B. Sulzberger
Table 3.1. Various pathways of H02·IOi· formation via photochemical reactions of eDOM
Intermolecular electron transfer from eDOM in its excited triplet state to O 2 (Haag and Mill 1990):
3 ·
+
-
eDOM +02 ~eDOM +Oi
Intramolecular electron transfer within eDOM in its excited singlet state and subsequent reaction of
the thereby formed biradical with 02 (Blough and Zepp 1995):
eDOM· ~ eDOM±
H-atom abstraction or homolytic bond cleavage of singlet excited eDOM, followed by reaction of the
radical with O 2 under formation of peroxyl radicals, and subsequent HOi abstraction (Blough and
Zepp 1995):
' COOM' ~ COOM- + H· (R·)
COOM-+ 02~ eDOMOO·
eDOMOO·~ H0 2 · + eDOM ox
Formation of solvated electrons (Zepp et al. 1987; Bruccoleri et al. 1993) and subsequent reaction
with 0 2:
hv
+ -
eDOM~ eDOM +e aq
H20 + CO2
Euphotic
Zone
+ NOi + Pot + Fe·
Photosynthesis
Primary Production
Thermocline
(-200m)
Deep Ocean
Hp + CO 2
} ____ - -
+ NOi + Pot + H!.
Respiration
Decomposition
>90%
Respiration
Decomposition
Organic
Carbon
Sedimentation
4
Sedimentation
<10%
7 Sediment 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 I I 7 I I I 7 I I I
Fig. 3.1. Fate of carbon in the oceans. Numbers are carbon fluxes in Gt yr- 1 (modified from Hohmann
et a1.1990)