Significance of Uranium Series Disequilibrium and Their Radiological Impacts In Abu Garadi Altered Granites.


 Radioactivity of U, Th series and 40K in the collected samples from Abu Garadi area were measured using Hyper Pure Germanium detector Gamma spectrometer (HPGe). 232Th, 226Ra, 40K and 238U contents were determined in the different samples that indicating high uranium high thorium type of these granites. The activity concentrations of 232Th, 238U, 234U/238U activity ratio of the studied altered granites ranged between 1.98 to 4.25 with 2.89 as an average, indicating that the samples passed from the incipience of the oxidation-reduction zone (234U/238U=1.98) to the reduction zone (234U/238U= 4.52). 238U/235U activity ratios showed broad range as a result of the alteration processes. 226Ra and 40K are very important in determination of different environmental hazard impacts. The activity concentrations average of 238U, 232Th, 226Ra and 40K were 6553.7 ± 3.1 Bq kg− 1, 3944 ± 0.9 Bq kg− 1 201.3 ± 1.1 Bq kg− 1 and 619.4 ± 0.02 Bq kg− 1. The absorbed gamma dose rate (D), external hazard index (Hex), annual effective dose rate equivalent, radium equivalent (Raeq), internal hazard index (Hin), gamma index (Iγ) as well as Excess Lifetime Cancer Risk (ELCR) were applied based on the measured radionuclide concentration of the 238U, 232Th, 226Ra and 40K.


Introduction
It is important to study the distribution of radionuclides and radiation levels in the environment to estimate radiation exposures' effect from terrestrial and extraterrestrial sources. The natural radioactivity is based on geological, geographical conditions and the rock types. Higher radiation levels are associating with igneous rocks, like granite, while lower radiation levels are connected to sedimentary rocks, although some phosphate and shale rocks have a high radionuclide's content. Natural radiations are caused by primordial nuclides such as the radionuclides from 238  In the environment natural radioactivity produces gamma radiations and increases the rate of background radiation. Everyone on the earth is affected by these ionizing radiations background.
External exposure is due to irradiation while internal exposure is due to inhalation and ingestion (Belvermis et al., 2010). 3 Gamma-ray spectrometry is the common techniques used to detect low-background radioactivity. The hyper-pure germanium (HPGe) gamma ray spectrometry is the most sensitive and effective tool used to evaluate radionuclide activity from lower to pCi (Harpy et al., 2019; El-Taher,

2011).
The different ranges of radioactivity makes the measurements complicated and it is necessary to calibrate the used detectors for small band widths. Furthermore, other samples may have high activity, which causes the measurements to be calculated at large distance between source and detector to ensure a low dead time and a point like geometry and to avoid coincidence losses, (Asaduzzaman et

al., 2016)
While the low radioactivity samples whose measurements may require that sources be positioned in a detector's vicinity. The exact radionuclides determination depends on accurate characterization of the detector used and the activity of the ɤ-ray emitting sources (Knoll, 2000; Gilmore and Hemingway JD, 1995). The most important properties of a ɤ-ray detector are the energy resolution and the detection efficiency that may reflect on the reliability of the results.
This work aims to study the disequilibrium of uranium series radionuclides and their radiological impacts in Abu Garadi altered granites, Central Eastern Desert, Egypt.

Geological setting
Environmental rock samples were collected from the top surface layers of Abu Garadi area then crushed and homogenized. Every sample was collected in a standard specification plastic container (212.63 cm 3 cylindrical volumes with an average diameter of 9.5cm and a height of 3cm). These containers have been carefully sealed and stored for at least four weeks to prevent contamination of the spectrometer and the escape of 222 Rn and 220 Rn radiogenic gasses to allow radioactive secular equilibrium to be achieved in the decay chains (Matolin, 1991; El-Bahi et al., 2017). 4 Gabal Abu Garadi area of Central-Eastern Egypt is located near the Red Sea coast and is represented by latitudes 25° 37′ 15″ N and 25° 37′ 55″ N and longitudes 34° 06′ 57″ and 34° 07′ 56″ E (Fig. 1).

Fig. 1 Sampling map of Gable Abu Garadi area.
The main rocks outcrop in Abu Garadi area includes stream sediments, alkali feldspar granites as well as metasediments. Metasediments are the main rocks surrounding the alkali feldspar granites that form lower to moderate outcroppings relative to the granite masses. They mainly consist of hornfels, schist and psammopelite. G. Abu Garadi forms a small mass with a surface area of approximately 2 km 2 and a height of approximately 110 m above sea level.

Gamma ray spectrometry
The samples were undergoed to analysis by using Hyper Pure Germanium (HpGe) gamma ray detector which has a relative efficiency of about 60%. The efficiency calibrations were achieved by using three reference materials RGU-1, RGTh-1 and RGK-1 for U, Th and K activity measurements Uncertainty of gamma-ray intensities was reduced by using efficiency specific method of the radionuclides, and self-absorption effects of the gamma photon emitting also; the influence of 6 235 U activity concentration were determined by the ɤ-lines 143.8 keV (10.5%), 163.4 keV (4.8%) and 205.3 keV (4.7%). 235 U activity concentration was calculated from the area of the peak at the next most probable energy, i.e., 143.76 keV (10.96 %). Then, the area of the 185.72 keV (57.2 %) 235 U peak was calculated using the branching ratio of that gamma ray, the efficiency, and the activity.
The 235 U area was subtracted from the area of the peak at 186 keV to obtain the area due to 226 Ra.
From this, the activity of 226 Ra in the sample was calculated.
The activity concentration of 226

Radionuclides Distributions
The activity concentrations of 238 U, 235 U, 234 U, 226 Ra, 214 Pb, 214 Bi, 232 Th and 40 K were measured in the collected samples (Bq Kg -1 ). The activity concentrations of the main radionuclides were reported in table 1. However, the activity concentrations of 226 Ra and 40 K were ranged between 134±0.9 and 245±0.8 Bq  (Table 1 and Fig 5). The geochemistry difference of the two isotopes could be attributed to the radium 28 deficiency. 226 35 We can estimate the effects of this radiation through the calculation of the following 36 parameters which also was tabled in   71 For studying the associated radiation hazards related to Radium equivalent activity which was 72 introduced in a single quantity to represent the specific activities of 226 Ra, 232 Th and 40 K.

73
It is supposed that 1 Bq kg -1 of 226   where Hex is the external hazard index and CRa, CTh, and CK are the specific activities of Ra, Th, 86 and K in Bg kg -1 , respectively. The upper limit of this index is 1.

87
The internal hazard index (Hin) is used to control the internal exposure to 222 Rn and its The results of external and internal hazard index were high than the worldwide average levels. Gamma Index (Iɤ) 95 The γ-radiation level index is performed as a scanning tool to identify materials that could 96 become health interest when used as building materials (EC, 1999).

97
To keep the radiation hazard insignificant the value of the γ-index must be less than unity that is, 98 the radiation exposure from construction materials due to radioactivity must be limited to1.5 mSva -1 .

99
The γ-index is calculated using the following equation potassium alteration due to its absorption on clay minerals (Fig 2 and Fig 3).  Fig 4).  The activity concentrations of 238 U, 235 U, 234 U, 226 Ra, 214 Pb, 214  high in the study area. This is attributed to the occurrences and areas of U-mineralization and then 151 limited areas for radiation sources and radiation exposure. The authors declare that they have no known competing financial interests or personal 159 relationships that could have appeared to influence the work reported in this paper.

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Ethical Approval 161 All authors clarify that this manuscript is original and haven't been published elsewhere in any 162 form or language (partially or in full), hadn't been submitted to more than one journal for 163 simultaneous consideration. Also we clarify that results presented clearly, honestly, and without 164 fabrication, falsification or inappropriate data manipulation (including image based manipulation). 166 We declare our agreement to participate in this work. 168 We declare our agreement to publish in this work.  Availability of data and materials 175 We declare that all data generated or analyzed during this study are included in this published 176 article 177