222Rn In Water Research Articles

Spatial distribution of radon contamination in hot springs water and its cancer and non-cancer risks in the Hunza-Nagar valley, Pakistan.

Radon (222Rn) is a ubiquitous radioactive gas and could threaten human life due to its potential for cancer and non-cancer risks. This study examined the measurement of 222Rn concentration and associated health risks in the hot springs of Hunza-Nagar valley. For this purpose, the hot springs water of Hunza and Nagar districts and the background sites were analyzed for 222Rn concentration using the RAD7 detector (Durridge Company, USA). The average concentrations of 222Rn were 46.1 ± 0.94, 65.3 ± 0.45, and 5.47 ± 0.25Bq/L in the Hunza district, Nagar district, and background sites, respectively. Results showed that 222Rn concentrations of hot springs water were multifold higher than the background sites. 222Rn concentrations for hot springs water in Hunza-Nagar valley had surpassed the maximum contamination level set by the US environmental protection agency (USEPA). Humans' annual mean exposure dose rates of various age groups were calculated for the estimated lifetime cancer risk (ELCR) and non-cancer risks. The total annual mean exposure doses from 222Rn in water (EwTotal) values were (187 ± 3.80, 265 ± 1.84, and 22.2 ± 1.02μSv/a) for infants (143 ± 2.92, 203 ± 1.40, and 17.0 ± 0.78μSv/a) children, and (138 ± 2.80, 196 ± 1.35, and 16.4 ± 0.76μSv/a) adults in the Hunza district, Nagar district, and background, respectively. Among the age groups of humans, infants showed a higher risk than others. Results showed that hot springs water consumption surpassed the world health organization threshold of 100μSv/y for chronic or non-cancer and USEPA 0.1 × 10-3 for ELCR risks.The concentration of 222Rn showed a positive correlation (> 0.68) with hot springs' water temperature and pH suggesting a common origin.

222Rn calibration procedure for water analyses by liquid scintillation counting

PurposeAmong the several methods to measure 222Rn in water, the liquid scintillation counting (LSC) technique is one of the most sensitive and widely used when analysing non-saline waters by liquid extraction, providing excellent accuracy, precision and low-level detection limits. When using the liquid scintillation counter Tri-Carb 3170 TR/SL (Perkin-Elmer) it is not possible to make an automatic determination of the alpha/beta discrimination parameter, being necessary to evaluate the pulse decay discriminator (PDD) value manually to the 222Rn determination. In this work, we describe the steps to perform the calibration of that type of equipment.MethodsThe method consists in the preparation of standard samples from a 226Ra certified standard solution and the adjustment of the PDD value by hand until the percentage of alpha events reaches a plateau of a near-constant fraction of total events. The process consists in taking several measures between PDD 80 and 200 with 15 min counting time each. Within the plateau, the alpha/beta ratio was used to determine the plateau final range as well as the optimum PDD value. After that, the calibration standards and blanks were measured and the region of interest (ROI) was established by finding the maximum value for the figure of merit (FOM) in the upper and lower limits.ResultsThe optimal PDD value of 148 was established by the alpha/beta ratio, and after that, it was possible to measure 226Ra standards to perform the calibration. An efficiency of (9.758±0.035) × 10–1 was obtained. In routine measurements, a detection limit of about 0.50 Bq L–1 is achieved for a 120 min counting time. To evaluate the uncertainty budget, the uncertainties of the net count rate, the efficiency, the sample amount and the decay correction factor were considered.ConclusionsA method was developed for the calibration of LSC Tri-Carb 3170 TR/SL with the optimization of the PDD using a 226Ra standard solution. The acquisition to obtain the plot of the variation of the events fraction in each window (alpha and beta) in function of PDD allowed to evaluate a plateau where the fraction of events was at a minimum. Afterwards, it was possible to measure the set of 226Ra standards after the equilibrium with 222Rn and determine the efficiency for 222Rn with a detection limit of about 0.50 Bq L–1 in routine analyses.

Uncertainty due to primary sampling of 222Rn in analyses of water

Measurement uncertainty is an important variable, to be accounted for when decisions have to be made based on measurement results. Measurement uncertainty is composed of two main components; one is related to the primary sampling, the other to the sample preparation and the subsequent analysis of the sample. The component related to the sample preparation and the analysis is commonly well evaluated in proficiency testing while there is generally no straightforward similar approach to evaluate sampling uncertainty. ISO 17025:2017 explicitly requires that testing laboratories performing sampling and analyses determine the uncertainty related to the primary sampling.In order to determine uncertainty arising in the primary sampling of 222Rn in water destined for human consumption, three laboratories IRE (BE), DiSa (LU) and SCK CEN (BE) initiated a joined sampling and measurement campaign. The dual split sample method in combination with ANOVA was used to evaluate the primary sampling uncertainty (precision) of the different methods. The tests showed that sampling bias is very probably, but that with good laboratory practice the sampling uncertainty precision and respectively bias can be kept below 5%.

Intercomparison exercises as a tool for improving the quality of radiochemical measurements in drinking waters – Radon-222 determinations

The results of a European intercomparison on 222Rn in water were analyzed to evaluate the performances of standard and non-standard methods. Then, results obtained with a specific LSC method (ISO 13164–4) based on two-phase liquid scintillation counting which has been employed by a considerable number of participants were examined in detail. This ISO LSC method was proved to be accurate, reliable and its reproducibility has been also sufficient. The intercomparison could be used as a collaborative study and the analysis of its results allowed to estimate the method reproducibility.

Riverine groundwater discharge estimation in a dynamic river corridor using 222Rn

AbstractGroundwater discharge flux into rivers (riverine groundwater discharge or RGD) is essential information for the conservation and management of aquatic ecosystems and resources. One way to estimate area‐integrated groundwater discharge into surface water bodies is to measure the concentration of a groundwater tracer within the water body. We assessed groundwater discharge using 222Rn, a tracer common in many surface water studies, through field measurements, surface water 222Rn mass balance model, and groundwater flow simulation, for the seldom studied but ubiquitous setting of a flooding river corridor. The investigation was conducted at the dam‐regulated Lower Colorado River (LCR) in Austin, Texas, USA. We found that 222Rn in both the river water and groundwater in the river bank changed synchronously over a 12‐hour flood cycle. A 222Rn mass balance model allowed for estimation of groundwater discharge into a 500‐m long reach of the LCR over the flood. The groundwater discharge ranged between negative values (indicating recharge) to 1570 m3/h; groundwater discharge from groundwater flow simulations corroborated these estimates. However, for the dynamic groundwater discharge estimated by the 222Rn box model, assuming whether the groundwater 222Rn endmember was constant or dynamic led to notably different results. The resultant groundwater discharge estimates are also highly sensitive to river 222Rn values. We thus recommend that when using this approach to accurately characterize dynamic groundwater discharge, the 222Rn in near‐stream groundwater should be monitored at the same frequency as river 222Rn. If this is not possible, the 222Rn method can still provide reasonable but approximate groundwater discharge given background information on surface water‐groundwater exchange time scales.

Exploration of Deep Ocean Ferromanganese Nodule Fields Using Radon as a Tracer

AbstractFerromanganese nodules (Fe‐Mn nodules) are considered as potential sources of in‐demand metals (such as manganese, cobalt, nickel, copper, and rare‐earth elements) that are used in high‐technology industries. The resource potential of Mn nodules in the world ocean remains uncertain due to technological and financial challenges. Here we propose an effective tracer: the natural radioactive radon isotope (222Rn) to assess the abundance of Fe‐Mn nodules on the sea floor. Significant linear relationships were observed between benthic excess 222Rn fluxes and concentrations with Fe‐Mn nodule occurrence and coverage on the global seafloor. Benthic excess 222Rn flux >107 dpm/m2/yr or bottom water 222Rn concentrations >2,000 dpm/m3 indicate the possibility of Fe‐Mn nodules occurrence at >80% and seabed coverage of >25%. Our results indicate radon, relatively easy to measure, could serve as a novel and efficient tool for targeting Fe‐Mn nodule resources in the global abyssal ocean.

Ba/Ca in foraminifera shells as a proxy of submarine groundwater discharge

AbstractSubmarine groundwater discharge (SGD) can have a profound influence on marine environments and elemental biogeochemical cycles in coastal waters. We have explored the feasibility of using Ba/Ca ratios of benthic foraminiferal shells as a proxy of SGD. Dissolved barium (DBa) displayed enrichment behavior in bottom waters indicating that SGD is a major DBa source in the Changjiang (Yangtze) Estuary. Foraminifera that lived in bottom waters with elevated 222Rn activities (high SGD) showed a larger range of Ba/Ca ratios than those that lived under low bottom water 222Rn activities (low SGD). Our findings support the view that benthic foraminiferal Ba/Ca ratios could be treated as a qualitative proxy of SGD. We propose that in areas where SGD is the main source of DBa, foraminiferal Ba/Ca ratios could be applied for long‐term historical SGD records.

Study on Estimation of Inhalation and Ingestion Dose due to <sup>222</sup>Rn Concentration in Different Types of Ground Water of Some Taluks of Uttara Kannada District, Karnataka, India

The primary goal of this study was to determine the risk due to radon concentration in drinking water. Water is essential for most of the life on the Earth, and the quality of drinking water is a key criterion for one's health. Radon (222Rn) and radium (226Ra) are the radioactive elements that can be found in water. Thirty samples of drinking water were collected in Haliyal, Joida, and Mundgod taluks of Uttara Kannada district. Emanometry technique was used to determine the concentration of 222Rn activity. The activity concentration of 222Rn in water varies between 3.78 ± 0.38 Bq l-1. and 135.96 ± 1.72 Bq l-1 with a mean value of 26.23 ± 0.65 Bq l-1. The cumulative average annual effective doses for all of the samples under investigation are well below the safe limit of 100 µSv y-1 suggested by WHO.

Spatial Patterns and Quantification of Lacustrine Groundwater Discharge Determined Based on 222Rn

AbstractLacustrine groundwater discharge (LGD) is of great importance to the hydrological cycle and the eco‐environment of lakes. LGD is often characterized by large spatial variability, but the spatial patterns of LGD have rarely been quantified, particularly at large whole‐lake scales. This study presents quantitative estimation of the spatial patterns of LGD in an oxbow lake in the central Yangtze River Basins by a segmented application of 222Rn mass balance model. The results show that the LGD rates in all points ranged from 10.05 to 197.25 mm/d, with an average of 61.23 mm/d. Larger LGD rates were not only occurring in the lakeshore area, but also in the lake center. The high LGD rate in the lake center area here was likely a result of a direct connection between the water‐rich confined aquifer and the lake. Sensitivity analysis of the 222Rn mass balance show that lake water 222Rn concentration, groundwater concentration, wind speed and water depth were sensitive parameters, which were important parameters in controlling the quantitative results of LGD. The average LGD rate uncertainty and percentage were 28.45 mm/d and 49.20%. This study thus provides a solution in quantifying the spatial patterns of LGD lakes.

Application of a mathematical model to an artificial aquifer under different recharge/discharge conditions using 222Rn as a tracer

Radon (222Rn), a radioactive gas of natural origin, was listed by the World Health Organization in 2009 as the second largest cause of lung cancer (3–14%) after tobacco. Global awareness of the importance of controlling its concentration in water led to the implementation of the European Directive 2013/51/Euratom, which establishes permitted levels in drinking water. This study applies a mathematical model to determine 222Rn concentration in water supplying an artificial aquifer over the full range of recharge/discharge conditions (volumes and times, and therefore flows). This was done by creating an artificial aquifer on a laboratory scale, which reproduces the recharges and discharges experienced by real aquifers through rainwater or groundwater. The equipment used in this study was an RTM 2100 with a specific system for continuous monitoring of 222Rn in water, a high-purity Ge detector for gamma spectrometry, and a portable liquid scintillation counter (LSC) called Triathler for specific measurements of 222Rn in water. The aim of this paper is to show the application of the mathematical model under different recharge/discharge conditions applied to the artificial aquifer. The concentration of 222Rn in water determined by the model can also be used as a tracer to find the origin and volume of water that reaches a real aquifer.

Measurement of radium and radon in water using a combination technique of radon-emanation and pair-measurements methods

Since 222Rn is continuously generated by the decay of 226Ra, it is difficult to analyze 222Rn in water containing 226Ra. To analyze 226Ra, a large amount of water is passed through a manganese fiber column to adsorb radium, and then radium delayed coincidence counting or gamma-ray spectroscopy is performed approximately four weeks later. A combination technique of radon-emanation and pair-measurement was tested to analyze 226Ra and 222Rn in water. 226Ra and 222Rn were accurately analyzed within approximately 8 d.

Tracing Bank Storage and Hyporheic Exchange Dynamics Using 222Rn: Virtual and Field Tests and Comparison With Other Tracers

AbstractDynamic hydrologic exchange flows in river beds and banks are important for many ecosystem functions throughout river corridors. Here we test whether the exchanges and the associated mixing between a flooding river and groundwater within the river’s bank can be effectively traced by Radon‐222 (222Rn), a naturally occurring, inert, radiogenic, and radioactive gas that can be analyzed and monitored in situ. The assessment was done by simulation of groundwater flow and reactive transport of 222Rn in the bank following a single, relatively rapid (hours long) flood wave and auxiliary field observations of 222Rn, temperature and total dissolved solids (a surrogate for any ionic conservative tracer). Results illustrate that 222Rn is more effective than temperature and total dissolved solids in tracing dynamic hyporheic exchange. 222Rn variations in space and time are larger than the analytical uncertainty of common measurement methods. The individual effects of aquifer hydraulic conductivity, dispersivity, river water 222Rn concentration, and bank topography were analyzed through sensitivity analysis. Larger hydraulic conductivity and dispersivity, lower 222Rn concentration in river water relative to groundwater, and gentler bank slopes resulted in a more prominent and traceable 222Rn signal. The transport and residence time of exchanged water may be estimated and interpreted using reactive transport models such as those implemented here. However, such application is sensitive to fluctuations in river water 222Rn, requiring it to be well characterized. The assessment provides guidance for using 222Rn as a tracer for groundwater and surface water interactions in dynamic settings.

Optimization of AlphaGUARD AquaKIT set-up for analysis of radon in water using stainless-steel bottles and its validation through IAEA standard samples

In this study, a system composed of an ionization chamber AlphaGUARD (PQ 2000), an AquaKIT set and an AlphaPUMP was calibrated to measure 222Rn in water. First, the system was checked for leakages using a NIST traceable 226Ra source. Then, we tested polyethylene terephthalate (PET) and stainless-steel bottles for sample storage estimating radon loss over time. Results showed that stainless-steel was a better suitable material for sample storage. Additionally, system setup was further validated by measuring IAEA reference materials issued within the framework of several interlaboratory intercomparisons. Finally, the procedure was applied to bottled mineral and tap waters collected in Sevilla (Spain) including annual effective dose for ingestion for adults children, and infants.

Occurrence of 222Rn and 226,228Ra in underground water and 222Rn in soil and their mutual correlations for underground water supplies in southern Greater Poland

European Union Council Directive 2013/51/EURATOM recently sets out so-called indicator parameters for: radon, tritium and indicative dose of water intended for human consumption. The aim of this research was to elaborate an effective procedure for determination of radon and radium 226,228Ra isotopes (which are potentially the main contributors to the internal dose from drinking and cooking water) and to find the possible relationships between these radionuclides in underground water reservoirs and 222Rn concentration in the soil gas in their vicinity. The research was performed by applying a non-volatile and water-immiscible scintillation cocktail based on a pure diisopropylnaphthalene (Ultima Gold F: UGF), which allow for efficient radon extraction from 0.5 dm3 of water samples to 20 cm3 of scintillation phase and its direct determination with a detection limit of 5 × 10–3 Bq dm−3. The further preliminary concentration of 3 dm3 of crude water samples by evaporation to 0.5 dm3 samples led to the removal of all unsupported 222Rn activity and allowed the 226Ra determination via equivalent 222Rn detection after one-month samples storage using a low-background Triathler liquid scintillation counter in the α/β separation counting mode. Together with determination of 226Ra isotope in water samples, the simultaneous measurements of 228Ra and 222Rn radionuclides concentrations in water as well as 222Rn activity in the soil gas around the water supply sites were performed. The achieved limit of 226Ra detection was at a very low level of 10–3 Bq dm−3. The measured values of 226Ra concentration in 50 public underground water supply units for the Kalisz district of Poland were relatively low and ranged from below detection limit to 28.5 × 10–3 Bq dm−3 with arithmetic mean and median values of 12.9 and 12.2 × 10–3 Bq dm−3, respectively. Weak correlations were observed between activity concentrations of 226Ra and 222Rn in the crude water samples (R2 = 0.31) and 222Rn in water and its concentration in the nearby soil gas (R2 = 0.48).

CONCENTRATION OF RADON AND OTHER ELEMENTS IN GROUNDWATERS OF THE JOS AND BUKURU YOUNGER GRANITE AQUIFERS

The Jos – Bukuru crystalline rocks have high radioactivity, but not much is known about the concentration of radon in waters of its aquifers. In this work, the activity concentrations of Radon-222 (222 Rn) were investigated from twenty (20) water samples collected at different locations within the Jos – Bukuru area. The analysis of radon was done using Liquid Scintillation counter. A total of fifteen (15) out of the twenty water samples were analysed for anions and cations. The anions (SO4-2 and Cl-) were analysed using a multiparameter and HCO3- by titration. The cations (major ions, trace elements and rare earth elements were analysed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Radon concentration in groundwater of the study area ranges from 1.62Bq/L to 24.55Bq/L with a mean value of 15.62Bq/L. only twenty five percent (25%) of the water sources had radon above the 10 Bq/L recommended by the WHO. These values were obtained within the Jos and Bukuru Boitite Younger Granite Aquifers. The variation in radon content in water are the results of: (1) the actual use of the wells in the area such as extraction of groundwater which increases the groundwater circulation thereby decreasing the radon content and (2) Bad well constructions with inflow of surface water and (3) bedrock geology. Radon behaved independently with regards to the major ions and some of the trace elements, but showed positive but not significant relationship with uranium and some of the rare earth elements indicating possible contribution of these elements to concentration of radon in the waters. The Annual Effective Doses due to ingestion of 222Rn in water for the three (3) categories of people varies from 0.038 mSv/y, 0.077 mSv/y and 0.271 mSv/y for adults, children and infants respectively. These are within the recommended limits of 0.1 mSv/y for adults and children but high for infants. The composition of the groundwaters in the area is dominated by natural water–rock interactions while other areas were highly impacted by anthropogenic sources. On the basis of TDS, all the samples are within the range of desirable to permissible for drinking.

Risk assessment of 226Ra and 222Rn from the drinking water in the Jalandhar and Kapurthla districts of Punjab

Naturally occurring Radium (226Ra) and Radon (222Rn) concentration in the drinking water samples of 20 villages of Jalandhar and Kapurthla districts of Punjab has been determined for health risk assessment. Activity concentration of 226Ra and 222Rn in the studied water samples varies from 0.08 to 0.13 Bq l−1 and 1.42 to 5.26 Bq l−1, with the average concentration of 0.1 Bq l−1 and 3.51 Bq l−1 respectively. The dose to the internal parts of the body is received from 222Rn through inhalation and ingestion while 226Ra contributes dose mainly through ingestion. The annual average inhalation and ingestion dose from 222Rn in water in the studied area is 0.89 nSv a−1 and 0.74 μSv a−1. The mean annual ingestion dose from 226Ra in water is 18.73 μSv a−1. The total mean annual effective dose due to 226Ra and 222Rn in water is 19.46 μSv a−1. As the total annual effective dose due to 226Ra and 222Rn in water samples of the study area is lower than the reference dose level of 10 mSv, the health hazards related to these radionuclides are expected to be negligible.

Does submarine groundwater discharge contribute to summer hypoxia in the Changjiang (Yangtze) River Estuary?

The Changjiang (Yangtze) River Estuary (CJE) is one of the largest and most intense seasonal hypoxic zones in the world. Here we examine the possibility that submarine groundwater discharge (SGD) may contribute to the summer hypoxia. Spatial distributions of bottom water 222Rn suggest a hotspot discharge area in the northern section of the CJE. SGD fluxes were estimated based on a 222Rn mass balance model and were found to range from 0.002 ± 0.004 to 0.022 ± 0.011 m3/m2/day. Higher SGD fluxes were observed during summer hypoxia period. The well-developed overlap of the distribution patterns for SGD flux and dissolved oxygen (DO) implies that SGD could be an important contributor to summer hypoxia in the region off the CJE. We suggest that SGD contributes to the seasonal hypoxia either: (1) directly via discharge of anoxic groundwaters together with reducing substances; and/or (2) indirectly by delivering excess nutrients that stimulate primary productivity with consequent consumption of DO during organic matter decomposition.

Water 222Rn for evaluating the variation in groundwater inflows to discharge of the Big Sioux River in different flow periods

Knowledge of seasonal water sources can help for improved management strategies to sustain agricultural productivity and ecosystem-services in a basin. This study defines the distribution of gaining reaches and evaluates groundwater inflows into the Big Sioux River located in eastern South Dakota using 222Rn mass balance approach during two distinctly different flow periods. The groundwater inflows estimated for the middle catchment were higher (up to 12.8 m3/m/day) compared to the values estimated for the upper catchment (up to 0.3 m3/m/day) in the Big Sioux River basin during both low- and high-flow periods. During low-flow period, the overall cumulative groundwater inflow ranged between 2529 and 211,166 m3/day that corresponded to 5 and 53% contribution to the total flow rate. The inflow during high-flow period ranged between 2467 and 332,740 m3/day corresponding to 2 and 55% of the total flow rate. Despite having elevated cumulative groundwater inflow during high-flow period, the relative contribution of groundwater inflow into the river was high during the low-flow period (a mean of 24% evaluated for the low-flow period vs. 18% for the high-flow period), potentially associated with high meltwater contribution derived from the spring snowmelt during that period. These estimations are expected to provide a better knowledge on seasonal water resource allocations that may be crucial for better water resource management strategies for the Big Sioux River basin.

Natural radionuclides 238U, 226RA, AND 222RN in the surface water of the ELKONSKY uranium-ore district (South Yakutiya)

Chemical composition of the surface water and the contents of the radionuclides 238U, 226Ra, and 222Rn in water was examined within the natural and man-made landscapes of South Yakutiya. It was demonstrated that intense water migration of these radionuclides from radioactive dump pits of the man-made landscapes of the Elkonsky uranium-ore district, which were created during the process of wide-scale exploration surveys for radioactive raw materials conducted during the last third of the 20th century, had occurred. Currently, the areas of water dissipation of 238U and 226Ra are detected at a distances of 2 km and greater from the source of the radioactive contamination along the outflow vector.

Evaluation of a radon-in-water pilot-proficiency test

A pilot proficiency test (PT) on measurements of the massic activity of 222Rn in drinking water was organised by JRC-Geel. Fourteen environmental radioactivity monitoring laboratories were invited to participate. The key aim of the study was to test, optimise and stream-line the complete process for conducting such a PT in order to perform a large scale Europe-wide PT in a robust manner. The process involved using all state-of-the art knowledge on sampling, transporting and measuring 222Rn in water. It was found that the majority of the participants’ results (92%) were within the ±15% reference range. The pilot-PT showed that the applied process was suitable and can be used for the large scale European PT planned for the third quarter of 2018.