Environmental Engineering Reference
In-Depth Information
peaks at Ex/Em
=
260/380-460 nm (Peak A) and 350/420-480 nm (Peak C),
marine humic-like (recently called photobleached fulvic-like) at 312/380-420 nm
(Peak M) and two protein-like peaks, i.e., tryptophan-like (275/340 nm; Peak T) and
tyrosine-like (275/310 nm; Peak B) peaks. Since then a number of studies have iden-
tified humic-like and protein-like substances in natural waters (Mopper and Schultz
1993
; de Souza-Sierra et al.
1994
; Determann et al.
1994
;
1996
; Mayer et al.
1999
;
Parlanti et al.
2000
; Yamashita and Tanoue
2003a
). Mostofa et al. (
2005a
) have
characterized the fluorescent whitening agents (FWAs) or components of house-
hold detergents (DAS1 and DSBP) in terms of their fluorescence characteristics at
Ex/Em
=
330-350/430-449 nm (Peak W) in sewerage-impacted rivers.
To find out more useful information in EEM spectra, Principal Component
Analysis (PCA), a multivariate data analysis method, has been applied to the study
of EEMs in marine science. PCA is a more comprehensive data analysis method
than the traditional 'peak picking' techniques (Persson and Wedborg
2001
).
However, the two-way PCA models are insufficient for the modeling of the essen-
tially three-way character of EEMs (Bro
1997
). Recently, parallel factor analysis
(PARAFAC), a statistical modeling approach, has been successfully applied to
decompose EEMs of complex mixtures in aqueous solution into their individual
fluorescent components (Bro
1997
,
1998
,
1999
; Ross et al.
1991
; Jiji et al.
1999
;
Baunsgaard et al.
2000
;
2001
; da Silva et al.
2002
; Stedmon et al.
2003
). The com-
bination of EEM and PARAFAC is widely applied to isolate and distinguish the
fluorescent components in terrestrial soil, pore waters and natural waters (Fulton
et al.
2004
; Cory and McKnight
2005
; Hall et al.
2005
; Stedmon and Markager
2005a
,
2005b
; Ohno and Bro
2006
; Muller-Karger et al.
2005
; Stedmon et al.
2007a
,
2007b
; Mostofa et al.
2010
).
FDOM components can undergo photoinduced decomposition by natural sunlight
in surface waters or in laboratory conditions. Photoinduced decomposition has been
observed for FDOM in rivers (Mostofa et al.
2005a
,
2007a
,
2010
; Gao and Zepp
1998
;
White et al.
2003
; Patel-Sorrentino et al.
2004
; Brooks et al.
2007
), lakes (Ma and
Green
2004
; Garcia et al.
2005
; Winter et al.
2007
; Mostofa KMG et al., unpublished
data), estuaries (Skoog et al.
1996
; Moran et al.
2000
; Osburn et al.
2009
), wet-
lands (Brooks et al.
2007
; Waiser and Robarts
2004
), marine waters (Stedmon et al.
2007a
,
2007b
; Skoog et al.
1996
; Ferrari et al.
1996a
; Kieber et al.
1997
; Miller
et al.
2002
; Lepane et al.
2003
; Bertilsson et al.
2004
; Boehme et al.
2004
; del Vecchio
and Blough
2004
; Zanardi-Lamardo et al.
2004
; Abboudi et al.
2008
), extracted
or standard fulvic acid and humic acid (Mostofa et al.
2005a
; Winter et al.
2007
;
Lepane et al.
2003
; Fukushima et al.
2001
; del Vecchio and Blough
2002
; Uyguner
and Bekbolet
2005
; Mostofa and Sakugawa
2009
), and fluorescent whitening agents,
standard or dissolved in natural waters (Mostofa et al.
2005a
,
2010
; Poiger et al.
1999
). FDOM components are also decomposed microbiologically, in deep natural
waters or upon dark incubation under laboratory conditions. A similar behavior has
been observed for extracted or standard fulvic and humic acids (Mostofa et al.
2010
,
2007a
; Garcia et al.
2005
; Moran et al.
2000
; Lepane et al.
2003
; Abboudi et al.
2008
).
Photochemistry is highly susceptible to degrade flurophores at both peak C- and
A-regions, whilst microbial degradation is more susceptible to decompose flurophores
