Application of airborne radiometric surveys for large-scale geogenic radon potential classification

Abstract

Background: Indoor radon represents an important health issue to the general population. Therefore, accurate radon risk maps help public authorities to prioritise areas where mitigation actions should be implemented. As the main source of indoor radon is the soil where the building is constructed, maps derived from geogenic factors ([e.g. geogenic radon potential [GRP]) are viewed as valuable tools for radon mapping.
 Objectives: A novel indirect method for estimating the GRP at national/regional level is presented and evaluated in this article.
 Design: We calculate the radon risk solely based on the radon concentration in the soil and on the subsoil permeability. The soil gas radon concentration was estimated using airborne gamma-ray spectrometry (i.e. equivalent uranium [eU]), assuming a secular equilibrium between eU and radium (226Ra). The subsoil permeability was estimated based on groundwater subsoil permeability and superficial geology (i.e. quaternary geology) by assigning a permeability category to each soil type (i.e. low, moderate or high). Soil gas predictions were compared with in situ radon measurements for representative areas, and the resulting GRP map was validated with independent indoor radon data.
 Results: There was good agreement between soil gas radon predictions and in situ measurements, and the resultant GRP map identifies potential radon risk areas. Our model shows that the probability of having an indoor radon concentration higher than the Irish reference level (200 Bq m-3) increases from c. 6% (5.2% – 7.1%) for an area classified as Low risk, to c. 9.7% (9.1% – 10.5%) for Moderate-Low risk areas, c. 14% (13.4% – 15.3%) for Moderate-High risk areas and c. 26% (24.5% – 28.6%) for High risk areas.
 Conclusions: The method proposed here is a potential alternative approach for radon mapping when airborne radiometric data (i.e. eU) are available.

Detailed Geogenic Radon Potential Mapping Using Geospatial Analysis of Multiple Geo-Variables—A Case Study from a High-Risk Area in SE Ireland

“…Ideally, a GRP estimation is derived from radon soil gas concentrations [ 22 ]. An alternative method to detect radon on the ground is to use airborne gamma spectrometry [ 18 , 23 ]. In Ireland, there are insufficient SGR data to generate useful radon potential maps.…”

“…Further refinement of the logistic regression radon map was conducted, resulting in a new map released by the EPA in May 2022. Furthermore, Elio et al [ 18 ] utilised the Tellus airborne geophysical data and subsoil permeability to produce a geogenic radon potential map of Ireland, which does not rely on indoor radon data. In this paper, the goal is to develop a geostatistical model to predict the geogenic radon potential for a high-risk area in southeastern Ireland that is underlain by granite and metasediments.…”

A Study of Natural Radioactivity Levels and Radon/Thoron Release Potential of Bedrock and Soil in Southeastern Ireland

“…Some countries have employed radiometric data to produce geogenic radon potential maps [ 18 , 28 ]. In this study, a statistical approach was employed for studying the radon release behavior of different rocks and soils.…”

“Following the Science”: In Search of Evidence-Based Policy for Indoor Air Pollution from Radon in Ireland

“…These scientific studies highlight the connection between practical and scientific knowledge. For example, indoor radon measurements have been used by scientists to estimate residential radon exposure [5] and combined with other data, such as geological information [23] and airborne radiometric data [67], to develop radon risk maps. Significantly, in 2017, a high-resolution radon risk map of Ireland was developed based on 31,910 indoor radon measurements combined with geological information [23].…”