Synchronous Fluorescence Spectra as Chemical Tracers of North Adriatic DOM
117
12°30'E
o
Fig. I. Map of sampling stations
which provided spectral selectivity and sensitivity for the characterization of algal EOM, as well
as of natural DOM samples (Mingazzini et al.
1995; Ferrari and Mingazzini 1995; Mingazzini
and Onorato 1998), were employed. A SPEX
FluoroMax spectrofluorimeter. equipped with a
150-W ozone-free Xenon lamp, was used. Spectra
were recorded in an excitation wavelength range
of 250-500 nm with 25 nm lU, 4.25 nm bandpass,
2 nm increment and Is integration time. No correction factors were applied. All spectra were
blank-subtracted using the Ultrapure water
spectrum, recorded immediately before samples
with the same instrumental parameters.
Analyses were performed at room temperature
using 1 cm path length cell (precision quartz
cuvette) as sample holder. Synchronous spectra
are presented in the figures on the excitation
wavelengths scale, while the fluorescence intensities are expressed as fluorescence units (F. U. =
cps X 10 3 ).
Adriatic Sea
km
5
!
10
!
Results and Discussion
Laboratory Cultures
12"50'E
7
Typical fluorescence spectra of the EOM produced by different species of marine diatoms are
illustrated in Fig. 2. Two main fluorescence signals are present in each of the four spectra. The
two maxima, which are respectively labelled A
and B, are referred to the two types of fluorescent
DOM observed in seawater. The fluorescence
peak. A (276 nm Ex max) representing the
"aminoacidic-like" component is referred to "relatively young" production by recent biological
activity and was observed to be produced both in
marine waters and in laboratory cultures
(Traganza 1969). The fluorescence peak. B (340
nm Ex max) representing the "humic-like" component is generally referred to "old" material,
such as humic compounds of terrestrial origin
(Mopper and Schultz 1993; De Souza Sierra et al.
117
12°30'E
o
Fig. I. Map of sampling stations
which provided spectral selectivity and sensitivity for the characterization of algal EOM, as well
as of natural DOM samples (Mingazzini et al.
1995; Ferrari and Mingazzini 1995; Mingazzini
and Onorato 1998), were employed. A SPEX
FluoroMax spectrofluorimeter. equipped with a
150-W ozone-free Xenon lamp, was used. Spectra
were recorded in an excitation wavelength range
of 250-500 nm with 25 nm lU, 4.25 nm bandpass,
2 nm increment and Is integration time. No correction factors were applied. All spectra were
blank-subtracted using the Ultrapure water
spectrum, recorded immediately before samples
with the same instrumental parameters.
Analyses were performed at room temperature
using 1 cm path length cell (precision quartz
cuvette) as sample holder. Synchronous spectra
are presented in the figures on the excitation
wavelengths scale, while the fluorescence intensities are expressed as fluorescence units (F. U. =
cps X 10 3 ).
Adriatic Sea
km
5
!
10
!
Results and Discussion
Laboratory Cultures
12"50'E
7
Typical fluorescence spectra of the EOM produced by different species of marine diatoms are
illustrated in Fig. 2. Two main fluorescence signals are present in each of the four spectra. The
two maxima, which are respectively labelled A
and B, are referred to the two types of fluorescent
DOM observed in seawater. The fluorescence
peak. A (276 nm Ex max) representing the
"aminoacidic-like" component is referred to "relatively young" production by recent biological
activity and was observed to be produced both in
marine waters and in laboratory cultures
(Traganza 1969). The fluorescence peak. B (340
nm Ex max) representing the "humic-like" component is generally referred to "old" material,
such as humic compounds of terrestrial origin
(Mopper and Schultz 1993; De Souza Sierra et al.