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601.
Fulvio Franchi Barbara Cavalazzi Catherine Pierre Roberto Barbieri 《Geological Journal》2015,50(5):634-650
New evidences based on a combination of field and laboratory investigations reinforce the hypotheses that the circulation of warm fluids has remarkably contributed to the origin and development of the Devonian Kess Kess mounds of the Hamar Laghdad Ridge (eastern Anti‐Atlas, Morocco). The limestones of the Hamar Laghdad Ridge were deposited above a structural high generated by calc‐alkaline volcanic activity that has probably fuelled the circulation of warm fluids throughout the overlying carbonate units. The geological and palaeontological attributes described throughout the succession of the Hamar Laghdad Ridge (from the Lochkovian to Frasnian intervals) are interpreted as the result of hydrothermal processes related to a volcanic system. In particular, these attributes seem consistent with a chemo‐physical environment fuelled by the circulation of warm and late magmatic fluids. These attributes include a very low oxygen stable isotope signature (δ18O ~ −10‰) for carbonates. Evidences for a late magmatic fluid circulation consist of volcanic glass and pyroclasts replacement with hydrothermal minerals such as quartz, anatase and clinochlore. Fluids circulating through veins and pores into sediments, and venting to the seafloor, probably induced the formation of cavities where monospecific trilobite communities were detected. The partially silicified trilobite remains are associated with traces of goethite. This iron‐bearing oxide mineral is also present in the upper part of the Hamar Laghdad Ridge. All these attributes are here interpreted as possible evidences for a low‐temperature hydrothermal venting system active during the Lochkovian–Frasnian time span. This study combines an updated revision with new petrographic, geological and geochemical results aimed at providing an overall framework on the origin and early diagenesis of the Devonian succession of Hamar Laghdad. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
602.
Numerical models of ionic diffusion in one and three dimensions: application to dehydration of mantle olivine 总被引:1,自引:0,他引:1
The hydrogen content of nominally anhydrous minerals is of great interest, because it can influence many physical and mechanical properties of mantle rocks. Moreover, the hydrogen diffusion profiles can be used to constrain timescales related to magma eruptions. Here, we report models of ionic diffusion for trace elements in anisotropic crystals and apply them to hydrogen diffusing out of mantle-derived olivine. We first compare and discuss the characteristics of 1D and 3D models and show that only 3D anisotropic diffusion models can lead to diffusion profiles exhibiting non-equilibrium plateau at the center of the solid along the slowest axis, as measured in natural samples. In a second part, we discuss the differences between hydration and dehydration of olivine for diffusion that is linked to two different atomic sites involved in hydrogen mobility. Finally, we apply our 3D anisotropic model to previous results on mantle-derived olivine from Pali-aike to better characterize diffusion coefficients and their anisotropy that could be relevant for dehydration of olivine. Our results show that dehydration has to be strongly anisotropic, with a fast [100] axis and a significantly slower [001] axis. 相似文献
603.
Economics of climate policy and collective decision making 总被引:1,自引:0,他引:1
Beat Bürgenmeier Andrea Baranzini Catherine Ferrier Céline Germond-Duret Karin Ingold Sylvain Perret Peter Rafaj Socrates Kypreos Alexander Wokaun 《Climatic change》2006,79(1-2):143-162
This paper explores the reasons why economic instruments of climate change are reluctantly applied and stresses the need for interdisciplinary research linking economic theory and empirical testing to deliberative political procedures. It is divided in three parts. The first one recalls the main issues in implementing Cost-Benefit Analysis such as information problems, uncertainties, discounting the future and irreversibilities. The second part shows how these issues can be treated in integrated assessment and techno-economic models and presents a case study, which shows that
- The chosen scenario tends to stabilize atmospheric CO2 concentration at around 550 ppm in the long run.
- Exclusion of possibility to trade CO2 emission permits under a cap regime would increase the cost of emission abatement for OECD countries.
- Combining different flexibility instruments might lead to significant gains in the overall cost of climate policy.
604.
605.
Yassaman Babaee Catherine N. Mulligan Md. Saifur Rahaman 《Environmental Earth Sciences》2017,76(19):650
Due to the severity of arsenic contamination of soil and water resources around the world, finding new adsorbents for arsenic removal from the water is of high importance. The present study investigates the possible use and effectiveness of starch-stabilized Fe/Cu nanoparticles for adsorption of arsenic from aqueous solutions. First, Fe/Cu nanoparticles at various starch concentrations of 0, 0.02, 0.04 and 0.06 wt% were synthesized and characterized by X-ray diffraction, transmission electron microscopy and zeta potential/particle size analyzer. Then 0.04 wt% stabilized Fe/Cu nanoparticles were tested for the sorption of As(III) and As(V) from synthetic arsenic-contaminated water. To have an understanding about the arsenic adsorption mechanism of nanoparticles, X-ray photoelectron spectroscopy (XPS) was performed before and after adsorption. The results showed that starch provides nanoparticles with a neutral surface and stabilization of nanoparticles is possible with 0.04 wt% or higher concentrations of starch. For 0.04 wt% starch-stabilized Fe/Cu nanoparticles, the adsorption isotherms fit well within the Langmuir equation, with maximum sorption capacities of 90.1 mg/g for As(III) and 126.58 mg/g for As(V) at a pH of 7.0 from the aqueous arsenic solutions. Examining the XPS spectra of nanoparticles before and after adsorption showed that arsenic adsorption by this nanoparticle can be due to the formation of inner-sphere arsenic complexes on the particle surface, and the surface oxygen-containing functional groups involved in adsorption. The high sorption capacity suggests the potential for applying starch-stabilized Fe/Cu nanoparticles to the contaminated waters for removal of arsenic. 相似文献