Identification and characterization of gamma radiation anomalies along the Trieste–Panarea routes aboard R/V Laura Bassi

Objective: This study aimed to identify, characterize, and determine the origin of semi-persistent gamma radiation anomalies in the Adriatic Sea along the Trieste-Panarea transect, establishing a high resolution radiometric baseline and assessing the influence of environmental parameters.Methods: In situ gamma-ray spectrometry was conducted using an RS-250 NaI(Tl) detector aboard the R/V Laura Bassi during four research cruises, covering a total distance of over 2500 nautical miles. The spectrometer was configured with 1024 energy channels with range 3 keV and provided a resolution of 6-7% at the 662 keV photopeak of 137Cs. More than 4000 recordings of the total gamma-ray count rate and full-spectrum data were collected. These radiological data were precisely synchronized and correlated with contemporaneous bathymetric, wind speed, air temperature, and humidity data.Results: Three persistent anomaly regions were identified in the Central Adriatic, Southern Adriatic, and Strait of Otranto, with peak total counts per 10-minute sample of 34,659, 76,854, and 32,415, respectively. Spectral analysis revealed these are primarily sourced from natural Uranium (214Bi, 214Pb), Potassium (40K), and Thorium (208Tl, 212Bi) decay series radionuclides, with a negligible anthropogenic 137Cs contribution. Correlation analyses showed weak relationships with environmental variables (R² < 0.25 for wind, temperature, humidity, depth), confirming the anomalies are not artifacts of atmospheric or surface conditions but are linked to seabed processes.Conclusion: The identified anomalies are natural features resulting from the oceanographic focusing of clay-rich, radiogenic sediments in specific depositional zones. This work provides a validated methodological inspection framework and a critical baseline for future geophysical mapping, environmental monitoring, and radiological assessment in the research cruises.