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1.
Itaipu Lake, which includes the Itaipu hydroelectric power plant, is one of the largest dams in the world and has a strong relationship with its surroundings. The flooded area has multiple uses such as navigation, recreation, water abstraction for industrial, urban and agricultural irrigation. The lake is located at the frontier between Brazil, Argentina and Paraguay. In this study, superficial sediments collected from nine sampling sites were analysed for grain size, organic matter and 16 priority polycyclic aromatic hydrocarbons (PAHs) using high-performance liquid chromatography (HPLC) with fluorescence detector. The total concentration of PAHs in the dry sediment ranged from 35.21 to 685.37 µg kg?1. Diagnostic ratios showed that the possible source of PAHs in the Itaipu Lake could be pyrolitic and petrogenic. The potential toxicity of sediment of PAHs varied from not detected to 127.70 µg g?1, suggesting that some adverse ecological effects would arise due to PAHs in these sediments.  相似文献   

2.
Electrical conductivities of Ni2SiO4, Fe2SiO4, and MgSiO3 were measured on synthetic powders in the temperature range 340° to 1,100° C and at pressures up to 20 kbars. For ternary compounds such as olivines and pyroxenes the control of two further variables, like the chemical activities of two components are needed, besides temperature and pressure. The activities of the corresponding binary oxides were controlled by equilibrating the samples with their neighbour-phases. Control of the oxygen partial pressure was achieved by buffer techniques. From the slopes of the lg σ vs. 1/T lines the activation energies were calculated for 10 kbar: 0.56 eV and 2.7 eV for Ni2SiO4 in equilibrium with SiO2 and Ni/NiO-buffer for the temperature range 500°–800°C and 800°–1,000°C resp. 0.52 eV for Fe2SiO4 in equilibrium with SiO2 and metallic iron, and 0.38 eV in equilibrium with SiO2 and magnetite; 1.11 eV for MgSiO3 in equilibrium with SiO2, and 1.25 eV in equilibrium with Mg2SiO4.  相似文献   

3.
This work is one of the stages of study of the deep C-O-H fluid and investigates the behavior of polycyclic aromatic hydrocarbons (PAHs) under conditions of the Earth’s mantle. The composition of the C-O-H fluid in the upper mantle is estimated as a mixture of H2O and CH4 with a minor amount of H2 and heavier hydrocarbons. Some theoretical calculations show that the stability of heavy hydrocarbons (alkanes, alkenes, and PAHs) increases with an increase in temperature. This paper presents the results of an XRD study of PAHs stability in multianvil presses on a Spring-8 accelerator (Japan). The primary compositions were chosen according to the abundance of PAHs in nature. In situ diffraction spectrums were recorded to determine the PAHs stability field. It was established that the PAHs become unstable at a pressure of 6–9 GPa and a temperature of 873–1073 K.  相似文献   

4.
Five different refraction formulas were applied to SiO2 polymorphs in order to determine the most suitable refractive index-density relation. 13 SiO2 polymorphs with topological different tetrahedral frameworks are used in this study including eight new low density SiO2 polymorphs — so called “guest free porosils”. These SiO2 polymorphs cover a density range from 1.76 to 2.92 g/cm3. The mean refractive indices (ovn) of the porosils have been determined by the immersion method, the densities (ρ) were calculated from the unit cell parameters. Assuming the polarizability (α) of all SiO2 polymorphs to be constant the general refractivity formula $$\{ 2\overline {11} 0\} \langle 0001\rangle $$ turned out to be the most suitable for SiO2 polymorphs. Regression analysis yields an electronic overlap parameter b=1.2(1).  相似文献   

5.
Infrared absorption spectra of the high-pressure polymorphs β-Mg2SiO4 and β-Co2SiO4 have been measured between 0 and 27 GPa at room temperature. Grüneisen parameters determined for 11 modes of β-Mg2SiO4 (frequencies of 300 to 1,050 cm?1) and 5 modes of β-Co2SiO4 (490 to 1,050 cm?1) range between 0.8 and 1.9. Averaging the mid-infrared spectroscopic data for β-Mg2SiO4 yields an average Grüneisen parameter of 1.3 (±0.1), in good agreement with the high-temperature thermodynamic value of 1.35. Similarly, we find a value of 1.05 (±0.2) for the average spectroscopic Grüneisen parameter of β-Co2SiO4.  相似文献   

6.
The object of the paper is to analyze changes in modal and port allocation of general cargo flows in Sweden's foreign trade between 1960 and 1976. It summarizes some results of a forthcoming report on the project ‘Tendencies in Liner Shipping’ financed by the ‘Transport Research Delegation’, Stockholm.  相似文献   

7.
The decomposition of fayalite (Fe2SiO4) in oxygen potential gradients is studied at T=1,418 K. The compound will be decomposed into its component oxides wüstite, Fe1?δO, and silica, SiO2, by the simultaneous action of two different oxygen partial pressures, exceeding a critical ratio, despite the fact that fayalite is stable at both the lower and the higher oxygen potential. A quantitative analysis of the decomposition process caused by defect fluxes within the bulk Fe2SiO4 is given.  相似文献   

8.
The data published earlier on zircon and sphene fission track ages and annealing are discussed in the light of different etching conditions used for age determination and annealing experiments in order to explain the age discordances of some zircon and sphene pairs, as well as numerous closing temperatures obtained for individual minerals. Using the new set of simple etching conditions, zircon (KOH melt) and sphene (HF+HCl), the annealing experiments indicate that tracks in sphene are annealed more easily than in zircon. The closing temperature of zircon and sphene have been calculated at 300° and 250° C respectively. The study reveals that both the fission track age and the closing temperature of a mineral can vary considerably if different etchants are used. For different etching conditions the closing temperatures (T) of sphene have the following order: T NaOH> T HF+HCl+HNO3+H2O> THF+HCl>THCl. An alternative method can be used to obtain thermal histories of rocks by selectively applying various etchants on the same mineral.  相似文献   

9.
Rates of shoreline change and overwash penetration distances were calculated for barrier islands along the Louisiana, Mississippi, and Alabama coasts with the orthogonal grid mapping system (OGMS). Average rates of shoreline change are exceptionally high in Louisiana, being of the order ?4.7 to ?7.4 m yr?1. Mississippi and Alabama recession rates are lower and range from ?2.0 to ?3.1 m yr?1 over the period of record. Erosion rates along the shorelines of these islands have remained relatively constant over the period of study with five exceptions in coastal Louisiana and the Chandeleur-Breton Islands Arc, and two exceptions along the Mississippi-Alabama barrier islands where they have accelerated. Mean overwash penetration is greatest along Dauphin Island, Alabama, and Cat Island, Mississippi: 207.6 and 197.9 m, respectively. The Chandeleur-Brenton Islands Arc range from 88.1 m at the central barrier to 180.4 along the flanks. The Mississippi islands range from 105.2 m on Ship Island to 200.5 m along central Horn Island. Mean overwash penetration along the Louisiana barriers is highly variable: 46.3 to 211.4 m.  相似文献   

10.
Experiments on the join Al2SiO5-“Mn2SiO5” of the system Al2O3-SiO2-MnO-MnO2 in the pressure/temperature range 10–20 kb/900–1050° C with gem quality andalusite, Mn2O3, and high purity SiO2 as starting materials and using /O2-buffer techniques to preserve the Mn3+ oxidation state had following results: At 20 kb/1000°C orange-yellow kyanite mixed crystals are formed. The kyanite solid solubility is limited at about (Al1.88Mn 0.12 3+ )SiO5 and, thus, equals approximately that on the join Al2SiO5-“Fe2SiO5” (Langer and Frentrup, 1973) indicating that there is no Jahn-Teller stabilisation of Mn3+ in the kyanite matrix. 5 mole % substitution causes the kyanite lattice constants a o, b o, c o, and V o to increase by 0.015, 0.009, 0.014 Å, and 1.6 Å3, resp., while α, β, γ, remain unchanged. Between 10 and 18 kb/900°C, Mn3+-substituted, strongly pleochroitic (emeraldgreen-yellow) andalusitess (viridine) was obtained. At 15 kb/900°C, the viridine compositional range is about (Al1.86Mn 0.14 3+ )SiO5-(Al1.56Mn 0,44 3+ )SiO5. Thus, Al→Mn3+ substitutional degrees are appreciably higher in andalusite than in kyanite, proving a strong Jahn-Teller effect of Mn3+ in the andalusite structure, which stabilises this structure type at the expense of kyanite and sillimanite and, thus, enlarges its PT-stability range extremely. 17 mole % substitution cause the andalusite constants a o, b o, c o, and V o to increase by 0.118, 0.029, 0.047 Å and 9.4 Å3, resp. At “Mn2SiO5”-contents smaller than about 7 mole %, viridine coexists with Mn-poor kyanite. At “Mn2SiO5”-concentrations higher than the maximum kyanite or viridine miscibility, braunite (tetragonal, ideal formula Mn2+Mn3+[O8/Si04]), pyrolusite and SiO2 were found to coexist with the Mn3+-saturated ky ss or and ss, respectively. In both cases, braunites were Al-substituted (about 1 Al for 1 Mn3+). Pure synthetic braunites had the lattice constants a o 9.425, c o, 18.700 Å, V o 1661.1 Å3 (ideal compn.) and a o 9.374, c o 18.593 Å3, V o 1633.6 Å3 (1 Al for 1 Mn3+). Stable coexistence of the Mn2+-bearing phase braunite with the Mn4+-bearing phase pyrolusite was proved by runs in the limiting system MnO-MnO2-SiO2.  相似文献   

11.
Polycyclic aromatic hydrocarbons (PAHs) are a group of aromatic hydrocarbons with high toxicity to human health. PAH emissions from industrial activities have become the primary sources of PAH contamination in Chinese watersheds. Here, we analyzed 10 individual priority PAHs in 120 water samples taken from middle reach of Huaihe River, China. The results show that the PAH levels in studied watershed are significantly lower as compared to other Chinese watersheds, approaching or slightly exceeding the PAH levels in watersheds from selected European and North American countries. We observe rather large variation in spatial and vertical PAH distributions, pointing to PAH inputs from local industrial emissions, and PAH cycle among atmosphere, water and sediment. Individual PAH ratios (i.e., phenanthrene/anthracene and fluorene/pyrene) and principal components analysis suggest a primarily pyrolytic PAH sources (combustion of coal and coke) in water column. Other accompanying PAH sources include emissions from steel industry and gasoline. Total toxic benzo[a]pyrene equivalent of PAHs in studied water column indicates that PAHs in watershed of middle reach of Huaihe River pose limited toxicity to the environment.  相似文献   

12.
Dykes of Chitaldurg and Newer Dolerite I are OFB and represent early attempts to rift and to generate oceanic crust. Shimoga dykes are CAB and belong to orogenic phase. Guntur dykes and Ananthapur-Chittoor dykes are OIB and these are related to ‘hot spot’. Newer Dolerite II is CONB and belongs to healing and filling of fractured crust. The Cuddapah dykes are transitional to all magma types and these represent a compound event of rifting and filling of fractured continental crust.  相似文献   

13.
Constants occurring in Seggern and Blandford's analytic expression of reduced displacement potential are computed for shot media of alluvium, salt and tuff. The amplitude spectra as well as impulse response of the source function for models of Haskell and Seggern are studied as a function of yield. It is shown that the maximum in amplitude spectrum shifts to lower frequency with increase in yield for a given model. The duration of impulse response is longer for Seggern's model as compared to Haskell's model for a given yield.  相似文献   

14.
The fish assemblages of two South Carolina estuarine tide pools located in the North Edisto River were sampled from June to October 1977, and during June and July 1978, by haul seine, lift net and channel net. The nekton was dominated numerically byFundulus heteroclitus, Leiostomus xanthurus, Menidia menidia andAnchoa mitchilli. Oyster reef areas were dominated numerically byGobiosoma bosci andF. heteroclitus. The relative abundance of tide pool fishes differs from deep water areas of the North Edisto River as described from otter trawls, but is similar to that described by others for South Carolina tidal creeks.  相似文献   

15.
Spectropolarimetric observations of a number of Active Galactic Nuclei obtained using the SCORPIO-2 aperture focal reducer installed on the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences are used to estimate physical parameters of these objects. The measured polarization and its wavelength dependence are consistent with the expectations of a standard accretion-disk model taking into account the effect of Faraday depolarization over the mean free path of the emitted photons. Estimates of the magnetic field in the accretion disk near the innermost stable orbit and the spin of the accreting central black hole are obtained. It is concluded that supermassive black holes with standard accretion disks and equal magnetic and radiative pressures are primarily Kerr black holes.  相似文献   

16.
An artificial neural network (ANN) toolbox is created within GIS software for spatial interpolation, which will help GIS users to train and test ANNs, perform spatial analysis, and display results as a single process. The performance is compared to that of the open source Fast Artificial Neural Network library and conventional interpolation methods by creating digital elevation models (DEMs) given that nearly exact solutions exist. Simulation results show that the advanced backpropagations such as iRprop speed up the learning, while they can get stuck in a local minimum depending on initial weight sets. Besides, the division of input–output examples into training and test data affects the accuracy, particularly when the distribution of the examples is skewed and peaked, and the number of data is small. ANNs, however, show the similar performance to inversed distance weighted or kriging and outperform polynomial interpolations as a global interpolation method in high-dimensional data. In addition, the neural network residual kriging (NNRK) model, which combines the ANN toolbox and kriging within GIS software, is performed. The NNRK outperforms conventional methods and well captures global trends and local variations. A key outcome of this work is that the ANN toolbox created within the de facto standard GIS software is applicable to various spatial analysis including hazard risk assessment over a large area, in particular when there are multiple potential causes, the relationship between risk factors and hazard events is not clear, and the number of available data is small given its performance for DEM generation.  相似文献   

17.
Infrared (IR) absorption spectra are presented for olivine (α) and spinel (γ) phases of A2SiO4 (A=Fe, Ni, Co) and Mg2GeO4. IR spectra of β phase (“modified spinel”) Co2SiO4 and of α Mg2SiO4 are also included. These results provide reference spectra for the identification of olivine high-pressure polymorphs. Isostructural and isochemical correlations are used to support a general interpretation of the spectra and to predict the spectrum of γ Mg2SiO4. A γ Mg2GeO4 sample equilibrated at 1,000° C shows evidence of partial inversion, but one equilibrated at 730° C does not. This suggests that partial inversion could occur in silicate spinels at elevated temperatures and pressures, however no evidence of inversion is seen in the ir spectra of the silicates in this study.  相似文献   

18.
It is a significant task to evaluate the seafloor stability for the exploitation of marine resources and the construction of marine structures. This paper analyzes the impact factors of submarine slope instability using geological and geophysical data of the Baiyun Sag in the Pearl River Mouth Basin and builds the evaluation index system of submarine slope instability. The weight of each index is calculated by analytic hierarchy process method to weaken subjective effect. Gray clustering method is applied to estimate the risk of submarine slope instability in Baiyun Sag qualitatively and quantitatively. The assessment standard is divided into five grades, and the whitening function of each gray cluster is determined by the assessment scheme. The gray evaluation weight vector of each indicator is calculated by the table-dispatching method. The gray assessment value is estimated by making the gray assessment weight vector single value, and the gray grade is determined according to the maximum principle. The evaluation results show quantitatively that the risk grade of submarine slope instability in the Baiyun Sag is medium, and the gray clustering method is reasonable and feasible.  相似文献   

19.
A pyralspite garnet from an anomalously magnetic concentrate of a pegmatitic cassiterite ore has been investigated using 57Fe nuclear gamma-ray resonance spectroscopy. The quadrupole splitting and isomer shift values of 3.6 mm/s and 1.4 mm/s, respectively, are among the largest observed for Fe2+ ions and indicate a very low covalency of the dodecahedral Fe2+ — O2-bonds. These data support the more recent and lower value (10.2–10.1 kcal/ mole) of White and Moore (1972) for the CFSE of the dodecahedral Fe2+ ion and suggest that the CFSE should be a useful approximation to the site preference energy of Fe2+ for this site.  相似文献   

20.
In this paper we present a theoretical investigation of the structures and relative stability of the olivine and spinel phases of Mg2SiO4. We use both a purely ionic model, based on the Modified Electron Gas (MEG) model of intermolecular forces, and a bond polarization model, developed for low pressure silica phases, to investigate the role of covalency in these compounds. The standard MEG ionic model gives adequate structural results for the two phases but incorrectly predicts the spinel phase to be more stable at zero pressure. This is mainly because the ionic modeling of Mg2SiO4 only accounts for 95 percent of the lattice energy. The remainder can be attributed to covalency and many-body effects. An extension of the MEG ionic model using “many-body” pair potentials corrects the phase stability error, but predicts structures which are in poorer agreement with experiment than the standard ionic approach. In addition, calculations using these many-body pair potentials can only account for 10 percent of the missing lattice energy. This model predicts an olivine-spinel phase transition of 8 GPa, below the experimental value of 20 GPa. Therefore, in order to understand more fully the stability of these structures we must consider polarization. A two-shell bond polarization model enhances the stability of both structures, with the olivine structure being stabilized more. This model predicts a phase transition at about 80 GPa, well above the observed value. Also, the olivine and spinel structures calculated with this approach are in poorer agreement with experiment than the ionic model. Therefore, based on our investigations, to properly model covalency in Mg2SiO4, a treatment more sophisticated than the two-shell model is needed.  相似文献   

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