Natural Radionuclide (Gamma and Alpha Emitters) in Grain Samples Collected from Kerbala Governorate, Iraq

The aim of this research is to detect nature radioactivity for gamma emitters (specic activity 238 U, 232 Th, and 40 K) using NaI(Tl) detectors and alpha emitters (concentrations of 222 Rn, 226 Ra, and 238 U) using CR-39 detectors in selected samples of grain that are collected from Kerbala governorate. Also, annual effective dose and some radiological parameters due to gamma and alpha emitters to assess the health risk were calculated. Results have been shown that the average value of specic activities for 238 U, 232 Th and 40 K were 6.61±0.91 Bq/kg, 3.07±0.22 Bq/kg and 227.59±32.34 Bq/kg respectively, while the average value of alpha emitters concentrations for 222 Rn, 226 Ra, and 238 U were 3.99±1.13 Bq/m 3 , 4.69±1.28 mBq/kg and 0.072±0.019 Bq/kg respectively. The results of average total of annual effective dose associated with the exposure due to gamma and alpha emitted from ingestion grain samples in the present study were 0.139±0.013 mSv/y and 0.172±0.047 µSv/y, respectively. The results of natural Radionuclide and radiological parameter hazard based on gamma and alpha emitters from grain samples were discovered to be within the world acceptable levels. Finally, natural radioactivity from the grain samples that collected from Kerbala governorate were safety for the human consumption. The data obtained in this study improve the suitability of the NaI(Tl) and CR-39 techniques for such complex samples. The results of radiological hazard due to natural radionuclides of gamma and alpha emitters in grain samples that collected from Kerbala governorate were less than acceptable levels that recommended by different world organization such as UNSCEAR, ICRP, OECD, WHO, and other. Also, the results of natural radioactivity in all types of grain samples were varied which depend on natural soil and natural of samples. It is found that, there is a high positive correlation coecient (R = 0.86) in all samples between 222 Rn concentrations that measured using CR-39 detector and 238 U that measured using NaI(Tl) detector. While another radionuclide, the correction coecient was low and negative quantity. Finally, it can be concluded that the grain samples in this work does not pose any severe health risks to human’s consumption.


Introduction
Gamma radiation is an electromagnetic radiation emitted from the nucleus of radioactive atom. It is consisting of photons that have been emitted from the nucleus. Photon radiation can also be hazardous if its emitting from nuclear materials is taken into the body [1]. While, alpha particles consist of two neutrons and two protons and it's emitted by a heavy radioactive element, such as Radium, Thorium, Uranium and Plutonium [2]. when alpha emitting nuclear material are taken into the body (for example, by breathing them in or by ingesting them), the energy of the alpha particles is completely absorbed into bodily tissues. For this reason, alpha radiation is only an internal hazard [3]. Gamma and alpha emitters are very important nature elements that contribute to a max part of radioactivity dose received by people, with a wide distribution have been discovered classi cation radiation are encountered in earth layers or bodies of water ocean, sea and lakes. It accumulated easily into the chain of food [4]. Natural radioactive decay series such as 238 U and 232 Th as well as singly occurring radionuclides such as 40 K exist in the earth and atmosphere in varied levels. The radioactivity present on air or in the agricultural land and in soil may transfer to the crops grown on it. It happens, however that an amount of some radioactive elements nd their way into human bodies. Ingestion with food or drinks, or with other materials which come into contact with the mouth [5]. This is usually a result of poor housekeeping, a lack of personal hygiene or allowing consumption of food in radioisotope areas. Ingested materials pass through the gastrointestinal tract with absorption and excretion being determined by solubility. Water soluble material will gain entry to the blood stream and be readily passed to body organs. Insoluble material will pass through the gut and be excreted [5]. Roots get their nutrients primarily from the solution of soil. Natural, radionuclides is found everywhere in the soil. It is transfer to plants through the consumption of radioactivity either through system of root or by external surfaces of plant [2]. Root uptake consumes the solutes in the solution of soil on a continuous basis However, it is also regenerated from the solid state of the soil. Because of the intricate, temporal, and geographical structure of the soil plant relationship, estimating radionuclide uptake from soil is di cult. People being are encouraged to consume very much grain in every day because this grain are rich in minerals, bers and protein. They are containing essential and toxic metals and radionuclides proven bene ts to the general health of People [6]. The grain contains protein, pectin, lipid, salt, and mineral in addition to being abundant in nutrient, bers of dietary, and carbohydrates [6]. A number of studies have determined the radiation content in grain [7][8][9][10]. As a result, the goal of this study is to research and analyze the level of radioactivity (gamma and alpha emitters) in grains samples in Kerbala governorate, Iraq.

Collections of Sample
Twenty of types of grains samples (wheat, barley, corn, millet, mungbean, and rice), these samples were collected from different sites of Kerbala Governorate. The grains samples were labeled with special codes. The information complete about samples was written, as shown in Table 1.

Preparations of Sample
After collecting the grains samples were transferred in nuclear laboratory in Kerbala university for preparation to measure gamma and alpha emitters. The preparation method of samples was done by several processing such as cleaned the samples, dried in an oven at 100 o C for 4 hours, crushed the samples, sieved by sieve for 2 mm mesh, weighted by digital balance, and put samples in marinelli beakers (I L) and plastic container (radius 5 cm, higher 7 cm) for measuring gamma and alpha emitters, respectably. Next, all samples were stored at least for1 month for getting secular equilibrium between radium-226 and radon-222 [11,12].

Experimental Methods
In the present study, it was measured gamma emitters (Uranium-238, Thorium-232, and Potsium-40) using NaI(Tl) detection system and alpha emitters (Radon-222, Radium-226, and Uraium-238) using CR-39 detectors. The NaI(Tl) detector was a 3"×3" crystal dimension which it is calibrated using 137 Cs, 22 Na, 60 Co, and 152 Eu. There are three energies of spectrum used to nd speci c activity of gamma emitters according to secular equilibrium propriety which it is 1764.5 KeV for 214 Bi ( 238 U or 226 Ra), 2614 KeV for 208 Tl ( 232 Th), and 1460 KeV for 40 Ar ( 40 K) [13]. A CR-39 detector has density 1.32 gm/m 3 , thickness 1mm and dimension 2.5×2.5cm 2 , which it is made by TASTRAK Analysis System, Ltd., UK. Also, it has special code that suited the TASL image system. The chemical etching procedure was carried out by NaOH with a 6.25 N at temperature 85 o C [14]. CR-39 in the present study was calibrated factor using standard source 226 Ra for different time exposure such as 0.5, 1, 1.5, 2, 2.5, and 3 days which it is equal (0.28±0.043) Track.cm 2 /Bqm -3 .day. The background radiation for two detection system (NaI(Tl) and CR-39) was measured at same container and time for sample measurements that used in the present study.

Gamma emitters
The speci c activity (A) for gamma emitters that depend on many parameters as shown in Equation (1) was found by following [15,16]: where, N is area of under photopeak, B is the areas under photopeak background. t is counting time which it is equal 18000 secs, ε is the e ciency of the detector, I γ is the probability of gamma emission, and m is the mass of sample.
Also, it was calculated threshold consumption rate (DI thresh ) in grains samples using equation (5), as where, E ave is equal 0.320 that means an acceptable limit of annual effective dose [5].
Finally, for gamma emitters theoretical equations, can be calculated Excess lifetime cancer risk (ELCR) using equation (6) [15,28]: where, DL is life expectancy (70 y) while RF is fatal risk factor in (Sievert) and it is pegged at 0.05 per Sievert.

Alpha emitters
222 Rn Concentrations that measured in the airspace of container (C) and within samples (C Rn ), were determined by equations (7) and (8), respectively, as following [29,12]: where ρ is the track density which determined by TASL device, T is time irradiation for sample with CR-39 detector in container which was equal 90 days, K is calibration factor, λ Rn is rador-222 of the decay constant which equal 0.1814 1/day, h is distance of samples to CR-39 detector, and l is higher of samples in container.
While, equation (9) was used to nd the effective radium content in sample (C Ra ) as following [5]: The uranium concentration (C U ) in samples of the present study in unit (ppm) was calculated using equation (10), which depend on secular equilibrium propriety between uranium-238 and radon-222, as following [30]: The equation (11) was used to determine AED due to alpha emitters in food samples which depend on many parameters such as speci c activity of radon-222, radium-226 and uranium-238 in sample (C Alpha ) in unit (Bq/kg), consumption rate of samples (I) in unit (Kg/y), and conversion dose factor (CF) in unit (Sv/Bq), as following [30] Where, the values of conversion dose factor are 3.5 nSv/Bq [27] for radon-222, 280 nSv/Bq [31] for radium-226 and 45 nSv/Bq for uranium-238 [31]. Finally, can be determined ELCR using equation (6).
Results And Discussion

Gamma emitters
The results of the speci c activity as well as stander division (S.D) of gamma emitters (uranium-238, thorium-232 and potassium-40) in different grain samples at Kerbala governorate were presented in Table (2). From Table (2), the range value of the speci c activity in unite Bq/kg for uranium-238, thourium-232 and potasium-40 were 88.67-586.61, 1.52-5.94, and 3.13-18.58, while the average value with stander error (S.E) were 227.59 ± 32.34, 3.07 ± 0.22, and 6.61 ± 0.91, respectively. The maximum of the speci c activity for or uranium-238, thourium-232 and potasium-40 were found in samples G14 (rice, Eayn Al-Tamr), G19 (rice, Aoun), and G10 (mung bean, Al-Jadwal Al-Gharbiu), while the minimum were in samples G2 (wheat, Al-Jadwal Al-Gharbiu), G13 (rice, USA), and G16 (rice, Al-Jadwal Al-Gharbiu), respectively. Also, from   Table (3) is shown the values of radium equivalent activity (Ra eq ) and internal hazard index (H in ) based on the speci c activity of 238 U, 232 Th, and 40 K in grain samples in the present study that calculates using equations (2) and (3) [27], respectively that is safety stage. The results of AED, DI thresh and ELCR in grains samples in present study were shown in Table 4. Based on the results (Table 4), the range value of AED in unit mSv/y due to 238 U, 232 Th and 40 K were 0.007-0.120, 0.005-0.049, and 0.008-0.187 with an average value 0.049 ± 0.007, 0.024 ± 0.002, and 0.065 ± 0.009, respectively. While, the range of total AED were 0.020-0.254 mSv/y, with an average 0.139 ± 0.013 mSv/y which it is lower than the acceptable limit 0.32 mSv/y that recommended by UNSCEAR 2008 [27]. The range value of DIthresh and average values (   (4) the results of ELCR were ranged between 0.049×10 − 3 to 0.716×10 − 3 , with an average value of (0.365 ± 0.03) ×10 − 3 . From these results found ELCR from all grain samples in the present study due to gamma emitters were within world limit that equal 2.5×10 − 3 [4,33]. From the results of natural radioactivity for gamma emitters were found that all grain samples in the present study were safety for human consumption.  Table 5, the range of C U in two unites ppm and Bq/kg were 0.0005-0.0279 and 0.006-0.345, with an average values 0.0058±0.0015 and 0.072±0.019, respectively. Results showed that the maximum values of alpha emitters (C, C Rn , C Ra , and C U ) was found in sample G19 (rice, Aoun) and the minimum was found in sample G6 (corn, Al-Jadwal Al-Gharbiu). Figure (4) [37]. Therefore, all values of radon gas concentration in grain samples of the present study were lower than the recommended values according to ICRP, U.S.EPA, WHO, and CFR U. Also, it is found that all values of C Ra and C U were lower than acceptable levels according to UNSCEAR [27] which equal 30 Bq/kg and 11.7 ppm, respectively.  Table (Table 6), it is found that the values of total AED were ranged from 0.003 µSv/y to 0.830 µSv/y, with an average value of 0.172±0.047 µSv/y which were less than 1.2 mSv/y as acceptable levels according to UNSCEAR report [38]. The results of ELCR×10 -6 due to alpha emitters were varies from 0.012 to 3.196, with an average 0.664±0.182, which is very nominal. The quantities of natural radioactivity (gamma and alpha emitters) of the grain samples in the present study were varied, because to natural of soil that grow of these grains such as type of soil, geological natural of the soil, and quantity of chemical fertilizers used for plants. As   The correlation coe cients between gamma emitters ( 238 U, 232 Th, and 40 K) using NaI(Tl) detector and 222 Rn concentrations using CR-39 were calculated in all grain samples of the present study, as shown in  Potassium-40 -0.14 -0.16 1

Conclusion
The data obtained in this study improve the suitability of the NaI(Tl) and CR-39 techniques for such complex samples. The results of radiological hazard due to natural radionuclides of gamma and alpha emitters in grain samples that collected from Kerbala governorate were less than acceptable levels that recommended by different world organization such as UNSCEAR, ICRP, OECD, WHO, and other. Also, the results of natural radioactivity in all types of grain samples were varied which depend on natural soil and natural of samples. It is found that, there is a high positive correlation coe cient (R = 0.86) in all samples between 222 Rn concentrations that measured using CR-39 detector and 238 U that measured using NaI(Tl) detector. While another radionuclide, the correction coe cient was low and negative quantity. Finally, it can be concluded that the grain samples in this work does not pose any severe health risks to human's consumption.

Declarations
-Availability of data and materials : The dataset supporting the conclusions of this article is available in the Zenodo repository via -Competing interests: No competing interests.
-Authors' contributions: The author(s) read and approved the nal manuscript.  Histogram of Uranium-238.