Determination of Natural Radionuclides for Water Resources on the West Bank of the Nile River, Assiut Governorate, Egypt

: Estimations of natural radioactivity levels were carried out for water (surface and groundwater) samples collected from the west bank of the Nile River in Assiut Governorate, Egypt. The activity concentrations in the water samples ranged from 19.20 ± 2.40 to 492.26 ± 71.52 mBq/L, from 15.58 ± 2.62 to 351.39 ± 66.13 mBq/L, and from 50.31 ± 5.58 to 2255.03 ± 249.42 mBq/L for 226 Ra, 232 Th, and 40 K, respectively. In this work, the recorded activity concentrations have been organized statistically using a dendrogram cluster and a principal coordinate analysis. In view of the groupings of radionuclide activity, the average annual effective doses through ingestion for adults, children, and infants, despite the responsibility of each explicit radionuclide to the total dose, were assessed and debated. Children had the most important measurement calculations, making them the most regarded mass gathering. All estimations for each different water type, as well as for each individual population group, scored well under the recommended reference value of 0.1 mSv resulting from a one year’s intake of drinking water in accordance with the recommendations of the European Commission (EC) in 1998.


Introduction
Natural radioactivity in water has been examined widely in different parts of the world to assess the radiological risks to people in view of using tainted water [1][2][3][4]. Radioactive materials enter explicitly into the body through drinking or as part of advanced lifestyles. They cause health problems as a result of the decay of these radionuclides into the body.
Radium is considered as a highly toxic element in water and requires attention for human health. Two natural radium isotopes are a cause of worry in public water supplies; 226 Ra, which is made as a result of the decay of 238 U, and 228 Ra, which is explicitly created through 232 Th decay. Radium propels into groundwater through aquifer solid disintegration, through direct recoil over the liquid-solid limit through its arrangement by its parent radioactive decay in the solid, and moreover through desorption. The movements of radium in water are a component of the geochemical properties of solids in the aquifer. The behavior of radium in the body is similar to that of calcium and a ratable fraction deposited in the bone, which in turn can cause bone and head-sinus cancer [5].
Quantitative and abstract information of the regular radioactivity occurring in waterways and beach front situations are basic, since it concerns the most abundant radionuclide ( 40 K) and other radionuclides liable to cause radiation protection problems under extreme conditions [6]. 40 K is discharged into water bodies, adding to the nearness of radioactive segments in drinking water. 40 K is the primary radioactive isotope of potassium. It decays explicitly into 40 Ca in the ground state through β-emanation (89%) and also to 40 Ar in a 1.46 MeV excited state pursued by a prompt 1.46 MeV gamma emission through electron capture (11%) due to water-shake/soil associations.
In the present work, water samples taken from different localities on the west bank of the Nile River in Assiut Governorate, Egypt, were examined to find the activity concentrations of the radionuclides 226 Ra, 228 Ra, 232 Th, and 40 K and to compute the radiological dose rates occurring from the use of this water. The annual effective doses, in addition to the cancer risk parameter will be calculated to study the quality of the water under investigation. The results enable the development of distribution maps for such radioelements in the area under investigation.

Study Area
Assiut Governorate is one of the governorates of Egypt that rests on the Nile Valley. It lies about 400 km south of Cairo and extends for about 120 km north-south along the banks of the Nile. It is located between latitudes 26 • 50 0" N and 27 • 37 45" N and longitudes 30 • 40 50" E and 31 • 31 0" E ( Figure 1). Assiut Governorate is the most populated governorate in Upper Egypt with more than 4.5 million inhabitants [7]. It comprises 11 districts, 52 local administrative units, 235 small villages (most of which depend on groundwater for drinking), and 971 tiny villages (that depend on groundwater, almost shallow private wells, for drinking). This work focuses on the five districts located on the western Nile bank: Dairut, Assiut, Abu Tig, Sedfa, and El-Ghanayim ( Figure 1). The area of interest is part of the Nile Valley of Egypt, where the only source of groundwater is the Quaternary aquifer. The fluctuating water level of the Nile and the irrigation network canals, which dissect the whole area, have a noticeable control on the groundwater conditions [8]. A semiconfined condition is the dominant case for the groundwater in the aquifer, however, when the cap layer (silt and clay) is absent, the aquifer is found under a phreatic condition. The water level of the Nile also affects the regional groundwater flow direction (generally from southeast to northwest) matching the course of the River Nile. The depth to groundwater in the study area ranges from 1 to 5 m, which indicates a direct contact between surface and groundwater [9].
The Quaternary aquifer (50-250 m thick) consists mainly of sands and gravels of high hydraulic conductivity at the bottom and is capped by silt and clay layers [10].
The aquifer in the area of interest is mainly recharged from the surface water bodies in the vicinity, with horizontal flux from the south, and the return flow from intensive irrigation activities. A thick impervious Pliocene clay layer, underlying the aquifer, prevents vertical leakage [11].

Samples Collection and Preparation
A total of 83 water samples (surface and groundwater) were collected from the west bank of the Nile River in Assiut Governorate, Egypt. The water samples were gathered in identical (1 liter) polyethylene Marinelli beakers (GA-MA & Associates Inc, USA), which were also used for measurement. Each beaker was consistently filled to the brim and a sealed cap was placed on top, to ensure that it was completely free of air. Acidification to pH ≤ 2, by adding HCl or HNO 3 , was performed to prevent microorganism growth. The samples were stored in the laboratory for the duration of at least 30 days to allow daughter products to reach a radioactive equilibrium with their parents, 226 Ra and 232 Th, before the radiometric analysis [12].

Radioactivity Measurements
All the samples were measured at the nuclear physics laboratory in the physics department at the Faculty of Science in Assiut University using a gamma ray spectrometer with an HPGe model GR4020 setup and a multichannel analyzer of 16,384 channels (Canberra Industries, Inc., USA). The detector had closed-end coaxial Gamma-ray detectors (p-type) made up of high purity germanium (HPGe) in a vertical configuration cooled by liquid nitrogen with the following specifications: resolution (FWHM) ≤ 2.000 keV and ≤ 0.925 keV at 1.33 MeV and 122 keV, respectively, with a relative efficiency of 40%. The germanium crystal was located within a lead shield for the reduction of the environmental background. The detector was shielded in a four-layered chamber with the following specifications: Outer Jacket 9.5 mm (3/8 in.), thick low carbon steel Bulk Shield 10 cm (4 in.), and thick low background lead with Graded Lining 1 mm (0.040 in.) tin and 1.6 mm (0.062 in.) copper [13].
The system was calibrated for both energy and efficiency. The energy calibration was carried out by acquiring a spectrum from radioactive standards of known energies such as 137 Cs (662 keV) and 60 Co (1332 and 1172 keV). For the efficiency calibration, Canberra's Geometry Composer was used instead of the standard source [13].
The spectra were analyzed by the computer software program Canberra's Genie2000 (Canberra Industries, Inc, USA) for the calculation of natural radioactivity.
The radioactivity concentration of 226

Statistical Analysis
The activity values of 226 Ra, 232 Th, and 40 K in the water samples were subjected to the PAST program where the dendrogram cluster analysis was performed. Samples were treated as stands where the application compiles and divides the similar ones, which are similar samples in regard to activity, and divides them into groups. After applying the dendrogram cluster analysis, the principal coordinate analysis (PCoA) was performed, which represents the statistical distribution of the samples in a statistical map which has axes PcoAaxis1 and PcoAaxis2.
Secondly, we used the SPSS program (IBM, USA) where the ANOVA table was ascertained. It contains a factor (F) value that represents the difference coefficient, and the differences were studied between the mean values for each group for 226 Ra, 232 Th, and 40 K. In the ANOVA table, F-values are shown in three forms. The first form, **F-value, implies that there are high contrasts between the groups and is called a high significant difference. The second form, *F-value, implies that there are contrasts between the estimations of the midpoints of the groups and is called a significant difference. The third form, F-value, implies there are no contrasts between the midpoints of the groups shaped and is called a non-significant difference. The F-value gave us an impression of the radiation activity behavior of 226 Ra, 232 Th, and 40 K in water.

Radiation Dose Estimation
The total annual effective doses were measured for different age groups according to the equation introduced by EPA (Environmental Protection Agency, USA) [14] and by Meltem and Gursel [15], using the data presented in Table 1: where E D (W) is the total annual effective dose (mSv y −1 ), A(W) is the radionuclide activity concentration (Bq/L), q(W) is the water consumption rate for a person in one year, which is 150, 350, and 500 L for infants, children, and adults, respectively [16], and C F (W) is the effective dose equivalent conversion factor (mSv Bq −1 ) ( Table 1).

Cancer Risk Estimation
The radiological risk related to the radium isotope can be evaluated by calculating the life-time cancer risk (R) using the following equation [20]: where MCL is the maximum contaminant level (Bq/L), RC is the mortality risk coefficient (7.17 × 10 −9 and 2.0 × 10 −8 Bq −1 for 226 Ra and 228 Ra, respectively) and TWI is the total water intake (2 L d −1 × 365.4 d year −1 × 70 year).

Activity Concentrations
The average activity concentrations of the measured radionuclides for the tested drinking water from the investigated areas are recorded in  Perceptibly, the maximum average activity concentration was found in the Sidfa and El-Ghanayim domains for 226 Ra concentrations, the Assiut area for 228 Ra focuses, and the Dairut region for 232 Th and 40 K activity concentrations ( Table 2).
The frequency distribution of 226 Ra, 232 Th, and 40 K activity concentrations were analyzed, and the histograms are given in Figure 2. The highest number of water samples for 226 Ra activity concentrations fluctuated between 80 and 200 mBq/L. The most astonishing focuses were in the range between 50 to 100 mBq/L for the 232 Th activity concentrations and the 40 K activity concentrations are increasingly present in the range between 0 to 800 mBq/L.

Dendrogram Cluster Analysis
As shown by cluster analysis, the activity concentrations of the measured radionuclides were portrayed into 83 stands and yielded four bunches at level 2 of the chain of significance, as in Figure 3.

Principal Coordinate Analysis
The principal coordinate analysis (PCoA) exhibits tremendous complexities between the four gatherings ( Figure 4). They are separated along PCoA hub 1 and PCoA hub 2. Stands of gatherings A and B take the most right 50% of the PCoA hub, while those of gatherings C and D take the other side (the negative piece of hub 1). A contour map ( Figure 5) illustrates that most stands of gatherings A, B, and D were arranged between latitude 26 • 55 and latitude 27 • 15 as shown in Figure 6. However, stands of gathering C were arranged between latitude 26 • 55 and latitude 27 • 10 . As shown in Figures 4 and 5, the gatherings appear within the statistical map to match their order on the map. For example, it is noticed that the groups (A and B) are statistically in the opposition direction of the gatherings (C and D) (Figure 4); in a similar way, for contour, stands of gatherings (A and B) are concentrated in one region as well as the stands of gatherings (C and D) as in ( Figure 5). Therefore, there is a statistical and contour match between them.
The ANOVA (Table 3) shows the mean estimations of the examined radionuclides in the Assiut water in the gatherings (A-D), where the most important estimations of the mean are found in gathering B and the slightest of the mean estimations are in gathering C for 226 Ra and 40 K. The F-value shows that there is an immense difference between the four gatherings for radium and potassium, while there is no significant difference between the four gatherings for the thorium isotope.

Distribution of Radionuclides in the Study Area
According to the distribution map of 226 Ra, 232 Th, and 40 K for the water samples taken from the west bank of the Nile River in Assiut Governorate, as shown in Figure 6, it was found that there were considerable variations in activity concentrations of 226 Ra, 232 Th, and 40 K, where some regions had high activity concentrations. For example, 226 Ra had high activity concentrations in the west of Assiut, in Abu Tig, and around Dairut and El-Ghanayim, as in Figure 6a

Total Annual Effective Doses
The total annual effective dose for all water samples changed from 8.17 to 83.69 µSv year −1 with a mean estimation of 38.61 µSv year −1 , from 14.30 to 146.65 µSv year −1 with a mean estimation of 68.01 µSvyear −1 , and from 13.99 to 127.08 µSvyear −1 with a mean estimation of 58.01 µSv year −1 for infants, children, and adults, respectively. Table 4 shows that doses received by children are higher than those received by infants and adults.
The mean annual effective doses on account of all radionuclides are 38.61, 68.01, and 58.01 µSv year −1 for infants, children, and adults, respectively. These estimations represent about 14.85%, 34.01%, and 58.01% of the proposed reference estimations of 260, 200, and 100 µSv year −1 for 226 Ra, 232 Th, and 40 K, respectively. The doses received in all examination regions by children were higher than those received by infants and adults, and doses received by adults were higher than those consumed by infants.

Risk Based on the Radium Isotopes
The annual effective doses (mSv year -1 ) for adults from radium isotopes and the associated cancer risk, due to water consumption in the examined areas of Assiut governorate, were determined. The annual effective dose decided from radium isotopes was changed from 3.9 × 10 −3 to 100.6 × 10 −3 mSv year −1 with a mean estimation of 41.6 × 10 −3 mSv year −1 and from 2.3 × 10 −3 to 277.3 × 10 −3 mSv year −1 with a mean estimation of 57.1 × 10 −3 mSv year −1 for 226 Ra and 228 Ra, respectively. The united ingestion of 226 Ra and 228 Ra was, consequently, found to stretch out from 8.4 × 10 −3 to 345.4 × 10 −3 mSv year −1 with a mean estimation of 83.6 × 10 −3 mSv year −1 , which is lower than the endorsed reference estimation of 0.1 mSv year −1 . Table 5 shows that the maximum estimation of radiological risk for water samples for 226 Ra in the Assiut domain is higher than the exchange zones. On the other hand, the maximum estimation of the radiological risk of water samples for 228 Ra in the Dairut zone is higher than those in different regions. Regardless, we found that the mean estimation of radiological risk for both 226 Ra and 228 Ra is acceptable in examination with the reference estimation reached out from 1 × 10 −4 to 1 × 10 −6 , which is regarded as an acceptable cancer incidence risk in the notice of data openness for radionuclides in drinking water that was disseminated by USEPA [21].  Figure 7 shows the histogram of the cancer risk based on the radium isotopes and shows that the cancer risk ranged from 7.04 × 10 −6 to 1.81 × 10 −4 , with an average estimation of 7.47 × 10 −5 for 226 Ra and from 4.77 × 10 −6 to 5.63 × 10 −4 with an average estimation of 1.16 × 10 −4 for 228 Ra.

Radionuclides and Physico-Chemical Parameters
In the tested water, the electrical conductivity ranges from 0.20 to 2.01 mS/cm, the total dissolved solids reached out from 0.09 to 1.01 ppt, the pH-esteem extended from 7.21 to 9.02, and the temperatures ranged from 18.2 to 28.1 • C. There was no correlation between the physico-chemical parameters and the radionuclides 226 Ra, 232 Th, and 40 K, where the correlation coefficients (R 2 ) in all cases were below 0.1.

Comparison with Similar Studies in Other Countries
The estimations of 226 Ra, 232 Th, and 40 K concentrations from the present work are different from those from other countries ( Table 6). The activity concentrations of 226 Ra and 232 Th from the present work are higher than that uncovered in Egypt (Qena and Safaga) [22], Sudan [23], and Ghana [24] and lower than those uncovered in Yemen [12], Nigeria [25], Turkey [26], Brazil [27], and China [28]. The estimations of 40 K concentration in this work show up much lower than are reported from other countries.

Comparison of 226 Ra and 228 Ra Concentrations in the Study Area and the Corresponding Values in Other Egyptian Cities
The estimations of the annual effective dose and the cancer risk for adults, based on 226 Ra and 228 Ra concentrations from the present work, appeared differently in relation to those from other Egyptian urban zones, as itemized by Abdellah and Diab [29]. The estimations of the annual effective doses and the cancer risks from the present work are higher than the estimations of annual effective doses and the cancer risks from other Egyptian urban zones, e.g., Cairo, El-Mansoura, Qalyub, Sixth of October, Alexandria, Tanta, Bani Suweif, the Sinai Peninsula, and Siwa Oasis.

Conclusions
A total of 83 water samples were assembled from the domain on the west bank of the Nile River in Assiut Governorate, Egypt. The natural radioactivity levels in the water samples were determined using a hyper pure germanium detector (HPGE). The mean activity concentration groupings of 226 Ra, 228 Ra, 228 Th, 232 Th, and 40 K were 203.60 ± 29.61 mBq/L, 113.42 ± 22.45 mBq/L, 64.39 ± 8.59 mBq/L, 81.40 ± 13.58 mBq/L, and 688.48 ± 76.25 mBq/L for the water samples, respectively. The total annual effective doses and the estimated cancer risk show that the radionuclides under this examination do not pose any significant health risks to the public.
The data obtained in this examination are considered benchmarks, which can be used to survey possible future changes. They should give a better than average example in setting measures for water quality in the country.