4 Results and discussion
4.1 Early diagenesis in the sediments of the Neckar River and its tributaries
4.1.1 Decomposition of organic matter by different oxidants
2 +
Porewater Mn , NO3-, Fe 2+, SO42-, NH4 +, alkalinity, PO43", pH,
and
conductivity profiles in the sediments at Lauffen are shown in Fig. 4.2. They
demonstrate anaerobic decomposition of organic matter below the sediment-water
interface.
Particles sinking to sediments include particulate organic matter (POC), ferric
oxides, carbonates, and silicates (Sigg 1986). On the sediment surface, these particles
are often resuspended by hydrodynamic forces or biological activities, before they
finally become part of the sediment.
hlt
J
atmosphere
ai!-.~le,
mlerlace
- ~] gas ~c~Jdge . . . .
w~et - -
hv
(volat01e forms)
C02. H20, nutrients "-"e
fp
rimar T production
1.. IdSOr#fxOa Onto
~_~suspended I~hcles.
f l o w / n
~ " ~ 1 ~ . ~ v / , , / o n
f l o w o u t
of par~acles
1""!
!
osorpt,o~ J
9 **
|
benlhk: boundary
*ft~scspeas,on ;'~ mte[,n.f
la;er
Io! pa/toctes ~, ;or pat.cles
l
((" ~ . - -
,!~,a,s,,.
"o.
partite rnezonf
mgantsms
Fig. 4.1. Transport processes near the sediment-water interface (Santschi et al. 1990)