Environmental Engineering Reference
In-Depth Information
of algal biomass, which was collected through filtration of surface lake waters
(~0 m) of Lake Hongfeng (China) using GF/F filters during the summer sea-
son (Mostofa et al.
2009b
). One generally observes high fluorescence intensity
in deeper lake or oceanic environments (Hayase et al.
1987
,
1988
; Hayase and
Shinozuka
1995
; Mostofa et al.
2005b
), which might be the effect of microbial
release of FDOM.
Studies on phytoplankton shows that fulvic-like and protein-like fluorescent
components are released during the cultivation of three kinds of phytoplankton
(
Microcystis aeruginosa
and
Staurastrum dorcidentiferum
of green algae and
Cryptomonas ovata
of dark-brown whip-hair algae collected from lake waters)
under a 12:12 h light/dark cycle in an MA medium and an improved VT medium
at 20 °C (Aoki et al.
2008
). The results demonstrate that produced new DOM
from three phytoplanktons can exhibit the different Ex/Em fluorescence properties
whereas
Microcystis
can produce the hydrophilic DOM fraction with fluorescence
peak at Ex/Em
=
340/430 nm (peak C) and Ex/Em
=
260/445 nm (peak A) whilst
hydrophobic acid (or autochthonous fulvic acids) fraction at Ex/Em
=
330/440 nm
and 250/455 nm. These two fractions also show the protein-like peak at Ex/
Em
=
290/335 nm and 280/350 nm (peak T) and the autochthonous fulvic acid
(M-like) at 320/385 nm and 330/385 nm (peak C-region), respectively (Table
2
)
(Aoki et al.
2008
). Correspondingly,
Staurastrum
can produce hydrophilic DOM
fraction at Ex/Em
=
340/420 nm and 280/425 nm and hydrophobic acid fraction
at Ex/Em
=
340/435 nm and 290/430 nm whereas these two fractions display
merely the protein-like peak at Ex/Em
=
270/375 nm and 290/365 nm, respec-
tively and do not show any autochthonous fulvic acid (M-like) fluorescence
(Table
2
) (Aoki et al.
2008
). Finally,
Cryptomonas
can produce the hydrophilic
DOM fraction at Ex/Em
=
350/440 nm and 280/440 nm and the hydrophobic acid
fraction at Ex/Em
=
350/440 nm and 290/450 nm whereas these two fraction also
exhibit the protein-like peak at Ex/Em
=
270/355 nm and 270/350 nm, respec-
tively and do not exhibit the autochthonous fulvic acid (M-like) fluorescence
(Table
2
) (Cammack et al.
2004
). Similarly, cultivation of three kinds of phyto-
plankton (
Prorocentrum donghaiense, Heterosigma akashiwo
and
Skeletonema
costatum
collected from sea water) can produce the visible humic-like (C-like and
M-like) and the protein-like or the tyrosine-like components in waters (Zhao et al.
2009
,
2006
). Therefore, production of the autochthonous DOM is largely depend-
ent on the phytoplankton communities in natural waters.
3.2 Photodegradation of FDOM in Natural Waters
Photodegradation can sequentially change the optical properties (fluorescence
peak and fluorescence intensity) of FDOM in waters. Photodegradation can
change the fluorescence peak position (Ex/Em) of various FDOM components in
waters (Mostofa et al.
2005a
,
2010
,
2007b
,
2011
; Moran et al.
2000
; Miller et al.
2009
). For instance, photodegradation can alter the terrestrial fulvic acid (C-like)
