Natural radioactivity and radiological hazards in ultrapotassic rocks from the Central Pontides, Türkiye

Primordial radionuclides (²²⁶Ra, ²³²Th, ⁴⁰K) are key contributors to natural radiation and tend to concentrate in specific lithologies in the Earth's crust. This study investigates Upper Cretaceous ultrapotassic rocks from the Central Pontides in Türkiye, where increasing constructional and industrial activities raise concerns about radiological exposure and environmental health risks. Gamma spectrometry analysis of powdered rock samples reveals that ²²⁶Ra (10.0–53.6 Bq/kg) and ²³²Th (9.3–65 Bq/kg) generally fall below global averages, whereas ⁴⁰K reaches notably high levels (97–1940 Bq/kg). Elevated ⁴⁰K levels in trachytic, leucite-bearing, and lamprophyric rocks from Amasya, Tosya, and Kalecik, result in radiological hazard parameters exceeding recommended limits, despite relatively modest ²²⁶Ra and ²³²Th activities. Correlation analyses indicate moderate relationships between ²²⁶Ra and ²³²Th, but weak correlations with ⁴⁰K, suggesting post-magmatic processes possibly influenced these rocks. These findings underscore the importance of ultra- and high-potassic rocks as potential gamma radiation sources in areas where land use, construction, and dust or soil mobilization increase interactions with biological organisms. Continuous monitoring of potassium-40 pathways and the proper management strategies are critical to mitigate possible health risks associated with elevated radionuclide concentrations.