Excitation emission fluorescence matrix (EEFM) of natural organic matter of small rivers in the Ceara state (Bresil)

Résumé En

The organic matter presents in water, plays a major role in the biochemical processes and the mobility of the pollutants and it can be observed according to its optical properties. These later enable to establish fluorescent fingerprints for various chemical groups present in the natural organic matter (NOM). Three-dimensional total fluorescence, proved to be an extremely powerful method to characterize and differentiate the natural water masses. The analysis of sample coming from various types of water (lakes, rivers, estuaries or oceans) or of distinct geographical origins leads indeed to obtain appreciably different spectra. These differences in the fluorescence properties of dissolved organic matter suggest differences in its composition according to the origin. These substances which present the remarkable property to fluoresce, are responsible of the colour of water, and they are constituted by functional groups presenting the properties of fluorescence, the fluorophores, of related structures to the amino acids (tyrosine or tryptophan) or to the humic substances (HS) terrigenous or marine. This work aims to characterize by fluorimetry the NOM of samples water taken in Fortaleza metropolitan area, located in the Northeast of the Ceara state (Brazil). The affluent studied are Rio Coco and Rio Pacoti. These two types of fluvial medium undergo deteriorations diametrically opposite. The study of the spectroscopic properties of NOM will allow in the other hand to follow the various phases of its evolution corresponding to the passage of the upstream of the river to an ecosystem of mangrove and finally to the marine environment. For the characterization of the organic matter, water of river, is analysed by excitation emission of fluorescence matrix (EEFM). The maximum intensity of fluorescence recorded with the wavelengths of excitation and emission fluorescence of the emission spectra obtained on 3D-matrix (EEFM), indicates that two kinds of fluorophores are distinguished : those of types C which are allotted a humic character, and those of types A which are allotted a fulvic one.