2o
The distribution of different oxidants in Fig. 4.2 displays the relative depth where
they are consumed. The vertical sequence coincides with the thermodynamic
principle. As the mineralization of organic matter is mainly biologically catalyzed and
releases energy and nutrients for production of biomass, organisms with more energyyielding metabolism succeed in competing with organisms with less energy-yielding
metabolism (Froelich et al. 1979, Berner 1980). However, a significant boundary
between oxic, suboxic, and anoxic zone described by Froelich et al. (1979) was not
found in the sediments at Lauffen. The mixing of the different zones would be caused
by a much higher input of organic matter compared to marine sediments.
0
20
4O
E
80
0
2
4
6
0
. . . . .
~ 20
4O
6O
9
Elsenz
80
0
2
4
6
a. Neckar River
O| |
; .......
"-Tt
2 . . . .
ill
t
z .......................
0
:~ ....
;; : ........
Kochendorf
80
o
2
4
i
b. tributaries
0
20 ~
4O
8
0
2
4
6
8
~nz
80:
8
0
2
4
6
8
Corg. (%)
Fig.43. Vertical distribution of Corg. in the sediments of the Neckar River and its tributaries
During the mineralization of orgy_ ic matter, organic P bound to biomass was also
released into the porewater as PO4 " (Fig. 4.2g). In addition, inorganic P adsorbed on
Fe/Mn oxide was also released with the reduction of Fe and Mn oxides. This may lead