| Home | E-Submission | Sitemap | Contact Us |  
top_img
J. Radiat. Prot. Res > Volume 47(1); 2022 > Article
Srivastava, Chahar, Chauhan, Krupp, and Scherer: Study of Naturally Occurring Radioactive Material Present in Deep Soil of the Malwa Region of Punjab State of India Using Low Level Background Gamma-Ray Spectrometry

Abstract

Background

Epidemiological observations such as mental retardation, physical deformities, etc., in children besides different types of cancer in the adult population of the Malwa region have been reported. The present study is designed to get insight into the role of naturally occurring radioactive material (NORM) in causing detrimental health effects observed in the general population of this region.

Materials and Methods

Deep soil samples were collected from different locations in the Malwa region. Their activity concentrations were determined using low-level background gamma-ray spectrometry. High efficiency and high purity germanium detector capped in a lead-shielded chamber having a resolution of 1.8 keV at 1,173 keV and 2.0 keV at the 1,332 keV line of 60Co was used in the present work. Data were evaluated with Genie-2000 software.

Results and Discussion

Mean activity concentrations of 238U, 232Th, and 40K in deep soil were found to be 101.3 Bq/kg, 65.8 Bq/kg, and 688.6 Bq/kg, respectively. The mean activity concentration of 238U was found to be three and half times higher than the global average prescribed by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). It was further observed that the activity concentration of 232Th and 40K has a magnitude that is nearly one and half times higher than the global average prescribed by UNSCEAR. In addition, the radioisotope 137Cs which is likely to have its origin in radiation fallout was also observed. It is postulated that the NORM present in high quantity in deep soil somehow get mobilized into the water aquifers used by the general population and thereby causing harmful health problems.

Conclusion

It can be stated that the present work has been able to demonstrate the use of low background gamma-ray spectrometry to understand the role of NORM in causing health-related effects in a general population of the Malwa region of Punjab, India.

Introduction

Naturally occurring radioactive material (NORM) namely 238U, 232Th, and 40K have been present in our surroundings since time immemorial. The carcinogenic radon as well as polonium is produced from their decay. Anthropogenic interventions like agriculture, industrial and mining activities may lead to the increase in their concentration [1]. NORM is known to cause not only chemical toxicity and radiological toxicity but combined synergetic effect of both [2]. Their exposures may cause kidneys and lungs related diseases, DNA damage and sub-cellular organelles activity, etc. [35].
Lately, there has been an increasing concern about harmful health effects arising from NORM in the Malwa region of Punjab State located in the North Western part of India. This region has been reported to have a high incidence of cancer [6, 7]. The incidence of cancer in India is estimated to be 80 per 100,000 population whereas incidence of cancer in the Malwa region of Punjab State in India is observed to be 90 per 100,000 population [8]. A number of researchers [911] have reported that the concentration of uranium in the groundwater in the Malwa region is significantly higher not only with respect to the permissible limit of 15–30 ppb prescribed by international regulators like the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) [12], the World Health Organization (WHO) [13] and the United States Environmental Protection Agency (EPA) [14] but also with respect to the concentration levels observed in other regions of India [1517].
Schnug and Lottermoser [18] stressed the significance of fertilizer-derived uranium for groundwater contamination in regions with a low geogenic uranium background. Punjab State being the food bowl of India has seen excessive use of chemical fertilizers in the past few decades. Therefore contribution from phosphate fertilizers which are known to be enriched with NORM also cannot be ruled out.
In the present work, the low-level background high-resolution gamma-ray spectrometer has been employed to obtain the concentration of NORM in deep soil samples to understand its contribution in bringing about detrimental public health effects reported in its general population.

Materials and Methods

1. Samples Collection

Soil Samples observed to be free of roots from the depth ranging between 30 cm and 180 cm which are normally expected to remain undisturbed from anthropogenic activity, soil erosion, soil turnover, irrigation, phytoaccumulation, etc., were collected by using the standard Auger method from 15 different locations of the Malwa region of Panjab State in India. The region in Malwa from where the samples were collected is shown encircled in red in Fig. 1 [19].

2. Sample Analysis

The samples after drying and pulverizing were placed in a petri dish after recording their mass. Each petri dish was sealed and kept for 5 weeks to ensure secular equilibrium between parent and daughter products. To avoid bias, the samples were encoded with neutral names. Their radionuclide content was determined using ultra-low-background gamma-ray spectrometric setup of the Radiation Counting Laboratory of Hochschule Mannheim, Mannheim, Germany, which is shown in Fig. 2.
The Petri dishes containing the samples were measured for 24 hours. Counting was carried out using 16k multichannel analyzers employing high-efficiency HPGe detectors kept in Pb shielded chambers. The detectors had a resolution of 1.8 keV at 1,173 keV line and 2.0 keV at the 1,332 keV line of 60Co.
Data was evaluated with Genie-2000 (Canberra Industries Inc., Meriden, CT, USA) by using efficiency curves for each detector measured with an aliquot of a standardized commercial multi-nuclide calibration solution (Eckert & Ziegler, Berlin, Germany) which was carefully mixed with silica gel and placed into a Petri dish of the same dimension (i.e., 90 mm or 70 mm diameter) as the samples and placed in identical positions as the samples.
The energy calibration was performed with the nuclides of the samples. A nuclide library based on the International Atomic Energy Agency (IAEA) isotope browser [20] was used for nuclide identification and activity calculation.
Background spectra were taken for 72 hours in order to keep the computational uncertainties small. Repeated background measurements revealed a stable situation during the counting campaign. In order to keep the background rates low, radiation shields built from 10 cm of old lead lined with 1 mm electrolytic copper surrounded the detectors. The internal volume of the shield was continuously rinsed by the evaporated nitrogen from the Dewar vessel.

3. Radioactivity Calculation

The activity of 238U was estimated by measuring the peak area under the gamma line of 214Pb occurring at 351.9 keV besides 609.3 keV gamma line of 214Bi. The 232Th activity was estimated by measuring the peak area under gamma lines of 228Ac namely 911.2 keV and 968.9 keV. The 40K activity was estimated using 1,461 keV gamma line peak area and activity of 137Cs was estimated by measuring the peak area under the 661.7 keV gamma line. The activities were obtained together with their standard uncertainties by a routine fitting of Gaussian distribution to each line. The same is performed with the background spectra. The count rates of gamma lines of interest were automatically subtracted from the sample spectra by a routine in Genie-2000 yielding net count rates. In the next step of analysis, the count rate of each gamma line was calculated by dividing by the counting efficiency at its energy as obtained from a standard fitting routine in Genie-2000. With the aid of a radionuclide library with data from the IAEA isotope browser, the gamma lines were identified. By using the emission rates of each gamma line, the activity of the nuclide was calculated as the weighted mean of the activities obtained for the gamma lines of interest of each radionuclide.
Typically, the nuclides of the 4n and 4n+2 natural decay series were observed, in some cases, also 235U and some of its descendants from the 4n+3 series. The thorium series reaches equilibrium quickly and, hence, in most cases, is found to be in secular equilibrium. This is different from the uranium series where hydrogeological separation of uranium and thorium from the radium is found frequently. Soluble uranyl and thorium cations can be dissolved in carbonaceous and sulfatic groundwater whereas radium is sparely soluble under these conditions. As a consequence, the direct progeny of 238U, 234Pa is not visible in the gamma-ray spectra, as well as 235U. This is relevant as the only gamma-ray emission of 226Ra at 186.2 keV (15.7%) coincides with the strongest gamma line of 235U. The contribution of this can be estimated from other strong gamma lines and be subtracted from the sum peak if present. If gamma lines of 234mPa and 235U were identified, the activity at 186 keV was attributed to 238U in equilibrium with 226Ra. In addition, the activity ratio of 235U and 238U was checked to be reasonable. In all other cases, activity was attributed to 226Ra separated geochemically from its longer-lived parents.

Results and Discussion

Table 1 gives the mean activity concentration of 238U, 232Th, 40K, and 137Cs based on three measurements for each of the 15 deep soil samples namely M1 to M15 collected from different locations in Malwa region. Table 1 also gives the overall mean activity concentration of the radioisotopes of interest with its associated 1σ standard deviation. In the case of 137Cs, only two samples yielded mean activity concentration above the limit of detection. Hence, a range is given. Table 2 gives the mean global NORM activity level prescribed by UNSCEAR [12]. The mean activity level of 238U, 232Th, 40K in soils from an area close to Malwa region which has been reported in literature [2123] is also shown in Table 2 along with the data obtained in the present work.
Table 1 shows that the activity concentration of 238U ranges between 65.5 Bq/kg and 154.4 Bq/kg. It is also observed that the activity concentration of 232Th ranges between 52.0 Bq/kg and 77.5 Bq/kg, whereas the activity concentration of 40K ranges between 585.3 Bq/kg and 895.2 Bq/kg. The mean and the associated standard deviation values of 238U, 232Th, and 40K are found to be 101.3±23.5 Bq/kg, 65.8±7.3 Bq/kg, and 688.6±93.9 Bq/kg, respectively.
In addition to the aforementioned radioisotopes, 137Cs with an activity concentration close to the limit of detection of ≤0.5 Bq/kg and, in some cases, around 1.5 Bq/kg was also observed. The presence of abovementioned radionuclides could perhaps be the trace to the radiation fallout, which may have found its way into the deep soil presumably as a result of irrigation and agricultural activities carried out over the years. A comparison of the data obtained in the present work with the global average data reported by UNSCEAR [12] shows that the 238U activity concentration determined in the present work has a magnitude which is nearly three and a half times higher than the global average whereas the activity concentration of 232Th and 40K has a magnitude which is nearly one and half times higher than the global average.
It is further observed that the deep soil NORM activity concentration which has been determined for the first time in the present work is significantly higher than the activity concentration reported in literature for top soils [12, 21, 22]. This could perhaps be due to the deep soil NORM concentration remaining unaffected by phytoaccumulation and other farm practices of the local area which lead to transportation of matter from the lower to the upper part of the soil. It can be further hypothesized that the NORM present in the deep soil of the Malwa region could lead to the enrichment of the groundwater of Malwa region by getting mobilized from the terrestrial to the aquatic environment when conducive geochemical conditions occur. The groundwater enriched in NORM is then somehow finding its way into the general population causing health problems.

Conclusion

It can be stated that the NORM activity concentration of the deep soil determined in the present work from area where the local population has been reported to be affected by detrimental health effects is comparatively higher and may lead to health-related problems if mobilized to aquifers. A more detailed study is needed to be carried out to get a clearer picture of the existing problem.

Acknowledgements

The authors are thankful to Ms. Archana Negi and Ms. Ritika Gupta for assistance in preparation and collection of samples. Alok Srivastava would like to place in record his special thanks to Panjab University, Chandigarh, India and Alexander von Humboldt Foundation, Bonn, Germany for providing him funds to carry out part of the research work in Germany. Neeraj Chauhan is grateful to the University Grants commission of Government of India for the grant of Junior Research Fellowship to him.

NOTES

Conflict of Interest

No potential conflict of interest relevant to this article was reported.

Author Contribution

Conceptualization: Srivastava A. Data curation: Chahar V, Chauhan N. Formal analysis: Chahar V, Chauhan N, Krupp D, Scherer U. Funding acquisition: Srivastava A, Scherer U. Methodology: Krupp D. Writing - original draft: Srivastava A. Writing - review & editing: Srivastava A, Krupp D, Scherer U. Investigation: Krupp D, Scherer U. Supervision: Srivastava A, Scherer U.

References

1. Bleise A, Danesi PR, Burkart W. Properties, use and health effects of depleted uranium (DU): a general overview. J Environ Radioact. 2003;64(2–3):93-112.
crossref pmid
2. Busby C, Schnug E. Advanced biochemical and biophysical aspects of uranium contamination. In: De Kok LJ, Schnug E. Loads and fate of fertilizer derived uranium. Leiden, Netherlands, Backhuys Publishers. 2008;11-22.

3. Kang JK, Seo S, Jin YW. Health effects of radon exposure. Yonsei Med J. 2019;60(7):597-603.
crossref pmid pmc
4. Bjorklund G, Christophersen OA, Chirumbolo S, Selinus O, Aaseth J. Recent aspects of uranium toxicology in medical geology. Environ Res. 2017;156:526-533.
crossref pmid
5. Harrison J, Leggett R, Lloyd D, Phipps A, Scott B. Polonium-210 as a poison. J Radiol Prot. 2007;27(1):17-40.
crossref pmid
6. Blaurock-Busch E, Busch YM, Friedle A, Buerner H, Parkash C, Kaur A. Comparing the metal concentration in the hair of cancer patients and healthy people living in the Malwa region of Punjab, India. Clin Med Insights Oncol. 2014;8:1-13.
crossref pmid pmc
7. Blaurock-Busch E, Friedle A, Godfrey M, Schulte-Uebbing CE, Smit C. Metal exposure in the children of Punjab, India. Clin Med Insights Ther. 2010;2:655.
crossref
8. Lavit K, Shalini S. Mitigating cancer mortality in Punjab: a challenge for development. Indian J Econ Dev. 2017;13(2a):36-41.
crossref
9. Bajwa BS, Kumar S, Singh S, Sahoo SK, Tripathi RM. Uranium and other heavy toxic elements distribution in the drinking water samples of SW-Punjab, India. J Radiat Res Appl Sci. 2017;10(1):13-19.
crossref
10. Kumar A, Usha N, Sawant PD, Tripathi RM, Raj SS, Mishra M, et al. Risk assessment for natural uranium in subsurface water of Punjab State, India. Hum Ecol Risk Assess. 2011;17(2):381-393.
crossref
11. Alrakabi M, Singh G, Bhalla A, Kumar S, Kumar S, Srivastava A, et al. Study of uranium contamination of ground water in Punjab state in India using X-ray fluorescence technique. J Radioanal Nucl Chem. 2012;294(2):221-227.
crossref
12. United Nations Scientific Committee on the Effects of Atomic Radiation. Sources and effects of ionizing radiation. 1:New York, NY, United Nations Scientific Committee on the Effects of Atomic Radiation. 2000.

13. World Health Organization. Guidelines for drinking-water quality. 4th ed. Geneva, Switzerland, World Health Organization. 2011.

14. United States Environment Protection Agency. 2011 edition of the drinking water standards and health advisories. Washington, DC, United States Environment Protection Agency. 2011.

15. Bhardwaj S, Shukla DP, Halder A. Spatial distribution of uranium and chemo-radiological assessment in Hamirpur district, Himachal Pradesh, India. J Radioanal Nucl Chem. 2020;324(2):467-480.
crossref
16. Kumar D, Singh A, Jha RK. Spatial distribution of uranium and basic water quality parameter in the capital of Bihar and consequent ingestion dose. Environ Sci Pollut Res Int. 2018;25(18):17901-17914.
crossref pmid
17. Bajaj M, Eiche E, Neumann T, Winter J, Gallert C. Hazardous concentrations of selenium in soil and groundwater in North-West India. J Hazard Mater. 2011;189(3):640-646.
crossref pmid
18. Schnug E, Lottermoser BG. Fertilizer-derived uranium and its threat to human health. Environ Sci Technol. 2013;47(6):2433-2434.
crossref pmid
19. Central Water Commission [Internet]. Chandigarh, India, Government of India. 2020;[cited 2022 Mar 1]. Available from: http://cwc.gov.in/ibo/about-basins .

20. International Atomic Energy Agency. IAEA isotope browser app now available in multiple languages [Internet]. Vienna, Austria, International Atomic Energy Agency. 2017;[cited 2022 Mar 1]. Available from: https://www.iaea.org/newscenter/news/iaea-isotope-browser-app-now-available-in-multiple-languages .

21. Srivastava A, Lahiri S, Maiti M, Knolle F, Hoyler F, Scherer UW, et al. Study of naturally occurring radioactive material (NORM) in top soil of Punjab State from the North Western part of India. J Radioanal Nucl Chem. 2014;302(2):1049-1052.
crossref
22. Kumar A, Kumar S, Singh J, Singh P, Bajwa BS. Assessment of natural radioactivity levels and associated dose rates in soil samples from historical city Panipat, India. J Radiat Res Appl Sci. 2017;10(3):283-288.
crossref
23. Srivastava A, Chahar V, Sharma V, Sun Y, Bol R, Knolle F, et al. Study of uranium toxicity using low-background gamma-ray spectrometry. J Radioanal Nucl Chem. 2017;314(2):1367-1373.
crossref

Fig. 1
Map showing the collection sites (encircled in red) in the Malwa region of Punjab State, India. Adapted from [19].
jrpr-2021-00031f1.jpg
Fig. 2
Ultra-low-background gamma-ray spectrometric setup of Hochschule Mannheim, Mannheim, Germany.
jrpr-2021-00031f2.jpg
Table 1
Mean Activity Concentration of 238U, 232Th, 40K, and 137Cs (unit: Bq/kg)
Sample number 238U 232Th 40K 137Cs
M1 113.6 74.7 801.3 ≤0.5
M2 87.7 62.9 716.8 ≤0.5
M3 90.2 72.7 895.2 ≤0.5
M4 88.9 67.0 719.9 ≤0.5
M5 111.2 77.5 651.0 ≤0.5
M6 65.5 52.0 663.6 1.4
M7 85.2 65.0 635.4 ≤0.5
M8 82.7 62.5 788.8 ≤0.5
M9 102.5 60.1 698.0 ≤0.5
M10 140.8 64.6 585.3 ≤0.5
M11 96.3 60.9 694.9 ≤0.5
M12 154.4 59.3 616.1 ≤0.5
M13 85.2 59.7 585.3 1.6
M14 98.8 72.7 629.1 ≤0.5
M15 118.6 74.3 732.4 ≤0.5
Mean±SDa) 101.3±23.5 65.8±7.3 688.6±93.9 ≤0.50–1.6

The activity concentration of 238U ranges between 65.5 Bq/kg and 154.4 Bq/kg, the activity concentration of 232Th ranges between 52.0 Bq/kg and 77.5 Bq/kg, whereas the activity concentration of 40K ranges between 585.3 Bq/kg and 895.2 Bq/kg.

In the case of 137Cs only two samples yielded mean activity concentration above the limit of detection. Hence, a range is given.

a) Associated standard deviation value.

Table 2
Activity Concentration Data Obtained in the Present Work along with the Data from Literature
NORM (Bq/kg)
UNSCEAR [12] Srivastava et al. [21] Kumar et al. [22] Srivastava et al. [23] Present work
238U 30a) 20.9±3.7 30.2±0.5 42.7±5.3 101.0±23.5
232Th 45a) 34.7±10.3 29.9±0.6 45.8±4.6 65.8±7.3
40K 420a) 407.0±113.0 291.0±1.0 587.0±52.8 688.0±94.0

Values are presented as mean±standard deviation.

The mean global NORM activity level prescribed by UNSCEAR [12]; the mean activity levels of 238U, 232Th, 40K in soils from area close to the Malwa region which have been reported in literature [2123].

NORM, naturally occurring radioactive material; UNSCEAR, United Nations Scientific Committee on the Effects of Atomic Radiation.

a) Recommended value.

Editorial Office
319, HIT, 22-2, Majo-ro, Seongdong-gu, Seoul 133-791, Korea
Tel: +82-2-2297-9775   Fax: +82-2-2297-9776
About |  Browse Articles |  Current Issue |  For Authors and Reviewers
Copyright © by Korean Association for Radiation Protection. Developed in M2PI