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Hartley A.J.,University of Aberdeen | Leleu S.,University of Aberdeen | Leleu S.,ENSEGID
Journal of the Geological Society | Year: 2015

The relationship between movement on the Highland Boundary Fault and deposition of the Lower Old Red Sandstone in the Midland Valley Basin of Scotland is controversial. Most models favour mid-Silurian to early Devonian sinistral movement on the Highland Boundary Fault and development of a transtensional Midland Valley Basin. To constrain Highland Boundary Fault movement during the late Silurian, we examine the basal Lower Old Red Sandstone alluvial succession exposed adjacent to the Highland Boundary Fault. A lack of synsedimentary fault movement indicators, coupled with an increase in stratal thickness across the fault, indicates that the Highland Boundary Fault was not active during Lower Old Red Sandstone sedimentation. A transtensional basin model cannot be sustained. © 2015 The Geological Society of London.


Hohener P.,Aix - Marseille University | Elsner M.,Helmholtz Center Munich | Eisenmann H.,Isodetect GmbH Ingolstadter Landstr. 1 | Atteia O.,ENSEGID
Journal of Contaminant Hydrology | Year: 2015

Spills of chloroethenes (CEs) at industrial and urban sites can create groundwater plumes in which tetrachloro- and trichloroethene sequentially degrade to dichloroethenes, vinyl chloride (VC) and ethene, or ethane under reducing conditions. For detoxification, degradation must go beyond VC. Assessments based on ethene and ethane, however, are difficult because these products are volatile, may stem from alternative sources, can be further transformed and are not always monitored. To alternatively quantify degradation beyond VC, stable carbon isotope mass balances have been proposed where concentration-weighted CE isotope ratios are summed up and compared to the original source isotope ratio. Reported assessments, however, have provided not satisfactorily quantified results entailing greatly differing upper and lower estimates. This work proposes an integrative approach to better constrain the extent of total chloroethene degradation in groundwater samples. It is based on fitting of measured concentration and compound-specific stable carbon isotope data to an analytical reactive transport equation simulating steady-state plumes in two dimensions using an EXCEL spreadsheet. The fitting also yields estimates of degradation rates, of source width and of dispersivities. The approach is validated using two synthetic benchmark cases where the true extent of degradation is well known, and using data from two real field cases from literature. © 2015 Elsevier B.V. All rights reserved.


Dumont M.,CNRS Paris Institute of Global Physics | Reninger P.A.,Bureau de Recherches Géologiques et Minières | Pryet A.,ENSEGID | Martelet G.,Bureau de Recherches Géologiques et Minières | And 2 more authors.
1st European Airborne Electromagnetics Conference - Held at Near Surface Geoscience 2015 | Year: 2015

Airborne electromagnetic (AEM) methods proved their accuracy in environmental studies during last decades. Volcanic islands are characterized by heterogeneous geology controlled by various complex factors. La Réunion Island, localized in the south-west part of the Indian Ocean, is composed by two shield volcanoes. Their structures are controlled by large erosive processes driven by steep topography, and weathering in inter-tropical climate and the cyclonic regime. In these conditions, in order to help interpreting a large regional AEM dataset resulting in millions of 3D resistivity values, we propose a strategy to delimit areas where the resistivity structure of the first 100 m of the underground have comparable behaviors - And accordingly comparable geological and/or hydrogeological characteristics. Agglomerative Hierarchical Clustering (AHC) analyzes variation between the vertical resistivity distributions of all inverted soundings. AHC results are hierarchized in clusters, each one being associated to an average depth-resistivity signature. The AHC method was applied on the AEM dataset acquired on La Réunion Island. Clusters are consistent with the geological background and inform on different geological and hydrogeological phenomena such as weathering. These subdomains will be used with the aim of evaluating various conceptual hydrogeological models throughout the island.


Schmutz M.,ENSEGID | Ghorbani A.,University of Yazd | Vaudelet P.,ENSEGID | Blondel A.,ENSEGID
Geophysics | Year: 2013

Spectral-induced polarization (SIP) is widely used for environmental and engineering geophysical prospecting and hydrogeophysics, but one major limitation concerns the electromagnetic (EM) coupling effect. The phase angles related to EM coupling may increase even at frequencies as low as 1 Hz, depending on the ground resistivity, the array type, and the geometry. Most efforts to understand and quantify the EM coupling problem (e.g., theory and computer codes) have been developed for dipole-dipole arrays. However, we used a Schlumberger array to acquire SIP data. We found that with this array, the use of an appropriate cable arrangement during data acquisition can reduce EM coupling effects in the same proportion as for the use of a dipole-dipole array, which is the pure response of the studied earth. To measure the influence of the cable layout, four cable configurations with the same electrode spacing were compared for modeling and experimental data. We discovered that the classical DC inline array was the worst one. As soon as the cables were arranged in another shape (triangle or rectangle), the coupling effect decreased significantly. The best configuration we checked was the rectangular one with an acquisition unit located at a lateral offset of 100 m from the electrode line, even if there was still some difference between the modeled and measured data. © 2014 Society of Exploration Geophysicists.


Blondel A.,ENSEGID | Schmutz M.,ENSEGID | Tichan F.,Tereo
Near Surface Geoscience 2012 | Year: 2012

An important dissolved plume consecutive to an ancient gasoline leakage is present on a gas station. A geophysical and geochemical study have been realized to find out in what proportion the changes of electrical properties induced by the dissolved plume may be linked to chemical variations. From a geoelectrical point of view, hydrocarbons plumes may be partially compared to saline ones increasing fluid mineralization. Therefore, electrolytic conduction may not be the only path of electrical conductivity; surface conductivity can also be modified by contamination and cause an increase of the global conductivity. A fixed acquisition system using electrical resistivity tomography has been installed. To monitor the spatial and temporal evolution of the contaminant plume, the resistivity values have been corrected from the temperature effect. The Archie's law have been used to calculate the pore fluid resistivity which has been linked to groundwater chemical analysis. Laboratory measurements, specifically spectral induced polarization and temporal induced polarization have also been performed. The results have been compared to in situ and laboratory analysis. Hydrocarbons as aliphatic molecules in dissolved phase seems less to be at the origin of the geophysical response in particular in clay-free medium, as their byproducts.


Hohener P.,Aix - Marseille University | Atteia O.,ENSEGID
Geochimica et Cosmochimica Acta | Year: 2014

In isotope geochemistry, the Rayleigh equation describes the evolution of isotope ratios in a parent compound as a function of reaction progress, and associated equations describe isotope ratios in an instantaneous product and an accumulated product. The Rayleigh equation is commonly used for fitting fractionation factors of processes undergoing kinetic isotope fractionation such as biochemical reactions. This work extends the equations associated with the Rayleigh equation for describing the isotope ratios in intermediate products in a chain of reacting species degrading with first-order kinetics. A general solution is presented for decay chains of any length, and explicit examples are presented for the biodegradation of a substrate or a mixture of substrates through 3 intermediate products to a final product. Applications of these analytical solutions for the fitting of enrichment factors for intermediate compounds in laboratory experiments are demonstrated with a spreadsheet. This avoids separate experiments to measure each intermediate product. The utility of the equations for the assessment of slopes in dual isotope plots is furthermore illustrated, and limitations of its use are critically discussed. © 2013 Elsevier Ltd.


Serra-Kiel J.,University of Barcelona | Gallardo-Garcia A.,University of Barcelona | Razin P.,ENSEGID | Robinet J.,ENSEGID | And 4 more authors.
Arabian Journal of Geosciences | Year: 2016

Here, the larger foraminifera found in Middle Eocene-Early Miocene rocks from Dhofar (Oman) and Socotra Island (Yemen) are studied in detail. The architectural analysis leads to the description of five new genera and nine new species: five agglutinated foraminifera, Pseudolituonella robineti n. sp., Socotraella ashawqi n. gen. n. sp., Pseudoaccordiella ayaki n. gen. n. sp., Barattolites andhuri n. sp., and Rogerella aydimi n. gen. n. sp.; and four porcellaneous foraminifera, Idalina grelaudae n. sp., Idalina pignattii n. sp., Macetadiscus incolumnatus n. gen. n. sp., and Omanodiscus tenuissimus n. gen. n. sp. The larger foraminifera identified in a composite section located in western Dhofar, in the Shuwaymiyah section located in eastern Dhofar, and in the Wadi Ayak section located on Socotra Island have facilitated the identification of the following larger foraminifera zones: SBZ 14–SBZ 15 (middle Lutetian), SBZ 16 (late Lutetian), SBZ 17 (Bartonian), SBZ 18 (latest Bartonian-earliest Priabonian), SBZ 19–SBZ 20 (Priabonian), SB 21–SB 22A (Rupelian), SB 22B–SB 23 (Chattian), and SB 24 (Aquitanian). All these data permit to assess the age of the following lithostratigraphic units: Dammam Fm.—Andhur Mb. lower Lutetian?-middle Lutetian age (SBZ 13?–SBZ 14 partim), Qara Mb. middle Lutetian (SBZ 14–SBZ 15), and Uyun Mb. upper Lutetian (SBZ 16); Aydim Fm.—Heiron Mb. Bartonian (SBZ 17), Moosak Mb. upper Bartonian-Priabonian (SBZ 18–SBZ 20), Tagut Mb. Priabonian (SBZ 19–SBZ 20), and Haluf Mb. Priabonian (SBZ 19–SBZ 20) to lower Rupelian (SBZ 21) on Socotra Island; Ashawq Fm. Rupelian (SB 21–SB 22A); and Mughsayl Fm. Chattian-Aquitanian (SB 23–SB 24). © 2016, Saudi Society for Geosciences.


Atteia O.,ENSEGID | Del Campo Estrada E.,French National Center for Scientific Research | Bertin H.,French National Center for Scientific Research
Reviews in Environmental Science and Biotechnology | Year: 2013

Soil flushing using aqueous solutions is employed to solubilise contaminants. As water solubility is the controlling mechanism of dissolution, additives (surfactants, cosolvents, etc.) are used to enhance efficiencies and reduce the treatment time compared to the use of water alone. The use of surfactant alone gives efficiencies of about 80-85 % in laboratory experiments, but the amounts of product to be injected are very important, which does not seem to be economically sustainable. Studies indicate that when soil flushing is applied in the field, efficiency is very variable; it can vary from almost 0 % to almost 100 %. This illustrates the importance of knowledge of the field (soil heterogeneities, type of contamination, etc.). Using only one product (surfactant, cosolvent, cyclodextrin) often gives moderate efficiencies and needs very large amounts of products, with a product:pollutant ratio higher than 100:1. On the other hand, the use of more complex methods involving micro emulsions or several products with polymer injection lead to high efficiencies at first and a product:pollutant ratio that can be lower than 5. The importance of the initial saturation of the non-aqueous phase liquid is highlighted: the higher the initial saturation, the higher the efficiency. For initial saturations lower than 1 %, soil flushing may not be a very efficient technique. This paper provides an overview of recent studies in the area of soil and groundwater remediation, from laboratory columns scale to pilot and real sites. The research has focused on chlorinated solvents as they are extremely difficult to treat. © 2013 Springer Science+Business Media Dordrecht.


Del Campo Estrada E.,French National Center for Scientific Research | Bertin H.,French National Center for Scientific Research | Atteia O.,ENSEGID
Transport in Porous Media | Year: 2015

Contamination of soil and groundwater with nonaqueous phase liquid represents a major environmental concern because of the negative effect on human health. Traditional soil flushing techniques have been proved ineffective in heterogeneous aquifers, since liquids for remediation flow preferentially through the most permeable layers and residual oil remains trapped in the low-permeability sediments. To improve the sweep efficiency, fluids with lower mobility than resident liquids can be injected, such as polymers or in situ generated foam. In addition, foam has the potential of selectively reducing mobility in higher-permeability layers compared to lower-permeability layers. The use of foams has not been popular because foam mobility is difficult to predict. In this paper, a series of 1D column experiments were conducted to investigate the variation of the resistance factor RF as a function of the permeability. Five types of sand and calibrated glass beads were used to obtain porous media of permeabilities ranging from 250 millidarcy to 100 Darcy. Two commercial nonionic surfactants, (Formula presented.) X-100 (commonly used but toxic) and sucrose laurate (environmentally friendly surfactant, biodegradable), were used at a concentration equal to 10 critical micelle concentration. Columns were first saturated with water and then flushed with 1.5 PV (pore volumes) of surfactant solution in order to achieve the adsorption of molecules into the soil matrix. Then, co-injection of air and surfactant solution was performed at a constant total rate to generate in situ foam. The quality of the foam was varied from 85 to 99 % to investigate the effect of this parameter on the resistance factor. A graphic showing the dependence of RF and the permeability is presented. Results suggest that for the same total flow rate, the RF decreases as permeability increases, but for permeabilities smaller than 1 Darcy, the RF is weak, probably due to the difficulty to generate stable foam under high capillary pressures. Variations in foam quality and surfactant type do not seem to have an important effect on the results regarding RF. The presented results are assistance for predicting foam behavior in porous media of different permeabilities. © 2015, Springer Science+Business Media Dordrecht.


PubMed | ENSEGID, Aix - Marseille University, Isodetect GmbH Ingolstadter Landstr. 1 and Helmholtz Center Munich
Type: | Journal: Journal of contaminant hydrology | Year: 2015

Spills of chloroethenes (CEs) at industrial and urban sites can create groundwater plumes in which tetrachloro- and trichloroethene sequentially degrade to dichloroethenes, vinyl chloride (VC) and ethene, or ethane under reducing conditions. For detoxification, degradation must go beyond VC. Assessments based on ethene and ethane, however, are difficult because these products are volatile, may stem from alternative sources, can be further transformed and are not always monitored. To alternatively quantify degradation beyond VC, stable carbon isotope mass balances have been proposed where concentration-weighted CE isotope ratios are summed up and compared to the original source isotope ratio. Reported assessments, however, have provided not satisfactorily quantified results entailing greatly differing upper and lower estimates. This work proposes an integrative approach to better constrain the extent of total chloroethene degradation in groundwater samples. It is based on fitting of measured concentration and compound-specific stable carbon isotope data to an analytical reactive transport equation simulating steady-state plumes in two dimensions using an EXCEL spreadsheet. The fitting also yields estimates of degradation rates, of source width and of dispersivities. The approach is validated using two synthetic benchmark cases where the true extent of degradation is well known, and using data from two real field cases from literature.

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