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INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 4, No 4, 2014
© Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0
Research article
ISSN 0976 – 4402
Distribution of 226Ra and 222Rn in bore well and lake water of Mysore
Taluk, Karnataka State, India
Rajesh. B.M1, Chandrashekara. M.S1, Nagaraja. P2, Chandrashekara. A3, Paramesh. L1
1- Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore 570006, Karnataka State, India.
2- Department of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore 570006, Karnataka State, India.
3- BARC, Yelawala, Mysore - 571130, Karnataka State, India.
msc@physics.uni-mysore.ac.in
doi: 10.6088/ijes.2014040400011
ABSTRACT
The dose due to Ra-226 and Rn-222 concentration to the population of Mysore taluk through
drinking water pathway was assessed using radon emanometry method. Radium-226 activity
concentration varies from BDL to 73 mBql-1 with a median of 17.9 mBql-1 and Radon-222
concentration varies from 0.5 to 643.9 Bql-1 with a median of 23.8 Bql-1. Committed effective
dose due to radium and radon concentration through drinking water path was found to vary
from 15.6 to be 57.1 µSvy-1 with a geometric mean of 31.3 µSvy-1.
Keywords: Ra-226, Rn-222, Effective dose, Emanometry, Mysore.
1. Introduction
Radium-226 is one of major radioactive element found in water and food. Since it has a long
half-life of 1622 years and its chemical behavior is similar to calcium, it can be accumulated
in the human bones through ingestion of water. It can be measured directly using its α or γray emissions or indirectly by the emanation of its short-lived daughter product 222Rn.
Maximum Contaminant Level for 226Ra in drinking water is reported as 740 mBql-1 (20 pCil1
) (USEPA, 2000). Radon-222 is a chemically inert, colorless, odorless and a radioactive
noble gas. It is a daughter product of radium-226 and has a half-life of 3.82 days. Radon is
soluble in water and its mole fraction solubility is 2.3×10-4 at 15°C and 1.25×10-4 at 37°C and
its solubility decreases with increase in temperature and increases with increase in pressure.
This property allows a high concentration of radon in ground waters. Emanation of radon in
the soil and water depends on the meteorological conditions like temperature, pressure and
shows positive correlation with radon concentration and humidity, rainfall shows negative
correlation (Iveta et al., 2009). Higher radon concentration in water depends on, groundwater
which is extracted from drill holes in rocks or from springs flowing through crystalline rocks,
because these have higher concentration of radium than the average bedrock. Radon gas can
dissolve in groundwater and later be released into the air during normal household activities
such as showering, dishwashing and doing laundry. When radon accumulates in indoor air, it
can pose an increased health risk. It is a major contributor to the ionizing radiation dose
received by the general population. Exposure to waterborne radon may occur by ingestion
and inhalation. When inhaled over prolonged periods it is capable of causing lung cancer.
One of the risks associated with ingestion of water containing radon and radon progeny is
stomach and colon cancer. A study on dissolved radionuclides in aquatic environment gives
the key aspect for evaluation and control of natural exposure (UNSCEAR, 2000).
Received on November 2013 Published on January 2014
558
Distribution of 226Ra and 222Rn in bore well and lake water of Mysore Taluk, Karnataka State, India
2. Study area
The study area is Mysore taluk, Karnataka State, India and it lies between 12°13″–12°25″N
latitude and 76°27″– 76°45″E longitude, at an altitude of about 767 m amsl (Figure1) forming
a part of the catchment zone of the Cauvery and Kabini rivers at north west and south east
respectively. The archean rocks of south India are best developed in Mysore and are made up
of schists, gnesis, pegmatites and granites. The soil in Mysore region is red sandy and loamy
as in entire district. The population of Mysore taluk is about 10.38 lakhs. The study area
consists of precambrian gneisses with enclaves of amphibolites and limited zones of
ultramafic rocks. Pegmatitic intrusions into the Precambrian gneisses and schists have also
been found in several areas. The occurrence of ground water is under unconfined aquifer
conditions. The thickness of the weathered zone varied between 3 m and 5 m over much of
the region. Outcrops of most of the rocks are present in almost all elevated regions and along
valley cuts. Large diameter shallow (10–12 m depth) dug-wells and deep (35–60 m depth)
bore wells provide the major source of water in the remaining portions of the study area. A
masonry wall is normally constructed in the dug-wells to a depth of 1 to 2 m below ground
level. In bore wells, depending upon the nature of rock formations, unslotted casing is
installed up to a depth of 5 to 6 m below ground level and slotted casings from 6 to 15 m,
depending upon the thickness of the weathered/fractured zones (Ramakrishnan and Swami
Nath, 1981; Shashikumar et al., 2008).
Figure 1: Study area
Rajesh. B.M
International Journal of Environmental Sciences Volume 4 No.4, 2014
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Distribution of 226Ra and 222Rn in bore well and lake water of Mysore Taluk, Karnataka State, India
3. Materials and methods
3.1 Estimation of 222Rn and 226Ra activity by Emanometry Method
Forty-five water samples were collected from ground water source like bore wells and
surface water like lakes at different locations of Mysore taluk. The 226Ra and 222Rn activity
concentration in water samples was estimated by the radon emanometry. Water sample was
collected in pre acid cleaned airtight plastic bottles in a gentle manner to prevent the air
bubbles inside the container and to control the aeration during the water sampling process,
which might lead to out gassing resulting in improper radon estimation. For radium, about 20
liter of water was collected and pre concentrated to 70 ml. In this method, about 70 ml of the
water sample was transferred into the bubbler of 100 ml size by the vacuum transfer
technique (Figure2) and it kept for a known period of 21 days to attain equilibrium between
radium and radon. The dissolved radon in the water was transferred into a pre-evacuated and
background counted ZnS (Ag) scintillation cell of size 150 cc. The scintillation cell was
stored for 180 minutes to allow radon to attain equilibrium with its daughters and then it was
coupled to a photomultiplier and programmable alpha counting system. The concentration
was calculated using the following equations (1) and (2) (Raghavayya et al., 1980;
Shashikumar et al., 2011) .
6 . 97 × 10 − 2 × D
222
Rn Bql − 1 =
V × E × e − λ T × 1 − e − λ t _________________________________ (1)
6 . 97 × 10 − 2 × D
226
Ra mBql − 1 =
V × E × 1 − e − λ t × e − λ T × 1 − e − λθ ____________________ (2)
(
(
)
(
)
) (
(
)
) (
) (
)
Where, D = counts above background, V = Volume of water (70 ml), E = Efficiency of the
scintillation cell (74 %), λ = decay constant for radon (2.098 x 10-6 s-1), T = Counting delay
after sampling, t = Counting duration (s) and θ = build up time in the bubbler (s).
Figure 2: Radon Bubbler
Rajesh. B.M
International Journal of Environmental Sciences Volume 4 No.4, 2014
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Distribution of 226Ra and 222Rn in bore well and lake water of Mysore Taluk, Karnataka State, India
3.2 Dose due to 222Rn and 226Ra concentration in water
The committed effective dose for the population of the region was estimated using the
concentration of 222Rn and 226Ra in water samples. The parameters for the inhalation pathway
were 222Rn concentration in water, air water concentration ratio of 10-4, indoor occupancy of
7,000 hours per year and inhalation dose coefficient applied is that for the gas. The effective
dose to the ingestion mainly depends upon the amount of water consumed by a human being
in a day. The dose due to inhalation and ingestion are calculated by the equation (3, 4 & 5)
(Kovacs et al., 2003; UNSCEAR, 2000; Yu et al., 1994).
Inhalation dose (Sv) = 222Rn conc. (Bq l-1) × 10-4 × 7,000 h × 0.4 × 9 nSv (Bq h m-3)-1____(3)
Ingestion dose (Sv) = 222Rn conc. (Bq l-1) × 365 l y-1 × 3.5 nSv Bq-1_________________ (4)
Ingestion dose (Sv) = 226Ra conc. (Bq l-1) × 365 l y-1 × 280 nSv Bq-1________________ (5)
Committed effective dose (Sv) = Dose conversion factor × water consumption × duration of
consumption × Concentration of 226Ra and 222Rn + Inhalation dose due to 222Rn
4. Results and discussion
The radon and radium concentration in different types of water samples was estimated using
radon emanometry. Radium concentration varies from 0.72 to 72.9 mBql-1 with a median of
17.9 mBql-1 and Radon concentration varies from 0.5 to 643.9 Bql-1 with a median of 23.8
Bql-1. In bore well it varies with an average of 21.7 mBql-1 and 64.5 Bql-1 and in lake it is
18.42 mBql-1 and 29.4 Bql-1. Distribution of 226Ra and 222Rn activity concentration and the
corresponding dose to the population at different hoblies of Mysore taluk is presented in table
1 and fig3. Statistical variation of 226Ra and 222Rn concentration in water samples is shown in
table 2.
19% of the samples show less than permissible limit of 11.1 Bql-1, which is proposed by
USEPA for radon concentration through water intake, only one sample shows concentration
above the 400 Bql-1, which resulting an indoor radon concentration of 150 Bqm-3 for which
remedial action is recommended by the USEPA. Low radon concentrations are observed in
surface water due to lack of major contact with radon emanating mineral material and also
aeration of radon gas to the atmosphere. Highest radon concentration of 643.9 Bql-1 is
observed in the Mysore hobli (Bandipalya village located behind the Chamundi hill) which is
rich in granite rocks. Previous studies on soil and rock samples at Chamundi hill show
highest concentrations of radium and thorium radionuclides. When granite rock contains high
radium concentrations, the ground water originating from granite formations is accompanied
by leaching out of radionuclides with ground water (Kerur et al., 2010; Mose et al., 2010).
Due to this reason, the highest radon concentrations in bore well water samples have been
observed. Radium concentration of 20 mBql-1 and above are seen in few ground water of
Yelwala hobli and in one lake at Mysore hobli (Kalkuare) shows 72.9 mBql-1, which result
was attributed with the local geological region and the same was confirmed by the highest
radon concentration. Activity concentration of 222Rn and 226Ra in bore well and lakes at
different villages of Mysore Taluk is presented in table 3 and table 4 respectively and
distribution of 226Ra and 222Rn in bore wells and lakes are presented in fig 4. The dose due to
222
Rn is divided into two parts, namely the dose from ingestion and the dose from inhalation.
For the ingestion and inhalation part, 222Rn and its progeny in water impart a radiation dose to
the stomach and lung respectively. Computing from the radium and radon activity
concentrations in water samples, the committed effective ingestion dose vary from 15.57 to
56.98 µSvy-1 and inhalation dose due to radon pathway vary from 0.01 to 0.08 µSvy-1.
Rajesh. B.M
International Journal of Environmental Sciences Volume 4 No.4, 2014
561
Distribution of 226Ra and 222Rn in bore well and lake water of Mysore Taluk, Karnataka State, India
According to WHO the dose received by population is below 100 µSvy-1 (Chandrashekara et
al., 2012; Shashikumar et al., 2008; WHO, 2012).
Table 1: 222Rn and 226Ra activity in water and the corresponding committed effective dose
Mysore
Taluk :
Hoblies
Yelawala
Jayapura
Mysore
Mysore
City
Varuna
Radon
Conc.
(Bq l-1)
Radium
Conc.
(m Bq l-1)
Inhalation
dose due to
222Rn
(µ Svy-1)
Ingestion dose
due to 222Rn
and 226Ra
(µ Svy-1)
25.52
30.5
42.7
20.1
18.3
23.78
0.064
0.076
0.011
34.66
40.83
56.98
Committed
effective dose
due to 226Ra
and 222Rn
(µ Svy-1)
34.72
40.91
57.09
18.27
5.68
0.046
23.92
23.97
12.02
1.84
0.032
15.54
15.57
5. Conclusion
222
Rn concentrations in 81% of the water samples are higher than the MCL 11.1 Bql-1
prescribed by the EPA. 226Ra activity concentration in Mysore city and the hoblies of Mysore
taluk was very much less than the guidance value of 740 mBql-1 proposed by the USEPA.
Consequently, the collective effective dose to the adult population was found to vary from
15.6 to be 57.1 µSvy-1, which is less than 100 µSvy-1 as recommended dose limits by WHO.
The reason for higher radon concentration due to local geology of this region, which consists
of different types of granites.
Figure 3: Distribution of 226Ra and 222Rn activity concentration in Mysore taluk
Rajesh. B.M
International Journal of Environmental Sciences Volume 4 No.4, 2014
562
Distribution of 226Ra and 222Rn in bore well and lake water of Mysore Taluk, Karnataka State, India
Table 2: Statistical variations of 226Ra and 222Rn in water samples
Sl. No
1.
2.
3.
4.
5.
6.
Statistical Variance
Max
Min
Average
GM
Median
SD
Rn-222 (Bql-1)
643.90
BDL
53.12
22.83
23.80
101.50
Ra-226 (mBql-1)
72.90
BDL
20.48
13.39
17.90
16.00
Table 3: Activity concentration of 222Rn and 226Ra in bore well water samples at different
villages of Mysore Taluk
Sl. No
Locations
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
Max
Min
Average
Erappanakoppalu
Seegalli
Ankanahalli
Gommata giri
Ratnahalli
Mallegowdana Koppalu
Hulikere
Naganahalli
Hulikere
Koorgalli
Hosakote
Sagarakatte
Krishna Raja Sagara
Kumarabidu
Belagola
Mandakalli
Bandipalya
Kumbara koppalu
Manasagangothri
T K Layout
Jayanagara
Lashkar Mohalla
Vijaya Nagara
Mahadevi Colony
Dandikere
Varuna
Chatnahalli
Puttegowdana Hundi
Varkodu
Chikkahalli
Type
Rn (BqL-1)
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
Bore well
12.5
97.9
19.7
147.5
108.7
18
39.6
16.9
40
27.3
42
18.4
23.8
30.5
63
92.3
643.9
194
10.6
12.3
13.3
28
-27.2
7.3
19.5
33.8
7.5
57.2
19.3
643
0.5
64.5
Ra (m BqL1)
6.3
47.8
29.5
39.5
47
34.7
27.6
10.2
29
16.3
16
10.2
18.2
18.3
39
33.7
-21.7
1.73
1.2
12.8
15.51
1.17
-BDL
-----47.8
BDL
21.7
Rajesh. B.M
International Journal of Environmental Sciences Volume 4 No.4, 2014
563
Distribution of 226Ra and 222Rn in bore well and lake water of Mysore Taluk, Karnataka State, India
Table 4: Activity concentration of 222Rn and 226Ra in lake water samples at different villages
of Mysore Taluk
Sl. No
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Locations
Nagavala
Ratnahalli
Nodehalli
Halebeedu
Belawadi
Mandakalli lake
Bandipalya
Kal kuare
Devikere
Hebbal Kere
Karanji kere
Dalvai lake
Marse
Shettikere
GiriBetta
Max
Min
Average
Type
Lake
Lake
Lake
Lake
Lake
Lake
Lake
Lake
Lake
Lake
Lake
Lake
Lake
Lake
Lake
Rn (BqL-1)
13.9
0.5
19.3
35.1
48
18.3
62.8
137.4
1.6
51.6
BDL
1.4
17.3
0.8
4.2
137.4
BDL
29.4
Ra (m BqL-1)
4.6
31.7
17.9
17.3
27.1
8.6
20.3
72.9
9.5
19.2
BDL
5
4.7
BDL
0.72
72.9
BDL
18.42
Figure 4: Distribution of 226Ra and 222Rn activity concentration in Bore wells and Lakes
Rajesh. B.M
International Journal of Environmental Sciences Volume 4 No.4, 2014
564
Distribution of 226Ra and 222Rn in bore well and lake water of Mysore Taluk, Karnataka State, India
Acknowledgement
This work had been carried out under the DAE, BRNS project. The authors thankful to the
Board of Research in Nuclear Sciences, Department of Atomic Energy, Government of India
for extending financial support for the present study. The authors sincerely thank Prof. P
Venkataramaiah, former Vice-Chancellor, Kuvempu University, India for his constant
guidance and encouragement.
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Distribution of 226Ra and 222Rn in bore well and lake water of Mysore Taluk, Karnataka State, India
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