Environmental Engineering Reference
In-Depth Information
The most common fluorescent DOM components isolated from DOM in natural
waters using PARAFAC modeling are allochthonous fulvic acids and humic acids
of vascular plant origin, autochthonous fulvic acids (termed C-like and M-like based
on the component's peak positions) of algal (or phytoplankton) origin, aromatic
amino acids (tryptophan, tyrosine and phenylalanine), FWAs (DAS1 and DSBP),
green algae, chlorophyll
a
(Chl
a
) and chlorophyll
b
(Table
2
) (Coble
1996
; Parlanti
et al.
2000
; Yamashita and Tanoue
2003a
; Mostofa et al.
2005a
, Mostofa et al.
2005b
,
2010
; Stedmon et al.
2003
,
2007a
; Stedmon and Markager
2005a
,
2005b
;
Ohno and Bro
2006
; Mostofa KMG et al., unpublished data; Fu et al.
2010
; Zhang
et al.
2009a
; Wedborg et al.
2007
; Hunt et al.
2008
; Luciani et al.
2008
; Kowalczuk
et al.
2009
; Zhao et al.
2009
; Baghoth et al.
2010
; Chen et al.
2010
; Dubnick et al.
2010
; Fellman et al.
2008
,
2009
,
2010
; Guo et al.
2010
; Singh et al.
2010
; Yu et al.
2010
; Wu et al.
2011
; Yamashita et al.
2010
,
2011
; Holbrook et al.
2006
; Balcarczyk
et al.
2009
; Santín et al.
2009
; Murphy et al.
2008
; Yamashita et al.
2008
; Li et al.,
Characteristics of sediment pore water dissolved organic matter in four Chinese lakes
using EEM spectroscopy and PARAFAC modeling, unpublished data; Yamashita and
Jaffé
2008
; Aoki et al.
2008
; Wang et al.
2007
). These fluorescent components gen-
erally exhibit fluorescence at peak C-, peak A-, peak T- and T
UV
-regions (Table
2
).
Their fluorescence properties are depicted in
Sect. 2.5
, as a function of the molecular
structure of the respective components.
2.4 Fluorescence Intensity of a Molecule and its
Normalization
A fluorescent molecule has one, two or several fluorescence peaks, and each peak can
be denoted as fluorophore or fluorochrome. For example, fulvic acid has two fluores-
cence peaks in EEM spectra, namely peak C at longer wavelength and peak A in the
shorter-wavelength UV region. The fluoresce intensity of fulvic acid is higher at peak
A-region compared to the peak C-region (Mostofa et al.
2009a
,
2005a
,
2010
; Coble
1996
; Yamashita and Jaffé
2008
). On the other hand, humic acid has several fluores-
cence peaks such as peak M, peak C and peak A. The peak A-region has usually the
highest fluorescence intensity (Mostofa et al.
2009a
,
2005a
,
2010
; Coble
1996
;
Yamashita and Jaffé
2008
). Tryptophan amino acid has two fluorescence peaks: peak
T at relatively longer wavelengths and peak T
UV
in the shorter-wavelength UV region
(Mostofa et al.
2009a
,
2005a
,
2010
; Coble
1996
; Yamashita and Jaffé
2008
). The latter
has usually the highest fluorescence intensity. The fluorophore or flurochrome at peak
C or peak A of humic and fulvic acids are the result of the contribution of several fluo-
rophores, because the macromolecular structures of these compounds generally include
a number of functional groups (Mostofa et al.
2009a
; Senesi
1990a
; Malcolm
1985
).
Tryptophan amino acid has only one florophore at each peak position (T and T
UV
) that
can be denoted as single fluorophore.
The fluorescence intensity of a sample is normalized to monitor the stability
of the light (or energy) emitted by the xenon lamp in the fluorometer, to compare
