Groundwater Radon Research Articles

Long-lasting patterns of radon in groundwater at Panzhihua, China: Results from DFA, fractal dimensions and residual radon concentration

Long-lasting patterns of radon in groundwater at Panzhihua, China: Results from DFA, fractal dimensions and residual radon concentration

F79GENOME-WIDE ASSOCIATION STUDY OF CIRCADIAN RHYTHMICITY IN 71,500 UK BIOBANK PARTICIPANTS AND POLYGENIC ASSOCIATION WITH MOOD INSTABILITY

Radon volatilization mechanism into the gas phase was hypothesized to explain the anomalous declines in groundwater radon precursory to three major earthquakes – (1) 2003 MW = 6.8 Chengkung, (2) 2006 MW = 6.1 Taitung, and (3) 2008 MW = 5.4 Antung in Taiwan. The epicenters were located 24 km, 52 km, and 13 km from the Antung radon-monitoring well D1, respectively. To verify the mechanism of in situ volatilization, we monitored groundwater-dissolved ethane in addition to radon and methane at well D1 in the Antung hot spring since November 30, 2010. The mechanism of in situ radon volatilization has been corroborated by the simultaneous concentration declines in groundwater-dissolved radon, methane, and ethane precursory to the 2011 MW 5.0 Chimei earthquake. The epicenter was located 32 km from the Antung radon-monitoring well D1. Observations at the Antung hot spring also suggest that radon is the best-choice tracer among the groundwater-dissolved gases for strain changes in the crust preceding an earthquake. On the southern segment of the Chihshang fault, the observed radon minima decrease as the earthquake magnitude increases.

Estimation of Annual Effective Dose Due to Ingestion and Inhalation of Radon in Groundwater from Kaduna, Nigeria

Estimation of Annual Effective Dose Due to Ingestion and Inhalation of Radon in Groundwater from Kaduna, Nigeria

Diurnal and Semidiurnal Cyclicity of Radon (222Rn) in Groundwater, Giardino Spring, Central Apennines, Italy

Understanding natural variations of Rn (222Rn) concentrations is the fundamental prerequisite of using this radioactive gas as a tracer, or even precursor, of natural processes, including earthquakes. In this work, Rn concentrations in groundwater were continuously measured over a seven-month period, during 2017, in the Giardino Spring, Italy, together with groundwater levels in a nearby well installed into a fractured regional aquifer. Data were processed to reduce noise, and then analyzed to produce the Fourier spectra of Rn concentrations and groundwater levels. These spectra were compared with the spectrum of tidal forces. Results showed that diurnal and semidiurnal cycles of Rn concentrations, and filtered oscillations of groundwater levels, in the nearby well, are correlated with solar and luni-solar components of tidal forces, and suggested no correlation with the principal lunar components. Therefore, influencing factors linked to solar cycles, such as daily oscillations of temperature and atmospheric pressure, and related rock deformations, may have played a role in Rn concentrations and groundwater levels. An open question remains regarding the correlation, which is documented elsewhere, of Rn concentrations and groundwater levels with the lunar components of the solid Earth tides.

Hydrogeochemistry and Occurrences of Uranium and Radon in Groundwater of in Chungwon, Korea

Hydrogeochemistry and Occurrences of Uranium and Radon in Groundwater of in Chungwon, Korea

Variations of Dissolved Helium and Radon in Groundwater of the Southern Baikal Region by Earthquakes

Variations of Dissolved Helium and Radon in Groundwater of the Southern Baikal Region by Earthquakes

Spatial distribution mapping and radiological hazard assessment of groundwater and soil gas radon in Ekiti State, Southwest Nigeria

Groundwater constitutes the major source of utility water in Ekiti State with the majority of the population depending on groundwater for drinking and other household uses. Soil in the area is commonly used as a component of building materials, which may produce radon in the indoor environment. Excessive concentrations of radon in water and soil can cause radiological health risks to human as witnessed by the increased cases of lung cancer among non-smokers in Nigeria, which may be traceable to the ingestion and inhalation 222Rn in drinking water and indoor air. In the present study, comparative in situ measurements of radon in groundwater and soil gas were carried out at one hundred selected locations across the Ekiti State in southwest Nigeria, using a RAD7 radon detector to generate a radon distribution map and to estimate radiation hazards due to radon. The concentrations of radon in groundwater ranged from 0.9 to 472 Bq L−1 with a mean of 34.7 ± 4.4 Bq L−1, while those of soil gas ranged from 0.1 to 315 kBq L−1 with a mean of 38.9 ± 1.4 kBq L−1. The total annual effective dose due to inhalation and ingestion of radon in groundwater amounted to 94.7 µSv year−1, which is lower than the reference dose of 100 µSv year−1 recommended by the World Health Organization (WHO). The radon map generated for groundwater and soil gas identified three distinct areas with radon levels ranging from low to high. The results of this study show that some locations (Emure, Gbonyin, Ijero and Ikole) show mean total annual effective doses which are higher than the recommended limit. It can then be inferred that the groundwater samples pose significant radiological hazards to the population and that the noticed increase in lung cancer cases may be attributed to the consumption of groundwater in the area.

Measurement of radon concentration in groundwater in the Ashanti region of Ghana

Radon in groundwater and their annual effective dose in the Ashanti region of Ghana have been determined using the continuous grab sampling technique and an AB-5 detector. Mean levels of radon were in the range of 0.51–46.16 Bq L−1. Effective annual doses ranged from 0.18–16.16, 0.13–12.08 and 0.09–8.31 μSv y−1 for infants, children and adults, respectively. These values are significantly lower than the reference level of 0.1 mSv y−1 recommended by the WHO and United Nations Scientific Committee on the Effects of Atomic Radiation for members of the public.

A comprehensive study of radon levels and associated radiation doses in Himalayan groundwater

The concentration of radon in groundwater is mainly governed by the radium content in the rocks of the aquifer. The internal exposure to high levels of radon in water is directly associated with the radiological risk to members of public. In this work, radon concentrations were measured in groundwater of Garhwal Himalaya, India, using scintillation detector-based RnDuo and silicon detector-based RAD7 monitors. An inter-comparison exercise was carried out between RnDuo and RAD7 techniques for a few samples to validate the results. The radiation doses associated with the exposure to radon in water were estimated from measured values of activity concentrations. An attempt has been made to see the effect of geology, geohydrology and different types of sources on radon levels in Himalayan groundwater. The experimental techniques and results obtained are discussed in detail.

Characterization of radon levels in soil and groundwater in the North Maladeta Fault area (Central Pyrenees) and their effects on indoor radon concentration in a thermal spa

Radon levels in the soil and groundwater in the North Maladeta Fault area (located in the Aran Valley sector, Central Pyrenees) are analysed from both geological and radiation protection perspectives. This area is characterized by the presence of two important normal faults: the North Maladeta fault (NMF) and the Tredós Fault (TF). Two primary aspects make this study interesting: (i) the NMF shows geomorphic evidence of neotectonic activity and (ii) the presence of a thermal spa, Banhs de Tredós, which exploits one of the several natural springs of the area and needs to be evaluated for radiation dosing from radon according to the European regulation on basic safety standards for protection against ionizing radiation. The average soil radon and thoron concentrations along a profile perpendicular to the two normal faults — 22 ± 3 kBq·m−3 and 34 ± 3 kBq·m−3, respectively — are not high and can be compared to the radionuclide content of the granitic rocks of the area, 25 ± 4 Bq·kg−1 for 226Ra and 38 ± 2 Bq·kg−1 for 224Ra. However, the hypothesis that the normal faults are still active is supported by the presence of anomalies in both the soil radon and thoron levels that are unlikely to be of local origin together with the presence of similar anomalies in CO2 fluxes and the fact that the highest groundwater radon values are located close to the normal faults. Additionally, groundwater 222Rn data have complemented the hydrochemistry data, enabling researchers to better distinguish between water pathways in the granitic and non-granitic aquifers. Indoor radon levels in the spa vary within a wide range, [7–1664] Bq·m−3 because the groundwater used in the treatment rooms is the primary source of radon in the air. Tap water radon levels inside the spa present an average value of 50 ± 8 kBq·m−3, which does not exceed the level stipulated by the Spanish Nuclear Safety Council (CSN) of 100 kBq·m−3 for water used for human consumption. This finding implies that even relatively low radon concentration values in water can constitute a relevant indoor radon source when the transfer from water to indoor air is efficient. The estimated effective dose range of values for a spa worker due to radon inhalation is [1–9] mSv·y−1. The use of annual averaged radon concentration values may significantly underestimate the dose in these situations; therefore, a detailed dynamic study must be performed by considering the time that the workers spend in the spa.

Anomalous decrease in groundwater radon before 2016 Mw 6.4 Meinong earthquake and its application in Taiwan

Recurrent groundwater radon anomalies were observed at the Paihe spring (P1) in southwestern Taiwan prior to the Mw 6.3 Jiasian and Mw 6.4 Meinong earthquakes that occurred on March 4, 2010 and February 5, 2016, respectively. Specifically, the concentration of groundwater radon decreased from background levels of 144 ± 7 and 137 ± 8 pCi/L to minima of 104 ± 8 and 97 ± 9 pCi/L prior to the 2010 Jiasian and 2016 Meinong earthquakes, respectively. The Paihe spring (P1) is located 46 km and 45 km, respectively, from the epicenters of the 2010 Mw 6.3 Jiasian and 2016 Mw 6.4 Meinong earthquakes. The above radon anomalies observed at the Paihe limestone spring corroborated that a small fractured aquifer can be used as an effective natural strain meter by applying radon as a tracer for earthquake warning in southwestern Taiwan. There are scientific difficulties and uncertainties in earthquake prediction. Nonetheless, a long-term monitoring of precursory declines in groundwater radon can provide useful data for forecasting local disastrous earthquakes.

Study of the Presence of Radon in Groundwater from Two Regions in Saudi Arabia

Groundwater samples with high total dissolved solids (TDS) were collected from private wells in Al Sharqiya and Tabouk regions in Saudi Arabia to determine the 222Rn activities and to investigate the factors that may control the presence of radon in these wells. The radon activity levels in Al Sharqiya groundwater wells showed an average value below the maximum contaminant level proposed by EPA for drinking water. In contrast, all the sampled wells in Tabouk region exhibited 222Rn concentrations exceeding 300 pCi/L, the maximum contaminant level (MCL) recommended by the USEPA, which may be explained by the nature of aquifers in both regions. Within the limited number of groundwater samples, it was observed that the radon content of Al Sharqiya sampled wells has good correlations with some chemical parameters (TDS and Eh) in these wells. The observed correlations between the water chemistry and the radon activities in groundwater do not necessarily imply a relationship between the two events. Furthermore, these chemical parameters may reflect the presence of nearby radium in rocks surface. Radon wasn’t influenced by the chemical environment in the investigated Tabouk wells but, may be is more controlled by other factors: the direct parent 226Ra content and the nature of the aquifer matrix (grain size and permeability in the Saq aquifer rocks).

The suitability of using dissolved gases to determine groundwater discharge to high gradient streams

Determining groundwater discharge to streams using dissolved gases is known to be useful over a wide range of streamflow rates but the suitability of dissolved gas methods to determine discharge rates in high gradient mountain streams has not been sufficiently tested, even though headwater streams are critical as ecological habitats and water resources. The aim of this study is to test the suitability of using dissolved gases to determine groundwater discharge rates to high gradient streams by field experiments in a well-characterized, high gradient mountain stream and a literature review. At a reach scale (550 m) we combined stream and groundwater radon activity measurements with an in-stream SF6 tracer test. By means of numerical modeling we determined gas exchange velocities and derived very low groundwater discharge rates (∼15% of streamflow). These groundwater discharge rates are below the uncertainty range of physical streamflow measurements and consistent with temperature, specific conductance and streamflow measured at multiple locations along the reach. At a watershed-scale (4 km), we measured CFC-12 and δ18O concentrations and determined gas exchange velocities and groundwater discharge rates with the same numerical model. The groundwater discharge rates along the 4 km stream reach were highly variable, but were consistent with the values derived in the detailed study reach. Additionally, we synthesized literature values of gas exchange velocities for different stream gradients which show an empirical relationship that will be valuable in planning future dissolved gas studies on streams with various gradients. In sum, we show that multiple dissolved gas tracers can be used to determine groundwater discharge to high gradient mountain streams from reach to watershed scales.

Radionuclides as natural tracers of the interaction between groundwater and surface water in the River Andarax, Spain

The identification of specific aquifers that supply water to river systems is fundamental to understanding the dynamics of the rivers' hydrochemistry, particularly in arid and semiarid environments where river flow may be discontinuous. There are multiple methods to identify the source of river water. In this study of the River Andarax, in the Southeast of Spain, an analysis of natural tracers (physico-chemical parameters, uranium, radium and radon) in surface water and groundwater indicates that chemical parameters and uranium clearly identify the areas where there is groundwater-surface water interaction. The concentration of uranium found in the river defines two areas: the headwaters with U concentrations of 2 μg L−1 and the lower reaches, with U of 6 μg L−1. Furthermore, variation in the 234U/238U isotopic ratio allowed us to detect the influence that groundwater from the carbonate aquifer has on surface water in the headwaters of the river, where the saline content is lower and the water has a calcium bicarbonate facies. The concentration of 226Ra and 222Rn are low in the surface waters: <1.6 × 10−6 μg L−1 and <5.1 × 10−12 μg L−1, respectively. There is a slight increase in the lower reaches where the water has a permanent flow, greater salinity and a calcium-magnesium-sulphate facies. All this is favoured by the influence of groundwater from the detritic aquifer on the surface waters. The results of this study indicate the utility in the use of physico-chemical and radiological data conjointly as tracers of groundwater-surface water interaction in semiarid areas where the lithology of aquifers is diverse (carbonate and detritic) and where evaporitic rocks are present.

Radon Concentration Measurement in Groundwater of Roorkee, Uttarakhand, India

Groundwater is the largest fresh water resource and radon is a radioactive naturally occurring noble gas that may be found anywhere in soil, air and water due to decay of uranium in rocks. It is important to investigate the radon in groundwater to safeguard against the health hazard caused due radon. The results presented here are from radon concentrations measured using RAD7 detector in 9 representative groundwater samples collected from hand pumps from southern parts of Roorkee in Haridwar district of Uttrakhand. Radon activity concentration was found in the range of 0.55+0.22 Bq L-1 to 3.39+0.28 Bq L-1 with an average value of 2.16+0.37 Bq L-1. Radon values were compared with United State Environmental Protection Agency value of 11 Bq L-1. The radon activity trend was found within the permissible limit.

Predictive radon potential mapping in groundwater: a case study in Yongin, Korea

The purpose of this work was to calculate the relationships between radon levels in groundwater and spatial factors (e.g., geology, topography, soil, and geochemistry), to integrate these relationships, and to map the radon potential levels using a probabilistic method and geographic information systems (GIS) in Yongin, Korea. Radon in groundwater is affected by topographic factors such as elevation and slope, geological factors such as lithology and geochemical factors. A spatial database containing radon, topographic, soil, geological and geochemical data was compiled for the study area using GIS. We then extracted 33 factors from geological maps, topographic maps, and geochemical data. The relationships between radon occurrence and these factors were evaluated using the frequency ratio method, which is one of a probabilistic model. Seven of factors (electrical conductivity (EC), SiO2, Sr, NO3, HCO3, DEM, and geology) had close relationships with 222Rn occurence and were combined to produce a radon potential map using spatial overlay. This radon potential map was validated by comparing with the existing occurrences of radon gas. Of the total number of radon occurrences, 50% were used for mapping, and the remaining 50% were used for model validation. The average radon potential index (RPI) value with radon concentration greater than radon content criterion was 43.69% higher than its average RPI value less than the criterion value in our samples. The average RPI value was 43.96% higher than US EPA’s alternative maximum contaminant level of 148 Bq/L. The radon potential map constructed in this study can serve as an important reference for potential radon exposure.

Spatial and temporal variations of radon concentrations in groundwater of hard rock aquifers in Madurai district, India

Radon (222Rn) and other radionuclides in groundwater can lead to health problems if present in higher concentrations. A study was carried out in Madurai district of Tamilnadu by collecting groundwater samples for four different seasons and aims to identify the regions with higher 222Rn concentration along with their spatial and seasonal variations. 222Rn has been compared with field parameters, log pCO2, major ions and uranium to detect the factors responsible for the higher concentration in groundwater. The weathering process induces the release of higher uranium ions from the granitic terrain from the rock matrix which enhances the 222Rn levels in groundwater.

Radon concentration distributions in shallow and deep groundwater around the Tachikawa fault zone

Groundwater radon concentrations around the Tachikawa fault zone were surveyed. The radon concentrations in shallow groundwater samples around the Tachikawa fault segment are comparable to previous studies. The characteristics of the radon concentrations on both sides of the segment are considered to have changed in response to the decrease in groundwater recharge caused by urbanization on the eastern side of the segment. The radon concentrations in deep groundwater samples collected around the Naguri and the Tachikawa fault segments are the same as those of shallow groundwater samples. However, the radon concentrations in deep groundwater samples collected from the bedrock beside the Naguri and Tachikawa fault segments are markedly higher than the radon concentrations expected from the geology on the Kanto plane. This disparity can be explained by the development of fracture zones spreading on both sides of the two segments. The radon concentration distribution for deep groundwater samples from the Naguri and the Tachikawa fault segments suggests that a fault exists even at the southern part of the Tachikawa fault line.

Radon-222 in groundwater and effective dose due to ingestion and inhalation in the city of Ibadan, Nigeria

Radon concentration in groundwater collected from the eleven Local Government Areas (LGAs) of Ibadan, Nigeria, was analyzed. Annual effective doses due to ingestion and inhalation of radon from the consumption of the water were determined. The arithmetic means (AMs) of radon concentration for the 11 LGAs varied from 2.18 to 76.75 Bq l−1 with a standard deviation of 1.57 and 70.64 Bq l−1, respectively. The geometric means (GMs) varied from 1.67 to 49.47 Bq l−1 with geometric standard deviation of 2.22 and 3.04, respectively. About 58% of the 84 water samples examined had a higher concentration of radon than the 11.1 Bq l−1 recommended by United States Environmental Protection Agency (USEPA); the AMs of six LGAs and GMs of three LGAs were higher than the recommended value. However the AMs and GMs of all the LGAs with about 93% of the water sampled were lower than the 100 Bq l−1 recommended by the World Health Organization and EURATOM drinking water directive. The concentration of radon varied with the geological formation of the area. The AMs of the annual effective dose due to ingestion of radon in water ranged from 0.036 to 1.261 mSv y−1, 0.071 to 2.521 mSv y−1 and 0.042 to 1.471 mSv y−1 for adult, child and infant, respectively and the GMs in the range of 0.026 to 0.813, 0.055 to 1.625 and 0.032 to 0.948 mSv y−1, respectively. The AMs of 10 LGAs and GMs of 7 LGAs were higher than the recommended reference dose level of 0.1 mSv y−1 from the consumption of water for the duration of one year for all the three categories of people. The AMs and GMs of the annual effective dose due to inhalation of radon in drinking water ranged from 0.533 to 18.82 μSv y−1 and 0.411 to 12.13 μSv y−1, respectively, contributing less to the overall dose.

Radon in Icelandic Cold Groundwater and Low-Temperature Geothermal Water

Samples of hot and cold water for radon analysis were collected from boreholes and springs in Iceland in 2014 and 2015. The majority of the samples was collected from municipal district heating services or potable water utilities. The total number of samples was 142, covering most towns and villages in Iceland. Radon activity is generally rather low, in most cases less than 5 Bq/L. Only 12 samples had a measured radon activity higher than 5 Bq/L, with a maximum activity of 10.8 Bq/L. The hot water samples generally have a higher radon activity than cold water samples, but samples from boiling borholes have a lower radon activity as radon fractionates into the vapour phase. The geographical distribution of the samples indicates that radon activity is generally lower within the active rift zones. This is most likely due to the very low uranium content of the tholeiites typically erupted within the rift zones. Higher radon values (> 5 Bq/L) are in most cases close to extinct central volcanoes and thus it seems plausible that the water sampled has been in contact with felsic rocks.