Abstract
Radon (222Rn) and thoron (220Rn) account for almost two-thirds of the annual average radiation dose received by the Irish population. A detailed study of natural radioactivity levels and radon and thoron exhalation rates was carried out in a legislatively designated “high radon” area, as based on existing indoor radon measurements. Indoor radon concentrations, airborne radiometric data and stream sediment geochemistry were collated, and a set of soil samples were taken from the study area. The exhalation rates of radon (E222Rn) and thoron (E220Rn) for collected samples were determined in the laboratory. The resultant data were classified based on geological and soil type parameters. Geological boundaries were found to be robust classifiers for radon exhalation rates and radon-related variables, whilst soil type classification better differentiates thoron exhalation rates and correlated variables. Linear models were developed to predict the radon and thoron exhalation rates of the study area. Distribution maps of radon and thoron exhalation rates (range: E222Rn [0.15–1.84] and E220Rn [475–3029] Bq m−2 h−1) and annual effective dose (with a mean value of 0.84 mSv y−1) are presented. For some parts of the study area, the calculated annual effective dose exceeds the recommended level of 1 mSv y−1, illustrating a significant radiation risk. Airborne radiometric data were found to be a powerful and fast tool for the prediction of geogenic radon and thoron risk. This robust method can be used for other areas where airborne radiometric data are available.
Highlights
IntroductionExposure to natural background radiation (especially radon) is an important environmental issue
Exposure to natural background radiation is an important environmental issue
These two units have lower levels of radon-related values compared to granites with microcline phenocryst, on average soils spatially associated with them exhibited enhanced levels of radon exhalation rates when compared with most other lithological types
Summary
Exposure to natural background radiation (especially radon) is an important environmental issue. As a consequence (and in accordance with EU regulation), most of the developed member states have active radon monitoring programs as part of their National Action Plans. Indoor radon and gamma radiation from primordial radionuclides (i.e., decay products of 238 U and 232 Th and 40 K) are responsible for most of the average annual dose absorbed by humans [1,2]. A natural radioactive gas, is produced via the decay chain of 238 U, 232 Th and 235 U. Inhalation of radon and subsequent emission of radioactive progeny (i.e., 218 Po, 214 Po, 214 Pb, 214 Bi) can cause the irradiation of lung and bronchial tissues, which is associated with a higher risk of developing lung cancer [2].
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