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Estimation of natural radionuclide and exhalation rates of environmental radioactive

pollutants from the soil of Northern India

Vandana Devi, Rishi Pal Chauhan

PII: S1738-5733(19)30664-3
DOI: https://doi.org/10.1016/j.net.2019.11.016
Reference: NET 976

To appear in: Nuclear Engineering and Technology

Received Date: 3 August 2019

Revised Date: 17 November 2019
Accepted Date: 18 November 2019

Please cite this article as: V. Devi, R.P. Chauhan, Estimation of natural radionuclide and exhalation
rates of environmental radioactive pollutants from the soil of Northern India, Nuclear Engineering and
Technology (2019), doi: https://doi.org/10.1016/j.net.2019.11.016.

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© 2019 Korean Nuclear Society, Published by Elsevier Korea LLC. All rights reserved.
 Estimation of natural radionuclide and exhalation rates of environmental
radioactive pollutants from the soil of Northern India
Vandana Devi, Rishi Pal Chauhan*
Department of Physics, National Institute of Technology, Kurukshetra, Haryana, India, 136119
Emails: [email protected], [email protected]*
Abstract:
The estimation of radioactivity level is vital for population health risk assessment and geological point of view
and can be evaluated as rate of exhalation and source concentration (226Ra, 232
Th and 40
K). The present study
deals with the soil samples for investigation of radionuclides content and exhalation rates of radon –thoron gas
from different sites in northern Haryana, India. Absorbed dose and associated index estimated in the present
study are the measures of environmental radioactivity to inhalation dose. Effective doses received by different
tissues and organs by considering different occupancy and conditions are also measured. Exhalation rates of
radon and thoron are measured with active scintillation monitors based on alpha spectroscopy namely
scintillation radon (SRM) and thoron (STM) monitors respectively. Sample height was optimized before
measurement of thoron exhalation rate using STM. Average values of radon and thoron exhalation are found
16.6 ± 0.7 mBqkg-1h-1 and 132.1 ± 2.6 mBqm-2s-1 respectively. Also, a simple approach was also adopted, to
evaluate the thoron exhalation which accomplished a lot of challenges, the results are compared with the data
obtained experimentally. The study is useful in the nationwide mapping of radon and thoron exhalation rates for
understanding the environmental radioactivity status.
Keywords: Radon, exhalation and emanation, radionuclide concentration, dose, health risk

1. Introduction
Radioactivity is widespread in environment due to primordial radionuclides in surrounding and has adverse
effects on human health. One of the main concerns for the environmental radioactivity is radon (222Rn), which
is the decay product of radium present in earth crust and is recognized as the important source of natural
radioactivity exposure. Primary source of radon is soil which contains about a thousand times soil gas
concentration than atmosphere concentration. Radon indoor level is influenced by underneath soil gas
concentration and is enhanced with the use of materials having high source content for construction purpose.
The contribution of environmental radioactivity from various samples can be defined as activity concentration
(Bq/kg) of radionuclides (226Ra, 232
Th and 40K) present in them and the exhalation rate. Concentration of radon
and its sources i.e. radionuclides (radium and thorium) vary with geological and environmental conditions.
Therefore, measurement of radionuclides content is an important issue not only for health effect estimation but
also from biochemical and geochemical point of view [1-7]. Several studies have been performed to study the
level of radon (222Rn) and thoron (220Rn) in dwellings in connection with radon soil gas concentration [8-9].
222
Knowledge of the amount of natural radionuclide and Rn - 220Rn exhalation rates in soil is vital to assess the
attainable radiological risk and associated hazards index to human health and additionally to develop standards
with their use [10-13].
Radon exhalation rates are reported by several researchers using different techniques but only few studies are
done with thoron. Thoron is the short-lived isotope of radon present in the thorium radioactive series. Thoron
exhalation rate is likewise a significant issue not just on accounts of difficulties in its estimation due to its short

1
half-life yet in addition because of its high dose conversion factors [1-3, 9-10]. In recent past Canister technique
was used for radon exhalation rate measurement [6, 12] but the difficulty with the technique arises because of
thoron interference and leakage. Also, thoron exhalation cannot be measured with this technique [14-16]. This
study deals with the radon as well as thoron exhalation rate measurement using scintillation cells equipped with
different monitors and sampling arrangement i.e. flow mode or diffusion mode for thoron and radon
respectively. Present study also deals with the difficulties associated with thoron measurement.
The present study evaluates both exhalation rates (222Rn and 220Rn) and their radionuclide contents from the soil
samples in the proximity of Karnal district, lies on the western bank of the river Yamuna in northern Haryana,
India. Study is performed for this inhabited area by keeping in mind that this area has not been studied for
environmental radon and thoron so far. Researchers have contemplated the radioactivity level and 222Rn - 220Rn
exhalation rate in soil [9-10, 17-19] in the northern India. But a combined study of radionuclides and exhalation
rates with active techniques has not been performed for the study area so far. The estimations of radiological
parameters which are screening tool for the risk appraisal with the utilization of these materials for construction
purpose and obtained results are compared with universal suggested criteria as well as with other studies [9-11].
This study is also helpful in mapping of exhalation rates in country by providing radon exhalation data with
geographical location of each sampling site.

2. Experimental procedure
2.1. Study area and sample collection details
Area under examination belongs to the vast Indo-Gangetic plain to the southwest of Shivalik hills. This area
represents almost an alluvial plain without any conspicuous topographical features. Map of the study area along
with sample collecting sites is represented in Fig. 1. The district is bounded by latitudes 29.25° and 29.59° and
longitudes 76.27° and 77.13°. The district is well populated and rich in educational and research institutes.
Clayey loam and sandy loam are the major soil types. Some part of the district is sandy loam to fine sandy loam
and Yamuna River is one of the sources of drainage. Study is performed with soil samples from thirty locations
by collecting 3-4 samples from diverse sites of study area with their exact geographical location. Among them
35% of the samples are within 15Km range of the Yamuna river. Samples were packed in clean and dry poly
bags. The samples were first made free of moisture by drying them at 100 ºC in oven till the constant weight
was achieved and homogenized by sieving using mesh of sieve size 150 µm. The samples were then processed
to carry out further studies of radionuclides and exhalation rates.
2.2. Measurement of radionuclides (226Ra, 232Th and 40K) content in samples under study
For gamma dose estimation, measurement of present radionuclides in the samples are important and carried out
using NaI(Tl) scintillation detector. The samples were packed in measuring beaker of same dimension that was
utilized for standardization of detector of 8 cm in height and 7cm in diameter. Packing was ensured to be air
tight by sealing the box with adhesive tape on circumference of lid. To ensure secular equilibrium between
radionuclide and decay products they were then placed for at least one month. NaI(Tl) used for the measurement
is 5.08 x 5.08 cm2 in size and coupled to1K MCA card. Before starting the measurement detector was calibrated
using Co and Cs source. Counts were obtained after a counting period of 4-5 hour. Activity concentrations of
radionuclides were calculated in Bq/kg by using the counts per second, efficiency and transition probability for
the corresponding peak under study [13-14, 20].

2
 Fig. 1. Guide of the region under study marked with sample collecting sites (by red dots).

2.3. Estimation of radon exhalation rates in the samples under investigation

222
The rate of radon emission per unit area i.e. Rn exhalation rate is measured in the collected soil samples
utilizing Scintillation radon monitor (SRM) developed and calibrated by Bhabha Atomic Research Centre,
Mumbai, India. SRM is an active device dependent on the alpha particles detection resulting from the decay of
radon and its produced progenies into the cell. Measuring arrangement consists of cylindrical accumulator of
height 5 cm and radius 15 cm, with provision to attach cell from upper side. ZnS(Ag)is utilized as scintillation
material in the cell have volume of 150 cc [21]. The sample to be tested, of known weight (1kg) was placed into
the radon-tight accumulator and the accumulator attached to SRM in sensitive mode as illuminated in Fig. 2.
Radon starts to build up inside and enters into the cell after crossing the pin hole arrangement which used to
avoid thoron interference present into the accumulator. Time cycle of one hour was used for measurement and
an inbuilt algorithm displayed the radon concentration at regular interval of one hour using a conversion factor
of 1.2 cph/Bqm-3. Radon mass exhalation rate (E) in (Bqkg h ) is calculated by analysis of growing radon
concentration (C) with time (t) using the following relation (1) [8, 19, 21-22].

1 + (1)

Where V account for the effective volume including the volume of the scintillation cell and accumulator, is
the effective decay of radon account for natural decay, leakage and back diffusion rate, is initial radon
concentration.

2.4. Measurement of radon emanation factor

Emanation factor (ε), measures the radon that finally enters the permeable arrangement of the sample after its
creation in grains of sample was calculated by the following equation (2):
ε = E/ARa λ (2)
Where, E is measured 222
Rn exhalation rate from Equation (1), λ (h ) is the
-1 222
Rn decay constant and ARa refer to
radium content of the soil sample [7, 22-23].

3
 Fig. 2. A schematic experimental setup for radon exhalation rate measurement.

2.5. Estimation of thoron exhalation rates in the samples under investigation

The precise estimation of 220Rn exhalation rate is crucial from the perspective of radiation assurance particularly
for the remarkable areas having high thoron source. Thoron exhalation rate in the soil samples under
investigation was estimated utilizing scintillation thoron monitor (STM). In light of small half life of thoron (55
s), it can't be estimated utilizing a similar plan as utilized for radon exhalation rate estimation. So as to recognize
thoron all the more adequately, thoron sampling was done in flow mode in a closed loop arrangement including
accumulator, monitor and pump represented schematically in Fig. 3. In the flow mode operation, pump was kept
ON continuously and cycle of 15 min was used for complete mixing and saturation enables the uniform thoron
distribution after its production. In the small air volume and with the use of pump to accomplish the proper air
mixing, thoron concentration attains saturation very quickly.

Fig. 3. A schematic representation of experimental setup for thoron exhalation rate measurement.

The rate of change of 220Rn concentration C (Bq/m3) in chamber involves two terms to be specific, its generation
rate and its rate of decay which can be depicted by the relation [21, 24-25].

(3)

Where, J (Bqm-2s-1) is exhalation rate of 220Rn and A is the area of surface emitting 220Rn. After achieving stable
220
thoron concentration in the accumulator, the Rn exhalation rate (J) rising up out the material would thus be

4
able to be determined from the experimentally registered data of thoron concentration (C) by taking mean of
concentrations in the close chamber and surface (A) to volume (V) ratio of chamber using the following relation
(4) [7,14,22-25].

(4)

2.6. Measurement of thoron emanation factor

Mass exhalation rates for 220Rn can be estimated knowing the density of soil samples ( ) and its diffusion length
( ) with the following relation [10-14].

(5)
!" #$% ('/")

Where, z refers to the height of soil sample in the chamber. Since for thoron diffusion length is very small in
materials like soil, utilizing this approximation, the relation for Jm can be presented as

(6)
!"

220
Since Rn diffusion length is small, therefore, only the top surface of samples enclosed in the chamber would
contribute to thoron in the chamber. The thoron originating from the top surface can be considered to be direct
220
emission from the material grains. Therefore, the Rn mass can be perceived as thoron emanation rather its
exhalation and utilized in present investigation [10-14].

3. Results and discussion

3.1. Radionuclides (226Ra, 232Th and 40K) and radium equivalent concentration in soil samples
For the estimation of potential hazard, radionuclides content are measured using gamma spectroscopy with
scintillation detector in Bq/kg for the study area. Obtained results of activity concentrations of radium, thorium
and potassium together with the statistical uncertainty are depicted in Table 1. The obtained values of radium
content ranged from 41.8 ± 2.9 Bq/kg to 71.9 ± 5.6 Bq/kg with average of 52.0 ± 1.3 Bq/kg while thorium in
soil samples ranged from 136.9 ± 30.2 to 257.1 ± 10.3 Bq/kg with average of 187.0 ±6.8 Bq/kg. Presence of
potassium content (40K) in materials is also responsible for external radiation exposure by emitting gamma
radiations. Therefore, potassium contents are also measured in all samples under study and its concentration
ranged from 737.4 ± 38.5 Bq/kg to 2172.9 ± 52.2 Bq/kg with average of 1332.6 ± 92.3 Bq/kg. Some samples
show concentration of potassium on higher side which is due to soil contamination with the use of fertilizers.
Study area is known as rice bowl of India and have good rice production region which is allowed to dispose in
the agriculture land. Hence the green paddy contains varying amounts of potassium content in the soil samples.
The used fertilizers and TENORM materials are responsible for slightly higher values of potassium content [26].

5
Table 1. Radium (226Ra), thorium (232Th) potassium (40K) content and radium equivalent activity (Raeq)
concentration in soil samples.

Sr. No. Sample Longitude and Radium Thorium Potassium Radium equivalent
226 232 40
(Sample Code) Location Latitude Ra Th K Raeq(Bq/kg)
(Bq/kg) (Bq/kg) (Bq/kg)
1 (K-1) Samana Bahu 76˚54’38”, 29˚53’48” 46.4 ± 3.2 158.6 ± 12.1 737.4 ± 38.5 329.9
2 (K-2) Kurak Jagir 76˚54’50”, 29˚45’31” 48.0 ± 1.7 214.1 ± 11.0 870.0 ± 4.7 421.1
3 (K-3) Nilokheri 76˚55’37”, 29˚50’17” 41.8 ± 2.9 157.3 ± 10.1 1860.4 ± 1.5 409.9
4 (K-4) Chirov 76˚54’55”, 29˚40’48” 65.9 ± 6.8 166.2 ± 1.4 808.8 ± 24.3 365.8
5 (K-5) Mohri Jagir 76˚46’22”, 29˚47’16” 48.2 ± 5.8 168.5 ± 5.4 1764.1 ± 64.4 425.1
6 (K-6) Golpura 76˚45’26”, 29˚49’30” 54.3 ± 4.2 163.5 ± 16.4 780.1 ± 5.9 348.2
(K-7) Katlaheri 76˚49’49”, 29˚38’18” 54.3 ± 2.5 249.9 ± 1.4 1961.0 ± 31.7 562.7
8 (K-8) Tarori 76˚55’49”, 29˚48’43” 58.7 ± 2.5 250.2 ± 31.6 790.4 ± 34.4 477.4
9 (K-9) Jalmana 76˚42’21”, 29˚35’17” 43.4 ± 3.1 145.7 ± 8.9 753.6 ± 13.1 309.8
10 (K-10) Sambli 76˚47’33”, 29˚46’14” 51.8 ± 2.9 155.6 ± 6.5 1793.6 ± 69.9 412.5
11 (K-11) Kachwa 76˚53’23”, 29˚43’52” 55.1 ± 1.9 223.1 ± 27.4 1759.7 ± 45.3 509.6
12 (K-12) Manchuri 76˚45’50”, 29˚36’35” 49.9 ± 2.5 153.5 ± 0.7 1798.7 ± 58.7 407.9
13 (K-13) Jundla 76˚52’30”, 29˚39’09” 51.3 ± 2.7 222.6 ± 18.3 837.7 ± 34.4 434.1
14 (K-14) Barthal 76˚52’36”, 29˚52’45” 45.8 ± 2.3 147.9 ± 15.8 1838.5 ± 109.5 398.9
15 (K-15) Jamba 76˚47’58”, 29˚51’15” 49.5 ± 6.4 139.3 ± 17.9 1719.5 ± 32.6 381.0
16 (K-16) Gonder 76˚43’34”, 29˚39’54” 49.1 ± 1.8 233.7 ± 10.6 783.9 ± 42.2 443.7
17 (K-17) Nising 76˚45’10”, 29˚41’13” 47.6 ± 4.6 172.0 ± 2.7 1815.6 ± 4.3 433.4
18 (K-18) Chourpura 76˚07’03”, 29˚48’35” 51.8 ± 6.1 165.4 ± 12.4 1068.2 ± 109.9 370.6
19 (K-19) Bhadson 76˚58’45”, 29˚54’35” 48.5 ± 2.0 235.0 ± 17.6 1158.4 ± 40.8 473.7
20 (K-20) Biana 77˚06’28”, 29˚50’20” 43.3 ± 1.3 166.4 ± 8.2 866.0 ± 16.2 347.9
21 (K-21) Kamalpur Roran 77˚02’35”, 29˚49’02” 54.7 ± 4.1 231.9 ± 34.7 864.1 ± 46.9 452.8
22 (K-22) Gheer 77˚06’46”, 29˚47’28” 43.3 ± 3.2 257.1 ± 10.3 1728.7 ± 86.3 544.1
23 (K-23) Ramba 77˚00’05”, 29˚47’34” 55.0 ± 3.8 171.2 ± 26.4 1937.7 ± 17.7 449.0
24 (K-24) Kunjpura 77˚03’54”, 29˚44’14” 44.5 ± 4.4 228.9 ± 15.9 779.3 ± 8.9 431.9
25 (K-25) Indri 77˚02’28”, 29˚52’05” 53.4 ± 2.4 136.9 ± 30.2 1925.1 ± 71.5 397.4
26 (K-26) Randoli 77˚08’48”, 29˚49’52” 64.4 ± 9.3 185.8 ± 5.1 2172.9 ± 52.2 497.4
27 (K-27) Balheri 77˚59’29”, 29˚42’52” 56.1 ± 6.4 164.2 ± 3.5 1795.7 ± 17.7 429.2
28 (K-28) Muradgarh 77˚04’36”, 29˚51’36” 56.7 ± 8.6 168.4 ± 17.2 950.0 ± 44.5 370.6
29 (K-29) Padhana 76˚56’41”, 29˚48’57” 71.9 ± 5.6 209.3 ± 19.5 1085.7 ± 16.2 454.8
30 (K-30) Mugal Mazra 77˚05’18”, 29˚45’24” 55.8 ± 4.4 166.6 ± 40.7 974.4 ± 159.2 369.0
AM±SE* 52.0 ± 1.3 187.0 ± 6.8 1332.6 ± 92.3 422 ± 10.9

* AM = Mean and SE = standard error = SD/√ N, Where SD is standard deviation and N is the no of observations.

For the comparison of different samples having non-uniform radionuclide concentration, a common index in
terms of radium equivalent is used. For the assessment of the radiological hazard and also to overcome non-
uniformity in concentrations of individual radionuclides, radium equivalent is calculated using relation given in
Table 2 [1-2]. Radium equivalent vary from 309.8 to 562.7 Bq/kg with average of 422.0 ± 10.9 Bq/kg and found
less than that of uranium mines studied by other researchers [13]. Fig. 4 shows a comparison of all radionuclides
content and radium equivalent concentration. The estimated values of Raeq are found on somewhat higher side
than referenced worldwide value, which can be explained on the basis that it is a common index and is the

6
weighted sum of all three radionuclides concentration (226Ra, 232Th and 40K) [1-4, 27]. As explained earlier that
some samples have high values of potassium content which are responsible for slightly higher radium equivalent
for the samples. Study area lies on the south of Shivalik hills and higher values of radioactivity contents present
in soil and sand of hilly area have been found [10,18]. This region is famous for agriculture especially for rice
production and Yamuna river water is the main source of irrigation. Yamuna is originating from hilly region
which brought down the soil from hill sand which accounts for radioactivity in this area. Flowing water extracts
the material containing high radium and thorium content which can account for the obtained values of radium
equivalent activity higher for some samples. Hence being the southwestern bank of the river the region may
have some higher level of radioactivity in the sand mixed soil [8-10, 17].The information of radioactivity levels
is valuable so as to set the standards and guidelines in the light of global recommendations. Due to the
increasing social concern, a large number of research groups are engaged in the estimation of natural
radioactivity on national as well as worldwide levels. The concentration of the radionuclides found here are
under the recommended level of UNSCEAR and OCED [1-2, 27].

Fig. 4. Comparison of radionuclides (226Ra, 232Th and 40K) concentration and radium equivalent in samples.

3.2. Radiological Hazard and Risk Index Assessment

Materials having radionuclides content are health hazardous and their hazard index depends on the
concentrations of radionuclides present in them with their use in construction and daily life. Different hazardous
terms and index were calculated from the measured radionuclides concentration using the relations given in
Table 2 [1-2, 28-30] and are found to be less than that of dose in uranium mines [13]. Assessed radiological risk
emerging from the utilization of soil in development of abodes in terms of absorbed dose and different index are
presented in Table 3. Estimated values of alpha index lies from 0.21 to 0.36 with average of 0.26 ± 0.01. Values
of alpha dose for all the samples under study are less than one which is recommended for safety [1-2, 28]. Also,
calculated average value of gamma dose is 1.55 ± 0.44, is within the safe limit because value of that index less
than 2 i.e. <2corresponds to 0.3 mSv annual dose rate. Internal as well external hazard lies within the safe limit.
Additionally, inferred estimations of external annual effective dose rates do not surpass the average worldwide
exposure of 2.4mSvy-1 arises from natural sources [1-4, 28]. Hence potential radiation hazard posed by these
materials for construction purpose is not hazardous as to restrict their use. Therefore, they can be exempted from
the restrictions concerning level of environmental radioactivity in the investigation area. In this manner, these

7
soils can be exempted from the restrictions concerning radioactivity. The human beings are exposed to different
level of environmental radioactivity which varies according to geographical variation, environmental condition
and individual’s living standard. The activity concentrations of radionuclides in the soil give essential and
principal information of radioactivity with an impact on general wellbeing, plants and creatures [10-11].

Table 2. Estimation of various radiological hazard and index from activity concentrations of radionuclides.
Sr. Radiological hazard Index Specifications
References
No. and Formula used (Recommended level / worldwide average)
Radium equivalent activity (Raeq) Below 370 - Fine for houses
370 to 740 - Fine for industrial area
1 Raeq = ARa + 1.43×ATh + 0.077×AK 740 to 2,220 - Fine for Construction of roads etc. [1-2, 29-31]
Where ARa, ATh and AK refers to content of 226Ra, 2,220 to 3,700 - Fine for non-residential foundations
232
Th and 40K respectively. Above 3,700 - Not to be used for any type of construction

Representative level index (RLI) Gamma radioactivity estimation which associated with
2 different concentrations of specific radionuclide [27, 32]
(Recommendation is Unity)
-# 1% 2
*+, + +
150 100 1500
Calculated for the center of a standard room
Absorbed gamma dose rate (DR) (4 m×5 m×2.8 m) having thickness of the walls and the
3 density of the structure(concrete) are 20 cm and [1-2, 30-32]
3- (nGyh )
2350 kg m−3 respectively as per UNSCAER (2000)
0.92 -# + 1.1 1% + 0.080 2
(Indoor DR worldwide average value is 84 nGy h−1)

Calculated using DR with conversion factor of 0.7 Sv Gy−1

Effective dose rate (HR) in mSvy−1
4 for 0.2 outdoor occupancy factor proposed by UNSCEAR [1-3]
(Permissible level is 1 mSvy−1).
HR=DR×8766×0.2×0.7×10−6

Alpha exposure assessment due to inhalation originating

Alpha index (Iα)
from soils when 222Rn concentration increases from 200
5 [1-2, 28-30]
Bqm-3 in dwellings due to contribution of soil
-#
,;
(Recommended level is Iα<1)
200 <= ⁄>?

Iγ≤2 refers to dose of 0.3 mSvy−1

Gamma index (Iγ)
2<Iγ≤6 refers to dose of 1 mSvy−1
6 [1-2, 28-30]
Iγ>6 refers to dose of more than 1 mSvy−1 and should be
-# 1% 2
,A + +
avoided
300 <= ⁄>? 200 <= ⁄>? 3000 <= ⁄>?

C < 1 correspond to 1.5 mSvy-1

External and internal radiation hazard indices
D
-# 1% 2
C D + + [1-2, 29, 32]
7 370 <=⁄>? 258 <=⁄>? 4810 <=⁄>? And
And
-# 1% 2 C $ < 1 correspond to 1.5 mSvy-1
C$ + +
185 <= ⁄>? 259 <= ⁄>? 4810 <= ⁄>?

3.2.1. Effective Dose Rate to Different Tissues and Organs

Dose to different body organs and tissues Horgans is a function of fraction of time spend i.e. occupational factor
(OF) and can be calculated by

Horgans = OF x Aedr x F (7)

Where, Aedr and F refer to annual effective dose rate and dose conversion factor respectively. Values of
conversion factors are different for different organs and are given by O’Brien and Sanna [33-34]. In literature,
occupancy factor is 0.8 which is commonly used all over the world, but according to living standards of peoples
in India, Sharma et al. [9] gave satisfactory reasons for the variability of occupational factors. Different
occupancy factors were analyzed according to the populace indoor occupancy. The fraction of time spend
depends on climate, season and life style etc. can be taken as 0.1 (<0.1assumed for peoples live in
towns/villages amid the summer season.), 0.5 (for residential communities and urban areas, the part of the time
spent inside in the midst of the summer season is 0.5.), 0.3 (the weighted normal of all the populace range) and

8
0.8(commonly used occupancy factor). Hence, here dose to different body organs (Lungs, Ovary, Red bone
marrow RBM, Testes and whole-body WB) is calculated using the average value of annual effective dose,
occupancy factors of 0.1, 0.3, 0.5 and 0.8 and corresponding conversion factor for different organs. Comparison
of annual effective dose to different body organs for different occupancy factor is given in Fig. 5 and shows the
straight forward dependence of dose to the occupancy factor. The estimated dose due to radionuclide content to
different body tissues and organs was found to be well within the recommendation of ICRP [3].

Table 3. Estimated various radiological dose and hazard index using radionuclides content in soil samples.
Sr. Sample Representative Absorbed Annual Alpha Gamma External Internal
No. Code level index gamma dose effective dose Index index radiation radiation
RLI (DR) (nGy/h) (HR) (mSv/y) Iα Iγ hazard Hex hazard Hin
1 (K-1) 2.39 148.0 0.18 0.23 1.19 0.89 1.02
2 (K-2) 3.04 187.8 0.23 0.24 1.52 1.14 1.27
3 (K-3) 3.09 191.9 0.24 0.21 1.55 1.11 1.22
4 (K-4) 2.64 164.5 0.20 0.33 1.32 0.99 1.17
5 (K-5) 3.18 197.6 0.24 0.24 1.59 1.15 1.28
6 (K-6) 2.52 156.4 0.19 0.27 1.26 0.94 1.09
7 (K-7) 4.17 257.8 0.32 0.27 2.08 1.52 1.67
8 (K-8) 3.42 211.2 0.26 0.29 1.71 1.29 1.45
9 (K-9) 2.25 139.5 0.17 0.22 1.12 0.84 0.95
10 (K-10) 3.10 192.7 0.24 0.26 1.55 1.12 1.25
11 (K-11) 3.77 233.6 0.29 0.28 1.89 1.38 1.52
12 (K-12) 3.07 190.8 0.23 0.25 1.53 1.10 1.24
13 (K-13) 3.13 193.1 0.24 0.26 1.56 1.18 1.31
14 (K-14) 3.01 187.2 0.23 0.23 1.50 1.08 1.20
15 (K-15) 2.87 178.7 0.22 0.25 1.43 1.03 1.16
16 (K-16) 3.19 196.6 0.24 0.25 1.59 1.20 1.33
17 (K-17) 3.25 201.6 0.25 0.24 1.62 1.17 1.30
18 (K-18) 2.71 168.4 0.21 0.26 1.36 1.00 1.14
19 (K-19) 3.45 212.6 0.26 0.24 1.72 1.28 1.41
20 (K-20) 2.53 156.6 0.19 0.22 1.26 0.94 1.06
21 (K-21) 3.26 201.4 0.25 0.27 1.63 1.23 1.37
22 (K-22) 4.01 247.4 0.30 0.22 2.01 1.47 1.59
23 (K-23) 3.37 209.6 0.26 0.28 1.69 1.22 1.36
24 (K-24) 3.11 191.3 0.23 0.22 1.55 1.17 1.29
25 (K-25) 3.01 187.6 0.23 0.27 1.50 1.08 1.22
26 (K-26) 3.74 232.6 0.29 0.32 1.87 1.35 1.52
27 (K-27) 3.21 200.0 0.25 0.28 1.61 1.16 1.31
28 (K-28) 2.70 167.5 0.21 0.28 1.35 1.00 1.15
29 (K-29) 3.30 204.9 0.25 0.36 1.65 1.23 1.42
30 (K-30) 2.69 167.0 0.20 0.28 1.34 1.00 1.15
Mean ± SE 3.10 ± 0.08 192.5 ± 5.1 0.24 ± 0.01 0.26 ± 0.01 1.55 ± 0.44 1.14 ± 0.03 1.28 ± 0.03

9
 Fig. 5. Annual effective doses to different body organs for different occupancy.

3.3. Radon exhalation and emanation rates in samples under study

Radon exhalation rate was measured using closed accumulator technique in which the sample enclosed
hermetically in accumulator (Fig. 2). Radon concentration builds up to attain a saturation concentration in the
222
closed chamber. The build-up of Rn concentration (C) in accumulator was measured for one hour cycle
represented in Fig. 6 and continued until it gets saturated. This equilibrium concentration estimated with the
following relation [31].
C = Ceq 1 (8)
222
Where, Ceq is the asymptotic value of Rn concentration and refers to effective decay constant. Obtained
results of equilibrium radon concentration are given in Table 4. Equilibrium concentration for the samples under
study ranged from 96.1 ± 4.8 to 219.9 ± 3.2 Bq/m3 with average concentration of 146.7 ± 5.8 Bq/m3. This
varying equilibrium radon concentration is because of different radioactivity content in samples (Table 1) and
different soil parameters which results into different values of exhalation rates.

Fig. 6. Typical graph showing radon builds up concentration with time cycle of one hour.

Estimated values of radon exhalation rates are depicted in Table 4 with mean and standard deviation. Radon
mass exhalation varies from 9.9 ± 0.7 mBqkg-1h-1 to 25.0 ± 1.5 mBqkg-1h-1, with average exhalation value of
16.6 ± 0.7 mBqkg-1h-1. The obtained 222Rn exhalation rates are below the world wide average value and also less
than that exhaled by the samples of coal and fly ash [19]. Radon emanation which is measures the amount of

10
222
Rn comes into pore space after its production is calculated from radium content present in samples (Table 1)
and final radon exhalation rate (Table 3) from the samples using equation 9. Emanation factor in the collected
soil samples are found to be 2.69 to 6.73 with average emanation factor of 4.30 ± 0.2 and presented in Table 4.
Values of observed emanation factors are of same order as observed by Sahoo et al. [23] for different
222
construction materials. A positive correlation of 0.51 is presented in Fig. 7 between Rn emanation and its
accumulated concentration in the chamber. In the accumulator containing a known weight of sample,
accumulated concentration depends on the amount of radon coming from grain to pore space. This concentration
increase with an increase in the emanation factor is represented by positive correlation.

Table 4. Radon-Thoron exhalation rates and emanation factor in soil samples.

Sr. Sample Equilibrium radon Radon exhalation Thoron exhalation % Radon Thoron emanation
No. Code concentration (Bq/m3) rate rate emanation (mBqOI J
N J
)
(mBqHI J
K J
) (mBqL M
N J
) (ε)
1 (K-1) 116.4 ± 2.6 12.9 ± 0.9 137.9 ± 8.7 3.70 6.90
2 (K-2) 133.8 ± 7.0 15.3 ± 1.2 122.2 ± 10.2 4.23 6.11
3 (K-3) 151.7 ± 8.0 21.1 ± 1.1 152.3 ± 11.5 6.73 7.61
4 (K-4) 134.5 ± 15.3 19.5 ± 1.5 142.7 ± 14.6 3.94 7.13
5 (K-5) 156.9 ± 4.1 15.2 ± 1.3 138.0 ± 9.8 4.19 6.90
6 (K-6) 198.9 ± 5.3 19.4 ± 0.9 145.9 ± 11.5 4.77 7.29
7 (K-7) 150.3 ± 4.4 14.5 ± 0.7 118.6 ± 8.6 3.56 5.93
8 (K-8) 145.6 ± 2.9 18.2 ± 1.1 142.0 ± 9.5 4.13 7.10
9 (K-9) 122.3 ± 6.4 9.9 ± 0.7 109.9 ± 13.5 3.03 5.50
10 (K-10) 151.0 ± 0.7 17.9 ± 0.9 134.0 ± 16.5 4.60 6.70
11 (K-11) 146.1 ± 5.8 18.1 ± 0.6 129.4 ± 18.4 4.39 6.47
12 (K-12) 135.2 ± 3.8 12.7 ± 1.0 122.6 ± 15.3 3.39 6.13
13 (K-13) 159.1 ± 4.2 18.0 ± 0.9 131.0 ± 18.6 4.66 6.55
14 (K-14) 125.7 ± 3.5 17.3 ± 1.1 147.5 ± 14.2 5.03 7.37
15 (K-15) 166.5 ± 6.3 18.8 ± 1.7 138.3 ± 17.6 5.07 6.92
16 (K-16) 182.0 ± 6.3 20.3 ± 1.3 138.7 ± 9.7 5.51 6.93
17 (K-17) 153.0 ± 8.7 16.5 ± 1.3 144.5 ± 10.3 4.62 7.22
18 (K-18) 152.6 ± 7.3 16.7 ± 1.5 136.1 ± 15.6 4.31 6.81
19 (K-19) 193.9 ± 4.9 22.8 ± 1.9 143.2 ± 9.6 6.26 7.16
20 (K-20) 139.3 ± 3.3 13. ± 0.9 126.5 ± 8.8 4.15 6.33
21 (K-21) 143.8 ± 4.6 18.4 ± 1.2 119.1 ± 12.3 4.47 5.95
22 (K-22) 103.2 ± 3.1 13.0 ± 0.8 110.2 ± 18.5 4.01 5.51
23 (K-23) 196.7 ± 3.3 19.7 ± 0.5 148.3 ± 17.9 4.78 7.41
24 (K-24) 96.5 ± 7.7 10.3 ± 0.6 112.2 ± 10.6 3.09 5.61
25 (K-25) 219.9 ± 3.2 25.0 ± 1.5 157.9 ± 12.2 6.24 7.89
26 (K-26) 106.0 ± 8.7 13.0 ± 1.1 115.9 ± 11.1 2.69 5.79
27 (K-27) 174.1 ± 7.3 17.3 ± 0.8 110.1 ± 10.5 4.11 5.51
28 (K-28) 99.4 ± 3.3 11.9 ± 0.9 123.3 ± 9.9 2.79 6.17
29 (K-29) 149.0 ± 3.6 17.9 ± 1.4 148.7 ± 15.6 3.33 7.43
30 (K-30) 96.1 ± 4.8 13.5 ± 1.5 115.0 ± 13.4 3.22 5.75
Mean ± SE 146.7 ± 5.8 16.6 ± 0.7 132.1 ± 2.6 4.3 ± 0.2 6.6 ± 0.1

11
 Fig. 7. Radon concentrations in correlation with radon emanation factor.

3.4. Ventilation rates influence on the indoor radon levels

Based on the obtained values of dose, alpha and gamma indices which lie in the safe limit, the material under
222
study can be used for construction purpose and indoor Rn level can be predicted from its exhalation rates
from walls and floor of a dwelling knowing the dimensions for a standard room. Present study modeled the
222
indoor Rn for the standard model room having dimension 4×4×2.8 m3 using the relation (9) by knowing its
area A (m2 )and volume V (m3) [8,35-36].

×
C= (9)
Q×

Where, E is the exhalation rate of the sample used in construction (Table 4). λs is sum of 222
Rn decay constant
-1 -1
(h ) and ventilation rate (h ). Effect of different ventilation rates for the model room on predicted concentration
are studied by taking different values of ventilation rates. Fig. 8 represents the variation of radon concentration
for the measured exhalation rates with different value of ventilation rates (0.2 to 0.8 h-1). It was observed that
with increase of ventilation rate from 0.2 to 0.8 radon concentration decrease to 25.70% from its initial value.
Results of modeling study by Chen et al. [35] suggests that if a room with air exchange rate of 0.3 h-1 have floor
222
covered with a material having relatively high Rn exhalation of 300 Bq/m2/d, then its contribution to indoor
radon concentration is only 18 Bqm-3 [35]. And for the study area, estimated exhalation rates are less than this
value hence, resulting radon concentration is also below 18 Bq/m3. The prediction of radon concentration using
exhalation rates for the samples under study are in agreement with the other study and safer to use [1-3].

12
 Fig. 8. Radon concentration corresponds to exhalation rates at different values of ventilation rates.

3.5. Thoron exhalation and emanation rates in samples under study

In recent past thoron was underestimated because of difficulties in measurement and calibration which makes its
case very different from that of radon due to its shorter half life (55s) as compared to long lived 222Rn. Different
half life of these two results into their distinct behavior such as different diffusion length, time required in
attainment of stable concentration (Fig. 6 and 9), height and amount of sample taken, dispersion behavior
(uniformity) and hence requirement of chamber size for exhalation measurement [15, 25, 37]. Due to these
difficulties associated with thoron the same measurement apparatus and procedure used for the radon case
cannot be applicable to thoron hence, the different monitors namely scintillation radon (SRM) and thoron
(STM) monitor were used for exhalation measurement. Scintillation monitors are employed for radon and
thoron exhalation measurements in different modes i.e. diffusion mode (SRM) and flow mode (STM)
respectively. Achievement of uniformity in the chamber of certain size depends on the diffusion length of gas in
air along with the chamber size. Because of difficulty in accomplishing uniformity for thoron in the chamber
used for radon of volume 3.5×10-3 m3, a different chamber of small volume 1.3×10-3 m3 is used for thoron
exhalation measurement. Thoron uniformly cannot be achieved without forces air mixing in the large chamber
because of short diffusion length. A pump having inlet and outlet was used to achieve a certain level of
homogeneity between the scintillation cell and accumulator of STM. Establishment of uniformity in case of
thoron requires the optimal minimum chamber size and forced air mixing within closed circuit [5,25, 37]. Fig. 6
represents the radon concentration growth with time measured using SRM which shows that radon attains a
asymptotic value after several cycles of one hour while thoron concentration measured using STM with small
air volume attains a stable concentration very quickly for the time cycle of 15 min (Fig. 9). In the accumulator
radon concentration grows with a slower rate by following a diffusion mechanism after emanation of radon into
pore space and starts to build up into the chamber to attain a stable concentration. Establishment of stable thoron
concentration is because of its larger decay constant 1.2 x 10-2 s-1, forced air mixing in the air present in the
chamber above the enclosed sample. During measurement of thoron concentration in the accumulator present air
volume is only 33% of total chamber volume (STM) and is very less as compare to accumulator used in SRM.
Air volume during thoron measurement is only 0.4×10-3 m3 which is only 12% of the volume of accumulator

13
used in SRM. It should be noticed that the equilibrium for comparatively long lived 222Rn implicates its uniform
220
distribution; while there is no such situation for the short lived Rn. Attainment of steady state thoron
concentration is illustrated graphically in Fig. 9. [14, 24].

Fig. 9. Typical graph showing thoron stable concentration with 15 minute time cycle.

3.5.1. Optimization of sample height for 220Rn exhalation rate measurement

The diffusion length of 220Rn in the soil is less as compared to that of radon and is of the order of 1 cm, which
makes its origin mainly from upper surface of the whole sample. Also the consequences of the thoron exhalation
measurements rely upon the thickness of sample placed which must be taken into account. So as to have thoron
exhalation not dependent on the test sample thickness, it should be as thick as three times the thoron diffusion
length, since it is not constantly known for a given sample, which could be in issue. If the thickness of the
measured sample is more than three diffusion lengths of thoron in the sample, its thoron exhalation rate value is
220
practically equivalent to the exhalation rate of same sample of vast thickness. The Rn concentration (C)
present in the chamber includes two terms in particular, its generation rate and its decay rate. In order to
optimize the sample height for thoron exhalation measurement with STM consists of accumulator of radius and
height of 12 cm thoron concentration was measured experimentally corresponding to varying height presented
in Fig. 10. Initially thoron concentration increases with the height of sample in the chamber because more the
amount of sample taken in the chamber more the thoron will be emerging out in chamber. Then, thoron
concentration attains a constant value within a range of sample height because only few upper layers contribute
to thoron concentration because of small diffusion length of thoron in soil (1 cm) and air (2.3 cm) in the certain
air volume present above the sample. After this thoron concentration again rise due to the emission of fixed
amount of thoron concentration in the small air volume than earlier [15, 25, 37]. For the exhalation rate
measurement optimized height range should be correspond to constant thoron concentration which is 7.5 cm to
9.5 cm in this case. Here within this range, variation of sample thickness do not cause high levels of uncertainty
in thoron concentration as well as in exhalation and it additionally gives high value of concentrations, which
makes the estimation more precise. Therefore, to measure the thoron exhalation rates of the soil samples under
study, the height of all samples was kept at 8 cm in order to keep up a generally small air volume in the
accumulator to ensure uniform mixing at the operating flow rate.

14
 Fig. 10. Optimization of sample height for thoron exhalation measurement using STM.

Thus, with the forced air mixing in the accumulation chamber and this optimized sample height, one can have
the thoron uniform distribution inside the chamber and thoron exhalation rates can be calculated using thoron
concentration in equation 4. Calculated values of exhalation rates for 220Rn for the soil samples under study are
depicted in Table 4 with arithmetic mean and standard deviation. Thoron surface exhalation varies from 109.9 ±
13.5 to 157.9 ± 12.2 mBqm-2s-1with an average of 132.1 ± 2.6 mBqm-2s-1. Also the emanation rate of 220Rn can
be calculated using its diffusion length and sample density for all the samples under study and is varying from
5.50 to 7.89 with an average of 6.60 ± 0.13. Fig. 11 delineates the variation of 222Rn and 220
Rn exhalation rates
222 220
for the soil samples. Rn and Rn exhalation rates are below the recommendation level [1-2], therefore the
222 220 222 220
region is safer as the exhalation rates of Rn and Rn are concerned. The variation in Rn and Rn
exhalation rate can also be attributed because of different radionuclide content and soil substructure of samples
as shown in Table 1.

Fig. 11. Variation of 222Rn and 220Rn exhalation rates for different samples.

222 220
Fig. 11 shows that the highest and lowest value of exhalation for both Rn and Rn are obtained from the
same soil samples. Minimum value of radon mass exhalation rate is 9.9 ± 0.7 mBqkg-1h-1 and thoron surface

15
exhalation rate is 109.9 ± 13.5 mBqm-2s-1 from the sample K-9 while the maximum value of radon exhalation
(25.0 ± 1.5 mBqkg-1h-1) and thoron exhalation (157.9 ± 12.2 mBqm-2s-1) are obtained from the sample K-25.
Also, Fig. 12 represents an observed positive correlation between 222Rn and 220Rn exhalation rates.

Fig. 12. Correlation of 220Rn exhalation rate with 222Rn mass exhalation rate in soil samples.

3.6. Estimation of thoron exhalation using radon exhalation rates

Detection of thoron and measurement of its exhalation rate is important by taking its radiological risk into
consideration especially for some regions having its high level; on the other hand its measurement is not a
simple task but consists of a lot of challenges described above. Any alternate method rather than the direct
measurement if available can be easily adopted by one for the 220Rn exhalation rates calculation in the samples.
One such theoretical approach is provided by Magnoni et al. [16], to estimate the exhalation rates of thoron
using the radon exhalation rates and the source term concentration both for radon and thoron. Operating in this
easy way, it would be possible to estimate the exhalation rates of 220Rn for the samples which radon exhalation
has been made using closed accumulator. Present study has measured all the parameters required for such
approach to predict thoron exhalation using that of radon and can estimate the correlation between predicted and
experimentally measured values using STM. Magnoni proposed the relation given below to estimate thoron
exhalation ( 1% ), in equation 10 using the radon exhalation rate ( -$ ) , radium concentration ( -# R ) and
thorium concentration( 1%ST R ) [16].

-$ . ._
UVWXYZ[ UVWXW`
1% (10)
\]^YZ[ \]^W`

Where λThoron and λRadon represents the decay constant for thoron and radon respectively. Fig.13 presented the
estimated thoron exhalation from radon exhalation based on the above relation with black dots. A test of this
222 220
method had also been performed by experimentally measuring Rn and Rn exhalation rate along with
theoretical calculations for the sienites sample utilizing alpha spectrometry technique. Result of test performed
by Magnoni et al. also shows significantly greater than those obtained theoretically, which is also observed in
this study. However, based on the test results, Magnoni et al. proposed an empirical relation to model the thoron
exhalation using the same parameters as in equation 10. Based on the assumption that the exhalation rate is not
only depends on the diffusion but is the result of direct recoil of gas atoms from the upper surface with alpha

16
 222 220
decay, he deduced an general empirical relationship between the Rn and Rn exhalation rates as following
[16].
UV UVWXYZ[
. 357 (11)
\` \]^YZ[

This relation can also be used as screening tools for other stony materials such as granites and similar rocks for
practical purposes. The values for thoron exhalation rates obtained using the parameters estimated in the present
study in the empirical relation (equation 11) are used to find he correlation with the experimentally obtained
values by red dots in Fig. 13. Correlation found between the experimentally observed values and the values
obtained using theoretical and empirical relation is R2 = 0.06, but the values of exhalation are more comparable
for empirical relation. Also, study conducted by Tokonami (2010) [38] founds no correlation between radon and
thoron, proposed formula by Magnoni et al. [16] needs some more validation to use this as a screening tool for
220
Rn exhalation rate estimation.

Fig. 13. Represents the correlation between experimental and theoretical values of thoron exhalation.
222
Table 5. Comparison of present study results with recent studies of Rn exhalation rates conducted in north
Indian regions.
S.N. Location Radon exhalation rate Technique Used (Reference)
(mBqKg-1h-1)
1. Panchkula 83 ± 5 Canister technique [18]
2. Morni Hills 122 ± 1 -do-
3. Yamuna nagar 73 ± 3 -do-
4. Naraingarh 50 ± 2 -do-
5. Ambala 79 ± 2 -do-
6. LalDhang 143 ± 6 -do-
7. Ponta Sahib 108 ± 9 -do-
8. DholaKuan 115 ± 7 -do-
9. Nahan 90 ± 3 -do-
10. Kala Amb 91 ± 2 -do-
11. Shivalik foot hills 50 ± 1-143 ± 6 Canister technique [17]
12 Udhampur (J&K) 11.57 - 65.62 SRM [9]
13. Kurukshetra 6 - 31 SRM [7]
14. Yamunanagar 29.2 - 73.1 SRM [10]
15. Ambala 28.2 - 60.7 -do-
16. Panchkula 34.3 - 76.8 -do-
17. Karnal 9.9 – 25.0 SRM (Present study)

In order to study the environmental radioactivity level, a comparative study was performed with the nearby
regions of the study area. On comparison with the other studies of northern India conducted in recent times, it is
observed that the values of exhalation rates for 222Rn and 220Rn are below than in the hilly areas and comparable

17
to nearby plain area of indo Gangetic plane. A comparison of the study area with other nearby hilly and plain
regions in terms of radon exhalation rates represented in Table 5.

4. Conclusions
The measurements of radionuclides (226Ra, 232
Th and 40
K) along with exhalation rates of radon-thoron in the
samples from northern part of India are presented. The following conclusions are drawn from the study:
• Estimated values of radioactivity content using gamma spectroscopy and different radiation hazard
index are within the recommendation levels by UNSCEAR and ICRP.
• Uniformity and stability during thoron measurement are achieved with air volume of 0.4×10-3 m3
which is only 12% of the SRM accumulator volume and forced thoron mixing. Optimized height for
measurement lies in the range corresponding to constant thoron concentration and optimum thickness
of the sample is nearly at top of the chamber.
• Average value of radon mass exhalation found 16.6 ± 0.7 mBqkg-1h-1, while that of thoron surface
exhalation was found 132.1 ± 2.6 mBqm-2s-1which are less than the world average values. Positive
222 220
correlations are observed between Rn and Rn exhalation rates from the soil samples. Radon
concentration was predicted using exhalation rates and observed that with increase of ventilation rate
from 0.2 to 0.8 h-1 the radon concentration decreased to 25.70% from its initial value.
• A different approach for 220Rn exhalation rate measurement, by measuring only the corresponding rate
for radon (SRM) was also tested and found a poor correlation hence, needs some more verification.
• A comparison with other studies indicated that the place and use of soil present in study area for
construction is considered to be safe for human habitation.
This study will be helpful in bridging the source radionuclides concentration for the area under study for future
research expeditions and is also helpful in mapping of country by providing radiological data with exact
geographical location of each sampling site.

Acknowledgments

The authors are thankful to the Director, National Institute of Technology Kurukshetra and the Head,
Department of Physics, NIT Kurukshetra for providing the facilities for the completion of the work and financial
help in the form of fellowship.

References
[1] UNSCEAR, Sources and Effects of Ionizing Radiation (Exposure from Natural Sources of Radiation),
New York, 1993. http://www.unscear.org/docs/ publications/1993/UNSCEAR_1993.
[2] UNSCEAR, Sources and Effects of Ionizing Radiation (Exposures from Natural Radiation Sources), New
York, 2000.
[3] ICRP Publication 115, Lung Cancer Risk from Radon and Progeny and Statement on Radon, 2010,
https://doi.org/10.1016/j.icrp.2011.08.011.
[4] S. Abdullahi, A.F. Ismail, S. Samat, Determination of indoor doses and excess lifetime cancer risks caused
by building materials containing natural radionuclides in Malaysia, Nuclear Engineering and Technology.
51 (2019) 325–336. doi:10.1016/j.net.2018.09.017.
[5] S. Maeng, S.Y. Han, S.H. Lee, Analysis of radon depth profile in soil air after a rainfall by using diffusion
model, Nuclear Engineering and Technology. (2019). doi:10.1016/j.net.2019.06.018.
[6] R. Kumar, D. Sengupta, R. Prasad, Natural radioactivity and radon exhalation studies of rock samples
from Surda Copper deposits in Singhbhum shear zone, Radiation Measurements. 36 (2003) 551–553.
doi:10.1016/S1350-4487(03)00201-4.

18
 [7] V. Devi, A. Kumar, R.P. Chauhan, A study on radionuclides content and radon exhalation from soil of
Northern India, Environmental Earth Sciences. 78 (2019) 506. doi:10.1007/s12665-019-8512-9.
[8] C. Papachristodoulou, K. Stamoulis, K. Ioannides, Temporal Variation of Soil Gas Radon Associated with
Seismic Activity: A Case Study in NW Greece, Pure and Applied Geophysics. (2019).
doi:10.1007/s00024-019-02339-5.
[9] S. Sharma, A. Kumar, R. Mehra, R. Mishra, Radiation hazards associated with radionuclides and
theoretical evaluation of indoor radon concentration from soil exhalation of Udhampur District, Jammu
and Kashmir State, India, Journal of Soils and Sediments. 19 (2019) 1441–1455. doi:10.1007/s11368-018-
2125-x.
[10] R.P. Chauhan, A. Kumar, N. Chauhan, M. Joshi, P. Aggarwal, B.K. Sahoo, Ventilation effect on indoor
radon–thoron levels in dwellings and correlation with soil exhalation rates, Indoor and Built Environment.
25 (2016) 203–212. doi:10.1177/1420326X14542887.
[11] M.A.E. Abdel-Rahman, S.A. El-Mongy, Analysis of radioactivity levels and hazard assessment of black
sand samples from Rashid area, Egypt, Nuclear Engineering and Technology. 49 (2017) 1752–1757.
doi:10.1016/j.net.2017.07.020.
[12] A.K. Mahur, R. Kumar, D. Sengupta, R. Prasad, Estimation of radon exhalation rate, natural radioactivity
and radiation doses in fly ash samples from Durgapur thermal power plant, West Bengal, India, Journal of
Environmental Radioactivity. 99 (2008) 1289–1293. doi:10.1016/j.jenvrad.2008.03.010.
[13] A.K. Mahur, R. Kumar, R.G. Sonkawade, D. Sengupta, R. Prasad, Measurement of natural radioactivity
and radon exhalation rate from rock samples of Jaduguda uranium mines and its radiological implications,
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and
Atoms. 266 (2008) 1591–1597. doi:10.1016/j.nimb.2008.01.056.
[14] P. Ujić, I. Čeliković, A. Kandić, Z. Žunić, Standardization and difficulties of the thoron exhalation rate
measurements using an accumulation chamber, Radiation Measurements. 43 (2008) 1396–1401.
doi:10.1016/j.radmeas.2008.03.003
[15] A. Kumar, R.P. Chauhan, Back diffusion correction for radon exhalation rates of common building
materials using active measurements, Materials and Structures. 48 (2015) 919–928. doi:10.1617/s11527-
013-0203-5.
[16] M. Magnoni, E. Chiaberto, A. Prandstatter, E. Serena, R. Tripodi, Thoron exhalation rate in stony
materials: A simplified approach, Construction and Building Materials. 173 (2018) 520–524.
doi:10.1016/j.conbuildmat.2018.04.053.
[17] R.P. Chauhan, P. Chauhan, A. Pundir, S. Kamboj, V. Bansal, R.S. Saini, Estimation of dose contribution
from 226Ra, 232Th and 40K radon exhalation rates in soil samples from Shivalik foot hills in India,
Radiation Protection Dosimetry. 158 (2014) 79–86. doi:10.1093/rpd/nct190.
[18] A. Pundir, R.Singh, S. Kamboj, Measurement of radon concentration and exhalation rates in soil samples
of some districts of Haryana and Himachal in India. Researcher 6(2014) 71-76.
[19] L.M. Singh, M. Kumar, B.K. Sahoo, B.K. Sapra, R. Kumar, Study of radon, thoron exhalation and natural
radioactivity in coal and fly ash samples of kota super thermal power plant, rajasthan, india, Radiation
Protection Dosimetry. 171 (2016) 196–199. doi:10.1093/rpd/ncw057.
[20] V. Devi, A. Kumar, R.P. Chauhan, Radiation doses due to background radioactivity in soil from inhabited
area of Northern Haryana, in: Advances in Basic Science (Icabs 2019), 2019: p. 120010.
doi:10.1063/1.5122506.
[21] J.J. Gaware, B.K. Sahoo, B.K. Sapra, Y.S. Mayya, Development of Online Radon and Thoron Monitoring
Systems for Occupational and General Environments, (2011) 45–51.
[22] J. Porstendorfer, Properties and behaviour of radon and thoron and their decay products in the air, J
Aerosol Sci. 25 (1994) 219–263.
[23] B.K. Sahoo, D. Nathwani, K.P. Eappen, T.V. Ramachandran, J.J. Gaware, Y.S. Mayya, Estimation of
radon emanation factor in Indian building materials, Radiation Measurements. 42 (2007) 1422–1425.
doi:10.1016/j.radmeas.2007.04.002.
[24] P. Tuccimei, M. Moroni, D. Norcia, Simultaneous determination of 222Rn and 220Rn exhalation rates
from building materials used in Central Italy with accumulation chambers and a continuous solid state

19
 alpha detector: Influence of particle size, humidity and precursors concentration, Applied Radiation and
Isotopes. 64 (2006) 254–263. doi:10.1016/j.apradiso.2005.07.016.
[25] S.D. Kanse, B.K. Sahoo, B.K. Sapra, J.J. Gaware, Y.S. Mayya, Powder sandwich technique: A novel
method for determining the thoron emanation potential of powders bearing high 224Ra content, Radiation
Measurements. 48 (2013) 82–87. doi:10.1016/j.radmeas.2012.10.014.
[26] H. Azeez, H. Mansour, S. Ahmad, Effect of Using Chemical Fertilizers on Natural Radioactivity Levels in
Agricultural Soil in the Iraqi Kurdistan Region, Polish Journal of Environmental Studies. 29 (2019) 1–10.
doi:10.15244/pjoes/106032.
[27] NEA-OECD, Exposure to Radiation from Natural Radioactivity in Building Materials, 1979, pp. 1e34.
https://www.oecd-nea.org/rp/reports/1979/ exposure-to-radiation-1979.pdf.
[28] EC, Radiation Protection 112: Radiological Protection principles Concerning the Natural Radioactivity of
Building Materials, Finland, 1999. https://eceuropa.eu/energy/sites/ener/files/documents/112.pdf.
[29] J. Beretka, P.J. Mathew, Natural Radioactivity of Australian Building Materials, Industrial Wastes and By-
products, Health Physics. 48 (1985) 87–95. doi:10.1097/00004032-198501000-00007.
[30] S. Righi, L. Bruzzi, Natural radioactivity and radon exhalation in building materials used in Italian
dwellings, Journal of Environmental Radioactivity. 88 (2006) 158–170.
doi:10.1016/j.jenvrad.2006.01.009.
[31] N.M. Hassan, T. Ishikawa, M. Hosoda, A. Sorimachi, S. Tokonami, M. Fukushi, S.K. Sahoo, Assessment
of the natural radioactivity using two techniques for the measurement of radionuclide concentration in
building materials used in Japan, Journal of Radioanalytical and Nuclear Chemistry. 283 (2010) 15–21.
doi:10.1007/s10967-009-0050-6.
[32] R. Ravisankar, K. Vanasundari, M. Suganya, Y. Raghu, A. Rajalakshmi, A. Chandrasekaran, S.
Sivakumar, J. Chandramohan, P. Vijayagopal, B. Venkatraman, Multivariate statistical analysis of
radiological data of building materials used in Tiruvannamalai, Tamilnadu, India, Applied Radiation and
Isotopes. 85 (2014) 114–127. doi:10.1016/j.apradiso.2013.12.005.
[33] K. O’Brien, R. Sanna, The distribution of absorbed dose-rates in humans from exposure to environmental
gamma rays. Health Phys. 30(1976)71–78.
[34] K. O’Brien, R. Sanna, The effect of male-female body-size difference on absorbed dose-rate distributions
in humans from natural gamma rays. Health Phys 34(1978) 107–112.
[35] J. Chen, N.M. Rahman, I.A. Atiya, Radon exhalation from building materials for decorative use, Journal of
Environmental Radioactivity. 101 (2010) 317–322. doi:10.1016/j.jenvrad.2010.01.005.
[36] A.K. Mahur, R. Kumar, M. Mishra, D. Sengupta, R. Prasad, An investigation of radon exhalation rate and
estimation of radiation doses in coal and fly ash samples, Applied Radiation and Isotopes. 66 (2008) 401–
406. doi:10.1016/j.apradiso.2007.10.006.
[37] I. Csige, Z. Szabó, C. Szabó, Experimental technique to measure thoron generation rate of building
material samples using RAD7 detector, Radiation Measurements. 59 (2013) 201–204.
doi:10.1016/j.radmeas.2013.07.003.
[38] S. Tokonami, Why is 220Rn (thoron) measurement important?, Radiation Protection Dosimetry. 141
(2010) 335–339. doi:10.1093/rpd/ncq246.

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 CONFLICT OF INTEREST

There is no conflict of interest of any kind with person or organization. The manuscript has not been
previously published, is not currently submitted for review to any other journal, and will not be submitted
elsewhere before a decision is made by this journal. Moreover, co-author has read the manuscript and
agreed to submit it in its current form for consideration of publication in this Journal. Every care has been
taken for preparation of manuscript according to journal instruction to authors.

Sincerely

R P Chauhan
Department of Physics
NIT Kurukshetra, India