Environmental Engineering Reference
In-Depth Information
from rivers and lakes; 300-340/423-464 and 235-260/425-464 nm for various
upstream and rivers, but not in the water Raman Unit (RU: nm
−
1
) calibration
(330-380/420-467 and 240-260/4420-467 nm, respectively); 295-310/443-
464 and 250-260/443-464 nm in lakes; 305/439 and 260/439 nm in estuaries,
which shifts to 360-385/478-504 and 250-270/478-504 nm in RU calibra-
tion; 320-325/422-454 and <250/422-454 nm in bay and marine waters (but
one finds 340-410/440-520 and 250/440-520 nm upon RU calibration in bay
waters from the Barataria Basin); 300-305/449 and 250/449 nm in irradiated
river waters; 315/429 nm in water extracted from sugar maple leaves; 315/447
and ~250/447 nm in plant biomass, manure and soil (Tables
1
,
2
) (Stedmon et
al.
2003
; Stedmon and Markager
2005b
; Ohno and Bro
2006
; Mostofa et al.
2010
; Mostofa KMG et al., unpublished data; Nakajima
2006
; Hunt et al.
2008
;
Kowalczuk et al.
2009
; Baghoth et al.
2010
; Chen et al.
2010
; Dubnick et al.
2010
; Fellman et al.
2010
; Guo et al.
2010
; Singh et al.
2010
; Yamashita et al.
2010
,
2011
; Balcarczyk et al.
2009
; Santín et al.
2009
). Note that longer excita-
tion-emission maxima have been observed at the C-region for SRFA dissolved in
sea water compared to Milli-Q water. This is presumably linked to the formation
of complexes of trace elements in seawater with the functional groups (or fluro-
phores) bound in SRFA. Complex formation can significantly enhance electron
promotion at peak C from the ground to the excited state by longer wavelength
energy. The lower excitation energy can shift the Ex/Em maxima to longer wave-
lengths. This will be explained in detail in the section that deals with the effect of
salinity.
The second component is denoted as allochthonous fulvic acid (A-like) and is
typically composed of a strong fluorescence shoulder (or peak) at Ex/Em
=
225-
250/413-448 nm (peak A-region) and of a minor peak at Ex/Em
=
280-295/414-
442 nm (peak C-region) (Fig.
3
b). The allochthonous fulvic acid (A-like) is
identified at 230/441 nm (peak A-region) in SRFA dissolved in Milli-Q waters;
225-230/414-442 nm (peak C-region) and 285-295/414-442 nm (minor peak
at peak C-region) in upstream waters (Figs.
2
b,
3
b); 225/432-442 nm in lakes;
240-250/416-448 nm in estuaries, and <260/(not mentioned) nm in marine waters
(Table
2
) (Stedmon et al.
2003
; Stedmon and Markager
2005b
; Mostofa KMG
et al., unpublished data; Yamashita et al.
2010
; Balcarczyk et al.
2009
).
The third component of allochthonous fulvic acid exhibits fluorescence excita-
tion-emission maxima at Ex/Em
=
285-310/387-429 nm (peak C-region) and Ex/
Em
=
230-260/387-429 nm (peak A-region). The fluorescence intensity at peak
A-region is >1.50 times higher than at C-region (Fig.
3
c; Table
2
). The Ex/Em
maxima of this component at peak C-region occur at relatively shorter wavelengths
compared to those of the allochthonous fulvic acid (C-like). Therefore, the third
component can be denoted as allochthonous fulvic acid (M-like). Allochthonous
fulvic acid (M-like) has been detected at Ex/Em
=
285-310/387-429 nm at peak
C-region and 230-240/387-429 nm at peak A-region in the waters of the Yellow
River and Heilongjiang (Amur) River watershed (China); 305/396 and 240/396 nm
in Occoquan Watershed (USA); 305/428 and <240-260/414-428 nm in marine
waters; 320/410 and 250/410 nm in drinking water treatment plants, and 312/417
