natural radioactivity in farm soil and phosphate fertilizer and its environmental implications in...

Journal of Environmental Radioactivity 84 (2005) 51e64

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Natural radioactivity in farm soil andphosphate 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 con-centration of background radionuclides such as 226Ra, 232Th and 40K of these samples weredetermined by gamma-ray spectrometry. The results show that these radionuclides were

present in concentrations of 366G 10.5, 66.7G 7.3 and 4G 2.6 Bq/kg for phosphatefertilizers. For farm soil and Nile island’s soil the corresponding values were 13.7G 7,12.3G 4.6, 1233G 646 and 11.9G 6.7, 10.5G 6.1, 1636G 417 Bq/kg, respectively. The

radium equivalent activity (Raeq), the representative level index, Igr, and absorbed dose in airfor all samples were calculated. The data were discussed and compared with those given in theliterature.� 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 � 2005 Elsevier Ltd. All rights reserved.

doi:10.1016/j.jenvrad.2005.04.007

mailto:[email protected]

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52 N.K. Ahmed, A.M. El-Arabi / J. Environ. Radioactivity 84 (2005) 51e64

1. Introduction

The natural radionuclides of soils and fertilizers consist mainly of 238U and 232Thisotopes with their daughter products. The knowledge of the concentrations anddistributions of the radionuclides in these materials are of interest since it providesuseful information in the monitoring of environmental contamination by naturalradioactivity. Further, data on natural radiation are important for designing rulesand regulations for radiation protection purposes. Phosphate fertilizers are usedextensively in the farming industry, and suspension of dust and thus naturalradioactivity 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 crustwhich is about around 4 ppm (Hursh and Spoor, 1973).

238U and 232Th concentrations in phosphate fertilizers are of critical importancedue to the concerns that via several pathways these radionuclides will reach andpotentially affect man. These radionuclides are introduced in the environmentbecause phosphate fertilizers contain natural radionuclides in relatively largequantities and enter agricultural land during cultivation. Additionally phosphogyp-sum also may be used as agricultural gypsum to deal with salinity. The mostimportant pathway is through direct inhalation of dusts resulting in radiation dosesreceived 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 theconcentration of P2O5 in various fertilizers (Bouwer et al., 1978). Spalding andSackett (1972) showed a direct relationship between uranium and P2O5 content offertilizers. The 232Th series has only a minor contribution to the radioactivity inphosphate compared with the uranium series (Hussein, 1994; Lalit et al., 1982). Inaddition, soils and phosphate fertilizers contain the naturally occurring 40K.

The natural radioactivity content of phosphate deposits at Uro and Kurunwestern Sudan and in soil had been determined by gamma spectrometry witha 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 thehigh natural radioactivity of phosphate ores. Their results show that the naturalradionuclides contained in Uro and Kurun ground rock phosphate contribute verylittle to the average terrestrial radiation exposure to the population.

Another study of the radioactivity of supper phosphate, triple supper phosphateand phosphogypsum in Arusha e Tanzania showed that 238U and its progenies hadhigh activity concentration of about 4000 Bq/kg (Makweba and Holm, 1993). Theexternal radiation arising from their use as phosphate fertilizers in agricultural fieldwas found to be less than 2% of the normal background (50 nGy/h). A study of thepresence of natural radioactivity at a phosphate fertilizer factory in an area of southwest Spain showed that significantly high levels of 238U and 232Th isotopes and 226Rawere detected in water and sediment samples collected in this area. These isotope

53N.K. Ahmed, A.M. El-Arabi / J. Environ. Radioactivity 84 (2005) 51e64

activities appeared to be very sensitive indicators of waste disposal practices in suchenvironment (Martinez-Aguirre et al., 1994).

In this article activity concentration of background radionuclides226Ra 232Th and40K in phosphate fertilizers and surface soil samples in the Qena governorate, UpperEgypt, have been determined by gamma-ray spectrometry with HPGe detector toestimate the doses which originate from the presence of these radionuclides in thesurrounding 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, UpperEgypt, Fig. 1 (15 samples phosphate fertilizers and 64 surface soil samples). The soilsamples were collected by a core method, in which cores of 10 cm diameter and 25 cmin 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 ofthe sites were fertilized with phosphate fertilizers that contain trace concentrationsof uranium and have been used since more than 30 years in quantities of about350e450 kg phosphate fertilizer per hectare. These sites are regularly irrigated. Thecollected samples were weighed individually, about 2 kg, air dried for 10 days andkept in an oven at 105 �C. After homogenization samples were sieved through a100-mesh sieve. The samples were prepared in the form of discs in dimensions of55 mm in diameter and 13 mm height and packed in plastic. The average sampleweight was 40 g for phosphate fertilizer and 60 g for farm soil. These samples werestored for a minimum period of one month to allow daughter products to come intoradioactive equilibrium with their parents 226Ra and 232Th and then were counted for600e900 min depending on the concentration of the radionuclides. The details ofsampling 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 anHPGe setup and multichannel analyzer 8192 channel. The detector used is coaxialclosed end, closed facing window geometry with vertical dipstick (500e800 mm). TheHPGe 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 at1.33 MeV 60Co is 30%. The detector is shielded in a chamber of four layers startingwith plexiglass (10 mm thick), copper (30 mm thick), lead (100 mm thick) and finallycadmium (3 mm thick). This shield serves to reduce different backgroundradioactivity.

The emitted X-rays from lead, which contains radioactive impurities due toantimony impurities, can be absorbed by lining the inside of the shield with a gradedlayer of 0.05 inch cadmium and 0.25 inch Perspex (Aziz, 1981). To minimize the effect


Fig. 1. Sampling location.


of the scattered radiation from the shield, the detector is located in the center of thechamber. Then the sample was placed over the detector for at least 10 h. The spectrawere either evaluated with the computer software programMaestro (EG&GORTIC),or manually with the use of a spread sheet (Microsoft Excel) to calculate the naturalradioactivity. 226Ra activity of the samples was determined via its daughters (214Pband 214Bi) through the intensity of the 351.9 keV and 609.3 keV g-lines. Several 214Pband 214Bi were also detected and monitored. 232Th activity was obtained through the208Tl and 228Ac emissions at 583.1 keV and 911.1 keV, respectively, and 40K activitydetermined from the 1460.7 keV emissions.

3. Results and discussion

A summary of measurements for the activity concentration (Bq/kg) of the naturalradioactivity due to 226Ra, 232Th and 40K of phosphate fertilizers, farm soil and Nileisland’s soil is given in Table 1(a,b,c). It can be concluded that 226Ra ranged from349G 10.2 to 384G 9.9 with an average value of 366G 10.5 Bq/kg in phosphatefertilizer samples. The corresponding values are from 9.3G 3.5 to 16.9G 3.1 with anaverage value of 13.7G 7 and from 8.7G 3.1 to 17.9G 3.4 with an average value of11.9G 6.7 Bq/kg, for farm soils and Nile island’s soils, respectively. The distributionof 226Ra activity concentrations in all samples are given in Fig. 2.

232Th activity concentrations in phosphate fertilizer samples ranged from58.7G 8.1 to 81.2G 6.9 with an average value of 66.7G 7.3 Bq/kg. For farm soiland Nile island’s soil the corresponding values are from 10G 2.9 to 16.1G 1.8 withan average value of 12.3G 4.6 and from 3.5G 3.1 to 16G 2.8 with an average valueof 10.5G 6.1 Bq/kg, respectively. The distribution of 232Th activity concentrations inall samples are given in Fig. 3.

40K values ranged from 2.9G 1.1 to 6.1G 1.5 with an average value of 4G 2.6in phosphate fertilizer samples, whereas the corresponding values for farm soil andNile island’s soil samples are from 838G 296 to 1692G 298 with an average valueof 1233G 646 and from 1401G 300 to 1870G 295 with an average value of1636G 417 Bq/kg, respectively. Fig. 4 describes the distribution of 40K in thesesamples.

Phosphatic fertilizer samples show significantly higher concentration of 226Ra.Sedimentary rock phosphates, in general contain appreciable amounts of uraniumand its decay products due to uranium dissolved in the form of uranyl complexes inthe sea water getting concentrated during the course of deposition while the rockswere formed (Wollenberg and Smith, 1964). 232Th content of phosphate fertilizerswas nearly six orders of magnitude lower when compared with 226Ra content. Theseconcentration values of 232Th in phosphate fertilizers are higher than the values ofspecific activity concentrations of Egyptian supper phosphate fertilizers determinedby Hussein (1994) and lower than the values of phosphate fertilizer determined byEl-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


insoluble. Consequently, concentrations of both nuclides in the products aredepleted from the secular equilibrium conditions.

The specific activity concentration of 40K in phosphate fertilizer reported here isbelow the activity of Egyptian phosphate fertilizers determined byEl-Bahi et al. (2004).

Table 1

Activity concentrations of 226Ra, 232Th, and 40K (Bq/kg) of fertilizers, farm soil and Nile island’s soil

samples

S.N. Ra-226 Th-232 K-40 S.N. Ra-226 Th-232 K-40

Fertilizer (a)

1 369G 9.8 58.7G 8.1 3.6G 1.4 9 372G 10.5 63.4G 7.4 3.8G 1.2

2 378G 9.9 63.4G 7.3 3.6G 1.3 10 359G 9.8 81.2G 6.9 4.6G 1.4

3 364G 9.9 67.2G 7.5 4.1G 1.6 11 349G 10.2 78.3G 7.2 5.7G 1.3

4 353G 11 64.3G 7.9 2.9G 1.1 12 378G 10.7 71.4G 7.9 6.1G 1.5

5 359G 12 67.2G 6.9 3.1G 1.2 13 384G 9.9 67.5G 6.9 3.2G 1.5

6 362G 9.6 65.1G 6.8 2.9G 1.1 14 376G 10.1 68.5G 6.2 4.2G 1.2

7 359G 10 59.8G 7.1 3.0G 1.4 15 368G 9.7 62.8G 5.8 5.3G 1.3

8 357G 9.8 61.4G 8.2 3.5G 1.9 Mean 366G 10.5 66.7G 7.3 4.0G 2.6

Island soil (c) Farm soil (b)

1 13.2G 3.2 9.4G 3.1 1617G 298 1 9.3G 3.5 10.1G 2.7 1346G 290

2 17.5G 3.5 16G 2.8 1772G 291 2 16.1G 2.8 11.5G 2.5 1445G 297

3 17.9G 3.4 11.5G 3.1 1401G 300 3 14.3G 2.9 13.7G 2.3 1575G 278

4 8.8G 3.1 10.9G 3.2 1443G 301 4 14.9G 3.1 11.8G 2.8 1205G 288

5 10.5G 3.4 15.4G 2.6 1714G 296 5 12.1G 3.3 11.3G 2.6 1543G 274

6 12.9G 3.2 13.5G 2.2 1811G 288 6 14.0G 3.1 10.0G 2.9 1692G 298

7 9.8G 3.6 11.6G 2.4 1643G 295 7 7.7G 3.4 13.2G 2.1 1411G 291

8 9.7G 3.5 11.7G 3.2 1796G 296 8 11.9G 2.3 10.3G 2.9 1623G 288

9 11.3G 3.1 14.3G 2.7 1812G 279 9 15.0G 3.5 13.5G 2.1 912G 275

10 14.6G 2.9 8.9G 2.4 1560G 301 10 15.4G 3.7 10.6G 2.6 984G 299

11 12.5G 3.2 14.2G 2.9 1814G 295 11 11.6G 3.2 14.4G 1.9 1449G 289

12 11.2G 3.2 14.8G 2.7 1678G 287 12 15.0G 3.1 16.1G 1.8 1070G 278

14 9.8G 2.9 11.5G 2.8 1870G 295 13 16.9G 3.1 12.3G 2.1 960G 289

15 9.9G 2.8 8.5G 2.9 1716G 297 15 14.2G 3.4 11.6G 2.4 838G 296

16 9.3G 2.9 5.5G 2.4 1631G 289 16 16.2G 2.9 13.0G 2.0 1276G 293

17 10.1G 2.7 4.3G 2.8 1420G 278 17 13.5G 2.1 11.2G 2.1 1189G 281

18 15.9G 3.1 3.5G 3.1 1553G 269 18 14.2G 3.5 11.6G 2.8 1351G 245

19 14.4G 2.8 6.7G 3.8 1446G 301 19 11.3G 2.8 12.4G 2.1 1241G 296

20 12.3G 3.1 8.1G 2.6 1612G 278 20 12.1G 2.1 13.5G 3.1 978G 281

21 12.9G 3.6 7.3G 3.5 1623G 298 21 13.4G 2.4 11.6G 3.4 1092G 278

22 9.1G 3.4 7.8G 2.7 1456G 245 22 15.2G 2.9 10.9G 2.9 1252G 301

23 13.2G 3.9 8.2G 2.9 1532G 263 23 11.9G 3.5 13.4G 2.4 1412G 289

24 12.3G 2.9 7.9G 3.8 1678G 300 24 14.1G 2.8 13.7G 2.4 1126G 278

25 10.1G 2.9 8.1G 3.1 1561G 279 25 13.2G 3.1 12.4G 3.1 1203G 301

26 15.9G 3.8 9.7G 3.4 1714G 312 26 14.3G 3.4 11.1G 2.5 1168G 304

27 14.4G 3.1 11.4G 2.8 1678G 274 27 15.4G 2.9 13.3G 3.2 986G 291

28 11.2G 2.4 13.5G 3.6 1542G 287 28 16.3G 3.8 14.0G 3.0 1215G 285

29 9.6G 2.9 10.5G 3.1 1563G 302 29 11.8G 3.7 11.8G 2.8 1098G 312

30 8.7G 3.1 10.3G 2.8 1621G 297 30 13.4G 2.6 12.3G 2.9 1123G 301

31 9.2G 2.7 9.6G 2.9 1671G 278 31 15.2G 3.1 11.6G 3.1 1078G 278

32 12.3G 2.1 13.4G 3.1 1568G 315 32 14.3G 2.7 12.7G 2.7 1243G 311

Mean 11.9G 6.7 10.5G 6.1 1636G 417 Mean 13.7G 7 12.3G 4.6 1233G 646


Fig. 5 shows the correlation between 226Ra, 232Th and 40K in all samples underinvestigation.

The determined activities of farm soil samples for 226Ra and 232Th are less thanthose published in the literatures (Hursh and Spoor, 1973). This is because the areaunder study is a sandy soil known to contain lesser radioactivity (Abbady et al.,1995). Concentration of background radionuclides in soil samples of Brazilian state

340 350 360 370 380 3900

2

4

6

(a) Fertilizers

Sam

ple

No.

Sam

ple

No.

Sam

ple

No.

Activity concentration (Bq/kg)



Ra-226

0

2

4

6

8

(b) Farm soils

8 10 12 14 16 18

8 10 12 14 16 18

0

2

4

6

8

(c) Nile island's soil

Ra-226

Ra-226

Fig. 2. Distribution of 226Ra in (a) phosphate fertilizers, (b) farm soils and (c) Nile island’s soils.


of Rio Grande do Norte, determined by gamma spectrometry, showed that theaverage 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 anactivity of 90, 286 and 1414 Bq/kg for 226Ra, 232Th and 40K, respectively.Radiological measurements in Santana do Matos showed that the external gammaexposure ranged from 200 to 330 nGy h�1 in the down-town area. These results arehigher than the present results of 226Ra and 232Th.

From the obtained results for the Nile island’s soil its clear that 226Ra and232Th are in the same range when compared with surface farm soil, but 40K is

55 60 65 70 75 80 850

2

4

6Th-232

0

2

4

6

8

10

0

2

4

6

8

(a) Fertilizer

Sam

ple

No.

Sam

ple

No.

Sam

ple

No.




(b) Farm soil

8642 10 12 14 16 18

131211109 14 15 16 17 18


Th-232

Th-232

Fig. 3. Distribution of 232Th 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 muddysand and it contains high percentage of calcium carbonate and highpotassium level. This may lead to the higher 40K concentration in the investigatedsamples.

1 2 3 4 5 6 7 80

2

4

6

8 K-40

800 1000 1200 1400 1600

140 160 180 200

0

2

4

6

8 K-40

0

2

4

6

8

10 K-40

(a) Fertilizer

Sam

ple

No.

Sam

ple

No.

Sam

ple

No.




(b) Farm soil


Fig. 4. Distribution of 40K in (a) phosphate fertilizers, (b) farm soils and (c) Nile island’s soils.


3.1. Calculation of radiological effects

The most widely used radiation hazard index Raeq is called the radium equivalentactivity. The radium equivalent activity is a weighted sum of activities of the 226Ra,232Th 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

1086 12 14 16 18

108 12 14 16 18

500

1000

1500

2000

800

1200

1600

2000

350 360 370 380 390

20

40

60

80

100

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

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

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

Tho

rium

-232

(B

q/kg

)

20

40

60

80

100

Tho

rium

-232

(B

q/kg

)

20

0

40

60

80

100

Tho

rium

-232

(B

q/kg

)Th-232

5

10

15

20Potassium

-40 (Bq/kg)

Potassium-40 (B

q/kg)Potassium

-40 (Bq/kg)

K-40

Th-232 K-40

Th-232 K-40

Fig. 5. The correlation between 226Ra with 232Th and 40K in all samples under investigation.


(Krisiuk et al., 1971; Stranden, 1979). Radium equivalent activity can be calculatedfrom the following relation suggested by Beretka and Mathew (1985).

RaeqZðATh!1:43ÞCARaCðAK!0:077Þ ð1Þ

where ATh is the specific activity of 232Th in Bq/kg; ARa is the specific activity of226Ra in Bq/kg; AK is the specific activity of 40K in Bq/kg.

Another radiation hazard index called the representative level index, Igr, is definedfrom the following formula (NEA-OECD, 1979; Alam et al., 1999).

IgrZ1

150 Bq=kgARaC

1

100 Bq=kgAThC

1

1500 Bq=kgAK 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).

DZ0:429AUC0:666AThC0:042AK 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 theabsorbed dose rate in air at a height of 1.0 m above the ground from measuredradionuclides concentrations in environmental materials.

The results for the radium equivalent activity, representative level index, Igr, andthe calculated dose rate in air at 1 m above the ground of the present work and otherstudies are presented in Table 2

Table 2 gives the estimated external gamma dose rate due to natural gammaemitters as measured in phosphate fertilizer, farm soil and Nile island’s soil. Themean absorbed dose rate of phosphate fertilizer is 200.6 nGy h�1, which is nearlythree times higher than the estimate of average global terrestrial radiation of55 nGy h�1 (UNSCEAR, 1993). The absorbed dose rate for farm soil and Nileisland’s soil are 67.3 and 82.7 nGy h�1, respectively. These values were slightly higherthan the estimated average global terrestrial radiation of 55 nGy h�1 but are in theworld range (28e120 nGy h�1) (UNSCEAR, 1993).

The average dose rate estimated for phosphate fertilizer presented in this study ishigher than the values calculated for the supper phosphate fertilizer determinedby Hussein (1994) and lower than the values calculated by El-Bahi for phosphatefertilizer (El-Bahi et al., 2004). The estimated dose rate for farm soil and Nile island’ssoil are comparable with the results in China (Ziqiang et al., 1988), Vietnam (Hienet al., 2002), Yugoslavia (Bikit et al., 2005) and Brazil (Malanca et al., 1993).

The use of phosphate fertilizers for growing crops and the resulting potentialincrease of background radiation doses give sufficient grounds for the justification ofthis kind of study. The ALARA-principle implies that reasonable measures must betaken not only to reduce radiation doses if necessary, and also that costs have to beweighed against the averted radiation doses (ICRP, 1990).

Table 2

Radium equi r of the present work and other studies

Country Radium

equivalent

(Bq/kg)

Level

index

(Igr)

Dose

rate

(n Gy/h)

References

Egypt 336 2.3a 144.5a Hussein (1994)

Egypt 177.1e El-Bahi et al. (2004)

445.9

China (Zhejia 184.9a 1.4a 90.6a Ziqiang et al. (1988)

Vietnam 62 Hien et al. (2002)

Yugoslavia

(Vojvodina

150a 1.1a 71.5a Bikit et al. (2005)

India Selvasekarapandian et al. (2000)

Japan Chen et al. (1993)

Ireland Mc Auley and Moran (1983)

Stromboli Brai et al. (2002)

Brazil 147.8a 1.1a 72.5a Malanca et al. (1993)

Egypt (Qena) .6 461.7 3.1 200.6 Present work

646 126.2 1.04 67.3 Present work

417 152.9 1.3 82.7 Present worka Calculated

62

N.K.Ahmed,A.M

.El-A

rabi/J.Enviro

n.Radioactivity

84(2005)51e

64

valent activity, representative level index, Igr, and the dose rate in ai

Sample Activity (Bq/kg)

226Ra 232Th 40K

Supper phosphate fertilizer 301 24 3

Phosphate ferilitzer 125.2e 446.1e

239.3 882.5

ng) Soil 38 57.6 838

Surface soil 59 401

)

Agricultural soil 39.3 53 454

Soil 104 217

Soil 54 794

Soil 62 350

Soil 68 454

Soil 29 46.6 677.8

Phosphate fertilizer 366G 10.5 66.7G 7.3 4G 2

Farm soil 13.7G 7 12.3G 4.6 1233G

Nile island’s soil 11.9G 6.7 10.5G 6.1 1636G

by the authors using their data given in the reference.


4. Conclusion

1. Fertilizer samples and surface soil of the Qena governorate were measured fortheir radioactivity content. The results show that the mean concentration valuesof 226Ra, 232Th and 40K in phosphate fertilizers were 366G 10.5, 67G 7.3 and4G 2.6 Bq/kg, respectively, while that of farm surface soil and Nile Island’s soilsamples were 13.7G 7, 12.3G 4.6, 1233G 646 and 11.9G 6.7, 10.5G 6.1,1636G 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 soiland Nile Island’s soil e are 461.7, 126.2 and 152.9 Bq/kg for Raeq and 3.1, 1.04and 1.3 Bq/kg for Igr, respectively.

3. The results indicate that the dose rate at 1 m above the ground from terrestrialsources in all samples under investigation were 200.6, 67.3 and82.7 nGy h�1for phosphate fertilizers, farm soil and Nile island’s soil, re-spectively, which is equivalent to 250, 83 and 101 mSv/Y, respectively. Thesevalues are higher than the estimate of average global terrestrial radiation of55 nGy h�1.

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