61
E
r,r
e-.N
0
40
60
8 0 ~
0
o I
20
:I
801
0
~
so[
1t30 2OO 300 400 500 0
Elscnz
100 2(10 3 ~ 4 ~ 5C)0 0
a. Neckar River
0 D
20
40
6O
Kochendorf
'~oo 2oo 360 ~o 5oo 800
b. tributaries
W
100 200 300 400 500
Pb (mg/kg)
Wieblingen
100 200 300 400 500
Fig. 4.27. Pb in the sediments (< 20 lam) of the Neckar River and its tributaries
In most porewater samples dissolved Pb was below the detection limit (2.5 riM). In
the samples near the sediment-water interface, Pb concentrations varied frorp 2.5 nM
to 6.1 nM, distinctively lower than international standard for drinking water (240 riM).
The solubility calculations indicate that PbS in these samples is supersaturated (3.6
< S1 < 4.8):
Pb 2+ + HS" --~ PbS ,1, + H +
The precipitation of PbS and the coprecipitation of Pb with FeS are also supported
by the strong reduction of SO42" in the sediments and the depletion of dissolved Pb in
the porewater.
E
r,r
e-.N
0
40
60
8 0 ~
0
o I
20
:I
801
0
~
so[
1t30 2OO 300 400 500 0
Elscnz
100 2(10 3 ~ 4 ~ 5C)0 0
a. Neckar River
0 D
20
40
6O
Kochendorf
'~oo 2oo 360 ~o 5oo 800
b. tributaries
W
100 200 300 400 500
Pb (mg/kg)
Wieblingen
100 200 300 400 500
Fig. 4.27. Pb in the sediments (< 20 lam) of the Neckar River and its tributaries
In most porewater samples dissolved Pb was below the detection limit (2.5 riM). In
the samples near the sediment-water interface, Pb concentrations varied frorp 2.5 nM
to 6.1 nM, distinctively lower than international standard for drinking water (240 riM).
The solubility calculations indicate that PbS in these samples is supersaturated (3.6
< S1 < 4.8):
Pb 2+ + HS" --~ PbS ,1, + H +
The precipitation of PbS and the coprecipitation of Pb with FeS are also supported
by the strong reduction of SO42" in the sediments and the depletion of dissolved Pb in
the porewater.