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ORIGINAL ARTICLE
Year : 2014  |  Volume : 37  |  Issue : 3  |  Page : 161-164  

Measurement of radon activity and exhalation rate in soil samples from Banda district, India


Department of Physics, Atarra PG College, Atarra, Banda, Uttar Pradesh, India

Date of Web Publication10-Apr-2015

Correspondence Address:
A K Choudhary
Department of Physics, Atarra PG College, Atarra, Banda 210 201, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-0464.154877

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  Abstract 

Radon activities and radon exhalation rates have been measured in soil samples collected from different location of Banda district of Uttar Pradesh in India using LR-115 type II solid state nuclear track detectors. Radon activity has been found to vary from (101.0) to (505.1) Bq/m 3 with an average value of (278.3) Bq/m 3 . Surface exhalation rate has been found to vary from (84.0) to (419.8) mBq/m 2 /h with an average value (231.3) mBq/m 2 /h, whereas mass exhalation rate has been found to vary from (2.1) mBq/kg/h to (10.6) mBq/kg/h with an average value of (5.8) mBq/kg/h. Effective dose from indoor inhalation exposure (radon) has been estimated, which is found to vary from (6.1) to (30.5) μSv/year with an average value of (16.8) μSv/year.

Keywords: Can technique, exhalation rate, LR-115 type II solid state nuclear tracks detectors, Radon


How to cite this article:
Choudhary A K. Measurement of radon activity and exhalation rate in soil samples from Banda district, India. Radiat Prot Environ 2014;37:161-4

How to cite this URL:
Choudhary A K. Measurement of radon activity and exhalation rate in soil samples from Banda district, India. Radiat Prot Environ [serial online] 2014 [cited 2020 May 30];37:161-4. Available from: http://www.rpe.org.in/text.asp?2014/37/3/161/154877


  Introduction Top


Studies of natural radioactivity are necessary because of their radiological impact. Besides, they act as excellent biochemical and geochemical traces in the environment. Over the past five decades, growing attention has been devoted to the effect of natural radioactivity. However, the importance of the contribution of environmental radon (Rn), to the natural radiation dose has only been realized for the past two decades and has been subject of relatively recent studies. More than half of the total natural environmental ionizing radiation dose to the world population is contributed by the radiation dose, resulting due to radon and its progenies. [1]

Henshaw et al., [2] has claimed that high levels of indoor radon exposure is associated with the risk of leukemia and certain other cancers, such as melanoma and cancers of the kidney and prostate. Presence of uranium rich material close to the surface of the earth can cause high radon exposure hazards. [3],[4],[5],[6],[7],[8]

Exhalation of 222 Rn, a radioactive inert gas, is associated with the presence of 226 Ra and its ultimate precursor uranium in the earth crust. Although these elements occur in virtually all types of rocks and soils, their concentration varies with specific sites and geological formation of materials.

The rate at which radon escapes or emanates from solid into the surrounding air is known as radon exhalation rate of the solid. This may be measured by either per unit mass or per unit surface area of the solid. Measurement of radon exhalation rate of soils and rocks are helpful to study radon health hazards.

Radiation data for the major part of Bundelkhand region including the area under the study have not been reported so far. Bundelkhand is an old landmass composed of horizontal rock beds resting on a stable foundation. The rugged landscape features undulating terrain with low rocky outcrops, narrow valleys, and plains. Surface rocks are predominantly granite of the lower pre-Cambrian/arcane period.

In the present study, radon activity and radon exhalation rate have been measured in soil samples locally available in 15 different places in Banda district of Bundelkhand region in India. The region being one of the most economically backward in India, people commonly use locally available soil as building materials here. The present study is aimed to assess the possible health hazard in the area associated with the utilization of soil as building material.


  Materials and methods Top


Among the different techniques available for radon measurements, the method based on the use of solid state nuclear tracks detectors is probably the most widely applied for long term radon measurements. Therefore in the present work, a passive method (can-technique) using LR-115 type II (Kodak-Path6, France) solid state nuclear track detectors has been employed for the study of radon exhalation rate and radium content of soil samples locally available in Banda and Karwi (Chitrakoot) district of Bundelkhand region. In this method, the samples of interest are enclosed in a sealed can. [9],[10],[11],[12] The cellulose nitrate LR-115 (12 μm thickness), is a very useful detector for the direct registration of alpha-particles, the sensitive surface of the detector faced to the samples. The tracks developed on these plastic detectors are not directly visible and have to be enlarged by proper chemical processing.

To study the migration and exhalation of radon in soils of different areas of Banda, Uttar Pradesh, India, the soil samples were collected from different places belonging to this area.

The samples from different places were finely powdered, sieved and dried in the oven. The fine powder (200 g) of the soil sample from each location was placed and sealed in different bottles for 30 days so as to attain the equilibrium. After 30 days, LR-115 type II plastic track detectors were fixed on the top inside of these glass bottles. The bottles were then sealed and left as such for 90 days so that the detectors can record the tracks of alpha-particles resulting from the decay of radon. The exposed detectors were then etched in NaOH solution (2.5N) at 60°C for 2 h using a constant temperature bath. The tracks were counted using Spark counter (manufactured by Pollteck Instruments Pvt. Ltd.,Mumbai, India). It is specially designed counter meant for counting the alpha tracks in pelliculable LR-115 detectors.

The accumulated radon concentration in Can is related to the alpha track density ρ (tr.cm -2 ) by the Eq. (1):

(1)



Where, K is the calibration factor of the plastic track detector (0.033 track. cm -2 . d -1 /Bq.m -3 ). [4],[5]

T is the effective exposure time, which is related to the actual exposure time t and decay constant λ for 222 Rn with the relation Eq. (2):

(2)



The radon exhalation rate in terms of area is calculated from the Eq. (3):

(3)



E a is the radon exhalation rate expressed in Bq/m 2 /h, C represents the integrated radon exposure (Bq.m -3 .h), V is the effective volume of the can, t is the decay constant for radon (h−1 ) and A is cross-sectional area of the can (m 2 ). The radon exhalation rate in terms of mass is calculated from the expression Eq. (4):

(4)



Were E m is the radon exhalation rate in terms of mass (Bq/kg/h) and M is the area of the sample.


  Results and discussion Top


The values of radon activity and radon exhalation rate in soil samples from 15 localities of district Banda, Uttar Pradesh, India are given in [Table 1]. It is evident from table that the radon exhalation rate in soil in terms of area varies from 83.96 mBq/m 2 /h in locality Atarra to 419.81 mBq/m 2 /h in Manikpur. The exhalation rate in terms of mass varies from 2.11 mBq/kg/h to 10.55 mBq/kg/h.
Table 1: Radon activity, radon exhalation rate and indoor inhalation exposure (radon) effective dose in soil samples from Banda, India

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Indoor internal exposure due to radon inhalation

Most of the poor population in Bundelkhand region lives in mud houses built of locally available soil. The contribution of indoor radon concentration from the soil samples was calculated from the following expression. [13]

(5)



Here, C Rn is radon concentration expressed in Bq/m 3 , E a is radon exhalation rate in Bq/m 2 /h, S is radon exhalation area (m 2 ), V is room volume (m 3 ) and g is air exchange rate (h−1 ).

For calculating the maximum radon concentration from the soil as building material, the room was considered as a cavity with S/V = 2.0 m−1 and air exchange rate of 0.5 h−1 . The annual exposure to potential alpha energy E p is related to the average radon concentration C Rn by the following relation:

(6)



Where, C Rn is in Bq/m 3 , n is the fraction of the time spent indoor. 8760 represents the number of hours per year; 170, the number of hours per working month and F the equilibrium factor for radon. F is taken as 0.42 as suggested by UNSCEAR. [14] The value of n was used 0.8.

From the indoor radon inhalation exposure, the effective doses were calculated by using a conversion factor [15] of 3.88 mSv per WLM. The values thus calculated are presented in [Table 1], which vary from 6.1 ± 0.3 to 30.5 ± 1.9 µSvy -1 with an average value of 16.8 ± 8.1 µSvy -1 .


  Conclusions Top


Based on the assessment of the collected soil samples, the effective doses from indoor radon inhalation exposure works out to be less than 0.3 mSv/year, the dose constraint recommended. [16] Thus, the soil appears to be safe and can be used as building materials without posing significant radiological threat to the population. The variation in exhalation rate in soil samples is due to the difference in uranium, radium concentration of soil and porosity of soil samples. Radiation dose assessment of the area under study and other parts of Bundelkhand region has not been reported so far. Therefore the result of the present study could not be compared.

 
  References Top

1.
United Nations. Sources, Effects and Risks of Ionizing Radiation. United Nations Scientific Committee on the Effects of Atomic Radiation, 1988 Report to the General Assembly, with annexes. United Nations, New York: United Nations Sales Publication E.88.IX.7; 1988.  Back to cited text no. 1
    
2.
Henshaw DL, Eatough JP, Richardson RB. Radon as a causative factor in induction of myeloid leukaemia and other cancers. Lancet 1990;335:1008-12.  Back to cited text no. 2
    
3.
Fahmia NM, El-Zaherb MA, El-Khatiba AM. Proceedings of the 9 th Radiation Physics and Protection Conference, Nov. 15-19, Nasr City, Cairo, Egypt; 2008. p. 15-9.  Back to cited text no. 3
    
4.
Abdelzaher M. Seasonal variation of radon level and radon effective doses in the Catacomb of Kom EI-Shuqafa Alexandria, Egypt. Pramana J Phys 2011;77:749-57.  Back to cited text no. 4
    
5.
Abd El-Zaher M. Seasonal variation of indoor radon concentration in dwellings of Alexandria city, Egypt. Radiat Prot Dosimetry 2011;143:56-62.  Back to cited text no. 5
    
6.
Archer VE, Wagoner JK, Lundin FE. Lung cancer among uranium miners in the United States. Health Phys 1973;25:351-71.  Back to cited text no. 6
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7.
Sevc J, Kunz E, Placek V. Lung cancer in uranium miners and long-term exposure to radon daughter products. Health Phys 1976;30:433-7.  Back to cited text no. 7
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8.
United Nations. Sources and Effects of Ionizing Radiation. United Nations Scientific Committee on the Effects of Atomic Radiation, 1993 Report to the General Assembly, with Scientific Annexes. United Nations, New York: United Nations Sales Publication E.94.IX.2; 1993.  Back to cited text no. 8
    
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Abu-Jarad F, Fremlin JH, Bull R. A study of radon emitted from building materials using plastic alpha-track detectors. Phys Med Biol 1980;25:683-94.  Back to cited text no. 9
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10.
Somogyi G, Hafez AH, Hunyadi I, Szilagly MT. Measurement of exhalation and diffusion parameters of radon in solids by plastic track detectors. Nucl Track Radiat Meas 1986;12:701-4.  Back to cited text no. 10
    
11.
Samuelsson C, Pettersson H. Exhalation of 222 Rn from porous materials. Radiat Prot Dosimetry 1984;7:95-100.  Back to cited text no. 11
    
12.
Ramola RC, Choubey VM. Measurement of radon exhalation rate from soil samples of garhwal Himalaya. India J Radioanal Nucl Chem 2004;256:219-23.  Back to cited text no. 12
    
13.
Mahur AK, Kumar R, Sengupta D, Prasad R. Estimation of radon exhalation rate, natural radioactivity and radiation doses in fly ash samples from Durgapur thermal power plant, West Bengal, India. J Environ Radioact 2008;99:1289-93.  Back to cited text no. 13
    
14.
United Nations Scientific Committee on the Effect of Atomic Radiation. Report to the General Assembly, Annex B: Exposures from Natural Radiation Sources, United Nations, New York; 2000.  Back to cited text no. 14
    
15.
International Commission on Radiological Protection. Protection Against Radon-222 at home and at Work. ICRP Publication 65. Annals of the ICRP 23(2). Oxford: Pergamon Press; 1993.  Back to cited text no. 15
    
16.
ICRP. Recommendations of the International Commission for Radiological Protection. Vol. 37. New York: ICRP Publication; 2007. p. 103.  Back to cited text no. 16
    



 
 
    Tables

  [Table 1]


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