Éditeur(s) : Université de Paris 7
Résumé : The Seine estuary and its adjacent region Pays de Caux are two significant sources of mercury for coastal marine environments. It is carried through fluvial means for the Seine bay and through karstic fresh water emergences for Pays de Caux's coastal area. Mercury cycle in the Seine estuary and bay is affected by additional anthropical activities. The estuary's maximal turbidity area acts like a trap and a chemical reactor for fluvial mercury. Within this area, we can confirm: (i) the non conservative behaviour of dissolved mercury; (ii) mercury enrichment of particles when comparing the Seine's and marine environment and we suggest mercury particle redistribution from the organic fraction to the oxyhydroxydes fraction. A large fraction of mercury is exported in this state towards coastal areas. Mercury reduction in surface coastal waters and its atmospherical recycling are major phenomena. Photoreduction and biological reduction play quantitative roles equivalent to total mercury recycling via the atmosphere corresponding approximately to 30 % of fluvial exchanges. We are demonstrating that reactive forms of mercury are supporting photoreduction. Mercury behaviour within Pays de Caux's karst depends of the hydrogeological context of the system (time and flow speed, turbidity, flow); regardless of the speciation and/or partition in underground waters, the total amount of mercury in intertidal areas is quantitatively the same as in the Seine estuary. Mercury brought through intertidal emergences (karstic exudations) is not « filtered » by a maximal turbidity area and is more widely bio-available for mussels than in the Seine estuary. Even being free from growth factor influences through simple models, mussels found in Pays de Caux still show one of the highest mercury contamination on the French coast; for the first time this places the emphasis on how much mercury is brought from underground waters to the coastal environment. Surface complexation modelisation tests are able to reproduce the major part of mercury partition in the Seine estuary and bay if a very low mercury exchangeable fraction and minimum complexation parameters are taken into account; thermodynamic calculations also suggest that a strong or highly concentrated « dissolved » ligand must be present in the water in order to compete with chlorocomplex formations and explain our measures.
L'estuaire de la Seine et la région adjacente du Pays de Caux sont deux sources significatives en mercure pour le milieu marin côtier. Les apports sont d'une part fluviatiles en ce qui concerne la Baie de Seine et karstiques via des émergences d'eau douce pour la zone côtière du Pays de Caux. Le cycle du mercure en estuaire et baie de Seine est perturbé par les apports liés aux activités anthropiques. La zone de turbidité maximum de l'estuaire joue le rôle de piège et de réacteur chimique pour le mercure fluviatile. Au sein de cette zone, nous mettons en évidence : (i) un comportement non-conservatif du mercure dissous; (ii) un enrichissement en mercure des particules par rapport à celles de la Seine et du milieu marin et suggérons une redistribution du mercure particulaire de la fraction organique vers la fraction oxyhydroxydes. C'est sous cette forme qu'une fraction importante du mercure est exportée vers la zone côtière. La réduction du mercure dans les eaux côtières de surface et son recyclage atmosphérique sont des phénomènes majeurs. En effet, la photoréduction et la réduction biologique jouent des rôles quantitativement équivalents avec un recyclage total du mercure via l'atmosphère correspondant à environ 30% des apports fluviatiles. Nous montrons que les formes réactives du mercure constituent le substrat de la photoréduction. Le comportement du mercure au sein du karst du Pays de Caux dépend du contexte hydrogéologiques du système (temps et vitesse de circulation, turbidité, débit) ; quelle que soit la spéciation et/ou la partition dans les eaux souterraines, l'apport en mercure total à la zone intertidale est quantitativement du même ordre de grandeur que les apports de la Seine. Le mercure apporté par les émergences intertidales (exutoires karstiques) n'est pas « filtré » par une zone de turbidité maximale et se trouve plus largement biodisponible pour les moules qu'en estuaire de Seine. En s'affranchissant, par des modèles simples, de l'influences des facteurs de croissance, les moules du Pays de Caux affichent toujours une contamination par le mercure parmi les plus élevées du littoral français; ceci met pour la première fois l'emphase sur l'importance de l'apport en mercure par des eaux souterraines dans un environnement côtier. Les essais de modélisation de complexation de surface reproduisent la majeure partie de la partition du mercure dans l'estuaire et la baie de Seine si l'on tient compte d'une fraction échangeable en mercure très faible et de paramètres de complexation minimums ; les calculs thermodynamiques suggèrent aussi qu'un ligand « dissous » fort ou présent à de fortes concentrations doit être présent dans l'eau afin d'entrer en compétition avec la formation de chlorocomplexes et expliquer nos mesures.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2001/these-1842.pdf
http://archimer.ifremer.fr/doc/00000/1842/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A set of four reactive flow-through experiments at temperature T = 100 degrees C and total pressure P=12 MPa was performed in limestone reservoir samples. By using various ranging from 0.7 to 10 MPa, these experiments mimic mass transfers occurring (1) near the injection well, where the brine is almost saturated with CO2 (i.e. P-CO2 approximate to P), and (2) at increasing distances from the injection well, where the fluid displays lower values and higher divalent cation concentrations due rock dissolution along the fluid pathway. Results for P-CO2 = 10 MPa show non-uniform dissolution features associated with transport-controlled mass transfer, while reaction-controlled uniform dissolution is observed for P-CO2 = 2.5 MPa. The experiment with P-CO2 = 6 MPa allows investigating in detail the transition from transport-to reaction-controlled dissolution. Conversely, the experiment reproducing conditions far from the injection well (P-CO2 = 0.7 MPa), shows a decrease of porosity triggered by the precipitation of Mg-rich calcite. For all the dissolution experiments, the time-resolved porosity phi(t) can be modeled by a simple non-linear equation including parameters that characterise the dissolution regime triggered by the reactivity of the inlet fluid (measured by the Damkohler number, Da). Furthermore, all dissolution experiments display power scaling between permeability (k) and porosity (phi) with distinctly different scaling exponents characterising the reactivity of the fluid percolating the sample, independently from the decrease with time of the reactive surface area. It is shown also that dissolution at moderate positive values of Da seems the most efficient to increase permeability and promote a rapid spreading of the reaction front, while inducing minimal modification of the porosity in the vicinity of the CO2 injection well. These results can be used to parameterize the k-phi function for modeling the earliest dissolution processes occurring in the vicinity of the reaction front.
ISSN: 0009-2541

hal-00445277
https://hal.archives-ouvertes.fr/hal-00445277
DOI : 10.1016/j.chemgeo.2009.03.028

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This study explores the dynamics of porosity and reactive surface area changes during porous limestone dissolution by CO2-rich water. The Sr and Ca concentrations in both the rock and the outlet solution are used to evaluate the reactive surface area changes of the two rock-forming calcites, i.e. micrite grains and sparite crystals, which have different trace element signatures. The geometric surface area measured with X-ray microtomography decreases slightly whereas the reactive surface area increases continuously with increasing porosity from 20.3 to 30.2%. Surprisingly, changes in reactive surface areas are very different between the two calcites. The reactive surface area changes in the micrite are parabolic while the reactive surface area of sparite increases greatly. The numerical model HYTEC is used to model the change in reactive surface areas during the experiment. Different geometrical models are tested. The model based on spherical-grain dissolution and spherical-pore growth fails to reproduce the experimental results, while the sugar-lump model provides reasonable agreement with the experiment.
ISSN: 0009-2541

hal-00445274
https://hal.archives-ouvertes.fr/hal-00445274
DOI : 10.1016/j.chemgeo.2009.01.032

Éditeur(s) : HAL CCSD
Résumé : When the upper crust below the mountain ranges shows crustal extension with a direction collinear to the convergence direction, it is generally accepted that it is the result of gravitational collapse. However, recent studies challenge this paradigm by showing that erosion induces uplift and extension in the central part of the low convergent mountain ranges. In this study, we investigate the impact of denudation on the seismotectonic regime of mountain ranges.In order to identify a relationship between seismotectonic regime and erosion, the first part of this work presents a compilation of data in the mountain ranges. Based on these observations, a simple kinematic model is proposed to predict the seismotectonic regime of the study ranges.For low convergence rate and moderate mean elevation ranges, this model predicts an extension regime when the denudation rate is 15% higher than the convergence rate.The second part is devoted to the development of thermomechanical 2D finite element models to study the impact of surface processes on the deformation of the Pyrenees. The results show that the isostatic response to erosion reactivates pre-existing structures. The kinematics of an inherited fault plane can be predicted due to the gradient of the horizontal surface velocity profile. Thus, a plane located in the eroded zone is reactivated in normal fault when near the border of the erosion area, this same plane is reactivated in reverse fault. These results suggest that the current deformation in the North Pyrenean Zone could be the result of surface processes.Given the small number of studies quantifying erosion rates in the Pyrenees, the models developed in the second part suffer from high uncertainty. To remedy this, we study the central Pyrenees through a study that combines two types of data : watershed denudation rates from cosmogenic isotopes concentration, and incision rates from sediments buried in the karst. These results are presented in chapter 3. Denudation profiles obtained are consistent with reactivation of a normal fault plane located in the North Zone of the Central Pyrenees.From our study in the Pyrenees, a good correlation appears between the value of the rate of erosion and the glacier occupation. Given that the glaciers where more developed in the Alps, it raises the question of the impact of the late-würmian deglaciation on the present deformation of this range. A numerical model detailing this relationship is presented in the fourth chapter. Theresults show that deglaciation of the western Alps is controlled by the rheological heterogeneity of the crust. Some of our models predict uplift rates consistent with those highlighted by geodesy.
Lorsque l’extension de la croûte sous les parties hautes des chaînes de montagnes est colinéaire à la direction de convergence, il est traditionnellement admis que le moteur est l’effondrement gravitaire. Pourtant, des études récentes remettent en cause ce paradigme en montrant que l’érosion induit un soulèvement et de l’extension dans la partie centrale des chaînes de montagne à faible taux de convergence. L’objectif de notre étude est d’étudier l’impact de la dénudation de la topographie sur le régime sismo-tectonique des chaînes de montagnes.La première partie de ce travail présente une compilation de données dans les chaînes de montagnes afin de dégager des relations entre régime sismo-tectonique et érosion. Sur la base de ces observations, un modèle cinématique simple permettant de prévoir le régime de la chaîne est proposé. Ainsi, pour les chaînes à faible taux de convergence et d’élévation moyenne, ce modèleprédit de l’extension lorsque le taux de dénudation est 15% plus élevé que le taux de convergence.La deuxième partie est consacrée au développement d’un modèle thermo-mécanique 2D en éléments finis pour étudier l’impact des processus de surface sur la déformation des Pyrénées.Les résultats montrent que la réponse isostatique à l’érosion permet de réactiver des structurespré-existantes. La cinématique d’un plan de faille hérité peut être prédite grâce au gradient du profil des vitesses de surface horizontales. Ainsi, un plan situé dans la zone d’érosion est réactivé en faille normale alors qu’en bordure de cette zone une faille est réactivée en régime inverse. Ces résultats suggèrent que la déformation actuelle des Pyrénées pourrait être la conséquence d’unprocessus d’érosion.Compte tenu du faible nombre d’études quantifiant les taux d’érosion dans les Pyrénées, les modèles développés dans la deuxième partie souffrent d’une forte incertitude. Pour y remédier, nous avons cherché à les quantifier dans les Pyrénées Centrales grâce à une étude qui combine deux types de données : taux de dénudation des bassins versants à partir des isotopes cosmogéniques, et vitesses d’incision à partir des sédiments piégés dans les karsts. Ces résultats sontprésentés dans la troisième partie. Les profils de dénudation obtenus sont compatibles avec unrejeu en faille normale d’un plan situé dans la Zone Nord Pyrénéenne des Pyrénées Centrales.Notre étude dans les Pyrénées, montre une bonne corrélation entre la valeur du taux d’érosion et la cartographie de l’occupation glaciaire. Les glaciers ayant été plus développés dans les Alpes, cela pose la question de l’impact de la déglaciation tardi-Wurmienne sur la déformation actuelle de cette chaîne. Un modèle numérique détaillant cette relation est présenté dans le quatrième chapitre. Les résultats montrent que la déglaciation des Alpes occidentales est contrôléepar l’hétérogénéité rhéologique de la croute. Certains de nos modèles prédisent des vitesses de surrection compatibles avec celles mises en évidence par la géodésie.
https://hal.archives-ouvertes.fr/tel-01262333

tel-01262333
https://hal.archives-ouvertes.fr/tel-01262333
https://hal.archives-ouvertes.fr/tel-01262333/document
https://hal.archives-ouvertes.fr/tel-01262333/file/these-Genti-2015-postjury.pdf

Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
1] Recent statistical analysis by Lallemand et al. (2008) of subduction zone parameters revealed that the back-arc deformation mode depends on the combination between the subducting (nu(sub)) and upper (nu(up)) plate velocities. No significant strain is recorded in the arc area if plate kinematics verifies nu(up) = 0.5 vsub - 2.3 (cm/a) in the HS3 reference frame. Arc spreading ( shortening) occurs if nu(up) is greater ( lower) than the preceding relationship. We test this statistical law with numerical models of subduction, by applying constant plate velocities far away from the subduction zone. The subducting lithosphere is free to deform at all depths. We quantify the force applied on the two converging plates to sustain constant surface velocities. The simulated rheology combined viscous (non-Newtonian) and brittle behaviors, and depends on water content. The influence of subduction rate vs is first studied for a fixed upper plate. After 950 km of convergence ( steady state slab pull), the transition from extensional to compressive stresses in the upper plate occurs for vs similar to 1.4 cm/a. The effect of upper plate velocity is then tested at constant subduction rate. Upper plate retreat ( advance) with respect to the trench increases extension ( compression) in the arc lithosphere and increases ( decreases) the subducting plate dip. Our modeling confirms the statistical kinematic relationship between vsub and nu(up) that describes the transition from extensional to compressive stresses in the arc lithosphere, even if the modeled law is shifted toward higher rates of upper plate retreat, using our set of physical parameters ( e. g., 100 km thick subducting oceanic plate) and short- term simulations. Our results make valid the choice of the HS3 reference frame for assessing plate velocity influence on arc tectonic regime. The subduction model suggests that friction along the interplate contact and the mantle Stokes reaction could be the two main forces competing against slab pull for upper mantle subductions. Besides, our simulations show that the arc deformation mode is strongly time dependent.
ISSN: 1525-2027

hal-00412328
https://hal.archives-ouvertes.fr/hal-00412328
https://hal.archives-ouvertes.fr/hal-00412328/document
https://hal.archives-ouvertes.fr/hal-00412328/file/arcayG32008.pdf
DOI : 10.1029/2007GC001875

Éditeur(s) : HAL CCSD Ocean Drilling Programm
Résumé : This paper provides a summary of postcruise scientific results from Ocean Drilling Program (ODP) Leg 209 available to date, building upon shipboard observations and syntheses summarized in the Leg 209 Initial Results volume. During Leg 209, 19 holes were drilled at 8 sites along the Mid-Atlantic Ridge from 14°43´ to 15°44´N, mainly in residual mantle peridotite intruded by gabbroic rocks, in order to understand the tectonic and structural processes responsible for formation of oceanic lithosphere with abundant residual peridotite exposed on the seafloor coupled with a relatively low proportion of volcanic rocks. Based on proportions of recovered lithologies, the entire area may be underlain by mantle peridotite with ~20%–40% gabbroic intrusions and impregnations. Impregnated peridotites with olivine + two pyroxenes + plagioclase + spinel that apparently formed in equilibrium probably record crystallization from primitive mid-ocean-ridge basalt at pressures of 0.5–0.6 GPa. Metamorphic equilibria record isobaric cooling to ~1100°C at this pressure. Thus, the conductively cooled thermal boundary layer beneath the Mid-Atlantic Ridge in this region is >15 km thick. Combined crystallization and reaction with residual peridotite formed a series of impregnated peridotites recording increasing Na content at nearly constant Mg#; this process could explain some of the variation in fractionation-corrected Na (e.g., Na = 8.0) observed in mid-ocean-ridge basalts. Clinopyroxene textures and compositions record such impregnation processes, and they are particularly well documented for Site 1274. Other Leg 209 gabbroic rocks formed from extensive crystallization of highly evolved melts, indicating that a substantial proportion of melt entering the thermal boundary layer crystallizes entirely beneath the seafloor, with no volcanic equivalent. Alteration of peridotites occurred over a range of temperatures and is the result of three distinct processes: rock-dominated serpentinization with formation of brucite in olivine-rich lithologies, fluid-dominated serpentinization with formation of magnetite and no brucite, and fluid-dominated talc alteration with addition of SiO2 as well as H2O and oxygen. The latter two processes also exhibit detectable trace element metasomatism that is distinct in its character from the igneous impregnation described in the previous paragraph. Microstructures show that most residual peridotites were not ductilely deformed at temperatures less than ~1200°C. Structural and paleomagnetic data require tectonic rotations of relatively undeformed blocks; some rotations probably exceeded 60° around nearly horizontal axes parallel to the rift axis. Rotations occurred along several generations of high-temperature mylonitic shear zones extending deeper than 15 km depth and numerous faults at lower temperature. Early formed shear zones and faults were passively rotated around later features; such a process could have produced low-angle fault surfaces without slip on low-angle faults. This region provides end-member examples of processes that are common at many or most slow-spreading ridges. Osmium isotope ratios indicate an ancient history of depletion for residual peridotites from the 14°–16°N region along the Mid-Atlantic Ridge. Though depleted Os isotope ratios in peridotite have been reported elsewhere along the global ridge system, the values from this region are among the most depleted. In general, Os isotope ratios from mid-ocean-ridge basalts are systematically more radiogenic than Os isotope ratios from ridge peridotite samples, suggesting a polygenetic heterogeneous source for mid-ocean-ridge basalts. Geochemical studies of zircons from Leg 209 gabbroic rocks and impregnated peridotites, together with other ridge and arc-related zircons, indicate that ridge zircons have systematically lower fractionation-corrected U and Th concentrations compared to arc zircons. This observation provides a tool for interpreting the tectonic provenance of ancient detrital zircons and indicates an arclike provenance for Hadean detrital zircons. Geobiological studies and aerobiological studies were also undertaken during Leg 209. The geobiological work found no measurable microbial enhancement of olivine dissolution rate, possibly because the samples from Leg 209 were sterile. The aerobiological study determined that dust from North Africa, collected from the derrick of the JOIDES Resolution during Leg 209, contains a variety of abundant microorganisms.
Proceedings ODP, scientific results, 209

hal-00407966
https://hal.archives-ouvertes.fr/hal-00407966
DOI : 10.2973/odp.proc.sr.209.001.2007

Éditeur(s) : Springer Berlin / Heidelberg
Résumé : The role of particles in the fate and speciation of trace metals in macrotidal estuaries was studied using a surface complexation model (MOCO). Cadmium was selected as the target metal contaminant due to its reactivity in estuaries: cadmium behavior is mainly controlled by heterogeneous processes (sorption/desorption) related to salinity and suspended matter gradients. Various scenarios of suspended matter distribution according to salinity were simulated. The impact of surface properties (specific surface area, density of surface sites, acido-basic properties, and complexation constant) was evaluated using data collected on particles from the Gironde, Loire, and Seine estuaries. Our results show that particle surface properties, evaluated on the basis of various parameters, are instrumental in "non-conservative" contaminant speciation in the estuarine environment. Their evaluation enables us to understand and simulate, to a large extent, the fate of "Cd-type" contaminants (whose behavior is controlled by competition between sorption and desorption processes). The natural variations of these properties can be responsible for significant modifications of the Cd speciation in the macrotidal estuaries where salinity and SM gradients are very strong.
The Handbook of Environmental Chemistry (1433-6839) (Springer Berlin / Heidelberg), 2006 , Vol. 5H , P. 265-301

Droits : 2006 Springer
http://archimer.ifremer.fr/doc/2006/publication-2005.pdf
DOI:10.1007/b89479
http://archimer.ifremer.fr/doc/00000/2005/

Éditeur(s) : HAL CCSD
Résumé : Thrusting fault zone in foreland basins are characterized by highly foliated zones generally enriched in phyllosilicates which can play a major role on the mechanical behaviour of the fault. In this context, investigations of synkinematic clay minerals permit to determine the origin of the fluid from which they precipitated as well as the mechanisms of deformation. Our study is focused on clay mineral assemblages (illite and chlorite) in a major thrust fault located in the Monte Perdido massif (southern Pyrenees), a shallow thrust that affects upper cretaceous-paleocene platform carbonates and lower Eocene marls and turbidites. It implied 3 km of displacement of the Monte Perdido thrust unit with respect to the underlying Gavarnie unit. In this area the cleavage development by pressure-solution is linked to the Monte Perdido and Gavarnie thrust activity. The core zone of the fault, about 6 m thick, consists of an interval of intensely deformed clay-bearing rocks bounded by major shear surfaces. The deformed sediment is markedly darker than the protolith. Calcite-quartz shear veins along the shear planes are abundant. Detailed SEM and TEM observations of highly deformed fault zone samples indicate that clay mineral enrichment in the core zone of the fault is not only related to passive increase by pressure-solution mechanism but that dissolution-recrystallization of phyllosilicates occurs during deformation. A mineral segregation is observed in the highly deformed zone. Newly formed 2M 1 muscovite is present along the cleavage whereas IIb chlorite crystals fill SV2 shear veins suggesting syntectonic growth of phyllosilicates in the presence of fluids in low-grade metamorphic conditions. These mineralogical reactions act as weakening processes and would favour Monte Perdido fault creeping.
Swiss Journal of Geosciences

hal-00795553
https://hal.archives-ouvertes.fr/hal-00795553
DOI : 10.1007/s00015-012-0098-0

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Numerical programs for simulating flow and reactive transport in porous media are essential tools for predicting reservoir properties changes triggered by CO2 underground injection. At reservoir scale, meshed models in which equations are solved assuming that constant macroscopic properties can be defined in each cells, are widely used. However, the parameterization of the dissolution-precipitation problem and of the feedback effects of these processes on the flow field is still challenging. The problem arises from the mismatch between the scales at which averaged parameters are defined in the meshed model and the scale at which chemical reactions occur and modify the pore network geometry. In this paper we investigate the links between the dissolution mechanisms that control the porosity changes and the related changes of the reactive surface area and of the permeability. First, the reactive surface area is computed from X-ray microtomography data obtained before and after a set of dissolution experiments of pure calcite rock samples using distinctly different brine-CO2 mixtures characterizing homogeneous to heterogeneous dissolution regimes. The results are used to validate the power law empirical model relating the reactive surface area to porosity proposed by Luquot and Gauze (2009). Second, we investigate the spatial distribution of the effective hydraulic radius and of the tortuosity, two structural parameters that control permeability, in order to explain the different porosity-permeability relationships observed for heterogeneous and homogeneous dissolution regimes. It is shown that the increase of permeability is due to the decrease of the tortuosity for homogeneous dissolution, whereas it is due to the combination of tortuosity decrease and hydraulic radius increase for heterogeneous dissolution. For the intermediate dissolution regime, identified to be the optimal regime for increasing permeability with small changes in porosity, the increase of permeability results from a large increase in the mean effective hydraulic radius of the sample.
ISSN: 0169-7722

hal-00617671
https://hal.archives-ouvertes.fr/hal-00617671
DOI : 10.1016/j.jconhyd.2010.07.004

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : The tropical coast of Queensland, Australia is experiencing rapid population and tourism growth. Heavy development pressure is being placed on the biophysical environment, which includes the largest sand island in the world (World Heritage listed), Fraser Island. Despite the existence of State planning legislation oriented towards environmental sustainability, it is apparent that little, if any, regard is being paid to the long-term effects of resort and canal-estate development on the underlying biophysical environment of the coast and islands. While the remarkable surface features of the tropical coastal environment such as the surf beaches, the unique dune lakes, and the coastal vegetation, as well as the prolific wildlife, are used as selling points for new settlement and above all tourism, little is known or apparently of major concern with respect to the long term environmental impact of coastal development. While the crowding effect of large numbers of visitors and their impact on the natural environment - through significant degradation, site hardening or lack of proper on-site management – has been identified as a particular problem in certain areas, there is little knowledge of impacts on the underlying coastal geomorphology. In particular, developmental choices are often made in ignorance of, or disregard of, the widespread existence of tropical acid sulfate soils in that coastal environment. Reactive soils such as these can, and do, greatly affect the biophysical outcomes of a development if they are exposed. This paper documents such impacts in the form of a case study of the acid sulfate soil problem in relation to the development of tourist resorts, and suggests that part of the solution is for the State Government to insist on enforceable standards relating to their development for tourism in the coastal zone. These would reduce the use by many resort owners of fancy golf course developments as an environmental cover up to make it look as if they put a lot of effort into protecting the environment….
La côte tropicale du Queensland est confrontée à un accroissement rapide de la population. Les fortes pressions anthropiques pèsent sur le milieu biophysique, qui comprend notamment a plus grande île de sable du monde, un site classé Patrimoine de l’Humanité, Port Hinchinbrook et Fraser Island. Malgré l’existence d’une législation nationale orientée vers la préservation de l’environnement, il est manifeste que peu d’attention est accordée aux effets à long terme des sites touristiques et du développement de l’urbanisation sur ces franges côtières sensibles. L’aspect massif des flux de visiteurs et leurs impacts sur le milieu naturel a été identifié comme un sujet d’inquiétude particulier dans certaines régions. La connaissance des impacts sur la géomorphologie côtière souterraine est très réduite et les choix de développement sont souvent faits dans l’ignorance ou au mépris de la présence répandue de terrains de sulfate d’acide dans ce milieu côtier. Des sols réactifs comme ceux-là peuvent affecter, et affectent, grandement les résultats géophysiques d’un développement lorsqu’ils sont connus. Des études de cas sur le problème des sols de sulfate d’acide suggèrent qu’une partie de la solution pour le gouvernement de l’Etat du Queensland est d’imposer des normes obligatoires pour le développement du tourisme dans la zone côtière.
Australie
Queensland

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.1272
http://journals.openedition.org/etudescaribeennes/1272

Éditeur(s) : HAL CCSD Taylor & Francis
Résumé : International audience
Abstract Indoor fungal contamination has been associated with a wide range of adverse health effects, including infectious diseases, toxic effects and allergies. The diversity of fungi contributes to the complex role that they play in indoor environments and human diseases. Molds have a major impact on public health, and can cause different consequences in hospitals, homes and workplaces. This review presents the methods used to assess fungal contamination in these various environments, and discusses advantages and disadvantages for each method in consideration with different health risks. Air, dust and surface sampling strategies are compared, as well as the limits of various methods are used to detect and quantify fungal particles and fungal compounds. In addition to conventional microscopic and culture approaches, more recent chemical, immunoassay and polymerase chain reaction (PCR)-based methods are described. This article also identifies common needs for future multidisciplinary research and development projects in this field, with specific interests on viable fungi and fungal fragment detections. The determination of fungal load and the detection of species in environmental samples greatly depend on the strategy of sampling and analysis. Quantitative PCR was found useful to identify associations between specific fungi and common diseases. The next-generation sequencing methods may afford new perspectives in this area.
ISSN: 1040-841X

hal-00874670
https://hal.archives-ouvertes.fr/hal-00874670
DOI : 10.3109/1040841X.2013.777687
PUBMED : 23586944

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This work shows the preparation and separation performance assessment of carbon membranes derived from phenolic resin by a vacuum-assisted method and carbonisation in an inert atmosphere. The vacuum time played an important role in tailoring the structure of the membranes. For instance, pore volumes and surface areas increased from 0.81 and 834 to 2.2 cm3g−1and 1910 m2g−1, respectively, as the vacuum time exposure increased from 0 to 1200 s. The significant structural changes correlated very well with water permeation, as fluxes increased by 91% as the vacuum time increased from 0 to 1200 s reaching up to 169 L m−2h−1at 5 bar. Molecular weight cut-off tests showed no rejection for the smaller glucose and sucrose molecules, though this increased to ~ 80% and full rejection for 36 kDa and 400 kDa polyvinyl pyrrolidine. Interestingly, FTIR spectra showed that the peaks of C–H stretching vibration (2800–3200 cm−1) and C–O stretching (1030 cm−1) became more pronounced as a function of increasing vacuum time, strongly suggesting that the use of vacuum further assisted in the polycondensation of phenolic oligomers. Based on these outcomes, a cluster to cluster model is proposed, whereby vacuum application promoted crosslinking reactions of the phenolic resin, creating microporous regions within the clusters, and mesoporous regions between the clusters. © 2016 Elsevier B.V
ISSN: 0376-7388

hal-01683220
https://hal.univ-antilles.fr/hal-01683220
DOI : 10.1016/j.memsci.2016.11.002

Éditeur(s) : HAL CCSD
Résumé : International audience
The anatomy of tension wood and opposite wood was compared in 21 tropical rain forest trees from 21 species belonging to 18 families from French Guyana. Wood specimens were taken from the upper and lower sides of naturally tilted trees. Measurement of the growth stress level ensured that the two samples were taken from wood tissues in a different mechanical state: highly tensile-stressed wood on the upper side, called tension wood and normally tensile-stressed wood on the lower side, called opposite wood. Quantitative parameters relating to fibres and vessels were measured on transverse sections of both tension and opposite wood to check if certain criteria can easily discriminate the two kinds of wood. We observed a decrease in the frequency of vessels in the tension wood in all the trees studied. Other criteria concerning shape and surface area of the vessels, fibre diameter or cell wall thickness did not reveal any general trend. At the ultrastructural level, we observed that the microfibril angle in the tension wood sample was lower than in opposite wood in all the trees except one (Licania membranacea).
IAWA Journal

hal-00194915
https://hal.archives-ouvertes.fr/hal-00194915
https://hal.archives-ouvertes.fr/hal-00194915/document
https://hal.archives-ouvertes.fr/hal-00194915/file/IAWA2006_RuelleClairBeauchenePrevostFournier_ccsd.pdf
IRD : PAR00001321

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Abstract View references (45)Graphene oxide-iron oxide (GO-Fe3O4) nanocomposites were synthesised by co-precipitating iron salts onto GO sheets in basic solution. The results showed that formation of two distinct structures was dependent upon the GO loading. The first structure corresponds to a low GO loading up to 10wt%, associated with the beneficial intercalation of GO within Fe3O4nanoparticles and resulting in higher surface area up to 409m2g-1. High GO loading beyond 10 wt% led to the aggregation of Fe3O4 nanoparticles and the undesirable stacking of GO sheets. The presence of strong interfacial interactions (Fe-O-C bonds) between both components at low GO loading lead to 20% higher degradation of Acid Orange 7 than the Fe3O4 nanoparticles in heterogeneous Fenton-like reaction. This behaviour was attributed to synergistic structural and functional effect of the combined GO and Fe3O4 nanoparticles.
ISSN: 2045-2322

hal-01683208
https://hal.univ-antilles.fr/hal-01683208
DOI : 10.1038/srep04594

Éditeur(s) : HAL CCSD
Résumé :  
The anatomy of tension wood and opposite wood was compared in 21 tropical rain forest trees from 21 species belonging to 18 families from French Guyana. Wood secimens were taken from the upper and lower sides of naturally titled trees. Measurement of the growth stress level ensured that the two samples were taken from wood tissues in a different mechanical state: highly tensile-stressed wood on the upper side, called tension wood and normally tensile-stressed wood on the lower side, called opposite wood. Quantitative parameters relating to fibres and vessels were measured on transverse sections of both tension and opposite wood to check if certain criteria can easily discriminate the two kinds of wood. We observed a decrease in the frequency of vessels in the tension wood in all the trees studied. Other criteria concerning shape and surface area of the vessels, fibre diameter or cell wall thickness did not reveal any general trend.At the ultrastructural level, we observed that the microfibril angle in the tension wood sample was lower than in opposite wood in all the trees except one (Licania membranacea).
IAWA Journal

hal-01032149
https://hal.archives-ouvertes.fr/hal-01032149