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Radon in soil poses a significant health risk when it accumulates inside dwellings. The estimation of radon potential is a difficult task due to the complex dynamics of radon within soil and its relations with the weather. This research focuses on the variability of radon activity, driven by environmental changes, assessed in two loam soils (loamy sand–granite soil and silty clay loam-calcareous soil) with different radium contents. We conducted an experiment with teow soil columns in a semi-controlled outdoor laboratory, in a warm semi-arid climate. We also examined the consequences of abundant rainfall on radon activity through artificial soil water content (SWC) experiment conditions. Statistical analyses reveal that SWC is the most significant parameter influencing radon activity in these experiments. Radon is proportional to SWC and inversely proportional to temperature, evapotranspiration, and pressure in both soils, while wind is negatively related only in the loamy sand soil. Based on our findings, we modelled radon potential considering different soils and climatic contexts. SWC influences radon potential by changing radon emanation, activity, and permeability, depending on the local soil texture and radium concentration.

Radon is a radioactive gas and a leading cause of lung cancer among non-smokers. An indicator of the level of risk associated with radon inhalation is the Geogenic Radon Potential (GRP) - a function of the soil gas radon concentration and the soil air permeability. Data is scarce on the variation of soil gas radon and GRP across different geological formations in southwest Nigeria. This study was designed to measure and develop a generalized predictive model for soil gas radon concentration and hence GRP on different bedrocks in southwest Nigeria. Soil gas radon was measured with a RAD 7 radon detector in 150 sites randomly selected over 20 major bedrocks. Soil air permeability was derived from soil saturated hydraulic conductivity measured using a constant head permeameter on undisturbed soil samples from the same sites. The GRP was obtained using Neznal relation. A 2 × 8 x 1 Artificial Neural Network (ANN) configuration culminated in the generation of a tested and validated predictive model for soil gas radon in southwest Nigeria. For the 150 sites, the range of values for soil gas radon concentration was 0.28–47.59 kBqm−3 and a mean of 10.39 ± 12.59 kBqm−3; soils on granitic bedrocks had the highest mean soil gas radon concentration (16.89 kBqm−3) and highest mean GRP (13.71). Sediments had the highest mean soil air permeability of 39.84 × 10−12 m2. Using Neznal classification, 75.30% of the sites were of low radon hazard rating. The developed predictive ANN model had a Goodness-of-Prediction (G) of 73.53%, Average Validation Error (AVE) of 0.073, Mean Bias Error (MBE) of 0.42, and Root Mean Square Error (RMSE) of 4.62kBqm−3, respectively. The model, validated using standard procedure had G, MBE, AVE, and RMSE of 86.49%, 0.61, 0.17, and 1.65kBqm−3, respectively which is an indication of good model performance.

The geogenic radon potential is primarily controlled by the geological characteristics of the site, such as the rock type and structural elements, as well as the permeability of the soil. Depending on the scope of the survey, the geogenic radon potential can be mapped based on measurements conducted in the field at various resolutions. Detailed surveys are generally labour-intensive and time-consuming. Therefore, a balance should be reached between the desired level of precision and the required amount of effort, delivering the best results with the least number of resources. The international literature describes a variety of surveying techniques. This study was undertaken in a region of the central zone of the Poiana Rusca Mountains (Southern Carpathians, Romania) that contains several metamorphic, volcanic, and sedimentary rock types. The primary objective of the study is to compare alternative sampling point configurations, which vary in number and arrangement. The objective was to achieve the most accurate representation of the calculated geogenic radon potential while limiting the number of measurements and the time and effort associated with them. Radon activity concentration and soil permeability data were collected from 34 locations using seven alternative layouts of the sampling points. The proposed layouts were based on various configurations of fifteen, nine, five, and three sampling points. Locally, in some of the metamorphic units and in the regions containing sedimentary deposits with volcanic intercalations, the geogenic radon potential was found to be elevated. The results indicate that the three-measuring-point configuration is acceptable for general geogenic radon potential surveys. [ABSTRACT FROM AUTHOR]

The Santo Domingo Diocesan School (Orihuela, SE Spain) is a singular case study that relates air quality monitoring and stone conservation. The monument suffers severe damage due to salt crystallization by rising damp, which is related to the indoor environment dynamics, high groundwater salt content, and microstructure, the building's porous stone (biocalcarenite). Results revealed that 222Rn concentration in indoor air is low due to the building's high ventilation rate, despite the medium-low geogenic radon potential in the area. Wavelets analysis showed that ventilation is caused by outdoor and indoor temperature variations and directly affects the 222Rn and CO2 dynamics inside the church. CO2, as well as relative humidity (RH), presented periodicities with intermediate frequencies (5–8 days) related to visits. These RH and temperature (T) variations intensified the salt damage by increasing the frequency of dissolution-crystallization cycles. The mineralogical characterization and geochemical calculations concluded that chlorides (halite and sylvite), sulfates (thenardite, epsomite, hexahydrite and aphthitalite) and nitrates (niter) present from dissolution forms to whiskers and hopper-type morphologies. This indicates high saturation values and, therefore, higher crystallization pressure values within the porous media of the biocalcarenite. On the contrary, the near-equilibrium crystal shape and incongruent precipitation reaction for humberstonite suggest a lower alteration for this salt on the building stone. [ABSTRACT FROM AUTHOR]

This study was performed to investigate radon levels in dwellings in the mining area near the town of Kosovska Mitrovica. The Passive radon technique based on the charcoal canister test kit conducted in summer and autumn 2019 showed unexpected results. The reference level of 300 Bq/m3 for indoor radon concentration was exceeded in 15 of 26 dwellings. Preliminary measurements of gamma dose rate in some dwellings built from local stone showed values from 0.30 to 0.45 μSv/h, while 75% of measurements in dwellings with stone foundations had radon above the reference level. The highest radon concentration (22 500 ± 220 Bq/m3) was measured in the cellar of one family house. The RAD7 device (Durridge Company, Inc.) was used to measure radon concentrations in water and nearby soil of some dwellings. Indoor radon concentration fluctuated significantly over two days; over a one‐day time scale, radon varied from 2843 ± 217 Bq/m3 at midnight to 1449 ± 104 Bq/m3 in the morning at one site, and abruptly decreased from a maximum of 2146 ± 262 Bq/m3 in one day to a minimum of 21 Bq/m3 the next day at another site. The influence of geological substrate on radon exposure was discussed through the estimation of geogenic radon potential, which varies from low the high radon index despite to high permeability of soil. [ABSTRACT FROM AUTHOR]

The geogenic radon potential is primarily controlled by the geological characteristics of the site, such as the rock type and structural elements, as well as the permeability of the soil. Depending on the scope of the survey, the geogenic radon potential can be mapped based on measurements conducted in the field at various resolutions. Detailed surveys are generally labour-intensive and time-consuming. Therefore, a balance should be reached between the desired level of precision and the required amount of effort, delivering the best results with the least number of resources. The international literature describes a variety of surveying techniques. This study was undertaken in a region of the central zone of the Poiana Rusca Mountains (Southern Carpathians, Romania) that contains several metamorphic, volcanic, and sedimentary rock types. The primary objective of the study is to compare alternative sampling point configurations, which vary in number and arrangement. The objective was to achieve the most accurate representation of the calculated geogenic radon potential while limiting the number of measurements and the time and effort associated with them. Radon activity concentration and soil permeability data were collected from 34 locations using seven alternative layouts of the sampling points. The proposed layouts were based on various configurations of fifteen, nine, five, and three sampling points. Locally, in some of the metamorphic units and in the regions containing sedimentary deposits with volcanic intercalations, the geogenic radon potential was found to be elevated. The results indicate that the three-measuring-point configuration is acceptable for general geogenic radon potential surveys.

Radon is a radioactive gas produced from the natural radioactive decay of uranium and is found in almost all rocks and soils. In confined places (e.g., dwellings, workplaces, caves, and underground mines), radon may accumulate and become a substantial health risk since it is considered the second most important cause of lung cancer in many developed countries. Radon risk assessment commonly considers either field or estimate values of the radon concentration and the gas permeability of soils. However, radon risk assessment from single measurement surveys to radon potential largescale mapping is strongly sensitive to the soil texture variability and climate changes, and particularly, to the soil water content dynamic and its effect on soil gas permeability. In this paper, the gas permeability of soils, and thus, the estimation of radon risk, is studied considering the effect of three different climates following the Köppen classification and four soil textures on soil water content dynamics. This investigation considers the CLIGEN weather simulator to elaborate 100-year length climatic series; Rosseta 3 pedotransfer function to calculate soil hydraulics parameters, and the HYDRUS-1D software to model the dynamics of water content in the soil. Results reveal that climate strongly affects gas permeability of soils and they must be considered as an additional factor during the evaluation of radon exposure risk. The impact of climate and texture defines the soil water content dynamic. Coarse soils show smaller gas permeability variations and then radon risk, in this case, is less affected by the climate type. However, in clay soils, the effect of climate and the differences in soil water content derive in gas permeability variations between 100 and 1,000 times through an annual cycle. As a result, it may cross the boundary between two radon risk categories. Results deeply confirm that both climate and texture should be compulsory considered when calculating the radon exposure risk and in the definition of new strategies for the elaboration of more reliable geogenic radon potential largescale maps.

The Santo Domingo Diocesan School (Orihuela, SE Spain) is a singular case study that relates air quality monitoring and stone conservation. The monument suffers severe damage due to salt crystallization by rising damp, which is related to the indoor environment dynamics, high groundwater salt content, and microstructure, the building’s porous stone (biocalcarenite). Results revealed that 222Rn concentration in indoor air is low due to the building’s high ventilation rate, despite the medium-low geogenic radon potential in the area. Wavelets analysis showed that ventilation is caused by outdoor and indoor temperature variations and directly affects the 222Rn and CO2 dynamics inside the church. CO2, as well as relative humidity (RH), presented periodicities with intermediate frequencies (5–8 days) related to visits. These RH and temperature (T) variations intensified the salt damage by increasing the frequency of dissolution-crystallization cycles. The mineralogical characterization and geochemical calculations concluded that chlorides (halite and sylvite), sulfates (thenardite, epsomite, hexahydrite and aphthitalite) and nitrates (niter) present from dissolution forms to whiskers and hopper-type morphologies. This indicates high saturation values and, therefore, higher crystallization pressure values within the porous media of the biocalcarenite. On the contrary, the near-equilibrium crystal shape and incongruent precipitation reaction for humberstonite suggest a lower alteration for this salt on the building stone.

In this study, five different methods for determining the geogenic radon potential are compared in the Mochovce region, Slovakia. Based on these methods, maps of radon potential were made and localities with suspected elevated indoor radon levels were identified. Subsequently, indoor radon concentrations measurements were performed there. Based on the measurements in six municipalities, an approximately linear relationship was found between the values of geogenic radon potential and indoor radon concentrations. These results confirm the usability of radon potential maps as valuable tools for characterizing radon-prone areas. [ABSTRACT FROM AUTHOR]

Many countries are developing a radon action plan to provide decision-makers with a reliable tool for reducing the harmful effects of radon exposure in dwellings and among the general public and, accordingly, to implement land development strategies. Mapping the geogenic radon release in different geological environments could assist in delineating areas that require priority monitoring and regulation, as well as applying radon reduction techniques in newly constructed buildings. In this paper, the activity concentration of 238U, 226Ra, 232Th and 40K and the exhalation rate of 222Rn have been estimated for the Silurian black shales of Villasalto, a district in the south-eastern Sardinia (Italy). The radioactivity of 226Ra, 232Th and 40K radionuclides was found relatively high (256.32 ± 87.00 Bq.kg−1), low (44.16 ± 9.47 Bq.kg−1) and moderate to high (856.28 ± 392.41 Bq.kg−1) respectively. The radon emanation coefficient (E) and the radon production rate (P Rn) have been calculated based on the analysis of the radon growth model inside a sealed chamber. E was found to correlate well with the activity concentration of 226Ra, as well as with the grain size of the soil/rock samples under investigation. P Rn was relatively high, ranging from 212.54 to 524.27 Bq.m−3.h−1. Furthermore, the mean value of the main radiation hazard indexes (i.e., the radium equivalent activity , the outdoor gamma-ray dose rate and the annual e ff ective dose) were found to be 299.07 ± 138.62 Bq.kg−1, 169.97 ± 75.58 nGy h−1 and 0.21 ± 0.09 mSv.y−1 respectively. • High levels of uranium and radon were found in Silurian Black Shales. • Correlation between radon coefficient and rock texture discovered. • Study provides insights into geological factors contributing to natural radioactivity. • Implications for radioprotection measures and identifying Radon Priority Areas investigated. • Continued research in this area is crucial for understanding potential health risks. [ABSTRACT FROM AUTHOR]

Abstract The Basic Safety Standard (BSS) Directive 2013/59/EURATOM of the European Union (EU) has stated the need for member states to establish national action plans to mitigate their general population's long-term risks of exposure to radon gas. Maps of radon-prone areas provide a useful tool for the development of such plans. This paper presents the maps of radon-prone areas in the Eastern Canary Islands (Gran Canaria, Fuerteventura and Lanzarote) obtained from assessment of Geogenic Radon Potential (GRP) distribution in the territory. GRP constitutes a magnitude that is contingent on both radon activity concentration and gas permeability of soils. An extensive campaign covering all geological formations of the Eastern Canary Islands was undertaken to locally sample these parameters. Geostatistical analysis of the spatial distribution of radon concentration in soils, permeability and GRP was performed on each of the islands, and the relationship between these magnitudes and the characteristic geological formations of the volcanic islands was investigated. Areas dominated by basic volcanic and plutonic rocks (originated by both recent and ancient volcanism) exhibit relatively low levels of radon in soils, and with the exception of specific cases of very high permeability, these areas are not classified as prone to radon risk according to international criteria. Areas in which intermediate or acidic volcanic and plutonic rocks predominate are characterised by greater radon activity concentration in soils, rendering them radon-prone. Given these results, Lanzarote is classified as an island with low radon risk all over its surface; Fuerteventura presents low-medium risk; and Gran Canaria contains extensive areas in the centre and north where the risk is medium or high. This classification is consistent with the risk maps obtained by National and European agencies from indoor radon measurements conducted on these islands. Graphical abstract Unlabelled Image Highlights • EU Member states have to establish action plans to mitigate radon exposure risks. • A study of Soil radon gas concentration and gas permeability of soils were performed. • Geogenic Radon Potential (GRP) distribution in the territory have been assessed. • Maps of radon prone areas in the Eastern Canary Islands are displayed based on GRP. • The subsequent zonal classification agrees with those provided by the authorities. [ABSTRACT FROM AUTHOR]

Abstract A detailed geochemical study on radon related to local geology was carried out in the municipality of Celleno, a little settlement located in the eastern border of the Quaternary Vulsini volcanic district (central Italy). This study included soil-gas and terrestrial gamma dose rate survey, laboratory analyses of natural radionuclides (238U, 226Ra, 232Th, 40K) activity in rocks and soil samples, and indoor radon measurements carried out in selected private and public dwellings. Soil-gas radon and carbon dioxide concentrations range from 6 to 253 kBq/m3 and from 0.3 to11% v/v, respectively. Samples collected from outcropping volcanic and sedimentary rocks highlight: significant concentrations of 238U, 226Ra and 40K for lavas (151, 150 and 1587 Bq/kg, respectively), low concentrations for tuffs (126, 123 and 987 Bq/kg, respectively), and relatively low for sedimentary rocks (108, 109 and 662 Bq/kg, respectively). Terrestrial gamma dose rate values range between 0.130 and 0.417 μSv/h, being in good accordance with the different bedrock types. Indoor radon activity ranges from 162 to 1044 Bq/m3; the calculated values of the annual effective dose varied from 4.08 and 26.31 mSv/y. Empirical Bayesian Kriging Regression (EBKR) was used to develop the Geogenic Radon Potential (GRP) map. EBKR provided accurate predictions of data on a local scale developing a spatial regression model in which soil-gas radon concentrations were considered as the response variable; several proxy variables, derived from geological, topographic and geochemical data, were used as predictors. Risk prediction map for indoor radon was tentatively produced using the Gaussian Geostatistical Simulation and a soil-indoor transfer factor was defined for a 'standard' dwelling (i.e., a dwelling with well-defined construction properties). This approach could be successfully used in the case of homogeneous building characteristics and territory with uniform geological characteristics. Graphical abstract Unlabelled Image Highlights • A detailed geochemical study on radon was carried out in a volcanic area of central Italy. • Geogenic Radon Potential map was developed using Empirical Bayesian Kriging Regression. • A soil-indoor transfer factor was defined for a 'standard' dwelling. • Indoor Rn partly depends on housing characteristics (e.g., tuff used as building material) [ABSTRACT FROM AUTHOR]

Radon is classified as a Class 1 carcinogen, being the leading cause of lung cancer in non-smokers. Understanding the prominent sources of radon helps to mitigate against the adverse effects of radon exposure. Considering soil-gas radon is the main contributor to indoor radon, it is possible that soil geochemistry can be used as a proxy for the soil radon emanation potential or geogenic radon classes for a particular location. This paper investigates the relationship between soil geochemistry and geogenic radon. A large area of 17,983 km2 from the West, Midlands and East of Ireland was selected to represent a range of geology types and radon categories. A rigorous assessment is presented to investigate the relationship of geogenic radon and topsoil geochemistry; using univariate processes (i.e. r2, Pearson r and heatmaps) and multivariate techniques (i.e. principle component analysis (PCA) and machine learning (ML) algorithms including Gaussian process regression, logistic regression and random forest). Here, PCA and ML techniques were used to test the utility of soil geochemistry to predict geogenic radon classes. Gaussian Process Regression yielded the highest accuracy (74%) and f1-score (0.74) of all models. The feature importance (i.e. highest ranking elements for predicting geogenic radon class) from the ML models outputs elements including [Y, Tl, Mn, Cr, Co, Be, Sc and Rb]. The PCA biplot demonstrates that these elements cluster in conjunction with higher geogenic radon categories. Multivariate data analysis reveals that certain elements important for predicting higher geogenic radon classes, also covary together within topsoil samples; here these are termed "radon-prone elements". Spatial covariance of radon-prone elements permits soil geochemistry to be used as a tool for understanding the distribution of geogenic radon. The methodology presented in this paper provides a comprehensive geo-statistical approach to investigate the relation between topsoil geochemistry and geogenic radon. This approach could be applied as a diagnostic tool to assist radon mitigation measures, hence adding value to legacy soil geochemistry datasets. • ML and PCA results indicate radon prone elements. • Gaussian process regression achieves the highest accuracy (74%) for classifying geogenic radon class. • Relationship between soil geochemistry and geogenic radon investigated. • Topsoil geochemical analysis significantly correlates to geogenic radon class. • Spatial covariance of elements (including Y, Tl, Mn, Cr, Co, Al, Rb) and elevated geogenic radon. [ABSTRACT FROM AUTHOR]

Abstract: Geogenic radon prone areas are regions in which for natural reasons elevated indoor radon concentrations must be expected. Their identification is part of radon mitigation policies in many countries, as radon is acknowledged a major indoor air pollutant, being the second cause of lung cancer after smoking. Defining and estimating radon prone areas is therefore of high practical interest. In this paper a method is presented which uses the geogenic radon potential as predictor and thresholds of indoor radon concentration for defining radon prone areas, from which thresholds for the geogenic radon potential are deduced which decide whether a location is flagged radon prone or not, in the absence of actual indoor observations. The overall results are different maps of radon prone areas, derived from the geogenic radon map, and depending (1) on the criterion which defines what a radon prone area is; and (2) on the choice of score whose maximization defines the optimal classifier. Such map is not the result of a transfer model (geogenic to indoor radon), but of the optimization of a classification rule. The method is computationally simple but has its caveats and statistical traps, some of which are also addressed. [Copyright &y& Elsevier]

A detailed investigation of geogenic radon potential (GRP) was carried out near Graiguenamanagh town (County Kilkenny, Ireland) by performing a spatial regression analysis on radon-related variables to evaluate the exposure of people to natural radiation (i.e., radon, thoron and gamma radiation). The study area includes an offshoot of the Caledonian Leinster Granite, which is locally intruded into Ordovician metasediments. To model radon release potential at different points, an ordinary least squared (OLS) regression model was developed in which soil gas radon (SGR) concentrations were considered as the response value. Proxy variables such as radionuclide concentrations obtained from airborne radiometric surveys, soil gas permeability, distance from major faults and a digital terrain model were used as the input predictors. ArcGIS and QGIS software together with XLSTAT statistical software were used to visualise, analyse and validate the data and models. The proposed GRP models were validated through diagnostic tests. Empirical Bayesian kriging (EBK) was used to produce the map of the spatial distribution of predicted GRP values and to estimate the prediction uncertainty. The methodology described here can be extended for larger areas and the models could be utilised to estimate the GRPs of other areas where radon-related proxy values are available.

Abstract: In order to evaluate the influence of faulting on the variability of geogenic radon at detailed scale (1:2000), data on gamma ray fluxes, U and Th concentrations in rocks, radon in soil-gas and radon in groundwater were collected in three target areas on the Oliveira do Hospital region (Central Portugal). This region stands on the Iberian Uranium Province, and is dominantly composed of Hercynian granites and metasedimentary rocks of pre-Ordovician age, crosscut by faults with dominant strike N35°E, N55°E and N75°E. Radiometric anomalies are frequent, associated with faults of the referred systems and metasedimentary enclaves; the analytical data confirms that these anomalies are produced by local high uranium contents in rocks and fault-filling materials (n =34, range 13–724ppm), while other radiogenic elements are relatively constant (e.g. Th 4–30ppm). Radon concentration in soil can be extremely high, up to 12,850kBqm−3 (n =215), with a large proportion of results above 100kBqm−3. Unsurprisingly, groundwater also shows high radon concentrations, with observed values in the range 150–4850Bq.L−1 (n =17). From the results it is concluded that metasedimentary enclaves, as well as faults, can accumulate uranium from circulating fluids, and as a consequence, strongly locally enhance geogenic radon potential. Due to this fact, for the purpose of land use planning in such uranium-enriched regions, very detailed geological mapping is needed to precisely recognize radon high risk areas. A correlation between radon concentration in soil or in groundwater and gamma ray fluxes was established pointing to the possible use of these fluxes as a first step in assessing geogenic radon potential, at least to geological setting similar to the study area. [Copyright &y& Elsevier]

Mapped geological units can be regarded as proxies standing for a complex series of subsoil geochemical and physical properties including the assigned radon activity concentration in soil gas, which is taken as best estimator of the regional geogenic radon potential. Areal distribution of measuring sites for soil gas in Germany is adapted to spatial variation of geology. A grid-based and distance-weighted interpolation procedure is applied, following geologically defined neighbourhood relations of measuring sites and accounting for isolated outcrops of known geology but without measurements. To investigate the statistical relationship between indoor radon, house type and building ground specifications, measurements of the indoor radon concentration have been carried out in more than 10,000 dwellings in different regions of Germany. Multiple regression analyses of variance reveal that besides region-specific geological properties and building characteristics, various house type and living style variables significantly contribute to the explained variance for ground floor radon concentrations. These parameters are also dominant in controlling the radon transfer relation from soil gas to indoor air. Risk prediction maps for radon in houses indicating the probability to exceed certain indoor threshold values can be useful especially for regions with no or only a few measurements of indoor radon. [ABSTRACT FROM AUTHOR]

Radon is a radioactive gas produced from the natural radioactive decay of uranium and is found in almost all rocks and soils. In confined places (e.g., dwellings, workplaces, caves, and underground mines), radon may accumulate and become a substantial health risk since it is considered the second most important cause of lung cancer in many developed countries. Radon risk assessment commonly considers either field or estimate values of the radon concentration and the gas permeability of soils. However, radon risk assessment from single measurement surveys to radon potential largescale mapping is strongly sensitive to the soil texture variability and climate changes, and particularly, to the soil water content dynamic and its effect on soil gas permeability. In this paper, the gas permeability of soils, and thus, the estimation of radon risk, is studied considering the effect of three different climates following the Köppen classification and four soil textures on soil water content dynamics. This investigation considers the CLIGEN weather simulator to elaborate 100-year length climatic series; Rosseta 3 pedotransfer function to calculate soil hydraulics parameters, and the HYDRUS-1D software to model the dynamics of water content in the soil. Results reveal that climate strongly affects gas permeability of soils and they must be considered as an additional factor during the evaluation of radon exposure risk. The impact of climate and texture defines the soil water content dynamic. Coarse soils show smaller gas permeability variations and then radon risk, in this case, is less affected by the climate type. However, in clay soils, the effect of climate and the differences in soil water content derive in gas permeability variations between 100 and 1,000 times through an annual cycle. As a result, it may cross the boundary between two radon risk categories. Results deeply confirm that both climate and texture should be compulsory considered when calculating the radon exposure risk and in the definition of new strategies for the elaboration of more reliable geogenic radon potential largescale maps., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Gil-Oncina, Valdes-Abellan, Pla and Benavente.)

Radon ( 222 Rn) is a natural radioactive gas formed in rocks and soil by the decay of its parent nuclide (238-Uranium). The rate at which radon migrates to the surface, be it along faults or directly emanated from shallow soil, represents the Geogenic Radon Potential (GRP) of an area. Considering that the GRP is often linked to indoor radon risk levels, we have conducted multi-disciplinary research to: (i) define local GRPs and investigate their relationship with associated indoor Rn levels; (ii) evaluate inhaled radiation dosages and the associated risk to the inhabitants; and (iii) define radon priority areas (RPAs) as required by the Directive 2013/59/Euratom. In the framework of the EU-funded LIFE-Respire project, a large amount of data (radionuclide content, soil gas samples, terrestrial gamma, indoor radon) was collected from three municipalities located in different volcanic districts of the Lazio region (central Italy) that are characterised by low to high GRP. Results highlight the positive correlation between the radionuclide content of the outcropping rocks, the soil Rn concentrations and the presence of high indoor Rn values in areas with medium to high GRP. Data confirm that the Cimini-Vicani area has inhalation dosages that are higher than the reference value of 10 mSv/y.

Radon is the second cause of lung cancer after smoking, therefore is acknowledged as a major indoor air pollutant. Geogenic radon potential indicates regions where for natural reasons elevated indoor radon levels or elevated probability of their occurrence can be expected. The most common procedure for establishing geogenic radon potential includes measurements of soil permeability and soil gas radon concentrations. These measurements are time-consuming and expensive therefore a limited number of measurements is carried out and their results are extrapolated to the specific area. Our research aimed to analyse the usefulness of ambient gamma dose rate survey to assess radon concentration in the environment and therefore geogenic radon potential. The measurements were carried out on two granite massifs with higher (Karkonosze) and lower (Strzelin) radioactive elements contents. Seasonal variations of atmospheric radon concentrations and ambient gamma dose rates were registered with higher values during warmer and lower during colder seasons. The opposite seasonal variations were observed for soil gas radon concentrations. No distinctive seasonal variations were recorded in results of uranium, thorium and potassium contents in soil measured in situ by the gamma-ray spectrometer. The correlation coefficients were calculated on the base of annual average data. The correlations between ambient gamma dose rate and radon concentration in soil and in the atmosphere were 0.83 and 0.62 respectively, which may suggest that ambient gamma dose rate can be a useful parameter to indicate geogenic radon potential. Unlabelled Image • Ambient gamma dose rate - an efficient indicator of geogenic radon potential • Seasonal variations of atmospheric radon concentrations • Seasonal variations of soil radon concentrations • Seasonal variations of ambient gamma dose rate • Lack of seasonal variations in in-situ survey of U, Th, K-40 [ABSTRACT FROM AUTHOR]

The radioactive gas radon (Rn) is considered as an indoor air pollutant due to its detrimental effects on human health. In fact, exposure to Rn belongs to the most important causes for lung cancer after tobacco smoking. The dominant source of indoor Rn is the ground beneath the house. The geogenic Rn potential (GRP) - a function of soil gas Rn concentration and soil gas permeability - quantifies what "earth delivers in terms of Rn" and represents a hazard indicator for elevated indoor Rn concentration. In this study, we aim at developing an improved spatial continuous GRP map based on 4448 field measurements of GRP distributed across Germany. We fitted three different machine learning algorithms, multivariate adaptive regression splines, random forest and support vector machines utilizing 36 candidate predictors. Predictor selection, hyperparameter tuning and performance assessment were conducted using a spatial cross-validation where the data was iteratively left out by spatial blocks of 40 km*40 km. This procedure counteracts the effect of spatial auto-correlation in predictor and response data and minimizes dependence of training and test data. The spatial cross-validated performance statistics revealed that random forest provided the most accurate predictions. The predictors selected as informative reflect geology, climate (temperature, precipitation and soil moisture), soil hydraulic, soil physical (field capacity, coarse fraction) and soil chemical properties (potassium and nitrogen concentration). Model interpretation techniques such as predictor importance as well as partial and spatial dependence plots confirmed the hypothesized dominant effect of geology on GRP, but also revealed significant contributions of the other predictors. Partial and spatial dependence plots gave further valuable insight into the quantitative predictor-response relationship and its spatial distribution. A comparison with a previous version of the German GRP map using 1359 independent test data indicates a significantly better performance of the random forest based map. Unlabelled Image • Mapping of the geogenic radon potential as hazard indicator for indoor radon • Comparison of three machine learning algorithms • Application of spatial cross-validation using spatial blocks to split the data • Partial and spatial dependence plots reveal predictor-response relationship • Random forest GRP map outperforms previous maps using geostatistics [ABSTRACT FROM AUTHOR]

Exposure to indoor radon at home and in workplaces constitutes a serious public health risk and is the second most prevalent cause of lung cancer after tobacco smoking. Indoor radon concentration is to a large extent controlled by so-called geogenic radon, which is radon generated in the ground. While indoor radon has been mapped in many parts of Europe, this is not the case for its geogenic control, which has been surveyed exhaustively in only a few countries or regions. Since geogenic radon is an important predictor of indoor radon, knowing the local potential of geogenic radon can assist radon mitigation policy in allocating resources and tuning regulations to focus on where it needs to be prioritized. The contribution of geogenic to indoor radon can be quantified in different ways: the geogenic radon potential (GRP) and the geogenic radon hazard index (GRHI). Both are constructed from geogenic quantities, with their differences tending to be, but not always, their type of geographical support and optimality as indoor radon predictors. An important feature of the GRHI is consistency across borders between regions with different data availability and Rn survey policies, which has so far impeded the creation of a European map of geogenic radon. The GRHI can be understood as a generalization or extension of the GRP. In this paper, the concepts of GRP and GRHI are discussed and a review of previous GRHI approaches is presented, including methods of GRHI estimation and some preliminary results. A methodology to create GRHI maps that cover most of Europe appears at hand and appropriate; however, further fine tuning and validation remains on the agenda.

Radon-222 is a radioactive natural gas produced by the decay of radium-226, known to be the main contributor to natural background radiation exposure. Effective risk management needs to determine the areas in which the density of buildings with high radon levels is likely to be highest. Predicting radon exposure from the location and characteristics of a dwelling could also contribute to epidemiological studies. Beginning in the nineteen-eighties, a national radon survey consisting in more than 10,000 measurements of indoor radon concentrations was conducted in French dwellings by the Institute for Radiological Protection and Nuclear Safety (IRSN). Housing characteristics, which may influence radon accumulation in dwellings, were also collected. More recently, the IRSN generated a French geogenic radon potential map based on the interpretation of geological features. The present study analyzed the two datasets to investigate the factors influencing indoor radon concentrations using statistical modeling and to determine the optimum use of the information on geogenic radon potential that showed the best statistical association with indoor radon concentration. The results showed that the variables associated with indoor radon concentrations were geogenic radon potential, building material, year of construction, foundation type, building type and floor level. The model, which included the surrounding geogenic radon potential (i.e. the average geogenic radon potential within a disc of radius 20 km centered on the indoor radon measurement point) and variables describing house-specific factors and lifestyle explained about 20% of the overall variability of the logarithm of radon concentration. The surrounding geogenic radon potential was fairly closely associated with the local average indoor radon concentration. The prevalence of exposure to radon above specific thresholds and the average exposures to radon clearly increased with increasing classes of geogenic radon potential. Combining the two datasets enabled improved assessment of radon exposure in a given area in France., (Copyright © 2013 Elsevier Ltd. All rights reserved.)