Research Journal of Environmental and Earth Sciences 4(9): 835-837,2012
ISSN: 2041-0492
© Maxwell Scientific Organization, 2012
Submitted: June 23, 2012
Accepted: July 28, 2012
Published: September 20, 2012
Levels of Radionuclide Contents in Stream Waters of Some Selected Rivers in
Ogbomoso Land, South West Nigeria
J.O. Ajayi, O. Adedokun and B.B. Balogun
Department of Pure and Applied Physics, Ladoke Akintola University of Technology, PMB 4000,
Ogbomoso, Oyo State, Nigeria
Abstract: The study aims at providing a base-line data for the effective monitoring of unforeseeable radioactive
fall-out in the investigated areas. Attempts were made to investigate the radionuclide concentration levels from ten
selected streams spread around the five local governments of Ogbomoso land, South-Western Nigeria during
2010/2011 stream flow season. The stream water samples collected from these selected streams were then analyzed
using gamma spectrometry with sodium iodide (NaI) detector connected to a multi-channel analyzer. All the stream
water samples from these streams were found to contain permissible levels of radionuclides with mean activity
values of 100.13±26.82, 6.03±2.10 and 5.54±1.76 for 40K, 238U and 232Th, respectively. The mean absorbed dose rate
of the water samples was found to be 0.10 mSv/year which is very low when compared to the International
Commission on Radiological Protection’s (ICRP) recommended limit of 1 mSv/year and therefore pose no
radiological hazard to the public.
Keywords: Gamma spectrometry, radionuclides, South western Nigeria, water streams
or anthropogenic including biological, chemical,
physical and radiological impurities such as industrial
and commercial solvents, heavy metals, acid salts,
radioactive materials and so on. Contaminants in
drinking water that have adverse health impact include
Inorganic Chemical Contaminants, Organic Chemical
Contaminants,
Microbiological
Contaminants,
Radiological
Contaminants
and
Turbidity
Contaminants.
This study presents an assessment of the level of
contamination of stream water by radiological
contaminants. For this purpose, the radioactivity from
three natural radionuclides was determined in water
samples collected from stream waters in the five local
government areas of Ogbomoso land with a population
of about nine hundred thousand people from ten
different locations.
INTRODUCTION
For the human race, water is as essential to life as
air to breath. Thus, the importance of investigating the
level of radionuclide element in stream water is very
important. This is particularly so in an area such as
Ogbomoso land where more than 90% of water for
domestic usage comes from streams, lakes and rivers.
Water can pick up radioactive materials as it flows
through rocks, soils or cracked cement surrounding a
water source therefore contaminating the water source.
The study of radio-nuclide concentration in
underground and spring water has been going on with
great efforts in many countries of the world by many
investigators (Tokossa et al., 1999; Haukson, 1981;
Wallenberg et al., 1985). According to Avwiri et al.
(2007), studies were carried out on water samples
collected from bore-holes in Port-Harcourt, Nigeria to
check the natural radionuclide concentration. Also
Vandenhove et al. (2006) in part of their work reported
on the radioactivity of bore-hole water in their study
area while Awodugba and Tchokossa (2008) reported
on the natural radionuclide concentration present in
water supply from bore-holes in Ogbomoso land.
Stream water does not exist in a pure form for any
appreciable length of time in nature. Even while water
fall as rain, water picks up small amount of
contaminants from the atmosphere and more as it filters
through the ground. These contaminants maybe natural
MATERIALS AND METHODS
The study was conducted in Ogbomoso metropolis,
South West Nigeria, during 2010/2011 stream flow
season of the various rivers. Ten stream water samples
were collected from 10 streams spread over the five
local government areas of Ogbomoso land. Odo
Attenda and Odo Wota in Ogbomoso North local
government; Odo Alapata, Odo Ora, Odo Alalubosa
and Odo Sunsun in Ogbomoso South local government;
Odo Kinnira and Odo Oba in Orire local government
Corresponding Author: J.O. Ajayi, Department of Pure and Applied Physics, Ladoke Akintola University of Technology, PMB
4000, Ogbomoso, Oyo State, Nigeria
835
Res. J. Environ. Earth Sci., 4(9): 835-837, 2012
Table 1: Streams and location of water samples in Ogbomoso land
Stream name
Local government
Odo Attenda stream
Ogbomoso North
Odo Alapata stream
Ogbomoso South
Odo Wota stream
Ogbomoso North
Odo Oba stream
Orire
Odo Ora stream
Ogbomoso South
Odo Ope stream
Surulere
Odo Oje stream
Ajaawa
Odo Alalubosa stream
Ogbomoso South
Odo Kinnira stream
Orire
Odo Sunsun stream
Ogbomoso South
while Odo Ope is in Surulere local government and
Odo Oje in Ajaawa local government respectively.
These and other relevant details about the samples are
given in Table 1.
The stream water samples were collected from
each of the selected streams by dipping the containers
in the stream water and fetching them into the container
manually. Containers for the samples were washed with
a solution of detergent and then rinsed with freshly
distilled Hydrochloric acid (HCl) to remove any
inorganic material that might have stuck to the walls of
the container before the samples were collected.
About 2 L of each water sample were taken and 20
mL of 1 MHCL added immediately. This is necessary
to fix the radioactive elements in the samples. The
containers were sealed tightly and wrapped with thick
vinyl tapes around their screw necks. Some 250 mL of
each water samples in tightly covered cylindrical
containers were stored for 4 weeks to reach secular
equilibrium between 238U and 232Th and their respective
progeny (Schotzing and Debertin, 1983; El-Tahaway
et al., 1994).
Gamma-ray
activity
measurement:
Activity
measurements were performed at the Centre for Energy
Research, Obafemi Awolowo University, Ile-Ife,
Nigeria with a gamma-ray spectrometry system based
on a NaI detector (Jibiri et al., 1999; Islam et al., 1990).
The analysis was performed using a Canberra S 100
computer analyzer. All the samples were counted for
25200 sec because of the low gamma counts in the
water and a Canberra Pb shield, 10 cm thick and
cylindrical in shape was used to reduce the gamma-ray
Table 2: Radionuclide concentration in the water samples
Stream name
Mean activity
Odo Attenda stream
Odo Alapata stream
Odo Wota stream
Odo Oba stream
Odo Ora stream
Odo Ope stream
Odo Oje stream
Odo Alalubosa stream
Odo Kinnira stream
Odo Sunsun stream
background (Gilmore and Hemingway, 1995; Knoll,
2000). Background spectra were collected also for
25200 sec/week and the counts subtracted from the
respective region of interest (Debertin and Helmer,
2000). The counting time was optimized to
accommodate the operating conditions and it was used
in order to minimize the statistical errors. The
efficiency calibration for the different energy peaks
different energy peaks was measured using the IAEA
reference samples. The energies of 1764.49, 1460.75,
1120.3, 911.07, 609.31, 583.19 and 351.92 keV were
used for the determination of the radionuclides present
in the water samples being 238U, 232Th and 40K (EPA,
2000; IAEA, 1989; ICRP, 1983; UNSCEAR, 2000).
The absorbed dose rates D, at 1.0 m above the
ground were calculated using the Beck et al. (1972)
relationship: distrupt;
D(nGy/h) = 0.048Ck±0.046Cu±0.662Cth
where, Cu, Cth and Ck are the activity concentrations of
U, 232Th and 40K, respectively in the water samples.
238
RESULTS AND DISCUSSION
The 238U, 232Th and 40K activities measured in the
stream water samples are presented in Table 2. The
possible sources of radionuclide contaminants of the
water from the streams are uncertain and may be due to
natural processes.
The mean activity of 40K, 238U, 232Th are
100.13±26.82, 6.03±2.10 and 5.54±1.76 Bq/L,
respectively while the calculated absorbed dose rate D
in mSv/year is shown in Table 3.
The absorbed dose rates as evident from Table 3,
were highest for Odo Kinnira stream water sample
followed by Odo Attenda, Odo Alapata, Odo Wota,
Odo Oba, Odo Ora, Odo Ope, Odo Oje, Odo Sunsun
and Odo Alalubosa in that order. The mean absorbed
dose rate for all the area is 0.10 mSv/year. This value
when compared with the ICPR standard value of 1
mSv/year is very low, hence, it can be concluded that
the radionuclide concentration of stream water in
Ogbomoso land is negligible and poses no radiological
hazard to the public.
K-40
100.37±23.47
75.44±18.97
132.38±34.56
87.23±27.39
63.15±17.98
133.53±31.09
90.49±27.38
22.05±8.09
225.25±52.97
71.35±26.32
100.13±26.82
836 U-238
9.044±3.11
14.46±5.12
1.72±0.98
8.78±0.34
5.03±1.87
7.35±2.12
3.70±1.23
3.16±1.40
5.55±2.02
1.52±0.69
6.03±2.10
Th-232
2.28±0.57
6.78±2.13
7.26±1.98
8.43±3.01
3.57±1.11
6.47±1.62
8.01±1.99
4.56±2.00
4.29±1.76
3.72±1.43
5.54±1.76
Res. J. Environ. Earth Sci., 4(9): 835-837, 2012
Table 3: Absorbed dose rates in water samples in mSv/year
Absorbed dose rate
Stream name
(mSv/year)
Mean dose
Odo Attenda stream
0.10
Odo Alapata stream
0.10
rate
Odo Wota stream
0.10
Odo Oba stream
0.10
Odo Ora stream
0.10
Odo Ope stream
0.10
Odo Oje stream
0.10
Odo Alalubosa stream
0.04
Odo Kinnira stream
0.12
Odo Sunsun stream
0.10
0.10
CONCLUSION
The study of the radionuclide concentration levels
in stream water samples from ten streams spread across
Ogbomoso land, South Western Nigeria has been
carried out. The mean absorbed dose rate of 0.10
mSv/year was obtained. This value is lower than the
ICPR standard value of 1 mSv/year and thus do not
pose any health or radiological danger to the populace
of the host community.
ACKNOWLEDGMENT
The authors wish to appreciate the effort of
Dr. Pascal Tchokossa in taking the measurements at the
Center for Energy Research, Obafemi Awolowo
University (O.A.U), Ile-Ife, Nigeria.
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