The Geogenic Radon Potential (GRP) defines the availability of radon generated in the ground for surface exhalation or infiltration into buildings. One way to quantify the GRP is through Rn concentration in soil gas and ground permeability. These quantities can be measured, but are available only regionally. Instead there have been attempts to estimate the GRP through proxy quantities, such as U content in the ground, Rn emanation coefficient or ambient dose rate. The difficulty is that relations between these and the GRP have to be established first. Only then, spatial estimation, i.e. mapping can be attempted, for which different techniques have been applied in the past Since 2008, the Radioactivity Environmental Monitoring (REM) group at the Joint Research Centre (JRC) of the European Commission is working on the development of a Europe wide map of Geogenic Radon Potential (GRP) in the framework of European Atlas of Natural Radiation (EANR) project. The Atlas currently includes maps of indoor Rn concentration, cosmic radiation, and of geochemical quantities (U, Th, K), but the GRP map turned out more complicated. The factors that control the GRP are source term and transport in the ground. The latter is additionally affected by factors related to tectonics, that is, presence of active faults, seismic and geothermal activity and volcanism. This work is an attempt to construct a GRP map on a European scale starting from proxy variables (already available in the literature or easily available on the web) affecting the global radon release, without the need for direct measurements of radon concentrations in soil gas. This approach does not suggest that soil Rn and permeability measurements should be bypassed, but it can easily and quickly help establish a preliminary GRP estimate of an area. The exercise presented here has been conducted using the following proxy variables: U, Th, and K radionuclide content in soil in term data interpolated at 10 km x10km grid cells, https://remon.jrc.ec.europa.eu/About/Atlas-of-Natural-Radiation)), the soil permeability in terms of percentage of topsoil fine fraction (<63 micro m) (estimated using LUCAS database (Ballabio et al., 2014)), the spatial distribution of world active faults (Global Faults layer from ArcAtlas, ESRI) and the location of earthquakes of local magnitude > 4 (USGS, https://earthquake.usgs.gov/earthquakes/browse/), the distribution of the global volcanism (Global Volcanism Program, Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution) and the geothermal areas in terms of heat flow (the heat flow map of Europe has been obtained by the analysis of the Global Heat Flow data maintained by the International Heat Flow Commission (IHFC) of the International Association of seismology and Physics of the Earth's Interior, IASPEI). All this information is transformed in raster layers according to a 10x10 km² grid, reclassified by using the Jenks Natural Break classification method and then summed to obtain a new grid map that represents the potential radon release map at European scale. All data has been integrated and analysed in the GIS environment. We would like to underline that the resulting map has not yet been validated neither against other existing regional GRP mapping approaches, nor against the European Radon Indoor Map, and that this exercise is only a preliminary proposal for a method that could be improved, both regarding selection of variables and statistical methodology. Furthermore, we would like to thank JRC/REM for making available part of the data used in this work through the EANR.
A preliminary exercise to derive the map of potential radon release at European scale
G Ciotoli;
2017
Abstract
The Geogenic Radon Potential (GRP) defines the availability of radon generated in the ground for surface exhalation or infiltration into buildings. One way to quantify the GRP is through Rn concentration in soil gas and ground permeability. These quantities can be measured, but are available only regionally. Instead there have been attempts to estimate the GRP through proxy quantities, such as U content in the ground, Rn emanation coefficient or ambient dose rate. The difficulty is that relations between these and the GRP have to be established first. Only then, spatial estimation, i.e. mapping can be attempted, for which different techniques have been applied in the past Since 2008, the Radioactivity Environmental Monitoring (REM) group at the Joint Research Centre (JRC) of the European Commission is working on the development of a Europe wide map of Geogenic Radon Potential (GRP) in the framework of European Atlas of Natural Radiation (EANR) project. The Atlas currently includes maps of indoor Rn concentration, cosmic radiation, and of geochemical quantities (U, Th, K), but the GRP map turned out more complicated. The factors that control the GRP are source term and transport in the ground. The latter is additionally affected by factors related to tectonics, that is, presence of active faults, seismic and geothermal activity and volcanism. This work is an attempt to construct a GRP map on a European scale starting from proxy variables (already available in the literature or easily available on the web) affecting the global radon release, without the need for direct measurements of radon concentrations in soil gas. This approach does not suggest that soil Rn and permeability measurements should be bypassed, but it can easily and quickly help establish a preliminary GRP estimate of an area. The exercise presented here has been conducted using the following proxy variables: U, Th, and K radionuclide content in soil in term data interpolated at 10 km x10km grid cells, https://remon.jrc.ec.europa.eu/About/Atlas-of-Natural-Radiation)), the soil permeability in terms of percentage of topsoil fine fraction (<63 micro m) (estimated using LUCAS database (Ballabio et al., 2014)), the spatial distribution of world active faults (Global Faults layer from ArcAtlas, ESRI) and the location of earthquakes of local magnitude > 4 (USGS, https://earthquake.usgs.gov/earthquakes/browse/), the distribution of the global volcanism (Global Volcanism Program, Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution) and the geothermal areas in terms of heat flow (the heat flow map of Europe has been obtained by the analysis of the Global Heat Flow data maintained by the International Heat Flow Commission (IHFC) of the International Association of seismology and Physics of the Earth's Interior, IASPEI). All this information is transformed in raster layers according to a 10x10 km² grid, reclassified by using the Jenks Natural Break classification method and then summed to obtain a new grid map that represents the potential radon release map at European scale. All data has been integrated and analysed in the GIS environment. We would like to underline that the resulting map has not yet been validated neither against other existing regional GRP mapping approaches, nor against the European Radon Indoor Map, and that this exercise is only a preliminary proposal for a method that could be improved, both regarding selection of variables and statistical methodology. Furthermore, we would like to thank JRC/REM for making available part of the data used in this work through the EANR.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
