Changes In Radon Concentration Research Articles

Hydrogeochemical changes with emphasis on trace elements in an artesian well before and after the September 8, 2018 Ms 5.9 Mojiang Earthquake in Yunnan, southwest China

Most groundwater geochemical studies associated with earthquakes have focused on changes in major ions and radon concentration. However, trace elements have also shown a dramatic response to earthquakes and attracted increasing attention. In this study, hydrochemical and water level changes were detected by an artesian well (DZ well) in Yunnan, China, during the 2018 Ms 5.9 Mojiang earthquake. The results show that the major and trace element concentrations changed considerably before and after the earthquake, which were attributed to the mixing of water from different aquifers due to the earthquake-induced alteration of permeability through wavelet analysis of continuous monitoring data and coseismic static strain. In addition, Self-Organizing Map (SOM) and K-means clustering algorithms were used to classify all water samples with 10 trace elements as variables, and the results showed that samples collected in pre- and post-earthquake can be categorized as two groups, showing a significant difference. We argue that the response of trace elements remains unaffected by their initial concentration levels. Notably, both high- and low-concentration trace elements (e.g., Cs, Rb, V, etc.) exhibit discernible changes in response to the Ms 5.9 Mojiang earthquake. These observations corroborate the efficacy of clustering methodologies in delineating seismic-induced concentration shifts and furnish fresh insights into the anomalous behavior of trace elements during the earthquake.

Influence of temperature on the radon concentration distribution in ramp under low-speed wind field: A numerical simulation study

By introducing the parameters of radon exhalation rate and radon diffusion coefficient, the distribution of radon concentration field on ramp under the condition of superposition of temperature field and flow field is simulated. The simulation results show that the distribution of radon concentration in the ramp under the condition of low-speed ventilation is greatly affected by the temperature field and flow field, and the change of radon exhalation caused by temperature is the main factor leading to the change of radon concentration in the ramp. The change of temperature will cause the overall increase of radon concentration in the ramp. Under the condition of constant flow field, the radon concentration in the chamber is more than two times higher than the average radon concentration in the ramp. Some areas severely exceeded the limit.

Time variation of radon in tap water in locations of a Greek area with geological background for elevated radon-in-water concentrations and correlation study between radon, gross alpha, uranium, and radium concentrations

Background: Radon (222Rn), a naturally occurring radioactive gas, dissolves in water, and it can be found in elevated concentrations in public water supplies when water originates from ground sources in areas rich in uranium. An area of great interest for measuring radon-in-water is the Migdonia basin in Northern Greece due to its geological background and because all of its villages are supplied with water from boreholes.
 Objectives: The main aim of this paper was to study the time variation of radon in tap water activity concentration in nine villages of the Migdonia basin supplied with water from boreholes and to determine factors that may affect it. Radon in water correlation between the source (borehole) and the consumption point (tap) was studied for some villages. Also, the correlation among radon, gross alpha, beta, uranium (238U), and radium (226Ra) activity concentration in water was studied.
 Design and methods: Water samples were collected and measured for their radon activity concentration from 66 villages in the Migdonia basin in order to find places with relatively high radon concentrations. The time variation of radon-in-water was studied for villages that showed relatively high radon concentrations for 3–4 years (2018–2022). All samples were measured for their 222Rn activity concentration using gamma-ray spectrometry. Water samples were also analyzed for their gross alpha, beta, and uranium isotopes activity concentration.
 Results and conclusions: Average radon in tap water activity concentrations measured in the area ranged from background concentrations to 185 Bq L-1. The corresponding annual effective doses from waterborne radon inhalation using both UNSCEAR and ICRP dose conversion factors ranged from 0.01 to 0.466 mSv y-1 and from 0.02 to 0.868 mSv y-1, respectively, while radon ingestion annual effective doses varied from 0.007 to 0.324 mSv y-1. Time variation of radon activity concentration in tap water for villages supplied from one borehole or a constant number of boreholes showed relatively low standard deviations (<24%) at a coverage factor of k = 1. Those deviations are probably caused by the time variation of boreholes’ radon concentration and water demand changes. A significant decline in radon concentration from the source (borehole) to the consumption point (tap water) was observed. Therefore, sampling should be performed at the consumption point. However, knowing the supplying borehole concentration is useful as it determines the potential for radon in drinking water. No apparent correlation was found among radon, gross alpha, beta, uranium, and radium concentrations in water. However, in some cases, remedial actions (withdrawal of boreholes) for uranium concentration also decreased radon concentration.

Effect of atmospheric temperature on underground radon: A laboratory experiment

The effect of atmospheric temperature on underground radon flow was investigated in a customized climate-controlled laboratory (CCL) system, which enabled us to isolate the impact of ambient atmospheric temperature variations on underground radon transport. The soil thermal gradients that developed, following atmospheric warming, acted as the driving force for the diffusive radon flow, resulting in a decrease in the radon concentration along the experimental column setup at a rate of ∼70 Bq∙m−3 per oC∙m−1 (∼0.4% of the radon concentration). When the ambient temperature decreased, compared to the soil temperature, an air-soil temperature difference developed along the column, which acted as a driving force for radon to flow along the column and promptly increased the radon concentration at a rate of ∼140 Bq∙m−3 per oC (∼0.8% of the radon concentration). The overall radon concentration changes under the experimental conditions were up to 30%. The changes in the molecular diffusion coefficient in the experimental temperature range were ∼7%, with thermal diffusion as a possible additional mechanism contributing to radon transport due to temperature. The cyclic changes in ambient temperature in the forced conditions experiments were found to be directly correlated with underground radon oscillations. The same frequency for ambient temperature and radon concentration, along the experimental column in low frequency warming-cooling cycles (i.e., 4–8 days), was found. This good correlation was lost at higher frequencies (two days or more), due to the asymmetrical response of radon to atmospheric warming and cooling. The results of this study explain some of the field observations in underground radon monitoring.

Radon Concentrations in Dwellings in the Mining Area-Are There Observed Effects of the Coal Mine Closure?

The article presents the results of radon research, carried out in the area of the mining commune in the Upper Silesian Coal Basin (USCB), Poland. Past investigations in the 1990s on radon concentrations in buildings, located within the mining area, showed that the indoor radon concentrations measured in the area affected by mining were higher than in buildings located outside that area. Currently, all underground hard coal mines within the boundaries of the observed commune have been closed. In 2020, after the closure of the last active mine, radon measurements were started again. The current results of indoor radon concentrations were compared with the archival results from the 1990s. It was found that the radon concentration increased significantly in the basements of buildings where measurements were made in 1990, 2020, and 2021: the maximum values were 260 Bq/m3, 644 Bq/m3, and 1041 Bq/m3, respectively. Therefore, these questions were posed: Do the mine closure processes increase radon migration? How long is the period of the occurrence of changes in radon concentrations in buildings after the cessation of mining operations?

Assessment of occupational exposure from radon in the newly formed underground tourist route under Ksi\u0105\u017c castle, Poland

In the present study, 222Rn activity concentrations in a newly formed underground tourist route under Książ castle, Poland, were investigated for periods undisturbed and disturbed by construction works. This preliminary assessment is based on the almost 3-year long continuous measurements (28 Oct. 2016–02 Jul. 2019) done with an SRDN-3 instrument. In detail described are radon concentrations for periods of renovation (11 Aug. 2018–10 Oct. 2018), opening (15 Oct. 2018–10 Apr. 2019) and operation and monitoring (11 Apr. 2019–02 Jul. 2019) of the facility. It was observed that after the termination of construction work, when natural ventilation returned to the state preceding this work, the absolute values of radon activity concentration decreased. The mean annual radon concentrations were higher than the reference level of radon concentration in underground spaces recommended by IAEA, ICRP, and by the EU Council Directive for workplaces. They reached 1179 Bq/m3 and 943 Bq/m3 in 2017 and 2018, respectively. Cyclically recurring daily changes in radon concentrations occurred only in April and October (so-called transitional periods) and only outside the period of construction work. The results confirmed; however, that these changes need not be considered when planning the work in the tunnel. The minimum effective dose rate from radon exposure occurs in colder periods of the year, from November to the end of March, where the mean effective dose rate value was found to be 0.0003 mSv/h. In contrast, the maximum dose rate of 0.014 mSv/h was observed from April to August.

Factors influencing temporal variations of radon concentration in high-rise buildings

Long-term radon time series were analyzed in 14 rooms and offices to search factors influencing indoor radon concentration in high-rise buildings. Radon entry to living rooms is determined both by diffusion from building materials and advection from adjoined low-ventilated spaces. Humans affect on seasonal and diurnal radon concentration changes in high-rise buildings by activating ventilation system. Indoor-outdoor temperature difference significantly influence on the air exchange rate under uncontrolled ventilation, which is especially important in new energy efficient buildings.

Factors influencing radon concentration during energy retrofitting in domestic buildings: A computational evaluation

The findings of recent research signalled increased radon levels following energy retrofitting of dwellings but to date, there have been limited quantitative data to support this observation. A modelling framework was developed that incorporates a dynamic radon entry rate, capturing changes in pressure differentials, to investigate changes in radon concentration following different energy-efficient retrofit measures in naturally-ventilated dwellings. Simulations examined a range of input criteria: dwelling type, air permeabilities, radon flow exponents, pre and post thermal retrofit characteristics, outdoor weather locations and corresponding wind profiles, as well as different ventilation guidelines. A total of 3,780 simulations were carried out. The air permeability of the building had the greatest impact on radon concentration with increases of up to 107%. Non-linear increases were observed arising from the impacts on pressure differentials due to changes in air permeability. The application of representative weather profiles associated with different locations (e.g. coastal, inland) resulted in differences of up to 37%. To a lesser extent, increased indoor temperature due to thermally retrofitting the building fabric, without changes in air permeability, resulted in radon levels increasing by 7%. Additionally, it was shown that the radon flow exponent was not a significant influence on radon concentrations following a retrofit. The addition of ventilation measures means that it is possible to achieve increased airtightness without impacting on the radon concentration. Overall, the simulations provide quantitative information that explains increased airtightness and elevated radon levels, highlighting the potential for radon concentrations to either increase or decrease following an energy retrofit.

Study On Radon Concentration Variation During Subway Construction.

The high radon concentration in the underground space of the subway station during construction often endangers the health of workers. Subway station project No. 16 in Beijing, while under construction, was selected as the main measuring point, a year's monitoring data was obtained to analyse the change of radon concentration. It was found that the concentration of radon was basically within the range of 5 ~ 500 Bq/m3 and showing a low level in the morning and a high level at noon, and presents the seasonal rule, compared with other seasons, the summer radiation is stronger. Furthermore, among the different measuring points, the radon concentration of the heading roadway is the highest, and the construction level of the station hall is the lowest. According to the comprehensive analysis, the concentration of radon during the construction of the subway station is mainly affected by the ambient temperature and air mobility.

Groundwater radon precursor anomalies identification by decision tree method

Radon in groundwater has long been recognized as a sensitive indicator of crustal stress. Significant changes in groundwater radon concentration before earthquakes have been documented in many studies. However, the radon concentration in groundwater may be affected by many interference factors. The anomalies before seismic activities may not be large enough to be clearly identified by the conventional statistical method. Therefore, new methods are needed to identify the possible pre-seismic anomalies. In this study, we investigated 38 years’ worth of radon time series data (1977–2015) in a hot spring to identify the possible precursor anomalies. We first identify the factors that may affect the radon fluctuations by wavelet coherence analysis, spring discharge, water temperature, rainfall and barometric pressure. All are found to be closely related to the radon fluctuation. The time series (1980–2008) were used for further decision tree analysis as a high correlation in the duration. Following this, we constructed the decision tree models based on these factors to model the “background” radon fluctuation and identify the anomalies by comparing the difference between the observed radon changes and the “background” fluctuations. The modeled “background” fluctuation is closely related to the observed data during the non-seismic activity period, with the correlation coefficient of 0.8. Following this, we compared the modeled “background” fluctuation of the radon time series with the observed one during the seismic activities period. The decision tree could identify 15 possible radon anomalies among the 24 chosen earthquakes. The identified anomalies are also supported by the anomaly changes in water temperature and spring discharge. Therefore, we believe that the decision tree method could be an efficient way to identify the possible precursor anomalies in future studies. Additionally, we explore the mechanism of radon anomalies. The plausible mechanism for the anomalous increase is that radon is continuously supplied from newly formed internal surfaces of the crack to the aquifer system. For the anomalous decrease, it might be related to radon partitioning into the gas phase and the change of mixing ratio of shallow and depth water.

Changes in groundwater radon concentrations caused by the 2016 Kumamoto earthquake

This study examined radon concentrations in springs in Kumamoto and Aso regions following the 2016 Kumamoto earthquake, in addition to monitoring springs near the Futagawa-Hinagu fault zone for more than two years following the earthquake to investigate the relationship between crustal deformation and the radon concentration variation. We compared these radon concentrations with those obtained prior to the earthquake. The springs that showed elevated radon concentrations were located within the compressive strain quadrant of the earthquake. The post-seismic concentration variations of the monitored springs can be explained by rock porosity changes. These results suggest that the radon concentration in spring water is affected by porosity changes caused by stress changes derived from earthquake deformation and subsequent post-seismic relaxation. Our results are consistent with the previously inferred permeability enhancement model. Mass conservation calculations for radon release yielded porosity changes ranging from 30% to 70% for some aquifer systems. This study explores the possibility of radon monitoring as a tool to investigate not only seismic precursors but also post-seismic crustal deformation and aquifer property changes due to large earthquakes on a regional scale.

Radon-222: environmental behavior and impact to (human and non-human) biota.

As an inert radioactive gas, 222Rn could be easily transported to the atmosphere via emanation, migration, or exhalation. Research measurements pointed out that 222Rn activity concentration changes during the winter and summer months, as well as during wet and dry season periods. Changes in radon concentration can affect the atmospheric electric field. At the boundary layer near the ground, short-lived daughters of 222Rn can be used as natural tracers in the atmosphere. In this work, factors controlling 222Rn pathways in the environment and its levels in soil gas and outdoor air are summarized. 222Rn has a short half-life of 3.82days, but the dose rate due to radon and its radioactive progeny could be significant to the living beings. Epidemiological studies on humans pointed out that up to 14% of lung cancers are induced by exposure to low and moderate concentrations of radon. Animals that breed in ground holes have been exposed to the higher doses due to radiation present in soil air. During the years, different dose-effect models are developed for risk assessment on human and non-human biota. In this work are reviewed research results of 222Rn exposure of human and non-human biota.

A COMPREHENSIVE CHARACTERISTIC OF 222Rn ACTIVITY CONCENTRATION CHANGES AND IONISING RADIATION EXPOSURE IN NEWLY DISCOVERED PARTS OF BEAR CAVE IN KLETNO, POLAND.

The article presents the results of research into 222Rn activity concentration changes and ionising radiation exposure in newly discovered parts of Bear Cave in Kletno, unknown until 2012. 222Rn activity concentration was registered at three measurement points located inside over 500-m-long newly discovered cave passages. The air in these parts of the cave is characterised by a stable temperature of about 5°C and a relative humidity of 100%. The measurements started in September 2013 and were completed by mid-July 2016. The measured data were recorded continuously, including hourly registration of 222Rn activity concentration with the use of three Polish semiconductor detectors SRDN-3a. Three data sets were obtained. Two of them, containing the same numbers of data, were recorded between 4 September 2013 and 10 July 2016 by SRDN-3a detectors no 7 and 9 located at sites no 1 and no 3, respectively. The third set comprises data registered between 27 October 2014 and 10 July 2016 by SRDN-3a probe no 8 at site no 2. Distinct daily changes in 222Rn activity concentration in the new parts of Bear Cave occur in early spring (from March to May) and in autumn (October). This observation confirms the notion that radon concentration changes depend on natural convective air exchange between the cave and the atmosphere. It has been shown that daily radon concentration changes in other seasons are irregular and rather small. The highest values of 222Rn activity concentration inside the cave are more frequent in daytime, i.e. from the morning to midday. The recorded annual mean values of 222Rn activity concentration in successive measurement years are comparable for all the three sites and range from 2690 to 3179Bqm-3 in 2013, from 2676 to 2973Bqm-3 in 2014, from 2587 to 2917Bqm-3 in 2015 and from 2581 to 3719Bqm-3 in 2016. These values exceed those recommended as maximum allowable radon concentrations in such spaces (0.5-1.5kBqm-3) and are many times as high as the values recommended for workplaces (0.3kBqm-3). The recorded values of 222Rn activity concentration in the air of the new parts of Bear Cave in Kletno result in a risk of exposure to a radiation dose higher than the national standard of 1mSv per year adopted for the general public. In the most unfavourable conditions, it appears as early as after 25hours spent inside the cave. The minimum effective dose to which a person staying inside the cave is exposed within 1hour is 0.002mSv, and the maximum dose is 0.04mSv. The results of the conducted measurements demonstrate the necessity of introducing appropriate solutions, crucial in terms of radiological protection and legislation, that would minimise the risk of exposure to ionising radiation in the new parts of Bear Cave.

Constructing Environmental Radon Gas Detector and Measuring Concentration in Residential Buildings

Background: From the health physics perspective, radon gas is one of the most dangerous gases in residential and business environments. According to the WHO (World Health Organization), radon gas is considered the second cause of lung cancer in societies after smoking. Methods: In this study, the environmental radon gas has been measured using a built radon gas detector on a specific preamplifier circuit and then the perceived results were compared with an Alpha-Guard detector. Specific activity and output ratio on radon concentration in air were measured on three different floors of a residential building covered by different materials. Results: The results showed a good correlation between the outputs and data gathered by the Alpha-Guard. In underground covered by plaster and cement, the detector responses showed approximately double amounts in comparison with the ground floor. The different covered places revealed dissimilar responses, so that the screened granite had greater amounts by 347 ± 37 Bq/m3. Besides, the minimum response was revealed on the first floor using Alpha-Guard by 47 ± 6 Bq/m3. Results confirmed that on each floor, which has a good ventilation system, the exposure due to the radon isotopes can be immensely reduced. Conclusions: This system can also be used to measure the radon concentration changes in the environment and groundwater.

Geochemical signals related to the 2011–2012 El Hierro submarine eruption

On 10 October 2011, a submarine volcanic eruption began 2 km south of the island of El Hierro (Canary Islands, Spain). It was the first eruption after 40 years of quiescence in the Canarian archipelago. Since mid-July 2011, a multiparametric network has been deployed by the Instituto Geográfico Nacional (hereinafter IGN) to monitor volcanic processes. The data recorded by five stations, measuring the air and soil temperature, CO2 and radon concentration in the air inside four galleries and one well, are the focus of the present paper. Two important anomalies were found that improve comprehension of the volcanic process. First, a clear increase in CO2 concentration in one gallery (from 825 ± 19 to 2305 ± 35 ppm) which seems to be mainly controlled by ground deformation measured during the unrest period preceding the eruption. Second, a relationship between radon concentration in air in a well located in the northern side of the island with seismic energy release (several peaks with up to 115% increase), and ground deformation (50% growth in background level), also before the eruption onset. Lastly, changes in radon concentration during eruptive period seem to be modulated by seismic activity (increases up to 233%), which in turn is likely related to variations in magma rheology.

Influence analysis of natural ventilation system on radon concentration in Interim Storage for Radioactive Waste

The release of radioactive contaminants in nuclear facilities or facilities associated with radioactive materials could be harmful to the workers. The mechanical and natural ventilation system in the nuclear facilities can eliminate or reduce this potential risk. The purpose of this study is to analyse the correlation of natural ventilation with radon concentration in Interim Storage for Radioactive Waste in BATAN. In this study, the radon sources are not only from soil and building materials but mainly from Ra-226 radioactive waste, which was used in Brachytherapy to kill cancer cells. The simulation analysis was conducted using multi-zone airflow and contaminant transport code, CONTAM. The numerical simulation results were validated with analytical calculation and experimental measurement. The experimental measurement was performed using an electronic radon detector with real time monitoring, DURRIDGE RAD7. The results show that the change of radon concentration can be affected not only by temperature difference between indoor and outdoor but also by temperature difference between one room and the other room connected to it. The simulation- and calculation in this study are relatively consistent to the measurement results.

Radon concentrations in multi-story buildings in Montenegro

Change of radon concentrations in dwellings with floor level was studied in six multi-story buildings, in four towns of Montenegro with different climate conditions. The annual aver- age radon activity concentrations in 35 dwellings are found to be very low, mostly at a level of 20-30 Bqm?3. Absorbed gamma dose rates in these dwellings are in the range of 14-58 nGyh?1. The low radon concentrations are a consequence of a good tightness of the structures in contact with the ground and a small contribution of building materials to radon indoors. A clear general trend of changes in radon concentrations with floor level is not observed. In most of the dwellings on different floors in the multi-story building radon concentration varies very little, mostly within measurement error. A small decrease in radon concentration is noted between the two or three floors closest to the ground, but only in some of the buildings. Therefore, a decrease of indoor radon concentration with floor level cannot be considered as a general characteristic of multi-story buildings. Although the seasonal radon variations have not been in the focus of this study, it was found that the average radon activity concentrations in dwellings of the multi-story buildings are higher in warmer than in cooler half-year period, what is contrary to the general rule for homes in the world and in Montenegro as well.

Non-parametric detection of atmospheric radon concentration anomalies related to earthquakes

Anomalous phenomena related to earthquakes have been studied to aid in the forecasting of large earthquakes. Radon (222Rn) concentration changes are known to be one of those phenomena. Many studies have quantified radon anomalies to identify physical aspects of radon emanations related to earthquakes. Here, we apply singular spectrum transformation, non-parametric analysis to estimate change points in time series, to atmospheric radon concentration. From 10 years of data from continuous observation of the atmospheric radon concentration over northeastern Japan and Hokkaido, we identify anomalies in the atmospheric radon concentration related to the moment releases of large earthquakes. Compared with a conventional model-based method, the singular spectrum transformation method identifies more anomalies. Moreover, we also find that change points in the atmospheric radon concentration prior to the 2011 Tohoku-Oki earthquake (Mw 9.0; 11 Mar. 2011, N38.1°, E142.9°) coincided with periods of other anomalous precursory phenomena. Our results indicate that singular spectrum transformation can be used to detect anomalies in atmospheric radon concentration related to the occurrences of large earthquakes.

Influence of Blasted Uranium Ore Heap on Radon Concentration in Confined Workspaces of Shrinkage Mining Stope

A calculation model for radon concentration in shrinkage mining stopes under various ventilation conditions was established in this study. The model accounts for the influence of permeability and area of the blasted ore heap, ventilation air quantity, and airflow direction on radon concentration in a confined workspace; these factors work together to allow the engineer to optimize the ventilation design. The feasibility and effectiveness of the model was verified by applying it to mines with elevated radon radiation exposure. The model was found to accurately changes in radon concentration according to the array of influence factors in underground uranium mines.

Monitoring and descriptive analysis of radon in relation to seismic activity of Northern Pakistan

Earthquakes are one of the major causes of natural disasters and its forecasting is challenging task. Some precursory phenomenon exists in theory in relation to earthquakes occurrence. The emission of radioactive gas named ’radon’ before the earthquakes is a potential earthquake precursory candidate. The study aims to monitor and to analyze the radon in relation to seismic activity in Northern Pakistan. For this purpose RTM-2200 has been used to monitor the changes in radon concentration from August 01, 2014 to January 31, 2015 in Northern Pakistan. Significant temporal variations has been observed in radon concentration. The bivariate analysis of radon with other variables manifests its positive relationship with air pressure and relative humidity and negative relationship with temperature. 2σ upper control limit on monthly basis are computed for detection of anomalous trends in the data. Overall increasing trend is detected in radon concentration. Five earthquakes from August 01, 2014 to January 31, 2015 have been selected from earthquake catalogue, depending upon their magnitude and distance from monitoring station and out of which radon concentration can be associated with only two earthquakes correlated with tectonic effect of radon concentration. Both of events have same magnitude 5.5 and occurred on September 13 and October 14, 2014 respectively. Very large variations have been observed in radon for the last two months of the study period, which may be occurred due to some other geological and environmental changes, but are not related to the earthquake activity.