Geochemical characterization and modeling of arsenic behavior in a highly contaminated mining soil     

Sara Bisone  Vincent Chatain  Denise Blanc  Mathieu Gautier  Rémy Bayard  Florence Sanchez  Rémy Gourdon 《Environmental Earth Sciences》2016,75(4):306

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Model parameter transfer for streamflow and sediment loss prediction with SWAT in a tropical watershed     

Vincent Roth  Tibebu Kassawmar Nigussie  Tatenda Lemann 《Environmental Earth Sciences》2016,75(19):1321

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Assessing soil water content spatio-temporal variability at the hillslope scale in a headwater catchment using a multi variable interpolation model based on EMI surveys (Draix,South Alps,France)     

Florian Mallet  Simon D. Carrière  Konstantinos Chalikakis  Vincent Marc 《Environmental Earth Sciences》2018,77(13):507

To improve flood prediction in headwater catchments, hydrologists need to know initial soil moisture conditions that precede rain events. In torrential hydrology, soil moisture mapping provides a valuable tool for investigating surface runoff generation processes. In these mountainous environments, soil moisture prediction is challenging because of highly heterogeneous land cover and soil properties. This survey propose a methodology to study spatial soil moisture variations in the mountainous and torrential environment of the Draix Bléone experimental site—Laval 0.86 km². This approach associates water content measurements at the plot scale with spatialized soil bulk electrical conductivity (EC_a) measurements combined in a multivariate statistical analysis based on topographical parameters. Between the summer of 2015 and winter of 2016, four geophysical surveys were conducted under various moisture conditions and along the same pathway, using the Slingram electromagnetic induction (EMI) technique (EM31 device) in horizontal dipole to identify changes in soil properties to a depth of 3 m. These results were analyzed to determine water dynamics in this mountainous catchment. Temporal variations of EC_a vary among land cover types (forest, grassland, and black marl). A significant relationship was observed between EC_a and soil water content (SWC) measured with capacitive sensors in forest and grassland. A multiple linear regression produced using the spatial interpolation code LISDQS shows a significant correlation between EC_a and landform units depicted on a high-resolution DEM. EC_a variations decrease with distance to talwegs. Riparian zones appear as potential hydrological contributing areas with patterns varying according to moisture status. This study shows that multiple linear regression analysis and EMI make it possible to fill gaps between SWC plot measurements, over wide areas that are steep and that present numerous obstacles due to vegetation cover.  相似文献   

Integration of In Situ Experiments and Numerical Simulations to Reveal the Physicochemical Circumstances of Organic and Inorganic Precipitation at a Thermal Spring     

Petra Kovács-Bodor  Dóra Anda  Laura Jurecska  Mihály Óvári  Ákos Horváth  Judit Makk  Vincent Post  Imre Müller  Judit Mádl-Szőnyi 《Aquatic Geochemistry》2018,24(3):231-255

Organic and inorganic precipitates are both characteristic in the active hypogenic karst area of Buda Thermal Karst in Hungary. As an active system, it is a good natural laboratory to study ongoing precipitation processes. Because of anthropogenic influence and the complexity of spring environments, it is challenging to reveal all the governing factors in the process of precipitation. In situ experiments, i.e. artificially controlled natural systems simplify the complexity by adding, excluding or stabilizing influencing parameters during the experiment. CO₂ degassing drives changes in the physicochemical parameters of spring waters from the discharge along their flow path. The rate and spatial extension of these changes depend on local hydrogeological, geological, climatic, topographical etc. factors, affecting precipitation processes. In this study, two one-day-long in situ experiments were executed to examine the physicochemical parameter changes of thermal water in a tunnel. The integration of the results with reactive transport models revealed the physicochemical processes of ingassing and degassing and predicted CaCO₃ precipitation along the flow path. Small-scale roughness of the channel surface seemed to further influence pH and concentration of HCO₃^?. After 6 weeks of thermal water flowing, organic precipitate (biofilm) formed close to the discharge and then, with a sharp change, inorganic precipitate (calcite) dominates a bit further from the discharge. In situ experiments and connected numerical simulations revealed the role of CO₂ degassing and calcite precipitation in the changes of physicochemical parameters, but organic precipitates also have to be considered near the discharge.  相似文献   

Groundwater flow in the transition zone between freshwater and saltwater: a field-based study and analysis of measurement errors     

Vincent E. A. Post  Eddie Banks  Miriam Brunke 《Hydrogeology Journal》2018,26(6):1821-1838

The quantification of groundwater flow near the freshwater–saltwater transition zone at the coast is difficult because of variable-density effects and tidal dynamics. Head measurements were collected along a transect perpendicular to the shoreline at a site south of the city of Adelaide, South Australia, to determine the transient flow pattern. This paper presents a detailed overview of the measurement procedure, data post-processing methods and uncertainty analysis in order to assess how measurement errors affect the accuracy of the inferred flow patterns. A particular difficulty encountered was that some of the piezometers were leaky, which necessitated regular measurements of the electrical conductivity and temperature of the water inside the wells to correct for density effects. Other difficulties included failure of pressure transducers, data logger clock drift and operator error. The data obtained were sufficiently accurate to show that there is net seaward horizontal flow of freshwater in the top part of the aquifer, and a net landward flow of saltwater in the lower part. The vertical flow direction alternated with the tide, but due to the large uncertainty of the head gradients and density terms, no net flow could be established with any degree of confidence. While the measurement problems were amplified under the prevailing conditions at the site, similar errors can lead to large uncertainties everywhere. The methodology outlined acknowledges the inherent uncertainty involved in measuring groundwater flow. It can also assist to establish the accuracy requirements of the experimental setup.  相似文献   

Sediment failures and flows in the Gulf of Cadiz (eastern Atlantic)     

T. Mulder  E. Gonthier  P. Lecroart  V. Hanquiez  E. Marches  M. Voisset 《Marine and Petroleum Geology》2009,26(5):660-672

Several types of sediment failures in the Gulf of Cadiz were observed using multibeam bathymetry, acoustic imagery and high-resolution seismic. These instabilities are mainly sediment failures and flows. Their width and length vary from 1 to more than 10 km. The failures are mainly related to high sedimentation rates, particularly in places where the Mediterranean Outflow Water (MOW) spills over, such as channel bends and the outer side of the giant contourite levee. Steep slopes are also a trigger for failure at the continental shelf-slope transition, on valley sides, on canyon flanks, and on the sides of bathymetric highs. Other mass movements are related to fluid escape (mud volcanoes) and earthquakes. In areas where the MOW flows along the seafloor, the constant shearing and related erosion can add to the overall stresses. The frequency of failures can be estimated using the deposits resulting of their distal transformations into turbidites.  相似文献   

Sublimation kinetics of CO₂ ice on Mars     

David G. Blackburn  Kathryn L. Bryson  Vincent F. Chevrier  Krista F. White 《Planetary and Space Science》2010,58(5):780-791

Dynamic models of the martian polar caps are in abundance, but most rely on the assumption that the rate of sublimation of CO₂ ice can be calculated from heat transfer and lack experimental verification. We experimentally measured the sublimation rate of pure CO₂ ice under simulated martian conditions as a test of this assumption, developed a model based on our experimental results, and compared our model's predictions with observations from several martian missions (MRO, MGS, Viking). We show that sun irradiance is the primary control for the sublimation of CO₂ ice on the martian poles with the amount of radiation penetrating the surface being controlled by variations in the optical depth, ensuring the formation and sublimation of the seasonal cap. Our model confirmed by comparison of MGS-MOC and MRO-HiRISE images, separated by 2-3 martian years, shows that ∼0.4 m are currently being lost from the south perennial cap per martian year. At this rate, the ∼2.4-m-thick south CO₂ perennial cap will disappear in about 6-7 martian years, unless a short-scale climatic cycle alters this rate of retreat.  相似文献   

Influence of bioturbation by the polychaete Nereis diversicolor on the structure of bacterial communities in oil contaminated coastal sediments   总被引：1，自引：0，他引：1  

Cuny P  Miralles G  Cornet-Barthaux V  Acquaviva M  Stora G  Grossi V  Gilbert F 《Marine pollution bulletin》2007,54(4):452-459

Patterns of change in the structure of bacterial communities monitored by ribosomal intergenic spacer analysis (RISA) in oil contaminated sediments inhabited or not by the marine polychaete Nereis diversicolor were studied during 45 days under laboratory conditions. Results supported by principal component analysis showed a marked response of the bacterial communities to the oil contamination and to the presence of N. diversicolor. Phylogenetic affiliation of specific RISA bands showed that, in the contaminated sediments, the presence of the marine polychaetes favoured the development of bacteria which may play an active role in natural bioremediation processes of oil polluted environments.  相似文献   

Computational issues of hybrid and multipoint mixed methods for groundwater flow in anisotropic media     

Vincent Fontaine  Anis Younes 《Computational Geosciences》2010,14(1):171-181

In this work, lowest-order Raviart–Thomas and Brezzi–Douglas–Marini mixed methods are considered for groundwater flow simulations. Typically, mixed methods lead to a saddle-point problem, which is expensive to solve. Two approaches are numerically compared here to allow an explicit velocity elimination: (1) the well-known hybrid formulation leading to a symmetric positive definite system where the only unknowns are the Lagrange multipliers and (2) a more recent approach, inspired from the multipoint flux approximation method, reducing low-order mixed methods to cell-centered finite difference schemes. Selected groundwater flow scenarios are used for the comparison between hybrid and multipoint approaches. The simulations are performed in the bidimensional case with a general triangular discretization because of its practical interest for hydrogeologists.  相似文献   

Evidence of Quaternary active folding near Utique (Northeast Tunisia) from tectonic observations and a seismic profile     

Lassaad Mejri  Vincent Regard  Sébastien Carretier  Stéphane Brusset  Mahmoud Dlala 《Comptes Rendus Geoscience》2010,342(11):864-872

The present-day seismicity in northeastern Tunisia reported from permanent networks is of low to moderate magnitude. However, earthquakes are mentioned in the literature, specially a destructive one in the antique city of Utique. Geologic, seismic, and neotectonic investigations in this area show that the Utique fold is closely related to the recent tectonic activity in this region. Data show that the Utique fold is built on an east-west fault, and we found evidence of activity of this fault in the past 20 kyr. A seismic section and balanced cross-section show that the slip rate is of the order of 0.38 mm.yr⁻¹. Our data show definitively the Late Pleistocene–Holocene activity of the Utique Fault; and we can predict the earthquake recurrence interval which should be of ∼10³–10⁴ yr. This high seismic risk zone deserves to be taken into account during the establishment of important regional development programs and in the application of seismic building codes.  相似文献