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Cephalonia Island, located in western Greece, is characterized by complex geological and tectonic conditions associated with the active Cephalonia Transform Fault Zone (CTFZ), and lies at the boundary between the Paxos (Pre-Apulian) Zone and the Ionian Zone (Lekkas, 1996). The Paxos Zone is mainly characterized by relatively undeformed carbonate platform formations consisting predominantly of limestones and dolomites, whereas the Ionian Zone includes carbonate sequences overlain by flysch deposits and affected by intense folding and thrusting (Zoumpoulis et al., 2010). The tectonic regime of Cephalonia is controlled by active fault systems associated with regional strike-slip deformation and the Ionian thrust front, resulting in extensive faulting and fracturing across the island (Brooks et al., 1984). These structural discontinuities significantly enhance rock permeability and facilitate radon migration through fault zones and fracture networks from the subsurface to the atmosphere (Su et al., 2021). The present study investigates the spatial variability of soil radon exhalation rates across Cephalonia Island and examines their relationship with lithology and tectonic structures.
Ιn situ radon exhalation measurements were conducted at selected locations representing different geological formations and structural settings. The accumulation chamber method was applied using AlphaGUARD, a portable radon detector (Ouzounis, Kaissas, 2024). Radon concentration was recorded with a sampling interval of 10 minutes, over a total duration of 2 hours. The exhalation rates were derived from the linear fitting of concentration’s raise versus time. The quality of each measurement was assessed using the coefficient of determination (R²) of the linear fit.
The measured radon exhalation rates show significant spatial variability across the study area. The lowest value was recorded at Lixouri (61 Bq m⁻² h⁻¹), while the highest value was observed at Chavdata (664 Bq m⁻² h⁻¹). Elevated radon exhalation rates were mainly associated with fractured carbonate formations and areas located near active fault zones. Intermediate values were measured in locations characterized by compact limestones or partial sedimentary cover. The high R² values obtained for most measurements indicate a good linear fit and reliable estimation of exhalation rates. The study provides preliminary data for radon potential assessment on Cephalonia Island and contributes to a better understanding of radon behavior in relation to lithology and structural features. Such information is important for environmental monitoring and for evaluating radon-related hazards in seismically active regions.
Lekkas, E. (1996). Neotectonic map of Cephalonia and Ithaca. National and Kapodistrian University of Athens
Zoumpoulis, E., Pomoni-Papaioannou, F., & Zelilidis, A. (2010). Studying in the Paxos Zone the carbonate depositional environment changes during Upper Cretaceous, in Sami area of Kefallinia Island, Greece. Bulletin of the Geological Society of Greece, XLIII(2), 793–801
Su, C., et al. (2021). Radon migration in fault zones and its relationship with tectonic activity. Journal of Environmental Radioactivity
Ouzounis, A. & Kaissas, I. (2025). A Review of Methodologies for Measuring Geogenic Rn Exhalation. HNPS Advances in Nuclear Physics, Vol.31