Sources and distributions of tetraether lipids in surface sediments across a large river-dominated continental margin   总被引：3，自引：0，他引：3  

Chun Zhu  Johan W.H. Weijers  Thomas WagnerJian-Ming. Pan  Jian-Fang ChenRichard D. Pancost 《Organic Geochemistry》2011,42(4):376-386

Glycerol dialkyl glycerol tetraether (GDGT)-based proxies are increasingly used in modern carbon cycling and palaeoenvironmental investigations. It is therefore crucial to examine the robustness (sources, transport and degradation) of all GDGT-based proxies in continental margins, where sedimentation rates and extent of carbon cycling are high. We have analyzed the distributions of GDGTs in surface sediments from the Lower Yangtze River and East China Sea (ECS) shelf. The results revealed multiple sources and complex shelf processes that govern the distributions. The isoprenoid GDGT-inferred sea surface temperatures (SSTs) are robust and reflect the satellite-derived annual mean SSTs on the shallow ECS shelf, confirming an origin from surface water column-dwelling crenarchaeota. The input from methanogen-sourced, isoprenoid GDGTs is significant in the river surface sediments but they are almost absent from the ECS shelf. Branched GDGTs are also abundant in the river sediments, but ca. 95% are degraded in the Yangtze estuary, a much greater extent than observed for other terrigenous organic matter (OM) proxies. There is also evidence for production of branched GDGTs in the oxic ECS shelf water column and the anoxic sediments/waters of the Lower Yangtze River. As a result, branched GDGT-based proxies in the lower river and ECS surface sediments do not reflect the catchment environmental conditions. The effective degradation in the estuary and widespread aquatic contributions of branched GDGTs improves our understanding of how to use branched GDGT-based proxies in marginal seas.  相似文献   

V oxidation state in Fe–Ti oxides by high-energy resolution fluorescence-detected X-ray absorption spectroscopy     

Amélie Bordage  Etienne Balan  Johan P. R. de Villiers  Robert Cromarty  Amélie Juhin  Claire Carvallo  Georges Calas  P. V. Sunder Raju  Pieter Glatzel 《Physics and Chemistry of Minerals》2011,38(6):449-458

The oxidation state of vanadium in natural and synthetic Fe–Ti oxides is determined using high-energy resolution fluorescence-detected X-ray absorption spectroscopy (HERFD-XAS). Eleven natural magnetite-bearing samples from a borehole of the Main Magnetite Layer of the Bushveld Complex (South Africa), five synthetic Fe oxide samples, and three natural hematite-bearing samples from Dharwar supergroup (India) are investigated. V K edge spectra were recorded on the ID26 beamline at the European Synchrotron Radiation Facility (Grenoble, France), and the pre-edge features were used to determine the local environment and oxidation state of vanadium. In the case of the magnetite samples (natural and synthetic), we show that vanadium is incorporated in the octahedral site of the spinel structure under two oxidation states: +III and +IV. The variations of the pre-edge area are interpreted as various proportions in V³⁺ and V⁴⁺ (between 9.5 and 16.3% of V⁴⁺), V³⁺ being the main oxidation state. In particular, the variations of the V⁴⁺/V³⁺ ratio along the profile of the Main Magnetite Layer seem to follow the crystallization sequence of the layer. In the case of the hematite samples from India, the pre-edge features indicate that vanadium is substituted to Fe and mainly incorporated as V⁴⁺ (between 40 and 72% of V⁴⁺). We also demonstrate the potentiality of HERFD-XAS for mineralogical studies, since it can filter out the unwanted fluorescence and give better resolved spectra than conventional XAS.  相似文献   

Institutional capacity-building for targeting sea-level rise in the climate adaptation of Swedish coastal zone management. Lessons from Coastby   总被引：1，自引：0，他引：1  

Sofie Storbjörk  Johan Hedrén 《Ocean & Coastal Management》2011,54(3):265-273

For coastal areas across the world, sea-level rise and problems of coastal erosion and coastal flooding are expected to increase over the next hundred years. At the same time political pressure for continued waterfront planning and development of coastal areas threatens to increase our societal vulnerability, and necessitating climate adaptation in coastal zone management. The institutional dimension has been identified as important for ensuring a more robust adaptation to both current climate variability and future climate change. In this paper, lessons regarding institutional constraints for climate adaptation are drawn from a Swedish case-study on local coastal zone management, illustrating the diverse and complex nature of institutional capacity-building. The aim of the paper is to illustrate critical factors that from an institutional perspective condition the capacity to achieve a more integrated, strategic and proactive climate adaptation and for turning “rules on paper” to working practice, based on case-study experiences from Coastby. Following and expanding a framework for analysing institutional capacity-building we learnt that a selective few key actors had played a critical role in building a strong external networking capacity with a flip-side in terms of a weak internal coordinating capacity and lack of mutual ownership of coastal erosion between sectoral units e.g. risk-management, planning and environment. We also found a weak vertical administrative interplay and lack of formal coherent policy, procedures and regulations for managing coastal erosion between local, regional and national administrations. Further, tensions and trade-offs between policy-agendas, values and political priorities posed a barrier for capacity-building in coastal zone management which calls for processes to mediate conflicting priorities in policy-making, planning and decision-making. The case-study suggests that the ability of the political administrative system to acknowledge and deal with institutional conflicts is a critical condition for ensuring an integrated and proactive climate adaptation in coastal zone management.  相似文献   

Vulnerability of solar energy infrastructure and output to climate change     

Anthony Patt  Stefan Pfenninger  Johan Lilliestam 《Climatic change》2013,121(1):93-102

This paper reviews the potential vulnerability of solar energy systems to future extreme event risks as a consequence of climate change. We describe the three main technologies likely to be used to harness sunlight—thermal heating, photovoltaic (PV), and concentrating solar power (CSP)—and identify critical climate vulnerabilities for each one. We then compare these vulnerabilities with assessments of future changes in mean conditions and extreme event risk levels. We do not identify any vulnerabilities severe enough to halt development of any of the technologies mentioned, although we do find a potential value in exploring options for making PV cells more heat-resilient and for improving the design of cooling systems for CSP.  相似文献   

Warming permafrost in European mountains   总被引：3，自引：0，他引：3  

Charles Harris  Daniel Vonder Mühll  Ketil Isaksen  Wilfried Haeberli  Johan Ludvig Sollid  Lorenz King  Per Holmlund  Francesco Dramis  Mauro Guglielmin  David Palacios 《Global and Planetary Change》2003,39(3-4):215-225

Here we present the first systematic measurements of European mountain permafrost temperatures from a latitudinal transect of six boreholes extending from the Alps, through Scandinavia to Svalbard. Boreholes were drilled in bedrock to depths of at least 100 m between May 1998 and September 2000. Geothermal profiles provide evidence for regional-scale secular warming, since all are nonlinear, with near-surface warm-side temperature deviations from the deeper thermal gradient. Topographic effects lead to variability between Alpine sites. First approximation estimates, based on curvature within the borehole thermal profiles, indicate a maximum ground surface warming of +1 °C in Svalbard, considered to relate to thermal changes in the last 100 years. In addition, a 15-year time series of thermal data from the 58-m-deep Murtèl–Corvatsch permafrost borehole in Switzerland, drilled in creeping frozen ice-rich rock debris, shows an overall warming trend, but with high-amplitude interannual fluctuations that reflect early winter snow cover more strongly than air temperatures. Thus interpretation of the deeper borehole thermal histories must clearly take account of the potential effects of changing snow cover in addition to atmospheric temperatures.  相似文献   

Local galactic evolution     

Johan Holmberg  Birgitta NordstrÖm  Bjarne Rosenkilde Jørgensen  Johannes Andersen 《Astrophysics and Space Science》2003,284(2):685-688

The evolution of the Solar neighbourhood is followed using a unique, magnitude complete and kinematically unbiased sample of 14,000 F, G, and K dwarfs. Metallicity, age, space motion and galactic orbits have been determined for all stars. The result is a detailed view of the complex evolution of the local Milky Way, which must be matched by any model for the chemical and dynamical evolution of the Galactic disk. E.g., such models must explain the shape and large scatter in the age-metallity relation as well as the overall metallicity distribution; the evolution of stellar kinematics with age; the distribution of stars in velocity space; and the contributions from the thick and thin disks to all these relations. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

White dwarfs and Galactic dark matter     

Chris Flynn  Janne Holopainen  Johan Holmberg 《Monthly notices of the Royal Astronomical Society》2003,339(3):817-824

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Latitudinal Variations of Diurnal Meteor Rates     

Csilla Szasz  Johan Kero  Asta Pellinen-Wannberg  John D. Mathews  Nick J. Mitchell  Werner Singer 《Earth, Moon, and Planets》2004,95(1-4):101-107

The presence of a diurnal variation in meteor activity is well established. The sporadic meteor count rates are higher on the local dawn side and lower on the local dusk side. This phenomenon is caused by the Earth’s orbital motion and rotation. Meteor radar measurements have been compared from Esrange, Kiruna, Sweden, at 68° N, from Juliusruh, Germany, at 55° N, and from Ascension Island, at 8° S, to investigate how the diurnal variation depends on season at different latitudes. Data have been used from vernal and autumnal equinoxes and summer and winter solstices to locate the largest seasonal differences.  相似文献   

Book reviews     

Thomas F. Moslow  Arnold H. Bouma  Arnold H. Bouma 《Geo-Marine Letters》1990,10(3):173-175

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On the mass-to-light ratio of the local Galactic disc and the optical luminosity of the Galaxy     

Chris Flynn  Johan Holmberg  Laura Portinari  Burkhard Fuchs  Hartmut Jahreiß 《Monthly notices of the Royal Astronomical Society》2006,372(3):1149-1160

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