Natural radioactivity in farm soil and phosphate fertilizer and its environmental implications in Qena governorate, Upper Egypt

Journal of Environmental Radioactivity 84 (2005) 51e64 www.elsevier.com/locate/jenvrad

Natural radioactivity in farm soil and phosphate fertilizer and its environmental implications in Qena governorate, Upper Egypt Nour Khalifa Ahmed*, Abdel Gabar Mohamed El-Arabi Physics Department, Faculty of Science Qena, South Valley University, Egypt Received 29 December 2004; received in revised form 17 February 2005; accepted 4 April 2005 Available online 13 June 2005

Abstract Samples of phosphate fertilizers and farm soils, taken to a depth of up to 30 cm in cultivated land, were collected over the Qena governorate, Upper Egypt. Activity concentration of background radionuclides such as 226Ra, 232Th and 40K of these samples were determined by gamma-ray spectrometry. The results show that these radionuclides were present in concentrations of 366 G 10.5, 66.7 G 7.3 and 4 G 2.6 Bq/kg for phosphate fertilizers. For farm soil and Nile island’s soil the corresponding values were 13.7 G 7, 12.3 G 4.6, 1233 G 646 and 11.9 G 6.7, 10.5 G 6.1, 1636 G 417 Bq/kg, respectively. The radium equivalent activity (Raeq), the representative level index, Igr, and absorbed dose in air for all samples were calculated. The data were discussed and compared with those given in the literature. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Radioactivity; Fertilizer; Soil; Hazard index

* Corresponding author. Tel.: C20 96 5211259. E-mail address: [email protected] (N.K. Ahmed). 0265-931X/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvrad.2005.04.007

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1. Introduction The natural radionuclides of soils and fertilizers consist mainly of 238U and 232Th isotopes with their daughter products. The knowledge of the concentrations and distributions of the radionuclides in these materials are of interest since it provides useful information in the monitoring of environmental contamination by natural radioactivity. Further, data on natural radiation are important for designing rules and regulations for radiation protection purposes. Phosphate fertilizers are used extensively in the farming industry, and suspension of dust and thus natural radioactivity present in fertilizers from both farm machinery and wind are common. The typical concentration of uranium in phosphate rocks is between 30 and 260 ppm (Altschuler, 1980) which by far exceeds its average abundance in the Earth’s crust which is about around 4 ppm (Hursh and Spoor, 1973). 238 U and 232Th concentrations in phosphate fertilizers are of critical importance due to the concerns that via several pathways these radionuclides will reach and potentially affect man. These radionuclides are introduced in the environment because phosphate fertilizers contain natural radionuclides in relatively large quantities and enter agricultural land during cultivation. Additionally phosphogypsum also may be used as agricultural gypsum to deal with salinity. The most important pathway is through direct inhalation of dusts resulting in radiation doses received mainly by farmers in the farming land (Scholten and Timmermans, 1996; Pfister et al., 1976). Uranium content of fertilizers can vary according to their phosphate content. Several studies have noted that the concentration of uranium follows the concentration of P2O5 in various fertilizers (Bouwer et al., 1978). Spalding and Sackett (1972) showed a direct relationship between uranium and P2O5 content of fertilizers. The 232Th series has only a minor contribution to the radioactivity in phosphate compared with the uranium series (Hussein, 1994; Lalit et al., 1982). In addition, soils and phosphate fertilizers contain the naturally occurring 40K. The natural radioactivity content of phosphate deposits at Uro and Kurun western Sudan and in soil had been determined by gamma spectrometry with a maximum activity concentration of 2600 Bq/kg natural 238U (Sam and Holm, 1995). The data indicate that 238U and its decay products contribute primarily to the high natural radioactivity of phosphate ores. Their results show that the natural radionuclides contained in Uro and Kurun ground rock phosphate contribute very little to the average terrestrial radiation exposure to the population. Another study of the radioactivity of supper phosphate, triple supper phosphate and phosphogypsum in Arusha e Tanzania showed that 238U and its progenies had high activity concentration of about 4000 Bq/kg (Makweba and Holm, 1993). The external radiation arising from their use as phosphate fertilizers in agricultural field was found to be less than 2% of the normal background (50 nGy/h). A study of the presence of natural radioactivity at a phosphate fertilizer factory in an area of south west Spain showed that significantly high levels of 238U and 232Th isotopes and 226Ra were detected in water and sediment samples collected in this area. These isotope

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activities appeared to be very sensitive indicators of waste disposal practices in such environment (Martinez-Aguirre et al., 1994). In this article activity concentration of background radionuclides226Ra 232Th and 40 K in phosphate fertilizers and surface soil samples in the Qena governorate, Upper Egypt, have been determined by gamma-ray spectrometry with HPGe detector to estimate the doses which originate from the presence of these radionuclides in the surrounding farming land.

2. Experimental methods 2.1. Sampling and sample preparation A total of 79 samples were collected from the area at the Qena governorate, Upper Egypt, Fig. 1 (15 samples phosphate fertilizers and 64 surface soil samples). The soil samples were collected by a core method, in which cores of 10 cm diameter and 25 cm in depth were used to take soil samples (American Society for Testing and Materials, 1983, 1986). The sampling sites were randomly selected in the cultivated land. Most of the sites were fertilized with phosphate fertilizers that contain trace concentrations of uranium and have been used since more than 30 years in quantities of about 350e450 kg phosphate fertilizer per hectare. These sites are regularly irrigated. The collected samples were weighed individually, about 2 kg, air dried for 10 days and kept in an oven at 105
C. After homogenization samples were sieved through a 100-mesh sieve. The samples were prepared in the form of discs in dimensions of 55 mm in diameter and 13 mm height and packed in plastic. The average sample weight was 40 g for phosphate fertilizer and 60 g for farm soil. These samples were stored for a minimum period of one month to allow daughter products to come into radioactive equilibrium with their parents 226Ra and 232Th and then were counted for 600e900 min depending on the concentration of the radionuclides. The details of sampling and sample preparation have been presented in Ahmed et al. (1995). 2.2. Experimental setup Each sample was measured with a gamma-ray spectrometer consisting of an HPGe setup and multichannel analyzer 8192 channel. The detector used is coaxial closed end, closed facing window geometry with vertical dipstick (500e800 mm). The HPGe detector is p-type with the following specifications: Resolution (FWHM) at 122 keV, 57Co is 1100 eV and at 1.33 MeV 60Co is 2.00 keV e relative efficiency at 1.33 MeV 60Co is 30%. The detector is shielded in a chamber of four layers starting with plexiglass (10 mm thick), copper (30 mm thick), lead (100 mm thick) and finally cadmium (3 mm thick). This shield serves to reduce different background radioactivity. The emitted X-rays from lead, which contains radioactive impurities due to antimony impurities, can be absorbed by lining the inside of the shield with a graded layer of 0.05 inch cadmium and 0.25 inch Perspex (Aziz, 1981). To minimize the effect

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Fig. 1. Sampling location.

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of the scattered radiation from the shield, the detector is located in the center of the chamber. Then the sample was placed over the detector for at least 10 h. The spectra were either evaluated with the computer software program Maestro (EG&G ORTIC), or manually with the use of a spread sheet (Microsoft Excel) to calculate the natural radioactivity. 226Ra activity of the samples was determined via its daughters (214Pb and 214Bi) through the intensity of the 351.9 keV and 609.3 keV g-lines. Several 214Pb and 214Bi were also detected and monitored. 232Th activity was obtained through the 208 Tl and 228Ac emissions at 583.1 keV and 911.1 keV, respectively, and 40K activity determined from the 1460.7 keV emissions.

3. Results and discussion A summary of measurements for the activity concentration (Bq/kg) of the natural radioactivity due to 226Ra, 232Th and 40K of phosphate fertilizers, farm soil and Nile island’s soil is given in Table 1(a,b,c). It can be concluded that 226Ra ranged from 349 G 10.2 to 384 G 9.9 with an average value of 366 G 10.5 Bq/kg in phosphate fertilizer samples. The corresponding values are from 9.3 G 3.5 to 16.9 G 3.1 with an average value of 13.7 G 7 and from 8.7 G 3.1 to 17.9 G 3.4 with an average value of 11.9 G 6.7 Bq/kg, for farm soils and Nile island’s soils, respectively. The distribution of 226Ra activity concentrations in all samples are given in Fig. 2. 232 Th activity concentrations in phosphate fertilizer samples ranged from 58.7 G 8.1 to 81.2 G 6.9 with an average value of 66.7 G 7.3 Bq/kg. For farm soil and Nile island’s soil the corresponding values are from 10 G 2.9 to 16.1 G 1.8 with an average value of 12.3 G 4.6 and from 3.5 G 3.1 to 16 G 2.8 with an average value of 10.5 G 6.1 Bq/kg, respectively. The distribution of 232Th activity concentrations in all samples are given in Fig. 3. 40 K values ranged from 2.9 G 1.1 to 6.1 G 1.5 with an average value of 4 G 2.6 in phosphate fertilizer samples, whereas the corresponding values for farm soil and Nile island’s soil samples are from 838 G 296 to 1692 G 298 with an average value of 1233 G 646 and from 1401 G 300 to 1870 G 295 with an average value of 1636 G 417 Bq/kg, respectively. Fig. 4 describes the distribution of 40K in these samples. Phosphatic fertilizer samples show significantly higher concentration of 226Ra. Sedimentary rock phosphates, in general contain appreciable amounts of uranium and its decay products due to uranium dissolved in the form of uranyl complexes in the sea water getting concentrated during the course of deposition while the rocks were formed (Wollenberg and Smith, 1964). 232Th content of phosphate fertilizers was nearly six orders of magnitude lower when compared with 226Ra content. These concentration values of 232Th in phosphate fertilizers are higher than the values of specific activity concentrations of Egyptian supper phosphate fertilizers determined by Hussein (1994) and lower than the values of phosphate fertilizer determined by El-Bahi et al. (2004). When phosphate rock reacts with sulfuric acid during digestion, radium is precipitated as insoluble radium sulfate. Thorium sulfate is also somewhat

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Table 1 Activity concentrations of samples

226

Ra,

232

Th, and

40

K (Bq/kg) of fertilizers, farm soil and Nile island’s soil

S.N.

Ra-226

Th-232

Fertilizer 1 2 3 4 5 6 7 8

(a) 369 G 9.8 378 G 9.9 364 G 9.9 353 G 11 359 G 12 362 G 9.6 359 G 10 357 G 9.8

K-40

58.7 G 8.1 63.4 G 7.3 67.2 G 7.5 64.3 G 7.9 67.2 G 6.9 65.1 G 6.8 59.8 G 7.1 61.4 G 8.2

3.6 G 1.4 3.6 G 1.3 4.1 G 1.6 2.9 G 1.1 3.1 G 1.2 2.9 G 1.1 3.0 G 1.4 3.5 G 1.9

Island soil (c) 1 13.2 G 3.2 2 17.5 G 3.5 3 17.9 G 3.4 4 8.8 G 3.1 5 10.5 G 3.4 6 12.9 G 3.2 7 9.8 G 3.6 8 9.7 G 3.5 9 11.3 G 3.1 10 14.6 G 2.9 11 12.5 G 3.2 12 11.2 G 3.2 14 9.8 G 2.9 15 9.9 G 2.8 16 9.3 G 2.9 17 10.1 G 2.7 18 15.9 G 3.1 19 14.4 G 2.8 20 12.3 G 3.1 21 12.9 G 3.6 22 9.1 G 3.4 23 13.2 G 3.9 24 12.3 G 2.9 25 10.1 G 2.9 26 15.9 G 3.8 27 14.4 G 3.1 28 11.2 G 2.4 29 9.6 G 2.9 30 8.7 G 3.1 31 9.2 G 2.7 32 12.3 G 2.1 Mean 11.9 G 6.7

9.4 G 3.1 16 G 2.8 11.5 G 3.1 10.9 G 3.2 15.4 G 2.6 13.5 G 2.2 11.6 G 2.4 11.7 G 3.2 14.3 G 2.7 8.9 G 2.4 14.2 G 2.9 14.8 G 2.7 11.5 G 2.8 8.5 G 2.9 5.5 G 2.4 4.3 G 2.8 3.5 G 3.1 6.7 G 3.8 8.1 G 2.6 7.3 G 3.5 7.8 G 2.7 8.2 G 2.9 7.9 G 3.8 8.1 G 3.1 9.7 G 3.4 11.4 G 2.8 13.5 G 3.6 10.5 G 3.1 10.3 G 2.8 9.6 G 2.9 13.4 G 3.1 10.5 G 6.1

1617 G 298 1772 G 291 1401 G 300 1443 G 301 1714 G 296 1811 G 288 1643 G 295 1796 G 296 1812 G 279 1560 G 301 1814 G 295 1678 G 287 1870 G 295 1716 G 297 1631 G 289 1420 G 278 1553 G 269 1446 G 301 1612 G 278 1623 G 298 1456 G 245 1532 G 263 1678 G 300 1561 G 279 1714 G 312 1678 G 274 1542 G 287 1563 G 302 1621 G 297 1671 G 278 1568 G 315 1636 G 417

S.N.

Ra-226

Th-232

9 10 11 12 13 14 15 Mean

372 G 10.5 359 G 9.8 349 G 10.2 378 G 10.7 384 G 9.9 376 G 10.1 368 G 9.7 366 G 10.5

63.4 G 7.4 81.2 G 6.9 78.3 G 7.2 71.4 G 7.9 67.5 G 6.9 68.5 G 6.2 62.8 G 5.8 66.7 G 7.3

3.8 G 1.2 4.6 G 1.4 5.7 G 1.3 6.1 G 1.5 3.2 G 1.5 4.2 G 1.2 5.3 G 1.3 4.0 G 2.6

10.1 G 2.7 11.5 G 2.5 13.7 G 2.3 11.8 G 2.8 11.3 G 2.6 10.0 G 2.9 13.2 G 2.1 10.3 G 2.9 13.5 G 2.1 10.6 G 2.6 14.4 G 1.9 16.1 G 1.8 12.3 G 2.1 11.6 G 2.4 13.0 G 2.0 11.2 G 2.1 11.6 G 2.8 12.4 G 2.1 13.5 G 3.1 11.6 G 3.4 10.9 G 2.9 13.4 G 2.4 13.7 G 2.4 12.4 G 3.1 11.1 G 2.5 13.3 G 3.2 14.0 G 3.0 11.8 G 2.8 12.3 G 2.9 11.6 G 3.1 12.7 G 2.7 12.3 G 4.6

1346 G 290 1445 G 297 1575 G 278 1205 G 288 1543 G 274 1692 G 298 1411 G 291 1623 G 288 912 G 275 984 G 299 1449 G 289 1070 G 278 960 G 289 838 G 296 1276 G 293 1189 G 281 1351 G 245 1241 G 296 978 G 281 1092 G 278 1252 G 301 1412 G 289 1126 G 278 1203 G 301 1168 G 304 986 G 291 1215 G 285 1098 G 312 1123 G 301 1078 G 278 1243 G 311 1233 G 646

Farm soil (b) 1 9.3 G 3.5 2 16.1 G 2.8 3 14.3 G 2.9 4 14.9 G 3.1 5 12.1 G 3.3 6 14.0 G 3.1 7 7.7 G 3.4 8 11.9 G 2.3 9 15.0 G 3.5 10 15.4 G 3.7 11 11.6 G 3.2 12 15.0 G 3.1 13 16.9 G 3.1 15 14.2 G 3.4 16 16.2 G 2.9 17 13.5 G 2.1 18 14.2 G 3.5 19 11.3 G 2.8 20 12.1 G 2.1 21 13.4 G 2.4 22 15.2 G 2.9 23 11.9 G 3.5 24 14.1 G 2.8 25 13.2 G 3.1 26 14.3 G 3.4 27 15.4 G 2.9 28 16.3 G 3.8 29 11.8 G 3.7 30 13.4 G 2.6 31 15.2 G 3.1 32 14.3 G 2.7 Mean 13.7 G 7

K-40

insoluble. Consequently, concentrations of both nuclides in the products are depleted from the secular equilibrium conditions. The specific activity concentration of 40K in phosphate fertilizer reported here is below the activity of Egyptian phosphate fertilizers determined by El-Bahi et al. (2004).

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Ra-226

Sample No.

6

4

2

0 340

350

360

370

380

390

Activity concentration (Bq/kg)

(a) Fertilizers Ra-226

8

Sample No.

6 4 2 0 8

10

12

14

16

18

Activity concentration (Bq/kg)

(b) Farm soils Ra-226

Sample No.

8 6 4 2 0 8

10

12

14

16

18

Activity concentration (Bq/kg)

(c) Nile island's soil Fig. 2. Distribution of

226

Ra in (a) phosphate fertilizers, (b) farm soils and (c) Nile island’s soils.

Fig. 5 shows the correlation between 226Ra, 232Th and 40K in all samples under investigation. The determined activities of farm soil samples for 226Ra and 232Th are less than those published in the literatures (Hursh and Spoor, 1973). This is because the area under study is a sandy soil known to contain lesser radioactivity (Abbady et al., 1995). Concentration of background radionuclides in soil samples of Brazilian state

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Sample No.

Th-232 4

2

0 55

60

65

70

75

80

85

Activity concentration (Bq/kg)

(a) Fertilizer 10

Th-232

Sample No.

8 6 4 2 0 9

10

11

12

13

14

15

16

17

18

Activity concentration (Bq/kg)

(b) Farm soil Th-232

Sample No.

8 6 4 2 0 2

4

6

8

10

12

14

16

18

Activity concentration (Bq/kg)

(c) Nile island's soil Fig. 3. Distribution of

232

Th in (a) phosphate fertilizers, (b) farm soils and (c) Nile island’s soils.

of Rio Grande do Norte, determined by gamma spectrometry, showed that the average concentrations of 226Ra, 232Th and 40K were 29, 47 and 678 Bq/kg, respectively (Malanca et al., 1993). The bedrock of Santana do Matos showed an activity of 90, 286 and 1414 Bq/kg for 226Ra, 232Th and 40K, respectively. Radiological measurements in Santana do Matos showed that the external gamma exposure ranged from 200 to 330 nGy h1 in the down-town area. These results are higher than the present results of 226Ra and 232Th. From the obtained results for the Nile island’s soil its clear that 226Ra and 232 Th are in the same range when compared with surface farm soil, but 40K is

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K-40

Sample No.

6 4 2 0 1

2

3

4

5

6

7

8

Activity concentration (Bq/kg)

(a) Fertilizer 8 K-40

Sample No.

6 4 2

0 800

1000

1200

1400

1600

Activity concentration (Bq/kg)

(b) Farm soil K-40

10

Sample No.

8 6 4 2 0 140

160

180

200

Activity concentration (Bq/kg)

(c) Nile island's soil Fig. 4. Distribution of

40

K in (a) phosphate fertilizers, (b) farm soils and (c) Nile island’s soils.

higher in the Nile island’s soil. The Nile island’s soil is yellowish or muddy sand and it contains high percentage of calcium carbonate and high potassium level. This may lead to the higher 40K concentration in the investigated samples.

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K-40

Th-232

80

20 15

60 10 40 5 20 350

360

370

380

Potassium-40 (Bq/kg)

Thorium-232 (Bq/kg)

100

390

Radium-226 (Bq/kg) Radium-226 activity concentration (Bq/kg) with thorium-232 and potassium-40 content in Fertilizer samples.

Th-232

K-40

2000

80 1500 60 1000

40 20

Potassium-40 (Bq/kg)

Thorium-232 (Bq/kg)

100

500 6

8

10

12

14

16

18

Radium-226 (Bq/kg) Radium-226 activity concentration (Bq/kg) with thorium-232 and potassium-40 content in Farm soil samples.

Th-232

K-40

2000

80 60

1600

40

1200

20

800

Potassium-40 (Bq/kg)

Thorium-232 (Bq/kg)

100

0 8

10

12

14

16

18

Radium-226 (Bq/kg) Radium-226 activity concentration (Bq/kg) with thorium-232 and potassium-40 content in Nile Island’s soil samples.

Fig. 5. The correlation between

226

Ra with

232

Th and

40

K in all samples under investigation.

3.1. Calculation of radiological effects The most widely used radiation hazard index Raeq is called the radium equivalent activity. The radium equivalent activity is a weighted sum of activities of the 226Ra, 232 Th and 40K radionuclides based on the assumption that 370 Bq/kg of 226Ra, 259 Bq/kg of 232Th and 4810 Bq/kg of 40K produce the same gamma ray dose rate

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(Krisiuk et al., 1971; Stranden, 1979). Radium equivalent activity can be calculated from the following relation suggested by Beretka and Mathew (1985). Raeq ZðATh !1:43ÞCARa CðAK !0:077Þ

ð1Þ

where ATh is the specific activity of 232Th in Bq/kg; ARa is the specific activity of Ra in Bq/kg; AK is the specific activity of 40K in Bq/kg. Another radiation hazard index called the representative level index, Igr, is defined from the following formula (NEA-OECD, 1979; Alam et al., 1999).

226

Igr Z

1 1 1 ARa C ATh C AK 150 Bq=kg 100 Bq=kg 1500 Bq=kg

ð2Þ

where ARa, ATh and AK having the same meaning as in Eq. (1). The total air absorbed dose rate (nGy/h) due to the mean activity concentrations of 238U 232Th and 40K (Bq/kg) can be calculated using the formula of Beck et al. (1972) and UNSCEAR (1988). DZ0:429AU C0:666ATh C0:042AK

ð3Þ

where AU, ATh and AK are the mean activity concentrations of 238U, 232Th and 40K, respectively, in (Bq/kg). Beck et al. (1972), derived this equation for calculating the absorbed dose rate in air at a height of 1.0 m above the ground from measured radionuclides concentrations in environmental materials. The results for the radium equivalent activity, representative level index, Igr, and the calculated dose rate in air at 1 m above the ground of the present work and other studies are presented in Table 2 Table 2 gives the estimated external gamma dose rate due to natural gamma emitters as measured in phosphate fertilizer, farm soil and Nile island’s soil. The mean absorbed dose rate of phosphate fertilizer is 200.6 nGy h1, which is nearly three times higher than the estimate of average global terrestrial radiation of 55 nGy h1 (UNSCEAR, 1993). The absorbed dose rate for farm soil and Nile island’s soil are 67.3 and 82.7 nGy h1, respectively. These values were slightly higher than the estimated average global terrestrial radiation of 55 nGy h1 but are in the world range (28e120 nGy h1) (UNSCEAR, 1993). The average dose rate estimated for phosphate fertilizer presented in this study is higher than the values calculated for the supper phosphate fertilizer determined by Hussein (1994) and lower than the values calculated by El-Bahi for phosphate fertilizer (El-Bahi et al., 2004). The estimated dose rate for farm soil and Nile island’s soil are comparable with the results in China (Ziqiang et al., 1988), Vietnam (Hien et al., 2002), Yugoslavia (Bikit et al., 2005) and Brazil (Malanca et al., 1993). The use of phosphate fertilizers for growing crops and the resulting potential increase of background radiation doses give sufficient grounds for the justification of this kind of study. The ALARA-principle implies that reasonable measures must be taken not only to reduce radiation doses if necessary, and also that costs have to be weighed against the averted radiation doses (ICRP, 1990).

62

Country

Sample

Activity (Bq/kg) 226

232

40

39.3

24 125.2e 239.3 57.6 59 53

3 446.1e 882.5 838 401 454

29 366 G 10.5 13.7 G 7 11.9 G 6.7

104 54 62 68 46.6 66.7 G 7.3 12.3 G 4.6 10.5 G 6.1

217 794 350 454 677.8 4 G 2.6 1233 G 646 1636 G 417

Ra

Egypt Egypt

Supper phosphate fertilizer Phosphate ferilitzer

301

China (Zhejiang) Vietnam Yugoslavia (Vojvodina) India Japan Ireland Stromboli Brazil Egypt (Qena)

Soil Surface soil Agricultural soil

38

a

Soil Soil Soil Soil Soil Phosphate fertilizer Farm soil Nile island’s soil

Th

Calculated by the authors using their data given in the reference.

K

Radium equivalent (Bq/kg)

Level index (Igr)

Dose rate (n Gy/h)

References

336

2.3a

Hussein (1994) El-Bahi et al. (2004)

184.9a

1.4a

144.5a 177.1e 445.9 90.6a 62 71.5a

150a

147.8a 461.7 126.2 152.9

1.1a

1.1a 3.1 1.04 1.3

72.5a 200.6 67.3 82.7

Ziqiang et al. (1988) Hien et al. (2002) Bikit et al. (2005) Selvasekarapandian et al. (2000) Chen et al. (1993) Mc Auley and Moran (1983) Brai et al. (2002) Malanca et al. (1993) Present work Present work Present work

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Table 2 Radium equivalent activity, representative level index, Igr, and the dose rate in air of the present work and other studies

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4. Conclusion 1. Fertilizer samples and surface soil of the Qena governorate were measured for their radioactivity content. The results show that the mean concentration values of 226Ra, 232Th and 40K in phosphate fertilizers were 366 G 10.5, 67 G 7.3 and 4 G 2.6 Bq/kg, respectively, while that of farm surface soil and Nile Island’s soil samples were 13.7 G 7, 12.3 G 4.6, 1233 G 646 and 11.9 G 6.7, 10.5 G 6.1, 1636 G 417 Bq/kg, respectively. 2. The means of radium equivalent activity (Raeq) and representative level index, Igr, for all samples under investigation e phosphate fertilizer, farm surface soil and Nile Island’s soil e are 461.7, 126.2 and 152.9 Bq/kg for Raeq and 3.1, 1.04 and 1.3 Bq/kg for Igr, respectively. 3. The results indicate that the dose rate at 1 m above the ground from terrestrial sources in all samples under investigation were 200.6, 67.3 and 82.7 nGy h1for phosphate fertilizers, farm soil and Nile island’s soil, respectively, which is equivalent to 250, 83 and 101 mSv/Y, respectively. These values are higher than the estimate of average global terrestrial radiation of 55 nGy h1. References Abbady, A., Ahmed, N.K., Saied, M.H., El-Kamel, A.H., Ramadan, S., 1995. Variation of Rn-222 concentration in drinking water in Qena. Bulletin of the Faculty of Science 24 (1-A), 101e106. Ahmed, N.K., Abbady, A., El-Kamel, A.H., Al-Kareem, A.G., 1995. Gamma ray analysis for U and Th in sedimentary rock samples from Gebel Anz, Upper Egypt. Bulletin of the Faculty of Science 24 (1-A), 43e54. Alam, M.N., Chowdhury, M.I., Kamal, M., Ghose, S., Ismal, M.N., 1999. The 226Ra 232Th and 40K activities in beach sand minerals and beach soils of Cox’s Bazar, Bangladesh. Journal of Environmental radioactivity 46 (2), 243e250. Altschuler, Z.S., 1980. The geochemistry of trace elements in marine phosphorites. 1. Characteristic abundances and enrichment. Society of Economic Paleontologists and Mineralogists Special Publication, vol. 29, pp. 19e30. American Society for Testing and Materials, 1986. Recommended practice for investigation and sampling soil and rock for engineering purposes. Annual Book of ASTM Standards, 420. ASTM, Philadelphia, PA. (04.08) Report No. D, pp. 109el13. American Society for Testing and Materials, 1983. Standard Method for Sampling Surface Soil for Radionuclides. ASTM, Philadelphia, PA. Report No. C, pp. 983e998. Aziz, A., 1981. Methods of low-level counting and spectrometry symposium. Berlin, pp. 221. Beck, H.L., Decompo, J., Gologak, J., 1972. In situ Ge(Li) and NaI(Tl) Gamma Ray Spectrometry. Health and safety laboratory AEC, New York, Report HASL258. Beretka, J., Mathew, P.J., 1985. Natural radioactivity of Australian building materials, industrial wastes and by-products. Health Physics 48, 87e95. Bikit, I., Slivka, J., Cˇonkic´, L.J., Krmar, M., Veskovic, M., Zˇikic´-Todorovic´, N., Varga, E., Curcic´, S., Mrdja, D., 2005. Radioactivity of the soil in Vojvodina (northern Province of Serbia and Montenegro). Journal of Environmental Radioactivity 78, 11e19. Bouwer, F.J., MeKlveen, J.W., McDowell, W.J., 1978. Uranium assay of phosphate fertilizers and other phosphatic materials. Health Physics 34, 345e352. Brai, M., Basile, S., Bellia, S., Hauser, S., Puccio, P., Rizzo, S., Bartolotta, A., Licciardello, A., 2002. Environmental radioactivity at Stromboil (Aeolian Islands). Applied Radiation and Isotopes 57, 99e107.

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