Spatial Distribution of the Natural Radioactivity
of the Water and its Association with the Physico-Chemical Parameters: Abu Tig, Assiut, Egypt
Ghada Salaheldin1*, Ahmed Sefelnasr2 and Hany El-Gamal1
1Department of Physics, Assiut University, Egypt
2Department of Geology, Assiut University, Egypt
Submission: March 21, 2019; Published: April 18, 2019
*Corresponding author: Ghada Salaheldin, Department of Physics, Faculty of Science, Assiut University, Assiut 71516, Egypt
How to cite this article: Ghada Salaheldin, Ahmed Sefelnasr, Hany El-Gamal. Spatial Distribution of the Natural Radioactivity of the Water and its Association
with the Physico-Chemical Parameters: Abu Tig, Assiut, Egypt. Int J Environ Sci Nat Res. 2019; 18(4): 555991. DOI:10.19080/IJESNR.2019.18.555991
Activity concentrations of radionuclides (226Ra, 222Rn, 232Th and 40K) and physico-chemical parameters (Temperature, pH-value and total dissolved solids (TDS)) were measured for drinking water samples collected from Abu Tig, Assiut Governorate, Egypt. The samples were measured by gamma-ray spectrometry technique using HPGe detector with specially designed shield. The average activity concentrations were (235.71 ± 34.04mBql−1), (58.26 ± 10.29mBql−1), (624.08 ± 69.29mBql−1) and (0.184 ± 0.11Bql−1) for 226Ra, 232Th, 40K and 222Rn respectively. The average annual effective doses due to ingestion of these waters were 60.79μSvyr−1, 74.75μSvyr−1, and 41.81μSvyr−1 for different age groups adults, children and infants, respectively. There is no correlation between radionuclides and physico-chemical parameters. The obtained results were lower than the reference level of the committed effective dose recommended value (0.1mSvyr−1) as reported by World Health Organization (WHO), indicating to the safe use of the examined water.
Keywords: Natural Radioactivity; Annual effective dose; Drinking water; Abu Tig
Most environmental studies provide the best ways to preserve water and improve its quality for the necessity of human life. Water may be a factor for the transport of pollutants by human consumption.
radionuclides cause health hazard by ingestion and through the human food chain when these radionuclides are taken to the body . So that it is necessary to achieve the minimum radiation exposure to the human body and not skipped the reference dose level (RDL) of the effective annual dose of drinking water consumption of 0.1mSvyr-1 reported by WHO .
The main naturally occurring radioactive isotopes in water are uranium isotopes, radium isotopes, and radon isotopes, these radionuclides are mainly soluble in water . The production of these radionuclides in groundwater is mainly from rock-water interactions. The levels of radioactivity in groundwater depends on many factors such as the concentrations of these radionuclides in the aquifer rocks, geomorphology, and lithology other ecological conditions of aquifer [4,5], depending also on chemical reactions and the physical processes of decay along the water-rock interface.
226Ra is an alpha emitter with longest a half-life of 1602yr, it originates from the 238U decay series and its descendant 222Rn has a half-life of 3.8d. 228Ra is a beta emitter with a half-life of 5.75yr and it originates from 232Th series. 40K is also radioactive and has a half-life of 1.3x 109yr. Generally, radium concentrations in surface water range from 0.01 to 0.1Bql-1 , while its concentration in groundwater can reach values up to 38Bql-1, depending on the factors mentioned previously. 222Rn is produced which is a gaseous radioisotope and diffuses into the pore water of rock formation. The 222Rn concentration in groundwater reaches to 183Bql-1 . The recommended reference level of radon concentration in tap water is 150Bql-1 as considered by .
The levels of detection of radon in water research are explained by the sovereignty of granite rocks as well as the rocks of aquifers under investigation. Increased risk of many types of cancer is associated with exposure to radon and its progeny . In addition, the high concentrations of 222Rn in water samples indicate the presence of the radon’s parent nuclide 226Ra in the water-rock/soil system, which is known as the health hazard when ingestion during drinking water .
The present study attempts to report the results of drinking
water radium, thorium, potassium and radon survey in Abu Tig,
Assiut Governorate, Egypt. The inhabitants of villages and rural
areas in the study area are totally dependent on groundwater
and on surface water of the Nile River for water supply.
The present work aims to understand the occurrence and
classification of natural radionuclides 226Ra, 232Th, 40K and 222Rn
in drinking water samples from study area and in a first approach
to estimate natural radionuclides exposure levels for inhabitants
of this region to estimate radiation doses for several ages due to
water consumption by people living in this region. The results
might provide some helpful information for management of
drinking water use.
Assiut Governorate is the most populated governorate in
Upper Egypt with more than 5 million inhabitants. Abu Tig
is a big district within Assiut Governorate that located on the
western bank of the river Nile, between Latitudes 26o 57’ 56.8”
and 27o 6’ 59.6” N and Longitudes 31o 11’52.9” and 31o 22’ 10.7”
E. Abu Tig has a surface area of about 129km2. It has almost
264,087 inhabitants. Physically, it is bounded to the east by
the River Nile and bounded on the western side by the Eocene
limestone plateau. The drinking water samples were collected
from the area under interest in the period of normal water flow
rates within the Nile (Figure 1).
A total of twenty-seven samples were collected from various
locations from the study region and classified into three types;
surface water, hand-dug wells and deep wells. Standard Polyethylene
Marinelli beakers (1 liter) are used as measuring containers.
Before utilizing, the containers are washed with HCl and
swilled with distilled water. A tad bit of nitric acid, around 0.5ml
HNO3 per liter, was added to clear solution to forbid any loss of
radium isotopes around the container walls, and to avert growth
of microorganisms . After filling up the beaker to the brim, a
tight cap is pressed on to completely remove the air from it. The
samples store for over thirty days to arrive secular equilibrium
before a radiometric analysis. Each sample is counted for almost
172800 second relying on the radionuclide’s concentrations.
Water samples were subjected to a gamma ray spectrometer
with a detector had closed-end coaxial Gamma-ray crystal made
of high purity germanium in a vertical configuration cooled
with liquid nitrogen. The energy resolution of the detector
reads approximately 2.000keV and ≤ 0.925keV at 1.33MeV and
122keV, respectively, while the relative efficiency is 40μ. The
germanium crystal is existed inside a lead shield to decrease the
environmental background. The shield consists of four layers
with the following specifications: a low carbon steel of 9.5mm
thick as an outer jacket, a bulk shield of lead of 10cm thickness,
and graded linings to absorb low energy X-rays of 1.0mm tin and
1.6mm copper .
The spectrometer was energy-calibrated using radioactive
standards of known energies such as 137Cs (662keV) and 60Co
(1172 and 1332keV) and it was calibrated for efficiency using
Canberra’s ISOCS calibration utility instead of standard source
226Ra concentration was determined using gamma-lines
of 214Bi and 214Pb for different energy (609.31, 1120.29, and
1764.49KeV) and (295.22 and 351.93KeV) respectively. The
concentration of 232Th was measured using gamma lines of
228Ac, 212Pb and 208Tl for different energy (911.2 and 968.97KeV),
(238.63KeV) and (583.19 and 2614KeV) respectively. Finally, 40K
concentration was determined one peak at 1460.8KeV.
To calculate possibility health hazards, the effective dose
radiation, DR (mSv/yr), doses arising from the ingestion of these
waters were assessed using following equation [8,13],
Where A is the activity (Bq/L), ID is effective dose equivalent
conversion factor (mSv/Bq), and IR is the ingestion of water
for a person in a year (L/yr). The conversion factors for infants
(9.6×10-4, 4.5×10-4 and 4.2×10-5mSv/Bq), for children (8×10-4,
2.9×10-4 and 1.3×10-5mSv/Bq) and for adults (2.8×10-4, 2.3×10-
4 and 6.2×10-6mSv/Bq), were utilized for 226Ra, 232Th and 40K respectively as reported by IAEA, ICRP, and WHO [14-16]. The
dose was estimated by knowing consumption rate for adults,
children and infants of 730, 350, and 150L/yr respectively.
Activity concentrations of 226Ra, 232Th and 40K for the drinking
water samples collected from various locations in Abu Tig region
are listed in Table 1 and shown in Figure 2. The concentrations
of 226Ra, 232Th and 40K changed from 59.04 ± 8.32 to 421.62 ±
58.11mBq/L, from 15.58 ± 2.62 to 153.07 ± 33.64mBq/L and
from 103.27 ± 11.48 to 1363.72 ± 150.98mBq/L, respectively.
The average measurements are 235.71 ± 34.04mBq/L, 58.26 ±
10.29mBq/L and 624.08 ± 69.29mBq/L for 226Ra, 232Th and 40K,
There is no clear correlation between 226Ra, 232Th and 40K
in this study region, where a weak correlation can be found
between (226Ra and 232Th), (226Ra and 40K) and (232Th and 40K)
with a correlation coefficient of R2= 0.1156, 0.1551 and 0.1794,
222Rn activity concentration in drinking water samples
fluctuated between 0.081 ± 0.05 to 0.789 ± 0.34Bq/L with an
average value of 0.184 ± 0.11, All the samples are below the
maximum contaminant level (MCL) of 11.1BqL-1  and 11BqL-1
as proposed by the US Environmental Protection Agency  the
concentration of radon changes depending on the zone resulting
from its geological structure. as well as, the depth of the source
of water, do not rule out climate change and geo-hydrological
processes occurring in the region . 222Rn concentration in
present work is greater than that reported in Egypt  and less
than that reported from other countries, as Table 2.
222Rn and 226Ra activity concentrations are listed in Table
1. There is no correlation between them where the correlation
coefficients R2 =0.0009 as shown in Figure 3.
Physico-chemical properties of drinking water samples
in study region are listed in Table 1. TDS, pH-value and water
temperature ranged from 0.09 to 0.98ppt, from 7.21 to 8.76 and
from 18.2 to 26.6°C, respectively. There is no correlation between
physico-chemical parameters and radionuclides 226Ra, 232Th, 40K
and 222Rn where the correlation coefficients R2 in all cases are
less than 0.2 as shown in Figure 4, except a moderate correlation
was observed between 226Ra activity concentration and pH-value
and TDS with correlation coefficient R2= 0.2159 and 0.2667
respectively. Also, between 222Rn activity concentration and pHvalue
with correlation coefficient R2=0.2527.
The annual effective doses are given in Table 3 for various
ages: adults, children and infants due to ingestion of 226Ra, 232Th
and 40K through drinking water from different areas in study
region. The annual effective dose fluctuated between 10.49 to
76.25μSvyr−1 with an average value of 41.81μSvyr−1, between
19.02 to 135.85μSvyr−1 with an average value of 74.75μSvyr−1
and between 15.87 to 114.50μSvyr−1 with an average value of
60.79μSvyr−1 for infants, children and adults respectively. Figure
5 shows that doses received by children were higher than that
received by infants and adults; this is because children have
small bodies. They are in the developmental stage, because
their organs and bones are not yet complete. Therefore, the
dose which they are exposed to is large compared to adults. In
addition to being shorter than adults, they may get a higher dose
of radioactive distributed in and deposited on the ground .
The estimated average values for the annual effective dose
for adults, children, and infants approximately %60.79, %37.38
and %16 of the recommended reference values of 100, 200 and
260μSvy−1 respectively [14,16,29-34].
The present study is a contribution to study behavior and
distribution of radioactivity levels of 226Ra, 222Rn, 232Th and 40K
which measured in drinking water from densely populated
area, which is Abu Tig city, Assiut Governorate, Egypt, using
gamma-ray spectrometry technique using HPGe detector. The
results clearly showed low concentrations of activity in the
studied area. The presence of 40K in groundwater is attributed
to the anthropogenic activities represented by the application
of the agricultural fertilizers. The results of this study include
the assessment of annual effective dose for adults, children and
infants. The results of doses which received by children are the
highest. The average annual effective doses for all radionuclides
of drinking water consumption per year is much less than the
recommended reference level and consequentially, therefore
recommend that, the water that has been investigated be
acceptable for human consumption for life. There is no clear
correlation between 226Ra and 222Rn, as well as, no correlation
between physico-chemical parameters and radionuclides.