Abstract
Presented are results on the Pu and Th isotopes activity concentration found in the upper part of bottom sediments collected from a deep part of 29 lakes in N-E Poland by diving in 2000. Analyses of Pu isotopic ratios allowed for the discussion of Pu origin. Maximum percentage of 239+240Pu activity from Chernobyl fallout was 24%. Surface deposition of 239+240Pu was calculated. No relationship was found between the plutonium and main chemical matrix components of sample nor with the trophic status of the lake. Pu activities were weakly correlated with measured previously 137Cs activities.
Highlights
Study on the plutonium concentration in forest litter [1,2,3] conducted on the area of North-Eastern Poland, especially in Augustow Primeval Forest, showed the significant deposition of Chernobyl plutonium on some areas there
Assumed 238Pu to 239,240Pu activity ratio in global fallout was equal to 0.03, and that for Chernobyl fallout was taken equal to 0.50, from 0.55 in fresh fallout, the percentage Fo of Chernobyl plutonium can be calculated [1] as follow: Fo 1⁄4
The men value is 19 Bq/m2 with standard deviation of 15 Bq/ m2. This suggested, that majority (60–70%) of plutonium was situated deeper in the sediment profiles. This was in a good consistency with results for Swedish lakes [12], where the maximum of Pu deposition was at about 3 cm, and whole deposit was in fist 6 cm of sediment
Summary
Study on the plutonium concentration in forest litter [1,2,3] conducted on the area of North-Eastern Poland, especially in Augustow Primeval Forest, showed the significant deposition of Chernobyl plutonium on some areas there. After performing analyses for all 29 lakes the 10 lakes for which additional profile taken close to first one was available (Białe Wigierskie, Gaładus, Garbas, Guzki, Płaskie, Rogale Duz_e, Sawinda Wielka, Sumowo, Toczyłowo, Zawadzkie) we did repeated analyses for plutonium using more than one layer. Those samples were sliced in 2 cm thick layers. Three slices were obtained, in two cases collected material allowed to use only two samples and in one case four layers were obtained This repeated analyses were performed for determination of alpha emitting plutonium isotopes only. For quality assurance a reference material IAEA 300 Baltic Sea sediment [7] was analysed as well
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