On the radiocesium carbonate barrier in organics-rich sediments of Lake Juodis, Lithuania

137Cs in Lake Tapeliai, Lithuania

“…However on the other hand, additional sedimentation in eutrophic shallow waters is possible due to the photosynthetic activity of green algae covering the bottom surfaces [22]. Sedimentation rates calculated using reference peaks of radiocesium activity concentrations in its vertical profiles due to Chernobyl deposits were in good agreement with other assessments consistent with the used sediment dating.…”

“…The main reasons for this conclusion were our earlier considerations [22] and the fact that an impact of contaminated air masses from Chernobyl on the area of Vilnius city was too short-term and not followed by precipitation contrary to global fallouts. The effects of Chernobyl deposits can be seen in the vertical profiles of radiocesium activity concentrations in sediment cores as small elevations or a somewhat plateau at sediment depths above the main peak, Figs.…”

“…As it was stated earlier [21], a simultaneous recording of water standard variables (pH, temperature, oxygen concentrations, and conductivity) could highly improve the significance of radiological data. Thus, a long-term permanent study of seasonal variations of the vertical structure and radiological data (on radiocesium) in Lake Juodis (54°46'49'' N, 25°26'29'' E) made it possible to determine that carbonate deposits, which were formed in shallow areas of the lake, were acting as a radiocesium barrier [22]. Further, it became possible to evidence that in autumn and winter a thermodynamic mechanism was responsible for the enrichment in radiocesium of the near-bottom water of the lake [23].…”

VARIATION OF SPECIFIC ACTIVITY OF137Cs IN THE BOTTOM GROUND OF WATER RESERVOIRS AND WATERSIDE SOIL IN VILNIUS CITY, LITHUANIA

“…4 was obtained from the bottom sediment samples collected from a depth of 3.9 m. Using the Gaussian formula for vertical profiles slopes of radiocesium specific activity of the bottom sediments (below the peak of the profile), it was found that characteristic half-widths of these slopes vary in the range 3.4-4.5 cm. Compared with the primary vertical profile, these small shifts in the shape of slopes formed during the fast phase of radiocesium free-ion diffusion [8,9]. This show limited possibility of radiocesium migration to deeper sediments under these conditions.…”

“…This enables to estimate the sedimentation rate, which is equal to 0.37 cm year -1 . By analogy with the previous measurements of radiocesium vertical distribution in bottom sediments [8], the maximum values of radiocesium specific activity are assigned to the moratorium period of nuclear explosion (1963). Vertical profiles of radiocesium specific activity of the bottom sediments taken from the deepest part of the lake Lydekinis are described by the highest specific activity values of bottom sediments near the surface (Fig.…”