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Journal of Applied Sciences and Environmental Management
World Bank assisted National Agricultural Research Project (NARP) - University of Port Harcourt
ISSN: 1119-8362
Vol. 9, Num. 3, 2005, pp. 27-29
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Journal of Applied Sciences & Environmental Management,
Vol. 9, No. 3, 2005, pp. 27-29
Determination
of Radionuclide Levels in Soil and Water around Cement Companies in Port
Harcourt
AVWIRI, G O
Department of Physics, university of Port Harcourt, P. M. B. 5323,
Port Harcourt, Nigeria
*Corresponding author: Email: goavwiri@yahoo.com
Code Number: ja05054
ABSTRACT:
The study of the radionuclide concentration levels in
soil and water samples in Eagle, Atlas and rock cement companies in Port Harcourt
was carried out. Soil and water samples collected from the respective
premises were analyzed using the gamma -ray spectrometry. The average absorbed
dose rates of the soil samples were 49.27nGy/h, 45.21nGy/h and 42.33nGy/h for
Eagle, Atlas and Rock cements respectively while the water values were
22.16nGy/h, 20.75nGy/h and 19.37nGy/h for the respective companies. Mean
dose rate equivalents of 0.18mSv/y and 0.39mS/y were obtained for the water
and soil samples. These results are lower than the International Commission
on Radiological Protection (ICRP) maximum permitted limit and therefore, have
no
significance radiological health burden on the environment and the populace.
@JASEM
Industrial
and domestic activities such as oil exploration and exploitation, manufacturing
and process industries may lead to the perturbation of the natural ecosystem
and the environment that ultimately occurs as pollution. Increase in the
background ionization radiation from numerous sources has various health side
effects on the populace. Some of the sources of radiations are cosmic rays and
natural radionuclide in air, food and drinking water (NCRP, 1976). Radiation
exposure can be external: natural radionuclides and cosmic rays and internal:
food, drinking water and the mineral contents of the body. The natural
radionuclides in the earth or soil and water of an environment are present as
daughters of uranium (238U), thorium (232Th) isotopes
distributed by natural geological and geochemical processes in addition to
potassium (4%) and small quantities of fission-product residues 137Cs
from atmospheric weapon test (Trimble, 1968). Exposure to excess level of
background ionization radiation causes somatic and genetic effects that tend to
damage critical and/or radiosensitive organs of the body, which ultimately can
lead to death (Ajayi, 1999). The major raw materials for the production of
cement are limestone (CaCO3), shale ash and ion oxide. They also
contain some elements like gypsum, which contains silicates and aluminates that
have ionization tendency (White, 1981).
The
natural radionuclide levels have been studied in surface soils in Ijero-Ekiti
(Ajayi, et, al. (1995)), in soil and water around a cement company in Ewekoro
by Jubiri et, al. (1999) and in rocks found in Ekiti by Ajayi et, al(1999).
Results from these studies revealed non-significant levels of radionuclides in
the environment. Port Harcourt, a major seaport in the Niger-Delta, plays host
to a number of companies that are involve in manufacturing, packaging,
processing and oil activities. The various rivers criss-crossing the city
encourage the sitting of industries in the hinterland. Three cement companies,
sited at Onne and Rumuolumeni exist in the city. They are Eagle, Rock and
Atlas cements. Their main operations involve the bulk importation of the
cement (dust) and then packaging into various sizes for domestic and industrial
usages. Part of the operations take place in the ship berthed in the river
such as the NewCalabarRiver for Eagle cement and River Nmu Ngololo for Rock and
Atlas cements. The locations of these companies are shown in Figures 1 and 2.
The
awareness of the potential degradation of the environment by the activities of
these companies is on the increase and there have been various claims and
counterclaims of degradation of the surface soil and rivers by the host
communities. This study, therefore, determine the level of natural radionuclide
concentrations in the soil and water in around the plants, estimates the level
of degradation of the radioactive equilibrium of the areas and ascertain the
radiological health side effects on the populace and the environment.
EXPERIMENTAL
METHODS
Sample Collection and Preparation: Nine soil
samples of about 500g were collected from the respective cement companys
premises and three samples were collected from the host community as indicated
in Table 1to serve for comparative assessment. The samples were kept in
polyethene bags and were properly labeled as shown in Table 1 and taken to the
laboratory for gamma (γ) ray analysis. The water samples were
collected from the rivers where the ships are berthed. About 6 litres of water
were collected at three points in each river. They are the berthing position
of the ship, 500m upstream and 500m downstream. The water samples were stored
in a refrigerator and kept for 30 days for secular equilibrium to be
established before the γ-ray analysis.
Table 1: Sampling Points of Soil and Water Samples
Location
Index
|
Locations
|
S11
|
Entrance
Gate of Eagle Cement Co.
|
S12
|
Storage/Bagging
Area of Eagle Cement Co.
|
S13
|
Admin
Block Area of Eagle Cement Co.
|
S21
|
Entrance
gate of Atlas Cement Co.
|
S22
|
Bagging
Area of Atlas Cement Co.
|
S23
|
Onne
Community, hosting Atlas Cement Co.
|
S31
|
Loading
Area of Rock Cement Co.
|
S32
|
Bagging
Area of Rock Cement Co.
|
S33
|
Admin
Block of Rock Cement Co.
|
W11
|
500m
upstream of Eagle Cement Co along NewCalabarRiver
|
W12
|
Berthing
Station of Ship/vessel
|
W13
|
500m
downstream of Eagle Cement along NewCalabarRiver
|
W21
|
500m
upstream of Atlas Cement Co along Nmu Ngololo River (FOT)
|
W22
|
Berthing
Station of Ship/vessel
|
W23
|
500m
downstream of Atlas Cement Co. a long Nmu Ngololo Rivers (FOT)
|
W31
|
500m
upstream of Rock Cement Co. along Nmu Ngololo River (FOT)
|
W32
|
Benthing
Station of Ship/vessel
|
W33
|
500m
downstream of Rock Cement Co. along Nmu Ngololo River (FOT)
|
Legend: 1st digit indicates sample Number, 2nd
digit indicates company i.e Eagle = 1, Atlas = 2, Rock = 3
Letter indicates type
of sample S = Soil, W = Water
Gamma
(γ) ray
Analysis: The method of γ-ray spectrometry as
has been severally reported (Ajayi et, al. (1990)), Jubiri, et, al. (1999) was
adopted in the analysis. The spectrometer consists of a Canberra 7.6cm
by 7.6cm NaI (Tl) (Model No 802 series) detector coupled to a Canberra
series 10 plus Multichannel Analyzer (MCA) through a pre-amplifier base. The
transition lines of 1.460 MeV of 40K, 1764.5 KeV of 214Bi
and 2614.7Kev of 208Tl were used to determine the concentrations of 40k,
238U and 232Th respectively. The soil samples were sieved
through a 2mm mesh screen and then placed in a container for 28 days to enable
them reach secular equilibrium before the analysis. The spectral for the
soils were measured by counting for 2 hours and the area under the photo peaks
were computed using the algorithm of the MCA. The water samples were transferred
to a one-litre Marinelli sample container, which fits into the detector.
Counting was done for 10 hours because of the natural low activities of
radionuclides in water. The areas under the photopeaks were similarly computed
as in the soil samples. Environmental shielding for the water was achieved
using a Canberra 10cm thick lead castle and 5cm thick lead castle was
used for the soil (Farai and Sanni, 1992).
The
specific activity concentrations Ack, Acu and AcTh
for 40K, 238U and 232Th respectively were
computed using the relation (Beck, et. al, 1972 ).
Ac = AAscms
Asm. (1)
Where
Ac = activity of sample, A = full peak area of samples, Asc =
activity concentration of standard sample, ms= mass of standard sample,
As = full peak of the standard sample and m = mass of sample.
The
absorbed dose rates D, at 1.0m above the ground were calculated using the Beck,
et al. (1972) relation.
D
= 0.042 AcK + 0.429AcU + 0.666AcTh. (2)
Where
0.042 = Dose constant for 40K, 0.429 = dose constant for 238U
and 0.666 dose constant for 232Th. Using the conversion factor of
0.70Sv/Gy (UNSCEAR), 1988), the dose equivalents in mSv/y were computed.
RESULTS
AND DISCUSSION
The
mean specific activities of the radionuclides concentration levels are
presented in Tables 2 and 3 for soil and water samples respectively. Table 4
shows the calculated absorbed dose rates for all samples. The average
absorbed dose rates of soil samples range from 49.27 nGy/h for Eagle Cement to
42.35nGy/h for the Rock cement and from 22.16 nGy/h to 19.37 nGy/h for the
Eagle cement and Rock Cements water samples respectively. The values of the
dose equivalents of the soil samples for all the companies are lower than the
average world soil average of 0.7mSv/y (ICRP, 1991). The dose equivalents of
all samples are comparable with those reported in literature (Myrick, et al
(1983) and Jubiri et, al. (1999). The results show that the Eagle cement
company, with longer period of operation has higher absorbed dose rates than
the newly established Atlas and Rock Cements. The trend of the results in the
soil samples shows that the specific activities of the radionuclides are higher
in the storage/baggage area for the companies compared to the other areas
within the premises. Also, the radionuclides activities are higher than that of
the host community. These results suggest that the sitting of the companies may
have degraded the immediate environment minimally. The water samples revealed
that the dose rates are highest at the berthing/baggaging stations with a
gradual decrease downstream. Though the dose equivalents are within the
acceptable values for water, the toxicity of cement will naturally perturb the
chemical equilibrium of the riverbanks thus making them unsuitable for natural
fish breeding.
Table 2: Mean Specific Activities of the radionuclides
in the Soil Samples
SL
|
Radionuclides
concentration (Bg/kg)
|
Abs.
Dose rate
nGy/h
|
40K
|
238U
|
232 Th.
|
S11
|
241.21
|
82.02
|
6.41
|
49.60
|
S12
|
654.12
|
61.41
|
4.50
|
56.92
|
S13
|
463.23
|
43.33
|
4.91
|
41.31
|
S21
|
389.21
|
51.21
|
7.53
|
43.32
|
S22
|
542.02
|
56.55
|
6.81
|
51.52
|
S23
|
315.64
|
45.54
|
3.01
|
34.79
|
S31
|
564.2
|
25.14
|
3.32
|
36.68
|
S32
|
772.19
|
23.31
|
8.22
|
47.91
|
S33
|
315.24
|
6061
|
4.85
|
42.47
|
MEAN
|
473.9S± 165.27
|
49.90
± 17.34
|
5.51
± 1.72
|
44.95
± 6.75
|
Table 3. Mean Specific Activities of the Radionuclides In Water
Samples
SL
|
Radionuclides
concentration (Bg/l)
|
Abs.
Dose rate
nGy/h
|
40K
|
238U
|
232 Th.
|
W11
|
0.1210
|
41.20
|
0.0342
|
17.70
|
W12
|
0.1614
|
60.31
|
0.0480
|
28.91
|
W13
|
0.1412
|
53.23
|
0.0582
|
22.87
|
W21
|
0.3143
|
32.11
|
0.0312
|
13.81
|
W22
|
0.6631
|
71.21
|
0.0901
|
30.63
|
W23
|
0.5214
|
41.34
|
0.0622
|
17.80
|
W31
|
0.2978
|
35.27
|
0.0021
|
15.18
|
W32
|
0.4321
|
56.38
|
0.0070
|
24.21
|
W33
|
0.610
|
43.56
|
0.0081
|
18.72
|
MEAN
|
0.3624± 0.19
|
48.29
±12.07
|
0.0379± 0.0296
|
20.76
± 5.18
|
Table 4. Absorbed Dose Rates in Soil and Water In mSv/y
Sample location
|
Absorbed dose rate (nGy/h)
|
mSv/y
|
S11
|
49.60
|
0.42
|
S12
|
56.92
|
0.48
|
S13
|
41.31
|
0.35
|
S21
|
43.32
|
0.39
|
S22
|
51.52
|
0.44
|
S23
|
34.79
|
0.30
|
S31
|
36.68
|
0.31
|
S32
|
47.91
|
0.41
|
S33
|
42.47
|
0.36
|
W11
|
17.70
|
0.15
|
W12
|
25.91
|
0.22
|
W13
|
22.87
|
0.19
|
W21
|
13.81
|
0.12
|
W22
|
30.63
|
0.26
|
W23
|
17.80
|
0.15
|
W31
|
15.18
|
0.13
|
W32
|
24.21
|
0.21
|
W33
|
18.72
|
0.16
|
Generally,
these results show that the radiological health burden due to the operations of
these companies on the human populace is very insignificant and has neither
health implications nor affect the background ionization radiation and the
results obtained could therefore be that due to natural ionization radiation of
the environment.
Conclusion:
The study of the radionuclide concentration levels in soil
and water in/around Eagle, Rock and Atlas cement companies in Port Harcourt
has been carried out. The average
dose rates equivalent of 0.18mSv/y and 0.39 mSv/y were obtained for the water
and soil samples respectively. These values are lower than the MPL and
therefore do not pose health problems to the populace of the host communities
and do not affect the background ionization radiation of the environment.
However, these values may increase with longer period of operation.
Acknowledgement:
The author is grateful to the University of Port Harcourt
for funding this project through the NUC Research grant and the Management
and Staff of the Centre for Energy Research and Development
(CERD), ObafemiAwolowoUniversity and the cement companies are
appreciated.
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