222Rn Concentrations Research Articles

Passive-Type Radon Monitor Constructed Using a Small Container for Personal Dosimetry.

The International Commission on Radiological Protection (ICRP) recently recommended a new dose conversion factor for radon based on the latest epidemiological studies and dosimetric model. It is important to evaluate an inhalation dose from radon and its progeny. In the present study, a passive radon personal monitor was designed using a small container for storing contact lenses and its performance was evaluated. The conversion factor for radon (222Rn), the effect of thoron (220Rn) concentration and the air exchange rate were evaluated using the calibration chamber at Hirosaki University. The minimum and maximum detectable radon concentrations were calculated. The conversion factor was evaluated as 2.0 ± 0.3 tracks cm−2 per kBq h m−3; statistical analyses of results showed no significant effect from thoron concentration. The minimum and maximum detectable radon concentrations were 92 Bq m−3 and 231 kBq m−3 for a measurement period of three months, respectively. The air exchange rate was estimated to be 0.26 ± 0.16 h−1, whose effect on the measured time-integrated radon concentration was small. These results indicate that the monitor could be used as a wearable monitor for radon measurements, especially in places where radon concentrations may be relatively high, such as mines and caves.

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.

Assessment of radiological dose from exposure to attached and unattached fractions of radon (222Rn) and thoron (220Rn) in indoor atmosphere

In this study pin hole dosimeter with deposition based progeny sensors were used to estimate 222Rn, 220Rn and their daughters in the indoor atmosphere. The estimated annual average indoor 222Rn and 220Rn activity concentration were found to be 76.4 Bq m−3 and 93.5 Bq m−3, respectively. The mean value of EEC for radon and thoron was 45.5 Bq m−3 and 1.3 Bq m−3 respectively. The annual effective dose due to indoor 222Rn and 220Rn were found to be 2.9 mSv y−1 and 0.4 mSv y−1 respectively. The estimated effective doses are well below the safe limit as suggested by ICRP for indoor exposure.

ASSESSMENT OF ANNUAL EFFECTIVE DOSE DUE TO INHALATION AND INGESTION OF RADON IN WATER SAMPLES FROM THE CEMENT INDUSTRIAL AREA OF SOKOTO, NORTH-WESTERN NIGERIA

Water remains the most abundant and critical commodity for guaranteeing the continuity of human lives on earth. Ensuring cleanliness of water for human consumption is of paramount importance. The 222Rn concentration has been assessed in drinking water samples collected from various water resources used by communities around Sokoto Cement Company, with the view of assessing the radiological risk, if any, to human health. The sources of collected water samples were hand pumps and hand dug wells and water seepages. Determination of radon concentration was conducted using liquid scintillation counter (Model: Tri-Carb-LSA1000) following standard procedures. The overall mean value of 222Rn concentration was found to be 34±3.7 Bq/L The resulting mean annual effective doses due to inhalation of radon in the water samples was 41 μSvy-1, while ingestion for adults, children and infants were 248±27 μSvy-1, 372±40 μSvy-1 and 434±47 μSvy-1 respectively. These values are above the recommended benchmarks prescribed by UNSCEAR, WHO, European commission and USEPA guiding the utilization of water for drinking and domestic purposes. This indicates that the water resources around the cement company are not safe for drinking and domestic purposes from the radiological point of view.

Methods for the experimental study of 220Rn homogeneity in calibration chambers

This work presents two experimental methods for the evaluation of 220Rn homogeneity in calibration chambers. The first method is based on LSC of the 220Rn decay products captured in silica aerogel. The second method is based on application of solid state nuclear track detectors facing the air of the calibration chambers. The performances of the two methods are evaluated by dedicated experiments. The repeatability of the LSC-based method, estimated as relative standard deviation of the LSC measurements of ten silica aerogel samplers exposed under the same conditions is found to be 1.6%. Both methods are applied to study thoron homogeneity in the commercially available 50 L AlphaGuard emanation and calibration container, which was empty and its fan was turned on. It was found that the 220Rn distribution in this case is homogeneous within 10%. Both methods are also applied to test the thoron homogeneity in the BACCARA chamber at IRSN during a thoron calibration exercise. The results show that, at the centre of the chamber where the inputs of the sampling systems of the radon/thoron detectors were put close to each other, the thoron inhomogeneity is less than 10%. However, regions of higher thoron concentrations are clearly identified near the walls and the upper part of the chamber, with 220Rn concentrations being up to 60% higher compared to the concentration at the reference point. These results highlight the importance of the control and assessment of thoron homogeneity in thoron calibrations and in the cases when radon monitors are checked for thoron influence.

Detection of Near-Surface Permeable Zones Based on Spatial Correlation Between Radon Gas Concentration and DTM-Derived Lineament Density

Radon-222 (Rn) concentrations in soil gas have been used to locate near-surface permeable zones (e.g., fractures, faults) along which hydrothermal fluids ascend in geothermal fields. However, permeable zone detection over a field is often difficult owing to limited numbers and locations of Rn data points. This study aims to develop methodology to enable the regional detection of permeable zones by multivariate geostatistical modeling of Rn concentrations using the Wayang Windu geothermal field (WWGF) in West Java, Indonesia as a model case. Rn concentrations were measured using sampled gases from 17 shallow drill holes with 3–5 m depth over a 5.30 × 9.20 km area. The measurements were repeated over five periods in 2016–2017. To supplement the Rn point data, we produced a digital terrain model with 20-m resolution using an unmanned aerial vehicle and extracted lineaments using the modified segment tracing algorithm (m-STA). Three types of lineament density maps with a grid-cell size of 0.25 × 0.25 km were prepared for the densities of lineament frequency (number), total length and number of intersections in a unit cell. The Rn concentrations measured during the five periods were mapped over the WWGF by the collocated cokriging method using Rn concentrations as the primary variable (point data) and lineament density as the secondary variable (within the grid-cell data). A fuzzy logic approach was then applied to assess permeability as an index of 0–1 by overlaying the estimated Rn concentrations and three types of lineament density. The detected permeable zones mainly overlap with the geothermal manifestations and regional faults, and the permeable indexes generally correspond with Rn concentrations from eight new drill holes, which verify the effectiveness of the proposed method.

Environmental Isotope of Radon-222 for Ciliwung River and Shallow Deep Water Interaction Study

Aquifer in river bank area is mostly susceptive toward pollution occurring in river. One of parameters to determine the interaction process between groundwater and river is a natural isotope of 222Rn. The significant difference of radon concentration in groundwater and river water can be utilized as a scientific basis for investigating groundwater infiltration in river bank. Those studied parameters are residence time and infiltration rate. The research using 222Rn had been conducted in shallow groundwater of Ciliwung river bank - South Jakarta during rainy and dry season. The range of 222Rn concentration in shallow groundwater monitored in dry season was between 666 - 2590 Bq/m3 which was higher than that of rainy season ranging at 440 to 1546 Bq/m3. Otherwise, concentration of 222Rn in river water could not be detected (its 222Rn concentration = 0 Bq/m3) due to its much lower concentration either rainy or dry season. During dry season monitoring, equilibration between groundwater and river water was reached at the distance approximately 98 - 140 m away from river side. Estimating residence time based on 222Rn concentration at nearest site from the river and at equlibration area was 4.2 days such that the infiltration rate from river water into aquifer might be 7.8 m/day.Keywords: 222Rn, groundwater, residence time, infiltration rate.

Assessment of Radiation Dose from the Consumption of Bottled Drinking Water in Japan.

Activity concentrations of 234U, 235U, 238U, 226Ra, 228Ra, 222Rn, 210Po, 210Pb, 40K, 3H, 14C, 134Cs and 137Cs were determined in 20 different Japanese bottled drinking water commercially available in Japan. The origins of the mineral water samples were geographically distributed across different regions of Japan. Activity concentrations above detection limits were measured for the radionuclides 234U, 235U, 238U, 226Ra, 228Ra and 210Po. An average total annual effective dose due to ingestion was estimated for adults, based on the average annual volume of bottled water consumed in Japan in 2019, reported to be 31.7 L/y per capita. The estimated dose was found to be below the recommended World Health Organisation (WHO) guidance level of 0.1 mSv/y for drinking water quality. The most significant contributor to the estimated dose was 228Ra.

Measurement of Radon Concentration and Estimation of Its Emission of Coal-Fired Power Plants

In the experiment, RAD7 multi-functional electronic radon meter was used to measure the radon (222Rn) concentration at key points in the production process of three typical coal-fired power plants in Hunan, Hubei and Jiangxi provinces along the Yangtze river in China. The results show that after the combustion of raw coal, the radon was released, which caused radon concentration after the boiler’s gas system to be significantly higher than the air intake. Combined with the measurement and survey data, two different estimation methods of radon emission were established. First, based on radon concentration measured on site and the air volume at each inlet and outlet, the normalized radon emission of three coal fired power plants are calculated to be 102 GBq/GWa order of magnitude. The second one is using activity concentration of 226Ra in combination with actual coal use to calculate the emission, in this way, that typical value of normalize radon emission 151.3 GBq/GWa is obtained. This study provides data support for the construction of nuclear power plants in inland China.

Insights on Climate-Driven Fluctuations of Cave 222Rn and CO2 Concentrations Using Statistical and Wavelet Analyses

Understanding the fluctuations in cave air concentrations and their climatic control is substantial not only to preserve the quality of indoor atmospheres but also to avoid the risk related to the presence of hazardous substances. In this study, we investigated the most influential factors affecting 222Rn and CO2 concentrations, the nature of their dynamics, and their coupling with climatic variations. For this purpose, we combined a set of mathematical methods that included a statistical and wavelet analysis of a 6-year time series in Rull Cave (Spain). Generally, the 222Rn and CO2 dynamic in cave air showed similar patterns. However, the obtained results show that these gases have a different frequency response. Thus, the annual component of 222Rn and CO2 is controlled by the relationship between external and internal temperatures. At low frequencies, both gases are affected by the same variables when the cave atmosphere reaches a minimum concentration. However, when the cave atmosphere is isolated from the outdoors, 222Rn and CO2 behave differently and disturbance caused by the visitors is evidenced in terms of the CO2 concentration; the latter observation was confirmed by the wavelet analysis at high frequencies. In contrast, the 222Rn concentration shows important variations following rainfall, which was weakly identified in the CO2 concentration.

The 222Rn and 220Rn concentrations in some dwellings of Mandya city and its surroundings, Karnataka, India

The measurement of 222Rn and 220Rn concentrations in air was carried out in 50 dwellings belonging to 20 locations in and around Mandya city, Karnataka. Annual mean values of 222Rn and 220Rn concentrations were found to be 22.4 ± 1.5 and 24.1 ± 1.8 Bq m−3, respectively. The total annual effective dose received by the general public due to radon and thoron was found to be 1.36 ± 0.08 mSv y−1. The doses to different organs and tissues were calculated using the International Commission on Radiological Protection (ICRP) model of the respiratory tract and inter-comparison was made. The flooring, roofing type and age of the buildings were noted and the radon levels with respect to these parameters were analysed and discussed. An attempt was made to predict the indoor radon levels in dwellings using the existing model which was based on the mass balance equation and the results were compared with measured values.

Vertical distribution of the radon concentration at Batu Pahat district, Johor, Malaysia

This study investigated the vertical distribution of radon, 222Rn concentrations in soil gas for different soil types and found the relation between the measured gamma dose rates and radon concentrations. The 222Rn concentrations in soil gas were measured at depth of 20 cm, 60 cm, 80 cm and 100 cm using semiconductor detector (RAD7) coupled with soil gas probe. The overall activity concentrations of 222Rnin soil were ranged from Minimum Detectable Activity (MDA)to 54000 ± 3000 Bq m−3 in Batu Pahat District. The results showed that the overall highest concentration of 222Rn was recorded at 40 cm depth for most of the soil types, which could be the most reliable for taking the radon measurements than other depths. Soil type 32 (Dystric Nitosolse Orthic Ferrasols-Rengam Jerangau) has the highest radon concentration, which was 12,462 ± 5237 Bq m-3. The gamma dose rates (GDR) above 1 m were measured using portable survey meters (Ludlum 19). A good relationship between radon concentrations in soil gas and the measured gamma dose rates was observed using Pearson Correlation. The results of 222Rn concentration in soil gas obtained from this study were in agreement with results reported by other researchers.

Radon concentration in drinking water and soil after the September 24, 2019, Mw 5.8 earthquake, Mirpur, Azad Jammu, and Kashmir: an evaluation for potential risk.

Radon (222Rn), a radioactive gas resulted from the natural decay of other radioactive elements, pose a threat to the exposed human population. Radon gas emits along the seismically active faults and increased the 222Rn contamination in sorroundingwater and soil. This study investigated the concentration of 222Rn in drinking water and soil after the September 24, 2019, Mw 5.8 earthquake, Mirpur District, Azad Jammu, and Kashmir (AJK). For this purpose, water (n = 24) samples were collected from the bore wells of orderly located houses and soil field sampling (n = 12) along with the NE-SW directions of fracture in the Mirpur District. Determined 222Rn in drinking water surpassed the maximum contamination level (MCL, 11.1kBq/m3) set by the US Environmental Protection Agency (US EPA) in 83%, 50%, and 33% of the sampling point at the site I, site II, and site III, respectively. However, that of soil 222Rn concentration was observed with the normal range (10-50kBq/m3). Potential exposure of 222Rn consumption in drinking water was the mean effective dose through ingestion (EWing, 0.003 ± < 0.001mSv/a), the effective dose for inhalation (EWInh, 0.038 ± 0.002mSv/a), and the total effective dose of human (EWT, 0.041 ± 0.002mSv/a). Exposure values along withthe rupture showed multifold higher risk values (up to 4 times) compared to background sites. These values were observed within the limits (0.1mSv/a) set by World Health Organization (WHO); however, surpassed the thresholds of the United Nations Scientific Committee on the effects of atomic radiations (UNSCEAR) for all exposure pathways. This study concluded that groundwater in the close vicinity should be avoided or boiled before used for drinking purposes.

Occurrence and Geochemistry of Lead-210 and Polonium-210 Radionuclides in Public-Drinking-Water Supplies from Principal Aquifers of the United States.

On the basis of lifetime cancer risks, lead-210 (210Pb) and polonium-210 (210Po) ≥ 1.0 and 0.7 pCi/L (picocuries per liter), respectively, in drinking-water supplies may pose human-health concerns. 210Pb and 210Po were detected at concentrations greater than these thresholds at 3.7 and 1.5%, respectively, of filtered untreated groundwater samples from 1263 public-supply wells in 19 principal aquifers across the United States. Nationally, 72% of samples with radon-222 (222Rn) concentrations > 4000 pCi/L had 210Pb ≥ 1.0 pCi/L. 210Pb is mobilized by alpha recoil associated with the decay of 222Rn and short-lived progeny. 210Pb concentrations ≥ 1.0 pCi/L occurred most frequently where acidic groundwaters inhibited 210Pb readsorption (felsic-crystalline rocks) and where reducing alkaline conditions favored dissolution of iron-manganese- (Fe-Mn-) oxyhydroxides (which adsorb 210Pb) and formation of lead-carbonate complexes (enhancing lead (Pb) mobility). 210Po concentrations ≥ 0.7 pCi/L occurred almost exclusively in confined Coastal Plain aquifers where old (low percent-modern carbon-14) groundwaters were reducing, with high pH (>7.5) and high sodium/chloride (Na/Cl) ratios resulting from cation exchange. In high-pH environments, aqueous polonium (Po) is poorly sorbed, occurring as dihydrogen polonate (H2PoO3(aq)) or, under strongly reducing conditions, as a hydrogen-polonide anion (HPo-). Fe-Mn- and sulfate-reduction and cation-exchange processes may mobilize polonium from mineral surfaces. Po2+ occurrence in low-to-neutral-pH waters is attenuated by adsorption.

Are surface water characteristics efficient to locate hyporheic biodiversity hotspots?

Location of river-groundwater exchange zones and biodiversity hotspot is essential for a river management plan, especially for Mediterranean karstic rivers. This location is often difficult and time-consuming when long river sectors are considered. We studied a 13 km-long sector of the Cèze River (Southern France) located in a karstic canyon. We compared five indicators of river-groundwater exchanges: longitudinal profiles of temperature, electrical conductivity and 222Rn concentrations in the surface water of the river, chemical characteristics of the hyporheic water and hyporheic biodiversity. Upwelling zones occurred downstream of geomorphological heterogeneities (here at the tail of gravel bars). Surface water chemistry, especially electrical conductivity and 222Rn concentrations, clearly traces large scale gaining sections, which were not associated to valley narrowing but with lateral springs, suggesting a crucial role of the geological structuration of the karstic plateau of Méjanne-le-Clap. Hyporheic water chemistry fits with the large-scale hydrological pattern, but with a high variability corresponding to local heterogeneities. The stygobite fauna (obligate groundwater organisms) and benthic EPTC (Ephemeroptera, Plecoptera, Trichoptera and Coleoptera) occurred preferentially in the gaining sections fed by groundwater, likely because of oligotrophic water and cooler temperature. The spatial distribution of river-groundwater exchange zone and hyporheic biodiversity may be thus predicted using changes in surface water chemistry, especially for electrical conductivity and 222Rn concentrations.

Numerical simulation of 222Rn profiling in an experimental chamber using CFD technique

Measurement of indoor 222Rn concentration and interpretation of distribution patterns are important for inhalation dosimetry in occupational and residential areas. Experimental determination of 222Rn concentration distribution and estimation of inhalation doses depend on the underlying aspects such as calibration of the detectors, accuracy of the techniques etc. Therefore, 222Rn concentration distribution needs to be very well understood in a closed domain for the controlled studies. In the recent times, Computational fluid dynamics (CFD) technique has gained a lot of attention for the prediction and visualization of indoor 222Rn concentration profiles and their mixing ability in the domain. The present study aims to simulate the effect of forced mixing on the 222Rn concentration profile in a 22 m3 experimental chamber. This chamber is designed for carrying out the controlled experiments, calibration and inter-comparison studies of various types of 222Rn detectors. Effect of different parameters such as time, flow rates, fan-off and fan-on conditions have been studied on the transient response, extent of the air mixing patterns and subsequently on 222Rn concentration profile in the chamber. Further, Non uniformity index (NUI) is introduced as a measure of the uniformity of the distribution in the closed domain. NUI is estimated for different cases in order to efficiently interpret the effect of above mentioned parameters on 222Rn profile in the chamber. This study will be useful to represent the turbulent conditions in real indoor domains and occupational facilities as U-mines during calibration and inter-comparison exercises of different 222Rn detectors.

Determination of radiation doses to the skin due to 238U and 232Th series for the therapeutic application in the Merzouga sand baths

Abstract In this work, we used CR-39 and LR-115 type II solid-state nuclear track detectors to measure 238U, 232Th,222Rn and 220Rn concentrations in Merzouga sand. The measured concentrations of 238U and 232Th in the studied sand samples vary from (332.59±16.62) mBq·cm−3 to (335.54±20.13) mBq·cm−3 and (80.43±4.02) mBq·cm−3 to (84.75±5.08) mBq·cm−3, respectively. We evaluated the radiation doses to the skin from the application of different sand baths by the patients by using a model based on specific alpha-dose and alpha-particle residual energy concepts. The maximum total equivalent dose to the skin due to the 238U and 232Th series from the cutaneous application of different sand baths by patients was found equal to (148.12±11.85) µSv y−1cm−2

National comparison of methods for determination of radon in water

Abstract The article describes three interlaboratory experiments concerning 222Rn determination in water samples. The first two experiments were carried out with the use of artificial radon waters prepared by the Laboratory of Radiometric Expertise (LER), Institute of Nuclear Physics, Polish Academy of Sciences in Kraków in 2014 and 2018. The third experiment was performed using natural environment waters collected in the vicinity of the former uranium mine in Kowary in 2016. Most of the institutions performing radon in water measurements in Poland were gathered in the Polish Radon Centre Network, and they participated in the experiments. The goal of these exercises was to evaluate different measurement techniques used routinely in Polish laboratories and the laboratories’ proficiency of radon in water measurements. In the experiment performed in 2018, the reference values of 222Rn concentration in water were calculated based on the method developed at LER. The participants’ results appeared to be worse for low radon concentration than for high radon concentrations. The conclusions drawn on that base indicated the weaknesses of the used methods and probably the sampling. The interlaboratory experiments, in term, can help to improve the participants’ skills and reliability of their results.

Geological basement control on 222Rn accumulation as an input function for hydrogeological systems on a loess aquifer, Argentina

The activity of 222Rn of the groundwater was measured in different wells in the Pampeano aquifer in southeastern Buenos Aires to assess how the hydrogeological characteristics of the study area, which involves type and depth of the bedrock, aquifer mineralogy and residence time along flowpaths, influences on 222Rn contents. Water samples, as well as sediment samples, were collected in multilevel piezometers in different sites of the Buenos Aires province for the determination of stable isotopes, 222Rn concentrations and mineralogical analyses. The identification of uranium-bearing minerals in the loess sediments of the Pampeano aquifer was carried out with a scanning electron microscope allowing identifying zircon and monazite. The 222Rn was determined with a RAD7 detector, showing a range of activities from 3.1 to 14.9 Bq/L. The results showed a relation between the 222Rn activity, the depth of the wells, and the proximity of the Precambrian basement. The activity of 222Rn increases linearly with increasing depth at a rate of 0.09 Bq·L−1·m−1. However, at the same depth the concentration of 222Rn in wells near the Precambrian basement showed to be three times higher than the concentrations in the wells that have a Paleozoic bedrock, clearly showing that the proximity of granitoids rocks results in higher concentrations of radon.

Excessive radon-based radiation in indoor air caused by soil building materials in traditional homes on Đồng Văn karst plateau, northern Vietnam

Radon-based radiation from natural soil building materials is an important factor likely influencing residents’ health as a contributing source of natural radiation. This survey aims to quantify the nuclide-specific α-radiation of isotopes 222Rn and 220Rn in common types of houses in a region of northern Vietnam, Đồng Văn karst plateau, to preliminarily (i) evaluate the total annual effective dose rates and (ii) assess the relative risk of cancer induction from indoor α-radiation for inhabitants. The average 222Rn concentrations in all house types were lower than 100 Bq m−3, but 220Rn abundances were far higher than 222Rn, even up to >1000 Bq m−3 in air close to a wall of unfired-soil bricks. The estimated total annual effective dose rates from indoor 222Rn and 220Rn and their progenies to residents with daily exposure of 13 h in the various types of houses range from 3.1 to 4.3 mSv a−1 for houses constructed with modified materials, but up to higher than 6 mSv a−1 in houses with raw building materials. The average risk of developing lung cancer as a consequence of a lifetime exposure to indoor α-radiation in affected homes ranges from 3.9% to 14.6%. 220Rn and its metallic progenies contribute more than 80% of the total average lung cancer risk from total radon, being responsible for a range of 2.7–14.6% of the risk of developing lung cancer.