Chemical investigations of Atlantis II and discovery brines in the Red Sea     

Lars-Göran Danielsson  David Dyrssen  Anders Granéli 《Geochimica et cosmochimica acta》1980,44(12):2051-2065

Analytical data for the Atlantis II and Discovery deeps in the Red Sea are given. The data were collected in March and June 1976 during the 22nd cruise of R/V Akademik Kurchatov in the Indian Ocean. On board analyses were performed of density, chlorinity, Mg, Ca, Sr and trace elements. The salinity, calculated from the density, is related to the chlorinity by S = 1.67 Cl + 4.02. The Ca-salinity relation is linear for both deeps showing that intermediate waters are formed by mixing of the brines with Red Sea water (RSDW). The hot brine (62°C) in the Atlantis II deep contains approx. 80 mg/kg of Fe and Mn while the warm brine (45°C) in the Discovery deep has a very low concentration of Fe and approx. 50 mg/kg of Mn. Mixing of RSDW containing 2 ml/l of oxygen with the anoxic deep brines causes precipitation of hydrous Mn(IV) and Fe(III) hydroxides. These two processes occur at different depths in the two deeps due to the formation of the warm (48–49°) intermediate brine in the Atlantis II deep. The oxidation-hydrolysis reactions proposed are supported by alkalinity-depth profiles and measurements of pH. These reactions also explain most of the trace element distributions and the composition of the SiO₂-Fe(III) hydroxide slurry recovered by some water samplers in the Atlantis II deep.  相似文献   

意大利埃特纳火山的三维速度结构与地震活动性   总被引：2，自引：2，他引：0  

Luca  G 《CT理论与应用研究》1998,7(1):43-51

本文的研究工作,得到了埃特纳火山下面的一组新的三维速度模型。作者们用１９８０年以来地方性地震在永久和临时地震台网在４个或更多台记录到的１２４９次地震的Ｐ和Ｓ波,被选来作走时反演。选择了几种判别标志与参数化办法以显示其类似的基本特征。表明在火山的东南象限在浅层,有Ｐ波的高速分怖,它同布格重力高异常有密切关系。在该区存在低的Ｖｐ／Ｖｓ比值;沿着中央火山管道,分布有高速Ｐ波和高的Ｖｐ／Ｖｓ比值;建议该处存在有稠密的侵入的岩浆体,延伸到２０千米左右的深度,该区附近有低速的Ｐ波速度。对震源的重新定位也显示出向外倾斜的易碎区,与中央火山管道延伸出一段Ｐ波高速异常区,位于中央火山口的附近。沿着中央火山口附近,有Ｐ波的低速区,它同次生的火山锥的分布有关,与部份熔融的深部岩浆库有联系。  相似文献   

Gaseous and Particulate Oxidized and Reduced Nitrogen Species in the Atmospheric Boundary Layer in Scandinavia in Spring     

Asgeir Sorteberg  Øystein Hov  Sverre Solberg  Kjetil Tørseth  Hans Areskoug  Martin Ferm  Kit Granby  Heikki Lättilä  Karin Persson  David Simpson 《Journal of Atmospheric Chemistry》1998,30(2):241-271

Observations of the concentration of several nitrogen containing compounds at five rural Scandinavian sites during March–June 1993 are reported. Total nitrate (NO ₃ ^- + HNO₃) and total ammonium (NH ₄ ⁺ + NH₃) were measured by denuder and filter pack. In general the methods agree well. At all sites the particulate fraction dominated, with the largest fraction of NO ₃ ^- and the lowest of NH ₄ ⁺ at the sites which were closest to the emission sources. The fraction of NO ₃ ^- of total nitrate increased with increasing NO₂ concentrations, indicating that the nighttime conversion of NO₂ to NO ₃ ^- is an important route of formation for NO ₃ ^- . A positive correlation was found between HNO₃ and O₃ in June at all sites, while no correlation was found early in the spring. Model calculations were made with a lagrangian boundary layer photooxidant model for the whole period, and compared to the measured concentrations. The calculated ratio between mean observed and modelled daily maximum concentrations of ozone over the measurement period were within +/–10% at all sites. The models ability to describe the daily ozone maximum concentration was satisfactory with an average deviation of 19–22% from the observed concentrations. HNO₃ was underestimated by over 50% at all sites except the one closest to the emission sources. The correlation between modelled and observed concentrations was generally best for the sites with shortest transport distance from the sources of emission.  相似文献   

Carbonyls and nonmethane hydrocarbons at rural European sites from the mediterranean to the arctic     

Sverre Solberg  Christian Dye  Norbert Schmidbauer  Alex Herzog  Robert Gehrig 《Journal of Atmospheric Chemistry》1996,25(1):33-66

Results of regular measurements during 1992–1995 of hydrocarbons and carbonyl compounds for a number of rural European monitoring sites are presented. The measurements are part of the EMEP programme for VOC measurements in Europe. In addition, several years of regular measurements are included from the Norwegian stations Birkenes at the south coast, and Zeppelin Mountain on Spitsbergen in the Arctic. The sampling frequency has been about twice per week throughout the years, implying that a substantial amount of measurement data are available. Almost all the chemical analyses have been performed by one laboratory, the EMEP Chemical Co-ordinating Centre located at NILU, which avoids problems of intercomparison and intercalibration among different laboratories. For the measured concentrations both seasonal and geographical variations are shown and discussed. The diurnal cycles of the hydrocarbon concentrations were studied in detail at one site, where the grab samples by EMEP where compared with a parallel continuous sampler, operated by EMPA, Switzerland. Hydrocarbons linked to natural gas and fuel evaporation become well mixed into the Arctic in the winter, whereas combustion products show a latitudinal gradient. The sum of oxygenated species constitutes about 5–15% of the sum of C₂–C₅ hydrocarbons in winter. In summer they are almost equal in magnitude, consistent with an increasing oxidation of hydrocarbons.  相似文献   

Direct N-body modelling of stellar populations: blue stragglers in M67     

Jarrod R. Hurley  †  Christopher A. Tout  Sverre J. Aarseth  Onno R. Pols 《Monthly notices of the Royal Astronomical Society》2001,323(3):630-650

We present a state-of-the-art N -body code which includes a detailed treatment of stellar and binary evolution as well as the cluster dynamics. This code is ideal for investigating all aspects relating to the evolution of star clusters and their stellar populations. It is applicable to open and globular clusters of any age. We use the N -body code to model the blue straggler population of the old open cluster M67. Preliminary calculations with our binary population synthesis code show that binary evolution alone cannot explain the observed numbers or properties of the blue stragglers. On the other hand, our N -body model of M67 generates the required number of blue stragglers and provides formation paths for all the various types found in M67. This demonstrates the effectiveness of the cluster environment in modifying the nature of the stars it contains, and highlights the importance of combining dynamics with stellar evolution. We also perform a series of N =10 000 simulations in order to quantify the rate of escape of stars from a cluster subject to the Galactic tidal field.  相似文献   

Flow behaviour of the submarine glacigenic debris flows on the Bear Island Trough Mouth Fan, western Barents Sea   总被引：3，自引：0，他引：3  

Jan Sverre Laberg  & Tore O. Vorren 《Sedimentology》2000,47(6):1105-1117

Using 3·5 kHz high-resolution seismic data, gravity cores and side-scan sonar imagery, the flow behaviour of submarine, glacigenic debris flows on the Bear Island Trough Mouth Fan, western Barents Sea was studied. During their downslope movement, the sediments within the uppermost part of the debris flows (<3 m) are inferred to have been deformed as a result of the shear stress at the debris–water interface. Thus, the uppermost part of the flow did not move downslope as a rigid plug. If present, a rigid part of the flow was located at least some metres below the surface. At c . 1000 to at least 1600 m water depth, the debris flows eroded and probably incorporated substrate debris. Further downslope, the debris flows moved passively over substrate sediments. The hypothesis of hydroplaning of the debris flow front may explain why the debris flows moved across the lower fan without affecting the underlying sediments. Detailed morphological information from the surface of one of the debris flow deposits reveals arcuate ridges. These features were probably formed by flow surge. Hydroplaning of the debris flow front may also explain the formation of flow surge. The long runout distance of some of the large debris flows could be due to accretion of material to the base of the debris flow, thereby increasing in volume during flow, and/or to hydroplaning suppressing deceleration of the flow.  相似文献   

Dynamics of water vapor flux and water separation processes during evaporation from a salty dry soil     

Meritxell Gran  Jesús Carrera  Jordi Massana  Maarten W. Saaltink  Sebastia Olivella  Carlos Ayora  Antonio Lloret 《Journal of Hydrology》2011,396(3-4):215-220

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A petrologic, geochemical and Sr–Nd isotopic study on contact metamorphism and degassing of Devonian evaporites in the Norilsk aureoles, Siberia     

Kwan-Nang Pang  Nicholas Arndt  Henrik Svensen  Sverre Planke  Alexander Polozov  Stephane Polteau  Yoshiyuki Iizuka  Sun-Lin Chung 《Contributions to Mineralogy and Petrology》2013,165(4):683-704

Devonian evaporites and associated sedimentary rocks in the Norilsk region were contact metamorphosed during emplacement of mafic sills that form part of the end-Permian (~252 Ma) Siberian Traps. We present mineralogical, geochemical and Sr–Nd isotopic data on sedimentary rocks unaffected by metamorphism, and meta-sedimentary rocks from selected contact aureoles at Norilsk, to examine the mechanisms responsible for magma-evaporite interaction and its relation to the end-Permian environmental crisis. The sedimentary rocks include massive anhydrite, rock salt, dolostone, calcareous siltstones and shale, and the meta-sedimentary rocks comprise calcareous hornfels, siliceous hornfels and minor meta-anhydrite and meta-sandstone. Contact metamorphism took place at low pressure and at maximum temperatures corresponding to the phlogopite-diopside stability field. Calcareous hornfels have high CaO, MgO, CΟ₂, SΟ₃, low SiO₂ and initial Sr isotopic ratios of 0.7079–0.7092, features indicative of calcareous siltstone protoliths. Siliceous hornfels, in contrast, have high SiO₂, Al₂O₃, Na₂O, low in other major element oxides and initial Sr isotopic ratios of 0.7083–0.7152, consistent with pelitic or shaley protoliths. Loss of CO₂ in a subset of calcareous hornfels can be explained by decarbonation reactions during metamorphism, but release of SO₂ from evaporites cannot be accounted for by a similar mechanism. Occurrences of wollastonite and a variety of hydrous minerals in the calcareous hornfels are consistent with equilibration with hydrous fluid, which was capable of leaching large quantities of anhydrite in the presence of dissolved NaCl. In this way, substantial sediment-derived sulfur could have been mobilized, incorporated into the magmatic system and released to the atmosphere. The release of CO₂ and SO₂ from Siberian evaporites added to the variety of toxic gases generated during metamorphism of organic matter, coal and rock salt, contributing to the end-Permian environmental crisis.  相似文献   

Measuring bluff erosion part 1: terrestrial laser scanning methods for change detection     

Stephanie S. Day  Karen B. Gran  Patrick Belmont  Tim Wawrzyniec 《地球表面变化过程与地形》2013,38(10):1055-1067

Human activities influence watershed sediment dynamics in profound ways, often resulting in excessive loading of suspended sediment to rivers. One of the primary factors limiting our ability to effectively manage sediment at the watershed scale has been our inability to adequately measure relatively small erosion rates (on the order of millimeters to centimeters per year) over annual and sub‐annual time scales on spatially‐extensive landforms, such as river banks and bluffs. Terrestrial laser scanning (TLS) can be employed to address this need. TLS collects high‐resolution data allowing for more accurate monitoring of erosion rates and processes, and provides a new opportunity to make precise measurements of geomorphic change on vertical landforms like banks and bluffs, but challenges remain. This research highlights challenges and limitations of using TLS for change detection on river banks and bluffs including the presence of vegetation, natural surface crenulations, and difficulties with creating benchmarks, and provides solutions developed to overcome these limitations. Results indicate that data processing algorithms for change detection can have a significant impact on the calculated erosion rates, with different methods producing results that can vary by over 100%. The most accurate change detection technique compares a point cloud to a triangulated irregular network (TIN) along a set of vectors that accommodate bluff curvature. This paper outlines a variety of methods used to measure bluff change via TLS and explains the accompanying error analysis that supports these methods. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Strong seasonality in sand loading and resulting feedbacks on sediment transport,bed texture,and channel planform at Mount Pinatubo,Philippines     

Karen B. Gran 《地球表面变化过程与地形》2012,37(9):1012-1022

Declining sand inputs to a channel with bimodal bed sediment can lead to degradation, armoring, and reduced bedload transport rates. Where sand loading is episodic, channels may alternate between high‐sand and low‐sand conditions, with ensuing responses in bed texture and bedload transport rates. The effects of episodic sand loading are explored through flow, grain size, and bedload transport measurements on the Pasig‐Potrero River, a sediment‐rich channel draining Mount Pinatubo, Philippines. Sand loading on the Pasig‐Potrero River is highly seasonal, and channel adjustments between seasons are dramatic. In the rainy season, inputs from sand‐rich 1991 eruption deposits lead to active, sand‐bedded, braided channels. In the dry season, many precipitation‐driven sand sources are cut off, leading to incision, armoring, and significantly lower bedload transport rates. This seasonal transition offers an excellent opportunity to examine models of degradation, incision, and armoring as well as the effectiveness of sediment transport models that explicitly encapsulate the importance of sand on transport rates. During the fall 2009 seasonal transition, 7·6 km of channel incised and armored, carving a 2–3 m deep channel on the upper alluvial fan. Bedload transport rates measured in the August 2009 rainy season were over four orders of magnitude greater than gravel‐bedded dry‐season channels surveyed in January 2010, despite having similar shear stress and unit discharge conditions. Within dry‐season incised channels, bed armoring is rapid, leading to an abrupt gravel‐sand transition. Bedload transport rates adjust more slowly, creating a lag between armoring and commensurate reductions in transport. Seasonal channel incision occurred in steps, aided by lateral migration into sand‐rich banks. These lateral sand inputs may increase armor layer mobility, renewing incision, and forming terraces within the incised seasonal channel. The seasonal incised channel is currently being reset by precipitation‐driven sand loading during the next rainy season, and the cycle begins again. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献