Determination of long-lived gamma emitters in some vegetarian products in Al-Najaf governorate using NaI(Tl)

In this study, gamma emitters including potassium-40, thorium-232, and uranium-238 were found in samples of 10 types of vegetarian products that were taken from various locations of Al-Najaf governorate. The experimental study is done by NaI(Tl) detectors that are produced by the ORTIC Analysis System. Also, some radiological risks due to these emitters as radium equivalent activity and internal hazard index were calculated using different theoretical equations. Given that all samples from Iraqi vegetarian products in the current study that tested for long-lived gamma emitters and risk factors for hazard were found to be below the global limit suggested by numerous organizations and commissions, one may conclude that there is no risk to human health from radiological hazard caused by gamma emitters.


Introduction
Radiation is emitted from the floor and walls of our homes, the food and drink we consume, and the air we breathe.The three forms of ionizing radiation that are most frequently encountered are alpha, beta, and gamma rays.Radiation can come from various sources, including natural radionuclides and manmade ones [1].Naturally occurring radioactive elements found in rocks, soil, water, and flora are among the terrestrial radiation sources.The uranium series, thorium series, and a single potassium series are the principal isotopes of concern for terrestrial radiation.In different parts of the planet, the amount of radiation from earthly sources varies.Higher portion levels are found in areas with high uranium and thorium concentrations in their soil [2].With half-lives spanning hundreds of millions of years, they appear to be eternal.Radiation poisoning might have long-lasting effects passed on via the family tree.Radiation may also contaminate water and soil, potentially killing off organisms at every food web level [2].Plant pollution has been traced to several possible causes.Radioactive waste falling to the ground is the root of the contamination problems [3].Plants absorb most contaminants through their roots.All parts of a plant that grow vertically, including stems, leaves, seeds, and flowers, are excellent conduits for their propagation.Radioactive elements like 40 K, 232 Th, and 238 U are found in soil worldwide [4].Natural conditions in the Earth's crust and surface are required for producing gamma and alpha radiation.You can find them worldwide at varying depths in the dirt.Because of fertilizer use, there are more naturally radioactive elements (radionuclides) in farmed places than in areas not planted [5].Radiation may have a wide range of effects on living organisms, including producing ionizing molecules inside the cells that compose the body.In the long run, this may significantly alter human genetics, which is more likely to be passed on to offspring.Humans may be damaged and put in danger in different ways depending on the radiation they are exposed to, how long they are exposed to it, and how sensitive their bodies are.However, plants are not the only way radiation enters the ground and water systems.So, these toxic plants are eaten by cows and cattle, which humans eat through the food chain [6].Numerous studies have been carried out to examine and calculate the levels of radioactive elements in agricultural crop samples in various regions of Iraq and other areas [7][8][9].The essential goal of the current research is to evaluate gamma emitters and some radiological risks in samples of vegetarian products gathered from different sites of the Al-Najaf governorate.Gamma-ray spectroscopy using a NaI(Tl) detector is used for the study.

Area of Study
Al-Najaf governorate is one of the provinces in southern Iraq, which lies at latitude 32 ° 01'44 "north, and longitude 44 ° 27'57.89"east.The city overlooks the Najaf Sea depression.The study area is characterized as a mixed gypsum desert, or sandy or sandy mixture, and sometimes covered by a layer of gravel, and because of its characteristics, it is exposed to air discharge processes as a result of multiple erosion factors [10].

Collection samples
Ten different vegetarian products, including tomatoes, potatoes, rice, corn, barley, pears, pomegranates, onions, and okra, are gathered from various locations of Al-Najaf governorate, as see Table 1.

Preparation samples
Vegetarian products samples have been homogenized, sieved, and dried.To prevent any humidity adsorption and to maintain the true weight, the samples are dried for (2-4) days at a temperature of (42-44) C before radioactivity measurements are made.Using a blender, the dried vegetarian products were ground and processed to create uniformly sized particles.Subsequently, weigh one kilogram of each sample of vegetarian products equally (using a highly accurate digital scale with a precision of 0.01%).The samples were then stored in the containers and each was given a unique code to help differentiate them.To achieve secular equilibrium between the isotopes in the natural decay series, the samples are sealed for approximately four weeks in Marinelli beakers (size one liter) [10].They were then placed in front of the detector to be counted.In the current work, a gamma spectrometric system with a NaI(Tl) scintillation detector with a 3-inch by 3-inch crystal dimension was used.Energy calibration is done by taking a spectrum reading from a source that emits gamma rays with known energy and comparing it to the peak location that was recorded.Known energies such as 22 Na, 60 Co, 152 Eu, and 137 Cs were used as the reference source for measuring the calibration and efficiency (see Figure 1).The measured resolution for the 137 Cs (661.66 keV) standard source energy is 8.9%.
where   ~ : transition probability, while t represents measurement time in seconds for obtained spectrum, and   represents the area under the peak after background subtraction from emitted gamma radiation.At the same time, A represents the activity sources during the experiment.The basic equations used in the present study are the specific activity (A), radium equivalent activity (Ra eq ), and internal hazard index (H in ) which are written as following equations [11,12]:

Results and Discussion
Table 2 demonstrate the natural radioactivity levels for 238 U, 232 Th, and 40 K for ten different vegetarian products sample types.With an average of 7.36 Bq/kg, the specific activity values for uranium-238 varied from 2.49 Bq/kg to 17.00 Bq/kg.According to Table 2, the data showed that the sample of barley had the highest amounts of 238U, whereas the sample of okra had lower levels.The data of specific activity of thorium-232 ranged from 3.11±0.07Bq/kg to 8.57±0.64Bq/kg, with an average of 4.75±0.55Bq/kg.From Table 2, the data revealed that the sample of Corn recorded the highest levels of 232 Th, while lower levels of 232 Th were recorded in the sample of Potato.The data of specific activity of potassium-40 ranged from 126.81±7.07Bq/kg to 319.66±12.57Bq/kg, with an average of 226.46±17.77Bq/kg.From Table 2, the data revealed that the sample of Corn recorded the highest levels of 40 K, while lower levels of 40 K were recorded in the sample of Potato.Table 3 shows the radiological risks such as Ra eq and H in of vegetarian products samples in the present study, respectively.The range values of Ra eq (Bq/kg) were from 19.5 in Potato to 49.9 in Corn.While, the range values of H in were from 0.065 in Okra to 0.170 in Corn.and H in was lower than unity depending on the report of radiation protection [15].The differences in the values of the specific activity for 238 U, 232 Th, and 40 K in the vegetarian products of the present study are attributable to the soil of cultivation type in this location which is taken from plant samples.Also, it is noted in all results that the specific activity of thorium and potassium as well as the values of radiological hazard in corn is larger than that of the other vegetarian products.These results are because certain elements absorb more than others.Also in all samples, it is noted that the values of specific activity of 40 K exceed markedly the values of both 238 U and 232 Th which may be because the activity concentrations differ geographically from one soil of cultivation to another.

Conclusions
The results of natural radioactivity of 214 Bi ( 238 U series), 208 Ti ( 232 Th series), and 40 K in samples of vegetarian products are found to be lower than the world average allowed maximum values of 35, 45, and 420, respectively.The values for the radium equivalent activity (Ra eq ) are found to be within the world average allowed maximum value of 370 Bq/kg.This study could be useful as baseline data for radionuclide concentration and radium equivalent activity.All values of internal hazard indices (H in ) are less than the world permissible value of unity.Therefore, it can be said that there are no potential radiation or health hazards associated with any of the varieties of Al-Najaf vegetarian products examined in this study.

Figure 2 .
Figure 2. Comparing the average value of the specific activity of 238 U, 232 Th, and 40 K in vegetarian products Samples with the average stranded values of UNDCEAR2008 [13].

Table 1 .
Information about vegetarian products samples

Table 2 .
[13] of specific activity The average's results values of the specific activity for 238 U, 232 Th, and 40 K in vegetarian products samples with standard values recommended by UNSCER 2008 are shown in Figure2.Also, the results of the specific activity of 238 U, 232 Th, and 40 K for all samples in the present study were within the average value of standard values which are 35 Bq/kg,45 Bq/kg, and 420 Bq/kg for 238 U, 232 Th and 40 K respectively, recommended by UNSCER 2008[13].

Table 3 .
[14] radiological risks When it is compared the average values of radiological risks for Ra eq and H in which it is equal to 31.62±2.96Bq/kgand 0.105±0.011,respectively in the current work with the value of the standard values average.The average value of Ra eq was less than that of the World record limit of 370 Bq/kg[14]

Table 4 .
[13]e 4 includes comparisons of specific activity of 238 U,232Th, and 40 K, in vegetarian product samples from different governorates of Iraq.It is noted the specific activity of 238 U in the study area is larger than Kerbala, Kirkuk, Tikrit, Baghdad, and Samawah governorates.Also, it is seen that the specific activity of 232 Th in the study area is lower than in Al-Diwaniyah, Kirkuk, Tikrit, and Baghdad governorates.While, the specific activity of 40 K in the study area is higher than in Al-Diwaniyah, Kirkuk, and Tikrit governorates.But it is found that the values of specific activity were lower than the world median according to UNSCEAR 2008[13].Comparisons of specific activity of 238 U, 232 Th, and 40 K with previous studies