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1.
Mathematical model of a Hot Dry Rock system 总被引：1，自引：0，他引：1
2.
Eolian dusts collected after dust storms contain aggregates that are cemented by evaporitic salts, mainly halite. They vary in shape, fabrics, and surface roughness. Aggregation changes grainshape, density and size distribution of dust particles (i.e., characteristics determining erosion and transport); on deposition in the sea, cements dissolve and aggregates disintegrate, leaving the resultant eolo-marine sediment component with a misleading paleo-climatic record. The eolian transport of salts with dust from the arid coastal plain to the sea constitutes a portion of anticyclic salt movement and probably plays a role in the geochemical balance of the oceans. 相似文献
3.
Ocean drilling has revealed the existence of vast microbial populations in the deep subseafloor, but to date little is known about their metabolic activities. To better understand the biogeochemical processes in the deep biosphere, we investigate the stable carbon isotope chemistry of acetate and other carbon-bearing metabolites in sediment pore-waters. Acetate is a key metabolite in the cycling of carbon in anoxic sediments. Its stable carbon isotopic composition provides information on the metabolic processes dominating acetate turnover in situ. This study reports our findings for a methane-rich site at the northern Cascadia Margin (NE Pacific) where Expedition 311 of the Integrated Ocean Drilling Program (IODP) sampled the upper 190 m of sediment. At Site U1329, δ13C values of acetate span a wide range from −46.0‰ to −11.0‰ vs. VPDB and change systematically with sediment depth. In contrast, δ13C values of both the bulk dissolved organic carbon (DOC) (−21.6 ± 1.3‰ vs. VPDB) and the low-molecular-weight compound lactate (−20.9 ± 1.8‰ vs. VPDB) show little variability. These species are interpreted to represent the carbon isotopic composition of fermentation products. Relative to DOC, acetate is up to 23.1‰ depleted and up to 9.1‰ enriched in 13C. Broadly, 13C-depletions of acetate relative to DOC indicate flux of carbon from acetogenesis into the acetate pool while 13C-enrichments of pore-water acetate relative to DOC suggest consumption of acetate by acetoclastic methanogenesis. Isotopic relationships between acetate and lactate or DOC provide new information on the carbon flow and the presence and activity of specific functional microbial communities in distinct biogeochemical horizons of the sediment. In particular, they suggest that acetogenic CO2-reduction can coexist with methanogenic CO2-reduction, a notion contrary to the hypothesis that hydrogen levels are controlled by the thermodynamically most favorable electron-accepting process. Further, the isotopic relationship suggests a relative increase in acetate flow to acetoclastic methanogenesis with depth although its contribution to total methanogenesis is probably small. Our study demonstrates how the stable carbon isotope biogeochemistry of acetate can be used to identify pathways of microbial carbon turnover in subsurface environments. Our observations also raise new questions regarding the factors controlling acetate turnover in marine sediments. 相似文献
4.
Shuchai Gan Verena B.Heuer Frauke Schmidt Lars W?rmer Kai-Uwe Hinrichs 《海洋学报(英文版)》2023,42(1):109-119
Marine sediments represent a major carbon reservoir on Earth. Dissolved organic matter(DOM) in pore waters accumulates products and intermediates of carbon cycling in sediments. The application of excitation-emission matrix spectroscopy(EEMs) in the analysis of subseafloor DOM samples is largely unexplored due to the redoxsensitive matrix of anoxic pore water. Therefore, this study aims to investigate the interference caused by the matrix on EEMs and propose a guideline to prepare pore water sam... 相似文献
5.
J. S. Lally A. H. Heuer G. L. Nord Jr. J. M. Christie 《Contributions to Mineralogy and Petrology》1975,51(4):263-281
Zoned lunar pyroxenes have been examined by high voltage (800–1000 kV) transmission electron microscopy and electron diffraction, with the particular aim of providing information on the cooling history of individual pyroxenes. Microstructures resulting from composition discontinuities occurring during continuous crystallization, exsolution lamellae of pigeonite and augite and the development of denuded zones, and anti-phase domains (APD's) in pigeonite have been studied with respect to their scale, morphology and micro-structural evolution. These features have been further interpreted with respect to a proposed pseudobinary phase diagram of constant En/Fs.Information found to be the most useful for determining cooling rates in pyroxenes are: for quickly cooled rocks; microstructural evolution and APD size for moderately cooled rocks; and denuded zone widths and APD morphology for slowly cooled rocks.Now at U.S. Geological Survey, 959 National Center, Reston, Virginia 22092. 相似文献
6.
Matthias Heuer Alexandra L. Huber Geoffrey D. Bromiley Karl Thomas Fehr Klaus Bente 《Physics and Chemistry of Minerals》2005,32(8-9):552-563
Clinopyroxenes of the solid solution series hedenbergite (CaFeSi2O6)–petedunnite (CaZnSi2O6) were synthesized at temperatures of 825–1200°C and pressures of 0.5–2.5 GPa. Compositions were determined by electron microprobe analysis. Selected crystals were investigated by means of single crystal diffraction and structure refinement and the structural distortion was studied depending on the substitution of iron by zinc on the octahedral M1 site. It is shown that the coordination of the M1 site has the most significant effect on M–O bond lengths, with changes on the other sites accommodating this distortion. The mean quadratic elongation and the octahedral angle variance as quantitative measures of the distortion of the coordination polyhedron were correlated with former results of 57Fe Mössbauer spectroscopy at 298 K. The results presented now complete an earlier work on synthetic, crystalline powders of the same material and deliver exact structural data that were not possible to obtain by Rietveld refinements on powder data. 相似文献
7.
M. Wilde-Piórko W. H. Geissler J. Plomerová M. Grad V. Babuška E. Brückl J. Cyziene W. Czuba R. England E. Gaczyński R. Gazdova S. Gregersen A. Guterch W. Hanka E. Hegedűs B. Heuer P. Jedlička J. Lazauskiene G. Randy Keller R. Kind K. Klinge P. Kolinsky K. Komminaho E. Kozlovskaya F. Krüger T. Larsen M. Majdański J. Málek G. Motuza O. Novotný R. Pietrasiak Th. Plenefisch B. Růžek S. Sliaupa P. Środa M. Świeczak T. Tiira P. Voss P. Wiejacz 《Studia Geophysica et Geodaetica》2008,52(3):439-448
8.
Hammerschmidt Sebastian B Wiersberg Thomas Heuer Verena B Wendt Jenny Erzinger Jörg Kopf Achim 《Geochemical transactions》2014,15(1):1-9
Background
Riverine particles undergo a rapid transformation when they reach estuaries. The rapid succession of hydrodynamic and biogeochemical regimes forces the particles to flocculate, settle and enter the sediment pool. The rates and magnitudes of flocculation depend on the nature of the particles which are primarily affected by the types and quantities of organic matter (OM). Meanwhile, the OM characteristics vary widely between environments, as well as within a single environment due to seasonal climate and land use variability. We investigated the effect of the OM types and quantities through laboratory experiments using natural estuarine particles from the Mississippi Sound and Atchafalaya Bay as well as model mixtures of montmorillonite and organic molecules (i.e., biopolymers (guar/xanthan gums) and humic acid).Results
Biopolymers promote flocculation but the magnitude depends on the types and quantities. Nonionic guar gum yields much larger flocs than anionic xanthan gum, while both of them exhibit a nonlinear behavior in which the flocculation is the most pronounced at the intermediate OM loading. Moreover, the effect of guar gum is independent of salinity whereas the effect of xanthan gum is pronounced at higher salinity. Meanwhile, humic acid does not affect flocculation at all salinity values tested in this study. These results are echoed in the laboratory manipulation of the natural estuarine particles. Flocculation of the humic acid-rich Mississippi Sound particles is unaffected by the OM, whereas that of biopolymer-rich Atchafalaya Bay particles is enhanced by the OM.Conclusions
Flocculation is positively influenced by the presence of biopolymers that are produced as the result of marine primary production. Meanwhile, humic acid, which is abundant in the rivers that drain the agricultural soils of Southeastern United States, has little influence on flocculation. Thus, it is expected that humic acid-poor riverine particles (e.g., Mississippi River, and Atchafalaya River, to a lesser degree) may be prone to rapid flocculation and settling in the immediate vicinity of the river mouths when mixed with biopolymer-rich coastal waters. It is also expected that humic acid-rich riverine particles (e.g., Pearl River) may resist immediate flocculation and be transported further away from the river mouth. 相似文献9.
John Kochendorfer Tilden P. Meyers John M. Frank William J. Massman Mark W. Heuer 《Boundary-Layer Meteorology》2013,147(2):337-345
In Kochendorfer et al. (Boundary-Layer Meteorol 145:383–398, 2012, hereafter K2012) the vertical wind speed $(w)$ measured by a non-orthogonal three-dimensional sonic anemometer was shown to be underestimated by $\approx $ 12 %. Turbulent statistics and eddy-covariance fluxes estimated using $w$ were also affected by this underestimate in $w$ . Methodologies used in K2012 are clarified here in response to Mauder’s comment. In addition, further analysis of the K2012 study is presented to help address questions raised in the comment. Specific responses are accompanied with examples of time series, calculated correlation coefficients, and additional explanation of the K2012 methods and assumptions. The discussion and analysis included in the comment and in this response do not affect the validity of the methods or conclusions presented in K2012. 相似文献
10.
A thermal and mechanical history of lunar gabbroic anorthosite 15418 (1140g) has been deduced from petrographic examination of both exterior and interior thin sections and electron microprobe analysis and transmission electron microscopy of interior thin sections. We suggest that the rock underwent two major shock events - an early brecciation and annealing that produced a recrystallized breccia, followed by a second shock event that melted the surface of the rock, vitrified the interior plagioclase and heavily deformed the mafic phases. This latter shock even was also followed by annealing which crystallized the shock-produced glass and promoted recovery and recrystallization of the deformed crystalline phases. The complex mechanical and thermal history of 15418 compared with other ANT suite rocks at Spur Crater suggests that it had a different provenance. 相似文献