts s -1, a s a m p l e size o f 10 g a n d a d e t e c t i o n efficiency o f a r o u n d 4 0 % , as p o i n t e d o u t b y N o u r e d d i n e et al. (1996).
Results and Discussion T h e a c t i v i t y c o n c e n t r a t i o n s o f n a t u r a l a n d artificial r a d i o n u c l i d e s m e a s u r e d b y direct c o u n t i n g g a m m a s p e c t r o m e t r y o r a l p h a s p e c t r o m e t r y (for p l u t o n i u m i s o t o p e s ) in t h e a n a l y s e d soil s a m p l e s , c o l l e c t e d a t t h e 48 selected sites, a r e listed in T a b l e 1 a n d T a b l e 2. T h e n a t u r a l a n d m a n - m a d e r a d i o -
Table 1. Activity concentrations of natural and artificial radionuclides in soil (Bq kg-1 dry mass) Location* 226Ra 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
19-129 29-56 6-60 53-60 39-45 42-63 5-80 5-84 57-73 39-64 8-70 39-63 36-72 20-109 52-107 11-35 17-61 44-93 35-112 27-28 58-124 42-47 76-82 28-55 27-52 67-84 31 11-78 12-52 23-51 36-55 11-36 17-176 46-49 30-62 37-48 27 48 18-42 44-57 36-127 20-56 / 76-107 18-55 25-37 8-74 45-51
214pb
214Bi
228Ac
6-34 26-35 5-37 23-35 29-30 33-37 9-30 2-48 39-52 28-34 30-107 19-28 8-31 19-85 43-52 24-35 17-44 34-55 13-39 9-14 32-82 22-23 4!-42 20-24 18±31 36-81 13 13-56 10--23 4-30 10-19 10-29 17-107 27-27 13-36 26-28 19 24 5-10 27-35 15-47 5-36 / 50-52 8-49 10-14 12-57 21-27
10-22 18-26 2-20 22-27 18-18 22-31 6-23 9-31 13-32 16-22 17-65 19-26 5-29 12-55 24-32 14-24 8-18 20-31 18-35 8-25 26-53 20-24 24-26 15-25 17-24 22-55 11 6-34 9-23 4-26 9-20 5-21 7-64 17-19 9-22 18-19 11 16 5-11 23-24 16-43 7-34 / 29-41 8-29 10-12 8-34 22-23
7-19 16-32 2-30 21-45 19-21 17-33 5-23 23-60 11-47 16-30 23-144 21-27 21-43 14-61 37-50 13-29 10-33 19-25 19-33 9-20 5-57 28-31 42-48 12-47 20-23 26-46 12 6-46 10-26 7-84 26-28 5-22 11-88 13-16 7-39 17-23 12 28 5-13 23 19-50 6-31 / 43-48 8-36 21-24 7-25 22-29
212Pb
4°K'
137Cs
2-10 74-438 17-31 83-541 3-30 35-712 20-25 193-273 18-19 334-348 19-37 222-328 3-22 68-293 8-52 53-903 12-38 189-626 14-28 263-314 11-69 397-965 8-38 261-324 7-60 262=643 16-32 303-1150: 41-69 234-579 2-24 198-422 7-32 215-506 24-30 221=356 22-38 175-358 5-17 245-257 23-54 564-833 6-31 528-608 35-43 435-437 19-59 191±363 12-34 174-536 29-39 331-710 14 219 7-44 91-316 3-37 199-514 2-97 181-482 24-29 467-482 5-22 97-290 13-97 82-777 11-14 132-150 16-55 156-509 13-19 118-150 15 378 30 453 7-15 93-329 4-36 235-303 33-46 234-1405 14--31 67-422 / / 46-47 609 3-23 148-689 6-33 301-412 5-24 93-376 21-25 469-585
/ 6-7 3-25 1,3 13-26 1-27 0.1-24 0.6-6 0.2-7 5.-16 0.1-15 8-11 11-24 5-19 7-41 2-7 0.2-15 1.9 5-12 3-16 9-12 0.5-1 10-16 0.3-2 4-34 5-:11 10 1-36 0.5-36 0.4-12 5-9 2-13 0.3-13 5-9 0.6-24 10-11 / 8 4-16 2-6 1-10 2-6 / 13-15 0.5-14 4-16 6-43 1-5
*In each location (administrative division), about five samples have been analysed.
B. Baggoura et aL
870
Table 2. Activity concentrations in Bq kg-~ dry mass of artificial alpha and gamma-emitting radionuclides in soil samples at different sampling points in Algeria
Samplingpoint
137Cs
39 47 47 46 05 25 42
15.8 + 1.7 22.1 _+2.3 15.8 ___1.7 26.1 ___2.7 15.5 _+2.0 34.2 _ 3.3 7.6 _+ 1.2
239 + 240pu
0.36 + 0.02 0.44 _+0.03 0.25 _+0.02 0.61 _+0.03 0.26 _+0.02 0.27 __.0.008 --
238pu
239 + 240pu/137Cs
238pu/239 + 2nOpu
< LD 0.013 _ 0.008 < LD < LD < LD 0.012 4- 0.008 --
0.023 + 0.003 0.020 _+0.002 0.015 +_0.002 0.023 _+0.003 0.017 ___0.003 0.008 __.0.001 --
-0.029 + 0.018 ---0.044 ___0.030
LD: limit of detection. nuclides consisted o f 238U a n d 232Th daughters, 4°K, 137Cs a n d p l u t o n i u m isotopes respectively. T h e radionuclides resulting from radioactive decay o f 238U a n d 232Th are mainly 226Ra, 214pb, 214Bi a n d 228Ac, 212pb, respectively. A m o n g the 238U d a u g h ters, 226Ra shows the highest value. Its range varies f r o m 5 to 176 Bq kg -I dry mass. The c o n c e n t r a t i o n s o f 214pb a n d 214Bi, however, vary between (2 a n d 107) a n d (3 a n d 65) Bq kg -1 dry mass, respectively. T h u s it appears that, in the 238U decay series, the 226Ra is significantly o u t o f radioactive equilibrium, since its average value ranges f r o m 32 to 71 Bq kg -1 dry mass a n d t h a t o f 214pb (which is the same as t h a t o f 214Bi) f r o m 21 to 40 Bq kg -1 dry mass. M o s t o f the highest values o f 226Ra have been recorded in the s o u t h e r n p a r t o f the country. T h e u p t a k e o f 226Ra by Algerian soil samples, as m e n t i o n e d above, is within the typical range observed in Spanish soil samples (13-165) Bq kg -1 dry mass b u t is higher t h a n the world average c o n c e n t r a t i o n , (10-50) Bq kg - l dry mass (Baeza, 1991; Pentreath, 1980; a n d K a t h r e n , 1984). T h e u p t a k e o f 226Ra varies from one area to the o t h e r a n d with the n a t u r e o f soil. T h e c o n c e n t r a t i o n s o f t h o r i u m daughters, namely 228Ac a n d 212pb, are in the range o f (3-144) a n d ( 2 - 9 7 ) B q kg -1 dry mass. The highest concentrations of these radioelements have been recorded in the south. T h e equilibrium, however, is observed for t h o r i u m daughters, since the average o f their m i n i m u m a n d m a x i m u m values are the same. These are (16-36) a n d (14-36) Bq kg -1 dry mass for 228Ac a n d 212pb, respectively. T h e u p t a k e o f t h o r i u m d a u g h t e r s b y the Algerian soil samples is lower t h a n t h a t observed in Spain [ ( 7 - 2 0 4 ) B q kg - l dry
mass] a n d higher t h a n the world average concentration, [(7 to 50) Bq kg - l dry mass]. Regarding 4°K, the c o n c e n t r a t i o n varies from (66 to l l 5 0 ) B q k g -1 dry mass, this is lower t h a n the world average, which is (48 to 1 5 8 5 ) B q k g -1 dry mass a n d lower t h a n t h a t m e a s u r e d in Spain, which is (100 to 7 0 0 ) B q k g -1 dry mass. T h e concent r a t i o n s o f the radioactive decay p r o d u c t s o f 23Su a n d 232Th, a n d 4°K, observed in the analysed soil samples, which are mainly fine a n d coarse sands c a r b o n a t e d , were c o m p a r e d to radioactive geological data. Hence, a c o m p a r i s o n o f the o b t a i n e d results with those reported by N C R P (1975), U n i t e d N a t i o n s (1977) a n d K a t h r e n (1984) was carried out, see Table 3. W e r e m a r k t h a t o u r results are, m o r e or less, close to the different reported values. Soil sample c o n c e n t r a t i o n s however, w h e n c o m p a r e d to those o f shales a n d sandstones (the closest to it in terms o f composition), show lower values. As to artificial radioactivity, 137Cs a n d P u isotopes were clearly observed in soil samples. T h e highest recorded value o f 137Cs was (41 + 4 ) B q kg -1 dry mass a n d is higher in areas where precipitation is m o r e frequent. T h e samples showed different values: almost 50% o f the total n u m b e r o f samples range from (0 to 5 ) B q kg - l dry mass; 13.6% f r o m (5 to 10) B q k g - l dry mass; 17.6% from (10 to 2 0 ) B q k g -1 dry mass; 6.2% f r o m (20 to 3 0 ) B q kg -1 dry mass a n d 12.6% for greater t h a n 30 Bq kg - l dry mass. The m e a n value for 137Cs for each site is reported o n Fig. 2 showing the different activity levels. However, for 238pu a n d 239 + 240pu ' activity c o n c e n t r a t i o n ranges a r e (0.012
Table 3. Comparison of the obtained results with those presented in the literature Radioelement
Nature of sample
Obtained results* (Bq kg-t)
NCRP 45 (Bq kg-I)
UNSCEAR Report 1977 (Bq kg-')
4°K
Soil
227-504
444
4°K 4°K 23Su
Shales Sandstones Soil
814 592-888 22
23Su 23Su 2S2Th
Shales Sandstones Soil
232Th 232Th
Shales Sandstones
--32.4-70.9; 20.5-40.2 (Decay products) --16-36; 14-36 (Decay products) ---
Wld average: 370 typical range: 110-740 703 370 Wld average: 26 typical range: 11-52 44 19 Wld average: 26 typical range 7-48 44 11
*Averages of the minimum and maximum values are given.
46 25-37 37 49 12-24
R.L. Kathren (Bq kg-1) -798 320 -46 6 ----
Natural and artificial radioactivity in Algeria to 0.013) and (0.24 to 0.61)Bqkg -1 dry mass, respectively. This artificial radioactivity may have different origins. Nuclear weapon and bomb tests and accidents being obviously the best candidates. To be more selective, we may pick up: global fallout from nuclear weapon tests; French nuclear bomb tests in the 60s in the Algerian Sahara desert and the Chernobyl accident of 1986. We then can consider this artificial radioactivity as being due to any single one or any combination of these sources. However, the lack of data, particularly those related to the French nuclear tests, in the open literature makes the evaluation of their respective contributions quite difficult. Nevertheless, based on available data we can put forward the following argumentation to shed some light on this particular point and come up with an acceptable conclusion. We start by noting that in March 1960 at Ispra (Italy), incidentally located at bird flight distance from Reggane (the site where the French nuclear tests in the atmosphere were performed) as is most of the Algerian coast line,
871
137Cs and some radionuclides of short half-life specific to those French nuclear explosions (14°Ba, 14°La, 147Nd, etc ..... ) were detected in air, the food chain and soil (Cigna e t al., 1961). The recorded level of ~37Cs was 11.1 B q m -2. It was considered then as background when compared with the 33300 Bq m -2 measured at the same location few years earlier, late in 1958. If we assume that the French nuclear tests fallout have had, approximately, the same impact on the northern part of Algeria, we may then consider this later as negligibly small compared with that of the Chernobyl accident, estimated to be 400 Bq m -2 by Olli (1990). We then examine, the ratios of 239 ÷ 240pu: 137Cs and 238pu: 239 + 240pu reported in Table 2 (Noureddine et al., 1996) and note that they are different from those given by Duriec e t al. (1984), Belyayev et al. (1990), Pavlotskaya et al. (1990), Kulakov et al. (1990) and Coughtrey et al. (1990). Hence, we see that the average ratio of 239 - 2 4 0 p u : 1 3 7 C s ( 0 . 0 2 ) obtained is twice lower than the one recorded before the Chernobyl accident
::'.
iiii|iiili~!ill
•
.
Oo°
•
• •
o . o . . l o ° o ,
o • OOO..
o
• •
° ..-
°
o ,
o ,
,
°
,..
"|
BqlKg I"
Il~*t r ~ a 11-3
3-6
I
s-9 9-12 >12 '
•
°
iiiiiiiii Fig. 2. Caesium-137concentration average.
200 K m
872
B. Baggoura et al.
-$~ I El
t I
I t
r-
I
tt~
I
I
° o...¢
•
I
I I
I !
I I I
t II¸
I m
I
t,....* C, n
t"--
'IU
I
I
I
I
:qt~Du a~J0x~ a ~
t
asop tmmm D
1
w
Natural and artificial radioactivity in Algeria (0.04). As for the ratio 23Spu:239 + 24°pu its values are in the typical range of global fallout in soil (0.03-0.05). We readily deduce that the 137Cs concentration due to the Chernobyl accident has added up to that of global fallout. If we note at last that 131I and 134Cs were qualitatively measured in milk, precipitation and grass samples collected throughout the northern part of Algeria right after the Chernobyl accident (May 1986), we then may safely conclude that Algeria has indeed been affected by the Chernobyl accident. Regarding the terrestrial g a m m a ray dose, 219 measurements were carried out. The mean value is 70.30 n G y h -1 with a range of 20-133.10 n G y h -1. The mean value for the terrestrial g a m m a dose rate is reported on Fig. 3. The annual average value of effective dose equivalent from terrestrial g a m m a rays for the country is about 8 . 6 4 x 1 0 - S S v . U N S C E A R ' s coefficient o f 0.7 Sv Gy -1 is used to convert the absorbed dose in air to effective dose equivalent for adults, considering an outdoor occupancy factor for Algerian people of about 0.2. Acknowledgements--Thanks are due to the sampling assistance of A. Allalou and N. Messen and their respective teams. The authors wish also to thank B. Yagoubi for the sample counting.
References Baeza, A. (1991) Natural radioactivity in soils of the province of Caceres (Spain): Salzburg, Austria, 22-28 September 1991. Fifth International Symposium of the Natural Radiation Environment. Belyayev, S. T., Borovov, A. A., Demin, V. F., RimskyKorsakov, A. A. and Khernvinov, A. N. (1990) The Chernobyl source term. Proceedings of a Seminar on comparative assessment of the environmental impact of radionuclides released during three major nuclear accidents: Kyshtym, Windscale, Chernobyl, Luxembourg, I-5 October 1990. Radiation Protection, Vol. I, p. 53. Commission of the European Communities. Cigna, A., Dominici, G., Malvicini, A. and Vido, L. (1961) Radioattivit~i dei Prodotti di Fissione nel Fallout Raccolto dopo l'Esplosione Nucleare Francese nel Sahara. Comitato Nazionale per l'Energia Nucleare, Centro di Studi Nucleari di Ispra, CNI-81.
873
Coughtrey, P. J., Kirtou, J. A. and Mitchell, N. G. (1990) Environmental distribution and transport of radionuclides in west Cumbria following the Windscale and Chernobyl accident. Proceedings of a Seminar on comparative assessment of the environmental impact of radionuclides released during three major nuclear accidents: Kyshtym, Windscale, Chernobyl, Luxembourg, 1-5 October 1990. Radiation Protection, Vol. I, p. 53. Commission of the European Communities. Duriec, S. T., Hallstanius, L. and Holm, E. (1984) A study of the transport of radionuclides in the sea by use of isotopic ratios. International Symposium on the behaviour of long-lived radionuclides in the marine environment. Radiation Protection, Vol. I. Commission of the European Communities. Kathren, R. L. (1984). Radioactivity in the Environment, Sources, Distribution and Surveillance. Battelle Pacific Northwest Laboratories, U.S.A., Harrowed Academic Publishers. Kulakov, V. M., Dobrynin, I. L., Kosyakov, V. N., Lisin, S. K., Rodionov, Y. F. and Shvetov, I. K. (1990) Plutonium release to the environment during Chernobyl accident. Proceedings of a Seminar on comparative assessment of the environmental impact of radionuclides, 1-5 October 1990. Radiation Protection, Vol. I, p. 53. Commission of the European Communities. NCRP (1975) National Council on Radiation Protection and Measurement, Report No. 45. Noureddine, A., Baggoura, B., Larosa, J. J., Vajda, N., (1996) Gamma and alpha-emitting radionuclides in some Algerian soil samples. Applied Radiation and Isotopes. Accepted for publication. Olli, P. (1990) Assessing Environmental Radioactivity. International Symposium on Environmental Contamination Following a Major Nuclear Accident, 16-20 October, 1989. IAEA-SM-306/122. Pavlotskaya, F. I., Gotyachenkova, T. A., Yenelyanov, V. V., Kazinskaya, I. E., Korobova, E. M. and Myasoyedov, B. F. (1990) Behaviour of 239pu and 24°pu in soils following the southern Urals and Chernobyl accidents. Proceedings of a Seminar on comparative assessment of the environmental impact of radionuclides released during three major nuclear accidents: Kyshtym, Windscale, Chernobyl, Luxembourg, 1-5 October 1990. Radiation Protection, Vol. I, p. 53. Commission of the European Communities. Pentreath, R. J. (1980) Nuclear Power, Man and the Environment. Taylor & Francis Ltd, London. United Nations (1977) Report of the United Nations Scientific Committee on the Effects o f Atomic Radiation to the General Assembly, with Annexes. Sources and Effects of lonising Radiation. United Nations Publication, New York.
Appl. Radiat. lsot. Vol. 49, No. 7, pp. 867-873, 1998
Pergamon
© 1998 Elsevier Science Ltd. All rights reserved
Printed in Great Britain 1350-4487/98 $19.00 + 0.00
PII:S0969-8043(97)10005-7
Level of Natural and Artificial Radioactivity in Algeria B. B A G G O U R A ,
A. NOUREDDINE*
and M. BENKRID
Centre de Radioprotection et de Sfiretr, Laboratoire d'Environnement, 02 Bd. F. Fanon, Bp 399 AlgerGare, Algiers, Algeria
(Received 17 June 1997,"accepted 21 August 1997) A national environmental sampling program was carried out during 1993 to determine natural and artificial radionuclides contents in the (0-15 cm) upper layer of the soil. The main objective was to establish a radioactive reference level in the whole territory, since 131I, 134Csand 137Cs w e r e detected in most of the analysed samples collected right after the Chernobyl accident (May 1986). Soil samples were analysed by direct counting by gamma-ray spectrometry. In addition, terrestrial gamma-ray dose rates in air have been measured out of doors throughout Algeria. In each of the 48 administrative divisions of the country selected sites were chosen to collect soil samples and measure gamma-ray dose rates. The gamma-emitting radionuclides resulting from the radioactive decay of 238U and 232Th, 4°K and 137Cs were detected in most of the analysed samples. Radioactivity concentrations in Bq kg- 1dry mass in soil samples of 226Ra, 214Pb, 214Bi, 2121Pb, 228Ac, 40K and 137Cs range between (5-176), (2-107), (3-65), (297), (3-144), (36-1405) and (0.3-41) respectively. In addition, six selected soil samples were analysed to determine plutonium isotopes contents. Radioactivity concentrations in Bq kg- 1 dry mass of 238Pu and 239 + 240pu vary between (0.012-0.013) and (0.24-0.61) respectively. The dose rates in air measured over the whole country were found to range between 20 and 133 nGy h -1. Presence of 137Cs has been clearly observed. An approach has been made to determine its origin, considering the global fallout, the Chernobyl accident and the French nuclear bomb tests in the 60s as the main potential sources. It is concluded that Algeria has indeed been affected by the Chernobyl accident. © 1998 Elsevier Science Ltd. All rights reserved
Introduction Following the Chernobyl accident on 26 April 1986, a considerable a m o u n t o f radioactive materials was released into the atmosphere contaminating the environment of the whole earth (Olli, 1990). Algeria, with its large coast line (1200 km) facing the European continent was certainly, in north Africa, the country the most exposed to this large scale contamination and might have been affected, to some extent, by the accident. The environmental impact and the change in the man-made radioactivity in the reference level associated to this accident offer an opportunity to launch a number of experimental research works to better identify and understand radioactive anomalies in the country in the future. Consequently two investigations related to the environmental impact of the Chernobyl accident o f 1986 on the Algerian soil have been carried out. The first one was performed in the first semester o f 1986, few weeks after the accident, covering the northern terrestrial strip along the Algerian coast about 1200 km long and 200 km wide. M o s t
of the samples were analysed to identify gammaemitting radionuclides, namely 131I, 134Cs and 137Cs. The second was carried out during 1993 to determine natural and artificial radionuclides contents in the upper layer of the soil throughout the Algerian territory.
ExperimentalMethod Sampling In the first campaign (1986), two mobile laboratories equipped with g a m m a ray detection devices were used. Sampling points, approximately a hundred kilometres apart from each other, were chosen in areas of high population density. Environmental samples, such as milk, rainfall water and grass were then collected manually. All the samples were collected during spring time. On-site g a m m a spectrometry measurements were performed to select samples to undergo detailed radionuclides identification. In the second campaign, in the early 90s, soil sampling was carried out over the whole territory that covers a total area of 2.341.000 km 2. Due to the heterogeneity of the environment, the country
*To whom all correspondence should be addressed. 867
868
B. Baggoura et al. 23
3e
11
Fig. 1. Administrative divisions. has been divided into three main zones: a northern zone, a small strip of land between the Mediterranean Sea and the Atlas mountains, heavily populated in which most agricultural and industrial activities of the country are performed; a central zone, a region located between the Atlas mountains and the Sahara desert, sparsely populated, where the main economic activity is ovine and cattle breeding; and finally a southern zone, a huge desert of approximately 2 million km 2 having a very low population density. The climate, type of vegetation, nature of soil and precipitation contents vary considerably from one zone to the other. Mobile laboratories, four-wheel drive vehicles and aeroplanes were the m a i n means used during the sampling phase. Field sampling was carried out in all the 48 administrative divisions of the country. Samples were picked up at several points at each of the above mentioned sites at different seasons, as shown in Fig. 1. A total number of 219 soil samples of different nature, mainly fine and coarse sands carbonated,
were manually collected in the (0-15)cm undisturbed upper layer using an appropriate shovel. They were dried at 80°C and then put into a 500 cm 3 Marinelli beaker for direct gamma counting after removing stone and grass from the samples and ground to pass a 60 mesh sieve. At the same time, terrestrial gamma-ray dose rates were measured at sampling locations by means of a pressurised argon ionisation chamber, type RSS-112 at 1 m above the top soil. Radioactivity measurement
Some environmental samples (milk, grass, precipitation) collected at several points in Algeria were analysed for qualitative analysis of gammaemitting radionuclides and NaI (Tl)detectors were used. For surface soil samples, a high purity germanium detector with relative efficiency of 23% and energy resolution of 2 keV for the 1332 keV 6°Co peak with a multichannel analyser (4096 channels) were used for gamma spectrometry analysis. Dried samples were placed either in polythene 500 cm 3
Natural and artificial radioactivity in Algeria Marinelli beakers or 250cm 3 plastic bottles of c y l i n d r i c a l f o r m , to be c o u n t e d l o n g e n o u g h to p r o d u c e a c c e p t a b l e c o u n t i n g statistics ( u s u a l l y 24 h). Efficiency c a l i b r a t i o n c u r v e s w e r e o b t a i n e d u s i n g a n I A E A 500 c m 3 M a r i n e l l i b e a k e r c o n t a i n i n g a refere n c e m a t e r i a l o f d e n s i t y 1 g c m -3, c o n t a m i n a t e d b y a s o l u t i o n o f t h e m u l t i - g a m m a e m i t t e r 152Eu. Efficiencies a t t h e e n e r g i e s o f i n t e r e s t w e r e i n t e r p o l a t e d f r o m c a l i b r a t i o n c u r v e s . T h e full e n e r g y peaks taken into account for the qualitative and q u a n t i t a t i v e a n a l y s i s o f 226Ra, 214pb, 214Bi, 212Pb, Z2SAc, 4°K, 134Cs, 137Cs a n d 131I a r e 1 8 6 . 2 k e V , 352.0 k e V , 609.3 k e V , 238.6 keV, 911 k e V , 1460.8 keV, 796 k e V , 661.7 k e V a n d 365.5 k e V respectively. T h e d e t e c t i o n l i m i t f o r t h e 137Cs is less t h a n 1 B q k g -1 d r y m a s s . N o t e t h a t o u r e n v i r o n m e n t a l l a b o r a t o r y h a s p a r t i c i p a t e d in t w o i n t e r n a t i o n a l i n t e r c o m p a r i s o n e x e r c i s e s ( I A E A - 326/327, IAEA-300/315) organised by the IAEA's labora-
869
t o r i e s at S e i b e r s d o r f a n d M o n a c o a n d all o u r results agreed within _10% with reference values. I n a d d i t i o n to t h e s e a n a l y s e s , six soil s a m p l e s were selected to u n d e r g o r a d i o c h e m i c a l s e p a r a t i o n f o r p l u t o n i u m i s o t o p e s d e t e r m i n a t i o n b y a l p h a spectrometry. The detection limit of plutonium isotopes is in t h e r a n g e o f 0 . 0 1 - 0 . 1 B q k g -1 d r y m a s s . T h e e v a l u a t i o n is b a s e d o n a n e s t i m a t i o n o f b a c k g r o u n d o f ( 1 - 9 ) × 10 -5 cts s -1, a s a m p l e size o f 10 g a n d a d e t e c t i o n efficiency o f a r o u n d 4 0 % , as p o i n t e d o u t b y N o u r e d d i n e et al. (1996).
Results and Discussion T h e a c t i v i t y c o n c e n t r a t i o n s o f n a t u r a l a n d artificial r a d i o n u c l i d e s m e a s u r e d b y direct c o u n t i n g g a m m a s p e c t r o m e t r y o r a l p h a s p e c t r o m e t r y (for p l u t o n i u m i s o t o p e s ) in t h e a n a l y s e d soil s a m p l e s , c o l l e c t e d a t t h e 48 selected sites, a r e listed in T a b l e 1 a n d T a b l e 2. T h e n a t u r a l a n d m a n - m a d e r a d i o -
Table 1. Activity concentrations of natural and artificial radionuclides in soil (Bq kg-1 dry mass) Location* 226Ra 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
19-129 29-56 6-60 53-60 39-45 42-63 5-80 5-84 57-73 39-64 8-70 39-63 36-72 20-109 52-107 11-35 17-61 44-93 35-112 27-28 58-124 42-47 76-82 28-55 27-52 67-84 31 11-78 12-52 23-51 36-55 11-36 17-176 46-49 30-62 37-48 27 48 18-42 44-57 36-127 20-56 / 76-107 18-55 25-37 8-74 45-51
214pb
214Bi
228Ac
6-34 26-35 5-37 23-35 29-30 33-37 9-30 2-48 39-52 28-34 30-107 19-28 8-31 19-85 43-52 24-35 17-44 34-55 13-39 9-14 32-82 22-23 4!-42 20-24 18±31 36-81 13 13-56 10--23 4-30 10-19 10-29 17-107 27-27 13-36 26-28 19 24 5-10 27-35 15-47 5-36 / 50-52 8-49 10-14 12-57 21-27
10-22 18-26 2-20 22-27 18-18 22-31 6-23 9-31 13-32 16-22 17-65 19-26 5-29 12-55 24-32 14-24 8-18 20-31 18-35 8-25 26-53 20-24 24-26 15-25 17-24 22-55 11 6-34 9-23 4-26 9-20 5-21 7-64 17-19 9-22 18-19 11 16 5-11 23-24 16-43 7-34 / 29-41 8-29 10-12 8-34 22-23
7-19 16-32 2-30 21-45 19-21 17-33 5-23 23-60 11-47 16-30 23-144 21-27 21-43 14-61 37-50 13-29 10-33 19-25 19-33 9-20 5-57 28-31 42-48 12-47 20-23 26-46 12 6-46 10-26 7-84 26-28 5-22 11-88 13-16 7-39 17-23 12 28 5-13 23 19-50 6-31 / 43-48 8-36 21-24 7-25 22-29
212Pb
4°K'
137Cs
2-10 74-438 17-31 83-541 3-30 35-712 20-25 193-273 18-19 334-348 19-37 222-328 3-22 68-293 8-52 53-903 12-38 189-626 14-28 263-314 11-69 397-965 8-38 261-324 7-60 262=643 16-32 303-1150: 41-69 234-579 2-24 198-422 7-32 215-506 24-30 221=356 22-38 175-358 5-17 245-257 23-54 564-833 6-31 528-608 35-43 435-437 19-59 191±363 12-34 174-536 29-39 331-710 14 219 7-44 91-316 3-37 199-514 2-97 181-482 24-29 467-482 5-22 97-290 13-97 82-777 11-14 132-150 16-55 156-509 13-19 118-150 15 378 30 453 7-15 93-329 4-36 235-303 33-46 234-1405 14--31 67-422 / / 46-47 609 3-23 148-689 6-33 301-412 5-24 93-376 21-25 469-585
/ 6-7 3-25 1,3 13-26 1-27 0.1-24 0.6-6 0.2-7 5.-16 0.1-15 8-11 11-24 5-19 7-41 2-7 0.2-15 1.9 5-12 3-16 9-12 0.5-1 10-16 0.3-2 4-34 5-:11 10 1-36 0.5-36 0.4-12 5-9 2-13 0.3-13 5-9 0.6-24 10-11 / 8 4-16 2-6 1-10 2-6 / 13-15 0.5-14 4-16 6-43 1-5
*In each location (administrative division), about five samples have been analysed.
B. Baggoura et aL
870
Table 2. Activity concentrations in Bq kg-~ dry mass of artificial alpha and gamma-emitting radionuclides in soil samples at different sampling points in Algeria
Samplingpoint
137Cs
39 47 47 46 05 25 42
15.8 + 1.7 22.1 _+2.3 15.8 ___1.7 26.1 ___2.7 15.5 _+2.0 34.2 _ 3.3 7.6 _+ 1.2
239 + 240pu
0.36 + 0.02 0.44 _+0.03 0.25 _+0.02 0.61 _+0.03 0.26 _+0.02 0.27 __.0.008 --
238pu
239 + 240pu/137Cs
238pu/239 + 2nOpu
< LD 0.013 _ 0.008 < LD < LD < LD 0.012 4- 0.008 --
0.023 + 0.003 0.020 _+0.002 0.015 +_0.002 0.023 _+0.003 0.017 ___0.003 0.008 __.0.001 --
-0.029 + 0.018 ---0.044 ___0.030
LD: limit of detection. nuclides consisted o f 238U a n d 232Th daughters, 4°K, 137Cs a n d p l u t o n i u m isotopes respectively. T h e radionuclides resulting from radioactive decay o f 238U a n d 232Th are mainly 226Ra, 214pb, 214Bi a n d 228Ac, 212pb, respectively. A m o n g the 238U d a u g h ters, 226Ra shows the highest value. Its range varies f r o m 5 to 176 Bq kg -I dry mass. The c o n c e n t r a t i o n s o f 214pb a n d 214Bi, however, vary between (2 a n d 107) a n d (3 a n d 65) Bq kg -1 dry mass, respectively. T h u s it appears that, in the 238U decay series, the 226Ra is significantly o u t o f radioactive equilibrium, since its average value ranges f r o m 32 to 71 Bq kg -1 dry mass a n d t h a t o f 214pb (which is the same as t h a t o f 214Bi) f r o m 21 to 40 Bq kg -1 dry mass. M o s t o f the highest values o f 226Ra have been recorded in the s o u t h e r n p a r t o f the country. T h e u p t a k e o f 226Ra by Algerian soil samples, as m e n t i o n e d above, is within the typical range observed in Spanish soil samples (13-165) Bq kg -1 dry mass b u t is higher t h a n the world average c o n c e n t r a t i o n , (10-50) Bq kg - l dry mass (Baeza, 1991; Pentreath, 1980; a n d K a t h r e n , 1984). T h e u p t a k e o f 226Ra varies from one area to the o t h e r a n d with the n a t u r e o f soil. T h e c o n c e n t r a t i o n s o f t h o r i u m daughters, namely 228Ac a n d 212pb, are in the range o f (3-144) a n d ( 2 - 9 7 ) B q kg -1 dry mass. The highest concentrations of these radioelements have been recorded in the south. T h e equilibrium, however, is observed for t h o r i u m daughters, since the average o f their m i n i m u m a n d m a x i m u m values are the same. These are (16-36) a n d (14-36) Bq kg -1 dry mass for 228Ac a n d 212pb, respectively. T h e u p t a k e o f t h o r i u m d a u g h t e r s b y the Algerian soil samples is lower t h a n t h a t observed in Spain [ ( 7 - 2 0 4 ) B q kg - l dry
mass] a n d higher t h a n the world average concentration, [(7 to 50) Bq kg - l dry mass]. Regarding 4°K, the c o n c e n t r a t i o n varies from (66 to l l 5 0 ) B q k g -1 dry mass, this is lower t h a n the world average, which is (48 to 1 5 8 5 ) B q k g -1 dry mass a n d lower t h a n t h a t m e a s u r e d in Spain, which is (100 to 7 0 0 ) B q k g -1 dry mass. T h e concent r a t i o n s o f the radioactive decay p r o d u c t s o f 23Su a n d 232Th, a n d 4°K, observed in the analysed soil samples, which are mainly fine a n d coarse sands c a r b o n a t e d , were c o m p a r e d to radioactive geological data. Hence, a c o m p a r i s o n o f the o b t a i n e d results with those reported by N C R P (1975), U n i t e d N a t i o n s (1977) a n d K a t h r e n (1984) was carried out, see Table 3. W e r e m a r k t h a t o u r results are, m o r e or less, close to the different reported values. Soil sample c o n c e n t r a t i o n s however, w h e n c o m p a r e d to those o f shales a n d sandstones (the closest to it in terms o f composition), show lower values. As to artificial radioactivity, 137Cs a n d P u isotopes were clearly observed in soil samples. T h e highest recorded value o f 137Cs was (41 + 4 ) B q kg -1 dry mass a n d is higher in areas where precipitation is m o r e frequent. T h e samples showed different values: almost 50% o f the total n u m b e r o f samples range from (0 to 5 ) B q kg - l dry mass; 13.6% f r o m (5 to 10) B q k g - l dry mass; 17.6% from (10 to 2 0 ) B q k g -1 dry mass; 6.2% f r o m (20 to 3 0 ) B q kg -1 dry mass a n d 12.6% for greater t h a n 30 Bq kg - l dry mass. The m e a n value for 137Cs for each site is reported o n Fig. 2 showing the different activity levels. However, for 238pu a n d 239 + 240pu ' activity c o n c e n t r a t i o n ranges a r e (0.012
Table 3. Comparison of the obtained results with those presented in the literature Radioelement
Nature of sample
Obtained results* (Bq kg-t)
NCRP 45 (Bq kg-I)
UNSCEAR Report 1977 (Bq kg-')
4°K
Soil
227-504
444
4°K 4°K 23Su
Shales Sandstones Soil
814 592-888 22
23Su 23Su 2S2Th
Shales Sandstones Soil
232Th 232Th
Shales Sandstones
--32.4-70.9; 20.5-40.2 (Decay products) --16-36; 14-36 (Decay products) ---
Wld average: 370 typical range: 110-740 703 370 Wld average: 26 typical range: 11-52 44 19 Wld average: 26 typical range 7-48 44 11
*Averages of the minimum and maximum values are given.
46 25-37 37 49 12-24
R.L. Kathren (Bq kg-1) -798 320 -46 6 ----
Natural and artificial radioactivity in Algeria to 0.013) and (0.24 to 0.61)Bqkg -1 dry mass, respectively. This artificial radioactivity may have different origins. Nuclear weapon and bomb tests and accidents being obviously the best candidates. To be more selective, we may pick up: global fallout from nuclear weapon tests; French nuclear bomb tests in the 60s in the Algerian Sahara desert and the Chernobyl accident of 1986. We then can consider this artificial radioactivity as being due to any single one or any combination of these sources. However, the lack of data, particularly those related to the French nuclear tests, in the open literature makes the evaluation of their respective contributions quite difficult. Nevertheless, based on available data we can put forward the following argumentation to shed some light on this particular point and come up with an acceptable conclusion. We start by noting that in March 1960 at Ispra (Italy), incidentally located at bird flight distance from Reggane (the site where the French nuclear tests in the atmosphere were performed) as is most of the Algerian coast line,
871
137Cs and some radionuclides of short half-life specific to those French nuclear explosions (14°Ba, 14°La, 147Nd, etc ..... ) were detected in air, the food chain and soil (Cigna e t al., 1961). The recorded level of ~37Cs was 11.1 B q m -2. It was considered then as background when compared with the 33300 Bq m -2 measured at the same location few years earlier, late in 1958. If we assume that the French nuclear tests fallout have had, approximately, the same impact on the northern part of Algeria, we may then consider this later as negligibly small compared with that of the Chernobyl accident, estimated to be 400 Bq m -2 by Olli (1990). We then examine, the ratios of 239 ÷ 240pu: 137Cs and 238pu: 239 + 240pu reported in Table 2 (Noureddine et al., 1996) and note that they are different from those given by Duriec e t al. (1984), Belyayev et al. (1990), Pavlotskaya et al. (1990), Kulakov et al. (1990) and Coughtrey et al. (1990). Hence, we see that the average ratio of 239 - 2 4 0 p u : 1 3 7 C s ( 0 . 0 2 ) obtained is twice lower than the one recorded before the Chernobyl accident
::'.
iiii|iiili~!ill
•
.
Oo°
•
• •
o . o . . l o ° o ,
o • OOO..
o
• •
° ..-
°
o ,
o ,
,
°
,..
"|
BqlKg I"
Il~*t r ~ a 11-3
3-6
I
s-9 9-12 >12 '
•
°
iiiiiiiii Fig. 2. Caesium-137concentration average.
200 K m
872
B. Baggoura et al.
-$~ I El
t I
I t
r-
I
tt~
I
I
° o...¢
•
I
I I
I !
I I I
t II¸
I m
I
t,....* C, n
t"--
'IU
I
I
I
I
:qt~Du a~J0x~ a ~
t
asop tmmm D
1
w
Natural and artificial radioactivity in Algeria (0.04). As for the ratio 23Spu:239 + 24°pu its values are in the typical range of global fallout in soil (0.03-0.05). We readily deduce that the 137Cs concentration due to the Chernobyl accident has added up to that of global fallout. If we note at last that 131I and 134Cs were qualitatively measured in milk, precipitation and grass samples collected throughout the northern part of Algeria right after the Chernobyl accident (May 1986), we then may safely conclude that Algeria has indeed been affected by the Chernobyl accident. Regarding the terrestrial g a m m a ray dose, 219 measurements were carried out. The mean value is 70.30 n G y h -1 with a range of 20-133.10 n G y h -1. The mean value for the terrestrial g a m m a dose rate is reported on Fig. 3. The annual average value of effective dose equivalent from terrestrial g a m m a rays for the country is about 8 . 6 4 x 1 0 - S S v . U N S C E A R ' s coefficient o f 0.7 Sv Gy -1 is used to convert the absorbed dose in air to effective dose equivalent for adults, considering an outdoor occupancy factor for Algerian people of about 0.2. Acknowledgements--Thanks are due to the sampling assistance of A. Allalou and N. Messen and their respective teams. The authors wish also to thank B. Yagoubi for the sample counting.
References Baeza, A. (1991) Natural radioactivity in soils of the province of Caceres (Spain): Salzburg, Austria, 22-28 September 1991. Fifth International Symposium of the Natural Radiation Environment. Belyayev, S. T., Borovov, A. A., Demin, V. F., RimskyKorsakov, A. A. and Khernvinov, A. N. (1990) The Chernobyl source term. Proceedings of a Seminar on comparative assessment of the environmental impact of radionuclides released during three major nuclear accidents: Kyshtym, Windscale, Chernobyl, Luxembourg, I-5 October 1990. Radiation Protection, Vol. I, p. 53. Commission of the European Communities. Cigna, A., Dominici, G., Malvicini, A. and Vido, L. (1961) Radioattivit~i dei Prodotti di Fissione nel Fallout Raccolto dopo l'Esplosione Nucleare Francese nel Sahara. Comitato Nazionale per l'Energia Nucleare, Centro di Studi Nucleari di Ispra, CNI-81.
873
Coughtrey, P. J., Kirtou, J. A. and Mitchell, N. G. (1990) Environmental distribution and transport of radionuclides in west Cumbria following the Windscale and Chernobyl accident. Proceedings of a Seminar on comparative assessment of the environmental impact of radionuclides released during three major nuclear accidents: Kyshtym, Windscale, Chernobyl, Luxembourg, 1-5 October 1990. Radiation Protection, Vol. I, p. 53. Commission of the European Communities. Duriec, S. T., Hallstanius, L. and Holm, E. (1984) A study of the transport of radionuclides in the sea by use of isotopic ratios. International Symposium on the behaviour of long-lived radionuclides in the marine environment. Radiation Protection, Vol. I. Commission of the European Communities. Kathren, R. L. (1984). Radioactivity in the Environment, Sources, Distribution and Surveillance. Battelle Pacific Northwest Laboratories, U.S.A., Harrowed Academic Publishers. Kulakov, V. M., Dobrynin, I. L., Kosyakov, V. N., Lisin, S. K., Rodionov, Y. F. and Shvetov, I. K. (1990) Plutonium release to the environment during Chernobyl accident. Proceedings of a Seminar on comparative assessment of the environmental impact of radionuclides, 1-5 October 1990. Radiation Protection, Vol. I, p. 53. Commission of the European Communities. NCRP (1975) National Council on Radiation Protection and Measurement, Report No. 45. Noureddine, A., Baggoura, B., Larosa, J. J., Vajda, N., (1996) Gamma and alpha-emitting radionuclides in some Algerian soil samples. Applied Radiation and Isotopes. Accepted for publication. Olli, P. (1990) Assessing Environmental Radioactivity. International Symposium on Environmental Contamination Following a Major Nuclear Accident, 16-20 October, 1989. IAEA-SM-306/122. Pavlotskaya, F. I., Gotyachenkova, T. A., Yenelyanov, V. V., Kazinskaya, I. E., Korobova, E. M. and Myasoyedov, B. F. (1990) Behaviour of 239pu and 24°pu in soils following the southern Urals and Chernobyl accidents. Proceedings of a Seminar on comparative assessment of the environmental impact of radionuclides released during three major nuclear accidents: Kyshtym, Windscale, Chernobyl, Luxembourg, 1-5 October 1990. Radiation Protection, Vol. I, p. 53. Commission of the European Communities. Pentreath, R. J. (1980) Nuclear Power, Man and the Environment. Taylor & Francis Ltd, London. United Nations (1977) Report of the United Nations Scientific Committee on the Effects o f Atomic Radiation to the General Assembly, with Annexes. Sources and Effects of lonising Radiation. United Nations Publication, New York.