Correlation and characterisation of individual glass shards from tephra deposits using trace element laser ablation ICP‐MS analyses: current status and future potential     

Nicholas J. G. Pearce  Joanna S. Denton  William T. Perkins  John A. Westgate  Brent V. Alloway 《第四纪科学杂志》2007,22(7):721-736

Laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) is a high spatial resolution analytical method which has been applied to the analysis of silicic tephras. With current instrumentation, around 30 trace elements can be determined from single glass shards as small as ～ 40 µm, separated from tephra deposits. As a result of element fractionation during the ablation process using a 266 nm laser, a relatively complex calibration strategy is required. Nonetheless, such a strategy gives analyses which are accurate (typically within ±5%) and have an analytical precision which varies from ～ ±2% at 100 ppm, to ～ ±15% at 1 ppm. Detection limits for elements used in correlation and discrimination studies are well below 1 ppm. Examples of the application of trace element analysis by LA‐ICP‐MS in tephra studies are presented from the USA, New Zealand and the Mediterranean. Improvements in instrumental sensitivity in recent years have the potential to lower detection limits and improve analytical precision, thus allowing the analysis of smaller glass shards from more distal tephras. Laser systems operating at shorter wavelengths (e.g. 193 nm) are now more widely available, and produce a much more controllable ablation in glasses than 266 nm lasers. Crater sizes of <10 µm are easily achieved, and at 193 nm many of the elemental fractionation issues which mar longer wavelengths are overcome. By coupling a short wavelength laser to a modern ICP‐MS it should be possible to determine the trace element composition of glass shards as small as 20 µm and, providing sample preparation issues can be overcome, the determination of the more abundant trace elements in glass shards as small as 10 µm is within instrumental capabilities. This will make it possible to chemically fingerprint tephra deposits which are far from their sources, and will greatly extend the range over which geochemical correlation of tephras can be undertaken. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

3D spectroscopy of z ∼ 1galaxies with gemini     

Joanna Smith  Andrew Bunker  Richard Bower 《Astrophysics and Space Science》2003,284(2):973-976

Area spectroscopy has significant advantages over both traditional imaging and long-slit spectroscopy: it is more efficient in observing time, and yields substantially more information. Through Integral Field Units, area spectroscopy is becoming an essential part of new facility instruments on the latest large telescopes. We have been undertaking a programme on the Gemini 8-m telescopes to demonstrate the power of integral field spectroscopy, using the optical GMOS spectrograph, and the new CIRPASS instrument in the near-infrared. Here we present some preliminary results from 3D spectroscopy of z ∼ 1 objects, mapping the emission lines in a 3CR radio galaxy and in a gravitationally lensed arc. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Temporal and spatial circulation patterns in the East Frisian Wadden Sea   总被引：2，自引：1，他引：1  

Emil V. Stanev  Sebastian Grayek  Joanna Staneva 《Ocean Dynamics》2009,59(2):167-181

This work deals with the analysis of simulations carried out with a primitive equation numerical model for the region of the East Frisian Wadden Sea. The model, with 200-m resolution, is forced by wind, air–sea heat, and water fluxes and river runoff and is nested in a German Bight 1-km-resolution numerical model, the latter providing tidal forcing for the fine resolution model. The analysis of numerical simulations is focused both on responses due to moderate conditions, as well as to extreme events, such as the storm surge Britta, for which the model demonstrates very good skills. The question addressed in this paper is how well the model output can be compressed with the help of empirical orthogonal function analysis. It is demonstrated that, for the short-time periods of the order of a spring–neap cycle, only a few modes are necessary to almost fully represent the circulation. This is just an illustration that the circulation in this region is subject to the dominating tidal forcing, creating clear and relatively simple response patterns. However, for longer periods of about several months, wind forcing is also very important, and correspondingly, the circulation patterns become much more complex. Possible applications of the results in hindcasting and forecasting of hydrodynamics and sediment dynamics in the coastal zone are considered.  相似文献   

Deep analyses of nulling in Arecibo pulsars reveal further periodic behaviour     

Jeffrey L. Herfindal  Joanna M. Rankin 《Monthly notices of the Royal Astronomical Society》2009,393(4):1391-1402

Numerous studies of conal pulsars, e.g. B1133+16, have revealed fluctuation features and a steady null fraction. Sensitive Arecibo observations provide an unprecedented ability to detect nulls and confirm previously found fluctuation features. By replacing each pulse with a scaled version of the average profile, we were able to quench all subpulse modulation, dubbed pulse-modulation quelling (PMQ). It was surprising to note that the low-frequency feature observed in the natural longitude resolved fluctuation spectra (LRF) persisted in the PMQ LRFs. It appears that we can conclude, then, that in the natural pulse sequence the nulls themselves reflect whatever underlying periodicity is responsible for the low-frequency feature. Conversely, the aggregate fluctuation power of the low-frequency feature changes little whether the pulse modulation is quelled or not, implying that the feature fluctuations are produced by the nulls!  相似文献   

Observations and interpretations at Vredefort,Sudbury, and Chicxulub: Towards an empirical model of terrestrial impact basin formation     

Richard A. F. GRIEVE  W. Uwe REIMOLD  Joanna MORGAN  Ulrich RILLER  Mark PILKINGTON 《Meteoritics & planetary science》2008,43(5):855-882

Abstract— The structural, topographic and other characteristics of the Vredefort, Sudbury, and Chicxulub impact structures are described. Assuming that the structures originally had the same morphology, the observations/interpretations for each structure are compared and extended to the other structures. This does not result in any major inconsistencies but requires that the observations be scaled spatially. In the case of Vredefort and Sudbury, this is accomplished by scaling the outer limit of particular shock metamorphic features. In the case of Chicxulub, scaling requires a reasoned assumption as to the formation mechanism of an interior peak ring. The observations/interpretations are then used to construct an integrated, empirical kinematic model for a terrestrial peak‐ring basin. The major attributes of the model include: a set of outward‐directed thrusts in the parautochthonous rocks of the outermost environs of the crater floor, some of which are pre‐existing structures that have been reactivated during transient cavity formation; inward‐directed motions along the same outermost structures and along a set of structures, at intermediate radial distances, during transient cavity collapse; structural uplift in the center followed by a final set of radially outward‐directed thrusts at the outer edges of the structural uplift, during uplift collapse. The rock displacements on the intermediate, inward and innermost, outward sets of structures are consistent with the assumption that a peak ring will result from the convergence of the collapse of the transient cavity rim area and the collapse of the structural uplift.  相似文献   

Genetic differentiation of the soft shore barnacle Fistulobalanus albicostatus (Cirripedia: Thoracica: Balanomorpha) in the West Pacific          下载免费PDF全文

Yen Wei Chang  Joanna S. M. Chan  Ryota Hayashi  Takuho Shuto  Ling Ming Tsang  Ka Hou Chu  Benny K. K. Chan 《Marine Ecology》2017,38(2)

This study examined the phylogeography of the barnacle Fistulobalanus albicostatus, which inhabits mangroves and estuarine shores in the West Pacific. Differentiation in the mitochondrial cytochrome c oxidase subunit I (COI) and 12S ribosomal RNA (12S) genes of 401 specimens of F. albicostatus was examined in samples from 16 locations in the West Pacific, ranging from Honshu to Southern China. Our results revealed that F. albicostatus comprises two major clades exhibiting a COI divergence ranging from 1.25% to 2.8%. Clade A demonstrated the widest distribution, ranging from Japan to China, and was divided into three subclades occurring in the South China Sea (A1), Okinawa (A2), and Honshu, Korea and Qingdao (A3). Clade B was determined to be endemic to Okinawa; i.e. two endemic lineages occur in this island. Thus, F. albicostatus resembles several inter‐tidal species in having clades that are endemic to Okinawan waters. Nevertheless, in contrast to the rocky inter‐tidal barnacles Tetraclita spp. and Chthamalus malayensis, F. albicostatus was not found to be separated into continental and oceanic populations, but instead is divided into northern and southern clades, probably because of the Yangtze River discharge, which limits gene flow between the northern and southern populations.  相似文献   

A statistical model for spatial inventory data: a case study of N2O emissions in municipalities of southern Norway   总被引：1，自引：0，他引：1  

Joanna Horabik  Zbigniew Nahorski 《Climatic change》2010,103(1-2):263-276

In this paper we apply a linear regression with spatial random effect to model geographically distributed emission inventory data. The study presented is on N₂O emission assessments for municipalities of southern Norway and on activities related to emissions (proxy data). Taking advantage of the spatial dimension of the emission process, the method proposed is intended to improve inventory extension beyond its earlier coverage. For this, the proxy data are used. The conditional autoregressive model is used to account for spatial correlation between municipalities. Parameter estimation is based on the maximum likelihood method and the optimal predictor is developed. The results indicate that inclusion of a spatial dependence component lead to improvement in both representation of the observed data set and prediction.  相似文献   

Transfer of organic contaminants to the Baltic in the Odra Estuary     

Kowalewska G  Konat-Stepowicz J  Wawrzyniak-Wydrowska B  Szymczak-Zyła M 《Marine pollution bulletin》2003,46(6):703-718

This paper describes the transfer of organic contaminants to the sea, using PAHs (12 compounds) and PCBs (11 congeners) as examples, through a eutrophicated coastal lagoon (Szczecin Lagoon, on the Polish-German border). The transfer of contaminants study was based on their concentration in recent sediments (0-10 cm), in relation to different environmental conditions such as temperature, salinity, turbidity, oxygen and nutrients in water, hydrological conditions, organic carbon and biomarkers (pigments and their derivatives) in sediments. Results include the data obtained between 1994 and 2000, also those on before and afterwards the great flood in July 1997, at different stations in the Lagoon and the adjacent Pomeranian Bay. The results indicated that the eutrophic estuary of the shape of lagoon acts as an effective trap for the hydrophobic organic pollutants. The abundance and taxonomy of plankton as well as detritus derived from it play an important role in bonding the studied compounds. The salinity gradient in the lagoon has a significant influence upon deposition of the pollutants from the water column to the sediments and the residence time of the compounds there depends strongly on oxic-anoxic status of the sediments and the strength of interaction with sediments resulting from polarity, the type and stability of associates formed, as well as on hydrological conditions. We conclude that eutrophication in this area prevents pollution of the sea to some extent.  相似文献   

Distribution and morphometric characteristics of icing fields in Svalbard     

Elzbieta Bukowska-Jania  Joanna Szafraniec 《Polar research》2005,24(1-2):41-53

Icing fields are common in Svalbard and very diverse with respect to shape. The occurrence and spatial structure of icing fields in front of glaciers were analysed using aerial photographs (at a scale of 1:50000) taken from 19 July to 25 August 1990–a unique set of images covering the whole archipelago in one summer season. Icing fields were observed in front of 217 glaciers. A total area of 12.3 km² appeared to be covered by the icings. This value, from late in the ablation season, is likely to be near the seasonal minimum. Of the 217 glaciers, 192 were selected for further analysis, carried out by stereoscopic observation of the aerial photographs. Striking difference in brightness of the icing fields in comparison to the surrounded terrain combined with field experience of the geomorphic setting of its occurrence made possible the complete inventory of the icing phenomena for the whole of Svalbard. Morphometric features were measured directly on photographs and on scanned portions of them. Results from field studies of melting and the decrease of the area of icing fields at the front of two glaciers are also presented. The shape and distribution of icings depend on a set of glaciological factors and on the glacial and geomorphologic setting. The duration of frigid temperatures in the winter when the icing fields were formed is also important. Results show that oval and circular shapes are characteristic for icing fields after surviving the ablation season. These fields have an important geomorphological influence on the outwash plains that currently develop in Svalbard.  相似文献   

The atmospheric distribution of lead over a number of marine regions     

R. Chester  E. Joanna Sharples  K. Murphy  A.C. Saydam  G.S. Sanders 《Marine Chemistry》1984,15(2):191

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