Heat Production Rate and Radiation Hazard Indices from Radioactive Elements in Different Types of Natural Water in Nineveh Governorate, Iraq.

: The current study sheds light on the measurement and estimation of the radioactivity of radionuclides ( 238 U, 226 Ra, 232 Th, and 40 k) in natural waters of different regions of Nineveh Governorate in Iraq.15 samples were collected from different sources of natural waters, where gamma-ray spectroscopy was used using NaI)TI) sodium iodide detector to determine the concentration of radioactivity in the samples. According to the results, the radioactivity concentration in the tested water sample were ranged from 0.36 ± 0.04-1.57 ± 0.09with an average value of 0.69 ± 0.06 Bq/l for 238 U, and 2.9 ± 0.02-0.88 ± 0.03 with an average value of 0.65 ± 0.03 Bq/l for 226 Ra Bq/l, and 0.48 ± 0.04-1.36 ± 0.06 with an average value of 0.88 ± 0.05 Bq/l for 232 Th, while for 40 K 13.00 ± 0.69-36.89 ± 1.12 with an average value of 25.1 ± 0.95 Bq/l, respectively. The results obtained from the water samples are below the safe and standard limits established by UNSCEAR. In addition to calculating the radiological hazard indicators that included Radium equivalent (Ra eq ), air absorbed dose rate (Dγ), effective annual equivalent dose rate (AEDE), indoor and outdoor radiation hazard (H) indices, lifetime cancer risk (ELCR), gonadotropin equivalent dose (AGDE), and ideal level index of gamma rays (Iγ) has been calculated. To verify its deleterious character. On the other hand, the results showed that the rate of heat production values ranged between 0.006-0.0015 µW/m 3 , which indicates a low rate of heat production and does not affect the temperature of the Earth's crust. Finally, In addition to physicochemical parameters such as PH, dissolved solids TDS, and electrical conductivity Ec. All tested data are within the permissible limit of WHO standards. The results of the current study can be used to provide essential baseline data for future epidemiological investigations and surveillance programs in the areas under study.


Introduction:
People are naturally and permanently exposed to natural radiation due to the concentrations of the basic radionuclides 238 U, 226 Ra, 232 Th and, 40 K found in the earth's crust, water, air and food, as well as building materials and the human body 1 .Radioactive pollution is one of the most dangerous types of environmental pollution.When radioactive materials reach the cells of the body, external and internal damages occur that may lead to human death.And that radioactive pollution occurs from natural sources such as rays emanating from outer space and radioactive gases rising from the earth's crust, or industrial sources that occur by humans, such as atomic reactors, nuclear power plants, and radioactive isotopes used in agriculture, medicine and industry 2 .The isotopes involved in radioactive or radiogenic heat production are referred to as primordial or primeval radioactive elements.In geophysics, primordial isotopes are nuclides that are abundant on Earth and have existed since the Earth's formation 3 .An essential factor in the Earth's surface heat flux is the quantity of naturally radioactive materials found in the planet's crust.The measurement of radioactive heat sources is a fundamental aim of heat-flow investigations, especially for the lithosphere of the continents, which has a complicated composition compared to the oceanic lithosphere 4 .The natural decay of atoms through the natural process known as radioactivity is a process that releases heat that increases the dissipation of energy associated with the slow cooling of the planet.Surface heat flux in continental regions, where the crust is typically thicker, can result mainly from radioactive decay 60%, a relevant contribution to heat dissipation from the core and mantle 40%.Geothermal energy, which is the extraction of heat from the Earth's interior, is widely used by humans to heat areas and produce electricity, usually in areas of the world where heat flow is much higher than the global average, such as in active volcanic regions 5 .However, the use of geothermal energy has been successfully extended in the past decades to other geological settings where heat flow is not very intense, but geothermal reservoirs can be created at higher depths through engineering techniques.This is the case, for example, in the deep geothermal projects in Stoltz and Landau, where reservoirs in California are located at a depth of 5 km.Both are characterized by the presence of granite, the rocks are usually very rich in radioactive elements, and the heat flux values are moderately higher than normal 6 .It is not only the heat content of the young Earth that supplies the main internal source of heat, but also the radioactive decay of the unstable isotopes of uranium ( 235 U; 238 U), thorium ( 232 Th), and potassium ( 40 K) 7 .The Tahir, & Alaamer 8 results of a study that included using Gamma-ray spectroscopy to determine the concentrations of natural radionuclides such as ( 226 Ra, 232 Th, and 40 k) in groundwater samples in Pakistan, have used the NaI(TI) detector.As well as calculating the annual effective dose (AEDE) and physiochemical parameters (PH, TDS, and Ec), revealed that all values are less than the World Health Organization's recommended values.AL-Ubaidi et al 9 ; Harb et al 10 , Some radioactive elements for 137 Cs, 238 U, 232 Th, and 40 K were identified from different water samples using Gamma-ray spectroscopy in conjunction with the hazard indicator.The results show that the concentrations of these elements were less than the global limit.Alam et al 11, In Kirkuk, the pH, TDS, and EC of nine tap water samples and 20 bottled water samples were measured.Each of these values was found to be within the appropriate WHO range.Amin & Jassim 12 , has used the NaI(TI) detector to examine and analyze drinking water samples for radionuclide levels and determined the yearly effective dose (AED) and total (AED) for all specimens that were less than the global standard value of 0.1mSv/y Alseroury et al 13 One of the researchers used HPGe to assess the concentrations of natural radioactive elements in groundwater in the Makkah region and found that the average values of the specific activity concentrations of these elements were less than the global limit.There is a survey conducted in Nigeria, Osun State by Oluyide et al 14 by using the NaI(TI) detector, to determine the radioactivity of 238 U, 232 Th, and 40 k.For 38 water samples conducted that there are indications of radiological hazards.The results show that the values of concentration of these elements were less than the global limit.The researcher Parhoudeh et al 15 observed the values of pH 8.12, TDS 285 ppm, and EC 446.19 µs/cm.Since the values of the parameters were above the recommended range, it was determined that Balad city tap water is unsafe.Al-Khashab et al 16 measured the pH, TDS, and EC and discovered that they were 7.7-8.7,226-302 mg/L, and 330-405 μs/cm, respectively, and that all the values are within the recommended ranges.Salman et al 17 were able to carry out a comprehensive radioactivity of 232 Th, 238 U, and 40 k.The NaI(Tl) detector was used to ascertain this.The researchers found that the lifetime risk of cancer was much lower than what the ICRP had determined, which means the samples are safe and healthy.Kurnaz et al 18 , there is a group of researchers who have estimated some of the radioactive elements 226 Ra, 232 Th and 40 k in samples of drinking water belonging to the Kastamonu region of the Black Sea in western Turkey using HPGe detector technology, researchers evaluated the concentration the values of these radioactive elements were consistent with the values allowed by the organization The World Health Organization's with the exception of 228 Ra was higher than the concentration recommended by WHO.The aim of the study is to estimate the concentration of radionuclides ( 238 U, 226 Ra, 232 Th, and 40 k), using gamma-ray spectroscopy by NaI(TI) detector, alongside the measuring of the heat production rate and radiation hazard indices in different types of natural waters in Nineveh Governorate, Iraq.In addition to measuring some physicochemical parameters.

Methodology Description of study areas
Nineveh Governorate was selected as a study site in this work.It is located in northwestern Iraq, and its center is the city of Mosul, 465 kilometers from Baghdad, the country's capital.With a population of nearly three million, Nineveh is the second-largest governorate after Baghdad.The province lies between longitudes of 36 degrees and latitudes of 43 degrees.The Tigris River runs through the province and divides Mosul into two Every beaker is entirely full, and the pressurized beaker is closed with a tight lid until all air is emptied.The water samples were kept in polyethylene canisters overnight to permit the suspension to precipitate.And each sample was tested.The transparent supernatant was filtered from each sample, and then the transparent supernatant was isolated.Additionally, by adding 0.5 mL of concentrate, the pure solution was acidified.To keep microorganisms at bay, use HNO3/L to prevent radium isotope loss around the walls of the container.The vibration was used to fully standardize water and samples.Table 1: Identification, types, and locations of water samples in Nineveh Governorate, as well as longitude and latitude coordinates.-Ray Spectrometry SPECTCH UCS-20 gamma-ray spectroscopy was used with a crystal of thalliumactivated sodium iodide (TI) detector with dimensions 3.8 * 2.5 cm. the detector is installed on a lead surrounded by a holder for the purpose of shielding and reducing the background radiation.The spectrum collection system consists of a basic amplifier, the main amplifier, and a high-voltage power source that supplies the detector with the necessary voltage, and the voltage used in this research is 600 volts, which is in the range of the detector's operating voltage.And a multi-channel analyzer, then connected to a computer to operate and display the output spectrum, before starting the spectrophotometric process, the energy efficiency calibration of the detector was also carried out with a reference source, using barium 133 Ba 661.6 Kev and 60 Kev power source.They must be taken into account before starting the analysis process in order to obtain accurate results, since the interpretation of the gamma spectrum depends on the radionuclides.The second energy is in place of the voltage and channel number.After which an efficiency calibration was performed using a standard source with known energies of the ( 152 Eu) isotope was used, which has a number of energies ranging from 1408.0, 121.8 Kev at the same experiment conditions (Marinelli vessel).

Calculation of Activity Concentration
The natural water samples collected from different regions were left by placing one liter of it in a sealed Marinelli vessel for 28 days, in order to reach the ideal balance between the parent nuclide and its daughter.The detector crystal is inserted quietly into the same container so that it is facing the sample to be examined.To prevent external radiation from reaching the detector, all of this is surrounded by sheets of lead 5 cm thick.And then the spectrum of gamma-rays emitted from the water sample is collected for a period of 18,000 seconds.By calculating the area under the gamma spectrum curve, the concentration of the radionuclide 226 Ra, 232 Th, and 40 K content in the samples are calculated using the radioactivity relationship as in the following formula 1 19 .It should be mentioned that the radiation background was measured for the same time period and its value is subtracted to get the actual radioactivity generated by the samples 20 .

𝐴 = (𝑁−𝐵)±√𝑁−𝐵 𝜀 𝛾 𝐼 𝛾 𝑡 𝑚
1 And A denotes the radioactivity in question in unit Bq/l N is the all area underneath the radioactive isotope energy's optical peak, B is the laboratory background radiation,   is the detector's efficiency at a specific energy of the measured nuclide's gamma line,   is the percentage severity of a gamma-ray emitted by the radioactive element, m, is indeed the sample volume mass in L, and t recording the time of the spectrum counting in seconds..The second term preceded by ±S.E sign in the above equation represents the percentage error in the spectrum counting.Table 1: indicates different types and locations of water samples collected in various regions of Nineveh province.Following the determination of the activity concentration levels of 238 U, 232 Th, and 40 K in samples, the activity concentration levels of radionuclides calculated by (Bq/l) are converted to the initial concentration (ppm, percent) of radionuclides using the conversion transactions described below 21 : 1 ppm of 238 U is equal to 12.35 Bq/l.

Effects of radiological hazards are assessed.
To determine the amount of radioactive hazard in the selected water samples, several risk indicators were computed, including: Radium Equivalent (  ): The equivalent activity of radium is defined as a radiation factor using the uniform distribution of natural radionuclides represented by 226 Ra, 232 Th, and 40 k, and it is measured in units of Bq/l, and Radium equivalent can be calculated through the following equation: Ra. eq (Bq/l) = A Ra + 1.43 A Th + 0.077A k 2 Where ARa, ATh, and AK are the specific activity of 226 Ra, 232 Th, and 40 k in units of Bq/l.The maximum universally permitted value of equivalent radium activity (Raeq) is 370 Bq/l 22 .

Absorbed Dose Rate in Air (Dγ)
The rate of absorbed dose of gamma rays in the air at one meter 1m above the ground level can be calculated using the specific activity of 226 Ra, 232 Th, and 40 k, and it can be calculated through the following equation 23

Annual Effective Dose Equivalent (AEDE)
The annual equivalent dose means that the radiological factor is used to judge the extent of the health effects resulting from the absorbed dose, and it is measured in units mSv/y.Effective as well as by using the external occupancy factor 0.2 and the internal occupancy factor 0.8.The annual effective dose equivalent (indoor) can also be calculated using the following equation 23

Hazard Index (H)
A Hazard guide is a radiological parameter used to identify and evaluate external and internal radiation hazards.The external hazard index (Hex) and the internal hazard index (Hin) are calculated through the following equations 24 : To get the gamma index (Guide) (Iγ), we use the following equation 25 : ≤ 1 8 And it should be≤ 1; the internationally agreedupon limit.

Life time cancer risk (ELCR)
The Excess Lifetime cancer risk (ELCR) was calculated using the following equation 26 .ELCR out = AEDE out * DL * RF 9 Where AEDE is the Annual Equivalent Dose Equivalent, DL is the average duration of life (estimated to 70 years), and RF is the Risk Factor (Sv -1 ), i.e. fatal cancer risk per Sievert.For stochastic effects, ICRP uses RF as 0.05 for public.

Annual gonadal dose equivalent (AGDE)
The gonads, the bone marrow and the bone surface cells are considered organs of interest by UNSCEAR (2000) because of their sensitivity to radiation.An increase in AGED has been known to affect the bone marrow, causing the destruction of the red blood cells that are then replaced by white blood cells.This situation results in a blood cancer called leukemia which is fatal.The AGED for the resident using such material for building by evaluated by the following equation 27 .AGDE(µSv y ⁄ ) = 3.09A U + 4.18A Th + 0.314A k 10 Where, ARa, ATh, and AK are the radioactivity concentration of 226 Ra, 232 Th and 40 K in water samples.

Heat Production Rate (HPR):
The estimation of the number of radioactive elements, the main internal heat source of the Earth.Has been the focus of various research over the last few decades due to its importance in modeling the thermal evaluation of natural waters.The radioactive isotopes 238 U, 232 Th, and 40 K contribute the majority of the terrestrial heat flux .Those elements are essential for understanding the mantle and crust of the earth 28 , as well as their heatgenerating potential, by considering the heat generation constant (amount of heat released per gram 238 U, 232 Th, and 40 K per unit time) it is possible to determine the rate of heat production rate using the values given in the following equation 29 .A (µWm −3 ) = 10 −5 ρ(9.52AU(ppm) + 2.56A Th(ppm) + 3.48A K(%) ) 11 Where A denotes the heat production rate in µWm 3 ,  is the sample density in kg/M 3 , AU and ATh denote the 238 U and 232 Th concentrations in ppm unit, and A.K denotes the total potassium concentration in percent%.

Results and Discussion:
The results showed that the concentration level of radioactive elements ranged between 0.36±0.04-1.57±0.09Bq/l, with an average value of 0.69±0.06Bq/l for 238 U all values were within the permissible limits 10 Bq/l 30 .and from 2.9±0.02-0.88 ± 0.03 Bq/l with an average value of 0.65±0.03Bq/l for 226 Ra It showed that it was within the permissible and estimated global rates 1Bq/l 30 , and was between 4.85±0.4-1.36±0.06Bq/l with an average value of 0.88±0.05Bq/l for 232 Th the average concentrations of radionuclides appeared which is less than the globally permissible value, which should not exceed 1Bq/l 30 , while the level concentration of radioelements of 40 k was higher and appeared to range between 13.00±0.69-36.89±1.12Bq/l with an average value of 25.1±0.95Bq/l in all samples was found to be lower than the recommended general mean limits 400 Bq/l 31 .The concentration levels of Natural radioactive elements in water samples tested for 238 U, 226 Ra, 232 Th, and 40 k in Bq/l units are shown.The Physiochemical parameters, as well as the geological composition of the Earth, cause changes in the levels of radioactive concentrations of 238 U, 226 Ra, 232 Th, and 40 K from one sample to another.Regarding the physical and chemical hazards, total dissolved solids (TDS), conductivity (Ec), and (pH) were measured as the pH levels of natural water samples from 7.40 -8.07, with An average value of 7.69 The pH level expressed in all water samples from the study area was found to be within the safe limit recommended by the World Health Organization 6.5-8.5 in 1971, the electrical conductivity (Ec) ranged between of 2.5-52.63µs/cm with an average value of (9.23) the maximum permissible limit of 1.500 µs/cm recommended By the LOCA 32 , and the dissolved solids (TDS) ranged between 156 -2011 ppm with a mean value of 493.6 ppm All values are within the permissible range 500 ppm recommended By the WHO, As represented in table 2.   There was no correlation discovered between uranium, radium, thorium, and pH in this research However, The concentration levels of 238 U, 226 Ra, and 232 Th in water samples decrease.As the pH increases.Natural water contains a high concentration of TDS, a positive correlation was observed between the radioactive elements and TDS, indicating that the movement of the radioactive elements in the water was significantly affected and controlled by TDS, Fig. 3-a, b, and c.The general rule is that the greater the TDS (or EC), It can be concluded in general from these correlation relations that most of the elements are positively correlated with each other, a direct relationship (the ratio of an increase leads to an increase in the other).The greater the radioactivity.This study's data may be useful in determining natural radionuclide background levels in drinking water, as well as in initiating safety standards for preserving radioactive materials by relevant authorities and providing clean drinking water to the general public.The concentrations of activity of natural radionuclides of concern in water samples from the current investigation were compared to levels reported for different locations of Iraq and the world in the Table .3. The radium equivalent value (Raeq) of the examined water samples varied from 2.44-5.15Bq/l with an average of 3.81 Bq/l, which is fewer than 370 Bq/l as illustrated in Fig. 4 The absorbed dose ratio varies from 1.18-2.54nGy/h with a mean of 1.85 nGy/h as illustrated in Fig .5 It is also fewer than the globally suggested minimum 55 nGy/h.Moreover, the annual efficacy value of the dose equal to indoor exposure (AEDEin) in the water samples ranged between 1.4-3.1*10 3 µSv/y and the overall mean is 2.22*10 3 µSv/y.As shown in Fig. 6, this value is less than the globally acceptable value of 0.1 µSv/y.The annual outdoor exposure dose value (AEDE out) in the water samples was 5-10.9*10 3 µSv/y, and the total average 7.94*10 3 µSv/y as shown in Fig .6, which is less than the universally permissible limit of 0.1 µSv/y 38  in Fig. 7.The external hazard index value for all samples of analysis water is much lower than the permissible global average, ranging between 6.5-13.9*10 3 , with a mean of 10.22*10 3 , as shown in Fig. 7 the gamma index ranges from 1.8-4*10 2 with an average of 2.91*10 2 Fig. 8 shows the values that are less than the permissible global value and should not exceed 0.1 µSv/y.The calculated value of ELCR varies from 5-10.9*10 3 mSv with an average of 8.02*10 3 mSv as seen in Fig. 9 The ELCR obtained values from water samples tested are lower than the global average 0.29 µSv the Table 4. Shows the AGDE calculated values in this study, and they vary from 8.41-18.45µSv/y, with a mean value of 13.59 µSv/y, indicating that the AGDE values of all water samples tested are less than the global average of 300 µSv/y 32 as seen in Fig. 10.international organization 10, 1, and 400 Bq/l respectively.These values were reflected in the heat production rates, which in turn were at a rate compatible with the permissible limits of less than 1 µw/m 3 .And the radiological hazard indicators showed that there are no abnormal values that negatively affect human life and health on those who drink or deal with these natural waters.We can confirm that the contribution of the 232 Th nuclide was it has a large percentage in the heat of production rate, followed by the two nuclides of 238 U and 40 K.

Figure 1 .
Figure 1.GPS coordinates were used to identify the location from which water samples were collected.
232  Th is equal to 4.06 Bq/l. 1 percent of 40 K equals 313 Bq/l.

Figure 2 .
Figure 2. the radioactivity concentration for( 238 U, 226 Ra, 232 Th, and 40 K) according to selected sample of natural sources.

Figure 3 -Figure 3 -
Figure 3-a.The correlation coefficient of uranium ( 238 U) with electrical conductivity (Ec) and the dissolved solids (TDS)

Figure 3 -
Figure 3-c.the correlation coefficient of Thorium ( 232 Th) with regard to electrical conductivity (Ec) and dissolved solids (TDS).
. The internal hazard index value was smaller than the internationally permitted value, and it varied from 0.76-15.6*10 2 with an average of 11.03*10 2 , as seen

Figure 4 .
Figure 4. Equivalent levels of radium activity (Raeq) in water samples in Nineveh province, Iraq.

Figure 5 .
Figure 5. Levels Absorbed dose rate in air (Dɣ) in water samples in Nineveh province, Iraq.

Figure 6 .
Figure 6.Annual effective dose equivalent rate of internal and external exposure (AEDE indoor) (AEDE outdoor) levels in water samples in Nineveh province, Iraq.

Figure 7 .
Figure 7. External and internal hazard index levels in water samples from Nineveh province, Iraq.

Figure 8 .
Figure 8. Levels of gamma radiation hazard index in water samples in Nineveh province, Iraq.

Table 2 . The total concentrations of radioactive elements ( 238 U, 232 Th, 226 Ra, and 40 K) Bq/l, in addition to the Physiochemical parameters in natural water samples in Nineveh Governorate. Physiochemical parameters Activity Concentrations in Bq/l Sample Code TDS ppm Ec µs/cm PH 40 k 232 Th 226 Ra 238
One can be noticed that the concentration of 40 k dominate over 238 U,226Ra, and 232 Th, which is what normally happens in all different samples of soils, air, and water, because it's high in Natural potassium As in the following Fig.2 and