Holocene sedimentary and environmental development of Aarhus Bay,Denmark – a multi-proxy study     

Peter Rasmussen  George Pantopoulos  Jørn B. Jensen  Jesper Olsen  Hans Røy  Ole Bennike 《Boreas: An International Journal of Quaternary Research》2020,49(1):108-128

Holocene sedimentation patterns and environmental development in Aarhus Bay, Denmark, were reconstructed based on proxy analyses of two sediment cores (M1 and M5). Together, the two cores offer an opportunity to examine the history of the area during the past c. 10 000 years. The investigation consisted of acoustic mapping and multi-proxy analyses of the sediment cores including macrofossils, sediment physical properties, sediment accumulation rates, grain size, and X-ray fluorescence elemental counts. Radiocarbon dating of the two sediment successions revealed that they cover the periods c. 10 000–3700 cal. a BP (M1) and c. 4400 cal. a BP to the present (M5). The data from the M1 site indicate the presence of a near-shore lake environment between c. 10 000 and 9000 cal. a BP. The first intrusion of marine water into the area is dated to c. 9000 cal. a BP. In the following c. 1300 years, brackish-water conditions prevailed in the area characterized by a mixture of taxa from marine, limnic and terrestrial habitats, reflecting a shallow estuarine environment. Around 7700 cal. a BP full marine conditions were established, accompanied by a marked increase in sedimentation rates. The changes to full marine conditions and higher sedimentation rates are probably due to a significant sea-level rise leading to flooding of former land areas and intensified erosion. A subsequent distinct decrease in sedimentation rates around 6350 cal. a BP is presumably linked to a previously documented sea-level drop about this time. Continuous sedimentation ceased around 3700 cal. a BP in the central part of the bay, most probably due to a major sea-level lowering involving widespread erosion. In the eastern and deeper part of the bay, sedimentation continued until today. Fully marine conditions prevailed there for at least the last 4400 years.  相似文献   

Simulating galaxy clusters – II. Global star formation histories and the galaxy populations     

Alessio D. Romeo  Laura Portinari  Jesper Sommer-Larsen 《Monthly notices of the Royal Astronomical Society》2005,361(3):983-996

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Tracer Tests and Image Analysis of Biological Clogging in a Two-Dimensional Sandbox Experiment   总被引：1，自引：0，他引：1  

Jesper Kildsgaard  Peter Engesgaard 《Ground Water Monitoring & Remediation》2002,22(2):60-67

A two-dimensional flow experiment on biological clogging was carried out by biostimulating a sandbox packed with sand inoculated with bacteria. Biostimulation consisted of continuously injecting nutrients (acetate and nitrate). Clogging was visualized by frequently carrying out colored tracer experiments using Brilliant Blue. The tracer experiments were recorded with a digital camera and converted to concentration maps using an image-analysis method that revealed in detail the complex spreading pattern surrounding clogged areas. Clogging resulted in a finger-like spreading of the tracer around the main clogged area. Fingers were asymmetric and their dominant direction changed over time. Although the flow field was complex around the main clogged area, the effect on the bulk hydraulic conductivity at the scale of the sandbox was very small.  相似文献   

Seismic Attenuation in Partially Saturated Dime-shaped Cracks     

H. Schütt  J. Köhler  O. Boyd  H. Spetzler 《Pure and Applied Geophysics》2000,157(3):435-448

—We have examined the effect of surface contamination on the attenuation and stiffness of compressional seismic waves in artificial cylindrical glass cracks that are partially saturated with water. The compression of the gap perpendicularly to its plane reduces the gap volume and forces the water to redistribute within the gap (conservation of volume of an incompressible liquid). On clean surfaces, the water can flow without significant resistance across the glass. This leads to a very low and almost constant attenuation over a wide frequency range (approx. 3 mHz to 10 Hz), while the sample stiffness is constant. In the case of propanol contaminated surfaces, both the attenuation and the stiffness are considerably higher than in the clean case, and display a considerable frequency dependence. Both effects can be explained with the Restricted Meniscus Motion Model. In this model, the redistribution of the liquid in the gap first leads to a change (increase) of the contact angle. The change of the meniscus curvature results in an increase of the pressure in the liquid and thus to a stiffening of the sample. When the resistive force, that prevents the contact line from sliding along the surface, is finally overcome, the contact line starts moving across the contaminated surface. The motion against the resistive force dissipates energy and increases the attenuation. The calculated data are in good agreement for both the clean and the contaminated case; the model parameters fall in the range that was established by independent experiments (e.g. ).  相似文献   

Fennoscandia revisited: a spatially improved tree-ring reconstruction of summer temperatures for the last 900 years   总被引：1，自引：0，他引：1  

Hans W. Linderholm  Jesper Björklund  Kristina Seftigen  Björn E. Gunnarson  Mauricio Fuentes 《Climate Dynamics》2015,45(3-4):933-947

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Overview of eutrophication indicators to assess environmental status within the European Marine Strategy Framework Directive   总被引：1，自引：0，他引：1  

João G. Ferreira  Jesper H. Andersen  Angel Borja  Suzanne B. Bricker  Jordi Camp  Margarida Cardoso da Silva  Esther Garcés  Anna-Stiina Heiskanen  Christoph Humborg  Lydia Ignatiades  Christiane Lancelot  Alain Menesguen  Paul Tett  Nicolas Hoepffner  Ulrich Claussen 《Estuarine, Coastal and Shelf Science》2011

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Are Damped Lyα Systems Large Galactic Discs?     

Jesper Sommer-Larsen 《Astrophysics and Space Science》2001,276(2-4):999-1006

The hypothesis that damped Lyα systems (DLAs) are large galactic discs (Milky Way sized) is tested by confronting predictions of models of the formation and evolution of (large) disc galaxies with observations, in particular the zinc abundance distribution with neutral hydrogen column density found for DLAs. A pronounced mismatch is found, strongly hinting that the majority of DLAs may not be large galactic discs. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Inhomogeneous primordial baryon distributions on subgalactic scales: high-z galaxy formation with warm dark matter     

Jesper Sommer-Larsen  Pavel Naselsky  Igor Novikov  Martin Götz 《Monthly notices of the Royal Astronomical Society》2004,352(1):299-310

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First results of the XI Groups Project: studying an unbiased sample of galaxy groups     

Jesper Rasmussen  Trevor J. Ponman  John S. Mulchaey  Trevor A. Miles  Somak Raychaudhury 《Monthly notices of the Royal Astronomical Society》2006,373(2):653-665

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Clay mineralogy, grain size distribution and their correlations with trace metals in the salt marsh sediments of the Skallingen barrier spit, Danish Wadden Sea     

Changling He  Jesper Bartholdy  Christian Christiansen 《Environmental Earth Sciences》2012,67(3):759-769

To understand the behavior of trace metals in the salt marsh at Skallingen, Danish Wadden Sea, we investigated a profile from surface to 25?cm depth of the salt marsh sediment, focusing primarily on clay mineralogy and grain size distribution of the sediments and their relationship with trace metals. The clay assembly of the sediment consists of illite, kaolinite and much less chlorite and smectite. The major clay minerals of illite, kaolinite as well as chlorite correlate very poorly with all the trace metals investigated, due probably to the weak competing strength of these clays compared with the other adsorbents and to low availability of the mobile trace metals in the system. Correlation between trace metals and clay minerals may therefore be used as an indicator in environmental assessment. Fine grain fractions of the sediment increased markedly after salt marsh invasion in about 1931 but decreased after 1964. This increase was contributed mainly by the grains finer than 20???m while the fraction of 40?C63???m actually decreased soon after the invasion. The relation between most of the trace metals and grain size distributions is close in general but far from linear. The drastic turning point is observed at about 30???m, around where the correlation coefficient r drops from 0.8 to 0.1. Adsorption is the controlling mechanism for the behavior of trace metals in the salt marsh. Fe/Mn (hydr)oxides and organic matter play the key role.  相似文献