Environmental Engineering Reference
In-Depth Information
in structural rigidity that inhibits the internal conversion, thereby leading to an increase
in fluorescence; (x) an increase in the solution redox potential, which enhances fluo-
rescence; and (xi) the concentrations of solutes in aqueous media that would normally
cause the fluorescence intensity to decrease when concentration is high.
External factors are: (xii) pH, considering that the fluorescence intensity mark-
edly increases with increasing pH;
(
xiii) exposure of the fluorophores to an heat
source, where increasing temperature causes fluorescence quenching; (xiv) com-
plexation of metal ions with florophores of an organic molecule which can change
the fluorescence intensity of that flurophore either enhanced or quenched compared
to the original fluorescent DOM (see also chapter
“
Complexation of Dissolved
Organic Matter with Trace Metal ions in Natural Waters
”
) (Wu et al.
2004a
,
2004b
,
2004c
; Smith and Kramer
1999
; Ohno et al.
2007
; Fu et al.
2007
; Zhang et al.
2010
; Manciulea et al.
2009
; Mounier et al.
2011
); (xv) inter- and intramolecular
fluorescence quenching of the florophores in organic substance in the presence of
other organic components (Marmé et al.
2003
; Sun et al.
2012
); (xvi) any changes
in the molecule upon photoinduced or microbial degradation processes can alter its
fluorescence properties, such as peak position and fluorescence intensity (Mostofa
et al.
2009a
; Senesi
1990a
; Wu et al.
2004a
). Light exposure can induce in a sub-
stantial decrease in the loss of fluorophore binding sites and the stability con-
stant (Wu et al.
2004a
; Kulovaara et al.
1995
; Bertilsson and Tranvik
2000
); and
(xvii) any changes in the molecule upon microbial degradation processes can
alter its fluorescence properties, such as peak position and fluorescence intensity
(Mostofa et al.
2009a
,
2007a
,
2005b
; Senesi
1990a
; Moran et al.
2000
).
2.2 Fluorescent Dissolved Organic Matter (FDOM)
and its Characterization Using EEM Spectroscopy
Fluorescent dissolved organic matter (FDOM) is operationally defined as the dis-
solved organic matter (DOM) fraction that shows significant fluorescence efficiency
or intensity at a particular excitation-emission wavelength (Mostofa et al.
2009a
).
The FDOM species that are commonly detected in aqueous solution are summarized
in Table
1
(Senesi
1990a
; Coble et al.
1990
,
1998
; Coble
1996
,
2007
; Mayer et al.
1999
; Parlanti et al.
2000
; Yamashita and Tanoue
2003a
; Mostofa et al.
2005a
,
2010
;
Mostofa KMG et al., unpublished data; Mostofa and Sakugawa
2009
; Komaki and
Yabe
1982
; Schwede-Thomas et al.
2005
; Nakajima
2006
; Baker
2005
; Zhang et al.
2010
; Sugiyama et al.
2005
; Liu and Fang
2002
; Provenzano et al.
2004
; Lu and
Allen
2002
; Moberg et al.
2001
; Determann et al.
1998
; Matthews et al.
1996
; Baker
and Curry
2004
). They are humic substances (fulvic and humic acids) of vascular
plant origin, marine humic-like compounds, autochthonous fulvic acids of algal ori-
gin, derived from photoinduced and microbial assimilation of lake algae, aromatic
amino acids (tryptophan, tyrosine and phenylalanine), proteins, diaminostilbene-type
(
DAS1) and distyryl biphenyl (DSBP) fluorescent whitening agents (FWAs), other
components of household detergents, and chlorophyll (Table
1
).
