Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
In this study we attempt to understand the water storage variations in a karst aquifer on the Larzac Plateau (South of France) using ground-based gravimetry. Surface to 60 m depth gravity measurements are performed three times a year since 2006 down a pothole, in complement to monthly absolute gravity (AG) measurements at three sites. The time variations of the surface to depth (STD) gravity differences are compared with the AG variations. Using a simple Bouguer plate model, we find that the STD gravity differences are very similar to the AG variations. The STD gravity differences are then used to determine apparent density values. These integrative density values are compared with measured grain densities from core samples to obtain an apparent porosity and saturation change representative of the investigated depth. The apparent porosity ranges from 4.8 to 7.3 per cent. We then discuss on the repartition of the apparent physical properties with respect to the epikarst and infiltration zone karst structures. We argue that AG and STD differences monitor epikarst water storage variations. Within this scope, we discuss the fact that seasonal scale water storage variation occurs predominantly in the epikarst.
ISSN: 0956-540X

hal-00413528
https://hal.archives-ouvertes.fr/hal-00413528
DOI : 10.1111/j.1365-246X.2009.04118.x

Éditeur(s) : Cayenne : Imprimerie du gouvernement
Résumé : Année 1916
Siècle(s) traité(s) : 20
Droits : Domaine public
Provenance : Collectivité territoriale de Guyane. Bibliothèque Alexandre-Franconie
Permalien : http://www.manioc.org/patrimon/FRA11243
FRA11243

Éditeur(s) : London : T. Becket and P. A. De Hondt
Résumé : "Document inclus dans un recueil. La page de titre du recueil porte "An inquiry into the nature, cause and cure of the croup"."

Droits : Domaine public
Provenance : Université de Nantes. Service commun de la documentation
Permalien : http://www.manioc.org/patrimon/NAN13002
NAN13002

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : Coarse woody debris (CWD, dead wood sections a parts per thousand yen10 cm diameter) represents a large store of carbon in tropical forests; however, estimates of the flux of carbon from CWD in these forests remain poorly constrained. The objective of this study was to resolve the dry/wet season response of respiration in CWD (R (cwd)), and investigate the importance of biotic and abiotic factors for predicting the seasonal change of R (cwd) at the ecosystem level. This study presents a 4-month time series of R (cwd) measurements conducted on 42 dead trees (26 species) at the Paracou Research Station in French Guiana. R (cwd) measurements were repeated 13 times on each CWD sample from July to November 2011, spanning the transition from wet to dry season, and then from dry season to the following wet season. Seasonal drought caused monthly R (cwd) to drop by 20.5 +/- A 5.1% over the wet-dry transition. Changes in woody tissue moisture content explained 41.9% of the measured seasonal variability in R (cwd), but 60% of the seasonal variability in mean forest R (cwd) rates could be modelled using surface soil water content. We estimate that R (cwd) is approximately 5% of annual ecosystem respiration (R (eco)) and that seasonal variations in R (cwd) contribute appreciably to seasonal variations of R (eco), and should be included in functional models simulating the response of tropical rainforest ecosystems to current and future climate.
ISSN: 1432-9840

hal-01032431
https://hal.archives-ouvertes.fr/hal-01032431
DOI : 10.1007/s10021-013-9684-x

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A shallow field experimental site for CO2 injection was established at Maguelone (Languedoc, France), in order to test in an integrated manner a suite of surface and downhole hydrogeophysical monitoring methods. The objective is to improve monitoring of gas transport in the shallow subsurface and to determine the sensitivity of CO2 monitoring systems for leakage detection. The site offers a natural laboratory to study the processes associated with CO2 injection in a clastic and clay-rich context saturated with saline fluids. Prior to CO2 injection, three nitrogen (N2) injections were undertaken in 2012 to measure the site response to neutral gas injection. In 2013, a volume of 111 m3 (mass of 220 kg) of CO2 was injected during 3.5 h at 15 m depth. During each experiment, the gas plumes were successfully detected from pressure monitoring, time-lapse induction logging and downhole resistivity monitoring with dipole–dipole array. Increases in resistivity are attributed to free gas propagation (either N2 or CO2) whereas decreases in resistivity correlate with CO2 dissolution in the pore fluid. Chemical analyses confirm this hypothesis with a decrease in pH and an increase in the concentration of dissolved species in the latter case.
ISSN: 1750-5836

hal-01355943
https://hal.archives-ouvertes.fr/hal-01355943
DOI : 10.1016/j.ijggc.2015.12.005

Éditeur(s) : HAL CCSD Elsevier
Résumé : This paper is the first presentation of a project called GHYRAF (Gravity and Hydrology in Africa) devoted to the detailed comparison between models and multidisciplinary observations (ground and satellite gravity, geodesy, hydrology, meteorology) of the variations of water storage in Africa from the Sahara and part to the monsoon equatorial part. We describe the various actions planned in this project. We first detail the actions planned in gravimetry which consist in two main surface gravity experiments: on the one hand the periodic repetition of absolute gravity measurements along a north-south monsoonal gradient of rainfall in West Africa, going from Tamanrasset (20 mm/year) in southern Algeria to Djougou (1200 mm/year) in central Benin; on the other hand the continuous measurements at Djougou (Benin) with a superconducting gravimeter to monitor with a higher sampling rate the gravity changes related to an extreme hydrological cycle. Another section describes the actions planned in GPS which will maintain and develop the present-day existing network in West Africa. The third type of actions deals with hydrology and we review the three sites that will be investigated in this joint hydrogeophysics project namely Wankama (near Niamey) and Bagara (near Diffa) in the Niger Sahelian zone and Nalohou (near Djougou) in the Benin monsoon zone. We also address the question of the ground truth of satellite-derived missions: in this context the GHYRAF project will lead to test the hydrology models by comparison both with in situ and satellite data such as GRACE, as well as to an important increase of our knowledge of the seasonal water cycle in Africa. We finally present preliminary results in GPS based on the analysis of the vertical motion of the Djougou site. The resulting absolute gravity changes related to the 2008 monsoon are finally given.
ISSN: 0264-3707

hal-00475660
https://hal.archives-ouvertes.fr/hal-00475660
DOI : 10.1016/j.jog.2009.09.014

Éditeur(s) : HAL CCSD
Résumé : Geological storage of CO2 is one of diverse technologies being explored to reduce atmospheric carbon fromindustrial processes (i.e. fossil fuel combustion). One of the specific features of CO2 injection is the possibility ofgeochemical reactions (dissolution – precipitation) between mobile reactive brine (e.g. formation water enrichedin CO2) and the host rock during the spatial and temporal evolution of CO2. That leads to modifications in thepore structure, which in turn change the flow dynamics of the reservoir (e.g. the permeability k). Then, thesesstructural modifications can largely control the injectivity, so that the pressure field in the reservoir and also theCO2 propagation. Accordingly, it is crucial to explore the changes in the reservoir properties (e.g. structural andhydrodynamic) induced during a CO2 injection and specially the relationships between them (e.g. k or reactivesurface-Sr versus porosity-φ , k versus rock heterogeneity), for developing predictive modelling tools of thetransport and reaction processes occurring during a CO2 injection and reliable risk assessment. In the case ofcarbonate rocks, the application of the predictive models of transport and reaction is still challenging, because oftheir high heterogeneity so that the incertitude in the reaction kinetics of carbonate minerals.From this perspective, we realized brine-enriched in CO2 percolation experiments through carbonate rocksamples in thermodynamic conditions expected during CO2 injection in deep reservoirs (T = 100°C et P =12MPa). The permeability changes k(t) is monitored during the experiments and the porosity variationφ (t) iscalculated from chemical analyses of the sampled outlet fluids, using ICP-EAS. The pore structure modificationsare investigated from high resolution X ray micro tomography images acquired from the synchrotron ofGrenoble (ESRF). Depending to the dissolution regime, controlled by the reservoir rock fabric and the chemicalcomposition of the brine (e.g. PCO2), we observed that a modification of pore structure can either improve(atypical result in dissolution context) or impair the value of the permeability k.
Le stockage géologique du CO2 est l’une des diverses technologies étant explorées afin deréduire les émissions de carbone atmosphérique des processus industriels (i.e. combustion del’énergie fossile). L’une des spécifiques caractéristiques de l’injection du CO2 en profondeurreste la possibilité de réactions géochimiques (dissolution-précipitation) entre la saumureréactive mobile (e.g. eau de formation enrichie en CO2) et la roche encaissante durantl’évolution spatiale et temporelle du CO2, conduisant à des modifications dans la structure despores et par conséquent dans les propriétés d’écoulement du réservoir (e.g. la perméabilité k).Donc, ces changements structuraux peuvent largement contrôler l’injectivité, ainsi que lechamp de pression dans le réservoir et aussi la propagation du CO2. Il demeure ainsi cruciald’explorer les changement dans les propriétés de réservoirs (e.g. structurales ethydrodynamiques) induits durant une injection de CO2 et explicitement les relations existantesentre eux (e.g. k ou surface réactive-Sr versus porosité-φ , k versus hétérogénéité de la roche),afin de développer des outils de modélisation prédictive des processus de transport etréactionnels se produisant durant une injection de CO2 et d’évaluer de façon fiable les risques.Dans le cas des réservoirs carbonatés, l’application des modèles prédictifs de transport réactifdemeure toujours un enjeu, car contrainte par la forte hétérogénéité en leur sein ainsi que parl’incertitude dans la cinétique de réactions des minéraux carbonatés dans ce contexte. Danscette optique, nous avons réalisé des expériences de percolation à travers des échantillons deroches carbonatées dans les conditions thermodynamiques de stockage en profondeur (T =100°C et P =12 MPa). L’évolution de la perméabilité k(t) est suivie au cours desexpériences ; et la variation de la porosité φ (t) est calculée à partir des résultats d’analyseschimiques au ICP-AES des fluides de sortie échantillonnés. L’investigation des modificationsapportées à la structure des pores est réalisée par le biais de la Micro-Tomographie hauterésolution à rayon X, acquise au synchrotron de Grenoble (e.g. ESRF).Dépendant du régime de dissolution, contrôlé par la fabrique de la roche réservoir et lacomposition chimique de la saumuré chargée en CO2 (e.g. PCO2 engagée), on a observéqu’une modification de la structure de la roche peut soit améliorer soit détériorer (résultatatypique en contexte de dissolution) la valeur de la perméabilité k.
https://hal.archives-ouvertes.fr/tel-01142136

tel-01142136
https://hal.archives-ouvertes.fr/tel-01142136
https://hal.archives-ouvertes.fr/tel-01142136/document
https://hal.archives-ouvertes.fr/tel-01142136/file/thesemangane2013.pdf

Éditeur(s) : Paris : Presses universitaires de France

Droits : Domaine public
Provenance : Université de Nantes. Service commun de la documentation
Permalien : http://www.manioc.org/patrimon/NAN13058
NAN13058

Éditeur(s) : Turin : Imprimerie Royale
Siècle(s) traité(s) : 19
Provenance : Archives départementales de Guadeloupe
Permalien : http://www.manioc.org/patrimon/ADG18153
ADG18153

Éditeur(s) : HAL CCSD Mineralogical Society of America
Résumé : International audience
In situ mineralization of CO2 in ultramafic rock-hosted aquifers is one of the promising solutions for decreasing CO2 concentrations in the atmosphere. Naturally altered ultramafic rocks suggest that carbonation processes are controlled by local heterogeneities in the structure of the rock and fluid transport at the water-rock interfaces. We studied the role of rock crystallographic anisotropy relative to the global fluid flow direction on the mineralization of CO2 by means of electron microscope analyses from the macro- to the micrometer scale (EBSD-FIB). The sample used for the measurements was a hot pressed olivine core percolated by water enriched in CO2 (pCO2 = 10 MPa) at 180 °C. During the percolation experiment, olivine was dissolved and two types of carbonates, dolomite, and magnesite, were precipitated on olivine surfaces. The results showed that the dissolution of olivine is controlled by its crystallographic properties as shown by the development of etch-pits only on the (010)ol planes and with elongated shapes parallel to the [010]ol axes. In contrast, the precipitation of carbonates is governed by hydrodynamic properties. Carbonates are heterogeneously distributed in the percolated rock. They are mainly located along the moderate (for dolomite) and the minor (for magnesite) flow paths, both oriented parallel to the principal fluid flow direction, which allow carbonates to be supplied with divalent cations (e.g., Ca2+, Mg2+, and Fe2+). In these flow paths, carbonate growth is systematically oriented normal to the flow that facilitates the development of chemical gradients with cationic supersaturation conditions for carbonate precipitation near the walls.In natural systems, the (010)ol planes are parallel to the Moho and the (100)ol planes are vertical; our study suggests that flow of CO2-rich fluids will induce precipitation of carbonates localized along, and preferentially clogging, vertical flow paths while favoring olivine dissolution along horizontal fluid pathways. This dual control of structure and fluid flow on carbonation mechanisms could be an important parameter allowing sustainable CO2 storage in peridotites, while limiting the risks of leakage toward the surface.
ISSN: 0003-004X

hal-01143393
https://hal.archives-ouvertes.fr/hal-01143393
DOI : 10.2138/am-2015-4913

Éditeur(s) : London : [s.n.]
Siècle(s) traité(s) : 17
Droits : Domaine public
Provenance : Archives départementales de Guadeloupe
Permalien : http://www.manioc.org/patrimon/ADG17037
ADG17037

Éditeur(s) : [S.l.] : Harper
Siècle(s) traité(s) : 19
Droits : Domaine public
Provenance : Université des Antilles. Service commun de la documentation
Permalien : http://www.manioc.org/patrimon/HASH40423832e7422746ff4d15
HASH40423832e7422746ff4d15

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
The aim of this study is to bring new information on water storage dynamics in karst systems from tiltmeter measurements. Newly developed long-base hydrostatic tiltmeters are installed at two sites on the Larzac plateau (France) in a karst aquifer of similar to 100 km(2) recharge area. Each site is located within a karst cave where two tilt directions are monitored. Significant reversible tilt deformation reaching amplitudes of 10(-6) to 10(-5) rad was observed at both sites following heavy precipitation. Elastic parameters were determined with an experiment in which a tiltmeter site was loaded by up to 25 t of weight at strategic locations at the ground surface. Mechanisms responsible for the observed tilt were then examined by means of finite element modeling. Deformation induced by water pressure changes in fractures is our preferred interpretation as the most plausible mechanism. Within this scope, we used the tiltmeter responses to extract time constants using lumped parameter modeling. Time constants are interpreted to be associated with the filling and emptying of fractures nearby the tiltmeters. These instruments therefore appear as useful tools to study the local dynamics of water infiltration in karst systems.
ISSN: 0043-1397

hal-00534461
https://hal.archives-ouvertes.fr/hal-00534461
DOI : 10.1029/2009WR008082

Éditeur(s) : Edinburgh, London
Siècle(s) traité(s) : 19
Provenance : Université Caen Normandie. Service commun de la documentation
Permalien : http://www.manioc.org/patrimon/CAE19033_4
CAE19033_4

Éditeur(s) : HAL CCSD
Résumé : International audience
The deformation of natural systems in response to subsurface water storage and redistribution provides insightsinto the main water flow path within heterogeneous systems, including the role of faults or fractures. A longbaseline tiltmeter was installed in the low-noise underground laboratory of Rustrel (LSBB) to study the responseof the Fontaine de Vaucluse (FDV) karst hydrosystem to water cycle. Tilt data and piezometric levels recorded in aborehole close to the LSBB show a strong correlation with the discharge of the system observed at the FDV spring30 km away. Over several months, tilt data were recorded on three base lines, thus allowing, for the first time,to study the tilt gradient variation that appears homogeneous. Such information provides a significant constrainton hydrological processes leading to the measured deformation. Several deformation models were tested usingthe ADELI code to estimate the type of hydro-mechanical structure that could reproduce the measured tilt andits gradient. On one hand, models show that uniform loading at the surface produces a much smaller signal thanobserved on measured data. On the other hand, the deformation related to the filling of a fracture following aprecipitation event requires unrealistic fracture size. Finally, we found that a suitable hydro-mechanical modelcorresponds to the loading of numerous fractures at the interface between the saturated and unsaturated zones. Sucha configuration predicts a tilt distribution in agreement with observations. This study suggests that tilt networksinto a karst system should provide key observation for deciphering hydrological processes
Geophysical Research Abstracts
Vienne, Austria

insu-01308594
https://hal-insu.archives-ouvertes.fr/insu-01308594

Éditeur(s) : Paris : Firmin Didot Frères

Droits : Domaine public
Provenance : Archives territoriales de Guyane
Permalien : http://www.manioc.org/patrimon/GAD12001
GAD12001

Éditeur(s) : London : H. Colburn and R. Bentley
Siècle(s) traité(s) : 19
Droits : Domaine public
Provenance : Collectivité territoriale de Martinique. Bibliothèque Schoelcher
Permalien : http://www.manioc.org/patrimon/SCH13082
SCH13082

Éditeur(s) : Paris : Emile Larose, Libraire-Editeur
Siècle(s) traité(s) : 20
Provenance : Archives départementales de Guadeloupe
Permalien : http://www.manioc.org/patrimon/ADG18123
ADG18123

Éditeur(s) : Paris : Typographie de Firmin Didot frères
Extrait de : Dépôt Général de la marine

Droits : Domaine public
Provenance : Université de Nantes. Service commun de la documentation
Permalien : http://www.manioc.org/patrimon/NAN13016-1
NAN13016-1

Éditeur(s) : Paris : Imprimerie Pradier
Siècle(s) traité(s) : 20
Provenance : Archives départementales de Guadeloupe
Permalien : http://www.manioc.org/patrimon/ADG18191
ADG18191