Abstract
The aim of this work was to calculate the values of the 234U/238U activity ratio in natural environment (water, sediments, Baltic organisms and marine birds from various regions of the southern Baltic Sea; river waters (the Vistula and the Oder River); plants and soils collected near phosphogypsum waste heap in Wiślinka (Northern Poland) and deer-like animals from Northern Poland. On the basis of the studies it was found that the most important processes of uranium geochemical migration in the southern Baltic Sea ecosystem are the sedimentation of suspended material and the vertical diffusion from the sediments into the bottom water. Considerable values of the 234U/238U are characterized for the Vistula and Oder Rivers and its tributaries. The values of the 234U/238U activity ratio in different tissues and organs of the Baltic organisms, sea birds and wild deer are varied. Such a large variation value of obtained activity ratios indicates different behavior of uranium isotopes in the tissues and organisms of sea birds and wild animals. This value shows that uranium isotopes can be disposed at a slower or faster rate. The values of the 234U/238U activity ratio in the analyzed plants, soils and mosses collected in the vicinity of phosphogypsum dumps in Wiślinka are close to one and indicate the phosphogypsum origin of the analyzed nuclides. Uranium isotopes 234U and 238U are not present in radioactive equilibrium in the aquatic environment, which indicates that their activities are not equal. The inverse relationship is observed in the terrestrial environment, where the value of the of the 234U/238U activity ratio really oscillates around unity.
Highlights
Natural uranium consists of three alpha radioactive isotopes: 99.2745 % of 238U, 0.7200 % of 235U, and 0.0054 % of 234U [1, 2]
The aim of this work was to calculate the values of the 234U/238U activity ratio in natural environment (water, sediments, Baltic organisms and marine birds from various regions of the southern Baltic Sea; river waters; plants and soils collected near phosphogypsum waste heap in Wislinka (Northern Poland) and deer-like animals from Northern Poland
The values of the activity ratio in the pore water samples from the southern Baltic ranged from 1.17 ± 0.03 to 1.18 ± 0.03 and are consistent with the value recorded for the Baltic waters (Table 1; Fig. 2) [31, 32]
Summary
Natural uranium consists of three alpha radioactive isotopes: 99.2745 % of 238U, 0.7200 % of 235U, and 0.0054 % of 234U [1, 2]. Uranium isotopes 234U and 238U are not present in radioactive equilibrium in the natural environment, which indicates that their activities are not equal. There are several reasons for the radioactivity disequilibrium: radioactive decay energy, related to the secretion of a particles with nuclei of atoms, causes a ‘‘kickback’’ to the newly created isotopes for distance 10-7–10-6 cm from sites in the crystal lattice occupied by atoms of the isotope 238U output. The 234U atoms are less related to the structure of minerals than the 238U atoms, and easier to diffuse to the surface of mineral grains and the cracks.
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