Microtextural constraints on the interplay between fluid–rock reactions and deformation     

Alexis K. Ault  Jane Selverstone 《Contributions to Mineralogy and Petrology》2008,156(4):501-515

Schists from two mylonitic localities in the footwall of a low-angle normal fault in the eastern Alps record different degrees of embrittlement during exhumation, depending on the extent to which fluid–rock reactions proceeded. At one site, graphitic schists preserve textural evidence for two metamorphic reactions that modified and/or fluid volume: (1) reaction between graphite and aqueous fluid that increased without changing the molar amount of fluid, and (2) replacement of titanite by rutile, calcite, and quartz. The latter reaction involved net consumption of increasingly CO₂-rich fluid. Areas where the first reaction proceeded are associated with abundant Mode I microcracks. Fluid inclusion arrays within the microcracks show that increased from ∼0.1 to 0.6 during decompression from 4.75 to 2 kbar at a reference temperature of 500°C. Titanite consumption is most pronounced within transgranular Mode I microcracks, but microcracks do not crosscut products of this reaction; fluid consumption during reaction was coeval with the end of microcracking, at least on a local scale. At the other site, graphitic schists lack small-scale Mode I cracks as well as evidence for graphite consumption during decompression. SEM imaging shows that graphite is anhedral and pitted at the first site, but occurs in clusters of euhedral grains at the second site. Mass balance calculations demonstrate that rocks with partially consumed graphite were infiltrated by an externally derived, H₂O-rich fluid that drove subsequent graphite-fluid reaction. Evidence for similar fluid infiltration is absent at the second site. Variations in the degree of reaction progress indicate that fluid pathways and deformation style were heterogeneous on the scale of millimeters to kilometers during exhumation from mid-crustal depths.  相似文献   

Anaerobic decomposition of tropical soils and plant material: Implication for the CO₂ and CH₄ budget of the Petit Saut Reservoir   总被引：1，自引：0，他引：1  

Frdric Gurin  Gwenaël Abril  Alexis de Junet  Marie-Paule Bonnet 《Applied Geochemistry》2008,23(8):2272-2283

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Geochemical processes underlying a sharp contrast in groundwater arsenic concentrations in a village on the Red River delta,Vietnam   总被引：1，自引：0，他引：1  

Elisabeth Eiche  Thomas Neumann  Michael Berg  Beth Weinman  Alexander van Geen  Stefan Norra  Zsolt Berner  Pham Thi Kim Trang  Pham Hung Viet  Doris Stüben 《Applied Geochemistry》2008

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Sensitivity of Turbine-Height Wind Speeds to Parameters in Planetary Boundary-Layer and Surface-Layer Schemes in the Weather Research and Forecasting Model     

Ben Yang  Yun Qian  Larry K. Berg  Po-Lun Ma  Sonia Wharton  Vera Bulaevskaya  Huiping Yan  Zhangshuan Hou  William J. Shaw 《Boundary-Layer Meteorology》2017,162(1):117-142

We evaluate the sensitivity of simulated turbine-height wind speeds to 26 parameters within the Mellor–Yamada–Nakanishi–Niino (MYNN) planetary boundary-layer scheme and MM5 surface-layer scheme of the Weather Research and Forecasting model over an area of complex terrain. An efficient sampling algorithm and generalized linear model are used to explore the multiple-dimensional parameter space and quantify the parametric sensitivity of simulated turbine-height wind speeds. The results indicate that most of the variability in the ensemble simulations is due to parameters related to the dissipation of turbulent kinetic energy (TKE), Prandtl number, turbulent length scales, surface roughness, and the von Kármán constant. The parameter associated with the TKE dissipation rate is found to be most important, and a larger dissipation rate produces larger hub-height wind speeds. A larger Prandtl number results in smaller nighttime wind speeds. Increasing surface roughness reduces the frequencies of both extremely weak and strong airflows, implying a reduction in the variability of wind speed. All of the above parameters significantly affect the vertical profiles of wind speed and the magnitude of wind shear. The relative contributions of individual parameters are found to be dependent on both the terrain slope and atmospheric stability.  相似文献   

Variability in inorganic and organic nitrogen uptake associated with riverine nutrient input in the Gulf of Riga, Baltic Sea     

Gry Mine Berg  Patricia M. Glibert  Niels O. G. Jørgensen  Maija Balode  Ingrida Purina 《Estuaries and Coasts》2001,24(2):204-214

Concentrations and rates of uptake of dissolved organic nitrogen (DON, free amino acids, and urea) and inorganic nitrogen (DIN, nitrate, and ammonium) were measured along two transects in the Gulf of Riga, a sub-basin of the Baltic Sea, during May and July 1996. Concentrations of total dissolved nitrogen (TDN) were 23±3 μg-at N 1⁻¹ in the northern region (mouth) and 41±5 μg-at N 1⁻¹ in the southern region (head) of the Gulf. Rates of nitrogen uptake, determined with¹⁵N-labeled substrates, reflected differences in TDN concentration between the regions. In May, uptake of DIN+DON measured 0.17 and 0.43 μg-at N 1⁻¹ h⁻¹ in the northern and southern parts of the Gulf, respectively. In July, DIN+DON uptake measured 0.38 and 0.68 μg-at N 1⁻¹ h⁻¹ in the north and south, respectively. Most of the variability in total nitrogen flux between the northern and southern regions was due to heterogeneity of DON utilization. Uptake of urea and dissolved free amino acid were up to 6 and 3 times greater in the south compared to the north. As evidenced by size-fractionation, plankton size structure appeared to play a role in the uptake of DON. The community in the southern part was largely composed of cells <5 μm, while up to 67% of the community in the northern part was composed of cells >5 μm. Our results indicate that DON was a major source of nitrogen to phytoplankton, particularly in the southern part of the Gulf.  相似文献   

Refashioning Racism:Immigration, Multiculturalism and an Election Year     

Paul Spoonley  Lawrence D. Berg 《New Zealand geographer》1997,53(2):46-50

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Numerical Assessment of a Landfill Compliance Limit     

Bruce R. Mensel  Donald A. Keefer  Robert A. Griffin  Richard C. Berg 《Ground water》1991,29(2):218-224

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Influence of snow and soil moisture initialization on sub-seasonal predictability and forecast skill in boreal spring   总被引：1，自引：0，他引：1  

Jaison Ambadan Thomas  Aaron A. Berg  William J. Merryfield 《Climate Dynamics》2016,47(1-2):49-65

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Statistische Untersuchungen zur Meteorotropie der fulminanten Lungenembolie     

H. Berg 《Theoretical and Applied Climatology》1951,3(1):308-323

Zusammenfassung Die fulminante Lungenembolie (252 sorgfältig geprüfte Fälle der Jahre 1929 bis 1940 aus dem Sektionsgut des Pathologischen Instituts der Universität Köln) zeigt in Köln keine Beziehung zum Durchzug meteorologischer Fronten. Dagegen ist in dem Jahr des Sonnenfleckenmaximums 1937 eine zwar schwache, aber statistisch gesicherte Beziehung zu den durch die erdmagnetischen Charakterzahlen beschriebenen solaren Störungen vorhanden. Dieser Zusammenhang wurde durch die Bearbeitung des Sektionsmaterials von 13 westdeutschen pathologischen Instituten erhärtet (226 Embolien).

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Summary The fulminant lung embolism (252 carefully examined cases of the years 1929–1940 of the results of the Pathologic Institute of Cologne University) shows no correlation with the passage of meteorological fronts in Cologne. But in the year 1937, a year with a sun-spot maximum, there is a weak but statistically significant correlation with solar disturbances, described by the international magnetic character-figures. This connexion has been asserted furthermore by the analysis of the obduction material of 13 pathological institutes of western Germany (226 embolisms).

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Résumé L'embolie pulmonaire foudroyante (252 cas soigneusement contrôlés des années 1929 à 1940 et tirés du matériel d'autopsies de l'Institut pathologique de l'Université de Cologne) ne montrent à Cologne aucune relation avec les passages des fronts. Par contre l'année du maximum de taches solaires 1937, il existe une relation faible mais statistiquement prouvée avec les perturbations solaires traduites par les caractères magnétiques internationaux. Cette relation a été rendue plus vraisemblable par le dépouillement du matériel d'autopsies de 13 instituts pathologiques de l'Allemagne occidentale (226 embolies).

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Mit 5 Textabbildungen.  相似文献   

Evidence for organic complexation of iron in seawater   总被引：1，自引：0，他引：1  

Constant M. G. van den Berg 《Marine Chemistry》1995,50(1-4)

Iron occurs at very low concentrations in seawater of oceanic origin and its low abundance is thought to limit primary production in offshore waters (Martin and Fitzwater, 1988). A new electrochemical method, cathodic stripping voltammetry (CSV), is used here to determine the speciation of iron in seawater originating from the Western Mediterranean taking advantage of ligand competition of an added electroactive ligand with the natural organic complexing matter to evaluate whether iron is organically complexed. The measurements indicate that iron occurs 99% (or 99.9% depending on which value is selected for α_Fe′) complexed by organic complexing ligands throughout the water column of the Western Mediterranean and by analogy probably also in other oceanic waters. The composition of the organic complexing ligands is as yet unknown, but the data indicate a major source from microorganisms (bacteria or phytoplankton) in and immediately below the fluorescence maximum in the upper water column. The organic complexes are apparently reversible releasing iron when the competing ligand is added and binding more iron when its concentration is increased. The organic complexing ligands occur at concentrations well above those of iron ensuring full complexation of this biologically essential element, and buffer the free iron concentration at a very low level against fluctuations as a result of removal by primary producers or inputs from atmospheric sources. The new data indicate that a re-evaluation of the concept of the bioavailable fraction of iron is required.  相似文献