Rapid, high-precision potentiometric titration of alkalinity in ocean and sediment pore waters     

Conny Haraldsson  Leif G. Anderson  Martin Hassellöv  Stefan Hulth  Kristina Olsson 《Deep Sea Research Part I: Oceanographic Research Papers》1997,44(12):2031-2044

A system for rapid, high precision potentiometric determination of alkalinity in sea water and sediment pore water is presented. Two titration units were used: a 40 ml unit for seawater and a small volume unit for sediment pore water. Titration time was normally less than 10 minutes per sample, including sample exchange. With a 40 ml sample volume, the relative standard deviation of the alkalinity obtained in the laboratory was 0.05% and at sea 0.1 %. The small-volume system (0.5–1.5 ml) gave a precision of 0.07%. Five titration points, in two groups after the second equivalence point, were used to evaluate the equivalence volume. Results from equilibrium calculations and computer simulated alkalinity titrations show that it was possible to use a non-modified Gran function [(V₀ +v)^*10^(E/Z)] and still achieve good accuracy and precision.  相似文献   

Rydberg matter in space: low-density condensed dark matter     

Shahriar Badiei  Leif Holmlid 《Monthly notices of the Royal Astronomical Society》2002,333(2):360-364

Here Rydberg matter is proposed as a candidate for the missing dark matter or dark baryonic matter in the Universe. Spectroscopic and other experimental studies give valuable information on the properties of Rydberg matter, especially its very weak interaction with light caused by the very small overlap with low states, and because of the necessary two-electron transitions even for disturbed matter. Recently, the unidentified infrared (UIR) bands have been shown to agree well with calculations and experiments on Rydberg matter. This is the reason for the present, somewhat speculative, proposal that dark matter has, at least partially, the form of Rydberg matter. The UIR bands have also been observed directly in emission from Rydberg matter in the laboratory. The unique space-filling properties of Rydberg matter are described: a hydrogen atom in this matter occupies a volume  5×10¹²  times larger than in its ground state or in a hydrogen molecule.  相似文献   

“Bush Doctors and Wild Medicine”: The Scale of Trade in Cape Town's Informal Economy of Wild-Harvested Medicine and Traditional Healing     

Leif M. Petersen  Andrew J. E. Charman  Eugene J. Moll  Ray J. Collins  Marc T. Hockings 《社会与自然资源》2014,27(3):315-336

South Africa's organically emerged cultural business of traditional healing is almost exclusively reliant on wild-harvested resources extracted from wilderness areas or open-access commons. The wild medicine business has been described for much of South Africa, although is little understood in Cape Town, the urban centerpiece of the Cape Floristic Region (CFR). A census of different traditional healer typologies in five typical working-class residential areas (representing ～71,500 residents) was conducted to assess the nature and extent of traditional medicine harvesting and trade. Extrapolating these findings for the city reveals a local industry of more than 15,000 practitioners collectively conducting trade worth US $15.6 million per year. More than 40% of the volume of traditional medicines traded in the city is harvested from the CFR. Future conservation approaches must consider that the business of traditional healing and dispensing wild-harvested medicines is both economically important and culturally entrenched.  相似文献   

Wood dynamics in upland streams under different disturbance regimes     

Leonora King  Marwan A. Hassan  Xiaohua Wei  Leif Burge  Xiaoyong Chen 《地球表面变化过程与地形》2013,38(11):1197-1209

This paper presents reach scale large wood (LW) budgets of 12 upland streams in the Okanagan Basin of British Columbia. The study included 100 m long reaches at three wildfire sites and three undisturbed sites in the Interior Douglas‐fir (IDF) biogeoclimatic zone, and three recent Mountain Pine Beetle (MPB) infestation sites and three undisturbed sites in the Montane Spruce (MS) zone. Detailed information on wood recruitment, output and storage were obtained from repeated annual surveys. Recruitment from the riparian zone was found to dominate wood inputs, with fluvial import of secondary importance. In undisturbed streams, wood exhumation was found to be of tertiary importance, but was not observed in disturbed streams. Relative wood length was found to be a strong predictor of wood stability, with wood length to channel width and wood diameter to channel depth ratios of 1:1 forming an approximate maximum threshold of wood mobility. Volumetric decomposition was, on average, a third of the value of fluvial export, and the average residence time of wood in the channels was 20 years. In undisturbed reaches, wood storage indicated a slow depletion of wood from the channels. In the disturbed reaches, wildfire was found to significantly increase annual wood recruitment by more than an order of magnitude over undisturbed or control streams. MPB had not significantly increased LW recruitment, but is expected to increase over the coming decades. Storage rates at the disturbed streams indicated a net accumulation of wood over the study period. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Composition and properties of glacigenic sediments in the southwestern Barents Sea     

Joar Sættem  Leif Rise  Dag Arne Westgaard 《Marine Georesources & Geotechnology》2013,31(3-4):229-255

Abstract

The composition and properties of glacigenic sediments in the southwestern Barents Sea are described based on data from 33 shallow boreholes (< 143 m below seabed) and 11 seabed cores (<4.2m below seabed). The cores are tied into a regional seismostratigraphic framework, illustrating the relationships between different boreholes.

A massive, muddy diamicton (silty, sandy clay with scattered gravel) is found in nearly all cores. Average clay content (<2 pm) of this lithology is about 38%, but varies between about 25% and 50%. Short intervals of finely laminated, waterlain sediments or gravelly sand are cored in a few occasions. A high content of sand and gravel in the cores from near the Norwegian coast shows an influence of sediment input from the mainland, while material eroded from sedimentary rocks dominates farther offshore.

The data presented on physical properties include undisturbed and remolded undrained shear strength, natural water content, bulk density, compressional sound velocity (P waves), Atterberg consistency limits, effective preconsolidation pressure, and consolidation coefficient.

Prediction of overconsolidation from seismic mapping of erosional surfaces is confirmed by the borehole cores. High compaction is found both in Weichselian and older deposits, with a general increase in compaction toward the east as well as toward shallower water. Cores that are “underconsolidated” at their present burial depth are also reported.

The average compressional sound velocity is about 1780 m/s for the borehole cores, 1550 m/s for the seabed cores, and increases with increasing shear strength and consolidation. Both horizontal and vertical sound velocities are measured in several cores, and although the data have a considerable scatter, a slightly aniso‐tropic sound velocity is indicated.  相似文献   

Long-term landscape development of the Coloradofjella plateau, central Spitsbergen, Svalbard     

Jakob Fjellanger  Leif Sørbel 《Polar research》2005,24(1-2):17-31

The development and age of the present geomorphology and superficial material of the Coloradofjella plateau, Spitsbergen, have been investigated through field surveying and laboratory sediment analyses. The focus was specifically on the role of glacial erosion and periglacial processes. The summit plain is deeply incised with large V-shaped valleys. Extensive networks of ice wedge polygons indicate that the fine-grained regolith is at least a few metres thick. An abundance of coarse-grained gabbroid erratics, clearly derived from sources further to the east, are distributed over parts of the summit plain. A vertical-walled dolerite dyke protruding up to 4 m above the adjacent surface shows no sign of glacial erosion. Our findings confirm that the present bedrock geomorphology and regolith in the summit plain survived at least the Late Weichselian glaciation. This is best explained by the ice sheet having been cold-based throughout its existence on the summit plain. Cold-based conditions imply that permafrost survived the last glacial cover. Based on the geomorphic evidence and estimates of Late Cenozoic erosion, we suggest that the present summit plains roughly represent the remains of a preglacial surface.  相似文献   

Mobilities of alkalis, alkaline earths and halogens during weathering     

B.I. Kronberg  H.W. Nesbitt  W.S. Fyfe 《Chemical Geology》1987,60(1-4):41-49

Concentrations of alkali metals, alkaline earths and halogens were monitored in an Australian weathering profile and in Brazilian soils and bauxite. The materials analysed are considered to represent a range of chemical weathering histories, which are distinguished with respect to their degree of leaching by the dominant aluminosilicate assemblages. During initial weathering concentrations of alkalis and alkaline earths are similar or enriched relative to average crustal abundances. As weathering proceeds depletion is attenuated by the capacity of a particular element to participate in adsorption and ion-exchange processes. Strong depletion of alkalis and alkaline earths is common as weathering advances, and clay minerals are replaced by Al-oxide phases (e.g., gibbsite), with much lower capacities for exchanging and incorporating ions. Halogen concentration trends are more variable. F retention during weathering is likely due to substitution in mineral phases for hydroxyl groups. Cl and I are commonly observed to accumulate as weathering advances and some of these accumulations may be due to atmospheric additions.  相似文献   

Detailed geochemical studies of the initial stages of weathering of alkaline rocks: Ilha de São Sebastião, Brazil     

B.I. Kronberg  K. Tazaki  A.J. Melfi 《Chemical Geology》1987,60(1-4):79-88

Detailed mineral and chemical studies of samples of syenite rocks with thick weathering rinds, found in the alkaline massifs on Ilha de São Sebastião, illustrate the complex interplay between variables controlling initial weathering processes. An array of geochemical information was obtained by optical and electron microscopy, X-ray analyses, mass spectroscopy and optical spectrometry. Sericite and metahalloysite are the principal phases nucleating and forming as the perthitic feldspar rock matrix disintegrates. Incipient feldspar dissolution and the formation of submicrometer X-ray opaque secondary phases were observed in “fresh rock” material using transmission electron microscopy. Pore waters, from which secondary phases nucleate and grow are under the constant influence, as alteration proceeds, of physical (e.g., accessibility of mineral surfaces to percolating fluids) and chemical (e.g. chemistry of minerals providing the dominant solutes) controls. Minor- and trace-element signatures do not vary significantly except for Zn, Rb, Sr, Y, REE and Pb. Lathanide mobilities appear related to their host-mineral stabilities with respect to ambient pore waters.  相似文献   

Why are offices where they are? The search for factors determining the location of company headquarters     

Leif Ahnström 《GeoJournal》1984,9(2):163-170

Cases are presented which illustrate three differenct ways in which the locations of corporate headquarters were established. The office is in a particular city or urban center because 1) the firm was founded there, the founder apparently making no assesment of the advantages of the place in comparison with other places, 2) the palce was considered the most appropriate for manufacturing or for some other operative activity, or 3) it met the requirements of the specific activities of the head office. Factors influencing the selection of head office locations are suggested, as well as factors conserving the locational pattern of such offices, i.e. obstacles to moves.  相似文献   

Stability,morphology and surface grain size patterns of channel bifurcation in gravel–cobble bedded anabranching rivers     

Leif M. Burge 《地球表面变化过程与地形》2006,31(10):1211-1226

This study presents the first detailed field‐based analysis of the morphology of bifurcations within anabranching cobble–gravel rivers. Bifurcations divide the flow of water and sediment into downstream anabranches, thereby influencing the characteristics of the anabranches and the longevity of river islands. The history, morphology, bed grain size, and flow vectors at five bifurcations on the Renous River, New Brunswick, Canada, were studied in detail. The angles of bifurcations within five anabranching rivers in the Miramichi basin were investigated. The average bifurcation angle was 47°, within the range of values cited for braided river bifurcations. Bifurcation angle decreased when anabranches were of similar length. Shields stresses in channels upstream of bifurcations were lower than reported values for braided rivers. Stable bifurcations displayed lower Shields stresses than unstable bifurcations, contrary to experimental results from braided river bifurcations. Bifurcations in anabranching rivers are stabilized by vegetation that slows channel migration and helps to maintain a uniform upstream flow field. The morphology of stable bifurcations enhances their stability. A large bar, shaped like a shallow ramp that increases in elevation to floodplain level, forms at stable bifurcations. Floodplains at stable bifurcations accrete upstream at rates between 0·9 and 2·5 m a^?1. Bars may also form within the entrance of an anabranch downstream of the bifurcation node. These bars are associated with bifurcation instability, forming after a period of stability or an avulsion. Channel abandonment occurs when a bar completely blocks the entrance to one anabranch. The stability of channels upstream of bifurcations and the location of bars at bifurcations influence bifurcation stability and the maintenance of river anabranching in the long term. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献