Radon Profiles Research Articles

A sensitive system based on radon amplification at soil-air interface: Aiming to advance earthquake precursor research

Radon, a natural radioactive gas, serves as a valuable tracer in geophysical research and atmospheric science such as detecting stress induced signal in bedrock. However, the conventional radon monitoring methods often lack the sensitivity required to accurately capture such signals. This limitation, coupled with interference from meteorological effects, poses challenges in distinguishing genuine stress-induced signals. In this study, we propose a novel approach utilizing radon concentration gradients at the soil-air interface to enhance sensitivity and detect stress induced radon signals more effectively. Drawing from pressure diffusion models, we demonstrate how seismic stress accumulation in bedrock alters radon profiles in the sub-soil, providing insights into the mechanisms underlying stress-induced radon variations. Building upon this theoretical framework, we introduce the “Bhabha Radon Observatory for Seismic Application (BhaROSA)," a remote sensing, solar-powered radon observatory designed for widespread deployment and continuous unattended monitoring for big database generation. Field experiments comparing BhaROSA's performance to conventional soil probe techniques validate and confirm the superior sensitivity in line with theoretical predictions. This innovative approach holds promise for improving our understanding of stress dynamics in bedrock and has potential applications in various geophysical and atmospheric science such as earthquake precursory research, geo-genic radon potential and risk assessment. To progress, we propose international alliance and application of deep learning to a big database of precursor signals, which may lead to more informed conclusions on earthquake predictability-an enduring and unsolved challenge for humanity.

Comparison of the Radon (222Rn) Profile at Two Stationary Locations of Uranium Mineralized Area of Jaduguda, India

Comparison of the Radon (222Rn) Profile at Two Stationary Locations of Uranium Mineralized Area of Jaduguda, India

Elevated radon level in drinking water of Ajodhya Hill Area of West Bengal, India: probable health impact on lung and stomach.

A screening survey has been carried out to measure the radon concentration in drinking water at various locations of Ajodhya hill and surrounding areas in Purulia district of West Bengal, India, using AlphaGUARD radon monitor. The obtained 222Rn concentration in ground water varies from 5.71 ± 0.29 to 579.47 ± 23.18Bq/l with an average of 110.00 ± 6.61Bq/l. Comparison between our results with the internationally recommended reference levels reveals that drinking of water from the majority of these tube-wells can pose significant health risks to the local people. Correlation study indicates that tube-well depth has significant influence on the radon level in water samples. Using 60l/yr and 1642.50l/yr water consumption estimated annual effective radon doses for most of the samples (almost 70% and 96%, respectively) are high compared to the World Health Organization (WHO) and the European Union (EU) Commission prescribed reference dose limit of 100 μSv/yr. Also, the evaluated Excess Lifetime Cancer Risk (ELCR) values associated with the tube-wells are showing serious threat to the health of the locals.The primary goal of this work is to develop a radon profile map of this area and to find out the possible reasons behind the elevated radon level in ground water. This type of work may play a very crucial role to aware the locals in perspective of human exposure to radon. The local health officials and the water quality regulators of India are requested to take necessary steps for protecting the local people from water radon hazard.

Exchange across the sediment-water interface quantified from porewater radon profiles

Water recirculation through permeable sediments induced by wave action, tidal pumping and currents enhances the exchange of solutes and fine particles between sediments and overlying waters, and can be an important hydro-biogeochemical process. In shallow water, most of the recirculation is likely to be driven by the interaction of wave-driven oscillatory flows with bottom topography which can induce pressure fluctuations at the sediment-water interface on very short timescales. Tracer-based methods provide the most reliable means for characterizing this short-timescale exchange. However, the commonly applied approaches only provide a direct measure of the tracer flux. Estimating water fluxes requires characterizing the tracer concentration in discharging porewater; this implies collecting porewater samples at shallow depths (usually a few mm, depending on the hydrodynamic dispersivity), which is very difficult with commonly used techniques. In this study, we simulate observed vertical profiles of radon concentration beneath shallow coastal lagoons using a simple water recirculation model that allows us to estimate water exchange fluxes as a function of depth below the sediment-water interface. Estimated water fluxes at the sediment water interface at our site were 0.18–0.25 m/day, with fluxes decreasing exponentially with depth. Uncertainty in dispersivity is the greatest source of error in exchange flux, and results in an uncertainty of approximately a factor-of-five.

Finite element modeling of radon distribution in natural soils of different geophysical regions

Radon migration from deep soil to the earth’s surface is investigated numerically using a developed Finite Element numerical model. The objectives of this study are: to predict the radon profile va...

RADON MIGRATION IN SOIL AND ITS RELATION TO TERRESTRIAL GAMMA RADIATION IN DIFFERENT LOCATIONS OF THE GREEK EARLY WARNING SYSTEM NETWORK

Radon concentration as function of the soil depth was measured during the years (2011-2015), in a location of the Aristotle University campus. Radium distribution in soil was found constant. On the contrary, as expected, radon concentration increases with soil depth. The experimental distribution was reproduced by solving the general transport equation (diffusion and advection). From the general radon migration (diffusion and advection) equation it was indirectly deduced, from the measured radon profile in the soil, the radon exhalation rate from the soil (26.7±4.5 Bq m-2 h-1). In the same location, during 2010-2015, 113 direct radon exhalation measurements were performed and give an average value for the 6 years of 21.1±3 Bq m-2 h-1. The comparison between the radon exhalation rates deduced by the indirect and direct method indicates the validity of the diffusion advection model predictions concerning the radon exhalation rate from soil. The relation between radon migration in soil and terrestrial gamma radiation was studied. In particular, in the present study was investigated the correlation between gamma radiation 1 m above soil and radon exhalation in six locations of the Greek early warning system network. A positive correlation between gamma dose rate in air and radon exhalation rate from soil was found.

Radon transport: laboratory and model study.

In order to exploit radon profiles for geophysical purposes and also to estimate its entry indoors, it is necessary to study its transport through porous soils. The great number of involved parameters and processes affecting the emanation of radon from the soil grains and its transport in the source medium has led to many theoretical and/or laboratory studies. The authors report the first results of a laboratory study carried out at the Radioactivity Laboratory of the Department of Physics and Astronomy (University of Catania) by means of a facility for measuring radon concentrations in the sample pores at various depths under well-defined and controlled conditions of physical parameters. In particular, radon concentration vertical profiles extracted in low-moisture samples for different advective fluxes and temperatures were compared with expected concentrations, according to a three-phase transport model developed by Andersen (Risø National Laboratory, Denmark), showing, in general, a good agreement between measurements and model calculations.

Upper-ocean gas dynamics from radon profiles in the Eastern Tropical South Pacific

Uncertainties in the dynamics of dissolved gases limit the accuracy of geochemical primary-productivity estimates. Mixed-layer ventilation, entrainment, and upwelling all affect the interpretation of geochemical data, yet they are rarely measured together. We report upper-ocean dissolved-gas dynamics in the Eastern Tropical South Pacific (10–20°S, 80–100°W) obtained from 222Rn distributions from a research cruise in February 2010. Radon-222-based surface ventilation measurements at seven stations were compared with gas transfer velocities calculated using empirical wind-speed parameterizations. Good agreement between the two methods was observed across different wind data products (ASCAT scatterometer and NCEP/NCAR meterological reanalysis) and grid scales (0.5°×0.5°, 1°×1°, and 2°×2°). Average wind speeds in the region were 5–8ms−1, corresponding to in situ gas transfer velocities of 1–3md−1. Averaged over the region, most recent gas exchange parameterizations performed similarly, and the results are robust with respect to both wind data products and grid scales. Non-steady-state conditions were observed at one station, possibly caused by a recent internal wave. These results suggest that 222Rn could be used to support measurements of biogeochemical O2 and CO2 fluxes in the upper ocean.

Hurst Exponent Analysis of Indoor Radon Profiles of Greek Apartment Dwellings

Radon and progeny (218Po, 214Pb, 214Bi and 214Po) are important indoor radioactive air pollutants with impact to humans. Radon is an inert gas that enters buildings from outdoor air, water and soil, especially via gaps around pipes and cables and through cracks in floors. Indoors, radon progeny remain free, or attach to indoor aerosols dust and water droplets. Hence, inhalable indoor radioactive mixtures are created which enter human lungs and irradiate tissues. The radiation exposure depends on several parameters some of which are the building characteristics, local geology, breathing rate and others. This work aimed to estimate Hurst exponents (H) of time-evolving radon signals of Greek apartment dwellings. The signals were collected with Alpha Guard Pro and include at least 24 hours of measurements in each dwelling. Hurst exponents were calculated by the R/S method through sliding on overlapping windows and lumping on nonoverlapping sequential windows. The scope was to identify whether radon dynamics are governed by persistent, antipersistent behavior or if these are uncorrelated. Most signals presented significant long-memory segments with important persistent sub- segments.

The Vertical Distribution of Radon in Clear and Cloudy Daytime Terrestrial Boundary Layers

Abstract Radon (222Rn) is a powerful natural tracer of mixing and exchange processes in the atmospheric boundary layer. The authors present and discuss the main features of a unique dataset of 50 high-resolution vertical radon profiles up to 3500 m above ground level, obtained in clear and cloudy daytime terrestrial boundary layers over an inland rural site in Australia using an instrumented motorized research glider. It is demonstrated that boundary layer radon profiles frequently exhibit a complex layered structure as a result of mixing and exchange processes of varying strengths and extents working in clear and cloudy conditions within the context of the diurnal cycle and the synoptic meteorology. Normalized aircraft radon measurements are presented, revealing the characteristic structure and variability of three major classes of daytime boundary layer: 1) dry convective boundary layers, 2) mixed layers topped with residual layers, and 3) convective boundary layers topped with coupled nonprecipitating clouds. Robust and unambiguous signatures of important atmospheric processes in the boundary layer are identifiable in the radon profiles, including “top-down” mixing associated with entrainment in clear-sky cases and strongly enhanced venting and subcloud-layer mixing when substantial active cumulus are present. In poorly mixed conditions, radon gradients in the daytime atmospheric surface layer significantly exceed those predicted by Monin–Obukhov similarity theory. In two case studies, it is demonstrated for the first time that a sequence of vertical radon profiles measured over the course of a single day can consistently reproduce major structural features of the evolving boundary layer.

Measurement of Radon Exhalation Rate from Building Materials used in the southwest coastal region of India

This paper presents the results of a sample survey carried out to study the radon profile and radon exhalation rate in commonly used building materials used for construction of dwellings around high background areas of south India. Simultaneously, radon concentrations were also measured using passive detector techniques. Experimental procedure used for the measurement was the track etch technique. Radon emanation rates from the building materials studied varied from 17.7—308 mBq · m-3 · h-1. Estimated exhalation rates have been compared with others found in the literature.

Using the Real-time Radon-222 Profile to Quantify the Specific Radon Production Rate in an Air-conditioned Building

The real-time indoor and outdoor radon-222 profiles on the fourth floor of a university library were measured through five consecutive days, with the Heating, Ventilating and Air Conditioning (HVAC) system operating on part load. The premises were served by a main air-handling unit (AHU-1) and a subordinate unit (AHU-2) of the HVAC system, but AHU-2 was shut down for maintenance. It required full operation of AHU-1 for 1.7h to reduce the radon concentration from the overnight peak down to the recommended action level (200Bq·m-3). Clear characteristics of indoor radon profiles were observed, with the diurnal variations of indoor radon concentrations strongly coupled to the operation schedule of AHU-1. The specific radon production (value-Φ) of the site could be quantified from the characteristic profiles. This can be used to investigate the radon emission rate of a site, as well as to simulate the indoor radon concentrations at different ventilation rates. The value-Φ was 21.0Bqh-1·m-3, with a standard deviation of 0.6Bqh-1·m-3. Furthermore, it was found that a morning purge, by the fresh air intake fan operating for 2h before library opening hours, could not effectively remove the overnight accumulation of the pollutant.

Unusual features of the distribution of Radon-222 in the bottom waters of the continental slope of the Mid-Atlantic Bight: Hydrodynamic implications

222Rn was measured in the near-bottom waters of the continental slope of the Mid-Atlantic Bight. Separate measurements of the 222Rn supported by dissolved 226Ra allowed the excess 222Rn that is derived from the underlying sediments to be distinguished. Measurements of production of 222Rn by the sediments were used to calculate fluxes of 222Rn from sediments that would be expected as a result of molecular diffusion. On the upper slope and on the lower slope excess 222Rn standing crops were, respectively, greater than and consistent with fluxes of radon from sediments by molecular diffusion as are typical of most ocean environments. On the middle slope, however, observed excess 222Rn concentrations and standing crops were significantly lower than what would be expected from the calculated fluxes from the underlying sediments. This unusual feature of low radon concentrations on the middle slope is referred to as the low-radon zone (LRZ). This LRZ was always present over several years and seasons, but was variable in intensity (excess-radon concentration and standing crop) and in location on the slope. Low concentrations of suspended particulate matter and low current velocities observed by others in the same region are consistent with low mixing as a possible cause of the LRZ. Radon profile shapes and recent work by others on near bottom mixing due to interactions between topography and internal waves, however, suggest that high mixing due to internal waves is a more likely cause of the LRZ.

Radon Measurement Protocol for Residences with Different Ventilation Rates

A radon measurement protocol is proposed for residential premises in which the radon production rate of a room is quantified as the product of the emanation rate from materials and their exposed area. The protocol is based on short-term continuous monitoring in which the sampled room is maintained in a well-sealed state for at least three days. To examine the practicality and accuracy of the protocol, a living room in a high-rise residential apartment was selected. No mechanical ventilation was used in the measurements from which a real-time indoor radon growth curve was obtained. The radon production rate of the sampled room was found to be 414.6 Bq h-1. A tracer gas test, to measure the leakage rate of the room, was conducted simultaneously at the startup of the measurement to check the accuracy of the protocol. The air exchange rate due to infiltration (leakage) obtained from the radon profile and tracer gas test were 0.041 and 0.046 h-1, respectively, a deviation of 12.2% from the result of tracer gas test. The test showed that the protocol could be accepted to quantify the radon production rate of a room. The relationships between the radon production rate, indoor radon level and ventilation rate of a room are also discussed in this paper.

Radon-222 signatures of natural ventilation regimes in an underground quarry

Radon-222 activity concentration has been monitored since 1999 in an underground limestone quarry located in Vincennes, near Paris, France. It is homogeneous in summer, with an average value of 1700 Bq m −3, and varies from 730 to 1450 Bq m −3 in winter, indicating natural ventilation with a rate ranging from 0.5 to 2.4×10 −6 s −1 (0.04–0.22 day −1). This hypothesis is supported by measurements in the vertical access pit where, in winter, a turbulent air current produces a stable radon profile, smoothly decreasing from 700 Bq m −3 at 20 m depth to 300 Bq m −3 at surface. In summer, a thermal stratification is maintained in the pit, but the radon-222 concentration jumps repeatedly between 100 and 2000 Bq m −3. These jumps are due to atmospheric pressure pumping, which induces ventilation in the quarry at a rate of about 0.1×10 −6 s −1 (0.009 day −1). Radon-222 monitoring thus provides a dynamical characterisation of ventilation regimes, which is important for the assessment of the long-term evolution of underground systems.

A tropospheric chemical‐transport model: Development and validation of the model transport schemes

AbstractWe describe a 3D off‐line chemical‐transport model (CTM) for studies of tropospheric chemistry. the tropospheric CTM is a development of the existing TOMCAT stratospheric CTM to which we have added a parametrized convection scheme and treatment of vertical diffusion. the CTM diagnoses the occurrence of convection during the model simulations from the forcing analysis fields of winds, temperature and humidity.The spatial distributions of the vertical mass fluxes calculated by these schemes appear realistic. the convective mass fluxes agree well with values derived from global analyses, having maximum values at low latitudes and at the intertropical convergence zone, although the TOMCAT cloud‐top height may be too low.We have used the model's convection scheme to diagnose the convective precipitation when forced by European Centre for Medium‐Range Weather Forecasts (ECMWF) initialized analyses. Despite the off‐line approach, the CTM‐diagnosed convective precipitation is in very good spatial agreement with global observations and output from a general‐circulation model (GCM), showing that not only does convective venting of tracers occur in the correct locations, but also that the convection scheme can be coupled to wet‐deposition schemes in full chemistry simulations. TOMCAT exhibits a low‐latitude bias in cloud amount, due to the model's neglect of mid‐level convection, and underestimates convective precipitation and cloud amount, the latter by at least 20% compared with GCM results. This underestimate may be due to excessive stability of the ECMWF analyses used in the off‐line model or to differences in the formulation of convection in the ECMWF forecast model and in TOMCAT.We have evaluated the CTM's transport processes by performing a range of simulations with a surface‐emitted radon (Rn) tracer. the agreement with radon observations improves with an increase in horizontal resolution from 7.5° × 7.5° to 2.8° × 2.8° and with the inclusion of vertical diffusion and convection in the model formulation. When run at a horizontal resolution of 2.8° × 2.8° TOMCAT captures the tracer transport and seasonal evolution in tracer transport associated with major meteorological features and with convective processes. TOMCAT reproduces the observed seasonality in radon at surface sites, but overestimates the surface radon concentration, partly due to insufficient vertical diffusion in the model. However, transient systems and their tracer transport within the boundary layer are simulated realistically. Compared with observations, the modelled radon profiles are too ‘C‐shaped’ (the modelled profile has a mid‐tropospheric minimum which is not present in the observations) which may be caused by the model's neglect of convective downdraughts and/or entrainment and detrainment rates that are too low in the cloud column, resulting in insufficient mixing within the cloud column. the radon concentration in the upper troposphere is underestimated by TOMCAT; this may be due to a number of factors: the underestimate in convective‐cloud amount, the way in which the base mass flux is calculated, the limitation of organized entrainment to subcloud levels, and a possible static stability of the analyses.

Validation of an off‐line three‐dimensional chemical transport model using observed radon profiles: 2. Model results

We parameterize radon emissions in the TOMCAT global off‐line three‐dimensional chemical transport model (CTM) and compare modeled radon profiles with spatially and temporally matched observations obtained near Moffett Field, California, in June 1994. The CTM was forced using European Centre for Medium‐Range Weather Forecasts analyses for April‐August 1994. To identify the origin of modeled radon, we divided the radon sources into three regions. We performed CTM sensitivity experiments at horizontal resolutions of 2.8° × 2.8° (latitude × longitude) and 7.5° × 7.5°, and with and without moist convection and/or vertical diffusion. At the higher resolution the full CTM (i.e., including convection and vertical diffusion) generally agrees well with the observations in the free troposphere. The observations exhibit free‐tropospheric radon peaks at altitudes where zonal wind speeds in the Pacific jet stream are greatest (generally at ≥7 km). In this region the modeled radon originates from Asia, and the observed variability in the radon concentration is reproduced. Thus, the model reproduces the position and strength of the jet. We identify observed radon peaks that may originate from convective lifting, as they do in the model results. If these observed peaks do originate from convection, then the full CTM captures the correct temporal variability in convection over Asia and the Pacific for the observation period. Quantitative comparison shows that the model‐data agreement is degraded if we decrease the model resolution to 7.5° × 7.5°, or remove the parameterizations of convection and/or vertical diffusion. This suggests a resolution of near 2.8° × 2.8° is needed in global models for realistic simulations of short‐lived species. We have identified certain shortcomings with TOMCAT: the model underestimates the amount of convective cloud, the convective cloud top height, and the amount of vertical diffusion. We identify improvements to ameliorate these problems.

Validation of an off‐line three‐dimensional chemical transport model using observed radon profiles: 1. Observations

We present in Table 1 of this paper a series of free tropospheric radon profiles, obtained in the summer of 1994 on flights originating from Moffett Field, California (37.4°N, 122.0°W). These data were collected with the intent of acquiring a high‐quality, statistically significant set of observations, in one season and at one location, suitable for use in the development and validation of three‐dimensional global circulation and chemical transport models, as demonstrated in the companion paper [Stockwell, et al., this issue]. The profiles, which extend from the surface to 11.5 kilometers, were obtained on 11 flights flown in the period June 3 to August 16. A series of high‐pressure whole‐air samples (typically 11 or 12 per profile) were collected as the plane ascended to altitude, and analyzed immediately after each flight in a ground‐based laboratory. A thorough discussion of sampling, analysis, calibration, and quality control procedures is provided.

Radon transport in a drilled well studied by etched track type radon monitors

We have measured the radon concentration profile along a 20 meter deep drilled well with etched track type radon monitors. The well has a diameter of 12 cm. It has water at 11.6 meter below the surface and exhales nearly 100% carbon dioxide of geological origin at rate of about 300 liters/hour. We made radon measurements both underwater and in the gaseous atmosphere. Radon transport models (such as microbubble, macrobubble, eddy diffusion, etc.) were tested to find the best fit to experimental radon profiles. The measuring site is at a geologically active area, and the effect of a small earthquake on the exhalation rate of CO 2 from the well was also observed.

Environmental tracer analysis of winter profile development in two basins of Shagawa Lake, Minnesota

Winter profile development was studied comparatively in two basins ( z max = 14 m) separated by a 6 m sill in Shagawa Lake, Minnesota. Based on physical arguments and profile measurements, heat and solutes released from shelf sediments in the western basin cause convective instability at 8–11 m. After a mid-winter interval of instability, radon profiles indicate very low rates of vertical mixing in the benthic boundary layers following their stabilization by ferrous iron. Because of hydrographic features, two types of plunging inflows sometimes enter the western basin in late winter; one anthropogenic inflow alters the lower profiles by adding sodium, radon, and oxygen; the second modifies the mid-depth region by adding ‘weathering tracers’ (especially calcium and silicon) derived from the Ely greenstone. The oxidation of Fe 2+ diffusing upward and laterally from the sediment-water interface is accompanied by near-complete coprecipitation of phosphorus. The oxidation of Fe 2+ has only a minor effect on silicic acid, probably because of unfavorably large Si:P and preferential association of Fe(III) with phosphorus. Despite low pH and temperature, detectable amounts of Mn 2+ oxidize and precipitate above iron in the water column. Solute profiles differentially register the complex effects of hydrodynamic vs. geochemical processes, and as a consequence, affect the estimation of solute budgets in ice-covered lakes.