73
for the mobility of heavy metals in sediments (F6rsmer et al. 1990; Catmano et al.
1992).
-I0
0
20
,.-, 40
v
8 0 .
6
9 ~- -I0
.~
o
2o
40
60
$
Lauffea 9
7
t
El~nz
80
-IC
0
20
40
60
gO
9
6
-!0 i
ot
i
20I
401
601
9
6
9 . Necl~r River
Kocher~orf
'
i
7
b. lrlbutlrk~
7
g
pH
-10
0
20
4O
60
8O
9
6
-I01
I]
2Ol
I
401
I
I
601
I
80 !
9
6
Wieblin8~
Schwur'~aeh
7
Fig. 4.34. The pH values in the porewater of the Neckar River and its tributaries
In the Neckar River and its tributaries, pH values varied from 7.3 to 8.2 (Fig. 4,34),
they were always higher than 4.5. It is then necessary to assess the buffer capacity of
the sediments.
For an estimation of sediments regarding theu" acid potential which can be
produced by the oxidation of su|fide compounds, the Acid Producing Capacity (APC)
and the Acid Neutralizing Capacity (ANC) are a useful tool. The important reactions
affecting pH values in sediments are as follows (Calmano et al. 1992):