- Email: [email protected]
Natural radioactivity concentrations in soil samples along the Amman Aqaba Highway, Jordan
Available online at www.sciencedirect.com
Radiation Measurements 36 (2003) 555 – 560 www.elsevier.com/locate/radmeas
Natural radioactivity concentrations in soil samples along the Amman Aqaba Highway, Jordan J. Al-Jundia;∗ , B.A. Al-Batainab , Y. Abu-Rukahc , H.M. Shehadeha a Department
of Physics, The Hashemite University, P. O. Box 150459, Zarqa, Jordan of Physics, Yarmouk University, Irbid, Jordan c Department of Earth and Environmental Sciences, Yarmouk University, Irbid, Jordan b Department
Received 21 October 2002; received in revised form 27 February 2003; accepted 7 May 2003
Abstract The speci3c activity and the gamma-absorbed dose rates of the terrestrial naturally occurring radionuclides (238 U; 232 Th, and 40 K) were determined in roadside soil cores obtained from eight sites along Amman Aqaba National Highway (AANH), using HPGe gamma-ray spectrometry. The soil activity ranged from 22 to 104 Bq kg−1 for 238 U, 21 to 103 Bq kg−1 for 232 Th, and 138 to 601 Bq kg−1 for 40 K. The highest mean value of 238 U was found in the core samples obtained from a site close to Al-Hassa phosphate mine. The study yielded an annual e:ective dose equivalent in the range of 40 –151 Sv. The average value falls within the global range of outdoor radiation exposure given in UNSCEAR-2000 publications. c 2003 Elsevier Ltd. All rights reserved. Keywords: Soil pollutant; Radioactivity measurements; Uranium; Thorium; Potassium
1. Introduction A signi3cant part of the total dose contribution in the form of natural sources comes from terrestrial gamma radionuclides (UNSCEAR, 2000). Only nuclides with half-lives comparable with the age of the earth or their corresponding decay products, existing in terrestrial materials, such as 40 K, 238 U and 232 Th radionuclides are of great interest. Abnormal occurrences of uranium and its decay products in rock and soil and thorium in monazite sands are the main sources of high natural background areas that have been identi3ed in several areas of the world, e.g., Yangjiang in China, Rasmar in Iran, Kerala coast of India, etc. (Zhu et al., 1993; Sohrabi, 1993; Sunta, 1993). Therefore, measurements of natural radioactivity in soil are of a great interest for many researchers throughout the world, which led to worldwide national surveys in the last two decades (McAulay and Moran, 1988; Karahan and Bayulken, 2000). This study complements a few other studies, which were conducted at di:erent ∗
Corresponding author. Tel.: +962-5-382-6600; fax: +962-5-382-6613. E-mail address: [email protected] (J. Al-Jundi).
locations in Jordan soils (Ahmad et al., 1997; Al-Jundi, 2002). The aim of this work is to measure the speci3c activity and the gamma-ray-absorbed doses of the naturally occurring radionuclides (238 U, 232 Th, and 40 K) in soil cores obtained from eight sites along Amman Aqaba National Highway. It crosses di:erent geographical areas, especially Hassa and Al-Abyad phosphate mines, making this area an interesting site for radiological studies. Such measurements determine the dose rate needed to implement precautionary measures whenever the dose is found to be above the recommended limits. The results also will be used to establish a baseline map for that area. This map will be used as a reference information to assess any changes in the radioactivity background level due to the change in the topography of the highway location, other developments and settlement around the highway, or any arti3cial inGuences on the environment. 2. Experimental Amman Aqaba National Highway (AANH), 350 km in length, is one of the important and busy national highways
c 2003 Elsevier Ltd. All rights reserved. 1350-4487/03/$ - see front matter doi:10.1016/S1350-4487(03)00202-6
556
J. Al-Jundi et al. / Radiation Measurements 36 (2003) 555 – 560
Fig. 1. Map shows sampling points along Amman Aqaba National Highway.
in Jordan (Fig. 1). It is the main highway connecting between the only port in Jordan, namely Aqaba, and other Jordanian Provinces and neighboring countries. Therefore, many industrial, urban planning and settlements are being established along AANH. Soil samples were collected from eight transects perpendicular to the traIc Gow at AANH (Fig. 1). Samples were taken from three depths (0 –5 cm, 5 –10 cm, 10 –20 cm) at eight sites. The sampling sites were located at a distance of 20 m from the roadside curb. Soil samples were crushed in the laboratory, oven dried at a temperature of 70◦ C for 24 h, and sieved through a 0:2 mm mesh. About 10 g of each sample was taken for chemical analysis. The concentration of Al2 O3 ; SiO2 ; K2 O, CaO and Fe2 O3 compounds in the samples were determined using Energy Dispersive X-ray Fluorescence (EDXRF) spectrometer in the Physics Department of Yarmouk University, Jordan. The remaining portions of the samples were then packed in plastic containers, weighed and carefully sealed and stored for at least 4 weeks before counting to allow time for 238 U and 232 Th to reach equilibrium with their respective progeny. The gamma-ray activities were measured using a low-level counting system consisting of a High-Purity Germanium (HPGe) computer controlled detector, by con-
ventional electronics, of 20% relative eIciency. The resolution was 2 keV for the 1333 keV 60 Co. The detector was shielded in a 10 cm thick lead internally lined with 2 mm copper foil. A reference sample from Gzech Metrological Institute, type CBSS1, was used for eIciency calibration in the same geometry as the measured samples. The activity of each sample was measured for 16 h. The gamma ray lines of 238:6 keV from 212 Pb, 911.2 and 969 keV gamma rays from 228 Ac and 583 keV gamma rays from 208 Tl were used to determine the 232 Th. The gamma-ray peak of 351:9 keV emitted by 214 Pb and 609:3 keV gamma rays emitted by 214 Bi were used to determine the 238 U. The activity of 40 K was evaluated using its 1460 keV gamma-ray line. The 186 keV peak from 226 Ra was not utilized, since the 185.7 peak from 238 U will overlap with the same line. Corrections to other peaks interference and background distribution due to the naturally occurring radionuclides in the environment around the detector were taken into consideration, more details can be found in Al-Jundi (2002). 3. Results and discussions The chemical composition for some of the collected samples (Abu-Rukah, 2001), indicates the variability of
J. Al-Jundi et al. / Radiation Measurements 36 (2003) 555 – 560 Table 1 Illustrates the speci3c activity of Location
1
Mean value 2
Mean value 3
Mean value 4
Mean value 5
Mean value 6
Mean value 7
Mean value 8
238 U; 232 Th
Soil depth (cm)
and
40 K
557
in soil samples (Bq kg−1 dry weight) and the organic content Organic matter %
Speci3c activity 238 U
232 Th
40 K
0 –5 5 –10 10 –15
8.4 6.0 7.5
35 26 22
40 32 30
434 390 351
0 –5 5 –10 10 –15
— — —
28 39 36 42
34 33 30 32
392 327 321 351
0 –5 5 –10 10 –15
— — —
39 75 41 89
32 28 28 23
333 214 265 251
0 –5 5 –10 10 –15
— — —
68 43 26 24
26 21 22 24
210 138 151 145
0 –5 5 –10 10 –15
6.0 6.0 4.9
31 35 41 40
22 28 29 34
145 250 276 279
0 –5 5 –10 10 –15
— — —
39 31 39 36
30 31 35 32
268 274 278 257
0 –5 5 –10 10 –15
— — —
35 32 34 28
33 27 30 36
270 316 343 339
0 –5 5 –10 10 –15
2.2 2.0 1.6
31 104 95 52
31 75 67 103
333 601 563 517
84
82
560
Mean value
the geological formations for the area studied. While Table 1 illustrates the speci3c activity of the natural radionuclide (238 U, 232 Th, and 40 K) in the samples collected along AANH. The speci3c activities are given throughout the paper in Bq kg−1 dry weight. The table also lists the respective mean values of the speci3c activity and the organic content of some samples. The mean activity of 238 U found ranged from 28 ± 7 to 84 ± 28 Bq kg−1 , the highest activity was found in locations 3 and 8. The 232 Th mean activity ranged from 22 ± 2 to 82 ± 19 Bg kg−1 , the highest activity was found in location 8. While the mean activity of 40 K
found, ranged from 145 ± 7 to 560 ± 42 Bq kg−1 . Apart from locations 3 and 8, the obtained results are comparable to the worldwide average concentrations of these radionuclides in soils reported by UNSCEAR (2000), which are 40 Bq kg−1 for 238 U and 232 Th, and 370 Bq kg−1 for 40 K. The results observed in sampling areas 3 and 8 can be explained with account to following considerations: area 3 is located close to Al-Hassa phosphate mine and area 8 is basically a small valley and very close to the beach. The high activity of this site is ascribed to the 3ne particle nature of soil, since the distributions of elements were found
558
J. Al-Jundi et al. / Radiation Measurements 36 (2003) 555 – 560
Table 2 Illustrates dose rates of Location (cm)
238 U, 232 Th
Soil depth
and
40 K
in soil samples and the annual e:ective dose equivalent
238 U
(nGy h−1 )
232 Th
(nGy h−1 )
40 K
(nGy h−1 )
Ann.e:. dose (Sv)
1
0 –5 5 –10 10 –15
15 11 9
27 21 20
19 17 15
76 62 56
2
0 –5 5 –10 10 –15
17 15 18
22 20 21
14 14 15
67 62 68
3
0 –5 5 –10 10 –15
32 18 38
18 18 16
9 11 11
74 59 82
4
0 –5 5 –10 10 –15
27 11 10
14 15 16
6 7 6
59 42 40
5
0 –5 5 –10 10 –15
15 18 17
19 19 23
11 12 12
57 62 66
6
0 –5 5 –10 10 –15
13 17 16
20 23 21
12 12 11
57 66 61
7
0 –5 5 –10 10 –15
14 15 12
18 20 24
13 15 15
57 63 64
8
0 –5 5 –10 10 –15
44 40 22
50 44 68
26 24 22
151 136 141
Table 3 Comparison of the average annual e:ective dose (Sv) obtained in the present study with those 3gures from other studies conducted world-wide Region
Annual e:ective dose equivalent (Sv)
Reference
AANH (Jordan) Russiafa city (Jordan) Nigeria Greece Rio Grande do Norte (Brazil) Nile delta (Egypt) Istanbul (Turkey) Namibia Kalpakkam (India)
40 –151 50 –290 32–284 220 –760 117–1361 9 –117 Average 80 110 –220 29 – 681
Present study Al-Jundi (2002) Jibiri (2001) Probonas and Kritidis (1993) Malanca et al. (1996) Ibrahim et al. (1993) Karahan and Bayulken (2000) Steinhausler and Lettner (1992) Kannan et al. (2002)
to be very particle-size-dependent (Randle and Al-Jundi, 2001). The external terrestrial gamma-radiation absorbed dose in air at a height of about 1 m above the ground
level was calculated by using the conversion factor of 0:043 nGy h−1 =Bq kg−1 for 40 K, 0:427 nGy h−1 =Bq kg−1 for 238 U, and 0:662 nGy h−1 =Bq kg−1 for 232 Th. The gamma dose rate was calculated from the concentration
J. Al-Jundi et al. / Radiation Measurements 36 (2003) 555 – 560
100
80
60
40
238
U concentration (Bqkg-1)
120
20 10
20
30
40 232
50
60
70
80
90
100 110
Th concentration (Bqkg-1)
Fig. 2. Correlation between soils.
238 U
and
232 Th
559
82 ± 19 and 145 ± 7 to 560 ± 42 Bq kg−1 , respectively. The calculated annual e:ective dose equivalent due to natural radioactivity was found to be in the range of 40 –151 Sv. The obtained 3gures are comparable with average world-wide 3gures. It is obvious that the high dose at location 3 is due to the presence of phosphate in the soils. The annual e:ective dose equivalent at location 8 was found to be higher than the measured doses at other locations. In sampling area 8 (located near to the Aqaba beach) the 232 Th contribution to the total annual e:ective dose equivalent was about 95%, which is two times more than that of 238 U. A weak correlation between the concentration of 238 U and 232 Th was found with a correlation coeIcient of 0.48. The results of this study can be used as a data baseline for preparing a radiological map of the study area, especially at the chosen settlement sites.
speci3c activity in
of radionuclides of the 238 U; 232 Th, and 40 K ranges between 9 and 44 nGy h−1 , 14 and 68 nGy h−1 , and 6 and 26 nGy h−1 , respectively. The annual outdoors e:ective dose equivalents were calculated utilizing a conversion coeIcient of 0:72 Sv Gy−1 for an absorbed dose in air to e:ective dose in human body. This calculation takes into account that people spend about 20% of their time outdoors. The calculated absorbed dose rates from outdoors terrestrial gamma radiation and the annual e:ective dose equivalent are given in Table 2. Samples from locations 3 and 8 were found to have more annual e:ective dose equivalent than those samples from other locations included in this study. The highest observed annual dose equivalents are 151 Sv for location 8. 232 Th contributes about 58% of the total dose. According to UNSCEAR (2000) report, the dose rate in air outdoors from terrestrial gamma-rays in normal circumstances is about 57 nGy h−1 . The national average ranges from 24 to 160 nGy h−1 , while the world-wide average annual e:ective dose is approximately 70 Sv. Thus, our results are in a good agreement with the average world-wide limits. Table 3 shows reported values of gamma-absorbed dose rate in air, from work conducted in the Middle East areas and world-wide for comparison with our data. Fig. 2 depicts the correlation between the activities of 238 U and 232 Th. It is obvious that the correlations is rather weak, with correlation coeIcient of 0.48, which agreed with a previous study on the correlation between 238 U and 232 Th in a sample obtained near and intact to old phosphate mines (Al-Jundi, 2002).
4. Conclusions The mean speci3c activities obtained in the soil samples collected from eight sites located along AANH for 238 U, 232 Th, and 40 K ranged from 28 ± 7 to 84 ± 28; 22 ± 2 to
References Abu-Rukah, Y., 2001. A study of soils, contaminated with heavy metals along the Amman Aqaba National Highway (Jordan). Freiberg 494, 53–62. Ahmad, N., Matiullah, Khatibeh, A., 1997. Indoor radon levels and natural radioactivity in Jordanian soil. Radiat. Protect. Dosim. 71 (3), 231–233. Al-Jundi, J., 2002. Population dosres from terrestrial gamma exposure in areas near to old phosphate mine, Russaifa, Jordan. Radiat. Meas. 35, 23–28. Ibrahim, N.M., Abdel-Ghani, A.H., Shawky, S.M., Ashraf, E.M., Faouk, M.A., 1993. Measurement of radioactivity levels in soil in the Nile delta and middle Egypt. Health. Phys. 64, 620–627. Jibiri, N.N., 2001. Assessment of health risk levels associated with terrestrial gamma radiation dose rates in Nigeria. Environ. Int. 27, 21–26. Kannan, V., Rajan, M.P., Lyengar, M.A., Ramesh, R., 2002. Distribution of natural and anthropogenic radionuclides in soil and beach sand samples of Kalpakkam (India). Appl. Radiat. Isot. 57, 109–119. Karahan, G., Bayulken, A., 2000. Assessment of gamma dose rates around Istanbul (Turkey). J. Environ. Radioact. 47, 213–221. Malanca, A., Gaidol3, L., Pessina, V., Dallara, G., 1996. Distribution of 226 Ra; 232 Th, and 40 K of Rio Grande do Norte (Brazil). J. Environ. Radioact. 30 (1), 55–67. McAulay, I.R., Moran, D., 1988. Natural radioactivity in soil in the Republic of Ireland. Radiat. Protect. Dosim. 24 (1/4), 47–49. Probonas, M., Kritidis, P., 1993. The exposure of the Greek population to natural gamma radiation of terrestrial origin. Radiat. Protect. Dosim. 46 (2), 123–126. Randle, K., Al-Jundi, J., 2001. Instrumental neutron activation analysis (INAA) of esturine sediments. J. Radioanal. Nucl. Chem. 249 (2), 361–367. Sohrabi, M., 1993. Recent radiological studies of high level natural radiation areas of Rasmar. In: Sohrabi, M., Ahmad, J.U., Durrani, S.A. (Eds.), Proceeding of the International Conference on High Levels of Natural Radiation, Rasmar, 1990. IAEA, Vienna. Steinhausler, F., Lettner, H., 1992. Radiometric survey in Namibia. Radiat. Protect. Dosim. 45 (1/4), 553–555.
560
J. Al-Jundi et al. / Radiation Measurements 36 (2003) 555 – 560
Sunta, C.M., 1993. A review of the studies of high background areas of the S-W coast of India. In: Sohrabi, M., Ahmad, J.U., Durrani, S.A. (Eds.), Proceeding of the International Conference on High Levels of Natural Radiation, Rasmar, 1990. IAEA, Vienna. UNSCEAR, 2000. Sources, E:ects and Risks of Ionizing Radiations. United Nations, New York.
Zhu, H., Huang, H., Song, J., Li, J., Zhang, J., Huang, J., Zha, Y., Guo, Y., 1993. Gamma radiation levels around the highest background area in Poland. In: Sohrabi, M., Ahmad, J.U., Durrani, S.A. (Eds.), Proceeding of the International Conference on High Levels of Natural Radiation, Rasmar, 1990. IAEA, Vienna.
Radiation Measurements 36 (2003) 555 – 560 www.elsevier.com/locate/radmeas
Natural radioactivity concentrations in soil samples along the Amman Aqaba Highway, Jordan J. Al-Jundia;∗ , B.A. Al-Batainab , Y. Abu-Rukahc , H.M. Shehadeha a Department
of Physics, The Hashemite University, P. O. Box 150459, Zarqa, Jordan of Physics, Yarmouk University, Irbid, Jordan c Department of Earth and Environmental Sciences, Yarmouk University, Irbid, Jordan b Department
Received 21 October 2002; received in revised form 27 February 2003; accepted 7 May 2003
Abstract The speci3c activity and the gamma-absorbed dose rates of the terrestrial naturally occurring radionuclides (238 U; 232 Th, and 40 K) were determined in roadside soil cores obtained from eight sites along Amman Aqaba National Highway (AANH), using HPGe gamma-ray spectrometry. The soil activity ranged from 22 to 104 Bq kg−1 for 238 U, 21 to 103 Bq kg−1 for 232 Th, and 138 to 601 Bq kg−1 for 40 K. The highest mean value of 238 U was found in the core samples obtained from a site close to Al-Hassa phosphate mine. The study yielded an annual e:ective dose equivalent in the range of 40 –151 Sv. The average value falls within the global range of outdoor radiation exposure given in UNSCEAR-2000 publications. c 2003 Elsevier Ltd. All rights reserved. Keywords: Soil pollutant; Radioactivity measurements; Uranium; Thorium; Potassium
1. Introduction A signi3cant part of the total dose contribution in the form of natural sources comes from terrestrial gamma radionuclides (UNSCEAR, 2000). Only nuclides with half-lives comparable with the age of the earth or their corresponding decay products, existing in terrestrial materials, such as 40 K, 238 U and 232 Th radionuclides are of great interest. Abnormal occurrences of uranium and its decay products in rock and soil and thorium in monazite sands are the main sources of high natural background areas that have been identi3ed in several areas of the world, e.g., Yangjiang in China, Rasmar in Iran, Kerala coast of India, etc. (Zhu et al., 1993; Sohrabi, 1993; Sunta, 1993). Therefore, measurements of natural radioactivity in soil are of a great interest for many researchers throughout the world, which led to worldwide national surveys in the last two decades (McAulay and Moran, 1988; Karahan and Bayulken, 2000). This study complements a few other studies, which were conducted at di:erent ∗
Corresponding author. Tel.: +962-5-382-6600; fax: +962-5-382-6613. E-mail address: [email protected] (J. Al-Jundi).
locations in Jordan soils (Ahmad et al., 1997; Al-Jundi, 2002). The aim of this work is to measure the speci3c activity and the gamma-ray-absorbed doses of the naturally occurring radionuclides (238 U, 232 Th, and 40 K) in soil cores obtained from eight sites along Amman Aqaba National Highway. It crosses di:erent geographical areas, especially Hassa and Al-Abyad phosphate mines, making this area an interesting site for radiological studies. Such measurements determine the dose rate needed to implement precautionary measures whenever the dose is found to be above the recommended limits. The results also will be used to establish a baseline map for that area. This map will be used as a reference information to assess any changes in the radioactivity background level due to the change in the topography of the highway location, other developments and settlement around the highway, or any arti3cial inGuences on the environment. 2. Experimental Amman Aqaba National Highway (AANH), 350 km in length, is one of the important and busy national highways
c 2003 Elsevier Ltd. All rights reserved. 1350-4487/03/$ - see front matter doi:10.1016/S1350-4487(03)00202-6
556
J. Al-Jundi et al. / Radiation Measurements 36 (2003) 555 – 560
Fig. 1. Map shows sampling points along Amman Aqaba National Highway.
in Jordan (Fig. 1). It is the main highway connecting between the only port in Jordan, namely Aqaba, and other Jordanian Provinces and neighboring countries. Therefore, many industrial, urban planning and settlements are being established along AANH. Soil samples were collected from eight transects perpendicular to the traIc Gow at AANH (Fig. 1). Samples were taken from three depths (0 –5 cm, 5 –10 cm, 10 –20 cm) at eight sites. The sampling sites were located at a distance of 20 m from the roadside curb. Soil samples were crushed in the laboratory, oven dried at a temperature of 70◦ C for 24 h, and sieved through a 0:2 mm mesh. About 10 g of each sample was taken for chemical analysis. The concentration of Al2 O3 ; SiO2 ; K2 O, CaO and Fe2 O3 compounds in the samples were determined using Energy Dispersive X-ray Fluorescence (EDXRF) spectrometer in the Physics Department of Yarmouk University, Jordan. The remaining portions of the samples were then packed in plastic containers, weighed and carefully sealed and stored for at least 4 weeks before counting to allow time for 238 U and 232 Th to reach equilibrium with their respective progeny. The gamma-ray activities were measured using a low-level counting system consisting of a High-Purity Germanium (HPGe) computer controlled detector, by con-
ventional electronics, of 20% relative eIciency. The resolution was 2 keV for the 1333 keV 60 Co. The detector was shielded in a 10 cm thick lead internally lined with 2 mm copper foil. A reference sample from Gzech Metrological Institute, type CBSS1, was used for eIciency calibration in the same geometry as the measured samples. The activity of each sample was measured for 16 h. The gamma ray lines of 238:6 keV from 212 Pb, 911.2 and 969 keV gamma rays from 228 Ac and 583 keV gamma rays from 208 Tl were used to determine the 232 Th. The gamma-ray peak of 351:9 keV emitted by 214 Pb and 609:3 keV gamma rays emitted by 214 Bi were used to determine the 238 U. The activity of 40 K was evaluated using its 1460 keV gamma-ray line. The 186 keV peak from 226 Ra was not utilized, since the 185.7 peak from 238 U will overlap with the same line. Corrections to other peaks interference and background distribution due to the naturally occurring radionuclides in the environment around the detector were taken into consideration, more details can be found in Al-Jundi (2002). 3. Results and discussions The chemical composition for some of the collected samples (Abu-Rukah, 2001), indicates the variability of
J. Al-Jundi et al. / Radiation Measurements 36 (2003) 555 – 560 Table 1 Illustrates the speci3c activity of Location
1
Mean value 2
Mean value 3
Mean value 4
Mean value 5
Mean value 6
Mean value 7
Mean value 8
238 U; 232 Th
Soil depth (cm)
and
40 K
557
in soil samples (Bq kg−1 dry weight) and the organic content Organic matter %
Speci3c activity 238 U
232 Th
40 K
0 –5 5 –10 10 –15
8.4 6.0 7.5
35 26 22
40 32 30
434 390 351
0 –5 5 –10 10 –15
— — —
28 39 36 42
34 33 30 32
392 327 321 351
0 –5 5 –10 10 –15
— — —
39 75 41 89
32 28 28 23
333 214 265 251
0 –5 5 –10 10 –15
— — —
68 43 26 24
26 21 22 24
210 138 151 145
0 –5 5 –10 10 –15
6.0 6.0 4.9
31 35 41 40
22 28 29 34
145 250 276 279
0 –5 5 –10 10 –15
— — —
39 31 39 36
30 31 35 32
268 274 278 257
0 –5 5 –10 10 –15
— — —
35 32 34 28
33 27 30 36
270 316 343 339
0 –5 5 –10 10 –15
2.2 2.0 1.6
31 104 95 52
31 75 67 103
333 601 563 517
84
82
560
Mean value
the geological formations for the area studied. While Table 1 illustrates the speci3c activity of the natural radionuclide (238 U, 232 Th, and 40 K) in the samples collected along AANH. The speci3c activities are given throughout the paper in Bq kg−1 dry weight. The table also lists the respective mean values of the speci3c activity and the organic content of some samples. The mean activity of 238 U found ranged from 28 ± 7 to 84 ± 28 Bq kg−1 , the highest activity was found in locations 3 and 8. The 232 Th mean activity ranged from 22 ± 2 to 82 ± 19 Bg kg−1 , the highest activity was found in location 8. While the mean activity of 40 K
found, ranged from 145 ± 7 to 560 ± 42 Bq kg−1 . Apart from locations 3 and 8, the obtained results are comparable to the worldwide average concentrations of these radionuclides in soils reported by UNSCEAR (2000), which are 40 Bq kg−1 for 238 U and 232 Th, and 370 Bq kg−1 for 40 K. The results observed in sampling areas 3 and 8 can be explained with account to following considerations: area 3 is located close to Al-Hassa phosphate mine and area 8 is basically a small valley and very close to the beach. The high activity of this site is ascribed to the 3ne particle nature of soil, since the distributions of elements were found
558
J. Al-Jundi et al. / Radiation Measurements 36 (2003) 555 – 560
Table 2 Illustrates dose rates of Location (cm)
238 U, 232 Th
Soil depth
and
40 K
in soil samples and the annual e:ective dose equivalent
238 U
(nGy h−1 )
232 Th
(nGy h−1 )
40 K
(nGy h−1 )
Ann.e:. dose (Sv)
1
0 –5 5 –10 10 –15
15 11 9
27 21 20
19 17 15
76 62 56
2
0 –5 5 –10 10 –15
17 15 18
22 20 21
14 14 15
67 62 68
3
0 –5 5 –10 10 –15
32 18 38
18 18 16
9 11 11
74 59 82
4
0 –5 5 –10 10 –15
27 11 10
14 15 16
6 7 6
59 42 40
5
0 –5 5 –10 10 –15
15 18 17
19 19 23
11 12 12
57 62 66
6
0 –5 5 –10 10 –15
13 17 16
20 23 21
12 12 11
57 66 61
7
0 –5 5 –10 10 –15
14 15 12
18 20 24
13 15 15
57 63 64
8
0 –5 5 –10 10 –15
44 40 22
50 44 68
26 24 22
151 136 141
Table 3 Comparison of the average annual e:ective dose (Sv) obtained in the present study with those 3gures from other studies conducted world-wide Region
Annual e:ective dose equivalent (Sv)
Reference
AANH (Jordan) Russiafa city (Jordan) Nigeria Greece Rio Grande do Norte (Brazil) Nile delta (Egypt) Istanbul (Turkey) Namibia Kalpakkam (India)
40 –151 50 –290 32–284 220 –760 117–1361 9 –117 Average 80 110 –220 29 – 681
Present study Al-Jundi (2002) Jibiri (2001) Probonas and Kritidis (1993) Malanca et al. (1996) Ibrahim et al. (1993) Karahan and Bayulken (2000) Steinhausler and Lettner (1992) Kannan et al. (2002)
to be very particle-size-dependent (Randle and Al-Jundi, 2001). The external terrestrial gamma-radiation absorbed dose in air at a height of about 1 m above the ground
level was calculated by using the conversion factor of 0:043 nGy h−1 =Bq kg−1 for 40 K, 0:427 nGy h−1 =Bq kg−1 for 238 U, and 0:662 nGy h−1 =Bq kg−1 for 232 Th. The gamma dose rate was calculated from the concentration
J. Al-Jundi et al. / Radiation Measurements 36 (2003) 555 – 560
100
80
60
40
238
U concentration (Bqkg-1)
120
20 10
20
30
40 232
50
60
70
80
90
100 110
Th concentration (Bqkg-1)
Fig. 2. Correlation between soils.
238 U
and
232 Th
559
82 ± 19 and 145 ± 7 to 560 ± 42 Bq kg−1 , respectively. The calculated annual e:ective dose equivalent due to natural radioactivity was found to be in the range of 40 –151 Sv. The obtained 3gures are comparable with average world-wide 3gures. It is obvious that the high dose at location 3 is due to the presence of phosphate in the soils. The annual e:ective dose equivalent at location 8 was found to be higher than the measured doses at other locations. In sampling area 8 (located near to the Aqaba beach) the 232 Th contribution to the total annual e:ective dose equivalent was about 95%, which is two times more than that of 238 U. A weak correlation between the concentration of 238 U and 232 Th was found with a correlation coeIcient of 0.48. The results of this study can be used as a data baseline for preparing a radiological map of the study area, especially at the chosen settlement sites.
speci3c activity in
of radionuclides of the 238 U; 232 Th, and 40 K ranges between 9 and 44 nGy h−1 , 14 and 68 nGy h−1 , and 6 and 26 nGy h−1 , respectively. The annual outdoors e:ective dose equivalents were calculated utilizing a conversion coeIcient of 0:72 Sv Gy−1 for an absorbed dose in air to e:ective dose in human body. This calculation takes into account that people spend about 20% of their time outdoors. The calculated absorbed dose rates from outdoors terrestrial gamma radiation and the annual e:ective dose equivalent are given in Table 2. Samples from locations 3 and 8 were found to have more annual e:ective dose equivalent than those samples from other locations included in this study. The highest observed annual dose equivalents are 151 Sv for location 8. 232 Th contributes about 58% of the total dose. According to UNSCEAR (2000) report, the dose rate in air outdoors from terrestrial gamma-rays in normal circumstances is about 57 nGy h−1 . The national average ranges from 24 to 160 nGy h−1 , while the world-wide average annual e:ective dose is approximately 70 Sv. Thus, our results are in a good agreement with the average world-wide limits. Table 3 shows reported values of gamma-absorbed dose rate in air, from work conducted in the Middle East areas and world-wide for comparison with our data. Fig. 2 depicts the correlation between the activities of 238 U and 232 Th. It is obvious that the correlations is rather weak, with correlation coeIcient of 0.48, which agreed with a previous study on the correlation between 238 U and 232 Th in a sample obtained near and intact to old phosphate mines (Al-Jundi, 2002).
4. Conclusions The mean speci3c activities obtained in the soil samples collected from eight sites located along AANH for 238 U, 232 Th, and 40 K ranged from 28 ± 7 to 84 ± 28; 22 ± 2 to
References Abu-Rukah, Y., 2001. A study of soils, contaminated with heavy metals along the Amman Aqaba National Highway (Jordan). Freiberg 494, 53–62. Ahmad, N., Matiullah, Khatibeh, A., 1997. Indoor radon levels and natural radioactivity in Jordanian soil. Radiat. Protect. Dosim. 71 (3), 231–233. Al-Jundi, J., 2002. Population dosres from terrestrial gamma exposure in areas near to old phosphate mine, Russaifa, Jordan. Radiat. Meas. 35, 23–28. Ibrahim, N.M., Abdel-Ghani, A.H., Shawky, S.M., Ashraf, E.M., Faouk, M.A., 1993. Measurement of radioactivity levels in soil in the Nile delta and middle Egypt. Health. Phys. 64, 620–627. Jibiri, N.N., 2001. Assessment of health risk levels associated with terrestrial gamma radiation dose rates in Nigeria. Environ. Int. 27, 21–26. Kannan, V., Rajan, M.P., Lyengar, M.A., Ramesh, R., 2002. Distribution of natural and anthropogenic radionuclides in soil and beach sand samples of Kalpakkam (India). Appl. Radiat. Isot. 57, 109–119. Karahan, G., Bayulken, A., 2000. Assessment of gamma dose rates around Istanbul (Turkey). J. Environ. Radioact. 47, 213–221. Malanca, A., Gaidol3, L., Pessina, V., Dallara, G., 1996. Distribution of 226 Ra; 232 Th, and 40 K of Rio Grande do Norte (Brazil). J. Environ. Radioact. 30 (1), 55–67. McAulay, I.R., Moran, D., 1988. Natural radioactivity in soil in the Republic of Ireland. Radiat. Protect. Dosim. 24 (1/4), 47–49. Probonas, M., Kritidis, P., 1993. The exposure of the Greek population to natural gamma radiation of terrestrial origin. Radiat. Protect. Dosim. 46 (2), 123–126. Randle, K., Al-Jundi, J., 2001. Instrumental neutron activation analysis (INAA) of esturine sediments. J. Radioanal. Nucl. Chem. 249 (2), 361–367. Sohrabi, M., 1993. Recent radiological studies of high level natural radiation areas of Rasmar. In: Sohrabi, M., Ahmad, J.U., Durrani, S.A. (Eds.), Proceeding of the International Conference on High Levels of Natural Radiation, Rasmar, 1990. IAEA, Vienna. Steinhausler, F., Lettner, H., 1992. Radiometric survey in Namibia. Radiat. Protect. Dosim. 45 (1/4), 553–555.
560
J. Al-Jundi et al. / Radiation Measurements 36 (2003) 555 – 560
Sunta, C.M., 1993. A review of the studies of high background areas of the S-W coast of India. In: Sohrabi, M., Ahmad, J.U., Durrani, S.A. (Eds.), Proceeding of the International Conference on High Levels of Natural Radiation, Rasmar, 1990. IAEA, Vienna. UNSCEAR, 2000. Sources, E:ects and Risks of Ionizing Radiations. United Nations, New York.
Zhu, H., Huang, H., Song, J., Li, J., Zhang, J., Huang, J., Zha, Y., Guo, Y., 1993. Gamma radiation levels around the highest background area in Poland. In: Sohrabi, M., Ahmad, J.U., Durrani, S.A. (Eds.), Proceeding of the International Conference on High Levels of Natural Radiation, Rasmar, 1990. IAEA, Vienna.