Radiation Protection and Environment Pub
ISSN 0972-0464
Radiation Protection and Environment / Volume 33 / Number 4 / October-December 2010 / Pages 157-224
Radiation
Protection and
Environment
Vol. 34 / Number 1 / January-March 2011
Publication of INDIAN ASSOCIATION FOR RADIATION PROTECTION (IARP)
www.iarp.org.in
NATURAL RADIOACTIVITY LEVELS IN SOME ENVIRONMENTAL
SAMPLES OF SHAHPUR REGION OF NORTH KARNATAKA, INDIA
B.R. Kerur, T. Rajeshwari, N.M. Nagabhushana, S. Anilkumar1, K. Narayani1,
A.K. Rekha1, B. Hanumaiah2
Department of Physics, Gulbarga University, Gulbaga, 1Radiation Safety Systems Division,
BARC, Mumbai, 2 Vice-Chancellor, Babasaheb Bhimrao Ambedkar University, Lucknow, India.
E-mail: kerurbrk@hotmail.com
ABSTRACT: The natural radioactivity due to Radium, Thorium and Potassium in environmental samples
such as soil and building materials contributes to the radiation dose received by human beings signiicantly.
For assessing the environmental radiological impact to public it is essential to evaluate the activity levels of
these nuclides. Using high-resolution Gamma ray spectrometry system the soil and few building material
samples viz., granite, sand, brick collected from Shahpur region of North Karnataka were analysed and the
radioactivity levels were estimated. The absorbed dose rate due to natural radionuclides was also calculated
and the results are reported in this paper. The results obtained were observed to be normal in comparison
with the World literature values for almost all samples whereas granite samples showed relatively higher
activity and hence higher dose. This study provides a baseline data of radioactivity background levels in the
Shahpur region of Gulbarga district and will be useful to assess any changes in the radioactive background
level due to various man made processes.
Keywords: Natural radioactivity, radionuclide, radioactive equilibrium
high even though activity of these materials is at low level
(low level radioactivity). Around the world there are some
areas with sizable population that have high background
radiation levels. The high background radiation areas
are found primarily in Brazil, India and China (Nambi
et al., 1994; Baranwal et al., 2006). Due to the advanced
technology and modernization a person is prone to the
internal and external radiation and knowledge of natural
radioactivity and the determination of amount of radiation
dose received become important.
1. INTRODUCTION
Radiation is present everywhere in the environment
of earth, below the earth and in the atmosphere. Man
knowingly or unknowingly is continuously being exposed
to the radiation, nature itself being the signiicant source
of radiations. Radionuclides are found naturally in
air, water and soil and even in human body. Natural
radioactivity is common in granites, soil, sand, water and
building materials present around us. Natural background
radiation is of terrestrial and extraterrestrial origin
(UNSCEAR, 2000). The main contribution to terrestrial
background radiation is from naturally occurring
radionuclides 226Ra, 232Th and their daughter products
and singly occurring natural radionuclides such as 40K,
87
Rb present in varying amounts in soil, rocks, granites
and building materials. Some of the radionuclides from
these sources are transferred to man through ingestion
or inhalation, while the extraterrestrial radiation originates
from outer space as primary cosmic rays. Furthermore,
because of the occurrence of radionuclides in soil and in
vegetation, exposures will occur as a result of ingestion
(El-Arabi, 2007).The environmental radioactivity and
associated external exposure due to gamma radiation
from the environmental materials like soil, rock, water
etc., depend mainly on the geological formation and
composition of the region (Ramola et al., 2008). Hence
it is present everywhere within us and surrounding
environment in different concentrations. Also it is found
by many researchers that the accumulated dose can be
Soil and other environmental materials are
important components of environment that not only
contains compounds that support life but also contains
signiicant quantity of various radionuclides such as
232
Th, 226Ra, 222Rn, 40K etc. the gamma radiations emitted
from which are harmful to the life. External gamma dose
rates depend on the activity concentrations of the natural
primordial radionuclides 232Th, 226Ra and their decay
products and 40K present in soil and rock, which in turn
depend on the rock formation and geological composition
of the region.
In this context, the present work involves the
estimation of activity of the primordial radionuclides
and associated radiation dose received from soil and
building material (granite, sand, brick) samples collected
from Shahpur region of Gulbarga district of North
Karnataka. The study will provide a baseline data of
natural background radiation level of the region, which
55
is essential for understanding the future changes in
natural background radiation of the region, as there are
no earlier results.
radium and thorium daughter peaks were calculated
and the background count rate was subtracted from the
respective count rate. Then the activity of the nuclide
was calculated from the prominent gamma energies
viz., the 226Ra activity was estimated using the 295.1 keV
and 351.9 keV gamma energies emitted by 214Pb and
609.3 keV and 934.0 keV emitted by 214Bi and 186.1 keV
emitted by 226Ra and determination of the activity from
232
Th is based on the detection of gamma rays 238.6 keV
from 212Pb, 338.5 keV and 911.2 keV from 228Ac and 583
keV from 208Tl and 1620 keV from 212Bi. The activity of 40K
is based on the detection of it's 1460.8 keV gamma ray.
The integral counts under preselected photopeaks were
determined by subtracting from the total counts under
corresponding photopeaks obtained for the background
(taken with an empty container under identical geometry).
Then the activity of the nuclide was calculated from the
prominent gamma energies using:
2. GEOLOGY OF THE AREA UNDER STUDY
The area under study represents a part of N-E
Karnataka, which is well known for granite production and
also taking part in iron, manganese and gold ore mining
operations. The present work has been carried out in
Shahpur region of Gulbarga district of North Karnataka,
India. The Shahpur region lies in the North latitude 15° 50'
and East longitudes 74° 34'. The study region is rich in
granitic rocks which demarcate the Archaean nucleus.
A large deposit of uranium has been found in one of the
villages Gogi of Shahapur and it is important to study the
distribution of radionuclides in the surrounding regions.
3. MATERIALS AND METHODS
Activity (Bq) = (Net area under PP cps × 100 × 100)
/ (Eficiency (%) × BR (%))
Standard procedures were followed for sample
collection and preparation, where surface soil over
an area 50 cm × 50 cm and 5 cm depth was mixed
thoroughly and about 2-3 kg of each sample was
collected. The details of the collected samples were
noted and then coded. The irst two letters correspond
to the type of sample, next two digits correspond to
district place (Gulbarga-01), next two correspond to
taluk’s place (Shahpur-07) and last two correspond to
serial number. These samples were pulverized to a ine
powder and then sieved. The samples were then placed
for drying at 110°C for 24 hour to ensure that the moisture
is completely removed. Each coded pulverized sieved
sample was then transferred to a 250 ml cylindrical plastic
container. The containers were then weighed and sealed
carefully from outside using an adhesive and stored for
four to ive weeks to attain secular equilibrium between
226
Ra and 222Rn and it's decay products.
4. RESULTS AND DISCUSSION
The results observed for the 226Ra, 232Th and
K activity concentrations obtained for each of the
measured sample together with their corresponding
total uncertainties are summarized in Table 1. The
concentration of thorium, radium and potassium are in
the range from 18.46 to 122.4 Bq/kg, 11.75 to 97.5 Bq/kg
and 197.8 to 1340 Bq/kg respectively. The mean activity
of the three radionuclides was observed to be 38.86 Bq/
kg, 18.94 Bq/kg, and 546.3 Bq/kg respectively for the soil
samples and 67.67Bq/kg, 45.28 Bq/kg and 806.6 Bq/
kg for the building material samples of Shahpur region.
A correlation was studied between 226Ra and 232Th for
the soil samples of the study region shown in Fig. 1.
Radium and thorium activity demonstrated a positive
correlation with a coeficient of 0.5733 which is low and
predicts a slight geochemical incoherency between the
samples collected from Shahpur region. The correlation
plots between 226Ra and 232Th for all the building material
samples showed a good positive linear correlation of
value 0.9530 (Fig. 2) which predicts that the radium
and thorium activity are geologically and geochemically
coherent in case of building materials of the study region.
A correlation between the granite samples showed a
good positive correlation of 0.9984 between three granite
samples as in Fig. 3 which shows that radium is intrinsic
in country rock at Shahapur and geochemical coherency
is maintained.
40
The samples were analyzed using a high-resolution
gamma spectrometry system. The system comprises of a
high purity Ge (HPGe) detector with a relative eficiency
of 50% and full width at half maximum (FWHM) of 2
keV for 1.332 MeV γ-ray line of 60Co. The output of the
detector was analyzed using a PC based 8k multichannel
analyzer system (GAMMAFAST, Eurosys Mesures).
The detector was surrounded by 3” lead shield on all
sides to reduce the background radiations originating
from building materials and cosmic rays (Anilkumar
et al., 2001). Eficiency calibration for the system was
carried out using the standard uranium ore (RGU, IAEA)
in geometry available for the sample counting. The
samples were counted for a period of 60,000 seconds
and the spectra were analyzed for the photo peaks due
to radium, thorium daughter products and 40K. The net
count rate under the most prominent photo peaks of
To assess the radiation hazard, the UNSCEAR
(2000) has given the dose conversion factors for
converting the activity concentrations of 226Ra, 232Th and
40
K into absorbed dose (nGy h-1 per Bqkg-1) as 0.462,
56
Table 1: Activity, total absorbed gamma dose rate and dose equivalents for the different soil samples
Activity Concentration in Bq/Kg
Sample
232
226
40
name
Th
Ra
K
Soil
SL010711
26.14±0.7
11.81±0.6
651.1±9.9
SL010712
29.31±0.7
13.48±0.6
713.2±9.9
SL010708
56.60±0.6
29.90±0.8
1084±10
SL010732
35.33±0.6
14.85±0.7
197.8±6.7
SL010733
37.91±0.6
20.92±0.7
249.4±6.9
SL010734
41.04±0.6
15.78±0.7
683.4±8.3
SL010739
48.97±0.7
12.34±1.1
817.8±9.4
SL010740
18.29±0.5
13.26±0.7
468.0±7.5
SL010741
49.33±0.8
19.45±0.8
218.6±7.2
SL010742
48.89±0.7
19.91±0.8
664.9±8.8
SL010771
26.90±1.5
18.03±1.8
641.1±8.4
SL010773
38.77±1.8
28.89±1.8
461.5±8.2
SL010774
47.75±1.7
27.65±1.4
251.2±6.4
Mean
38.86
18.94
546.3
Building materials
GT010703
110.2±1.
69.92±0.4
1340±14.4
GT010704
106.6±1.0
52.35±1.1
1322±12.3
GT010709
121.1±0.4
68.65±0.7
987.3±10.3
GT010710
117.2±0.9
97.51±0.7
1121±13
GT010713
122.4±1.4
89.45±1.1
1234±17
GT010714
115.2±2.0
91.25±1.0
1125±14
SA010715
22.97±0.8
11.75±1.6
569.4±8.1
SA010716
18.46±0.8
15.42±1.0
687.5±11.7
SA010717
19.01±0.5
16.14±1.1
705.7±13.1
SA010718
17.65±0.7
14.57±0.8
667.6±15.7
BK010705
31.11±0.7
22.12±0.5
249.4±7.0
BK010706
40.91±0.5
18.32±0.8
220.6±7.2
BK010707
36.91±0.7
21.22±0.7
256.4±6.1
BK010708
41.89±0.6
23.92±0.6
275.2±8.5
Mean
67.67±13.0
45.28±9.3 806.6±113.0
226
Correlation between
for soil samples
R = 0.5733
32
Ra and
Dose rate
nGyh-1
Total effective Annual effective dose
dose µ Svy-1
equivalent µ Svy-1
48.40±1.1
53.67±1.5
93.20±1.1
36.45±1.3
42.96±1.0
60.58±1.0
69.38±1.3
36.69±0.9
47.90±1.1
66.45±1.1
51.31±2.1
56.01±2.3
52.09±1.9
55.01
296.8
329.1
571.5
223.5
263.4
371.5
425.4
225.0
293.7
407.5
314.6
343.4
319.4
337.3
237.4
263.3
457.2
178.8
210.7
297.2
340.3
150.0
235.0
326.0
251.7
274.7
255.5
267.5
154.7±1.4
143.7±1.6
146.0±0.9
162.6±1.4
166.7±2.1
158.6±2.2
43.05±1.5
46.94±1.4
48.37±1.5
45.23±1.4
39.41±1.0
42.37±1.0
42.79±1.0
47.83±1.0
92.03
978.9
881.2
895.4
996.9
1022
972.8
264.0
287.8
296.6
277.3
241.7
259.8
262.4
293.3
587.5
789.1
705.0
716.3
797.5
817.6
778.2
211.2
230.2
237.3
221.8
193.4
207.8
209.9
234.7
453.6
232
Th activity
226
30
232
Correlation between Ra and Th
activity for building material samples
R = 0.9530
100
28
Ra activity Bq/kg
80
24
22
20
18
60
40
226
226
Ra activity Bq/kg
26
16
20
14
12
0
10
15
20
25
30
35
40
45
50
55
0
60
40
60
80
100
120
140
Th activity Bq/kg
Th activity Bq/kg
Fig. 1: Correlation between 232Th and
for Shahapur region soil samples
20
232
232
226
Fig. 2: Correlation between 232Th and 226Ra activity for
Shahapur region building materials’ samples
Ra activity
57
0.604 and 0.0417 respectively. Using these factors, the
total absorbed gamma dose rate in air at 1m above the
ground level is calculated by using the formula:
rate measured from the study area with the national and
international literature values. Our measured values are
well within the national and UNSECAR 2000 reported
values.
D = (0.604CTh + 0.462CRa + 0.0417CK) nGyh-1
5. CONCLUSION
Where, CRa, CTh and CK are the activity concentrations
of Radium, Thorium, and Potassium in the samples in Bq/
kg respectively. It is clearly observed from the Table 1
that the mean gamma absorbed dose rate for soil is
55.01nGy h-1 and 92.03 nGy h-1 for building material
samples. Annual effective dose equivalent received by
a member is estimated using a conversion factor of 0.7
SvGy-1, with an outdoor occupancy of 20% assuming
that a person spends about 80% of his time indoors
(UNSCEAR, 2000). In the present case the annual
effective dose equivalent received from soil and building
material samples of Shahapur region is estimated to be
267.5 µ Svy-1 and 453.6 µ Svy-1. It can be observed from
the table that the building material samples especially
granite samples show a higher activity hence higher
dose which is not ignorable and may pose radiological
hazards in due future. The use of these materials for
construction purposes has to be given a second thought
from radiological point of view. In Table 2 gives the
comparison of the activity of radionuclides and dose
100
232
Correlation between
for granite samples
R= 0.9984
Th and
The results obtained have shown that the total
effective dose rate due to natural radioactivity of soil
varies from 223 to 572 µSvy-1, which infer that the
radiations are natural background radiations. The present
study shows that the values obtained in the present study
are well comparable with the national and international
values. Hence the study of natural radiation background
of this area is quite constant with other literature values
(places) and also over the period of time i.e., these values
practically independent of human practices and activities
at present. Further work is continued on varieties of the
samples in and around of this region (Rajeshwari, 2008
and Nagabhushan, 2009).
6. ACKNOWLEDGEMENTS
The authors are thankful to Dr. D.N. Sharma, Head,
RSSD, for his interest in this work and for analysing the
samples at their Laboratory. Authors are also grateful
to Shri D.A.R. Babu, Head, RMS and TS, RSSD, for his
encouragement and support in this work.
226
Ra activity
7. REFERENCES
Anil Kumar, Narayani Krishnan, S, Sharma, D N, and
Abani M C, (2001), Background Spectrum analysis: A
method to monitor the performance of a gamma ray
spectrometer, Radiation Protection and Environment,
24 (1&2), 195-200
80
70
226
Ra activity Bq/kg
90
60
Baranwal V C, Sharma S P, Sengupta D, Sandilya, M
K, Bhaumik B K, Guin R and Saha S K, (2006), A new
high background radiation area in the Geothermal region
of Eastern Ghats Mobile Belt (EGMB) of Orissa, India,
Radiation Measurements, 41, 602-610
50
106
108
110
112
114
116
118
232
Th activity Bq/kg
Fig. 3: Correlation between 232Th and
for Shahapur region granite samples
226
Ra activity
El-Arabi, A M, (2007), 226Ra, 232Th and 40K concentrations
Table 2: Comparison of the activities of radionuclides and dose rate in soil samples of Shahapur with
other literature values of the world
Location
Shahapur samples
Kalpakkam, tamilnadu
Kaiga: Mean
All India
China
USA
World Average
232
Th in Bq/kg
18–56
15–776
14.3
17–158
1–360
4–130
11–64
226
Ra in Bq/kg
12–30
5–71
33.0
7–152
2–690
4–140
16–110
40
K in Bq/kg Dose rate in nGy h-1
References
200–1084
36–70
Present work
200–854
24–556
Kannan et al (2002).
113.7
28.8
Narayana et al (2001)
43–766
–
Kamath et al (1996)
9–1800
13–760
UNSCEAR (2000)
100–700
26–278
UNSCEAR (2000)
140–850
38–293
UNSCEAR (2000)
58
Nambi, K S V, Subba Ramu, M C, Eappen, K P,
Ramachandran, T V, Murleedharan, T S, Shaik, A N,
(1994), A new SSNTD method for the measurement of
radon-thoron mixed working levels in dwellings, Bulletin
of Radiation Protection 17, 34-35.
in igneous rocks from eastern desert, Egypt and it's
radiological implications, Rad. Meas. 42, 94-100.
Kamath, R R, Menon, M R, Shukla, V K, Sadasivan, S,
Nambi, K S V, (1996), Natural and fallout radioactivity
measurement of Indian soils by gamma spectrometric
technique. Fifth National Symposium on Environment,
Calcutta, India, Saha institute of Nuclear Physics.
Narayana, Y, Somashekarappa, H M, Karunakara, N,
Avadhani, D N, Mahesh, H M, Siddappa, K, (2001),
Natural Radioacitivity in the soil samples of Coastal
Karnataka of South India, Health Physics Society, 80,
24-33.
Kannan, V, Rajan, M P, Iyengar, M A R, Ramesh, R, (2002),
Distribution of natural and anthropogenic radionuclides in
soil and beach sand samples of Kalpakkam (India) using
high pure germanium (HPGe) gamma ray spectrometry,
Appl. Rad. Isotopes, 57, 109-119.
Rajeshwari T, (2008), Natural Radionuclides Distribution
in Soil of Donimalai Region, Sandur of North Karnataka,
M Phil Dissertation. Gulbarga University, Gulbarga
Nagabhushan N M, (2009), Radiation studies of
environmental samples of North Karnataka, India, Ph D
Thesis. Gulbarga University, Gulbarga.
UNSCEAR (2000), Sources and Effects of Ionizing
Radiation. United Nations Scientiic Committee on the
Effect of Atomic Radiation, United Nations, New York.
Announcement
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59
Radiation Protection and Environment / Volume 33 / Number 4 / October-December 2010 / Pages 157-224
Radiation
Protection and
Environment
Vol. 34 / Number 1 / January-March 2011
Publication of INDIAN ASSOCIATION FOR RADIATION PROTECTION (IARP)
www.iarp.org.in
NATURAL RADIOACTIVITY LEVELS IN SOME ENVIRONMENTAL
SAMPLES OF SHAHPUR REGION OF NORTH KARNATAKA, INDIA
B.R. Kerur, T. Rajeshwari, N.M. Nagabhushana, S. Anilkumar1, K. Narayani1,
A.K. Rekha1, B. Hanumaiah2
Department of Physics, Gulbarga University, Gulbaga, 1Radiation Safety Systems Division,
BARC, Mumbai, 2 Vice-Chancellor, Babasaheb Bhimrao Ambedkar University, Lucknow, India.
E-mail: kerurbrk@hotmail.com
ABSTRACT: The natural radioactivity due to Radium, Thorium and Potassium in environmental samples
such as soil and building materials contributes to the radiation dose received by human beings signiicantly.
For assessing the environmental radiological impact to public it is essential to evaluate the activity levels of
these nuclides. Using high-resolution Gamma ray spectrometry system the soil and few building material
samples viz., granite, sand, brick collected from Shahpur region of North Karnataka were analysed and the
radioactivity levels were estimated. The absorbed dose rate due to natural radionuclides was also calculated
and the results are reported in this paper. The results obtained were observed to be normal in comparison
with the World literature values for almost all samples whereas granite samples showed relatively higher
activity and hence higher dose. This study provides a baseline data of radioactivity background levels in the
Shahpur region of Gulbarga district and will be useful to assess any changes in the radioactive background
level due to various man made processes.
Keywords: Natural radioactivity, radionuclide, radioactive equilibrium
high even though activity of these materials is at low level
(low level radioactivity). Around the world there are some
areas with sizable population that have high background
radiation levels. The high background radiation areas
are found primarily in Brazil, India and China (Nambi
et al., 1994; Baranwal et al., 2006). Due to the advanced
technology and modernization a person is prone to the
internal and external radiation and knowledge of natural
radioactivity and the determination of amount of radiation
dose received become important.
1. INTRODUCTION
Radiation is present everywhere in the environment
of earth, below the earth and in the atmosphere. Man
knowingly or unknowingly is continuously being exposed
to the radiation, nature itself being the signiicant source
of radiations. Radionuclides are found naturally in
air, water and soil and even in human body. Natural
radioactivity is common in granites, soil, sand, water and
building materials present around us. Natural background
radiation is of terrestrial and extraterrestrial origin
(UNSCEAR, 2000). The main contribution to terrestrial
background radiation is from naturally occurring
radionuclides 226Ra, 232Th and their daughter products
and singly occurring natural radionuclides such as 40K,
87
Rb present in varying amounts in soil, rocks, granites
and building materials. Some of the radionuclides from
these sources are transferred to man through ingestion
or inhalation, while the extraterrestrial radiation originates
from outer space as primary cosmic rays. Furthermore,
because of the occurrence of radionuclides in soil and in
vegetation, exposures will occur as a result of ingestion
(El-Arabi, 2007).The environmental radioactivity and
associated external exposure due to gamma radiation
from the environmental materials like soil, rock, water
etc., depend mainly on the geological formation and
composition of the region (Ramola et al., 2008). Hence
it is present everywhere within us and surrounding
environment in different concentrations. Also it is found
by many researchers that the accumulated dose can be
Soil and other environmental materials are
important components of environment that not only
contains compounds that support life but also contains
signiicant quantity of various radionuclides such as
232
Th, 226Ra, 222Rn, 40K etc. the gamma radiations emitted
from which are harmful to the life. External gamma dose
rates depend on the activity concentrations of the natural
primordial radionuclides 232Th, 226Ra and their decay
products and 40K present in soil and rock, which in turn
depend on the rock formation and geological composition
of the region.
In this context, the present work involves the
estimation of activity of the primordial radionuclides
and associated radiation dose received from soil and
building material (granite, sand, brick) samples collected
from Shahpur region of Gulbarga district of North
Karnataka. The study will provide a baseline data of
natural background radiation level of the region, which
55
is essential for understanding the future changes in
natural background radiation of the region, as there are
no earlier results.
radium and thorium daughter peaks were calculated
and the background count rate was subtracted from the
respective count rate. Then the activity of the nuclide
was calculated from the prominent gamma energies
viz., the 226Ra activity was estimated using the 295.1 keV
and 351.9 keV gamma energies emitted by 214Pb and
609.3 keV and 934.0 keV emitted by 214Bi and 186.1 keV
emitted by 226Ra and determination of the activity from
232
Th is based on the detection of gamma rays 238.6 keV
from 212Pb, 338.5 keV and 911.2 keV from 228Ac and 583
keV from 208Tl and 1620 keV from 212Bi. The activity of 40K
is based on the detection of it's 1460.8 keV gamma ray.
The integral counts under preselected photopeaks were
determined by subtracting from the total counts under
corresponding photopeaks obtained for the background
(taken with an empty container under identical geometry).
Then the activity of the nuclide was calculated from the
prominent gamma energies using:
2. GEOLOGY OF THE AREA UNDER STUDY
The area under study represents a part of N-E
Karnataka, which is well known for granite production and
also taking part in iron, manganese and gold ore mining
operations. The present work has been carried out in
Shahpur region of Gulbarga district of North Karnataka,
India. The Shahpur region lies in the North latitude 15° 50'
and East longitudes 74° 34'. The study region is rich in
granitic rocks which demarcate the Archaean nucleus.
A large deposit of uranium has been found in one of the
villages Gogi of Shahapur and it is important to study the
distribution of radionuclides in the surrounding regions.
3. MATERIALS AND METHODS
Activity (Bq) = (Net area under PP cps × 100 × 100)
/ (Eficiency (%) × BR (%))
Standard procedures were followed for sample
collection and preparation, where surface soil over
an area 50 cm × 50 cm and 5 cm depth was mixed
thoroughly and about 2-3 kg of each sample was
collected. The details of the collected samples were
noted and then coded. The irst two letters correspond
to the type of sample, next two digits correspond to
district place (Gulbarga-01), next two correspond to
taluk’s place (Shahpur-07) and last two correspond to
serial number. These samples were pulverized to a ine
powder and then sieved. The samples were then placed
for drying at 110°C for 24 hour to ensure that the moisture
is completely removed. Each coded pulverized sieved
sample was then transferred to a 250 ml cylindrical plastic
container. The containers were then weighed and sealed
carefully from outside using an adhesive and stored for
four to ive weeks to attain secular equilibrium between
226
Ra and 222Rn and it's decay products.
4. RESULTS AND DISCUSSION
The results observed for the 226Ra, 232Th and
K activity concentrations obtained for each of the
measured sample together with their corresponding
total uncertainties are summarized in Table 1. The
concentration of thorium, radium and potassium are in
the range from 18.46 to 122.4 Bq/kg, 11.75 to 97.5 Bq/kg
and 197.8 to 1340 Bq/kg respectively. The mean activity
of the three radionuclides was observed to be 38.86 Bq/
kg, 18.94 Bq/kg, and 546.3 Bq/kg respectively for the soil
samples and 67.67Bq/kg, 45.28 Bq/kg and 806.6 Bq/
kg for the building material samples of Shahpur region.
A correlation was studied between 226Ra and 232Th for
the soil samples of the study region shown in Fig. 1.
Radium and thorium activity demonstrated a positive
correlation with a coeficient of 0.5733 which is low and
predicts a slight geochemical incoherency between the
samples collected from Shahpur region. The correlation
plots between 226Ra and 232Th for all the building material
samples showed a good positive linear correlation of
value 0.9530 (Fig. 2) which predicts that the radium
and thorium activity are geologically and geochemically
coherent in case of building materials of the study region.
A correlation between the granite samples showed a
good positive correlation of 0.9984 between three granite
samples as in Fig. 3 which shows that radium is intrinsic
in country rock at Shahapur and geochemical coherency
is maintained.
40
The samples were analyzed using a high-resolution
gamma spectrometry system. The system comprises of a
high purity Ge (HPGe) detector with a relative eficiency
of 50% and full width at half maximum (FWHM) of 2
keV for 1.332 MeV γ-ray line of 60Co. The output of the
detector was analyzed using a PC based 8k multichannel
analyzer system (GAMMAFAST, Eurosys Mesures).
The detector was surrounded by 3” lead shield on all
sides to reduce the background radiations originating
from building materials and cosmic rays (Anilkumar
et al., 2001). Eficiency calibration for the system was
carried out using the standard uranium ore (RGU, IAEA)
in geometry available for the sample counting. The
samples were counted for a period of 60,000 seconds
and the spectra were analyzed for the photo peaks due
to radium, thorium daughter products and 40K. The net
count rate under the most prominent photo peaks of
To assess the radiation hazard, the UNSCEAR
(2000) has given the dose conversion factors for
converting the activity concentrations of 226Ra, 232Th and
40
K into absorbed dose (nGy h-1 per Bqkg-1) as 0.462,
56
Table 1: Activity, total absorbed gamma dose rate and dose equivalents for the different soil samples
Activity Concentration in Bq/Kg
Sample
232
226
40
name
Th
Ra
K
Soil
SL010711
26.14±0.7
11.81±0.6
651.1±9.9
SL010712
29.31±0.7
13.48±0.6
713.2±9.9
SL010708
56.60±0.6
29.90±0.8
1084±10
SL010732
35.33±0.6
14.85±0.7
197.8±6.7
SL010733
37.91±0.6
20.92±0.7
249.4±6.9
SL010734
41.04±0.6
15.78±0.7
683.4±8.3
SL010739
48.97±0.7
12.34±1.1
817.8±9.4
SL010740
18.29±0.5
13.26±0.7
468.0±7.5
SL010741
49.33±0.8
19.45±0.8
218.6±7.2
SL010742
48.89±0.7
19.91±0.8
664.9±8.8
SL010771
26.90±1.5
18.03±1.8
641.1±8.4
SL010773
38.77±1.8
28.89±1.8
461.5±8.2
SL010774
47.75±1.7
27.65±1.4
251.2±6.4
Mean
38.86
18.94
546.3
Building materials
GT010703
110.2±1.
69.92±0.4
1340±14.4
GT010704
106.6±1.0
52.35±1.1
1322±12.3
GT010709
121.1±0.4
68.65±0.7
987.3±10.3
GT010710
117.2±0.9
97.51±0.7
1121±13
GT010713
122.4±1.4
89.45±1.1
1234±17
GT010714
115.2±2.0
91.25±1.0
1125±14
SA010715
22.97±0.8
11.75±1.6
569.4±8.1
SA010716
18.46±0.8
15.42±1.0
687.5±11.7
SA010717
19.01±0.5
16.14±1.1
705.7±13.1
SA010718
17.65±0.7
14.57±0.8
667.6±15.7
BK010705
31.11±0.7
22.12±0.5
249.4±7.0
BK010706
40.91±0.5
18.32±0.8
220.6±7.2
BK010707
36.91±0.7
21.22±0.7
256.4±6.1
BK010708
41.89±0.6
23.92±0.6
275.2±8.5
Mean
67.67±13.0
45.28±9.3 806.6±113.0
226
Correlation between
for soil samples
R = 0.5733
32
Ra and
Dose rate
nGyh-1
Total effective Annual effective dose
dose µ Svy-1
equivalent µ Svy-1
48.40±1.1
53.67±1.5
93.20±1.1
36.45±1.3
42.96±1.0
60.58±1.0
69.38±1.3
36.69±0.9
47.90±1.1
66.45±1.1
51.31±2.1
56.01±2.3
52.09±1.9
55.01
296.8
329.1
571.5
223.5
263.4
371.5
425.4
225.0
293.7
407.5
314.6
343.4
319.4
337.3
237.4
263.3
457.2
178.8
210.7
297.2
340.3
150.0
235.0
326.0
251.7
274.7
255.5
267.5
154.7±1.4
143.7±1.6
146.0±0.9
162.6±1.4
166.7±2.1
158.6±2.2
43.05±1.5
46.94±1.4
48.37±1.5
45.23±1.4
39.41±1.0
42.37±1.0
42.79±1.0
47.83±1.0
92.03
978.9
881.2
895.4
996.9
1022
972.8
264.0
287.8
296.6
277.3
241.7
259.8
262.4
293.3
587.5
789.1
705.0
716.3
797.5
817.6
778.2
211.2
230.2
237.3
221.8
193.4
207.8
209.9
234.7
453.6
232
Th activity
226
30
232
Correlation between Ra and Th
activity for building material samples
R = 0.9530
100
28
Ra activity Bq/kg
80
24
22
20
18
60
40
226
226
Ra activity Bq/kg
26
16
20
14
12
0
10
15
20
25
30
35
40
45
50
55
0
60
40
60
80
100
120
140
Th activity Bq/kg
Th activity Bq/kg
Fig. 1: Correlation between 232Th and
for Shahapur region soil samples
20
232
232
226
Fig. 2: Correlation between 232Th and 226Ra activity for
Shahapur region building materials’ samples
Ra activity
57
0.604 and 0.0417 respectively. Using these factors, the
total absorbed gamma dose rate in air at 1m above the
ground level is calculated by using the formula:
rate measured from the study area with the national and
international literature values. Our measured values are
well within the national and UNSECAR 2000 reported
values.
D = (0.604CTh + 0.462CRa + 0.0417CK) nGyh-1
5. CONCLUSION
Where, CRa, CTh and CK are the activity concentrations
of Radium, Thorium, and Potassium in the samples in Bq/
kg respectively. It is clearly observed from the Table 1
that the mean gamma absorbed dose rate for soil is
55.01nGy h-1 and 92.03 nGy h-1 for building material
samples. Annual effective dose equivalent received by
a member is estimated using a conversion factor of 0.7
SvGy-1, with an outdoor occupancy of 20% assuming
that a person spends about 80% of his time indoors
(UNSCEAR, 2000). In the present case the annual
effective dose equivalent received from soil and building
material samples of Shahapur region is estimated to be
267.5 µ Svy-1 and 453.6 µ Svy-1. It can be observed from
the table that the building material samples especially
granite samples show a higher activity hence higher
dose which is not ignorable and may pose radiological
hazards in due future. The use of these materials for
construction purposes has to be given a second thought
from radiological point of view. In Table 2 gives the
comparison of the activity of radionuclides and dose
100
232
Correlation between
for granite samples
R= 0.9984
Th and
The results obtained have shown that the total
effective dose rate due to natural radioactivity of soil
varies from 223 to 572 µSvy-1, which infer that the
radiations are natural background radiations. The present
study shows that the values obtained in the present study
are well comparable with the national and international
values. Hence the study of natural radiation background
of this area is quite constant with other literature values
(places) and also over the period of time i.e., these values
practically independent of human practices and activities
at present. Further work is continued on varieties of the
samples in and around of this region (Rajeshwari, 2008
and Nagabhushan, 2009).
6. ACKNOWLEDGEMENTS
The authors are thankful to Dr. D.N. Sharma, Head,
RSSD, for his interest in this work and for analysing the
samples at their Laboratory. Authors are also grateful
to Shri D.A.R. Babu, Head, RMS and TS, RSSD, for his
encouragement and support in this work.
226
Ra activity
7. REFERENCES
Anil Kumar, Narayani Krishnan, S, Sharma, D N, and
Abani M C, (2001), Background Spectrum analysis: A
method to monitor the performance of a gamma ray
spectrometer, Radiation Protection and Environment,
24 (1&2), 195-200
80
70
226
Ra activity Bq/kg
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Baranwal V C, Sharma S P, Sengupta D, Sandilya, M
K, Bhaumik B K, Guin R and Saha S K, (2006), A new
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Th activity Bq/kg
Fig. 3: Correlation between 232Th and
for Shahapur region granite samples
226
Ra activity
El-Arabi, A M, (2007), 226Ra, 232Th and 40K concentrations
Table 2: Comparison of the activities of radionuclides and dose rate in soil samples of Shahapur with
other literature values of the world
Location
Shahapur samples
Kalpakkam, tamilnadu
Kaiga: Mean
All India
China
USA
World Average
232
Th in Bq/kg
18–56
15–776
14.3
17–158
1–360
4–130
11–64
226
Ra in Bq/kg
12–30
5–71
33.0
7–152
2–690
4–140
16–110
40
K in Bq/kg Dose rate in nGy h-1
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