Lithological control of natural radioactivity in Baltic coastal sands and implications for pre-operational radiological monitoring

Abstract

Abstract Natural radioactivity in coastal sediments reflects both geological provenance and sedimentary processes, and its quantification is essential for environmental monitoring in areas of planned nuclear infrastructure. This study establishes pre-operational baseline levels of 40 K, 226 Ra and 232 Th in coastal sands of the southern Baltic Sea prior to nuclear power plant construction. Fifteen samples collected along an east–west transect were analysed by gamma spectrometry, and radiological hazard indices were calculated. Activity concentrations ranged from 120 to 322 Bq kg −1 for 40 K, 2.3–12.0 Bq kg −1 for 226 Ra and 1.9–8.7 Bq kg −1 for 232 Th. Multivariate analysis revealed clear spatial differentiation between a barrier–embayment sector enriched in 226 Ra and 232 Th and a moraine-dominated sector characterized by higher 40 K. Principal Component Analysis explained 88.6% of total variance, indicating strong lithological control, while a significant 226 Ra– 232 Th correlation (R 2  = 0.896) suggests a common mineralogical carrier. All radiological indices remained below recommended limits, confirming the low-background nature of the sediments. Comparison with global data shows that the studied sands fall within the lower range of quartz-dominated coastal systems and lack heavy-mineral enrichment. The results provide a robust baseline for future radiological monitoring in dynamic glacial coastal environments.