Relationships between geogenic radon potential and gamma ray maps with indoor radon levels at Caprarola municipality (central Italy)

Exposures to relatively high indoor radon (222Rn) levels represents a serious public health risk because Rn is associated with lung cancer (Darby et al., 2001; WHO, 2009; Oh et al., 2016; Sheen et al., 2016). The risk is high because radon, and its short-lived decay products in the atmosphere, contributes for about 60% of the total annual effective dose (UNSCEAR, 2000; WHO, 2009). Cancer risk is increased by smoking being almost 9 times higher than the risk to non-smokers exposed to similar levels (EPA, 2009). Due to these reasons, it is very important to assess the indoor exposure of public to radon and their daughters. Rn is a natural ubiquitous gas and its abundance is mainly controlled by the geology, and in particular by the soil and rock content of its parent nuclide (238U). Furthermore, bedrock characteristics (i.e. permeability and porosity) and also fault activity can affect the amount of Rn released in the ground (Ciotoli et al., 2007; Barnet et al., 2018). As such, in conditions of permeable and/or fractured bedrock and high uranium content, high indoor radon concentrations are expected (Bossew and Lettner, 2007; Gruber et al., 2013; Cinelli et al., 2015; Ielsch et al., 2017; Ciotoli et al., 2017). A non-natural contribution that controls the indoor Rn levels is home construction type and building materials (Vauptic et al., 2002; Appleton, 2007). Additionally, meteorological factors, such as wind, temperature and humidity, can affect the rate of Rn entry into the buildings (Porstendörfer et al., 1994; Miles et al., 2005; Schubert et al., 2018). In this work, we propose a new geospatial technique to construct the geogenic radon potential (GRP) map of the Caprarola municipality (northern Lazio, central Italy) characterized by recent (about 100 Kyr) volcanic deposits with high content in radon parent nuclides (Ciotoli et al., 2017). GRP map has been obtained by using Empirical Bayesian Kriging Regression (EBKR) technique with soil gas radon, as the response variable, and a number of proxy variables (i.e. content of the radiogenic parent nuclides, the emanation coefficient of the outcropping rocks, the diffusive 222Rn flux from the soil, the soil-gas CO2 concentration, the Digital Terrain Model (DTM), the permeability of the outcropping rocks and the gamma dose radiation of the shallow lithology. Furthermore, possible relationships between predicted soil radon values (i.e. GRP) and gamma radiation distribution with the indoor concentrations measured in private and public buildings has been investigated, respectively. The obtained results confirm that GRP maps provide the local administration of a useful tool for land use planning and that, the mapping of gamma emission, allows to a fast and effective evaluation of indoor radon hazard because it is mainly influenced by the building materials rather than other anthropic controls

European Atlas of Natural Radiation

Natural ionizing radiation is considered as the largest contributor to the collective effective dose received by the world population. The human population is continuously exposed to ionizing radiation from several natural sources that can be classified into two broad categories: high-energy cosmic rays incident on the Earth’s atmosphere and releasing secondary radiation (cosmic contribution); and radioactive nuclides generated during the formation of the Earth and still present in the Earth’s crust (terrestrial contribution). Terrestrial radioactivity is mostly produced by the uranium and thorium radioactive families together with potassium. In most circumstances, radon, a noble gas produced in the radioactive decay of uranium, is the most important contributor to the total dose. This Atlas aims to present the current state of knowledge of natural radioactivity, by giving general background information, and describing its various sources. This reference material is complemented by a collection of maps of Europe displaying the levels of natural radioactivity caused by different sources. It is a compilation of contributions and reviews received from more than 80 experts in their field: they come from universities, research centres, national and European authorities and international organizations. This Atlas provides reference material and makes harmonized datasets available to the scientific community and national competent authorities. In parallel, this Atlas may serve as a tool for the public to: • familiarize itself with natural radioactivity; • be informed about the levels of natural radioactivity caused by different sources; • have a more balanced view of the annual dose received by the world population, to which natural radioactivity is the largest contributor; • and make direct comparisons between doses from natural sources of ionizing radiation and those from man-made (artificial) ones, hence to better understand the latter.JRC.G.10-Knowledge for Nuclear Security and Safet

High Radon Areas in the Walloon Region of Belgium

Indoor radon data from Southern Belgium are organised in 35 geological units (GUs), most of which are homogeneous with respect to the radon risk. The percentage of cases above the reference level (400 Bq m−3; 300 Bq m−3 in the future) is calculated for these GUs from the observations and from the log-normal distribution fitted to the data. Affected areas are defined as areas with more than 1 % of houses above the reference level. In the north of the region, the old Palaeozoic basement is generally covered by Silesian, Cretaceous and Tertiary rocks, which are unaffected. The affected areas here are hot spots associated with specific Palaeozoic outcrops. In the south, there is generally no cover above Palaeozoic formations, which are often radon affected. The affected areas of Ardenne and Condroz dominate this part, but unaffected areas occur like Famenne and Gaume. About 48 % of the Walloon region is expected to be radon affected.JRC.E.8-Nuclear securit

HOMOGENEITY OF GEOLOGICAL UNITS WITH RESPECT TO THE RADON RISK IN THE WALLOON REGION OF BELGIUM

In the perspective of mapping the indoor radon risk, an important step is to define geological units well-correlated with indoor radon. The present paper examines this question for the Walloon region of Belgium, using a database of more than 18000 indoor radon measurements. With few exceptions like Carboniferous and Tertiary, the series is found to be the most appropriate geological division, but a further division according to the massif or region is necessary to define geological units with a reasonable uniformity of the radon risk. 35 units are defined, 6 of which still presenting an important lack of homogeneity.JRC.E.8-Nuclear securit

Mapping potassium and thorium concentrations in Belgian soils

The European Atlas of Natural Radiation developed by the Joint Research Centre (JRC) of the European Commission includes maps of potassium K and thorium Th. With several different databases available, including data (albeit not calibrated) from an airborne survey, Belgium is a favourable case for exploring the methodology of mapping for these natural radionuclides. Harmonized databases of potassium and thorium in soil were built by radiological (not airborne) and geochemical data. Using this harmonized database it was possible to calibrate the data from the airborne survey. Several methods were used to perform spatial interpolation and to smooth the data: moving average (MA) without constraint, or constrained by soil class and by geological unit. Overall, there was a reasonable agreement between the maps on a 1 × 1 km2 grid obtained with the two datasets (airborne data and harmonized soil data) with all the methods. The agreement was better when the maps are reduced to a 10 km × 10 km grid used for the European Atlas of Natural Radiation. The best agreement was observed with the MA constrained by geological unit.JRC.G.10-Knowledge for Nuclear Security and Safet

URANIUM IN SOIL AND GAMMA DOSE RATE AS PROXIES FOR THE INDOOR RADON RISK: SITUATION IN BELGIUM

Radon risk maps are usually based either on indoor radon data, or on measurements of soil gas radon and soil permeability. If these data are not available or not sufficient, it was suggested that other data could be used as an approximate substitute (a proxy) to the missing information, like the concentration of 238U or 226Ra in soils or the terrestrial gamma dose rate (TGDR). We examine here the correlation between airborne measurements of soil U and indoor radon, and between airborne U and TGDR, and their link with affected/unaffected areas. No clear correlation is found between airborne U and affected areas, as strongly affected areas are not characterised by a higher U level. Only the moderately affected area of Condroz can be connected to a higher U level, related to a few U anomalies. TGDR shows a rather good correlation with airborne U, but its relation with radon risk is less clear. Soil uranium and TGDR may help to screen out areas with very low U and very low TGDR, which have a low indoor radon risk, but they cannot be considered as good proxies for predicting radon affected areas in Belgium.JRC.G.10-Knowledge for Nuclear Security and Safet

VARIABILITY OF INDOOR RADON RISK BETWEEN AND WITHIN GEOLOGICAL UNITS

The variations of the indoor radon risk between and within geological units in the Walloon region of Belgium are studied with two tools: - The analysis of variance of indoor radon data - The geostatistical mapping of the percentage of cases above 400 Bq/m3 using the moving average method. Both methods converge to the same conclusions: - The influence of geology on indoor radon concentration is stronger than the influence of geographical variation within the geological units on indoor radon concentration - The geographical variation of the risk within the geological unit is not small and cannot be neglected in radon risk mapping.JRC.E.8-Nuclear securit

Brittle fractures and ductile shear bands in argillaceous sediments: inferences from Oligocene Boom Clay (Belgium)

Fractures, from vertical joints to micro-scale slickensides, are common in many muds and mudstones. Their origin and formation mechanism remains enigmatic because of the rock-soil transitional behaviour of argillaceous sediments. However, they can have an important impact on the fluid-flow properties and mechanical strength of the rock. The nature of small-scale fractures studied in the field and in the laboratory is discussed using fabric, strain and paleostress analyses, for the case of Oligocene Boom Clay (Belgium). Non-dilatant ductile and dilatant brittle structures develop successively in the stress path of the deforming mud, which remains close to its critical stress state due to its low strength. The transition between the failure modes depends on the mean effective stress, the water content, the amount of strain and the burial-uplift history. The specific stress path initially follows a K-0 path that is left when differential stress increases, due to both uplift and compaction-induced endogenous forces, reflected by a decrease in effective confining pressure prior to failure, and far-field tectonic forces, reflected by the distinct and regular orientation of fractures. The related deformation is ductile, causing distributed microshear bands, up to the dilatancy boundary, beyond which extensional fractures develop. (C) 2005 Elsevier Ltd. All rights reserved.status: publishe