Dissertations / Theses on the topic 'Teneur d'eau'
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Van, Hullebusch Eric. "Contribution à l'étude du devenir, de la mobilité et de l'impact de métaux utilisés pour le traitement de plans d'eau eutrophes : cas de l'aluminium et du cuivre." Limoges, 2002. http://www.theses.fr/2002LIMO0016.
Eichinger, Marie. "Dégradation bactérienne du carbone organique dissous dans la colonne d'eau : une approche couplée expérimentation - modélisation." Aix-Marseille 2, 2007. http://theses.univ-amu.fr.lama.univ-amu.fr/2007AIX22098.pdf.
This thesis aims to utilise both experimental and modelling approaches to investigate growth of pelagic heterotrophic bacteria that utilise dissolved organic carbon (DOC) as nutritive resource. Two main axes merge from this work: (1) the study of growth models, constructed from experimental results, with a view to implement them in ecosystem models, and (2) the investigation of the environmental factors influencing the bacterial growth efficiency (BGE) with these models. The main objective consists of the study of bacterial growth in different environmental contexts and to deduce a suitable mathematical formulation for describing the interaction between growth and DOC to include this in a biogeochemical model later on. Firstly, bacterial production and respiration data, obtained during the POMME program that carried out in the Northeast Atlantic Ocean according to several depths and seasons, allowed the application of the Monod model that uses Michaelis-Menten kinetics. The coupled study of the model with data permitted to show that BGE varies according to depth and season. BGE has been estimated experimentally directly from data but also with the model, as BGE is one of the parameter. We have thus highlighted that this model, often utilised in biogeochemical models to represent bacterial growth, is not sufficient. In order to use mechanistic models to describe bacterial growth, we decided to realise biodegradation experiments, in artificial and controlled medium, with a monospecific bacterial strain and a unique carbon substrate. Two kinds of experiments were realised: batch-kind experiments where all the carbon substrate was introduced since the beginning of the experiment, and experiments where the carbon substrate was periodically pulsed. The total amount of substrate put in both systems was the same. These experiments first allowed highlighting key processes: the refractory DOC production that accumulates in batches, the variation of the specific bacterial carbon content during an experiment, the maintenance process at the respiration level when bacteria are starved as well as the instantaneous response to an environmental perturbation. BGE have also been estimated for each experiment and according to different methods: experimentally directly from the data sets and from various models, each of them comprising a different level of complexity. Three models were utilised: the Monod model, the Marr-Pirt model and a mechanistic model resulting from the DEB (Dynamic Energy Budget) theory and specifically constructed for the pulse substrate experiment. We highlighted that what else the method used, BGE value is always higher for the pulse experiment than for the batch-kind experiment. BGE values were also always higher when the maintenance process was taken into account in their estimation. This would mean that BGE value is under-estimated with the classical method of estimation, i. E. With batch experiments and without considering the maintenance process. This would lead to the conclusion that the bacterial role as CO2 producer is over-estimated. The DEB model, highly complex for the representation of only one bacterial species and a unique substrate, was also simplified in view of its implementation in a biogeochemical model later on. We have demonstrated that the original system with 4 differential equations can be reduced to a system with 2 differential equations, where growth can be expressed by a logistic equation with a variable carrying capacity. The simplification of this model does not imply any loss of performance at the level of model dynamics and reduces the calibration and simulation time
Kengni, Lucas. "Mesure in-situ des pertes d'eau et d'azote sous culture de maïs irriguée : application à la plaine de la Bièvre (Isère)." Grenoble 1, 1993. http://www.theses.fr/1993GRE10067.
Kuppel, Sylvain. "Assimilation de mesures de flux turbulents d'eau et de carbone dans un modèle de la biosphère continentale." Versailles-St Quentin en Yvelines, 2012. http://www.theses.fr/2012VERS0041.
Assimilating terrestrial ecosystem data is an approach increasingly used to fill the gap between experimental observations and the ecophysiological theory as embodied in process-based land surface models. In this thesis, we have sought to use the information content of eddy covariance measurements of net carbon dioxide (NEE) and latent heat (LE) fluxes made at the sites of the FLUXNET global network, aiming at optimizing key parameters of the ORCHIDEE vegetation model and at refining the uncertainty budget. A Bayesian statistical approach has been chosen, so as to account for prior knowledge of the uncertainties related to the model parameters, the model equations, and the measurements. The major line of work has been to develop a data assimilation method where observations from several flux sites are simultaneously used as a constraint, in order to optimize a unique set of parameters considered as generic within a given class of ecosystem. We found that this multi-site approach significantly improves the model-data agreement at seasonal and annual time scales, with performances fairly similar to those brought by site-scaled, independently optimized parameters (single-site approach). We notably discuss the fact that the multi-site parameters’ values are not always a mere average of their single-site counterparts. Making use complementary data, we also evaluated the ability of the multi-site optimizations to improve the simulation of the gross carbon fluxes (photosynthesis and respiration) at the site scale, while at the global scale we considered the modeled phenology of the leaf cover and the seasonal cycle of the atmospheric CO2 concentration. Within our methodological developments, we have also proposed a technique to infer the statistical structure of the error stemming from inadequate and/or missing process representations in a global vegetation model such as ORCHIDEE. Focusing on net carbon fluxes, our results suggest that this « model error » deserves an explicit representation in the uncertainty budget inherent to carbon cycle modeling
Féray, Christine. "Nitrification en sédiment d'eau douce : incidence de rejets de station d'épuration sur la dynamique de communautés nitrifiantes." Lyon 1, 2000. http://www.theses.fr/2000LYO10058.
Despreaux, Marc. "Le phosphore et l'azote dans les sédiments du fleuve Charente (France) : variations saisonnières et mobilité potentielle." Lyon 1, 1990. http://www.theses.fr/1990LYO10007.
Ouedraogo, Francois. "Etude des transferts d'eau à l'interface sol-atmoshpère. Cas d'un sol du Burkina Faso à faible teneur en eau." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2008. http://tel.archives-ouvertes.fr/tel-00731139.
Ouedraogo, François. "Etude des transferts d'eau à l'interface sol-atmosphère : cas d'un sol du Burkina Faso à faible teneur en eau." Montpellier 2, 2008. http://www.theses.fr/2008MON20235.
The transfer of water at the soil-atmosphere interface is addressed through a thermo dynamical approach which constitutes a general framework for describing both the thermodynamical status of the water in the soil and the transfer mechanisms at stake: liquid phase filtration, water vapor diffusion, liquid-vapor phase change. An experimental characterization of a soil has been carried out and completed with bibliographical data. Experimental tests of water transfer in columns of the same soil, placed in drying atmosphere enabled the establishment of the global kinetic of water loss and the evolution of the profiles of the water content through time. A numerical simulation of the water transfer in the neighborhood of the interface is proposed. A study about the sensitiveness to the physical parameters of the soil is presented. The results of the numerical model are then compared with the tests of the transfer on the columns. The correspondence is good on the basis of an adjustment of the hydrologic parameters as mentioned in the literature. Water and vapor fluxes evolutions in low water content soils allow the description of transfer mechanisms near the interface. It is shown that the phase change which ensures the continuity of the transfers between the soil and the atmosphere relates to a few centimeters of the soil under that interface
Humbert, Hugues. "Etude de la sorption des matières organiques naturelles par les résines échangeuses d'ions : intérêt pour la production d'eau potable." Poitiers, 2006. http://www.theses.fr/2006POIT2256.
Natural Organic Matter (NOM) represents through Total Organic Carbon (TOC) a key parameter for the control of drinking water quality. The first objective of this study was to evaluate the efficacy of the Anion Exchange Resin (AER) MIEX® and different other AER for the elimination of Dissolved Organic Carbon (DOC) from a high DOC content surface water. The performances of these AER were compared with those of coagulation/flocculation at laboratory scale as well as pilot scale. The second objective of this study was to determine the impact of AER treatment on the reduction of competition mechanisms between NOM and pesticides for the adsorption on activated carbon and on the reduction of membrane fouling (ultrafiltration). Various analytical tools (fluorescence spectroscopy, size exclusion chromatography, pyrolysis GC/MS (gas chromatography/mass spectrometry)) were used in order to characterize NOM of raw and treated waters. As well as MIEX® resin, whole studied AER proved to be an interesting alternative to coagulation/flocculation for DOC removal. Moreover, the interest of AER lies in its combination with activated carbon for the reduction of competition mechanisms between NOM and pesticides
Bourget, Sébastien. "Limnologie et charge en phosphore d'un réservoir d'eau potable sujet à des fleurs d'eau de cyanobactéries : le lac St-Charles, Québec." Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/28078/28078.pdf.
Benyahia, Mohamed. "Etude de la contamination du bivalve d'eau douce Dreissena polymorpha par le plomb : bioaccumulation, distribution tissulaire et élimination du métal : incidence de paramètres biotiques et abiotiques." Metz, 1991. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1991/Benyahia.Mohamed.SMZ9112.pdf.
Freshwater mussels (Dreissena polymorpha) were exposed to lead under laboratory conditions. Patterns of accumulation in whole animals were linear at low concentrations and the tissues lead concentrations were proportional to lead in the medium. At high concentrations of lead in the medium, the accumulation proceeded at a high rate in a saturating mode. Under cyclic conditions of exposure, kinetic of lead accumulation showed a pronounced biphasic mode. It is argued that the biphasic course of accumulation seemed to indicate that the animal acts as a multi-compartments accumulation system. The chelation of lead by EDTA decreased strongly its toxicity and bioaccumulation. In the presence of zinc, uptake of lead in whole Dreissena was reduced in the initial phase of accumulation. Thereafter, the antagonistic effect of Zn decreased and became not significant at the end of exposure period. A rise in temperature decreased lead accumulation by mussels. The results also indicate that accumulation were greatly affected by seasonal conditions. In spring, the rate of uptake was the faster and lead body burden was the most important. By means of histochemical staining method and microanalytical technique (LAMMA), lead has been localized mainly in granules of renal cells and in cytoplasm of granulocytes in gills, pericardial gland, byssal gland and digestive epithelium. The depuration process were low and occured sloly compared to accumulation. The original lead concentrations in the soft parts did not influence significantly the rate of elimination. The presence of EDTA or a rise in tempeature enhanced the rate of lead elimination. In all conditions, the total depuration were not attained and the tissue lead concentrations remained at high levels in comparison to controls
Mortillaro, Jean-Michel. "Caractérisation et dynamique de la matière organique du fleuve et des plaines d'inondation du bassin central amazonien." Paris, Muséum national d'histoire naturelle, 2012. http://www.theses.fr/2012MNHN0003.
River ecosystems have a key role in the processes, which control the storage of atmospheric CO2. However, because of strong spatial and temporal variabilities in the sources of organic matter (OM), their relative contribution to the carbon dynamics of large river ecosystems is not fully understood. The present work aimed to characterize the sources of OM in the central Amazon basin. The fatty acids (FA) and stable carbon and nitrogen isotopic (δ13C, δ15N) compositions of OM were investigated in five floodplains (locally called Várzea), the Amazon River and four of its main tributaries (Solimões, Negro, Madeira and Tapajós). The OM analyzed includes macrophytes (Eichornia sp. , Paspalum repens, Pistia stratiotes and Salvinia auriculata), plankton samples, suspended particulate organic matter (SPOM), sediments and soils from the flooded forest. A seasonal characterization of this OM, according to the annual oscillation in the hydrological cycle, indicates a strong autotrophic production from cyanobacteria in Várzea during the drought season. At this season, a transfer of OM, resulting from cyanobacteria and decomposition of macrophytes, has been evidenced from the Várzea to the rivers. However, these plants, which use different pathways of photosynthesis, do not contribute equally to OM and to the food web. Thus, a degradation experiment showed the decomposition dynamics of these macrophytes and the role of micro-organisms. The characterization of OM sources, their spatial and seasonal variabilities, the processes involved in its degradation as well as its utilization by consumers, indicate that the OM produced in Várzea constitute the major source of respired carbon in rivers from the Amazon basin and results from phytoplanktonic production
Maarouf, Abdelmalek. "Etude expérimentale de la bioaccumulation et du relargage du zinc chez Dreissena polymorpha (bivalve d'eau douce) : cinétique et mécanisme de contamination et de décontamination." Metz, 1988. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1988/Maarouf.Abdelmalek.SMZ8816.pdf.
In Dreissena polymorpha, the LC5028d of zinc (oligo-element) is 10,9 ppm. This metal is bioaccumulated but showed little toxicity. Contamination and decontamination dynamism varies with seasons. Zinc exposure is followed by adsorption to the shell, and by adsorption and absorption in the soft part of the mussel. Analysis of the kinetic of absorption showed an exponential and diphasic process in spring, linear in winter, and very limited and triphasic in automn (saturating kinetic). Comparison of the concentration factors of different compartments, allows to establish the following organotropism/ Byssus, mantle, gills, soft part, "rest of soft part". Rate of decontamination was found very feeble in spring. In contrast, it is much more important in automn and winter. The biological half life as determined in automn is 29,5 days. The effects of biotics factors (seasons and food) and abiotics factors (EDTA, tempe rature and lead) on zinc uptake and depuration show a big ecotoxicological complexity due several interactions between these factors, zinc concentrations in the medium and exposure time. External factors produce some modification on the physico-chemistry, kinetic and ecotoxicological aspects of metallic contamination and/or decontamination. Analysis by differencial impulsion polarography made evidence of the presence of metallothionein-like proteins (PTS : sulfurated thermoresistent proteins) in both control and zinc exposed animals. PTS concentrations are about 300mg/kg weight. Exposure to zinc doesn't lead to any quantitative modification of PTS content in Dreissena. Dreissena may be used as bioindicator of metallic contamination of the freshwaters, with the best accuracy in spring
Maurice, Laurence. "Modélisation du cycle de dégradation bactérienne de la matière organique. Application à la zone de turbidité maximale de l'estuaire de la Loire." Toulouse, INPT, 1993. http://www.theses.fr/1993INPT041G.
Lloret, Emily. "Dynamique du carbone organique dans des petits bassins versants tropicaux : exemple de la Guadeloupe." Paris 7, 2010. http://www.theses.fr/2010PA077068.
The main purposes of this work were to evaluate the carbon export of small mountainous rivers from tropical volcanic island (Guadeloupe, French West Indies), and to estimate the impact of extreme meteorological events on this export, and to identify the sources of organic carbon during the different hydrological stages of the rivers (low water level and floods). We carried out a detail study on stream waters, soils and soil solutions. We have analyzed the concentrations of carbon (DOC, POC, DIC) and the carbon isotopic composition (δ¹³C), as well as the spectroscopic (UV-Vis) characteristics of dissolved organic matter. The results have shown that the specific annual fluxes of DOC, POC and DIC were respectively of 5. 4, 7. 8 and 12. 4 tC km⁻². An⁻¹. The organic carbon fluxes of Guadeloupean rivers are similar to the reported export from large rivers. The export of total organic carbon from Guadeloupean rivers is more important than the export of inorganic carbon, indicating the major implication of organic carbon to the global carbon cycle. The carbon export during extreme meteorological events (instantaneous discharge more than 30 m³ s⁻¹) represents 15%, 20% and 5% of the annual export of DOC, POC an DIC, respectively. The main sources of POC are litter and soil surface layers. The sources of DOC vary with the hydrological stages (low water level and floods). During low water level, the rivers are mainly fed by the groundwater (identified by soil solution collected by lysimeters). During floods, the DOC mainly comes from the quick flow and hypodermic flow of soil surface layers (identified by soil solution obtained by extraction in laboratory)
Patryl, Luc. "La radioactivité naturelle des sédiments de la Loire (France) : relations avec la lithologie." Tours, 2000. http://www.theses.fr/2000TOUR4038.
Calendini, Serge. "Impact d'une ancienne mine d'arsenic sur les composantes hydrochimiques et hydrobiologiques d'un réseau hydrographique de Corse." Corte, 2000. http://www.theses.fr/2000CORT3055.
Bonneris, Emmanuelle. "Étude de l'implication de différents ligands cellulaires dans la séquestration du cadmium, du cuivre, et du zinc chez les mollusques bivalves d'eau douce exposés à une contamination environnementale." Université Joseph Fourier (Grenoble), 2004. http://www.theses.fr/2004GRE18001.
The main goal of this research was to evaluate the involvement of different cellular ligands in cadmium, copper and zinc sequestration in bivalves. Indigenous specimens of the bivalve Pyganodon grandis were collected from nine lakes along a metal contamination gradient in the Rouyn-Noranda area (Quebec). In these chronically exposed animals, the accumulated Cd concentrations depend on the environmental dissolved Cd concentrations, and on the nature and the abundance of the biological ligands, which differed among organs (gills versus digestive gland). In the digestive gland, Cd is largely sequestered by the metallothioneins (MT), whereas granules represent the main sink for Cd, Cu and Zn in the gills. A transplantation experiment, involving a change in the exposure regime, demonstrated the precocity of Cd sequestration at the granules level, which appears concomitantly with MT biosynthesis. A molecular approach biology carried out in the laboratory on Dreissena polymorpha aimed at studying the precocity of the response of an isoform of MT
Fontvieille, Dominique. "La circulation du carbone organique dans les écosystèmes lotiques : cas du phénomène d'autoépuration." Lyon 1, 1987. http://www.theses.fr/1987LYO10047.
Ouro-Boya, Boukari Sahidou. "Evaluation de l'état d'une eau de rivière par analyse multidimensionnelle utilisant des paramètres caractéristiques de la matière organique dissoute." Poitiers, 2004. http://www.theses.fr/2004POIT2255.
This study aims to show the possibilities offered by the PCA in the description of the physicochemical quality of a river and to evaluate the anthropic contribution of the dissolved organic matter (DOM) to the degradation of this quality. Being based on an analytical follow-up in 13 stations of Vienne river, it was shown that the study of the bivaried correlations allows to reveal perturbations of the environment, by the organic discharges. Various PCA made it possible to specify with a good objectivity the spatial and temporal changes in water quality in Vienne river. In addition, dispersion in the PCA plan of the individuals representative of the same station can be used to evaluate the disturbances related to the anthropic contributions. In order to acquire a better knowledge of the evolution of the DOM of a rivers, research were carried out on the study of OM extracts isolated through various analytical techniques from characterization
Zinflou, Corinne. "Élaboration d'une méthode d'analyse de la capacité de réparation de l'ADN : Application à une population exposée à l'arsenic via la consommation d'eau souterraine." Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/28407/28407.pdf.
Gabelle, Cédric. "Étude de la contamination des sédiments par les métaux dans les canaux et rivières du Nord de la France." Lille 1, 2006. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2006/50376_2006_90.pdf.
Laguionie, Philippe. "Mesures in situ et modélisation du transport des sédiments en rivière : application au bassin versant de la Vilaine." Rennes 1, 2006. http://www.theses.fr/2006REN1S160.
Cazelles, Bernard. "Modélisation d'un écosystème lotique : dynamique du carbone organique dissous et des microorganismes benthiques dans un cours d'eau cours." Lyon 1, 1987. http://www.theses.fr/1987LYO10068.
Garcia, Esteves Javier. "Géochimie d'un fleuve côtier méditerranéen : la Têt en Roussillon : Origines et transferts de matières dissoutes et particulaires de la source jusqu'à la mer." Perpignan, 2005. http://www.theses.fr/2005PERP0672.
The purpose of this work was the study of the chemical and mineralogical composition in the dissolved and particulate matter of the river Têt (Pyrénées-Orientales) in order to identify the major sources of these materials, and to propose detailed budgets with respect to their fluxes to the Mediterranean Sea. The main objective was to develop a geochemical and hydrosedimentological model that is able to distinguish between the part of the materials that come from natural sources, and the part that is released or retained by human activities. The scientific approach was constructed on a weekly survey during one hydrological year (2000-2001), from the headwaters down to the river mouth. The overall observations allowed the identification of five major sources that contributed to the material fluxes: rainfall, road salting, agriculture, urban waters and chemical rock weathering. For each source, the respective contributions were quantified. The particulate matter fluxes were determined by etablishing empirical models between the suspended matter concentrations and runoff, which also allowed a prediction of the carbon fluxes. All particulate matter fluxes were affected by the existence of a major reservoir lake and their retention rates in this lake could be estimated. The distinction between the natural and anthropogenic matter fluxes finally also allowed the proposition of a model about the functioning of a natural erosion that takes into account the spatial variability of the chemical and mechanical erosion in the basin, and that also distinguishes the contributions of silicate and carbonate weathering in the overall release of alkalinity to the river
Msokar, Sawsan. "Étude de la matière organique dans deux écosystèmes estuariens : Les estuaires de la Seine et de l'Authie." Lille 1, 2003. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2003/50376-2003-61-62.pdf.
Pastor, Lucie. "Etude de l'impact des apports du Rhône sur la biogéochimie des sédiments du prodelta." Paris 7, 2010. http://www.theses.fr/2010PA077069.
TThe main purpose of this work was to study the biogeochemical processes in sediments from the Rhône prodelta area (France), and to assess which parameters are likely to control the carbon mineralization within this highly dynamic System. Microelectrodes were used to measure high-resolution sediment profiles of oxygen and calculate the corresponding diffusive fluxes through the water/sediment interface. In parallel, sediment cores incubations were assessed to directly measure the benthic fluxes of oxygen and nutrients. Core slicing under nitrogen atmosphere allowed for the determination of several dissolved species (Fe²+, Mn²+, H^S, NOs⁻, NH₄⁺, PO₄³⁻, DOC, DIC, SO4²⁻) together with solid phase characteristics (porosity, Mn, Fe, P, Corg et Cinorg, N). These measurements were combined with a numerical diagenetic model to quantify the mineralization processes together with fluxes of degraded organic carbon and its burial. Results show that respiration processes are largely influenced by the Rhône River particulate inputs. This influence in terms of particulate export is restricted to the prodelta area. The organic matter from the Rhône River is composed of fresh terrestrial material as indicated by high first-order degradation constants (22-29 yr⁻¹). The high sedimentation rates are mainly responsible for the massive burial of carbon, together with an intense anaerobic degradation (e. G. Sulfate reduction). Precipitation of diagenetic products was evidenced (>98%) as well as secondary and transitory reactions like the anaerobic nitrification after the deposition of an organic-rich layer. The pulsed inputs of the Rhône River have some compositional differences that may lead to changes in mineralization rates. A flood of the Rhône River occurred in June 2008 and delivered a significant amount of new particulate matter (5. 4 106 tC in 10 days leading to a ~30 cm flood deposit in the prodelta). An immediate response of the prodeltaic System was observed, with (1) the rapid migration of the redox front (in a few hours), (2) a drop in oxygen consumption (20-30%), (3) the reduction of authigenic iron oxides at the old sediment/water interface and (4) a massive production of dissolved manganese within the flood deposit
Portuguez, Etienne. "Gouttes millimétriques d'eau en milieu confiné : comportement au cours du séchage." Thesis, Limoges, 2016. http://www.theses.fr/2016LIMO0130/document.
This work aims at improving the understanding of the specific mechanisms of the drying of ceramic materials. This step is crucial when manufacturing a piece. Indeed, besides the optimization of the sample composition, the temperature and the relative humidity have to be controlled so that the weight loss andthe shrinkage do not cause any stress development, leading to cracks formation which can damage the final piece after a heat treatment. After a presentation of the different known drying mechanisms, this thesis highlights a set of measuring benches conceived within an instrumented climatic chamber. A firststudy concerning the behavior of the shaping liquid as a function of temperature and relative humidity isrealized. Then, this liquid is inserted between two parallel and identical substrates in order to reproduce the case of a liquid bridge within a pore. The hydrophilic and hydrophobic contacts are then studied.Finally, drying experiences are carried out on ceramic materials to correlate the different observations.The obtained results demonstrate the importance of a compromise when selecting the drying parameters.The temperature and the relative humidity not only influence the kinetics of the process during the liquiddeparture, but also modify the contact with the solid phase of the ceramic piece. At the end of drying, the rupture of liquid bridges is brutal and can explain some macroscopic phenomena observed when dryinglarge pieces
Daniel-David, Delphine. "Etude du mécanisme de désémulsification des émulsions de type eau dans pétrole brut par des polymers siliconés." Compiègne, 2006. http://www.theses.fr/2006COMP1636.
Viscoelastic films of aggregated asphaltenes prevent the coalescence of water droplets in water -in-oil emulsions formed during crude oil exploitation. Demulsifying surfactants are used to promote phase separation before oil refining process. The aim of this PhD thesis is to explain a destabilization mechanism for a silicone polyether copolymer, by relating its structure to its performance. The copolymer was first characterized at the air/water interface in order to understand its adsorption without the presence of the indigenous crude oil components. Various techniques have been used to elucidate the destabilisation mechanism by the copolymer. The proposed destabilisation mechanism is as follows : the copolymer first adsorbs at the crude oil water interface into packing defect sites due to its high affinity for the oil water interface. Then, the copolymer molecules disrupt the asphaltene network, allowing the coalescence of water droplets
Molenat, Jérôme. "Rôle de la nappe sur les transferts d'eau et de nitrate dans un bassin versant agricole : étude expérimentale et modélisation." Rennes 1, 1999. http://www.theses.fr/1999REN1A004.
Agricultural non-point-source pollution is a major source of sanitary and environmental water quality problems. Control requires a detailed knowledge, at all time scales, of pollutant transfer in surface and subsurface runoff. This thesis aims to establish transfer times for nitrate in a simple catchment, through an understanding of the reservoirs and mechanisms responsible for seasonal and multi-annual variations in river nitrate levels. The hydrological dynamics of three agricultural catchments (Kervidy, Mélarchez and Mercube) have been studied from measurements of total rainfall and discharge. An existing method based on sepectral analysis of time series has been further developed to sperate groundwater and storm discharge contributions. This analysis provides the parameters for a groundwater model, which has been extended to model nitrate transfer. A catchment experiment has been set up at Kervidy (Morbihan, Brittany). Piezometers, installed along three slope catenas, monitor water level and sample the concentration of nitrate, sulphate and chloride in the groundwater. These measurements have been used to identify the water table dynamics and chemistry. Seasonal variations in nitrate pathways have been interpreted from the analysis of these data. The field study has also been used to set up a distributed numerical model for groundwater behaviour in the Kervidy catchment
Zhang, Guorong. "Étude et maîtrise de la qualité d'eau de la ressource à la distribution à Macao." Paris 12, 1992. http://www.theses.fr/1992PA120056.
Lucia, Magali. "Analyse de la contamination polymétallique des oiseaux aquatiques : Etude expérimentale de la bioaccumulation du cadmium, réponses adaptatives et effets toxiques associés." Pau, 2009. http://www.theses.fr/2009PAUU3039.
Throughout their life, birds evolve in environments where anthropogenic pressures could be at the origin of numerous pollutions. The current study aimed, among all these potential contaminations, to assess and understand toxic effects of metals on aquatic birds at environmental and experimental scales. To address these issues, bird populations situated on wetlands of the Southwest Atlantic coast of France have been sampled. The implementation of this field study was in relation with the longstanding contamination of water and sediment reported on the Gironde estuary. This sampling enabled to determine the main metals accumulated by inhabiting or transient species of this impacted ecosystem. This work also aimed to identify factors involved in variation of observed levels between species. In parallel, studies have been performed to assess cadmium bioaccumulation and associated toxic effects in two species of aquatic birds. This experimental work enabled the comparison of interspecific responses related to cadmium exposure. Thus, kinetic of contamination led on Anas platyrhynchos and Cairina moschata demonstrated marked discrepancies between species for metal accumulation and implementation of detoxification process such as metallothioneins. A complementary study was also performed to assess cadmium impairment on lipid metabolism of birds. This metabolism providing essential energetic reserves during migration or reproduction was affected by the metal at different levels. Cadmium triggered both modifications of fatty acids synthesis in liver and changes in lipids transfer and storage in peripheral tissues
Denison, Francis. "Spéciation de l'uranium (VI), modélisation, incertitude et implication pour les modèles de biodisponibilité : application à l'accumulation dans les branchies chez un bivalve d'eau douce." Aix-Marseille 1, 2004. http://www.theses.fr/2004AIX11023.
Foucher, Delphine. "Géochimie du mercure dans des sédiments estuariens et côtiers : cas de la Seine (France) et de la baie de Kaštela (Croatie)." Lille 1, 2002. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2002/50376-2002-333.pdf.
Jouniaux, Laurence. "Les effets électriques liés aux circulations d'eau dans les roches." Habilitation à diriger des recherches, Université Louis Pasteur - Strasbourg I, 2007. http://tel.archives-ouvertes.fr/tel-00137155.
Mes thèmes de recherche concernent donc principalement les effets électriques liés aux circulations d'eau dans les roches. Les signaux électriques induits par les circulations d'eau sont appelés effets d'électrofiltration ou électrocinétiques et sont dus à la présence d'ions dans l'eau pouvant créer un courant électrique. Ce courant électrique engendre lui-même un champ magnétique. Ces effets reflètent principalement l'interaction électrique entre la roche et l'eau (appelée double- ou triple-couche électrique). En présence d'eau, des réactions chimiques et physiques se produisent à l'interface entre la roche et l'eau, dont il résulte un excédent d'ions négatifs liés à la roche, et par suite, un excédent d'ions positifs sur une couche de faible épaisseur au voisinage de l'interface, le reste du fluide restant neutre [voir Fig. B1 de Guichet et al., GJI, 2006]. Lorsque le fluide est en mouvement, ces ions positifs sont entraînés et engendrent ainsi un courant électrique, dit courant électrique de convection. Ce courant est contre-balancé par un courant de conduction (loi d'Ohm), et il en résulte une différence de potentiel électrique, on parle de potentiel d'électrofiltration ou potentiel électrocinétique.
La différence de potentiel électrique ainsi générée est proportionnelle au gradient de pression d'eau, ce qui en fait une méthode de choix pour la détection des circulations d'eau en subsurface. Les mesures en laboratoire sont effectuées de l'échelle centimétrique à l'échelle métrique et sont nécessaires pour contraindre les modèles de calcul des champs électriques et magnétiques induits par les circulations de fluides dans la croûte. Il est à noter que sur le terrain, les Potentiels Spontanés (PS), c'est-à-dire les potentiels électriques mesurés passivement entre deux électrodes, dont les mesures se sont largement développées ces dix dernières années, peuvent être induits par une circulation d'eau (soumise à une force liée à un gradient de pression), mais aussi par un flux de chaleur (soumis à une force liée à un gradient de température), ou encore par un gradient de concentration chimique. Ceci peut se voir dans les relations des flux couplés [Onsager, 1931 ; Sill, 1983] où chaque flux Ji (flux électrique, flux hydrique, flux de chaleur, flux de matière) est lié aux forces Xj (gradient de potentiel électrique, de pression hydrique, de température, de concentration) à travers les coefficients de couplage Lij. Pour ma part, j'ai concentré mes recherches sur une meilleure quantification du champ électrique lié aux circulations d'eau dans les roches. Le coefficient de couplage électrocinétique ou d'électrofiltration, , peut-être mesuré en laboratoire. Il est à noter que le coefficient d'électrofiltration ne dépend pas en principe de propriétés telles que porosité ou perméabilité, ce qui amène le gradient de pression hydrique à jouer le premier rôle dans la génération des potentiels d'électrofiltration [pour plus de détails on peut consulter le paragraphe " Electrokinetic Phenomena " de Jouniaux and Pozzi, JGR, 1997, et l'appendice B de Guichet et al., GJI, 2006].
Cette thématique de recherche a donc un intérêt potentiel, et déjà en partie éprouvé, pour la détection à distance et la caractérisation des fluides dans le sous-sol. La communauté scientifique essaie de développer son potentiel en tant qu'outil d'imagerie, d'une part dans le domaine des ressources en eau : profondeur de nappe aquifère, suivi de transferts hydrauliques, caractérisation des flux contaminés, et d'autre part dans le domaine de la géophysique des réservoirs : détection d'hydrocarbones grâce aux conversions sismo-électromagnétiques.
El, Mostafa Benmoussa. "Ecologie des communautés périphytiques : étude en laboratoire et en milieu naturel des conditions de développement et des caractéristiques de fonctionnement de trois types de biodermes." Toulouse 3, 1995. http://www.theses.fr/1995TOU30279.
Millet, Pierre. "Modélisation du transfert et du transport de composés organiques des matériaux dans l’eau potable : Applications aux réseaux d’eau intérieurs." Rennes, Ecole nationale supérieure de chimie, 2017. http://www.theses.fr/2017ENCR0039.
The French Public Health Code sets out the requirement on tap water quality and the materials used in the contact of drinking water are subject to the Attestation of Sanitary Conformity. However, organoleptic degradation can remain in tap water. A bibliographic study has shown that organoleptic degradation could be caused by the presence of chemicals migrating from materials and by complex hydrodynamic phenomenon. A compartmental model has been developed. It models the transfer and the transport of chemicals from materials to water. This approach allows to combine the study of transfer of chemical from the material and the study of hydrodynamics in private water installations. It provides the opportunity i)- to observe the impact of dynamic operating conditions on the concentration of chemicals in tap water ii)- to make diagnostics of the installation to avoid disagreements and iii)- to study the quantity of chemicals deliver in tap water in function of consumption habits of the users. The study of chemicals transfer phenomenon in dynamic conditions has shown the impact of water temperature, turbulent agitation and duration of the use of materials on migration kinetics of chemicals. However, the experiences made with compartmental model have indicated that the leaching of chemicals in dynamic conditions was negligible compared with the leaching of chemicals in static conditions. Indeed, the static contact time is far more important that the dynamic one. However, it has been shown that the hydrodynamics could have a significant impact on tap water quality, particularly due to exchanges between different parts of the networks. Finally, the complex scenario development based on consumption habits of the users have shown that the quantity of chemicals ingest by the consumers were strongly dependant of the consumption behaviour of the users. The approach could be a part of a process like the threshold of toxicological concern based on the prediction of the daily quantities of chemicals ingest
Hachgenei, Nico. "Transfert d'eau et de résidus pharmaceutiques vétérinaires dans un bassin versant agricole de méso-échelle soumis aux crues éclairs." Thesis, Université Grenoble Alpes, 2022. http://www.theses.fr/2022GRALU007.
This work focuses on environmental transfer of residues of veterinary drugs entering the environment via dung from treated animals. It is studied under the conditions of a meso-scale catchment under Mediterranean climate with extensive agriculture.In a first step, interviews with livestock breeders were conducted to identify the treatment practices. 14 pharmaceutically active compounds (PhAC) were identified to be systematically used in the catchment, 10 of which antiparasitic drugs. Antibiotics were of significant use only for goats. We chose Ivermectin (IVM) as a representative molecule for those antiparasitic drugs and did further transfer experiments on this compound.For these experiments, we developed a device to sample intact soil monoliths and subject them to simulated rainfall. Dung from untreated cows was spiked to a realistic concentration (3 mg kg−1) as reported in literature and placed on the soil. Consecutive intense rain events were simulated and surface runoff and drainage flow were measured and sampled at high frequency. Concentration values of up to 3855 ng L−1 were observed in overland flow (OF). The concentration in drainage flow was significantly reduced in soils from the sedimentary foothills part of the study site (< 150 ng L−1). On soils from the Coiron basaltic plateau, water repellency led to strong preferential flow and the concentration of IVM was not substantially reduced by leaching through the soil. Higher initial soil moisture led to increased retention of IVM through both drainage and OF. Overall, up to 1 % of the initial mass of IVM was exported during two consecutive rain events. In addition, we could show that drying of cow dung effectively reduces the mobilization of IVM. In general, more OF and a higher export of IVM were observed on soils from the Coiron plateau. On this scale, soil water repellency (SWR) seems to play a substantial role in the generation of OF.Finally, in order to link those results to the catchment scale and the overall problematic of transfer of pharmaceutical residues to surface water bodies, a semi-distributed conceptual hydrological model was developed on the scale of the Claduègne catchment using SAS functions and age tracking in order to estimate transit time distributions (TTD) on an hourly time step. The model was calibrated against observed discharge, silica concentration and deuterium isotope ratio of the water molecule at the outlet. The model predicts fractions of up to 60 % of discharge at the outlet of an age below one day during major flood events. Over the whole observation period, this fraction represents 8.4 % of the total runoff. In average, 25 % of the discharge are less than 30 d old.The analysis of a few stream water samples from the Claduègne catchment for three veterinary pharmaceuticals revealed that Fenbendazole (FBZ) and Mebendazole (MBZ) were only present at detectable concentrations throughout flood events, indicating a strong importance of preferential flow for their transfer into the streams. Concentrations of the pork antiparasitic FBZ of up to 28.4 ng L-1 were observed during a small flood event in summer, which is 355 time the predicted no effect concentration (PNEC) for fish.This thesis shows that high amounts of IVM can be mobilized from cow dung and transferred through and over soil at the plot-scale, despite the fact that IVM is generally considered immobile due to its hydrophobicity and therefore strong adsorption to the soil's organic matter. The highest mobilization of IVM was observed under the condition of intense precipitation on dry soil due to water repellency causing strong preferential flow (including OF). Preliminary results on the catchment scale suggest that this mechanism may as well be effective on this scale, despite the smaller amplitude of the hydrological response. An age tracking model reveals a high fraction of event water in the discharge at the Claduègne outlet during major flood events
Lenoble, Véronique. "Elimination de l'Arsenic pour la production d'eau potable :oxydation chimique et adsorption sur des substrats solides innovants." Phd thesis, Université de Limoges, 2003. http://tel.archives-ouvertes.fr/tel-00105947.
(agriculture, extraction et exploitation de minerais principalement) ont conduit à son accumulation dans l'environnement.
L'abaissement à 10 µg/L de la limite de qualité pour l'arsenic dans l'eau de consommation pose la question de l'efficacité des
traitements existants. De nouvelles techniques plus performantes d'élimination de l'arsenic sont donc de plus en plus
nécessaires. L'objectif de ce travail est de développer de nouvelles méthodes d'analyses de l'arsenic, fiables et utilisables sur le
terrain, ainsi que des méthodes simples d'élimination de l'arsenic, de mise en œuvre facile et applicables à de petites unités de
traitement comme celles rencontrées en zones à habitat dispersé (débit < 10 m3/h).
L'adsorption de As(III) et As(V), méthode répondant aux critères précédemment définis, a été étudiée. Tout d'abord des
supports classiques ont été considérés : des (oxy)hydroxydes de fer; puis des supports innovants : des argiles pontées dérivées
d'une montmorillonite. Celle-ci a été modifiée par différents polycations (fer, titane et aluminium) de façon à créer des sites
favorables à l'adsorption. L'adsorption a été réalisée selon différentes conditions, et dans des milieux plus ou moins complexes.
Il s'avère que les (oxy)hydroxydes de fer fixent plus d'arsenic que les argiles pontées, tant sous la forme As(III) que As(V).
Néanmoins, l'étude de la désorption a montré que l'argile pontée au fer était le seul support régénérable quasiment à 100%.
Connaissant les différences de comportement selon la nature des espèces de l'arsenic inorganique As(III) et As(V), l'oxydation
de As(III) par différents oxydants usuels a été l'objet d'une partie de l'étude. Les oxydants testés sont H2O2, NaOCl, FeCl3,
KMnO4 et MnO2(s), couramment employés dans les traitements. De façon à quantifier la capacité oxydante de ces réactifs, une
méthode colorimétrique a été développée. Celle-ci, facilement transposable sur le terrain, peut être appliquée aux eaux peu
chargées en phosphate avec une limite de quantification de 20 µg As/L. Il s'avère que les oxydants les plus facilement
utilisables dans une unité de potabilisation sont KMnO4 et FeCl3. A la suite de cette étude, un support à base d'une résine de
polystyrène recouverte d'oxyde de manganèse a été synthétisé. Ce solide combine des propriétés d'oxydation et d'adsorption
simultanées. Les capacités d'adsorption de ce solide vis-à-vis de As(V) et de As(III) sont remarquables et supérieures à une
majorité des adsorbants étudiés récemment.
La dernière partie a consisté en l'étude de la faisabilité des procédés mis au point sur un milieu plus proche des conditions
naturelles. Pour cela, une eau artificielle représentative des eaux de type granitique, habituellement concernées par la pollution
arséniée, a été préparée à partir de la compilation des compositions d'eaux souterraines destinées à la production d'eau potable.
Ainsi, les concentrations en ions majeurs communes à ces eaux ont pu être déterminées. Cette eau artificielle a ensuite été
utilisée après dopage en As(III) et As(V) dans diverses expériences d'oxydation et d'adsorption de façon à appréhender les
mécanismes mis en jeu dans le milieu naturel. Il apparaît que les ions majeurs ont peu d'influence sur ces procédés, démontrant
leur applicabilité au sein d'une filière de traitement.
Vrel, Anne. "Reconstitution de l’historique des apports en radionucléides et contaminants métalliques à l’estuaire fluvial de la Seine par l’analyse de leur enregistrement sédimentaire." Caen, 2012. http://www.theses.fr/2012CAEN2060.
The Seine estuary is the outlet of a highly anthropogenized catchment area. Marginal areas of the river have trapped fine-grained sediment particles which a number of contaminants are bound to; they give access to the sedimentary records of the past decades. Corings were carried out in three areas: the Seine River, the upper Seine estuary, and at the river mouth. After dating, these cores have led to reconstruct the history of the inputs particulate elements in each of these areas. The comparison of the time series of elemental concentrations between (i) suspended matter during the last decades and (ii) dated sediments along the cores shows that the latter are representative of the former. Particulate fluxes of 55 stable elements and 18 radionuclides were estimated, from 1960 to 2002. Comparison of data acquired in the Seine River and in the upper estuary led to distinguish and quantify the intra-estuarine sources of contaminants that are dominated by phosphogypsum discharges during the 1970s in the Rouen harbour area (upper estuary). The intensity of tidal pumping up to the upper estuary was quantified using transuranics activity ratios. Based on the atmospheric 137Cs activities over the last decades and core derived 137Cs activities, a transfer model from the watershed to the river, based on a solid wash-off transfer function by runoff and erosion, is then proposed
Kébré, Marcel Bawindsom. "Gestion des Ressources en Eau dans les Régions Arides: Analyse Expérimentale d'un Sol Type du Burkina Faso et Modélisation Numérique des Transferts d'Eau." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2013. http://tel.archives-ouvertes.fr/tel-01012040.
Kadlecova, Milada. "Contamination mercurique des sédiments et cours d'eau du nord de la France et de la République Tchèque." Thesis, Lille 1, 2011. http://www.theses.fr/2011LIL10148/document.
Mercury (Hg) is naturally occurring toxic element; however global mercury emissions are dominated by anthropogenic sources. The global cycle of mercury has seen an increase in mercury deposition, especially in aquatic ecosystems, since the beginning of the industrial revolution. First part of the thesis summarizes the source of mercury, its properties and toxicity from the general point of view, but also the current state of knowledge on the biogeochemical cycle of mercury and in particular behaviour of mercury inside the sediments of the aquatic environment and factors influencing its transformation into methylated form. The sediment in aquatic systems may acts as the ultimate sink, where mercury in its various complexes is deposited. The mercury in sediments can then be converted to its more toxic organic form, methylmercury (MeHg), by the transformation processes controlled by various physical, chemical and biological factors. More over remobilization of mercury species from sediments is possible due to diffusion and resuspension and so sediments may act as potential source of mercury for aquatic biota. Bioaccumulation and biomagnifications can then continue up the food chain where humans, among other animals, consume the organic mercury. It is clear that determination of total mercury is not sufficient to understand its fate in the environment; determination of MeHg provides very useful additional information. The sensitive and precise analytical method for MeHg determination is necessary. The methodological part of the thesis deal with the methods for determination of mercury species in sediments. The method for methylmercury determination in sediments using automated Headspace sampler equipped with Trap and coupled with Gas Chromatography and Atomic Fluorescence Detector was developed and is define. The special attention is also given to the necessity of clean sampling procedures and the proper storage and pre-treatment of the samples and the field study of Hg distribution in sediments. The mercury contamination of sediments from the South Moravia and Northern France are compared. The mercury species and other elements (Fe, Mn, S) were analysed in sediments and/or pore water and/or surface water collected from the sampling sites in the Deûle and Lys River (France) and Jihlava and Morava River (Czech Republic). In order to better assess the mercury contamination of aquatic ecosystem, the pore water concentration could be evaluated to understand the availability of mercury from sediment. The use of diffusive gradient in thin film (DGT) technique is applied to measure pore water mercury concentration in river sediments. Different resins gels for mercury determination are used: Spheron-Thiol, Duolite GT-73 and TiO2. River Deûle act as a sink for enormous anthropogenic Hg from the industrial activities and is considered as a potential significant source of methylmercury to the surrounding environment. The last part of thesis deals with the application of well-established isotope experiments to study methylation/demethylation processes in sediments of Deûle River. For this purpose, species-specific isotopically enriched tracers in the form of inorganic mercury IHg (199Hg) and MeHg (201MeHg) have been added to the sediment slurries. Mercury labelled species were used as the tracers to follow their chemical fate and calculate the extent of the transformation reaction yield occurring during the 24 hours experiment. This experiment methodology is refined by applying advanced matrix algebra to resolve the contributions of several different enriched stable isotope species specific tracers to the isotope pattern found, making the calculation of methylation/demethylation rates possible
Robin, Joël. "Dynamique saisonnière du phytoplancton en étang de pisciculture de la plaine du Forez (Loire) : essais de contrôle des cyanobactéries." Lyon 1, 1999. http://www.theses.fr/1999LYO10265.
Kane, Didier. "Mise au point d'une méthode non-destructive de mesure de mesure de la teneur en vapeur d'eau d'un boîtier hermétique, à cavité, de composant électronique par capteur hygrométrique in-situ à conductivité de surface." Lyon, INSA, 1985. http://www.theses.fr/1985ISAL0019.
Nehme, Nada. "Évaluation de la qualité de l’eau du bassin inférieur de la rivière du Litani, Liban : approche environnementale." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0296/document.
The objective of this study was to evaluate water quality of the lower Litani River and assess its feasibility for multi-purpose usage as one of the solutions to the aggravated water problems in Lebanon, To identify possible sources of metals (i.e. geological and/or anthropogenic) and then to characterize the chemical behavior of these metals in water and bed sediments, water and bed load sediments were sampled at six representatives sites which are investigated over three seasons of the year 2011-2012 (i.e. rainy, mid-rainy and dry seasons), The PCA (principal component analysis) method was used to interpret the elemental concentrations in the river water. Results show that among 18 variables, which were evaluated to characterize their physic-chemistry and metals, there are only 4 (Fe, NO2-, CaCO3, Cu) that were determined the type of environmental studied; Three groups were identified and differentiated by PCA according to the seasons. The first group includes all statements made in the mid rainy season and has a dialogue rich in Fe and NO2, and low in NH4 and EC. The second group formed in dry season, and surveys show physicochemical characteristics opposite to those in the first group, the third group formed in mid rainy, and showed the low concentration of K+, PO43- and Cl-. Sediments were characterized by a set of cations exchange capacity, granulometric, diffraction (XRD) and Fourier transformed infrared spectroscopy (FTIR( The FTIR analysis shows that the amount of montomorillonite is less than kaolinite and very much less than quartz and calcite. Pearson’s correlation was also performed in this study to compare to and determine the correlation between heavy metals in the sediments. Geo-accumulation (Igeo) index, Contamination Factor (Cf), and contamination degree (Cd) were also applying to assess the level of contamination in the sites. The results shows that the concentration of Pb, Fe are high in the site S5, S6 and the value of Cr ,Ni, are high in the S6, this results suggest that special attention must be given to the issue of element re-mobilization, because a large portion of elements in sediments are likely to release back into the water column. All the sites are characterized by moderate to highly microbial polluted range. The degree of contamination was increased in dry season. However, no critical physicochemical pollution has been reported in this part of the river; except the high concentration of Fe and NO2- in all investigated sites due to the reject of wastewater and to the distribution of touristic activities in the LLRB, the Concentrations of seven heavy metals is high(Cu, Fe, Cd , Mn , Cr, Zn, Ni and Pb) for sediment is higher according to Consensus-based sediment quality guidelines of Wisconsin (Wisconsin Department of Natural Resources, 2003) were applied to assess metal contamination in sediment
Rakotovololona, Lucia. "Quantification expérimentale et modélisation de la production, des flux d'eau et d'azote en systèmes de culture biologiques." Thesis, Paris, Institut agronomique, vétérinaire et forestier de France, 2018. http://www.theses.fr/2018IAVF0024.
Nowadays, in a context of global changes, addressing the interlinked challenges of food security and environmental impacts is fundamental for the sustainability of agricultural systems. Therefore, the thesis aimed to assess agronomic and environmental performances of organic systems, by coupling the experimental monitoring of a 35 organic fields network in the Northern region of France with modeling the soil-crop continuum, to better understand the underlying processes in water and nitrogen dynamics within those systems, and to promote a more sustainable management.Water drainage and nitrate leaching were assessed by coupling soil, crop and climate data within LIXIM model. Then we analyzed N leaching pattern under diverse organic arable fields to explain its main driving factors. Leaving aside the strong soil type effect and the importance of climatic conditions on drainage, the combination of previous crops and autumn field management appeared to be a key determinant of nitrate leaching in the studied organic systems, as they both drive the amount of soil mineral nitrogen before draining period and explain the position of nitrate in the soil profile. We also showed the dichotomous role of legumes as preceding crop in organic cropping systems and the poor performance of the standard catch crops, sown in late summer in this context.Yield gap of cereals was investigated using a deterministic modeling approach as a diagnosis tool, to contribute in improving the productivity of organic agriculture. The soil-crop model STICS was used to estimate the potential yields of each studied winter wheat and winter triticale crop fields in their given soil and climate conditions. Our results reasserted how nitrogen stress could explain a major part of the yield gap occurring in organic crops and outweigh biotic limiting factors impacts, for cropping systems relying on few or no manures for nitrogen supply.Lastly, we aimed to address the challenge of nitrogen supply in organic arable systems for a better nitrogen use efficiency and improved crop yields. We used the model STICS to simulate the impact of alternative nitrogen management practices by carrying out a numerical experiment in a participatory approach involving farmers, technical advisors and researchers. The findings emphasized the importance of crop succession design and management practices, particularly the implementation of catch crops and the timing of the destruction of perennial legume crops. Optimizing the farmer’s actual practices could then be possible, reducing the potential emissions of nitrogen via leaching or gaseous losses, without decreasing the nitrogen supply for the following crop.Organic arable cropping systems, within the studied soil, technics and climate contexts, can achieve agronomic performances combined with low environmental impacts, with well-managed nitrogen practices
Robert, Anne. "Minéralisation in situ de la matière organique le long de la colonne d'eau : application sur une station eulérienne." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4045/document.
The carbon cycle is mostly driven by production and remineralisation processes which are constraining organic matter concentration along the water column. The main actors of the remineralisation are the heterotrophic prokaryotes, which actions can be measured from surface to deep by the prokaryotic respiration. During this PhD thesis, a long term real time monitoring of hydrological and biogeochemical conditions (potential temperature, salinity and dissolved oxygen O2) has been carried out between 2008 and 2010 in the North Occidental Mediterranean Sea, at the ANTARES site. Influence of punctual events has been observed which seem to be related to winter deep sea convection and subsequent advection, changing hydrological and biogeochemical properties observed at the ANTARES site. These direct or indirect modifications will have consequences on the organic matter concentration and therefore on the deep-sea remineralisation potential. The temporal monitoring of O2 concentration has also allow us to estimate the deep water oxygen consumption of 2.6 µmol O2 dm-3 a-1, during a three year period. The development in our laboratory in collaboration with Centre de Physique des Particules de Marseille (CPPM) of a new equipressured tool, the IODA6000 (In situ Oxygen Dynamics Autosampler), measuring directly and at high frequency the O2 concentration, allowed us to measure PR rates at 2000 m depth since December 2009 at the ANTARES site. This unique ongoing time series shows a mean prokaryotic respiration rates higher (0.2 µmol O2 dm-3 d-1) than expected by literature (5.5 10-3 µmol O2 dm-3 d-1), with a high temporal variability (from 8 10-3 to 0.5 µmol O2 dm-3 d-1)
Khdhiri, Hatem. "Épuration en eaux courantes : évaluation et modélisation de la capacité d'oxygénation dans les cascades et les chutes d'eau." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0216/document.
This work represents a part of polluted watercourses restoration by intensification of self-purification mechanisms essentially the degradation of organic matter and nitrogen. The main objective is to evaluate and model the air-water oxygen transfer by major hydraulic structures, namely stepped cascades and waterfalls. Aeration experiments conducted in a geometrically adjustable laboratory pilot, serving as stepped cascade and waterfall were used to assess the aeration potential of these structures as well as to study the geometrical an operating parameters effects. In a first approach, a global semi-empirical correlation for aeration efficiency calculation in stepped cascades, valid for a wide range of parameters, was developed, depending on water discharge, number of steps and chute slope, basing on our experimental measurements and data collected in publications. The same procedure was followed for developing a semi-empirical correlation to estimate the aeration efficiency of waterfalls in terms of the chute height, downstream water level and flowrate. In order to take into account the oxygen transfer phenomenon characteristics in stepped cascade (water volume and air-water exchange interfacial area), tracer experiments were associated with aeration experiments to allow measuring water volume and correlating the volume oxygen transfer coefficient kLa with the various parameters involved in the aeration mechanism. The interfacial specific area was numerically simulated using VOF approach depending on operating and geometrical parameters. A predictive equation for liquid film transfer coefficient kL calculation based on the parameters of influence was issued from both the simulations and experimental aeration measures
Masavang, Supuksorn. "Sugar reduction in extruded cereal based products : impact of water content on the structure and molecular dynamics in such material." Thesis, Bourgogne Franche-Comté, 2019. http://www.theses.fr/2019UBFCK025/document.
Low-moisture biopolymer-based systems are commonly encountered in food. Obviously, understanding the physical basis of their quality: e.g texture, or performance over time or as a function of their composition is of primary importance. The objectives of this work were to evaluate how the presence of sucrose and water content affects physico-chemical properties. The physical stability of these materials were monitored through an insight at different molecular scales. Then the relations between the multi-scale studies were investigated. The effect of sucrose (0–20%) and feed water (10 and 15%) on extrusion blends was studied using a twin screw extruder under the same processing settings. The physical and microstructural properties of extruded products were examined at various RH. Reducing both sugar levels and feed water increased die pressure and specific mechanical energy, as a consequence, it reduced starch degradation and increased in viscosity. The effect was more pronounced with increasing feed water content. The increased die pressure resulted in higher expansion of the porous extrudates. Sucrose was shown to increase the bulk density and reduce the pore size, this was particularly evident by using neutron imaging technique. This technique was applied for the first time in extrudate. 2D tomography images indicated internal structural differences between extrudates containing different sucrose content and stored at low and high % RH, while 3D image analysis showed impact of these factors on pore size distribution and % porosity were not significant. The extruded samples were in the amorphous state as a result of starch gelatinization and sugar melting. Their thermal properties were analyzed with DSC and their Tg were studied. The DSC thermograms were thoroughly studied through a Gaussian deconvolution of the first derivative of their heat low. This approach evidenced a multiple phase behavior with different glass transitions in composite systems. They were associated with either a polymer-rich phase and/or a plasticizer-rich phase which behavior depended on the sample water content. Physical aging accompanied with an increase in rigidity at low aw, resulted in an increased bulk density and more pronounced with increasing sucrose content. Sorption isotherms showed the water content of extrudates decreased when product contains high sucrose at low aw range and the inverse effect was observed at high aw. Apparent kinetics of water diffusion showed two different sorption sites, the first kinetics was almost constant and could be adsorption phenomena at the surface. The second one reflected first an initial slowing in dynamics whereas a sharp increase was found at higher water content. Addition of sucrose or water decreased both Tgs in extrudates. Young's modulus showed water acts as anti-plasticizer at low aw, while it shows a plasticizing effect at high aw. A stability map can explain the brittle-ductile transition occurred below Tg. Fast field cycling NMR study at low frequency highlighted that T1 depended on sucrose and water content. T1 and T2 measured using Low field NMR decrease as a function of water content, while the impact pf sucrose were not significant. T2 showing a minimum probably indicating the exchange of protons of water and macromolecules in composite system. The impact of sucrose content was not significant for T1 and for T2 at low water content. FFC NMR showed T1 results consistent with the LF NMR measurement.In conclusion, physicochemical studies of the influence of water and sucrose content on glassy materials showed that the material properties can be investigated at different levels from the macro- to the microscopic scale and these results clearly presented the need for complementary techniques to probe the dynamics in the glassy state of heterogeneous food systems that could be facilitated to manage the stability during storage of this type of dry products
Gras, Jean-Philippe. "Approche micromécanique de la capillarité dans les milieux granulaires : rétention d'eau et comportement mécanique." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2011. http://tel.archives-ouvertes.fr/tel-00821687.