Characterization of dissolved organic matter in the Piauí river estuary, Northeast Brazil

Abstract

A espectroscopia de fluorescência e o carbono orgânico dissolvido (COD) foram utilizados para caracterização da matéria orgânica dissolvida (MOD) no estuário do Rio Piauí, um estuário tropical situado no Estado de Sergipe, nordeste do Brasil. As intensidades de fluorescência foram maiores no período chuvoso e menores no período seco, evidenciando que a variabilidade das propriedades fluorescentes da MOD é ditada, principalmente, pela descarga fluvial e pelo processo de diluição no estuário. No período chuvoso, os compostos tipo triptofano e húmicos predominaram na composição da MOD, enquanto no período seco ocorreu um aumento significativo dos constituintes tipo proteínas. As relações das intensidades de fluorescência com a salinidade sugerem um comportamento não conservativo para a MOD fluorescente. O COD mostrou um comportamento conservativo no período seco e não conservativo no período chuvoso, com produção de COD na parte superior do estuário. A complexação da MOD com o Cu(II), estudada usando a técnica de supressão da fluorescência, evidenciou o potencial de complexação dos fluoróforos tipo proteínas, tripofano e húmico.Fluorescence spectroscopy and dissolved organic carbon (DOC) measurements were used to characterize the dissolved organic matter (DOM) in the Piauí 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 proteinlike 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.Keywords: natural organic matter, Piauí River, estuary, fluorescence IntroductionDissolved organic matter (DOM) is a complex heterogeneous mixture of macromolecules formed by the decomposition of biological material derived from animals or plants. DOM represents one of the main reservoirs of carbon on the Earth's surface, and exhibits a variety of ecologically and geochemically important properties including the ability to absorb light, bind with trace metals and organic pollutants, adsorb substances onto its surface and undergo aggregation, as well as photochemical reactivity. [1][2][3] The DOM present in natural waters can have either autochtone or allochtone origins. Allochtone organic matter is introduced into aquatic systems by leaching from ...

Characterising the sources and fate of dissolved organic matter in Shark Bay, Australia: a preliminary study using optical properties and stable carbon isotopes

“…Characterisation of DOM by traditional chemical techniques, 13 C-NMR, py-GC/MS, mass spectrometry, and others, can be laborious and expensive (Stabenau et al 2004;Maie et al 2005;Maie et al 2006bMaie et al , 2006c. In lieu of such exhaustive characterisation, optical methods, such as UV-visible and fluorescence spectroscopy, have been used successfully to elucidate DOM source, fate, and transport in sub-tropical estuaries and many other types of freshwater and saline ecosystems (McKnight et al 2001;Maie et al 2006a;Jaffé et al 2008;Yamashita et al 2008;Chen et al 2010;Costa et al 2011;Fellman et al 2011). Optical properties have been widely used in characterising DOM, however, the application of stable carbon isotopes of DOM has been less frequently reported (Maie et al 2006b;Osburn and Stedmon 2011;) mainly because of analytical limitations (Osburn and St-Jean 2007).…”

Review of Fluorescence Spectroscopy in Environmental Quality Applications

“…Synchronized fluorescence by a conventional spectrofluorometer at Δλ = 30 nm between emission and excitation wavelengths was applied in an estuary located in northeast Brazil [ 71 ]. Four peaks were identified at wavelengths 278–280 nm (peak I), 350 nm (peak II), 385 nm (peak III) and 458–460 nm (peak IV).…”

Matéria Orgânica Dissolvida Cromófora E Não Cromófora Em Sistemas Fluviais Tropicais

“…Com relação à composição, Costa et al (2011) observaram que a MOD variou sazonalmente no estuário do rio Piauí, no estado de Sergipe. No período chuvoso, compostos como o triptofano e húmicos predominaram na composição da MOD, enquanto no período seco ocorreu um aumento significativo de constituintes proteicos, com predomínio de matéria orgânica derivada da produção microbiana primária, associada à atividade biológica costeira (Costa et al 2011).…”