Chernobyl-Born Radionuclides In Geological Environment - Groundwater Vulnerability: Chernobyl Nuclear Disaster - page 27

and loams. Depression landforms are absent or very rare. Linear forms dominate,
such as gullies and ravines, especially deep in the side part of the Dnieper Upland.
Central areas on the right bank of the Dnieper have reduced smoothed ter-
rain, loamy sod-podzolic soils, and sandy-loamy composition of the aeration
zone. Depressions forms are available here.
Northern and eastern regions of the left bank of the Dnieper are related to
the sandur outwash plains of Ukrainian Polesye and first-second terraces of the
Dnieper and Pripyat [ Shestopalov , 2001].
Characteristic for the sandur plains are water-glacial, aeolian, and partially
glacial deposits with sandy, loamy-sandy, and sandy-loamy composition. Their
surface is mainly represented by aeolian positive (swells, elongated sandy ranges,
cirques with relative elevation 5-12 m) and negative (sinks, interrange cauldrons,
coombs) relief forms. Less characteristic are ancient forms of relief such as
humps, hills, and depressions of preglacial and glacial origin. With increasing dis-
tance from the Pripyat and Uzh rivers toward the watershed, the surface of san-
dur plains becomes more flat. The absolute elevation of sandur plains ranges
from 120 to 140 m, and the average density of erosion network is about 0.2 km/
km 2 . Because of the low-developed erosion (drainage) network, light mechanical
composition of soil cover, and large number of closed low-runoff areas, the area
is characterized by low surface runoff which slightly increases from west to east.
Terraces of the Dnieper and Pripyat are also plains. Their alluvial deposits
consist of interbedded sands with different grain size and sandy loams. The
depressions are widely spread here, especially in the eastern part of the territory
on the terraces of the Dnieper.
The hydrogeological conditions of the study area (Kyiv region and the CEZ)
are characterized by the presence of four principal aquifers (water-bearing
complexes): (1) Quaternary (depth to 30m), (2) Eocene (depth to 100m), (3)
Cenomanian-Callovian (depth to 150 m), and (4) Bajocean (depth to 280 m).
The Quaternary aquifer is related to the recent alluvial deposits of floodplains
and river beds, alluvial and lacustrine deposits of the first and second floodplain
terraces, and fluvioglacial, lacustrine-glacial, and lacustrine-alluvial deposits.
The deposits are represented by quartz sands of different grain size often interlaid
with loamy sands, sandy loams, and clays. This aquifer is of general occurrence
over the studied area. It is underlain by a low-permeable layer of Neogene red
clay and in the places of its absence by water-bearing sandy Oligocene-Pliocene
deposits.
The Eocene water-bearing complex is of general occurrence over the area.
The deposits are composed of quartz sands. At the base of the Eocene aquifer,
the Upper Cretaceous marl-chalk layer is present, being the regional low-
permeable bed. Almost over the whole territory the Eocene aquifer is overlain by
a low-permeable layer of Kyiv suite composed of marl and siltstone. The water
head above the top of the aquifer ranges from 8 to 50-80 m. In the late 1960s a
depression cone in the groundwater levels was formed around Kyiv City caused