78
Peter Stille and Graham Shields
river sediments investigated show Cs concentrations, which are similar to those of
the suspended phases. However, there can be Ia~e variations in concentration
from site to site (Fig. 4.29). Mundschenk (1992) related these variations to grain
size effects (Fig. 4.30). From Fig. 5.30 we can tell that not only 137Cs but also
t~Ru and I~Ce concentrations are strongly dependent on ~ain size distribution in
the sediment. Thus, I~Ce could only be detected in the finest ~ain size fraction of
the sediment. Fine grained sediments are obviously more enriched in these
radionuctides than coarse grained sediments. Other important studies in this vane
are those of Waber et al. (1987) and yon Gunten et al. (1988). These authors
profited from the permanently installed system of investigation wells, which are
located near the river Glair (Switzerland); they have already been discussed in
another connection (Fig. 4.12). Here it was possible to observe the migration
behavior of the radionuclides released from Chernobyl into groundwater systems.
~'
R H I N E
r n
~n-~' . . . . . . . . ~ .......... ' . . . . . . . . . . ' . . . . . . . . . . . . . . .
r . . ~
1986
19~7
19e8
)9e9
1990
1991
10'
10 z
O"
rrl 10"1
0
10-z
10 "~
M O S E L
1986
1967
1986
1989
1990
199!
Fig. 4.~-7. t37Cs activity in unfiltered v.'ater samples from the Rhine and M o s e l rivers
between 1986 and 1991. (Mundschenk 19921