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Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 1
CHAPTER-I
INTRODUCTION:
All living organisms are continuously bombarded by radiation emanated
from naturally occurring radionuclide’s. There are two main sources of
background radiations, they are Terrestrial sources and Extra - terrestrial
sources.
Terrestrial sources: Terrestrial radiation is due to primordial radionuclide’s
such as 40
K , 238
U 232
Th present in varying amount in soil, rocks, water and
building materials and atmosphere. They were present at the origin of the earth
and have half lives that are of the same order of magnitudes as the age of the
earth. Although natural abundance of 40K ,238U and 232Th varies with
geological condition , they are widely distributed in the earth’s crust. Some
radionuclide like 232
Th has several members of its decay chain.
232Th ----->
228Ra ----->
228Ac ----->
228 Th ----->
224Ra ----->
220Rn 216Po -----
>212
Pb ----->212
Bi ---->
212Po ----->
208Pb (stable)
The artificial radiation is primarily from medical imaging. Other human
contributors include smoking, air travel, radioactive building materials,
historical nuclear weapons testing, nuclear power accidents and nuclear industry
operation. Radiation treatment for various diseases also accounts for some dose,
both in individuals and in those around them.
https://en.wikipedia.org/wiki/Medical_imaging
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 2
Extra - terrestrial sources: Cosmic rays that are extraterrestrial in nature are
important sources of external exposure. Cosmic radiations primarily consisting
of 87% proton, 12% alpha particles and 1% heavier nuclei. When these
radiations interacts with atoms and molecules in the atmosphere to create an air
shower of secondary radiation, including X-rays, muons, protons , pions,
electrons, and neutrons. The intensity of cosmic ray background increases
rapidly with altitude. The cosmic radiation at sea level usually manifests as 511
keV gamma rays from annihilation of positrons created by nuclear reactions of
high energy particles and gamma rays.
About 88% of the total exposure is from natural sources remaining 12%
is from artificial sources of radiation. Radiation from radio nuclides in earth’s
crust and in other terrestrial matrices give rise to both external and internal
exposure. Natural radiation levels generally remain constant with time but may
vary significantly with location due to variation in regional geology.
POLONIUM (210
Po):
Polonium is a chemical element with symbol Po with atomic number 84. It
was discovered in 1898 by Marie Curie and Pierre Curie. A rare and highly
radioactive element with no stable isotopes, polonium is chemically similar to
bismuth and tellurium, and it occurs in uranium ores.
https://en.wikipedia.org/wiki/Air_shower_(physics)https://en.wikipedia.org/wiki/Air_shower_(physics)https://en.wikipedia.org/wiki/X-rayhttps://en.wikipedia.org/wiki/Muonhttps://en.wikipedia.org/wiki/Protonhttps://en.wikipedia.org/wiki/Pionhttps://en.wikipedia.org/wiki/Electronhttps://en.wikipedia.org/wiki/Neutronhttps://en.wikipedia.org/wiki/Positronhttps://en.wikipedia.org/wiki/Chemical_elementhttps://en.wikipedia.org/wiki/Atomic_numberhttps://en.wikipedia.org/wiki/Marie_Curiehttps://en.wikipedia.org/wiki/Pierre_Curiehttps://en.wikipedia.org/wiki/Radioactivehttps://en.wikipedia.org/wiki/Isotopes_of_poloniumhttps://en.wikipedia.org/wiki/Bismuthhttps://en.wikipedia.org/wiki/Telluriumhttps://en.wikipedia.org/wiki/Uraniumhttps://en.wikipedia.org/wiki/Ore
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 3
2I0Po is a decay product of
210Bi which in turn is the decay product of
210Pb. It has a half life of 138.4 days and is an alpha emitter. The intermediate
isotope 210
Bi with a half life of five days is a β emitter. The main source of 210
Po
in the environment is 222
Rn, which is exhaled from earth's crust. 222
Rn ultimately
decays to the nuclides 210
Pb and 210
Bi. These radionuclides attach themselves to
aerosol particles and return to the earth by gravitational, electrostatic and by
atmospheric precipitation. The 222
Rn remaining within the earth's crust decays in
situ to 210
Pb and 210
Po. A small quantity of 210
Po also forms in the atmosphere
by the disintegration of 210
Bi and returns to the earth through atmospheric
precipitation. The first two processes are responsible for the supported 210
Po and
the third process is responsible for unsupported 210
Po.
Due to the α activity of 210
Po, it produces greater biological effect than
210Pb the β emitter. The equivalent dose resulting from a single disintegration of
210Po is 1000 times greater than the decay of
210Pb (Parfenov, 1974). Hence it is
grouped under highly toxic radioisotopes. The total amount of 210
Po in the
earth's crust is approximately 2.3 x 10-14
% of the total weight. From the
geophysical point of view, polonium is very important because of the
substantial decay energy involved and the corresponding contribution to the
heat balance of the earth's crust (Parfenov, 1974).
210Po content in the soil varies widely throughout the globe from 8.14 Bq
kg-1
to 219 Bq kg-1
(Parfenov, 1974). US Atomic Energy Commission reports
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 4
the 210
Po content of various soils as 33 Bq kg-1
in brown soils, 58.1 Bq kg-1
in
bruizen soils, 55.87 Bq kg-1
in gray brown, etc.
210Po whose half life is 138 days has appreciable growth in vegetation
during single growing season and has an additional build up during food storage
reaching equilibrium in one year.
Polonium has 33 known isotopes, all of which are radioactive. They
have atomic masses that range from 188 to 220 u. 210
Po (half-life 138.376 days)
is the most widely available radionuclide. The longer-lived 209
Po (half-life 125.2
± 3.3 years, longest-lived of all polonium isotopes) and 208
Po (half-life 2.9
years) can be made through the alpha, proton, or deuteron bombardment of lead
or bismuth in a cyclotron.
210Po is an alpha emitter that has a half-life of 138.4 days; it decays directly to
its stable daughter isotope, 206Pb. A milligram (5 curies) of 210Po emits about as
many alpha particles per second as 5 grams of 226Ra. A few curies (1 Ci equals
37 GBq) of 210Po emit a blue glow which is caused by excitation of surrounding
air.
https://en.wikipedia.org/wiki/Isotopes_of_poloniumhttps://en.wikipedia.org/wiki/Radioactivityhttps://en.wikipedia.org/wiki/Atomic_masshttps://en.wikipedia.org/wiki/Atomic_mass_unithttps://en.wikipedia.org/wiki/Leadhttps://en.wikipedia.org/wiki/Bismuthhttps://en.wikipedia.org/wiki/Cyclotronhttps://en.wikipedia.org/wiki/Alpha_decayhttps://en.wikipedia.org/wiki/Decay_producthttps://en.wikipedia.org/wiki/Leadhttps://en.wikipedia.org/wiki/Radiumhttps://en.wikipedia.org/wiki/Curiehttps://en.wikipedia.org/wiki/Becquerelhttps://en.wikipedia.org/wiki/Excited_state
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 5
LIST OF TABLES:
Table1: Origin of 210
po from the uranium series
Element Symbol
Atomic
Number
Z
Mass
Number A
Half-Life
(T1/2) in
Radiation
given out
Uranium I UI 92 238 4.5X109yr α
Uranium X1 UX1 90 234 24.1 day β, γ
Uranium X2 UX2 91 234 1.17 min β, γ
Uranium II UII 92 234 2.52X105yr Α
Ionium Io 90 230 8.0X104yr α, γ
Radium Ra 88 226 1622 yr α, γ
Radon Rn 86 222 3.825 day Α
Radium A RaA 84 218 3.05 min α, β
Radium B RaB 82 214 27.0 min β, γ
Radium C RaC 83 214 20.0 min β, α, γ
Radium C′ RaC′ 84 214 1.6X10-4
sec Α
Radium C″ RaC″ 81 210 1.30 min Β
Radium D (Lead
210)
RaD
(Pb-210) 82 210 22 yr β, γ
Radium E
(Bismuth-210)
RaE
(Bi-210) 83 210 5 day Β
Radium F
(Polonium)
RaF
(Po-210) 84 210 138 day α, γ
Radium G (Lead) RaG
(Pb) 82 206 Stable lead
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 6
Table-2: Natural exposure levels in high background areas.
Kerala, India 1600mRy-1
Black Forest, Germany 1800mRy-1
Central City, Colorado 2200mRy-1
Guarapari, Brazil 17000mRy-1
Ref: Iyengar (1989)
Table-3: Estimated Annual Exposure of Man to Natural Sources of
Radiation
In Areas of Normal Background.
Sources
Annual Exposure (mRy-1
)
External Internal Total
Cosmic rays
Ionizing component
Neutron component
Cosmogenic nuclides
28.0
2.0
- -
--
--
1.5
28.0
2.0
1.5
Primordial nuclides in soils and
rocks
Potassium-40
Rubedium-87
Uranium-238 series
Thorium-232 series
12.0
--
9.0
14.0
18.0
0.6
95.0
19.0
30.0
0.6
104.0
33.0
Total 65.0 134.1 194.1
By: Iyengar (1989)
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 7
Table-4: Singly occurring radio nuclides of terrestrial origin
Radionuclide
Abundance (%) Half-life (Years) Principal
Radiation
40K 0.012 1.2610
9 -
87V 0.25 610
15
87Rb 27.9 4.810
10
-
115In 95.8 6.010
14
-
123Te 0.87 1.210
13 EC
138La 0.089 1.1210
11
-
142Ce 11.07 >510
16
144Nd 23.9 2.410
15
148Sm 11.27 >210
14 -
176Lu 2.6 2.210
10
-
190Pt
0.013 6.910
11
EC-Electron Capture
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 8
Table-5: Gamma absorbed dose recorded in some places of Karnataka and
its comparison with all India and World average.
Gamma absorbed dose
nGyh-1
Region Reference
Literature values
77.4-146.2 Shimoga Anandaram (1998)
50-250 Mysore Nagaiah (1996)
75 Karnataka
Average
Nambi et al (1987)
24-85 World range UNSCEAR (1988)
89 All India
Average
Nambi etal (1987)
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 9
SIGNIFICANCE OF THE STUDY:
The occurrence of radio nuclides varies from place to place on the globe
depending on regional geology and geography. For example, the high
background radiation along the coastal belt of South India, places like Brazil
etc, has been found due to the presence of monazite sand. Relatively high
background radiation levels were also observed in some parts of Singhbhum
District, India, Southern Saskatchewan, Germany etc., due to the presence of
granites. The local population in such localities receives relatively a higher
radiation dose. Several researchers have measured the 210
Po activity in and
around nuclear power plants such as Kalpakkam and Kaiga (near the study
area of the present investigation). Measurement shows that 210
Po activity is
considerably high in these regions than other areas. Thus the characterization of
the various environmental matrices with respect to their radioactivity content is
essential for correlation of dose estimates.
The geology of Uttara Kannada includes Granites, Lateritic rocks, Iron
ore, Bauxite ore etc., and Soil types include lateritic soil, alluvial soil, red loamy
soil, cotton soil etc. As granites contain higher concentration of 235U and 232
Th
and also 40
K, one can expect higher terrestrial radiation level in this region.
Consequently, dose to population in this region could be higher than normal. It
was therefore proposed to study radiation level and 210
Po activity in various
environmental matrices of Costal uttarakannada. This type of work has not been
carried out so far in this part of the country and happens to be first of its kind.
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 10
OBJECTIVES:
The objectives of the present study were,
1. Estimation of ambient gamma exposure level in and around Costal Uttara
Kannada and hence to assess annual dose to the population.
2. Estimation of 210
Po in Soil, Rocks, sand and Minerals, collected from
various locations in and around Costal Uttara Kannada.
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 11
CHAPTER-II
REVIEW OF LITERATURE
I. AMBIENT GAMMA RADIATION LEVEL:
1. The World average for terrestrial gamma radiation dose rate is about 59
nGyh-1
UNSCEAR (2009) , The overall terrestrial gamma dose in Spain
as 53. nGyh-1
Quindos et al (1994). The average gamma ray dose at
outdoor environments of Canada (Grasty, Carson JM, et al (1984) ranges
from 18-44 nGyh-1
in Bulgaria (Vassilev 1991) with an average of 70
nGyh-1
for the outdoor and an average of 75 nGyh-1
for the indoor
environs. The Malaysian average is 92 nGyh-1
but the highest average
terrestrial gamma radiation dose rates was recorded in Rembau district is
383 18 nGyh-1 which is 4 times higher than Malaysian average and 6
times higher than world average.
2. In India, the average gamma absorbed dose in Karnataka as reported by
Nambi et al (1987) amounts to 85 nGyh-1
and All India Average reported
by the same group is 89 nGyh-1
. In the environs of Goa external dose
rates range from 30-87.8 nGyh-1
with a geometric mean of 70.3 nGyh-1
(Avadhani et al ,1998). In Singhbhum district, India gamma dose rates
range from 75.7 to 200.1nGyh-1
. Further they have found higher dose
rates near granite rocks (Raghuvanshi et al, 1994). Gamma absorbed dose
recorded in and around Shimoga by Anandaram (1998) ranges from 77.4
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 12
to 146.2 nGyh-1
.Gamma absorbed dose recorded in and around Mysore
by Nagaiah (1996) ranges from 50 to 250 nGyh-1
.
3. Olarinoye et al (2010) have measured the background radiation level at
the vicinity of three campuses of two major tertiary institutions in Minna,
Nigeria, using a portable Geiger-Mueller tube – based environmental
radiation dosimeter. They have reported the dose rate ranging from 0.125
– 0.184 . They have also reported the annual effective dose as
0.189 .
4. Maharana et al (2010) have measured gamma radiation levels (indoor and
outdoor) in the villages surrounding the uranium-enriched regions around
Jaduguda, India, using card-based CaSO(4):Dy thermoluminescent
dosemeters. They have reported the annual indoor and outdoor gamma
dose values as 980 and 924 , respectively.
5. Gerald Pinto et al (2010) have measured the gamma absorbed dose rates
in Udupi and Karkala taluks of coastal Karnataka, India, using the GM-
Survey meter. They have reported the dose rate ranging from 70 to
123
6. WENG Jianqing et al (1992~2004) have measured the ambient gamma
radiation level in Qinshan Nuclear Power Plants (QNPP) Base, the
northeast of Zhejiang Province using thermoluminescent dosimeter
(TLD). They have reported the dose rate ranging from 84 - 113 nGyh-1
,
with an average of 96nGyh-1
in the 13 years.
http://www.sciencedirect.com/science/article/pii/S100180420860010X
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 13
7. IdrishMiah (2003) has measured Indoor gamma dose rate in air using
TLDs in the Dhaka district, Bangladesh. He has reported the average
annual effective dose and the collective dose equivalent for the residents,
respectively as, 0.86 mSv and 172.2 man-Sv.
8. Sreenath Reddy et al (2010) have measured the natural background
gamma radiation levels in the Hyderabad and its surroundings,
India,using thermoluminescence (TL) dosimeters and Geiger-Muller
based R-survey meter. They have reported the dose rate ranging from
226 - 506 nGyh-1
for urban Hyderabad and 190- 462 nGyh-1
for
surroundings of Hyderabad.
9. Mohanty et al (2003) have measured The external gamma dose rate level
of Erasama coastal Region, eastern coast of Orissa, India. They have
reported the absorbed gamma dose rates in air due to the naturally
occurring radionuclides ranging from 650 - 3150 nGyh-1
, with a mean
value of 1925 718 nGyh-1.
10. Senthilkumar et al (1996) have measured Gamma absorbed dose rates in
air outdoors from soil samples collected from Thanjavur (Tamil Nadu,
India) using g-ray spectrometry. They have reported the dose rate
ranging between 32 nGy.h -1
and 59.1 nGy.h -1
, with an arithmetic mean
of 43.3 ±9 nGy.h -1
.
11. Sriharsha et al (2008) have measured the gamma exposure rate in Mysore
and Chamaraj Nagar district, Karnataka, India using Environmental
http://www.jmp.org.in/searchresult.asp?search=&author=B+Senthilkumar&journal=Y&but_search=Search&entries=10&pg=1&s=0
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 14
radiation dosimeter. They have reported the dose rate varying 122.7 to
231.4 nGyh-1
inside the temples and between 141.8 to 340.2 nGyh-1
outside the temples of the region. They have also reported the indoor dose
rate varying 112.2 to 197.5 nGyh-1
, with a median of 127.0 nGyh-1
. and
outdoor dose rate varying 140.9 to 298.4 nGyh-1
, with a median of
216.2nGyh-1
II. 210
Po IN THE ENVIRONMENTAL MATRICES:
INTERNATIONAL STATUS:
1. Richard B. Holtzman (1980) has reported the mean intake of 210Po as 0.06
Bq/day in U.S diets.
2. Fernando P. Carvallho (1995) has measured the 210Po in food stuffs. An
activity concentration of 210
Po as 0.23 Bq/Kg in rice, 0.18 Bq/Kg in
potato, 0.054 Bq/kg in leafy vegetables and 0.023 Bq/kg in non leafy
vegetables has been reported.
3. Korenkov et al (2000) have measured the 210Po content in the superficial
soil layer of Moscow. They have reported the activity range of 210
Po as
30-50 Bk/kg.
4. Ashraf E.M. Khater and H.A. AL-Sewaidan (2008) have measured the
210Po content in the selected phosphate fertilizers samples used in Saudi
Arabia. They have reported the activity range of 210
Po as 0.5–110 Bqkg-1
with a mean value of 25 Bqkg-1
.
http://www.ncbi.nlm.nih.gov/pubmed?term=Korenkov%20IP%5BAuthor%5D&cauthor=true&cauthor_uid=10900787
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 15
5. Che Abdul Rahim Mohamed et al (2006) have measured the 210Po and
210Pb content in in sediment around the Sabah water at Teluk Brunei,
Sipitang, Teluk Kimanis, Kota Kinabalu and Kuala Penyu in Malaysia.
They have reported the activity range of 210
Po as 0.413 dpm/g to 8.491
dpm/g and 210
Pb as 0.023 dpm/g to 2.767 dpm/g.
NATIONAL STATUS:
1. Rajan et al (1980) have reported the activity 0.12 Bq kg -1in Sweet potato,
0.23Bq kg -1
in Spinach for 210
Po respectively from the Kalpakkam
region.
2. Karunakara et al(1993) have investigated 210Po activity in the two types
of vegetation species collected from Kaiga. They have reported 210
Po
activity in Careya arborea to range from 1.81-5.16 Bq kg-1
In Terminalia
paniculata the 210
Po activity ranges from 2.82-5.20 Bq kg-1
.
3. Karunakara et al (1993) have reported geometric mean of 97.89Bq kg-1as
the activity of 210
Po in soil samples of Kaiga.
4. Anandaram(1998) has measured 210Po activity concentration in the soils
of Shimoga and has reported it to vary form 4.7- 43.5 Bq kg-1
.
5. Similar type of measurement by Nagaiah(1996) in the soils of Mysore
reports 210
Po activity to vary from 7.6-37.3 Bq kg-1
.
6. Raja and Shahul Hameed (2010) have measured the 210Po and 210Pb
content in the sediments of Parangipettai Coast, South East Coast of
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 16
India, They have reported the activity concentration of 210
Po and 210
Pb in
sediments as 4.38 Bq kg -1
and 2.31Bq kg -1 respectively.
7. Marbaniang et al (2010) have measured the 210Po content in the soil
samples at Domiasiat uranium deposit area, West Khasi Hills,
Meghalaya, India. They have reported the mean activity of 210
Po in soil
as124.8 +/-5.7 Bq kg-1
.
http://www.ncbi.nlm.nih.gov/pubmed?term=Marbaniang%20DG%5BAuthor%5D&cauthor=true&cauthor_uid=19242810
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 17
CHAPTER-III
ABOUT STUDY AREA: COSTAL UTTARAKANNADA DISTRICT:
The Uttara Kannada district is located in Karnataka state of India
between north latitudes130 55’ 02”to 15
0 31’ 01” and east longitudes 74
00’35”
to 75010’ 23”.The total area of Uttara kannada district is 10291 sq.km and the
total population in the district is around 14.36 lakh (as per 2011census), out of
which rural population constitutes 10.18 lakh. The District experiences tropical
monsoon climate.Genarally the weather is hot and humid on the coastal areas
throughout the year. The district falls under the Hilly agro climatic zone except
for western parts of Karwar, Ankola, Kumta, Honnavar and Bhatkal taluks
which fall under coastal agroclimatical zone. The temperatures start rising from
January to May. The highest day time temperatures rise sometime up to 380C.
Average annual rainfall is around 1166.3 - 3672.5 mm.
The geographical conditions are most favorable in the formation of
different types of soils. Heavy rainfall and alternative seasons of heat and cold
have lead to the formation of lateritic soil. Such lateritic rocks are the parent
material of rock types in and around Uttara kannada. The dense forest of
Western Ghats have provided very conducive environment for soil formation.
The hills of Western Ghats are covered by iron rich lateritic soil which is
reddish brown in colour. The narrow strip of Sharavathi enriches the river banks
and the flood plains with alluvial soil, which is the most potential soil for
agriculture. Along the coast the costal alluvial soil is occurring on western most
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 18
parts of the district. The most rugged hilly parts of the district are covered by
hilly type soil and surrounded by lateritic soil having less rugged features. On
eastern parts, the lateritic soils change to red loamy soils. Some parts on eastern
most parts of Mundgod taluk are covered by semi black cotton soils. In the
district there are two big and two medium sized industries and 7736 small
industries are located in the district. Main surface water resources Kali and
Kadra rivers are used for generating electricity Major Atomic power plant is
situated in the bank of River Kali at Kaiga.
Laterite Soil:
Laterite is a soil and rock type rich in iron and aluminum, and is
commonly considered to have formed in hot and wet tropical areas. Nearly all
lateritic are of rusty-red coloration, because of high iron oxide content. Laterite
(brick stone) occurs all along the coastal part and is restricted to the upper part
of the rock formation and is one of the important building stones of the district.
Alluvial Soil:
Alluvial soils are formed mainly due to silt deposited by Indo-Gangetic-
Brahmaputra Rivers. In coastal regions some alluvial deposits are formed due to
wave action. Rocks of the Himalayas form the parent material. Thus the parent
material of these soils is of transported origin.
https://en.wikipedia.org/wiki/Ironhttps://en.wikipedia.org/wiki/Aluminiumhttps://en.wikipedia.org/wiki/Iron_oxide
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 19
Characteristics:
They are immature and have weak profiles due to their recent origin.
Most of the soil is Sandy and clayey soils are not uncommon.
The soil is porous because of its loamy (equal proportion of sand and
clay) nature.
Porosity and texture provide good drainage and other conditions
favorable for agriculture.
Chemical Properties:
The proportion of nitrogen is generally low.
The proportion of Potash, phosphoric acid and alkalies are adequate
The proportion of Iron oxide and lime vary within a wide range.
Granite:
Though both granite and gneiss share common mineralogy, they differ in
the mode of origin. While, granite represents a typical igneous rock, gneiss is a
metamorphosed form of granite formed under specific temperature and pressure
within the earth's crust. However, they exhibit similar physical features. Both
are hard rocks and generally occur below the lateritic cover in some parts of
Uttara Kannada district.
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 20
Figure 1Geological Map of the Study Area
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 21
CHAPTER-IV
NUCLEAR INSTRUMENTATION:
1. MICRO R SURVEY METER
MICRO R SURVEY METER (Type: UR 705) manufactured by Nucleonic
Systems is exclusively meant for low level radiation measurement. It is an ideal
choice for environmental radiation monitoring and also for geological
prospecting for radioactive minerals.
SPECIFICATIONS OF MICRO R SURVEY METER
MICRO R SURVEY METER (Type: UR 705) manufactured by
NUCLEONIX SYSTEMS is primarily designed to measure low level gamma
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 22
and X-radiation. This portable survey meter, designed around integrally coupled
1” X 1” NaI (Tl) Scintillator to a 1
“ PMT, will offer an optimum
performance in counting low level Gamma radiation dose rate
TABLE-6: TECHNICAL SPECIFICATIONS OF SURVEY METER
Detector NaI (Tl) Scintillator, 1” d X 1” h Coupled to
Photomultiplier Tube. Detector assembly is
inside the survey meter enclosure.
Calibration Accuracy Better than +/- 10% (Specified with a Cs -137
standard source) from 100µR h-1
onwards.
Acquisition mode CPS: 0-50000 , CPM 0-5000
Dose rate 1-10000 µR h-1
Over range It can Show over range above the 10,000 µR h-1
Data Storage Can store up to 1000 data readings. Stored data
can be recalled back on to the display
Display Indication Dot Matrix LCD display for dose rate
Sensitivity 1 µR h-1
or 0.01 µ Sv h-1
User Interface START, STOP, PROG, STORE, INC, DEC,
POWER ON command buttons for setting of
parameter and operation of the instrument.
Power 6V, DC , BPL Excel or DURACELL ULTRA ,
Size AA , MN 1500 LR 6 (4 X 1.5V) Alkaline
cells
Dimension 106 W X 196 L X 95 H in mm ( Approx)
Weight 2 Kg
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 23
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 24
Block diagram Description:
A. +5V Regulator Output:
Unit draws power from +6V (1.5Vx4) dry cells. A low dropout regulator
provided, regulates and gives out +5V. This also provides signal for low battery
indication.
B. HV Circuit
This is a blocking oscillator based on DC to DC converter circuit which
generates required HV to the Plastic Scintillator assembly, gamma probe.
C. Gamma Detector Probe:
This is a 1”x1” NaI or 2”x2” NaI optically coupled to 1’ or 2” PMT. Also
it contains HV bleeder circuit required for the probe assembly.
D. Pulse Amplifier/ Discriminator Circuit
This receives negative tail pulses from the gamma probe and amplifies these
signals considerably before they are passed into discriminator followed by
which to monostable, to generate TTL SIGNALS. Input stage of amplifier is a
charge sensitive stage.
E. Real Time Clock (Optional)
This is a signal RTC chip with battery backup. It is provided only in case
the user specifically orders the unit with RTC. This facilitates the user to log
and store dose rate and RTC information simultaneously. Note: In normal
Micro-R Survey Meter RTC is not provided.
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 25
F. Microcontroller and Associated Circuit Blocks:
TTL pulses from the detectors are counted in a digit BCD counter, which
is interfaced to microcontroller. These counts are read by microcontroller,
counted for a Time Constant (TC) and shown on a LCD dot-matrix display in
terms of dose rate, CPS or CPM. There is a choice of three TCs, for the user.
The user interface to the unit is through keypad consisting of SIX
command buttons. Unit has additionally EEPROM chip which allows the user
to store readings up to 1000. Future the stored data readings can be down loaded
into PC under the control of data communication software. There is an RS232
port provided (optionally) for connecting to PC for data transfer. This unit
works on dry cells 4x1.5V (6V).
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 26
CHAPTER-V
METHODOLOGY:
AMBIENT GAMMA LEVEL:
The ambient gamma exposure in the environs of Costal Uttarkannada was
measured using an environmental radiation dosimeter (sensitivity 1R/h).
Measurements were made 1m above the ground level both in disturbed and
undisturbed areas of study locations.
210Po ANALYSIS
COLLECTION OF ENVIRONMENTAL SAMPLES:
SOIL:
An area of about 10 sq. meter on an open, undisturbed and level ground
surface, away from public road and building was selected. After removing the
top layer of vegetation and root a pit was dug up to 6 centimeters. The soil from
the pit was collected in a polythene bag and sealed. The radiation level was also
noted using radiation dosimeter.
Sample processing:
The soil sample collected from various sampling locations was dried
overnight in oven at 1100C and cooled.
ACTIVITY OF 210
Po IN SOIL
210Po is volatile. Processing of the samples at high temperature is likely to
lead to loss of polonium. So wet ashing of environmental samples was carried at
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 27
a temperature of 90°C for the radiochemical separation of 210
Po. Initially the
radionuclide’s were leached from the sample using nitric acid. After obtaining
the white residue the sample was treated with 10 ml of concentrated
hydrochloric acid and evaporated to near dryness. This procedure was repeated
5 to 6 times so as to bring the sample into HC1 medium. Finally the residue was
treated with 400 ml of 0.5N hydrochloric acid and stirred. If any turbidity
occurs the solution was filtered through Whatman 42 filter paper. The solution
was used for the analysis of 210
Po by electrochemical displacement method.
SPONTANEOUS DEPOSITION OF 210
Po
The sample solution was kept on a magnetic stirrer provided with heating
arrangement. The temperature of the solution was maintained between 90° C to
95° C. About 100 mg of ascorbic acid was added to the solution to reduce ferric
ions in the solution to ferrous ions which otherwise would interfere in the 2I0
Po
deposition. A clean, brightly polished and background counted (on both sides)
silver disc (0.1 cm thick and 3.5 cm dia) was suspended into the solution.The
solution was then stirred using the magnetic stirrer for a period of 6 hours.
Distilled water was added in small dose occasionally to maintain the level of
solution as well as to wash 210
Po sticking to the beaker and glass rod. At the end
of the plating period, the disc was removed, washed with distilled water, ethyl
alcohol and dried under IR lamp. It was then counted both sides for alpha
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 28
activity in an alpha counting system. The 210
Po activity was calculated using the
relation.
Where,
A = Activity in Bq kg-1
S = Background subtracted sample counts per sec
SD = Standard deviation = (Cs / Ts2+ Cb / Tb
2)
½
Cs and Cb are the sample and background counts respectively,Ts and Tb
are the sample and background counting periods respectively (s).
ε = Efficiency of the alpha counting system (%)
W = Mass of the dry sample taken for analysis in g
M = Moisture content in the sample (%)
Ep = plating efficiency (%)
The plating efficiency of the Po was determined through Po standard of known
activity spiked in the sample. The sample was brought to solution from using
radiochemical procedures as explained above. The Po in the solution was placed
on a silver planchet and the percentage of recovery was calculated using the
alpha counts obtained.
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
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RESULTS AND DISCUSSIONS:
TABLE-7: AMBIENT GAMMA EXPOSURE LEVEL IN THE STUDY
AREA
Sl.No. Location No. of
Readings
Absorbed Dose
in
Annual
Effective Dose
in
1
SDMCollege
Surroundings
60 76.3 93.5
2 ITI College 60 77.9 95.5
3 APMC Ramthirtha 60 86.7 106.3
4
Lateritic stone
Quarry
60
82.6 101.3
5
Indore stadium
Behind SDM college
60 96.7 118.6
6
Anjumanabad ,
Bhatkal
60
95.6 117.2
7
Near Karki
Mudaganapati
Temple
60
81.5 100.0
8 Apsarkonda 60 82.6 101.3
9
Granitic stone
Quarry near Karwar
60 131.3 161.0
10
Chandavar Stone
Quarry
60
119.4 146.4
11 Aresamikere 60 75.4 92.5
12 Kalsanmoote 60 61.1 74.9
13
Manki College
Ground
60
69.9 85.7
14 Anantavadi 60 73.8 90.5
15 Hosapattana bridge 60 62.4 76.5
16 Muroor Kumta 60 66.9 82.0
17 Kasarkod beach 60 45.6 55.9
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 30
Figure 2: Variation of Dose rate with Location
The knowledge of natural radiation level is very important due to the fact
that it accounts for the largest contribution to collective dose received by man.
This study provides the base line data required to assess the exposure of
population in areas of high natural radioactivity chosen for this study. The
ambient gamma levels have been measured at 17 different regions present in the
Uttara Kannada District The measurements have been made using
environmental radiation dosimeter ER-705. The results are summarized in Table
7
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
Dose rate in (nGyh-1)
Dose rate in (nGy/h)
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 31
It can be seen that the mean gamma dose rates vary from 45.6 to 131.3
nGyh-1
. Similar to the observations made elsewhere, ( Bruno Sansoni 1982,
Nagaiah,1996 Anandaram,1998)) higher than normal dose rates were found in
the regions where granitic outcrops were prominent and granite quarrying is
taking place. Granitic quarry near Karwar, Chandavar stone quarry, fall under
this category. Indoor stadium behind SDM college premises, Anjumabad in
Bhatkal, though the places are lateritic , the dose rates in these places were
found to be relatively high compared to the dose rate in Manki college ground,
Hosapattana Bridge, Kalsanmoote, etc. Very low dose rate was observed in the
Kasarkod beach, which is slightly low compared to dose rate of 75 nGy.h-1
in
Karnataka (Nambi etal 1987, BARC highlights, 1988) and is significantly low
compared to the dose rate observed near areas such as Ullal beach,
Manavalakurichi (Kerala), Kalpakkam beach, South west coast of Tamilnadu,
etc., where monazite is known to occur. Since the number of observations made
at sea level was small as compared to readings taken elsewhere in the study
area. Abnormal weather conditions and rough sea conditions might have
influenced significantly in obtaining such low dose rates. More definitive
conclusions can be drawn only after studying primordial radionuclide
distribution in this region.
The gamma dose rate in the Granitic quarry near Karwar, Chandavar
stone quarry, premises were found to be 131.3 and 119.4 respectively, which
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 32
are marginally high compared to the dose rates observed in general. It is known
that elevated levels of uranium, thorium and decay products are generally
present in granites. The higher radiation levels around these places are
obviously due to the presence of granitic outcrops in these regions.
The values of gamma dose rate obtained in the present study are
comparable with those obtained in the other environs and also with the world
average. They are well within the ranges of values observed at other places.
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 33
CONCLUSIONS AND SCOPE FOR FUTURE STUDY
The measurement of environmental is very much important, since
inhabitants of earth are continuously being exposed to such radiations ever since
the birth of this planet. In this respect monitoring of harmful health effects
caused by such radiations to the general public becomes highly essential. The
readings shown in this study have been taken very much painstakingly during
all the three seasons with the available resources and equipments. The authors
express their sincerest gratitude to the UGC for its constant encouragement and
support during all the stages of this project.
The Analysis of 210
Po as proposed in the project earlier is due on the part
of authors because of shortage of funding and will be taken up for the future
studies.
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 34
PHOTOGRAPHS
Behind S.D.M College
APMC Ramathirtha
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 35
Kasarkod Beach
Lateritic Stone Quarry
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 36
Lateritic Stone Quarry at Manki
Action Photograph
Studies On Terrestrial Gamma – Radiation And Polonium- 210 Activities In And Around Costal Uttarkannada
S. D. M. Degree College, Honnavar 37
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