The natural river water reference material SLRS‐6 (NRC‐CNRC) is the newest batch of a quality control material routinely used in many international environmental laboratories. This work presents a nine‐laboratory compilation of measurements of major and trace element concentrations and their related uncertainties, unavailable in the NRC‐CNRC certificate (B, Cs, Li, Ga, Ge, Hf, Nb, P, Rb, Rh, Re, S, Sc, Se, Si, Sn, Th, Ti, Tl, W, Y, Y, Zr and REEs). Measurements were mostly made using inductively coupled plasma‐mass spectrometry. The results are compared with equivalent data for the last batch of the material, SLRS‐5, measured simultaneously with SLRS‐6 in this study. In general, very low concentrations, close to the quantification limits, were found in the new batch. The Sr isotopic ratio is also reported. 相似文献
An experimental study has been performed to investigate the effect of the biocalcification process on the microstructural and the physical properties of biocemented Fontainebleau sand samples. The microstructural properties (porosity, volume fraction of calcite, total specific surface area, specific surface area of calcite, etc.) and the physical properties (permeability, effective diffusion) of the biocemented samples were computed for the first time from 3D images with a high-resolution images obtained by X-ray synchrotron microtomography. The evolution of all these properties with respect to the volume fraction of calcite is analysed and compared with success to experimental data, when it is possible. In general, our results point out that all the properties are strongly affected by the biocalcification process. Finally, all these numerical results from 3D images and experimental data were compared to numerical values or analytical estimates computed on idealized microstructures constituted of periodic overlapping and random non-overlapping arrangements of coated spheres. These comparisons show that these simple microstructures are sufficient to capture and to predict the main evolution of both microstructural and physical properties of biocemented sands for the whole range of volume fraction of calcite investigated. 相似文献
Human expectations regarding weather and climate sometimes lead to perceptions of climate change which are not supported by observational evidence. This paper analyses two very characteristic complaints about current climate in Switzerland, i.e., the lack of snow in winter and the lack of sunshine in summer, through a statistical investigation of climatological data. As one major problem of public perception of climate in mid-latitude regions is linked to the strong variability of the climatic parameters, the paper suggests means of presenting climatic data which include a measure of this variability. Such presentations would help overcome the common confusion between the terms weather and climate, and stress the fact that short-term extreme events are not necessarily indicative of a long-term shift in climate. 相似文献
Continuous pollen and isotopic records were established for core BAN 84 09 GC retrieved from the anoxic Bannock Basin in the Eastern Mediterranean. On the basis of two 14C dates, they document the palaeoclimate between about 25.7 ka B.P. and 5.2 ka B.P. in the northern borderlands of the Ionian Basin. The upper half of the core has been redeposited.
The isotopic record displays a correlation with pollen percentages that is strong and positive for Artemisia (sage-brush) and negative for Quercus (oak). The last glacial maximum and the deglaciation are identified by these combined taxa, together with Chenopodiaceae. The glacial maximum around 18 ka B.P. (which has elsewhere been dated from 20 to 15 ka B.P.) has pollen percentages that are high for Artemisia and low for Quercus. The climate in the pollen source area was arid, cold in winter, briefly warm in summer and sustained the vegetation of a semi-desert. The onset of deglaciation after 18 ka B.P. coincides with that of the decline in Artemisia pollen percentage. However, this decline does not indicate reduced aridity, because it is accompanied by a pollen percentage rise of the even more arid herbs Chenopodiaceae and Ephedra. Throughout the deglaciation from 18 to 11 ka B.P., the aridity progressively increases, culminating at 11 ka B.P. This trend is briefly interrupted by a more humid event, shown by a peak in Artemisia pollen percentage and a smaller peak in oak; these two peaks are coeval with the Bölling-Alleröd chronozone (13-11 ka B.P.). Maximum aridity occurs during the Younger Dryas chronozone (11-10 ka B.P.). Afterwards, the oak pollen percentage begins a steady increase, and its maximum value is coeval with the lowest isotopic value, dated at 8760 ± 170 yr B.P. This period was one of high moisture, warm summers, and, according to altitude, mild to cool winters. This climate sustained forests that were Mediterranean in the lowlands and warm temperate in the uplands. A high pollen concentration is observed during this period and reveals the presence of sapropel S1, which is otherwise unrecognizable in this entirely black core. During the following period between 8760 ± 170 and 5200 yr B.P., the δ180 reverts to slightly higher values and the Quercus pollen percentage decreases, while the pollen percentage of the wetter Ostrya, the oriental hornbeam, increases. The high pollen concentration during the deposition of sapropel S1 cannot have been caused by increased pollen input into the sea, this pollen being wind-borne, nor by increased pollen production for all taxa, both trees and herbs. We conclude that it is entirely due to increased preservation of this allochtonous organic material by the deep anoxia of the bottom water, below a thick anoxic water column. The coincidence of sapropel deposition with warm and humid local climate as well as with the second global meltwater pulse suggests that the cessation of bottom-water ventilation was due to decreased surface water density, resulting from less saline incoming Atlantic surface water, increased local runoff, and warmer winters. 相似文献
The Restefond fault, located in the Late Eocene-Early Oligocene Alpine foreland basin, affects the well lithified and low porosity Grès d??Annot. The fault core zone is characterized by the occurrence of highly deformed sandstone lenses. Deformation inside the lenses corresponds to mm to sub-mm-spaced cleavage planes rich in phyllosilicates and up to cm-thick and dm-long quartz-calcite pure extensional veins. The cleavages are mostly composed of newly-formed synkinematic white mica and chlorite. By using thermodynamic thermometers based on the chemical composition of chlorite, a temperature of 200?±?20?°C of fault activity was computed. This temperature shows that the Restefond fault was active at burial conditions comprised between 6.5 and 8?km, assuming a mean geothermal gradient between 25 and 30?°Ckm?1. The petrophysic properties of sandstones from the core zone and in the hanging and foot wall of the fault were determined on drilled plugs following three spacial directions. The permeability of the highly deformed sandstone from the core zone is about one order of magnitude higher than in the host rock. This increase in permeability occurs in the direction parallel to the S?CC structures and is explained by the occurrence of well-connected micropores localized between platy phyllosilicates. This study shows that the fault petrophysic properties are mostly controlled by the precipitation of synkinematic phyllosilicates under deep burial conditions. 相似文献
The Humic Ion Binding Model VI (Model VI) - previously used to model the equilibrium binding of rare earth elements (REE) by humic acid (HA) - was modified to account for differences in the REE constant patterns of the HA carboxylic and phenolic groups, and introduced into PHREEQC to calculate the REE speciation on the HA binding sites. The modifications were shown to greatly improve the modeling. They allow for the first time to both satisfactorily and simultaneously model a large set of multi-REE experimental data with the same set of equations and parameters. The use of PHREEQC shows that the light rare earth elements (LREE) and heavy rare earth elements (HREE) do not bind to HA by the same functional groups. The LREE are preferentially bound to carboxylic groups, whereas the HREE are preferentially bound to carboxy-phenolic and phenolic groups. This binding differentiation might lead to a fractionation of REE-HA patterns when competition between REE and other metals occur during complexation. A survey of the available data shows that competition with Al3+ could lead to the development of HREE-depleted HA patterns. This new model should improve the hydrochemical modeling of the REE since PHREEQC takes into account chemical reactions such as mineral dissolution/precipitation equilibrium and redox reactions, but also models kinetically controlled reactions and one-dimensional transport. 相似文献
The mineralogy and the trace element compositions of hydrothermally-altered volcanic materials collected from ash fall deposits and in four debris-avalanche deposits (DADs) at La Soufrière volcano in Guadeloupe have been determined. Phreatic explosions of the 1976 eruption and flank collapse events have sampled various parts of the active and ancient hydrothermal systems of the volcano. Hydrothermal mineral assemblages (smectite + silica polymorphs ± pyrite/jarosite ± gypsum) are typical of rock alteration by low-temperature acid-sulphate fluids. High-temperature mineral assemblages are rare, indicating that phreatic explosions and flank collapse events have sampled mainly the upper parts of the volcanic edifice.Andesitic eruptive products affected by shallow hydrothermal alteration are complex assemblages of volcanic materials (glass, phenocrysts and xenocrysts with complex magmatic histories) of different ages and compositions. The use of incompatible element ratios and REE compositions normalised to an unaltered reference material overcomes the interpretation difficulties related to mass balance effects of alteration processes and the petrologic heterogeneity of the initial material.REE and other incompatible elements (Th, U, Hf, Zr) are mainly concentrated in the glassy matrix of unaltered andesitic rocks. Secondary S-bearing mineral phases (e.g., gypsum, jarosite) that have precipitated from acid-sulphate fluids do not contain substantial incompatible elements (REE, U, Th, Hf, Zr). Compositional variations of incompatible elements in hydrothermally-altered andesitic materials reflect mainly volcanic glass–smectite transformation, which is characterised by (i) strong depletion of alkalis and alkaline earths (Ba, Sr) and first transition series elements (Zn, Cu, Cr, Co, Ni), (ii) immobility of highly incompatible elements (Th, Zr, Hf, LREE) and (iii) strong depletion of MREE and HREE. The sigmoid shape of normalised REE pattern is characteristic of glass–smectite transformation by low-temperature acid-sulphate fluids. This transformation also produces significant variations in U/Th values, which offer the opportunity to date the cessation of hydrothermal alteration and to reconstruct the evolution in space and time of hydrothermal activity in a volcanic edifice. 相似文献