Heavy Metal Removal from Soils Using Magnetic Separation: 1. Laboratory Experiments     

Nan Feng  Gabriel Bitton  Philip Yeager  Jean-Claude Bonzongo  Ali Boularbah 《洁净——土壤、空气、水》2007,35(4):362-369

The removal of Cu, Zn, and Cd from a sandy soil was investigated using iron filings as an adsorbent, and subsequently recovering the iron filings by magnetic separation. The best treatment was obtained by using 5% iron filings and 3 h contact time between iron filings and the soil. The metal removal efficiency from soil extracts was evaluated, using MetPLATE^TM, a toxicity test that is specific for heavy metals, and the 48 h Ceriodaphnia dubia acute toxicity test. The toxicity removal was generally higher than 95% for Cu after a single treatment. With regard to Zn-spiked soil, the toxicity removal was 96.1%, 70.0%, and 49.6% after single treatment at the input concentration of 200 mg/kg, 400 mg/kg, and 800 mg Zn²⁺/kg soil, respectively. After two or three successive treatments, more than 90% of the toxicity was removed for 400 mg/kg and 800 mg/kg Zn-spiked soils. In the case of Cd-spiked soil, a single treatment removed 51.1% of the toxicity from 200 mg/kg Cd-spiked soil extracts while more than 90% of the toxicity was removed after two or three treatments. Chemical analysis and a mass balance study were also carried out to investigate the Cu distribution in the soil fractions. The results indicate that, before treatment, a large portion of Cu was immobilized in the soil matrix. Following magnetic separation, Cu was removed from both the soil matrix and extracts and was indeed adsorbed and concentrated on the iron filings. The retrieval of Cu by iron filings was further examined by energy dispersive X-ray spectroscopy (EDS).  相似文献   

Assessing the propensity of landfill soils to undergo reductive iron dissolution     

Yu Wang  Saraya Pleasant  Brajesh Dubey  Dean Rhue  Jean-Claude Bonzongo  Timothy Townsend 《Environmental Earth Sciences》2018,77(8):306

Naturally occurring iron from soil and aquifer sediments at waste disposal sites often becomes liberated into groundwater as a result of reductive dissolution. Research was conducted to evaluate an appropriate procedure for assessing a soil’s propensity to undergo iron reductive dissolution. Soil samples collected from waste disposal sites in Florida were characterized by pH, organic carbon content, total iron content, amorphous iron content, citrate-dithionite-bicarbonate extractable iron, and qualitative X-ray diffraction analysis, followed by a series of extraction tests designed to simulate the reductive dissolution process. Over a 30-day period, biological reducing tests released 13–260 mg/kg Fe(II) from soils, and a chemical reducing test released 2.2–178 mg/kg Fe(II) from soils. Soil amorphous iron content was shown to be the most effective parameter for assessment of iron reductive dissolution potential through standard soil characterization. These results suggest that biological reducing tests may be helpful for assessing long-term soil iron reductive dissolution potential, and that soil amorphous iron content provides a good indication of the potential for a soil to undergo reductive dissolution at a landfill site.  相似文献   

Gradual diversions of the Rio Pastaza in the Ecuadorian piedmont of the Andes from 1906 to 2008: role of tectonics, alluvial fan aggradation, and ENSO events     

Carolina Bernal  Frédéric Christophoul  Jean-Claude Soula  José Darrozes  Luc Bourrel  Alain Laraque  José Burgos  Séverine Bès de Berc  Patrice Baby 《International Journal of Earth Sciences》2012,101(7):1913-1928

The successive courses of the Rio Pastaza in the upper Amazonian Puyo plateau (Ecuador) during the past century have been followed using historical maps, aerial photographs, satellite imagery, topographic and river long profiles, and field studies. The abrupt change in direction of the Rio Pastaza from transverse to longitudinal was a result of two avulsions occurred between 1906 and 1976 at the braided-meandering transition of the former alluvial plain. These avulsions are related to aggradation at the toe of a braided piedmont fan prograding on to a hinterland-dipping topographic slope formed by ongoing tectonic backtilting. The main avulsion proceeded by annexation of a south-dipping depression created in front of the cordillera by backtilting of the plateau. A partial and gradual avulsion having occurred upstream of the former site between 1976 and 2008 is marked by the progressive predominance of a newly formed inner branch. Tectonic backtilting enhanced aggradation upstream of the initial site while it offered the newly avulsed channel a still more favorable way along the cordillera by creating a westward lateral slope. The correlation between ENSO events and the occurrence of the 1976–2008 avulsions strongly suggests that the triggers of the avulsions were the floods caused by the high water and sediment discharges associated with ENSO (La Ni?a) events contrasting with the regular monthly discharge and the lack of actual ‘normal’ floods during the inter-ENSO periods.  相似文献   

Mg/Ca-paleothermometry in the western Mediterranean Sea on planktonic foraminifer species Globigerina bulloides: Constraints and implications     

Soumaya Boussetta  Nejib Kallel  Franck Bassinot  Laurent Labeyrie  Jean-Claude Duplessy  Nicolas Caillon  Fabien Dewilde  Hélène Rebaubier 《Comptes Rendus Geoscience》2012,344(5):267-276

We generated a high-resolution SST_Mg/Ca record for the surface-dwelling planktonic foraminifera Globigerina bulloides from the core MD99-2346 collected in the Gulf of Lion, and compared it to that obtained using modern analogue techniques applied to fossil foraminiferal assemblages (SST_MAT). The two temperature records display similar patterns during the last 28,000 years but the SST_Mg/Ca estimates are several degrees warmer (∼ +4 °C) than SST_MAT. The temperature shift between SST_Mg/Ca and SST_MAT remained relatively constant over time. This seems to exclude a bias on the Mg/Ca record associated with salinity or secondary Mg-rich calcite encrustation on the foraminiferal tests during early diagenesis. Therefore, anomalously high Mg/Ca suggests either: (1) the empirical equation for G. bulloides of Elderfield and Ganssen (2000) is incorrect; or (2) there is a specific Mediterranean genotypes of G. bulloides for which a specific Mg/Ca-temperature calibration is needed.  相似文献   

Application de la méthode des simulations croisées à l’analyse de tendances dans la relation pluie-débit à partir du modèle GR2M : cas du bassin versant du N’zi-Bandama (Côte d’Ivoire)     

Amani Michel Kouassi  Tozan Michel N’guessan Bi  Koffi Fernand Kouamé  Kassi Alexis Kouamé  Jean-Claude Okaingni  Jean Biemi 《Comptes Rendus Geoscience》2012,344(5):288-296

The study area is the N’zi watershed, sub-watershed of the Bandama River (Ivory Coast). The N’zi watershed is located between longitudes 3°49′ and 5°22′ West and latitudes 6°00′ and 9°26′ North and covers an area of 35,500 km². This study aims to identify trends in the rainfall-runoff relationship by using a monthly conceptual model. The methodology has consisted on the one hand in highlighting the existence of interannual climate and hydrological variability by using the method of segmentation of Hubert, and on the other hand, in applying the crossed simulations method by using the GR2M model, over several 7-year sub-periods. The results of the application of the method of segmentation of Hubert have demonstrated the presence of a hydroclimatic variability in the N’zi watershed. The modifications of the climate and physical conditions of the flow resulted in a modification of the hydrological response of the watershed translated by a non-stationarity in the rainfall-runoff relation.  相似文献   

Preliminary report on a dinosaur tracksite from Lower Cretaceous strata in Mount Lebanon     

Raymond Gèze  Isabelle Veltz  Jean-Claude Paicheler  Bruno Granier  Roland Habchi  Dany Azar  Sibelle Maksoud 《Arabian Journal of Geosciences》2016,9(19):730

A dinosaur tracksite was discovered in Batha on the side of the road from Harissa to Ghosta (Keserwan, Lebanon). About ten trackways are exposed at the top of two beds of Lower Cretaceous limestones over an area of approximately 1000 m². These footprints were probably made by at least two dinosaur species, Sauropoda and either Theropoda or Ornithopoda. The site, which is the first record from Lebanon, should be protected to allow further scientific investigations.  相似文献   

Assessing physical vulnerability in large cities exposed to flash floods and debris flows: the case of Arequipa (Peru)     

Jean-Claude Thouret  Susanne Ettinger  Mathieu Guitton  Olivier Santoni  Christina Magill  Kim Martelli  Giulio Zuccaro  Victor Revilla  Juan Antonio Charca  Anita Arguedas 《Natural Hazards》2014,73(3):1771-1815

Understanding the physical vulnerability of buildings and infrastructure to natural hazards is an essential step in risk assessment for large cities. We have interpreted high spatial resolution images, conducted field surveys, and utilized numerical simulations, in order to assess vulnerability across Arequipa, south Peru, close to the active El Misti volcano. The emphasis of this study was on flash floods and volcanic or non-volcanic hyperconcentrated flows, which recur on average every 3.5 years across the city. We utilized a geographic information system to embed vulnerability and hazard maps as a step to calculate risk for buildings and bridges along the Río Chili valley and two tributaries. A survey of ~1,000 buildings from 46 city blocks, different in age, construction materials, and land usage, provided architectural and structural characteristics. A similar survey of twenty bridges across the three valleys was based on structural, hydraulic, and strategic parameters. Interpretation of high spatial resolution (HSR) satellite images, which allows for quick identification of approximately 69 % of the structural building types, effectively supplemented field data collection. Mapping vulnerability has led us to pinpoint strategic areas in case of future destructive floods or flows. Calculated vulnerability is high if we examine structural criteria alone. We further consider physical setting with the most vulnerable city blocks located on the lowermost terraces, perpendicular or oblique to the flow path. Statistical analysis conducted on 3,015 city blocks, considering nine criteria identified from HSR images, indicated that building-type heterogeneity and the shape of the city blocks, along with building and street network density, are the most discriminant parameters for assessing vulnerability.  相似文献   

Undrained Monotonic Response and Instability of Medium-Dense Sandy Soil     

Noureddine Della  Mostefa Belkhatir  Ahmed Arab  Jean Canou  Jean-Claude Dupla 《Marine Georesources & Geotechnology》2013,31(6):487-495

A series of undrained monotonic triaxial compression tests were performed on natural, medium-dense (relative density (RD) = 50%) Chlef sand containing 0.5% of non-plastic fines, under different confining pressures of 50 kPa, 100 kPa, and 200 kPa. This article focuses on distinctive states of the monotonic undrained response of sands, namely the critical state, the phase transformation state, the quasi-steady state, and the state of undrained instability (onset of flow liquefaction). Specimens were prepared using dry funnel pluviation and wet deposition to investigate the effect of the initial sand fabric on these states. The present data suggest that the initial fabric of the sand appears to have a significant effect on the undrained behavior in the early stages of shearing, with its influence vanishing at large strains. Wet deposition specimens demonstrate considerably larger undrained instability state strength than their dry funnel pluviation counterparts, and a unique critical state locus is reached by both dry funnel pluviation and wet deposition.  相似文献   

Synthetic fluid inclusions. XV. TEM investigation of plastic flow associated with reequilibration of fluid inclusions in natural quartz   总被引：1，自引：0，他引：1  

Maxim O. Vityk  Robert J. Bodnar  Jean-Claude Doukhan 《Contributions to Mineralogy and Petrology》2000,139(3):285-297

The nature and abundance of dislocations in quartz surrounding fluid inclusions were studied to obtain a better understanding of processes associated with fluid inclusion reequilibration. Synthetic fluid inclusions containing 10 wt% NaCl aqueous solution were formed in three samples at 700 °C and 5 kbar. One of the samples was quenched along an isochore to serve as a reference sample. The other two samples were quenched along a P-T path that generated internal pressures in excess of the confining pressure. The two samples were held at the final reequilibration P-T conditions of 625 °C and 2 kbar for 30 and 180 days, respectively. Following the experiments, microstructures associated with fluid inclusions were examined with the TEM. Quartz in healed fractures in the reference sample that was quenched isochorically shows a moderate dislocation activity. Quartz adjacent to reequilibrated fluid inclusions in the other two samples, however, showed a marked increase in dislocation activity compared to the un-reequilibrated sample. Deformation of the inclusion walls occurred anisotropically by expansion of mobile dislocations in their slip systems. Dislocation expansion was controlled by glide in the rhombohedral planes {1 0 1 1} that was restricted to narrow zones (≤3 μm) in the immediate vicinity of the fluid inclusion walls outside of the healed fracture plane. These plastic zones were observed after both short term (30 days) and long term (180 days) experiments and are attributed to hydrolytic weakening of quartz around fluid inclusions owing to diffusion of water into the quartz matrix during the experiment. The close spatial association of submicroscopic water bubbles with dislocations, and the rarity of water bubbles in the reference sample, show clearly that in both the 30 and 180 day experiments reequilibration involves water loss from the fluid inclusions. Our results indicate that synthetic fluid inclusions in this study recover (chemically and volumetrically), even at relatively fast experimental loading rates, such that internal stresses never reach the point of brittle failure. The driving force for fluid inclusion deformation involves two related mechanisms: plastic deformation of hydrolytically weakened wet quartz in the healed fracture, and water leakage associated with preexisting and strain-induced dislocations. Received: 5 May 1998 / Accepted: 10 February 2000  相似文献   

Reconstructing fluvial incision rates based on palaeo-water tables in chalk karst networks along the Seine valley (Normandy,France)     

Carole Nehme  Andrew Farrant  Daniel Ballesteros  Dominique Todisco  Joel Rodet  Diana Sahy  J. Michael Grappone  Jean-Claude Staigre  Damase Mouralis 《地球表面变化过程与地形》2020,45(8):1860-1876

Quantifying rates of river incision and continental uplift over Quaternary timescales offer the potential for modelling landscape change due to tectonic and climatic forcing. In many areas, river terraces form datable archives that help constrain the timing and rate of valley incision. However, old river terraces, with high-level deposits, are prone to weathering and often lack datable material. Where valleys are incised through karst areas, caves and sediments can be used to reconstruct the landscape evolution because they can record the elevation of palaeo-water tables and contain preserved datable material. In Normandy (N. France), the Seine River is entrenched into an extensive karstic chalk plateau. Previous estimates of valley incision were hampered by the lack of preserved datable fluvial terraces. A stack of abandoned phreatic cave passages preserved in the sides of the Seine valley can be used to reconstruct the landscape evolution of the region. Combining geomorphological observations, palaeomagnetic and U/Th dating of speleothem and sediments in eight caves along the Lower Seine valley, we have constructed a new age model for cave development and valley incision. Six identified cave levels up to ∼100 m a.s.l. were formed during the last ~1 Ma, coeval with the incision of the Seine River. Passage morphologies indicate that the caves formed in a shallow phreatic/epiphreatic setting, modified by sediment influxes. The valley's maximum age is constrained by the occurrence of late Pliocene marine sand. Palaeomagnetic dating of cave infills indicates that the highest-level caves were being infilled prior to 1.1 Ma. The evidence from the studied caves, complemented by fluvial terrace sequences, indicates that rapid river incision occurred during marine isotope stage (MIS) 28 to 20 (0.8–1 Ma), with maximal rates of ~0.30 m ka⁻¹, dropping to ~0.08 m ka⁻¹ between MIS 20–11 (0.8–0.4 Ma) and 0.05 m ka⁻¹ from MIS 5 to the present time. © 2020 John Wiley & Sons, Ltd.  相似文献