Use of γ-spectrometry for the evaluation of radioactive pollution of water systems of Lithuania

Full text: After the Chernobyl Power Plant accident water systems of Lithuania were polluted by the artificial radionuclides from the 4th reactor. During 1987-1994 137Cs concentrations were evaluated in the sediments of the Lithuania part of the Baltic Sea (up to ∼ 450 Bq/kg), Klaipeda strait (up to ∼ 300 Bq/kg), Curonia Gulf (up to ∼ 190 Bq/kg) and of number of radionuclides accumulation zones of Neris and Nemunas rivers (up to ∼ 120 Bq/kg, sediments dr. w.). 137Cs concentrations in diluted from in the Baltic Sea water are measured up to ∼ 100 Bq/m3, in the Curonian Gulf - up ∼ 2,6 Bq/m3. In summer total 137Cs concentration in the water of Nemunas river is up to ∼ 20 Bq/m3 and in the Neris river - up to ∼ 10 Bq/m3. Extreme 137Cs concentration in Neris river water in 1992 fall (due to the devastation of the accumulation zones) was measured up to 600 Bq/m3. Suspended matter 137Cs partition coefficients in rivers water were measured in the range 5-95 m3/kg. Maximal values of these coefficients were found for the phytoplankton in the Curonian Gulf (up to 720 m3/kg). Contemporary 137Cs pollution of the main Lithuanian rivers Nemunas and Neris was found to be relative with the radionuclide transport through the boundary of Byelorussia and domestic 137Cs runoff from the Lithuanian watersheds. Measured values of the 137Cs runoff modulus of the Lithuanian watersheds (1.0 · 10-3 - 2.2 · 10-3) in 1993 are in good agreement with contemporary published ones. All samples (sediments, radiochemically treated water and suspended matter) were analyzed for 137Cs in a standard geometry (plastic box, volume ∼ 100 cm3) using Ge(Li)-detector coupled to a multichannel (1024) analyzer calibrated by 137Cs standards of Russian Scientific Research Institute of Physical Technical and Radiometrical Measurements (Moscow). (author)