Search results for " petrology"
showing 10 items of 1353 documents
Molecular Selectivity of CH 4 –C 2 H 6 Mixed Hydrates: A GCMC Study
2021
International audience; In this paper, we report the first grand canonical Monte Carlo simulation study aiming at characterizing the competitive trapping of CH4 and C2H6 molecules into clathrate hydrates under temperature conditions typical of those encountered at the surface of Titan. Various compositions of the fluid in contact with the clathrate phase have been considered in the simulations, including pure methane, pure ethane, and mixed fluids made of various methane/ethane ratios. The trapping isotherms obtained from the simulations clearly show that ethane molecules can be enclathrated at lower pressures than methane molecules. In addition, they provide evidence that the methane molec…
The role of slabs and oceanic plate geometry in the net rotation of the lithosphere, trench motions, and slab return flow
2012
[1] Absolute plate motion models with respect to a deep mantle reference frame (e.g., hot spots) typically contain some net rotation (NR) of the lithosphere. Global mantle flow models for the present-day plate setting reproduce similarly oriented NRs but with amplitudes significantly smaller than those found in some high NR Pacific hot spot reference frames. It is therefore important to understand the mechanisms of NR excitation, which we attempt here with two-dimensional cylindrical models of an idealized Pacific domain. We study the influence of slab properties, oceanic ridge position, continental keels, and a weak asthenospheric layer on NR and trench migration. Fast slab return flow dev…
Soil gas prospection of He,222Rn and CO2: Vulcano Porto area, Aeolian Islands, Italy
1997
Abstract In March 1994, soil gases were sampled in the area of Vulcano Porto, on the island of Vulcano, using a grid of about 200 points/km 2 . Analysed gases were CO 2 , He and 222 Rn and, over a smaller area, H 2 S. Some of the samples were also analysed for the isotope composition of CO 2 C. Three anomalous CO 2 degassing areas were identified: Grotta dei Palizzi, the area near the Telephone Exchange, and the area near the beach fumaroles. The behaviour of He and 222 Rn is different in these 3 areas. The concentration of He is much lower than that of atmospheric He (down to −3950 ppb) in the isthmus, and only in the area near Grotta dei Palizzi does it have values significantly higher th…
Selenium and heavy metals content in some Mediterranean soils
2010
Abstract The study of metal contents in industrial, agricultural or/and polluted soils compared with natural or unpolluted soils is currently necessary to obtain reference values and to assess soil contamination. Nonetheless, very few works published appear in international journals on elements like Se, Li and Sr in Spanish soils. This study determines the total levels of Se, Li, Sr, As, Cd, Co, Cr, Cu, Ni, Pb, V, Zn, Fe, Mn and Ba in 14 natural (unpolluted) soils (Gypsisols, Leptosols, Arenosols and Acrisols), 14 agricultural soils (Anthrosols, Fluvisols and Luvisols), and 4 industrial–urban affected-surface soil horizons (Anthrosols and Fluvisols) of Eastern Spain. The geochemical baselin…
Organometal(loid) species in geochemical exploration : preliminary qualitative results
1998
Abstract Organic and other volatile metal(loid) species (e.g. hydrides) in environmental gases can be determined with high sensitivity and selectivity by low-temperature gas chromatography coupled on-line to plasma mass spectrometry (LTGC/ICP–MS). A standard reference solution is analysed simultaneously for calibration of the results as well as for monitoring the excitation conditions in the plasma. This highly sensitive analytical method was applied in field screening tests at Cu and Hg deposits in Germany. In some of the soil gas and soil samples investigated, organic compounds of several elements (e.g. As, Hg) could clearly be identified. The implications of these results with respect to…
Short-term changes in soil Munsell colour value, organic matter content and soil water repellency after a spring grassland fire in Lithuania
2014
Abstract. Fire is a natural phenomenon with important implications on soil properties. The degree of this impact depends upon fire severity, the ecosystem affected, topography of the burned area and post-fire meteorological conditions. The study of fire effects on soil properties is fundamental to understand the impacts of this disturbance on ecosystems. The aim of this work was to study the short-term effects immediately after the fire (IAF), 2, 5, 7 and 9 months after a low-severity spring boreal grassland fire on soil colour value (assessed with the Munsell colour chart), soil organic matter content (SOM) and soil water repellency (SWR) in Lithuania. Four days after the fire a 400 m2 plo…
Water and Geodynamics
2006
Hydrogen is the most abundant element (Fig. 1⇓) in the galaxy and our solar system (Lodders 2003). Therefore it is not astonishing that hydrogen is a key player in the geodynamic evolution of planets. Its fate in the early Earth, after condensation of the solar nebula, the accretion of our planet and hydrogen reprocessing through early asteroidal and cometary bombardment (Dauphas et al. 2000) and segregation of a proto-Earth into iron core and silicate mantle is described elsewhere in this volume (Marty and Yokochi 2006). Figure 1. Abundance of elements in the solar system in numbers of atoms per 106 atoms of silicon (Lodders 2003). This chapter concerns itself with the geodynamics of the m…
Low temperature headspace desorption of volatile organic compounds trapped in air sampling solid-supports
2009
Environmental context. The monitoring of volatile organic compounds (VOCs) in air is of great importance for air quality on both local and global scales. The determination of VOCs can be carried out by gas chromatography–mass spectrometry (GC-MS) after active or passive sampling and (high temperature) thermal desorption. An attractive alternative would be to combine GC-MS with headspace (HS) systems as it allows simpler, faster, low temperature desorption. We present here the first report of HS-GC-MS for the determination of VOCs in air sampled using solid supports. Abstract. The use of a headspace (HS) for low temperature desorption of VOCs, previously sorbed from indoor air on solid supp…
Changes in fluid geochemistry and physico-chemical conditions of geothermal systems caused by magmatic input: The recent abrupt outgassing off the is…
2005
Abstract Hydrothermal systems and related vents can exhibit dramatic changes in their physico-chemical conditions over time as a response to varying activity in the feeding magmatic systems. Massive steam condensation and gas scrubbing processes of thermal fluids during their ascent and cooling cause further compositional changes that mask information regarding the conditions evolving at depth in the hydrothermal system. Here we propose a new stability diagram based on the CO2-CH4-CO-H2 concentrations in vapor, which aims at calculating the temperatures and pressures in hydrothermal reservoirs. To filter gas scrubbing effects, we have also developed a model for selective dissolution of CO2-…
FUNCTIONALIZED HALLOYSITE NANOTUBES FOR ENHANCED REMOVAL OF Hg2+ IONS FROM AQUEOUS SOLUTIONS
2021
AbstractWater is essential for humans, animals, and plants; pollutants, usually derived from anthropogenic activities, can have a serious effect on its quality. Heavy metals are significant pollutants and are often highly toxic to living organisms, even at very low concentrations. Among the numerous removal techniques proposed, adsorption onto suitable adsorbent materials is considered to be one of the most promising. The objective of the current study was to determine the effectiveness of halloysite nanotubes (HNT) functionalized with organic amino or thiol groups as adsorbent materials to decontaminate polluted waters, using the removal of Hg2+ ions, one of the most dangerous heavy metals…