Radon Monitoring Research Articles

Study of radon/thoron exhalation rate, soil-gas radon concentration, and assessment of indoor radon/thoron concentration in Siwalik Himalayas of Jammu & Kashmir

ABSTRACTIn the present study, the soil-gas radon concentration was assessed at different depth intervals, i.e., 15 cm, 30 cm, 60 cm, and 100 cm from the 30 villages of Jammu & Kashmir, India using RAD7, an electrostatic solid state alpha detector. The radon mass exhalation and thoron surface exhalation rate has also been measured in the selected 18 soil samples out of 30 of different grain sizes (i.e., 1 mm, 300 µm, 150 µm). The active radon and thoron concentrations were also assessed in the 20 villages. Both the exhalation rates and active radon/thoron concentration were measured using SMART Rn Duo, a portable radon monitor. The average values of soil-gas radon concentration were 210 ± 84 Bq m−3, 1261 ± 963 Bq m−3, 4210 ± 1994 Bq m−3, and 671 ± 305 Bq m−3 at the depth intervals of 15 cm, 30 cm, 60 cm, and 100 cm, respectively. The exhalation rate of radon and thoron from soil was found to decrease with the increase of grain size, as smaller soil particles make relatively more contribution to radon and thoron exhalations from the ground surface than larger soil particles. The measured Pearson's correlation coefficient was obtained as statistically significant between different quantities under two-tailed test.

Setup and procedure for routine measurements of radon exhalation rates of building materials

A practical procedure and the necessary setup for routine measurement of the exhalation rate of 222Rn from building materials are described. The setup comprises a continuous radon monitor, based on an ionization chamber, and a relatively large-volume accumulation chamber. The experimentalist can interact with the setup in real time via a PC. Therefore it is possible to determine the exhalation rates by determining the optimum accumulation time before the effects of back-diffusion and radon decay set in. This, in turn, reduces the time required to test a sample and makes the setup useful for routine measurements. The exhalation rate values (Bq m−2 h−1) for selected building materials made from gypsum, marble, ceramic, and granite were found to be 1.63, 2.29, 3.99 and 5.39 Bq m−2 h−1, respectively. The optimal test-times for the samples ranged from 9 to 19 h.

Parameter Variations in the Subsoil Radon Field at the Paratunka Station of the Petropavlovsk-Kamchatsky Geodynamic Test Site in 2011–2016

A network of stations for subsoil radon monitoring is in operation at the Petropavlovsk-Kamchatsky geodynamic testing area and is aimed at detection of strong earthquake precursors. At all stations, measurements are carried out using gas-discharge counters located at different depths within aeration zones of soft sediments. The volume activity of radon (VA Rn) is monitored at the most equipped station Paratunka (PRT) at three measurement sites located across the regional fault. The radon flux density (RFD) is measured from the surface. The article reviews responses in the dynamics of VA Rn and RFD from the surface at the PRT station prior to the Kamchatka earthquakes with magnitudes М W > 5 that occurred over the period of 2011–2016. The revealed RFD seasonal cycle is likely related to the seasonal variations in air temperature. The postseismic effect caused by the strongest deep Okhotsk earthquake (May 24, 2013, М W = 8.3) is detected in the RFD data. The behavior of VA Rn dynamics during time periods of the strong earthquakes is different. The results confirm the existing opinion on the formation of narrowly localized zones of Rn runoff to the atmosphere owing to both vertical and horizontal irregularities in the top layer of soil, which can react differently to changes in the geoenvironment stress–strain. On the basis of the real-time radon monitoring data, the authors have issued partially successful short-term prediction for several earthquakes. The results of this work confirm the opinion of many researchers that radon monitoring can be used in the short-term prediction of strong earthquakes.

Influence of meteorological parameters on the soil radon (Rn222) emanation in Kutch, Gujarat, India

The soil radon (Rn222) and thoron (Rn220) concentrations recorded at Badargadh and Desalpar observatories in the Kutch region of Gujarat, India, have been analyzed to study the sources of the radon emissions, earthquake precursors, and the influence of meteorological parameters on radon emission. Radon and meteorological parameters were recorded using Radon Monitor RMT 1688-2 at these two stations. We used the radon data during February 21, 2011 to June 8, 2011, for Badargadh and March 2, 2011 to May 19, 2011, for the Desalpar station with a sampling interval of 10min. It is observed that the radon concentrations at Desalpar varies between 781 and 4320Bqm-3with an average value of 2499Bqm-3, whereas thoron varies between 191 and 2017Bqm-3with an average value of 1433.69Bqm-3. The radon concentration at Badargadh varies between 264 and 2221Bqm-3with an average value of 1135.4Bqm-3, whereas thoron varies between 97 and 556Bqm-3. To understand how the meteorological parameters influence radon emanation, the radon and other meteorological parameters were correlated with linear regression analysis. Here, it was observed that radon and temperature are negatively correlated whereas radon and other two parameters, i.e., humidity and pressure are positively correlated. The cross correlogram also ascertains similar relationships between radon and other parameters. Further, the ratio between radon and thoron has been analyzed to determine the deep or shallow source of the radon emanation in the study area. These results revealed that the ratio radon/thoron enhanced during this period which indicates the deeper source contribution is prominent. Incidentally, all the local earthquakes occurred with a focal depth of 18-25km at the lower crust in this region. We observed the rise in the concentrations of radon and the ratio radon/thoron at Badargadh station before the occurrence of the local earthquakes on 29th March 2011 (M 3.7) and 17th May 2011 (M 4.2). We clearly observed the radon level crossing the mean + 2*sigma level before the occurrence of these events. We conclude that these enhanced radon emissions are linked with alteration of the crustal stress/strain in this region as this observing station is near the epicenters of the earthquakes. We did not observe considerable variations in radon at the Desalpar station which is far from the earthquake location.

Monitoring of soil radon by SSNTD in Eastern India in search of possible earthquake precursor

The present paper deals with monitoring soil radon-222 concentration at two different locations, designated Site A and Site B, 200 m apart at Jadavpur University campus, Kolkata, India, with a view to find possible precursors for the earthquakes that occurred within a few hundred kilometers from the monitoring site. The solid state nuclear track detector CR-39 has been used for detection of radon gas coming out from soil. Radon-222 time series at both locations during the period August 2012–December 2013 have been analysed. Distinct anomalies in the soil radon time series have been observed for seven earthquakes of magnitude greater than 4.0 M that occurred during this time. Of these, radon anomalies for two earthquakes have been observed at both locations A and B. Absence of anomalies for some other earthquakes has been discussed, and the observations have been compared with some earthquake precursor models.

Indoor radon regulation using tabulated values of temporal radon variation

Mass measurements of indoor radon concentrations have been conducted for about 30 years. In most of the countries, a national reference/action/limit level is adopted, limiting the annual average indoor radon (AAIR) concentration. However, until now, there is no single and generally accepted international protocol for determining the AAIR with a known confidence interval, based on measurements of different durations. Obviously, as the duration of measurements increases, the uncertainty of the AAIR estimation decreases. The lack of the information about the confidence interval of the determined AAIR level does not allow correct comparison with the radon reference level. This greatly complicates development of an effective indoor radon measurement protocol and strategy.The paper proposes a general principle of indoor radon regulation, based on the simple criteria widely used in metrology, and introduces a new parameter – coefficient of temporal radon variation KV(t) that depends on the measurement duration and determines the uncertainty of the AAIR. An algorithm for determining KV(t) based on the results of annual continuous radon monitoring in experimental rooms is proposed. Included are indoor radon activity concentrations and equilibrium equivalent concentration (EEC) of radon progeny. The monitoring was conducted in 10 selected experimental rooms located in 7 buildings, mainly in the Moscow region (Russia), from 2006 to 2013. The experimental and tabulated values of KV(t) and also the values of the coefficient of temporal EEC variation depending on the mode and duration of the measurements were obtained. The recommendations to improve the efficiency and reliability of indoor radon regulation are given. The importance of taking into account the geological factors is discussed. The representativity of the results of the study is estimated and the approach for their verification is proposed.

Test mode of operation network of monitoring subsoil radon in the south of Sakhalin

Radon monitoring in the literature is recognized as a promising method for the prediction of earthquakes. In the last decade, the promise of the radon method for predicting subduction earthquakes has been convincingly demonstrated on Kamchatka. The results obtained on the Kamchatka, give reason to hope for the detection of predictive anomalies in the radon field and for weaker, but not less dangerous, small-focus earthquakes on the Sakhalin Island. The southern part of Sakhalin Island is a region of high seismic hazard. On Sakhalin Island, in a test mode, a network of three radon monitoring stations in the subsoil air is launched using the forced convection method to search for earthquake precursors. Based on the literature data, it is assumed that the effectiveness of radon monitoring near the focal zone of small-focus earthquakes on Sakhalin Island will be significantly higher compared to the conditions of the subduction zone in Kamchatka. Data from the network of radon monitoring stations can be used as an additional parameter to substantiate the conclusions on possible scenarios for the evolution of the seismic process in the south of Sakhalin.

Мониторинг радона и физико-химических характеристик подземных вод Южного Прибайкалья

Мониторинг радона и физико-химических характеристик подземных вод Южного Прибайкалья

RADON MAPPING IN CROATIA AND ITS RELATION TO GEOLOGY

Radon is known as the main contributor to the natural background radiation exposure and mapping of different radon phenomenon presents an important task in both scientific and regulatory context. Considering the aspect of radon effects on health, identification of areas with elevated radon levels is a crucial step in radon monitoring and prevention of adverse effects on the populations and the environment. Different needs regarding the monitoring of the environmental radioactivity levels in Europe led to the initiatives such as the development of the European Atlas of Natural Radiation (EANR). To present different methods of radon mapping, European Indoor Radon Map and European Geogenic Radon Map projects are described briefly. The aim of this paper is to present the mapping of different aspects of radon (indoor and geogenic) and its importance in data visualization and information dissemination. The practical experiences worldwide provide context for future activities of radon mapping in Croatia. Existing Croatian initiatives in the field of radon risk research are mostly related to the investigations of indoor radon concentrations and identification of radon prone areas through one national study and several focused studies. Comparison of indoor radon levels in Croatia and several geological parameters identified new areas appropriate for future research that could lead towards a geogenic map of radon potential in Croatia. Keywords: radon mapping, geology, Croatia, GIS, natural radioactivity.

Assessment of annual effective dose due to outdoor radon activity in the environment of Bengaluru

Soil is the major source of radon to enter the living environment. In the present study, an effort was made to see the contribution of radon activity to the dose received by the public of the study region. The radon activity in soil gas and radon exhalation rate from the surface soil were measured in the Bangalore University campus using a continuous radon monitoring device called RAD7. The value obtained in the present investigation is ranged from 1690 ± 362 to 7390 ± 324 Bq/m3, with the geometric mean (GM) of 4120 ± 307 Bq/m3, and 13.97 ± 7.55–24.82 ± 8.38 mBq/m2/s, with the GM of 18.13 ± 6.52 mBq/m2/s, respectively. The radon exhalation rate was also calculated using the values obtained from the radon activity in soil gas and is compared with the measured value. The annual effective dose (AED) was estimated from the measured radon concentration near to the soil surface and is found to be ranged from 0.02 to 0.07 mSv/y, with the GM of 0.04 mSv/y. The AED due to inhalation is well within the global average as reported in the UNSCEAR 2000, which indicates that there is no threat to the human due to the outdoor radon concentration in the study area.

Radon Levels in a Hospital in Niterói Municipality-RJ, Brazil

Uranium and radium are present in soil, rocks, water and building materials, therefore the presence of 222Rn in the air is natural, and its concentration is determined mainly by physical factors such as soil cover, altitude, porosity and soil particle size, and meteorological conditions. In rooms with poor ventilation,222Rn can accumulate to high concentrations, which increases the risk of developing lung cancer due to continuous exposure to this gas. In this work,222Rn was monitored, with the aid of a real-time radon monitor, RAD7, in offices and rooms at Hospital Universitario Antonio Pedro in order to evaluate the levels of 222Rn to which people are exposed. In general, the values measured in this work are similar to values observed in other studies around the world. The obtained 222Rn level of 40 Bq m-3 is close to the world average of 37 Bq m-3 defined by the United States Environmental Protection Agency (US EPA).

Concentration of Radon Released from Marine Sediment Around Hajjam Island, Southern Iraq, North West Arabian gulf, using CR-39 detector

Hajjam Island lies in the lower reaches of Khor Al-Zubair southern of Iraq, it is the unity island in the Iraqi marine water. 15 sediment samples were collected from sites around the island and transferred to the lab in Marine Science Centre for radiological investigation. Two methods were adopted, Active and Passive, for determination of Radon in which an environmental radon monitoring system comprising a radon-cup, an etching system, and a track counting system, was constructed. The radon cup is a cylindrical chamber with a radius of 3.5 cm and a height of 15 cm in combination with a CR-39 detector. The effected radium concentrations from sediment samples were found to range from 0.0013 to 0.0049 with an average value of 0.0028 Bq/Kg. Concentrations of radon measured by passive method were 132±34 to 414±108 with average value 287±45 Bq/m 3 and by active method were 401±26 to 145±9 with average value 263±20 Bq/m 3 . The area and mass exhalation rates were found to be 0.1 to 0.31 with average value of 0.220 Bq/m 2 /h and 0.002 to 0.006 with average value 0.004 Bq/kg/h respectively. The values are found to be safe for sediment use.

Integrated radon monitoring in Tatun Volcanic Areas of Northern Taiwan

Integrated radon monitoring in Tatun Volcanic Areas of Northern Taiwan

Characterising fifteen years of continuous atmospheric radon activity observations at Cape Point (South Africa)

This paper describes and discusses fifteen years (1999–2013) of continuous hourly atmospheric radon (222Rn) monitoring at the coastal low-altitude Southern Hemisphere Cape Point Station in South Africa. A strong seasonal cycle is evident in the observed radon concentrations, with maxima during the winter months, when air masses arriving at the Cape Point station from over the African continental surface are more frequently observed, and minima during the summer months, when an oceanic fetch is predominant. An atmospheric mean radon activity concentration of 676 ± 2 mBq/m3 is found over the 15-year record, having a strongly skewed distribution that exhibits a large number of events falling into a compact range of low values (corresponding to oceanic air masses), and a smaller number of events with high radon values spread over a wide range (corresponding to continental air masses). The mean radon concentration from continental air masses (1 004 ± 6 mBq/m3) is about two times higher compared to oceanic air masses (479 ± 3 mBq/m3). The number of atmospheric radon events observed is strongly dependent on the wind direction. A power spectral Fast Fourier Transform analysis of the 15-year radon time series reveals prominent peaks at semi-diurnal, diurnal and annual timescales. Two inter-annual radon periodicities have been established, the diurnal 0.98 ± 0.04 day−1 and half-diurnal 2.07 ± 0.15 day−1. The annual peak reflects major seasonal changes in the patterns of offshore versus onshore flow associated with regional/hemispheric circulation patterns, whereas the diurnal and semi-diurnal peaks together reflect the influence of local nocturnal radon build-up over land, and the interplay between mesoscale sea/land breezes. The winter-time diurnal radon concentration had a significant decrease of about 200 mBq/m3 (17%) while the summer-time diurnal radon concentration revealed nearly no changes. A slow decline in the higher radon percentiles (75th and 95th) for the winter and spring seasons is found over the 15-year data set, with most of the change occurring in the first 9 years (1999–2007). This observed inter-annual decline appears to be associated with changes in the frequency of air masses having originated from over the African continental surfaces, and no significant trend is found in the lower radon percentiles associated with oceanic air masses. The general decrease of atmospheric radon-associated with continental air-masses at Cape Point could be attributed to changing meteorological conditions, possibly driven by climate change.

МОНИТОРИНГ РАДОНА КАК ИНДИКАТОРА СЕЙСМОТЕКТОНИЧЕСКИХ СОБЫТИЙ НА ПЛОЩАДКЕ АЭС «БУШЕР-1» И ПРИЛЕГАЮЩЕЙ ТЕРРИТОРИИ ПРОВИНЦИИ БУШЕР ИСЛАМСКОЙ РЕСПУБЛИКИ ИРАН

МОНИТОРИНГ РАДОНА КАК ИНДИКАТОРА СЕЙСМОТЕКТОНИЧЕСКИХ СОБЫТИЙ НА ПЛОЩАДКЕ АЭС «БУШЕР-1» И ПРИЛЕГАЮЩЕЙ ТЕРРИТОРИИ ПРОВИНЦИИ БУШЕР ИСЛАМСКОЙ РЕСПУБЛИКИ ИРАН

Radiological survey of the covered and uncovered drilling mud depository

In petroleum engineering, the produced drilling mud sometimes contains elevated amounts of natural radioactivity. In this study, a remediated Hungarian drilling mud depository was investigated from a radiological perspective. The depository was monitored before and after a clay layer was applied as covering.In this study, the ambient dose equivalent rate H*(10) of the depository has been measured by a Scintillator Probe (6150AD-b Dose Rate Meter). Outdoor radon concentration, radon concentration in soil gas, and in situ field radon exhalation measurements were carried out using a pulse-type ionization chamber (AlphaGUARD radon monitor). Soil gas permeability (k) measurements were carried out using the permeameter (RADON-JOK) in situ device. Geogenic radon potentials were calculated. The radionuclide content of the drilling mud and cover layer sample has been determined with an HPGe gamma-spectrometer. The gamma dose rate was estimated from the measured radionuclide concentrations and the results were compared with the measured ambient dose equivalent rate.Based on the measured results before and after covering, the ambient dose equivalent rates were 76 (67–85) nSv/h before and 86 (83–89) nSv/h after covering, radon exhalation was 9 (6–12) mBq/m2s before and 14 (5–28) mBq/m2s after covering, the outdoor radon concentrations were 11 (9–16) before and 13 (10–22) Bq/m3after covering and the soil gas radon concentrations were 6 (3–8) before and 24 (14–40) kBq/m3 after covering. Soil gas permeability measurements were 1E-11 (7E-12-1E-11) and 1E-12 (5E-13-1E-12) m2 and the calculated geogenic radon potential values were 6 (3–8) and 12 (6–21) before and after the covering. The main radionuclide concentrations of the drilling mud were CU-238 12 (10–15) Bq/kg, CRa-226 31 (18–40) Bq/kg, CTh-232 35 (33–39) Bq/kg and CK-40 502 (356–673) Bq/kg. The same radionuclide concentrations in the clay were CU-238 31 (29–34) Bq/kg, CRa-226 45 (40–51) Bq/kg, CTh-232 58 (55–60) Bq/kg and CK-40 651 (620–671) Bq/kg.According to our results, the drilling mud depository exhibits no radiological risk from any radiological aspects (radon, radon exhalation, gamma dose, etc.); therefore, long term monitoring activity is not necessary from the radiological point of view.

Distribution of 222Rn in groundwater and estimation of resulting radiation dose to different age groups: A case study from Bangalore City

ABSTRACTIngesting waters holding high levels of natural occurring radioactive element like Radon would contribute to increase in the effective dose received by people followed by an increased prevalence of cancer. The current study is an attempt to describe the extent of contribution of 222Rn to natural background radiation and the resultant effective dose to public of different age groups. In order to do so, 65 groundwater samples from selected parts of Bangalore city were collected and analyzed for radon activity using RAD7 radon monitor coupled with RAD H2O accessories. The radon activity was in the range of 3.05–696 Bq/L (mean: 91.39 Bq/L) and 92.31% of the groundwater samples recorded elevated radon concentration above the United States environmental protection agency (USEPA's) Maximum Contaminant Level (MCL) value of 300 pCi/L, corresponding to 11.1 Bq/L. The mean annual effective dose contribution of people falling under different age groups (viz., infants, children, teens: males and females, adults: males and females, pregnant and lactating women) due to ingestion of water-borne 222Rn ranged from 0.082 to 0.444 mSv/y and was found to be higher in all the age groups of males compared to respective female age groups, but well within the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and World Health Organization (WHO) proposed limit of 1 mSv/y.

SIGNAL DECOMPOSITION AND ANALYSIS FOR THE IDENTIFICATION OF PERIODIC AND ANOMALOUS PHENOMENA IN RADON TIME-SERIES.

This work concerns continuous monitoring of radon and thoron specific activity in soil gas within the framework of identifying possible anomalies. It is based on the analysis of a medium-term data record obtained from soil gas in an area of geophysical interest. The RaMonA spectrometric system is also used to measure the climatic parameters and a specific analysis of the alpha spectra is performed to better determine the alpha lines intensity. Since radon emission is also influenced by meteorological parameters, it is mandatory to differentiate the changes due to the deep phenomena. Different procedures are utilized to reach the above objective: statistical analysis using the Empirical Mode Decomposition technique, the Multiple Linear Regression method and the Remote Radon Estimation by using of the thoron trend to eliminate the locally produced radon fraction. The results of such methods are compared to recognize and to highlight radon anomalies.

MULTI-YEAR MONITORING OF RADON IN BOREHOLES AT THE MODRA GEOPHYSICAL OBSERVATORY, SLOVAKIA.

Long-term radon monitoring was performed in two boreholes, at a depth of 13 m in the 40 m deep V-2 borehole (August 2003-September 2005), and at 3 m depth in the 10 m deep V-3 borehole (August 2003-April 2008). Diurnal, multi-day and annual variations in radon time-series were observed. Daily average of radon activity in V-2 borehole was significantly higher and ranged from 6.5 to 383.7 kBq/m3, while in V-3 borehole only between 1.2 and 139.4 kBq/m3. The seasonal pattern was more pronounced in V-3 time series, with the maximum occurring from October to March. Multi-day variations (2-10 days) were registered in V-2 and V-3 mostly simultaneously, with higher discrepancy in spring and summer periods, when radon activity in V-3 borehole was low. Diurnal radon variations with two maxima and two minima per day were registered in both boreholes. The influence of meteorological parameters on radon concentrations was investigated. The overall impression is that seasonal variation in radon in V-3 borehole seems to be connected with the temperature variation. Multi-day variations of radon in both boreholes coincided with the atmospheric pressure changes. An increase in radon activity was observed in V-3 borehole after the rainfall in spring and summer seasons.

ASSESSMENT OF RADIUM ACTIVITY CONCENTRATION AND RADON EXHALATION RATES IN IBERIAN PENINSULA BUILDING MATERIALS.

Radium (226Ra) is a natural radioactive element of the uranium decay series, which could also be present in building materials. Radon (222Rn) is continuously produced by the decay of 226Ra and its presence inside buildings can contribute to the increase of the population exposure to ionizing radiation. In this work, the amount of radium activity concentration and radon exhalation rates in several types of building materials that are commonly used in the Iberian Peninsula have been tested. The radium activity concentration was measured by gamma-ray spectrometry, whereas the radon exhalation rates were carried out using a continuous radon monitor (active measuring technique) and a solid state nuclear track detectors (passive measuring technique). The 226Ra mean values range from 5.0 to 123.4 Bq kg-1. As expected, the results show that the radon exhalation rate is higher in granites samples relatively to others building materials analysed. A positive correlation was found between radium activity concentration and radon exhalation rates in both techniques. The emanation fraction and alpha index were also calculated.