Methane in the southern North Sea: Sources, spatial distribution and budgets   总被引：3，自引：0，他引：3  

Maik Grunwald  Olaf Dellwig  Melanie Beck  Joachim W. Dippner  Jan A. Freund  Cora Kohlmeier  Bernhard Schnetger  Hans-Jürgen Brumsack 《Estuarine, Coastal and Shelf Science》2009,81(4):445-456

Measurements of methane (CH₄) so far have always shown supersaturation in the entire North Sea relative to the atmospheric partial pressure and the distribution of surface CH₄ reveals a distinct increase towards the shore. Since North Sea sediments presumably are an insignificant source for CH₄ the coastal contribution via rivers and tidal flats gains in importance.In this work, CH₄ data from the River Weser, the back barrier tidal flats of Spiekeroog Island (NW Germany), and the German Bight are presented. Results from the River Weser are compared to other rivers draining into the German Bight. Measurements in the tidal flat area of Spiekeroog Island highlight this ecosystem as an additional contributor to the overall CH₄ budget of the southern North Sea. A tidally driven CH₄ pattern is observed for the water column with maximum values during low tide. Tidal flat sediments turn out to be the dominating source because pore waters discharged during low tide are highly enriched in CH₄. In contrast, the freshwater contribution to the tidal flats by small coastal tributaries has almost no impact on water column CH₄ concentrations. The CH₄ level seems to be disturbed irregularly by wind forcing due to elevated degassing and prevention of advective flow when tidal flats remain covered by water.Based on our data, two model calculations were used to estimate the impact of tidal flats on the CH₄ budget in the German Bight. Our results demonstrate that the back barrier tidal flats of the east Frisian Wadden Sea contribute CH₄ in an order of magnitude between the Wash estuary and River Elbe and thus have to be considered in budget calculations.  相似文献   

Late‐stage deformation in a collisional orogen (Western Alps): nappe refolding,back‐thrusting or normal faulting?     

Stefan Bucher  Stefan M. Schmid  Romain Bousquet  Bernhard Fügenschuh 《地学学报》2003,15(2):109-117

ABSTRACT Nappe refolding, back-thrusting and normal faulting frequently cause severe late-stage overprinting of the architecture of an orogen. A combined investigation of nappe stack polarity, kinematics of shearing and metamorphic gradients in the Western Alps develops criteria for distinguishing between these three modes of late-stage deformation. This distinction is a prerequisite for any retro-deformation necessary for understanding the main tectonic and metamorphic evolution of collisional orogens. In the case of the Western Alps overprint was by mega-scale nappe refolding in the Oligocene. This implies exhumation of the HP-rocks prior to postnappe folding, i.e. during nappe stacking and by foreland-directed ascent within a subduction channel.  相似文献   

International viewpoint and news     

Anne Marie de Grosbois  Bernhard Wagenbreth 《Environmental Geology》2007,53(2):469-470

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Environmental changes in the northern Altai during the last millennium documented in Lake Teletskoye pollen record   总被引：1，自引：0，他引：1  

Andrei A. Andreev  Roberto Pierau  Ivan A. Kalugin  Andrei V. Daryin  Lyubov G. Smolyaninova  Bernhard Diekmann 《Quaternary Research》2007,67(3):394-399

A high-resolution pollen record from Lake Teletskoye documents the climate-related vegetation history of the northern Altai Mountain region during the last millennium. Siberian pine taiga with Scots pine, fir, spruce, and birch dominated the vegetation between ca. AD 1050 and 1100. The climate was similar to modern. In the beginning of the 12th century, birch and shrub alder increased. Lowered pollen concentrations and simultaneous peaks in herbs (especially Artemisia and Poaceae), ferns, and charcoal fragments point to colder and more arid climate conditions than before, with frequent fire events. Around AD 1200, regional climate became warmer and more humid than present, as revealed by an increase of Siberian pine and decreases of dry herb taxa and charcoal contents. Climatic conditions were rather stable until ca. AD 1410. An increase of Artemisia pollen may reflect slightly drier climate conditions between AD 1410 and 1560. Increases in Alnus, Betula, Artemisia, and Chenopodiaceae pollen and in charcoal particle contents may reflect further deterioration of climate conditions between AD 1560 and 1810, consistent with the Little Ice Age. After AD 1850 the vegetation gradually approached the modern one, in conjunction with ongoing climate warming.  相似文献   

Taming the flood—How far can we go with trees?          下载免费PDF全文

Chris Soulsby  Jonathan Dick  Bernhard Scheliga  Doerthe Tetzlaff 《水文研究》2017,31(17):3122-3126

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Identification of groundwater recharge sources and processes in a heterogeneous alluvial aquifer: results from multi‐level monitoring of hydrochemistry and environmental isotopes in a riverside agricultural area in Korea     

Byoung‐Young Choi  Seong‐Taek Yun  Bernhard Mayer  Gi‐Tak Chae  Kyoung‐Ho Kim  Kangjoo Kim  Yong‐Kwon Koh 《水文研究》2010,24(3):317-330

We evaluated sources and pathways of groundwater recharge for a heterogeneous alluvial aquifer beneath an agricultural field, based on multi‐level monitoring of hydrochemistry and environmental isotopes of a riverside groundwater system at Buyeo, Korea. Two distinct groundwater zones were identified with depth: (1) a shallow oxic groundwater zone, characterized by elevated concentrations of NO₃^? and (2) a deeper (>10–14 m from the ground surface) sub‐oxic groundwater zone with high concentrations of dissolved Fe, silica, and HCO₃^?, but little nitrate. The change of redox zones occurred at a depth where the aquifer sediments change from an upper sandy stratum to a silty stratum with mud caps. The δ¹⁸O and δ²H values of groundwater were also different between the two zones. Hydrochemical and δ¹⁸O? δ²H data of oxic groundwater are similar to those of soil water. This illustrates that recharge of oxic groundwater mainly occurs through direct infiltration of rain and irrigation water in the sandy soil area where vegetable cropping with abundant fertilizer use is predominant. Oxic groundwater is therefore severely contaminated by agrochemical pollutants such as nitrate. In contrast, deeper sub‐oxic groundwater contains only small amounts of dissolved oxygen (DO) and NO₃^?. The ³H contents and elevated silica concentrations in sub‐oxic groundwater indicate a somewhat longer mean residence time of groundwater within this part of the aquifer. Sub‐oxic groundwater was also characterized by higher δ¹⁸O and δ²H values and lower d‐excess values, indicating significant evaporation during recharge. We suggest that recharge of sub‐oxic groundwater occurs in the areas of paddy rice fields where standing irrigation and rain water are affected by strong evaporation, and that reducing conditions develop during subsequent sub‐surface infiltration. This study illustrates the existence of two groundwater bodies with different recharge processes within an alluvial aquifer. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

The Alpine nappe stack in western Austria: a crustal-scale cross section     

Hannah Pomella  Hugo Ortner  Michael Zerlauth  Bernhard Fügenschuh 《International Journal of Earth Sciences》2015,104(3):733-745

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Timing and conditions of brittle faulting on the Silltal-Brenner Fault Zone,Eastern Alps (Austria)     

Neil Mancktelow  Horst Zwingmann  Marion Campani  Bernhard Fügenschuh  Andreas Mulch 《Swiss Journal of Geoscience》2015,108(2-3):305-326

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Potential impacts of urban area expansion on groundwater level in the Gaza Strip: a spatial-temporal assessment     

Tamer Eshtawi  Mariele Evers  Bernhard Tischbein 《Arabian Journal of Geosciences》2015,8(12):10565-10584

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Inter-laboratory comparison of oxygen isotope compositions from biogenic silica     

Bernhard Chapligin  Melanie J. Leng  Anne Alexandre  Akira Ijiri  Aldo Shemesh  Ulrike Herzschuh  Hanno Meyer  Yusuke Okazaki  Zachary D. Sharp  Corinne Sonzogni  Florence Sylvestre  Ruth Yam 《Geochimica et cosmochimica acta》2011,75(22):7242-7256

Several techniques have been introduced in the last decades for the dehydration and release of O₂ from biogenic silica (opal-A) for oxygen-isotope analysis. However, only one silica standard is universally available: a quartz standard (NBS28) distributed by the IAEA, Vienna. Hence, there is a need for biogenic silica working standards. This paper compares the existing methods of oxygen-isotope analyses of opal-A and aims to characterize additional possible working standards to calibrate the δ¹⁸O values of biogenic silica. For this purpose, an inter-laboratory comparison was organized. Six potential working standard materials were analysed repeatedly against NBS28 by eight participating laboratories using their specific analytical methods. The materials cover a wide range of δ¹⁸O values (+23 to +43‰) and include diatoms (marine, lacustrine), phytoliths and synthetically-produced hydrous silica. To characterize the proposed standards, chemical analyses and imaging by scanning electron microscopy (SEM) were also performed. Despite procedural differences at each laboratory, all methods are in reasonable agreement with a standard deviation (SD) for δ¹⁸O values between 0.3‰ and 0.9‰ (1σ). Based on the results, we propose four additional biogenic silica working standards (PS1772-8: 42.8‰; BFC: 29.0‰; MSG60: 37.0‰; G95-25-CL leaves: 36.6‰) for δ¹⁸O analyses, available on request through the relevant laboratories.  相似文献