59
1981, 1986; MOiler et al. 1993). Inspite of a significant decrease of the heavy metal
pollution, the sediments are still moderately to strongly polluted in respect to Cd in the
younger sediment layer. New studies of the sediment assessment show that the
concentrations of particulate Cd remained constant or increased slightly compared to
1985 (MOiler et al. 1993). This can be attributed to the resuspension and transport of
the old sediments by hydrodynamic forces such as flood, which frequently occurs in
the drainage area of the Neckar River.
a. N e c k a r R i v e r
0
40
E 6O
80
~
o
r,_
~ 20
40
60
Kochendorf
_
80t
20 40 60 80 100 0 1'0 20 30 40
2'0 40 60 80 100
r
b. tributaries
Elsenz
z
80
0
2 4
6
8 10 0 20 40 60 80 100
0~
20
80
50 0
Wieblingen
Cd ( m g / k g )
Fig. 4.26. Cd in the sediments (< 20 lain) of the Neckar River and its tributaries
In contrast to the high contents of Cd in solid phase, dissolved Cd could only be
detected in some samples in the uppermost layer of the Neckar River sediments
(Table.4.3). The concentrations of the dissolved Cd were lower than international
standard for drinking water (44 nM, WHO). The dissolved Cd appears to be rapidly