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La particularité des sols côtiers de Nouvelle-Calédonie est d’être essentiellement formés de latérites, exploitées depuis des décennies pour leurs teneurs en éléments traces métalliques (ETM) tels que le nickel, le chrome, le cobalt ou le manganèse. De par sa forte productivité en matière organique, la mangrove constitue un réservoir important de matière organique dissoute (MOD) qui peut être transportée vers l’Océan sur de grandes distances. Les observations menées soulèvent la question du rôle puit/source que joue la mangrove vis-à-vis de la dynamique des ETM à l’interface Terre-Mer à l’aval des massifs miniers de Nouvelle-Calédonie. Le projet TREMOR a ainsi, pour objectif d’apporter des éléments de réponses à cette question en s’appuyant sur les propriétés de fluorescence d’une fraction de la MOD, appelée Matière Organique Dissoute Fluorescente ou MODF, pour mieux comprendre l’origine, les sources et les puits de la MODF identifiée dans les rivières et dans le lagon de Nouvelle-Calédonie et évaluer l’influence de cette MODF sur la dissémination et la toxicité des ETM au sein du littoral à l’aval des sites miniers de Nouvelle-Calédonie.

Laboratory male pupae of Culex pipiens were exposed to 23, 41, 74 and 128 Gy doses of gamma radiation according to the LD 25, LD 50 , LD 75 and LD 90 calculation, respectively. The inherited deleterious effects of gamma radiation were observed in the F 1 , F 2 and F 3 generations. Levels of sterility index in the F 1 and F 2 were higher than those of untreated control but in the F 3 generation there was a semi-sterility compared with the control. Ultrastructure of normal males' testes of C . pipiens was studied using transmission electron microscopy. Histopathological responses were observed in the irradiated testes of C . pipiens . Gamma radiation had greatly affected the testes, such as (i) rupture, necrosis, degeneration and small vacuoles were reported in the testicular wall (ii) an abnormal distribution of the developmental stages of spermatogonia and spermatocytes leading to a general decrease in the rate of spermatogenesis; and (iii) deformity of sperm inhibitting the movements and the fertility of the sperm led to the decrease in the reproductive potential of C . pipiens . Consequently, these radiation doses are consistent with those used in the already established Sterile Insect Technique (SIT) programmes against Culex pipiens .

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Polycyclic aromatic hydrocarbons (PAHs) and pesticides are among the most widespread organic contaminants in aquatic environments. Because of their aromatic structure, PAHs and pesticides have intrinsic fluorescence properties in the ultraviolet/blue spectral range. In this study, excitation–emission matrix (EEM) fluorescence spectroscopy and parallel factor (PARAFAC) analysis were used to characterise and discriminate fluorescence signatures of nine PAHs and three pesticides at the µg L-1 level in the presence of humic substances (0.1-10 mg C L-1). These contaminants displayed a diversity of fluorescence signatures regarding spectral position (λEx: 220-335 nm, λEm: 310-414 nm), Stokes shift (39-169 nm) and number of peaks (1-8), with detection limits ranging from 0.02 to 1.29 µg L-1. The EEM/PARAFAC method applied to mixtures of PAHs with humic substances validated a seven-component model that included one humic-like fluorophore and six PAH-like fluorophores. The EEM/PARAFAC method applied to mixtures of pesticides with humic substances validated a six-component model that included one humic-like fluorophore and three pesticide-like fluorophores. The EEM/PARAFAC method adequately quantified most of the contaminants for humic substance concentrations not exceeding 2.5 mg C L-1. The application of this method to natural (marine) samples was demonstrated through (1) the match between the Ex and Em spectra of PARAFAC components and the Ex and Em spectra of standard PAHs, and (2) the good linear correlations between the fluorescence intensities of PARAFAC components and the PAH concentrations determined by GC-MS.

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., Abbad Nabila, Mounier S. Excitation emission fluorescence matrix (EEFM) of natural organic matter of small rivers in the Ceara state (Bresil). In: 31èmes Journées de l’Hydraulique de la Société Hydrotechnique de France. Morphodynamique et gestion des sédiments dans les estuaires, les baies et les deltas. 22 et 23 SEPTEMBRE 2009. 2009.