Environmental Engineering Reference
In-Depth Information
fulvic acid (<10 kDa) exhibit relatively high fluorescence intensity, which gradu-
ally decreases with an increase in molecular weight (Hayase and Tsubota
1985
;
Levesque
1972
; Gosh and Schnitzer
1980
; McCreary and Snoeyink
1980
; Visser
1984
). The fulvic acid fluorophores have relatively smaller functional groups and
show higher fluorescence intensity at peak C- and A-regions compared to humic
acids (Hayase and Tsubota
1985
; Mostofa et al.
2009a
,
2005a
).
Photobleached Allochthonous Fulvic Acids
Photobleached fulvic acid generally arises from the degradation of fluorophores
bound to the allochthonous fulvic acid (generally C-like), which thus results in the
excitation-emission maxima of peak C having relatively shorter wavelengths com-
pared to those of the initial fluorescence maxima (Fig.
3
d, e). Photoinduced deg-
radation causes decomposition of allochthonous fulvic acids (C-like, A-like and
M-like) in natural waters (Fig.
3
d, e) (Mostofa et al.
2005a
; Mostofa et al.
2005b
,
2010
,
2007a
; Moran et al.
2000
). In field observations of the waters of Lake Biwa,
the fluorescence excitation-emission maxima at the peak C-region are detected at
(d)
(e)
Peak A Peak M
(f)
(g)
Peak A
Peak C
Peak A
Peak M
d
,
e
The fluorescent components of standard Suwannee River Humic Acids in EEM data of its
aqueous samples identified using PARAFAC modeling. PARAFAC analysis is conducted on earlier
published and their respective a.u. data.
Data source
Mostofa et al. (
2005a
).
f
,
g
The fluorescent
component of photobleached fulvic acids of irradiated river waters (3 h irradiation by midday sunlight,
Nanming River, China) and lake surface waters during the summer stratification period (2.5-20 m,
Lake Biwa, Japan) identified using PARAFAC modeling.
Data source
Mostofa et al. (
2010
,
2005b
).
