Measurement of Natural Radioactivity Level and Radilogical Hazards in Sample of Bale Zone Oromia Ethiopia Using Gamma Spectrometry
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Date
2021-10-27
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Addis Ababa University
Abstract
In this study, our objective was to measure the level of activity concentration and
radiological hazards of soil samples from agricultural and virgin lands of Bale zone,
Oromia, Ethiopia. The activity concentrations of naturally occurring radionuclides
238U, 232Th, and 40K were calculated total for of twelve(12) which is six(6) from
agricultural and the other six(6) from virgin soil samples randomly collected from
four kebele's of Bale zone southeastern part of Ethiopia by mixing equal masses of
soil from three di_erent depths starting from 0 to 10cm,then 0 to 20cm, and 0 to
30cm. Gamma-ray spectrometer was applied using high-purity germanium (HPGe)
gamma-ray detector and a PC-based MCA that uses Genie 2000 Spectroscopy Software.
Additionally, in our some soil samples of two sites there is an arti_cial radionuclide
of 137Cs that fallout from any nuclear accidents can be seen when the
samples analyzed by Gamma-ray spectrometry using high-purity germanium. The
mean value of radioactivity concentrations of 238U , 232Th, and 40K were found to be
21:74_0:569 with ranged from 6:565_0:206 to 41:15_0:748, 71:72_1:95 with ranged
from 26:2_0:77 to 122_2:57 and 1111:5_3:39 Bq kg1 with ranged from 555_8:94
to 2180 _ 3:21 Bq kg1 , respectively, in agricultural soils and 18:89 _ 0:667 with
ranged from 7:54_0:378 to 30:25_1:340, 69:93_2:38 with ranged from 36:2_0:96
to 121:0_2:55, and 642:83_4:39 Bq kg1 with ranged from 413_7:01 to 808_1:21
Bq kg1 , respectively, in virgin soils. The radioactivity concentrations in agricultural
soils are higher than those in virgin soils as of phosphate fertilizers added to
agricultural land soils. Out of twelve samples the activity concentrations of the arti
_cial radionuclide 137Cs was measured by HPGe only in six samples. The mean
value was 1:542 _ 0:635 Bq kg1 with ranged of 0:451 _ 0:507 to 2:19 _ 0:151 Bq
kg1. The minimum activity concentration value of 137Cs was obtained for a soil
sample collected from virgin land, similarly the maximum value was measured in a
soil sample collected from virgin land site, which is no health e_ects on the people
living around the sites where soil samples were collected.
The Gamma-ray radiation of radiological hazards caused by speci_c radionuclides
of 238U, 232Th, and 40K was evaluated using di_erent hazard indices. The
mean values of radium equivalent activity (Raeq), absorbed dose rates (DR), annual
e_ective dose(ADR), external hazard index(Hex), and internal hazard index(Hin)
are 209:88 _ 3:617 Bqkg1 which ranged from 93:45 _ 2:110 to 296:46 _ 4:543 Bq
kg1, 101:76 _ 1:873 nGy h1 which ranged from 45:85 _ 1:001 to 138:73 _ 1:988
iii
nGy h1, 0:12 _ 0:002 mSvy1 with ranged from 0:06 _ 0:001 to 0:17 _ 0:002mSv
y1, 0.57, ranged from 0.25 to 0.80, and 0.625, ranged from 0.29 to 0.91, respectively,
were found in agricultural soils and 168:40_4:402 Bqkg1 with ranged from
98:92 _ 2:283 to 256:05 _ 4:147 Bqkg1, 79:28 _ 1:954 nGy h1 with ranged from
46:87 _ 1:058 to 119:01 _ 1:815 nGy h1, 0:098 _ 0:002 mSv y1 with ranged from
0:06 _ 0:001 to 0:15 _ 0:002 mSv y1, 0.46 with ranged from 0.27 to 0.69, and 0.51
with ranged from 0.31 to 0.75, respectively, were found in virgin soils samples. Further,
the annual dose rate was calculated only for outdoor. In a comparison of the
world wide average value calculated by UNSCEAR and ICRP with our results mean
value for absorbed dose rates (DR),and annual e_ective dose(ADR) were out of the
recommended mean values of 59nGy/h and 0.07mSv/y by these institutions. But,
others like radium equivalent activity (Raeq), external hazard index(Hex), and internal
hazard index(Hin) mean values were within the recommended value. Finally,
in all radiological hazard indices when we compare two sites( agricultural and virgin
lands), the mean values of agricultural soil were greater than the mean values of
virgin soil samples.
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Keywords
Natural Radionuclides, Activity Concentration Level, Radiological Hazard and HPGe Gamma-Ray Spectrometry