Preferential Flow and Migration Zones in Geological Environment - Groundwater Vulnerability: Chernobyl Nuclear Disaster - page 56

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Cations (mg/l) Anions (mg/l)

Depression center Background area

Figure 3.14 Comparison of the chemical composition of groundwater of the upper aquifer
in the depression central active and background zones by data from the observation plot
Liutezh (Kyiv region, sampling performed in October 2006).

radionuclides from the watershed area to the central depression part and their
further penetration into groundwater. In the central active parts of some depressions
the Chernobyl-born radionuclides 137 Cs and 90 Sr were found in rock samples even at
depths significantly below the groundwater table. For example, at the Veresok site in
the CEZ the radionuclides were found at a depth of 17 m, and the groundwater table
depth was 4 m. At the corresponding background area the depth of radionuclide
penetration did not exceed 6 m. Generally, within the Kyiv region the radionuclides
were found at depths of 100 m and deeper [ Shestopalov , 2001].
The surface postaccident contamination with radionuclides ( 90 Sr and 137 Cs) in
the CEZ reached values up to 10 6 Bq/m 2 , and in the Kyiv region contamination
was up to 10 4 Bq/m 2 . The comparison was performed of the intensities of vertical
radionuclide transport in the central active and background parts of depressions.
For this purpose the rock samples were taken in pits to a depth of 1 m and ana-
lyzed in the radiochemical laboratory for radionuclide concentrations. The
obtained vertical concentration distributions for 90 Sr (depression of “Veresok”
observation plot, CEZ) and 137 Cs (“Liutezh” observation plot, Kyiv region) for
depression central zones and corresponding background sites are shown on