Towards a better understanding of the Oulmes hydrogeological system (Mid-Atlas,Morocco)

Located in the Mid-Atlas (Morocco), the Oulmes plateau is famous for its mineral water springs “Sidi Ali” and “Lalla Haya” commercialised by the company “Les Eaux minérales d’Oulmès S.A”. Additionally, groundwater of the Oulmes plateau is intensively exploited for irrigation. The objective of this study, essentially performed from data collected during isotopic (summer 2004) and piezometric and hydrogeochemical field campaigns (spring 2007), is to improve the understanding of the Oulmes hydrogeological system. Analyses and interpretation of these data lead to the statement that this system is constituted by a main deep aquifer of large extension and by minor aquifers in a perched position. However, these aquifers interact enough to be in total equilibrium during the cold and wet period. As highlighted by isotopes, the origin of groundwater is mainly infiltration water except a small part of old groundwater with dissolved gas rising up from the granite through the schists.     

Speciation and solubility of heavy metals in contaminated soil using X-ray microfluorescence, EXAFS spectroscopy, chemical extraction, and thermodynamic modeling

Synchrotron-based X-ray radiation microfluorescence (μ-SXRF) and micro-focused and powder extended X-ray absorption fine structure (EXAFS) spectroscopy measurements, combined with desorption experiments and thermodynamic calculations, were used to evaluate the solubility of metal contaminants (Zn, Cu, Pb) and determine the nature and fractional amount of Zn species in a near-neutral pH (6.5-7.0) truck-farming soil contaminated by sewage irrigation for one hundred years. Zn is the most abundant metal contaminant in the soil (1103 mg/kg), followed by Pb (535 mg/kg) and Cu (290 mg/kg). The extractability of Zn, Pb, and Cu with citrate, S,S-ethylenediaminedisuccinic acid (EDDS), and ethylenediaminetetraacetic acid (EDTA) was measured as a function of time (24 h, 72 h, 144 h), and also as a function of the number of applications of the chelant (5 applications each with 24 h of contact time). Fifty-three percent of the Zn was extracted after 144 h with citrate, 51% with EDDS and 46% with EDTA, compared to 69, 87, and 61% for Cu, and 24, 40, and 34% for Pb. Renewing the extracting solution removed more of the metals. Seventy-nine, 65, and 57% of the Zn was removed after five cycles with citrate, EDDS and EDTA, respectively, compared to 88, 100, and 72% for Cu, and 91, 65, and 47% for Pb. Application to the untreated soil of μ-SXRF, laterally resolved μ-EXAFS combined with principal component analysis, and bulk averaging powder EXAFS with linear least-squares combination fit of the data, identified five Zn species: Zn-sorbed ferrihydrite, Zn phosphate, Zn-containing trioctahedral phyllosilicate (modeled by the Zn kerolite, Si₄(Mg_1.65Zn_1.35)O₁₀(OH)₂ · nH₂O), willemite (Zn₂SiO₄), and gahnite (ZnAl₂O₄), in proportions of ∼30, 28, 24, 11, and less than 10%, respectively (precision: 10% of total Zn). In contrast to Cu and Pb, the same fractional amount of Zn was extracted after 24 h contact time with the three chelants (40-43% of the initial content), suggesting that one of the three predominant Zn species was highly soluble under the extraction conditions. Comparison of EXAFS data before and after chemical treatment revealed that the Zn phosphate component was entirely and selectively dissolved in the first 24 h of contact time. Preferential dissolution of the Zn phosphate component is supported by thermodynamic calculations. Despite the long-term contamination of this soil, about 79% of Zn, 91% of Pb, and 100% of Cu can be solubilized in the laboratory on a time scale of a few days by chemical complexants. According to metal speciation results and thermodynamic calculations, the lower extraction level measured for Zn is due to the Zn phyllosilicate component, which is less soluble than Zn phosphate and Zn ferrihydrite.     

Radio Investigations Of 19p/Borrelly In Support To The Deep Space 1 Flyby

NASA's Deep Space 1 mission flew by Comet 19P/Borrelly on September 22, 2001.We present observations of molecular species obtained with the 30-m telescope of theInstitut de Radioastronomie Millimétrique (IRAM) and the Nançay radio telescopeat and near the time of this flyby. OH, HCN, and CS production rates were measured,while upper limits were deduced for CO, H₂CO and H₂S.     

4D GPS water vapor tomography: new parameterized approaches

Water vapor is a key variable in numerical weather prediction, as it plays an important role in atmospheric processes. Nonetheless, the distribution of water vapor in the atmosphere is observed with a coarse resolution in time and space compared to the resolution of numerical weather models. GPS water vapor tomography is one of the promising methods to improve the resolution of water vapor measurements. This paper presents new parameterized approaches for the determination of water vapor distribution in the troposphere by GPS. We present the methods and give first results validating the approaches. The parameterization of voxels (volumetric pixels) by trilinear and spline functions in ellipsoidal coordinates are introduced in this study. The evolution in time of the refractivity field is modeled by a Kalman filter with a temporal resolution of 30 s, which corresponds to the available GPS-data rate. The algorithms are tested with simulated and with real data from more than 40 permanent GPS receiver stations in Switzerland and adjoining regions covering alpine areas. The investigations show the potential of the new parameterized approaches to yield superior results compared to the non parametric classical one. The accuracy of the tomographic result is quantified by the inter-quartile range (IQR), which is decreased by 10–20% with the new approaches. Further, parameterized voxel solutions have a substantially smaller maximal error than the non parameterized ones. Simulations show a limited ability to resolve vertical structures above the top station of the network with GPS tomography.     

Topological changes of the photospheric magnetic field inside active regions: A prelude to flares?

The detection of magnetic field variations as a signature of flaring activity is one of the main goals in solar physics. Past efforts gave apparently no unambiguous observations of systematic changes. In the present study, we discuss recent results from observations that scaling laws of turbulent current helicity inside a given flaring active region change in response to large flares in that active region. Such changes can be related to the evolution of current structures by a simple geometrical argument, which has been tested using high Reynolds number direct numerical simulations of the MHD equations. Interpretation of the observed data within this picture indicates that the change in scaling behavior of the current helicity seems to be associated with a topological reorganization of the footpoint of the magnetic field loops, namely with the dissipation of small scales structures in turbulent media.     

Carboniferous convergence and subsequent crustal extension in the southern Schwarzwald (SW Germany)

Abstract

Detailed structural analysis in the southwestern part of the Variscan Sehwarzwald Massif (SW Germany) indicates polyphase, synmetamorphic deformation in ductile shear zones. The tectono-melainnrphir evolution is characterized by orogenic crustal shortening and subsequent late- orogenic crustal extension in Carboniferous times. Convergence is responsible for an KSK trending, north dipping thrust zone with intense deformation in orthogneissic S-C type mylonites Superposed on schistose and folded metasediments presumably lower Carboniferous in age. Southeastward thrust-’“g parallel to pervasive stretching lineation, similar to the pre-dominant oblique convergent structures ill the central part of the massif, is related to crustal stacking. Relations of early granite intrusions with the outlasting retrograde tectonics Point to a Lower Carboniferous (Late-Visean) age of shortening.

Subsequent crustal extension is indicated by a broad N-S trending and west dipping ductile shear zone within high grade meetamorphic (I1T7LP) gneisses. Retrograde stretching lineatone marked by sillimanite to chlorite anr consistent with a top-to-the-west shearing on the western flank of a large progressively warping domai structure. Intensely sheared and boudinaged granitic rocks are syn-tectonic and seal the age of extension at about 325 Ma (Lower/ Upper Carboniferous boundary). During progressively cataclastic stages of tectonic denudation the still active detachment controlled formation of an adjacent late Paleozoic (Stephano-Pcrniian) continental basin supersedding high-grade gneiss. As elsewhere in the Varisean belt, the late extensional process in the tectono-”“‘tainorphie evolution of the southern Sehwarzwald is related rapid uplift, exhumation and thinning by a gravitational collaps of a previously thickened crust.     

Maris Gullying: canonical analysis of erosion and sedimentation sequences (Baronnies - France)

Abstract

The gullying action on Jurassic and Cretaceous marls in the Baronnies is observed, warm season after cold season, thanks to a network of measuring stakes arranged in 12 gullies. The climate, characterized by summer heath, rather cold but luminous winters, and quite heavy rain, can be classified as mountainous-mediterranean. Seasonal ablation/sedimentation measures have been carried out upon 119 stakes five times within two years (768 days): two in automn, two in early spring (april), and one at end-of-spring.

Ablation and sedimentation sequences are described among the stakes population by Correspondance Factor Analysis (CFA), and their covariations in space and time are explained by Canonical Correspondance Analysis (CCA) according to biophysical environment variables.

Axis 1 of the CFA opposes ground level variations according to their amplitude, high or moderate, regardless of the direction of variation and of measurement date. Axis 2 presents a temporal variation, opposing, on one side, sedimentation sequences at post-winter terms and ablation sequences at postsummer terms, to their converse on the other side.

The CCA indicates that talwegs in their medium and lower parts are more likely to undergo hard gullying or strong accumulation, especially on steep, or conversely flat, vegetationfree slopes of oxfordian marls; on the contrary, interfluve ridges and Gonson moderate gentle to moderate slopes on cenomanian marls, possibly with some vegetation are less dynamic (canonical axis 1). This result allows to extend former observations on rythmic, contrasted variations of gullies bottoms, well different of interfluves and gonson, progressive, regular, ones.

Owing to their varied reactions to seasonal erosive agents (cryoclasty, concentrated run-off), upper parts of talwegs and lower parts of gully slopes and interfluves (canonical axis 2) originate seasonal contrasts revealed by CFA’s axis 2. However, to insure this point of view, more sampling is needed.     

The effect of heterogeneity of diffusion parameters on chloride transport in low-permeability argillites

Understanding flow and transport in low-permeability media is very important in the context of nuclear waste disposal, oil and gas reservoirs and long term evolution of groundwater systems. In low-permeability media, transport by diffusion is often the most important mass transport process. This study investigates the effect of the heterogeneity of diffusion parameters on mass transport in low-permeability media. A geostatistical approach for integrating heterogeneity of diffusion parameters in groundwater flow and transport models is proposed and applied to the Toarcian argillites in France which are studied in the framework of feasibility of storing radioactive waste in deep clayey massifs. Stochastic fields of the diffusion parameters of the Toarcian argillites (France) are generated based on 64 measured values of diffusion coefficient and diffusion accessible porosity and used as input for a 3D local-scale groundwater flow and transport model. The chloride concentrations computed by these heterogeneous models are compared to the measured chloride concentrations and to concentrations calculated with a model in which the Toarcian argillites are subdivided into several homogeneous zones. The heterogeneous simulations result in a slightly better correspondence between measured and calculated values and have the additional advantage that the measured diffusion coefficient values in the Toarcian are perfectly honored in the model. This study shows that small-scale variability of diffusion parameters has a significant effect on solute concentrations and omitting this heterogeneity may be a problem in transport calculations in low-permeability media, depending on the specific setting and objectives of the study.     

The application of remote sensing and structural analysis in groundwater exploration in basement terrains, Darfur region, Western Sudan

Darfur region is one of the most vulnerable areas in Sudan that suffer from shortage in water supply. The objective of the current study is to utilize remote sensing techniques combined with the structural analysis to recognize the most potential fracture zones for groundwater occurrences in the hard rock terrains of Darfur region. The old ductile deformation features in Darfur region delineated from Landsat imageries are used for the structural analysis to determine and classify the fractures in the hard rock terrains of the region. Based on the structural analysis conducted in this study, Darfur region was divided into two domains—the western domain of the pre-Pan-African age that is affected by the two deformational phases (D1 and D2), and the eastern domain represented by the basement related to the Pan-African orogeny. The most potential fractures in the western domain are in the NW–SE and NE–SW trends that classified as extensional and release open fractures for the deformations D1 and D2. In the eastern domain, the main potential fractures for groundwater occurrence are in E–W and N–S directions that are classified as extensional and release open fractures of the deformation D3. From the results of the structural analysis, the main potential fracture systems in Darfur region trend are NW–SE, NE–SW, and E–W directions. The intersections of these fracture systems are the most promising targets for drilling, with consideration of the topography, the rates of recharge, and the underlying geology. The geophysical data and boreholes information in Zalingei and north of El Geneina areas in West Darfur confirm the results obtained from remote sensing data and structural analysis, in which the NW–SE, NE–SW, and E–W fractures trends are the most potential fractures in Darfur region.