Paleomagnetic study of Middle-Upper Jurassic sediments from the Polish segment of the Pieniny Klippen Belt     

Jadwiga Kruczyk  Magdalena Kądziałko-Hofmokl 《Acta Geophysica》2006,54(2):205-224

Middle-Upper Jurassic carbonates exposed in 7 separate fragments of three tectonic units were sampled in the Polish segment of the Pieniny Klippen Belt in 1981, before construction of the Niedzica-Czorsztyn dam. Demagnetization experiments performed about 20 years ago and analyzed lately with modern program package revealed the presence of Middle Miocene overprints acquired in the normal and reversed geomagnetic field, and pre-folding components of natural remanence acquired during the Middle-Upper Jurassic. A paleolatitude of 36N±7° was obtained for the studied area for this time on the basis of 3 normal and 1 reversed components. Three pre-folding pole positions are situated between pole positions of the normal and reversed Stable European Middle Jurassic field. The obtained paleomagnetic results imply several prefolding (pre-Upper Miocene) and postfolding (post-Upper Miocene) episodes of rotations of the studied fragments.  相似文献   

Method for correction of the prestack migration amplitude of converted waves     

Andrzej Kostecki  Anna Półchłopek 《Acta Geophysica》2006,54(2):113-125

The paper presents a method for correction of amplitude of prestack migration using the reflectivity function. The solution of wave equations for heterogeneous media expressed in the form of Neumann series for converted waves was used to find the reflectivity function. The performance of the proposed method was verified using synthetic models of wavefields. The synthetic models of wavefields were also used to compare amplitude correction levels required by the presented method and the standard amplitude correction methods, i.e., the methods using the spherical divergence and extention factor.  相似文献   

Editorial: Progress in urban climate     

T. Oke  K. Kłysik  C. Bernhofer 《Theoretical and Applied Climatology》2006,84(1-3):1-2

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Structural evidence for the sorption of Ni(II) atoms on the edges of montmorillonite clay minerals: a polarized X-ray absorption fine structure study   总被引：1，自引：0，他引：1  

Rainer Dähn  André M Scheidegger  Michel L Schlegel  Bart Baeyens  Daniel Chateigner 《Geochimica et cosmochimica acta》2003,67(1):1-15

The nature of surface complexes formed on Ni uptake onto montmorillonite (a dioctahedral smectite) has been investigated over an extended time period by polarized extended X-ray absorption fine structure (P-EXAFS) spectroscopy. Self-supporting films of Ni-sorbed montmorillonite were prepared by contacting Ni and montmorillonite at pH 7.2, high ionic strength (0.3 M NaClO₄), and low Ni concentration ([Ni]_initial = 19.9 μM) for 14- and 360-d reaction time. The resulting Ni concentration on the clay varied from 4 to 7 μmol/g. Quantitative texture analysis indicates that the montmorillonite particles were well orientated with respect to the plane of the film. The full width at half maximum of the orientation distribution of the c* axes of individual clay platelets about the normal to the film plane was 44.3° (14-d reaction time) and 47.1° (360-d reaction time). These values were used to correct the coordination numbers determined by P-EXAFS for texture effects. Ni K-edge P-EXAFS spectra were recorded at angles between the incident beam and the film normal equal to 10, 35, 55, and 80°. Spectral analysis led to the identification of three nearest cationic subshells containing 2.0 ± 0.5 Al at 3.0 Å and 2.0 ± 0.5 Si at 3.12 Å and 4.0 ± 0.5 Si at 3.26 Å. These distances are characteristic of edge-sharing linkages between Al and Ni octahedra and of corner-sharing linkages between Ni octahedra and Si tetrahedra, as in clay structures. The angular dependence of the Ni-Al and Ni-Si contributions indicates that Ni-Al pairs are oriented parallel to the film plane, whereas Ni-Si pairs are not. The study reveals the formation of Ni inner-sphere mononuclear surface complexes located at the edges of montmorillonite platelets and thus that heavy metals binding to edge sites is a possible sorption mechanism for dioctahedral smectites. Data analysis further suggests that either the number of neighboring Al atoms slightly increases from 1.6 to 2 or that the structural order of the observed surface complexes increases from 0.01 Ų to 0.005 Ų with increasing reaction time. On the basis of the low Ni-Al coordination numbers, it appears that over an extended reaction time period of 1 yr the diffusion of Ni atoms in the octahedral layer is not the major uptake mechanism of Ni onto montmorillonite.  相似文献   

Explicit Symplectic Integrator for Highly Eccentric Orbits     

Sławomir Breiter 《Celestial Mechanics and Dynamical Astronomy》1998,71(4):229-241

An explicit symplectic integrator is constructed for perturbed elliptic orbits of an arbitrary eccentricity. The perturbation should be Hamiltonian, but it may depend on time explicitly. The main feature of the integrator is the use of KS variables in the ten-dimensional extended phase space. As an example of its application the motion of an Earth satellite under the action of the planet's oblateness and of lunar perturbations is studied. The results confirm the superiority of the method over a classical Wisdom–Holman algorithm in both accuracy and computation time. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Chlorophyll a and phytoplankton in the Pomeranian Bay during and after the flood event     

Sławomira Gromisz  Mariusz Zalewski  Stanisław Ochocki  Janina M. Kownacka 《Ocean Dynamics》1998,50(2-3):203-213

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Thermal metamorphism of primitive meteorites—XL The enstatite meteorites: origin and evolution of a parent body     

Swarajranjan Biswas  Thomas Walsh  Gerhard Bart  Michael E. Lipschutz 《Geochimica et cosmochimica acta》1980,44(12):2097-2110

We report neutron activation data for Ag, As, Bi, Cd, Co, Cs, Cu, Ga, In, Rb, Se, Te, Tl and Zn in samples of Abee heated at temperatures of 1000–1400°C in a low-pressure environment (initially ~ 10^?5 atm H₂) and in 9 enstatite achondrites (aubrites) and the silicate portion of the unique stony-iron, Mt Egerton. Trace element losses in heated Abee progress with temperature, the lowest retention being 2.4 × 10^?6 of initial contents. These data indicate trace element loss above 1000°C via diffusion-controlled processes having apparent activation energies of 8–55 kcal/mol ; only Co exhibits a significantly higher energy. These trace element data and those for aubrites, Mt Egerton and E4–6 chondrites, and mineralogic and isotopic evidence link all enstatite meteorites to a common parent body. Volatile, mobile elements vary inversely with cobalt content in aubrites and Mt Egerton but directly in E4–6 chondrites; this is inconsistent with all genetic models positing fractionation of such elements during nebular condensation and accretion. However, the data are consistent with the idea that aubrites and Mt. Egerton reflect fractional crystallization of a magma produced from enstatite chondrite-like parent material (probably E6) and late introduction of chalcophiles and mobile elements transported by FeS-Fe eutectic from an E4–6 region experiencing open-system metamorphism. As suggested earlier, the only primary process that affected enstatite meteorites involved fractionation of non-volatile lithophiles from sulfides and metal during condensation and accretion of chondritic parent material from the nebula. If, as seems likely, volatile/mobile elements reflect secondary processes, they can only be used to establish alteration conditions within the enstatite parent body and not to estimate temperatures during primary nebular condensation and accretion.  相似文献   

Tag retention and survival of fish tagged in controlled pond experiments     

Wiesław Wiśniewolski  Jerzy Nabiałek 《Aquatic Sciences - Research Across Boundaries》1993,55(2):143-152

Fish survival, tag retention and tag loss were evaluated in pond experiments and described by linear regression equations. Tagging of fish had no significant influence on their survival. However, loss of tags caused strong differences between actual fish survival and the survival rate e^–z estimated on recovered tags. Mathematical functions were derived to correct tag loss. Values of those functions depend upon the type of tag and time after tagging. The B-type of tagging, which approximated the Swedish Carlin method, appeared to be most effective. The rate of tag loss was independent of the fish species (common carp, tench) used in the experiments.  相似文献   

Rapid migration of heavy metals and <Superscript>137</Superscript>Cs in alluvial sediments,Upper Odra River valley,Poland     

Dariusz Ciszewski  Agnieszka Czajka  Sylwia Błażej 《Environmental Geology》2008,55(7):1577-1586

The studies presented explore post-depositional changes of zinc, cadmium, lead, manganese and ¹³⁷Cs distribution in alluvial sediments accumulated in the upper Odra River valley in southern Poland. The rate of these changes was estimated by comparing metal and ¹³⁷Cs distributions in four vertical alluvial profiles with a history of river pollution and sediment deposition. The untypical ¹³⁷Cs distribution with peaks in the surface 40–60 cm and lower down, even at a depth of 2.5 m in strata deposited before the beginning of nuclear tests in 1954, indicates rapid post-depositional migration of this isotope from the surface and its retention in lower, less permeable layers. Moreover, the highest concentrations of lead, zinc and cadmium were found at a depth of 4 m in sediments accumulated in the mid-nineteenth century in spite of the growth of industrialization and the pollution of the Odra River with heavy metals until the end of the twentieth century. The post-depositional changes in heavy metals and ¹³⁷Cs are rapid in comparison with the slow element migration usually observed in uninundated soils. This difference is explained by the frequent and easy infiltration of polluted river water into the gravelly and sandy sediments present in the profiles.  相似文献   

Quantifying the effectiveness of climate change mitigation through forest plantations and carbon sequestration with an integrated land-use model     

Jelle G van Minnen  Bart J Strengers  Bas Eickhout  Rob J Swart  Rik Leemans 《Carbon balance and management》2008,3(1):1-20

Background

Carbon plantations are introduced in climate change policy as an option to slow the build-up of atmospheric carbon dioxide (CO₂) concentrations. Here we present a methodology to evaluate the potential effectiveness of carbon plantations. The methodology explicitly considers future long-term land-use change around the world and all relevant carbon (C) fluxes, including all natural fluxes. Both issues have generally been ignored in earlier studies.

Results

Two different baseline scenarios up to 2100 indicate that uncertainties in future land-use change lead to a near 100% difference in estimates of carbon sequestration potentials. Moreover, social, economic and institutional barriers preventing carbon plantations in natural vegetation areas decrease the physical potential by 75–80% or more. Nevertheless, carbon plantations can still considerably contribute to slowing the increase in the atmospheric CO₂ concentration but only in the long term. The most conservative set of assumptions lowers the increase of the atmospheric CO₂ concentration in 2100 by a 27 ppm and compensates for 5–7% of the total energy-related CO₂ emissions. The net sequestration up to 2020 is limited, given the short-term increased need for agricultural land in most regions and the long period needed to compensate for emissions through the establishment of the plantations. The potential is highest in the tropics, despite projections that most of the agricultural expansion will be in these regions. Plantations in high latitudes as Northern Europe and Northern Russia should only be established if the objective to sequester carbon is combined with other activities.

Conclusion

Carbon sequestration in plantations can play an important role in mitigating the build-up of atmospheric CO₂. The actual magnitude depends on natural and management factors, social barriers, and the time frame considered. In addition, there are a number of ancillary benefits for local communities and the environment. Carbon plantations are, however, particularly effective in the long term. Furthermore, plantations do not offer the ultimate solution towards stabilizing CO₂ concentrations but should be part of a broader package of options with clear energy emission reduction measures.  相似文献