Concentration distributions of radionuclides in sediments along the Romanian sector of the Danube river and the Black sea coast

Concentration distributions of 238U, 232Th, 226Ra, 210Po, 137Cs and 238,239,240Pu in sediment samples, collected along the Romanian sector of the Danube River and the Black Sea coast, indicated the same pattern of accumulation of the radionuclides in the investigated samples. The mineralogical structure of sediment samples investigated by X-ray diffraction on random and oriented slides and the cation exchange capacity determined by the silver-thiourea procedure were used to explain this pattern of accumulation. The clay mineral content of the samples, the type of clay mineral and the geochemical behaviour of the radionuclides are discussed as important factors for a preferential accumulation of contaminants in sediments