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 (E²²²_Rn) and thoron (E²²⁰_Rn) 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: E²²²_Rn [0.15–1.84] and E²²⁰_Rn [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.

E3S Web of Conferences, open access proceedings in environment, energy and earth sciences

Submarine groundwater discharge (SGD) is a major yet often overlooked driver of coastal carbon cycling. We examined two contrasting coastal basins: a bay dominated by karstic groundwater discharge and a fjord influenced by riverine inputs in the west coast of Ireland. Radioisotope-based (Ra and Rn) models and seasonal measurements were used to quantify water and carbon fluxes. We hypothesize that high-alkalinity groundwater from karstic aquifers delivers elevated dissolved carbon (DIC and DOC) and modulates air-sea CO2 exchange and carbon outwelling to the ocean. We further assess whether groundwater inputs act to buffer or intensify coastal acidification along the land–ocean continuum, providing new insights into how groundwater chemistry regulates carbonate equilibria and CO2 dynamics in contrasting coastal environments. Groundwater discharge was about 30% lower than river discharge yet contributed ~34 times more DIC (899 ± 453 vs 26 ± 22 mmol m2 d-1) and similar DOC fluxes (62 ± 31 vs 65 ± 51 mmol m2 d-1, respectively) to the coastal basins. Rivers (TA/DIC = 0.5 ± 0.2) showed a stronger acidifying effect than groundwater (TA/DIC = 0.9 ± 0.1) due to the strong buffering capacity of karst aquifers derived from carbonate dissolution. Bicarbonate outwelling from the coastal basins to the ocean and CO2 emissions to the atmosphere from the SGD influenced bay (155 ± 63 and 155 ± 121 mmol m2 d-1, respectively) exceeded those from the river fed fjord (87 ± 109 and 67 ± 33 mmol m2 d-1), highlighting the disproportionate role of groundwater-derived alkalinity in regulating carbon fluxes across the land-ocean interface.