Environmental Engineering Reference
In-Depth Information
of Dissolved Organic Matter with Trace Metal ions in Natural Waters
”
). The transfor-
mation of FCCs to NCCs can be depicted shortly as below (Eqs.
5.1
-
5.4
):
FCCS
+
H
υ →
FCCS
+
+
E
−
(5.1)
E
−
+
O
2
→
O
•−
(5.2)
2
O
•−
2
+
2H
+
→
H
2
O
2
→
HO
•
(5.3)
FCC
+
+
HO
•
→
FCC
−
OH
→
NCC
−
OH
(5.4)
where FCCs upon illumination by light are excited and produce e
−
, (Eq.
5.1
) which
then reacts with aqueous dissolved oxygen to generate O
2
•
−
(Eq.
5.2
). O
2
•
−
then
produces H
2
O
2
and subsequently HO
•
upon several pathways as mentioned earlier
(Eq.
5.3
). The HO
•
radical can then react with FCC
+
to convert it into FCCs-OH
and then into NCCs-OH (Eq.
5.4
). Organic peroxides (ROOH) are produced either
by similar processes or by breakdown of other organic components. They can gen-
erate the organic peroxide radical (RO
•
) and give NCC-OR. These reactions are
extensively discussed in earlier chapters (see chapters
“
Photoinduced and Microbial
dation of chloroplast lysate or leaf extracts can be induced by intrinsic (per)oxidation
with phenolic compounds and H
2
O
2
, and by lipoxygenation with linolenic acid ('oxi-
dative Chl bleaching') (Janave
1997
; Johnson-Flanagan and Spencer
1996
; Adachi et
al.
1999
). Similarly, peroxidase or oxidase activity rise in parallel to the degreening
of seeds or cotyledons in some plants (Johnson-Flanagan and Spencer
1996
; Adachi
et al.
1999
). Therefore, HO
•
•
may play a significant role in the transformation
of FCCs to NCCs in vacuole. Chl breakdown is a prerequisite to detoxify potentially
phototoxic pigments within the vacuoles, to allow the remobilization of nitrogen from
Chl-binding proteins that takes place during senescence (Hörtensteiner
2006
).
On othe other hand, Chl
b
is degraded to chlorophyllide
b
by chlorophyl-
lase, then chlorophyllide
b
is converted to chlorophyllide
a
by 'Chl
b
reductase'
(Schelbert et al.
2009
; Ito et al.
1996
; Folly and Engel
1999
; Scheumann et al.
1999
; Tanaka and Tanaka
2006
; Rüdiger
2003
). The further degradation of chloro-
phyllide
a
proceeds in similar ways as mentioned before.
or RO
6 Chl Acting as Universal Signature of Cyanobacteria
(Algae) or Phytoplankton Dynamics
Chl
a
concentrations are very variable in waters, ranging from 0.0 to 280
μ
g L
−
1
in
streams and rivers, 0.01-850
μ
g L
−
1
in lakes, 0.0-919
μ
g L
−
1
in reservoirs, 0.0-
220
μ
g L
−
1
in estuaries, 0.0-2080
μ
g L
−
1
in coastal and marine waters, and 0.06-
