Light as a driver of phytoplankton growth and production in the freshwater tidal zone of a turbid estuary   总被引：2，自引：0，他引：2  

Rita B. Domingues  Tnia P. Anselmo  Ana B. Barbosa  Ulrich Sommer  Helena M. Galvo 《Estuarine, Coastal and Shelf Science》2011,91(4):282

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Zum 65. geburtstag des Prof. Dr. Mikuláš Konček     

Alois Gregor 《Studia Geophysica et Geodaetica》1965,9(4):422-422

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Sensitivity of coastal polynyas and high-salinity shelf water production in the Ross Sea,Antarctica, to the atmospheric forcing   总被引：1，自引：1，他引：0  

Pierre Mathiot  Nicolas C. Jourdain  Bernard Barnier  Hubert Gallée  Jean Marc Molines  Julien Le Sommer  Thierry Penduff 《Ocean Dynamics》2012,62(5):701-723

Coastal polynyas around Antarctica are the place of intense air–sea exchanges which eventually lead to the formation of high-salinity shelf waters (HSSW) over continental shelves. Here, the influence of atmospheric forcing on coastal polynyas in the Ross Sea is studied by contrasting the response of a regional ocean/sea-ice circulation model to two different atmospheric forcing sets. A first forcing (DFS3) is based on ERA40 atmospheric surface variables and satellite products. A second forcing (MAR) is produced on the basis of ERA40 with a dynamical downscaling procedure. As compared to DFS3, MAR forcing is shown to improve substantially the representation of small-scale patterns of coastal winds with stronger katabatic winds along the coast. The response of the ocean/sea-ice model to the two forcing sets shows that the MAR forcing improves substantially the geographical distribution of polynyas in the Ross Sea. With the MAR forcing, the polynya season is also shown to last longer with a greater ice-production rate. As a consequence, a greater flow of dense water out of the polynyas is found with the MAR forcing and the properties of HSSW are notably improved as compared to the DFS3 forcing. The factors contributing to the activity of Terra Nova Bay and Ross Ice Shelf polynyas in the model are studied in detail. The general picture that emerges from our simulations is that the properties of HSSW are mostly set by brine rejection when the polynya season resume. We found that coastal polynyas in the Ross Sea export about 0.4 Sv of HSSW which then flows along three separate channels over the Ross Shelf. A 6-month time lag is observed between the peak of activity of polynyas and the maximum transport across the sills in the channels with a maximum transport of about 1 Sv in February. This lag corresponds to the time it takes to the newly formed HSSW to spread from the polynya to the sills (at a speed of nearly 2 cm s⁻¹).  相似文献   

Does Pumping Volume Affect the Concentration of Micropollutants in Groundwater Samples?          下载免费PDF全文

Inge H. van Driezum  Julia Derx  Ernis Saracevic  Alexander K.T. Kirschner  Regina Sommer  Andreas H. Farnleitner  Alfred Paul Blaschke 《Ground Water Monitoring & Remediation》2017,37(4):82-88

Information on concentrations of micropollutants (such as pharmaceuticals, pesticides, and industrial chemicals) in most highly dynamic riverbank filtration (RBF) systems is lacking, in contrast to data on standard chemical parameters. Sampling protocols have thus far been based on the stabilization of standard chemical parameters in relatively pristine environments. To determine whether groundwater samples for micropollutant analysis can be taken at a similar pumping volume as samples for testing standard chemical parameters in both environments, three groundwater monitoring wells in an RBF system were sampled at two points in time (after pumping of 3 well volumes and after pumping of 15 well volumes). Micropollutant concentrations were not significantly different between the two sampling points; therefore, appropriate samples can be drawn after pumping 3 well volumes. For a specific microbiological parameter (leucin incorporation), a statistically significant difference was found.  相似文献   

Tracing the temporal evolution of soil redistribution rates in an agricultural landscape using 239+240Pu and 10Be     

Francesca Calitri  Michael Sommer  Kevin Norton  Arnaud Temme  Dagmar Brandová  Raquel Portes  Marcus Christl  Mike E. Ketterer  Markus Egli 《地球表面变化过程与地形》2019,44(9):1783-1798

Two principal groups of processes shape mass fluxes from and into a soil: vertical profile development and lateral soil redistribution. Periods having predominantly progressive soil forming processes (soil profile development) alternate with periods having predominantly regressive processes (erosion). As a result, short-term soil redistribution – years to decades – can differ substantially from long-term soil redistribution; i.e. centuries to millennia. However, the quantification of these processes is difficult and consequently their rates are poorly understood. To assess the competing roles of erosion and deposition we determined short- and long-term soil redistribution rates in a formerly glaciated area of the Uckermark, northeast Germany. We compared short-term erosion or accumulation rates using plutonium-239 and -240 (^239+240Pu) and long-term rates using both in situ and meteoric cosmogenic beryllium-10 (¹⁰Be). Three characteristic process domains have been analysed in detail: a flat landscape position having no erosion/deposition, an erosion-dominated mid-slope, and a deposition-dominated lower-slope site. We show that the short-term mass erosion and accumulation rates are about one order of magnitude higher than long-term redistribution rates. Both, in situ and meteoric ¹⁰Be provide comparable results. Depth functions, and therefore not only an average value of the topsoil, give the most meaningful rates. The long-term soil redistribution rates were in the range of −2.1 t ha^-1 yr^-1 (erosion) and +0.26 t ha^-1 yr^-1 (accumulation) whereas the short-term erosion rates indicated strong erosion of up to 25 t ha^-1 yr^-1 and accumulation of 7.6 t ha^-1 yr^-1. Our multi-isotope method identifies periods of erosion and deposition, confirming the ‘time-split approach’ of distinct different phases (progressive/regressive) in soil evolution. With such an approach, temporally-changing processes can be disentangled, which allows the identification of both the dimensions of and the increase in soil erosion due to human influence. © 2019 John Wiley & Sons, Ltd.  相似文献   

The use of numerical modeling to optimize the construction of lined sections for a regionally-significant irrigation canal in Egypt     

Eltarabily  Mohamed Galal  Moghazy  Hossam Eldin  Abdel-Fattah  Sommer  Negm  Abdelazim M. 《Environmental Earth Sciences》2020,79(3):1-11

Environmental Earth Sciences - Water balance is considered as an important tool to assess the amount of water and its availability in a region. The Small Aral Sea is a salt lake in the territory of...  相似文献   

Combined fitting of Ulysses/COMPTEL GRB spectra     

T. Aigner  J. Greiner  M. Sommer  O. R. Williams  R. M. Kippen  K. Hurley  M. Boër  M. Niel 《Astrophysics and Space Science》1995,231(1-2):165-168

This paper describes a comparison of observations of the HH 30 jet/counterjet system and theoretical models of jets propagating in a strongly stratified medium. We find that the observed westward bending of the HH 30 jet and counterjet can be explained as the result of a plane-parallel pressure stratification of the surrounding environment. This model predicts specific properties for the kinematics of the outflow, that could be straight-forwardly checked with future spectroscopic and proper motion studies of HH 30.  相似文献   

Laser Ablation In Situ Silicon Stable Isotope Analysis of Phytoliths     

Daniel A. Frick  Jan A. Schuessler  Michael Sommer  Friedhelm von Blanckenburg 《Geostandards and Geoanalytical Research》2019,43(1):77-91

Silicon is a beneficial element for many plants and is deposited in plant tissue as amorphous bio‐opal called phytoliths. The biochemical processes of silicon uptake and precipitation induce isotope fractionation: the mass‐dependent shift in the relative abundances of the stable isotopes of silicon. At the bulk scale, δ³⁰Si ratios span from ?2 to +6‰. To further constrain these variations in situ, at the scale of individual phytolith fragments, we used femtosecond laser ablation multi‐collector inductively coupled plasma‐mass spectrometry (fsLA‐MC‐ICP‐MS). A variety of phytoliths from grasses, trees and ferns were prepared from plant tissue or extracted from soil. Good agreement between phytolith δ³⁰Si ratios obtained by bulk solution MC‐ICP‐MS analysis and in situ isotope ratios from fsLA‐MC‐ICP‐MS validates the method. Bulk solution analyses result in at least twofold better precision for δ³⁰Si (2s on reference materials ≤ 0.11‰) over that found for the means of in situ analyses (2s typically ≤ 0.24‰). We find that bushgrass, common reed and horsetail show large internal variations up to 2‰ in δ³⁰Si, reflecting the various pathways of silicon from soil to deposition. Femtosecond laser ablation provides a means to identify the underlying processes involved in the formation of phytoliths using silicon isotope ratios.  相似文献   

In memoriam Gernot Bretschko (1938–2002)     

Alois Herzig  Fritz Schiemer 《Limnologica》2002,32(4):289

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Niederschlagsänderungen Während Eines Jahres in Ihrer Beziehung zu den Frontalzonen     

Alois Gregor  Zdenêk Gregor 《Studia Geophysica et Geodaetica》1958,2(4):362-396

Резюме Целью настоящей работы является анализ колебаний осадков последовательно, месяц за месяцем, в течение года, касающийся областей Сев. Америки, Атлантического океана и Европы и сравнение полученных результатов с колебаниями фронтальных зон на названном выше пространстве. Зависимость осадков от изменений температуры исключается, вследствие того, что осадки выражаются в процентах максимального количества осадков, которое могло бы выпасть из нижней половины тропосферы. Во второй части работы приводится приблпженная оценка роли конвекции в осадках в Европе.

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Anschrift: Ke Karlovu 3, Praha 2.

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Anschrift: Letiště Praha-Ruzyně.  相似文献