Measurement of uranium and radon concentration in drinking water samples and assessment of ingestion dose to local population in Jalandhar district of Punjab,India

Abstract

A study was conducted to assess the concentration of uranium and dissolved radon in drinking water samples collected from Jalandhar district of Punjab, India. The samples were analysed for dissolved radon using scintillation cell method. Laser fluorimetry was used for measurement of uranium concentration. Correlation analysis of radon and uranium concentrations and salinity and total dissolved solids with uranium was carried out. The uranium concentration in water samples varied from a minimum value of 1.53 ± 0.06 mg m⁻³ to 50.2 ± 0.08 mg m⁻³ with a geometric mean value of 14.85 mg m⁻³. The radon concentration in water varied from a minimum value of 0.34 ± 0.07 kBq m⁻³ to a maximum value of 3.84 ± 0.48 kBq m⁻³ with a geometric mean value of 1.46 kBq m⁻³. Ingestion dose to local population, due to radon and uranium in drinking water, for different age categories, was computed and results are being reported in this paper.

Keywords

Radon Uranium Ingestion dose

Introduction

Radioactive contamination of ground water is a matter of great concern as it could lead to ingestion dose in humans. Uranium, a naturally occurring radioactive element, is important from a point of view of environmental radioactivity as it contributes a number of radioactive elements through its decay chain. Uranium is found naturally in different valance states from +2 to +6 with hexavalent state being most common.¹ It is found in nature in different types of rocks such as granites, sand stones and other mineral deposits.² Through the process of leaching from natural deposits, uranium enters the ground water and ultimately reaches the food chain through plants and drinking water. Though the normal concentration of uranium in ground water is reported to be in the range 0.1 to 10 mg m⁻³, higher concentrations are possible in areas having elevated levels of uranium in rocks and soil.³ Concentration of uranium in groundwater depends on geomorphological, lithological and geological conditions of the area.⁴ Health risks to humans from uranium are twofold: radiation exposure through its decay chain and chemical toxicity. The major contribution of radiation dose in uranium decay series comes from Radon (²²²Rn) and its short-lived progenies, which is the largest single source of radiation exposure to humans. Of the total radiation received by humans, radon and its decay products contributes 51% through inhalation and 0.21% through ingestion.⁵ Due to this reason, past studies had focused on measurement of radon concentration in indoor air in order to assess the inhalation dose. Radon dissolved in water could lead to radiation exposure through ingestion in addition to its contribution to indoor air.⁶ Radon in water if accompanied by elevated levels of uranium could lead to significant radiation dose in children and infants.⁷ Therefore, a proper assessment of radon and uranium together in drinking water is essential to assess the radiation dose and the associated health risk to public if any. Very few studies have been conducted in India to measure the uranium and radon concentration in drinking water.^8–11 In this context, a survey was carried out to assess the concentration of dissolved radon and uranium in drinking water samples in Jalandhar district of Punjab, India. The survey also assumes significance, since elevated levels of uranium has been reported, in some samples, from adjoining regions of Punjab state in recent studies.^12–14

Study area and geology

The study area for this survey, as shown in Figure 1, lies between 30° 59': 31° 37' north latitude and 75° 04': 75° 57' east latitudes. The study area is part of Bist Doab tract, having inter alluvial plain between rivers Sutlej and Beas. The Jalandhar district has tropical and dry subhumid climate. The district has geological formation of quaternary age with recent alluvial deposits.¹⁵ Some parts of the district have undifferentiated aeolian flat sand sheet while the major portion has fertile soil. Ground water is the main source of water supply for rural as well as urban areas.

Figure 1.

Map depicting the study area.

Experimental

A total of 43 water samples, from different sources like hand pumps, tube wells, wells etc. were collected in leak tight bottles. During collection, due care was taken to avoid loss of dissolved radon, by avoiding bubbling. Measurements for pH of collected samples were taken at the sampling site, while measurements for physico-chemical parameters such as salinity, TDS (total dissolved solids) and dissolved radon were performed in our laboratory on the same day. Commercially available standard water testing kit was used for measurement of physico-chemical parameters. After completion of measurements for physico-chemical parameters and dissolved radon, water samples were analysed for uranium using laser fluorimetry. Brief details of experimental procedures adopted for radon and uranium measurements are described below.

Radon measurement in water

A schematic diagram of the experimental set up to measure dissolved Radon in water samples is shown in Figure 2. The set up consists of a water bubbler and a continuous radon monitor, SMART RnDuo (BARC, Mumbai). SMART RnDuo is a commercially available, portable continuous monitor for radon, thoron and gross alpha in air. It is based on the principle of detection of alpha particles by scintillations with ZnS:Ag. The details of detection and measurement principle are discussed elsewhere.¹⁶ The water bubbler was connected to RnDuo as shown. The bubbler kit is capable of transferring major fraction of radon dissolved in water to air volume within 1 min. Before the start of experiment, radon in the set up including detector volume was flushed out for 5 min by operating the inbuilt micropump of the monitor. Then connection was made as shown in Figure 2, and the pump was kept on again for 5 min so that the dissolved radon was transferred to detector volume in the monitor.

Figure 2.

A schematic of experimental setup for radon in water measurement.

SMART RnDuo was operated in 15 min cycle and the measurement was continued for 1 h. The radon concentration in water was calculated from the concentration measured in air by using equation (1)

C_{W} = C_{a} (K + \frac{V_{a}}{V_{W}})

(1)

where C_w is radon concentration in water (Bq m⁻³), C_a is radon concentration in air volume measured by monitor (Bqm⁻³), V_a and V_w are volumes of air and water, respectively, and K is partition coefficient between air and water.

Uranium measurement in water

The uranium concentration in water was measured using laser fluorimeter LF-2 (Quantalase, India). The fluorimeter uses, as excitation source, pulsed UV LEDs emitting at 400 nm using suitable filters. The instrument has dynamic range of 0.26 mg m⁻³ to 1000 mg m⁻³ and an accuracy of better than 10%. The instrument requires an analyte volume of 6 ml. The set up was calibrated using the standard solution before measurements. Measurements were taken in calibrated fluorescence mode. Details of measurement protocol are described elsewhere.¹⁷

Calculation of ingestion dose

Ingestion dose to local population due to uranium and radon in drinking water has been calculated for different age categories, i.e., for children of age 1 year, 10 years and adults. Different daily water intake for each age category has been considered.

Ingestion dose due to uranium has been calculated using equation (2)

D_{U} = U \times f \times W \times DCF

(2)

where D_U is annual ingestion dose due to uranium (µSv y⁻¹), U is uranium concentration water (mg m⁻³), f is mass to activity conversion factor for uranium (25 Bq mg⁻¹), W is annual intake of water (m³) and DCF is dose conversion factor for uranium (Sv Bq⁻¹).

Similarly, ingestion dose due to radon has been calculated using equation (3)

D_{Rn} = C_{Rn} \times W \times DCF

(3)

where D_Rn is ingestion dose due to radon (µSv y⁻¹), C_Rn is concentration of radon in water (Bq m⁻³), W is annual intake of water (m³) and DCF is dose conversion factor for radon (Sv Bq⁻¹).

Average daily intake of 1.3 × 10⁻³ m³ has been considered for children of age 1 year. Average daily intakes of 2.1 × 10⁻³ m³ and 2.4 × 10⁻³ m³ have been taken for female and male children of age 10 years, respectively. For adult females and males, values of 2.7 × 10⁻³ m³ and 3.7 × 10⁻³ m³ per day, respectively, have been taken.³ Dose conversion factors of 2.3 × 10⁻⁸, 5.9 ×10⁻⁹ and 3.5 × 10⁻⁹ Sv Bq⁻¹ have been considered for calculating the ingestion dose due to radon for age categories of 1 year, 10 years and adults, respectively.¹⁸ Similarly, dose conversion factors of 1.2 × 10⁻⁷, 6.8 × 10⁻⁸ and 4.5 × 10⁻⁸ Sv Bq⁻¹ have been taken for calculating the ingestion dose due to uranium for the three age categories.¹⁹ Conversion factor of 25 Bq mg⁻¹ was used for converting uranium mass to activity.²⁰

Results and Discussion

The frequency distributions of measured values of radon and uranium water are shown in Figure 3.

Figure 3.

Frequency distribution of radon and uranium in ground water.

The data distribution shows deviations from normal distribution. The results of measurements and statistical analysis are summarised in Table 1. Distributions for radon and uranium are both skewed to the right indicating long right tail as compared to left tail with skewness being more defined in case of uranium than in case of radon. The value of kurtosis for uranium distribution is 1.89 while for radon it is −1.09. Positive value for uranium indicates a heavy tailed distribution for uranium while a negative value for radon indicates a light tailed distribution. The uranium concentration in water samples varied from a minimum value of 1.53 mg m⁻³ to 50.2 mg m⁻³ with a geometric mean value of 14.85 mg m⁻³ and geometric standard deviation (GSD) 1.94. Out of 43 samples analysed, only 5 samples have uranium concentration higher than the limit of 30 mg m⁻³ prescribed by United States Environmental Protection Agency (US EPA).²¹ However, all the samples have uranium concentration within the limit of 60 mg m⁻³ prescribed by Atomic Energy regulatory Board of the Government of India.²² The radon concentration in water varied from a minimum value of 0.34 ± 0.07 kBq m⁻³ to a maximum value of 3.84 ± 0.48 kBq m⁻³ with a geometric mean value of 1.46 kBq m⁻³ and geometric standard deviation 2.08. The concentration of radon in all water samples analysed was found to be within the safe limit of 11 kBq m⁻³ prescribed by US EPA.

Table 1.

Summary of results of measurements and statistical analysis.

	TDS (ppt)	Salinity (ppt)	pH	²²²Rn Conc: (kBq m⁻³)	Uranium Conc. (mg m⁻³)
Min.	0.173	0.205	6.99	0.34 ± 0.07	1.53 ± 0.06
Max.	0.706	0.878	8.13	3.84 ± 0.48	50.20 ± 0.08
Mean	0.355	0.420	7.63	1.81	17.66
SD	0.159	0.187	0.28	1.05	9.62
GM	0.323	0.383	7.62	1.46	14.85
GSD	1.549	1.538	1.04	2.08	1.94
Skewness	0.687	0.747	−0.23	0.25	1.01
Kurtosis	−0.829	−0.581	−0.62	−1.08	1.89
1-st Quartile	0.219	0.259	7.41	1.14	10.96
3-rd Quartile	0.47	0.553	7.81	2.64	22.70

ppt: parts per thousand; TDS: total dissolved solids.

The values of radon and uranium measured in water are consistent with earlier reported results from other regions of the state. Uranium concentration in water in samples from Amritsar and Gurdaspur district of Punjab have been reported to be in the range 1.24 mg m⁻³ – 45.42 mg m⁻³ with mean value of 14.91 mg m⁻³.¹⁴ Water samples from Malwa region of Punjab state have reported values of uranium in the range 5.41 mg m⁻³ – 43.39 mg m⁻³.¹³ The values of radon in water samples from Mansa and Muktsar districts of Punjab have been reported to be in the range 0.4 kBq m⁻³ – 17 kBq m⁻³, while for Bathinda district, values have been reported in the range 0.9 kBq m⁻³ – 5.1 kBq m⁻³.^23–24

The pH for water samples was in the range 6.99 to 8.13. The measured values of TDS for water samples were in the range 0.173 ppt to 0.706 ppt. Totally nine water samples had TDS value greater than the permissible limit of 0.500 ppt. The values of the salinity for analysed water samples were in the range 0.205 ppt to 0.878 ppt. The correlations of U with radon, salinity and TDS are shown in Figure 4. For both salinity and TDS, a correlation with uranium concentration was established with correlation coefficients of 0.69 and 0.68, respectively. Uranium is present in the form of soluble complexes under oxidising conditions, and in reducing conditions, it is present in the form of insoluble complexes.²⁵ Soluble complexes are released into ground water in high ionic strength conditions due to high salinity and TDS.¹⁷ Poor correlation has been observed between radon dissolved in water and uranium concentration with correlation coefficient being 0.04.

Figure 4.

Correlation analysis of uranium with TDS, salinity and radon.

Similar results have been reported by Ryan et al.²⁶ The possible reason for this poor correlation may be the fact that radon in ground water is transported to very limited distance due to its lower half-life (3.82 days) as compared to Uranium (∼ 10⁹ year), which can travel a very long distance. Hence, radon in water is virtually an indicator of radioactivity in local rocks while Uranium in water is an indicator of radioactivity in local as well as distant rocks. Due to this reason, radon and Uranium in water may not correlate well.

The calculated values of ingestion dose due to radon, uranium and total ingestion dose are summarised in Table 2. The ingestion dose due to radon is maximum for age group 1 year and minimum for adult females. The higher value of ingestion dose for age group 1 year is due to the higher dose conversion factor for this age group, though the annual intake of water is less for this age group as compared to other age groups. For other two age groups, 10 year old and adults, average dose rates are less for females compared to their male counterparts. This variation is due to the lesser annual intake of water.

Table 2.

Calculated values of ingestion doses due to radon, uranium and total ingestion dose.

	Ingestion dose due to Rn (µSv y⁻¹) Age groups
	1 Y	10 Y (Male)	10 Y (Female)	Adult (Male)	Adult (Female)
Min.	3.75	1.78	1.56	1.63	1.19
Max.	41.90	19.84	17.36	18.15	13.24
Mean	19.77	9.36	8.19	8.56	6.25
SD	11.49	5.44	4.76	4.98	3.63
GM	15.89	7.52	6.58	6.88	5.02
GSD	2.08	2.08	2.08	2.08	2.08
1-st Quartile	12.44	5.89	5.15	5.39	3.93
3-rd Quartile	28.86	13.67	11.96	12.50	9.12
	Ingestion dose due to uranium (µSv y⁻¹)
Min.	2.18	2.28	1.99	2.32	1.70
Max.	71.46	74.76	65.41	76.27	55.66
Mean	25.14	26.30	23.01	26.83	19.58
SD	13.70	14.33	12.54	14.62	10.67
GM	21.14	22.11	19.35	22.56	16.46
GSD	1.94	1.94	1.94	1.94	1.94
1-st Quartile	15.60	16.32	14.28	16.65	12.15
3-rd Quartile	32.31	33.80	29.57	34.48	25.16
	Total ingestion dose due to uranium and radon (µSv y⁻¹)
Min.	17.48	15.68	13.72	15.77	11.51
Max.	85.28	81.30	71.14	82.25	60.02
Mean	45.56	36.34	31.80	36.09	26.33
SD	18.56	15.92	13.93	16.03	11.70
GM	41.75	33.02	28.89	32.70	23.86
GSD	1.55	1.57	1.57	1.58	1.58
Skewness	0.40	0.75	0.75	0.77	0.77
Kurtosis	−0.54	0.51	0.51	0.65	0.65
1-st Quartile	31.58	24.78	21.68	24.26	17.71
3-rd Quartile	56.78	45.76	40.04	45.46	33.18

Similarly, ingestion dose due to uranium in water is maximum for males of age group 10 years and minimum for adult females. Again the dose conversion factors and annual intake of water are the main controlling factors for variation of dose rates among different age groups. Total ingestion dose due to radon and uranium is again maximum for age group 1 year with a geometric mean value of 41.75 µSv y⁻¹ and minimum for adult females with geometric mean value of 23.86 µSv y⁻¹. These results indicate that the age group of 1 year is most radiosensitive and most vulnerable to radiation hazard as compared to other age groups. However, all the calculated values of annual dose are within the safe limit of 100 µSv y⁻¹ recommended by World Health Organisation (WHO).²⁷ Contribution of Rn to total ingestion dose varied from a minimum value of 3.7% to a maximum value of 93.0% with a geometric mean value of 26.3% and GSD value of 1.99. The first quartile and third quartile values of this distribution are 19.1 and 40.9, respectively. These values indicate that for 25% of cases, contribution of Rn to total ingestion dose is less than 19.1%, and for 75% of cases, the contribution of Rn is less than 40.9%. So we can say that major component of ingestion dose due to water comes from the uranium concentration in water.

Conclusions

The measured concentrations of uranium in water samples from the district were in the range 1.53 ± 0.06 mg m⁻³ – 50.2 ± 0.08 mg m⁻³ with geometric mean value of 14.85 mg m⁻³. The radon concentration in water was in the range 0.34 ± 0.07 kBq m⁻³ – 3.84 ± 0.48 kBq m⁻³ with geometric mean value of 1.46 kBq m⁻³. These values are within the safe limits prescribed by regulatory bodies such as US EPA and Atomic Energy regulatory Board India. Total ingestion dose to local population due to radon and uranium, for all age groups, varied from a minimum value of 10.21 µSv y⁻¹ to a maximum value of 85.28 µSv y⁻¹. This is also within the safe limit of 100 µSv y⁻¹ prescribed by WHO. The ground water of the district under investigation can be labelled safe from radioactive hazard. Ingestion dose values come out to be maximum for age group of 1 year. Contribution of radon to total ingestion dose for 75% of the samples is less than 40.9%.

Footnotes

Author’s Contributions

Manish Kumar (MK), Anjali Kaushal (AK), Atul Bhalla (AB) and Rajan Jakhu (RJ) were responsible for field studies and experimental work. B. K. Sahoo (BKS), Amit Sarin (AS), Rohit Mehra (RM) and Navjeet Sharma (NS) were responsible for analysis of data, interpretation of results and drafting of this manuscript.

Acknowledgements

Authors express their gratitude to Board of Research in Nuclear Sciences, Department of Atomic Energy, Mumbai, India for providing financial assistance under a major research project (Project No. 2013/36/54-BRNS) for this work.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

References

Banks

Royset

Strand

Skarphagen

. Radioelement (U, Th, Rn) concentrations in Norwegian bedrock groundwater. Environ Geol 1995; 25: 165–180.

Carvalho

Oliveira

Lopes

Batista

. Radionuclides from past uranium mining in rivers of Portugal. J Environ Radioact 2007; 98: 298–314.

Kumar

Kaur

Mehra

Sumit

Rosaline

Singh

Bajwa

. Quantification and assessment of health risk due to ingestion of uranium in groundwater of Jammu district, Jammu & Kashmir, India. J Radioanal Nucl Chem 2016; 310: 793–793. doi: 10.1007/s10967-016-4933-z.

Nagaiah

Mathews

Mysore Balakrishna

Rajanna

Naregundi

. Influence of physico-chemical parameters on the distribution of uranium in the ground water of Bangalore, India. Radiat Prot Environ 2013; 36(4): 175–180.

UNSCEAR. Sources and effects of ionizing radiations. Report to the general assembly with scientific annexes. New York: United Nations Scientific Committee on Effects of Atomic Radiation, 2000.

Prichard

. The transfer of radon from domestic water to indoor air. J Am Water Works Assoc 1987; 79(4): 159–161.

Sharma

Singh

. Human kidney and skeleton uranium burden, radiation dose and health risks from high uranium contents in drinking water of Bathinda district (Malwa region) of Punjab state, India. Radiat Prot Dosim 2017. DOI: 10.1093/rpd/ncx002.

Singh

Bajwa

. Estimation of uranium and radon concentration in some drinking water samples. Radiat Meas 2008; 43: 523–526.

Somlai

Tokonami

Ishikawa

Vancsura

Gaspar

Jobbagy

Somlai

Kovacs

. 222Rn concentration of water in the Balaton Highland and in the southern part of Hungary and the assessment of the resulting dose. Radiat Meas 2007; 42: 491–495.

10.

Singh

Garg

Yadav

Kishore

Pulhani

. Uranium in groundwater from Western Haryana, India. J Radioanal Nucl Chem 2014; 301: 427–433.

11.

Bajwa

Sharma

Walia

Virk

. Measurements of natural radioactivity in some water and soil samples of Punjab state, India. Indoor Built Environ 2003; 12: 357–361.

12.

Kumar

Usha

Pramila

Tripathi

Sanu

Rout

Supreeta

Singh

Kumar

Kushwaha

. Risk assessment for natural uranium in subsurface water of Punjab state in India. International Journal of Human and Ecological Risk Assessment 2010; 17(2): 381–393.

13.

Mehra

Singh

. Uranium studies in water samples belonging to Malwa region of Punjab using track etching technique. Radiat Meas 2007; 42: 441–445.

14.

Rani

Singh

Duggal

Balaram

. Uranium estimation in drinking water samples from some areas of Punjab and Himachal Pradesh, India using ICP-MS. Radiat Prot Dosim 2013; 157(1): 1–6.

15.

CGWB. Ground Water Scenario of Jalandhar District of Punjab. Chandigarh, India: Central Ground Water Board, Govt. of India Report, 2007.

16.

Gaware

Sahoo

Sapra

Mayya

. Development of online radon and thoron monitoring systems for occupation and general environments. BARC News Letter 2011; 318: 45–51.

17.

Kumar

Rout

Narayanan

Mishra

Tripathi

Singh

Kumar

Kushwaha

. Geochemical modelling of uranium speciation in the subsurface aquatic environment of Punjab State in India. J Geology Mining Res 2011; 3(5): 137–146.

18.

NRC. Risk assessment of radon in drinking water. National Research Council Report. Washington, DC: National Academy Press, 1999.

19.

IAEA. Radiation protection and safety of radiation sources: international basic safety standards. Safety Standards Series No. GSR Part 3 (Interim). Vienna, Austria: International Atomic Energy Agency, 2011.

20.

Sahoo

Mohapatra

Chakrabarty

Sumesh

Jha

Tripathi

Puranik

. Determination of uranium at ultra trace level in packaged drinking water by laser fluorimeter and consequent ingestion dose. Radioprotection 2010; 45(1): 55–66.

21.

USEPA. Current drinking water standards. United States Environmental Protection Agency. Ground Water and Drinking Water Protection Agency. New York: Wade Miller Associates, 2003.

22.

AERB. Drinking water specifications in India. Mumbai, India: Atomic Energy Regulatory Board, Department of Atomic Energy, Govt. of India, 2004.

23.

Mehra

Bangotra

Kaur

. ²²²Rn and ²²⁰Rn levels of Mansa and Muktsar district of Punjab, India. Front Environ Sci 2015; 3: 1–7.

24.

Duggal

Mehra

Rani

. Determination of ²²²Rn level in groundwater using a Rad7 detector in the Bathinda district of Punjab, India. Radiat Prot Dosim 2013; 156(2): 239–245.

25.

Musa ISM. Radon in natural waters: analytical methods; correlation to environmental parameters; radiation dose estimation; and GIS applications. PhD Thesis, Linkoping University, Sweden, 2003.

26.

Ryan TP, Sequeira S, McKittrick L and Colgan PA. Radon in drinking water in Co. Wicklow – a pilot study. Radiological Protection Institute of Ireland, http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/35/068/35068433.pdf (2003, accessed 8 April 2017).

27.

WHO. Guidelines for drinking water quality. World Health Organisation Recommendations. Vol. 1, 3rd ed. Geneva: WHO, 2004.