Radon Changes Research Articles

Measurement of radon decays with the LVD-setup for neutrino searching

The LVD (Large Volume Detector), located at the Low Background Laboratory, Gran Sasso, Italy, is built to detect neutrinos from stellar core collapses in our Galaxy. The peculiarity of the search for rare events requires close attention to the background of the experiment, such as the natural radioactivity of the rock and detector materials and the interaction of cosmic ray muons underground. The LVD is capable of detecting gamma quanta from the decay of radon daughter nuclei. We convincingly show the connection between the change in the background counting rate from gammas in the detector and the change in the concentration of radon nuclei in the experimental hall. We also point out the existence of another source of radon change, this is seismic activity.

Radon on Mt. Etna (Italy): a useful tracer of geodynamic processes and a potential health hazard to populations

Radon gas and its radioactive daughters have been extensively studied on Mt. Etna, both in local volcanic rocks and in all types of fluid emissions from the volcano (crater gases, fumaroles, mofettes, soil gases, groundwaters). The first measurements date back to 1976 and were carried out both in local volcanic rocks and in the crater plume. Since then, fifty-four scientific articles have been published. The largest majority of them (more than 50%) correlated radon emissions with volcanic activity and/or magma dynamics inside Mt. Etna. Many others were focused on possible correlations between time variations of in-soil radon and tectonic activity. The concentration of radionuclides in Etna volcanic rocks was measured on several occasions in order to set background values of radon parents and to study the dynamics of Etna magmas. Some articles analyzed the concentrations of radon in Etna groundwaters and their temporal changes in relation to volcanic activity. Only a few studies focused on methodological aspects of radon measurements in the laboratory. Finally, in recent years, geoscientists began to analyze the possible negative effects on human health from high concentrations of indoor radon in houses near active faults. The overall results show that, in most cases, it is possible to understand the endogenous mechanisms that cause changes in soil radon release from rocks and its migration to the surface. Several physical models were produced to explain how those changes were correlated with Etna’s volcanic activity, making them potential precursors, especially in the cases of eruptive paroxysms. More complex is the analysis of radon changes in relation to tectonic activity. Indeed, if measurements of radon in soil is now considered a robust methodology for identifying buried faults, radon time variations are not always clearly correlated with seismic activity. This difficulty is likely due to the complex interplay between tectonic stress, magma migration/eruption and gas release through faults. In any case, the potential high hazard for human health due to high concentrations of indoor radon in houses close to faults seems to be a well-established fact, which requires particular attention both from the scientific community and the public health authorities.

Некоторые результаты работ по оценке эманаций радона Унальского хвостохранилища

Introduction. Despite the significant contribution of scientists to the study of the existing technogenic impact of the Unal tailing dump on the environment, studies on it of such parameters as the stress-strain state of the tailing dump body, radon emanation have not been previously studied. Materials and research methods. The purpose of the studies described in the work was to study the presence and magnitude of radon emanations in the subsoil air of the surface of the Unal tailing dump for further assessment of the applicability of the method to take into account the stress-strain state of the body. As a result of field studies, the authors measured the equivalent equilibrium volumetric activity of radon-222 (hereinafter EEVA) in the reference points selected according to the previously proposed algorithm for selecting reference points, which is based on the methodology for determining the stress-strain state of a body undergoing change. As a result of the studies, the values of radon emanation data were determined, the data obtained on EEDA were processed and systematized for subsequent analysis and evaluation using specialized software and algorithmic software. Research results. As a result of the analysis and evaluation of the obtained data on EEDA, after establishing the fact of the presence of radon emanations from the area, it can be concluded that it is necessary to conduct a second expedition in order to prove the hypothesis of the possible use of EEDA to assess and characterize the stress-strain state of the tailings body (in relation to the Unal tailings) and substantiate occurrence of serious consequences in case of a potential change in the state of the body of the tailing dump during seasonal flooding, seismic and technogenic impacts. In the course of this work on the analysis of the results of experimental studies in the scientific and educational center of the SFU branch in Gelendzhik and field studies, the following conclusions can be formulated. As a result of a number of research activities to assess the geo-ecological sustainability of tailings using seismic and satellite GPS equipment (including the justification of control well locations for monitoring radon emanations), the hypothesis was confirmed that the current values can be estimated from variations in changes in radon 222 emanations stress-strain state of the body of the tailing dump, which makes a significant contribution to the development of express methods for diagnosing the level of pollution of anomalous zones and assessing the risk for adjacent media using the latest geophysical, geochemical and geostatic methods. The proposed method for analyzing the stress-strain state of the tailing dump body and other parameters of its internal structure can also be used to monitor other alluvial and bulk man-made massifs formed as a result of the activities of mining and processing plants located in various regions of the Russian Federation.

Radon degassing triggered by tidal loading before an earthquake

The presence of anomalous geochemical changes related to earthquakes has been controversial despite widespread, long time challenges for earthquake prediction. Establishing a quantitative relationship among geochemical changes and geodetical and seismological changes can clarify their hidden connection. Here we determined the response of atmospheric radon (222Rn) to diurnal tidal (K1 constituent) loading in the reported 11-year-long variation in the atmospheric radon concentration, including its anomalous evolution for 2 months before the devastating 1995 Kobe earthquake in Japan. The response to the tidal loading had been identified for 5 years before the occurrence of the earthquake. Comparison between these radon responses relative to crustal strain revealed that the response efficiency for the diurnal K1 tide was larger than that for the earthquake by a factor of 21–33, implying the involvement of crustal fluid movement. The radon responses occurred when compressional crustal stress decreased or changed to extension. These findings suggest that changes in radon exhaled from the ground were induced by ascent flow of soil gas acting as a radon carrier and degassed from mantle-derived crustal fluid upwelling due to modulation of the crustal stress regime.

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.

Implication of Radon Monitoring for Earthquake Surveillance Using Statistical Techniques: A Case Study of Wenchuan Earthquake

The seismotectonically induced changes in groundwater radon (Rn) are considered to be strong imputes for the surveillance of imminent major earthquakes. Groundwater facilitates the migration of soil gases as a result of tectonic stresses. In this regard, a radon time series is statistically analysed to identify the radon anomalies possibly induced by Wenchuan earthquake. The statistical analysis mainly involves the deterministic analysis of the Rn data and residual Rn analysis using a criterion x¯±2σ of anomaly selection having a confidence interval of 95%. The deterministic analysis reveals that the Rn time series follows a persistent trend 0.5≤H≤1 which confirms the absence of a chaotic regime. On the other hand, the residual Rn shows a notable upsurge straddling the time of the Wenchuan earthquake in the form of pre- and post earthquake changes at monitoring stations having RE/RD≤0.3. The residual Rn level passes the anomaly selection criterion x¯±2σ and is declared as a tectonically induced Rn anomaly. Contrary to this, the response of distant monitoring stations (RE/RD>0.3) to this particular earthquake further validates the link between Rn and earthquake activity. In a nutshell, the present study highlights the potential implications of earthquake-induced radon anomalies for earthquake prediction research.

Radon and moisture impacts from interventions integrated with housing energy retrofits.

Energy retrofits can reduce air exchange, raising the concern of whether indoor radon and moisture levels could increase. This pre/post-intervention study explored whether simple radon interventions implemented in conjunction with energy retrofits can prevent increases in radon and moisture levels. Treatment homes (n=98) were matched with control (no energy retrofits or radon intervention) homes (n=12). Control homes were matched by geographic location and foundation type. t-tests were used to determine whether post-energy retrofit radon and moisture level changes in treatment homes significantly differed from those in control homes. The radon interventions succeeded in preventing statistically significant increases in first floor radon using arithmetic (p=0.749) and geometric means (p=0.120). In basements, arithmetic (p=0.060) and geometric (p=0.092) mean radon levels statistically significantly increased, consistent with previous studies which found that basement radon levels may increase even if first floor levels remain unchanged. Changes in infiltration were related to changes in radon (p=0.057 in basements; p=0.066 on first floors). Only 58% of the change in infiltration was due to air sealing, with the rest due to weather changes. There was no statistically significant association between air sealing itself and radon levels on the first floor (p=0.664). Moisture levels also did not significantly increase.

Analyses of Influencing Factors for Radon Emanation and Exhalation in Soil

The study on radon emanation and exhalation in soil is more and more important for environmental protection, and many influencing factors on radon emanation coefficient and exhalation in soil have been well documented. In order to evaluate the radon change and key influencing factors, this paper made an overall summary based on these studies. The main results show that the change laws of emanation coefficient with elevated temperature of radon can be divided into three types and they relate to the moisture state and content of soil. The normalized radon exhalation has a negative linear correlation with temperature, and the maximum emanation coefficient has a positive linear correlation with heating rate and specific surface. The pores with different size have different effects on the emanation coefficient of radon in the soil, e.g., the micro-pores increase emanation coefficient, and the mezzo-pores decrease emanation coefficient. Taken together, our results offered guiding significance for the evaluation of radon in soil and in air when soil state changes. Lastly, the existing problems and research directions were also given.

Decadal radon cycles in a hot spring

AbsatrctA high-fidelity record covering nearly 40 years of water-dissolved radon from the hot spring site of BangLazhang (BLZ), Southwestern China is presented to study multi-year periodicities of radon. Ancillary observational data, i.e., water temperature, spring discharge rate, barometric pressure, combined with regional rainfall, galactic cosmic rays (GCR flux is modulated by solar wind and thus a proxy for solar activity) and regional seismicity from the same period are considered to identify potentially influencing factors controlling the changes in radon. Variations in radon concentration and ancillary observational data are studied using continuous Wavelet Power Spectrum (WPS), Wavelet Coherence (WTC), and Partial Wavelet Coherence (PWC). The results show that the long-period radon concentration is characterized by a quasi-decadal (8–11 years) cycle, matching well with the concurrent periodicity in water temperature, spring discharge rates and GCR. PWCs of radon, discharge rate and water temperature suggest that water temperature variations explain most of the coherent variability of radon and the discharge rate. We tentatively conclude that radon variations are mainly explained by variations in water temperature and spring discharge, which are modified and modulated by earthquakes and quasi-decadal variations of an unidentified process. The influence of solar activity on the decadal periodicity is discussed.

What happens to in‐soil Radon activity during a long‐lasting eruption? Insights from Etna by multidisciplinary data analysis

AbstractWe analyze short‐ to long‐term changes (from days to months) in Radon (Rn) activity measured nearby (<2 km) the eruptive fractures that fed a lava effusion at Mt. Etna, Italy, between 13 May 2008 and 6 July 2009. The N120‐140°E eruptive fractures opened between 3050 and 2620 m above sea level before a dike‐forming intrusion fed the ∼14 month‐long lava emission. Our high‐rate data streams include: Rn, ambient parameters (barometric pressure and soil temperature), and seismic data (earthquakes and volcanic tremor) recorded from January 2008 to July 2009. The analysis highlights repeated episodes of rock‐fracturing related to seismic swarms, and vigorous gas pulses and peak values in Rn emissions (maximum ∼4.1×105 Bq/m3 on 16 November 2008), which we interpreted in a conceptual model as the response to inputs from the magmatic system during the eruption. This multidisciplinary study: (i) provides evidence of a close relationship between Rn emission at a fumarole near the summit active craters and local earthquakes, and (ii) enables exploring the important role of the volcanic source on the temporal development of the Rn flux, which may account for the much higher (≫94 m/d) ascent speed of the Rn carrier (vapor) than diffusion. The close location of Rn probes to the active conduits, along with the application of our multidisciplinary approach, may shed new light on the internal dynamics of other active volcanoes worldwide.

Detection of earthquake induced radon precursors by Hilbert Huang Transform

Continuous measurement of radon-222 concentration in soil was carried out across duration of one year at a geologically faulted area having high regional heat flow to detect anomalies caused by seismic activities. The data reveals a range of periodicities present in the radon time series. To identify seismic induced radon changes we treat the time series data through various filtering methods to remove inherent periodicities. The Ensemble Empirical Mode Decomposition (EEMD) is deployed to decompose the signal into its characteristic modes. Hilbert Huang Transform (HHT) is applied for the first time on the physically significant modes obtained by EEMD to represent time–energy–frequency of the recorded soil radon time series. After removing the periodic and quasi-periodic constituents from the original time series, the simulated result shows a forceful correlation in recorded radon-222 anomalies with regional and local seismic events.

Seasonal emanation of radon at Ghuttu, northwest Himalaya: Differentiation of atmospheric temperature and pressure influences

Continuous monitoring of radon along with meteorological parameters has been carried out in a seismically active area of Garhwal region, northwest Himalaya, within the frame work of earthquake precursory research. Radon measurements are carried out by using a gamma ray detector installed in the air column at a depth of 10m in a 68m deep borehole. The analysis of long time series for 2006–2012 shows strong seasonal variability masked by diurnal and multi-day variations. Isolation of a seasonal cycle by minimising short-time by 31 day running average shows a strong seasonal variation with unambiguous dependence on atmospheric temperature and pressure. The seasonal characteristics of radon concentrations are positively correlated to atmospheric temperature (R=0.95) and negatively correlated to atmospheric pressure (R=−0.82). The temperature and pressure variation in their annual progressions are negatively correlated. The calculations of partial correlation coefficient permit us to conclude that atmospheric temperature plays a dominant role in controlling the variability of radon in borehole, 71% of the variability in radon arises from the variation in atmospheric temperature and about 6% of the variability is contributed by atmospheric pressure. The influence of pressure variations in an annual cycle appears to be a pseudo-effect, resulting from the negative correlation between temperature and pressure variations. Incorporation of these results explains the varying and even contradictory claims regarding the influence of the pressure variability on radon changes in the published literature. Temperature dependence, facilitated by the temperature gradient in the borehole, controls the transportation of radon from the deep interior to the surface.

Identifications and removal of diurnal and semidiurnal variations in radon time series data of Hsinhua monitoring station in SW Taiwan using singular spectrum analysis

Over the past three decades, anomalous temporal changes in radon concentrations have been reported in relation to earthquake occurrences. However, radon anomalies in all cases are not only controlled by seismic activity, but also by meteorological parameters which make isolation of earthquake precursory signals complicated. In the present study, characteristics of temporal variability of soil gas radon concentrations at the Hsinhua monitoring station, southern Taiwan, have been examined using singular spectrum analysis (SSA). In order to make continuity and regularity of the data before applying the SSA, the radon data were carefully edited for gaps and discontinuous jumps following intervals of malfunctioning of equipments. Digital filter has been applied in eliminating the long-term trend in the data and retains variations of <30 days. The radon changes exhibit dominant daily variations, which are controlled by atmospheric temperature inducted evaporation in surface water saturated soil (capping effect). The causal relationship is marked by a clear phase lag of 2–3 h in the sense that peak in the daily variation of radon succeeds the peak in temperature. Aperiodic variations in soil radon intensity in the range of 2–10 days are negatively correlated with temperature, while positively correlated with pressure. However, the negative correlation of the soil radon with temperature is found to be pseudo-effect arising due to interrelation between temperature and pressure.

Characteristic behavior of water radon associated with Wenchuan and Lushan earthquakes along Longmenshan fault

In China, numerous subsurface, surface water well and spring parameters are being monitored through a large network of stations distributed in China sponsored by China Earthquake Administration (CEA). All the data from these network is managed by China Earthquake Network Center (CENC). In this paper, we have used numerous data (water radon, gas radon, water level, water temperature) available through CENC for the period 2002–2014 and studied the behavior and characteristics of water 222radon [Rn(w)]. The observed parameters were also complemented by rainfall data retrieved from Tropical Rainfall Measuring Mission (TRMM) satellite. Our detailed analysis shows pronounced changes in the observed parameters (especially water and gas radon) prior to the earthquake. The changes in water radon, ground water level and rainfall showing characteristics behavior for Wenchuan and Lushan earthquakes. The long term data analysis of water radon and water level at various locations around epicenters of two major earthquakes along Longmenshan fault show a positive and negative relation of water radon and water level prior to these earthquakes. It is difficult to find any trend of water radon and changes in water radon pattern with these two earthquakes that could prove as a reliable precursor of earthquakes. Changes in the water radon concentrations from one location to other may be associated with the changes in ground water regime and geological settings in the epicentral and surrounding regions.

Evidence of both M2 and O1Earth tide waves in radon‐222 air concentration measured in a subglacial laboratory

Many earthquake‐related radon‐222 temporal changes have been recorded since the 1960s and are frequently discussed, sometimes initiating a controversial debate on the relevance of radon‐222 as an earthquake precursory signal. The diurnal S1–O1 and semidiurnal S2–M2 Earth tide signatures in radon signals are acquired in a natural context. This can be used to calibrate the radon changes under strain accumulation close to epicentral areas, which are often discussed but are rarely evidenced by experimental data. The analysis of a 10 month time series acquired in the subglacial laboratory of the Argentière glacier, Mont Blanc Massif, French Alps, demonstrates here the unambiguous episodic appearance of the M2–O1 waves in the radon signal with significant amplitudes of 36 and 50 Bq m−3, respectively. We thus prove that radon variations induced by gravitational M2 and O1 waves are detectable in a natural environment. In this particular place, the radon response is probably amplified by cyclic stress variations applied on the upstream side of the natural rock dam into which the laboratory is drilled. The amplification of the radon signal is induced by poroelastic deformation under this particular mechanical forcing. This can elucidate why most precedent studies failed to detect M2–O1 signatures in radon signals recorded in other underground laboratories.

Measurements of soil radon in south Russia for seismological application: Methodological aspects

As a first step in the monitoring of soil radon in search of harbingers of earthquakes, an investigation of suitable measurement techniques was conducted. As a result of these investigations, the following recommendations are made. Semiconductor and scintillation (ZnS) counters are the most suitable for Rn monitoring with chambers for natural drift of emanations to the detector. The method of compulsory selection of soil air is hardly effective. Soil aerosols might enter the drift chamber; these aerosols transfer many radioactive isotopes. The most suitable locations for placement of detectors of radon are cellars. Measurements should be continuous in character. The choice of a place for monitoring near mud volcanoes and faults should be determined by an Rn survey. In mud volcanoes, the best locations are areas with an average concentration of radon. For faults, identical tendencies of change in radon are maintained at some distance from the borders of the fault. For large faults, this distance is equal to half the width of the fault. For small faults, this distance increases by up to 3 times the fault width. All the recommendations were applied in the Northern Caucasus. Reliable results of the changes in soil radon were obtained during strong geophysical processes.

Comparison of urinary excretion of radon from the human body before and after radon bath therapy

Theoretically, the human body absorbs radon through the lungs and the skin and excretes it through the lungs and the excretory organs during radon bath therapy. To check this theory, the radon concentrations in urine samples were compared before and after radon bath therapy. During the therapy, the geometric mean (GM) and the geometric standard deviation of the radon concentration in air and in the bath water were 979 Bq m(-3), 1.58 and 73.6 Bq dm(-3), 1.1, respectively. Since radon was detected in each urine sample (GM around 3.0 Bq dm(-3)), urinary excretion of radon was confirmed. The results of this study can neither reject nor confirm the hypothesis of radon absorption through the skin. A 15 times higher increment of inhaled radon level did not cause significant changes in radon of urine samples.

Radon in the investigations of geo‐hazards in Polish collieries

AbstractOutbursts (releases of gas and coal from exposed coal face) are dangerous events in coal mines, potentially leading to damage in the galleries and casualties among miners. For that reason, monitoring of this hazard is very important in collieries with seams prone to outbursts. Current hazard indicators are not sufficient for the proper prediction of geodynamic events and any effort to find a new and better method of monitoring is thus desirable. During the 1980s and 1990s, attempts were undertaken to apply specific radiometric methods to support the prediction of outbursts in collieries in the Lower Silesian Coal Basin (LSCB) in south‐western Poland. This idea was developed as an analogy to the study of radon changes in groundwater prior to earthquakes. This study investigates the hypothesis of possible variations of radon emanation from coal seams prior to outbursts. Techniques and a methodology of radon observation in gas samples from strata were developed and applied. It has been stated that there is a degree of correlation between the temporal and spatial variations of radon level and the hazard level of an outburst. In the 1990s, all collieries in LSCB were abandoned and further investigations were thus stopped. In the last few years, the occurrences of outbursts were noticed in the collieries of Upper Silesian Coal Basin. For that reason, we initiated the monitoring of radon concentration as sampled from headings in dangerous coal seams. The purpose of the research is an attempt to introduce a new parameter, ‘the radon indicator of outburst hazard’, which could be used to support other routinely applied techniques of outburst prediction. This study provides some results from previous investigations performed in the collieries of the LSCB, as background and calibration to the preliminary results of the new research, performed in one of the coal mines in Upper Silesia region.

Termal Suların Radyoaktivite ve Kimyasal İçeriklerinin İncelenmesi; İzmir, Seferihisar Bölgesi Örneği

Agricultural terrains which are spontaneously irrigated by geothermal waters are affected by harmful contents of those waters especially boron. In the present study, Seferihisar-Doganbey Fault zone where thermal waters are exist, were selected as study area. In date interval July 2005-December 2007, water samples were collected in a month period from determined stations. Radon measurements in water samples were performed by using collector method. Also analysis of pH, EC (electrical conductivity), Na 2 CO 3 , Na + , K + , Ca ++ +Mg ++ , Cl - , HCO 3 - , SO 4 = and B (Boron) have performed for those water samples. It is observed that radon changes for Cumah Station in interval of 0.1Bq/L-16.67Bq/L, for Karakoc Station in interval of 0.29Bq/L-10.26Bq/L, for Doganbey1 Station in interval of 0.33Bq/L -56.36Bq/L, for Doganbey 2 Station in interval of 0.34Bq/L-7.7Bq/L. Unstable variations of radon values provide requirement of periodical radon measurements along the study.

Characterization of airborne radon released by domestic showering and the use of a washing machine

Water originated from groundwater systems can have relatively high concentration of radon. In many situations, radon is released from the water and mixes with the indoor air. In the present study, laboratory experiments were conducted to characterize the airborne radon released by showering and the use of a washing machine. The followings were discussed: (1) a comparison between the loss of waterborne radon and the increase of airborne radon, (2) time-related changes in airborne radon after the water use, (3) changes in the equilibrium factor, and (4) the relationship between radon concentration and the distance from the source of radon release.