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The article proves that the need for the development of intercultural communication skills in the learning process is due to external causes of globalization and internal requirements of the modern ethnocultural situation in Ukraine, as well as the needs of pedagogical science, which takes into account global development trends: anthropocentrism, search for value orientations and new worldview, the need for acquisition of intercultural interaction skills that ensure competitiveness in the global community. According to the author, the skills of intercultural communication of future specialists are characterized by the integrity of formation of personal qualities and abilities, the ability to switch from one culture-specific code to another, taking into account their differences, flexibly vary communication strategies and tactics, maintain a positive attitude; choice of verbal and non-verbal means. In this regard, the author proposed the idea of using Web 2.0 in the formation of intercultural communication skills. Experimental application of a special method of working with educational Internet resources based on Web 2.0 technologies was tested in the Practical English academic course. It was found that the use of Web 2.0 in the development of intercultural communication skills in the process of studying at higher educational institutions opens up a wide range of opportunities for educational practice: the use of free electronic resources used for educational purposes; independent creation of network content; interpersonal interactions of the subjects of the educational process. To analyse the results obtained and objectively consider the dynamics of changes in the level of development of intercultural communication skills, control and measuring materials selected were the assignments of the Level 6 Certificate of General Language Proficiency (CAE Advanced) and a test to determine the level of development of learning strategies - the Strategy Inventory for Language Learning (SILL) Version 7.0. It was found that the use of educational Internet resources based on Web 2.0 technologies activates the professionally significant qualities of future specialists, the ability to carry out intercultural communication, expands the horizons of the worldview and the sphere of professional activity to the maximum possible extent, professional mobility, which is a condition and basis of professionalism and mastery. The proposed methods, techniques and technologies can be used regardless of the foreign language and have transnational significance.

Throughout this book, it has been clearly shown that a better understanding of the coupling phenomena between the mechanics and the reactivity of a material should involve the use of new analysis techniques. Many of them have permitted shedding new light concerning the problems addressed. In particular it has been shown that it is necessary to analyze the process at an increasingly finer scale in order to best understand the phenomena's heterogeneity. Indeed, corrosion mechanisms rarely result from uniform and homogeneous processes, making their modeling difficult. Furthermore, the addition of mechanical stress leads, in most cases, to locating the material's vulnerability. This is why it has been important for us, in this chapter, to develop some techniques which are used or usable for analyzing the influence of mechanics on metallic materials' reactivity. For this, we introduce some localized in situ measurement techniques explaining the measurement principle, their applications as well as their limitations.

The impact of a mechanical state, or even a mechanical loading, on the corrosion process is a fundamental issue in the management of the sustainability of structures and infrastructures subject to an environment characterized as aggressive for the material. This investigation is naturally multi-scale with the presence of a potentially heterogenous deformation state from the atomic scale up to the structure, passing by the great variety of crystalline defects associated with the metallurgy of alloys. Like many physical-chemical couplings, thermo-kinetic formalisms are particularly well adapted to investigating the corrosion processes and the development of a predictive framework. Thus, the consequences of a mechanical state on a fundamental corrosion process results in modifications of the kinetic constants, their associated energies and frequencies. The loads and/or mechanical state are expressed in various ways from which we distinguish the elastic distortion and the various expressions of plasticity. Thus, the production and mobility of defects associated with plastic deformation leads to an elastic energy stored in relation to the multiplication and formation of dislocation structures and a profound modification of the surface in association with the emergence of dislocations individually or collectively. Each of these elements can affect all the fundamental processes associated with corrosion: charge transfer, adsorption, growth and stability of an oxide film and localized corrosion. It is therefore appropriate in each case to develop dedicated and multi-scale experimental approaches.

Electrochemical Impedance Spectroscopic technique (EIS) and Local Electrochemical Impedance Spectroscopic technique (LEIS) have been used to investigate the corrosion behavior of zinc–nickel + chromate conversion coating on carbon steel. The measurements were conducted in chloride media, 0.6 M and 10 mM NaCl solutions with coating with and without artificial defect. An electrical equivalent circuit was proposed to analyze the EIS spectra in 0.6 M NaCl solution. LEIS was also performed in the vicinity of a scratch exposing the carbon steel to the corrosive solution. It was shown that the local impedance measurement was very useful to characterize in situ the electrochemical reactivity around a defect.

International audience; This paper presents experimental evidences of an intrinsic coupling between the alpha and Q parameters of constant phase elements (CPE) used in equivalent electrical circuits for EIS data fitting. Clear correlations have been found for two different experimental conditions, anodic dissolution and scale deposit, for which CPE behavior appears as the result of a time constant distribution originated from surface inhomogeneity. Results are in agreement with a coupling function that relates CPE parameters with interfacial quantities such as the ohmic and charge transfer resistances, and also with a characteristic interfacial capacitance whose meaning is addressed here. Although this relationship was initially derived from a theoretical model in which perfect CPE behavior was caused by a double-layer capacity distribution along the interface, it has been extensively used in the literature to estimate interface capacitance from CPE parameters in very different complex systems without any definitive evidence of it. However, its exportability to real systems can be explained from the fact that it can be deduced from simple and general arguments. In this paper we argue on these ideas in the basis of experimental evidences.

The growth of electrolytic copper dendrites between two coplanar copper discs, 250 μm in diameter, was investigated in oxalic acid medium containing copper sulphate by a technique based on the coupling of electrochemical measurements and microvideo optical in situ observations. The influence of the oxalic acid concentration, the potential difference applied between the two microelectrodes, and a laminar flow perpendicular or parallel to the electric field was investigated on the growth rate of the dendrites and on the short circuit time. Contrarily to solutions of oxalic acid alone, the activation current was diffusion-limited. The growth rate of the dendrites was proportional to the electric field. At the end, the technique was used to study the dendrite growth on a tantalum cathode where a morphology transition was evidenced.

The growth of electrolytic copper dendrites between two coplanar copper disc electrodes, 250 μm in diameter, was investigated in oxalic acid medium by a technique based on the coupling of electrochemical measurements and optical in situ observations. The current transients observed when a potential difference was applied between the two microdiscs were recorded. Simultaneously, the length of the dendrite was measured in real time thanks to a microvideo equipment. After some image processing, the growth rate of the dendrite was calculated by considering the increase of its length for a time increment. It was shown that the current transients exhibited a steep increase when the dendrites reach the anode and then formed a short circuit between the two copper discs. Depending on the experimental conditions, two types of dendrite morphology were observed: a filamentary growth and hierarchically branched thick structures. A strong relationship between the current transients, the change of the growth rate with time and the morphology of the dendrites was demonstrated. Low deposition currents are associated with a constant growth rate and filamentary dendrites whereas higher currents are associated with increasing growth rate with respect to time and hierarchical dendritic morphology.

The growth of electrolytic copper dendrites between two coplanar copper discs, 250 μm in diameter, was investigated in oxalic acid medium by a technique based on the coupling of electrochemical measurements and microvideo optical in situ observations. The influence of the oxalic acid concentration, the potential difference applied between the two microelectrodes, and a laminar flow perpendicular or parallel to the electric field was investigated on the growth rate of the dendrites and on the short circuit time. It was shown that during the incubation time, the copper ions dissolved from the anode are transported to the cathode mainly by migration. The growth rate of the filamentary dendrites increases with the oxalic acid concentration, activation current, and potential. Then, various techniques able to eliminate, or at least to slow, the dendrite development were studied. The addition of a supporting electrolyte, buffered solutions, or inhibitors slows or eliminates the deposit growth. At the end, the influence of the size of the anion and of the presence of dissolved oxygen in the solution was examined. In particular, the absence of oxygen in the solution prevents the deposit growth at the time scale of the experiment as there is practically no cathodic reaction available during the incubation time to compensate the anodic dissolution current.

An impinging jet cell was used to investigate the influence of the convection on the kinetics of scale deposition in a carbonically pure water. CaCO 3 crystallized due to the increase of the local pH obtained by the reduction of dissolved oxygen. The working electrode was the transparent electrode of an electrochemical quartz crystal microbalance which records versus time the mass of the deposit and the microscope image of the electrode/solution interface. The chronoelectrogravimetric curves showed that the rate of the CaCO 3 deposition increased with the convection until a limiting value of the Reynolds number Re while the current of oxygen reduction continues to increase following a Re 1/2 law. This result was confirmed by the measurement of the growth rate of the two CaCO 3 crystal forms obtained by using the optical method. On the contrary, the nucleation rate was not influenced by the flow rate. It was shown that the kinetics of scale deposition was directly linked to the interfacial pH; a theoretical approach gives the interfacial pH with respect to the Re number.

International audience; The friction stir welded (FSW) assembly of 2050-T8 and 7449-T79 was studied by local electrochemical techniques, namely SECM and LEIS, under non-corrosive and low corrosive conditions. During the FSW process, it generates different well defined microstructural zones giving rise to a galvanic coupling at their interfaces. SECM and LEIS measurements were carried out to investigate the local electrochemical behavior around these interfaces. SECM results clearly showed a change of the electrochemical kinetic on the passive layer between both materials in the different microstructural zones of the welded assembly whereas the LEIS techniques allowed the investigation of the interface on a larger scale.

The effects of a superimposed magnetic field B on the structure of nickel electrodeposits prepared from a quiescent Watts solution were studied by scanning electron microscope and transmission electron microscopy investigations. It was observed that B can induce a change of the surface morphology and of the preferential growth direction of the nickel grains. In the absence of organic inhibitor, it is shown that these effects result from an inhibition of nickel electrocrystallization in relation to the mass-transport enhancement of H + ions promoted by the magnetic field. The phenomenon is much more important in the presence of a strong inhibitor such as 2-butyne-1,4-diol, the activity of which is also under mass-transport limitation. The presence of the magnetically induced convective flow is directly illustrated by the perturbations of the relief of the deposit in the vicinity of attached bubbles. These results demonstrate that most structural modifications of nickel electrodeposits observed in the presence of a magnetic field are consequences of convection phenomena induced by a magnetohydrodynamic effect.

International audience; The study of galvanic coupling between two metals is still a relevant topic, particularly in aerospace andautomotive industries. The development of local electrochemical techniques leads to a better understandingof the phenomena occurring at the interfacial zone. Galvanic coupling between carbon steel and zincwas investigated by local electrochemical impedance spectroscopy (LEIS) in a 0.06 g L−1 NaCl solution.Voltammetry and conventional electrochemical impedance experiments were also performed to betteranalyze the local impedance data. Local measurements carried out at a fixed frequency showed that zincdissolution was more significant at the steel/zinc interface. A particular shape of the local impedance diagramwas observed above the zinc surface with the presence of a large inductive loop in the low-frequencyrange. Numerical simulations, performed by using finite element method, allowed the local experimentaldiagrams obtained over the zinc sample to be validated taking into account the radial contribution of thecurrent between both materials in galvanic coupling.

International audience; This paper addresses the effects of corrosion on the high cycle fatigue (HCF) strength of a high mechanical strength martensitic stainless steel (X12CrNiMoV12-3) that is used in aeronautic applications. HCF tests (between 105 and 107 cycles) were carried out in two environments: (i) in air and (ii) in an aqueous solution (pH = 6) of 0.1 M NaCl + 0.044 M Na2SO4 at a loading frequency of 120 Hz. Surface crack initiation is observed in air, whereas in solution, the crack initiated at corrosion defects. The decrease observed in the corrosion fatigue strength of specimens at 107 cycles was 33% of that of similar specimens tested in air. The electrochemical behaviour of the passive film was investigated during fatigue testing in a NaCl aqueous solution by monitoring the free potential and through electrochemical impedance spectroscopy (EIS). Based on fractography analysis and the EIS tests results, fatigue crack initiation mechanisms in air and in the NaCl aqueous solution were identified. A scenario for fatigue crack initiation is proposed based on the physical evidence. Local passive film ruptures are the cause of the corrosion fatigue crack initiation. The film is broken by material strain from the applied cyclic stress during fatigue testing, causing increased local corrosive attack. This effect has been shown at 10 Hz and 120 Hz because the characteristic time for repassivation for the steel is very low compared to the period of the cyclic loading.

The electrochemical behavior of the stainless steel 304L was studied under static mechanical stress. In a first approach, the elastic domain of the material was investigated by using the scanning electrochemical microscope (SECM). The Fe(CN)63− was used as mediator to characterize the electrochemical reactivity of the passive layer of SS 304L under various stress strengths. Keywords: Scanning electrochemical microscopy, Heterogeneous electron transfer, Stress corrosion, Passive layer

International audience; Corrosion sensitivity of a friction stir welded (FSW) AA2024-T3 aluminum alloy has been investigated using both normalized intergranular corrosion test (ASTM-G110) and local electrochemical open circuit potential measurements. In addition, Vickers microhardness and microstructural analysis have been performed. The HAZ close to the TMAZ is the most sensitive to intergranular corrosion because of the presence of continuous lines of S′(S) intergranular precipitates at grain boundaries. Pitting corrosion is due to the intermetallic particles. Their fragmentation produced by stirring effect modifies the pitting corrosion behavior. Microhardness variations depend on the relative volume fraction of GPB zones and S′(S) intragranular precipitates.

International audience; Electrodeposition of CaCO3 was studied under the influence of magnesium ions present in a carbonically pure water. The investigation was performed using electrochemical, gravimetric and optical methods. The chronoamperometric measurements confirmed the inhibiting property of Mg2+ when its concentration is higher than 120 mg L−1 in a solution containing 160 mg L−1 of Ca2+. The optical technique led the nucleation-growth process to be accessed by means of an optical microscope positioned behind a transparent electrode. The increase of Mg2+ concentration changed drastically the calcite morphology. At 360 mg L−1 of Mg2+, the calcite morphology was optically amorphous but the Raman spectrum confirmed its structure. The crystal growth was recorded in situ and the image analysis software characterised the nucleation process as well as the growth rate of the crystals. It allowed the influence of the Mg2+ ions on the crystallisation process of CaCO3 to be quantified.

Lithium intercalation hosts are a key point to the energy density of the largely used LiCoO2 (even if of high cost and toxicity) as well as of manganese oxides which have been investigated most extensively. Iron oxides are attractive electrode materials for low-voltage rechargeable lithium batteries from both cost and environmental standpoints. However, search for iron oxides of conventional crystalline structures and micrometer particle sizes as lithium intercalation cathodes, has been greeted with disappointing results. Here we report on the synthesis, characterizations, electrochemical study and electrochemical impedance spectroscopy (EIS) of a nanocrystalline γ-Fe2O3 that simultaneously exhibits high lithium insertion capacity and good capacity retention upon cycling. These properties reveal thermodynamics of the nanocrystalline material inherently different from those of its microcrystalline counterpart. Moreover, EIS showed that the intercalation process of the lithium ion occurs according to two processes involving first the reduction of the surface Fe3+ with concomitant charge neutralization by Li+ ions onto the surface defects of the nanoparticle followed by the reduction of the core Fe3+ with insertion of the Li+ deeper in the particle.

International audience; A novel technique allowed EIS and microscopical observation of the interface between electrode and solution to be coupled in situ. The electrochemical reduction of oxygen was investigated by using this device when the electrode surface was progressively covered by an insulating layer of scale deposit. It was shown that two time domains can be distinguished from the initial time of the experiment corresponding to a bare electrode up to a totally blocked surface. In the first part of the experiment, EIS showed one time constant which characterizes the charge transfer process of water reduction. When the percentage of coverage reached more than 80%, this latter electrochemical contribution to EIS was negligible and the reduction process of oxygen was highlighted by two time constants observed from impedance diagrams. The high frequency response characterized the charge transfer process and the low frequency loop identified the diffusion process of oxygen. An electrochemical model was proposed to explain the shape of the impedance spectra plotted with respect to the time of coverage. The good correlation between the experimental and the fitted model curves led to the change versus time of the different parameters of the equivalent circuit. It notably showed that the double layer capacity was directly proportional to the active surface measured by the microscope observation until the surface was totally covered, according to the expectations in the experimental conditions used here.

An original technique allowed three in situ measurements to be obtained simultaneously, i.e. electrochemical and mass measurements and a microscope image of the interface between electrode and solution. The nucleation-growth process of CaCO3 deposition was investigated by varying different parameters which influenced the supersaturation coefficient, the Ca2+ concentration, pH and convection of the carbonically pure water near the substrate. The results showed that the variation of the scaling rate was due, for the two first cases, to an influence of the nucleation process whereas for the last case, the kinetics of scale deposition were modified by a shift of the growth rate.

Nanoscale materials offer the advantage of combining structural effects (inside grain structure) with surface effects or grain-boundary effects. Therefore, the electrochemistry of this type of materials is very different from that of traditional microcrystalline ones mainly due to the contribution of the 'surface defects' allowing strong coulombic interactions between the inserted lithium ions and the surface ions called 'electrochemical grafting'. When electrochemical grafting is the first electrochemical step to take place, it can favor the power density and the cycling life of electrode materials. As illustrative examples, electrochemical behaviors of nanocrystalline oxides such as LiMn 2 O 4 , γ-Fe 2 O 3 , and of nanohybrid inorganic-organic materials such as γ-Fe 2 O 3 /PPY (PPY = polypyrrole) are presented.

Magnetically induced effects on electrolytic currents have been studied for various electrochemical systems. For all investigated cases, significant modification was found to be strictly relevant to transport process and magnetic effects were proved to be MHD (i.e. MagnetoHydroDynamic) phenomena. This holds for a reversible system (ferri-ferrocyanide) as well as for non reversible systems such as the electrocrystallization of Zn, or Ni from a pure or adulterated Watts bath. Assuming that the well-known magnetic effects on electrolytic currents in the bulk of solutions keep valid in the close vicinity of the electrode, the MHD phenomena are explained by taking into account the space charge of the diffuse layer. Theoretical expressions which depend on bulk composition and hydrodynamic conditions can thus be obtained. A comparison with experimental results under stationary or dynamic conditions was undertaken. For the latter case, two methods were employed : either classical electrochemical impedance spectroscopy (EIS) or MHD transfer function analysis. For both cases, a good agreement was found between expected physical values and calculated ones. Moreover, new results on electrocrystallization of Ni and Zn have been found.

A conductive transparent electrode is used to observe and quantify the nucleation-growth process of scale deposition. The deposition is accelerated by increasing the interfacial pH induced by an electrochemical reaction on the electrode surface. Three measurements were simultaneously obtained with respect to time. The chronoelectrogravimetric and chronoamperometric curves showed that an increase of the supersaturation in the vicinity of the electrode increased the rate of scale deposition. This result was highlighted in the first instants of deposition when overlapping of crystals was not predominant. The third measurement was the in situ observation by a microscope through the transparent electrode. It allowed the count of crystals and the surface of the individualized crystals to be measured vs. time. It was shown that the increase of the local concentration of calcium and carbonate ions had no influence on the growth rate of both varieties of crystal present on the electrode surface, namely, vaterite and calcite. On the contrary, the count of the particles showed that the increase of the kinetic of scale deposition was only due to the enhancement of the nucleation rate. Thus, for the lowest investigated supersaturation, the number of nuclei increased linearly with time, whereas the highest supersaturation promoted a faster nucleation rate and a higher proportion of calcite. © 2003 The Electrochemical Society. All rights reserved.

This paper is devoted to the description of magnetic field effects on zinc electrodeposition from basic media. The major effect of the magnetic field stems from a slight magnetohydrodynamic forced convection located close to the cathodic interface. Classical impedance analysis reveals that the reaction mechanism is governed by two diffusing species, Zn(II) and OH-, the contributions of which have been discerned. This leads to a good agreement between experimental and theoretical impedance diagrams and shows, once again, that the magnetic field exerts no effect upon the transfer kinetics.

Les substances humiques se fixent en surface des minéraux argileux et modifient les sites d'adsorption des polluants organiques hydrophobes (POH). Parallèlement, les substances humiques dissoutes complexent les POH non ioniques selon des mécanismes de liaison réversible généralement évalués par le coefficient de partage Koc. Les solutés humiques seraient ainsi responsables du transport des POH dans les écosystèmes aquatiques par solubilisation de la fraction adsorbée sur le sédiment. Notre étude a pour objectif la quantification et la modélisation de ces phénomènes pour des composés modèles disponibles commercialement : kaolinite, pyrène et acide humique Aldrich purifié.L'isotherme d'adsorption de l'acide humique (AH) sur la kaolinite à pH 6,5 et à force ionique 10-2 M suit une loi de Freundlich, dont les valeurs du modèle sont KF =0,79 et nF =1,90. Dans les mêmes conditions expérimentales, le pyrène, composé modèle à quatre noyaux du groupe des hydrocarbures aromatiques polycycliques (HAP), semble s'adsorber en formant des microcristaux à la surface de l'argile. La présence d'acide humique fixé sur la kaolinite modifie l'adsorption du pyrène, qui se modélise par une isotherme de Freundlich de paramètres K'F =0,30 et n'F =2,00.Les interactions entre le pyrène et l'acide humique dissous ont été quantifiées par spectroscopie d'extinction de fluorescence et relation de Stern-Volmer. La fraction humique dissoute non adsorbée sur le minéral argileux se caractérise par de plus fortes valeurs de Koc que l'acide humique initial (2,95.105 L.kg-1 contre 1,86.105 L.kg-1). L'hypothèse de fractionnement des substances humiques lors de l'adsorption sur l'argile est confirmée par les variations du poids moléculaire moyen des AH, déterminé par chromatographie d'exclusion stérique, et des variations des intensités de fluorescence des fractions chromatographiées.Les résultats obtenus pour la quantification du pyrène désorbé du solide argileux dans l'eau pure et dans une solution d'AH (50 mg.L-1) tendent à minimiser le rôle de la matière organique naturelle dissoute dans le transfert des polluants hydrophobes du milieu solide au milieu liquide., Humic substances become fixed to the surface of clay minerals and modify the adsorption sites of hydrophobic organic pollutants (HOP). The dissolved humic substances complex the HOP according to reversible binding mechanisms normally assessed by the Koc distribution coefficient. The humic solutes could thus be responsible of transporting HOP in aquatic ecosystems by solubilising the adsorbed fraction on sediment. Our study aims to quantify and model these phenomena using commercially available compounds:- pyrene, a polycyclic aromatic hydrocarbon (PAH) generally used as fluorescence probe and able to bind strongly to humic acid (AH); - a commercially available humic acid (Aldrich), with a high molecular weight and high aromaticity, which can easily adsorb onto colloidal matter and strongly bind PAH; - kaolinite clay, a ubiquitous mineral in aquatic systems, with a particle size distribution in aqueous solution similar to that observed in lake waters.We also have chosen physico-chemical conditions representative of freshwater: pH (6.5) and ionic strength (10-2 M). The adsorption isotherm of the humic acid (HA) on kaolinite at pH=6.5 and at ionic strength 10-2 M follows a Freundlich isotherm, for which model values are fixed at KF =0.79 and nF =1.90. The carboxylic groups of the dissolved HA, which represented more than half the total acidity, were not protonated under these conditions. Despite the negative surface charge of the particles, kaolinite was able to adsorb about 0.2 mgC.g-1 of HA. A decrease in the solution pH occurred as the adsorbed HA quantity increased, suggesting a chemisorption of HA onto clay. The high-pressure size exclusion chromatogram (HPSEC) of the non-adsorbed HA, isolated after centrifugation of the colloidal solution, reflects the selective adsorption of the HA. The higher the molecular weight of the HA (>70 000 Da), the better the adsorption. The hypothesis of the selective adsorption of the humic substances onto clay was also confirmed by the fluorescence variations of the chromatographed fractions.Using the same experimental conditions, pyrene seemed to adsorb and generate micro-crystals on the surface of the clay. The first part of the isotherm fits the pyrene monomer adsorption onto the hydrophobic siloxane surface of the clay. In the second part, the dramatic increase in the adsorption isotherm could be attributed to the formation of pyrene micro-crystals on the solid surface. For a residual pyrene concentration equal to 40 nmol.L-1, the PAH quantity adsorbed onto kaolinite clay (7 nmol.g-1) was about twenty times lower than the quantity adsorbed onto montmorillonite clay (150 nmol.g-1). This could be explained by the inaccessibility of the interlayer cavity of kaolinite to any solute.Natural colloids are often coated by a humic layer. This coating can thus modify HOP adsorption onto the particles. The presence of humic acid fixed on kaolinite effectively modifies pyrene adsorption. This adsorption can be modelled by a Freundlich isotherm with the parameters K'F =0.30 and n'F =2.00. The adsorbed HA molecules seem to limit the formation of pyrene micro-crystals, even if the pyrene adsorption is not competitive with the HA fixation. Indeed, no HA desorption occurs during pyrene fixation onto the organic coated kaolinite.The interactions between pyrene and dissolved humic acid have been quantified by extinction fluorescence spectroscopy and the Stern-Volmer relationship. The unabsorbed, dissolved humic fraction is characterised by Koc values higher than the initial humic acid (2.95 x 105 L.kg-1 compared to 1.86 x 105 L.kg-1). These two values are of the same magnitude as the published value obtained for the non-purified Aldrich HA (2.3±0.3 x 105). The Koc value obtained for the non-adsorbed fraction of HA is unexpected because of the low molecular weight of these molecules. This Koc value can be related either to a better accessibility of the HA hydrophobic cavity for pyrene, or rather to a more efficient fluorescence quenching of pyrene by the humic solutes.The dissolved humic acid may complex the non-ionic PAH according to reversible bonding mechanisms. Therefore, HA can act as a carrier of hydrophobic contaminants if it is able to desorb HOP from the surface of the particles. The results obtained for the quantification of the desorbed pyrene in pure water and in a HA solution (50 mg.L-1) tend to minimise the role of dissolved natural organic matter in the transport of hydrophobic pollutants from the solid to the liquid medium. The values of pyrene concentration in solution obtained after 24 hours contact with kaolinite clay sorbed pyrene with pure water or with the HA solution were very low (respectively 2.4 nM and 12.9 nM) and below the water solubility of pyrene (802 nM). It has been previously demonstrated that the desorption kinetics of pyrene from quartz material are not influenced by the organic matter content of the solution (SCHMITT, 1999). Our results demonstrate that the HA content of the solution did not greatly modify the quantity of pyrene desorbed from clay minerals.

A very recent paper, referred to below as Paper I, had been devoted to the description of magnetic field effects on the structural features of nickel electrodeposits grown from a Watts solution, either pure or in the presence of small amounts of a primary brightener and leveling agent such as 2-butyne-1,4-diol (BD). The conclusions of Paper I stressed the major effect of the magnetic field which was supposed to come down to a magnetohydrodynamic forced convection close to the cathodic interface. This convection enhances those among the cathodic reactions which are likely to be mass-transport controlled, which is the case for the hydrogen electrode reaction as well as for the catalytic hydrogenation undergone by BD on the cathodic surface. The aim of this paper is to describe the results of electrochemical studies which have been carried out with the same system so as to check the validity of our assumption.

[This corrects the article DOI: 10.1371/journal.pone.0167316.].