The rest-frame ultraviolet spectra of GRBs from massive rapidly rotating stellar progenitors     

Peter B. Robinson  Rosalba Perna  Davide Lazzati  Allard J. van Marle † 《Monthly notices of the Royal Astronomical Society》2010,401(1):88-98

The properties of a massive star prior to its final explosion are imprinted in the circumstellar medium (CSM) created by its wind and termination shock. We perform a detailed, comprehensive calculation of the time-variable and angle-dependent transmission spectra of an average-luminosity gamma-ray burst (GRB) which explodes in the CSM structure produced by the collapse of a  20 M_⊙  , rapidly rotating,   Z = 0.001  progenitor star. We study both the case in which metals are initially in the gaseous phase and the situation in which they are heavily depleted into dust. We find that high-velocity lines from low-ionization states of silicon, carbon and iron are initially present in the spectrum only if the metals are heavily depleted into dust prior to the GRB explosion. However, such lines disappear on time-scales of a fraction of a second for a burst observed on-axis, and of a few seconds for a burst seen at high latitude, making their observation virtually impossible. Rest-frame lines produced in the termination shock are instead clearly visible in all conditions. We conclude that time-resolved, early-time spectroscopy is not a promising way in which the properties of the GRB progenitor wind can be routinely studied. Previous detections of high-velocity features in GRB ultraviolet spectra must have been either due to a superposition of a physically unrelated absorber or due to a progenitor star with very unusual properties.  相似文献   

Mercury concentration,speciation and budget in volcanic aquifers: Italy and Guadeloupe (Lesser Antilles)     

E. Bagnato  A. Aiuppa  F. Parello  W. D'Alessandro  P. Allard  S. Calabrese 《Journal of Volcanology and Geothermal Research》2009,179(1-2):96-106

Quantifying the contribution of volcanism to global mercury (Hg) emissions is important to understand the pathways and the mechanisms of Hg cycling through the Earth's geochemical reservoirs and to assess its environmental impacts. While previous studies have suggested that degassing volcanoes might contribute importantly to the atmospheric budget of mercury, little is known about the amount and behaviour of Hg in volcanic aquifers. Here we report on detailed investigations of both the content and the speciation of mercury in aquifers of active volcanoes in Italy and Guadeloupe Island (Lesser Antilles). In the studied groundwaters, total Hg (THg) concentrations range from 10 to 500 ng/l and are lower than the 1000 ng/l threshold value for human health protection fixed by the World Health Organization [WHO (1993): WHO Guidelines for Drinking Water Quality- http://www.who.int/water_sanitation_health/GDWQ/index.htlm]. Positive co-variations of (THg) with sulphate indicate that Hg-SO₄-rich acid groundwaters receive a direct input of magmatic/hydrothermal gases carrying mercury as Hg⁰_(gas). Increasing THg in a volcanic aquifer could thus be a sensitive tracer of magmatic gas input prior to an eruption. Since the complex behaviour and toxicity of mercury in waters depend on its chemical speciation, we carefully determined the different aqueous forms of this element in our samples. We find that dissolved elemental Hg⁰_(aq) and particulate-bound Hg (Hg_P) widely prevail in volcanic aquifers, in proportions that highlight the efficiency of Hg adsorption onto colloidal particles. Moreover, we observe that dissolved Hg⁰_aq and Hg(II) forms coexist in comparable amount in most of the waters, in stark contrast to the results of thermodynamic equilibrium modelling. Therefore, chemical equilibrium between dissolved mercury species in volcanic waters is either prevented by natural kinetic effects or not preserved in collected waters due to sampling/storage artefacts. Finally, we provide a first quantitative comparison of the relative intensity of aqueous transport and atmospheric emissions of mercury at Mount Etna, a very active basaltic volcano.  相似文献   

一种新型人工“流体包裹体”：融合二氧化硅毛细管技术          下载免费PDF全文

倪培  丁俊英  I-Ming Chou  Jean Dubessy 《地学前缘》2011,18(5):132-139

利用融合二氧化硅毛细管技术制作了纯H2O体系、纯CO2体系、H2O-NaCl体系和H2O-CO2体系的人工包裹体样品,并对样品进行了显微测温和激光拉曼光谱测试工作。实验结果显示毛细管样品中的流体成分具有代表性,而且常规的流体包裹体显微测温和显微激光拉曼光谱分析技术完全适于毛细管样品的测试。对样品的显微测温和拉曼光谱研究...  相似文献   

Atmospheric analysis of the M/L and M/T dwarf binary systems LHS 102 and Gliese 229     

S. K. Leggett  Peter H. Hauschildt  F. Allard  T. R. Geballe  E. Baron 《Monthly notices of the Royal Astronomical Society》2002,332(1):78-90

We present  0.9–2.5 μm  spectroscopy with   R ∼800  and  1.12–1.22 μm  spectroscopy with   R ∼5800  for the M dwarfs Gl 229A and LHS 102A, and for the L dwarf LHS 102B. We also report IZJHKL ' photometry for both components of the LHS 102 system, and L ' photometry for Gl 229A. The data are combined with previously published spectroscopy and photometry to produce flux distributions for each component of the kinematically old disc M/L dwarf binary system LHS 102 and the kinematically young disc M/T dwarf binary system Gliese 229. The data are analysed using synthetic spectra generated by the latest 'AMES-dusty' and 'AMES-cond' models by Allard & Hauschildt. Although the models are not able to reproduce the overall slope of the infrared flux distribution of the L dwarf, most likely because of the treatment of dust in the photosphere, the data for the M dwarfs and the T dwarf are well matched. We find that the Gl 229 system is metal-poor despite having kinematics of the young disc, and that the LHS 102 system has solar metallicity. The observed luminosities and derived temperatures and gravities are consistent with evolutionary model predictions if the Gl 229 system is very young  (age∼30 Myr)  with masses (A,B) of (0.38,≳0.007) M_⊙, and the LHS 102 system is older, aged  1–10 Gyr  with masses (A,B) of (0.19,0.07) M_⊙.  相似文献   

Opaque minerals,magnetic properties,and paleomagnetism of the Tissint Martian meteorite     

Jérôme Gattacceca  Roger H. Hewins  Jean‐Pierre Lorand  Pierre Rochette  France Lagroix  Cécile Cournède  Minoru Uehara  Sylvain Pont  Violaine Sautter  Rosa. B. Scorzelli  Chrystel Hombourger  Pablo Munayco  Brigitte Zanda  Hasnaa Chennaoui  Ludovic Ferrière 《Meteoritics & planetary science》2013,48(10):1919-1936

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Mercury gas emissions from La Soufrière Volcano, Guadeloupe Island (Lesser Antilles)     

E. Bagnato  P. Allard  F. Parello  A. Aiuppa  S. Calabrese  G. Hammouya 《Chemical Geology》2009,266(3-4):276-282

Quantifying mercury (Hg) emissions from active volcanoes is of particular interest for better constraining the global cycle and environmental impact of this highly toxic element. Here we report on the abundance of total gaseous (TGM = Hg⁰_(g) + Hg^II_(g)) and particulate (Hg_(p)) mercury in the summit gas emissions of La Soufrière andesitic volcano (Guadeloupe island, Lesser Antilles), where enhanced degassing of mixed hydrothermal-magmatic volatiles has been occurring since 1992 from the Southern summit crater. We demonstrate that Hg in volcanic plume occurs predominantly as gaseous mercury, with a mean TGM/Hg_(p) mass ratio of ~ 63. Combining the mean TGM/H₂S mass ratio of the volcanic plume (~ 3.2 × 10^− 6), measured close to the source vent, with the H₂S plume flux (~ 0.7 t d^− 1), determined simultaneously, allows us to estimate a gaseous mercury emission rate of 0.8 kg yr^− 1 from La Soufrière summit dome. Somewhat lower TGM/S_tot mass ratio in fumarolic gases from the source vent (4.4 × 10^− 7) suggests that plume chemical composition is not well represented by the emission source (fumaroles) due to chemical processes prior to (or upon) discharge. Current mercury emission from La Soufrìere volcano represents a very small contribution to the estimated global volcanic budget for this element.  相似文献   

Organic complexation and translocation of ferric iron in podzols of the Negro River watershed. Separation of secondary Fe species from Al species     

E. Fritsch  Th. Allard  M. Bardy  Y. Li 《Geochimica et cosmochimica acta》2009,73(7):1813-168

The development of podzols in lateritic landscapes of the upper Amazon basin contributes to the exportation of organic carbon and associated metals in the black waters of the Negro River watershed. We have investigated the distribution of Fe^III in the clay-size fraction of eight organic-rich horizons of waterlogged plateau podzols, to unravel the weathering conditions and mechanisms that control its transfer to the rivers. The speciation and amount of Fe^III stored in residual mineral phases of laterites, or bound to organic compounds of weakly and well-expressed podzols, were determined by electron paramagnetic resonance spectroscopy combined with chemical analyses.Reducing conditions restrict the production of organo-Fe complexes in the subsoil B-horizons of waterlogged podzols and most of the Fe²⁺ released from the dissolution of Fe-oxides is exported to the rivers via the perched groundwater. However, significant amounts of diluted Fe^III bound to organic ligands (Fe^III_OM) and nano Fe-oxides are produced at the margin of the depression in the topsoil A horizons of weakly expressed podzols due to shorter periods of anoxia. The downward translocation of organically bound metals from topsoil A to subsoil B-horizons of podzols occurs in shorter distances for Fe than it does for Al. This separation of secondary Fe species from Al species is attributed to the physical fractionation of their organic carriers in texture contrasted B-horizons of podzols, as well as to the effect of pH on metal speciation in soil solutions and metal binding onto soil organic ligands (mostly for Al). This leads us to consider the topsoil A horizons of weakly expressed podzols, as well as the subsoil Bh horizon of better-expressed ones, as the main sources for the transfer of Fe^III_OM to the rivers. The concentration of Fe^III_OM rises from soil sources to river colloids, suggesting drastic biogeochemical changes in more oxygenated black waters of the Negro River watershed. The contribution of soil organic matter to the transfer of Fe to rivers is likely at the origin of the peculiar Fe isotope pattern recently recognized in podzolic environments.  相似文献   

A statistical adjustment of Haldorsen's conditioned Boolean simulation algorithm   总被引：1，自引：0，他引：1  

Roderik J. Berkhout  Antonio G. Chessa  Allard W. Martinius 《Mathematical Geology》1996,28(6):791-810

This paper presents a new simulation algorithm for generating realizations of a Boolean model for sandstone reservoirs conditional on sandstone body intersections in wells. It is a statistically corrected version of the conditional simulation algorithm originally proposed by Haldorsen. In previous work it was shown that the conventional algorithm does not reproduce the correct statistics for sandstone body size at the well locations. The simulation of a Boolean model, given grain intersections on line transects, must be in accordance with the conditional distribution of the model, which implies that sandstone bodies intersected by wells and sandstone bodies in the interwell area should be simulated independently. Based on the conditional distribution a simulation algorithm is developed, which is compared to Haldorsen's algorithm by simulating an outcrop section of fluvial sandstone deposits. Simulations are conditioned on data of two fictitious wells. It turns out that the adjusted algorithm gives better results for the sand fraction that is connected to a set of wells, and also for the sand fraction that would be connected to an infill well.  相似文献   

Geochemical mapping of magmatic gas–water–rock interactions in the aquifer of Mount Etna volcano     

L. Brusca  A. Aiuppa  W. D'Alessandro  F. Parello  P. Allard  A. Michel 《Journal of Volcanology and Geothermal Research》2001,108(1-4)

Systematic analysis of major and minor elements in groundwaters from springs and wells on the slopes of Mt. Etna in 1995–1998 provides a detailed geochemical mapping of the aquifer of the volcano and of the interactions between magmatic gas, water bodies and their host rocks. Strong spatial correlations between the largest anomalies in pCO₂ (pH and alkalinity) K, Rb, Mg, Ca and Sr suggest a dominating control by magmatic gas (CO₂) and consequent basalt leaching by acidified waters of the shallow (meteoric) Etnean aquifer. Most groundwaters displaying this magmatic-type interaction discharge within active faulted zones on the S–SW and E lower flanks of the volcanic pile, but also in a newly recognised area on the northern flank, possibly tracking a main N–S volcano-tectonic structure. In the same time, the spatial distribution of T°C, TDS, Na, Li, Cl and B allows us to identify the existence of a deeper thermal brine with high salinity, high content of B, Cl and gases (CO₂, H₂S, CH₄) and low K/Na ratio, which is likely hosted in the sedimentary basement. This hot brine reaches the surface only at the periphery of the volcano near the Village of Paternò, where it gives rise to mud volcanoes called “Salinelle di Paternò”. However, the contribution of similar brines to shallower groundwaters is also detected in other sectors to the W (Bronte, Maletto), SW (Adrano) and SE (Acireale), suggesting its possible widespread occurrence beneath Etna. This thermal brine is also closely associated with hydrocarbon fields all around the volcano and its rise, generally masked by the high outflow of the shallow aquifer, may be driven by the ascent of mixed sedimentary–magmatic gases through the main faults cutting the sedimentary basement.  相似文献   

Finite element analysis of three-dimensional groundwater flow problems     

P.W. France 《Journal of Hydrology》1974,21(4):381-398

A numerical method is presented for analysing either steady state or transient three-dimensional groundwater flow problems. The governing equation is formulated in terms of the finite element process using the Galerkin approach, and cubic isoparametric elements are used to simulate the flow domain as these permit accurate modelling of curved boundaries. Particular attention is paid to the time dependent movement of the phreatic surface where an iterative technique based on the replacement of the original transient problem by a discrete number of steady state problems is used to effect a solution. Furthermore, in tracing the movement of the surface use is made of the element formulation theory in order to compute the normal to the boundary.The validity of the technique is first established by analysing a radially symmetrical problem for which an alternative analytical solution is available. Finally, a general three-dimensional flow system is studied for which there is no known analytical solution. It is shown that relatively few elements are required to yield practical solutions.  相似文献