Uranium, Radium and Radon Measurements in the ... - Springer Link

Environ Monit Assess (2007) 128:301–309 DOI 10.1007/s10661-006-9313-7

ORIGINAL ARTICLE

Uranium, Radium and Radon Measurements in the Environs of Nurpur Area, Himachal Himalayas, India Surinder Singh & Dinesh Kumar Sharma & Sunil Dhar & Arvind Kumar & Ajay Kumar

Received: 23 February 2006 / Accepted: 8 May 2006 / Published online: 21 October 2006 # Springer Science + Business Media B.V. 2006

Abstract LR-115 plastic track detectors have been used for the measurement of radon exhalation rate and radium concentration in soil and rock samples from Nurpur and its adjoining areas of Kangra district, Himachal Pradesh, India. Uranium concentration is also determined in these samples using fission track technique. The work is undertaken to explore the possibility of uranium prospection and health risk assessments due to uranium and radium in the study area. A positive correlation has been observed between uranium and radon exhalation rate in soil and rocks. Keywords LR-115 plastic . Radon . Radium . Rock . Soil . Uranium

1 Introduction The earth is radioactive since its creation. The radioactive elements such as uranium, radium and radon are present is soil, air and water. The inhalation and ingestion of these radionuclides above the permissible S. Singh (*) : D. K. Sharma : A. Kumar : A. Kumar Department of Physics, G.N.D.U, Amritsar, Punjab 143005, India e-mail: [email protected] S. Dhar Department of Geology Govt. College, Dharamsala, H.P. 176215, India

level becomes a health hazard. Therefore, concern of the monitoring of these radionuclides in the environs is increasing at all levels, due to their harmful effects. If inhaled or ingested uranium activity poses increased risk of lung and bone cancer (Agency for Toxic Substances and Disease Registery (ATSDR), 1999). Due to chemical toxicity, ingestion of uranium can cause damage to internal organs notably the kidneys (Lussenhop, Gallimore, Sweat, Struxness, & Robinson, 1958; Hursh & Spoor, 1973). The most serious health hazard associated with the uranium is lung cancer (Kathern & Moore, 1986; Kathern, McInroy, Moore, & Dietert, 1989), due to the inhalation of uranium decay product; radon. Although the kidney is considered to be the primary target in both acute and chronic situations (Legget, 1989), experimental evidence suggests that the respiratory and reproductive system are also affected by exposure (United Nations Scientific Committee on the Effects of Atomic Radiations (UNSCEAR), 2000). Uranium is the ultimate source of radium and radon. Radon isotopes are the decay products of radium in the uranium decay series. As an inert gas radon can diffuse through the soil and enter the atmosphere. Radon exposure is associated with the risk of leukemia and certain other cancers, such as malenoma and cancers of kidney and prostate (Henshaw, Eotough, & Richarbson, 1990). If uranium rich material lies close to the surface of earth there can be high radium expose hazards (Archer, Wagoner, & Lundin, 1973; Sevc, Kunz, & Placek, 1976; UNSCEAR, 1993).

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Radium is a solid radioactive element, which decays to radon, emitting alpha particles followed by gamma radiations. It is the concentration of radium, which governs how many radon atoms are formed and emanate from the mineral grains or matter. The measurements of radon thus necessitate the need for uranium and radium estimation in the parent source for public health risk assessments. The distribution of uranium is heterogeneous and is distributed in the form of plates, inclusions and veins. Soil and rocks used as building materials contains radioactive nuclides such as thorium and uranium that occurs in earth_s crust (Adams 1962; Greyh & Lorch, 1964). The analysis of rock samples for uranium prospection has been investigated by some authors (Wright & Shulhof, 1957; Grutt, 1972; Coppens and Bernand, 1978; Azam & Prasad, 1989; Jojo, 1993; Jojo, Rawat, & Prasad, 1994). The measurements of uranium, radium concentrations and radon exhalation rate have been carried out in Hamirpur, Kullu and Una districts of Himachal Pradesh (Kumar, Singh, & Singh, 2001; Singh, Kumar, Jojo, & Prasad, 1998a; Singh, 2001a; Singh, Singh, & Kumar, 2001b). In the present investigations, the survey has been carried out first time for the measurements of uranium, radium concentrations and radon exhalation rate in soil and rock sample from Kangra district, Himachal Pradesh. The aim of the work is to explore the possibility of uranium exploration and health risk assessments of uranium and radium in the study area. 2 Experimental Method 2.1 Geology of area Himachal Pradesh lies in the north-western Himalayas with mountainous terrain between the river Ravi in the North-West and Tons (Yamuna) in the South-West falling within the latitude 30°220 –33°100 N and longitude 70°460 –79°000 E. The district Kangra in the state of Himachal Pradesh lies between 31°400 – 32°250 North latitudes and 75°350 –77°50 East longitudes. The district is bounded on the South-West by Una district, on the North-West by district Gurdaspur of Punjab, on the North by Lahul-Spiti and Chamba districts, on the east by Kullu and Mandi districts, while on South it touches Hamirpur district (Figure 1). The elevation generally varies from 500 to 5,500 m from mean Sea level. Geologically the state is marked

Environ Monit Assess (2007) 128:301–309

by diversed lithology ranging in age, right from Archean-Proterozoic transition period. The area under study represents a thick succession of lower, middle and upper Shiwalik sediments which comprises mainly the sand stones, clays and boulder conglomerates and which are succeeded by recent alluvium towards the south. Stratigraphically the Shiwaliks are divided into lower, consisting of highly compact hard red and green sand stone, purple shale_s and pseudo conglomerates, overlain by the middle, comprising of loose grey sand stones and greyish clay, further overlain by the upper Shiwaliks, soft friable loose sandstone, clays and conglomerates. 2.2 Uranium estimation For the estimation of uranium content in soil and rock samples, the fission track technique has been used (Fisher, 1970; Fleischer, Price, & Walker, 1975; Singh, Singh, Singh, & Virk, 1986; Azam & Prasad, 1989; Jojo, 1993; Kumar, Malhorta, Singh, & Singh, 1995; Singh, Singh, Singh, & Virk, 1988; Singh, Singh, Sandhu, & Singh, 1999a; Singh, Sengupta, & Prasad, 1999b; Singh 2001a, b; Kalsi, Ramaswami, Sexena, & Manchanda, 2005). A homogeneous mixture was made by taking 50 mg of soil or rock samples powder (200 mesh sieve) from each village and 100 mg of methyl cellulose (act as binder and is free from uranium). The small and thin pellets (0.1 cm thick) of these geological samples from different villages were made using a hydraulic pellet-making machine. These pellets were enclosed in a aluminium capsule after placing them inbetween the lexan plastic track detector discs and irradiated with thermal neutrons at Bhaba Atomic Research Centre Mumbai, India with a thermal neutron fluence of 2 × 1015 neutrons cm−2 in Cirus Reactor. The fission fragments resulting from (n, f) reaction in 235 U are recorded by lexan plastic track detectors kept in contact with the soil and rock samples and the standard material (Fischer glass). After etching in 6.25 N NaOH solution at 70 °C for 30 min, the developed fission tracks were counted using an optical microscope at a magnification of 400×. Uranium concentration was calculated using the relation (Fleischer et al., 1975): TX IS RS UX ¼ US TS IX RX where TX and TS represents the fission track density for sample and standard material, respectively, (Fischer


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Figure 1 Map of Hamachal Pradesh showing Nurpur area surveyed during the present investigations.

glass, U concentration is 20 ppm). IX and IS are the isotopic abundance ratios of 235U to 238U in the unknown and standard samples, respectively. R is the mean range of fission fragments (mg cm–2). Since the tracks are sensitive to etching and annealing conditions so all the measurements were carried out under similar conditions. IS/IX and RS/RX have been taken as unity assuming that the isotopic abundance (IS and IX) and the range of fission fragments (RS and RX) are the same for the sample and the standard (Fleischer et al., 1975). Therefore the above equation becomes TX UX ¼ US TS In order to avoid errors due to external contamination and roughness at the peripheral zones, only the central region of the detector disc was scanned. The detection limit and precision of uranium determination by fission track technique are reported to be 0.05 ppm and 5%–10%, respectively (Fleischer et al., 1975). 2.3 Estimation of radium and radon exhalation rate in geological samples The ‘Can technique’ (Alter & Price, 1972; Abu-Jarad, 1988; Somogyi, 1990; Khan, Prasad, & Tyagi, 1992) is

used for the measurement of radium and radon exhalation rate in some soil and rock samples from different villages of the area. The dried samples from different villages are finely powdered and sieved through a 200 mesh sieve. The fine powder (250 g) of samples from each village is placed in different glass bottles and sealed with thin polyethylene sheets for 30 days so as to attain the equilibrium. After one month, LR-115 type 2 plastic track detectors are fixed on the lower side of cork lids, which are then gently pressed against the polyethylene sheets on the glass bottles (acting as emanation chambers, Figure 2) so that the equilibrium is not disturbed or there is minimum possible disturbance, if any. The bottles are then sealed and left as such for 90 days so that the detectors can record α-particles resulting from the decay of radon. The exposed detectors are etched in 2.5 N NaOH solution at 60 °C for 2 h using a constant temperature bath. The tracks are counted using an optical microscope at 400X magnification. The ‘Can technique’ proposed by Alter and Price (1972) and later developed by Somogyi (1990) is used to calculate the radium concentration in soil and rock samples. The radium concentration is calculated using the relation: ρhA CRA ¼ KTe M

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the bottle (m2). The radon exhalation rate in terms of mass is calculated from the expression: CV 1

EM ¼ M T þ 1=1 e1 T 1 Here EM is the radon exhalation rate in terms of mass (Bq kg−1h−1) and M is the mass of soil/rock sample (250 gm). A calibration constant of 4.8 × 102 tracks cm−2 day−1 per WL of radon at equilibrium determined by Subba Ramu, Muraleedharan, and Ramachandran (1988) is used for the conversion of track density into radon concentration (Bq m−3). 3 Results and Discussion

Figure 2 The apparatus used to study the radium and radon exhalation rate of soil and rock samples.

where CRA is the effective radium content of the given sample (Bq kg−1), ρ is the track density (track cm−2 ), M is the mass of the sample (250 g), A is the area of cross-section of bottle (7.55 × 10−3 m2), h is the distance between the detector and the top of the sample (0.153 m), K is the sensitivity factor, which is equal to 0.0245 tracks cm−2 d−1 per Bq m−3 (Azam, Naqvi, & Srivastava, 1995) and Te is the effective exposure time (in days) which is related with the actual exposure time t and decay constant 1 for 222Rn with the relation: . 1 Te ¼ T 1 1 1 e T The radon exhalation rate in terms of area is calculated from the equation (Abu-Jarad, 1988; Khan et al., 1992). CV 1 1

EM ¼ A T þ 1 1 e T 1 where EA is the radon exhalation rate expressed in Bq m−2 h−1, C is the integrated radon exposure (Bq m−3 h), V is the effective volume of the bottle in cubic meter (m3), T is the exposure time in hour (h), 1 is the decay constant for radon (h−1) and A is the area of

The value of uranium, radium and radon exhalation rate in soil and rock samples from different locations in Nurpur area of district Kangra, Himachal Pradesh are given in Tables I, II, and III. It is evident from the tables that the uranium concentration in soil varies from 0.75 mg kg−1 in village Khajjian to 2.06 mg kg−1 in village Nanoohan with an average of 1.49 mg kg−1. In rocks it varies from 0.37 mg kg−1 in village

Table I Values of uranium concentration is soil and rock samples from Nurpur area district Kangra, Himachal Pradesh Sr. no.

Village/location

Uranium conc. (mg kg−1) Soil

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

Raja ka Talab Dehri Rehan Harnota Bharmar Jawali Pharian Batt-bhallun Ganoh Garan Larath Nanoohan Banal Dhameta Jassur Nurpur Khajjian Dahab

1.43 1.32 1.49 1.39 0.99 1.82 1.63 1.61 1.46 1.37 1.69 2.06 1.63 1.15 1.06 1.43 0.75 1.15

Rocks ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.04 * 0.04 0.04 0.04 0.03 0.04 0.04 0.04 0.04 0.04 0.04 0.05 0.04 0.03 0.03 0.04 0.03 0.03

1.12 0.65 1.27 1.28 1.02 2.79 0.85 4.42 1.45 0.84 0.80 2.83 2.10 1.01 1.62 1.72 0.37 0.70

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.03 * 0.03 0.04 0.05 0.03 0.05 0.03 0.07 0.04 0.03 0.03 0.05 0.05 0.03 0.04 0.04 0.02 0.03

*The errors shown in the results are (1σ) statistical counting errors: Where 1σ = uranium conc./√ N, where N is the number of tracks.


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Table II Values of radium and radon exhalation rate from soil samples of Nurpur area, district Kangra (H.P.) Sr. no.

Village/ location

Radium conc. (Bq. kg−1)

Radon exhalation rate EA (mBq m−2 h−1)

EM (mBq kg−1 h−1)

1.

Raja ka Talab Dehri Rehan Harnota Bharmar Jawali Pharian Battbhalun Ganoh Garan Larath Nanoohan Banal Dhameta Jassur Nurpur Khajjian Dahab

24.72

1,077.11

32.52

22.06 15.35 11.54 16.93 25.72 15.22 14.10

959.89 668.44 502.12 736.55 1,119.87 662.10 613.00

28.98 20.18 15.16 22.24 33.82 19.99 18.51

26.71 17.13 18.05 18.43 16.66 19.82 21.26 15.55 12.53 21.66

1,162.64 744.47 785.65 801.49 725.46 861.68 925.04 676.36 544.89 942.47

35.11 22.48 23.72 24.20 21.90 26.02 27.93 20.42 16.45 28.46

2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

−1

Khajjian to 4.42 mg kg in village Batt-Bhalun with an average of 1.41 mg kg−1. The radium concentration in soil varies from 11.54 Bq kg−1 in village Harnota to 26.71 Bq kg−1 in village Ganoh. In rocks it varies from 2.58 Bq kg−1 in village larath to 26.06 Bq kg−1 in village Jawali with a exceptionally high value of 96.06 Bq kg−1 in village Batt-Bhallun. The radium activity in soil is found to be more than the rocks of the study area. The radon exhalation rate in soil varies from 502 m Bq m−2 h−1 (15.16 m Bq kg−1 h−1) in village Harnota to 1163 m Bq m−2 h−2 (35.11 m Bq kg−1 h−1) in village Ganoh. In rock samples it varies from 106 m Bq m−2 h−1 (3.17 m Bq kg−1 h−1) in village larath to 1149 m Bq m−2 h−2 (34.69 m Bq kg−1 h−1) in village Jawali, except one high value of 3932 m Bq m−2 h−2 (119 m Bq kg−1 h−1) in village Batt-Bhallun. In the present investigations the observed values of uranium concentration in soil and rock samples are comparable to those determined in the soil and rocks of Una district (Kumar et al., 2001) but are lower than reported in the soil and rocks of Hamirpur and Kullu districts of Himachal Pradesh (Singh et al., 1998a, b,

2001a; Singh, Malhotra, Kumar, & Singh, 2001c; Singh, Kumar, & Singh, 2002). The average values of uranium contents in the study area are comparable to the world average of uranium in soil 2.1 mg kg−1, (Kaul, Umamaheshwar, Chandrasekaram, Deshmukh, & Swarnkar, 1993). The values of radium and radon exhalation rate in soil and rock samples observed in the present investigation are quite lower than the values determined by Singh et al. (1998a, b, 2001a, c) in Hamirpur and Kullu districts of Himachal Pradesh. The high uranium, radium and radon values in some areas of Hamirpur and Kullu districts may be due to the presence of uranium mineralization in these areas reported earlier by some authors (Narayan Dass, Parathasarthy, & Taneja, 1979; Kaul et al., 1993). It can be seen from the Tables II and III that the radon exhalation rate varies appreciably from one place to another. This variation may be due to the differences in radium content (Ramachandran & Subba Ramu, 1989) and porosity of the soil (Folkerts, Keller, & Muth, 1984). The maximum acceptable value of radium activity in soil and rocks (building materials) must be less

Table III Values of radium and radon exhalation rate from rock samples of Nurpur area district Kangra, (H.P.) Sr. no.

Village/ location

Radium conc. (Bq kg−1)

Radon exhalation rate EA (mBq m−2 h−1)

EM (mBq kg−1 h−1)

1.

Raja ka Talab Dehri Rehan Harnota Bharmar Jawali Pharian Battbhallun Ganoh Garan Larath Nanoohan Banal Dhameta Jassur Nurpur Khajjian Dahab

8.72

352.17

10.76

4.67 4.95 4.67 4.74 26.06 5.02 96.06

191.44 202.87 191.44 194.30 1,148.71 205.72 3,931.90

5.77 6.11 5.77 5.86 34.69 6.20 118.73

3.21 4.04 2.58 14.87 14.10 5.09 5.72 18.43 4.74 3.07

131.43 165.73 105.71 608.63 577.20 208.59 234.30 754.37 194.30 125.72

3.96 4.99 3.17 18.36 17.42 6.29 7.07 22.76 5.86 3.78

2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

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Environ Monit Assess (2007) 128:301–309 40

35

-1

-1

Radon Exhalation Rate( mBq kg h )

30

25

20

15

10

5

0 0

0.5

1

1.5

2

2.5

Uranium Conc.(mg/kg) Figure 3 Uranium concentration vs radon exhalation rate in soil.

than 370 Bq kg−1 for safe use i.e., to keep the external dose below 1.5 mGy per year (OECD, 1979; Beretka & Mathew, 1985). The observed values of radium activity in soil and rock samples in the present study are less than this maximum permissible value and Figure 4 Uranium concentration vs radon exhalation rate in Rocks.

much lower than the global value of 30 Bq kg−1 (UNSCEAR, 1993) and those reported by Nageswara Rao, Bhati, Rama Seshu, and Reddy (1996) (average value 43.8 Bq kg−1) and Mittal et al., (1998) (average value 46.17 Bq kg−1) for soil of Rajasthan area. The


307 5

Figure 5 Uranium concentration in soil vs uranium concentration in rocks. Uranium Conc. in Rocks(mg/kg)

4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 0

0.5

1

1.5

2

2.5

Uranium Conc. in Soil(mg/kg)

values of radium contents in soil are lower than that in the soil of Aligarah, Dhanbad, Jaduguda, Jasilmar and Tehri areas but are higher than those reported in the soil of Jamnagar, Ooty and Poona areas (Mishra & Sadasivan, 1971; Kamath, Menon, Shukla, Sadasivan, & Nambi, 1996; Sadasivan & Shukla, 2001; Sadasivan, Shukla, Chinnasakei, & Sartandel, 2003; Ramachandran, Eappen, Nair, Mayya, & Sadasivan, 2003). The radium contents in the rocks of the study area are either comparable or lower than those reported in other major studies (Sankaran, Jayaswal, Nambi, & Sunta, 1986; Ramachandran et al., 2003). The values of uranium concentration in soil are well below the levels generally observed in the uranium rich soils (20– 200 ppm, Jonsson, 1991) and are thus not significant from the exploration point of view. Thus, the results reveal that the area is safe as for as the health hazard effects of uranium and radium are concerned. Figures 3 and 4 show the graphs between uranium concentrations and radon exhalation rates in soil & rock samples of the study area, respectively. The figures show the general trend that as the content of uranium (the parent source) increases, the content of the corresponding daughter i.e., radium also increases which enhances the radon exhalation rate. A positive but weak correlation has been observed between uranium and radon exhalation rate in soil (Figure 3). However a strong positive correlation has been observed between uranium and radon exhalation rate in rock samples (Figure 4). Similar behavior has also been

observed earlier by (Kumar et al., 2001) for the soils of Una district of Himachal Pradesh, India and by Singh et al., 1999b in the rocks from the uranium mining areas of Bihar state in India. A positive correlation has also been observed between uranium contents in soils and rocks of the study area (Figure 5). These results support the fact that the concentration of uranium in soils depends largely on the presence of uranium in associated parent material i.e., Rocks (World Health Organization (WHO), 2001). 4 Conclusions (1) The average values of uranium contents in the study area are comparable to the world average of uranium in soil. (2) The values of radium and radon exhalation rate in soil and rock samples of the study area are quite lower than the areas known for uranium mineralization. Therefore, the use of these geological samples for construction activities is considered to be safe. (3) The values of uranium and radium concentrations are below the recommended safe limits. The values of uranium concentrations are not significant from exploration point of view. (4) The results reveal that the area is safe as for as the health hazard effects of uranium and radium are concerned. (5) A positive correlation has been observed between uranium concentration and radon exhalation rate

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