PLUTONIUM CONTENT IN BLACK SEA SEDIMENTS AND ALGAE

摘要

The content of Pu, ~(238)U, ~(232)Th, ~(226)Ra and ~(137,134)Cs in Black Sea bottom sediments was determined by alpha and gamma spectroscopy for five seasons. The obtained data show that radionuclide concentrations strongly depend on the sediment nature: results for sandy sediments are within close range, while those for mud and silt vary to a much greater extent. Two types of algae were studied alpha spectrometrically for Pu, U, Th, ~(226)Ra and ~(210)Po content. The obtained values for Pu are in the lower limits of literature data which is quite clear as there are no plutonium discharge facilities at the Bulgarian Black Sea coast. The obtained values for the activity ratio ~(238)Pu/~(239+240)Pu are higher for Bjala sediments compared to those of Kaliakra. The ratio values are out of the variation range for the global contamination with weapon tests fallout plutonium which is probably due to Chernobyl accident contribution. The dependence of natural nuclide content on the sediment type as well as the variation of nuclide accumulation for two types of algae in two sampling location for five consecutive seasons is evaluated. No serious contamination with natural radionuclides in the algae is observed.