Abstract
Fluorescence spectroscopy and dissolved organic carbon (DOC) measurements were used to characterize the dissolved organic matter (DOM) in the Piaui River estuary, a tropical estuary situated in the State of Sergipe, Northeast Brazil. Fluorescence intensities were greater during the rainy period than the dry period, demonstrating that variability in the fluorescence properties of the DOM was determined mainly by the fluvial discharge and the dilution processes occurring in the estuary. During the rainy period, tryptophan-like and humic substances were the main components of the DOM, while during the dry period there was a significant increase of protein-like constituents. Relationships identified between fluorescence intensities and salinity were indicative of non-conservative behavior of the fluorescent DOM. DOC showed behavior that was conservative during the dry period, and non-conservative during the rainy period, with production of DOC in the upper reaches of the estuary. The complexation of DOM with Cu(II), studied using the fluorescence suppression technique, showed the complexation potentials of protein, tryptophan and humic type fluorophores.
Highlights
Dissolved organic matter (DOM) is a complex heterogeneous mixture of macromolecules formed by the decomposition of biological material derived from animals or plants
This work provides the first information concerning the properties of the dissolved organic matter in the estuary of the Piauí River of Northeast Brazil
Analysis of synchronized fluorescence spectra showed that the DOM was mainly composed of humic substances and organics associated with urban and industrial wastes discharged into the Piauí River and transported downstream to the estuarine region
Summary
Dissolved organic matter (DOM) is a complex heterogeneous mixture of macromolecules formed by the decomposition of biological material derived from animals or plants. The DOM present in natural waters can have either autochtone or allochtone origins. Allochtone organic matter is introduced into aquatic systems by leaching from the soil, and comprises dissolved organic matter derived from the soil as well as from direct decomposition of plant foliar litter. Autochtone organic matter is formed in the aquatic medium itself by the chemical, photochemical and bacterial degradation of natural biological material. It is more labile, and is preferentially utilized, degraded and mineralized during heterotrophic activity.[4]
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