Spatial distribution, radiological risk assessment and positive matrix factorization of gamma-emitting radionuclides in the sediment of the Boka Kotorska Bay

Highlights: • The activity concentrations are correlated with most major elements. • Calcium and silicon are not related to natural radioactivity. • The spatial distribution of technogenic and primordial radionuclides is different. • Four potential sources are apportioned by positive matrix factorization. • Radiological risk is more pronounced in the inland of the bay. Surface sediment from the Boka Kotorska Bay (Adriatic Sea) was analyzed for the content of technogenic cesium (¹³⁷Cs) and naturally occurring (⁴⁰K, ²²⁶Ra, ²³²Th, ²³⁸U) radionuclides. The activity concentrations of the radionuclides have been correlated with the major elements (Si, Al, Ca, Fe, K, Mg, Ti, P, Mn) content of sediment samples. The spatial interpolation identified primordial radioactivity more pronounced in the inland of the bay. Correlation and hierarchical cluster analyses clearly distinguished ²²⁶Ra, ²³²Th, and ²³⁸U from ¹³⁷Cs. In addition, a strong association between primordial radionuclides and most major elements was found. Positive matrix factorization apportioned technogenic and natural radionuclides sources, while Si and Ca were separated from other elements. Radiological hazard parameters (Ra_eq, D, AEDE, H_in, H_ex, AGDE, AUI) that include the doses and indices, and the excess lifetime cancer risk indicate that the risk in the studied area due to gamma radiation is within the acceptable level.