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1.
Ingi Olafsson Eirik Sundvor Olav Eldholm Kjersti Grue 《Marine Geophysical Researches》1992,14(2):137-162
Analysis in both the x—t and —p domains of high-quality Expanded Spread Profiles across the Møre Margin show that many arrivals may be enhanced be selective ray tracing and velocity filtering combined with conventional data reduction techniques. In terms of crustal structure the margin can be divided into four main areas: 1) a thicker than normal oceanic crust in the eastern Norway Basin; 2) expanded crust with a Moho depth of 22 km beneath the huge extrusive complex constructed during early Tertiary breakup; 3) the Møre Basin where up to 13–14 km of sediments overlie a strongly extended outer part with a Moho depth at 20 km west of the Ona High; and 4) a region with a 25–27 km Moho depth between the high and the Norwegian coast. The velocity data restricts the continent-ocean boundary to a 15–30 km wide zone beneath the seaward dipping reflector wedges. The crust west of the landward edge of the inner flow is classified as transitional. This region as well as the adjacent oceanic crust is soled by a 7.2–7.4 km s–1 lower crustal body which may extend beneath the entire region that experienced early Tertiary crustal extension. At the landward end of the transect a 8.5 km s–1 layer near the base of the crust is recognized. A possible relationship with large positive gravity anomalies and early Tertiary alkaline intrusions is noted. 相似文献
2.
H. E. Scheel H. Areskoug H. Geiss B. Gomiscek K. Granby L. Haszpra L. Klasinc D. Kley T. Laurila A. Lindskog M. Roemer R. Schmitt P. Simmonds S. Solberg G. Toupance 《Journal of Atmospheric Chemistry》1997,28(1-3):11-28
Surface ozone data from 25 Europeanlow-altitude sites and mountain sites located between79°N and 28°N were studied. The analysiscovered the time period March 1989–February 1993.Average summer and winter O3 concentrations inthe boundary layer over the continent gave rise togradients that were strongest in the north-west tosouth-east direction and west-east direction, respectively. WintertimeO3 ranged from 19 to 27 ppbover the continent, compared to about 32 ppb at thewestern border, while for summer the continentalO3 values ranged between 39 and 56 ppb and theoceanic mixing ratios were around 37 ppb. In the lowerfree troposphere average wintertime O3 mixingratios were around 38 ppb, with only an 8 ppbdifference between 28°N and 79°N. For summerthe average O3 levels decreased from about 55 ppbover Central Europe to 32 ppb at 79°N. Inaddition, O3 and Ox(= O3 + NO2)in polluted and clean air were compared. Theamplitudes of the seasonal ozone variations increasedin the north-west to south-east direction, while thetime of the annual maximum was shifted from spring (atthe northerly sites) to late summer (at sites inAustria and Hungary), which reflected the contributionof photochemical ozone production in the lower partsof the troposphere. 相似文献
3.
S. Solberg T. Krognes F. Stordal OØ Hov H. J. Beine D. A. Jaffe K. C. Clemitshaw S. A. Penkett 《Journal of Atmospheric Chemistry》1997,28(1-3):209-225
Simultaneousindependent measurements of NOy and NOx(NOx= NO + NO2) by high-sensitivitychemiluminescence systems and of PAN (peroxyacetylnitrate) and PPN (peroxypropionyl nitrate) by GC-ECDwere made at Spitsbergen in the Norwegian Arcticduring the first half year of 1994. The average mixingratio of the sum of PAN and PPN (denoted PANs)increased from around 150 pptv in early winter to amaximum of around 500 pptv in late March, whereasepisodic peak values reached 800 pptv. This occurredsimultaneously with a maximum in ozone which increasedto 45–50 ppbv in March–April. The average NOxmixing ratio was 27 pptv and did not show any cyclethrough the period. The NOy mixing ratio showeda maximum in late March, while the difference betweenNOy and PAN decreased during spring. This is anindication of the dominance of PAN in the NOybudget in the Arctic, but possible changes in theefficiency of the NOy converter could alsocontribute to this. Although most PAN in theArctic is believed to be due to long range transport,the observations indicate local loss and formationrates of up to 1–2 pptv h-1 in April–May.Measurements of carbonyl compounds suggest thatacetaldehyde was the dominant, local precursor ofPAN.Now at 1. 相似文献
4.
Increased use of wood can substitute more energy demanding products and thus contribute to a long-term solution to the global warming problem. The aim of this article is to provide an empirical study on this substitution impact, its cost-effectiveness, and which methodological assumptions that are of highest importance for the results obtained. We have made a case study where we compare use of various flooring materials. The results show that floor covering in solid oak causes lower greenhouse gas (GHG) emissions than the other materials. The difference can be ranked in the following order, after their potential for reduction in GHG emissions: Carpet in wool, carpet in polyamide, vinyl, and linoleum. At 2% pro anno discount rate, the avoided GHG emission in tons per m3 of oak flooring used is 0.1–1.9 for linoleum, and 11.8–15.5 for wool carpets. Unless the solution in solid oak is on total less expensive over the lifetime of the building, only the price of avoided emissions from a substitution between solid oak and carpet in wool is reasonable, compared to present carbon fees. The assumptions that influence the result most are choice of discount rate, carbon fixation on forest area, and waste handling. Empirical case studies like this indicate GHG emission reduction potentials caused by substitution, but should be complemented by dynamic input/output analyses and econometric studies. To analyse the flow of CO2 over time, they should also be linked to forest management models. 相似文献
5.
Sverre Solberg Norbert Schmidbauer Arne Semb Frode Stordal Øystein Hov 《Journal of Atmospheric Chemistry》1996,23(3):301-332
Several years of measurements of ozone, hydrocarbons, sulphate and meteorological parameters from Spitsbergen in the Norwegian Arctic are presented. Most of the measurements were taken on the Zeppelin Mountain at an altitude of 474 m a.s.l. The focus is the episodes of ozone depletion in the lower troposphere in spring, which are studied in a climatological way. Episodes of very low ozone concentrations are a common feature on the Zeppelin Mountain in spring. The low ozone episodes were observed from late March to the beginning of June. When the effect of transport direction was subtracted, the frequenty of the low ozone episodes was found to peak in the beginning of May, possibly reflecting the seasonal cycle in the actual depletion process. Analyses based on trajectory calculations show that most of the episodes occurred when the air masses were transported from W-N. Ozone soundings show that the ozone depletion may extend from the surface and up to 3–4 km altitude. The episodes were associated with a cold boundary layer beneath a thermally stable layer, suppressing mixing with the free troposphere. The concentration of several individual hydrocarbons was much lower during episodes of low ozone than for the average conditions. The change in concentration ratio between the hydrocarbons was in qualitative agreement with oxidation of hydrocarbons by Br and Cl atoms rather than by OH radicals. 相似文献
6.
Is pure groundwater safe to drink?: natural "contamination' of groundwater in Norway 总被引：1，自引：0，他引：1
David Banks Aase Kjersti Midtgrd Geir Morland Clemens Reimann Terje Strand Kjell Bjorvatn & Ulrich Siewers 《Geology Today》1998,14(3):104-113
The title of this article is designed to provoke. Naturally occurring parameters are, by definition, not contamination. Nevertheless, nature is not necessarily nice, and naturally occurring trace toxins can be every bit as undesirable as their counterparts derived from human pollution. 相似文献
7.
Pyrite: physical and chemical textures 总被引：9，自引：0，他引：9
Pyrite may crystallize initially in forms as diverse as framboids or cubes depending upon the temperatures and pressures.
Fluid-rich diagenesis or low-grade metamorphism clearly results in thorough recrystallization and the common formation of
cubes. Once these have formed, the pyrite becomes much more refractory and retains many characteristics even in deposits which
have undergone penetrative deformation. This is in strong contrast to the behavior of most of the accompanying sulfides, which
often undergo ductile deformation, solid state or chemical remobilization, and annealing. Pyrite deforms sparingly until there
is brittle failure; however, there may be significant pyrite corrosion and regrowth during metamorphism as the result of sulfur
exchange with other minerals, especially pyrrhotite. Pyrite fabrics may also be significantly modified by pressure solution
or Coble creep. Optical microscopic examination and electron microprobe chemical mapping of pyrites from a variety of mineral
deposits, including several high-grade metamorphic ones, reveals that the pyrites frequently contain both physical and chemical
textures that may be interpreted in terms of the depositional and the post-depositional history of the deposits. Inclusions
of sulfides or other minerals reveal information on the timing of the crystallization or recrystallization of the pyrite;
chemical mapping of elements such as Ni, Co, and As reveals information on the relative time of transport of these elements
in the ore fluids.
Received: 19 March 1997 / Accepted: 14 May 1998 相似文献
8.
Laboratory hydrofracture experiments were performed on triaxially stressed specimens of oil shale and low-permeability granite. The results show that either shear or tension fractures could develop depending on the level of differentials stress, even in specimens containing preexisting fractures. With 1 kb of confining pressure and differential stress greater than 2kb, hydraulic fluid diffusion into the specimens reduced the effective confining pressure until failure occurred by shear fracture. Below 2kb of differential stress, tension fractures occurred. These results suggest that hydraulic fracturing in regions of significant tectonic stress may produce shear rather than tension fractures. In this casein situ stress determinations based on presumed tension fractures would lead to erroneous results. 相似文献
9.