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 137 Cs. 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 ( 214 Bi, 214 Pb), Potassium ( 40 K), and Thorium ( 208 Tl, 212 Bi) decay series radionuclides, with a negligible anthropogenic 137 Cs 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.