Soil and plant composition in the Noun river catchment basin,Western Cameroon: a contribution to the development of a biogeochemical baseline   总被引：1，自引：0，他引：1  

Clémentine Njofang  Jörg Matschullat  Akoa Amougou  Jean Pierre Tchouankoué  Hermann Heilmeier 《Environmental Geology》2009,56(7):1427-1436

Soils and selected edible plants of the Noun river catchment basin of western Cameroon were sampled to investigate the distribution of trace elements, based on the preliminary idea of unusual anomalies. Analytical techniques for trace elements included ICP-AES, GF-AAS, and ICP-MS. Further soil analyses comprised the mineralogy and contents of the biogenic elements carbon, nitrogen and sulphur (CNS). The trace element concentrations in the soils reflect those of the lithogeochemical background of the pluto-volcanic rocks of the region. This is consistent with the results from the mineralogical analyses and physicochemical parameters such as pH, taken in the field, which also do not suggest any geochemical anomaly. Most trace elements analyzed in the plants showed concentrations that reflect those of the soils (Al, Fe, Ti, and Rb). However, some trace elements were enriched in the plants as compared to the soils, such as Zn, Cu, Cd, Mo (excluding yam), Ni (peanut), Ba (peanut), Sr (peanut, bean), and B. Trace elements such as As, Cr, V, and Se were not bioavailable for all the analyzed plants. Besides, trace elements such as Cu, Zn, Mo, Fe, Al, Ni, B, Ti, Rb, Cs, and Ba were in the range of phytotoxicity and reached or exceeded human food tolerance level (Cu). The plants with seeds showed a higher absorption of trace elements compared to plants with tubercles.  相似文献   

Late Permian to Middle Triassic correlations and palaeogeographical reconstructions in south-western European basins: New sedimentological data from Minorca (Balearic Islands, Spain)     

Bastien Linol  Antoine Bercovici  Sylvie Bourquin  Jos Bienvenido Diez  Jos Lpez-Gmez  Jean Broutin  Marc Durand  Uxue Villanueva-Amadoz 《Sedimentary Geology》2009,220(1-2):77-94

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Iron isotope fractionation between pyrite (FeS₂), hematite (Fe₂O₃) and siderite (FeCO₃): A first-principles density functional theory study     

Marc Blanchard  Franck Poitrasson  Michele Lazzeri  Etienne Balan 《Geochimica et cosmochimica acta》2009,73(21):6565-776

In addition to equilibrium isotopic fractionation factors experimentally derived, theoretical predictions are needed for interpreting isotopic compositions measured on natural samples because they allow exploring more easily a broader range of temperature and composition. For iron isotopes, only aqueous species were studied by first-principles methods and the combination of these data with those obtained by different methods for minerals leads to discrepancies between theoretical and experimental isotopic fractionation factors. In this paper, equilibrium iron isotope fractionation factors for the common minerals pyrite, hematite, and siderite were determined as a function of temperature, using first-principles methods based on the density functional theory (DFT). In these minerals belonging to the sulfide, oxide and carbonate class, iron is present under two different oxidation states and is involved in contrasted types of interatomic bonds. Equilibrium fractionation factors calculated between hematite and siderite compare well with the one estimated from experimental data (ln α⁵⁷Fe/⁵⁴Fe = 4.59 ± 0.30‰ and 5.46 ± 0.63‰ at 20 °C for theoretical and experimental data, respectively) while those for Fe(III)_aq-hematite and Fe(II)_aq-siderite are significantly higher that experimental values. This suggests that the absolute values of the reduced partition functions (β-factors) of aqueous species are not accurate enough to be combined with those calculated for minerals. When compared to previous predictions derived from Mössbauer or INRXS data [Polyakov V. B., Clayton R. N., Horita J. and Mineev S. D. (2007) Equilibrium iron isotope fractionation factors of minerals: reevaluation from the data of nuclear inelastic resonant X-ray scattering and Mössbauer spectroscopy. Geochim. Cosmochim. Acta71, 3833-3846], our iron β-factors are in good agreement for siderite and hematite while a discrepancy is observed for pyrite. However, the detailed investigation of the structural, electronic and vibrational properties of pyrite as well as the study of sulfur isotope fractionation between pyrite and two other sulfides (sphalerite and galena) indicate that DFT-derived β-factors of pyrite are as accurate as for hematite and siderite. We thus suggest that experimental vibrational density of states of pyrite should be re-examined.  相似文献   

Natural convection of compressible and incompressible gases in undeformable porous media under cold climate conditions     

Marc Lebeau  Jean-Marie Konrad 《Computers and Geotechnics》2009

A numerical model for convective heat and mass transport of compressible or incompressible gas flows with soil-water phase change is presented. In general, the gaseous phase is considered as compressible and the model accounts for adiabatic processes of compression heating and expansion cooling. The inherently compressible gaseous phase may nevertheless be considered as incompressible by adopting the Oberbeck–Boussinesq approximations. The numerical method used to solve the equations that describe natural convection is based on a Galerkin finite element formulation with adaptive mesh refinement and dynamic time step control. As most existing numerical studies have focused on the behavior of incompressible fluids, model substantiation examines the influence of fluid compressibility on two-widely used benchmarks of steady-state convective heat and mass transport. The relative importance of the effect of pressure-compressibility cooling is shown to increase as the thermal gradient approaches the magnitude of the adiabatic gradient. From these results, it may be concluded that pore-air compressibility cannot be neglected in medium to large-sized enclosures at small temperature differentials. After demonstrating its ability to solve fairly complex transient problems, the model is used to further our understanding of the thermal behavior of the toe drain at the LA2-BSU dam in the province of Quebec, Canada.  相似文献   

Holocene and Pleistocene fringing reef growth and the role of accommodation space and exposure to waves and currents (Bora Bora,Society Islands,French Polynesia)     

Eberhard Gischler  J. Harold Hudson  Marc Humblet  Juan Carlos Braga  Dominik Schmitt  Anja Isaack  Anton Eisenhauer  Gilbert F. Camoin 《Sedimentology》2019,66(1):305-328

Holocene fringing reef development around Bora Bora is controlled by variations in accommodation space (as a function of sea‐level and antecedent topography) and exposure to waves and currents. Subsidence ranged from 0 to 0·11 m kyr^?1, and did not create significant accommodation space. A windward fringing reef started to grow 8·7 kyr bp , retrograded towards the coast over a Pleistocene fringing reef until ca 6·0 kyr bp , and then prograded towards the lagoon after sea‐level had reached its present level. The retrograding portion of the reef is dominated by corals, calcareous algae and microbialite frameworks; the prograding portion is largely detrital. The reef is up to 13·5 m thick and accreted vertically with an average rate of 3·12 m kyr^?1. Lateral growth amounts to 13·3 m kyr^?1. Reef corals are dominated by an inner Pocillopora assemblage and an outer Acropora assemblage. Both assemblages comprise thick crusts of coralline algae. Palaeobathymetry suggests deposition in 0 to 10 m depth. An underlying Pleistocene fringing reef formed during the sea‐level highstand of Marine Isotope Stage 5e, and is also characterized by the occurrence of corals, coralline algal crusts and microbialites. A previously investigated, leeward fringing reef started to form contemporaneously (8·78 kyr bp ), but is thicker (up to 20 m) and solely prograded throughout the Holocene. A shallow Pocillopora assemblage and a deeper water Montipora assemblage were identified, but detrital facies dominate. At the Holocene reef base, only basalt was recovered. The Holocene windward–leeward differences are a consequence of less accommodation space on the eastern island side that eventually led to a more complex reef architecture. As a result of higher rates of exposure and flushing, the reef framework on the windward island side is more abundant and experienced stronger cementation. In the Pleistocene, the environmental conditions on the leeward island side were presumably unfavourable for fringing reef growth.  相似文献   

Climatic and sea‐level control of Jurassic (Pliensbachian) clay mineral sedimentation in the Cardigan Bay Basin,Llanbedr (Mochras Farm) borehole,Wales     

Jean‐Franois Deconinck  Stephen P. Hesselbo  Pierre Pellenard 《Sedimentology》2019,66(7):2769-2783

Early Jurassic climate is characterized by alternating cold and warm periods highlighted by studies based notably on oxygen isotopes measured on belemnite guards and other marine invertebrate shells. These climatic changes include changes in the hydrological cycle, and consequently weathering and runoff conditions. In order to clarify the erosion and weathering conditions during the Pliensbachian, this study determined the mineralogical composition of the clay fraction of 132 samples taken from the entire stage drilled in the Llanbedr (Mochras Farm) borehole (Cardigan Bay Basin). The clay mineral assemblages are composed of various proportions of chlorite, illite, illite/smectite mixed‐layers (R1 I–S), smectite and kaolinite, with possibly occasional traces of berthierine. The occurrence of abundant smectite indicates that the maximum burial temperature never exceeded 70°C. Consequently, clay minerals are considered mainly detrital, and their fluctuations likely reflect environmental changes. The variations in the proportions of smectite and kaolinite are opposite to each other. Kaolinite is particularly abundant at the base of the jamesoni Zone, in part coinciding with the δ¹³C negative excursion corresponding to the Sinemurian/Pliensbachian Boundary Event, and through the davoei Zone, whilst smectite is abundant in the upper part of jamesoni and base of ibex zones and through the subnodosus/gibbosus subzones of the margaritatus Zone. The kaolinite‐rich intervals reflect an intensification of hydrolysis and an acceleration of the hydrological cycle, while the smectite‐rich intervals indicate a more arid climate. The spinatum Zone is characterized by a distinct clay assemblage with abundant primary minerals, R1 I–S, kaolinite reworked from previously deposited sediments or from Palaeozoic rocks, and probably berthierine originating from contemporaneous ironstone‐generating environments of shallower waters. This mineralogical change by the end of the Pliensbachian likely reflects a transition from a dominant chemical weathering to a deeper physical erosion of the continent, probably related to a significant sea‐level fall consistent with a glacio‐eustatic origin.  相似文献   

New Apatite Fission-Track Ages of the Western Kuqa Depression: Implications for the Mesozoic–Cenozoic Tectonic Evolution of South Tianshan, Xinjiang     

YANG Wei  LI Jianfeng  GUO Zhaojie  Marc JOLIVET  Gloria HEILBRONN 《《地质学报》英文版》2017,91(2):396-413

The Mesozoic–Cenozoic uplift history of South Tianshan has been reconstructed in many ways using thermochronological analyses for the rocks from the eastern Kuqa Depression. The main difference in the reconstructions concerns the existence and importance of Early Cretaceous and Paleogene tectonic activities, but the existence of a Cenozoic differential uplift in the Kuqa Depression remains enigmatic. Here, we present new apatite fission-track ages obtained for 12 sandstone samples from the well-exposed Early Triassic to Quaternary sequence of the Kapushaliang section in the western Kuqa Depression. The results reveal that there were four pulses of tectonic exhumation, which occurred during the Early Cretaceous(peak ages of 112 and 105 Ma), Late Cretaceous(peak age of 67 Ma), Paleocene–Eocene(peak ages at 60, 53, and 36 Ma), and early Oligocene to late Miocene(central ages spanning 30–11 Ma and peak ages of 23 and 14 Ma), respectively. A review of geochronological and geological evidence from both the western and eastern Kuqa Depression is shown as follows.(1) The major exhumation of South Tians Shan during the Early Cretaceous was possibly associated with docking of the Lhasa block with the southern margin of the Eurasian plate.(2) The Late Cretaceous uplift of the range occurred diachronically due to the far-field effects of the Kohistan-Dras Arc and Lhasa block accretion.(3) The Paleogene uplift in South Tianshan initially corresponded to the far-field effects of the India–Eurasia collision.(4) The rapid exhumation in late Cenozoic was driven by the continuous far-field effects of the collision between India and Eurasia plates. The apatite fission-track ages of 14–11 Ma suggest that late Cenozoic exhumation in the western Kuqa Depression prevailed during the middle to late Miocene, markedly later than the late Oligocene to early Miocene activity in the eastern segment. It can be hypothesized that a possible differential uplift in time occurred in the Kuqa Depression during the late Cenozoic.  相似文献   

A reactive transport simulator for variable porosity problems     

Fabien Georget  Jean H. Prévost  Bruno Huet 《Computational Geosciences》2017,21(1):95-116

ReactMiCP, a new reactive transport simulator was developed based on the semismooth speciation solver SpecMiCP. Its main feature is a sequential iterative operator splitting algorithm where macroscopic model parameters are explicitly included in the formulation. Its correctness, robustness, and efficiency are tested against the MoMaS benchmark and two sets of cement paste lab experiments. We show that a robust speciation solver is a key requirement for good performance of the reactive transport simulator. We also demonstrate that a sequential iterative solver should be preferred over non-iterative solvers when using operator splitting. The flexibility and the speed of the simulator are used to test the influence of the database, the initial condition, and the diffusion coefficient model for the cement paste simulations.  相似文献   

Stratigraphic and structural controls on groundwater flow in an outcropping fossil fan delta: the case of Sant Llorenç del Munt range (NE Spain)     

Marc Anglés  Albert Folch  Oriol Oms  Eudald Maestro  Josep Mas-Pla 《Hydrogeology Journal》2017,25(8):2467-2487

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Evaluation of levels of antibiotic resistance in groundwater-derived <Emphasis Type="Italic">E. coli</Emphasis> isolates in the Midwest of Ireland and elucidation of potential predictors of resistance     

Jean O’Dwyer  Paul Hynds  Matthieu Pot  Catherine C. Adley  Michael P. Ryan 《Hydrogeology Journal》2017,25(4):939-951

Antibiotic-resistant (pathogenic and non-pathogenic) organisms and genes are now acknowledged as significant emerging aquatic contaminants with potentially adverse human and ecological health impacts, and thus require monitoring. This study is the first to investigate levels of resistance among Irish groundwater (private wells) samples; Escherichia coli isolates were examined against a panel of commonly prescribed human and veterinary therapeutic antibiotics, followed by determination of the causative factors of resistance. Overall, 42 confirmed E. coli isolates were recovered from a groundwater-sampling cohort. Resistance to the human panel of antibiotics was moderate; nine (21.4%) E. coli isolates demonstrated resistance to one or more human antibiotics. Conversely, extremely high levels of resistance to veterinary antibiotics were found, with all isolates presenting resistance to one or more veterinary antibiotics. Particularly high levels of resistance (93%) were found with respect to the aminoglycoside class of antibiotics. Results of statistical analysis indicate a significant association between the presence of human (multiple) antibiotic resistance (p?=?0.002–0.011) and both septic tank density and the presence of vulnerable sub-populations (<5 years). For the veterinary antibiotics, results point to a significant relationship (p?=?<0.001) between livestock (cattle) density and the prevalence of multiple antibiotic resistant E. coli. Groundwater continues to be an important resource in Ireland, particularly in rural areas; thus, results of this preliminary study offer a valuable insight into the prevalence of antibiotic resistance in the hydrogeological environment and establish a need for further research with a larger geological diversity.  相似文献