L'utilisation de pesticides sur les surfaces agricoles conduit à une contamination généralisée des eaux de surface et de subsurface en France. Dans l'attente d'une évolution profonde des pratiques agricoles et d'une baisse durable de l'utilisation des pesticides, il est intéressant de chercher à limiter des transferts des zones agricoles aux zones aquatiques. Pour mieux agir sur les voies de transfert, il est nécessaire d'approfondir les connaissances des processus en jeu et de leurs interactions éventuelles et de tirer au mieux partie des observations du terrain.L'objectif de cette thèse est l'intégration de processus de transferts réactif dans le modèle hydrologique à base physique CATHY (CATchment HYdrology), capable de simuler en 3 dimensions les écoulements de l'eau de façon couplée surface-subsurface et le transport advectif dans des situations variablement saturées. En subsurface, les processus d'adsorption linéaire et de dégradation du premier ordre sont implémentés. Un module de mélange des solutés entre la lame ruisselante et la première couche de sol est ajouté, qui permet de simuler la remobilisation des solutés de la subsurface dans le ruissellement. Le couplage surface-subsurface des écoulement est très efficace dans ce modèle, et le couplage du transport de soluté adoptant la même stratégie a été amélioré pour mieux respecter la conservation de la masse.Le modèle est en premier lieu testé sur des données issues d'expérimentations de transfert de subsurface sur une maquette de laboratoire à petite échelle (2 m de long, o.5 m de large, 1 m de profondeur). Les résultats sont confrontés aux chroniques de flux massiques observées et une analyse de sensibilité de type Morris est menée. Le modèle est capable de reproduire de façon satisfaisante les observations, et très satisfaisante après une légère calibration. Les conductivités à saturation horizontale et verticale, la porosité et le paramètre $n$ de la courbe de rétention influencent de façon non négligeable les résultats hydrodynamiques et de transfert de soluté. Dans un second temps, le modèle est évalué sur les données issus d'un versant viticole réel (0.6 ha) dans un contexte orageux avec de fortes interactions surface-subsurface. Une analyse de sensibilité globale est menée, et met en valeur les mêmes paramètres que la méthode de Morris. Les interactions entre les paramètres influencent fortement la variabilité des sorties hydrodynamiques et de transfert. La conservation de la masse est très correctement assurée malgré la complexité de la simulation.Le modèle auquel on aboutit correspond bien aux objectifs de départ, sa validation est solide, même si elle n'est rigoureusement valable que dans les contextes précis où elle a été réalisée. On a montré que le modèle était robuste et capable de reproduire des données observées. D'autres processus manquent encore pour représenter toutes les voies de transfert à l'échelle du versant, notamment la représentation du transfert préférentiel en subsurface et du transport sédimentaire en surface. / Pesticide use on agricultural surfaces leads to a broad surface and subsurface water contamination in France. Awaiting a deep agricultural practices evolution and a sustained fall of the pesticide use, it is of interest to limit transfers form agricultural fields to rivers. In order to constrain those transfers, a deepen knowledge of processes at stake and their potential interactions is necessary, as well as taking full advantages of fields observations.The aim of this PhD is the reactive transfer processes integration in the Hydrological physically-based model CATHY (CATchment HYdrology) which simulates surface-subsurface coupled water flow and advectiv solute transport in three dimensions and in variably saturated situations. Linear adsorption and first order decay are implemented in subsurface. A mixing modules is added, and evens the concentration between surface runoff and subsurface first layer. This module simulates the solute mobilisation from soil to surface runoff. The water flow surface-subsurface coupling procedure is very accurate in CATHY, and the transport coupling procedure is improve in order to respect the mass conservation.The model is first evaluated on subsurface transfer laboratory experimentation data at a small scale (2 m long, o.5 m wide, 1 m deep). Results are compared to mass flux evolution in time and a Morris sensitivity analysis is conducted. The model is able to acceptably reproduce observation, and properly after a slight calibration. Horizontal and vertical saturated conductivities, porosity and the $n$ parameter of retention curve significantly influence hydrodynamics and solute transport. As a second step, the model is evaluated on data from a field wine hillslope on an intense rain event, therefore in a context with a lot of surface-subsurface interactions. A global sensitivity analysis is conducted and highlights same parameters as the Morris method. Interactions between parameters highly influence the variability of hydrodynamic and solute transfer outputs. Mass conservation is accurate despite the complexity of the context.The resulting model meets the objectives, its evaluation is strong even if its theoretically only valid in the precise context in which the evaluations where conducted. The model is robust and able to reproduce observed data. Some complementary processes are still missing in the model to properly represent transfer ways at the hillslope scale, such as subsurface preferential transfers and surface sedimentary transport.

Le présent travail a pour objectif d’étudier la synergie entre la déformation plastique et les processus d’adsorption et d’absorption de l’hydrogène en surface et en subsurface du nickel monocristallin. La Réaction d’Evolution de l’Hydrogène (REH) et l’absorption de l’hydrogène en subsurface (RAH)partagent le plus souvent l’intermédiaire commun : l’hydrogène adsorbé (Hads). Le chemin réactionnel de la REH sur des surfaces de nickel (100) en milieu acide sulfurique peut être présenté par un mécanisme de Volmer-Heyrovsky. Les paramètres cinétiques élémentaires correspondants comme les coefficients de symétrie, les enthalpies d'activation, le nombre de sites actifs, ont été simulés via un modèle thermocinétique en utilisant les données expérimentales. Ces paramètres peuvent être affectés par la déformation plastique. Cette dernière modifie la densité et la distribution des dislocations stockées affectant la rugosité de surface à l'échelle atomique et engendrant des sites actifs supplémentaires d'adsorption. En revanche, l’émergence de ligne de glissement à la surface conduit à un phénomène de désactivation associé la formation de plan plus compact (111). L’entrée d’atomes d’hydrogène associée à l’étape de transfert surface-Subsurface peut être mesurée à l’aide d’une méthode potentiostatique de type pulsé. Cette dernière a permis de caractériser la diffusion et le piégeage de l'hydrogène en subsurface. Deux zones peuvent être distinguées, l’une proche de la surface (subsurface) et l’autre au coeur de l'échantillon. Dans ce cas, le coefficient de diffusion associé à la subsurface semble être beaucoup plus élevé que celui obtenu au coeur du métal. En revanche,l’application d’une contrainte mécanique conduit à une augmentation de la densité de pièges. Cette dernière, développée au voisinage de la surface : « subsurface », est plus faible que celle à coeur du matériau, ce qui suggère un effet adoucissant en subsurface. / The present work has for objective to study the synergy between the plastic strain and the processes of adsorption and absorption of hydrogen on the surface and the subsurface of nickel single crystal.Hydrogen Evolution Reaction (HER) and Hydrogen Absorption in subsurface (HAR) share mostly the common intermediate: the adsorbed hydrogen (Hads). The HER pathway on nickel (100) single crystal surfaces in sulphuric acid medium can be related by a Volmer-Heyrovsky mechanism. The corresponding elementary kinetic parameters as symmetry coefficients, activation enthalpies, number of active sites, have been identified via a thermokinetic model using experimental data. These parameters can be affected by defects associted with plastic strain. Irreversible plastic strain modifies the density and the distribution of storage dislocations affecting the surface roughness at atomic scale and generating additional active adsorption sites. Further more, surface emergence of mobile dislocations induces the formation of slip bands, which modify the surface roughness and the electronic state of the surface and increases the (111) surface density. The entry of hydrogen atoms associated to the transfer step surface-Subsurface can be measured using a potentiostatic double-Steptechnique (pulse method). This last allowed to characterizing the diffusion and trapping of hydrogen in the subsurface. Two domains can be distinguished, that of the subsurface and that of the bulk of the sample. In this case, the diffusion coefficient near the surface (subsurface) seems to be much higher than that obtained in the bulk of the metal. On the other hand, the application of mechanical stressleads to an increase of traps density. This last, developed near the surface: « subsurface », is lower than that at the bulk of material, which suggest a softening effect in the subsurface.

Les tourbillons océaniques de subsurface sont des structures dynamiques qui peuplent l'océan global. Ils sont souvent générés à partir de courants d'échanges entre les bassins d'évaporation semi-fermés (comme la Mer Méditerranée, la Mer Rouge et le Golfe Persique) et l'océan ouvert ou pendant des processus de convection profonde. Ces tourbillons peuvent maintenir une géométrie cohérente sur des échelles de temps pluriannuelles et sont capables, du fait de leur migration, de transporter des quantités significatives de chaleur, sel et nutriments. Les tourbillons de subsurface contribuent donc à la redistribution tridimensionnelle des traceurs océaniques à échelle globale, d'où l'intérêt de connaître leurs positions et déplacements.En général, les tourbillons sont capables de modifier localement la surface de la mer, en générant des anomalies qui permettent leur suivi à travers des observations satellitaires. Notre étude se base sur l'utilisation de modèles analytiques et numériques pour caractériser les signatures induites à la surface par les tourbillons de subsurface; en particulier les anomalies de l'élévation (SSH), de température (SST) et de salinité (SSS) de la surface océanique.D'abord, nous avons étudié les signatures de surface (en SSH) dans un cadre idéalisé. Leurs propriétés ont été mises en relation avec la structure tridimensionnelle des tourbillons, nous permettant de déterminer que seulement les tourbillons de subsurface de meso-échelle océanique sont détectables via les observations altimétriques actuelles. En outre, en utilisant un modèle réaliste, nous avons étudié les signatures de surface des tourbillons d'eau méditerranéenne (MEDDIES) en termes de SSH, SST et SSS. L'étude a mis en évidence des différences entre les signatures en SSH et les signatures thermohalines: les premières montrent des intensités et des structures horizontales toujours liées aux changements structurels des Meddies, alors que les deuxièmes sont plutôt pilotées par la dynamique locale de surface.Enfin, nos résultats montrent que le suivi automatique des tourbillons de subsurface est plutôt envisageable à partir des techniques altimétriques, en valorisant aussi l'apport des futures missions satellitaires à haute résolution, comme SWOT. / Subsurface-intensified vortices are ubiquitous in the world ocean. They are often generated by water mass exchanges between semi-closed evaporation basins (e.g.: Mediterranean Sea, Red Sea, Persian Gulf) and the open ocean or during deep convection processes. These vortices can maintain a coherent geometry during inter-annual timescales and, due to their migration, they are able to carry large amounts of heat, salt and nutrients. Hence, the class of subsurface-intensified vortices participates to the redistribution of oceanic tracers along the three dimensions and at global scale, justifying the interest in determining their positions and mean pathways in the ocean. In general, vortices are able to locally modify the ocean surface generating anomalies that allow one to track them via satellite sensors. Our study, based on the use of analytical and numerical models, deals with the characterization of the sea-surface anomalies generated by subsurface-intensified vortices in terms of Sea-Surface Height (the elevation of the oceanic free-surface, SSH), Sea-Surface Temperature (SST) and Sea-Surface Salinity (SSS).In a first analysis, we have studied the SSH anomalies generated by subsurface vortices in an idealized context. Their properties have been related to the three-dimensional structure of the vortex, allowing us to state that only subsurface mesoscale vortices can be detected by the presentday altimetric observations. Furthermore, using a realistic model, we have studied the sea-surface expression of Mediterranean Water Eddies (MEDDIES) in SSH, SST and SSS. The study has evidenced the main differences between the Meddies-induced SSH anomalies and their thermohaline surface anomalies (i.e., SST and SSS): the first exhibit horizontal structures and intensities that can always be related to the Meddy structural changes at depth, while the second are mostly driven by the local surface dynamics.These studies show that the automatic tracking of subsurface-intensified vortices is mostly possible in an altimetric perspective, further confirming the importance of future high-resolution altimetric satellite missions, like SWOT.

Geologic sequestration of anthropogenic carbon dioxide (CO2) greenhouse gas emissions is an engineering solution that potentially reduces CO2 emissions released into the atmosphere thereby limiting their effect on climate change. This study focuses on Woodside field as a potential storage and sequestration site for CO2 emissions. The Woodside field is positioned on a doubly plunging, asymmetrical anticline on the northeast flank of the San Rafael Swell. Particular focus will be placed on the Permian White Rim Sandstone, Black Box Dolomite and Black Dragon Member of the Triassic Moenkopi Formation as the reservoir/seal system to store and sequester CO2 at Woodside field. The White Rim Sandstone, the primary target reservoir, is divided into three stratigraphic intervals based on facies analysis: a lower sand sheet facies (about 60 ft or 18 m), a thick middle eolian sandstone facies (about 390 ft or 119 m), and an upper marine reworked facies (about 70 ft or 21 m). Porosity and permeability analyses from the outcrop indicate good reservoir quality in the eolian sandstone and reworked facies. Porosity in the White Rim Sandstone ranges from 7.6 to 24.1% and permeability reaches up to 2.1 D. The maximum combined thickness of the three facies is 525 ft (160 m) at Woodside field providing a significant volume of porous and permeable rock in which to store CO2. The Black Box Dolomite is the secondary potential reservoir for CO2 storage at Woodside field and has a gross thickness up to 76 ft (23 m). The Black Box Dolomite is divided into four lithofacies: a basal nodular dolomudstone (8.2 -15 ft or 3.5-4.5 m), a dolowackestone (25-37 ft or 7.5-11 m), a dolomitic sandstone (0-8.2 ft or 0-2.5 m), and an upper sandy dolowackestone (0-16 ft or 0-4.9 m). Porosity and permeability analyses indicate reservoir potential in the dolowackestone, dolomitic sandstone, and sandy dolowackestone lithofacies. Porosity in the Black Box Dolomite ranges from 6.6 to 29.2% and permeability reaches up to 358 mD. The nodular dolomudstone lithofacies has relatively poor reservoir quality with porosity up to 9.4% and permeability up to 0.182 mD. This lithofacies could act as a baffle or barrier to fluid communication between the White Rim Sandstone and Black Box Dolomite. The Black Dragon Member of the Triassic Moenkopi Formation will serve as the seal rock for the relatively buoyant CO2 stored in the underlying formations. The Black Dragon Member is comprised of four lithofacies: a chert pebble conglomerate; an interbedded sandstone, siltstone, and shale; a trough cross-stratified sandstone, and an oolitic and algal limestone. The Black Dragon Member has a maximum thickness of 280 ft (85 m) at Woodside field. Mudstone beds contain from 0.16 to 0.47% porosity. QEMSCAN analysis indicates several minerals within shale beds that may react with a CO2-rich brine including calcite (18.73 to 23.43%), dolomite (7.56 to 7.89%), alkali feldspar (4.12 to 4.43 %), glauconite (0.04 to 0.05%), and plagioclase (0.03 to 0.04%). Silty mudstones comprise 75% of this member at Black Dragon Canyon. Volumetric estimates for Woodside field were calculated based on the 10th, 50th, and 90th percent probabilities (P10, P50, and P90). The White Rim Sandstone is the primary target reservoir and has capacity to hold 2.2, 8.8, or 23.7 million metric tonnes (P10, P50, and P90 respectively) of CO2 within the structural closure of Woodside field. The Black Box Dolomite may hold 0.5, 1.8, or 4.5 million metric tonnes, respectively of additional CO2 within the structural closure of Woodside field. These two formations combined have the capacity to store up to 28.3 million metric tonnes (P90) of CO2.

No description available.

No description available.

Master of Science / Department of Agronomy / Scott A. Staggenborg / In recent years, subsurface drip irrigation (SDI) acres have increased substantially. The use of SDI on corn (Zea Mays L.) in the Great Plains has increased due to increased land costs, reduced irrigation water availability, and higher commodity prices. Applying phosphorus (P) fertilizer through a SDI system becomes a major advantage, but further investigation of the interaction between water and fertilizer is needed. Sub-surface drip irrigation systems can be used to better improve the application efficiencies of fertilizers, applying in wet soil-root zones can lead to better uptake of soil applied materials. The objectives of this study were to determine how corn responds to P fertilizer applied via SDI and to create methodologies to simulate fertilizer and irrigation water compatibility tests for use in SDI systems. A plot sized SDI system was installed near Manhattan, KS to evaluate P treatments. Eight separate P fertilizers were applied via SDI mid-season at a rate of 34 kg P2O5 ha-1 and split-plots were created with 2x2 starter band at planting. Nitrogen was a non-limiting factor, with 180 kg N ha-1 applied as urea. Both starter fertilizer and injected fertilizer affected corn grain yield as indicated by the starter by treatment interaction. Split applying starter fertilizer at planting increased yield. A secondary laboratory study was conducted to evaluate the water and fertilizer interactions. A filtration system was used to simulate field conditions and each fertilizer/water mix was filtered through a 400 mesh filter paper to evaluate fertilizer precipitant formation. Sixteen common fertilizers were analyzed with different rates of Avail. Differences were observed between fertilizer treatments, visually and quantitatively. A secondary P soil movement field study was performed to quantify P concentrations around the SDI emitter. Soils were sampled in a 30.5 cm by 30.5 cm square adjacent to the emitter on a control treatment and a fertilized treatment, in both years of the study. Visual and quantitative differences were observed between the two treatments in both years of the study. When P fertilizers were added to the SDI system, higher P concentrations were found very close to the emitter orifice. Control treatments exhibited lower P concentrations around the emitter than fertilized treatments.

For most electromagnetic (EM) geophysical systems, the contamination of primary fields on secondary fields ultimately limits the capability of the controlled-source EM methods. Null coupling techniques were proposed to solve this problem. However, the small orientation errors in the null coupling systems greatly restrict the applications of these systems. Another problem encountered by most EM systems is the surface interference and geologic noise, which sometimes make the geophysical survey impossible to carry out. In order to solve these problems, the alternating target antenna coupling (ATAC) method was introduced, which greatly removed the influence of the primary field and reduced the surface interference. But this system has limitations on the maximum transmitter moment that can be used. The differential target antenna coupling (DTAC) method was proposed to allow much larger transmitter moments and at the same time maintain the advantages of the ATAC method. In this dissertation, first, the theoretical DTAC calculations were derived mathematically using Born and Wolf's complex magnetic vector. 1D layered and 2D blocked earth models were used to demonstrate that the DTAC method has no responses for 1D and 2D structures. Analytical studies of the plate model influenced by conductive and resistive backgrounds were presented to explain the physical phenomenology behind the DTAC method, which is the magnetic fields of the subsurface targets are required to be frequency dependent. Then, the advantages of the DTAC method, e.g., high-resolution, reducing the geologic noise and insensitive to surface interference, were analyzed using surface and subsurface numerical examples in the EMGIMA software. Next, the theoretical advantages, such as high resolution and insensitive to surface interference, were verified by designing and developing a low-power (moment of 50 Am²) vertical-array DTAC system and testing it on controlled targets and scaled target coils. At last, a high-power (moment of about 6800 Am²) vertical-array DTAC system was designed, developed and tested on controlled buried targets and surface interference to illustrate that the DTAC system was insensitive to surface interference even with a high-power transmitter and having higher resolution by using the large-moment transmitter. From the theoretical and practical analysis and tests, several characteristics of the DTAC method were found: (1) The DTAC method can null out the effect of 1D layered and 2D structures, because magnetic fields are orientation independent which lead to no difference among the null vector directions. This characteristic allows for the measurements of smaller subsurface targets; (2) The DTAC method is insensitive to the orientation errors. It is a robust EM null coupling method. Even large orientation errors do not affect the measured target responses, when a reference frequency and one or more data frequencies are used; (3) The vertical-array DTAC method is effective in reducing the geologic noise and insensitive to the surface interference, e.g., fences, vehicles, power line and buildings; (4) The DTAC method is a high-resolution EM sounding method. It can distinguish the depth and orientation of subsurface targets; (5) The vertical-array DTAC method can be adapted to a variety of rapidly moving survey applications. The transmitter moment can be scaled for effective study of near-surface targets (civil engineering, water resource, and environmental restoration) as well as deep targets (mining and other natural-resource exploration).

Reservoir heterogeneities exhibit a wide range of length scales, and their interaction with various transport mechanisms control the overall performance of subsurface flow and transport processes. Modeling these processes at large-scales requires proper scale-up of both heterogeneity and the underlying transport mechanisms. This research demonstrates a new reservoir modeling procedure to systematically quantify the scaling characteristics of transport processes by accounting for sub-scale heterogeneities and their interaction with various transport mechanisms based on the volume averaging approach. Although treatments of transport problems with the volume averaging technique have been published in the past, application to real geological systems exhibiting complex heterogeneity is lacking. A novel procedure, where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a small sub-volume of the reservoir, can be integrated with the volume averaging technique to provide effective description of transport at the coarse scale. In a volume averaging procedure, scaled up equations describing solute transport in single-phase flow are developed. Scaling characteristics of effective transport coefficient corresponding to different reservoir heterogeneity correlation lengths as well as different transport mechanisms including convection, dispersion, and diffusion are studied. The method is subsequently extended to describe transport in multiphase systems to study scaling characteristics of processes involving adsorption and inter-phase transport. Key conclusions drawn from this dissertation show that 1) variance of reservoir properties and flow responses generally decrease with scale; 2) scaling of recovery processes can be described by the scaling of effective mass transfer coefficient (Keff); in particular, mean and variance of Keff decrease with length scale, similar in the fashion of recovery statistics (e.g., variances in tracer breakthrough time and recovery); 3) the scaling of Keff depends on the underlying heterogeneity and is influenced by the dominant transport mechanisms. To show the versatility of the approach for studying scale-up of other transport mechanisms, it is also applied to derive scaled up formulations of non-Newtonian polymer flow to investigate the scaling characteristics of the apparent viscosity and effective shear rate in porous media. / text

The site-specific management of alfalfa has not been well-evaluated, despite the economic importance of this crop. The objectives of this work were to i) characterize the effects of soil moisture deficits on alfalfa and alfalfa yield components and ii) evaluate the use of canopy reflectance patterns in measuring treatment-induced differences in alfalfa yield. A randomized complete block design with five replicates of subsurface drip irrigation (SDI) and rainfed treatments of alfalfa was established at the University of Kentucky Animal Research Center in 2003. Potassium, as KCl, was broadcast on split-plots on 1 October 2004 at 0, 112, 336, and 448 kg K2O ha-1. In the drought year of 2005, five harvests (H1 - H5) were taken from each split-plot and from four locations within each SDI and rainfed plot. One day prior to each harvest, canopy reflectance was recorded in each plot. Alfalfa yield, yield components, and leaf area index (LAI) were determined. In 2005, dry matter yields in two harvests and for the seasonal total were increased (Pandlt;0.05) by SDI, but SDI did not affect crown density. Herbage yield was strongly associated with yield components but yields were most accurately estimated from LAI. Canopy reflectance within blue (450 nm), red (660 nm) and NIR bands were related to LAI, yield components, and yield of alfalfa and exhibited low variance (cv andlt; 15%) within narrow ( 0.125 Mg ha-1) yield ranges. Red-based Normalized Difference Vegetation Indices (NDVIs) and Wide Dynamic Range Vegetation Indices (WDRVIs) were better than blue-based VIs for the estimation of LAI, yield components, and yield. Decreasing the influence of NIR reflectance in VIs by use of a scalar (0.1, 0.05, or 0.01) expanded the range of WDRVI-alfalfa yield functions. These results indicate that VIs may be used to estimate LAI and dry matter yield of alfalfa within VI-specific boundaries.