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Radioactivity concentrations and dose assessment for soil samples around Adana, Turkey
Available online at www.sciencedirect.com
Journal of Environmental Radioactivity 99 (2008) 1018e1025 www.elsevier.com/locate/jenvrad
Radioactivity concentrations and dose assessment for soil samples around Adana, Turkey M. Degerlier a,*, G. Karahan b, G. Ozger a b
a University of Cukurova, Science and Art Faculty Department of Physics, Balcali Adana, Turkey C¸ekmece Nuclear Research and Training Centre, P.O. Box 1, Atatu¨rk Airport, 34831-Istanbul, Turkey
Received 15 June 2007; received in revised form 23 November 2007; accepted 4 December 2007 Available online 12 February 2008
Abstract The concentrations of natural radionuclides in surface soils around Adana, Turkey were determined using gamma ray spectrometry with an HPGe detector. The natural gamma ray radioactivity of the terrestrial radionuclides in air was calculated throughout different areas of Adana. The average activity concentrations of 238U, 232Th and 40K were found to be 17.6, 21.1 and 297.5 Bq kg1, respectively. Outdoor gamma dose measurements in air 1 m above ground level were determined by using a portable gamma scintillation detector. The gamma dose measurements in air were taken from the same places where soil samples were taken. Average outdoor gamma dose rates in sample stations were determined as 67 nGy h1. The annual effective dose to the public was found to be 82 mSv. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Natural radioactivity; Soil; Gamma dose; Adana
1. Introduction Natural radioactivity is wide spread in the earth’s environment; it exists in soil, plants, water and air. Environmental natural gamma radiation is formed from terrestrial and cosmic sources (Merdano˘glu and Altınsoy, 2006). Natural radionuclides in soil generate a significant component of the background radiation exposure of the population (Karahan and Bayulken, 2000). Gamma radiation intensity in a region depends on soil and geographic structure. The natural radioactivity in soil comes mainly from the 238U, 232Th decay series and natural 40K, respectively (UNSCEAR, 2000). The main objective of this study was to identify and determine natural radionuclide activity concentrations in soil samples collected from 38 locations around Adana city and to evaluate the annual effective dose from outdoor terrestrial radiation. In addition, the natural gamma radiation coming
* Corresponding author. Tel.: þ90 533 779 76 89, þ39 388 477 64 01. E-mail addresses: [email protected], [email protected]. it, [email protected] (M. Degerlier). 0265-931X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvrad.2007.12.015
from terrestrial radionuclides in air was also investigated in the Adana region. This study would be useful for establishing base line data on the gamma background radiation levels in different areas of Adana, Turkey for assessment of radiation exposures to the population. 2. Materials and methods Adana is located in the southern part of Anatolia in Turkey (Fig. 1). The surface area of Adana is about 17.2 km2 and its population is approximately 2 million. The land in this region contains alluvial soil, colluvial soil, brown forest soil, limeless brown forest soil and red brown Mediterranean soil. Soil samples were taken with 25 cm diameter cores collected at 38 different locations and at different depths ranging from 0 to 30 cm. These samples were taken from uncultivated fields and sampling stations were chosen close to populated areas. The soil samples were dried, pulverized, homogenized and sieved through 2 mm mesh. The meshed soil samples were transferred to Marinelli beakers of 1000 ml capacity. The soil samples were weighed, carefully sealed and stored for 30 days to allow secular equilibrium between thorium and radium and their decay products (Mollah et al., 1987). Gamma spectroscopic measurements were performed using a coaxial HPGe detector having a 16% relative efficiency. A detection system containing a Canberra Model 2020 Amplifier and a Canberra S-85 Multi Channel
M. Degerlier et al. / Journal of Environmental Radioactivity 99 (2008) 1018e1025
1019
Fig. 1. A map of Turkey. Table 1 Activity concentrations of radioisotopes in the Region
238
238
U series,
Aladag Kokezli (Aladag) Darilik (Aladag) Average Karaisali Kelceler (Karaisali) Salbas (Karaisali) Karaisali (Centre) Average Pozanti Tekir (Pozanti) Kamis xli girisx (Pozanti) Kamisli cikis (Pozanti) Kamisli (Pozanti) Average Feke Feke (Centre) Akoluk (Feke) Average
40
K and
137
Cs in soil samples from Adana, Turkey Th series (Bq kg1)
232
U (Bq kg ) Ra
Average
Th,
1
226
Yuregir Balcali (Yuregir) Yeniyayla (Yuregir) Mustafalar (Yuregir) Camlica (Yuregir) Balcali kayi. (Yuregir)
232
214
Pb
214
Bi
228
Ac
K (Bq kg1)
40
Cs (Bq kg1)
137
208
Tl
27.8 1.4 10.3 0.7 5.07 0.7 13.4 1.4 26.05 2.5
17.7 0.4 5.8 0.2 7.8 0.4 9.2 0.5 15.4 0.6
16.2 0.4 4.8 0.2 8.5 0.4 7.5 0.5 12.4 0.5
23.6 0.6 8.4 0.4 14.9 0.6 14.6 0.9 25.4 0.9
27.2 0.5 8.4 0.3 13.8 0.5 14.5 0.7 28.1 0.9
296.6 3.1 110.7 2.5 190.2 3.3 175.1 5.2 274.5 4.7
5.8 0.2 22.4 1.5 12.5 0.3 6.6 0.3 18.6 0.4
16.52 1.3
11.18 0.4
9.87 0.4
17.38 0.7
18.4 0.6
209.4 3.8
13.2 0.5
11.02 0.4 0.5 0.1
9.1 0.4 1 0.1
11.4 0.6 0.7 0.2
9.5 0.5 0.6 0.2
190 4.1 9.6 0.8
28.0 0.4 2.6 0.2
7.96 0.6
5.8 0.2
5.05 0.3
6.05 0.4
5.0 0.3
99.8 2.5
30.6 0.3
26.0 1 23.5 0.9 29 1.4
20.4 0.3 20.2 0.3 20.8 0.4
20.0 0.3 21.7 0.3 21.7 0.4
27.6 0.5 19.9 0.5 22.9 0.5
28.2 0.4 24.9 0.5 28.4 0.5
462.4 3.6 330.1 3.1 415.1 3.5
0.9 0.1 8.4 0.2 0.1 0.1
26.2 1.1
20.5 0.3
21.15 0.4
23.5 0.5
27.2 0.5
402.5 3.4
3.1 0.1
16.5 1.0 13.5 0.8 19.2 1.2 6.4 0.5
12.4 0.4 8.1 0.2 15.5 0.3 2.4 0.1
12.1 0.4 7.5 0.2 16.1 0.3 2.0 0.1
8.1 0.5 4.7 0.3 18.1 0.5 2.8 0.2
9.2 0.4 6 0.3 24.1 0.5 3.7 0.2
158.8 3.5 112.4 2 274.7 3.1 86.5 1.7
4.5 0.2 1.7 0.1 6.2 0.2 1.7 0.1
13.9 0.9
9.6 0.3
9.5 0.3
8.4 0.4
10.7 0.4
158.1 2.6
3.5 0.1
27.2 2.5 104.1 4.9
22.6 0.7 67.8 1.0
21.3 0.7 70.7 1.4
39.4 1.2 55.1 1.7
43.5 1.1 58.5 1.4
793.4 7.7 310.6 6.5
11.5 0.4 4.7 0.4
65.6 3.7
45.2 0.9
46.0 1.1
47.3 1.5
51 1.3
552.0 7.1
8.1 0.4
15.7 1.1 0.2 0.02
(continued on next page)
M. Degerlier et al. / Journal of Environmental Radioactivity 99 (2008) 1018e1025
1020 Table 1 (continued) Region
U (Bq kg1)
226
Ra
Saimbeyli Drayli (Saimbeyli) Saimbeyli (Centre) Average Yumurtalik Hamzali (Yumurtalik) Zeytinbeyli (Yumurtalik) Incirli (BotaseYumurtalik) Zeytinbeli (Yumurtalik) Yumurtalik (Centre) Botas (Yumurtalik) Golovasi (Yumurtalik) Average Ceyhan Ceyhan (Centre) Narlik (Ceyhan) Ceyhan (Centre) Kosreli (Ceyhan) Tatlikuyu (Ceyhan) Yalak (Ceyhan) Sagkaya (Ceyhan) Average Karatas Karatas (Centre) Average Kozan Culluusagi (Kozan) Kozan (Centre) Average Imamoglu Hacihasanli (Imamoglu) Average Tufanbeyli Tufanbeyli (Centre) Catalcam (Tufanbeyli) Average
Th series (Bq kg1)
238
232 214
Pb
214
228
Bi
Ac
K (Bq kg1)
40
Cs (Bq kg1)
137
208
Tl
39 1.3 36.7 2.1
32.0 0.4 28.3 0.7
28.4 0.4 23.1 0.6
35.2 0.6 49.9 1.2
39.0 0.5 54.9 1.1
626.8 4.3 385.9 5.9
7.5 0.2 1.5 0.2
37.8 1.7
30.2 0.5
25.7 0.5
42.5 0.9
47 0.8
506.4 5.1
4.5 0.2
10.0 0.6 17.3 1.0 11.2 0.5 17.8 1.2 7 0.5 14.3 1 13.4 1.3
7.7 0.2 14.2 0.3 10.2 0.2 9.9 0.2 6.3 0.2 8.5 0.3 12 0.5
7.4 0.2 14.3 0.3 10.1 0.2 10.1 0.3 6.4 0.2 8.2 0.3 11.4 0.5
8.2 0.3 16.0 0.5 7.3 0.3 13.9 0.4 3.9 0.2 19.7 0.5 9.4 0.7
8.8 0.3 17.4 0.5 8.6 0.3 15.4 0.4 3.7 0.2 20.6 0.5 18.2 0.7
378.8 3.4 299.7 3.3 116.7 1.8 222.1 2.8 170.9 2.2 112.6 2.0 270.0 4.96
7 0.2 8.3 0.2 2.0 0.1 7.7 0.2 0.5 0.6 2.6 0.1 3.9 0.2
14.09 0.8
10.5 0.2
10.5 0.3
11.4 0.4
12.6 0.4
254.3 2.8
6.3 0.2
21.4 1.1 6.6 0.4 15 1.5 16.1 1.2 27.3 2.1 14.9 1.1 11.6 1.1
17.9 0.3 2.6 0.1 11.9 0.5 14.3 0.5 14.3 0.6 10.3 0.4 15.2 0.5
16.8 0.3 0.9 0.1 10.6 0.5 14.0 0.5 12.7 0.6 8.5 0.4 11.96 0.4
16.2 0.5 2.4 0.3 18.9 0.8 14.4 0.7 22.9 1.1 9.8 0.6 21.9 0.8
15 0.4 3.5 0.2 20.7 0.7 15.96 0.6 26.5 1 10.3 0.5 24.8 0.8
274.6 2.8 63.7 0.5 284.5 5.7 291.2 4.9 310.5 6.9 397.09 5.3 250.4 4.4
2.8 0.1 13.0 0.2 4.5 0.3 8.9 0.3 14.3 0.4 6.2 0.2 6.4 0.3
16.1 1.2
12.3 0.4
10.8 0.4
15.2 0.7
16.7 0.6
267.4 4.4
8.0 0.3
12.3 0.9
9.1 0.3
9.8 0.3
8.7 0.4
8.4 0.3
144.1 2.2
0.5 10.3
12.3 0.9
9.1 0.3
9.8 0.3
8.7 0.4
8.4 0.3
144.1 2.2
0.5 10.3
32.3 1.7 40.7 3.1
31.8 0.5 23.8 0.6
28.95 0.5 23.3 0.7
55.6 0.9 36.8 1.1
58.2 0.7 37.2 0.9
814.2 4.8 471.3 6.2
1.6 0.2 10.6 0.4
36.5 2.4
27.8 0.55
26.1 0.56
46.2 1.005
47.7 0.8
642.7 5.5
6.1 0.3
21.5 0.8
17.3 0.3
16.2 0.3
17.4 0.5
19.2 0.4
344 3.2
0.2 0.1
21.5 0.8
17.3 0.3
16.2 0.3
17.4 0.5
19.2 0.4
344 3.2
0.2 0.1
37.7 1.81 39.1 1.3
25.7 0.5 31.5 0.4
21 0.5 27.7 0.4
36.7 0.9 44 0.7
40.2 0.8 44.9 0.6
430.3 5.8 455.6 3.7
6.5 0.3 6.8 0.16
38.4 1.5
28.6 0.4
24.3 0.4
40.3 0.8
42.5 0.7
442.9 4.7
6.6 0.2
Analyzer with Model 8087 4K ADC was used for the measurements. The detector was shielded in a 10 cm thick lead well, internally lined with 2 mm thick copper and 2 mm thick cadmium foils. The overall detector resolution (FWHM) of 1.9 keV was obtained for the 1332 keV gamma line of 60Co. Energy calibration and relative efficiency calibration of the gamma spectrometer were carried out using 109Cd, 57Co, 113Sn, 134Cs, 137Cs, 188Y and 60Co calibration sources in 1000 ml Marinelli beaker covering the energy range from 80 to 2500 keV. The counting time for each sample, as well as for background, was 50,000 s. Sample preparation and counting procedures were performed in the Cekmece Nuclear Research and Training Centre, Department of Health Physics Counting Laboratory, Istanbul, Turkey. The contribution of natural radionuclides to the absorbed dose rate in air depends on the concentration of the radionuclides in soil. The largest part of the gamma radiation comes from terrestrial radionuclides. There is a direct correlation between terrestrial gamma radiation and radionuclide concentration
in soil. Gamma dose rates were measured 1 m above ground by a portable digital environmental radiation dosimeter which contains a gamma scintillation detector Eberline, SPA-6) directly mounted to a microcomputer (Eberline, ESP-2 Model). Gamma spectroscopy was used to determine the activities of 238U, 232Th, 40 K and 137Cs. The activity concentrations of 232Th and 238U were calculated assuming secular equilibrium was established with their decay products. For concentrations of 232Th and 238U, the following gamma transition lines were used; 232Th series: 228Ac (911 keV), 208Tl (583.1 keV); 238U series: 226Ra (186.0 keV), 214Pb (351.9 keV) and 214Bi (609.2 keV). The activity concentration of 40K was determined from the peak area of 1460 keV line. The 661.66 keV gamma transition was used to determine the 137Cs concentration. If a radionuclide activity in soil is known then its exposure dose rate in air at 1 m above the ground can be found. The conversion factor of 238U, 232Th and 40 K is 0.427, 0.662 and 0.043 nGy h1 per Bq kg1, respectively (Beck, 1972).
M. Degerlier et al. / Journal of Environmental Radioactivity 99 (2008) 1018e1025
1021
Table 2 Average activity of soil samples (Bq kg1 dry weight) for the 238U and 232Th series, absorbed dose rates in air, annual effective dose, and soil type in Adana, Turkey Region
Yuregir Balcali fen edeb. (Yuregir)
238
U series (Bq kg1)
20.6 0.7
232
Th series (Bq kg1)
25.4 0.6
Annual effective dose equivalent (mSv)
Absorbed (terrestrial)
Terrestrial and cosmic
Measured (terrestrial and cosmic)
3.8
5.4
66.4
47.0
1.3
5.6
68.4
16.3
6.96 0.4
Mustafalar (Yuregir)
7.1 0.5
14.4 0.6
2.1
5.9
72.5
25.4
Camlica (Yuregir) Balcali kayikhane (Yuregir)
10.0 0.8 17.9 1.2
14.6 0.8 26.7 0.9
2.1 3.7
5.6 5.7
68.2 69.4
26.3 45.6
Average
12.6 0.7
12 0.63
17.9 0.6
2.6
5.6
69
32.1
10.5 0.56
2.0
3.8
46
24.8
Darilikustu boyalik (Aladag)
0.6 0.1
0.6 0.2
0.1
2.3
28.1
1.9
Average
6.3 0.4
5.6 0.4
1.1
3.0
37.0
13.3
22.1 0.54 21.8 0.5 23.8 0.7
27.9 0.5 22.4 0.5 25.7 0.5
4.8 3.8 4.5
9.3 7.9 9.1
114.1 96.9 112
58.6 47 55.2
22.6 0.6
25.3 0.5
4.4
8.8
107.6
53.6
13.7 0.6 9.7 0.4 17 0.6 3.6 0.2
8.6 0.5 5.4 0.3 21.1 0.5 3.2 0.2
1.8 1.3 3.3 0.7
5.6 6.2 6.2 6.2
68.2 75.7 75.7 75.7
22.5 15.4 40.5 9.1
11 0.5
9.6 0.4
1.8
6.0
73.8
21.9
23.7 1.3
41.4 1.2
7.2
13.4
164.3
87.9
Akoluk (Feke)
80.9 2.4
56.8 1.6
8.6
14.4
176.6
104.2
Average
52.3 1.9
49.1 1.4
46.3
13.5
165.6
96.4
33.1 0.7
37.1 0.6
6.6
8.8
107.6
80.5
Saimbeyli (Centre)
29.4 1.12
52.4 1.1
6.4
11.1
136.1
78.3
Average
31.2 0.9
44.8 0.9
6.5
9.9
121.8
79.4
18.5 0.6 3.4 0.2 12.5 0.8 14.8 0.7 18.1 1.1 11.2 0.61 12.9 0.7 13.1 0.7
15.6 0.5 2.9 0.2 19.8 0.8 15.2 0.66 24.7 1.0 10.06 0.52 23.4 0.8 15.9 0.6
3 0.53 3.1 2.9 3.7 2.9 3.2 2.8
5.3 4.08 5.3 4.6 6.6 6.1 5.6 5.4
Karaisali Kelceler (Karaisali) Salbas (Karaisali) Karaisali (Centre) Average Pozanti Tekir (Pozanti) Kamisli giris (Pozanti) Kamisli cikis (Pozanti) Kamisli (Pozanti) Average Feke Feke (Centre)
Saimbeyli Drayli (Saimbeyli)
Ceyhan Ceyhan (Centre) Narlik (Ceyhan) Ceyhan (Centre) Kosreli (Ceyhan) Tatlikuyu (Ceyhan) Yalak (Ceyhan) Sagkaya (Ceyhan) Average
64.8 50.04 64.8 56.2 80.7 74.6 68.1 65.6
Soil type
Terrestrial
Yeniyayla (Yuregir)
Aladag Kokezli (Aladag)
8.4 0.34
Absorbed dose rate in air (108 Gy h1)
36.8 6.5 37.6 35.4 45.9 35 38.9 33.7
Red brown Mediterranean Red brown Mediterranean Red brown Mediterranean Colluvial soil Red brown Mediterranean
soil soil soil
soil
Limeless brown forest soil Colluvial soil
Brown forest soil Brown forest soil Brown forest soil
Brown forest soil Colluvial soil Colluvial soil Colluvial soil
Limeless brown forest soil Limeless brown forest soil
Limeless brown forest soil Limeless brown forest soil
Alluvial soil Colluvial soil Alluvial soil Alluvial soil Alluvial soil Alluvial soil Alluvial soil (continued on next page)
M. Degerlier et al. / Journal of Environmental Radioactivity 99 (2008) 1018e1025
1022 Table 2 (continued ) Region
Karatas Karatas (Centre) Average Yumurtalik Zeytinbeli (Yumurtalik) IncirlieBotas (Yumurtalik) Yumurtalik (Centre) Zeytinbeyli (Yumurtalik) Botas (Yumurtalik) Golovasi (Yumurtalik) Hamzali (Yumurtalik) Average Kozan C¸ulluusagi (Kozan) Kozan (Centre) Average Imamoglu Hacihasanli (Imamoglu) Average Tufanbeyli Tufanbeyli (Centre) Catalcam (Tufanbeyli) Average
238 U series (Bq kg1)
232 Th series (Bq kg1)
Absorbed dose rate in air (108 Gy h1)
Annual effective dose equivalent (mSv)
Absorbed (terrestrial)
Terrestrial and cosmic
Measured (terrestrial and cosmic)
Terrestrial
10.4 0.5
8.5 0.4
1.6
4.95
60.7
19.9
10.4 0.5
8.5 0.4
1.6
4.95
60.7
19.9
15.3 0.6 10.5 0.3 6.6 0.3 12.6 0.6 10.3 0.5 12.3 0.75 8.4 0.3
16.7 0.5 7.9 0.3 3.8 0.2 14.7 0.4 20.2 0.5 13.8 0.7 8.5 0.3
3.05 1.5 1.3 2.5 2.3 2.6 2.6
4.8 4.0 4.9 4.8 3.7 4.5 4.4
59 49.6 59.8 59 45.3 55.7 54
37.4 18.11 15.5 30.3 27.7 31.9 31.3
10.8 0.5
12.2 0.4
2.2
4.5
54.6
27.4
31.0 0.9 29.2 1.5
56.9 0.8 37.0 1
8.6 5.7
14.4 10.5
176.6 128.8
105.3 70.2
30.1 1.2
46.9 0.9
7.2
12.5
152.7
87.8
18.3 0.5
18.3 0.4
3.5
6.9
84.9
42.6
18.3 0.5
18.3 0.4
3.5
6.9
84.9
42.6
28.1 0.9 32.8 0.7
38.4 0.9 44.4 0.6
5.6 6.3
8.8 8.8
107.6 107.3
68.6 77.2
30.5 0.8
41.3 0.8
5.9
8.8
107.4
72.9
The contribution of terrestrial gamma radiation to absorbed doses in air was calculated using the following formula (Beck, 1972): D nGy h1 ¼ 0:427CU þ 0:662CTh þ 0:043CK where D is the dose rate at 1 m above ground, CU, CTh, and CK are the activity concentrations of 238U, 232Th, and 40K in the soil samples. The annual effective dose equivalent (AEDE) was calculated as follows; AEDE ¼ ADRA DCF OF T: The most appropriate average value of the quotient of effective dose equivalent rate to absorbed dose rate in air (ADRA) was taken, as in the UNSCEAR (1982) report to be 0.7 Sv Gy1 for environmental exposures to gamma rays of moderate energy. A dose conversion factor (DCF) of 0.7 Sv Gy1 and an outdoor occupancy factor (OF) of 0.2 were used as recommended by UNSCEAR (1988). T is the time factor (8760 h).
3. Results and discussions The average radionuclide activity concentrations in the soil samples taken from 38 locations are reported in Table 1. Specific activities of 238U, 232Th, 40K and 137Cs are reported in Bq kg1 dry weight. The mean activity concentrations of 238 U, 232Th and 40K in surface soil samples from Adana region are 17.6, 21.1 and 297.5 Bq kg1, respectively. The worldwide
Soil type
Brown forest soil
Colluvial soil Colluvial soil Colluvial soil Colluvial soil Brown forest soil Colluvial soil Colluvial soil
Brown forest soil Brown forest soil
Colluvial soil
Limeless brown soil Limeless brown forest soil
average concentrations of these radionuclides are reported by UNSCEAR (2000) as 35, 30 and 400 Bq kg1, respectively. 137 Cs was also seen in the samples and analyzed in this work. The anthropogenic radionuclide 137Cs, deposited in the soil of Adana presumably as a result of atmospheric fallout of radioactivity following the Chernobyl accident on 26 April 1986, and other previous atmospheric tests of nuclear devices around the world. The 137Cs activities varied from 0.1 to 28.0 Bq kg1 in this study. The average 137Cs activity was measured to be 6.8 Bq kg1. The largest 137Cs activity was measured in the town of Kokezli, within the Aladag region of Adana. The calculated absorbed dose and the measured dose rates in air 1 m above ground are given in Table 2. The absorbed doses were calculated only from outdoor terrestrial gamma radiation. But the measured doses have contributions from both outdoor terrestrial gamma radiation and cosmic rays. In order to determine cosmic ray contribution in outdoor absorbed radiation doses, it is necessary that select a suitable place where terrestrial gamma radiation effect minimize. Lakes are most suitable places to measure cosmic rays. Seyhan Dam Lake in Adana city centre was selected for this aim. The measurement was presumably taken deepest part of the lake water. Minimum levels gamma rays come from lake water and coast were neglected. The cosmic ray contribution was found to be about 9.5 nGy h1
M. Degerlier et al. / Journal of Environmental Radioactivity 99 (2008) 1018e1025
Fig. 2.
1023
U radioactivity concentration in soil samples (Bq kg1).
238
by measuring exposure rates with a portable gamma scintillation detector (ESP-2, SPA-6) on Seyhan Dam Lake. The measured absorbed doses (outdoor terrestrial and cosmic) are thus higher than the calculated absorbed doses (outdoor terrestrial) as seen in Table 2. The difference between them ranges between
11.47 and 56.68 nGy h1, being derived from cosmic radiation and the other terrestrial radionuclides. The difference between outdoor measured absorbed doses and calculated absorbed doses is 11.5 and 15.0 nGy h1 in near Seyhan Dam Lake. This suggests in turn that our measurements are correct.
1024
M. Degerlier et al. / Journal of Environmental Radioactivity 99 (2008) 1018e1025
Fig. 3.
Th radioactivity concentration in soil samples (Bq kg1).
232
Fig. 2 shows 238U radioactivity concentrations and Fig. 3 shows the 232Th radioactivity concentrations in soil samples. The largest contribution from the natural radionuclides in Adana soil samples to the absorbed doses in air was generally due to the 232Th series expect in the Culluusagi (Kozan), Saimbeyli, Feke and Tufanbeyli regions. The largest contribution in both of these regions comes from 40K. The highest concentration of 238U was measured in Akoluk (Feke) region. Fig. 4 shows the different 238U
between 232Th radioactivity concentrations in various towns of the Adana region of Turkey. The largest 238U and 232Th concentrations were observed in Feke, Saimbeyli, Kozan, and Tufanbeyli. The smallest 238U and 232Th concentrations were observed in Aladag. These towns inside north part of region have high elevation. Fig. 5 shows 238U between 232Th differences among various soil types. The largest activity concentrations were measured in limeless brown forest soil and limeless brown soil. The
M. Degerlier et al. / Journal of Environmental Radioactivity 99 (2008) 1018e1025
238
232
Fig. 4. U and Th radioactivity concentration in various towns of the Adana region of Turkey.
smallest 238U and 232Th concentrations were observed in colluvial soil samples. It was observed that the activity concentrations vary depending on the geological and geographical conditions of different regions. The most important reason for the higher activity concentrations with respect to the others in some regions is a higher uranium and thorium content in rock and soil structure in these regions. The outdoor gamma measured dose rates (terrestrial and cosmic) in air 1 m above ground ranged between 23 and 144 nGy h1. The average calculated (terrestrial) outdoor gamma radiation dose and the mean measured (terrestrial and cosmic) outdoor gamma radiation dose were about 54 and 67 nGy h1, respectively. The average annual effective dose equivalents from the calculated outdoor terrestrial gamma radiation and the measured outdoor gamma radiation (terrestrial plus cosmic) at 1 m above ground in Adana were found to be about 44 and 82 mSv, respectively. The world average annual effective dose equivalent (AEDE) from outdoor terrestrial gamma radiation is 70 mSv (UNSCEAR, 2000) thus the average annual effective dose for Adana region is higher than that of the worldwide average value.
4. Conclusion This study intended to define the radioactivity concentrations and dose in soil samples for a region of the world where little published data exists on such topics, the Adana region located in the southern part of Turkey. A total of 38 measurements were made covering the 12 areas in Adana. The
Fig. 5. 238U and region of Turkey.
1025
232
Th activity concentrations in soils found in the Adana
radioactivity concentrations of 238U, 232Th and 40K in the soil of the Adana region compare suitably with literature values. Acknowledgements The authors thanks to Health Physics Department of Cekmece Nuclear Research and Training Centre e Turkish Atomic Energy Department for their cooperation to perform this work. The authors wish to thank Prof. Dr. Vedat PESTEMALCI, Prof. Dr. Gulten GUNEL and Dr. Aysun UGUR for their kind help. References Beck, H.L., 1972. The Physics of Environmental Radiation Fields. Natural Radiation Environment II, Cohewan. Canada. NF-720805 P2. In: Proceedings of the Second International Symposium on the Natural Radiation Environment. Karahan, G., Bayulken, A., 2000. Assessment of gamma dose rates around Istanbul (Turkey). Journal of Environmental Radioactivity 47, 213e221. Merdano˘glu, B., Altınsoy, N., 2006. Radioactivity concentrations and dose assessment for soil samples from Kestanbol granite area, Turkey. Radiation Protection Dosimetry 121 (No. 4), 399e405. Mollah, S., Rahman, N.M., Kodlus, M.A., Husain, S.R., 1987. Measurement of high natural background radiation levels by TLD at Cox and Bazar coastal areas in Bangladesh. Radiation Protection Dosimetry 18 (1), 39e41. UNSCEAR, 1982. United Nations Scientific Committee on the Effects of Atomic Radiation, Sources and Biological Effects of Ionizing Radiation. United Nations, New York. UNSCEAR, 1988. United Nations Scientific Committee on the Effects of Atomic Radiation, Sources and Biological Effects of Ionizing Radiation. United Nations, New York. UNSCEAR, 2000. United Nations Scientific Committee on the Effects of Atomic Radiation, Sources and Biological Effects of Ionizing Radiation. United Nations, New York.
Journal of Environmental Radioactivity 99 (2008) 1018e1025 www.elsevier.com/locate/jenvrad
Radioactivity concentrations and dose assessment for soil samples around Adana, Turkey M. Degerlier a,*, G. Karahan b, G. Ozger a b
a University of Cukurova, Science and Art Faculty Department of Physics, Balcali Adana, Turkey C¸ekmece Nuclear Research and Training Centre, P.O. Box 1, Atatu¨rk Airport, 34831-Istanbul, Turkey
Received 15 June 2007; received in revised form 23 November 2007; accepted 4 December 2007 Available online 12 February 2008
Abstract The concentrations of natural radionuclides in surface soils around Adana, Turkey were determined using gamma ray spectrometry with an HPGe detector. The natural gamma ray radioactivity of the terrestrial radionuclides in air was calculated throughout different areas of Adana. The average activity concentrations of 238U, 232Th and 40K were found to be 17.6, 21.1 and 297.5 Bq kg1, respectively. Outdoor gamma dose measurements in air 1 m above ground level were determined by using a portable gamma scintillation detector. The gamma dose measurements in air were taken from the same places where soil samples were taken. Average outdoor gamma dose rates in sample stations were determined as 67 nGy h1. The annual effective dose to the public was found to be 82 mSv. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Natural radioactivity; Soil; Gamma dose; Adana
1. Introduction Natural radioactivity is wide spread in the earth’s environment; it exists in soil, plants, water and air. Environmental natural gamma radiation is formed from terrestrial and cosmic sources (Merdano˘glu and Altınsoy, 2006). Natural radionuclides in soil generate a significant component of the background radiation exposure of the population (Karahan and Bayulken, 2000). Gamma radiation intensity in a region depends on soil and geographic structure. The natural radioactivity in soil comes mainly from the 238U, 232Th decay series and natural 40K, respectively (UNSCEAR, 2000). The main objective of this study was to identify and determine natural radionuclide activity concentrations in soil samples collected from 38 locations around Adana city and to evaluate the annual effective dose from outdoor terrestrial radiation. In addition, the natural gamma radiation coming
* Corresponding author. Tel.: þ90 533 779 76 89, þ39 388 477 64 01. E-mail addresses: [email protected], [email protected]. it, [email protected] (M. Degerlier). 0265-931X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvrad.2007.12.015
from terrestrial radionuclides in air was also investigated in the Adana region. This study would be useful for establishing base line data on the gamma background radiation levels in different areas of Adana, Turkey for assessment of radiation exposures to the population. 2. Materials and methods Adana is located in the southern part of Anatolia in Turkey (Fig. 1). The surface area of Adana is about 17.2 km2 and its population is approximately 2 million. The land in this region contains alluvial soil, colluvial soil, brown forest soil, limeless brown forest soil and red brown Mediterranean soil. Soil samples were taken with 25 cm diameter cores collected at 38 different locations and at different depths ranging from 0 to 30 cm. These samples were taken from uncultivated fields and sampling stations were chosen close to populated areas. The soil samples were dried, pulverized, homogenized and sieved through 2 mm mesh. The meshed soil samples were transferred to Marinelli beakers of 1000 ml capacity. The soil samples were weighed, carefully sealed and stored for 30 days to allow secular equilibrium between thorium and radium and their decay products (Mollah et al., 1987). Gamma spectroscopic measurements were performed using a coaxial HPGe detector having a 16% relative efficiency. A detection system containing a Canberra Model 2020 Amplifier and a Canberra S-85 Multi Channel
M. Degerlier et al. / Journal of Environmental Radioactivity 99 (2008) 1018e1025
1019
Fig. 1. A map of Turkey. Table 1 Activity concentrations of radioisotopes in the Region
238
238
U series,
Aladag Kokezli (Aladag) Darilik (Aladag) Average Karaisali Kelceler (Karaisali) Salbas (Karaisali) Karaisali (Centre) Average Pozanti Tekir (Pozanti) Kamis xli girisx (Pozanti) Kamisli cikis (Pozanti) Kamisli (Pozanti) Average Feke Feke (Centre) Akoluk (Feke) Average
40
K and
137
Cs in soil samples from Adana, Turkey Th series (Bq kg1)
232
U (Bq kg ) Ra
Average
Th,
1
226
Yuregir Balcali (Yuregir) Yeniyayla (Yuregir) Mustafalar (Yuregir) Camlica (Yuregir) Balcali kayi. (Yuregir)
232
214
Pb
214
Bi
228
Ac
K (Bq kg1)
40
Cs (Bq kg1)
137
208
Tl
27.8 1.4 10.3 0.7 5.07 0.7 13.4 1.4 26.05 2.5
17.7 0.4 5.8 0.2 7.8 0.4 9.2 0.5 15.4 0.6
16.2 0.4 4.8 0.2 8.5 0.4 7.5 0.5 12.4 0.5
23.6 0.6 8.4 0.4 14.9 0.6 14.6 0.9 25.4 0.9
27.2 0.5 8.4 0.3 13.8 0.5 14.5 0.7 28.1 0.9
296.6 3.1 110.7 2.5 190.2 3.3 175.1 5.2 274.5 4.7
5.8 0.2 22.4 1.5 12.5 0.3 6.6 0.3 18.6 0.4
16.52 1.3
11.18 0.4
9.87 0.4
17.38 0.7
18.4 0.6
209.4 3.8
13.2 0.5
11.02 0.4 0.5 0.1
9.1 0.4 1 0.1
11.4 0.6 0.7 0.2
9.5 0.5 0.6 0.2
190 4.1 9.6 0.8
28.0 0.4 2.6 0.2
7.96 0.6
5.8 0.2
5.05 0.3
6.05 0.4
5.0 0.3
99.8 2.5
30.6 0.3
26.0 1 23.5 0.9 29 1.4
20.4 0.3 20.2 0.3 20.8 0.4
20.0 0.3 21.7 0.3 21.7 0.4
27.6 0.5 19.9 0.5 22.9 0.5
28.2 0.4 24.9 0.5 28.4 0.5
462.4 3.6 330.1 3.1 415.1 3.5
0.9 0.1 8.4 0.2 0.1 0.1
26.2 1.1
20.5 0.3
21.15 0.4
23.5 0.5
27.2 0.5
402.5 3.4
3.1 0.1
16.5 1.0 13.5 0.8 19.2 1.2 6.4 0.5
12.4 0.4 8.1 0.2 15.5 0.3 2.4 0.1
12.1 0.4 7.5 0.2 16.1 0.3 2.0 0.1
8.1 0.5 4.7 0.3 18.1 0.5 2.8 0.2
9.2 0.4 6 0.3 24.1 0.5 3.7 0.2
158.8 3.5 112.4 2 274.7 3.1 86.5 1.7
4.5 0.2 1.7 0.1 6.2 0.2 1.7 0.1
13.9 0.9
9.6 0.3
9.5 0.3
8.4 0.4
10.7 0.4
158.1 2.6
3.5 0.1
27.2 2.5 104.1 4.9
22.6 0.7 67.8 1.0
21.3 0.7 70.7 1.4
39.4 1.2 55.1 1.7
43.5 1.1 58.5 1.4
793.4 7.7 310.6 6.5
11.5 0.4 4.7 0.4
65.6 3.7
45.2 0.9
46.0 1.1
47.3 1.5
51 1.3
552.0 7.1
8.1 0.4
15.7 1.1 0.2 0.02
(continued on next page)
M. Degerlier et al. / Journal of Environmental Radioactivity 99 (2008) 1018e1025
1020 Table 1 (continued) Region
U (Bq kg1)
226
Ra
Saimbeyli Drayli (Saimbeyli) Saimbeyli (Centre) Average Yumurtalik Hamzali (Yumurtalik) Zeytinbeyli (Yumurtalik) Incirli (BotaseYumurtalik) Zeytinbeli (Yumurtalik) Yumurtalik (Centre) Botas (Yumurtalik) Golovasi (Yumurtalik) Average Ceyhan Ceyhan (Centre) Narlik (Ceyhan) Ceyhan (Centre) Kosreli (Ceyhan) Tatlikuyu (Ceyhan) Yalak (Ceyhan) Sagkaya (Ceyhan) Average Karatas Karatas (Centre) Average Kozan Culluusagi (Kozan) Kozan (Centre) Average Imamoglu Hacihasanli (Imamoglu) Average Tufanbeyli Tufanbeyli (Centre) Catalcam (Tufanbeyli) Average
Th series (Bq kg1)
238
232 214
Pb
214
228
Bi
Ac
K (Bq kg1)
40
Cs (Bq kg1)
137
208
Tl
39 1.3 36.7 2.1
32.0 0.4 28.3 0.7
28.4 0.4 23.1 0.6
35.2 0.6 49.9 1.2
39.0 0.5 54.9 1.1
626.8 4.3 385.9 5.9
7.5 0.2 1.5 0.2
37.8 1.7
30.2 0.5
25.7 0.5
42.5 0.9
47 0.8
506.4 5.1
4.5 0.2
10.0 0.6 17.3 1.0 11.2 0.5 17.8 1.2 7 0.5 14.3 1 13.4 1.3
7.7 0.2 14.2 0.3 10.2 0.2 9.9 0.2 6.3 0.2 8.5 0.3 12 0.5
7.4 0.2 14.3 0.3 10.1 0.2 10.1 0.3 6.4 0.2 8.2 0.3 11.4 0.5
8.2 0.3 16.0 0.5 7.3 0.3 13.9 0.4 3.9 0.2 19.7 0.5 9.4 0.7
8.8 0.3 17.4 0.5 8.6 0.3 15.4 0.4 3.7 0.2 20.6 0.5 18.2 0.7
378.8 3.4 299.7 3.3 116.7 1.8 222.1 2.8 170.9 2.2 112.6 2.0 270.0 4.96
7 0.2 8.3 0.2 2.0 0.1 7.7 0.2 0.5 0.6 2.6 0.1 3.9 0.2
14.09 0.8
10.5 0.2
10.5 0.3
11.4 0.4
12.6 0.4
254.3 2.8
6.3 0.2
21.4 1.1 6.6 0.4 15 1.5 16.1 1.2 27.3 2.1 14.9 1.1 11.6 1.1
17.9 0.3 2.6 0.1 11.9 0.5 14.3 0.5 14.3 0.6 10.3 0.4 15.2 0.5
16.8 0.3 0.9 0.1 10.6 0.5 14.0 0.5 12.7 0.6 8.5 0.4 11.96 0.4
16.2 0.5 2.4 0.3 18.9 0.8 14.4 0.7 22.9 1.1 9.8 0.6 21.9 0.8
15 0.4 3.5 0.2 20.7 0.7 15.96 0.6 26.5 1 10.3 0.5 24.8 0.8
274.6 2.8 63.7 0.5 284.5 5.7 291.2 4.9 310.5 6.9 397.09 5.3 250.4 4.4
2.8 0.1 13.0 0.2 4.5 0.3 8.9 0.3 14.3 0.4 6.2 0.2 6.4 0.3
16.1 1.2
12.3 0.4
10.8 0.4
15.2 0.7
16.7 0.6
267.4 4.4
8.0 0.3
12.3 0.9
9.1 0.3
9.8 0.3
8.7 0.4
8.4 0.3
144.1 2.2
0.5 10.3
12.3 0.9
9.1 0.3
9.8 0.3
8.7 0.4
8.4 0.3
144.1 2.2
0.5 10.3
32.3 1.7 40.7 3.1
31.8 0.5 23.8 0.6
28.95 0.5 23.3 0.7
55.6 0.9 36.8 1.1
58.2 0.7 37.2 0.9
814.2 4.8 471.3 6.2
1.6 0.2 10.6 0.4
36.5 2.4
27.8 0.55
26.1 0.56
46.2 1.005
47.7 0.8
642.7 5.5
6.1 0.3
21.5 0.8
17.3 0.3
16.2 0.3
17.4 0.5
19.2 0.4
344 3.2
0.2 0.1
21.5 0.8
17.3 0.3
16.2 0.3
17.4 0.5
19.2 0.4
344 3.2
0.2 0.1
37.7 1.81 39.1 1.3
25.7 0.5 31.5 0.4
21 0.5 27.7 0.4
36.7 0.9 44 0.7
40.2 0.8 44.9 0.6
430.3 5.8 455.6 3.7
6.5 0.3 6.8 0.16
38.4 1.5
28.6 0.4
24.3 0.4
40.3 0.8
42.5 0.7
442.9 4.7
6.6 0.2
Analyzer with Model 8087 4K ADC was used for the measurements. The detector was shielded in a 10 cm thick lead well, internally lined with 2 mm thick copper and 2 mm thick cadmium foils. The overall detector resolution (FWHM) of 1.9 keV was obtained for the 1332 keV gamma line of 60Co. Energy calibration and relative efficiency calibration of the gamma spectrometer were carried out using 109Cd, 57Co, 113Sn, 134Cs, 137Cs, 188Y and 60Co calibration sources in 1000 ml Marinelli beaker covering the energy range from 80 to 2500 keV. The counting time for each sample, as well as for background, was 50,000 s. Sample preparation and counting procedures were performed in the Cekmece Nuclear Research and Training Centre, Department of Health Physics Counting Laboratory, Istanbul, Turkey. The contribution of natural radionuclides to the absorbed dose rate in air depends on the concentration of the radionuclides in soil. The largest part of the gamma radiation comes from terrestrial radionuclides. There is a direct correlation between terrestrial gamma radiation and radionuclide concentration
in soil. Gamma dose rates were measured 1 m above ground by a portable digital environmental radiation dosimeter which contains a gamma scintillation detector Eberline, SPA-6) directly mounted to a microcomputer (Eberline, ESP-2 Model). Gamma spectroscopy was used to determine the activities of 238U, 232Th, 40 K and 137Cs. The activity concentrations of 232Th and 238U were calculated assuming secular equilibrium was established with their decay products. For concentrations of 232Th and 238U, the following gamma transition lines were used; 232Th series: 228Ac (911 keV), 208Tl (583.1 keV); 238U series: 226Ra (186.0 keV), 214Pb (351.9 keV) and 214Bi (609.2 keV). The activity concentration of 40K was determined from the peak area of 1460 keV line. The 661.66 keV gamma transition was used to determine the 137Cs concentration. If a radionuclide activity in soil is known then its exposure dose rate in air at 1 m above the ground can be found. The conversion factor of 238U, 232Th and 40 K is 0.427, 0.662 and 0.043 nGy h1 per Bq kg1, respectively (Beck, 1972).
M. Degerlier et al. / Journal of Environmental Radioactivity 99 (2008) 1018e1025
1021
Table 2 Average activity of soil samples (Bq kg1 dry weight) for the 238U and 232Th series, absorbed dose rates in air, annual effective dose, and soil type in Adana, Turkey Region
Yuregir Balcali fen edeb. (Yuregir)
238
U series (Bq kg1)
20.6 0.7
232
Th series (Bq kg1)
25.4 0.6
Annual effective dose equivalent (mSv)
Absorbed (terrestrial)
Terrestrial and cosmic
Measured (terrestrial and cosmic)
3.8
5.4
66.4
47.0
1.3
5.6
68.4
16.3
6.96 0.4
Mustafalar (Yuregir)
7.1 0.5
14.4 0.6
2.1
5.9
72.5
25.4
Camlica (Yuregir) Balcali kayikhane (Yuregir)
10.0 0.8 17.9 1.2
14.6 0.8 26.7 0.9
2.1 3.7
5.6 5.7
68.2 69.4
26.3 45.6
Average
12.6 0.7
12 0.63
17.9 0.6
2.6
5.6
69
32.1
10.5 0.56
2.0
3.8
46
24.8
Darilikustu boyalik (Aladag)
0.6 0.1
0.6 0.2
0.1
2.3
28.1
1.9
Average
6.3 0.4
5.6 0.4
1.1
3.0
37.0
13.3
22.1 0.54 21.8 0.5 23.8 0.7
27.9 0.5 22.4 0.5 25.7 0.5
4.8 3.8 4.5
9.3 7.9 9.1
114.1 96.9 112
58.6 47 55.2
22.6 0.6
25.3 0.5
4.4
8.8
107.6
53.6
13.7 0.6 9.7 0.4 17 0.6 3.6 0.2
8.6 0.5 5.4 0.3 21.1 0.5 3.2 0.2
1.8 1.3 3.3 0.7
5.6 6.2 6.2 6.2
68.2 75.7 75.7 75.7
22.5 15.4 40.5 9.1
11 0.5
9.6 0.4
1.8
6.0
73.8
21.9
23.7 1.3
41.4 1.2
7.2
13.4
164.3
87.9
Akoluk (Feke)
80.9 2.4
56.8 1.6
8.6
14.4
176.6
104.2
Average
52.3 1.9
49.1 1.4
46.3
13.5
165.6
96.4
33.1 0.7
37.1 0.6
6.6
8.8
107.6
80.5
Saimbeyli (Centre)
29.4 1.12
52.4 1.1
6.4
11.1
136.1
78.3
Average
31.2 0.9
44.8 0.9
6.5
9.9
121.8
79.4
18.5 0.6 3.4 0.2 12.5 0.8 14.8 0.7 18.1 1.1 11.2 0.61 12.9 0.7 13.1 0.7
15.6 0.5 2.9 0.2 19.8 0.8 15.2 0.66 24.7 1.0 10.06 0.52 23.4 0.8 15.9 0.6
3 0.53 3.1 2.9 3.7 2.9 3.2 2.8
5.3 4.08 5.3 4.6 6.6 6.1 5.6 5.4
Karaisali Kelceler (Karaisali) Salbas (Karaisali) Karaisali (Centre) Average Pozanti Tekir (Pozanti) Kamisli giris (Pozanti) Kamisli cikis (Pozanti) Kamisli (Pozanti) Average Feke Feke (Centre)
Saimbeyli Drayli (Saimbeyli)
Ceyhan Ceyhan (Centre) Narlik (Ceyhan) Ceyhan (Centre) Kosreli (Ceyhan) Tatlikuyu (Ceyhan) Yalak (Ceyhan) Sagkaya (Ceyhan) Average
64.8 50.04 64.8 56.2 80.7 74.6 68.1 65.6
Soil type
Terrestrial
Yeniyayla (Yuregir)
Aladag Kokezli (Aladag)
8.4 0.34
Absorbed dose rate in air (108 Gy h1)
36.8 6.5 37.6 35.4 45.9 35 38.9 33.7
Red brown Mediterranean Red brown Mediterranean Red brown Mediterranean Colluvial soil Red brown Mediterranean
soil soil soil
soil
Limeless brown forest soil Colluvial soil
Brown forest soil Brown forest soil Brown forest soil
Brown forest soil Colluvial soil Colluvial soil Colluvial soil
Limeless brown forest soil Limeless brown forest soil
Limeless brown forest soil Limeless brown forest soil
Alluvial soil Colluvial soil Alluvial soil Alluvial soil Alluvial soil Alluvial soil Alluvial soil (continued on next page)
M. Degerlier et al. / Journal of Environmental Radioactivity 99 (2008) 1018e1025
1022 Table 2 (continued ) Region
Karatas Karatas (Centre) Average Yumurtalik Zeytinbeli (Yumurtalik) IncirlieBotas (Yumurtalik) Yumurtalik (Centre) Zeytinbeyli (Yumurtalik) Botas (Yumurtalik) Golovasi (Yumurtalik) Hamzali (Yumurtalik) Average Kozan C¸ulluusagi (Kozan) Kozan (Centre) Average Imamoglu Hacihasanli (Imamoglu) Average Tufanbeyli Tufanbeyli (Centre) Catalcam (Tufanbeyli) Average
238 U series (Bq kg1)
232 Th series (Bq kg1)
Absorbed dose rate in air (108 Gy h1)
Annual effective dose equivalent (mSv)
Absorbed (terrestrial)
Terrestrial and cosmic
Measured (terrestrial and cosmic)
Terrestrial
10.4 0.5
8.5 0.4
1.6
4.95
60.7
19.9
10.4 0.5
8.5 0.4
1.6
4.95
60.7
19.9
15.3 0.6 10.5 0.3 6.6 0.3 12.6 0.6 10.3 0.5 12.3 0.75 8.4 0.3
16.7 0.5 7.9 0.3 3.8 0.2 14.7 0.4 20.2 0.5 13.8 0.7 8.5 0.3
3.05 1.5 1.3 2.5 2.3 2.6 2.6
4.8 4.0 4.9 4.8 3.7 4.5 4.4
59 49.6 59.8 59 45.3 55.7 54
37.4 18.11 15.5 30.3 27.7 31.9 31.3
10.8 0.5
12.2 0.4
2.2
4.5
54.6
27.4
31.0 0.9 29.2 1.5
56.9 0.8 37.0 1
8.6 5.7
14.4 10.5
176.6 128.8
105.3 70.2
30.1 1.2
46.9 0.9
7.2
12.5
152.7
87.8
18.3 0.5
18.3 0.4
3.5
6.9
84.9
42.6
18.3 0.5
18.3 0.4
3.5
6.9
84.9
42.6
28.1 0.9 32.8 0.7
38.4 0.9 44.4 0.6
5.6 6.3
8.8 8.8
107.6 107.3
68.6 77.2
30.5 0.8
41.3 0.8
5.9
8.8
107.4
72.9
The contribution of terrestrial gamma radiation to absorbed doses in air was calculated using the following formula (Beck, 1972): D nGy h1 ¼ 0:427CU þ 0:662CTh þ 0:043CK where D is the dose rate at 1 m above ground, CU, CTh, and CK are the activity concentrations of 238U, 232Th, and 40K in the soil samples. The annual effective dose equivalent (AEDE) was calculated as follows; AEDE ¼ ADRA DCF OF T: The most appropriate average value of the quotient of effective dose equivalent rate to absorbed dose rate in air (ADRA) was taken, as in the UNSCEAR (1982) report to be 0.7 Sv Gy1 for environmental exposures to gamma rays of moderate energy. A dose conversion factor (DCF) of 0.7 Sv Gy1 and an outdoor occupancy factor (OF) of 0.2 were used as recommended by UNSCEAR (1988). T is the time factor (8760 h).
3. Results and discussions The average radionuclide activity concentrations in the soil samples taken from 38 locations are reported in Table 1. Specific activities of 238U, 232Th, 40K and 137Cs are reported in Bq kg1 dry weight. The mean activity concentrations of 238 U, 232Th and 40K in surface soil samples from Adana region are 17.6, 21.1 and 297.5 Bq kg1, respectively. The worldwide
Soil type
Brown forest soil
Colluvial soil Colluvial soil Colluvial soil Colluvial soil Brown forest soil Colluvial soil Colluvial soil
Brown forest soil Brown forest soil
Colluvial soil
Limeless brown soil Limeless brown forest soil
average concentrations of these radionuclides are reported by UNSCEAR (2000) as 35, 30 and 400 Bq kg1, respectively. 137 Cs was also seen in the samples and analyzed in this work. The anthropogenic radionuclide 137Cs, deposited in the soil of Adana presumably as a result of atmospheric fallout of radioactivity following the Chernobyl accident on 26 April 1986, and other previous atmospheric tests of nuclear devices around the world. The 137Cs activities varied from 0.1 to 28.0 Bq kg1 in this study. The average 137Cs activity was measured to be 6.8 Bq kg1. The largest 137Cs activity was measured in the town of Kokezli, within the Aladag region of Adana. The calculated absorbed dose and the measured dose rates in air 1 m above ground are given in Table 2. The absorbed doses were calculated only from outdoor terrestrial gamma radiation. But the measured doses have contributions from both outdoor terrestrial gamma radiation and cosmic rays. In order to determine cosmic ray contribution in outdoor absorbed radiation doses, it is necessary that select a suitable place where terrestrial gamma radiation effect minimize. Lakes are most suitable places to measure cosmic rays. Seyhan Dam Lake in Adana city centre was selected for this aim. The measurement was presumably taken deepest part of the lake water. Minimum levels gamma rays come from lake water and coast were neglected. The cosmic ray contribution was found to be about 9.5 nGy h1
M. Degerlier et al. / Journal of Environmental Radioactivity 99 (2008) 1018e1025
Fig. 2.
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U radioactivity concentration in soil samples (Bq kg1).
238
by measuring exposure rates with a portable gamma scintillation detector (ESP-2, SPA-6) on Seyhan Dam Lake. The measured absorbed doses (outdoor terrestrial and cosmic) are thus higher than the calculated absorbed doses (outdoor terrestrial) as seen in Table 2. The difference between them ranges between
11.47 and 56.68 nGy h1, being derived from cosmic radiation and the other terrestrial radionuclides. The difference between outdoor measured absorbed doses and calculated absorbed doses is 11.5 and 15.0 nGy h1 in near Seyhan Dam Lake. This suggests in turn that our measurements are correct.
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M. Degerlier et al. / Journal of Environmental Radioactivity 99 (2008) 1018e1025
Fig. 3.
Th radioactivity concentration in soil samples (Bq kg1).
232
Fig. 2 shows 238U radioactivity concentrations and Fig. 3 shows the 232Th radioactivity concentrations in soil samples. The largest contribution from the natural radionuclides in Adana soil samples to the absorbed doses in air was generally due to the 232Th series expect in the Culluusagi (Kozan), Saimbeyli, Feke and Tufanbeyli regions. The largest contribution in both of these regions comes from 40K. The highest concentration of 238U was measured in Akoluk (Feke) region. Fig. 4 shows the different 238U
between 232Th radioactivity concentrations in various towns of the Adana region of Turkey. The largest 238U and 232Th concentrations were observed in Feke, Saimbeyli, Kozan, and Tufanbeyli. The smallest 238U and 232Th concentrations were observed in Aladag. These towns inside north part of region have high elevation. Fig. 5 shows 238U between 232Th differences among various soil types. The largest activity concentrations were measured in limeless brown forest soil and limeless brown soil. The
M. Degerlier et al. / Journal of Environmental Radioactivity 99 (2008) 1018e1025
238
232
Fig. 4. U and Th radioactivity concentration in various towns of the Adana region of Turkey.
smallest 238U and 232Th concentrations were observed in colluvial soil samples. It was observed that the activity concentrations vary depending on the geological and geographical conditions of different regions. The most important reason for the higher activity concentrations with respect to the others in some regions is a higher uranium and thorium content in rock and soil structure in these regions. The outdoor gamma measured dose rates (terrestrial and cosmic) in air 1 m above ground ranged between 23 and 144 nGy h1. The average calculated (terrestrial) outdoor gamma radiation dose and the mean measured (terrestrial and cosmic) outdoor gamma radiation dose were about 54 and 67 nGy h1, respectively. The average annual effective dose equivalents from the calculated outdoor terrestrial gamma radiation and the measured outdoor gamma radiation (terrestrial plus cosmic) at 1 m above ground in Adana were found to be about 44 and 82 mSv, respectively. The world average annual effective dose equivalent (AEDE) from outdoor terrestrial gamma radiation is 70 mSv (UNSCEAR, 2000) thus the average annual effective dose for Adana region is higher than that of the worldwide average value.
4. Conclusion This study intended to define the radioactivity concentrations and dose in soil samples for a region of the world where little published data exists on such topics, the Adana region located in the southern part of Turkey. A total of 38 measurements were made covering the 12 areas in Adana. The
Fig. 5. 238U and region of Turkey.
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232
Th activity concentrations in soils found in the Adana
radioactivity concentrations of 238U, 232Th and 40K in the soil of the Adana region compare suitably with literature values. Acknowledgements The authors thanks to Health Physics Department of Cekmece Nuclear Research and Training Centre e Turkish Atomic Energy Department for their cooperation to perform this work. The authors wish to thank Prof. Dr. Vedat PESTEMALCI, Prof. Dr. Gulten GUNEL and Dr. Aysun UGUR for their kind help. References Beck, H.L., 1972. The Physics of Environmental Radiation Fields. Natural Radiation Environment II, Cohewan. Canada. NF-720805 P2. In: Proceedings of the Second International Symposium on the Natural Radiation Environment. Karahan, G., Bayulken, A., 2000. Assessment of gamma dose rates around Istanbul (Turkey). Journal of Environmental Radioactivity 47, 213e221. Merdano˘glu, B., Altınsoy, N., 2006. Radioactivity concentrations and dose assessment for soil samples from Kestanbol granite area, Turkey. Radiation Protection Dosimetry 121 (No. 4), 399e405. Mollah, S., Rahman, N.M., Kodlus, M.A., Husain, S.R., 1987. Measurement of high natural background radiation levels by TLD at Cox and Bazar coastal areas in Bangladesh. Radiation Protection Dosimetry 18 (1), 39e41. UNSCEAR, 1982. United Nations Scientific Committee on the Effects of Atomic Radiation, Sources and Biological Effects of Ionizing Radiation. United Nations, New York. UNSCEAR, 1988. United Nations Scientific Committee on the Effects of Atomic Radiation, Sources and Biological Effects of Ionizing Radiation. United Nations, New York. UNSCEAR, 2000. United Nations Scientific Committee on the Effects of Atomic Radiation, Sources and Biological Effects of Ionizing Radiation. United Nations, New York.