Sources of polyfluoroalkyl compounds in the North Sea, Baltic Sea and Norwegian Sea: Evidence from their spatial distribution in surface water   总被引：2，自引：0，他引：2  

Lutz Ahrens  Wolfgang Gerwinski  Ralf Ebinghaus 《Marine pollution bulletin》2010,60(2):255-5700

The spatial distribution of 15 polyfluoroalkyl compounds (PFCs) in surface water was investigated in the North Sea, Baltic Sea and Norwegian Sea. In addition, an interlaboratory comparison of the sampling techniques and analysis was conducted. Highest concentration in the North Sea was found near the coast, whereas the ∑PFC concentration decreased rapidly from 18.4 to 0.07 ng l⁻¹ towards the open North Sea. The river Elbe could identify as a local input source for PFCs into the North Sea, whereas perfluorobutanoic acid (PFBA) was transported into the sampling area with the easterly current. In contrast to the North Sea, the distribution of PFCs in the Baltic Sea was relatively homogenous, where diffuse sources dominated. In general, the composition profile was influenced from local sources caused by human activities, whereas atmospheric depositions of here analysed PFCs were negligible, but it could have possibly an influence on low contaminated sites like the open North Sea or Norwegian Sea.  相似文献   

Single-grain and multigrain luminescence dating of on-ice and lake-bottom deposits at Lake Hoare,Taylor Valley,Antarctica     

G.W. Berger  P.T. Doran  K.J. Thomsen 《Quaternary Geochronology》2010,5(6):679-690

The large radiocarbon (¹⁴C) reservoir effect in Antarctica varies regionally and with settings. Luminescence sediment dating has potential as an alternate geochronometer. Extending our earlier tests of the effectiveness of resetting of photon-stimulated-luminescence (PSL) that employed only multi-aliquot analyses of fine-silt grains, we applied single-aliquot multigrain, and single-grain-quartz (SGQ) PSL procedures to a variety of samples from on and under the meters-thick perennial ice cover at Lake Hoare. These procedures yielded quartz sand age estimates for ice-surface sand (the source of the lake-bottom sand) of 10–80 a. Sand within a small dune on the perennial lake ice in front of Canada Glacier gave an SGQ age estimate of 48 ± 23 a. These methods produced realistic age estimates in lake-bottom short cores that are at least 5–20 times younger than comparable (uncorrected-for-reservoir) ¹⁴C results. Near-core-top PSL age estimates ranged from zero to ～500 a, depending on the core site. Four of the 7 short cores revealed clear linear age-depth trends for the upper few cm of core. These results demonstrate that for such lake-core deposits, single-aliquot and single-grain PSL dating can replace ¹⁴C dating, at least in Lake Hoare, because PSL dating lacks a significant ‘zero-point’ offset such as the ¹⁴C reservoir effect, and because PSL dating of quartz is applicable to samples as old as ～150 ka under normal sedimentary conditions. Moreover, these results imply that isolated paleo-lake-bottom deposits (e.g., microbial-mat sand mounds above present lake levels) throughout the McMurdo Dry Valleys can now be dated directly.  相似文献   

Analysis of the effect of trees on block propagation using a DEM model: implications for rockfall modelling     

David Toe  Franck Bourrier  Ignacio Olmedo  Jean-Matthieu Monnet  Frédéric Berger 《Landslides》2017,14(5):1603-1614

The objective of this research was to use numerical models based on mechanical approaches to improve the integration of the protective role of forests against rockfall into block propagation models. A model based on the discrete element method (DEM) was developed to take into account the complex mechanical processes involved during the impact of a block on a tree. This modelling approach requires the definition of many input parameters and cannot be directly integrated into block propagation models. A global sensitivity analysis identified the leading parameters of the block kinematics after impact (i.e. block energy reduction, trajectory changes, and rotational velocity): the impact velocity, the tree diameter, and the impact point horizontal location (i.e. eccentricity). Comparisons with the previous experimental and numerical studies of block impacts on trees demonstrated the applicability of the DEM model and showed some of the limitations of earlier approaches. Our sensitivity analysis highlights the significant influence of the impact velocity on the reduction of the block’s kinetic energy. Previous approaches usually also focus on parameters such as impact height, impact vertical incidence, and tree species, whose importance is only minor according to the present results. This suggests that the integration of forest effects into block propagation models could be both improved and simplified. The DEM model can also be used as an alternative to classical approaches for the integration of forest effects by directly coupling it with block propagation models. This direct coupling only requires the additional definition of the location and the diameter of each tree. Indeed, the input parameters related to the mechanical properties of the stem and the block/stem interaction in the DEM model can be set to average values because they are not leading parameters. The other input parameters are already defined or calculated in the block propagation model.  相似文献   

Determination of the Tin Stable Isotopic Composition in Tin‐bearing Metals and Minerals by MC‐ICP‐MS          下载免费PDF全文

Gerhard Brügmann  Daniel Berger  Ernst Pernicka 《Geostandards and Geoanalytical Research》2017,41(3):437-448

This study uses MC‐ICP‐MS for the precise analysis of the stable tin isotopic composition in ore minerals of tin (cassiterite, stannite), tin metal and tin bronze. The ultimate goal is to determine the provenance of tin in ancient metal objects. We document the isotope compositions of reference materials and compare the precision of different isotope ratios and the accuracy of different procedures of mass fractionation correction. These data represent a base with which isotopic data of future studies can be directly compared. The isotopic composition of cassiterite and stannite can be determined after reduction to tin metal and bronze, respectively. Both metals readily dissolve in HCl, but while the solutions of tin metal can be directly measured, the bronze solutions must be purified with an anion exchanger. The correction of the mass bias is best performed with an internal Sb standard and an empirical regression method. A series of Sn isotope determinations on commercially available mono‐element Sn solutions as well as reference bronze materials and tin minerals show fractionations ranging from about ?0.09‰ to 0.05‰/amu. The combined analytical uncertainty (2s) was determined by replicate dissolutions of reference materials of bronze (BAM 211, IARM‐91D) and averages at about 0.005‰/amu.  相似文献   

Suspended particulate matter and vertical fluxes of sedimentary material in bays of the Murmansk (Barents Sea) and Karelian (White Sea) coasts     

M.?V.?MityaevEmail author  M.?V.?Gerasimova  V.?Ja.?Berger 《Oceanology》2017,57(2):306-314

Synchronous measurement of the total suspended organic and mineral particulate matter, together with vertical sedimentary matter flux, carried out in various areas of Yarnyschnaya Inlet (Murmansk coast of the Barents Sea) and Chupa Inlet (Karelian coast of the White Sea) revealed that the seston organic component plays no part in sedimentation, being almost completely utilized in the water column, while the majority of mineral matter is transported out of the bay. The total amount of suspended matter and its components in the water column is estimated, as well as the total flux of sedimentary matter to the bottom of Chupa and Yarnyschnaya inlets.  相似文献   

High Zn and Cd accumulation in the oyster Crassostrea rhizophorae, and its relevance as a sentinel species     

de Freitas Rebelo M  do Amaral MC  Pfeiffer WC 《Marine pollution bulletin》2003,46(10):1354-1358

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Morphological variation in a late glacial population ofBosmina longispina Leydig (Crustacea,Cladocera) from the Lobsigensee (Swiss Plateau). Studies in the Late-Quaternary of Lobsigensee 9   总被引：2，自引：0，他引：2  

Dr. Wolfgang Hofmann 《Aquatic Sciences - Research Across Boundaries》1984,46(1):139-146

A late glacial population ofBosmina longispina Leydig from the Lobsigensee (Swiss Plateau) showed significant morphological variation, particularly in the number of antennule segments, in the period from the Oldest Dryas to the Preboreal. As there was no indication of introgressive hybridisation it is presumed that the variation is a result of environmental changes. The subfossilBosmina longispina resembles recent fennoscandian and late glacial north German forms rather than recent alpine populations.  相似文献   

A fresh look at the low-mass X-ray binaries     

Annette Gallas  Wolfgang Kundt  Joseph Mohr 《Astrophysics and Space Science》1991,185(1):37-49

The reported systemic velocities of the low-mass X-ray binaries (=LMXBs) are found to be unreliable, because of intrinsic Doppler shifts. We argue that the non-globular-cluster LMXBs form a disk population, whose typicalz-velocities are unlikely to exceed 30 km s^–1. They are moderately old and rare (among neutron-star sources) and have oscillated through the disk a number of times.  相似文献   

Spacecraft orbit analysis     

Wolfgang Kundt 《Astrophysics and Space Science》1973,21(2):487-493

The true orbit of a spacecraft differs from its reference orbit by small deviations due to erros in planetary and initial data, radiation and impact accelerations, and correction terms to Newton's theory of gravitation. These distortions are usually small enough to haveadditive effects on range, at the 10 m accuracy level, throughout the mission. Closed form expressions are derived (in cylindrical coordinates) for thedeviation inrange due to any given perturbing acceleration.  相似文献   

Neogene carbonate stratigraphy of Ontong Java Plateau (Western Equatorial Pacific): three unexpected findings     

W.H. Berger  R. Stax 《地学学报》1994,6(5):520-534

The Neogene carbonate stratigraphy of five sites drilled on Ontong Java Plateau during Leg 130 reveals a number of patterns which are unexpected, and which we refer to as loss paradox, equatorial insensitivity , and climate paradox . They denote the following unresolved questions.

• 1

  The loss of carbonate at depth (as derived from differences in accumulation rates) is much greater than suggested by the change in carbonate percentages (calculated under the assumption that carbonate dissolution is the cause of loss). This indicates an important role for redeposition processes, such as winnowing (bottom currents), sifting (resuspension and catabatic flow) and episodic sloughing or solifluction (presumably stimulated by earthquakes).
• 2

  Accumulation rates are not markedly increased at the time a site crosses the equator. There are several possible reasons. Equatorial upwelling may be unimportant in controlling sedimentation rates this far in the western Pacific, or its output may be spread over a considerable distance from the equator. Alternatively, increased supply below the equator is compensated for by increased removal (e.g. from resuspension by bioturbation, combined with catabatic flow). It is conceivable that errors in the timescale could also produce the effect seen.
• 3

  There is an overall tendency for agreement between the stratigraphic patterns of carbonate content and of accumulation rates, but neither pattern is readily explained by reference to changes in climate (represented by benthic δ¹⁸O) or in sea-level (as derived from sequence stratigraphy).

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