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Featured researches published by M. Wartel.


Water Research | 1992

Variability of dissolved Mn and Zn in the Seine estuary and chemical speciation of these metals in suspended matter

A. Boughriet; B. Ouddane; Jean-Claude Fischer; M. Wartel; G. Leman

Abstract A general study of manganese and zinc in both dissolved and particulate forms in waters from the Seine river, its estuary and the Bay of Seine (in northern France) has been undertaken in order to investigate their fate and transport processes in riverine, estuarine and coastal environments. These samples have been analyzed using graphite-furnace atomic absorption spectroscopy (GFAAS), inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and differential pulse anodic stripping voltammetry (DPASV). In this work, we have considered the different parameters (salinity, pH, temperature and total suspended matter) which may influence the metal distribution in the estuary, and have surveyed the evolution of these metals (with numerous soluble organic and inorganic ligands) in aqueous phases and their interaction with the various inorganic and organic solid fractions which compose the particles. The results show that dissolved Mn and Zn are mainly influenced by salinity. Furthermore, their variability is governed by temporal and spacial changes in tidal stress. Indeed, the distributions of dissolved Mn and Zn are linked to the internal properties of particles and the flow of sediments regulated by the tidally-induced perturbations in the estuary bed. Since the cause of these observations is in connection with the interactions between the liquid phase and the solids present, we have also undertaken the chemical speciation of Mn and Zn in the particles. The results obtained confirm the non-conservative behavior of these two metals. Owing to the paramagnetic properties of Mn, we have been able to analyze particles using electron spin resonance spectroscopy in order to gain further information about the nature of Mn compounds, their oxidation states and their combinations.


Talanta | 2002

Use of constrained DET probe for a high-resolution determination of metals and anions distribution in the sediment pore water

H Dočekalová; O Clarisse; S Salomon; M. Wartel

The constrained DET (diffusive equilibrium in thin films) probe filled with agarose gel was successfully used for measuring depth profiles of metals and anions in estuarine sediments at high-resolution (mm). The agarose gel was tested for equilibration times and recoveries. For manganese (10 mg l(-1)), the equilibration time between an aqueous solution and the agarose gel was reached after 60 min. In the presence of humic acids it was five times longer. As a consequence, for field applications a deployment time of 5-24 h was applied. The subsequent elution of manganese into nitric acid was completed in less than 10 min even without mixing. For agarose gel in contact with solutions of 10 mg l(-1) ions (cadmium, copper and manganese, bromide, chloride, nitrate and sulfate), recoveries obtained were close to 100%. DET probes were applied in test laboratory sediment and in real sediment in the Authie (France) estuary. Depth profiles for 19 elements (Ag, As, Ba, Bi, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se, Sr, Tl, V, and Zn) and four anions (bromide, chloride, nitrate and sulfate) were established for the test laboratory sediment. In the real sediment, the pore water concentrations of iron and manganese using gel probes were comparable with those obtained by a conventional method (box core-anoxic slicing followed by centrifugation).


Marine Chemistry | 1990

Interaction of manganese(II) with carbonates in seawater: Assessment of the solubility product of MnCO3 and Mn distribution coefficient between the liquid phase and CaCO3 Particles

M. Wartel; M. Skiker; Y. Auger; A. Boughriet

The chemical behavior of Mn derived from wastes discharged from a ferromanganese factory located in the harbour at Boulogne-sur-Mer (in Northern France) and its binding characteristics on particulate surfaces have been studied using furnace atomic absorption spectroscopy, plasma atomic emission (ICP), and electron spin resonance (ESR) spectroscopy. The renewal of seawater contributes to the alteration of Mn2+-Ca2+-CO2−3 systems. The evolution of ESR spectra observed with deep-water and surface-water particles accounts for these interactions and the extent of the incorporation of Mn2+ on CaCO3 surfaces to form solid solutions according to xMn2++CaCO3(8)→MnxCa1-xCO3(8)+xCa2+ At concentrations of Mn(II) close to 1.8 μM, rhodochrosite slowly appears in the solid phase. Taking into account the concentrations of several ionic and neutral species (or complexes) involved in seawater, the solubility product of MnCO3 and the corresponding enthalpy have been assessed in marine environments by computational procedures: Ps = 5.8×10−12 and δHs⋍6.1 J mol−1. For low concentrations of dissolved Mn, calcite governs the partitioning equilibria. The distribution coefficient, Di, between the concentrations of Mn(II) and Ca(II) in the solid and solution phases has been used as a valuable means of assessing the extent of the surface phenomena induced by Mn2+ on calcite and to show the state of complete equilibrium, i.e. when the solid phase is regular. The equilibrium constant for the Mn2+-exchange reaction as Mn2++CaCO3(8) ⇌ MnCO3(8)+Ca2+ has also been calculated in natural media. The seawater sampling carried out near the ferromanganese factory at periods of spring tides has allowed us to propose that calcite makes an essential contribution to the stabilization of Mn(II).


Marine Chemistry | 1992

Electron spin resonance investigations of Mn compounds and free radicals in particles from the Seine river and its estuary

A. Boughriet; B. Ouddane; M. Wartel

Abstract Paramagnetic species associated with particles in water samples from the Seine river and its estuary (in Northern France) were studied by electron spin resonance (ESR) spectroscopy. The ESR spectra obtained for these particles show the presence of: (1) Mn(II) embedded in calcite lattices in the form of a solid solution of Mn 2+ CaCO 3 (Mn x Ca 1- x CO 3 ): (2) Mn(III) ions associated with Fe(III) oxides; (3) organic radicals identified as semiquinone-type compounds. Because the solubility product for MnCO 3 is never exceeded in these systems, the broad resonance of rhodochrosite is not detected. To confirm the importance of the role of iron on the paramagnetic behaviour of particulate Mn(III), we carried out several experiments with Mn(OH) 2 Fe(OH) 3 (co) precipitates. The detailed study of the ESR spectra obtained for these Mn-Fe oxides indicates that excess iron (with respect to manganese) stabilizes Mn(III) ions in the precipitates: the Fe/Mn weight ratio found in the particles from the Seine river is in the 60–75 range. When these particles were heated or treated with acid, the ESR spectra changed significantly. The results indicate that valuable information can be obtained from ESR spectroscopy, particularly on Mn(II), Mn(III) and Mn(IV).


Marine Chemistry | 1997

Origin and transport of organic matter across the Seine estuary: Fatty acid and sterol variations

Guy Thoumelin; L. Bodineau; M. Wartel

Abstract Suspended matter (SPM), particulate organic carbon (POC), dissolved and particulate fatty acids (FA), and sterols (ST) have been analyzed in the Seine estuary to assess the sources and transport of organic matter. Two sampling sites have been chosen: the first at Buoy 26 near the Normandie Bridge, in the estuarine mixing zone (October 28th 1993) and the second at La Bouille (November 4th 1993) in the upper fluvio-estuarine zone, which is only exposed to tidal pulse influence. At each site, samples were collected every 1h30 during an entire tidal cycle. In surface waters, in the particulate phase, C16, C18 and C20 polyunsaturated FA, branched C15 and C17 FA, long chain C26–C32 FA and the faecal ST coprostanol indicate, respectively, planktonic, bacterial, terrestrial, and sewage organic matter inputs. Diatoms were the predominant planktonic contributors at the time of our study, but other species may have been present especially in the fluvio-estuarine zone. Terrestrial plant and sewage particulate organic matter are transported seaward at La Bouille and are trapped in the ETM in which a bacterial imprint is also noticeable. A punctual event such as a recent diatom bloom decay, was also possibly the cause of the important concentrations of dissolved FA and ST during the flood at La Bouille. At Buoy 26, dissolved FA were also decoupled from particulate FA. Due to the presence of ubiquitous compounds, no precise origin can be attributed to this dissolved fraction. In ETM, organic matter is better characterized in the particulate phase.


Marine Chemistry | 1997

Speciation of dissolved and particulate manganese in the Seine river estuary

B. Ouddane; E. Martin; A. Boughriet; Jean-Claude Fischer; M. Wartel

Abstract During four surveys covering various hydrodynamic conditions samples were collected in the Seine river estuary for the study of dissolved and particulate manganese. A new analytical method for direct determination of dissolved manganese was used in this study (atomic absorption spectrometry with Zeeman non-specific absorption correction). Generally, dissolved manganese versus salinity curves exhibits a peak concentration in the low salinity zone. Speciation studies of dissolved and particulate manganese have been performed in order to establish a model for manganese behaviour in the Seine estuary. Taking into consideration the solution composition as well as the values of stability constants of the complexes, dissolved manganese speciation has been calculated using an equilibrium Speciation program. Sequential extraction procedures (Tessiers scheme) have been applied to assess the manganese distribution in solid samples (sediment, suspended matter). Operational nature of empiricism inherent to these procedures has been partly eliminated by determining physicochemical form of Mn by electron spin resonance owing to the paramagnetic properties of manganese. This study has allowed us to show that manganese behaviour in the Seine estuary is strongly influenced, (i) in solid samples, by the presence of calcium carbonate which stabilise the Mn(II) form; (ii) in solution, by the increase of salinity, calcium, magnesium and suspended matter concentrations, by complexes formation and by diffusion from sediments to water.


Journal of Electroanalytical Chemistry | 1985

Electrochemical oxidation of nitrogen dioxide in aprotic media: Kinetic and thermodynamic constants relative to the equilibria N2O4 ⇄ 2 NO2 and N2O4 ⇄ NO2+ + NO2−

A. Boughriet; M. Wartel; J.C. Fischer; Claude Bremard

The equilibrium constant value of the homolytic dissociation: N2O4 ⇄ 2 NO2 has been determined in some aprotic media using NMR and ESR techniques. From these results, we have undertaken the electrochemical study of the N2O4 oxidation in these solvents. N2O4 undergoes an electron transfer preceded by a monomerization reaction as follows: Mathematical models applied to this process, have allowed us to obtain the rate constants k1, k−1, and the standard potential of the NO2+/NO2 and NO2+/12 N2O4 systems. Hence, it has been possible to derive the value of the equilibrium constant for the ionic dissociation: N2O4 ⇄ NO2+ + NO2−.


Journal of Environmental Monitoring | 1999

Distribution of iron and manganese in the Seine river estuary: approach with experimental laboratory mixing

Baghdad Ouddane; Mohamed Skiker; Jean Fischer; M. Wartel

The physico-chemical behaviour of iron and manganese has been observed during many surveys covering various hydrodynamic conditions in the Seine river estuary system. The results obtained confirm the non-conservative behaviour of these two metals. Generally, dissolved iron exhibits non-conservative removal and shows a rapid decrease in low salinity; it is moved from fresh waters with high concentrations to saline waters with very low concentrations. This can be attributed to the flocculation processes as confirmed by laboratory experiments. Dissolved manganese versus salinity curves exhibit a peak concentration in the low salinity zone. Laboratory mixing experiments have been undertaken comparing iron and manganese adsorption/desorption from suspended material versus salinity, using a series of water samples collected in the up-river and marine regions in order to assess the importance of particulate material and salinity on iron and manganese distributions. The salinity was controlled by varying the marine to fresh water ratio. The reaction kinetics aspect is developed in more detail for manganese in the last series of remobilization experiments starting from a stock of suspended particles collected in the upstream river site (Caudebec) in mixtures of waters, according to time and salinity. This study has allowed us to show that iron and manganese behaviour in the Seine estuary is strongly influenced: (i) by the high turbidity zone and by the presence of calcium carbonate which could stabilise the Mn(II) form; and (ii) by the increase of salinity, calcium, magnesium and suspended matter concentrations and by complex formation.


Marine Chemistry | 1991

Seasonal variation of Mn2+ adsorption on to calcareous surfaces in the English Channel, and its implication on the manganese distribution coefficient

M. Wartel; M. Skiker; Y. Auger; A. Boughriet; E. Puskaric; P. Guegueniat

Dissolved and particulate manganese in seawater samples derived from the English Channel has been analyzed using graphite furnace atomic absorption (GFAAS), and inductively coupled plasma atomic emission (ICP-AES) spectroscopies. Because of the high contents of carbonate minerals found in the suspended matter samples, the English Channel constitutes an ideal field area for the study of the Mn 2+ /Ca 2+ /CaCO 3 system


Analytica Chimica Acta | 1979

Determination des constantes de dissociation ionique du chlorure de nitrosyle et de N2O4 dans le sulfolane

M. Wartel; Abdelhatef Boughriet; Jean-Claude Fischer

Determination of the ionic dissociation constants of nitrosyl chloride and dinitrogen tetroxide in sulpholane. A silver chloride—silver electrode is used to study electrochemical systems involving nitrosyl chloride and dinitrogen tetroxide in sulpholane: Ag↓ + NOCl ⇌ AgCl↓ + NO+ + e- and Ag↓ + NOCl + NO-3 ⇌ AgCl↓ + N2O4 + e- The dissociation constants of these two NO+ donors determined in this way are: K(NOCl) = 10-11.8 mol l-1 and K(N2O4) = 10-7.2 mol l-1. A titration of N2O4 solutions alone or in the presence of nitric acid is described. This titration is possible in mixtures which contain up to 90% (w/w) nitric acid.

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Jean-Claude Fischer

Centre national de la recherche scientifique

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B. Ouddane

Centre national de la recherche scientifique

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Jean Fischer

Centre national de la recherche scientifique

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Claude Bremard

Centre national de la recherche scientifique

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C. Cordier

Centre national de la recherche scientifique

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Guy Thoumelin

Lille University of Science and Technology

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Gabriel Billon

Centre national de la recherche scientifique

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