Dust particles in the atmospheres of terrestrial planets and their roles for prebiotic chemistry: An overview     

Vladimir A. Basiuk  Rafael Navarro-Gonzalez 《Astrophysics and Space Science》1996,236(1):61-75

The available literature on sources, chemical composition, and importance of dust particles for the origins of life is analyzed. The most abundant sources of dust on the early terrestrial planets are sedimentation of interplanetary dust, meteoritic/cometary impacts, and volcanic eruptions. Interplanetary dust can originate directly from interstellar space, from evaporation of cometary bodies, from collisional destruction of asteroidal and meteoritic bodies, and nucleation in sunspots. Many rather complex organic species, including those of prebiotic interest, have been identified in the interstellar medium and cometary dust. Some of them are believed to formvia catalytic processes on the surfaces of dust particles. However, the mechanisms are not known, and even simulating experiments are difficult to perform due to insufficient knowledge of physical conditions in the space media and of chemical composition and properties of the dust. Besides the catalytic roles, cometary dust is believed to be the best delivery vehicle for organic matter of space origin to the atmospheres of terrestrial planets. Abundant sources of catalytically active fine dust can be volcanoes. Various organic and biological compounds have been found in terrestrial volcanic gases and ash, which are assumed to formvia the catalytic Fischer-Tropsch reactions. At present the eruptions on the Earth provide a unique opportunity to observein situ the formation of organic matter, and knowledge of the ash composition and local conditions allows to perform simulating experiments.  相似文献   

Coupled thermo-hydro-bio-geochemical reactive transport model of CERBERUS heating and radiation experiment in Boom clay     

Guoxiang Zhang  Javier Samper  Luis Montenegro 《Applied Geochemistry》2008

Final disposal of high-level radioactive waste in deep repositories in clay formations is being considered by several countries. Repository safety assessment requires the use of numerical models of groundwater flow, solute transport and chemical processes. These models are being developed from data and knowledge gained from in situ experiments such as the CERBERUS experiment carried out at the HADES facility excavated in the Boom clay formation at Mol (Belgium). This long-term experiment is aimed at evaluating the effect of heating and radiation in Boom clay. The test was performed in a cased well drilled at 223 m depth and lasted from 1989 to 1994. A ⁶⁰Co source of 400 TBq and two heaters were emplaced inside the well. Dose rate, temperature, porewater pressure and pH/Eh were measured in situ during the experiment and gas and porewater samples were taken for chemical analyses. Here a coupled thermo-hydro-geochemical (THC) model of the CERBERUS experiment is presented which accounts simultaneously for heating, radiation, solute diffusion and a suite of geochemical reactions including: aqueous complexation, acid–base, redox, mineral dissolution/precipitation, cation exchange and gas dissolution/ex-solution. Computed results indicate that heating and radiation causes a slight oxidation, a decrease in pH, slight changes in porewater chemistry and pyrite dissolution near the well. THC model results follow the general evolution of chemical data, but cannot fit SO₄ data. Model discrepancies are partly overcome when microbially-mediated Fe and SO₄ reduction are taken into account in a coupled thermo-hydro-bio-geochemical (THBC) model. This THBC model captures the trends of geochemical data, improves the fit to dissolved SO₄ and predicts pyrite precipitation, a process observed near the CERBERUS well. The ability of the THBC numerical model to reproduce the overall trends of geochemical data of the CERBERUS experiment provides confidence in such a model as a suitable tool for the long-term prediction of geochemistry in the near field of a HLW repository in clay. However, the small number of available chemical data throughout the experiment and the lack of DOC and microbial data allow only a partial validation of the THBC model.  相似文献   

Coupled thermo-hydro-chemical models of compacted bentonite after FEBEX in situ test     

Javier Samper  Liange Zheng  Luis Montenegro  Ana María Fernández  Pedro Rivas 《Applied Geochemistry》2008

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Influence of surface heterogeneities of building granite on its thermal response and its potential for the generation of thermoclasty     

Miguel Gómez-Heras  Bernard J. Smith  Rafael Fort 《Environmental Geology》2008,56(3-4):547-560

Surface properties, especially albedo, and aspect are widely accepted as strong influences on the surface thermal response of building stone to insolation. However, the influence that adjacent areas of stone with very different surface properties may have on the thermal response of a patch of stonework, and the ways in which spatial variation in thermal characteristics might enhance stone decay has received relatively little attention. This paper examines the differential thermal response of granite used in construction that results from the presence of dark coloured micro-granular enclaves within a leucocratic host. Surface temperatures and temperature differences between enclaves exhibiting mico-spalling, enclaves with no spalling and the surrounding stone were measured for different aspects and seasons on a 20th century building in Madrid. These data were used to calculate a number of “indices” related to short-term temperature cycling and temperature gradients that have the theoretical capability of generating irreversible deformation of the stone. These indices suggest that micro-spalling of enclaves, compared to a lack of similar decay on the host-rock, is related to their differential thermal response to insolation, most importantly the lower albedo and thermal conductivity values of the enclaves. However, these factors are not sufficient on their own to trigger spalling, and breakdown was only observed where enclaves also experienced repeated, short-term surface temperature cycling caused by, for example, temporary shading by adjacent vegetation. These rapid temperature reversals are identified as a key contributory factor to the thermally driven decay observed on some of the enclaves.  相似文献   

Very low grade metamorphism of the Taveyanne formation of western Switzerland   总被引：1，自引：1，他引：1  

David Schmidt  Susanne T. Schmidt  Joseph Mullis  Rafael Ferreiro Mählmann  Martin Frey 《Contributions to Mineralogy and Petrology》1997,129(4):385-403

The andesitic early Oligocene Taveyanne metagreywacke of the Helvetic nappes of western Switzerland shows an increase of metamorphic grade from zeolite facies through lower greenschist facies. Electron microprobe analysis, fluid inclusion thermometry, stable isotope analysis, coal rank, illite and chlorite crystallinity and thermodynamic calculations were carried out to determine metamorphic conditions. Evaluation of all techniques used in this study suggest that only combinations of different parameters yield reliable information to constrain very low-grade metamorphic conditions. Electron microprobe analyses are presented for actinolite, chlorite, epidote, phengite, laumontite, prehnite, pumpellyite, and titanite. With increasing metamorphic grade, chlorite is enriched in tetrahedral Al, pumpellyite becomes poorer in Fe_tot and more homogeneous in chemical composition, and titanite tends to incorporate Ti at the expense of Al and Fe³⁺. Metamorphic P-T conditions were determined by a combination of fluid inclusion microthermobarometry, stable isotope thermometry on quartz-calcite veins, chlorite “geothermometry” and thermodynamic calculations. Peak temperatures range from 210–250 °C for zeolite facies to 270–300 °C for prehnite-pumpellyite facies to 300–360 °C for pumpellyite-actinolite facies. An evaluation of 289 chlorite analyses indicates that the tetrahedral Al content is negatively correlated with the saponite component. Temperatures derived from chlorite “geothermometry” match maximum temperature conditions mentioned above. Illite crystallinity data for shales and slates intercalated with the Taveyanne metagreywacke indicate that the diagenetic zone correlates with the zeolite facies, the upper anchizone with the prehnite-pumpellyite facies, and the lower epizone with the pumpellyite-actinolite facies. A comparison of coal rank and illite crystallinity data (n=12,r=0.91) yielded R _max values of 2.9 and 5.5% for the lower and upper boundary of the anchizone, respectively. Received: 2 August 1996 / Accepted: 16 July 1997  相似文献   

Multi-temporal assessment of ground cover restoration and soil erosion risks along petroleum and gas pipelines in Azerbaijan using GIS and remote sensing     

Emil R. Bayramov  Manfred F. Buchroithner  Rafael V. Bayramov 《Environmental Earth Sciences》2016,75(3):256

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Ionic and elemental composition of PM<Subscript>2.5</Subscript> aerosols over the Caribbean Sea in the Tropical Atlantic     

Rafael Jusino-Atresino  James Anderson  Yuan Gao 《Journal of Atmospheric Chemistry》2016,73(4):427-457

To characterize atmospheric particulate matter equal or less than 2.5 μm in diameter (PM_2.5) over the Tropical Atlantic Ocean, aerosol sampling was carried out in Puerto Rico during August and September, 2006. Aerosols were analyzed by ion chromatography for water-soluble inorganic and organic ions (including Na⁺, NH₄ ⁺, Mg²⁺, Ca²⁺, K⁺, Cl^?, SO₄ ^2?, NH₄ ⁺, F^?, methanesulfonate (MSA), and oxalate), by inductive coupled plasma mass spectrometry (ICPMS) for trace elements (Al, Fe, Zn, Mn, Cu, Ni, V, Pb, Cr, Sb, Co, Sc, Cd), and by scanning electron microscopy for individual aerosol particle composition and morphology. The results show that the dominant cations in aerosols were Na⁺, (mean: 631 ng m^?3), accounting for 63.8 % of the total cation and NH₄ ⁺ (mean: 164 ng m^?3), accounting for 13.8 % of the total cation measured in this study. The main inorganic anions were Cl^? (576 ng m^?3, 54.1 %) and SO₄ ^2? (596 ng m^?3, 38.0 %). The main organic anion was oxalate (18 ng m^?3). Crustal enrichment factor calculations identified 62 % of the trace elements measured (Cu, Ni, V, Co, Al, Mn, Fe, Sc, and Cr) with crustal origin. Single particle analysis demonstrated that 40 % of the aerosol particles examined were Cl^? rich particles as sodium chloride from seawater and 34 % of the total particles were Si-rich particles, mainly in the form of aluminosilicates from dust material. Based on the combination of air-mass trajectories, cluster analysis and principal component analysis, the major sources of these PM_2.5 particles include marine, Saharan dust and biomass burning from West Africa; however, volcanic emissions from the Soufriere Hills in Montserrat had significant impact on aerosol composition in this region at the time of sample collection.  相似文献   

Free and open source software for geospatial applications (FOSS4G) to support Future Earth     

Maria Antonia Brovelli  Marco Minghini  Rafael Moreno-Sanchez  Ricardo Oliveira 《International Journal of Digital Earth》2017,10(4):386-404

ABSTRACT

The development, integration, and distribution of the information and spatial data infrastructure (i.e. Digital Earth; DE) necessary to support the vision and goals of Future Earth (FE) will occur in a distributed fashion, in very diverse technological, institutional, socio-cultural, and economic contexts around the world. This complex context and ambitious goals require bringing to bear not only the best minds, but also the best science and technologies available. Free and Open Source Software for Geospatial Applications (FOSS4G) offers mature, capable and reliable software to contribute to the creation of this infrastructure. In this paper we point to a selected set of some of the most mature and reliable FOSS4G solutions that can be used to develop the functionality required as part of DE and FE. We provide examples of large-scale, sophisticated, mission-critical applications of each software to illustrate their power and capabilities in systems where they perform roles or functionality similar to the ones they could perform as part of DE and FE. We provide information and resources to assist the readers in carrying out their own assessments to select the best FOSS4G solutions for their particular contexts and system development needs.  相似文献   

The Canary Islands fishing policy     

Carlos Angel Pérez Labajos  Beatriz Blanco Rojo  Rafael Mazas Arranz 《Marine Policy》1996,20(6):463-474

In the last 20 years the Canary Islands fishing fleet has gone from the privileged position of enjoying abundant catches in the old “Canary Islands-Saharan” fishing grounds to the precarious situation in which it currently finds itself. This paper aims to determine what the future holds for The Canaries fishing sector. Hence, fishing rights and policies are analysed and the special aids received from the EC are compared with those applied in other similar ultraperipheric regions. The adoption of a more interventionist role by the Canary Islands administration may solve at least part of the problem faced by this sector.  相似文献   

Study of the growth of southern black and white monkfish stocks   总被引：1，自引：0，他引：1  

Duarte  Rafael; Azevedo  Manuela; Pereda  Pilar 《ICES Journal of Marine Science》1997,54(5):866-874

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