222Rn In Groundwater Research Articles

Spatial patterns and controlling factors of radon concentration in Quaternary alluvial-lacustrine aquifer systems

Radon (222Rn), naturally occurring in subsurface environments, is a significant environmental carcinogen when consumed via 222Rn-enriched groundwater and acts as a valuable geochemical tracer of the interaction between groundwater and surface water. Identifying the spatial patterns and influential factors of 222Rn in groundwater is therefore critical. However, there is a scarcity of specific studies on alluvial-lacustrine plains. In this study, 170 groundwater samples were collected to analyze the spatial patterns and controlling factors of 222Rn in the central Yangtze River plain, a typical alluvial-lacustrine plain. Through correlation and principal component analyses, as well as a random forest model (RF), it was determined that the groundwater 222Rn concentration was affected by several factors, including the hydrogeochemical environment, its associated water-rock interactions, the provenance of aquifer sediments, their mineral composition, and spatial distances from bedrock. Specifically, a thinner layer of Quaternary strata closer to the bedrock, combined with a less reducing hydrogeochemical setting and shorter-term water-rock interactions, along with a higher presence of silicate minerals in the aquifer sediments, promoted the accumulation of 222Rn in groundwater. An RF model was employed to predict the spatial distribution of the 222Rn concentration in the alluvial-lacustrine aquifer, revealing elevated groundwater 222Rn concentrations around local uplifts within the plain, at its edges, and near shallow-buried faults. The insights gained from this study can be applied to similar alluvial-lacustrine plains globally.

Spatial distribution of radon concentration and risk evaluation through consumption of groundwater in the District of Kotli, Azad Jammu and Kashmir

Radon (222Rn) is naturally readily water-soluble, posing a cancer risk to the exposed community. Human exposure in the community may occur via 222Rn intake in drinking water. Groundwater is used for drinking and other domestic purposes in the region. Higher concentrations of 222Rn in groundwater have been reported near Kotli district, Azad Jammu, and Kashmir. This investigation aimed to measure 222Rn concentrations in groundwater and evaluate the associated risk assessment for children and adults in the Kotli district. 222Rn concentrations were measured in randomly collected groundwater samples of Kotli (n = 25) and Sehnsa (n = 15) towns in the Kotli district using the portable Radon Detector (RAD7, Durridge Company, United States of America). Among the studied areas, the Sehnsa showed a higher average 222Rn concentration (7.6 ± 0.2 Bq/L) in groundwater compared to Kotli (6.0 ± 1.9 Bq/L). The average concentrations of 222Rn were found within the recommended limit (11.1 Bq/L) of the United States Environmental Protection Agency (USEPA), except for 10% of sampling sites. 222Rn concentrations were used for the calculation of total effective dose for ingestion and inhalation pathways (EwTotal) values for infants (24.5 ± 7.5 and 30.7 ± 0.9 μSv/a), children (18.1 ± 5.5 and 23.5 ± 0.7 μSv/a), and adults (18.1 ± 5.5 and 22.7 ± 0.3 μSv/a) in the Kotli and Sehnsa, respectively. This study noted that EwTotal and estimated lifetime cancer risk (ELCR) values were found within the World Health Organization (WHO) and European Commission (EU) acceptable limits (<100 μ Sv/a and 0.1 × 10−3).

Estimation of radiation dose due to U and 222Rn in groundwater to the population of Kodagu district, Karnataka, India

Abstract Systematic studies on natural radioactivity in the groundwater of Kodagu district, India were carried out. LED fluorimetric technique to measure uranium activity and emanometric technique to measure 222Rn activity in groundwater samples were used. The concentration of U and 222Rn in the water samples was observed to vary from 0.44 to 8.81 μg L−l with a geometric mean of 2.04 μg L−l and 1.54 to 9.61 Bq L−1 with a geometric mean of 3.59 Bq L−1, respectively. The estimated concentrations of uranium and radon in groundwater were within the recommended standard limits. The radiation dose due to U and 222Rn in groundwater was estimated and the total dose due to these radionuclides was found to vary from 4.51 to 30.28 μSv y−1 which was below the prescribed safe limit of 0.1 mSv y−1 by the WHO.

Measurement of 222Rn in ground water and NORMs in top soil in the environs of Rooppur Nuclear Power Plant site and associated health hazard

Measurement of 222Rn in ground water and NORMs in top soil in the environs of Rooppur Nuclear Power Plant site and associated health hazard

Radiotoxicity and health risk assessment of 222Rn in groundwater using statistical and Monte Carlo simulation approaches

Water is an important natural resource to humans, and itsquality has been a big concern from time immemorial. Water is polluted by the increasing activities of man. Pollutants of major concern include naturally occurring radioactive materials (NORM), heavy and potentially toxic metals, which are ubiquitous in the environment. Naturally occurring radionuclides such as 222Rn are the major precursors of lung and other types of cancer in humans. Exposure to radon in drinking water in excess of 300 pCi/L is treated as a radiological risk, while toxic metals in excess of the World Health Organization (WHO) maximum permissible levels in drinking water are considered both environmental and health risks to humans. A total of 34 groundwater samples were collected in the Akoko area of Ondo State, Nigeria for 222Rn activity concentration determination. The water samples were collected using standard techniques. RAD7 solid-state-detector was utilized for the 222Rn measurements. The results show the activity concentration of 222Rn ranging from 76 pCi/L to 3593 pCi/L with a mean value of 705 ± 76 pCi/L. Inhalation and ingestion doses from 222Rn dissolved in groundwater were evaluated for the infants, children, and adult populations in the study area. Radiological risks were evaluated through statistical and Monte Carlos simulation methods. It can be concluded from this study that there exists a likelihood of radiation-induced health risks due to inhalation of 222Rn from the sampled water.

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.

Comparison of Radon Gas in Different Water Samples at Al Haidariya City, Iraq

This study aims to measure the radon (222Rn) concentrations in the three types of water (groundwater, surface water, and health drinking water) in Al Haidariya city at Al-Najaf governorate, Iraq using RAD-7 detectors. The results show that the average of 222Rn in groundwater, surface water, and health drinking water were (0.276 Bq/L, 0.182 Bq/L and 0.132 Bq/L3) respectively, whereas the average of annual effective dose was (0.706 μSv/y,0.46 μSv/y and 0.337 μSv/y), respectively, While lifetime cancer risk (×10-4) with an average (0.027, 0.018 and 0.013) respectively. According to the results of 222Rn, the samples can be arranged in order groundwater, surface water and health drinking water. The results of the radon concentrations and the rate of annual effective dose for all water samples were significantly lower than the USEPA and WHO recommended respectively. The environmental effects of radioactive radon gas are almost non-existent, because the lifetime risk of cancer in all samples is less than the permissible safety limit for healthy drinking water, and therefore it does not affect human health.

Distribution of 222Rn in Seawater Intrusion Area and Its Implications on Tracing Submarine Groundwater Discharge on the Upper Gulf of Thailand

Abstract Radon (222Rn) has been widely employed as a tracer for estimating submarine groundwater discharge (SGD). However, the uncertainty of the SGD estimation remains significant, due to the spatial variability of radon in groundwater. In this study, we analyzed the hydrochemical proprieties of seawater and coastal groundwater in the Upper Gulf of Thailand and discussed the distribution characteristics of 222Rn in aquifers in terms of aquifer lithology, groundwater system recharge conditions, and water retention time. The results suggested that the residence time of groundwater and the process of groundwater salinization have the greatest impact on the distribution of 222Rn activity. A 222Rn mass balance model, synthesizing the distribution characteristics of 222Rn in groundwater and tidal influences on SGD, was built to estimate the submarine groundwater discharge in the Upper Gulf of Thailand. The result showed that the SGD flux of the Upper Gulf of Thailand was 0.0203 m/d. Moreover, there is a positive correlation between tidal height and the activity of 222Rn in groundwater. The SGD observed during the low tide was about 1.25 times higher than that observed during the high tide. This may influence the marine geochemical cycles of elements and their impact on marine ecosystems.

Development of data-driven models for estimating the probability of high-concentration occurrence of naturally occurring radioactive materials in groundwater

High-concentration occurrence probability estimation models was developed to estimate 238U and 222Rn in groundwater using in-situ monitoring data (i.e., geological rock types, well depth, T, pH, Eh, EC, DO, and HCO3). The estimation models are based on a non-linear data-driven method to improve their effectiveness for applications in different estimation cases using various in-situ monitoring data. When developing the models, most sensitive in-situ monitoring data are selectively utilized to train the models, where various statistical and correlation analyses are applied to overcome challenges, including model overfitting during training, a highly nonlinear correlation between input and target variables, and poor training due to low-quality monitoring data. Based on statistical analysis results, all input variables, except for Eh and well depth, are used for developing the 238U and 222Rn estimation models, respectively. Actual data collected from groundwater quality monitoring networks of South Korea from 2007 to 2019 are used to validate the developed models. Although it is difficult to characterize 222Rn occurrence using the geochemical conditions of groundwater because the gaseous phase behavior of 222Rn highly depends on structural geology, the 222Rn estimation model achieves reasonable performance with more than 70% accuracy. In addition, compared to the 222Rn estimation model, the 238U estimation model achieves higher classification accuracy with approximately 80%. Consequently, we can confirm that the developed estimation models can be effectively used to estimate the probability of high-concentration risk of 238U and 222Rn in groundwater. Conclusively, the practical applicability of the developed models is wide, as the models have been developed using direct observable and real-time data.

Annual effective dose from 222Rn in groundwater of a Nigeria University campus area

Radon, the heaviest among the noble gases in the periodic table of element is a radioactive nuclide that is naturally available in rocks, soil and water. It has become the subject of many research efforts in recent years due to its leading role in causing cancer. In this study, a total of 68 groundwater samples were collected and assayed using alpha spectrometry with RAD7 radon detector with RAD-H2O accessories manufactured by Durridge CO (USA). The 222Rn concentration measured were in the range of 0.6–36.2 Bq L−1 with an average of 13.33 Bq L−1, 7.0–41.5 Bq L−1 with mean value 23.3 Bq L−1 and 0.6–27.4 Bq L−1 with an average value of 7.4 Bq L−1 for hand dug wells (HDW), hand pumped boreholes (HPB) and motorized boreholes (MBH), respectively. About 54, 86 and 15% of samples from the HDW, HPB and MBH, respectively, exceeded the parametric reference level of 11.1 Bq L−1 suggested by United State of America Environmental Protection Agency but lower than the permissible limit of 100 Bq L−1 by World Health Organization (WHO) and European Union. The average annual effective doses resulting from inhalation and ingestion of radon in water obtained for the three groundwater sources are less than recommended limits by WHO and ICRP. The data obtained from this study are comparable with similar studies conducted in Nigeria and other parts of the world as reported in literature. Continuous radon monitoring in drinking water and indoor environment is however recommended for the study area.

Efficient radon removal using fluorine-functionalized natural zeolite

Radon (Rn) can easily leak into the environment through groundwater owing to its high water solubility. Therefore, studying the chemical factors influencing the content and removal of Rn from groundwater is crucial for the evaluation and mitigation of its radiological risks to public health. In this study, we conducted a redundancy analysis (RDA) of Rn in groundwater and performed batch sorption experiments for efficient Rn removal from the groundwater collected from Daejeon using natural zeolite (NZ) and fluorine-functionalized natural zeolite (FFNZ) sorbents. The redundancy analysis revealed a positive correlation between the concentrations of Rn and fluorine (F) in groundwater, indicating that F can support the long-term retention of Rn in groundwater. NZ and FFNZ achieved ~40% and ~70% removal of Rn, respectively, following 24 h of treatment, indicating a significant impact of F (in FFNZ) toward Rn removal from groundwater. Based on the results, Rn is considered to interact with F through the van der Waals force, which limits the volatilization of Rn from the solution. Similarly, the fluorine-functionalized sorbent would interact preferentially with Rn, thereby enhancing its sorption and removal from groundwater.

Health Risk Implication and Spatial Distribution of Radon in Groundwater Along the Lithological Contact in South India.

The presence of radioactive elements in groundwater results in high health risks on surrounding populations. Hence, a study was conducted in central Tamil Nadu, South India, to measure the radon levels in groundwater and determine the associatedhealth risk. The study was conducted along the lithological contact of hard rock and sedimentary formation. The concentrations of uranium (U) varied from 0.28 to 84.65µg/L, and the radioactivity of radon (Rn) varied from 258 to 7072Bq/m3 in the collected groundwater samples.The spatial distribution of Rn in the study area showed that higher values were identified along the central and northern regions of the study area. The data also indicate that granitic and gneissic rocks are the major contributors to Rn in groundwater through U-enriched lithological zones. The radon levels in all samples were below the maximum concentration level, prescribed by Environmental Protection Agency. The effective dose levels for ingestion and inhalation were calculated according to parameters introduced by UNSCEAR and were found to be lesser (0.235-6.453 μSvy-1) than the recommended limit. Hence, the regional groundwater in the study area does not pose any health risks to consumers. The spatial distribution of Rn's effective dose level indicates the higher values were mainly in the central and northern portion of the study area consist of gneissic, quarzitic, and granitic rocks. The present study showed that Rn concentrations in groundwater depend on the lithology, structural attributes, the existence of uranium minerals in rocks, and the redox conditions. The results of this study provide information on the spatial distribution of Rn in the groundwater and its potential health risk in central Tamil Nadu, India. It is anticipated that these data will help policymakers to develop plans for management of drinking water resources in the region.

Natural 222Rn as a tracer of mixing and volatilization in a shallow aquifer during a CO2 injection experiment

AbstractThis study aims to evaluate the application of 222Rn in groundwater as a tracer for monitoring CO2 plume migration in a shallow groundwater system, which is important to detect potential CO2 leakage in the carbon capture and storage (CCS) project. For this research, an artificial CO2‐infused water injection experiment was performed in a shallow aquifer by monitoring hydrogeochemical parameters, including 222Rn. Radon in groundwater can be a useful tracer because of its sensitivity to sudden changes in subsurface environment. To monitor the CO2 plume migration, the data were analysed based on (a) the influence of mixing processes on the distribution of 222Rn induced by the artificial injection experiment and (b) the influence of a carrier gas role by CO2 on the variation of 222Rn. The spatio‐temporal distributions of radon concentrations were successfully explained in association with horizontal and vertical mixing processes by the CO2‐infused water injection. Additionally, the mixing ratios of each monitoring well were calculated, quantitatively confirming the influence of these mixing processes on the distribution of radon concentrations. Moreover, one monitoring well showed a high positive relationship between 222Rn and Total dissolved inorganic carbon (TIC) by the carrier gas effect of CO2 through volatilization from the CO2 plume. It indicated the applicability of 222Rn as a sensitive tracer to directly monitor CO2 leakage. When with a little effect of carrier gas, natural 222Rn in groundwater can be used to compute mixing ratio of CO2‐infused water indicative of CO2 migration pathways. CO2 carrier gas effect can possibly increase 222Rn concentration in groundwater and, if fully verified with more field tests, will pose a great potential to be used as a natural tracer for CO2.

Geochemistry of U and Th of Mesozoic granites in South Korea: implications of occurrences of different U-host minerals and dissolved U and Rn between Jurassic and Cretaceous granite aquifers

Rn concentrations are generally high in the groundwaters of Mesozoic granite area in Korea. However, those groundwaters generally do not show a close relation between Rn and U concentrations even though Rn is a daughter nuclide of U. For example, both U and Rn concentrations are very high in the Jurassic granite of Daejeon-Cheongju area (Jgr-DJ), while only Rn concentrations are high in the Cretaceous granites of the Ogcheon belt (Cgr-OB). This study was initiated to explore the cause of this mismatch between these two different geological settings. For this study, we reviewed all data for the U and Rn concentrations in groundwaters, which had been reported since 1996 by the South Korean governmental authorities. The whole rock geochemical data for the Korean Mesozoic granites were also reviewed to discuss the U-enrichment processes in these two granites. This study found out that the difference in the U-host minerals is the essential reason for the differences in the occurrences of dissolved U and Rn in groundwaters of both geological settings. The geochemical data strongly suggest that Jgr-DJ is the major source of U and Rn in groundwater. However, Cgr-OB rarely provide U species to groundwater even though it acts as the substantial Rn source. This discrepancy is found to be the results of the differences in U-host minerals in each Mesozoic granite and their solubility. Monazite is the major U-bearing mineral in Cgr-OB. Its solubility is very low and, thus, cannot provide aqueous uranium species to groundwater even though it can emit radon gas to groundwater. In Jgr-DJ, uraninite, which can be easily oxidized to highly soluble ions and complexes, is the main U-host mineral; thus, it can cause high Rn and U concentrations. The cause of U-host mineral contrast between Cgr-OB and Jgr-DJ can be explained by the difference in their U-enrichment processes, such as primary magmatic crystallization and secondary hydrothermal alteration in each granite.

Factors controlling the distribution of radon (222Rn) in groundwater of a tropical mountainous river basin in southwest India

Studies on occurrence of radon in the environment are receiving growing attention worldwide due to its adverse impact on human health. Despite that, the dissolved radon in water is found to be a useful tracer in many hydrogeological studies. Although, several studies focused on the occurrence of high 222Rn in groundwater, the processes responsible for its variation is still not well understood. Hence, an attempt has been made in the present study to elucidate the underlying factors influencing the abundance 222Rn in hard rock (gneissic) aquifers of Karamana River Basin, southwest India. 222Rn in groundwater was analyzed in 71 dug wells during the pre-monsoon period of 2017.A large variability in 222Rn activities (170–68,350 Bq/m3) was noticed in groundwater and high activities were mainly seen in the khondalite formation. No significant dependencies between 222Rn activity and depth to water table, groundwater temperature and electrical conductivity were observed. However, majority of the presence of high 222Rn activity in groundwater matches with the location of lineaments. Furthermore, radium content in the host rock, degree of weathering and fracturing and the emanation coefficient of the rock were found to have an important bearing on the occurrence of radon in groundwater. The underlying factors influencing the abundance of radon in hard rock aquifers were also conceptualized. Thus, the study highlights the usefulness of 222Rn as a potential tool in delineating the macro-structural features like fractures/lineaments that are significant repositories of groundwater, which could be explored for groundwater development in hard rock terrains.

222Rn, 210Pb and 210Po in coastal zone groundwater: Activities, geochemical behaviors, consideration of seawater intrusion effect, and the potential radiation human-health risk

Groundwater quality in human-influenced coastal landscapes is receiving novel attention. Radionuclides have been recognized as another important monitoring indicator in many developed countries due to the discovery of extremely high level of natural 210Po (up to 10,000 Bq/m3) and radium and radon isotopes. This study aims to evaluate the groundwater quality in the Beibu Bulf-Guangxi coast from radiological point of view. 210Po, 210Pb and 222Rn activities in 20 wells ranged from 0.24 ± 0.05 to 6.96 ± 1.62 Bq/m3, 2.17 ± 0.12 to 13.08 ± 0.74 Bq/m3 and 1500 ± 200 to 31,800 ± 900 Bq/m3, respectively. Compared with research data of other countries, groundwaters in this area have 210Po, 210Pb and 222Rn activity within low levels. The large deficiencies of 210Po and 210Pb relative to 222Rn in groundwaters implied that 210Po and 210Pb are strong particle-reactive radionuclides and they might be controlled by similar scavenging processes in groundwaters due to a good positive correlation between 210Pb and 210Po (R2 = 0.67, p < 0.01). The concentrations of 210Po and 210Pb decreased with increasing pH values and salinity, which indicated that geochemical behaviors of 210Po and 210Pb in groundwater were influenced by seawater intrusion and pH changing. Groundwater 222Rn activity concentrations decreased with increasing salinity in coastal zone, which may be caused by dilution due to seawater intrusion or intensified 222Rn escaping from well-developed pores in coastal zone. The estimated annual ingestion doses for infants, children and adults were well below the recommended reference dose level (RDL) of 0.2–0.8 mSv/a, suggesting that consumption of analyzed groundwaters is safe from radiological point of view.

Hydrological connectivity in the aquifer–river continuum: Impact of river stages on the geochemistry of groundwater floodplains

The study is based on a complex and unique data set of 222Rn activity, water stable isotopes, and physicochemical parameters (i.e., temperature, electrical conductivity, pH) produced to better understand the hydrogeochemical connectivity between groundwater and river water in a meander floodplain of the Matane River, QC, Canada. Using an array of 21 piezometers implanted into an 18 ha meander floodplain, the geochemical properties of shallow groundwater were investigated over nine sampling campaigns between 2011 and 2017. The river is in gaining conditions most of the year, although losing conditions are temporally observed along high river discharge. The objective was to explore the seasonal geochemical variations in response to river discharge with a specific focus on the spatial extent of the hyporheic zone. A thorough examination of temperature, δ18O, electrical conductivity, and 222Rn in groundwater indicated that the geochemical properties of shallow groundwater varied in space and time. Multivariate statistical analyses (i.e., clustering and canonical redundancy analysis) showed that river discharge is a key factor controlling shallow groundwater geochemistry, whatever the season. The hyporheic zone, where groundwater mixes with river water, extended far from the riverbank. These results support the concept of the hyporheic corridor and integrated river management by providing a geochemical viewpoint on river-aquifer connectivity.

Optimization of dissolved Radon monitoring in groundwater to contribute to the evaluation of the seismic activity: an experience in central-southern Italy

Anomalies in Radon (222Rn) concentrations prior to earthquakes have been widely documented in seismogenic areas worldwide, but questions about their predictability remain largely unanswered. Even if it is not universally accepted, the analysis of the high-resolution time series of Rn (222Rn) concentrations in groundwater, air and soil has been proposed as a suitable method to identify seismic precursors. This study, which is aimed at identifying potential gas-geochemical precursors to nearby earthquakes, analyses groundwater Rn concentrations, which were continuously measured between April 2017 and December 2019. We conducted a detailed time series analysis of dissolved Rn in two springs emerging along two active fault zones in the inner sector of the central-southern Apennines (i.e. the Matese and Morrone fault zones) in Italy. We used a simple statistical method to identify seismic precursor anomalies in Rn concentrations. Anomalies are commonly assumed as values exceeding ± 2σ. Furthermore, we calculated the strain radius (for which a gas-geochemical precursor was expected) and the epicentral distance (from both our monitoring stations) of each seismic event of Mw ≥ 3.5 that occurred in the monitoring area. Results from our ongoing research are promising and show significant correlations between seismic signals and Rn concentrations. However, longer time series data that include more energetic earthquakes are needed to shed light on the behaviour of this gas in relation to crustal deformation processes.

Correlations of 226Ra and 222Rn activity concentrations in surface soil and groundwater of basement complex geological area of southwest Nigeria

The quantitative evaluations of naturally occurring radioisotopes in environmental media have provided significant information on the geological and radiological characteristics of different environments around the world. In furtherance to a preliminary study within southwest Nigeria set out to determine the distribution of 222Rn in groundwater and soil gas, the present study employed a well-shielded NaI(Tl) and RAD 7 detectors to determine activity concentrations of 226Ra and 222Rn in the media. Samples were collected from 100 sampling sites spatially distributed within the study area. Multivariate statistics were employed to extract the relationships between the activity concentrations of 226Ra and 222Rn in order to ascertain their origin and behavior in the basement complex geological area of southwest Nigeria. The mean activity concentration of 226Ra falls below the world average value of 35 Bq kg−1 in soil as reported by UNSCEAR, and 222Rn mean activity concentration is lower than 100 Bq l−1 recommended by WHO and European Commission as the criterion level in utility water for the members of the public. It can therefore be concluded that there is no significant radiological risks to the environment and human health due the presence of the measured radionuclides in soil and groundwater.

Factors Controlling the Spatial and Temporal Variability in Groundwater 222Rn and U Levels

Radon (222Rn) and uranium (U) measurements were conducted in 98 groundwater samples in Yongin area, Korea to identify the factors controlling their levels and spatial distributions. Groundwater samples were obtained from the different depth of wells used for drinking water and irrigation. 222Rn and U concentrations were measured using a liquid scintillation counter (LSC) equipped with a pulse-shape analyzer and inductively coupled plasma mass spectrometers (ICP-MS), respectively. Large variations were observed in groundwater concentrations of 222Rn and U, ranging between 0.6 ± 0.1–673.7 ± 8.7 Bq L−1 and 0.02–117.00 µg L−1, respectively. Correlation analysis revealed no significant relationship between field parameters (temperature, electrical conductivity, pH, and dissolved oxygen) and 222Rn or U concentrations. The fact that 222Rn and U concentrations were higher in granite areas than gneiss areas suggests that lithology plays a significant role in controlling the levels and spatial distributions of the two radionuclides. Furthermore, groundwater 222Rn and U behaviors have been affected by the existence of fault and well depth. Especially, the temporal monitoring of 222Rn suggests that 222Rn concentrations in the shallow groundwater may be controlled by variation in rainfall and artificial effects such as water curtain cultivation conducted in the winter season in this study area.