Geoscience Reference
In-Depth Information
150
100
450
400
Exc (nm)
50
350
300
0
300
350
400
450
550
500
600
650
700
Emission Wavelength (nm)
3500
3000
2500
2000
1500
450
1000
400
Exc (nm)
350
500
300
0
300
350
400
450
550
500
600
650
700
Emission Wavelength (nm)
Figure 3.1 (
cont.)
exhibits some variability. For this reason, it is useful to specify a humic-like C component
that includes both peaks.
Humic-like C component is the predominant type found in soils, most freshwater sam-
ples, rivers, and the deep ocean. The range in composition across these environments is
reflected in the wide range of excitation and emission wavelengths given in
Table 3.1
for
the peak C maximum. Environments dominated by humic substances leached from soils
tend to be the most complex pool observed. Across the range of environments, the position
of the overall fluorescence maximum from the humic-like C component varies, with older
or more terrestrial material showing the most red-shifted excitation and emission maxima
(
Figure 3.2
). Some researchers working in peaty waters have designated subregions of peak
