Environmental Assessment of Heavy Metal Pollution in Freshwater Sediment,Serbia          下载免费PDF全文

Sanja M. Sakan  Gordana J. Dević  Dubravka J. Relić  Ivan B. Anđelković  Nenad M. Sakan  Dragana S. Đorđević 《洁净——土壤、空气、水》2015,43(6):838-845

  相似文献   

Perspectives of Cross-Correlation in Seismic Monitoring at the International Data Centre   总被引：1，自引：0，他引：1  

Dmitry Bobrov  Ivan Kitov  Lassina Zerbo 《Pure and Applied Geophysics》2014,171(3-5):439-468

We demonstrate that several techniques based on waveform cross-correlation are able to significantly reduce the detection threshold of seismic sources worldwide and to improve the reliability of arrivals by a more accurate estimation of their defining parameters. A master event and the events it can find using waveform cross-correlation at array stations of the International Monitoring System (IMS) have to be close. For the purposes of the International Data Centre (IDC), one can use the spatial closeness of the master and slave events in order to construct a new automatic processing pipeline: all qualified arrivals detected using cross-correlation are associated with events matching the current IDC event definition criteria (EDC) in a local association procedure. Considering the repeating character of global seismicity, more than 90 % of events in the reviewed event bulletin (REB) can be built in this automatic processing. Due to the reduced detection threshold, waveform cross-correlation may increase the number of valid REB events by a factor of 1.5–2.0. Therefore, the new pipeline may produce a more comprehensive bulletin than the current pipeline—the goal of seismic monitoring. The analysts’ experience with the cross correlation event list (XSEL) shows that the workload of interactive processing might be reduced by a factor of two or even more. Since cross-correlation produces a comprehensive list of detections for a given master event, no additional arrivals from primary stations are expected to be associated with the XSEL events. The number of false alarms, relative to the number of events rejected from the standard event list 3 (SEL3) in the current interactive processing—can also be reduced by the use of several powerful filters. The principal filter is the difference between the arrival times of the master and newly built events at three or more primary stations, which should lie in a narrow range of a few seconds. In this study, one event at a distance of about 2,000 km from the main shock was formed by three stations, with the stations and both events on the same great circle. Such spurious events are rejected by checking consistency between detections at stations at different back azimuths from the source region. Two additional effective pre-filters are f–k analysis and F _prob based on correlation traces instead of original waveforms. Overall, waveform cross-correlation is able to improve the REB completeness, to reduce the workload related to IDC interactive analysis, and to provide a precise tool for quality check for both arrivals and events. Some major improvements in automatic and interactive processing achieved by cross-correlation are illustrated using an aftershock sequence from a large continental earthquake. Exploring this sequence, we describe schematically the next steps for the development of a processing pipeline parallel to the existing IDC one in order to improve the quality of the REB together with the reduction of the magnitude threshold.  相似文献   

Adaptive Blending of Model and Observations for Automated Short-Range Forecasting: Examples from the Vancouver 2010 Olympic and Paralympic Winter Games     

Monika E. Bailey  George A. Isaac  Ismail Gultepe  Ivan Heckman  Janti Reid 《Pure and Applied Geophysics》2014,171(1-2):257-276

An automated short-range forecasting system, adaptive blending of observations and model (ABOM), was tested in real time during the 2010 Vancouver Olympic and Paralympic Winter Games in British Columbia. Data at 1-min time resolution were available from a newly established, dense network of surface observation stations. Climatological data were not available at these new stations. This, combined with output from new high-resolution numerical models, provided a unique and exciting setting to test nowcasting systems in mountainous terrain during winter weather conditions. The ABOM method blends extrapolations in time of recent local observations with numerical weather predictions (NWP) model predictions to generate short-range point forecasts of surface variables out to 6 h. The relative weights of the model forecast and the observation extrapolation are based on performance over recent history. The average performance of ABOM nowcasts during February and March 2010 was evaluated using standard scores and thresholds important for Olympic events. Significant improvements over the model forecasts alone were obtained for continuous variables such as temperature, relative humidity and wind speed. The small improvements to forecasts of variables such as visibility and ceiling, subject to discontinuous changes, are attributed to the persistence component of ABOM.  相似文献   

Weak-anisotropy approximations of P-wave phase and ray velocities for anisotropy of arbitrary symmetry     

Véronique Farra  Ivan Pšenčík 《Studia Geophysica et Geodaetica》2016,60(3):403-418

We test the accuracy of the previously derived weak-anisotropy approximations of the P-wave phase and ray (group) velocities. The formulae are of varying accuracy, and are applicable to weak or moderate anisotropy of arbitrary symmetry and orientation. They have a form of expressions for squares of phase velocity depending on the phase-velocity direction and of ray velocity depending on the ray-velocity direction. Both velocities are expressed in terms of three elements of the rotated Christoffel matrix, which depend linearly on the parameters specifying the medium, the weak-anisotropy parameters. The least accurate formulae are fully independent of the choice of a reference isotropic medium and depend linearly on weak-anisotropy parameters. The most accurate formulae depend only slightly on the ratio of S- and P-wave velocities of a reference medium, their dependence on weak-anisotropy parameters being quadratic. We show that the accuracy of the formulae is quite high, in fact, in some cases, it is close to the accuracy of the socalled anelliptic approximations, very accurate approximations based on a perturbation of the elliptical anisotropy.  相似文献   

Book Review: Seismic Ray Theory By Vlastislav Červený, Cambridge University Press, 2001, 722 pp., hardcover,euro 45 (£90), ISBN 0-521-36671-2     

Pšenčík  Ivan 《Studia Geophysica et Geodaetica》2002,46(2):383-386

Studia Geophysica et Geodaetica -  相似文献   

Approximate Relation Between the Ray Vector and the Wave Normal in Weakly Anisotropic Media     

Pšenčík  Ivan  Vavryčuk  Václav 《Studia Geophysica et Geodaetica》2002,46(4):793-807

Determination of the ray vector (the unit vector specifying the direction of the group velocity vector) corresponding to a given wave normal (the unit vector parallel to the phase velocity vector or slowness vector) in an arbitrary anisotropic medium can be performed using the exact formula following from the ray tracing equations. The determination of the wave normal from the ray vector is, generally, a more complicated task, which is usually solved iteratively. We present a first-order perturbation formula for the approximate determination of the ray vector from a given wave normal and vice versa. The formula is applicable to qP as well as qS waves in directions, in which the waves can be dealt with separately (i.e. outside singular directions of qS waves). Performance of the approximate formulae is illustrated on models of transversely isotropic and orthorhombic symmetry. We show that the formula for the determination of the ray vector from the wave normal yields rather accurate results even for strong anisotropy. The formula for the determination of the wave normal from the ray vector works reasonably well in directions, in which the considered waves have convex slowness surfaces. Otherwise, it can yield, especially for stronger anisotropy, rather distorted results.  相似文献   

Les argiles bleues du Cambrien inférieur de Saint-Pétersbourg et leur fissuration. Implications pour des stockages souterrains     

Marcel Arnould  Jean-Yves Boisson  Ivan P Ivanov 《Comptes Rendus Geoscience》2002,334(16):1135

The Lower Cambrian Saint Petersburg blue clays are composed of predominant illite and chlorite, sometimes accompanied by kaolinite. The <0.1 μm fraction has a high content of illite–smectite mixed layers. Particle-size distribution is more than 50% of clay particles and about 30% of silts. These blue clays correspond to plastic (and soft) clays; they may be compared to the Callovian clays of Bure (France), where storage of natural waste is envisaged. To cite this article: M. Arnould et al., C. R. Geoscience 334 (2002) 1135–1140.

Résumé

Les « argiles bleues » du Cambrien Inférieur de Saint-Pétersbourg sont constituées d'illite dominante et de chlorite, avec parfois présence de kaolinite. Des interstratifiés illite/montmorillonite sont très abondants dans la phase <0,1 μm. Du point de vue granulométrique, outre plus de 50% de particules argileuses, il existe une phase silteuse de l'ordre de 30%. Du point de vue pétrophysique, ce sont des argiles plastiques, de consistance molle. Elles sont subhorizontales et ont jusqu'à 116 m d'épaisseur. Outre l'absence de métamorphisme, malgré leur âge, leur caractère le plus remarquable est leur réseau de fracturation, bien observable en carrière. Les joints sont nets, sans remplissage ni cimentation. Les plans verticaux sont particulièrement développés. Le volume unitaire des blocs de matrice ne dépasse guère 1 m³. Des traces d'oxydation témoignent de circulations d'eau. Ces argiles silteuses anciennes peuvent aider à mieux connaı̂tre et comprendre les argilites silteuses épigénétiques calloviennes du site de Bure (Haute-Marne, France), où un stockage souterrain de déchets nucléaires est envisagé. Pour citer cet article : M. Arnould et al., C. R. Geoscience 334 (2002) 1135–1140.  相似文献   

In situ Measurement of H2O and CH4 with Telecommunication Laser Diodes in the Lower Stratosphere: Dehydration and Indication of a Tropical Air Intrusion at Mid-Latitudes     

Georges Durry  Alain Hauchecorne  Joelle Ovarlez  Henri Ovarlez  Ivan Pouchet  Virginie Zeninari  Bertrand Parvitte 《Journal of Atmospheric Chemistry》2002,43(3):175-194

Telecommunication laser diodes emitting near 1.39 m and 1.65 m in combination with direct-differential absorption spectroscopy are efficient tools to monitor in situ stratospheric H₂O andCH₄ with a good precision error (a few percents), a high temporal resolution (ranging from 10 ms to 1 s), a large dynamic range in the concentration measurements (four orders of magnitude) and a high selectivity in the analyte species. To illustrate the capability of laser probing technique, we report balloonborne H₂Oand CH₄ simultaneous measurements obtained on October 2001 atmidlatitudes (43° N). The H₂O vertical profile achieved with the lasersensor in the lower stratosphere is compared with the H₂O data yielded by a balloonborne frost-point hygrometer. The total hydrogen mixing ratio in the lower stratosphere, 2[CH₄] + [H₂O], appears to beconstant at 7.5 ± 0.1 ppmv. Nevertheless, an unexpected largedehydration of 0.5 ppmv was detected by both the laser sensor and thehygrometer between 16 km and 23 km. We suspect the occurrence of a tropicalair intrusion into mid-latitudes. We support this interpretation using a high-resolution advection model for potential vorticity.  相似文献   

A CENSUS OF THE METEORITES OF ROOSEVELT COUNTY,NEW MEXICO     

Glenn I. Huss  Ivan E. Wilson 《Meteoritics & planetary science》1973,8(3):287-290

In the five years from June, 1967, to June, 1972, a total of 99 meteorites were found in Roosevelt County, New Mexico and in adjoining Curry County. Of this number, 74 were found by one man. The finds include two achondrites, one pallasite, one carbonaceous chondrite, and 95 chondrites. They appear to represent more than 50 separate meteorite falls. The finding of a large number of meteorites in a small area provides data for an estimate of the probable quantity and average size of the meteorite specimens reaching the earth. The problems involved in allocating a total of 17 available local place names among more than 50 meteorite falls are discussed.  相似文献   

Magnitude of harvest of Atlantic horseshoe crabs,<Emphasis Type="Italic">Limulus polyphemus</Emphasis>, in Pleasant Bay,Massachusetts     

Deborah?Rutecki  Ruth?H.?CarmichaelEmail author  Ivan?Valiela 《Estuaries and Coasts》2004,27(2):179-187

Atlantic horseshoe crabs,Limulus polyphemus, are currently harvested for biomedical, scientific, and bait purposes. In recent years, changes in population abundance and magnitude of harvesting have raised concerns about the status of this resource. We found horseshoe crab harvest in Pleasant Bay, Massachusetts, was selective by sex and size. Biomedical harvest preferred larger individuals and females, the scientific harvest preferred smaller individuals and males, and the bait harvest preferred females. Total 2001 harvest for all purposes accounted for the mortality of ∼1–2% the adult population. Biomedical harvest accounted for the greatest loss of horseshoe crabs from Pleasant Bay, ∼1–1.6% of the total population. Although biomedical harvest had the lowest associated mortality rate (∼10–15%), many more crabs were harvested from Pleasant Bay for biomedical purposes than for other uses. The scientific harvest accounted for the mortality of ∼0.4% of the population, and bait harvest accounted for the smallest mortality at ∼0.06% of the population. Harvest mortality rate was estimated to be lower in Pleasant Bay than in other Cape Cod areas and may be lower than natural mortality in the population. This study is the first qualitative investigation of commercial harvest on horseshoe crab populations and emphasizes that harvest pressures on different populations need to be individually evaluated.  相似文献