Spectral emissivity measurements of Mercury's surface indicate Mg- and Ca-rich mineralogy, K-spar, Na-rich plagioclase, rutile, with possible perovskite, and garnet     

A.L. Sprague  K.L. Donaldson Hanna  J. Helbert  J.B. Warell 《Planetary and Space Science》2009,57(3):364-383

Mid-infrared 2-D spectroscopic measurements from 8.0 to 12.7 μm of Mercury were taken using Boston University's Mid-Infrared Spectrometer and Imager (MIRSI) mounted on the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii, 7-11 April 2006. Measurements reported here cover radar bright region C, a dark plains region west of Caloris Basin, and the interior of Caloris Basin. By use of spectral deconvolution with a large spectral library composed of many mineral compositions and grain size separates, we fitted, or “unmixed”, the Mercury spectra. We find mineral suites composed of magnesium-rich orthopyroxene and olivine, Ca-, Mg-, Na-rich clinopyroxene, potassium feldspar, and Na-bearing plagioclase feldspar. Both Ca- and Mg-rich garnet (pyrope and grossular, respectively) are apparently present in small amounts. Opaque minerals are required for spectral matching, with rutile (TiO₂) repeatedly providing the “best fit”. However, in the case of the radar bright region C, perovskite also contributed to a very good fit. Caloris Basin infill is rich in both potassium feldspar and Na-rich plagioclase. There is little or no olivine in the Caloris interior smooth plains. Together with the high alkali content, this indicates that resurfacing magmas were low to intermediate in SiO₂. Data suggest the dark plains exterior to Caloris are highly differentiated low-iron basaltic magmas resulting in material that might be classified as oligoclase basalts.  相似文献   

Reactive transport of gentisic acid in a hematite-coated sand column: Experimental study and modeling     

K. Hanna  B. Rusch  A. Hofmann 《Geochimica et cosmochimica acta》2010,74(12):3351-4418

The adsorption of gentisic acid (GA) by hematite nano-particles was examined under static and dynamic conditions by conducting batch and column tests. To simulate natural sediments, the iron oxide was deposited on 10 μm quartz particles. The GA adsorption was described by a surface complexation model fitted to pH-adsorption curves with GA concentrations of 0.1-1 mM in a pH range of 3-10. The surface was described with one type of site (FeOH°), while gentisic acid at the surface was described by two surface complexes (FeLH₂°, log K_int = 8.9 and FeLH⁻, log K_int = −8.2). Modeling was conducted with PHREEQC-2 using the MINTEQ database. From a kinetic point of view, the intrinsic chemical reactions were likely to be the rate-limiting step of sorption (∼10⁻³ s⁻¹) while external and internal mass transfer rates (∼10² s⁻¹) were much faster. Under flow through conditions (column), adsorption of GA to hematite-coated sand was about 7-times lower than under turbulent mixing (batch). This difference could not be explained by chemical adsorption kinetics as shown by test calculations run with HYDRUS-1D software. Surface complexation model simulations however successfully described the data when the surface area was adjusted, suggesting that under flow conditions the accessibility to the reactive surface sites was reduced. The exact mechanism responsible for the increased mobility of GA could not be determined but some parameters suggested that decreased external mass transfer between solution and surface may play a significant role under flow through conditions.  相似文献   

Variation of the magnetic properties in a basaltic dyke with concentric cooling zones     

B.M Smith  M Prévot 《Physics of the Earth and Planetary Interiors》1977,14(2):120-136

The effects of the variation of magnetic grain size on the magnetic properties of rocks have been studied throughout a reversely magnetized basaltic dyke with concentric cooling zones.Except in a few tachylites in which the magnetic mineral is a Ti-rich titanomagnetite, in the bulk of the dyke the magnetization is carried by almost pure magnetite grains. Although the percentage p of these magnetic oxides varies slightly, the large changes in the various magnetic parameters observed across the dyke are essentially attributable to large variations in the grain size of the magnetic particles.From the outer scoria region, where the magnetic grains are a mixture of single-domain (SD) and superparamagnetic (SP) grains, to the tachylite zone with finely crystallized basaltic glass containing interacting elongated SD particles, one observes an increase of both the ratio of the saturation remanent magnetization and the saturation induced magnetization J_rs/J_is, the bulk coercive force H_c, the median destructive field MDF, the intensity of the remanent magnetization J_r, and the Koenigsberger ratio Q. In the tachylites these parameters reach unusually high values, for subaerial basalts: These parameters decrease in the basalt toward the centre of the dyke where pseudo-single-domain (pseudo-SD) particles coexist together with multidomain (MD) grains. The susceptibility remains approximately constant from the inner basalt to the tachylite, but increases in the scoria up to values 10 times higher owing to the presence of SP particles. The magnetic viscosity increases also drastically toward the margin of the dyke due to an increase of the fraction of the SD particles just above the superparamagnetic threshold.  相似文献   

Permittivity in the microwave region of some natural minerals     

F. F. Hanna  I. K. Hakim  A. M. Bishai  A. L. Saad 《Pure and Applied Geophysics》1982,120(4):772-777

The permittivity measured at a frequency of 10 GHz normalized to constant density is the same within the experimental error for talc, baryte and dolomite. In the case of clay and kaolin, it is about 10% higher. This is attributed to the high content of Al₂O₃ (30–40%) in them, which interpretation is proved by experiment.  相似文献   

Modified equations for the determination of odd zonal harmonics     

Dr. Xavier Berger  Pr. Georges Ligier 《Journal of Geodesy》1978,52(2):101-105

The development of the analytical theory of the motion of an artificial satellite (Berger, 1972–1975) points out the great importance of the second, third order and coupling terms between zonal harmonics. These terms have been added to the equations established byKing-Hele andCook (1968–1973) for the determination of odd zonal harmonics. This solution is compared with theirs. It satisfies all the equations much better and especially the equations relating to near-critical inclination satellites.  相似文献   

The longitudinal movement of stratospheric ozone waves as determined by satellite     

Pr. Elmar R. Reiter  Dr. James E. Lovill 《Meteorology and Atmospheric Physics》1974,23(1):13-27

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Die Existenz,Beschaffenheit und Bedeutung einer Zwischenschicht zwischen Gletschereis und Felsuntergrund     

Prof. Dr. O. Förtsch  Präsident Dr. H. Vidal 《International Journal of Earth Sciences》1968,57(3):1019-1033

Zusammenfassung Fast unter allen Gletschern, einschließlich des Eisschildes auf Grönland, ist durch seismische Messungen eine Zwischenschicht zwischen Eis und Fels festgestellt worden. Sie ist auch in den Vorfeldern der Gletscher unter fluviatilen Ablagerungen vorhanden. Seismische Wiederholungsmessungen in Abständen von 25 bis 30 Jahren haben ergeben, daß sich die Morphologie der Oberkante der Zwischenschicht durch Sedimentation und Erosion beachtlich verändert. Es ist naheliegend, daß man sich die Zwischenschicht als gefrorene Grundmoräne vorstellt. Gegen diese Anschauung spricht aber die Existenz derselben in den Vorfeldern der Gletscher.Die beobachteten Geschwindigkeiten seismischer Wellen in der Zwischenschicht mit Werten zwischen 4000 und 5000 m/s können auch in verwitterten Gesteinen auftreten. Die erwähnten Veränderungen der Gestalt der Eisunterkante in relativ kurzer Zeit ist jedoch mit einer Deutung der Zwischenschicht als verwitterter Fels nicht in Einklang zu bringen.Die Verfasser nehmen an, daß die Zwischenschicht aus sehr dicht gepackten Sedimenten besteht. Mit dieser Annahme lassen sich alle Beobachtungsergebnisse erklären.

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Seismic measurements have shown nearly under all glaciers, including the iceshields of Greenland, a band between ice and rockbasement. This band exists also under the fluviatil sediments in the forefield of the glaciers. Seismic remeasurements in an interval of about 25–30 years have shown, that the morphology of the surface of the band has been heavily changed by sedimentation and erosion.It is evident that one imagines the band to be a frozen ground moraine. But the existence of the band in the forefield of glaciers demonstrates that this opinion must be wrong.The measured velocities of seismic waves between 4000 and 5000 m/s are possible also in weathered rocks. The above mentioned changes of the contour of the bottom of the ice during a relatively short period however cannot be reconciled with the interpretation of the band as weathered rock.The authors assume that the band consists of very densely packed sediments. This assumption explains all results of the observations.

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Résumé Presque sous tous les glaciers inclusivement l'Inlandeis du Groenland on a constaté par des mesurages séismiques une couche intermédiaire entre la glace et le roc. Cette couche existe aussi sous les sédiments fluviatils dans les glacis des glaciers. Pendant un intervalle de 25 à 30 ans des remesurements séismiques ont prouvé que la morphologie du bord supérieur de la couche intermédiaire a été considérablement changée par la sédimentation et l'érosion.On est bien tenté de croire, que la couche intermédiaire fût une moraine inférieure glacée. Mais l'existence de cette couche intermédiaire dans les glacis des glaciers démontre que cette opinion est incorrecte.Les vitesses des ondes séismiques mesurées de 4000 à 5000 m/s dans la couche intermédiaire se trouvent aussi dans des rocs décomposés. Mais les changements de la forme du bas de la glace pendant une période relativement courte ne peuvent pas être mis d'accord avec l'interprétation de la couche intermédiaire comme roc décomposé.Les auteurs supposent, que la couche intermédiaire se compose de sédiments très denses. Cette opinion prouve toutes les résultats d'observation.

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Air quality model performance evaluation   总被引：3，自引：0，他引：3  

J. C. Chang  S. R. Hanna 《Meteorology and Atmospheric Physics》2004,87(1-3):167-196

Summary This paper reviews methods to evaluate the performance of air quality models, which are tools that predict the fate of gases and aerosols upon their release into the atmosphere. Because of the large economic, public health, and environmental impacts often associated with the use of air quality model results, it is important that these models be properly evaluated.A comprehensive model evaluation methodology makes use of scientific assessments of the model technical algorithms, statistical evaluations using field or laboratory data, and operational assessments by users in real-world applications. The focus of the current paper is on the statistical evaluation component. It is important that a statistical model evaluation exercise should start with clear definitions of the evaluation objectives and specification of hypotheses to be tested. A review is given of a set of model evaluation methodologies, including the BOOT and the ASTM evaluation software, Taylors nomogram, the figure of merit in space, and the CDF approach. Because there is not a single best performance measure or best evaluation methodology, it is recommended that a suite of different performance measures be applied. Suggestions are given concerning the magnitudes of the performance measures expected of good models. For example, a good model should have a relative mean bias less than about 30% and a relative scatter less than about a factor of two.In order to demonstrate some of the air quality model evaluation methodologies, two simple baseline urban dispersion models are evaluated using the Salt Lake City Urban 2000 field data. The importance of assumptions concerning details such as minimum concentration and pairing of data are shown. Typical plots and tables are presented, including determinations of whether the difference in the relative mean bias between the two models is statistically significant at the 95% confidence level.  相似文献   

Tracing the anthropogenic lead sources in coastal sediments of SE-pacific (36 degrees Lat. S) using stable lead isotopes     

Muñoz PN  Garbe-Schönberg CD  Salamanca MA 《Marine pollution bulletin》2004,48(7-8):688-697

This study evaluates the main sources of antropogenic Pb in one of the most industrialized centers of the southern Chilean coast (36 degrees S). Stable lead isotopes ((206)Pb/(207)Pb, (208)Pb/(207)Pb) were used to trace main Pb sources to coastal sediments, considering the suspended particulate matter (SPM) from marine (traps), continental (rivers) and industrial effluents, sediments and leaded gasoline samples. The atmospheric input was evaluated through natural collectors; i.e. Raqui-Tubul salt marsh. Results show that marine samples lie on a trend between industrial effluents ( approximately 1.16, 2.44) and natural sources (1.20, 2.50), not related to gasoline consumption. Salt marsh sediments show comparable isotopic composition to marine samples, suggesting the importance of the atmospheric input in the coastal sediments, not related to the leaded gasoline composition either. The continental input (1.18, 2.48) is highly influenced by precipitation, being difficult to separate both sources (atmosphere and continental runoff), showing also similar isotopic ratio to marine sediments. The signal of industrial emissions is masked with the introduction of Pb with higher isotopic ratios, compared to the values observed in the material collected from traps (SPM approximately 1.19, 2.48). The contribution of more radiogenic Pb by the upwelling is suggested.  相似文献   

Abiotic typology of Polish lakes   总被引：3，自引：0，他引：3  

Agnieszka Kolada  Hanna Soszka  Dorota Cydzik  Ma&#x;gorzata Go&#x;ub 《Limnologica》2005,35(3):145-150

According to the requirements of the Water Framework Directive 2000/60/EC, all member states of the EU have to establish the typology of their surface waterbodies. The typology is aimed at defining the type-specific reference conditions against which the ecological state of waters can be assessed. The abiotic typology of Polish lakes of an area greater than 50 ha was established based on morphometric, hydrographic and physico-chemical data taken from the Polish national monitoring dataset. The current dataset comprises 749 out of a total of 1042 lakes with an area greater than 50 ha in Poland. Lake types were identified based on a combination of abiotic characteristics of lakes specified in Annex II of the Water Framework Directive such as ecoregions, size, altitude, mean depth, geology and an additional factor – Schindler's ratio. Altogether 13 abiotic lake types were established.  相似文献