Abstract
Estuaries are located at the ocean-continent interface and consequently they present characteristics
of both environments. Knowing the source of the estuarine organic matter, as well as quantifying the
contribution of each (marine and/or continental) is essential to understand the role of estuarine
circulation as a transference element of coastal zone material. The aim of this study was to investigate
the Dissolved Organic Matter‟s (DOM) composition and behaviour in the Paranaguá Estuarine System
and demonstrate the contribution of allochthonous (Nhundiaquara river) DOM to the estuarine waters.
To do so, fluorescence spectroscopy technique with emission spectrum, simple and synchronised
excitation was employed. Two classes of fluorophores were assessed with the fluorescence emission:
one was excitable within the range of 310 – 390nm and the other 410 – 470nm. Initially, the
characteristic signature of each environment (fresh and estuarine waters) was determined by
measuring their emission wave-length; it was observed that only the first class of fluorophores has a
typical signature of each environment. Shorter wave-lengths were detected in salt-water samples in
relation to Nhundiaquara river samples. These signatures made it possible to trace DOM‟s behaviour
in the estuary as well as the alterations of the allochthonous DOM‟s when it reaches the mixture zone.
Based on that, it was suggested that allochthonous DOM which reaches the estuary is not only
subjected to physical-chemical changes between continental and marine environments, but the
photobleaching process and bacterial degradation are also determinant in the transformation of these
material. The consequence of such processes is the reduction on the emission wave-length.
Additionally, by means of a Principal Component Analysis (PCA), physical-chemical data of estuarine
water were used to verify which environmental variables were correlated to alterations on emission
wave-length. The results showed, for the first class of fluorophores, a positive correlation between the
wave-lengths emissions and the concentrations of a-chlorophyll. Still in this group of fluorophores, a
negative correlation between this group of variables (wave-lengths emissions and a-chlorophyll) and
salinity, concentrations of TOP, organic-N, NOB
2
B, NOB
3
B, and NHB
4
B. The PCA results for the second class
of fluorophores showed a positive correlation between wave length emissions, salinity, TOP, organic-
N, NOB
2
B, NOB
3
B, and NHB
4
B. Negative correlations were found between this group of variables and
concentrations of a-chlorophyll. For the two classes of fluorophores, the correlations have more weight
during dry season, probably because during the rainy season occurs an increasing on the DOM‟s
sources, which would make it difficult to verify such correlations. In this study, it was also verified that
the methodology of simple excitation was unable to track the DOM in the estuary. In the other hand,
the spectra obtained with the synchronised excitation technique made possible the determination of
the sources, sinks, and the behaviour of fluorescent dissolved organic matter (FDOM). From these
determinations, it was possible to affirm that the input of allochthonous materials is determinant in the
composition of the DOM in the Paranaguá Estuarine System. In addition, a high productivity of fresh
autochthonous material was observed, which it may be a result of bacterial of phytoplankton
production. It was also suggested that both allochthonous and autochthonous DOM are influenced by
anthropogenic impacts, since the presence of naphthalene, high concentration of protein-based
substances, as well as domestic effluents contamination was detected in the estuarine waters.
Key words: Fluorescence; Humic substances; Marine DOM; Fulvic acid; Synchronous fluorescence
spectroscopy