Results 1 - 10 of 300987
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[en] Carbon capture and storage technologies represent the most suitable solutions related to the high anthropogenic CO2 emissions to the atmosphere. As a consequence, monitoring of the possible CO2 leakages from an artificial deep geological CO2 storage is indispensable to guarantee its safety. Fast surficial travertine precipitation related to these CO2 leakages can be used as an alert for these escapes. Since few studies exist focusing on the long-term behaviour of an artificial CO2 DGS, natural CO2 storage affected by natural or artificial escapes must be studied as natural analogues for predicting the long-term behaviour of an artificial CO2 storage. In this context, a natural CO2 reservoir affected by artificial CO2 escapes has been studied in this work. This study has mainly focused on the current travertines precipitation associated with the upwelling CO2-rich waters from several hydrogeological wells drilled in the Ganuelas-Mazarron Tertiary basin (SE Spain), and consists of a comprehensive characterisation of parent-waters and their associated carbonates, including elemental and isotopic geochemistry, mineralogy and petrography. Geochemical characterisation of groundwaters has led to recognise 4 hydrofacies from 3 different aquifers. These groundwaters have very high salinity and electrical conductivity; are slightly acid; present high dissolved inorganic carbon (DIC) and free CO2; are oversaturated in both aragonite and calcite; and dissolve, mobilize and transport low quantities of heavy and/or toxic elements. Isotopic values indicate that: i) the origin of parent-waters is related to rainfalls from clouds originated in the Mediterranean Sea or continental areas; ii) the origin of C is mainly inorganic; and iii) sulphate anions come mainly from the dissolution of the Messinian gypsum from the Tertiary Basin sediments. Current travertines precipitation seems to be controlled by a combination of several factors, such as: i) a fast decrease of the hydrostatic pressure and the pCO2, resulting in a rapid degassing process; and ii) microbes and algae activity. This process leads to an increase in pH that favours the carbonates precipitation. Although there are not master physicochemical parameters controlling the precipitation of calcite or aragonite from their respective parent-waters, it is suggested that some parent-waters have the most suitable physicochemical features for the precipitation of one or another polymorph. Finally, the d13C values of DIC and carbonates could be used as good tracers for CO2 leakages from an artificial CO2 DGS. (Author) 101 refs.
[en] In this study, we investigated the effect of uniaxial strain (compression and elongation) on the band gap values of pristine graphene mono-sheet as well as boron-doped, nitrogen-doped, and boron-nitrogen co-doped graphene mono-sheet. Although a clear band gap opening was observed in all graphene mono-sheet structures, the rate of band gap opening in pristine graphene mono-sheet is higher than the rate of band gap opening in doped graphene mono-sheet with symmetric behaviour was observed when the applied strain is in the armchair direction. However, a clear discrepancy was observed in the calculated band gap values when the applied strain is in the zigzag direction. Additionally, we found that the rate of change in the Fermi energy with respect to the applied strain depends crucially not only on the dopant type but also on the strain type whether it is compression or elongation. (paper)
[en] The role of energy cannot be passed over in the process of economic growth and development in any economy. China consumes colossal quantity of energy; thus, the central objectives of this study is to empirically evaluate the linkages among energy use, environment by CO2 emissions, human health by health expenditures, Foreign Direct Investment (FDI) inflows, and real GDP per capita used for economic growth over the period of 1995–2016 for China. The nature of the data directed to employ the Canonical cointegrating regression (CCR) method for unknown parameter estimation. Four equations have estimated namely for FDI, health, environment, and economic growth. The result for China during the period under the study reveals that energy consumption has significant positive impact on FDI, health, environment, and economic growth. The study results suggest that policy makers need to chalk out effective policy for effective utilization of energy so as to encourage permissible economic growth and development in China.
[en] The major goal of the carbonate research program at Stony Brook is to better understand the conditions and processes leading to regional diagenesis of carbonate rocks. Our research focuses on studies of ancient, massive dolostones, but we are also studying limestone diagenesis for its own importance, and as it relates to dolomitization. Our approach has been to carry out a very detailed petrographic and geochemical case study to the Mississippian Burlington-Keokuk Fms. of Iowa, Illinois and Missouri, and to develop this as a testing ground for new geochemical and modelling techniques, and for testing various models for regional dolomitization in epicontinental carbonates. The ideas and techniques developed in our Burlington-Keokuk studies are being expanded and applied to carbonate sequences of other ages (Devonian to Neogene), and other tectono-sedimentary settings. The emphasis of this report will be on new developments and results on the Burlington-Keokuk studies and on our diagenetic studies of other strata. Recent research on Burlington-Keokuk rocks include development and application of boron isotopes and the U--Th--Pb system to dolomite studies, investigations of porosity and permeability in the dolostones. Projects on other strata include dolomitization and limestones diagenesis of Devonian carbonates of Alberta and Western Australia, Miocene reefal carbonates of Spain, Neogene carbonates of Curacao and Bonaire, Waulsortian limestones of Ireland, modelling of trace elements and stable isotopes, and experimental growth of calcites to investigate crystallographic controls of trace element incorporation. 118 refs., 46 figs
[en] Two types of shock wave experiments have been conducted on samples of Blair dolomite. The first employed a light-gas gun to produce uniaxial strain, while the second used a spherical high-explosive charge to cause radial deivergent flow. Comparisons of data taken from these two types of experiments (at strain rates of 106/s and 104/s, respectively) with quasi-static data (at 10-4/s) show that Blair dolomite is strongly time dependent in its behavior. This time dependence appears over the entire stress interval from 0.24 to 5.33 GPa
[en] We research the adsorption geometries and electronic structures of pristine graphene (p-GR) and Li-doped graphene (Li-GR) before and after CO adsorption by first-principles. The adsorption energies E_a_d of CO on p-GR and Li-GR are calculated. The results demonstrate that E_a_d of CO on Li-GR is from −3.3eV to −3.5eV, meanwhile Q is up to 0.13e, which indicate that strong electrostatic attractions occur between CO and Li-GR, while CO is physically adsorbed on p-GR. The obvious accumulated charge in electron density difference and increasing carrier density suggest that the conductivity of Li-GR is improved considerably after CO adsorption. An adsorption mechanism is also proposed. Our results provide a path to achieving CO sensors with high performance. (paper)
[en] The graphite tube cuvettes for the flameless atom absorption spectroscopy are provided with a surface coating of Zr-, Ti-, Nb-, Hf- or Va- carbide or carbonitride, respectively. This is performed by a electrolytic treatment and a drying of the mould body under protective gas conditions. (RW)
[de]Die Grafitrohr-Kuevetten fuer die flammenlose Atomabsorptionsspektroskopie werden zur Erhoehung ihrer Verschleissfestigkeit mit einer Zr-, Ti-, Nb-, Hf - oder Va- Karbid bzw. Karbonitrid-Oberflaechenschicht versehen. Hierzu erfolgt eine elektrolytische Behandlung und eine Trocknung des Formkoerpers unter Schutzgas. (RW)
[en] The temperature dependence of carbon isotopic fractionations between calcite and graphite, and between dolomite and graphite are calibrated by the calcite-dolomite solvus geothermometry using marbles collected from the contact metamorphic aureole in the Kasuga area, central Japan. The carbon isotopic fractionations systematically decrease with increasing metamorphic temperature. The concordant relationships between the fractionations and solvus temperatures which are presented, are approximately linear with T-2 over the temperature range, 400 deg to 680 deg C. They suggest that carbon isotopic equilibria between carbonates and graphite were attained in many cases. The equation for the calcite-graphite system has a slope steeper than Bottinga's (1969) results. It is, however, in good agreement with that of Valley and O'Neil (1981) in the temperature range from 600 deg to 800 deg C. Because of the relatively high sensitivity to temperature, these isotopic geothermometers are useful for determining the temperatures in moderate- to high-grade metamorphosed carbonate rocks. (author)